Note: Descriptions are shown in the official language in which they were submitted.
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A PREDEFINED PATTERN
FIELD OF THE INVENTION
The present invention relates to absorbent articles such as diapers, training
pants, adult incontinence 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.
Absorbent articles such as diapers, training pants, adult incontinence
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.
It has been recognized in the prior art that storage of acquired urine close
to
the respective body exit may bear inherent disadvantages. The human urethra is
located almost in between the legs of the human being. Hence, storage in
particular of larger amounts of urine close to the urethra would lead to
increased
bulk in between the legs of the wearer. Increased bulk, of course, limits the
mobility of the wearer and thus is uncomfortable. It is therefore desirable to
store
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the acquired urine away from the point of acquisition.
Liquid distribution away from the point of acquisition also has further
advantages. Since a larger area may be used for storage of the acquired urine
away from the point of acquisition, the caliper of the storage area as a whole
may
be reduced. Hence, the article for handling body urine which comprises the
storage member appears less bulky.
PCT patent publication WO 98/22067 (Matthews et al.) provides a personal
care product in which the ratio of the amount of liquid stored in the center
region
to the amount of liquid storage in at least one of the end regions 30 minutes
after
an insult is less than 5:1. This prior art, however, fails to provide an
absorbent
article which transports a larger amount of urine away from the acquisition
region. In addition, it fails to provide a sufficiently rapid liquid
transportation away
from the acquisition region.
PCT patent application WO 98/43578 (LaVon et ai.) provides an absorbent
. article comprising absorbent core with a crotch region and at least one
waist
region whereby said crotch region has a lower ultimate liquid storage
capability
than the waist region. The article further has an improved liquid handling
performance such as an acquisition rate of at least 0.6 milliliters per second
in
the fourth gush.
Hence, it is an object of the present invention to overcome the problems of
the prior art absorbent articles.
It is a further object of the present invention to provide an absorbent
article
which transports urine away from the acquisition region immediately after
acquisition of the urine.
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Is a further object of the present invention to provide an absorbent article
which stores a substantial amount of urine outside the acquisition region.
SUMMARY OF TH INVFNTICJ~[~J
The present invention further provides an absorbent article comprising an
acquisition region, a waist region separate from said acquisition region. The
absorbent article is characterized in that the article has a fill pattern
difference of
less than 30% according to the Instantaneous Storage Pattern test method
defined herein.
The present invention further provides a process for handling urine in ah
absorbent article, the article comprising an acquisition region and at least
one
waist region being separate from said acquisition region. The process for
handling urine comprising the steps of:
- acquiring liquid into said article at said acquisition region, the amount of
said liquid being a fraction A of the total design capacity of the article;
- transporting a fraction B of said acquired liquid to at feast one of said
waist regions, said fraction B being at least 20%.
The process of the present invention is characterized in that for any value of
said fraction A between 20% and 100% said fraction B differs by less than 30%
from the value of fraction B for a fraction A of 20%.
~EIAILED DESCRIP ION 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
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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.
It is one aspect of the present invention to provide an article for managing
urine. It is another aspect of the present invention to provide a process for
storing
urine in an article for managing urine in a instantaneous fill pattern.
The absorbent article of the present invention is capable of rapidly
distributing the acquired urine away from its acquisition region to at least
one of
its waist regions. For the purpose of this invention, this capability is
quantified by
the Instantaneous Storage Pattern Test method defined hereinafter. According
to
this test, the absorbent article according to the present invention has a fill
pattern
difference of less than 30 percent, preferably a fill pattern difference of
less than
percent, more preferably a fill pattern difference of less than 10 percent,
most
preferably a fill pattern difference of less than 5 percent.
Preferably, the absorbent article of the present invention further rapidly
20 acquires urine in an in-use configuration. For the purposes of the present
invention, this capability is quant~ed by the curved acquisition test
disclosed
hereinafter. The absorbent article according to the present invention has a
liquid
acquisfion rate in the fourth gush of at least 2 milliliters per second,
preferably a
liquid acquisition rate in the fourth gush of at least 2.5 milliliters per
second, more
preferably a liquid acquisition rate in the fourth gush of at least 3
milliliters per
second, most preferably a liquid acquisition rate in the fourth gush of at
least 4
milliliters per second.
The entire absorbent article of the present invention is intended to be worn
by a wearer such that the wearer retains his mobility during use of the
article of
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the present invention. !n some embodiments of the present invention, the
absorbent article of the present invention comprises an attachment means which
is unitary with the article. The term "unitary" 9S tlSPl~ hr~rain inriir~fce
f~~. .~,..
attachment means is joined to the absorbent article and that the attachment
5 means is not intended to be separated from the article during use of the
article.
The attachment means is intended to hold the absorbent article of the present
invention around the lower torso of the wearer during use. Suitable attachment
means such as for example adhesive tapes, mechanical fasteners, garment like
articles, and the like are well known in the art. Alternatively, the absorbent
article
7 0 of the present invention may be attached to the lower torso of the wearer
by an
attachment means which is not unitary with the article such as for example a
pant.
It is further desirable for the absorbent article of the present invention
that it
is sufficiently flexible to readily conform with the body of the wearer during
use.
For the purpose of the present invention, a Cartesian coordinate system is
defined as follows. The z - direction is defined to be perpendicular to the
surface of the acquisition region at the intended loading point. The x -
direction
is defined to coincide with the longitudinal dimension of the absorbent
article. In
the case of a diaper, the x - direction runs from the front region of the
article
(which comes into contact the front waist region of the wearer during use) to
the
back region of the article (which comes into contact with a back waist region
of
the wearer during use). Accordingly, the y - direction coincides with a
transverse dimension of the absorbent article which runs from the left to the
right
of the wearer during use. It is to be understood in this context that this
Cartesian
coordinate system is only a truly Cartesian coordinate system when the article
is
in the flat out configuration. For typical in use conditions, the
configuration of the
article is such that x -, y -, and z - direction as defined above only form a
focally
perpendicular set of coordinates.
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The term "instantaneous fill pattern" as used herein refers to a loading
distribution between the acquisition region and the waist region of the
article that
is present already at loadings which are small compared to the total capacity
of
the article and that is present on a time scale short compared to the average
time
interval between subsequent gushes.
The article of the present invention has a total design capacity. The term
"total design capacity" as used herein refers to the maximum volume of urine
that
the article is designed to absorb. Typically, the total design capacity equals
the
combined capacity of all storage members under typical usage conditions. If
the
storage members can not be identified, then the total design capacity may be
determined by the Capacity Dunk Test defined hereinafter. The total design
capacity is also related to the amount of urine exudates by the user of the
article
during the intended usage period. Some articles according to the present
invention may be designed to have replaceable storage members. In this case,
the total design capacity is related to the capacity of a single storage
member or
a single set of storage members.
The article for managing urine of the present invention comprises at least
one acquisition region. The term "acquisition region" as used herein refers to
that
region of the article which comprises the intended loading point of the
article. The
term "loading point" as used herein is that point or region of the article
which is
intended to be positioned closest to the exit of the urethra of the wearer
during
use. Typically, the acquisition region is dimensioned such that it allows for
variation of the mutual relative positioning of the respective body exit with
respect
to the article. The acquisition region may also comprise means for
intermediate
storage of the acquired liquids. Generally, the acquisition region extends
over at
least a third of the longitudinal dimension of the absorbent article
{typically one
third), extends over the entire transverse dimension of the absorbent article,
and
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extends over the entire caliper of the absorbent article. Further, the
acquisition
region is positioned within the absorbent article such that the intended
loading
point is centered with respect to the acquisition region.
The article for managing urine of the present invention comprises at least
one waist region. The term "waist region" as used herein refers to those
regions
forward and/or backward of the above mentioned acquisition region of the
absorbent article. Accordingly, the waist regions may account for up to two
thirds
of the longitudinal dimension (x-direction) of the absorbent article. Like the
acquisition region, the waist region extends over the entire transverse
dimension
of the absorbent. article and extends over the entire caliper of the absorbent
article. The waist regions are typically intended to be positioned in close
proximity to the front waist region or the back waist region respectively of
the
wearer during use.
It is to be understood in this context that these regions are defined in a
purely geometric way. In particular, there is no need that the positioning of
these
regions is reflected in the structure of the article such as by a change in
material.
In at least one of these waist regions, at least one liquid storage member
may be positioned. The intention of the liquid storage member is to ultimately
hold the liquid until the end of the intended usage period. In one embodiment
of
the present invention, the storage member holds the urine by a means selected
from the group of capillary pressure and osmotic pressure. For example, the
storage member may comprise a pad of cellulosic fibers and optionally a
particulate superabsorbent polymeric material dispersed therein. Other
suitable
storage member include but are not limited to HIPE foams, superabsorbent
fibers, and the like. Yet other suitable storage members are well known in the
art.
Optionally, the absorbent article according to the present invention may
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8
comprise a liquid handling member which is intended to transport urine from
the
acquisition region to a waist region and potentially to a storage member
positioned inside a waist region.
The process for handling urine according to the present invention comprises
a step of acquiring urine into the article of the present invention at the
acquisition
region of the article. Typically, the step is triggered by the disposal of
urine onto
the acquisition region of the article by the wearer. Preferably, the
acquisition rate
of the article during the step is sufficiently high to minimize liquid runoff
from the
article which subsequently may lead to leakage and to minimize skin contact
with
the urine. During 'this acquisition step, a certain volume of urine is
acquired into
the article which is a fraction A of the total design capacity of the
absorbent
article.
The process for handling urine according to the present invention comprises
a step of transporting urine away from the acquisition region to at least one
of the
waist regions. The urine may be further transported into at least one storage
member positioned in at least one of the waist regions. During the step of
transportation a fraction B of the acquired liquid is transported away from
the
acquisition region into at least one of the waist regions. Fraction B is at
least 20
percent, preferably at least 50 percent, more preferably at least 75 percent,
most
preferably at least 95 percent.
During the process of the present invention, fraction B remains relatively
unchanged for a wide range of loads of the absorbent article. Thus, even small
loads of urine would already be distributed away from the acquisition region
of
the article and will not contribute to the bulk of the acquisition region. For
any
value of fraction A between 20 percent and 100 percent, the value of fraction
B
differs by less than 30 percent from the value of fraction B for a fraction A
of 20
percent, preferably by less than 20 percent, more preferably by less than 10
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9
percent and most preferably by less than 5 percent. In other words, the
instantaneous loading pattern which stores a fraction B of the acquired liquid
away from the acquisition region will remain constant up to the full load of
the
absorbent article. Preferably, the value of fraction B remains unchanged also
for
values of fraction A lower than 20 percent and particularly down to 5 percent.
Optionally, the step of transporting liquid away from the acquisition region
may be carried out substantially immediately subsequent to the step of
acquiring
liquid into the absorbent article. Hence, the acquisition region is only bulky
for a
shorter period of time and may be ready earlier for the acquisition of
additional
gushes of liquid.
Optionally, the step of transporting liquid away from the acquisition region
may be carried out by an optional liquid handling member of the present
invention.
It is a further aspect of the present invention to provide a process for
handling urine for incontinent person of all ages. This process a step of
attaching
the absorbent article to the lower torso of the wearer. During the step, the
attachment of the article is achieved by means of a suitable attachment means.
The attachment means be unitary with the article or may non-unitary with the
article. The step may be carried out by the wearer himself or the step may be
carried out by a caregiver. The purpose of the step is to align urethra with
the
acquisition region of the article. The process for handling urine for
incontinent
persons further comprises the steps of the process for handling urine in an
absorbent article according to 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
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membrane material is available from SEFAR of Riischlikon, Switzerland, under
the designation SEFAR 03-20/14. A suitable foam material is available from
Recticel of Brussels, Belgium, under the designation Bulpren S10 black. A
suitable technique to completely envelope the foam material with the membrane
5 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
10 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 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 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.
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11 ~ oZ l.? a ~(~ - 177~11~
For application of the liquid handling member in an absorbent article
according to the present invention, the liquid handling member is combined
with
' a storage member. The term "liquid storage member" refers to an 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 and/or
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 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 liquid
handling member. A suitable storage member is for example a superabsorbent
polymer such as available from CHEMDAL, United Kingdom, under the
designation ASAP400.
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 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
entitled "High flux liquid transport members comprising two different
permeability
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MISSING AT THE TIME OF PUBLICATION
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12
regions" (P&G case CM1840MQ) filed in the name of Ehrnsperger et al., "Liquid
transport member for high flux rates between two port regions" (PB~G case
CM1841 MQ) filed in the name of Ehrnsperger et al., "Liquid transport member
for
high flux rates against gravity" (P8~G case CM1842MQ) filed in the name of
Ehrnsperger et al., "Liquid transport member having high permeability bulk
regions and high bubble point pressure port regions" (P8G case CM1843MQ)
filed in the name of Ehmsperger et al. All of these documents are enclosed
herein by reference.
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 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
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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 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 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 feast 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 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
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
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absorbent article around the lower torso of the wearer.
METHODS
Unless stated otherwise, all methods are carried out at ambient conditions,
i.e. 32 +/- 2 ° Celsius and 30-50% relative humidity.
Unless stated otherwise, the synthetic urine used in the test methods is
commonly known as Jayco SynUrine 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/l of Na2S04; 0.85 g/l of
(NH4)hi2P04; 0.15
gll (NH4)H2P04; 0.19 gll of CaCl2; ad 0.23 g/l 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.
Ca aci r Dunk Test
This test is intended to measure the total capacity of an absorbent article.
As the first step of this test, the test specimen is completely immersed in
synthetic urine for 10 minutes.
Then, the test specimen is put with its acquisition region facing the glass
frit
on a sufficiently large glass frit which is in direct liquid communication
with a
liquid reservoir filled with synthetic urine. Hence, this glass frit provides
a
hydrohead of about 1 mm. After thirty minutes, the test specimen is removed
from
the glass frit.
Finally, the total capacity of the test specimen is determined by weighing
the liquid uptake of the test specimen.
instantaneous Storage Pattern ~PCt MAthnri
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This test method is intended to measure the ratio of the liquid stored
outside the acquisition region of an article of the present invention.
Therefore, the
distribution of stored liquid is measured shortly after the liquid has been
acquired
at the loading point within the acquisition region. This method is suitable
for
5 absorbent articles according to the present invention.
For the purpose of this test method, samples of the article to be tested are
loaded with one or more gushes of synthetic urine onto the intended loading
point of the article while the article is configured to resemble as closely as
10 possible an in-use configuration. For example, the article may be loaded
while it
is attached to a mannequin modeling the body shape of an average user or the
article may be loaded while the article is held upright in a curved shape. For
this
test, a gush is defined as having the volume of 20% of the total design
capacity
of the article to be tested. The gushes are disposed onto the loading point of
the
15 article in 5 minute intervals at a rate of about 5ml/s or at the maximum
rate not
causing liquid to run-off whichever is lower. The 5 minute interval starts
when the
preceding gush is completely absorbed by the article.
For the purpose of this test method, the loading or liquid uptake of the
acquisition region and the storage regions of the article to be tested have to
be
measured separately. There exists a variety of potentially suitable test
methods
to determine the liquid uptake of a certain region. It will be readily
apparent to the
skilled person which method is the most suitable for the article to be tested.
The
potentially suitable methods range from very simple methods such as severing
the article into its different regions and weighing its weight increase to
more
complex methods such as x-ray analysis and nuclear magnetic resonance
spectroscopy. In x-ray analysis, the effect that the amount of energy absorbed
when the article is exposed to x-rays is proportional to the amount of liquid
per
unit surface area contained in the article is used to determine the water
content
of specific regions of the article. . For example, such a method is described
in an
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article entitled "Fluid distribution: Comparison of x-ray imaging data" by
David F.
Ring, Oscar Lijap, and Joseph Pascente in Nonwoven World magazine, summer
1995, at pp. 65 -- 70. Suitable x-ray systems are available for example from
LIXI
Inc. of Downers Grove, Illinois, USA, under the designation SA-100-2 SERIES,
MODEL HLA-40-440M02. The system uses Bio-scan software from Optimas.
The x-ray system may for example be operated with an exposure time of two
second, with a tube voltage of 50kV, and a current of 12mA. It is to be noted,
however, that for exposure time, tube voltage, and current different values
have
to be chosen depending on the specific properties of the test specimen to be
examined. It is also well known in the art to determine the water content of a
specific region of a article by nuclear magnetic resonance spectroscopy. In
all
methods, particular care has to be taken that the weight of the liquid (bound
liquid as well as free liquid) which is stored in either one of the regions is
exactly
accounted for. It is also important that only the liquid uptake is measured by
comparing a loaded article with an unloaded article.
The total design capacity of the test specimen may for example be obtained
by the Capacity Dunk Test defined herein. The gush size for this test is
obtained
by dividing the total design capacity of the test specimen by 5.
As a second step, a first sample of the article is loaded with a first gush of
synthetic urine at its intended loading point. The loadings of the acquisition
region and the storage region of the article are measured five minutes after
the
gush has been absorbed completely. The loadings will be referred to as A, and
S, respectively. Then, a second sample of the article to be tested is loaded
with 5
subsequent gushes with a 5 minute waiting time between two subsequent
gushes. The loadings of the acquisition region and the storage region of the
article are measured five minutes after the fifth gush has been absorbed
completely. The loadings will be referred to as A5 and SS respectively.
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The fill ratio R; of a sample of the article loaded with i gushes is the ratio
of
the loading of the storage region to the loading of the acquisition region and
is
given by
The fill pattern difference D represents the relative change of the fill ratio
from 20% loading to 100% loading. Accordingly,~D is obtained by
The fill pattern difference should be measured for five pairs of sample
articles and subsequently the results should be averaged in order to reduce
statistical fluctuation of the results.
Curved acq~risition Method
The curved acquisition test methods aims at simulating the introduction of
urine into a device for managing urine. A similar test method is described in
PCT
patent application No. 1899/00741 (PEG case CM2060FQ) incorporated herein
by reference.
The following describes key principles of the test:
1. The device is held in a curved configuration to more realistically
simulate the position of the device 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
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18
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 devices for handling urine of the
baby diaper type, and in particular for devices 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 device which
utilizes
a flexible, soft air bag which is used to simulate various 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 1899100741 (P8~G case CM2060FQ), .or measuring the caliper,
or measuring the liquid distribution, such as by determining the load in
various
sections of the test specimen.
For test specimens having the above mentioned size, the standard protocol
loads the test specimen four .times with 75 ml +/- 2 mi, at a rate of 15
ml/sec,
delivered at one hour 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.
The test equipment is schematically depicted in Fig. 6 of PCT patent
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19
(err, a~aa fq
~~5 ~x~~~ ~~
application No. 1899/00741 (P&G case CM2060FQ) incorporated herein by
reference. 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 ~2° (90°F~ 3° F)
Relative Humidity: 50 % t 10
If a deviation form this protocol is deemed appropriate, this must be stated
explicitly in the protocol.
The Curved Acquisition Tester comprises four important parts: (The size of
the unit is adapted for baby diapers and may have to be changed accordingly
for
absorbent article for other intended uses.)
a) A holding unit which is essentially made of perspexlplexiglas. 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 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
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MISSING AT THE TIME OF PUBLICATION
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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
5 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
10 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
15 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 A60G (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. G-07523-20, having a Easy-Load Pump
20 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 intemrption of the electric current through the
electrolyte fluid, once the tube is being 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
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mm, which can be inflated by means of a hand pump and a valve with
a pressure recording device, 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,
Ratingen7Germany, D-64293 Darmstadt.
Stees fo_ r setting,~l t~ h, a A~uisition Echipm~nt
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 device 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 towards the loading unit (and hence the backsheet towards the
cushion), so as to have the opening aligned with the loading point of the
device. The device is then positioned onto the curved loading unit without
cutting the leg elastics or other elastic, if present, with the marked loading
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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 device should resemble a typical in use configuration as close as
possible. The device is then positioned together with the loading unit into
the tester, and the electrode cables are connected.
5) The lid is closed, and fixed with screws.
6) The cushion is then inflated 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
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 for 5 minutes.
10) The loading cycle (step 7, 8 and 9) 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 m!) by the
time in
seconds required for each gush. (If the acquisition rates are getting close to
the
liquid delivery rates (i.e. 15 mi/sec), test conditions can be changed and
respectively recorded.)
