Note: Descriptions are shown in the official language in which they were submitted.
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1
ABSORBENT ARTICLE COMPRISING A LIQUID HANDLING MEMBER HAVING HIGH SUCTION AND
HIGH
PERMEABILTTY
FIELD OF THE INVENTION
The present invention relates to devices for managing body fluids such
as urine, sweat, saliva, blood, menses, purulence, or fecal material, and in
particular to their ability to acquire and retain aqueous based materials. The
invention further relates to disposable absorbent articles such as baby
diapers or training pants, adult incontinence products, and feminine hygiene
products and other body liquid handling articles such as catheters, urinals,
and the like.
The invention further relates to devices for managing body liquids
comprising a liquid handling member having high suction and high
permeability.
BACKGROUND
Devices for managing body fluids are well known in the art and are
frequently used for a wide variety of purposes. For example, the devices
serve hygienic purposes such as diapers, sanitary napkins, adult incontinence
CA 02333760 2004-04-08
2
products, underarm sweat pads, and the like. There is another class of such
devices which serve medical purposes such as wound dressings or drainages,
catheters, and the like. Accordingly such devices have been designed to cope
with a large variety of different body liquids such as for example urine,
sweat,
saliva, blood, menses, purulence, fecal material, and the like.
The ability to provide better performing devices such as diapers has been
contingent on the ability to develop relatively thin absorbent cores or
structures
that can acquire and store large quantities of discharged body fluids, in
particular
urine.
In addition, it is preferred to provide structures having a low capacity in
the
regions between the legs of the wearer such as in PCT application US 97105046,
filed on March 27, 1997, relating to the movement of fluid through certain
regions
of the article comprising materials having good acquisition and distribution
properties to other regions comprising materials having specific liquid
storage
capabilities.
Most of the absorbent articles comprise therefore at least one fluid
handling member that is designed for quickly acquiring and/or transporting
liquid
away from the loading point.
Examples of suitable liquid transport members based on crosslinked and
curled cellulose are disclosed in European patent application No. 0 512 010
(Cook et al.). Further examples of suitable liquid transport members having
high
vertical liquid transport rates are disclosed in European patent application
No. 0
809 991. (Schmidt et al.). Other suitable liquid transport members based on
HIPE
foams are disclosed in US patent 6013589 (DesMarais et al.)
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Example structures comprising liquid transport members to transport
liquid out of the crotch region are disclosed in PCT patent application WO
98/43580 (LaVon et al.).
Whilst such liquid transport members have been designed with capillary
transport mechanisms in mind, thus aiming at positioning materials with
smaller capillaries and/ or increased hydrophilicity closer to the ultimate
storage material, and materials with larger pores and less hydrophilicity
closer
to the loading zone, it has in addition been recognized, that
acquisition/distribution materials have the tendency to not only transport the
fluid, but also to retain the liquid, which can result under specific
conditions to
undesired effects, such as rewet or reduced fluid acquisition andlor
distribution performance, which is particularly pronounced for
acquisition/distribution materials being designed to balance acquisition and
distribution properties.
Accordingly, liquid storage members have been developed, which have
an improved balance of the fluid handling properties such that well performing
acquisition/distribution materials or members can be dewatered efficiently by
the storage materials or members. This is typically achieved by fluid storage
materials or members having a high liquid suction capability.
In PCT patent application No. U.S. 98/05044 (Palumbo et al.), absorbent
structures are disclosed which comprise materials exhibiting a high liquid
suction capability. These materials disclosed by the prior art employ small
capillaries such as ~ obtained by a small capillary HIPS foam, a mixture of
superabsorber and high surface area fibers and the like to provide the high
liquid suction capability. These structures have, however, the disadvantage
that the small capillaries limit the liquid permeability thus providing large
flow
resistance and slow rate for liquid being absorbed.
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Hence, it is an object of an aspect of the present invention to provide a
liquid handling member which overcomes the problems posed by the prior art.
It is a further object of an aspect of the present invention to provide a
liquid handling member which exhibits a high liquid suction capability in
combination with a high liquid permeability and I or a high absorbent rate.
It is a further object of an aspect of the present invention to provide a
device for handling body liquids comprising a liquid handling member which
exhibits a high liquid suction capability in combination with a high liquid
permeability and / or a high absorbent rate.
SUMMARY OF THE INVENTION
The present invention provides a liquid handling member to be used in a
device for handling by liquids.
One aspect of the present invention is a liquid handling member for
absorbing a body liquid wherein said liquid handling member has a capillary
sorption absorption height at 50% of its capacity at 0 cm absorption height
(CSAH50) according to the Capillary Sorption Test of at least 50cm and wherein
said liquid handling member has a liquid permeability of at least 5 Darcy
according to the Saturated Liquid Permeability Test.
The liquid handling member may have a liquid permeability of at least 10
Darcy and preferably at least 20 Darcy according to the Saturated Liquid
Permeability Test.
Another aspect of the invention is a liquid handling member for absorbing
a body liquid wherein the liquid handling member has a capillary sorption
absorption height at 50% of its capacity at Ocm absorption height (CSAH50)
according to the Capillary Sorption Test of at least 80cm and wherein the
liquid
handling member has a liquid permeability of at least 2 Darcy according to the
Saturated Liquid Permeability Test.
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Another aspect of the invention is a liquid handling member for absorbing
a body liquid wherein the liquid handling member has a capillary sorption
absorption height at 50% of its capacity at Ocm absorption height (CSAH50)
according to the Capillary Sorption Test and wherein the liquid handling
member
has an absorption time to 80% of its capacity of less than 5 seconds according
to
the Demand Absorbency Test.
The liquid handling member preferably has a capillary sorption absorption
capacity at 100cm absorption height of at least 5g/g, preferably at least
10g/g.
The invention further relates to absorbent structures, comprising a first
region for acquisition/distribution of fluid and a second region for storage
of fluid.
The first region comprises at least one member for acquiring and / or
transporting
liquid whereas the second region comprises said liquid handling members.
The present invention further provides a device for handling body liquids
comprising a liquid handling member or an absorbent structure according to the
present invention. The present invention further relates to absorbent articles
such
as baby diapers comprising a liquid handling member or an absorbent structure
according to the present invention.
BRIEF DESCRIPTION OF THE FIGURES
Figures 1, 2A and 2B show a schematic drawing of the setup for the liquid
permeability test.
Figure 3 shows a schematic drawing of the setup for the capillary sorption
test.
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DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in the following by means of a variety
of different embodiments and by means of a variety of different features.
Further embodiments of the present invention may be obtained by combining
features of one embodiment with features of another embodiment disclosed
herein and/or with other features disclosed herein. These further
embodiments are considered to be implicitly disclosed herein and hence form
part of the present invention. It will be apparent to the skilled person that
combinations of certain features may lead to non-functional articles not
forming part of this present invention.
The present invention provides liquid handling members to be used in
devices for handling body liquids. The present invention further provides
devices for handling body liquids which comprise the liquid handling member
of the present invention such as for example baby diapers, training pants,
sanitary napkins, adult incontinence devices, bed mats, and the like.
The term "handling body liquid" includes but is not limited to acquiring,
distributing, and storing body liquid.
It is one aspect of the present invention to provide a liquid handling
member which combines high liquid suction capability with a high liquid
permeability. In the context of the present invention, the term "liquid
permeability" includes both in-plane and transplanar permeability. Saturated
liquid permeability of a liquid handling member in the context of the present
invention is defined in the saturated state, i.e. when the member has
absorbed at least 90% of its capacity. It will be clear to the man skilled in
the
art that a high liquid permeability throughout the entire absorbent cycle is
desired. In one embodiment of the present invention it is therefore preferred,
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7
that the liquid handling members exhibit high liquid permeability both in the
saturated as well in the unsaturated state. The high liquid suction capability
allows that well performing acquisition/distribution materials or members can
be dewatered efficiently by the storage materials or members. A high liquid
permeability in in-plane as well as transplanar direction allows efficient
distribution of the acquired body liquids within the liquid handling member of
the present invention, in particular distribution against gravity and
relatively
high flux rates.
For the purpose of this invention, traps-planar permeabiflty'~s quantified
by the permeability test defined hereinafter. It is recognized, however, that
members having high in-plane permeability are also part of the scope of the
present invention. The liquid handling member of the present invention has a
permeability of at least 2 Darcy, preferably at least 5 Darcy, more preferably
at least 10 Darcy, and most preferably a permeability of at least 20 Darcy.
It is another aspect of the present invention to provide liquid handling
member which combines a high liquid suction capability with a fast absorption
rate such as for example expressed by a fast absorption time to 80% capacity
in the demand absorbency test. A fast 80 percent capacity absorption time is
representative of the ability of liquid handling member to efficient be used
the
majority of its absorbent capacity in a fast and efficient way in order to
avoid
that the liquid storage becomes the rate limiting step for the performance of
the device.
For the purpose of this invention, liquid suction is quantified by the
capillary sorption test defined hereinafter. The liquid handling member of the
present invention has a capillary Sorption Absorption Height at 50% of its
capacity at 0 centimeter absorption height of at least 50 centimeter,
preferably
of at least 80 cm, more preferably of at least 100 cm.
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For the purpose of this invention, the 80 percent capacity absorption time
is quantified by the demand absorbency test defined hereinafter. The liquid
handling member of the present invention has a 80 percent absorption time of
less than 5 seconds, preferably a 80 percent absorption time of less. than 2
second, more preferably of less than 1.5 seconds, most preferably of less than
1
second.
It is another aspect of the present invention to provide a liquid handling
member having a capillary absorption capacity of at least 5g/g, preferably at
least
10g/g at a high hydrostatic height of at least 50cm, preferably at least
100cm. A
high absorbent capacity allows storage of larger quantities of body liquids
such
as for example urine gushes.
In the following, a suitable embodiment of the liquid handling member will
be described. The liquid handling member is assembled from an inner material
which is completely enveloped by a membrane. Suitable membrane materials are
available from SEFART"" of Ruschlikon, Switzerland, under the designation
SEFART"" 03-10/2 and under the designation SEFART"~ 03-5/1. A suitable foam
material for use as inner material is available from Recticel of Brussels,
Belgium,
under the designation Bulpren S10 black. Other suitable inner materials may be
obtained by punching holes of 2 mm diameter at a density of about 2 holes per
square centimeter into materials available from Fisher Scientific of Germany,
under the designation D&N PelleusT"" ball size 5 and under the designation D&N
PelleusT"' ball size 7. A suitable technique to completely envelope the foam
material with the membrane material is to wrap the membrane material around
the foam material and to subsequently heat seal all open edges of the membrane
material. It will be readily apparent to the skilled practitioner to choose
other
similarly suitable materials. Depending on the specific intended application
of the
liquid handling member, it may also be required to choose similar materials
with
slightly different properties. After assembly, the liquid handling member is
activated by immersing the liquid handling member in water or in synthetic
urine
until the liquid handling
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member is completely filled with liquid and until the membranes are completely
wetted with liquid. After activation, a part of.the liquid inside the liquid
handling
member may be squeezed out by applying an external pressure to the liquid
handling member. If the activation of the liquid handling member was
successful,
the liquid handling member should not suck air through the membranes.
Other liquid handling members suitable for the purposes of the present
invention are described for example in the PCT patent application No.
PCT/US98/13497 entitled "Liquid transport member for high flux rates between
two port regions" filed in the name of Ehrnsperger et al. filed on June 29,
1998,
and in the following PCT patent applications co-filed with the present
application
and entitled "High flux liquid transport members comprising two different
permeability regions", (CA 2,336,019), "Liquid transport member for high flux
rates between two port regions", (CA 2,335,774), "Liquid transport member for
high flux rates against gravity", (CA 2,336,205) and "Liquid transport member
having high permeability bulk regions and high bubble point pressure port
regions", (WO 00/00136).
The particular geometry of the liquid handling member of the present
invention can be varied according to the specific requirements off the
intended
application. If, for example, the liquid handling member is intended to be
used in
an absorbent article the liquid handling member may be defined such that its
zone of intended liquid acquisition fits between the legs of the wearer and
further
that its intended liquid discharge zone matches the form of the storage member
associated to it. Accordingly, the outer dimensions of the liquid handling
member
such as length, width, or thickness may also be adapted to the specific needs
of
the intended application. In this context, it has to be understood, however,
that
the design of the outer form of the liquid
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handling member may have an impact on its performance.
In one embodiment of the present invention, the liquid handling member
of the present invention is geometrically saturated or substantially
geometrically saturated with free liquid. The term "free liquid" as used
herein
refers to liquid which is not bound to a specific surface or other entity.
Free
liquid can be distinguished from bound liquid by measuring the proton spin
relaxation time T2 of the liquid molecules a according to NMR (nuclear
magnetic resonance) spectroscopy methods well known in the art.
The term "geometrically saturated" as used herein refers to a region of a
porous material in which the liquid accessible void spaces have been filled
with a liquid. The void spaces referred to in this definition are those which
are
present in the current geometric configuration of the porous material. In
other
words, a geometrically saturated device may still be able to accept additional
liquid by and only by changing its geometric configuration for example by
swelling, although all voids of the device are filled with liquid in the
current
geometric configuration. A device for handling liquids is called geometrically
saturated, if all porous materials that are part of the device and intended
for
liquid handling are geometrically saturated.
The tens "porous material" as used herein refers to materials that
comprise at least two phases a solid material and a gas or void phase and
optionally a third liquid phase that may be partially or completely filling
said
void spaces. The porosity of a material is defined as the ratio between the
void volume and the total volume of the material, measured when the material
is not filled with liquid. Nof~limiting examples for porous materials are
foams
such as polyurethane, H1PE (see for example PCT patent application
W094/13704), superabsorbent foams and the like, fiber assemblies such as
meltblown, spunbond, carded, cellulose webs, fiber beds and the like, porous
particles such as clay, zeolites, and the like, geometrically structured
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materials such as tubes, balloons, channel structures etc. Porous materials
might absorb liquids even if they are not hydrophilic. The porosity of the
materials is therefore not linked to their affinity for the liquid that might
be
absorbed.
The term "substantially geometrically saturated" as used herein refers to
a member in which at least 90% of the macroscopic void volume of the
member are geometrically saturated, preferably at least 95% of the
macroscopic void volume of the device are geometrically saturated, more
preferably 97% of the macroscopic void volume of the device are
geometrically saturated, most preferably 99% of the macroscopic void volume
of the device are geometrically saturated.
It is another aspect of the present invention to provide an absorbent
structure comprising a first region for acquisition/distribution of fluid and
a
second region for storage of fluid. The first region comprises at least one
member for acquiring and I or transporting liquid such those well known in the
art. The second region comprises a liquid handling member according to the
present invention.
Device for handlin4 body liguid
It is one aspect of the present invention to provide a device for handling
body liquids which comprises a liquid transport member according to the
present invention andlor an absorbent structure according to the present
invent;on: Such devices include but are not limited to disposable absorbent
articles such as baby diapers or training pants, adult incontinence products,
and feminine hygiene products and other body liquid handling articles such as
catheters, urinals, and the like.
In one embodiment of the present invention, the device for handling
body liquids is a disposable absorbent article such as a diaper, a training
pant, a sanitary napkin, an adult incontinence device, or the Eike that
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comprises the liquid handling member of the present invention. Such an
absorbent article may further comprise a liquid pervious topsheet, a liquid
impervibus backsheet at least partially peripherally joined to the topsheet.
The
absorbent article may further comprise a first liquid handling member which
may
serve as a acquisition and / or distribution member for the body liquid.
Topsheets,
backsheet, and absorbent cores suitable for the present invention are well
known
in the art. In addition, there are numerous additional features known in the
art
which can be used in combination with the absorbent article of the present
invention such as for example closure mechanisms to attach the absorbent
article
around the lower torso of the wearer.
METHODS
Unless stated otherwise, all tests are carried out at about 32°C
+/- 2°C
and at 35+/- 15% relative humidity.
Unless stated otherwise, the synthetic urine used in the test methods is
commonly known as Jayco SynUrineT"" and is available from Jayco
Pharmaceuticals Company of Camp Hill, Pennsylvania. The formula for the
synthetic urine is: 2.0 g/: of KCI; 2.0 g/I of Na2S04; 0.85 g/I of (NH4)H2P04;
0.15
g/I (NH4)H2P04; 0.19 g/I of CaCl2; and 0.23 g/I 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.
Capillary Sorption Test
Purpose
The purpose of this test is to measure the capillary sorption absorbent
capacity, as a function of height, of liquid handling members of the present
invention. This test may also be used to measure the capillary sorption
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absorbent capacity of devices for handling body liquids according to the
present invention. Capillary sorption is a fundamental property of any
absorbent that governs how liquid is absorbed intb the absorbent structure.
In the Capillary Sorption experiment, capillary sorption absorbent capacity is
measured as a function of fluid pressure due to the height of the sample
relative to the test fluid reservoir.
The method for determining capillary sorption is well recognized. See
Burgeni, A.A. and Kapur, C., "Capillary Sorption Equilibria in Fiber Masses,"
Textile Research Journal, 37 (1967), 356-366; Chatterjee, P.K., Absorbency,
Textile Science and Technology 7, Chapter 11, pp 29-84, Elsevier Science
Publishers B.V, 1985; and U.S. Patent No. 4,610,678, issued September 9,
1986 to Weisman et al. for a discussion of the method for measuring capillary
sorption of absorbent structures.
Principle
A porous glass frit is connected via an uninterrupted column of fluid to a
fluid reservoir on a balance. The sample is maintained under a constant
confining weight during the experiment. As the porous structure absorbs fluid
upon demand, the weight loss in the balance fluid reservoir is recorded as
fluid uptake, adjusted for uptake of the glass frit as a function of height
and
evaporation. The uptake or capacity at various capillary suctions (hydrostatic
tensions or heights) is measured. Incremental absorption occurs due to the
incremental lowering of the frit (i.e., decreasing capillary suction).
Time is also monitored during the experiment to enable calculation of
initial effective uptake rate (g/g/h) at a 200 cm height.
Reagents
Test Liquid: Synthetic urine is prepared by completely dissolving the
following materials in distilled water.
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Compound F.W. Concentration (g/L)
KCI 74.6 2.0
Na2S04 142 2.0
(NH4)H2P04 115 0.85
(NH4)2HP04 132 0.15
CaCl2 2H20 147 0.25
MgCl2 6H20 203 0.5
General Description of Apparatus Set U~p
The Capillary Sorption equipment, depicted generally as 520 in Figure 3,
used for this test is operated under TAPPI conditions (50% RH, 25°C). A
test
sample is placed on a glass frit shown in Figure 3 as 502 that is connected
via a
continuous column of test liquid (synthetic urine) to a balance liquid
reservoir,
shown as 506, containing test liquid. This reservoir 506 is placed on a
balance
507 that is interfaced with a computer (not shown). The balance should be
capable of reading to 0.001 g; such a balance is available from Mettler Toledo
as
PR1203 (Hightstown, NJ). The glass frit 502 is placed on a vertical slide,
shown
generally in Figure 3 as 501, to allow vertical movement of the test sample to
expose the test sample to varying suction heights. The vertical slide may be a
rodless actuator which is attached to a computer to record suction heights and
corresponding times for measuring liquid uptake by the test sample. A
preferred
rodless actuator is available from Industrial Devices (Novato, CA) as item
202X4X34N-1 D4B-84-P-C-S-E, which may be powered by motor drive ZETAT"~
6104-83-135, available from CompuMotor (Rohnert, CA). Where data is
measured and sent from actuator 501 and balance 507, capillary sorption
absorbent capacity data may be readily generated for each test sample. Also,
computer interface to actuator 501 may allow for controlled vertical movement
of
the glass frit 502. For example, the actuator may be directed to move the
glass
frit 502 vertically only after "equilibrium" (as defined below) is reached at
each
suction height.
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15
The bottom of glass frit 502 is connected to TygondT"" tubing 503 that
connects the frit 505 to three-way drain stopcock 509. Drain stopcock 509 is
connected to liquid reservoir 505 via glass tubing 504 and stopcock 510. (The
stopcock 509 is open to the drain only during cleaning of the apparatus or air
bubble removal.) Glass tubing 511 connects fluid reservoir 505 with balance
fluid
reservoir 506, via stopcock 510. Balance liquid reservoir 506 may consist of a
lightweight 12 cm diameter glass dish 506A and cover 506B. The cover 506B has
a hole through which glass tubing 511 contacts the liquid in the reservoir
506.
The glass tubing 511 must not contact the cover 506B or an unstable balance
reading will result and the test sample measurement cannot be used. In this
context, it is to be understood that the volume of the liquid reservoir needs
to be
compatible with the absorbent capacity of the liquid handing member or the
device to be tested. Hence, it may be necessary to choose a different liquid
reservoir.
The glass frit diameter must be sufficient to accommodate the
piston/cylinder apparatus, discussed below, for holding the test sample. The
glass fit 502 is jacketed to allow for a constant temperature control from a
heating
bath. A suitable frit is a 350 ml fritted disc funnel specified as having 4 to
5.5 mm
pores, available from Corning Glass Co. (Corning, NY) as #36060-350F. The
pores are fine enough to keep the frit surface wetted at capillary suction
heights
specified (the glass frit does not allow air to enter the continuous column of
test
liquid below the glass frit).
As indicated, the frit 502 is connected via tubing to fluid reservoir 505 or
balance liquid reservoir 506, depending on the position of three-way stopcock
510.
Glass frit 502 is jacketed to accept water from a constant temperature
bath. This will ensure that the temperature of the glass frit is kept at a
constant
temperature of 88°F (31 °C) during the testing procedure. As is
CA 02333760 2004-04-08
16
depicted in Figure 3, the glass frit 502 is equipped with an inlet port 502A
and
outlet port 502B, which make a closed loop with a circulating heat bath shown
generally as 508. (The glass jacketing is not depicted in Figure 3. However,
the
water introduced to the jacketed glass frit 502 from bath 508 does not contact
the
test liquid and the test liquid is not circulated through the constant
temperature
bath. The water in the constant temperature bath circulates through the
jacketed
walls of the glass frit 502.)
Reservoir 506 and balance 507 are enclosed in a box to minimize
evaporation of test liquid from the balance reservoir and to enhance balance
stability during pertormance of the experiment. This box, shown generally as
512,
has a top and walls, where the top has a hole through which tubing 511 is
inserted.
The glass frit 502 is shown in more detail in Figure 2B. Figure 2B is a
cross-sectional view of the glass fit, shown without inlet port 502A and
outlet port
502B. As indicated, the glass frit is a 350 ml fritted disc funnel having
specified 4
to 5.5 mm pores. Referring to Figure 2B, the glass frit 502 comprises a
cylindrical
jacketed funnel designated as 550 and a glass frit disc shown as 560. The
glass
frit 502 further comprises a cylinder/piston assembly shown generally as 565
(which comprises cylinder 566 and piston 568), which confines the test sample,
shown as 570, and provides a small confining pressure to the test sample. To
prevent excessive evaporation of test liquid from the glass frit disc 560, a
TefIonT"" ring shown as 562 is placed on top of the glass frit disc 560 The
Teflond
T"' ring 562 is 0.0127 cm thick (available as sheet stock from McMasterCarr as
#
8569K16 and is cut to size) and is used to cover the frit disc surface outside
of
the cylinder 566, and thus minimizes evaporation from the glass frit The ring
outer diameter and inner diameter is 7 6 and 6 3 cm, respectively The inner
diameter of the TefIonT"" ring 562 is about 2 mm less than the outer diameter
of
cylinder 566. A Viton~ O-ring (available from McMasterCarr as # AS568A-1 50
and AS568A-1 51) 564 is placed on top of TefIonT"" ring 562 to seal the space
between the inner
CA 02333760 2004-04-08
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wall of cylindrical jacketed funnel 550 and TefIonT"~ ring 562, to further
assist in
prevention of evaporation. If the O-ring outer diameter exceeds the inner
diameter of cylindrical jacketed funnel 550, the O-ring diameter is reduced to
fit
the funnel as follows: the O-ring is cut open, the necessary amount of O-ring
material is cut off, and the O-ring is glued back together such that the O-
ring
contacts the inner wall of the cylindrical jacketed funnel 550 all around its
periphery. While the above described frit represents one suitable example of
frit,
it may be necessary to use of frit having dimensions different from the above
dimensions in order to better fit the dimensions of the liquid handling member
or
the device to be tested. The surface area of the frit should resemble as
closely as
possible the surface area of the acquisition zone of the liquid handling
member or
the device in order to fully use the acquisition zone and in order to minimize
the
evaporation from the frit.
As indicated, a cylinder/piston assembly shown generally in Figure 28 as
565 confines the test sample and provides a small confining pressure to the
test
sample 570. Referring to Figure 2C, assembly 565 consists of a cylinder 566, a
cup-like TefIonOT"~ piston indicated by 568 and, when necessary, a weight or
weights (not shown) that fits inside piston 568. (Optional weight will be used
when necessary to adjust the combined weight of the piston and the optional
weight so a confining pressure of 0.2 psi is attained depending on the test
sample's dry diameter. This is discussed below.) The cylinder 566 is Lexan~TM
bar stock and has the following dimensions: an outer diameter of 7.0 cm, an
inner
diameter of 6.0 cm and a height of 6.0 cm. The TefIonCST"" piston 568 has the
following dimensions: an outer diameter that is 0.02 cm less than the inner
diameter of cylinder 566. As shown in Figure 2D, the end of the piston 568
that
does not contact the test sample is bored to provide a 5.0 cm diameter by
about
1.8 cm deep chamber 590 to receive optional weights (dictated by the test
sample's actual dry diameter) required to attain a test sample confining
pressure
of 0.2 psi (1.4 kPa). In other words, the total weight of the piston 568 and
any
optional weights (not shown in figures) divided by the test sample's actual
diameter
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18
(when dry) should be such that a conftning pressure of 0.2 psi is attained.
Cylinder 566 and piston 568 (and optional weights) are equilibrated at 31
°C
for at least 30 minutes prior to conducting the capillary sorption absorbent
capacity measurement. Again, the above described dimensions are chosen to
fit the above described exemplary frit. Of course, when a different frit is
chosen the dimensions of the cylindeNpiston assembly need to be adjusted
accordingly.
A non-surfactant treated or incorporated apertured film (14 cm x 14 cm)
(not shown) is used to cover the glass frit 502 during Capillary Sorption
experiments to minimize air destablization around the sample. Apertures are
large enough to prevent condensation from forming on the underside of the
film during the experiment.
Test Sample Preparation
For the present procedure, it is important, that the dimensions of the
sample and of the frit should not be too different. To achieve this, two
approaches can be taken:
a) For test samples, which can be readily adjusted to a suitable size,
such as by cutting these, both the size of this cutting as well as of
the frit are chosen to be a circular shaped structure of 5.4 cm
diameter, such as can be done by using a conventional arc punch.
b) When the test sample cannot readily be cut to this dimension, the
size and preferably also the shape of the frit has to be adjusted to
the size and shape of the test sample.
In both cases, the test sample can be a readily separable element of a
member or a device, it can be a particular component of any of these, or can
be a combination of components thereof. It might also be necessary to adjust
the size of the liquid reservoir to match the varying requirements.
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The dry weight of the test sample (used below to calculate capillary
sorption absorbent capacity) is the weight of the test sample prepared as
above under ambient conditions.
Experimental Set Up
1. Place a clean, dry glass frit 502 in a funnel holder attached to the
vertical slide 501. Move the funnel holder of the vertical slide such that
the glass frit is at the 0 cm height.
2. Set up the apparatus components as shown in Figure 3, as discussed
above.
3. Place 12 cm diameter balance liquid reservoir 506 on the balance 507.
Place plastic lid 5068 over this balance liquid reservoir 506 and a plastic
lid over the balance box 512 each with small holes to allow the glass
tubing 511 to fit through. Do not allow the glass tubing to touch the lid
5068 of the balance liquid reservoir or an unstable balance reading will
result and the measurement cannot be used.
4. Stopcock 510 is closed to tubing 504 and opened to glass tubing 511.
Fluid reservoir 505, previously filled with test fluid, is opened to allow
test fluid to enter tubing 511, to fill balance fluid reservoir 506.
5. The glass frit 502 is leveled and secured in place. Also, ensure that the
glass frit is dry.
6. Attach the Tygond tubing 503 to stopcock 509. (The tubing should be
long enough to reach the glass frit 502 at its highest point of 200 cm with
no kinks.) Fill this Tygond tubing with test liquid from liquid reservoir
505:
7. Attach the Tygond tubing 503 to the level glass frit 502 and then open
stopcock 509 and stopcock 510 leading from fluid reservoir 505 to the
glass frit 502. (Stopcock 510 should be closed to glass tubing 511.)
The test liquid fills the glass frit 502 and removes all trapped air during
filling of the level glass frit. Continue to fill until the fluid level
exceeds
the top of the glass frit disc 560. Empty the funnel and remove ail air
bubbles in the tubing and inside the funnel. Air bubbles may be
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removed by inverting glass frit 502 and allowing air bubbles to rise and
escape through the drain of stopcock 509. (Air bubbles typically collect
on the bottom of the glass frit disc 560.) Relevel the frit using a small
enough level that it will fit inside the jacketed funnel 550 and onto the
surface of glass frit disc 560.
8. Zero the glass frit with the balance liquid reservoir 506. To do this, take
a piece of Tygonb tubing of sufficient length and fill it with the test
liquid.
Place one end in the balance liquid reservoir 506 and use the other end
to position the glass frit 502. The test liquid level indicated by the tubing
(which is equivalent to the balance liquid reservoir level) is 10 mm below
the top of the glass frit disc 560. If this is not the case, either adjust the
amount of liquid in the reservoir or reset the zero position on the vertical
slide 501.
9._ Attach the outlet and inlet ports from the temperature bath 508 via
tubing to the inlet and outlet ports 502A and 502B, respectively, of the
glass frit. Allow the temperature of the glass frit disc 560 to come to
31°C. This can be measured by partially filling the glass frit with
test
liquid and measuring its temperature after it has reached equilibrium
temperature. The bath will need to be set a bit higher than 31 °C to
allow
for the dissipation of heat during the travel of water from the bath to the
glass frit.
10. The glass frit is equilibrated for 30 minutes.
Ca~illarv Somtion Parameters
The following describes a computer program that will determine how
long the glass frit remains at each height.
In the capillary sorption software program, a test sample is at some
specified height from the reservoir of fluid. As indicated above, the fluid
reservoir is on a balance, such that a computer can read the balance at the
end of a known time interval and calculate the flow rate (Delta reading/time
interval) between the test sample and reservoir. For purposes of this method,
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the test sample is considered to be at equilibrium when the flow rate is less
than a specified flow rate for a specified number of consecutive time
intervals.
It is recognized, that for certain material, actual equilibrium may not be
reached when the specified "EQUILIBRIUM CONSTANT' is reached. The
time interval between readings is 5 seconds.
The number of readings in the delta table is specked in the capillary
sorption menu as "EQUILIBRIUM SAMPLES". The maximum number of
deltas is 500. The flow rate constant is specified in the capillary sorption
menu as "EQUILIBRIUM CONSTANT'.
The Equilibrium Constant is entered in units of grams/sec, ranging from
0.0001 to 100.000.
The following is a simplified example of the logic. The table shows the
balance reading and Delta Flow calculated for each Time Interval.
Equilibrium Samples = 3
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Equilibrium Constant = 0.0015
22
Time Balance Delta
IntervalValue Flow
(g) (glsec)
0 0
1 0.090 0.0180
2 0.165 0.0150
3 0.225 0.0120
4 0.270 0.0090
5 0.295 0.0050
6 0.305 0.0020
7 0.312 0.0014
8 0.316 0.0008
9 0.318 0.0004
Delta Table:
Time 0 1 2 3 4 5 6 7 8 g
Deltal99990.01800.01800.01800.00900.00900.00900.00140.00140.0014
Delta299999999 0.01500.01500.01500.00500.00500.00500.00080.0008
Delta399999999 9999 0.01200.01200.01200.00200.00200.00200.0004
The equilibrium uptake for the above simplified example is 0.318 gram.
The following is the code in C language used to determine equilibrium
uptake:
takedata. c 'I
int take data(int equil samples,double equilib~um constant)
double delta;
static double deltas[500]; I' table to store up to 500 deltas'I
double value;
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double prev_value;
clock t next time;
int i;
23
for (i=0; i<equif_samples; i++)
deltas[iJ = 9999.; I' initialize all values in the delta table to 9999.
gms/sec 'I
delta table index = 0; /' initialize where in the table to store the next
delta 'I
equilibrium reached = 0; /' initialize flag to indicate equilibrium has not
been
reached 'I
next time = clockQ; I' initialize when to take the next reading 'I
prev_reading = 0.; r initialize the value of the previous reading from the
balance
./
while (!equilibrium reached) { r start of loop for checking for equilibrium '/
next_time +_ 50001; I' calculate when to take next reading 'I
while (dock() < next_time); I* wait until 5 seconds has elasped from prey
reading'/
value = get balance_reading(); I' read the balance in grams 'I
delta = fabs(prev_value - value) I 5.0; l' calculate absolute value of flow in
last 5 seconds
./
prey value = value; r store current value for next loop '/
deltas[delta table index) = delta; P store current delta value in the table of
deltas '!
delta table index++; r increment pointer to next position in table '/
if (delta table index == equil samples) /' when the number of deltas = the
number of '/
delta table index = 0; r equilibrium samples specified, !'
/' reset the pointer to the start of the table. This way '/
P the table always contains the last xx current samples. 'I
equilibrium reached =1; r set the flag to indicate equilibrium is reached '/
for (i--0; i < equil samples; i++) I' check all the values in the delta table
'I
if (deltas[iJ >= equilibrium constant)/' if any value is > or = to the
equilibrium constant'I
equilibrium reached = 0; r set the equlibrium flag to 0 (not at equilibrium)
'I
} r go back to the start of the loop '/
Caoillary So~r~tion Parameters
Load Description (Confining Pressure): 0.2 psi load
Equilibrium Samples (n): 50
Equilibrium Constant: 0.0005 g/sec
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Setup Height Value: 100 cm
Finish Height Value: 0 cm
24
Hydrostatic Head Parameters: 200, 180, 160, 140, 120, 100, 90, 80, 70, 60,
50, 45, 40, 35, 30, 25, 20, 15, 10, 5 and 0 cm.
The capillary sorption procedure is conducted using all the heights
specified above, in the order stated, for the measurement of capillary
sorption
absorbent capacity. Even if it is desired to determine caoillarv sor~tinr,
absorbent capacity at a particular height (e.g., 35 cm), the entire series of
hydrostatic head parameters must be completed in the order specified.
Although all these heights are used in performance of the capillary sorption
test to generate capillary sorption isotherms for a test sample, the present
disclosure describes the storage absorbent members in terms of their
absorbent properties at specified heights of 200, 140, 100, 50, 35 and 0 cm.
Ca~illarv Somtion Procedure
1) Follow the experimental setup procedure.
2) Make sure the temperature bath 508 is on and water is circulating through
the glass frit 502 and that the glass frit disc 560 temperature is
31°C.
3) Position glass frit 502 at 200 cm suction height. Open stopcocks 509 and
510 to connect glass frit 502 with the balance liquid reservoir 506.
(Stopcock 510 is closed to liquid reservoir 505.) Glass frit 502 is
equilibrated for 30 minutes.
4) Input the above capillary sorption parameters into the computer.
5) Close stopcocks 509 and 510.
6} Move glass frit 502 to the set up height, 100 cm.
7) Place Teflon~ ring 562 on surface of glass frit disc 560. Put O-ring 564
on Teflon~ ring. Place pre-heated cylinder 566 concentrically on the
Teflon~ ring. Place test sample 570 concentrically in cylinder 566 on
glass fit disc 560. Place piston 568 into cylinder 566. Additional
confining weights are placed into piston chamber 590, if required.
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8) Cover the glass frit 502 with apertured film.
9) The balance reading at this point establishes the zero-or tare reading.
10) Move the glass frit 502 to 200 cm.
11 ) Open stopcocks 509 and 510 (stopcock 510 is closed to fluid reservoir
505) and begin balance and time readings.
Glass Frit Correction (blank correct u~takel
Since the glass frit disc 560 is a porous structure, the glass frit (502)
capillary sorption absorption uptake (blank correct uptake) must be
determined and subtracted to get the true test sample capillary sorption
absorption uptake. The glass frit correction is performed for each new glass
frit used. Run the capillary sorption procedure as described above, except
without test sample, to obtain the Blank Uptake (g). The elapsed time at each
specified height equals the Blank Time (s).
Evaporation Loss Correction
1 ) Move the glass frit 502 to 2 cm above zero and let it equilibrate at this
height for 30 minutes with open stopcocks 509 and 510 (closed to
reservoir 505).
2) Close stopcocks 509 and 510.
3) Place Tefion~ ring 562 on surface of glass frit disc 560. Put O-ring 564
on Teflon~ ring. Place pre-heated cylinder 566 concentrically on the
Teflon~ ring. Place piston 568 into cylinder 566. Place apertured film on
glass frit 502.
4) Open stopcocks 509 and 510 (closed to reservoir 505) and record
balance reading and time for 3.5 hours. Calculate Sample Evaporation
(g/hr) as follows:
[balance reading at 1 hr - balance reading at 3.5 hr) / 2.5 hr.
Even after taking al! the above precautions, some evaporative loss will
occur, typically around 0.10 gmlhr for both the test sample and the frit
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26
correction. Ideally, the sample evaporation is measured for each newly
installed glass frit 502.
Cleanin4 the E4uipment
New Tygond tubing 503 is used when a glass frit 502 is newly installed.
Glass tubing 504 and 511, fluid reservoir 505, and balance liquid reservoir
506 are cleaned with 50% Clorox Bleach~ in distilled water, followed by
distilled water rinse, if microbial contamination is visible.
a. Cleaning after each experiment
At the end of each experiment (after the test sample has been
removed), the glass frit is forward flushed (i.e., test liquid is introduced
into
the bottom of the glass frit) with 250 ml test liquid from liquid reservoir
505 to
remove residual test sample from the glass frit disc pores. With stopcocks
509 and 510 open to liquid reservoir 505 and closed to balance liquid
reservoir 506, the glass frit is removed from its holder, turned upside down
and is rinsed out first with test liquid, followed by rinses with acetone and
test
liquid (synthetic urine). During rinsing, the glass frit must be tilted upside
down and rinse fluid is squirted onto the test sample contacting surface of
the
glass frit disc. After rinsing, the glass frit is forward flushed a second
time
with 250 ml test liquid (synthetic urine). Finally, the glass frit is
reinstalled in
its holder and the frit surface is leveled.
b. Monitoring 4iass frit performance
Glass frit performance must be monitored after each cleaning procedure
and for each newly installed glass frit, with the glass frit set up at 0 cm
position. 50 ml of test liquid are poured onto the leveled glass frit disc
surface
(without Teflon~ ring, O-ring and the cylinderlpiston components). The time it
takes for the test fluid level to drop to 5 mm above the glass frit disc
surface is
recorded. A periodic cleaning must be performed if this time exceeds 4.5
minutes.
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c. Periodic cleaning
Periodically, (see monitoring frit performance, above) the glass frits are
cleaned thoroughly to prevent clogging. Rinsing fluids are distilled water,
acetone, 50% Clorox Bleach~ in distilled water (to remove bacterial growth)
and test liquid. Cleaning involves removing the glass frit from the holder and
disconnecting all tubing. The glass frit is forward flushed (i.e., rinse
liquid is
introduced into the bottom of the glass frit) with the frit upside down with
the
appropriate fluids and amounts in the following order:
1. 250 ml distilled water.
2. 100 ml acetone.
3. 250 ml distilled water.
4. 100 ml 50:50 Clorox~/distilled water solution.
5. 250 ml distilled water.
6. 250 ml test fluid.
The cleaning procedure is satisfactory when glass frit performance is
within the set criteria of fluid flow (see above) and when no residue is
observable on the glass frit disc surface. If cleaning can not be performed
successfully, the frit must be replaced.
Calculations
The computer is set up to provide a report consisting of the capillary
suction height in cm, time, and the uptake in grams at each specified height.
From this data, the capillary suction absorbent capacity, which is corrected
for
both the frit uptake and the evaporation loss, can be calculated. Also, based
on the capillary suction absorbent capacity at 0 cm, the capillary absorption
efficiency can be calculated at the specified heights. In addition, the
initial
effective uptake rate at 200 cm is calculated.
Blank Correct Uptake
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Blank Time(s)~ Blank Evap.(g / hr)
Blank Correct Uptake (g) = Blank Uptake(g) - 3600(s / hr)
Capillary Suction Absorbent Capacity ("CSAC")
~ - ~ T>rr>r (s) * Sa~ie F~ap' (g/ lr) - Haic Caiad L~ake(g)
= 3600s/tr
Initial Effective Uptake Rate at 200 cm ("IEUR")
IEUR (g/g/hr) - CSAC at 200 cm (g/g)
Sample Time at 200 cm (s}
Reporting
A minimum of two measurements should be taken for each sample and
the uptake averaged at each height to calculate Capillary Sorption Absorbent
Capacity (CSAC) for a given absorbent member or a given high surface area
material.
With these data, the respective values can be calculated:
- The Capillary Sorption Desorption Height at which the material has
released x% of its capacity at 0 cm (i.e. of CSAC 0), (CSDH x)
expressed in cm;
- The Capillary Sorption Absorption Height at which the material has
absorbed y % of its capacity at 0 cm (i.e. of CSAC 0), (CSAH y)
expressed in cm;
- The Capillary Sorption Absorbent Capacity at a certain height z
(CSAC z) expressed in units of g {of fluid} / g { of material};
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especially at the height zero (CSAC 0), and at heights of 35cm,
40cm, etc
- The Capillary Sorption Absorption Efficiency at a certain height z
(CSAE z) expressed in %, which is the ratio of the values for CSAC
0 and CSAC z.
If two materials are combined (such as the first being used as
acquisition / distribution material, and the second being used as liquid
storage
material), the CSAC value (and hence the respective CSAE value) of the
second material can be determined for the CSDH x value of the first material .
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 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 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 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
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30
basket may be brought into contact with the surface of the liquid in the
liquid
reservoir. The liquid reservoir is placed on the electronic-balance connected
to a computer to read out the weight of the liquid about every 0.01 sec 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 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.
Before the test, the liquid reservoir is filled with synthetic urine. The
amount 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 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 signficant dependence of its absorbent properties on
temperature.
The test is setup by lowering the empty basket until the mesh is just
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. If necessary, the mesh needs to be brought back into contact with
the liquid and zero level be readjusted.
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3I
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
provide a pressure of 165 Pa for better cantact of the member to the
mesh.
During the test, the liquid uptake by the liquid handing member is
recorded by measuring the weight decrease of the liquid in the liquid
reservoir. The test is stopped after 30 minutes.
At the end of the test, the total liquid uptake of the liquid handling
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 the weight vs. time measurement curve.
Saturated Liauid Permeability Test
In order to measure the saturated liquid permeability, the liquid
permeability test as described below is executed with the test sample being at
100% saturation. Saturation in this context is defined as the test sample
having absorbed 100% of its capacity that it has in the demand absorbency
test.
Generally, the test can be carried out with a suitable test fluid
representing the transport fluid, such as with Jayco SynUrine as available
from Jayco Pharmaceuticals Company of Camp Hill, Pennsylvania, and can
be operated-under controlled laboratory conditions of about 23 +/ 2°C
and at
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32
50 +/-10% relative humidity. However, when using polymeric foam materials,
such as disclosed in US-A-5.563.179 or US-A-5.387.207, it has been found
more useful to operate the test at an elevated temperature of 31 °C,
and by
using de-ionized water as test fluid.
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/~) * (OP/L)
where:
Q= Volumetric Flow Rate [cm3ls];
A= Cross Sectional Area [cm2];
k= Permeability (cm2 ) (with 1 Darcy corresponding to 9.869* 10''3 m2);
rl= Viscosity (Poise) [Pa*s];
OP/I_= Pressure Gradient [Palm];
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 the volumetric flow rate through the sample:
k= (Q/A) * (L/eP) * ~
The test can be executed in two modifications, 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 transplanar pem~eability test can be see in Figure
1 which is a schematic diagram of the overall equipment and - as an insert
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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 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 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 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, 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 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 at any pressure head
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34
up to 80 cm water (about 7.8 kPa), which can be adjusted 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 liquid 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 2/97, and modified according to the present description. 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 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 1/16" (about 0.159
cm) should be available to cover the range from 1/16" -1/2" (about 0.159 cm
to about 1.27 cm) thickness.
Further a pressurized air supply is required, of at least 60 psi (4.1 bar),
to operate the respective valves.
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 members of the
present invention are required, wherein the test as outlined below is run at
the
lowest and highest pressure. The number of members is then adjusted so as
to maintain the flow rate during the test between 0.5 cm'/seconds at the
lowest pressure drop and 15 cm'Isecond at the highest pressure drop. The
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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.
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}.
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 l.4kPa) on
the sample (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 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
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can also be assessed in this preparatory test, with monitoring of the
respective 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, 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.
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 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 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 is started on the computerized unit (19190).
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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 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).
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 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 and/or graphical form).
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.
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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 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 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 Corrected Pressure is the DP that should be used in the pemneability
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.
Three measurements should be taken for each sample at each head
and the resutts 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.
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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 ZA
and 2B 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 2 is denoted (20210), correlating to the numeral (19110) of Figure 1,
and so on. Thus, the transplanar simplified sample cell (19120) of Figure 1 is
replaced by the in-plane 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 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 (20120) in the above transplanar
test, except that the filling tube is directed to the inlet connection (20232)
the
bottom of the cell (20220). Figure 2A shows a partly exploded view of the
sample cell, and Figure 2B 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 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
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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 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 (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 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
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.
