Note: Descriptions are shown in the official language in which they were submitted.
WU 94/10958 ~ ~~ 4 ~ a . ~ ~ ' PCT/US93/10890
--ABSORBENT INCLUDING SUPER ABSORBENT AND CAPACITY MONITOR--
BACKGROUND OF THE INVENTION
1. Field of the Invention.
This invention relates to the field of absorbent products including super
absorbent
polymers, especially foe use try persons with urinary incontinence. More
specifically, the
invention relates to such products including a sensor or monitor which
provides an
1:0 indication when thG absorption capacity of the super absorbent polymer has
been exceeded.
'. Dcscriptiort of the Prior Art
here are numerous examples of wetness indicating devices which have been
proposed
for use in diapers and other absorbcnc products foe use by persons with
urinary incontinence.
Onc example of a wetness indicator is represented by a class of hot melt
adhesive products
which include a wetness indicating component: US Patent Nos. 4,743,238,
6,035,691,
5,066,711 and 5;089,548 disclose various hot melt adhesives with wetness
indicators, many
of which would be suitable for use in a. capacity monitor according to the
present invention.
These hot melt products arc in wide use in disposable diapers today. In
conventional use,
they are applied in the forrtti of a narrow straight bead, a thin ribbon or a
spiral bead to a
water impervious backing sheet and are in direct contact~with; and in liquid
communicable
relation with, an absorbent layer of fluff. Tests conducted on scvcr~l
commercially available
disposable diaper products including uch conveneionally applied hot melt
adhesives with
wetness indicators demonstrate that the wetness indicators provide a positive
indication of
wetness, i:c;, a color change in the hot melt, when no more than 1 ~
milliliters of a U:9~'o
NaCI solution was deposited thcrcc~n: Even 3 milliliters of such solution was
sufficient to
''effect a color change in some of the conventionaC applied hot melt adhesives
with'wctness
indicator. The color change occtsrrcd over relatively short tcneths, i.c.,
betwecn'r: inch and
and 'fx inches, of the beads or ribbons of hot melt adhcsiv~ with wetness
indicator at the
low volume levels of 6 to 16 milliliters.
US Patent No3.731686 discloses a mpisturc indicating strip which is designed
for use
with diapers: and other absorbent products. One end of the strip is attached
to the inside of
the diaper or the like and the other end, which is impregnated with a color
change chcnnical. '
extends out of the diaper. Liquid is transported by capillary action from
inside the diaper
or the like to the color change chemical outside the diaper.
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US Patent No. 3,759.261 discloses diapers having a layer with a pattern
printed thereon
<..
and one or more layers which maskath~ pattern when dry. When wetted, the
masking layers
.; .
no longer mask the pattern which ~ becomes visible through a backing sheet,
thereby
providing a wetness indicating function.
US Patent No. 3,952,746 discloses a humidity indicator strip incorporated in a
diaper
including a water impervious backing sheet. A portion of the strip extends
through an ,
opening formed in the backing sheet.
US Patent No. 4;02~;?11 discloses a diaper including a wetness indicator
comprising
a layer of water soluble or water dispersible coloring agent applied to the
water impervious
backing sheet. Vlrhen dry, the coloring agent is clearly visible through the
backing sheet but,
when wetted, the coloring agent is dispersed and is no longer visible through
the backing
sheet.
US Patent No. 4,231.370 discloses a wetness indicator in a diaper structure.
The wetness
indicator is positioned between a water impervious backing sheet and an
absorbent core and
comprises a flexible pH-changc/colar-change coating which is preferably
applied to the
backing sheet and visible thcrcthrough. The preferred coating material
comprises first and
second latexes, an acid buffer and bromo-phenol blue.
US Patent No. 4 ~$?;153 discloses a diaper including a saline water indicating
material
positioned between a backing sheet and an absorbent core, and visible through
the backing
sheet; The preferred indicating material comprises ' a water-insoluble
polymeric ion
exchanger and a water-insoluble polymeric exchanged ion indicator in intimate
contact with
each other.
US Patent No. 4,S0?,121 discloses a diaper including a wetness indicator
comprising
a color change chemical which is isolated from the absocbcnt portions of the
diaper so 'as
to prevent contact between a wearer of the tiiapcr and the color change
chemical. Means are
provided for supporting one way capillary action to transport liquid from the
absorbent
portions to the indicator to trigger the color change.
US Patent No. 4,704,108 discloses a wetness indicator comprising. two metal
strips
incorporated in a diaper and circuitry far detecting changes in the electrical
conductivity in
absorbent portions of the diaper due to the presence of moisture therein.
US Patent No. 4,?05,513 discloses a wetness indicator for diapezs. The
indicaeor
comprises ' indicts printed in waterproof ink on a paper carrier strip. !fig
paper strip is
positioned adjacent to a wator impervious backing sheet and the indicia is
masked by the
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strip so long as it remains dry. When wetted, ~hc carrier strip no longer
masks the indicia
and it becomes visible through the backing sheet to indicate wetness.
US Patent No. 4,738,674 discloses an absorbent product including a moisture
indicator
which provides an indication of wetness at a point remote from where liquid is
actually
deposited on the product. The indicator includes a wicking strip for
transporting liquid from
a point where it is deposited to an edge of the product where it contacts a
moisture
indicating substance which can provide a visual indication, such as a color
change, that it
has been wetted.
US latent No. 4,834,733 discloses a diaper including an actuating member which
shrinks when wetted and it is connected to an indicating mechanism so that,
when moisture
contacts the actuating member, it shrinks and displaces the indicating
me~anism providing
an indication that fluid has been deposited in the diaper.
US Patent No. 5,078,7U8 discloses a diaper comprising a transparent or
translucent,
water impervious backing sheet and an absortxnt core. Opening are provided in
the core so
that urine or stools deposited in the diaper arc visible through the backing
sheet to indicate
the need for a change.
Super absottxnt materials have been incorporated itt commercially available
diapers and
the like, for many years. US Patent No. 5,U72,687.
discloses several varieties of absorbent diaper products including sups
absorbent materials. Known super absofbcnts absorb large amounts of liquid and
liquid
absorbed in super absorbents can not be squeezed back out of the super
absorbents. This is
to be contrasted with fluff which is compvscd of cellulose or the like fibers.
Fluff can
absorb many times its weight in liquid but liquid absorbed in fluff can tx
squeezed back out
of the fluff. In a diaper, squeeze out of urine from fluff can cause leakage
and prolonged
skin contact with urine soaked fluff can cause damage to healthy skin and
inhibit healing
of damaged skin.
Each super absorbent polymer has a "speed" which is used herein to mean the
rate at
which the super absorbent will absorb liquid. The speed of a super absorbent
depends upon
many factors including its composition, the quantity of liquid it has alrtady
absorbed and
the amount of liquid available to,bc absorbed. 1=or a given liquid, each super
absorbent also
has a "free swell capacity" which is used herein to mean the maximum amount of
liquid
which unrestrained super absorbent particles will ultimately absorb when
exposed to an
excessive amount of a liquid, i.e., one which fat exceeds the capacity of the
super absorbent
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relative to that liquid. A given super absorbent with a given capacity for a
given liquid will
have a different, somewhat lower capacity for that liquid when the super
absorbent is
contained in, for example, an absorbent core of a diaper. The term "in--situ
capacity" will
be used hereinafter to refer to the volume of a given liquid which is absorbed
by super
absorbent associated with an absorbent core containing at least oneother,
different absorbent
material, such as fluff, within thirty minutes after the liquid is..clcposited
slowly in a single
spot in the absorbent core. The in-situ capacity of super absorl~eitt in such
an absorbent core
does not include the capacity of the fluff or other absorbenf~~rinaterial in
the core; the term
refers only to the capacity of the super absorbent to absorb a given liquid,
under the recited
1U conditions, within thirty minutes of the time tht: liquid is deposited.
Some super absorbents arc fast and some are slow. In granular form,
commercially
available super absorbents take approximately one to three minutes to absorb
their free swell
capacity of water, when unrestrained and exposed to large amounts of water.
When super
absorbents are incorporated in absorbent cores with other absorbent materials,
such ,as fluff,
they absorb liquid more slowly than this, largely because they are in contact
with less Liquid.
All super absorbents have a given speed when drSA, and, as they absorb liquid,
the speed and
remaining capacity of the super absorbent, decreases.
Same of the characteristics discussed in the preceding paragraph are
illustrated in Fig.
1 in respect of super absorbents contained in absorbent fluff cores in
diapers. Fig. 1 is a plot
of data collected from tests made of a commercial ~rsion of several medium
sized
SIimLine~ diapers manufactured by Principle Business Enterprises, Ine. In the
test; many
different quantities of a U.9% NaCI solution were deposited on SlimLine medium
size
diapers. For each quantity of solution, the diapers were tested for skin
wetness at different
intervals of time after the solution was deposited. In the skin wetztess test,
a medium size
SlimLinc diaper was placed, with its water impervious backing sheet facing
downwardly,
on a level surface: In the center of the diaper, a given quantity of a~U.9%
NaCI solution was
deposited at the rate of 7.U milliliters per second: Absorbent, paper
toweling, cut into three
inch by five inch rectangles, was stacked, the stack was weighed and its dry
weight was
recorded. At various time intervals after the U.9% NaCI solution had been
deposited an the
diaper, a previously weighed stack of paper toweling was placed on top of the
diaper and
a three inch by five inch: z~cctangularlv shaped five potmd weight was placed
om top of the
paper toweling. After fifteen seconds; the weight was removed from the paper
toweling and
it was reweighed. The weight of the dry toweling was subtracted from the
weight of the wet
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CA 02149325 2002-11-25
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paper toweling to give a skin wetness number corresponding with the weight of
0.996 NaCI
solution which was released by the diaper into the paper toweling. The time
which elapsed
before the skin wetness number was 0.0 grams for a given quantity of liquid
was plotted for
several different quantities of liquid and the results arcshown in Fig. 1. The
medium sized
SlimLine diapers which were tested had 12 grams of Aridall 1465 super
absorbent material-,
', available from trltemdal, in the fluff layer. At relatively low volume
levels, the speed of the
super absorbent in the Sliml.inc diapers is relatively fast, as rc(lcctcd by
the steep slope of
the plot on the Ieft~side of Fig. 1. At higher volume levels, the slope of the
plot is not as
steep and this reflects the well known phcnontcnon associated with super
absorbents used
in absorbent products, namely, the speed of a super absorbent irtaterial
daxease~ as it
absorbs.liquid. As the capacity of thc~sttpcr absorbent is used up, the~-deed
decreases and
the slope of a plot like that shown in Fig. 1 approaches zero. It will be
appreciated that the
in-situ capacity of the super absorbent in a medium SIimLinc diaper for
synthetic urine is
approximately 400 to 450 milliliters. The plot in Fig. 1 provides a good way
to approximate
in-situ capacity because, for example, the fluid volume of about 425
milliliters at thirty
minutes elapsed is almost entirely absorbed within the super absorbent
material, whereby
the skin wetness number is 0.0 because the super absorbent dues not release
liquid under
pnssurc. The volume :of 285 milliliters associated with a skin wetness of 0.0
after ten
minutes is significant, in terms of the medium SIimLinc, because it is
preferred that skin not
be in contact with a diaper with skin wetness in excess of O.U for mere than
ten minutes.
In a SlimLinc diaper, which comprises a substantial quantity of absorbent
cxllulose fluff
(70 grams) as well as the 12 grams of super absorbent polymer, liquid is
immediately
absorbed into the fluff rnmponent and, over time, the liquid is withdrawn from
the fluff and
absorbed by the super absorbent polymer. So long as the in-situ capacity of
the super
absorbent is not exceeded by the quantity of liquid. the fluff layer will,
within thirty
minutes, dry out in the sense that it will preferentially give up absorbed
liquid for absorption
by the super absorbent polymer in the diaper.
it tias been determined that urine absorbed in and held by super absorbent
material in
a disposable diaper is innocuous to a wearer and skin adjacent to and in
contact with a
diaper which contains urine held by super absorbent material (and no urine
held in a fluff
layer) is not damaged by such contact. This is true even for relatively large
volumes of urine
such as 100 or 200 milliliters. Prolonged exposure of skin to urine, either
direct exposure
to urine or exposure to urine which is atxtorbcd in fluff, can damage healthy
skin by causing
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26815-48
a rash or other reaction while prolonged ezposurc of already damaged skin can
inhibit
hearing and aggravate the damage to the skin:
As noted above, when only 15 milliliters of 0.996 NaCI solution is applied to
commercially available diapers including conventionally applied hot melt
adhesives with .
wetness indicators, the wetness indicators change color signalling the need
for a change of
the diaper. 'this was true, even for commercially available diap~:rs which
included super .'
absorbent materials. It will be appreciated that such use of hot melt
adhesives with wetness
indicators in a SIimLinc diaper, or other diaper including super absorbent
material, would
provide,,in many cases, a premature indication of the need for a diaper change
because:
1. it takes a~roximatciy two minutes for the super. absorbent
polymer in medium Slim_ Linc diapers .to completely atisofb 100
milliliters of 0.99t~ NaCI solution (0.0 skin wetness) but-the~super
absorbcnt has a rcmaininR in-situ capacity to completely absorb, in
ten minutes, another 2.t)0 milliliters of 0.996 NaCI solution;
2. in the two minutes that it takes for 1U0 milliliters of 0.9°Xo NaCI
solution to be absorbed out of the fluff into the super absorbent, that
quantity of 0.996 NaCI solution in the fluff would trigger a color .
change in conventionally applied hot melt adhesives with wetness
~ indicators.
While this phenomenon might increase salts of SIimLinc diapers and other
products
incorporating conventionally applied hot melt adhesives with wetness
indicators, it would
also unneocssarily increase the bucdcn on already overburdened landfills as
well as the
burden on care givers who tend to the changing of absorbent products used by
persons with
urinary incontinence. So, there is demonstrated a steed for a capacity monitor
which is
capable of providing a reliable indication of when the in-situ capacity of
super absorbent
material has been exceeded, without providing a premature indication. such as
when there
is substantial remaining in-situ capacity in the super absorbent.
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26815-48
SUi~ARY OF THE INVENTION
According to one aspect of the present invention,
there is provided a diaper including a capacity monitor,
said diaper comprising an absorbent core including super
absorbent material, a hydrophilic cover sheet and a water
impervious, translucent or transparent backing sheet, said
core being positioned between said cover sheet and said
backing sheet and said super absorbent material in said
diaper having a given in-situ capacity for synthetic urine,
said capacity monitor comprising an indicator extending
longitudinally a substantial distance, said indicator being
operable to provide a visually perceptible change when wet,
said indicator being positioned in said diaper adjacent to
said backing sheet so that the change of the indicator is
visually perceptible through said sheet and a substantially
water impervious baffle positioned inside the diaper between
said backing sheet and said absorbent core so as to cover
said indicator and separate it from said absorbent core,
said baffle having a width which is greater than that of
said indicator and a free edge around which synthetic urine
can migrate from said absorbent core to said indicator, said
baffle being operable to prevent the flow of synthetic urine
into wetting relationship with said indicator when the
diaper contains an amount of synthetic urine which is less
than a given percent of the in-situ capacity of the super
absorbent, and ineffective to prevent such flow when the
diaper contains an amount of synthetic urine which is
greater than the given percent of the in situ capacity of
the super absorbent, the given percent being at least 20.
According to another aspect of the present
invention, there is provided a diaper including a capacity
monitor, said diaper comprising an absorbent core comprising
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26815-48
a fluff component and a super absorbent component, a
hydrophilic cover sheet and a water impervious, translucent
or transparent backing sheet, said core being positioned
between said cover sheet and said backing sheet and said
super absorbent material in said diaper having a given in-
situ capacity for synthetic urine, said capacity monitor
comprising an indicator extending longitudinally a
substantial distance, said indicator being operable to
provide a visually perceptible change when wet, said
indicator being positioned in said diaper adjacent to said
backing sheet so that the change of the indicator is
visually perceptible through said backing sheet and a
substantially water impervious baffle positioned inside the
diaper between said backing sheet and said absorbent core so
as to cover said indicator and separate it from said
absorbent core, said baffle having a width which is greater
than that of said indicator and a free edge around which
synthetic urine can migrate from said absorbent core to said
indicator, said baffle being effective, in cooperation with
the components of the diaper, to prevent the flow of
synthetic urine into wetting relationship with said
indicator when the diaper contains an amount of synthetic
urine which is less than a given percent of the in-situ
capacity of the super absorbent, and ineffective to prevent
such flow when the diaper contains an amount of synthetic
urine which is greater than the given percent of the in situ
capacity of the super absorbent, the given percent being at
least 20.
According to still another aspect of the present
invention, there is provided a diaper including a capacity
monitor, said diaper comprising an absorbent core including
a fluff component and a super absorbent component, a
hydrophilic cover sheet and a water impervious, translucent
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26815-48
or transparent backing sheet, said core being positioned
between said cover sheet and said backing sheet and said
super absorbent material in said diaper being operable to
absorb up to a given, maximum quantity of a desired liquid
to the extent that, ten minutes after deposition of said
given amount of liquid, said diaper has a skin wetness
number of substantially zero, said capacity monitor
comprising a hot melt adhesive containing a color change
indicator, and extending longitudinally a substantial
distance, said indicator being operable to provide a
visually perceptible color change when said hot melt
adhesive is wet, said hot melt adhesive being positioned in
said diaper adjacent to said backing sheet so that the
change of color of the indicator is visually perceptible
through said backing sheet and a substantially water
impervious baffle positioned inside the diaper between said
backing sheet and said absorbent core so as to cover said
hot melt adhesive and separate it from said absorbent core,
said baffle having a width which is greater than that of
said hot melt adhesive and a free edge around which liquid
can migrate from said absorbent core to said hot melt
adhesive, said baffle cooperating with the components of the
diaper to control the migration of liquid from said at least
one absorbent component to said indicator so that said given
quantity of desired liquid deposited on the diaper produces
a visually perceptible change over a predetermined length of
said indicator and indicia provided on said diaper and
visible through said backing sheet, said indicia being
operable to indicate the predetermined length of said hot
melt adhesive which undergoes a visually perceptible change
when said given quantity of desired liquid is deposited on
the diaper.
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According to yet another aspect of the present
invention, there is provided an absorbent product including
a capacity monitor, said product comprising an absorbent
core including super absorbent material, said core having a
first and a second side, and a water impervious, translucent
or transparent backing sheet, said backing sheet being
positioned adjacent to said first side of said core and said
super absorbent material in said absorbent product having a
given in-situ capacity for liquid, said capacity monitor
comprising an indicator extending longitudinally a
substantial distance, said indicator being operable to
provide a visually perceptible change when wet, said
indicator being positioned in said absorbent product between
said backing sheet and said core so that the change of the
indicator is visually perceptible through said backing sheet
and a substantially water impervious baffle positioned
inside the diaper between said backing sheet and said
absorbent core so as to cover said indicator and separate it
from said absorbent core, said baffle having a width which
is greater than that of said indicator and a free edge
around which liquid can migrate from said absorbent core to
said indicator, said baffle being operable to prevent the
flow of a liquid into wetting relationship with said
indicator when the core contains an amount of the liquid
which is less than a given percent of the in-situ capacity
of the super absorbent, and ineffective to prevent such flow
when the core contains an amount of the liquid which is
greater than the given percent of the in situ capacity of
the super absorbent, the given percent being at least 20.
The instant invention is based upon the discovery
of a capacity monitor which is operable to provide a visible
signal when the in-situ capacity of super absorbent material
in a given absorbent core has been, or is close to being,
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26815-48
exceeded by liquid absorbed in the absorbent core. In a
diaper comprising a water impervious backing sheet and an
absorbent core comprising fluff and super absorbent
material, the monitor comprises an indicator, such as a hot
melt adhesive with a wetness indicator between the absorbent
core and the backing
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WO 94!10958 ' PGT/US93/10890
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sheet. The monitor further comprises a substantially water impervious baffle
positioned
between the absorbent core and the hot melt adhesive, to prevent substantial
contact between
the indicator and liquid contained in the absorbent core, except when the
quantity of such
liquid exceeds a predetermined threshold volume of liquid: The monitor may
further
comprise a strip of non-woven material, or the like, positioned between the
indicator and
the backing sheet to prevent sticking therebetween: When a quantity of liquid
which exceeds
the threshold volume of liquid is deposited in the diaper, some of the liquid
will migrate
around the baffh and trigger a color change or the like in the indicator. The
threshold level -
is predetermined, for a given diaper, relative to the in--situ eapacity of-the
super absorbent
!U material in the absorbent core of the diaper: Preferably, the threshold
volume is at least 20%
of the in-situ capacity of the super absorbent. More preferably, the threshold
is at !cast 3U%
of the in-situ capacity while 4U% is mare preferred still. In some cases, the
threshold may
approach or even exceed the in-situ capacity' of the super absorbent in the
absorbent core,
if the other absorbent material therein is adequate to 'take up the slack. 'W
hen a strip of
non-woven material, or the like, is proyidcd between the indicator and the
backing sheet,
it facilitates the transfer of liquid from the core to the indicator so that a
change in the
indicator occurs reliably when the threshold amount is exeeedec3; thereby
overcoming any
tendency of the indicator to stick to the backing shoes and prevent a change
in the indicator.
Iri cases where the threshold is substantially below the in-situ capacity of
the . super
absorbent; the monitor may further;comprisc printed i'~dicia which provides a
visually
discernible signal which, together with the degree or extent or length
indicator which
changes color or the like, provides an indication of the remaining in-situ
capacity, if any,
of the super absorbent material in the absorbent core.
BRIEF DESCRIPTION OF THE 17RAWINGS
FIG. 1 is plot of elapsed time before a prior art diaper including super
absorbent
material achieves a zero skin wetness number: versus quantity of liquid
deposited in the
diaper.
FIG. 2 plan view, partially broken away, of a diaper incorporating a capacity
monitor
according to the present invention.
FTG. 3 is a crass sectional view, taken along the lines 3 - 3 of Fig. 2,
showing some
details of the capacity monitor according to fhc present invention.
'1~0 94/k09S8 . ~ PCT/US93/10890
FIG. 4 plan view, partially broken away, of .. ~; :preferred embodiment of a
diaper
incorporating a capacity monitor according to~ the pi~esent invention.
FIG. 5 is,a cross sectional view, taken along the lines 5 - 5 of Fig. 4,
showing some
details of a preferred capacity monitor according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to Fig. 2, a disposable diaper is indicated generally at 10. The
diaper 10
comprises a water impervious backing shcef 13, a non--woven facing sheet 14
which would
contact a wearer's skin when the diaper 1U is in use and an absorbent core 16.
In acebrdance
with the invention, the absorbent core has at least two absorbent 'components,
which are
illustrated in and discussed below in connection with Fig. 3. Specifically,
the core 16 has
an absorbent fluff component and -a Super absorbent cotttponent. In accordance
with the
present invention, the super absorbent may be incorporated into the absorbent
core in ariy
suitable manner including those disclosed in said US Patent No. 5,072,687. The
patent
discloses the deposition of particulate super absorbent into a fluff Layer or
ball. Also
disclosed is a construction wherein super absorbent is contained in a
laminate, i.e., one of
more sheets of tissue with super absorbent adhered to and supported thereon,
and the
laminate is incorporated in an absorbent core. A combination of these
constructions is also
disclosed where loose super absorbent particles arid laminate containing super
absorbent are
combined with an absorbent cellulose fluff ball. lfic~e components of diaper
IO are .
conventional and are well known in the industry.
A portion of the water impervious backing sheet 12 has been cut away in Fig. 2
to
illustrate a capacity monitor; according to the present invention, indicated
generally at 20.
The monitor 20 comprises a baffle 22 which extends along the longitudinal
centerline of the
diaper 10 and an indicator 24 which'undergoes a visually perceptible change
when wetted.
The indicator 24 is positioned between the backing sheet I?. and the absorbent
core 16. The
baftlc 22, in turn; is positioned between the absorbent core 1G and the
indicator 24. The
baffle 2,2 is operable to prevent contact between liquid held in the absorbent
Gore 16 and the
indicator 24. Tlte rnonitar 20 is constructed, however; so that when there is
quantity of
liquid in the absorbent core which approaches or exceeds the in-situ capacity
of he super
absorbent in the absorbent core, the some of the liquid will contact the
inditratar 24 effecting
a perceptible change in it. Further details of construction for the digger i0
as well as the
capacity monitor 20 arc discussed below with reference to °Fig. 3.
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;..Y WO 94/)10958 ~ ~ ~ ~ ~ ~ ~ . .. ~ : PCT/US93/10890
'~ :; J
The baffle 23 may comprises a sheet of polymeric, water impervious film or
paper
which has been treated ox coated to render it water impervious or
substantially so. The baffle
22 is positioned between the absorbent core l6 and the water impervious
backing sheet 12.
The core 16, as previously irxdicated, includes a fluff component 26 and a
super absorbent
component which, in the illustrated embodiment, comprises discreet particles
of super
absorbent 28 carried in the fluff 26. A layer of tissue 30 is positioned
between the fluff 26
and the non-woven facing sheet 14. As disclosed in US Patent No. 5,072,687, a
layer of
laminate (not shown) may bG setbstitutcd for the tissue layer 30, or combined
with it and
positioned between the fluff layer 2G and the tissue Iaycr 30; The monitor 20
further
comprises the indicator 24 which is positioned between the baffle 23 and the
water
impervious backing sheet 12, The baffle 2? physically separates the fluff
layer 26 and the
absorbent core 1 G from the indicator 24 so than there is no direct contact
between the
indicator 24 and the fluff layer 26 or the absorbent core 1G.
The baffle 22 is comprised, at leash in part, of a hydrophobic material so
that it
constitutes a .physical barrier to the flow of liquid from the fluff layer 26
through the baffle
22 to he indicator 24. With the baffle ?2 in place, liquid in the fluff layer
26 can reach the
indicator 24 only if it travels around free edges 32 of the baffle and travels
between the
baffle 2? and the water impervious backing sheet 12 to reach the indicator 24.
So long as
the volume of Liquid in the diaper is such that the liquid can be held tightly
or fairly tightly
in the absorbent components of the'absorbent core 16, the liquid will not
reach the indicator.
When the volume of Liquid in the diaper exceeds the volume which the absorbent
components of the core 16 can hold fairly ightiy; there will be excess Liquid
in the diaper
IO such as would tend to pooh or puddle adjacent to or on the surface of the
backing sheet
I2 near the baffle 22 and some of it would travel around the free edges 32 of
the baffle 22
and teach the indicator. In other words, there is a threshold level of liquid
which must be
deposited on the absorbent core in order for any liquid to reach the
indicator. Thus, the
movement of liquid from the absorbent core 16 to the indicator 24 is enabled
when there
is enottglz liquid. The edges 32 of the baffle 22 are free edges in the sense
that they are not
adhered to he backing sheet 12. Care must be taken, in producing a diaper with
a capacity
monitor 20 according to the invention in case the diaper includes conventional
lines of hot
melt adhesive without a wetness indicator 33 to adhere the absorbent core 16
to the backing
sheet''12. Such adhesive Lines 33 must-not completely adhere the free edges 32
of the baffle
CA 02149325 2002-11-25
26815-48
?? to the backing sheet 12, or vice versa. Instead, the hot melt adhesive
lines 33 would be
positioned, as shown in Fig. 3, where they do not engage the free edges 32 of
the bafflc'22.
The indicator 24 preferably comprises a hot melt adhesive with a wetness
indicator. A
preferred iridicator material is NICOL-MELT 82525 'which is available ttuough
Swift
Adhesives or its parent Reichhotd Chemical. This particular hot melt material
is translucent
and has a yellow color when it is allied, for example, to the baffle, ?.?. or
the water
impervious backing sheet i2. In the illustrated embodiment, it is preferred
that the indicator
consist of a ribbon of the indicated hot melt adhesive with wetness indicator
having a width
of approximately one quarter to one half inch (0.5 to 1.5 centimeters) and a
thickness of
l0 about one mil (0.035 millimeter). Insofar as the operability of
th'te~~present invention is
~r:~.
concerned, the indicator may be applied either to the backing sheet 13 or the
baffle 22.
Upon contacting most liquids, including synthetic and non-synthetic urine, the
NICOL-
MELT will change color, at the contact areas, from a tight or faint
translucent yellow to a
relatively dark and deep blue. This color change is readily pcroeivable
through the water
impervious cover 12 which, as previously mcntioried, is transparent of
translucent.
The baffle 22 has a width which exceeds the width of the indicator 24.
Consequently,
free edge portions 32 of the baftlc ?3 overlap edges 34 of the indicator 24,
thereby
hindering liquid in the absorbent core 16 from traveling to the indicator 24.
Good results
have been obtained with a coated paper baffle having a width of approximately
bnc and one
quarter inches (3 centimeters) and an indicator.having a width of about vne
quartet inch, so
that at (cast one half inch (1 ~5 centimeters) of the baffle overlapped the
edge of the
indicator on each side.
The indicator 24 comprising the hot melt adhesive with wdncss indicator serves
the
color ottattge function noted above and can also serve to secure the baffle 22
in the diaper
10 relative td the water impervious backing sheet 12 as well as the bther
ctimporibnts.
Nowevcr, the baffle 22 does not need to be adhered by an indicator 24 to the
backing sheet
12; the absorbent core 1G is secured to the backing sheet 12, as by adhesive
lines 3~ and
the baffle 22 could be held captive between the backing sheet 12 and the
abstirbtnt core 1G.
As previously noted, the overlapping, free edge portiotrs 32 of the baffle 22
are trot adhered
to the backing sheet 12 so that liquid can travel from the absorbent core 16,
between the
baffle 22 and the backing sheet 12 and reach the indicator 24.
In accordance with the invention, the diaper components just described
cooperate to
determine, for a given diaper, the threshold ~vel of liquid which will be
effective tv change
*Trade-mark
to
W~ 94/10958 ~ ~ ~ ~ ~ ~ ~ . ~ P~.'T/US93110890
~~:i~;":
l;a.~.~.
the indicator 24. It will be appreciated that there is a wide range of
thresholds which arc
encompassed by the broader aspects of the present invention. The threshold
volume can be
affected by controlling:
- the degree of overlap of the free edges of the baffle;
- the identity and shape of the particular indicator;
- the identity and quantity of the super absorbent;
- details of construction of the absorbent component; and
- the amount and type of fluff, or the like, in the absorbent core.
Generally speaking, increasing the amount of overlap of the baffle 22 will
increase the
threshold level while decreasing the am~unt of overlap has the og~osite
effect. The threshold
could he increased by incorporating a particularly fast super absorbent in the
absorbent core.
As previously indicated, it is preferred, in a diaper according to the present
invention; to
have a threshold of at least 20% of the ire-situ capacity of the super
absorbent in the diaper.
A 30% threshold is rriore preferred while 40% is still more preferred. It will
be appreciated
that a threshold approaching or even exceeding the in-situ capacity of the
super absorbent
component could be operable in a diaper according to the present invention.
Since the
absorbent core of a diaper according to the invention includes another
absorbent component;
such as fluff, a capacity monitor could be incorporated in a diaper according
to the invention
having a threshold exceeding the in-situ capacity of the supea absorbent if,
for example; ehe
fluff component could handle the excess volume of liqui8: lZcgardlcss of the
threshold value
of a particular combination of diaper and monitor, if the threshoid is
exceeded, liquid will
reach some portion of the indicator.
Prior art diapers which include super absorbent and fluff and further include
hot melt
adhesives with wetness indicators; do not have baffles corresponding with the
baffle 24.
Consequently, these diapers ha a minuscule thresholds of 5; 1U or 15
milliliters of synthetic
urine: A quantity of liquid in excess of these minor thresholds will effect a
change in the
wetness indicators in the hot melt adhesive, indicating the need for a diaper
change, even
if the vast majority of the in-situ capacity of super absorbent material in
the diapers is
unused. It-is estimated hat the threshpld of such prior art diapers is less
than 5°l0 of the in-
situ capacity of super absorbent in the diapers. In contrast, a capacity
monitor in a diaper
according to the present invention has a threshold of at least 20% of the in-
situ capacity
of super absorbent in the diaper,' although 30 to 40%- thresholds are
preferred:
EXAIvf Pi,ES l and 2
11'
WO 94/10958 .. PGT/US93/10890 ,.. :.~.
Some medium SlimLinc diapers were produced but were modified to include
capacity
,;
monitors according to the invention. liz~all of the diapers tested, the
indicator was a ribbon,
approximately one quarter inch wide and one mil thick, of NICOL-MELT 82525 hot
melt
adhesive with' wetness indicator. The baffles wart made of paper which had
been
treated/coated to make it impervious to liquid: The baffles were one and one
half inch wide.
Indica was printed on the baffle paper and was visible through; the indicator
and the water
impervious backing sheet: The indicia comprised the word "KOMFORT" in ,a
repeating
pattern extending down the center of the diaper, as indicated by the reference
numeral 40.
Tie letters were sized and positioned so that each word was four and one half
inches tong.
14 The diapers had absorbent cores comprising 12 grams of Aridall super
absorbent dispersed
in ?0 grams of cellulose fluff.
One such diaper was tested by depositing in it 0.9°l0 NaCL solution at
a rate of 7
milliliters per second, in 4U milliliter increments with a final increment of
45 milliliters. The
increments were timed to be at least ten minutes apart and, ten minutes after
each 40
milliliter deposit, the indicator 24 was observed for evidence of a change in
color. The
results of this test are set forth below:
EXAMPLE Total Volurcae of Description of color change
0:9!a
NaCI incrementally
deposited on diaper
(milliliters)
t 40 no color change
1 80 no color change
'20: 1 120 no color change
~
1 160 color change in 1/2 inch
length'af indicator
1, ~~ color change in three 1/2
inch lengths of the indicator
1 240 color change in three 1/2
inchlengths of the indicator
I X85 color'change in four 1/2
inch tengths of the indicator
Seven
diapers
produced
as-described
above
were
sizrtilariy
tested
except
that
the
0.9l0
NaCI seven different quantities
solution on seven
was
deposited
at a
controlled
rate
in
WO 94/10958 2 ~ ~ ~ ~ ~ ~ P'CT/liJS93/10890
~~~Sx'.' . .. -.
different diapers. The results are set forth below:
EXAMPLE Total Volume of Dcscziption of color change
0,9%
NaCI deposited on
diapers (milliliters)
2a 40 no color change
2b 80 no color change
2c '12p no 'color change
2d 160 color change in twa areas;
about 1 inch length, each
,i IOU color change in three ,areas,
about l inch in length,
each
2f 2.~0 color change in three areas,
about 1 inch in length,
each
z0 12g 285 color change in trvo areas.
about l inch in length,
each
These
tests
dernonstratc
that
the threshold
of the
capacity
monitor
which
in the
modified
medium
SlimLina
diaper
was -between
120 and
160 milliliters,
regardless
of whether
liquid
was applied
all at
once
or in
spaced
apart
intervals.
With
one exception;
these
tests
indicate
that;
once
the threshold
was exceeded,
there
was a
color
change
in a
portion
of the
indicator
and he
length
of the
affected
portion
was proportionate
to the
volume
of liquid
which
exceeded
the threshold.
In a
diaper
according
to the
invention,
having
a threshold
which
is
significantly
below
the in-situ
capacity
of the
super
absorbent,
indicia
such
as 40;
having
a predetermined
icngth
can be
combined
with
the monitor
so as
to provide
an indication
of
the
remaining
in-situ
capacity
(or othcx
measure
of capacity)
when
the threshold
is
exceeded:
With
reference
to Fig.
2, the
length
of the
repeating'
indicia
~0 has
been
predetermined
relative
to a
particular
capacity
of a
diaper
corresponding
with
Examples
1
and 2a-2g.
The length
of the
indicia
4t? was
based
upon
the capacity
of the
diaper
to retain
synthetic
urine
with
skin
wetness
of 0.0
after
ten minutes
which:
as shown
in Fig:
1, is
about
285 milliliters.
With
a threshold,
of between
120 and
160 milliliters,
exhaustion
of the
remaining
capacity
of the
diaper
(approximately
140 millitifcrs)
will
be associated
with
a
color
change
in the
indicator
over
approximatelyfour
and one
half
inches
of its
length:
The
indicia
40 provide
a convenient
measure
of this
length
as well
as a
convenient
way to
ascertain,
far example
when
substantially
Icss
than
four
and one
half
inches
of the
indicator
WO 94/10958 ' . ' ' PC>f/US93/10890
~~'.°
w~:d~
has chanced color, that the diaper still has substantial capacity to absorb
additional synthetic
urine and exhibit, ten minutes after the synthetic urine is deposited, skin
wetness of U.U.
It has been determined that the hot melt adhesive with wetness indicator 24
(Fig. 3) can
stick to the backing sheet 1? to such an extent that it prevents a change from
occurring in
the indicator ?4, even when liquid in an amount excceciing the threshold
amount is absorbed
in the absorbent core. Thisproblem is exacerbated by heat. It has further been
determined
that problems associated with sticking between the indicator 24 and the
backing sheet I2
can be overcome in a prcf~rred embodiment of the present invention which is
described
below with reference to Figs. :l and 5
In a preferred embodiment, a comfort monitor indicated generally at 20' (Figs.
~ and
5) includes a strip of non-woven material 42-positioned between the backing
sheet.12 and
the indicator ?4: Preferably, as shown in Fig. 5, the width of the non-woven
strip ~42 is less
than the width of the baffle 3, but is greater than the width of the indicator
strip 24. Non-
woven material is generally hydrophobic, rncaning that it repels water and
other liquids. In
accordance with the preferred embodiment of the present invention, the non-
woven strip 42
is treated with a surfactant (not shown) to make it hydrophilic. As a
consequence, the rested
non-woven strip can transmit liquid, when available, into contact with the
indicator 2~ to
effect a color change in the indicator. This construction has been found to
preserve the
threshold properties discussed above; while ensuring that liquid; in an amount
exceeding the
threshold; will reach the indicator 24 and effect a changs~ in it. Further;
the strategic use of
a hydrophilic strip of .non-woven; or the like, as described above; prevents
the indicator;.
when exposed to high tempcxatures; from sticking to the backing sheet l2 to
such an extent
that the monitor is rendered inoperable.
'f'he . foregoing description is infcndcd to enable those skilled in the art
to practice the
present invention and con5titutcs the best mode presently known for practicing
the invention.
For example, although the invention has been described in the context, of a
diaper product,
it will be appreciated that the invention has broader application to the field
of products
having an absorbent corn including super absorbent polymer with a capacity
moriieor for
indicating when' a threshold amount of liquid has been absorbed in the core.
Undoubtedly,
modifications will occur to those skilled in the art, and such modifications
may b~ resorted
to without departing from the spirit and scope of fhe invention disclosed
herein and claimed ;
below.
