Note: Descriptions are shown in the official language in which they were submitted.
~25~3'~3
ABSORBENT STRUCTURE CONTAINING CORRUGA~ED W~B LAYERS
ASSOCIATED WITH SUPERABSORBENT
Background of the Invention
The present invention relates to new and improved
absorbent structures and more particularly to new and
improved absorbent structures incorporating therein
corrugated web layers which are associated with
superabsorbent.
Disposable absorbent products have been known for some
time, including such products as disposable diapers,
sanitary napkins, wound dressings, bandages, incontinent
pads, and the like. These products incorporate an
absorbent batt which is used to absorb and hold, or
contain, body fluids. Initially in many of these
products, especially diapers and sanitary napkins, the
absorbent batt comprised what is termed "wadding" or plies
of tissue. The wadding was disposed between a liquid-
impermeable backing and a liquid-permeable facing and the
plies of tissue were used to absorb and, hopefully,
contain the liquid within the product. A diaper which
utilizes such an absorbent batt is disclosed in
U.S. Reissue Patent No. 26,151.
The wadding type of batt was replaced, for the most part,
by an improved absorbent batt which comprises what is
termed "fluffed woodpulp fibers~. This absorbent batt
comprises a layer of individualized woodpulp fibers with
the layer having substantial thickness. A diaper which
incorporates such a fluffed woodpulp absorbent batt is
described in U.S. Patent No. 2,788,003. This diaper had
JBD-32
~Z53320
improved absorbent capacity and somewhat better contain-
ment than a diaper using a wadding layer. Also, the
fluffed woodpulp layer is quite soft, flexible and
conformable, and hence produces an improved diaper over
diapers using wadding as the absorbent layer.
Though the fluffed woodpulp absorbent batts have improved
capacity, the efficiency with which the capacity is used
in a diaper or sanitary napkin is poor. The reason for
this is that the fluid to be absorbed is generally
deposited in a localized area within the absorbent batt
and the ability of the fluid to move along the plane of
the batt is poor. The fluid tends to follow a radial
wicking path and consequently moves to the closest edge of
the batt where it generally is no longer contained and the
product leaks.
U.S. Patent No. 3,017,304 discloses an absorbent product
which incorporates in the product a densified paper-like
layer. This paper-like layer acts as a wick, i.e., li~uid
which is placed on the layer tends to move rapidly along
the plane of the layer. When incorporated in combination
with fluffed woodpulp fiber, the resultant product uses
the absorbent capacity of the fluffed woodpulp much more
efficiently. ~iapers which incorporate this paper-like
layer combined with fluffed woodpulp are disclosed and
described in U.~. Patent Nos. 3,612,055 and 3,938,522.
This concept of combining wicking ability, or a capillary
skin or layer, with fluffed woodpulp fibers has gained
wide acceptal~ce in many absorbent products, including
disposable diapers and sanitary napkins. ~ven though
these products make much greater use of the capacity of
the absorbent batt, they still do not totally contain the
absorbed liquid. It is probable that these products will
leak before the full capacity of the batt is used for
JBD-32
- ~2S~3320
absorption or,~at the very least, before the entire liquid
void by the user is absorbed. This is especially true
when pressure is placed on the batt while wet. For
example, a baby sitting down on a previously wetted diaper
will very often cause the batt to leak.
An incontinent adult faces many problems. First, the void
of urine of an adult generally is much higher in volume
than that of an infant. Second, a bulge under clothing
due to a diaper is accepted by society for an infantr but
the ambulatory adult with an incontinence problem longs
for a product which is not visible through ordinary
clothing. Third, the proportions and shape of the legs
and torso of the adult differs considerably from those of
an infant. Therefore, a mere enlargement of an infant
diaper, such as that shown in U.S. Patent 4,253,461, is
not a satisfactory product.
A number of years ago "superabsorbent materials", i.e.,
materials which will absorb many times their weight of
liquid were developed. Since the development of such
materials, there have been many attempts to incorporate
them in absorbent products such as diapers and sanitary
_ napkins to enhance the absorptive performance of these
products. Theoretically, a minimum amount of
superabsorbent incorporated in a product would make that
product perform as well as or better than the prior art
products. Perhaps one of the first products to
incorporate such a superabsorbent material in a disposable
diaper is disclosed in U.S. Patent No. 3,670,731. This
patent discloses an absorbent dressing comprising an
absorbent layer sandwiched between a permeable facing and
an impermeable backing sheet. The absorbent layer
contains water-insoluble cross-linked hydrocolloid polymer
as the superabsorhent material.
JBD-32
~53~20
Even though superabsorbent materials have been available
for some time, they have not gained wide acceptance in
absorbent products such as dispGsable diapers and sanitary
napkins. A primary reason for this lack of acceptance is
failure to develop a product capable of economically
utilizing the highly increased absorptive capacity of the
superabsorbent material. In order to economically utilize
a superabsorbent, the liquid being absorbed must be
transported to the superabsorbent material. In other
words, the superabsorbent material must be placed in
contact with the liquid. Furthermore, as a superabsorbent
material absorbs the liquid, it must be allowed to swell.
If the superabsorbent is prevented from swelling, it will
cease absorbing liquid. Hence, if the superabsorbent
material is to function in diapers and sanitary napkins,
werein the liquid to be absorbed is placed in a small void
area, the structure of the absorbent layer containing
superabsorbent materials appears to be critical. Over the
years a number of techniques have been disclosed in an
attempt to provide structures which make efficient use of
the superabsorbent material. Such products are disclosed
in U.S. Patent Mo. 4,103,062; 4,102,340 and 4,235,237.
In addition, methods for incorporating superabsorbents
into suitable layers or suitable configurations which can
be placed in an absorbent product, are disclosed in
U.S. Patent No. 4,186,165; 4,340,057 and 4,364,992. To
date, none of these products has met with any substantial
commercial success.
In both the infant diaper and adult incontinent product
marketplace, a product is needed which has a large storage
capacity. For instance, shaped containers have been
suggested. However, these containers have been
substantially rigid, do not stay in place, and are guite
uncomfortable. A product with a substantially large
liquid storage capacity, with an ability to move liquid
JBD-32
lZS~32~
away from the void zone, which is disposable, which i5
comfortable, and which does not show through wearing
apparel is needed in the marketplace.
S The present invention provides a new and improved
absorbent product which provides a large storage capacity
and ability to transport liquid from the void zone which
is soft and comfortable and which can be designed so as
not to be apparent through normal clothing. In addition,
the new absorbent product will contain absorbed liquid
even when pressure is placed upon the product during use.
Summary of the Invention
The present invention provides a disposable absorbent
product comprising a corrugated fibrous web having
associated therewith at least about 10% by weight of said
web of superabsorbent. The product also comprises a
liquid-impermeable barrier covering at least one side of
the web, and a li~uid-permeable facing covering at least
the other side of the web. The corrugated web is
stabilized to retain its transverse folds when wet.
The fihrous web comprises substantially hydrophobic,
resilient, preferably synthetic fibers generally in the
form of a nonwoven web.
The superabsorbent in the form of particles, globules,
film pieces, granules, powder or the like is distributed
in the product and is associated with the fibrous web in
such a manner as to permit maximum utilization of the
superabsorbent as it contacts the liquid.
JBD-32
12S~3~
6--
The liquid-impermeable barrier generally is a waterproof
type film such as polyethylene or polypropylene. It
covers at least one side of the corrugated fibrous web.
The liquid-permeable facing generally is a nonwoven fabric
or a perforated film or the like. The facing covers at
least one side of the corrugated web, that slide being the
side opposite the one covered by the barrier.
After or during corrugation of the web, the web is
stabilized to retain its transverse folds, even when the
product becoMes wet. The stabilization is provided by
applying a layer of adhesive on one side of the web or by
placing fusible fibers in the fibrous layer and raising
the temperature of the web to a temperature close to the
melting point of the fusible fibers. This stabilization
is effected by the transverse folds partially adhering one
to another.
When the absorbent product of the present invention is
utilized, the liquid enters the corrugated web and the web
because of its open structure, provides a large storage
area. The superabsorbent is placed in contact with the
liquid and the containing features of the web coupled with
the liquid-impermeable barrier provide time for the
superabsorbent to absorb the liquid and swell. The
corrugations of the corrugated web preferably are placeA
in an absorbent structure, such as a diaper or incontinent
product, so as to lie parallel to the longitudinal axis of
the product.
BRIFF DESCP~IPTION OF THE DRAWINGS
Figure 1 is a perspective view of one e~bodiment of the
present invention, the view being partially broken away
for clarity;
JBD-32
1;Z5~3Z~
Figure 2 is an enlarged cross-sectional view through lines
2-2 of Figure l;
Figure 3 is a perspective view illustrating another
embodiment of the present invention;
Figure 4 is a perspective view illustrating a further
embodiment of the invention;
Figure 5 is an enlarged cross-sectional view through lines
5~5 of Figure 4;
Figure 6 is a perspective view illustrating a still
further embodiment of the present invention; and
Figure 7 is an enlarged cross-sectional view through lines
7-7 of Figure 6.
DETAIL~D DESCRIPTION OF THE IN FMTIOrl
Figure 1 provides a perspective view of an absorbent
product 10 having a corrugated fibrous web 12 sandwiched
between a liquid-permeable facing 16 and a liquid-
impermeable barrier 18. The absorbent product permits
ingress of liquid through the liquid-permeable facing 16
into the corrugateA web 12, which web contains
superabsorbent materials. The corrugated web 12 is
stabilized by the fusion of fusible fibers so that when
the liquid enters the product, its transverse folds of the
corrugation remains substantially stable.
Figure 2 provides an enlarged cross-sectional view along
lines 2-2 of Figure 1. The portion of the absorbent
product 20 consists of the corrugated web 22 containing
superabsorbent 24 distributed throughout the corrugated
fibrous web 22. Fusible fibers 26 have been rendered
1253;:~2(~
sufficiently tacky to secure the corrugations so as to
prevent destruction or interference with the transverse
folds even when the product is wet. The liquid-permeable
facing 16 permits ingress of liquid into the product and
the liquid-impermeable barrier 18 prevents the spilling of
liquid from the product.
Referring to Fi~ure 3, a diaper 30 is depicted. A liquid-
permeable facing 32 such as a nonwoven fabric provides the
diaper surface. A liquid-impermeable substance 34 such as
a polyethylene film, provides a liquid-impermeable barrier
for the diaper. The diaper structure 30 contains a
corrugated fibrous web 33 sandwiched between the facing 32
and the backing 34. The corrugated web 33 is that which
is described in Figure 1. The diaper side edges are
gathered in the crotch region by elastic members 37. To
secure the diaper about the waist of the wearer, tape tabs
39 are provided. The diaper product 30 generally has the
corrugated web 33 placed in such a manner that the
corrugations run parallel to the longitudinal axis of the
product.
Referring now to Figure 4, a urinary pad 40 is depicted.
The urinary pad 40 has a liquid-permeable facing 42
covering the entire upper surface. Immediately beneath
the facing 42 is a liquid barrier 44 which encompasses the
entire product except for the opening 45 on the upper
surface which lies immediately below the facing 42. The
opening 45 permits ingress of fluids. The li~uid barrier
44, which encompasses the vast majority of the corrugated
web absorbent portion, prevents the leakage of liquid
after its entry into the product. The corrugated fibrous
web contains superabsorbent,
Figure 5 is an enlarged cross-sectional view of Figure 4
taken along lines 5-5. The facing 52 is the layer which
JBD-32
- l~S33;~0
is placed against the skin of the wearer. The liquid
barrier 54 encompasses the corrugated web 53 containing
the superabsorbent except for the opening 55 through which
liquid is permitted to enter. The corrugated web 53 is
similar to that depicted in Figure 2. As shown in
Figure 5, the corrugations of the corrugated web run
parallel to the longitudinal axis of the product.
Figure 6 depicts a sanitary napkin 60 having a fabric
overwrap 62 which is liquid-permeable.
Figure 7 depicts an enlarged cross-sectional view of
Figure 6 taken along line 7-7. The cross-sectional
portion of product 70 is provided with a liquid-permeable
overwrap 71 appearing with its overlapped portion on the
upper surface of the drawing. Immediately below is a
moisture-impermeable barrier 74 which encompasses the
sides and the bottom of the product. The corrugated web
consists of a fibrous web layer 76 and another layer 78
which layer has a higher capillary pressure than the
fibrous web layer 76. Superabsorbent 75 is placed in the
pockets created by the base of the corrugations of the web
and the liquid-impermeable backing 74. The superabsorbent
is substantially trapped in this pocket. The overwrap 72
provides the facing on the lower surface in the drawing.
The facing 72 is placed against the skin of the wearer.
These and other pro~ucts such as incontinent pads, wound
dressings and the like may be prepared in accordance with
the present invention.
In the absorbent products of the present invention, the
corrugated fibrous web consists of one or two or more
layers. The fibrous web layer initially receiving the
liquid void is the fibrous layer of the corrugated fibrous
web having the lowest capillary pressure. The requirement
JBD-32
~ZS33ZO
--10--
for this fibrous web layer is the ability to accept liquid
rapidly and at the same time to maintain the void volume,
even with body weight pressure applied, until the
remaining portions of the structure substantially drain
the liquid from this first fibrous web and begin
transporting the liquid away to another part of the
product. Draining of the liquid from the first fibrous
web generally is accomplished by immediate contact, by the
first fibrous web layer, with a higher capillary pressure
region in the form of a second layer, united with, but
discrete from the first fibrous layer. The higher
capillary pressure of the second layer provides the means
for draining a substantial portion of the liquid load from
the first fibrous layer and the higher capillary pressure
also assists in transporting the liquid from the void zone
to another part of the product. In the ~eantime, the
superabsorbent associated with the second layer is
absorbing liquid and swelling either within the
corrugations or the zone in which the superabsorbent was
placed.
What appears to be only a s~all difference in capillary
pressure, is all that is requireA for the second layer to
attract and drain the first fibrous layer of liquid the
latter has received. The force causing a liquid to enter
a cylindrical capillary is expressed by the equation:
P - (2v cos e)
r
wherein the force is represented by the capillary pressure
and:
P is the capillary pressure,
v is the surface tension of the liquid,
e is the liquid-fiber contact angle, and
JBD-32 r is the capillary radius.
125~2~?
With a given liquid, the pressure (capillary force)
increases with the cosine of the liquid-fiber contact
ang~e (reaching a maximum where the angle is zero) and
also increases with narrower capillary radii so that
narrower capillaries will draw liquid from the wider
ones.
The relative wickability between the first fibrous layer
and the second layer is affected by both the relative
densities of the layers and the relative wettability of
the individual fibers in each layer. The individual
fibers of the second layer have substantially smaller
liquid-fiber contact angles than those of the first
fibrous layer overcoming the density difference and
providing a significant overall increase in capillary
pressure to absorb liquid into the second layer.
The second layer fibers (or particles) and the density of
the layer are selected to create the small, but
significant difference in capillary pressure from the
first fibrous layer.
mhe first fibrous layer is preferably a fibrous web which
is of substantially high loft and which upon dry
co~pression, followed by release, has a tendency to return
substantially to its original thickness. For instance,
fibrous webs formed from synthetic staple fibers such as
polyethylene, polypropylene, polyester, nylon, bi-
component fibers, mixtures thereof, and the like are
particularly suitable. ~owever, cellulosic fibers such as
rayon may be used. Generally, the fibers are carded to
form a web which is then stabilized if needed.
Stabilization may be achieved by heat-through bonding,
adhesive bonding, point embossing with heat or adhesive or
both, and the like. The stabilizing process is selected
according to the fibers used and the process used to form
JBD-32 the web. Other suitable procedures for for~ing a web
i;~S3~0
include air-laying, wet-laying, spun-bonding, laying of
melt blown fibers and other known techni~ues. The fibrous
web before corrugation preferably has a dry bulk of at
least about 10 cc per gram and a weight less than about
4 ounces per square yard.
In one embodiment, a blend of staple polyester fibers with
a minor portion of fusible fibers, such as lower melt
polyester fibers, are air-laid to form a web. The web is
subsequently lightly bonded by passing hot air through the
fibers making the fusible fibers tacky so as to stick to
each other and the staple fibers, to provide the desired
degree of integrity to the web structure.
The second fibrous (or particle) layer is generally
comprised of fibers having a lower liquid-contact angle or
a layer having a narrower capillary radii, or both.
~xamples of such fibers include hydrophilic fibers such as
rayon fibers, cellulosic fibers, or peat moss, or mixtures
thereof, or acrylic fibers, or the like. Cellulosic
fibers inclucle woodpulp fibers, cotton linters and the
like.
- The woodpulp fibers generally are those that are used to
form the fluff or fibrous batt layer in conventional
absorbent products such as disposable diapers, sanitary
napkins, etc. Other cellulosic fibers that might be used
are rayon fibers, flax, hemp, jute, ramie, cotton, and the
like. The fibers, or peat moss, or mixtures thereof are
placed in such a way as to form a layer in which the
particles are close to one another so as to promote
wicking of liquid in the plane of the layer.
The second layer can be preformed and placed next to the
first fibrous layer or, the particles (fibers or peat moss
JBD-32
12s33z~
-13-
or mixtures thereof) can be air-laid or wet-laid onto the
first fibrous layer before the transverse folding or
corrugating takes place.
Corrugating or transverse folding of the web, whether the
web be one, two or more layers, is provided by known
procedures such as that exemplified in U.S. Patent
4,111,733.
After or during corrugating, the fibrous web, whether it
be a one or two layer structure, is stabilized to prevent
the corrugations from pulling apart and flattening out.
~ne method of stabilizing the web is accomplished by using
adhesive binders which may be a latex resin or other
adhesive. A typical way to stabilize the corrugated
material is to spray an adhesive on one corrugated surface
thereof. Generally, the surface selected for the
stabilizing is the surface opposite that which will
receive liquid initially. Thereby, the non-stabilized
surface is open and available to receive fluids. Another
method of stabilizing the web is provided by adding a
minor portion of fusible fibers to the fiber blend which
forms the corrugated fibrous web. The corrugated web is
_ subjected to temperatures sufficient to substantially melt
the fusible fibers, thereby providing light, but
sufficient, bonding between the corrugations.
Any additional layer~ provided in the corrugated fibrous
web generally are comprised of fibers (or in the case of
peat moss, particles), which when placed in the form of a
layer provide a higher capillary pressure than the
capillary pressure of any layer preceding it. As a
result, each subsequent layer brings liquid from the
previous layer and tends to wick the liquid away from the
receiving zone. To summarize, the second or subsequent
fibrous layer is generally comprised of fibers having a
lZS332~
-14-
lower liquid-contact angle or wherein the layer has a
narrower capillary radii or both.
The superabsorbent associated with the corrugated fibrous
web is generally a water-insoluble but water-swellable
polymeric substance capable of absorbing water in an
amount which is at least 10 times the weight of the
substance in dry form. The superabsorbent material is in
the form of particles, or fibers, or spheres, or bits of
film, or qlobules or the like. In addition, the
superabsorbent may be formed in situ by spraying a liquid
monomer solution onto the fibrous web and subsequently
polymerizing and cross-linking the monomers to provide the
water-insoluble, water-swellable polymeric substance.
One type of suitable superabsorbent in the form of
particles or fibers may be described chemically as having
a backbone of natural or synthetic polymers with
hydrophilic groups or polymers containing hydrophilic
groups being chemically bonded to the backbone or an
intimate admixture therewith. Included in this class of
materials are such modified natural and regenerated
polymers as polysaccharides including, for example,
cellulose and starch and regenerated cellulose which are
modified by being carboxyalkylated, phosphonoalkylated,
sulphoalkylated or phosphorylated to render them highly
hydrophilic. Such modified polymers may also be cross-
linked to improve their water-insolubility.
These same polysaccharides may also serve, for example, as
the backbone onto which other polymer moieties may be
bonded by graft copolymerization techniques. Such grafted
polysaccharides and their method of manufacture are
described in U.S. Patent No. 4,105,033 to Chatterjee et
al. and may be described as polysaccharide chains having
JBD-32
S33~Q
grafted thereon a hydrophilic chain of the general
formula:
~CH2) - CR1 1 ~CH2) - CR2
L ~ r L C = 0 ~
wherein A and B are selected from the group consisting of
-oR3,-o (alkali metal), -OHNH3, - NH2, wherein Rl, ~2and
R3 are selected from the group consisting of hydrogen and
alkyl having 1 to 4 carbon atoms, wherein r is an integer
having a value of 0 to about 5000 or more, s is an integer
having a value of 0 to about 5000 or more, r plus s is at
least 500, p is an integer having a value of zero or 1 and
q is an inte~er having a value of 1 to 4. The preferred
hydrophilic chains are hydrolyzed polyacrylonitrile chains
and copolvmers of polyacrylamide and polysodium acrylate.
In addition to modified natural and regenerated polymers,
the hydrocolloid particle component may comprise wholly
synthetic hydrophilic particles. Examples of those now
known in the art are polyacrylonitrile fibers which may be
modified by grafting moieties thereon such as polyvinyl
alcohol chains, polyvinyl alcohol itself, hydrophilic
polyurethane, poly(alkyl pho5phonates), partially
hydrolyzed polyacrylamides ( e . g ., poly(N-N-dimethyl
acrylamide), sulfonated polystyrene, or a class of
poly(alkylene oxide). These highly hydrophilic synthetic
polymers may be modified by other chemical treatments such
as cross-linking or hydrolysis. Further examples known in
the art are the non-ionic hydrophilic polymers such as
polyoxyethylene, polyoxypropylene and mixtures thereof
JB~-32
izs~
-16-
which have been suitably cross-linked, either chemically
or by irradiation~ Still another more recent type is a
derivative of isobutylene-maleic anhydride copolymer.
Hydrophilic polymers formed from water-soluble acrylate
monomers, such as sodium, potassium, ammonium (or
combinations of cations), acrylate, may be placed on the
absorbing layer by spraying or otherwise placing a
solution thereon followed by polymerization and cross-
linking, for example, by irradiation.
Other suitable superabsorbent includes naturally occurringmaterials such as gums, and the like. Guar gum acacia gum
and locust bean gum are examples of suitable gums.
The superabsorbent is associated with the second layer
sufficiently that liquid entering the layer will be placed
in contact with the superabsorbent. If the superabsorbent
is a powder, it may be sprinkled on the fibrous web either
in dry form or the web or superabsorbent may be moist. If
the superabsorbent is in granular form, it may be
desirable to slightly moisten the superabsorbent before
placing it in contact with the web. The superabsorbent
will contain particles or globules etc. which range in
size from about 0.005 millimeters in diameter to globules
that may be continuous along fibers for a distance up to
several inches. The superabsorbent may be incorporated
within the fibrous web structure before corrugation or it
may be added to the product subsequently by placing it
along the folds of the corrugation. In addition the
superabsorbent may be placed between the multiple layers
of the corrugated web before corrugation, if desired, or
between the corrugated web and the liquid-impermeable
backing.
JBD-32
iZ53320
-17-
The web corrugations range from about three to about six
or even eight per inch of corrugated web. The corrugated
web is generally from about 1/4 to about 3 inches
preferably from about 1/2 to about one inch thick.
It has been found that using a corrugated web as the
provider of void volume to contain body fluids has many
advantages. For instance, fibers may be used to form the
web that in the non-corrugated web form do not have enough
wet resilience to retain void volume when the web becomes
wet. Corrugating of the web provides the highly desirable
resilience in the product that is required to initially
accept and hold a high volume of fluid. Also it has been
found that superabsorbent may be randomly distributed in
small or large quantities within the web with surprisingly
high utilization of the superabsorbent. It is theorized
that the wet resilience of the corrugated web permits the
void volume to remain available almost in totality when
large quantities of fluid are present in the web. This
would permit the superabsorbent to swell, as it captures
the liquid, without substantial inhibition.
In one embodiment of the present invention, a blend of
staple polyester fibers with a minor portion, about 10-15
percent, of fusible fibers, such as lower melt polyester
fibers, are carded to form a web. The web is corrugated
and then subsequently lightly bonded by p~ssing hot air
through the fibers making the fusible fibers tacky so as
to stick to each other and the staple fibers, to provide
the desired degree of integrity to the web structure. The
superabsorbent is then placed in the pockets of the
corrugated web and the corrugated web is fixed in placed
on a polyethylene film which provides a liquid-impermeable
barrier. A facing which is a polyester nonwoven having a
thickness of about 5 mils and weighing about 0.7 ounce per
sq. yd. is placed on the surface of the corrugated web
JBD-32
;125~}3Z~
-18-
opposite the polyethylene sheet; and the polyethylene film
and the polyester nonwoven are adhered to each other on
the outside edges of the product.
The superabsorbent generally is present in an amount
between 10~ and about 100% by weight of the fibrous web.
Preferably, the superabsorbent is present in an amount
from about 50~ to about 90% by weight of the fibrous web.
The web generally is corrugated such that the height or
thickness of the corrugated web is from about 1/4 to about
3 inches preferably about 1/2 inch to one inch and
contains about 4 folds per inch of corrugated web.
However, the corrugated web may contain as few as two
folds up to about 10 folds per inch of corrugated web
depending on the thickness of the web prior to corrugation
and the height of the corrugated web.
~uitable liquid-permeable facings include a nonwoven
fabric having a high degree of moisture permeability. For
example, the fabric may be polyester, polyethylene,
polypropylene, nylon, rayon, or the like. Preferably, the
fabric used for the facing is a light-weight fabric in the
range of ~.3-5.0 ounce per sq. yard and with a density
_ less than about 0.2 grams per cc. The most suitable
fabrics have unusually high elongation, loft, softness,
and drape characteristics. Though the facin9 is liquid-
permeable, it is preferably of the type, which, after
permeation of the liquid, prevents strike-back of the body
fluid when the absorbent product is approaching
saturation.
Suitable liquid-impermeable barriers include films which
are solid films such as polyethylene, polypropylene, and
the like and breathable films which do not allow liquid to
pass therethrough. The films generally are inexpensive,
relatively thin, and flexible.
JBD-32
1253~2~
Examples of methods of preparing the absorbent product of
the present invention are as follows. These examples are
not intended to be limiting in any way and extensions and
modifications thereof without departure from the spirit
and scope of the invention will become apparent from these
examples.
Example I
A fibrous web is formed of polyester fibers, the fibers
being staple fibers except for about 10-15% of fusible
polyester fibers, the latter having a melting point of
about 275F. The web is formed by carding the fibers.
The web is heat-bonded lightly by passing air, having a
temperature of about 275F., through the web for a few
seconds. The resulting web is about 25 grams per
sq. meter basis weight. The specific polyester fibers
used are identified as type 676 Dacron, and type 5~1
Dacron fibers manufactured and sold by E.I. duPont &
Company. The flexible longitudinal web is subjected to
corrugating in accordance with the procedure set forth in
U.S. Patent 4,111,733 and subjected to heat to a
temperature of about 275F. during or subsequent to
_ corrugation in order to again render the fusible fibers
sufficiently tacky to adhere to themselves and to the
staple fibers of the web in order to stabilize the
corrugatefl web.
The corrugating provides a final product having a
thickness of approximately 3/4 inch and which weighs about
13 oz. per yd. in its corrugated form. There are
approximately four corrugations per inch. A powdered
superabsorbent polymer is uniformly sprinkled into the
pockets created by the corrugation of the nonwoven
polyester fibrous web. The superabsorbent is present at a
concentration of about 400 grams per sq~ meter of web.
lZS~3;20
-20-
The particular superabsorbent used is identified as
Permasorb #10, manufactured by National Starch and
Chemical Corporation. The corrugated fiber web containing
the superabsorbent is placed on a polyethylene film
wherein the film extends at least one inch beyond the
corrugated web on each side of the web. Polyester facing
in the form of a nonwoven polyester fiber web having a
weight of about 0.7 oz/sq. yd is placed over the
corrugated web and extends beyond it on all sides by at
least one inch. The polyethylene backing and the
polyester facing are adhered to each other by use of hot
- melt adhesive on all four sides to provide a unitary
disposable absorbent product. The product, when prepared
in a size of approximately 12 in. by 12 in., will hold up
to about 200 mililiters of urine when the urine is
discharged onto the facing at least about 3 inches from
the edge of the product.
Example II
The same polyester fibrous web formed in Example I is
subjected to flooding with an aqueous solution of 38%
solids, the solution solids being 90~ sodium acrylate and
10~ acrylic acid. The resulting flooding substantially
coats the fibers of the web with the aqueous solution.
Vacuum in the amount of 1 inch of mercury is used to draw
the excess solution from the web. The web is then
subjected to 6 megarads electron beam radiation after
which about 70 grams per sq. meter of polysodium acrylate
is present. The web is again flooded suhjected to vacuum
and irradiated with 6 megarads of electron beam radiation
to yield a total of about 140 grams per sq. meter of
polysodium acrylate. After flooding a third time with the
same monomer solution and after the vacuum treatment, the
web is subjected to 12 megarads of electron beam radiation
which polymerizes and cross-links the monomer and forms
- 125332()
-21-
polysodium acrylate substantially affixed to the polyester
fibers of the web. Approximately 200 grams/sq. meter of
polysodium acrylate is present in the substrate. This is
equivalent to about 800% dry-add-on.
s
Staple acrylic fibers are deposited on the polyester web
so as to create an intimate layer having a weight of about
30 grams/sq. meter of acrylic fibers. The two-layer web
is subjected to heat-through bonding wherein the fusible
fibers in the polyester web assist in at least partially
uniting the acrylic fiber layer to the polyester web. The
two-layer flexible longitudinal web is then subjected to
corrugating again in accordance with the procedures set
forth in U.S. Patent NO. 4,111,733. Following
corrugating, the web is stabilized in its corrugated form
by spraying an elastomer solution onto the surface wherein
the acrylic fibers are at the peaks of the corrugation.
The aqueous dispersion of the elastomer is cured and the
product is thereby stabilized. The corrugated product is
placed on a liquid-impermeable diaper backing and a facing
is placed on the other surface. The backing and facing
are united in the margins by known procedures. Tape tabs
are then applied at one end of the diaper to provide a
disposable diaper product which will receive and retain up
to about 300 milliliters of urine.
Exam~le III
The corrugated web prepared in Example II is placed in a
sanitary napkin so that the corrugations are parallel to
the longitudinal axis of the sanitary napkin product. The
liquid barrier is a polyethylene film and the overwrap is
a polyester nonwoven fabric as described above. Adhesive
lines are placed on the under side of the product and
release film strips are placed over the adhesive lines.
JBD-3~
~ZS~3;~(~
Upon removal of the release film strips, the product is
readily adhered to the underclothing of the user.
Other methods for preparing the corrugated fibrous web and
combining the superabsorbent and preparing a finished
product may be used.
From the foregoing it will be observed that numerous
variations and modifications may be effected without
departing from the true spirit and scope of the novel
concept of this invention.
JBD-32
. .
