Note: Descriptions are shown in the official language in which they were submitted.
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WO 00/00142 PCTNS99/14649
ABSORBENT ARTICLE EXHIBITING HIG SUSTAINED ACQUISITION
RATES
FIELD OF THE INVENTION
The present invention relates to absorbent articles for handling urine such
as diapers, training pants, adult incontinence absorbent articles, bed mats,
and
the like. In particular, the present invention relates to those absorbent
articles
which store urine by means of either capillary or osmotic pressure.
BACKGROUND
Absorbent articles such as diapers, training pants, adult incontinence
absorbent articles, bed mats, and the like are well known in the art and are
frequently used for example for babies, toddlers, incontinent persons, and bed-
ridden persons.
For many of the intended use conditions, it is desirable for these absorbent
articles to exhibit sustained high acquisition rates. For example, in the
field of
baby diapers it is desired to acquire the discharged urine at a high rate,
most
preferably with the speed the urine is discharged from the body. This high
absorption rate guarantees that all of the discharged urine is actually
acquired
into the absorbent article. Otherwise, urine which is not readily acquired may
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2
move on the surface of the absorbent article and on the skin leading to
prolonged
skin contact with urine. In addition, urine not acquired by the absorbent
article
may run off and result in leakage from the absorbent article.
There are certain usage conditions which require a particularly good
acquisition performance of the absorbent article. Frequently, urine is
discharged
from the body in a direction which is different from the direction of gravity.
When
such urine comes into contact with an absorbent article, the absorbent article
is
required to acquire that urine against gravity. For example, when the user of
the
absorbent article lies on his back the direction of urine discharge is
anywhere
between hori2ontal and upwards. Hence, urine which is not immediately acquired
into the absorbent article will either drip off from the absorbent article or
run down
the absorbent article and cause the above problems.
Apparently, the higher the rate of urine acquisition by the absorbent article
is the less urine may run off from the topsheet of the absorbent article. More
preferably, the liquid acquisition rate of the absorbent article is at least
at the 50
percentile of urination speed of the intended uses of the absorbent article.
Most
preferably, the liquid acquisition rate is at least at the 95 percentile of
the
intended uses of the absorbent article.
In addition, it is desirable for such absorbent articles to exhibit such high
liquid absorption rates even for a plurality of subsequent gushes. For
example, in
the field of baby diapers the typical usage time span on average covers about
four liquid gushes. Of course, it is then desired that the absorbent article
also
absorbs the fourth gush at a sufficiently high rate.
It is further important that the liquid is acquired by the absorbent article
and
held with sufficient force to not run out of the absorbent article again. This
means
that the absorbent article must be able to intermediately store the acquired
liquid
in case it is not directly absorbed by the ultimate storage material.
CA 02334158 2004-06-03
3
In the prior art, many of the absorbent articles have not being able to
provide sufficiently high absorption rates, and in particular have not been
able
to provide to absorption rates in the range of urine discharge ranges of the
body. Hence, the discharged urine either stayed on the topsheet of the
absorbent article thereby causing prolonged skin contact with the liquid or
was
running off the topsheet of the absorbent article thereby resulting in
leakage.
Hence, it is an object of an aspect of the present invention to provide
an absorbent article which overcomes the problems posed by the prior art
absorbent articles.
It is a further object of an aspect of the present invention to provide the
absorbent article which exhibits a low liquid drip off in the first gush and
preferably also in the fourth gush.
It is a further object of an aspect of the present invention to provide an
absorbent article which exhibits sustained high absorption rates in the first
gush and preferably also in subsequent gushes up to the fourth gush.
SUMMARY OF THE INVENTION
The present invention provides an absorbent structure comprising a first
member for liquid acquisition and liquid distribution and a second member for
ultimate storage of the acquired liquid. The absorbent structure of the
present
invention article has a liquid drip off ratio of less than 50 percent in the
fourth
gush of 75 ml at l5ml/s according to the liquid drip off test defined herein.
Alternatively, the absorbent structure of the present invention has a liquid
drip
off ratio of less than 4 percent in the first gush of 75 ml at 15m1/s
according to
the liquid drip off test defined herein. Alternatively, the absorbent
structure has
a liquid drip off ratio of less than 60 percent in the third gush of 110 ml at
22m1/s according to the liquid drip off test defined herein. Alternatively,
the
absorbent structure has a liquid drip off ratio of less than 4 percent in the
first
gush of 110 ml at 22 ml/s according to the liquid drip off test defined
herein.
CA 02334158 2004-06-03
4
The present invention further provides an absorbent article comprising
an absorbent structure according to the present invention.
In accordance with one embodiment of the present invention, there is
provided an absorbent structure comprising a first member for liquid
acquisition and liquid distribution, and a second member for ultimate storage
of acquired liquid, wherein the absorbent structure has a liquid drip off
ratio of
less than 50 percent in a fourth gush of 75 ml at 15 ml/s.
In accordance with another embodiment of the present invention, there
is provided an absorbent structure comprising a first member for liquid
acquisition and liquid distribution, and a second member for ultimate storage
of acquired liquid wherein the absorbent structure has a liquid drip off ratio
of
less than 4 percent in a first gush of 75 ml at 15 ml/s.
In accordance with a further embodiment of the present invention,
there is provided an absorbent structure comprising a first member for liquid
acquisition and liquid distribution, and a second member for ultimate storage
of acquired liquid wherein the absorbent structure has a liquid drip off ratio
of
less than 60 percent in a third gush of 110 ml at 22 ml/s.
In accordance with a further embodiment of the present invention,
there is provided an absorbent structure comprising a first member for liquid
acquisition and liquid distribution, and a second member for ultimate storage
of acquired liquid wherein the absorbent structure has a liquid drip off ratio
of
less than 4 percent in a first gush of 110 ml at 22 ml/s.
In accordance with a further embodiment of the present invention,
there is provided an absorbent article comprising an absorbent structure
comprising a first member for liquid acquisition and liquid distribution, a
second member for ultimate storage of acquired liquid, wherein the absorbent
structure has an acquisition rate of a first gush of at least 5 ml/s.
CA 02334158 2004-06-03
4a
In accordance with a further embodiment of the present invention,
there is provided an absorbent article comprising an absorbent structure
comprising a first member for liquid acquisition and liquid distribution, a
second member for ultimate storage of acquired liquid, wherein the absorbent
structure has an acquisition rate of a fourth gush of at least 2 mils.
In accordance with a further embodiment of the present invention,
there is provided an absorbent article comprising an absorbent structure
comprising a first member for liquid acquisition and liquid distribution, a
second member for ultimate storage of acquired liquid, wherein the absorbent
article is a disposable absorbent article.
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 andlor 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 absorbent structure to be used in
absorbent articles such as for example baby diapers, training pants, adult
incontinence absorbent articles, bed mats, and the like. The present invention
further provides the respective absorbent articles.
The term "handling urine" includes but is not limited to acquiring,
distributing, and storing urine.
' CA 02334158 2004-06-03
4b
The present invention provides an absorbent structure comprises a first
member for liquid acquisition and liquid distribution and a second member for
ultimate storage of the acquired liquid. In some embodiments, a unitary
member may serve a first member and as a second member in the absorbent
structure of the present invention.
The absorbent structure of the present invention is able to acquire
urine against gravity. Under many in use conditions, the direction of gravity
is
CA 02334158 2000-12-04
WO 00/00142 PCT/US99/14649
substantially different from being perpendicular to the surface of the
absorbent
structure through which urine is to be acquired into the absorbent structure.
In
other words, the urine is pulled away from the direction of optimum liquid
acquisition into the absorbent structure by the gravitational forces. To
readily
5 acquire urine under in-use conditions, the absorbent structure must not
solely
relying on gravitational forces for liquid acquisition. Preferably, the
absorbent
structure of the present invention is able to acquire urine against gravity at
least
at the average rate with which urine is discharged from the body of the
intended
user. More preferably, the absorbent structure of the present invention is
able to
acquire urine against gravity at least at the 95 percentile of the urine
discharge
rate of the intended user.
The term "urine discharge rate" as used herein refers to the rate at which
urine is discharged from the respective urethra of the wearer. The urine
discharged rate varies substantially for the different usage contexts. For
example
in the baby diaper context, it is known that urine is discharged from the
toddler's
urethra on average at a rate of up to 15 milliliters per second. The 95
percentile
of the toddler's urine discharge rate is 22 milliliters per second. It is
further known
that urination rates of up to ~40m1/s can be found at adult incontinent
persons.
For the purposes of the present invention, the ability to acquire urine
against gravity is quantified by the liquid drip off test defined hereinafter.
The
liquid drip off value in the first gush is representative of the overall
liquid drip off
performance of the absorbent structure, where as the liquid drip off value in
the
further gushes is representative of sustained low drip off perfomlance even
for
subsequent gushes. The absorbent structure according to the present invention
has a liquid drip off value in the first gush of 75m1 at 15m1/s of less than 4
percent, preferably a liquid drip off value in the first gush of less than 3
percent,
more preferably a liquid runoff value in the first gush of less than 2
percent, most
preferably a liquid drip off value of less than 1 percent. Optionally, the
absorbent
structure of the present invention has a liquid drip off value in the second
gush of
75m1 at 15m1/s of less than 20 percent, preferably of less than 15 percent,
more
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6
preferably of less than 10 percent, most preferably of less than 5 percent.
Optionally, the absorbent structure of the present invention has a liquid drip
off
value in the third gush of 7 5ml at 15m1/s of less than 40 percent, preferably
of
less than 20 percent, more preferably of less than 10 percent, most preferably
of
less than 5 percent. Optionally, the absorbent structure of the present
invention
has a liquid drip off value in the fourth gush of 75m1 at 15m1/s of less than
50
percent, preferably of less than 25 percent, more preferably of less than 10
percent, most preferably of less than 5 percent. Optionally, the absorbent
structure according to the present invention has a liquid drip off value in
the first
gush of 110m1 at 22m1/s of less than 4 percent, preferably a liquid drip off
value
in the first gush of less than 3 percent, more preferably a liquid runoff
value in the
first gush of less than 2 percent, most preferably a liquid drip off value of
less
than 1 percent. Optionally, the absorbent structure of the present invention
has a
liquid drip off value in the second gush of 110m1 at 22mlls of less than 20
percent, preferably of less than 15 percent, more preferably of less than 10
percent, most preferably of less than 5 percent. Optionally, the absorbent
structure of the present invention has a liquid drip off value in the third
gush of
110m1 at 22mlls of less than 40 percent, preferably of less than 20 percent,
more
preferably of less than 10 percent, most preferably of less than 5 percent.
Optionally, the absorbent structure of the present invention has a liquid drip
off
value in the fourth gush of 110m1 at 22m1/s of less than 60 percent,
preferably of
less than 30 percent, more preferably of less than 15 percent, most preferably
of
less than 5 percent.
Conventional absorbent structures such as those used in conventional
absorbent articles have been found to exhibit much higher liquid drip off
value for
all above gushes numbers, all above gush sizes, and all above gush rates.
The absorbent article of the present invention exhibits a high acquisition
rate. In particular, the absorbent article exhibits a high sustained
acquisition rate,
i.e. the high acquisition rate even for a plurality of subsequent gushes. High
absorption rates are desired for manifold reasons. Fast acquisition of the
liquid
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7
into the absorbent article ensures a short skin contact time with the urine.
Prolonged skin contact with liquids such as urine may result in overhydrated
skin
and even in dermatitis. Furthermore, urine that is not readily acquired into
the
absorbent article may run off of the surface of the absorbent article and may
in
turn cause leakage of the urine.
For the purposes of the present invention, the liquid acquisition rates of the
absorbent article of the present invention are quantified by the curved
acquisition
test disclosed hereinafter. The absorbent article according to the present
invention has a liquid acquisition rate in the first gush of at least 5
milliliters per
second, preferably a liquid acquisition rates in the first gush of at least 10
milliliters per second, more preferably a liquid acquisition rate and the
first gush
of at least 15 milliliters per second, most preferably a liquid acquisition
rate in the
first gush of at least 22 milliliters per second. Alternatively the absorbent
article
according to the present invention has a liquid acquisition rate in the fourth
gush
of at least 2 milliliters per second, preferably a liquid acquisition rate in
the fourth
gush of at least 5 milliliters per second, more preferably a liquid
acquisition rate
in the fourth gush of at least 10 milliliters per second, most preferably a
liquid
acquisition rate in the fourth gush of at least 15 milliliters per second.
The absorbent article .according to the present invention has a z-direction.
The term "z - direction" as used herein refers to the direction which is
perpendicular to the surface of the absorbent article in the vicinity of the
intended
loading point. The z - direction is also referred to as the caliper of the
absorbent
article. It is desirable for the absorbent article according the present
invention to
have a loading point z - direction which is as small as possible in order to
not
exhibit high bulk between the legs of the wearer.
Preferably, the absorbent article according to the present invention has a
loading point z - direction of less than 30 mm, more preferably of less than
20
mm, most preferably of less than 15 mm.
CA 02334158 2005-O1-13
8
The absorbent article according to the present invention has a y - direction.
The term " y - direction" as used herein refers to the direction which is
tensioned
to the surface of the absorbent article in the vicinity of the loading point
and
which is perpendicular to the longitudinal dimension of the absorbent article.
It is
desirable for the absorbent article according to the present invention to have
a
loading point y - direction which is as small as possible in order to not
exhibit
high above it necks of the wearer.
Preferably, the absorbent article according to the present invention has a
loading point y - direction of less than 100 milliliters, more preferably of
less than
80 milliliters, most preferably of less than 60 mm.
It is another aspect of the present invention to provide an absorbent
structure and the respective absorbent article which comprise absorbent
gelling
material, also known as superabsorbent material. Suitable examples of suitable
superabsorbent polymers, often also referred to as "hydrogel forming polymer"
or
"absorbent gelling material", are described in U.S. Patent 5,562,646 (Goldman
et al.), issued Oct. 8, 1996 and U.S. Patent 5,599,335 (Goldman et al.),
issued
Feb. 4, 1997.
It is another aspect of the present invention to provide a liquid handling
member to be used as a first member in the absorbent structure of the present
invention.
In the following, a suitable embodiment of the liquid handling member will
be described. The liquid handling member is assembled from an open celled
foam material which is completely enveloped by a membrane. A suitable
membrane material is available from SEFAR of Ruschlikon, Switzerland, under
the designation SEFART"" 03-20/13. A suitable foam material is available from
Recticel of Brussels, Belgium, under the designation BulprenT"" S10 black. A
suitable technique to completely envelope the foam material with the membrane
CA 02334158 2000-12-04
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9
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
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.
The particular geometry of the liquid handling member of the present
invention can be varied to 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 speck needs of
the intended application. In this context, it has to be understood , however,
that
the design of the outer fom~ of the liquid handling member may have an impact
on its performance. For example, the cross section of the liquid handling
member
directly impacts on its flow rate.
For application of the liquid handling member in an absorbent article
according to the present invention, the liquid handling member may be combined
with a storage member. The term "liquid storage member" refers to an absorbent
article which is capable of acquiring and storing liquid. The volume of the
liquid
storage member may vary with the amount of stored liquid such as by swelling.
Typically, the storage member will imbibe the liquid by means of capillary
suction
CA 02334158 2005-O1-13
andlor osmotic pressure. Other storage members may also use vacuum as a
means to~ store the liquid. The liquid storage member is further capable of
holding
at least a portion of the stored liquid under pressure. Suitable storage
members
are well known in the . art and may comprise for example a super absorbent
5 polymeric material such as polyacrylate. The storage member may further
comprise a fibrous structure, such as a pad of cellulosic fibers, in which the
particulate superabsorbent material is dispersed. In order to pick up the
liquid
discharged from the liquid handling member, the storage member may be placed
in direct liquid communication with the intended liquid discharge zone of the
10 liquid handling member. A suitable storage member is for example a
superabsorbent polymer such as available from CHEMDAL, United Kingdom,
under the designation ASAP400T""
Further examples of suitable superabsorbent polymers, often also referred
to as "hydrogel forming polymer".or "absorbent gelling material", are
described in
U.S. Patent 5,562,646 (Goldman et al.), issued Oct. 8, 1996 and U.S. Patent
5,599,335 (Goldman et al.), issued Feb. 4, 1997.
Other liquid handling members suitable far the purposes of the present
invention are described for example in the PCT patent application No.
PCT/US98I13497 entitled °Liquid transport member for high flux rates
between
two port regions" filed in the name of Ehmsperger et al. filed on June 29,
1998,
and in the following PCT patent applications co-filed with the present
application
entitled "High flux liquid transport members comprising two different
permeability
regions" PCT Application WO 00/00146 filed in the name of Ehmsperger et al., ,
"Liquid transport member for high flux rates between two port regions" PCT
Application WO 00/00143 filed in the name of Ehmsperger et ai., "Liquid
transport .
member for high flux rates against gravity" PCT Application WO 00100138 filed
in
the name of Ehrnsperger et al., uLiquid transport member having high
permeability
.30 bulk regions and high bubble point pressure port regions" PCT Application
WO
00/00136 filed in the name of Ehrnsperger et al.
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11
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. 'T'he 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 term "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.
Non-limiting examples for porous materials are foams such as polyurethane,
HIPE (see for example PGT 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 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
CA 02334158 2005-O1-13
12
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.
In one embodiment of the present invention, the absorbent article is a
disposable absorbent article such as a diaper; a training pant, a sanitary
napkin,
an adult incontinence absorbent article, or the like. Such an absorbent
article
may further comprise a liquid pervious topsheet, a liquid impervious backsheet
at
least partially peripherally joined to the topsheet. The absorbent article may
further comprise an absorbent core which may serve as a storage member for
the urine. Topsheets, backsheet, and absorbent cores suitable for the present
invention are welt 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.
Unless stated otherwise, all tests are carried out at about 32°C +I-
2°C and at
35+I-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 gl: of KCI; 2.0 gll of Na2S04; 0.85 gll of (NH4)H2P04;
0.15
gll (NH4)H2P04; 0.19 gll of CaCl2; ad 0.23 g/l of MgCl2. All of the chemicals
are
CA 02334158 2005-O1-13
13
of reagent grade. The pH of the synthetic Urine is in the range of 6.0 to 6.4.
The liquid drip off test aims at simulating the dispension of urine onto a
absorbent article for managing urine when the wearer Pies on the back . The
following test is suitable for absorbent articles as a whole and it may also
be
used for any member or any combination of members of a absorbent article such
as absorbent structure according to the present invention. This test is
carried out
using de-ionized water as the test liquid.
The following describes key principles of the test:
1. The test specimen is affixed to the lower surface of a support structure
which forms an angle of 14 degrees with the horizontal plane.
2. The test liquid is dispensed onto the absorbent article at a urination rate
representative of the intended user group.
3. Liquid that is not readily acquired into and held in the article will drip
off
from the absorbent article because of the sloped inverse configuration.
Similar tests for example for nonwoven materials are well known in the art
such as EDANAT"" test method 152.0 - 99 "nonwoven special runoff' except for
the
inverse configuration of the absorbent article which leads to test liquid
dripping
off from the test specimen rather than liquid running off from it.
The following description is adopted for absorbent articles for handling body
liquids of the baby diaper type, and in particular for absorbent articles
intended
for babies in the weight range of about 9 to 18 kg. For these babies, the
average
urination rate to this 15 milliliters per second, the 95 percentile of the
urination
rate for the same babies is ~at 22 milliliters per second. Nonetheless, the
skilled
person wilt be able to readily adopt this method for other purposes, such as
for
other sizes, or adult incontinence applications. When there is a need for
adoption
of the method, the single gush volume and the delivery rate should be adjusted
to better reflect the average gush volume and urination rate of a member of
the
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14
intended user group. The number of gushes used in this test should be three or
four depending on whether the total volume delivered by three or four gushes
is
closest to the total capacity of the absorbent article to be tested. The
diameter of
the tube and the orifice should be adjusted along with the gush size such that
the
linear velocity of the test liquid at the orifice remains constant.
The test specimen is held on the lower surface of a flat support structure
which forms an angle of 14 degrees with a horizontal. The support structure is
not absorbent and may be made from wide variety of suitable materials such as
for example Plexiglas. The 'test specimen is affixed to the lower surface of
the
support surface by any suitable means which does not interfere with the liquid
handling of the test specimen such as for example adhesive tapes. When the
test specimen affixed to the support structure, the liquid receiving surface
of the
test specimen to be tested should point downwards. The configuration of the
test
specimen on the support structure should be as flat as possible. The test
specimen is oriented such that its longitudinal dimension coincides with the
slope
of the support structure. The front region of the test specimen should be
placed
towards the upper end of the support structure where as the back region of the
test specimen should be placed towards the lower end of the support structure.
A
liquid receptacle of adequate size is placed below the support structure in
order
to collect liquid dripping,off from the absorbent article.
For test specimen's having the above-mentioned size, the first test protocol
loads the test specimen four times with 75 milliliters plus minus 2
milliliters of test
liquid, at a rate of 15 milliliter per second, delivered at five minute
intervals.
Alternatively, the second test protocol loads the test specimen four times
with
110 milliliters plus minus 2 milliliters of test liquid at a rate of 22
milliliters per
second, delivered at five minute intervals. The present description refers to
an
automated procedure, including automatic data capturing. Of course, analogous
systems can be used such as manual recording of data, as long as the described
principles are followed.
CA 02334158 2005-O1-13
The test liquid is dispensed from a 4.8 mm inner diameter flexible tube
(outer diameter 14.4 mm), Such . as TygonT"" R-3603, available from Fisher
Scientific, Germany, connected to test a liquid metering pump such as for
5 example available from Ismatec t_aboratoriumstechnik of Wertheim Mondfeld,
Germany, under the designation MCP-Z Gear Pump, having a pump head
available from of Ismatec Laboratoriumstechnik of Wertheim Mondfeld, Germany
under the designation Micropump MOD O/C 020-000, with a pump control unit to
allow start and stop of the pump based upon electrical signals. 1t is
particularly
10 important that the orifice has an inner diameter of 4.8 mm in order to
control the
velocity at which test liquid is discharged from the orifice. The tube and the
orifice
are configured such that the test liquid is dispensed from the tube in a
direction
perpendicular to the surface of the absorbent article. The orifice of the tube
is
positioned about 20 mm plus minus 1 mm away from the loading point of the
15 absorbent article.
The test liquid dripping off from the test specimen is collected in the liquid
receptacle placed below the support structure. The receptacle is dimensioned
such that all of the test liquid dripping off from the test specimen is
collected. The
amount of test liquid received by the receptacle is determined by the weight
increase of the receptacle during the test procedure. The weight increase of
the
liquid receptacle is measured with digital balance having an accuracy of 10
micrograms.
Upon finishing of the above 4 liquid dispension cycles, the liquid drip-off
for
each of the gushes has been obtained. The liquid drip-off for each of the
gushes
is reported as the percentage of the total volume of a respective single gush
that
has dripped off from the surface into the receptacle.
Curved Acauisition Test M~hod
The curved acquisition test method aims at simulating the introduction of
urine into a absorbent article for managing body liquids. A similar test
method is
CA 02334158 2004-06-03
16
described in PCT Patent Application No. 1899100741 (WO 99155264).
The following describes key principles of the test:
1. The absorbent article is held in a curved configuration to more
realistically
simulate the position of the absorbent article on a standing or sitting
wearer.
2. The realistic, curved configuration requires that the liquid applied must
be
distributed against gravity.
3. The overall configuration provides key data on acquisition, distribution
and
storage of the liquid within the various materials thereby providing a better
understanding of material properties, and their combined performance.
4. The apparatus includes a pressurized air cushion, allowing to better
analyze
products which have either a varying thickness throughout various parts
thereof, or which exhibit a pronounced thickness change throughout the
loading process.
The following description is adopted for absorbent articles for handling
body liquids of the baby diaper type, and in particular for absorbent articles
intended for babies in a weight range of about 9 to 18 kg. Nonetheless, the
skilled person will be able to readily adopt it for other purposes, such as
for other
sizes, or adult incontinence applications. The test specimen is held in a
curved
Plexiglas absorbent article which utilizes a flexible, soft air bag which is
used to
simulatewarious baby pressures between 0.69 kPa - 6.9 kPa (0.1-1 psi), and the
test specimen is loaded with subsequent gushes of liquid, with appropriate
waiting time in between. The key result from this test is the time for the
fluid of
each of the gushes to penetrate into the test specimen. After the loading of
the
test specimen by this test, the test specimen can be used for further
analysis,
such as measuring the rewet, preferably by the Post Curved Acquisition
Collagen
Rewet Method (PCACORM) described in PCT Patent Application No. 1B99I00741
(WO 99/55264), or measuring the caliper, or measuring the liquid distribution,
such
as by determining the load in various sections of the test specimen.
CA 02334158 2004-06-03
17
For test specimens having the above mentioned size, the standard
protocol loads the test specimen four times with 75 m! +!- 2 ml, at a rate of
15
ml/sec, delivered at 5 minute intervals. The present description refers to an
automated procedure, including automatic data capturing. Of course, analogous
systems can be used, such as manual recording of data, as tong as the
described principles are followed.
The test equipment is schematically depicted in Fig. 6 of PCT Patent
Application No. 1899/00741 (WO 99/55264). The complete equipment, or
preferably a multiplicity thereof for ease of replication, is placed inside a
controlled
condition chamber, with room temperature and humidity within the following
limits:
Temperature: 32°C t2° (90°Ft 3° F)
Relative Humidity: 50 % t 10 °Jo
If a deviation from this protocol is deemed appropriate, this must be stated
explicitly in the protocol.
The Curved Acquisition Tester comprises four important parts (The size of
this unit is designed for baby diapers. Accordingly, the size may need to be
adopted for absorbent article intended for different user groups):
a) A holding unit which is essentially made of perspex/pfexigias. It has
been found that suitable plates of 5 mm thickness provide sufficient
strength for operating without undue deformation.
The essential part of the holding unit is a trough having an upper
rectangular opening of 130 mm extending outside of the plane of
drawing, and a width of 260 mm. The rectangular through has a length
of about 200 mm and ends in a semi-cylindrical form having a radius of
130 mm. The holding unit has one or more means to retain the loading
CA 02334158 2005-O1-13 ,
18
unit in place, here shown by a hinged lid and corresponding fixation
means, such as screws. The holding unit further comprises means for
stable support.
b) A loading unit comprising a liquid application means is designed to fit
into the through of the holding unit, by having a rectangular section
having a length of about 180 mm, and having cross-section of about
100 mm by 128 mm, ending in a semi-cylindrical section having a
radius of 100 mm. The loading unit further comprises a flange, which
allows to hang the unit into the trough by being larger than said trough
opening, and which also prevents the loading unit to be pushed out of
the trough by being hold by said lid. The clearance for the vertical
movement of the loading unit is about 4 cm. The total loading unit is
made from the same material as the holding unit, and can have a
weight of about 1 kg, including the liquid application means.
c) The liquid application means comprises a Plexiglas tube having an inner
diameter of 47 mm, and a height of about 100 mm. It is firmly affixed to
a circular opening having a diameter of about 50 mm through the
loading unit,- positioned centered around the lowermost point ~ of the
semi-cylindrical portion. The opening of the tube is covered by a open
mesh (such as of wire mesh with openings of about 2 mm separated by
threads of 1 mm), so as to be flush with the opening of the loading unit.
A 6 mm diameter flexible tube, such as Norpren A60GT"" (6404-17),
available from Cole Parmer Instrument Company, IL, US, is connected
to a test fluid metering pump, such as Digital Pump, Catalog, by No. 6-
07523-20, having a Easy-load Pump Head, No. G-07518-02, both by
Cole-Parmer Instrument Company, IL, US, with a pump control unit to
allow start and stop of the pump based upon electrical signals. Two
electrodes are positioned at two opposite points just inside the mesh at
the lower end of the Plexiglas tubing, to be able to detect interruption of
the electric current through the electrolyte fluid, once the tube is being
CA 02334158 2000-12-04
WO 00/00142 PCT/US99/14649
19
emptied. The electrodes are connected via cable to a time signal
measuring unit.
d) A pressure generating means comprises a flat, flexible air cushion, such
as generally available for medical purposes (blood pressure
measurement), having an uninflated dimension of 130 mm by 600 mm,
which can be inflated by means of a hand pump and a valve with a
pressure recording absorbent article, which can be connecting to an
electrical transducer so as to provide an electrically recordable signal
corresponding to the pressure.
This system is designed to operate at pressures of up to 6.89
kPa (1 psi), and is set for the standard procedure to 2.07 kPa (0.3 psi).
e) Optionally, the apparatus can comprise an automatic control unit, such
as a suitable computer control unit, connected to the pump control unit,
the timer and the pressure recorder which also can operate several
measuring units in parallel. Suitable software is for example LabView
by National Instruments, Munich, Germany. A complete test equipment
can be delivered by High Tech Company, Ratingen/Germany, D-64293
Darmstadt.
1 ) Calibration of pump: before starting the experiment, the pump should be
calibrated to ensure a flow rate of 75 ml per 5 seconds. If necessary, tubing
should be replaced.
2) Preparation and thermal equilibration of test fluid;
3) Positioning of the cushion into the trough without folds or creases;
4) Weighing of the entire absorbent article to be tested to the nearest 0.01 g
on a
top loading balance. Marking of the loading point onto the test specimen with
a pen. Positioning and fixation (such as by suitable adhesive tape) of the
test
specimen to the loading unit, such that the liquid receiving surface is
oriented
CA 02334158 2000-12-04
WO 00/00142 PCT/US99/14649
towards the loading unit (and hence the backsheet towards the cushion), so
as to have the opening aligned with the loading point of the absorbent
article.
The absorbent article is then positioned onto the curved loading unit without
cutting the leg elastics or other elastic, if present, with the marked loading
5 point located under the center of the tube, and attached to the loading unit
by
suitable attachment means, such as tape. Generally, the configuration of the
absorbent article should resemble a typical in use configuration as close as
possible. The absorbent article is then positioned together with the loading
unit into the tester, and t'he electrode cables are connected.
10 5) The lid is closed, and fixed with screws.
6) The cushion is then inrlated to the desired pressure, i.e. 2.07kPa
(0.3psi),
thereby pushing the loading unit against the lid, and thus exerting the
pressure on the test specimen.
7) The end of the flexible tube is positioned such that it directs to the
center of
15 the opening, and extends about 5 cm (2 in) into the tube.
8) The liquid pump is started for the preset time (i.e. 5 seconds), and at the
same time acquisition time timer.
9) Upon emptying of the Plexiglas tube the electrodes provide a signal
stopping
the acquisition time timer, upon which the waiting time is started at the
timer
20 for 5 minutes.
10) The loading cycle (step 7 and 8) is repeated to a total of four times.
Results
Upon finishing of the above cycle, the respective acquisition rates can be
calculated for each "gush° by dividing the load per gush (i.e. 75 ml)
by the time in
seconds required for each gush. (If the acquisition rates are getting close to
the
liquid delivery rates (i.e. 15 ml/sec), test conditions can be changed and
respectively recorded.)
