Note: Descriptions are shown in the official language in which they were submitted.
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Hi4h flux liquid transport members comprising
s two different permeability regions
f0
FIELD OF THE INVENTION
The present invention relates to liquid transport members useful for a wide
range of applications requiring high flow and/or flux rate, wherein the liquid
can
be transported through such a member, and/ or be transported into or out of
such
zo a member. Such members are suitable for many applications, as - without
being
limited to - disposable hygiene articles, water irrigation systems, spill
absorbers,
oil/water separators and the like. The invention further relates to liquid
transport
systems comprising said liquid transport members and articles utilizing these.
BACKGROUND
The need to transport liquids form one location to another is a well known
problem.
Generally, the transport will happen from a liquid source through a liquid
transport member to a liquid sink, for example from a reservoir through a pipe
to
so another reservoir. There can be differences in potential energy between the
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reservoirs (such as hydrostatic height) and there can be frictional energy
losses
within the transport system, such as within the transport member, in
particular if
the transport member is of significant length relative to the diameter
thereof.
For this general problem of liquid transport, there exist many approaches to
s create a pressure differential to overcome such energy differences or losses
so
as to cause the liquids to flow. A widely used principle is the use of
mechanical
energy such as pumps. Often however, it will be desirable to overcome such
energy losses or differences without the use of pumps, such as by exploiting
hydrostatic height differential (gravity driven flow), or via capillary
effects (often
,o referred to as wicking).
In many of such applications, it is desirable to transport the liquids at high
rates, i.e. high flow rate (volume per time), or high flux rate (volume per
time per
unit area of cross-section).
Examples for applications of liquid transport elements or members can be
~s found in fields like water irrigation such as described in EP-A-0.439.890,
or in the
hygiene field, such as for absorbent articles like baby diapers both of the
pull-on
type or with fastening elements like tapes, training pants, adult incontinence
products, feminine protection devices.
A well known and widely used execution of 'such liquid transport members
so are capillary flow members, such as fibrous materials like blotting paper,
wherein
the liquid can wick against the gravity. Typically such materials are limited
in their
flow and/or flux rates, especially when wicking height is added as an
additional
requirement. An improvement particularly towards high flux rates at wicking
heights particularly useful for example for application in absorbent articles
has
is been described in EP-A-0.810.078.
Other capillary flow members can be non-fibrous, but yet porous structures,
such as open celled foams. In particular for handling aqueous liquid,
hydrophilic
polymeric foams have been described, and especially hydrophilic open celled
foams made by the so called High Internal Phase Emulsion (HIPE)
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polymerization process have been described in US-A-5.563.179 and US-A-
5.387.207.
However, in spite of various improvements made on such executions, there
is still a need to get significant increase in the liquid transport properties
of liquid
s transport members.
In particular, it would be desired to obtain liquid transport members, that
can
transport liquid against gravity at very high flux rates.
In situations wherein the liquid is not homogeneous in composition (such as
a solution of salt in water), or in its phases (such as a liquidlsoiid
suspension), it
,o can be desired to transport the liquid in its totality, or only parts
thereof. Many
approaches are well known for their selective transport mechanism, such as in
the filter technology.
For example, filtration technology exploits the higher and lower permeability
of a member for one material or phase compared to another material or phase.
~s There is abundance of art in this field, in particular also relating to the
so called
micro-, ultra-, or nano-filtration. Some of the more recent publications are:
US-A-5.733.581 relating to melt-blown fibrous filter;
US-A-5.728.292 relates to non-woven fuel filter;
WO-A- 97/47375 relating to membrane filter systems;
Zo WO-A- 97/35656 relating to membrane filter systems;
EP-A-0.780.148 relating to monolithic membrane structures;
EP-A-0.773.058 relating to oleophiiic filter structures.
Such membranes are also disclosed to be used in absorbent systems.
In US-A-4.820.293 (Kamme) absorbent bodies are disclosed, for being
is used in compresses, or bandages, having a fluid absorbent substance
enclosed
in a jacket made of one essentially homogeneous material. Fluid can enter the
body through any part of the jacket, and no means is foreseen for liquid to
leave
the body.
Therein, fluid absorbent materials can have osmotic effects, or can be gel-
3o forming absorbent substances enclosed in semipermeable membranes, such as
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cellulose, regenerated cellulose, cellulose nitrate, cellulose acetate,
cellulose
acetate butyrate, polycarbonate, polyamide, fiberglass, polysulfone, of
polytetrafluoroethylene, having pore sizes of between 0.001 ~m and 20 Vim,
preferably between 0.005 ~m and 8 Vim, especially about 0.01 Vim.
s In such a system, the permeability of the membrane is intended to be such
that the absorbed liquid can penetrate, but such that the absorbent material
is
retained.
ft is therefore desired to use membranes having a high permeability K and a
low thickness d, so as to achieve a high liquid conductivity k/d of the layer,
as
being described herein after.
This can be achieved by incorporation of promoters with higher molecular
weight (e.g., polyvinyl pyrrolidone with a molecular weight of 40,000), such
that
the membranes can have larger pores leading to larger membrane permeability
k. The maximum pore size stated therein to be useful for this application is
less
rs than 0.5 Vim, with pore sizes of about 0.01 ~m or less being preferred. The
exemplified materials allow the calculation of kld values in the range of 3 to
7
10-'4 m.
As this system is quite slow, the absorbent body can further comprise for
rapid discharge of fluids a liquid acquisition means, such as conventional
Zo acquisition means to provide interim storage of the fluids before these are
slowly
absorbed.
A further application of membranes in absorbent packets is disclosed in US-
A-5.082.723, EP-A-0.365.565, or US-A-5.108.383 (White; Allied-Signal).
Therein, an osmotic promoter, namely a high-ionic strength material such
zs as NaCI, or other high osmolality material like glucose or sucrose is
placed inside
a membrane such as made from cellulosic films. As with the above disclosure,
fluid can enter the body through any part of the jacket, and no means is
foreseen
for liquid to leave the body. When these packets are contacted by aqueous
liquids, such as urine, the promoter materials provide an osmotic driving
force to
so pull the liquid through the membranes. The membranes are characterized by
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having a low permeability for the promoter, and the packets achieve typical
rates
of 0.001 ml/cm2/min. When calculating membrane conductivity k/d values for
'the
membranes disclosed therein, values of about 1 to 2 * 10''5 m result. An
essential property of membranes useful for such applications is their ":>alt
s retention", i.e. whilst the membranes should be readily penetrable by the
liquid,
they must retain a substantial amount of the promoter material within ithe
packets. This salt retention requirements provides a limitation in pore size
which
will limit liquid 'flux.
US-A-5.082.723 (Gross et al.) discloses an osmotic material like NaCI which
so is enclosed by superabsorbent material, such as a copolymer of acrylic acid
and
sodium acrylate, thereby aiming at improving absorbency, such as enhanced
absorptive capacity on a "gram per gram" basis and absorption rate.
Overall, such fluid handling members are used for improved absorbency of
liquids, but have only very limited fluid transport capability.
~s Thus, there remains still a need to improve the liquid transport
properties, in
particular to increase the flow and/or flux rates in liquid transport systems.
OBJECTS OF ASPECTS OF THE INVENTION
Hence it is an object of an aspect of the present invention to provide a
liquid
2o transport member composed of at least two regions exhibiting a difference
in
permeability.
It is a further object of an aspect to provide liquid transport members
exhibiting
improved liquid transport, as expressed in significantly increased liquid flow
rates,
and especially liquid flux rates, i.e, the amount of liquid flowing in a time
unit through
2s a certain cross-section of the liquid transport member.
It is a further object of an aspect of the present invention to allow such
liquid
transport against gravity.
It is a further object of an aspect of the present invention to provide such
am
improved liquid transport member for fluids with a wide range of physical
properties,
so such as for aqueous (hydrophilic) or non-aqueous, oily or lipophilic
liquids.
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It is a further object of an aspect of this invention to provide liquid
transport
systems, comprising in addition to the liquid transport member a liquid sink
and/or
liquid source.
It is an even further object of an aspect of the present invention to provide
any
s of the above objects for being used in absorbent structures, such as can be
useful in
hygienic absorbent products, such as baby diapers; adult incontinence
products,
feminine protection products.
It is an even further object of an aspect of the present invention to provide
any
of the above objects for use as water irrigation systems, spill absorber, oil
absorber',
~o water/oil separators.
SUMMARY OF THE INVENTION
The present invention is a liquid transport member having at least one bulk:
region with an average permeability kp, and a wall region that completely
~s circumscribes said bulk region, whereby the wall region further .comprises
at
least one port region having a thickness d and an average pemneability kF,
throughout this thickness, whereby the bulk ~ region has an average fluid
permeability kb which is higher than the average fluid permeability !cp of the
port
region and that said port region has a ratio of fluid permeability to
thickness in the
zo direction of .fluid transport, k~/dp of at least 10'' m. Preferably, the
bulk region has
a fluid pem~eability of at least 10'" m2, preferably at least 10$ mZ, more
preferably
at least 10-' m2, most preferably at least 10'S m2, but preferably of not more
than
10-2 m2. In another preferred embodiment, the said port region has a fluid
permeability of at least fi"10'x° m2, preferably at least 7*10''8 m2,
more preferably
25 at least 3*10''° m2, even more preferably of at least 1.2*10'" m2,
or even at least
7*10'" m2, most preferably at leasfi 10'9 mZ, or a- ratio of fluid
permeability to
thickness in the direction of fluid transport, k~ldP of at.least 5*10~' m,
preferably at
least 10$ m, preferably at least 10'5 m.
In a further preferred embodiment of the present invention, the bulk region
3o has an average dry density of more than 0.009 g/cm3.
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In a particular aspect of the invention, the liquid transport member comprises
a first material in a first region, and wherein the member further comprises
an
additional element in contact with the first materials of the first region
which
extends into a neighbouring second region of said liquid transport member that
is
s in contact with the wall region. The additional element can be in contact
with the
wall region and can extend into the neighbouring second region, and can have a
capillary pressure for absorbing the liquid that is lower than the bubble
point
pressure of the liquid transport member. The additional element can comprise a
softness layer.
In a further aspect of the invention, the ratio of permeability of the bulk
region
to the permeability of the port region of the Liquid handling member is at
least 10,
preferably at least 100, more preferably at least 1000, and even more
preferably
at least 100,000. The liquid handling member can exhibit a bubble point
pressure
when measured with water having a surface tension of 72 mN/m of at least 1
r5 kPa, preferably at least 2 kPa, more preferably at least 4.5 kPa, even more
preferably 8 kPa, most preferably 50, and the port region of the member can
exibit a a bubble point pressure when measured with water having a surface
tension of 72 mNlm of at least 1 kPa, preferably at least 2 kPa, more
preferably
at least 4.5 kPa, even more preferably 8 kPa, most preferably 50 and when
Zo measured with an aqueous test solution having a surface tension of 33 mNlm
of
at least 0.67 kPa, preferably at least 1.3 kPa, more preferably at least 3.0
kPa,
even more preferably 5.3 kPa, most preferably 33 kPa.
In yet a further aspect, a liquid transport member according to the present
invention can loose more than 3% of the initial liquid when submitted to the
Zs closed system test.
A liquid transport member can have a bulk region which has a larger average
pore size than said port region, preferably such that the ratio of average
pore
size of the bulk region and the average pore size of the port region is at
least 10,
preferably at least 50, more preferably at least 100, and even more preferably
at
30 least 500, and most preferably at least 350, and the bulk region can have
an
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average pore size of at least 200Nm, preferably at least 500Nm, more
preferably
of at least 1000Nm, and most preferably of at least 5000Nm, or a porosity of
at
least 50%, preferably at least 80%, more preferably at least 90%, even more
preferably of at least 98%, and most preferably of at least 99%. In a further
s aspect, the port region can have a porosity of at least 10%, preferably at
least
20%, more preferably of at least 30%, and most preferably of at least 50%, or
an
average pore size of no more than 100Nm, preferably no more than 50Nm, more
preferably of no more than 10~rm, and most preferably of no more than 5Nm, but
preferably not less than 1 Nm, preferably at least 3Nm. Further, the port
region
~o can have an average thickness of no more than 100Nm, preferably no more
than
50Nm, more preferably of no more than 10Nm, and most preferably of no more
than SNm. The bulk region and the wall region can have a volume ratio of at
least
10, preferably at least 100, more preferably at least 1000, and even more
preferably at least 100,000.
rs In yet a further embodiment, the port region is hydrophilic, preferably by
having a receding contact angle for the liquid to be transported of less than
70
degrees, preferably less than 50 degrees, more preferably less than 20
degrees,
and even more preferably less than 10 degrees. In a particular embodiment, the
port region does not reduce the surface tension of the transported liquid. In
a
2o further embodiment, the port region is oleophilic, preferably by having a
receding
contact angle for the liquid to be transported of less than 70 degrees,
preferably
less than 50 degrees, more preferably less than 20 degrees, and even more
preferably less than 10 degrees.
In yet another aspect of the present invention, the liquid transport member or
zs the bulk region thereof comprises a material which is expandable upon
liquid
contact and collapsible upon liquid removal, preferably by a volume expansion
factor of at least 5.
A liquid transport member according to the present invention can be sheet
like shape, or has a cylindrical like shape, or can have a cross-section area
along
3o the direction of liquid transport is not constant. The port region of the
the member
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preferably have a larger area than the average cross-section of the member
along the direction of liquid transport, preferably by at least a factor of 2,
preferably a factor of 10, most preferably a factor of 100.
The bulk region of a liquid transport member can comprise material selected
s from the groups of fibers, particulates, foams, spirals, films, corrugated
sheets, or
tubes, and the wall region can comprise material selected from the groups of
fibers, particulates, foams, spirals, films, corrugated sheets, tubes, woven
webs,woven fiber meshes, apertured films, or monolithic films. The foam can be
an pen cell reticulated foam, preferably selected from the group of cellulose
~o sponge, polyurethane foam, HIPE foams, and the fibers can be made of
polyolefins, polyesters, polyamids, polyethers, polyacrylics, polyurethanes,
metal,
glass, cellulose, cellulose derivatives.
A liquid transport member can comprise a porous bulk region that is wrapped
by a separate wail region. It also can comprise soluble materials, such as in
the
~s port region. The membranes in the port region can comprise stimulus
activatable
membrane- materials, such as a membrane, which changes its hydrophilicity
upon a temperature change.
The liquid transport member can be initially partially or essentially filled
with
liquid., or it can be initially under vacuum.
2o In a further aspect of the present invention, the liquid transport member
is
suitable for the transport of water-based liquids or of viscoelastic liquids,
of bodily
discharge fluids, as urine, blood menses, sweat or feces, or of oil, grease,
or
other non-water based liquids. Such a transport can be also selective, such as
for oil or grease, but not water based liquids.
25 I yet a further aspect, a liquid transport can exhibit properties or
parameter
which are established prior to or at the liquid handling, preferably by
activation by
contact with the liquid, pH, temperature, enzymes, chemical reaction, salt
concentration or mechanical activation.
In yet a further aspect, the present invention relates to a liquid transport
so system having a liquid transport member as described in the above, in
addition to
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a source or sink of liquid, each of the sink or source possibly being outside
or
inside of the member. Such a system can exhibit an absorbent capacity of at
least 5glg, preferably at least 10g/g, more preferably at least 50g1g on the
basis
of the weight of the said system, when submitted to the Demand Absorbency
s Test.. Such a system can comprise materials in the sink, which have an
absorption capacity in the teabag test of at least 10 glg, preferably at least
20 glg
and more preferably at least 50 g/g on the basis of the weight of the sink
material. The sink material can also exhibit an absorbent capacity of at least
5
g/g, preferably of at least 10 g/g, more preferably of at least 50 glg on the
basis
ro of the weight of the sink material, when measured in the Capillary Sorption
Test
at a pressure up to the bubble point pressure of the port region, and which
has
an absorbent capacity of at less than 5 g/g, preferably of less than 2 g/g,
more
preferably of less than 1 g/g and most preferably of less than 0.2g/g, when
measured in the Capilalry Soprtion Test at a pressure exceeding the bubble
point
,s pressure of the port region. A system can comprise superabsorbent material
or
open celled foam of the High Internal Phase Emulsion (HIPE) type.
In yet a further aspect, the invention is concerned with an article including
a
liquid transport member or system. Such an article can be a baby or adult
incontinence diaper, a feminine protection pad, a pantiliner, or a training
pant, or
Zo a grease absorber, or a water transport member.
fn yet a further aspect, the present invention is concerned with the method of
making a liquid transport member, comprising the steps of a) providing a bulk
region material or a void space; b) providing a wall material comprising a
port
region; c) completely enclosing said bulk region material or said void space
by
is said wall material; d) providing a transport enabiement means selected from
d 1 )
vacuum; d2) partial or essentially complete liquid filling; d3) expandable
elastics I
springs. The method can further comprise the step of applying activation
means,
such as e1) a liquid dissolving port region; e2) a liquid dissolving
expandable
elastication / springs; e3) a removable release element; or e4) a removable
3o sealing packaging. Alternatively, the method can comprise the steps of a)
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wrapping a highly porous bulk material with a separate wall material that
comprises at least one permeable port region, b) completely sealing the wall
region, and c) evacuating the member essentially of air, optionally filling
the
member with liquid.
According to an aspect of the present invention, there is provided a liquid
transport member comprising at least one bulk region having an average
permeability kb, and a wall region that completely circumscribes the bulk
region, the wall region further comprising at least one port region having a
thickness d and an average permeability kp throughout this thickness, wherein
the average fluid permeability kb of the bulk region is higher than the
average
fluid permeability kP of the at least one port region and wherein the at least
one port region has a ratio of fluid permeability to thickness in the
direction of
fluid transport, k~/dP, of at least 10-' m.
In a further embodiment, the invention provides an article comprising a
liquid transport member as described above.
In a further embodiment, the invention provides a method of making a
liquid transport member comprising the steps of
a) providing a bulk region material or a void space;
b) providing a wall material comprising a port region;
c) completely enclosing the bulk region material or the void space by
the wall material;
d) providing a transport enablement means selected from the group
consisting of:
d1 ) vacuum;
d2) partial or essentially complete liquid filling; and
d3) expandable elastics/springs.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1: Schematic diagram of conventional open siphon.
Fig. 2: Schematic diagram of a liquid transport member according to the
present invention.
Fig. 3 A, B: Conventional Siphon system, and liquid transport member
according to the present invention.
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Fig. 4: Schematic cross-sectional view through a liquid transport
member.
Fig. 5 A, B, C: Schematic representation for the determination of port
region thickness.
Fig. 6: Correlation of permeability and bubble point pressure.
Fig. 7 to 12: Schematic diagrams of various embodiments of liquid
transport member according to the present invention.
Fig. 13 A, B, C: Liquid Transport Systems according to the present
invention.
Fig. 14: Schematic diagram of an absorbent article.
Fig. 15 to16 A, B: Absorbent Article comprising a liquid transport
member.
Fig. 17 A to 18 A, B: Specific embodiments of liquid transport member.
Fig. 19 to 20 A, B: Liquid permeability test.
Fig. 21 A - D: Capillary absorption test.
DETAILEp DESCRIPTION OF THE INVENTION
General definitions
As used herein, a "liquid transport member" refers to a material or a
composite of materials, which is able to transport liquids. Such a member
contains at least two regions, an "inner" region, for which the term "bulk"
region can be used
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interchangeably, and a wall region comprising at least one "port" region. The
terms "inner" and "outer" refer to the relative positioning of the regions,
namely
meaning, that the outer region generally circumscribes the inner region, such
as
a wall region circumscribing a bulk region
s As used herein, the term "Z-dimension" refers to the dimension orthogonal to
the length and width of the liquid transport member or article. The Z-
dimension
usually corresponds to the thickness of the liquid transport member or the
article.
As used herein, the term "X-Y dimension" refers to the plane orthogonal to the
thickness of the member, or article. The X-Y dimension usually corresponds to
~o the length and width, respectively, of the liquid transport member, or
article. The
term layer also can apply to a member, which - when describing it in spherical
or
cylindrical co-ordinates - extends in radial direction much less than in the
other
ones. For example, the skin of a balloon would be considered a layer in this
context, whereby the skin would define the wall region, and the air filled
center
f5 part the inner region.
As use herein, the term "layer" refers to a region whose primary dimension is
X-Y, i.e., along its length and width. It should be understood that the term
layer is
not necessarily limited to single layers or sheets of material. Thus the layer
can
comprise laminates or combinations of several sheets or webs of the requisite
zo type of materials. Accordingly, the term "layer' includes the terms
"layers" and
"layered".
For purposes of this invention, it should also be understood that the term
"upper" refers to members, articles such as layers, that are positioned
upwardly
(i.e. oriented against the gravity vector) during the intended use. For
example, for
is a liquid transport member intended to transport liquid from a "lower"
reservoir to
an "upper" one, this is meant to be transport against gravity.
All percentages, ratios and proportions used herein are calculated by weight
unless otherwise specified.
As used herein, the term "absorbent articles" refers to devices which absorb
so and contain body exudates, and, more specifically, refers to devices which
are
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placed against or in proximity to the body of the wearer to absorb and contain
the
various exudates discharged from the body. As used herein, the term "body
fluids" includes, but is not limited to, urine, menses and vaginal discharges,
sweat and feces.
s The term "disposable" is used herein to describe absorbent articles which
are
not intended to be laundered or otherwise restored or reused as an absorbent
article (i.e., they are intended to be discarded after use and, preferably, to
be
recycled, composted or otherwise disposed of in an environmentally compatible
manner).
As used herein, the term "absorbent core" refers to the component of the
absorbent article that is primarily responsible for fluid handling properties
of the
article, including acquiring, transporting, distributing and storing body
fluids. As
such, the absorbent core typically does not include the topsheet or backsheet
of
the absorbent article.
~s A member or material can be described by having a certain structure, such
as
a porosity, which is defined by the ratio of the volume of the solid matter of
the
member or material to the total volume of the member or material. For example,
for a fibrous structure made of polypropylene fibers, the porosity can be
calculated from the specific weight (density) of the structure, the caliper
and the
Zo specific weight (density) of the polypropylene fiber:
V"o;d / Vtocai = (1 - Pbulk / Prnateria~)
The term "activatable" refers to the situation, where a certain ability is
restricted by a certain means, such that upon release of this means a reaction
is such as a mechanical response happens. For example, if a spring is held
together by a clamp (and thus would be activatable), releasing of the clamp
results in activating the expansion of the spring. For such springs or other
members, materials or systems having an elastic behavior, the expansion can be
defined by the elastic modulus , as well known in the art.
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Basic erinciples and definitions
Liquid transport mechanism in conventional capillary flow systems
Without wishing to be bound by any of the following explanations, the basic
functioning mechanism of the present invention can be best explained by
s comparing it to conventional materials
In materials, for which the liquid transport is based on capillary pressure as
the driving force, the liquid is pulled into the pores that were initially dry
by the
interaction of the liquid with the surface of the pores. Filling the pores
with liquid
replaces the air in these pores. If such a material is at least partially
saturated
,o and if further a hydrostatic, capillary, or osmotic suction force is
applied to at
least one region of that material, liquid will be desorbed from this material
if the
suction pressure is larger than the capillary pressure that retains the liquid
in the
pores of the materials (refer e.g., to "Dynamics of fluids in porous media" by
J.
Bear, Haifa, pub!. Dover Publications Inc., NY, 1988).
rs Upon desorption, air will enter the pores of such conventional capillary
flow
materials. tf additional liquid is available, this liquid can be pulled into
the pores
again by capillary pressure. If therefore a conventional capillary flow
material is
connected at one end to a liquid source (e.g., a reservoir) and on the other
end
to a liquid sink (e.g., a hydrostatic suction), the liquid transport through
this
2o material is based on the absorption / desorption and re-absorption cycle of
the
individual pores with the capillary force at the liquid / air-interface
providing the
internal driving force for the liquid through the material.
This is in contrast to the transport mechanism for liquids through transport
members according to the present invention.
Siahon analoqY
A simplifying explanation for the functioning of the present invention can
start with comparing it to a siphon (refer to Fig. 1 ), well known from
drainage
systems as a tubing in form of a laying "S" (101). The principle thereof is,
that -
once the tubing (102) is filled with liquid (103) - upon receipt of further
liquid (as
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indicated by 106) - entering the siphon at one end, almost immediately liquid
leaves the siphon at the other end (as indicated by 107), as - because the
siphon is being filled with incompressible liquid - the entering liquid is
immediately
displacing liquid in the siphon forcing the liquid at the other end to exit
the
s siphon, if there is a pressure difference for the liquid between the point
of entry
and the point of exit of said siphon. In such a siphon, liquid is entering and
leaving the system through an open surface inlet and outlet "port regions"
(104
and 105 respectively).
The driving pressure to move liquid along the siphon can be obtained via a
variety of mechanisms. For example, if the inlet is at a higher position than
the
outlet, gravity will generate a hydrostatic pressure difference generating
liquid
flow through the system.
Alternatively, if the outlet port is higher than the inlet port, and the
liquid has
to be transported against gravity, the liquid will flow through this siphon
only if an
,s external pressure difference larger than hydrostatic pressure difference is
applied. For example, a pump could generate enough suction or pressure to
move liquid through this siphon. Thus, liquid flow through a siphon or pipe is
caused by an overall pressure difference between its inlet and outlet port
region.
This can be described by well known models, such as expressed in the Bernoulli
Zo equation.
The analogy of the present invention to this principle is schematically
depicted in Fig. 2 as one specific embodiment. Therein, the liquid transport
member (20'I ) does not 'need to be s-shaped, but can be a straight tube
(202).
The liquid transport member can be filled with liquid (203), if the inlet and
outlet
25 of the transport member are covered by inlet port materials (204) and
outlet port
materials (205). Upon receipt of additional liquid (indicated by 206) which
readily
penetrates through the inlet port material (204), liquid (207) will
immediately
leave the member through the outlet region (205), via the outlet port
material.
Thus, a key difference in principle is, that the inlet and/or outlet ports are
so not open surfaces, but have special permeability requirements as explained
in
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more detail hereinafter, which prevent air or gas from penetrating into the
transport member, thus the transport member remains filled with liquid.
A liquid transport member according to the present invention can be
combined with one or more liquid sources) and/or sinks) to form a liquid
s transport system. Such liquid sources or sinks can be attached to the
transport
member such as at inlet andlor outlet regions or the sink or the source can be
integral with the member. A liquid sink can be - for example - integral with
the
transport member, when the transport member can expand its volume thereby
receiving the transported liquid.
ro A further simplifying analogy to a siphon system in comparison to a Liquid
Transport System can be seen in Fig. 3 A {siphon) and 3B (present invention).
When connecting a liquid (source) reservoir (301 ) with a lower (in the
direction of
gravity) liquid (sink) reservoir (302) by a conventional tube or pipe with
open
ends (303) in the shape on an inverted "U" (or "J"), liquid can flow from the
upper
rs to the lower reservoir only if the tube is kept full with liquid by having
the upper
end immersed in liquid. If air can enter the pipe such as by removing the
upper
end (305) from the liquid, the transport will be interrupted, and the tube
must be
refilled to be functional again.
A liquid transport member according to the present invention would look
2o very similar in an analog arrangement, except for the ends of the transport
member, inlet (305) and outlet port (306), comprising inlet and outlet port
materials with special permeability requirements as explained in more detail
hereinafter instead of open areas. The inlet and outlet materials prevent air
or
gas from penetrating into the transport member, and thereby maintain the
liquid
2s transport capability even if the inlet is not immersed into the liquid
source
reservoir. If the transport member is not immersed into the liquid source
reservoir, liquid transport will obviously stop, but can commence immediately
upon re-immersion.
In broader terms, the present invention is concerned with liquid transport,
so which is based upon direct suction rather than on capillarity. Therein, the
liquid is
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transported through a region through which substantially no air (or other gas)
should enter this member (or at least not in a significant amount). The
driving
force for liquid flowing through such a member can be created by a liquid sink
and liquid source in liquid communication with the member, either externally,
or
s internally.
There is a multitude of embodiments of the present invention, some of
which will be discussed in more detail hereinafter. For example, there can be
members where the inlet and I or outlet port materials are distinctly
different from
the inner or bulk region, or there can be members with gradual change in
so properties, or there can be member executions wherein the source or sink is
integral with the transport member, or wherein the entering liquid is
different in
type or properties from the liquid leaving the member.
Yet, all embodiments rely on the inlet or outlet port region having a
different
permeability for the transported liquid as well as for surrounding gas such as
air
~s than the inner / bulk region.
Within the context of the present invention, the term "liquid" refers to
fluids
consisting of a continuous liquid phase, optionally comprising a discontinuous
phase such as an immiscible liquid phase, or solid or gases, so as to form
suspension, emulsions or the like. The liquid can be homogeneous in
2o composition, it can be a mixture of miscible liquids, it can be a solution
of solids
or gases in a liquid, and the like. Non-limiting examples for liquids that can
be
transported through members according to the present invention include water,
pure or with additives dr contaminants, salt solutions, urine, blood,
menstrual
fluids, fecal material over a wide ranged of consistencies and viscosities,
oil, food
Zs grease, lotions, creams, and the like.
The term "transported liquid" or "transport liquid" refers to the liquid which
is
actually transported by the transport member, i.e., this can be the total of a
homogeneous phase, or it can be the solvent in a phase comprising dissolved
matter, e.g., the water of a aqueous salt solution, or it can be one phase in
a
so multiphase liquid, or it can be that the total of the multicomponent or
multiphase
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liquid. Henceforth, it will become readily apparent for which liquid the
respective
liquid properties, e.g., the surface energy, viscosity, density, etc., are
relevant for
various embodiments.
Whilst often the liquid entering the liquid transport member will be the same
s or of the same type as the liquid leaving the member or being stored
therein, this
does not necessarily need to be the case. For example when the liquid
transport
member is filled with an aqueous liquid, and - upon appropriate design - an
oily
liquid is received by the member, the aqueous phase may leave the member
first. In this case, the aqueous phase could be considered "replaceable
liquid".
~o
Geometric description of Transport Member Re ions
A liquid transport member in the sense of the present invention has to
comprise at least two regions - a "bulk region" and a "wall region" comprising
at
least one liquid permeable "port region". The geometry, and especially the
~s requirement of the wall region completely circumscribing the bulk region is
defined by the following description (refer to Fig.4), which considers a
transport
member at one point in time.
The bulk / inner regions (403) and the wall region (404) are distinctively
different and non-overlapping geometric regions with regard to each other as
well
Zo as with regard to the outside region (i.e. "the rest of the universe").
that can be
defined by the following characterization (refer to Fig.4): Thus, any point
can only
belong to one of the regions.
The bulk region (403) is connected, i.e. for any two points A' and A" inside
the bulk region (403), there is at least one continuous (curved or straight)
line
Zs connecting the two points without leaving the bulk region (403).
For any point A inside the bulk region (403), all straight rodlike rays having
a circular thickness of at least 2 mm diameter intersect the wall region
(404). A
straight ray has the geometrical meaning of a cylinder of infinite length in
analogy
to point A being a light source, and the rays being rays of light, however,
these
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rays need to have a minimum geometrical "thickness" (as otherwise a line can
pass through the pore opening of the port regions (405)). This geometrical
thickness is set at 2 mm - which of course has to be considered in an
approximation in the proximity of the point A (not having a three-dimensional
s extension to be matched with such a rodlike ray).
The wall region (404) completely circumscribes the bulk region (403). Thus,
for any points A" - belonging to the bulk region (403) - and C - belonging to
the
outer region- any continuous curved rod (in analogy to a continuous curved
line
but having circular thickness of 2 mm diameter), intersects the wall region
(404).
A port region (405) connects a bulk region (403) with the outside region,
and there exists at least one continuous curved rod connecting any point A
from
the bulk regions with any point C from the outside region having a circular
thickness of 2mm, that intersects the port region (405).
The term "region" refers to three-dimensional regions, which can be of any
,s shape. Often, but not necessarily, the thickness of the region can be thin,
such
that the region appears like a flat structure, such as a thin film. For
example,
membranes can be employed in a film form, which - depending on the porosity
can have thickness of 100 p.m or much less, thus being much smaller than the
extension of the membrane perpendicular thereto (i.e. length and width
zo dimension).
A wall region may be arranged around a bulk region for example in an
overlapping arrangement, i.e. that certain parts of the wall region material
contact
each other and are connected to each other such as by sealing. Then, this
sealing should have no openings which are sufficiently large to interrupt the
is functionality of the member, i.e. the sealing line could be considered to
belong
either to an (impermeable) wall region, or a wall region.
Whilst a region can be described by having at least one property to remain
within certain limits so as to define the common functionality of the
subregions of
this region, other properties may well change within this sub-regions.
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Within the current description, the term "regions" should be read to also
encompass the term "region", i.e. if a member comprises certain "regions", the
possibility of comprising only one such region should be included in this
term,
unless othenrvise explicitly mentioned.
s The "port" and "bulk / inner" regions can be readily distinguished from one
another, such as a void space for one region and a membrane for another, or
these regions can have a gradual transition with respect to certain relevant
parameters as will be described hereinafter. Hence it is essential, that a
transport
member according to the present invention has at least one region satisfying
the
,o requirements for the "inner region" and one region satisfying the
requirements for
the wall region", (which in fact can have an very small thickness relative to
its
extension in the other two dimensions, and thus appear more as a surface than
a
volume). The wall region comprises at least a port region, which may comprise
further regions, in particular inlet and / or outlet region.
~s Thus, for a liquid transport member, the transport path can be defined as
the path of a liquid entering a port region and the liquid exiting a port
region,
whereby the liquid transport path runs through the bulk region. The transport
path can also be defined by the path of a liquid entering a port region and
then
entering a fluid storage region which is integral within the inner region of
the
Zo transport member, or alternatively defined as the path of a liquid from a
liquid
releasing source region within the inner region of the transport member to an
outlet port region.
The transport path of an liquid transport member can be of substantial
length, a length of 100 m or even more can be contemplated, alternatively, the
25 liquid transport member can also be of quite short length, such as a few
millimeters or even less. Whilst it is a particular benefit of the present
invention to
provide high transport rates and also enable large amounts of liquid to be
transported, the latter is not a requirement. It can also be contemplated,
that
only small amounts of liquid are transported over relatively short times, for
3o example when the system is used to transmit signals in the form of liquids
in
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order to trigger a certain response to the signal at an alternative point
along the
transport member.
In this case, the liquid transport member may function as a real-time
signaling device. Alternatively, the transported liquid may perform a function
at
s the outlet port, such as activating a void to release mechanical energy and
create
a three-dimensional structure. For example, the liquid transport member may
deliver a triggering signal to a responsive device comprising a compressed
material that is held in vacuum compression within a bag, at least a portion
of
which is soluble (e.g., in water). When a threshold level of the signaling
liquid
(e.g., water) delivered by the liquid transport member dissolves a portion of
the
water soluble region and discontinuously releases the vacuum, the compressed
material expands to form a three dimensional structure. The compressed
material, for example, may be a resilient plastic foam that has a shaped void
of
sufficient volume to capture bodily waste. Alternatively, the compressed
material
~s may be an absorbent material that functions as a pump by drawing fluid into
its
body as it expands (e.g., may function as a liquid sink as described below).
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The liquid transport can take place along a single transport path or along
multiple paths, which can split or re-combine across the transport member.
Generally, the transport path will define a transport direction, allowing
definition of the transport cross sectional plane which is perpendicular to
said
s path. The inner / bulk region configuration will then define the transport
cross
sectional area, combining the various transport paths.
For irregularly shaped transport members and respective regions thereof, it
might be necessary to average the transport cross-section over the length of
the
one or more transport paths) either by using incremental approximations or
,o differential approximations as well known from geometrical calculations.
It is conceivable, that there will be transport members, wherein the inner
region and port regions are readily separable and distinguishable. in other
instances, it might take more effort to distinguish and/or to separate the
different
regions.
~s Thus, when the requirements are described for certain regions, this should
be read to apply to certain materials within these regions. Thereby, a certain
region can consist of one homogeneous material, or a region can comprise such
a homogeneous material. Also, a material can have varying properties and/ or
parameters, and thus comprise more than one region. The following description
2o will focus on describing the properties and parameters for the functionally
defined
regions.
General functional description of Transport member
As briefly mentioned in the above, the present invention is concerned with a
Zs liquid transport member, which is based upon direct suction rather than on
capillarity. Therein, the liquid is transported through a region into which
substantially no air (or other gas) should enter (at all or at least not in a
significant amount). The driving force for liquid flowing through such a
member
can be created by a liquid sink and/or liquid source in liquid communication
with
3o the transport member, either externally, or internally.
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The direct suction is maintained by ensuring that substantially no air or gas
enters the liquid transport member during transport. This means, that the wall
regions including the port regions should be substantially air impermeable up
to a
certain pressure, namely the bubble point pressure as will be discussed in
more
s detail.
Thus, a liquid transport member must have a certain liquid permeability (as
described hereinafter). A higher liquid permeability provides less flow
resistance,
and thus is preferred from this point of view.
In addition, the liquid transport member should be substantially
,o impermeable for air or gas during the liquid transport.
However, for conventional porous liquid transport materials, and in
particular those materials, that function based on capillary transport
mechanisms,
liquid transport is generally controlled by the interaction of pore size and
permeability, such that open, highly permeable structures will generally be
J5 comprised of relatively large pores. These large pores provide highly
permeable
structures, however these structures have very limited wicking heights for a
given
set of respective surface energies, i.e., a given combination of type of
material
and liquids. Pore size can also affect liquid retention under normal use
conditions.
so In contrast to such conventional capillary governed mechanisms, in the
present invention, these conventional limitations have been overcome, as it
has
been surprisingly found, that materials exhibiting a relative lower
permeability can
be combined with materials exhibiting a relative higher permeability, and the
combination provides significant synergistic effects.
25 In particular, it has been found, that when a highly liquid permeable
material
having large pores is surrounded by material having essentially no air
permeability up to a certain pressure, the already referred to bubble point
pressure, but having also relatively low liquid permeability, the combined
liquid
transport member will have a high liquid permeability and a high bubble point
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pressure at the same time, thus allowing very fast liquid transport even
against
an external pressure.
Accordingly, the liquid transport member has an inner region with a liquid
permeability which is relatively high to provide maximum liquid transport
rate. The
s permeability of a port region, which can be a part of the wall region
circumscribing the bulk region, is substantially less. This is achieved by
port
regions having a membrane functionality, designed for the intended use
conditions. The membrane is permeable to liquids, but not to gases or vapors.
Such a property is generally expressed by the bubble point pressure parameter,
~o which is - in short - defined by the pressure up to which gas or air does
not
penetrate through a wetted membrane.
As will be discussed in more detail, the property requirements have to be
fulfilled at the time of liquid transport. It can be, however, that these are
created
or adjusted by activating a transport member, e.g., prior to usage, which -
without
rs or prior to such activation - would not satisfy the requirements but does
so after
activation. For example, a member can be elastically compressed or collapsed,
and expand upon wetting to then create a structure with the required
properties.
Generally, for considering how fast and how much liquid can be transported
over a certain height (i.e. against a certain hydrostatic pressure) capillary
flow
Zo transport is dominated by surface energy effects mechanisms and pore
structure,
which is determined by number of pores, as well as the shape, size, and also
pore size distribution.
If, for example, in conventional capillary flow systems or members which
are based on capillary pressure as the driving force, liquid is removed at one
end
2s of a capillary system such as by a suction means, this liquid is desorbed
out of
the capillaries closest to this suction device, which are then at least
partially filled
by air, and which are then refilled through capillary pressure by liquid from
adjacent capillaries, which are then filled by liquid from following adjacent
capillaries and so on.
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Thus, liquid transport through a conventional capillary flow structure is
based upon absorption - desorption and re-absorption cycle of the individual
pores.
The flow respectively flux is determined by the average permeability along
s the pathway and by the suction at the end of the transport path. Such a
local
suction will generally also be dependent on the local saturation of the
material,
i.e. if the suction device is able to reduce the saturation of the region
close to it,
the flow/fiux will be higher.
However, even if said suction at the end of the transport path is higher than
o the capillary pressure inside the capillary structure, the internal driving
force for
liquid is given by the capillary pressure thus limiting liquid transport
rates. In
addition, such capillary flow structures cannot transport liquid against
gravity far
heights larger than the capillary pressure, independent of the external
suction.
A specific idealized execution of such porous liquid transport members are
re so-called "capillary tubes", which can be described as parallel pipes with
the
inner tube diameter and wall thickness defining the overall openness (or
porosity)
of the system. Such systems will have a relative large flux against a certain
height if these are "mono-porous", i.e., if the pores have the same, optimal
pore
size. Then the flow is determined by the pore structure, the surface energy
zo relation, and the cross-sectional area of the porous system, and can be
estimated by well know approximations.
Realistic porous structures, such as fbrous or foam type structures, will not
transport like the ideal Structures of capillary tubes. Realistic porous
structures
have pores that are not aligned, i.e. not straight, as the capillary tubes and
the
Zs pore sizes are also non-uniform. Both of these effects often reduce the
transport
efficiency of such capillary systems.
For one aspect of the present invention, however, there are at least two
regions within the transport member with different pore sizes, namely the one
or
more port regions) having smaller pore sizes (which in conventional systems
so would result in very low flow rates) and the inner region having a
substantially
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larger pore sizes (which in conventional systems would result in very low
achievable transport heights).
For the present invention, however, the overall flow and transport height
through the transport member are synergistically improved by the high
s permeability of the inner region (which therefore can be relatively long
whilst
having small cross-sectional areas), and by the relatively high bubble paint
pressure of the port regions (which can have sufficiently large surfaces, and/
or
small thickness). In this aspect of the invention, the high bubble point
pressure of
the port regions is obtained by the capillary pressure of the small pores of
said
~o port region, which will - once wetted - prevent air or gas from entering
the
transport member.
Thus, very high fluid transport rates can be achieved through relatively
small cross-sectional areas of the transport member.
In another aspect, the present invention is concerned with liquid transport
~s members, which - once activated, and/or wetted - are selective with regards
to
the fluids they transport. The port regions of the transport member are - up
to a
certain limit as can be expressed by the bubble point pressure - closed for
the
ambient gas (like air), but relatively open for the transport liquid (like
water).
The port regions do not require a specific directionality of their properties,
zo i.e. the materials used therein can be used in either orientation of liquid
flow there
through. Nor is it a requirement for the membranes to have different
properties
(such as permeability) with regard to certain parts or components of the
liquid.
This is in contrast to the membranes such as described for osmotic absorbent
packets in US-A-5.108.383 (White et al.), where the membranes have to have a
Zs low permeability for the promoter material, such a salt, respectively salt-
ions.
Bulk region
In the following section, the requirements as well as speck executions for
the "inner region" or "bulk region" will be described.
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A key requirement for the bulk region is to have a low average flow
resistance, such as expressed by having a permeability k of at least 10 -" m2,
preferably more than 10-8 mz, more preferably more than 10'' m2, and most
preferably more than 10'5 m2. The bulk region may actually be a void which is
s circumscribed, and thusly defined by the wall regions as described
hereinafter,
but for particular applications it can be desirable that the bulk region is
made of a
open porous material, thus exhibiting a certain "dry density" (as being
defined as
the density of the material excluding the fluid contained in the pores), and a
certain maximum permeability in the inner regions, such as no more then 10'Z
mz.
ro One important means to achieve high permeabilities for the inner regions
can be achieved by utilizing material providing relatively high porosity.
Such a porosity, which is commonly defined as the ratio of the volume of
the materials that makes up the porous materials to the total volume of the
porous materials, and as determined via density measurements commonly
~s known, should be at least 50%, preferably at least 80%, more preferably at
feast
90%, or even exceeding 98%, or 99%. In the extreme of the inner region
essentially consisting of a single pore, void space, the porosity approaches
or
even reaches 100%. Materials suitable for the inner region can have a non-zero
dry density, but not exceeding 0.30 g/m2, preferably less than 0.2 glmz, or
more
Zo preferably less than 0.1 glm2, or even less than 0.05 g/m2. Another
important
means to achieve high permeabilities for the inner region is using materials
with
large pores The inner region can have pores, which are larger than about 200
Vim, 500 Vim, 1 mm or even 9 mm in diameter or more. For certain applications,
such as for irrigation or oil separation, the inner region can have pores as
large
Zs as 10 cm.
Such pores may be smaller prior to the fluid transport, such that the inner
region may have a smaller volume; and expand just prior or at the liquid
contact.
Preferably, if such pores are compressed or collapsed, they should be able to
expand by a volumetric expansion factor of at least 5, preferably more than
10.
so Such an expansion can be achieved by materials having an elastic modulus of
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more than the external pressure which, however, must be smaller than the
bubble point pressure.
High porosities can be achieved by a number of materials, well known in
the art as such. For example fibrous members can readily achieve such porosity
s values. Non-limiting examples for such fibrous materials that can be
comprised in
the bulk region are high-loft non-wovens, e.g., made from polyolefin or
polyester
fibers as used in the hygienic article field, or car industry, or for
upholstery or
HVAC industry. Other examples comprise fiber webs made from cellulosic fibers.
Such porosities can further be achieved by porous, open celled foam
structures, such as - without intending any limitation - for example
pulyurethane
reticulated foams, cellulose sponges, or open cell foams as made by the High
Internal Phase Emulsion Polymerization process (HIPE foams), all well known
from a variety of industrial applications such as filtering technology,
upholstery,
hygiene and so on.
~s Such porosities can be achieved by wall regions (such as explained in more
detail hereinafter) which circumscribe voids defining the inner region, such
as
exemplified by pipes. Alternatively, several smaller pipes can be bundled.
Such porosities can further be achieved by "space holders", such as
springs, spacer, particulate material, corrugated structures and the like.
2o The inner region pore sizes or permeabiiities can be homogeneous
throughout the inner region, or can be inhomogeneous.
It is not necessary, that the high porosity of the inner region is maintained
throughout al! stages between manufacture and use of the liquid transport
member, but the voids within the inner region can be created shortly before or
zs during its intended use.
For example, bellow like structures held together by suitable means can be
activated by a user, and during its expansion, the liquid penetrates through a
port
region into the expanding inner region, thereby filling the transport member
completely or at least sufficiently to not hinder the liquid flow.
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Alternatively, open celled foam materials, such as described in (US-A-
5.563.179 or US-A-5.387.207) have the tendency to collapse upon removal of
water, and the ability to re-expand upon re-wetting. Thus, such foams can be
transported from the manufacturing site to the user in a relatively dry, and
hence
s thin (or low-volume), and only upon contact with the source liquid increase
their
volume so as to satisfy the void permeability requirements.
The inner regions can have various forms or shapes. The inner region can
be cylindrical, ellipsoidal, sheet like, stripe like, or can have any
irregular shape.
The inner regions can have constant cross-sectional area, with constant or
,o varying cross-sectional shape, like rectangular, triangular, circular,
elliptical, or
irregular. A cross-sectional area is defined for the use herein as a cross-
section
of the inner region, prior to addition of source liquid, when measured in the
plane
perpendicular to the flow path of the transport liquid, and this definition
wilt be
used to determine the average inner region cross-sectional area by averaging
~s the individual cross-sectional areas all over the flow path(s).
The absolute size of the inner region should be selected to suitably match
the geometric requirements of the intended use. Generally, it will be
desirable to
have the minimum dimension for the intended use. A benefit of the designs
according to the present invention is to allow much smaller cross-sectional
areas
Zo than conventional materials. The dimensions of the inner region are
determined
by the permeability of said inner region, which can be very high, due to
possible
large pores, as the inner region does not have to be designed under the
contradicting requirements of high flux (i.e. large pores) and high vertical
liquid
transport (i.e. small pores). Such large pemeabilities allow much smaller
cross-
Zs sections, and hence very different designs.
Also the length of the inner region can be significantly larger than for
conventional systems, as also with regard to this parameter the novel
transport
member can bridge longer distances and also greater vertical liquid transport
heights.
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The inner region can be essentially non-deformable, i.e. maintains its
shape, form, volume under the normal conditions of the intended use. However,
in many uses, it will be desirable, that the inner region allows the complete
member to remain soft and pliable.
The inner region can change its shape, such as under deforming forces or
pressures during use, or under the influence of the fluid itself. The
deformability
or absence thereof can be achieved by selection of one or more materials in
the
inner region (such as a fibrous member), or can be essentially determined by
the
circumscribing regions, such as by the wall regions of the transport member.
One
such approach is to utilize elastomeric materials as the wall material.
The voids of the inner region can be confined by wall regions only, or the
inner region can comprise internal separations therein.
If, for example, the inner region is made up of parallel pipes, with
impermeable cylindrical walls, these would be considered to be such internal
rs separations, thereby possibly creating pores which are unitary with the
inner,
hollow opening of the pipes, and possibly other pores created by the
interstitial
spaces between the pipes. If, as a further example, the inner region comprises
a
fibrous structure, the fiber material can be considered to form such internal
separations.
zo The internal separations of the inner region can have surface energies
adapted to the transported liquid. For example, in order to ease wetting
and/or
transport of aqueous liquids, the separations or parts thereof can be
hydrophilic.
Thus, in certain embodiments relating to the transport of aqueous liquids, it
is
preferred to have the separations of the inner regions to be wettable by such
is liquids, and even more preferred to have adhesion tensions of more than 65
mN/m, more preferably more than 70mN/m. In case of the transported liquid is
oil
based, the separations or parts thereof can be oleo- or lipophilic.
The confining separations of the inner region may further comprise
materials which significantly change their properties upon wetting, or which
even
3o may dissolve upon wetting. Thus, the inner region may comprise an open cell
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foam material having a relatively small pore at least partially being made of
soluble material, such as polyvinylalcohol or the like. The small porosity can
draw
in liquid at the initial phase of liquid transport, and then rapidly dissolve
so as to
then leave large voids filled with liquid.
s Alternatively, such materials may fill larger pores, completely or
partially,
For example, the inner region can comprise soluble materials, such as
poiy(vinyl)
alcohol or polyvinyl) acetate. Such materials can fill the voids, or support a
collapsed state of the voids before the member is contacted with liquid. Upon
contact with fluid, such as water, these materials may dissolve and thereby
~o create empty or expanded voids.
In one embodiment, the voids of the inner region (which can make up
essentially the complete inner region) are essentially completely filled with
an
essentially incompressible fluid.
The term "essentially completely" refers to the situation, where sufficient
~s void volume of the inner region is filled with the liquid such that a
continuous flow
path can be established.
Preferably, most of the void volume, preferably more than 90%, more
preferably more than 95%, and even more preferably more than 99%, including
100%, is filled with the liquid. The inner region can be designed so as to
enhance
Zo accumulation of gas or other liquid in parts of the region where it is less
detrimental. The remainder of the voids can then be filled with other fluid,
such as
residual gas or vapors, or immiscible liquid like oil in an inner region
filled with
aqueous liquids, or can be solids, like particulates, fibers, films.
The liquid comprised in the inner region can be of the same type as the
z5 liquid being intended to be transported.
For example, when water based liquids are the intended transported
medium, the inner region of the transport member can be filled with water - or
if
oil is the intended transport liquid, the inner region can be filled with oil.
The liquid in the inner region can also be different - whereby these
3o differences can be relatively small in nature (such as when the intended
transport
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liquid is water, the inner region liquid can be an aqueous solution, and vice
versa). Alternatively, the intended transport liquid can be quite different in
its
properties, when compared to the liquid which has been pre-filled into the
inner
region, such as when the source liquid is oil, which is transported through a
pipe
s initially filled with water and closed by suitable inlet and outlet ports,
whereby the
water leaves the member by a suitable outlet port region, and the oil enters
the
member by a suitable inlet port region. In this specific embodiment, the total
amount of transported liquid is limited by the amount which can be received
within the member respectively the amount of liquid exchanged, unless there
~o were, for example, outlet part regions comprising materials with properties
compatible with the liquids so as to allow functionality with one or both of
the
liquids.
The liquid of the inner region and the liquid to be transported can be
mutually soluble, such as salt solutions in water. For example, if the liquid
~s transport member is intended for the transport of blood or menses, the
inner
region can be filled with water.
In another embodiment, the inner region comprises a vacuum, or a gas or
vapor below the corresponding equilibrium, ambient or external, pressure at
the
respective temperatures, and volumetric conditions. Upon contact with the
Zo transported liquid, the liquid can enter into the inner region by the
permeable port
regions (as described hereinafter), and then fill the voids of the inner
region to
the required degree. Thereafter, the now filled inner region functions like a
"pre-
filfed° region as described in the above.
The above functional requirements and structural embodiments of the inner
zs region can be satisfied by a number of suitable structures. Without being
limited
in creating structures satisfying suitable inner regions, the following
describes a
range of preferred embodiments.
A simple and yet very descriptive example for an inner region is an empty
tube defined by impermeable or semi-permeable walls, as already discussed and
so depicted in Fig. 2. The diameter of such tubes can be relatively large
compared
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to diameters commonly used for transport in capillary systems. The diameter of
course depends highly on the specific system and intended use.
For example, for hygiene applications such as diapers, pore sizes of 2 - 9
mm or more have been found to function satisfactorily.
s Also suitable is the combination of parallel tubes of a suitable diameter of
from about 0.2 rnm to several cm to a tube bundle, such as (in principle)
known
from other engineering design principles such as heat exchanger systems.
For certain applications, pieces of glass tubes can provide the right
functionality, however, for certain applications such structures may have some
o mechanical strength constraints. Suitable tubes can also be made of silicon,
rubber, PVC, etc., e.g., Masterflex 6404-17 by Norton, distributed by the
Barnant
Company, Barrington, Illinois 60010 U.S.
Yet another embodiment can be seen in the combination of mechanically
expanding elements, such as springs or which can open void space in the
,s structure if the expansion direction is oriented such that the appropriate
pore size
is also oriented along the flow path direction.
Such materials are well known in the art, and for example disclosed in US-
A-5.563.179, US-A-5.387.207, US-A-5.632.737 all relating to HIPE foam
materials, or in US-A-5.674.917 relating to absorbent foams, or in EP-A-
Zo 0.340.763, relating to highly porous fibrous structures or sheets, such as
made
from PET fibers.
Other materials can be suitable. even when they do not satisfy all the above
requirements at the sarrte time, if this deficiency can be compensated by
other
design elements.
is Other materials having relatively large pores are highloft non-woven,
filter
materials as open cell foams from Recticel in Brussel, Belgium such as
Bulpren,
Filtren (Filtren TM10 blue, Filtren TM20 blue, Filtren TM30 blue, Filtren
Firend 10
black, Filtren Firend 30 black, Filtren HC 20 grey, Filtren Firend HC 30 grex,
Bulpren S10 black, Bulpren S20 black, Bulpren S30 black).
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Another material having relatively large pores - even though the porosity is
not particularly high - is sand with particles larger than 1 mm, specifically
sand
with particles larger than 5 mm Such fibrous or other materials may , for
example
become very useful by being corrugated, however, excessive compression
s should be avoided. Excessive compression can result in a non-homogeneous
pore size distribution with small pores within the inner material, and
insufficiently
open pores between the corrugations.
A further embodiment to exemplify a material with two pore size regions can
be seen in PCT application US97I20840, relating to a woven loop structure.
ro The inner region may comprise absorbent materials, such as super
absorbent gelling materials or other materials as described for being suitable
as
a liquid sink material herein after. Further, the promoter materials of
Membrane
Osmotic packets, (MOP) such as disclosed in US-A-5.082.723 (White, Allied
Signals) can be suitable for being used in the inner region.
~s The inner region may further be constructed form several materials, i.e.
for
example from combinations of the above.
The inner region may also comprise stripes, particulates, or other in-
homogeneous structures generating large voids between themselves and acting
as space holders.
Zo As will be described in more details for the port regions, the fluids in
the
inner region must not prevent the port regions from being filled with the
transport
liquid.
Thus, the degree of vacuum, for example, or the degree of miscibility or
immiscibility must not be such that liquids from the port region are drawn
into the
Zs inner region without the port regions) being refilled with transport
liquid.
Wall re4ion
The liquid transport member according to the present invention comprises
in addition to the inner regions a wall region circumscribing this inner
region in
so the geometric definition as described hereinbefore. This wall region must
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comprise at least one port region, as described hereinafter. The wall region
can
further comprise materials, which are essentially impermeable to liquids
and/or
gases, thereby not interfering with the liquid handling functionality of the
port
regions, and also preventing ambient gases or vapors from penetrating into the
s liquid transport member.
Such walls can be of any structure or shape, and can re present the key
structural element of the liquid transport member. Such walls can be in the
shape
of a straight or bent pipe, of a flexible pipe, or of cubical shape and so on.
The
walls can be thin, flexible films, circumscribing the inner region. Such walls
can
,o be expandable, either permanently via deformation or elastically via an
elastomeric film, or upon activation.
Whilst the wall regions as such are an essential element for the present
invention, this is particularly true for the port region comprised in such
wallregions, and described in the following. The properties of the remaining
parts
rs of the wall regions can be important for the overall structure, for
resilience, and
other structural effects.
Port reg~ion(s)
The port regions can generally be described to comprise materials which
2o have different permeabilities for different fluids, namely they should be
permeable for the transport liquid, but not for the ambient gas (like air),
under
otherwise same conditions (like temperature, or pressure, ...? and once they
are
wetted with I filled with the transport liquid or similarly functioning
liquid.
Often, such materials are described as membranes with respective
Zs characteristic parameters.
!n the context of this invention, a membrane is generally defined as a
region, that is permeable for liquid, gas or a suspension of particles in a
liquid or
gas. The membrane may for example comprise a microporous region to provide
liquid permeability through the capillaries. In an alternative embodiment, the
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membrane may comprise a monolithic region comprising a block-copolymer
through which the liquid is transported via diffusion.
For a given set of conditions, membranes will often have selective transport
properties for liquids, gases or suspensions depending on the type of medium
to
s be transported. They are therefore widely used in filtration of fine
particles out of
suspensions (e.g. in liquid filtration, air filtration). Other type of
membranes show
selective transport for different type of ions or molecules and are therefore
found
in biological systems (e.g. cell membranes, molecular sieves) or in chemical
engineering applications (e.g. for reverse osmosis).
Microporous hydrophobic membranes will typically allow gas to permeate,
while water-based liquids will not be transported through the membrane if the
driving pressure is below a threshold pressure commonly referred to as
"breakthrough" or "bridging" pressure.
In contrast, hydrophilic microporous membranes will transport water based
~s liquids. Once wetted, however, gases (e.g. air) will essentially not pass
through
the membrane if the driving pressure is below a threshold pressure commonly
referred to as "bubble point pressure".
Hydrophilic monolithic films will typically allow water vapor to permeate,
while gas will not be transported rapidly through the membrane.
Zo Similarly, membranes can also be used for non-water based liquids such as
oils. For example, most hydrophobic materials will be in fact oleophilic. A
hydrophobic microporous membrane will therefore be permeable for oil but not
for water and can be used to transport oil, or also separate oil and water.
Membranes are often produced as thin sheets, and they can be used alone
is or in combination with a support layer (e.g. a nonwoven) or in a support
element
(e.g. a spiral holder). Other forms of membranes include but are not limited
to
polymeric thin layers directly coated onto another material, bags, corrugated
sheets.
Further known membranes are "activatable" or "switchable" membranes
so that can change their properties after activation or in response to a
stimulus. This
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change in properties might be permanent or reversible depending on the
specific
use. For example, a hydrophobic microporous layer may be coated with a thin
dissolvable layer e.g. made from poly(vinyl)alcohol. Such a double layer
system
will be impermeable to gas. However, once wetted and the poly(vinyl)alcohol
film
s has been dissolved, the system will be permeable for gas but still
impermeable
for aqueous liquids.
Conversely, if a hydrophilic membrane is coated by such a soluble layer, it
might become activated upon liquid contact to allow liquid to pass through,
but
not air.
In another example, a hydrophilic microporous membrane is initially dry. In
this state the membrane is permeable for air. Once wetted with water, the
membrane is no longer air permeable. Another example for a reversible
switching of a membrane in response to a stimulus is a microporous membrane
coated with a surfactant that changes its hydrophilicity depending on
,s temperature. For example the membrane will then be hydrophilic for warm
liquid
and hydrophobic for cold liquid. As a result, warm liquid will pass through
the
membrane while cold liquid will not. Other examples include but are not
limited to
microporous membranes made from an stimulus activated gel that changes its
dimensions in response to pH, temperature, electrical fields, radiation or the
like.
Properties of port regions
The port regions can be described by a number of properties and
parameters.
A key aspect of the port region is the permeability.
is The transport properties of membranes may in general be described by a
permeability function using Darcy's law which is applicable to all porous
systems:
q= 1 /A * dV/dt = kh * ~p/L
Thus, a volumetric flow dV/dt through the membrane is caused by an
external pressure difference op (driving pressure), and the permeability
function
3o k may depend on the type of medium to be transported (e.g. liquid or gas),
a
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threshold pressure, and a stimulus or activation. Further relevant parameters
impacting on the liquid transport are the cross-section A, the volume V
respectively the change over time thereof, and the length L of the transport
regions, and the viscosity rl of the transported liquid.
s For porous membranes, the macroscopic transport properties are mainly
depending on the pore size distribution, the porosity, the tortuosity and the
surface properties such as hydrophilicity.
If taken alone, the permeability of the port regions should be high so as to
allow large flux rates there through. However, as permeability is
intrinsically
connected to other properties and parameters, typical permeability values for
port
regions or port region materials will range from about 6*10-2°m2, to
7*10~'Bm2, or
3*10''° m2, up to 1.2 * 10-'°m2 or more.
A further parameter relevant for port regions and respective materials is the
bubble point pressure, which can be measured according to the method as
described hereinafter.
Suitable bubble point pressure values depend on the type of application in
mind. The table below lists ranges of suitable port region bubble point
pressure
(bpp) for some applications, as determined for respective typical fluids:
Application bpp (kPa)
broad range typical range
Diapers 4.5 to 35 4.5 to 8
Catamenials 1 to 35 1 to 5
Irrigation ' <2 to > 50 8 to 50
Grease absorption 1 to 20 1 to 5
Oil Separation < 1 to about 50
Zo In a more general approach, it has been found useful, to determine the bpp
for a
material by using a standardized test liquid, as described in the test methods
hereinafter.
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Port rection thickness and size
The port region of a liquid transport member is defined as the part of the
wall having the highest permeability. The port region is also defined by
having
the lowest relative permeability when looking along a path from the bulk
region to
s a point outside the transport member.
The port region can be constructed by readily discernible materials, and
then both thickness and size can be readily determined. The port region can,
however, have a gradual transition of its properties either to other,
impermeable
regions of the wall region, or to the bulk region. Then the determination of
the
o thickness and of the size can be made as described hereinafter. When looking
at
a segment of the wall region, such as depicted in Figure 5A, this will have a
surface, defined by the cornerpoints ABCD, which is oriented towards the inner
or bulk region, and a surface EFGH oriented towards the outside of the member.
Thus the thickness dimension is oriented along the lines AE, BF, and so on,
i.e.
~s when using Cartesian co-ordinates, along the z-direction. Analogously, the
wall
region will have the major extension along the two perpendicular directions,
i.e.
x-, and y- direction.
Then, the port region thickness can be determined as follows:
a) In case of essentially homogeneous port region properties at least in
zo the direction through the thickness of the region, it is the thickness of a
material having such a homogeneous permeability (such as with a
membrane film);
b) It is the thickness of the membrane if this is combined with a carrier (be
this carrier inside or outside of the membrane) - i.e. this refers to a non-
25 continuous / step change function of the properties along this path.
c) For a material having a (determinable) continuous gradient permeability
across any segment as in Figure 5A, the following steps can be taken
to reach a determinable thickness (refer to Figure 5B):
c0) First, a permeability profile is determined along the z-axis, and the
so curve k~~~ vs r is plotted; for certain members, the porosity or pore size
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curve can also be taken for this determination with appropriate changes
of the subsequent procedure.
c1 ) Then the point of lowest permeability (km;~ is determined, and the
corresponding length reading (r~m;~~) is taken.
s c2) As the third step, the "upper port region permeability" is determined as
being 10 times the value of km;~
c3) As the curve has a minimum at k~,~ there will be two corresponding r ,~~er
and r o~,e~, defining the inner and outer limit of the port region
respectively.
ro c4) The distance between the two limits defines the thickness, and the
average k ~, a"erage will be determined across this.
If this approach fails due to indeterminable gradient permeability, porosity
or pore size, the thickness of the port region will be set to 1 micrometer.
As indicated in the above, it will often be desirable to minimize the
thickness
rs of the port region, respectively the membrane materials comprised therein.
Typical thickness values are in the range of less than 100~m, often less than
50
Vim, 1 O~m, or even less than 5~cm.
Quite analogously, the x-y extension of the port region can be determined.
In certain liquid transport member designs it will be readily apparent, which
part
zo of the wall region are port regions. In other designs, with gradually
changing
properties across the wall region, the local permeability curves along the x-
and y
direction of the wall region can be determined, and plotted analogously to
Figure
5B as shown in Figure '5C. In this instance, however, the maximum permeability
in the wall region defines the port regions, hence the maximum will be
25 determined, and the region having permeabilities of not less than a tenth
of the
maximum permeability surrounding this maximum is defined as the port region.
Yet another parameter useful for describing aspects of the port regions
useful for the present invention is the permeability to thickness ratio, which
in the
context of the present invention is also referred to as "membrane
conductivity".
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This reflects the fact, that - for a given driving force - the amount of
liquid
penetrating through a material such as a membrane is on one side proportional
to the permeability of the material, i.e. the higher the permeability, the
more liquid
will penetrate, and on the other side inversely proportional the thickness of
the
s material.
Henceforth, a material having a lower permeability compared to the same
material having a decrease in thickness, shows that thickness can compensate
for this permeability deficiency (when regarding high rates a being
desirable).
Thus, this parameter can be very useful for designing the port region
ro materials to be used.
Suitable conductivity k/d depends on the type of application in mind. The
table below lists ranges of typical kld for some exemplary applications:
Application k/d (10-9 m)
broad range typicat range
Diapers 10~ to 1000 150 to 300
Feminine protection ......... 100 to 500
Irrigation ......... 1 to 300
Grease absorption ......... 100 to 500
Oil Separation 1 to 500
Of course, the port regions have to be wettable by the transport fluid, and
~s the hydrophilicity or lipophilicity should be designed appropriately, such
as by
using hydrophilic membranes in case of transporting aqueous liquids, or
hydrophobic membranes in case of lipophilic or oily liquids.
The surface properties in the port region can be permanent, or they can
change with time, or usage conditions.
Zo It is preferred, that the receding contact angle for the liquid to be
transported is less than 70°, more preferably less than 50°,
even more preferred
less than 20° or even less than 10°. Further, often it is
preferred, that the material
has no negative impact on the surface tension of the transported liquid.
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For example, a lipohilic membrane may be made from lipophilic polymers
such as polyethylene or polypropylene and such membranes will remain
liphophilic during use.
Another example is a hydrophilic material allowing aqueous liquids to be
transported. If a polymer like polyethylene or polypropylene is to be used,
this
has to be hydrophilized, such as by surfactants added to the surface of the
material or added to the bulk polymer, such as adding a hydrophilic polymer
prior
to forming the port material. In both instances, the imparted hydrophilicity
may be
permanent or not, e.g. it could be washed away with the transport liquid
passing
,o therethrough. However, as it is an important aspect of the present
invention, that
the port regions remain in a wetted state so as to prevent gas passing
through,
the lack of hydrophilizer will not be significant once the port regions are
wetted.
Maintainin4 liguid filling of membrane
~s For a porous membrane to be functional once wetted (permeable for liquid,
not-permeable for air) at least a continuous layer of pores of the membrane
always need to be filled with liquid and not with gas or air. Thus, it can be
desirable for particular applications to minimize the evaporation of the
liquid from
the membrane pores, either by a decrease of the 'vapor pressure in the liquid
or
Zo by an increase the vapor pressure in the air. Possible ways to do this
include -
without any limitation:
Sealing of the membrane with a impermeable wrap to avoid evaporation
between production and usage. Use of strong desiccants (e.g. CaCl2) in the
pores, or use of a liquid with low vapor pressure in the pores that mixes with
the
25 transported fluid, such as glycerin.
Alternatively, the port region may be sealed with soluble polymers, such as
poly vinyl alcohol, or poly vinyl acetate, which are dissolved upon contact
with
liquids and which thereby activate the functionality of the transport member.
Apart from the liquid handling requirements, the port regions should satisfy
so certain mechanical requirements.
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First, the port regions should not have any negative effect on the intended
use conditions. For example when such members are intended in hygienic
absorbent articles, the comfort and safety must not be negatively impacted.
Thus it will often be desirable, that the port regions are soft, and flexible,
but
s this may not always be the case. However, the port region should be
sufficiently
strong to withstand practical use stress, such as tear stress or puncturing
stress
or the like.
In certain designs, it might be desirable for the port region materials to be
extensible or collapsible, or bendable.
~o Even a single hole in the membrane (e.g. caused by puncturing during use),
a failure in membrane sealing (e.g. owing to production), or the membrane
tearing (e.g. due to in-use pressure being exerted) can under various
conditions
lead to a failure of the liquid transport mechanism. Whilst this can be used
as a
destructive test method to determine if a materials or member functions
~s according the present invention, and as described hereinafter, this is not
desirable during its intended use. If air or another gas penetrates into the
inner
region, this may block the liquid flow path within the region, or it may also
interrupt the liquid connection between the bulk and port regions.
A possibility to make an individual member more robust, is to provide in
Zo certain parts of the inner region remote from the main liquid flow path, a
pocket
where air that enters the system is allowed to accumulate without rendering
the
system non functional.
A further way to 'address this issue is to have several liquid transport
member in a (functionally or geometrically) parallel arrangement instead of a
Zs single liquid transport member. If one of the members fails, the others
will
maintain the functionality of the "liquid transport member battery".
The above functional requirements of the port regions can be satisfied by a
wide range of materials or structures described by the following structural
properties or parameters.
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The pore structure of the region, respectively of the materials therein, is an
important parameter impacting on properties like permeability and bubble point
pressure.
Two key aspects of the pore structure are the pore size, and pore size
s distribution. A suitable method to characterize these parameters at least on
the
surface of the region is by optical analysis. Another suitable method for the
characterization of these properties and parameters is the use of a Capillary
Flow
Porosimeter, such as described hereinafter.
As has been discussed above in the context of permeability, permeability is
To influenced by the pore size and the thickness of the regions, respectively
the part
of the thickness which is predominantly determining the permeability.
Henceforth, it has been found, that for example for aqueous systems typical
average pore size values for the port region are in the range of 0.5 ~m to 500
Vim. Thus the pores have preferably an average size of less than 100 Vim,
~s preferably less than 50 p.m, more preferably less than 10 p,m or even less
than 5
Vim. Typically, these pores are not smaller than 1 um.
It is an important feature for example of the bubble point pressure, that this
will depend on the largest pores in the region, which are in a connected
arrangement therein. For example, having one larger pore embedded in small
20 ones does not necessarily harm the performance, whilst a "cluster" of
larger
pores together might very well do so.
Henceforth, it will be desirable to have narrow pores size distribution
ranges.
Another aspect relate to the pore walls, such as pore wall thickness, which
is should be a balance of openness and strength requirements. Also the pores
should be well connected to each other along the flow direction, to allow
liquid
passing through readily.
As some of the preferred port region materials can be thin membrane
materials, these in themselves may have relatively poor mechanical properties.
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Henceforth, such membranes can be combined with a support structure, such as
a coarser mesh, threads or filaments, a non-woven, apertured films, or the
like.
Such a support structure could be combined with the membrane such that it
is positioned towards the inner / bulk region or towards the outside of the
s member.
Size / surface area of port regions
The size of the port regions is essential for the overall performance of the
transport member, and needs to be determined in combination with the
o "permeability to thickness" (k/d)ra~~o of the port region.
The size has to be adapted to the intended use, so as to satisfy the liquid
handling requirements. Generally, it will be desirable to have the liquid
handling
capability of the innerlbulk region and the port regions to be compatible,
such
that neither is a grossly limiting factor for liquid transport compared to the
other.
~s As the flux of the port regions will generally be lower than the flux
through the
inner region, it may be preferred to design the port regions larger in size
(surface) than the cross-section of the inner region.
Thereby, the exact design and shape of the port regions can vary over a
wide range.
2o For example, if the transport members function is intended to provide a
trigger or signal from one port region to another, the port regions can be
relatively small, such as about the size of the cross-section of the inner
region,
such that a substantially smaller transport member results.
Or, when liquids are to be quickly captured and transported, distributed or
Zs stored, the member can be shaped for example in the shape of a , dog bone
with
relatively large port regions at either end of the transport member or
alternatively,
the port regions can be spoon shaped so as to increase the receiving area.
Alternatively, the port regions can be non-flat, such as for example
corrugated, or folded, or having other forms so as to create relative large
surface
so area to volume ratios, such as well known in the filter technology.
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Whilst the inlet port and the outlet port can be designed to satisfy the same
basic requirements, and thus can be one and the same material, this does not
need to be the case. The inlet and outlet port regions can be different with
regard
to one or more material or performance parameters. The different port regions
can be readily discernible, such as by being represented by different
materials
and/or by being separated by other materials, or the port regions can differ
by a
property or parameter gradient, which can be continuous or stepwise.
One essentially continuous material can have a gradient of properties
along either the surface of the material, in the thickness dimension, or both,
so as
to to be able to represent several parts of the wall or inlet or outlet port
regions.
The port region properties may be constant over time, or they may change
with time, such as being different before and during use.
For example, the port regions can have properties unsuitable for functioning
in members according to the present invention until the point of use. The port
,s regions may be activated, for example by manual activation, intervention by
the
person using the member, or by an automatic activation means, such as by
wetting of the transport member. Other alternative mechanisms for activation
of
the port regions can include temperature changes, for example to the body
temperature of a wearer, or pH, for example of the transport liquid, or an
2o electrical or mechanical stimulus.
As has been discussed in the context of osmotic packet materials in the
above, membranes useful for the present invention have no specific requirement
of a certain salt impermeability.
Whilst the port regions and suitable materials have been described with
Zs regard to their properties or descriptive parameters, the following will
describe
some of the materials that satisfy these various requirements, thereby
focusing
on the transport of aqueous liquids.
Suitable materials can be open celled foams, such as High Internal Phase
Emulsion foams, can be Cellulose Nitrate Membranes. Cellulose Acetate
so Membranes, Polyvinyldifluorid films, non-wovens, woven materials such as
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meshes made from metal, or polymers as Polyamide, or Polyester. Other suitable
materials can be apertured Films, such as vacuum formed, hydroapertured,
mechanically or Laser apertured, or films treated by electron, ion or heavy-
ion
beams.
s Specific materials are Cellulose acetate membranes, such as also disclosed
in US 5,108,383 (White, Allied-Signal Inc.), Nitrocellulose membranes such as
available from e.g. from Advanced Microdevices (PVT) LTD, Ambala Cantt.
INDIA called CNJ-10 (Lot # F 030328) and CNJ-20 {Lot # F 024248), Cellulose
acetat membranes, Cellulose nitrate membranes, PTFE membranes, Polyamide
so membranes, Polyester membranes as available e.g. from Sartorius in
Gottingen,
Germany and Millipore in Bedford USA, can be very suitable. Also microporous
films, such as PEIPP film filled with CaC03 particles, or filler containing
PET films
as disclosed in EP-A-0.451.797.
Other embodiments for such port region materials can be ion beam
rs apertured polymer films, such as made from PE such as described in "Ion
Tracks
and Microtechnofogy - Basic Principles and Applications" edited by R. Spohr
and
K.Bethge, published by Vieweg, Wiesbaden, Germany 1990.
Other suitable materials are woven polymeric meshes, such as polyamide
or polyethylene meshes as available from Ve~seidag in Geldern-Waldbeck,
zo Germany, or SEFAR in Riischlikon, Switzerland. Other materials which can be
suitable for present applications are hydrophilized wovens, such as known
under
the designation DRYLOFT ~ from Goretex in Newark, DE 19711, USA.
Further, certain non-woven materials are suitable, such as available under
the designation CoroGard ~ from BBA Corovin, Peine, Germany, can be used,
zs namely if such webs are specially designed towards a relatively narrow pore
size
distribution, such as by comprising suitable "melt-blown" webs.
For applications with little requirements for flexibility of the members, or
where even a certain stifFness is desirable, metal filter meshes of the
appropriate
pore size can be suitable, such as HIGHFLOW of Haver & Bocker, in Oelde,
so Germany.
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Additional Elements
Whilst the definition of bulk, wall, and outer region has been made in the
above in relation to the function of each of these regions, there may
optionally
s elements be added to the materials forming these regions, which can extend
into
a neighbouring region without extending the liquid handling functionality, but
rather improve other properties, such as the mechanical strength, or tactile
or
visual aspects of the materials forming the regions or of the complete
structure.
For example, a support structure may be added to the outside of the wall or
port
,o region, which may be so open that it does not impact on the fluid handling
properties, and as such would be considered functionally to belong to the
outer
region. When such an open support element extends from the wall region into
the inner or bulk region, it will functionally belong to the bulk region. If
there is a
gradual transition between these materials and/or elements, the definitions
made
~s for the respective functional regions will enable a clear distinction of
the region
forming materials, and the additional elements.
In addition to the innerlbulk and wall regions, the liquid transport member
according to the present invention can optionally contain other elements, such
as
liquid impermeable walls or separations, in addition to the wall region with'
one or
zo more port regions.
Further, there can be additional elements outside of the wall regions, such
as materials to provide enhanced physical strength, or improved tactile feel
or
the tike. Whilst such external elements might be arranged such that liquid
flows
there-through, they do not contribute to the essential functionality of the
liquid
zs transport member. Thus, such elements should not be a flow limiting factor,
and
may not function as a port region. Such elements can be integral with the wall
region.
Further, there can be elements attached to or integral with the liquid
transport member to aid its implementation into an absorbent system, or an
so article comprising an liquid transport member.
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Transport member functionality
During absorption, both liquid transport members according to the present
invention as well as certain conventional materials do not draw air into their
s respective structures, for conventional materials, fibrous materials or
conventional foams, the liquid pulled into the structure displaces air within
the
structure. However, conventional porous materials, such as fibrous structures,
typically do draw air into themselves during desorption, air enters as liquid
is
drawn out of the structure. The liquid transport member according to the
present
so invention does not draw air into the structure under normal usage
conditions.
The property that determines the point at which air will enter the system is
referred to herein as bubble point pressure. Air will not enter the transport
member until the bubble point pressure (bpp) is reached, due to the membrane
functionality of the port regions) material.
~s Thus, once liquid has entered the member, it will not be replaced by air -
up
to the bpp of the member.
Permeability
A further property of the liquid transport member is the permeability k
Zo (liquid transport member) as the average permeability along the flow path
of the
transported liquid.
The liquid transport member accordyng to the present invention has a
permeability which is .higher than the permeability of a capillary system with
equal liquid transport capability. This property is referred to as the a
"critical
Zs permeability" k(crit). The critical permeability of the liquid transport
member of
the present invention is preferably at least twice as high as a capillary
system
with equal vertical liquid transport capability more preferably at least four
times
as high, and most preferably at least ten times greater than a capillary
system
with equal vertical liquid transport capability.
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For capillary tubes, the permeability k {crit} can be determined via the
adhesion tension as derived from Darcy's law as follows:
k {crit} _ (g{liquid transport member}I2)* (a*cos(O))**2 I (bpp {liquid
transport
member}**2)
s wherein
k {crit} is the critical permeability in units of [m~]
~ {liquid transport member} is the average porosity of the liquid transport
member [-];
a {liqu} is the surface energy of the liquid in [cP]
a*cos(O) defines the adhesion tension in [cPJ with the receding contact
angle O.
bpp {liquid transport member} is the bubble point pressure of the liquid
transport member, expressed in [kPa], as discussed in the above.
The maximum value which can be reached for such a system can be
~s approximated by assuming the maximum value for the term cos(O), namely 1:
k {crit, max} _ (~ {liquid transport member} 12 )* a {liquid}**2 I (bpp
{liquid
transport member}) **2
Another way to express the k {crit} is via the ability of the member to
transport liquid vertically at least against a hydrostatic pressure
corresponding to
Zo a certain height h and gravity constant g:
k {crit, max} _ (s {liquid transport member}I2) * a{liqu}**2 /
(p{liqu}*g*h)**2.
The permeability. of a material or transport member can be determined by
various methods, such as by using the Liquid Transport test or the
Permeability
Test, both as described hereinafter, and then compared to the critical
25 permeability as calculated from the above equations.
Whilst the bpp property has already been discussed in the context of the
port regions, also the complete transport member can be described thereby.
Accordingly, suitable bpp for the member depends on the intended use, and
suitable as well as typical values and ranges are essentially the same for the
so member as for the port region as described above.
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A liquid transport member according to the present invention can also be
described by being substantially air impermeable up to a certain bpp, whereby
the liquid transport member of the present invention has an overall
permeability
which is higher than the permeability for a given material having a
homogeneous
s pore size distribution and an equivalent bpp.
Yet another way to describe the functionality of a liquid transport member is
by using the average fluid permeability kp of the bulk/inner region, and the
bubble
point pressure of the member.
The liquid transport member according to the present invention should have
a relatively high bpp {liquid transport member} and a high k {liquid transport
member} at the same time. This can be graphically represented when plotting
k{liquid transport member} over bbp in a double logarithmic diagram (as in
Fig. 6
wherein the bbp is expressed in "cm height of water column°, which then
can be
readily converted into a pressure).
~s Therein, for a given surface energy combination of the liquid and the
member materials generally a top left to down right correlation can be
observed.
Members according to the present invention are have properties in the upper
right region (1) above the separation line (L), whilst properties of
conventional
materials are much more in the left lower corner in the region (II), and have
the
20 limitations of the pure capillary transport mechanism, as schematically
indicated
by the straight line in the log-log diagram.
Yet another way to describe the functionality of the liquid transport member
is to consider the effect of liquid transport as a function of the driving
force.
In contrast, for liquid transport members according to the present invention,
zs the flow resistance is independent from the driving force as long as the
pressure
differential is less than the bpp of the transparent member. Thus the flux is
proportional to the driving pressure (up to the bpp).
A liquid transport member according to the present invention can further be
described by having high flux rates, as calculated on the cross-sectional area
of
so the inner region. Thus, the member should have an average flux rate at
0.9kPa
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additional suction pressure differential to the height Ho when tested in the
Liquid
Transport Test at a height Ho, as described herein after, of at least 0.1
g/s/cm2,
preferably of at least 1 g/cm2lsec, more preferably at least 5 glcm2lsec, even
more
preferably at least 10 g/cmZlsec, or even at least 20 g/cm2lsec, and most
s preferably at least 50 glcm2/sec.
In addition to the above requirements, the liquid transport member should
have a certain mechanical resistance against external pressure or forces.
For certain embodiments, the mechanical resistance to external pressures
or forces can be relatively high to prevent squeezing liquid out of , the
transport
,o member, which for example, can be achieved by using stiff I non-deformable
material in the inner region.
For certain other embodiments, this resistance can be in a medium range,
thus allowing exploitation of external pressure or forces on the transport
member
for creating a "pumping effect°.
15 In order to further explain suitable structures for a liquid transport
member,
the above mentioned simple example of a hollow tube having an inlet and
outlet,
said inlet and outlet being covered, i.e. closed, by membranes is considered.
This type of structure can alternatively inciude a further support structure
such
as an open mesh attached to the port region membrane towards the inner
Zo region.
Therein, the permeability requirement can be satisfied by the membrane
itself, i.e. not considering the effect of the support structure, if the
support
stnrcture is sufficiently open to have no negative impact on the overall
permeability or on the liquid handling properties thereof. Then, the thickness
of
is the port region refers to the thickness of the membrane only - i.e. not
including
the thickness of the support structure. It will become apparent in the
specific
context, if for example such a support structure should be seen as an element
of
the port region having no significant impact on the port region properties, or
- for
example if the support structure has a significant thickness and thus impacts
on
so the permeability for the liquid after the port region is penetrated -
whether the
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support structure should be considered as a part of the inner region. If, for
example, the support structure becomes more extended in thickness, still
remaining connected with the membrane, it yet can be considered as
functionally
belonging to the inner region, such as when the permeability of the composite
"support - inner void° is sign~cantly impacted by the permeability of
the support
structure.
Accordingly, this principle should be considered for each of the respective
aspects, such as when looking at the port region(s), the bulk regions or the
complete transport member.
,o The following describes how various elements can be combined to create
structures suitable as a liquid transport member. It should be noted, that
because
of the multiple design options one or the other structure might not be
discernible
by all of the above described properties, but it will be readily apparent to
the
skilled person to design even further options following the general teachings
in
~5 combination with the more specific embodiments.
Relative permeability
If the permeability of both the inner/bulk region and the port regions can be
determined independently, it is preferred that one or both of the port regions
2o have a lower liquid permeability than the inner region.
Thus, a liquid transport member should have a ratio of the permeability of
the bulk region to the port region of preferably at least 10:1, more
preferably at
least 100:1, even more'preferably at least 1000:1, even ratios of 100,000:1
are
suitable.
Relative arrang~~ement of regions
Depending on the specific embodiments, there can be various combinations
of the inner region, and the wall with the port region.
At least a portion of the port regions) have to be in liquid communication
so with the inner region, so as to allow fluid to be transferred thereto.
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The inner/bulk region should comprise larger pores than the wall region.
The pore size ratio of inner pores to port region pores are preferably at
least 3:1,
more preferably at least 10:1, even more preferably at least 100:1 and most
preferable at least 350:1.
s The area of the port regions will typically be as large larger than the
cross-
section of the inner regions, thereby considering the respective regions
together,
namely - if present - the inlet regions or respectively the outlet regions. In
most
instance, the port regions will be twice as large as said inner region cross-
section, often four times as large, or even 10 times as large.
Structural relation of regions
The various regions can have , similar structural properties or different,
possibly complementing structural properties, such as strength, flexibility,
and the
like.
rs For example, all regions can comprise flexible material designed to
cooperatively deform, whereby the inner region comprises a thin-until-wet
material which expands upon contact with the transported liquid, the port
regions) comprise flexible membranes, and the walls can be made of liquid
impermeable flexible film.
Zo The liquid transport member can be made of various materials, whereby
each region may comprise one or more materials.
For example, the inner region may comprise porous materials, the walls
may comprise a film material, and the ports may comprise a membrane material.
Alternatively, the transport member may consist essentially of one material
Zs with different properties in various regions, such as a foam with very
large pores
to provide the functionality of the inner region, and smaller pores
surrounding
these with membrane functionality as port materials.
One way to look at a liquid transport member is to see the inner region
being enclosed by at least one wall and/or port region. A very simple example
for
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this is the above mentioned tube filled with liquid and closed by membranes at
both ends, as indicated in Figure 7.
Such members can be considered to be a "Closed Distribution Member", as
the inner region (703) is "enclosed" by the wall region (702) comprising port
s regions (706, 707). It is characteristic for such systems, that - once the
transport
member is activated, or equilibrated - a puncturing of the outer wall region
can
interrupt the transport mechanism. The transport mechanism can be maintained
if only a small amount of air enters the system. This small quantity of air
can be
accumulated in an area of the inner region wherein it is not detrimental to
the
c liquid transport mechanism.
For the example of the hollow tube with at least one open port, puncturing
the walls will result in immediate interruption of the liquid transport and
fluid loss.
This mechanism can be exploited to define the "Closed System Test", as
described in the below, which is a "sufficient but not necessary" condition
for
~s liquid transport member according to the present invention (i.e. all
transport
members which satisfy this test can be considered to function within the
principles of the present invention, but not all transport members which fail
this
test are outside the principle).
In a further embodiment as depicted in Figure 8, the liquid transport
zo member may comprise several inlet and/or several outlet port regions, for
example as can be achieved by connecting a number of tubes (802) together
and closing several end openings with inlet ports 806 and an outlet port 807,
thereby circumscribing the inner region 803, or a "split" system where fluid
is
transported simultaneously to more than one location (more than one exit
port).
zs Alternatively, the transport to different locations may be selective (e.g.,
the voids
in a transport material on the route to one port may be filled with a water
soluble
material, and the voids in the transport material on the route to a second
port
may be filled with an oil soluble material. Also, the transport medium may be
hydro- and/or oleophilic to further enhance the selectivity.)
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In yet a further embodiment as indicated in Figure 9, the inner region (903)
can be segmented into more than one region, such as can be visualized by
looking a bundle of parallel pipes, held in position by any suitable fixation
means
(909), circumscribed by a wall region (902), comprising port region (907), and
the
s inner separation means (908). It also can be contemplated, that at least
some of
the membrane material is placed inside the innerlbulk regions, and the
membrane material can even form the walls of the pipes.
In an even further embodiment (Fig. 10), the outer wall region consists
essentially of permeable port region (1006), i.e., the inner region (1003) is
not
~o circumscribed by any impermeable region at all. The port region may have
the
same permeability, or can have a different degree of permeability. Thus the
inner
region may be wrapped by a membrane material. Also, the port region and the
inner region can be connected by a gradual transition region, such that the
transport member appears to be a unitary material with varying properties.
~s In further embodiments (Fig. 11A-D), the liquid transport member can have
one or more port regions {1106), these being either inlet or outlet port
regions,
i.e., the member is designed to receive and/or release liquid. To achieve
this,
parts of the wall region (1102) can be deformable, such that the total member
can increase the volume of the inner region (1103), so as to accommodate the
2o additionally received volume of liquid, or so as to accommodate the
initially
contained liquid, which then can be released through the port region(s). In
these
members, a liquid sink or source can be integrally combined with the liquid
transport member. The liquid transport member can have a liquid sink or source
integrally incorporated therein, such as depicted by elements (1111) in Fig.
11.
is For example structures made according to the teachings of US-A-5.108.383
{White) disclosure can be considered as a liquid transport member according to
the present invention if - and only if - these are modified according to the
requirements for the bulk region and port regions as defined herein above.
Because of the specific functioning mechanism, these structures otherwise miss
ao the broad applicability of the present invention, which is - due to the
additional
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requirements for the inner and port regions - not restricted to osmotic
driving
forces (i.e. the presence of promoters), nor do the membranes of the present
invention have to satisfy the salt rejection properties required by the MOP
structures according to US-A-5.108.383.
s A further embodiment can comprise highly absorbent materials such as
superabsorbent materials or other highly absorbent materials as described in
more detail in U.S. Patent Application Serial No. 09/042429, filed March 13,
1998, in the name of T. DesMarais et al., combined with a port region made of
a
suitable membrane, and flexibly expandable walls to allow for an increase in
the
o volume of the storage member. A further embodiment of such an system with a
liquid sink integral with the liquid transport member, is a "Thin-until-wet"
material
in combination with a suitable membrane. Such materials are well known such as
from US-A-5.108.383, which are open celled porous hydrophilic foam materials,
such as produced by High Internal Phase Emulsion process. The pore size,
,s polymer strength, Glass Transition Temperature Tg) and the hydrophilic
properties are designed such that the pores collapse when they are dewatered
and at least partially dried, and expand upon wetting. A specific embodiment
is a
foam layer, which can expand its caliper upon absorption of liquid, and (re-)
collapse upon further removal of liquid.
Zo In even a further embodiment, the inner region can be void of liquid at the
beginning of the liquid transport process (i.e. contains a gas at a pressure
less
than the ambient pressure surrounding the liquid transport member). In such
cases, the liquid supplied by a liquid source can penetrate through the inlet
port
regions) to first fill the voids of the membrane and then the inner region.
The
zs wetting then initiates the transport mechanisms according to the present
invention thereby wetting, and penetrating the outlet port region. In such an
instance, the inner regions may not be completely filled with the transport
fluid,
but a certain amount of residual gas or vapor may be retained. If the gas or
vapor
is soluble in the transported liquid, it is possible that after some liquid
passes
3o through the member, that substantially all of the initially present gas or
vapor is
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removed, and the inner regions become substantially free of voids. Of course,
in
cases with some residual gas or vapor being present in the inner region, this
may
reduce the effective available cross-section of the fluid member, unless
specific
measures are taken, such as indicated in Fig.12, with wall region (1202)
s comprising port regions (1206 and 1207) circumscribing the inner region
(1203)
and with region (1210) to allow gas to accumulate.
Yet another embodiment can use different types of fluid - for example, the
member can be filled with an aqueous based liquid, and the transport mechanism
is such, that a non-aqueous, possibly immiscible liquid (like oil) enters the
liquid
~o transport member via the inlet port while the aqueous liquid leaves the
member
via the outlet port.
In yet even further embodiments of the present invention, one or more of
the above described embodiments can be combined.
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Liauid Transport System
The following describes suitable arrangement of such a liquid transport
member to create a suitable Liquid Transport System (LTS) according to the
present invention.
s A Liquid Transport System within the scope of the present invention
comprises the combination of at least one liquid transport member with at
least
one further liquid sink or source in liquid communication with the member. A.
System can further comprise multiple sinks or sources, and also can comprise
multiple liquid transport members, such as in a parallel arrangement. The
latter
~o can create a redundancy, so as to ensure functionality of the system even
if a
transport member fails.
The source can be any form of free liquid or loosely bound liquid so as to
be readily available to be received by the transport member.
For example a pool of liquid, or a freely flowing volume of liquid, or an open
,s porous structure filled with liquid.
The sink can be any form of a liquid receiving region. In certain
embodiments, it is preferred to have the liquid more tightly bound than the
Liquid
in the liquid source. The sink can also be an element or region containing
free
liquid, such that the liquid would be able to flow freely or gravity driven
away from
zo the member. Alternatively, the sink can contain absorbent, or
superabsorbent
material, absorbent foams, expandable foams, alternatively it can be made of a
spring activated bellows system, or it can contain osmotically functioning
material, or combinations thereof.
Liquid communication in this context refers to the ability of liquids to
transfer
is or to be transferred from the sink or source to the member, such as can be
readily achieved by contacting the elements, or bringing the elements so
closely
together, that the liquid can bridge the remaining gap.
Such a liquid transport system comprises a liquid transport member
according to the above description plus at least one liquid sink or source.
The
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term at least applies to systems, where the liquid transport member itself can
store or release liquids, such that a liquid transport system comprises
a sink and a liquid releasing liquid transport member; or
a source and a liquid receiving liquid transport member; or
s a sink and a source and a liquid transport member.
In each of these options, the liquid transport member can have liquid
releasing or receiving properties in addition to a sink or source outside of
the
member.
At feast a portion of the port regions) must be in liquid communication with
,o the source liquid and where applicable the sink material. One approach is
to
have the port region material form the outer surface of the liquid transport
member, in part or as the whole outer surface, so as to allow liquids such as
liquids of the liquid source or sink to readily contact the port regions. The
effective port region size can be determined by the size of the liquid
~s communication with the sink or source respectively. For example, the total
of the
port regions can be in contact with the sink or source, or only a part
thereof.
Alternatively, e.g., when there is one homogeneous port region, this can be
distinguished into separate effective inlet port regions and effective outlet
port
regions where the port region is in contact with the liquid source and/or
sink,
Zo respectively.
It will be apparent, that a sink must be able to receive liquid from the
member (and where applicable from the respective port regions), and a source
must be able to release liquid to the member (and where applicable to the
respective port regions).
Zs Henceforth, a liquid source for a liquid transport member according to the
present invention can be a free flowing liquid, such as urine released by a
wearer, or a open water reservoir.
A liquid source region 1303 can also be an intermediate reservoir, such as
a liquid acquisition member in absorbent articles.
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Analogously, a liquid sink can be a free flow channel, or an expanding
reservoir, e.g., a bellowed element combined with mechanical expansion or
spacer means, such as springs.
A liquid sink region can also be an ultimate liquid storage element of
s absorbent members, such as being useful in absorbent articles and the like.
Two or more liquid transport systems according to the present invention can
also be arranged in a "cascading design" (Fig. 13), with wall regions (1302),
port
regions (1306, 1307) and liquid sink materials (1311). Therein, the overall
fluid
flow path will go through one liquid transport system after the next. Thereby,
the
o inlet port region of a subsequent liquid transport system can take over the
sink
functionality of a previous system, such as when the inlet and outlet port
regions
are in fluid communication with each other. Such a fluid communication can be
direct contact, or can be via an intermediate material.
A specific embodiment of such a "cascade" can be seen in connecting two
,s or more "membrane osmotic packets" comprising membranes of appropriate
properties,. whereby the osmotic suction power increases with subsequent
packets. Each of the packets can then be considered a liquid transport member,
and the connection between the packets will defne the inlet and outlet port
regions of each packet or member. Thereby, the packets can be enclosed by one
2o material (such as one type of flexible membrane), or even several packets
can
have a unitary membrane element.
In a preferred embodiment, a liquid transport system has an absorption
capacity of at least 5g/g, preferably at least 10 g/g, more preferably at
least
50g1g and most preferably at least 75 g/g on the basis of the weight of the
liquid
is transport system, when measured in the Demand Absorbency Test, as described
hereinafter.
In yet another preferred embodiment, the liquid transport system contains a
sink comprising an absorbent material having a capillary and/or osmotic
absorption capacity of at least 10 g/g, preferably at least 20 glg and more
ao preferably at least 50 g/g, on the basis of the weight of the absorbent
material,
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when measured in the Teabag Centrifuge Capacity Test, as described
hereinafter.
In yet a further preferred embodiment, the liquid transport system comprises
an absorbent material providing an absorbent capacity of at least 5 g/g,
s preferably at least 10 g/g, more preferably at least 50 glg, or most
preferably of at
least 75 glg up to a capillary suction corresponding to the bubble point
pressure
of the member, especially of at least 4 kPa, preferably at least 10 kPa, when
submitted to the Capillary Sorption test, such as described in the test
section of
the copending PCT application US98113497, filed June 29, 1998. Such materials
~o further exhibit preferably a low absorbent capacity in the Capillary
Sorption Test
above the bubble point pressure, such as 4kPa or even 10 kPa, of less than 5
glg, preferably less than 2 glg, more preferably less than 1 glg, and most
preferably less than 0.2 glg. In certain specific embodiments, the liquid
transport
member can contain superabsorbent materials or foam made according to the
~s High Internal Phase Emulsion polymerization, such as described in PCT
application US98/05044. Typically, the suction of the liquid sink material
will not
exceed the bubble point pressure of the port region.
Applications
Zo There is a wide field for applying liquid transport members or systems
according to the present invention. The following should not be seen to be
limiting in any way, but rather to exemplify areas, where such members or
systems are useful.
Suitable applications can be found for a bandage, or other health care
is absorbent systems. In another aspect, the article can be a water transport
system or member, optionally combining transport functionality with filtration
functionality, e.g. by purifying water which is transported. Also, the member
can
be useful in cleaning operation, so as by removing liquids or as by releasing
fluids in a controlled manner. A liquid transport member according to the
present
so invention can also be a oil or grease absorber.
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One specific application can be seen in self-regulating irrigation systems for
plants. Thereby, the inlet port can be immersed into a reservoir, and the
transport
member can be in the form of a long tube. In contrast to known irrigation
systems
(such as known under BLUMAT as available from Jade @ National Guild, PO
s Box 5370, Mt Crested Butte, CO 81225), the system according to the present
invention will not loose its functionality upon drying of the reservoir, but
remain
functional until and after the reservoir is refilled.
A further application can be seen in air conditioning systems, with a similar
advantage as described for the irrigation systems. Also, because of the small
,o pore sizes of the port regions, this system would be easier to clean than
conventional wetting aids, such as porous clay structures, or blotter paper
type
elements.
Yet a further application is the replacement of miniature pumps, such as
can be envisaged in biological systems, or even in the medical field.
~s An even further application can be seen in selective transport of liquids,
such as when aiming at transporting oil away from an oillwater mixture. For
example, upon oil spillages on water, a liquid transport member can be used to
transfer the oil into a further reservoir. Alternatively, oil can be
transported into a
liquid transport member comprising therein a sink functionality for oil.
Zo An even further application uses the liquid transport member according to
the present invention as a transmitter for a signal. In such an application,
the
total amount of transported liquid does not need to be very large, but rather
the
transport times should be short. This can be achieved, by having a liquid
filled
transport member, which upon receipt of even a little amount of liquid at the
inlet
Zs port practically immediately releases liquid at the outlet port. This
liquid can then
be used to stimulate further reaction, such as a signal or activated a
response,
e.g., dissolving a seal to release stored mechanical energy to create a three
dimensional change in shape or structure.
An even further application exploits the very short response times of liquid
so transport and practically immediate response time.
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A particularly useful application for such liquid transport members can be
seen in the field of absorbent articles, such as disposable hygiene articles,
such
as baby diapers or the like for disposable absorbent article.
s Absorbent Articles - 4eneral description
An absorbent article generally comprises:
- an absorbent core or core structure (which may comprise the improved
fluid transport members according to the present invention, and which
may consist of additional sub-structures);
~o - a fluid pervious topsheet;
- a substantially fluid impervious backsheet;
- optionally further features like closure elements or elastification.
Figure 14 is a plan view of an exemplary embodiment of an absorbent
~s article of the invention which is a diaper.
The diaper 1420 is shown in Figure 14 in its flat-out, uncontracted state
(i.e.
with elastic induced contraction pulled out except in the side panels wherein
the
elastic is left in its relaxed condition) with portions of the structure being
cut-away
to more clearly show the construction of the diaper 1420 and with the portion
of
zo the diaper 1420 which faces away from the wearer, the outer surface 1452,
facing the viewer. As shown in Figure 14, the diaper 1420 comprises a
containment assembly 1422 preferably comprising a liquid pervious topsheet
1424, a liquid impervious backsheet 1426 joined with the topsheet 1424, and an
absorbent core 1428 positioned between the topsheet 1424 and the backsheet
is 1426; elasticized side panels 1430; elasticized leg cuffs 1432; an elastic
waist
feature 1434; and a closure system comprising a dual tension fastening system
generally multiply designated as 1436. The dual tension fastening system 1436
preferably comprises a primary fastening system 1438 and a waist closure
system 1440. The primary fastening system 1438 preferably comprises a pair of
3o securement members 1442 and a landing member 1444. The waist closure
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system 1440 is shown in Figure 14 to preferably comprise a pair of first
attachment components 1446 and a second attachment component 1448. The
diaper 1420 also preferably comprises a positioning patch 1450 located
subjacent each first attachment component 1446.
s The diaper 1420 is shown in Figure 14 to have an outer surface 1452
(facing the viewer in Figure 14), an inner surface 1454 opposed to the outer
surface 1452, a first waist region 1456, a second waist region 1458 opposed to
the first waist region 1456, and a periphery 1460 which is defined by the
outer
edges of the diaper 1420 in which the longitudinal edges are designated 1462
ro and the end edges are designated 1464. The inner surface 1454 of the diaper
1420 comprises that portion of the diaper 1420 which is positioned adjacent to
the wearer's body during use (i.e. the inner surface 1454 generally is formed
by
at least a portion of the topsheet 1424 and other components joined to the
topsheet 1424). The outer surface 1452 comprises that portion of the diaper
~s 1420 which is positioned away from the wearer's body (i.e. the outer
surface
1452 generally is formed by at least a portion of the backsheet 1426 and other
components joined to the backsheet 1426). The first waist region 1456 and the
second waist region 1458 extend, respectively, from the end edges 1464 of the
periphery 1460 to the lateral centerline 1466 of the diaper 1420. The waist
Zo regions each comprise a central region 1468 and a pair of side panels which
typically comprise the outer lateral portions of the waist regions. The side
panels
positioned in the first waist region 1456 are designated 1470 while the side
panels in the second wiaist region 1458 are designated 1472. While it is not
necessary that the pairs of side panels or each side panel be identical, they
are
is preferably mirror images one of the other. The side panels 1472 positioned
in the
second waist region 1458 can be elastically extensible in the lateral
direction (i.e.
elasticized side panels 1430). (The lateral direction (x direction or width)
is
defined as the direction parallel to the lateral centreline 1466 of the diaper
1420;
the longitudinal direction (y direction or length) being defined as the
direction
3o parallel to the longitudinal centreline 1467; and the axial direction (Z
direction or
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thickness) being defined as the direction extending through the thickness of
the
diaper 1420).
Figure 14 shows a specific of the diaper 1420 in which the topsheet 1424
and the backsheet 1426 have length and width dimensions generally larger than
s those of the absorbent core 1428. The topsheet 1424 and the backsheet 1426
extend beyond the edges of the absorbent core 1428 to thereby form the
periphery 1460 of the diaper 1420. The periphery 1460 defines the outer
perimeter or, in other words, the edges of the diaper 1420. The periphery 1460
comprises the longitudinal edges 1462 and the end edges 1464.
o While each elasticized leg cuff 1432 may be configured so as to be similar
to any of the leg bands, side flaps, barrier cuffs, or elastic cuffs described
above,
it is preferred that each elasticized leg cuff 1432 comprise at least an inner
barrier cuff 1484 comprising a barrier flap 1485 and a spacing elastic member
1486 such as described in the above-referenced US Patent 4,909,803. In a
rs preferred embodiment, the elasticized leg cuff 1432 additionally comprises
an
elastic gasketing cuff 14104 with one or more elastic strands 14105,
positioned
outboard of the barrier cuff 1484 such as described in the above-references US
Patent 4,695,278.
The diaper 1420 may further comprise an elastic waist feature 1434 that
2o provides improved fit and containment. The elastic waist feature 1434 at
least
extends longitudinally outwardly from at least one of the waist edges 1483 of
the
absorbent core 1428 in at least the central region 1468 and generally forms at
least a portion of the end edge 1464 of the diaper 1420. Thus, the elastic
waist
feature 1434 comprises that portion of the diaper at least extending from the
is waist edge 1483 of the absorbent core 1428 to the end edge 1464 of the
diaper
1420 and is intended to be placed adjacent the wearer's waist. Disposable
diapers are generally constructed so as to have two elastic waist features,
one
positioned in the first waist region and one positioned in the second waist
region.
The elasticized waist band 1435 of the elastic waist feature 1434 may
so comprise a portion of the topsheet 1424, a portion of the backsheet 1426
that
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has preferably been mechanically stretched and a bi-laminate material
comprising an elastomeric member 1476 positioned between the topsheet 1424
and backsheet 1426 and resilient member 1477 positioned between backsheet
1426 and elastomeric member 1476.
s This as well as other components of the diaper are given in more detail in
WO 93116669 which is incorporated herein by reference.
Absorbent core
The absorbent core should be generally compressible, conformable, non-
irritating to the wearer's skin, and capable of absorbing and retaining
liquids such
as urine and other certain body exudates. As shown in Figure 14, the absorbent
core has a garment surface, a body surface, side edges, and waist edges. The
absorbent core may - in addition to the liquid transport member according to
the
present invention - comprise a wide variety of liquid-absorbent or liquid
handling
,s materials commonly used in disposable diapers and other absorbent articles
such as - but not limited to - comminuted wood pulp which is generally
referred to
as airfelt; meltblown polymers including co-form; chemically stiffened,
modified or
cross-linked cellulosic fibers; tissue including tissue wraps and tissue
laminates.
General examples for absorbent structures are described in U.S. Patent
Zo 4,610,678 entitled "High-Density Absorbent Structures" issued to Weisman et
al.
on September 9, 1986; U.S. Patent 4,673,402 entitled "Absorbent Articles With
Dual-Layered Cores" issued to Weisman et al. on June 16, 1987; U.S. Patent
4,888,231 entitled "Absorbent Core Having A Dusting Layer" issued to Angstadt
on December 19, 1989; EP-A-0 640 330 of Bewick-Sonntag et al.; US 5 180 622
Zs (Berg et al.); US 5 102 597 (Roe et al.); US 5 387 207 (Dyer et al.). Such
and
similar structures might be adapted to be compatible with the requirements
outlined below for being used as the absorbent core 28.
The absorbent core can be a unitary core structure, or it can be a
combination of several absorbent structures, which in turn can consist of one
or
so more sub-structures. Each of the structures or sub-structures can have an
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essentially two-dimensional extension (i.e. be a layer) or a three-dimensional
shape.
The liquid transport member according to the present invention can
comprise at least one inlet port region, which should be located in the
loading
s zone of the article. This port region can be made from flexible membrane
material satisfying the requirements as described herein, which can be
connected to a high resiliency, open fibrous structure forming the inner
region,
which can be wrapped in flexible impermeable films to form the wall regions
which can be adhesively closed at all edges except for the port region. In
order to
,o allow good overall sealing, the impermeable film can overlap the port
region
somewhat so as to allow also adhesive bonding there between.
Figure 15 shows a specific embodiment of an article as shown in Figure 14,
- with analogous numerals - and Figure 16A shows a partly exploded simplified
cross-sectional view along A - A of Figure 15, again with analogous numbering.
~s Therein, an absorbent core (1528!1628) is made of suitable liquid handling
member which is constructed from a wall region (1502,1602), port regions
(1506,
1507, 1606), and inner region (1503, 1603). The member may be connected to a
liquid sink (1511, 1611), and optionally a topsheet (1524, 1624) is attached.
The
sink (1511, 1611 ) can comprise ultimate storage material, such as
2o superabsorbent material, or highly absorbing porous material.
The inner regions can be filled with liquid, such as water, so as to be ready
for liquid transport there through immediately after receipt of the liquid at
the inlet
port. Alternatively, the inner region can be under a vacuum, which can suck in
liquid through the inlet port such as upon activation of a barrier film like a
is polyvinyl alcohol film which can dissolve upon wetting. Once the inner
region is
filled with liquid, and thus also the outlet port region becomes wetted by the
liquid, the transport mechanism as for a pre-filled system takes place.
The embodiment as shown in Figure 16B differs from the one of Figure 16A
in that the inner regions comprise ultimate liquid storage material, such as
so superabsorbent material, or highly absorbing porous material therein. Also
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promotor materials for enhancing osmotic liquid storage mechanisms - such as
disclosed in the hereinbefore mentioned US-publication US-A-5.108.383 (White,
Allied Signal) - can be within the inner region. In this instance, it may be
preferable to have the inner region not prefilled - or at least not to a major
degree
s - with transport liquid, but rather to keep the inner region under vacuum
until the
transport liquid is to be received.
The absorbent core can be designed so as to not require any further fluid
handling element.
For example, the area of the inlet port region can be adjusted to its
,o permeability and caliper so as to enable the port region to immediately
acquire
the liquid at the gush rate, and the inner region can be adjusted by its
permeability and cross-sectional area so as to immediately transmit the liquid
to
the ultimate storage region .
Alternatively, the absorbent core may comprise other fluid handling
~s elements, such as acquisition regions, or interim storage regions, or the
like.
Also, the "cascading liquid transport member" or "MOP" can be suitable
elements
within the core construction.
Method of making liquid transport members
The liquid transport members according to the present invention can be
Zo produced by various methods, which have to have in common the essential
steps
of combining a bulk or inner region with a wall region comprising port regions
with appropriate selection of the respective properties as described in the
above.
This can be achieved by starting from a homogeneous material, and imparting
therein different properties. For example, if a member is a polymeric foam
2s material, this can be produced form one monomer with varying pore sizes,
which
will then be polymerized to form a suitable member.
This can also be achieved by starting from various essentially
homogeneous materials and combining these into the a member. In this
execution, a wall material can be provided, which may have homogeneous or
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varying properties, and a bulk material can be provided, which can be open
porous material, or a void space can be defined to represent the bulk region.
The
two materials can the be combined by suitable techniques, such as by wrapping
or enveloping as well known in the art, such that the wall material completely
s circumscribes the bulk region or bulk region material.
In order to enable liquid transport, the bulk region can be filled with
liquid, or
can be subjected to vacuum, or can be equipped with other aids so as to
created
vacuum, or liquid filling.
Optionally, the method of forming a member according to the present
o invention can comprise the step of applying activation means, which can be
of
the mechanical type such as by providing a removable release element, such as
being well known for example as a release paper for covering adhesives, or by
providing a packaging design, which allows the sealing of the member until
use,
whereby at the time of use such a packaging sealing is opened or removed. This
,s activation means can also comprise materials which react upon the transport
liquid, such as dissolve. Such materials may be applied in the port regions,
e.g.
to open the port regions upon use, or such materials may be applied to the
bulk
regions, such as to allow expansion of these regions upon wetting.
The making of members according to the present invention can be done in
2o an essentially continuous way, such as by having various materials provided
in
roll form, which are then unwound and processed, or any of the materials can
be
provided in discrete form, such as foam pieces, or particulates.
Examples
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The following section provides specific suitable examples for liquid transport
members and systems according to the present invention, thereby starting by
describing various samples suitable for being used in certain regions of these
members or systems.
S-1 Samples suitable for port regions:.
S-1.1: - Woven filter mesh HIFLO ~, type 20 such as available from Haver
8~ Boecker, Oelde, Germany, made from stainless steel, having, designed for
filtering down to 19 ~m to 20um, at a porosity of 61 %, and a caliper of 0.09
mm.
S-1.2a: - Polyamide mesh Monodur Type MON PA 20 N such as available
from Verseidag in Geldern-Waldbeck, Germany.
S-1.2b: Polyamide mesh Monodur Type MON PA 42.5 N such as available
from Verseidag in Geldern-Waldbeck, Germany.
S-1.3a: Polyester mesh such as 07-20/13 of SEFAR in Ruschlikon,
~s Switzerland.
S-1.3b: Polyamide mesh 03-15/10 of SEFAR in Ruschlikon, Switzerland.
S-1.3c: Polyamide mesh 03-20/14 of SEFAR in Ruschlikon, Switzerland.
S-1.3d: Polyamide mesh 03-1/1 of SEFAR in Ri.ischlikon, Switzerland.
S-1.3e: Polyamide mesh 03-5/1 of SEFAR in Ruschlikon, Switzerland.
Zo S-1.3f: Polyamide mesh 03-1012 of SEFAR in RUschlikon, Switzerland.
S-1.3g: Polyamide mesh 03-11/6 of SEFAR in Ruschlikon, Switzerland.
S-1.4: Cellulose acetate membranes such as described in US 5,108,383
(White, Allied-Signal Inc.j.
S-1.5: HIPE foam produced according to the teachings of U.S. Patent
is Application Serial No.091042429, filed March 13, 1998 by T. DesMarais et
al.
titled "High Suction polymeric foam", the disclosure of which is incorporated
herein by reference.
S-1.6: Nylon Stockings e.g. of 1.5 den type, commercially available in
Germany, such as from Hudson.
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S-2 Samples suitable for wall regions not representin~port regions
S-2.1: Flexible adhesive coated film, such as commercially available under
the trade name "d-c-fix" from Alkor, Grafelfing, Germany.
S-2.2: Plastic funnel Catalog # 625 617 20 from Fisher Scientific in
s Nidderau, Germany.
S-2.3: Flexible tubing (inner diameter about 8 mm) such as Masterflex
6404-17 by Norton, distributed by the Barnant Company, Barrington, Illinois
60010 U.S.A..
S-2.4: Conventional polyethylene film such as used as backsheet material
ro in disposable diapers, such as available from Clopay Corp., Cincinnati, OH,
US,
under the code DH-227.
S-2.5: Conventional polyethylene film such as used as backsheet material
in disposable diapers, such as available from Nuova Pansac SpA in Milano,
Italy
under the code BS code 441118.
,s S-2.6: Flexible PVC tube e.g. Catalog # 620 853 84 from Fisher Scientific
in
Nidderau, Germany.
S-2.7: PTFE Tube e.g. Catalog # 620 456 68 from Fisher Scientific in
Nidderau, Germany.
2o S-3 Samples suitable inner region
S-3.1: Void as created by any stiff wall/port region.
S-3.2: Metallic springs having a outer diameter of 4 mm and a length of
about 6 cm with any applied force, as available from Fedemfabrik Dietz in
Neustadt, Germany under the designation "federn° article # DD/100.
Zs S-3.3: Open cell foams from Recticel in Brussels, Belgium such as Filtren
TM10 blue, Filtren TM20 blue, Filtren TM30 blue, Filtren Firend 10 black,
Filtren
Firend 30 black, Filtren HC 20 grey, Filtren Firend HC 30 grex, Bulpren S10
black, Bulpren S20 black, Bulpren S30 black).
S-3.4: HIPE foams as produced according to the teachings of U.S. Patent
ao Application Serial No.09/042418, filed March 13 1998 by T. DesMarais et al.
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titled "Absorbent Materials For Distributing Aqueous Liquids", the disclosure
of
each of which is incorporated by reference.
S-3.5: Particulate pieces of S-3.4 or S-3.3.
s S-4 Samples for pressure gradient creation means
S-4.1: Osmotic pressure gradient materials according to the teachings of
US -A-5,108,383 (White, Allied Signal).
S-4.2: Height difference between inlet and outlet generating a hydrostatic
height generated pressure difference.
fo S-4.3: Various partially saturated porous materials (Absorbent foams,
superabsorbent materials, particles, sand, soils) generating a capillary
pressure
difference
S-4.4: Difference in air pressure at the inlet and the outlet as e.g.
generated
by a vacuum pump (airtight sealed) to the outlet.
Example A for Transport member
Combination of wall region with port region, inner region filled with liquid:
A-1 ) A ca 20 cm long tube (S-2.6) is connected in an air tight way with a
plastic funnel (S-2.2). Sealing can be made with Parafilm M (available from
2o Fischer Scientific in Nidderau, Germany catalog number 617 800 02). A
circular
piece of port material (S-1.1 ), slightly larger than the open area of the
funnel is
sealed in an air tight way with the funnel. Sealing is made with suitable
adhesive,
e.g., Pattex T"" of HenketKGA, Germany.
Optionally a port region material (S-1.1 ) may be connected to the lower end
is of the tube and be sealed in a air tight way. The device is filled with a
liquid such
as water by putting it under the liquid and removing the air inside the device
with
a vacuum pump tightly connected to the port region. In order to demonstrate
the
functionality of a member, the lower end does not need to be sealed with a
port
region, but then the lower end needs to be in contact with the liquid or needs
to
so be the lowest part of the device in order to not allow air to enter the
system.
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A-2) Two circular (e.g. of a diameter of about 1.2 cm) port region materials
as in S-1.1 are sealed in an air tight way (e.g. by heating the areas intended
to
become the port regions and pressing the ends of S-2.3 onto these areas, such
that the plastic material of S-2.3 starts melting, thereby creating a good
s connection) at the two ends of a ca 1 m long tube as the one of S-2.3. One
end
of the tube is dropped into the liquid such as water, the other end is
connected to
a vacuum pump creating an air pressure substantially smaller than atmospheric
pressure. The vacuum pump draws air from the tube until effectively all air is
removed from the tube and replaced by the liquid. Then the pump is
disconnected from the port and thus the member is created.
A-3) A ca 10 cm X 10 cm rectangular sheet of foam material (S-3.3, Filtren
TM 10 blue) "sandwiched" on one side by a wall material as S-2.5 of dimensions
ca 12 cm X 12 cm, on the other side by a port region material of dimensions ca
12 cm X 12 cm as S-1.3a. The wall material S-2.5 and the port region material
S-
s 1.3a are sealed together in the overlap region in a convenient air tight
way, e.g.,
by gluing with the above mentioned commercially available Pattex T"" adhesive
of
Henkel KGA, Germany. The device is immersed under a liquid such as water,
and by squeezing the device, air is forced out. Releasing squeezing pressure
from the device whilst keeping it under liquid, the inner region is filled
with liquid.
Zo Optionally (if necessary) a vacuum pump can suck the remaining air inside
the
device through the port region while the device is under the liquid.
A-4) Figures 17, 17A schematically show a distribution member, suitable
for example for absorbent articles, such as a disposable diapers.
The inlet port region (1706) is made of port region material such as S-1.3b,
2s the outlet port region (1705) is made of port region material such as S-
1.3c. In
combination with an impermeable film material (1702) such as S-2.3 or S-2.4,
each of the port regions forms a pouch, which can have dimensions of about
10cm by 15 cm for the inlet port region respectively 20 cm by 15 cm for the
outlet port region. The port materials of the pouches overlap in the crotch
region
so (1790) of the article, and a tube (1760) is positioned therein.
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The inner regions within the pouches (1740, 1750) can be S-3.3 (Filtren
TM10 blue), and the inlet and outlet regions respectively inner regions
enclosed
by them, can be connected by tubes (1760) such as S-2.6 of an inner diameter
of
about 8 mm.
Wall and port material (1702, 1707, 1706) must be sufficiently larger than
the inner material to allow airtight sealing of wall material to port
material. Sealing
is done by overlapping of a ca 1.5 crn wide stripe of wall and port material
and
can be done in any convenient air tight way e.g. by using the above mentioned
Pattex T~' adhesive. Sealing of the tubes to the inner regions (1740 and 1750)
is
not required, if the tube (1760) is attached to the wall regions (1702, 1706,
1705)
such that the distance between the tubing (1760) and the inner regions is such
that a void space will be maintained therebetween during use. The rest of the
operation to create a functioning liquid distribution member is also analogous
to
A-3. Optionally the device can be filled with other liquids in a similar
fashion.
~s A5) In Figures, 18A, 18B a further example for a liquid distribution member
(1810), also useful for construction of disposable absorbent articles, such as
diapers, is schematically depicted, omitting other elements such as adhesives
and the like.
Therein, inlet (1806) and outlet port (1807) regions having a dimension of
2o about 8 cm by 12 cm are made from sheets of port material S-1.2a , the
other
wall regions (1802) are made of wall material S-2.1. Inner material (1840) are
stripes of material S-3.3 (Bulpren S10 black) having dimension of about 0.5 cm
by 0.5 cm by 10 cm, placed at a distance of about 1 cm to each other, under
the
inlet and outlet regions (1806, 1807 respectively) and spacer springs S-3.2
is (1812) in the remaining areas. Individual layers (wall and port material)
are
sealed and further filled with a liquid such as water as described in A-3.
Optionally the device can be filled with other liquids in a similar fashion.
A6) Spacer materials such as springs according to S-3.2 are positioned
between an upper and a lower sheet of port material S-1.2ba, having a
3o dimension of 10 cm by 50 cm, such that the springs are equally distributed
over
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the area in a region of about 7 cm times 47 cm leaving the outer rim (1813) of
about 1.5 cm free of springs, with a distance of about 2 mm between the
individual springs. Upper and lower port material are sealed in an air tight
way by
overlapping ca 1.5 cm and sealing in a convenient air tight way such as by
gluing
s with the above mentioned Pattex 7"" adhesive. The device is immersed under
the
testing liquid, by squeezing the device air is forced to leave the interior of
the
device. Releasing the squeezing pressure while being immersed, the member
will be filled with liquid. Optionally (if necessary) a vacuum pump can suck
the
remaining air from inside the member through the port region while the device
is
ro under the liquid.
Example B for Transport system (i.e. member and (source and/or sink
B-1 ) As a first example for a liquid transport system, a liquid transport
member according to A-1 ) is combined with particulate superabsorbent
material,
rs such a available under the designation W80232 from HULS-Stockhausen GmbH,
Marl, Germany, with coarse particles being removed by sieving through a 300
~m metal sieve. 7.5 g of this material have been evenly sprinkled over the
outlet
port region of A-1, thereby creating a liquid sink.
B-2) To exemplify the use of absorbent foam materials to create an
zo absorbent system, a sheet of three layers of HIPE foam produced as for S-
1.54
each having a thickness of about 2 mm, and a corresponding basis weight of
about 120 g/m2 are positioned on the outlet port of a liquid transport member
according to A-1. The sheets were cut circular with a diameter of about 6 cm,
and
a segment of about 10° was cut out to provide better conformity to the
port region
2s surface. Optionally a weight corresponding to a pressure of about 0.2 psi
can be
applied to enhance liquid contact between outlet and sink material.
B-3) The liquid transport member according to A-1 has been combined with
a circular cut out section of ca 6 cm diameter taken from a commercially
available
diaper core, consisting of a essentially homogeneous blend of superabsorbent
so material such as ASAP2300 commercially available from CHEMDAL Corp. UK,
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and conventional airfelt at a 60 % by weight superabsorber concentration and a
basis weight of the superabsorbent of about 400 g/m2 ). This cut out is placed
in
liquid communication with the outlet port region of A-1 to create a liquid
transport
system.
s B-4) To further exemplify an application of a liquid transport system, the
liquid transport member of A-2 has been positioned between a liquid source
reservoir and a flower pot, such that a portion of the inlet port region is
immersed
in the liquid reservoir, and the outlet port being put into the soil of the
flower pot.
The relative height of the reservoir and the flower pot is of no relevance for
this
,o length of the member, and would not be up to a length of the member of
about
50 cm.
B-5) A further application of a liquid transport system with an integral
liquid
sink which can be constructed by creating a liquid transport member as in A-3,
but filling it with oil (instead of water). When squeezing the member {so as
to
~s create expanding voids within the member), and immediately thereafter
contacting it with cooking oil {so as to simulate a kitchen frying pan), the
system
will rapidly absorb the oil in the pan.
B-6) When combining a liquid transport member according to A-4 or A-5
with a liquid sink such as used in B-1 or B-2 , optionally covering the sink
so material by a containment Payer, such as a non-woven web, the structure can
function as a absorbent pad, whereby the urine as released by the wearer can
be
seen to provide the liquid source.
METHODS
25 Activation
As the properties which are relevant for the liquid handling ability of a
liquid
transport member according to the present invention are considered at the time
of liquid transport, and as some of the materials or designs might have
properties
which differ from these, for example to ease transport or other handling
between
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manufacturing of the member and its intended use, such members should also
be activated before they are submitted to a test.
The term "activation" means, that the member is put into the in use
condition, such as by establishing a liquid communication along a flow path,
or
s such as by initiating a driving pressure differential, and this can be
achieved by
mechanical activation simulating the pre-use activation of a user (such as the
removal of a constraining means such as a clamp, or a strip of a release paper
such as with an adhesive, or removal of a package seal, thereby allowing
mechanical expansion optionally with creation of a vacuum within the member).
,o Activation can further be achieved by another stimulus transmitted to the
member, such as pH or temperature change, by radiation or the like. Activation
can also be achieved by interaction with liquids, such as having certain
solubility
properties, or changing concentrations, or are carrying activation ingredients
like
enzymes. This can also be achieved by the transport liquid itself, and in
these
~s instances, the member should be immersed in testing liquid which should be
representative for the transport liquid, optionally removing the air by means
of a
vacuum pump, and allowing equilibration for 30 minutes. Then, the member is
removed from the liquid, a put on a coarse mesh (such as a 14 mesh sieve) to
allow dripping off of excess liquid.
Closed System Test
Princple
The test provides a simple to execute tool to assess if a transport material
or member satisfies the principles of the present invention. It should be
noted,
2s that this test is not useful to exclude materials or members, i.e. if a
material or
members does not pass the Closed System Test, it may or may not be a liquid
transport member according to the present invention.
Execution
First, the test specimen is activated as described herein above, and the
so weight is monitored. Then, the test specimen is suspended or supported in a
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position such that the longest extension of the sample is essentially aligned
with
the gravity vector.. For example, the sample can be supported by a support
board or mesh arranged at an angle of close to 90° to the horizontal,
or the
sample can be suspended by straps or bands in a vertical position.
s As a next step, the wall region is opened in the uppermost and in the
lowermost parts of the sample, i.e., if the sample has opposite corners, then
at
these corners, if the sample has a curved or rounded periphery, then at the
top
and bottom of the sample. The size of the opening has to be such as to allow
liquid passing through the lower opening and air passing through the upper
~o opening which is sufficient to allow liquid flowing out without adding
pressure or
squeezing. Typically, an opening having an inscribed circular diameter of at
least
2 mm is adequate.
The opening should be done at a location of the material or member which
is not positioned at the upper end of the member, as then no liquid could
leave
~s the member or material in analogy to a glass or cup which is open.
The opening can be done by any suitable means, such as by using a pair of
scissors, a clipping tongue, needle, a sharp knife or a scalpel and the like.
If a slit
is applied to the sample, it should be done such that the flankes of the slit
can
move away from each other, so as to create a two-dimensional opening.
zo Alternatively, a cut can remove a part of the wall material thus creating
an
opening.
Care should be taken that no additional weight is added, or pressure or
squeezing is exerted ort the sample. Similarly, care should be take, that no
liquid
is removed by the opening means, unless this could be accurately considered
Zs when calculating the weight differences.
The weight thereof is being monitored (such as by catching the liquid in a
Petri dish, which is put on a scale. Alternatively, the weight of the material
or
member can be determined after 10 minutes and compared to the initial weight.
Care should be taken, that no excessive evaporation takes place, if this
so would be the case, this can be determined by monitoring the weight loss of
a
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sample without having it opened over the test time, and by then correcting the
results accordingly.
if the dripping weight is more than or equal to 3% of the initial weight, then
the tested material or member has passed this test, and is a liquid transport
s member according to the present invention.
If the dripping weight is less than 3% of the initial total weight, then this
test
does not allow assessment whether the material is a liquid transport member
according to the present invention or not.
~o Bubble Point Pressure (port region)
The following procedure applies when it is desired to asses the bubble point
pressure of a port region or of a material useful for port regions.
First, the port region respectively the port region material is connected with
a funnel and a tube as described in example A-1. Thereby, the lower end of the
,s tube is left open i.e. not covered by a port region material. The tube
should be of
sufficient length, i.e. up to 10m length may be required.
In case the test material is very thin, or fragile, it can be appropriate to
support it by a very open support structure (as e.g. a layer of open pore non-
woven material) before connecting it with the funnel and the tube.
Zo In case the test specimen is not of sufficient size, the funnel may be
replaced by a smaller one (e.g. Catalog # 625 616 02 from Fisher Scientific in
Nidderau, Germany).
If the test specimen is too large size, a representative piece can be cut out
so as to fit the funnel.
is The testing liquid can be the transported (quid, but for ease of
comparison,
the testing liquid should be a solution of 0.03% TRITON X 100, such as
available
from MERCK KGaA, Darmstadt, Germany, under the catalog number 1.08603, in
destilled or deionized water, thus resulting in a surface tension of 33 mNlm,
when
measured according to the surface tension method as described further.
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The device is filled with testing liquid (e.g. distilled water, or oil
depending
on the intended use) by immersing it in a reservoir of sufficient size filled
with the
testing fluid and by removing the remaining air with a vacuum pump.
Whilst keeping the lower (open) end of the funnel within the liquid in the
s reservoir, the part of the funnel with the port region is taken out of the
liquid. If
appropriate - but not necessarily - the funnel with the port region material
should
remain horizontally aligned.
Whilst slowly continuing to raise the port material above the reservoir, the
height is monitored, and it is carefully observed through the funnel or
through the
~o port material itself (optionally aided by appropriate lighting) if air
bubbles start to
enter through the material into the inner of the funnel. At this point, the
height
above the reservoir is registered to be the bubble point height.
From this height H the bubble point pressure bpp is calculated as:
BPP = p ~ g ~ H with the liquid density p, gravity constant g ( g ~ 9.81
m/s2).
~s In particular for bubble point pressures exceeding about 50 kPa, an
alternative- determination can be used, such as commonly used for assessing
bubble point pressures for membranes used in filtration systems.
Therein, the wetted membrane is separating two gas filled chambers, when
one is set under an increased gas pressure (such as an air pressure), and the
2o point is registered when the first air bubbles "break through".
Alternatively, the
PMI permeameter or porosity meter, as described in the test method section
hereinafter, can be used for the bpp determination.
Bubble aoint pressure lfiduid transport member)
is For measuring the bubble point pressure of a liquid transport member
(instead of a port region or a port region material), the following procedure
can be
followed.
First, the member is activated as described above. The testing liquid can be
the transported liquid, but for ease of comparison, the testing liquid should
be a
so solution of 0.03. % TRITON X-100, such as available from MERCK KGaA,
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Darmstadt, Germany, in destilled or deioniZed water, resulting in a surface
tension of 33 mN/m, when measured according to the surface tension method as
desribed further.
A part of a port region under evaluation is connected to a vacuum pump
s connected by a tightly sealed tubelpipe (such as with Pattex T"" adhesive as
described above).
Care must be taken, that only a part of the port region is connected, and a
further part of the region next to the one covered with the tube is still
uncovered
and in contact with ambient air.
~o The vacuum pump should allow to set various pressures p~a~, increasing
from atmospheric pressure Pay, to about 100 kPa . The set up (often integral
with
the pump) should allow monitoring the pressure differential to the ambient air
(0p
= Pay pya~) and of the gas flow.
Then, the pump is started to create a light vacuum, which is increased
~s during the test in a stepwise operation. The amount of pressure increase
will
depend on the desired accuracy, with typical values of 0.1 kPa providing
acceptable results.
At each level, the flow will be monitored over time, and directly after the
increase of Op, the flow will increase primarily because of removing gas from
the
Zo tubing between the pump and the membrane. This flow will however, rather
quickly level off, and upon establishing an equilibrium 0p, the flow will
essentially
stop. This is typically reached after about 3 minutes.
This step change increase is continued up to the break through point, which
can be observed by the gas flow not decreasing after the step change of the
2s pressure, but remaining after reaching an equilibrium level essentially
constant
over time.
The pressure 0p one step prior to this situation is the bpp of the liquid
transport member.
For materials having bubble point pressures in excess of about 90 kPa, it
ao will be advisable or necessary to increase the ambient pressure surrounding
the
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test specimen by a constant and monitored degree, which is the added to op as
monitored.
Surface Tension Test method
s The surface tension measurement is well known to the man skilled in the art,
such as with a Tensiometer K10T from Kruss GmbH, Hamburg, Germany using
the DuNouy ring method as described in the equipment instructions. After
cleaning the glassware with iso-propanol and de-ionized water, it is dried at
105°C. The Platinum ring is heated over a Bunsen-burner until red heat.
A first
,o reference measurement is taken to check the accuracy of the tensiometer.
A suitable number of test replicates is taken to ensure consistency of the
data.
The resulting surface tension of thet liquid as expressed in units of mN/m can
be
used to determine the adhesion tension values and surface energy parameter of
the respective liquid/solid/gas systems. Destilled water will generally
exhibit a
,s surface tension value of 72mN/m, a 0.03% X-100 solution in water of 33
mNlm.
Li4uid Transport Test
The following test can be applied to liquid transport members having
defined inlet and outlet port regions with a certain transport path length
H°
zo between inlet and outlet port regions. For members, where the respective
port
regions cannot be determined such as because they are made of one
homogeneous material, these regions may be defined by considering the
intended use thus defining the respective port regions.
Before executing the test, the liquid transport member should be activated if
zs necessary, as described in the above.
The test specimen is placed in a vertical position over a liquid reservoir,
such as by being suspended from a holder, such whereby the inlet port remains
completely immersed in liquid in the reservoir The outlet port is connected
such
as via a flexible tubing of 6 mm outer diameter to a vacuum pump - optionally
so with a separator flask connected between the sample and the pump - and
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sealed in an air tight way as described in the above bubble point pressure
method for a liquid transport member. The vacuum suction pressure differential
can be monitored and adjusted.
The lowermost point of the outlet port is adjusted to be at a height Ho above
the liquid level in the reservoir.
The pressure differential is slowly increased to a pressure Po = 0.9kPa + p g
Ho with the liquid density p, and gravitational constant g ( g ~ 9.81 m/s~2).
After reaching this pressure differential, the decrease of the weight of the
liquid in the reservoir is monitored, preferably by positioning the reservoir
on a
scale measuring the weight of the reservoir, and connecting the scale to a
computing equipment. After an initial unsteady decrease (typically taking not
more than about one minute), the weight decrease in the reservoir will become
constant (i.e. showing a straight line in a graphical data presentation). This
constant weight decrease over time is the flow rate (in g/s) of the liquid
transport
~5 member at suction of 0.9kPa and a height Ho.
The corresponding flux rate of the liquid transport member at 0.9kPa
suction and a height Ho is calculated from the flow rate by dividing the flow
rate
with the average cross section of the liquid transport member along a flow
path,
expressed in g/slcm2.
2o Care should be take, that the reservoir is large enough so that the fluid
level
in the reservoir does not change by more than 1 mm.
in addition, the effective permeability of the liquid transport member can be
calculated by dividing the flux rate by the average length along a flow path
and
the driving pressure difference (0.9kPa).
Li4uid Permeability Test
Generally, the test should be carried out with a suitable test fluid
representing the transport fluid. For example, when the application is in the
context of absorbent disposable articles, Jayco SynUrine ss available from
Jayco
ao Pharmaceuticals Company of Camp Hill, Pennsylvania has been found to be
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suitable. The formula for the synthetic urine is: 2.0 g/: of KCI; 2.0 g/l of
Na2S04;
0.85 g/l of (NH4)04; 0.15 g/l (NH4)04; 0.19 g/l of CaCl2; ad 0.23 gll of
MgCl2. All
of the chemicals are of reagent grade. The pH of the synthetic Urine is in the
range of 6.0 to 6.4. Also for such applications, it has been found useful to
carry
s out the tests under controlled laboratory conditions of about 23 +/-
2°C and at 50
+!-10% relative humidity. Test specimen are stored under these conditions for
at
least 24 hours before testing, and - if applicable - activated as described in
the
above.
The present Permeability Test provides a measure for permeability for two
,o special conditions: Either the permeability can be measured for a wide-
range of
porous materials (such as non-wovens made of synthetic fibres, or cellulosic
structures) at 100% saturation, or for materials, which reach different
degrees of
saturation with a proportional change in caliper without being filled with air
(respectively the outside vapour phase), such as the collapsible polymeric
foams,
,s for which the permeability at varying degrees of saturation can readily be
measured at various thicknesses.
In particular for polymeric foam materials, such as disclosed in US-A
5.563.179 or US-A-5.387.207 it has been found useful to operate the test at an
elevated temperature of 31 °C, so as to better simulate in-use
conditions for
zo absorbent articles.
In principle, this tests is based on Darcy's law, according to which the
volumetric flow rate of a liquid through any porous medium is proportional to
the
pressure gradient, with the proportionality constant related to permeability.
Q/A = (k/rl) * (OP/L)
is where:
Q= Volumetric Flow Rate [cm'Is];
A= Cross Sectional Area [cm2];
k= Permeability (cmz ) (with 1 Darcy corresponding to 9.869* 10''3 m2);
rl= Viscosity (Poise) [Pa*s];
so oPIL= Pressure Gradient [Palm];
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L= caliper of sample [cm].
Hence, permeability can be calculated - for a fixed or given sample cross-
sectional area and test liquid viscosity - by measurement of pressure drop and
s the volumetric flow rate through the sample:
k= (Q/A) * (UOP) * ~
The test can be executed in two modifications, the first referring to the
,o transplanar permeability (i.e. the direction of flow is essentially along
the
thickness dimension of the material), the second being the in-plane
permeability
(i.e. the direction of flow being in the x-y-direction of the material).
The test set-up for the transplanar permeability test can be see in Figure 19
which is a schematic diagram of the overall equipment and - as an insert
diagram
,s - a partly exploded cross-sectional, not to scale view of the sample cell.
The test set-up comprises a generally circular or cylindrical sample cell
(19120), having an upper (19121) and lower (19122) part. The distance of these
parts can be measured and hence adjusted by means of each three
circumferentially arranged caliper gauges (19145) and adjustment screws
zo (19140). Further, the equipment comprises several fluid reservoirs (19150,
19154, 19156) including a height adjustment (19170) for the inlet reservoir
(19150) as well as tubings (19180), quick release fittings (19189) for
connecting
the sample cell with ttie rest of the equipment, further valves (19182, 19184,
19186, 19188). The differential pressure transducer (19197) is connected via
zs tubing (19180) to the upper pressure detection point (19194) and to the
lower
pressure detection point (19196). A Computer device (19190) for control of
valves is further connected via connections (19199) to differential pressure
transducer (19197), temperature probe (19192), and weight scale load cell
(19198).
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The circular sample (19110) having a diameter of 1 in (about 2.54 cm) is
placed in between two porous screens (19135) inside the sample cell (19120),
which is made of two 1 in (2.54 cm) inner diameter cylindrical pieces (19121,
19122) attached via the inlet connection (19132) to the inlet reservoir
(19150)
s and via the outlet connection (19133) to the outlet reservoir (19154) by
flexible
tubing (19180), such as tygon tubing. Closed cell foam gaskets (19115) provide
leakage protection around the sides of the sample. The test sample (19110) is
compressed to the caliper corresponding to the desired wet compression, which
is set to 0.2 psi (about 1.4 kPa) unless otherwise mentioned. Liquid is
allowed to
,o flow through the sample (19110) to achieve steady state flow. Once steady
state
flow through the sample (19110) has been established, volumetric flow rate and
pressure drop are recorded as a function of time using a load cell (19198) and
the differential pressure transducer (19197). The experiment can be performed
at any pressure head up to 80 cm water (about 7.8 kPa), which can be adjusted
~s by the height adjusting device (19170). From these measurements, the flow
rate
at different pressures for the sample can be determined.
The equipment is commercially available as a Permeameter such as
supplied by Porous Materials, Inc, Ithaca, New York, US under the designation
PMI Liquid Permeameter, such as further described in respective user manual of
Zo 2I97. This equipment includes two Stainless Steel Frits as porous screens
(19135), also specified in said brochure. The equipment consists of the sample
cell (19120), inlet reservoir (19150), outlet reservoir (19154), and waste
reservoir
(19158) and respective filling and emptying valves and connections, an
electronic
scale, and a computerized monitoring and valve control unit (19190).
Zs The gasket material (19115) is a Closed Cell Neoprene Sponge SNC-1
(Soft), such as supplied by Netherland Rubber Company, Cincinnati, Ohio, US. A
set of materials with varying thickness in steps of 1/16" (about 0.159 cm)
should
be available to cover the range from 1/16" -1I2" (about 0.159 cm to about 1.27
cm) thickness.
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Further a pressurized air supply is required, of at least 60 psi (4.1 bar), to
operate the respective valves.
Test fluid is deionized water.
The test is then executed by the following steps:
1 ) Preparation of the test sample(s):
In a preparatory test, it is determined, if one or more layers of the test
sample are required, wherein the test as outlined below is run at the lowest
and
highest pressure. The number of layers is then adjusted so as to maintain the
ro flow rate during the test between 0.5 cm'lseconds at the lowest pressure
drop
and 15 cm3/second at the highest pressure drop. The flow rate for the sample
should be less than the flow rate for the blank at the same pressure drop. If
the
sample flow rate exceeds that of the blank for a given pressure drop, more
layers
should be added to decrease the flow rate.
~s Sample size: Samples are cut to 1" (about 2.54 cm) diameter, by using an
arch punch, such as supplied by McMaster-Carr Supply Company, Cleveland,
OH, US. If samples have too little internal strength or integrity to maintain
their
structure during the required manipulation, a conventional low basis weight
support means can be added, such as a PET scrim or net.
Zo Thus, at least two samples (made of the required number of layers each, if
necessary) are precut. Then, one of these is saturated in deionized water at
the
temperature the experiment is to be performed (70 ° F, (31 ° C)
unless otherwise
noted).
The caliper of the wet sample is measured (if necessary after a stabilization
25 time of 30 seconds) under the desired compression pressure for which the
experiment will be run by using a conventional caliper gauge (such as supplied
by AMES, Waltham, MASS, US) having a pressure foot diameter of 1 1/8 "
(about 2.86 cm), exerting a pressure of 0.2 psi (about 1.4 kPa) on the sample
(19110), unless otherwise desired.
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An appropriate combination of gasket materials is chosen, such that the
total thickness of the gasketing foam (19115) is between 150 and 200% of the
thickness of the wet sample (note that a combination of varying thicknesses of
gasket material may be needed to achieve the overall desired thickness). The
3 gasket material (19115) is cut to a circular size of 3" in diameter, and a 1
inch
(2.54 cm) hole is cut into the center by using the arch punch.
In case, that the sample dimensions change upon wetting, the sample
should be cut such that the required diameter is taken in the wet stage. This
can
also be assessed in this preparatory test, with monitoring of the respective
~o dimensions. If these change such that either a gap is formed, or the sample
forms wrinkles which would prevent it from smoothly contacting the porous
screens or frits, the cut diameter should be adjusted accordingly.
The test sample (19110) is placed inside the hole in the gasket foam
(19115), and the composite is placed on top of the bottom half of the sample
cell,
~s ensuring that the sample is in flat, smooth contact with the screen
(19135), and
no gaps are formed at the sides.
The top of the test cell (19121) is laid flat on the lab bench (or another
horizontal plane) and all three caliper gauges (19145) mounted thereon are
zeroed.
Zo The top of the test cell (19121) is then placed onto the bottom part
(19122)
such that the gasket material(19115) with the test sample (19110) lays in
between the two parts. The top and bottom part are then tightened by the
fixation
screws (19140), such that the three caliper gauges are adjusted to the same
value as measured for the wet sample under the respective pressure in the
zs above.
2) To prepare the experiment, the program on the computerized unit
(19190) is started and sample identification, respective pressure etc. are
entered.
3) The test will be run on one sample (19110) for several pressure cycles,
with the first pressure being the lowest pressure. The results of the
individual
so pressure runs are put on different result files by the computerized unit
(19190).
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Data are taken from each of these files for the calculations as described
below.
(A different sample should be used for any subsequent runs of the material.)
4) The inlet liquid reservoir (19150) is set to the required height and the
test
is started on the computerized unit (19190).
s 5) Then, the sample cell (19120) is positioned into the permeameter unit
with Quick Disconnect fittings (19189).
6) The sample cell (19120) is filled by opening the vent valve (19188) and
the bottom fill valves (19184, 19186). During this step, care must be taken to
remove air bubbles from the system, which can be achieved by turning the
~o sample cell vertically, forcing air bubbles - if present - to exit the
permeameter
through the drain.
Once the sample cell is filled up to the tygon tubing attached to the top of
the chamber (19121), air bubbles are removed from this tubing into the waste
reservoir (19156).
~s 7) After having carefully removed air bubbles, the bottom fill valves
(19184,
19186) are closed, and the top fill (19182) valve is opened, so as to fill the
upper
part, also carefully removing all air bubbles.
8) The fluid reservoir is filled with test fluid to the fill line (19152).
Then the flow is started through the sample by initiating the computerized
zo unit (19190).
After the temperature in the sample chamber has reached the required
value, the experiment is ready to begin.
Upon starting the experiment via the computerized unit (19190), the liquid
outlet flow is automatically diverted from the waste reservoir (19156) to the
outlet
is reservoir (19154), and pressure drop, and temperature are monitored as a
function of time for several minutes.
Once the program has ended, the computerized unit provides the recorded
data (in numeric andlor graphical form).
If desired, the same test sample can be used to measure the permeability
so at varying pressure heads, with thereby increasing the pressure from run to
run.
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The equipment should be cleaned every two weeks, and calibrated at least
once per week, especially the frits, the load cell, the thermocouple and the
pressure transducer, thereby following the instructions of the equipment
supplier.
The differential pressure is recorded via the differential pressure transducer
s connected to the pressure probes measurement points (19194, 19196) in the
top
and bottom part of the sample cell. Since there may be other flow resistances
within the chamber adding to the pressure that is recorded, each experiment
must be corrected by a blank run. A blank run should be done at 10, 20, 30,
40,
50, 60, 70, 80 cm requested pressure, each day. The permeameter will output a
ro Mean Test Pressure for each experiment and also an average flow rate.
For each pressure that the sample has been tested at, the flow rate is
recorded as Blank Corrected Pressure by the computerized unit (19190), which
is further correcting the Mean Test Pressure (Actual Pressure) at each height
recorded pressure differentials to result in the Corrected Pressure. This
~s Corrected Pressure is the DP that should be used in the permeability
equation
below.
Permeability can then be calculated at each requested pressure and all
permeabilities should be averaged to determine the k for the material being
tested.
zo Three measurements should be taken for each sample at each head and
the results averaged and the standard deviation calculated. However, the same
sample should be used, permeability measured at each head, and then a new
sample should be used to do the second and third replicates.
The measuring of the in-plane permeability under the same conditions as
Zs the above described transplanar permeability, can be achieved by modifying
the
above equipment such as schematically depicted in Figures 20A and 20B
showing the partly exploded, not to scale view of the sample cell only.
Equivalent
elements are denoted equivalently, such that the sample cell of Figure 20 is
denoted (20210), correlating to the numeral (19110) of figure 19, and so on.
3o Thus, the transplanar sample cell (19120) of frgure 19 is replaced by the
in-plane
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simplified cell (20220), which is designed so that liquid can flow only in one
direction (either machine direction or cross direction depending on how the
sample is placed in the cell). Care should be taken to minimize channeling of
liquid along the walls (wall effects), since this can erroneously give high
s permeability reading. The test procedure is then executed quite analogous to
the
transplanar test.
The sample cell (20220) is designed to be positioned into the equipment
essentially as described for the sample cell (19120) in the above transplanar
test,
except that the filling tube is directed to the inlet connection (20232) the
bottom
,o of the cell (20220). Figure 20A shows a partly exploded view of the sample
cell,
and Figure 20B a cross-sectional view through the sample level.
The test cell (20220) is made up of two pieces: a bottom piece (20225)
which is like a rectangular box with flanges, and a top piece (20223) that
fits
inside the bottom piece (20225) and has flanges as well. The test sample is
cut
to the size of 2" in x 2"in (about 5.1 cm by 5.1 cm) and is placed into the
bottom
piece. The top piece (20223) of the sample chamber is then placed into the
bottom piece (20225) and sits on the test sample (20210). An incompressible
neoprene rubber seal (20224) is attached to the upper piece (20223) to provide
tight sealing. The test liquid flows from the inlet reservoir to the sample
space via
2o Tygon tubing and the inlet connection (20232) further through the outlet
connection (20233) to the outlet reservoir. As in this test execution the
temperature control of the fluid passing through the sample cell can be
insufficient due to lower flow rates, the sample is kept at the desired test
temperature by the heating device (20226), whereby thermostated water is
is pumped through the heating chamber (20227). The gap in the test cell is set
at
the caliper corresponding to the desired wet compression, normally 0.2 psi
about 1.4 kPa}. Shims (20216) ranging in size from 0.1 mm to 20.0 mm are used
to set the correct caliper, optionally using combinations of several shims.
At the start of the experiment, the test cell (20220) is rotated 90°
(sample is
so vertical) and the test liquid allowed to enter slowly from the bottom. This
is
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necessary to ensure that all the air is driven out from the sample and the
inlet/outlet connections (20232/20233). Next, the test cell (20220) is rotated
back to its original position so as to make the sample (20210) horizontal. The
subsequent procedure is the same as that described earlier for transplanar
s permeability, i.e. the inlet reservoir is placed at the desired height, the
flow is
allowed to equilibrate, and flow rate and pressure drop are measured.
Permeability is calculated using Darcy's law. This procedure is repeated for
higher pressures as well.
For samples that have very low permeability, it may be necessary to
o increase the driving pressure, such as by extending the height or by
applying
additional air pressure on the reservoir in order to get a measurable flow
rate. In
plane permeability can be measured independently in the machine and cross
directions, depending on how the sample is placed in the test cell.
,s Optical Determination of Pore Size
Optical determination of pore size is especially used for thin layers of
porous system by using standard image analysis procedures know to the skilled
artisan.
Zo The principle of the method consists of the following steps: 1 ) A thin
layer of
the sample material is prepared by either slicing a thick sample 'into thinner
sheets or if the sample itself is thin by using it directly. The term "thin"
refers to
achieving a sample caliper low enough to allow a clear cross-section image
under the microscope. Typical sample calipers are below 200Nm. 2) A
zs microscopic image is obtained via a video microscope using the appropriate
magnification. Best results are obtained if about 10 to 100 pores are visible
on
said image. The image is then digitized by a standard image analysis package
such as OPTIMAS by BioScan Corp. which runs under Windows 95 on a typical
IBM compatible PC. Frame grabber of sufficient pixel resolution (preferred at
30 least 1024 x 1024 pixels) should be used to obtain good results. 3) The
image is
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converted to a binary image using an appropriate threshold level such that the
pores visable on the image are marked as object areas in white and the rest
remains black. Automatic threshold setting procedures such as available under
OPTIMAS can be used. 4) The areas of the individual pores (objects) are
s determined. OPT1MAS offers fully automatic determination of the areas. 5)
The
equivalent radius for each pore is determined by a circle that would have the
same area as the pore. If A is the area of the pore, then the equivalent
radius is
given by r=(A/~)''. The average pore size can then be determined from the pore
size distribution using standard statistical rules. For materials that have a
not
,o very uniform pore size it is recommended to use at least 3 samples for the
determination.
Liauid Permeability Test
Generally, the test should be carried out with a suitable test fluid
~s representing the transport fluid. For example, when the application is in
the
context of absorbent disposable articles, Jayco SynUrine ss available from
Jayco
Pharmaceuticals Company of Camp Hill, Pennsylvania has been found to be
suitable. The formula for the synthetic urine is: 2.0 g/: of KCI; 2.0 gll of
Na2S04;
0.85 gll of (NH4)2HP04; 0.15 gll (NH4)H2P04; 0.19 gll of CaCl2; ad 0.23 g/l of
Zo MgCl2. All of the chemicals are of reagent grade. The pH of the synthetic
Urine is
in the range of fi.0 to 6.4.. Also for such applications, it has been found
useful to
carry out the tests under controlled laboratory conditions of about 23 +/-
2°C and
at 50 +/-10% relative humidity. Test specimen are stored under these
conditions
for at least 24 hours before testing, and - if applicable - activated as
described in
is the above.
The present Permeability Test provides a measure for permeability for two
special conditions: Either the permeability can be measured for a wide range
of
porous materials (such as non-wovens made of synthetic fibres, or cellulosic
structures) at 100% saturation, or for materials, which reach different
degrees of
so saturation with a proportional change in caliper without being filled with
air
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(respectively the outside vapour phase), such as the collapsible polymeric
foams,
for which the permeability at varying degrees of saturation can readily be
measured at various thicknesses.
In particular for polymeric foam materials, it has been found useful to
s operate the test at an elevated temperature of 31 °C, so as to better
simulate in-
use conditions for absorbent articles.
In principle, this tests is based on Darcy's law, according to which the
volumetric flow rate of a liquid through any porous medium is proportional to
the
pressure gradient, with the proportionality constant related to permeability.
ro Q/A = (k/rl) * (eP/L)
where:
Q= Volumetric Flow Rate [cm'/s];
A= Cross Sectional Area [cm~J;
k= Permeability (cm2 ) (with 1 Darcy corresponding to 9.869* 10-" mz);
rl= Viscosity (Poise) [Pa*s];
oPIL= Pressure Gradient [Palm];
L= caliper of sample [cm].
Hence, permeability can be calculated - for a fixed or given sample cross-
Zo sectional area and test liquid viscosity - by measurement of pressure drop
and
the volumetric flow rate through the sample:
k= (Q/A) * (UeP) * ,1
25 The test can be executed in two mod~cations, the first referring to the
transplanar permeability (i.e. the direction of flow is essentially along the
thickness dimension of the material), the second being the in-plane
permeability
(i.e. the direction of flow being in the x-y-direction of the material).
The test set-up for the simplified, transplanar permeability test can be see
in
so Figure 19 which is a schematic diagram of the overall equipment and - as an
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insert diagram - a partly exploded cross-sectional, not to scale view of the
sample cell.
The test set-up comprises a generally circular or cylindrical sample cell
(19120), having an upper (19121) and lower (19122) part. The distance of these
s parts can be measured and hence adjusted by means of each three
circumferentially arranged caliper gauges (19145) and adjustment screws
(19140). Further, the equipment comprises several fluid reservoirs (19150,
19154, 19156) including a height adjustment (19170) for the inlet reservoir
(19150) as well as tubings (19180), quick release fittings (19189) for
connecting
,o the sample cell with the rest of the equipment, further valves (19182,
19184,
19186, 19188). The differential pressure transducer (19197) is connected via
tubing (19180) to the upper pressure detection point (19194) and to the lower
pressure detection point (19196). A Computer device (19190) for control of
valves is further connected via connections (19199) to differential pressure
~s transducer (19197), temperature probe (19192), and weight scale load cell
(19198).
The circular sample (19110) having a diameter of 1 in (about 2.54 cm) is
placed in between two porous screens (19135) inside the sample cell (19120),
which is made of two 1 in (2.54 cm) inner diameter cylindrical pieces (19121,
zo 19122) attached via the inlet connection (19132) to the inlet reservoir
(19150)
and via the outlet connection (19133) to the outlet reservoir (19154) by
flexible
tubing (19180), such as tygon tubing. Closed cell foam gaskets (19115) provide
leakage protection around the sides of the sample. The test sample (19110) is
compressed to the caliper corresponding to the desired wet compression, which
is is set to 0.2 psi (about 1.4 kPa) unless othervvise mentioned. Liquid is
allowed to
flow through the sample (19110) to achieve steady state flow. Once steady
state
flow through the sample (19110) has been established, volumetric flow rate and
pressure drop are recorded as a function of time using a load cell (19198) and
the differential pressure transducer (19197). The experiment can be performed
so at any pressure head up to 80 cm water (about 7.8 kPa), which can be
adjusted
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by the height adjusting device (19170). From these measurements, the flow rate
at different pressures for the sample can be determined.
The equipment is commercially available as a Permeameter such as
supplied by Porous Materials, Inc, Ithaca, New York, US under the designation
s PMI Liquid Permeameter, such as further described in respective user manual
of
2/97. This equipment includes two Stainless Steel Frits as porous screens
(19135), also specified in said brochure. The equipment consists of the sample
cell (19120), inlet reservoir (19150), outlet reservoir (19154), and waste
reservoir
(19156) and respective filling and emptying valves and connections, an
electronic
~o scale, and a computerized monitoring and valve control unit (19190).
The gasket material (19115) is a Closed Cell Neoprene Sponge SNC-1
(Soft), such as supplied by Netherland Rubber Company, Cincinnati, Ohio, US. A
set of materials with varying thickness in steps of 1116" (about 0.159 cm)
should
be available to cover the range from 1/16" -1/2" (about 0.159 cm to about 1.27
,s cm) thickness.
Further a pressurized air supply is required, of at least 60 psi (4.1 bar), to
operate the respective valves.
Test fluid is deionized water.
The test is then executed by the following steps:
11 Preparation of the test sample(s):
In a preparatory test, it is determined, if one or more layers of the test
sample are required, wherein the test as outlined below is run at the lowest
and
highest pressure. The number of layers is then adjusted so as to maintain the
2s flow rate during the test between 0.5 cm'/seconds at the lowest pressure
drop
and 15 cm3/second at the highest pressure drop. The flow rate for the sample
should be less than the flow rate for the blank at the same pressure drop. If
the
sample flow rate exceeds that of the blank for a given pressure drop, more
layers
should be added to decrease the flow rate.
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Sample size: Samples are cut to 1" (about 2.54 cm) diameter, by using an
arch punch, such as supplied by McMaster-Carr Supply Company, Cleveland,
OH, US. if samples have too little internal strength or integrity to maintain
their
structure during the required manipulation, a conventional low basis weight
support means can be added, such as a PET scrim or net.
Thus, at least two samples (made of the required number of layers each, if
necessary) are precut. Then, one of these is saturated in deionized water at
the
temperature the experiment is to be performed .(70° F, (31 ° C)
unless otherwise
noted).
~o The caliper of the wet sample is measured (if necessary after a
stabilization
time of 30 seconds) under the desired compression pressure for which the
experiment will be run by using a conventional caliper gauge (such as supplied
by AMES, Waltham, MASS, US) having a pressure foot diameter of 1 1/8 "
(about 2.86 cm), exerting a pressure of 0.2 psi (about 1.4 kPa) on the sample
~s (19110), unless otherwise desired.
An appropriate combination of gasket materials is chosen, such that the
total thickness of the gasketing foam (19115) is between 150 and 200% of the
thickness of the wet sample (note that a combination of varying thicknesses of
gasket material may be needed to achieve the overall desired thickness). The
2o gasket material (19115) is cut to a circular size of 3" in diameter, and a
1 inch
(2.54 cm) hole is cut into the center by using the arch punch.
1n case, that the sample dimensions change upon wetting, the sample
should be cut such that the required diameter is taken in the wet stage. This
can
also be assessed in this preparatory test, with monitoring of the respective
25 dimensions. If these change such that either a gap is formed, or the sample
forms wrinkles which would prevent it from smoothly contacting the porous
screens or frits, the cut diameter should be adjusted accordingly.
The test sample (19110) is placed inside the hole in the gasket foam
(19115), and the composite is placed on top of the bottom half of the sample
cell,
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ensuring that the sample is in flat, smooth contact with the screen (19135),
and
no gaps are formed at the sides.
The top of the test cell (19121) is laid flat on the lab bench (or another
horizontal plane) and alt three caliper gauges (19145) mounted thereon are
s zeroed.
The top of the test cell (19121 ) is then placed onto the bottom part (19122)
such that the gasket material(19115) with the test sample (19110) lays in
between the two parts. The top and bottom part are then tightened by the
fixation
screws (19140), such that the three caliper gauges are adjusted to the same
,o value as measured for the wet sample under the respective pressure in the
above.
2) To prepare the experiment, the program on the computerized unit
(19190) is started and sample identification, respective pressure etc. are
entered.
3) The test will be run on one sample (19110) for several pressure cycles,
~s with the first pressure being the lowest pressure. The results of the
individual
pressure runs are put on different result files by the computerized unit
(19190).
Data are taken from each of these files for the calculations as described
below.
(A different sample should be used for any subsequent runs of the material.)
4) The inlet liquid reservoir (19150) is set to the required height and the
test
so is started on the computerized unit (19190).
5) Then, the sample cell (19120) is positioned into the permeameter unit
with Quick Disconnect fittings (19189).
6) The sample cell (19120) is filled by opening the vent valve (19188) and
the bottom fill valves (19184, 19186). During this step, care must be taken to
Zs remove air bubbles from the system, which can be achieved by turning the
sample cell vertically, forcing air bubbles - if present - to exit the
permeameter
through the drain.
Once the sample cell is filled up to the tygon tubing attached to the top of
the chamber (19121), air bubbles are removed from this tubing into the waste
so reservoir (19156).
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7) After having carefully removed air bubbles, the bottom fill valves (19184,
19186) are closed, and the top fill (19182) valve is opened, so as to fill the
upper
part, also carefully removing all air bubbles.
8) The fluid reservoir is filled with test fluid to the fill line (19152).
s Then the flow is started through the sample by initiating the computerized
unit (19190).
After the temperature in the sample chamber has reached the required
value, the experiment is ready to begin.
Upon starting the experiment via the computerized unit (19190), the liquid
outlet flow is automatically diverted from the waste reservoir (19156) to the
outlet
reservoir (19154), and pressure drop, and temperature are monitored as a
function of time for several minutes.
Once the program has ended, the computerized unit provides the recorded
data (in numeric andlor graphical form).
~s If desired, the same test sample can be used to measure the permeability
at varying pressure heads, with thereby increasing the pressure from run to
run.
The equipment should be cleaned every two weeks, and calibrated at least
once per week, especially the frits, the load cell, the thermocouple and the
pressure transducer, thereby following the instructions of the equipment
supplier.
zo The differential pressure is recorded via the differential pressure
transducer
connected to the pressure probes measurement points (19194, 19196) in the top
and bottom part of the sample cell. Since there may be other flow resistances
within the chamber adding to the pressure that is recorded, each experiment
must be corrected by a blank run. A blank run should be done at 10, 20, 30,
40,
25 50, 60, 70, 80 cm requested pressure, each day. The permeameter will output
a
Mean Test Pressure for each experiment and also an average flow rate.
For each pressure that the sample has been tested at, the flow rate is
recorded as Blank Corrected Pressure by the computerized unit (19190), which
is further correcting the Mean Test Pressure (Actual Pressure) at each height
so recorded pressure differentials to result in the Corrected Pressure. This
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Corrected Pressure is the DP that should be used in the permeability equation
below.
Permeability can then be calculated at each requested pressure and all
permeabilities should be averaged to determine the k for the material being
s tested.
Three measurements should be taken for each sample at each head and
the results averaged and the standard deviation calculated. However, the same
sample should be used, permeability measured at each head, and then a new
sample should be used to do the second and third replicates.
o The measuring of the in-plane permeability under the same conditions as
the above described transplanar permeability, can be achieved by modifying the
above equipment such as schematically depicted in Figures 20A and 20B
showing the partly exploded, not to scale view of the sample cell only.
Equivalent
elements are denoted equivalently, such that the sample cell of Figure 20 is
rs denoted (20210), correlating to the numeral (19110) of figure 19, and so
on.
Thus, the transplanar simplified sample cell (19120) of figure 19 is replaced
by
the in-plane simplified sample cell (20220), which is designed so that liquid
can
flow only in one direction (either machine direction or cross direction
depending
on how the sample is placed in the cell). Care should be taken to minimize
Zo channeling of liquid along the walls (wall effects), since this can
erroneously give
high permeability reading. The test procedure is then executed quite analogous
to the transplanar simplified test.
The sample cell (20220) is designed to be positioned into the equipment
essentially as described for the sample cell (20120) in the above transplanar
test,
25 except that the filling tube is directed to the inlet connection (20232)
the bottom
of the cell (20220). Figure 20A shows a partly exploded view of the sample
cell,
and Figure 20B a cross-sectional view through the sample level.
The test cell (20220) is made up of two pieces: a bottom piece (20225)
which is like a rectangular box with flanges, and a top piece (20223) that
fits
so inside the bottom piece (20225) and has flanges as well. The test sample is
cut
.~-
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to the size of 2" in x 2"in (about 5.1 cm by 5.1 cm) and is placed into the
bottom
piece. The top piece (20223) of the sample chamber is then placed into the
bottom piece (20225) and sits on the test sample (20210). An incompressible
neoprene rubber seal (20224) is attached to the upper piece (20223) to provide
tight sealing. The test liquid flows from the inlet reservoir to the sample
space via
Tygon tubing and the inlet connection (20232) further through the outlet
connection (20233) to the outlet reservoir. As in this test execution the
temperature control of the fluid passing through the sample cell can be
insufficient due to lower flow rates, the sample is kept at the desired test
temperature by the heating device (20226), whereby thermostated water is
pumped through the heating chamber (20227). The gap in the test cell is set at
the caliper corresponding to the desired wet compression, normally 0.2 pSi
(about 1.4 kPa). Shims (20216) ranging in size from 0.1 mm to 20.0 mm and
fixation screw (20240) are used to set the correct caliper, optionally using
,s combinations of several shims.
At the start of the experiment, the test cell (20220) is rotated 90°
(sample is
vertical) and the test liquid allowed to enter slowly from the bottom. This is
necessary to ensure that all the air is driven out from the sample and the
inlet/outlet connections (20232120233). Next, the test cell (20220) is rotated
Zo back to its original position so as to make the sample (20210) horizontal.
The
subsequent procedure is the same as that described earlier for transplanar
permeability, i.e. the inlet reservoir is placed at the desired height, the
flow is
allowed to equilibrate, and flow rate and pressure drop are measured.
Permeability is calculated using Darcy's law. This procedure is repeated for
is higher pressures as well.
For samples that have very low permeability, it may be necessary to
increase the driving pressure, such as by extending the height or by applying
additional air pressure on the reservoir in order to get a measurable flow
rate. In
plane permeability can be measured independently in the machine and cross
so directions, depending on how the sample is placed in the test cell.
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Demand absorbency test
The demand absorbency test is intended to measure the liquid capacity of
liquid handling member and to measure the absorption speed of liquid handling
s member against zero hydrostatic pressure. The test may also be carried out
for
devices for managing body liquids containing a liquid handling member.
The apparatus used to conduct this test consists of a square basket of a
sufficient size to hold the liquid handling member suspended on a frame. At
least
the lower plane of the square basket consists of an open mesh that allows
liquid
~o penetration into the basket without substantial flow resistance for the
liquid
uptake. For example, an open wire mesh made of stainless steel having an open
area of at least 70 percent and having a wire diameter of 1 mm, and an open
mesh size of at about 6mm is suitable for the setup of the present test. In
addition, the open mesh should exhibit sufficient stability such that it
substantially
~s does not deform under load of the test specimen when the test specimen is
filled
up to its full capacity.
Below the basket, a liquid reservoir is provided. The height of the basket
can be adjusted so that a test specimen which is placed inside the basket may
be brought into contact with the surface of the liquid in the liquid
reservoir. The
Zo liquid reservoir is placed on the electronic balance connected to a
computer to
read out the weight of the liquid about every 0.01sec during the measurement.
The dimensions of the apparatus are chosen such that the liquid handling
member to be tested'fits into the basket and such that the intended liquid
acquisition zone of the liquid handing member is in contact with the lower
plane
is of the basket. The dimensions of the liquid reservoir are chosen such that
the
level of the liquid surface in the reservoir does not substantially change
during
the measurement. A typical reservoir useful for testing liquid handling
members
has a size of at least 320 mm x 370 mm and can hold at least about 4500 g of
liquid.
so Before the test, the liquid reservoir is filled with synthetic urine. The
amount
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of synthetic urine and the size of the liquid reservoir should be sufficient
such that
the liquid level in the reservoir does not change when the liquid capacity of
the
liquid handing member to be tested is removed from the reservoir.
The temperature of the liquid and the environment for the test should reflect
s in-use conditions of the member. Typical temperature for use in baby diapers
are
32 degrees Celsius for the environment and 37 degrees Celsius for the
synthetic
urine. The test may be done at room temperature if the member tested has no
significant dependence of its absorbent properties on temperature.
The test is setup by lowering the empty basket until the mesh is just
ro completely immersed in the synthetic urine in the reservoir. The basket is
then
raised again by about 0.5 to 1 mm in order to establish an almost zero
hydrostatic
suction, care should be taken .that the liquid stays in contact with the mesh.
!f
necessary, the mesh needs to be brought back into contact with the liquid and
zero level be readjusted.
~s The test is started by:
1. starting the measurement of the electronic balance;
2. placing the liquid handling member on the mesh such that the
acquisition zone of the member is in contact with the liquid;
3. immediately adding a low weigh on top of the member in order to
Zo provide a pressure of 165 Pa for better contact of the member to the
mesh.
During the test, the liquid uptake by the liquid handing member is recorded
by measuring the weigfit decrease of the liquid in the liquid reservoir. The
test is
stopped after 30 minutes.
is At the end of the test, the total liquid uptake of the liquid handing
member is
recorded. In addition, the time after which the liquid handling member had
absorbed 80 percent of its total liquid uptake is recorded. The zero time is
defined as the time where the absorption of the member starts. The initial
absorption speed of the liquid handling member is-from the initial linear
slope of
so the weight vs. time measurement curve.
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Teaba4 Centrifuge Capacity Test ~TCC test)
Whilst the TCC test has been developed specifically for superabsorbent
materials, it can readily be applied to other absorbent materials.
s The Teabag Centrifuge Capacity test measures the Teabag Centrifuge
Capacity values, which are a measure of the retention of liquids in the
absorbent
materials.
The absorbent material is placed within a "teabag", immersed in a 0.9% by
weight sodium chloride solution for 20 minutes, and then centrifuged for 3
~o minutes. The ratio of the retained liquid weight to the initial weight of
the dry
material is the absorptive capacity of the absorbent material.
Two litres of 0.9% by weight sodium chloride in distilled water is poured into
a
tray having dimensions 24 cm x 30 cm x 5 cm. The liquid filling height should
be
about 3 cm.
,s The teabag pouch has dimensions 6.5 cm x 6.5 cm and is available from
Teekanne in Diisseldorf, Germany. The pouch is heat sealable with a standard
kitchen plastic bag sealing device (e.g. VACUPACK2 PLUS from Krups,
Germany).
The teabag is opened by carefully cutting it partially, and is then weighed.
zo About 0.2008 of the sample of the absorbent material, accurately weighed to
+/-
0.0058, is placed in the teabag. The teabag is then closed with a heat sealer.
This is called the sample teabag. An empty teabag is sealed and used as a
blank.
The sample teabag and the blank teabag are then laid on the surface of the
is saline solution, and submerged for about 5 seconds using a spatula to allow
complete wetting (the teabags will float on the surface of the saline solution
but
are then completely wetted). The timer is started immediately.
After 20 minutes soaking time the sample teabag and the blank teabag are
removed from the saline solution, and placed in a Bauknecht WS130, Bosch 772
so NZK096 or equivalent centrifuge (230 mm diameter), so that each bag sticks
to
CA 02336019 2000-12-22
WO 00/00146 PCT/US99I14796
- 106 -
the outer wall of the centrifuge basket. The centrifuge lid is closed, the
centrifuge
is started, and the speed increased quickly to 1,400 rpm. Once the centrifuge
has been stabilised at 1,400 rpm the timer is started. After 3 minutes, the
centrifuge is stopped.
s The sample teabag and the blank teabag are removed and weighed
separately.
The Teabag Centrifuge Capacity (TCC) for the sample of absorbent material
is calculated as follows:
TCC = [(sample teabag weight after centrifuging) - (blank teabag weight after
centrifuging) - (dry absorbent material weight)] = (dry absorbent material
weight).
