U.S. patent number 3,670,731 [Application Number 04/551,772] was granted by the patent office on 1972-06-20 for absorbent product containing a hydrocolloidal composition.
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Carlyle Harmon.
United States Patent |
3,670,731 |
Harmon |
June 20, 1972 |
ABSORBENT PRODUCT CONTAINING A HYDROCOLLOIDAL COMPOSITION
Abstract
An absorbent dressing having an absorbent layer defined by water
soluble hydrocolloidal composition capable of absorbing of at least
about fifteen times its weight of body exudate and retaining said
exudate under pressure of up to about 2.5 p.s.i.
Inventors: |
Harmon; Carlyle (Scotch Plains,
NJ) |
Assignee: |
Johnson & Johnson
(N/A)
|
Family
ID: |
26644222 |
Appl.
No.: |
04/551,772 |
Filed: |
May 20, 1966 |
Current U.S.
Class: |
604/368;
525/333.5; 602/42; 604/372; 428/327; 525/329.4; 525/383;
604/364 |
Current CPC
Class: |
A61L
15/60 (20130101); A61L 15/60 (20130101); A61F
13/539 (20130101); A61F 13/00008 (20130101); A61F
13/534 (20130101); A61L 15/225 (20130101); A61L
15/225 (20130101); A61F 13/206 (20130101); C08L
33/26 (20130101); C08L 33/26 (20130101); A61F
2013/530496 (20130101); A61F 2013/00748 (20130101); A61F
2013/00859 (20130101); A61F 2013/00251 (20130101); A61F
2013/00744 (20130101); Y10T 428/254 (20150115); A61F
13/202 (20130101); A61F 2013/530481 (20130101); A61F
2013/53445 (20130101); A61F 2013/53051 (20130101) |
Current International
Class: |
A61F
13/20 (20060101); A61F 13/00 (20060101); A61F
13/15 (20060101); A61F 13/22 (20060101); A61L
15/22 (20060101); A61L 15/60 (20060101); A61L
15/16 (20060101); A61f 013/16 () |
Field of
Search: |
;128/156,284,285,287,290,296 ;260/47,77.5,88.1 ;117/136 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Rosenbaum; Charles F.
Claims
I claim:
1. An absorbent dressing comprising an absorbent layer sandwiched
between a liquid permeable facing sheet and a backing sheet, said
absorbent layer containing at least about 5 percent by weight,
based on the total weight of the dressing, of a hydrocolloidal
polymer composition rendered substantially water insoluble by
crosslinking, and having from about 25 to about 72 percent of its
molecular structure composed of hydrophillic groups, said
hydrocolloidal composition being further defined as providing a
gelatinous agglomerate of liquid-swollen particulate members in the
presence of a quantity of body exudate, as capable of absorbing at
least about 15 times its weight in body exudate, as capable of
retaining said absorbed exudate under a pressure of up to about 2.5
p.s.i., and as having a minimum average molecular weight per
crosslinkage of about 13,000.
2. The dressing of claim 1 wherein said hydrocolloidal composition
is incorporated within a fibrous mass to define said absorbent
layer.
3. The dressing of claim 2 wherein said hydrocolloidal composition
is selected from the group consisting of crosslinked polystyrene
sulfonate and crosslinked polyacrylamide.
4. The absorbent dressing of claim 2 in the form of a catamenial
device.
5. A disposable diaper comprising absorbent layers sandwiched
between a liquid permeable facing sheet and a liquid permeable
backing sheet, said absorbent layer containing at least about 5
percent by weight, based on the total weight of the diaper, of a
hydrocolloidal polymer composition rendered substantially water
insoluble by crosslinking, and having from about 25 to about 72
percent of its molecular structure composed of hydrophillic groups,
said hydrocolloidal composition being further defined as providing
a gelatinous agglomerate of liquid-swollen particulate members in
the presence of body exudate, as capable of absorbing at least
about 15 times its own weight in body exudate, as capable of
retaining said absorbed exudate under a pressure of up to about 2.5
p.s.i., and as having a minimum average molecular weight per
crosslinkage of about 13,000.
6. The diaper of claim 5 wherein said hydrocolloidal composition is
incorporated within a fibrous mass to define the absorbent
layer.
7. The diaper of claim 5 wherein said hydrocolloidal is selected
from the group consisting of
A. ##SPC4##
where
Y is a member of the group selected from, ammonium or an alkali
metal ion,
m is a number from 1 to 100,
n is a number from 0 to 100, and defines the degree of
hydrolysis,
m plus n is equal to 100, and
Z is a number from 1 to 30, and Z times 100 is equal to the number
of mer units between crosslinks.
and,
B. ##SPC5##
where
Z is a number from 100 to 3,000 and defines the number of mer units
between crosslinks, and
Y is a member of the group consisting of hydrogen, ammonium, and an
alkali metal ion.
8. The diaper of claim 6 wherein said hydrocolloidal composition is
selected from the group consisting of crosslinked polystyrene
sulfonate and crosslinked polyacrylamide.
9. As an article of manufacture, a flexible support adapted to be
caused to conform to a surface of an animal body, said support
confining a dry, solid, water-swellable, water-insoluble,
physiologically unobjectionable polymeric sorbent so as to present
said sorbent for the sorption of aqueous fluid elaborated by the
animal to which said article is applied and said polymeric sorbent
being a lightly crosslinked polymer and being selected from the
group consisting of polystyrene-sulfonate, and alkali metal salts
thereof as contain sulfonate or carboxylate groups.
10. An absorbent dressing comprising an absorbent layer sandwiched
between a liquid permeable facing sheet and a backing sheet, said
absorbent layer containing a hydrocolloidal polymer composition
rendered substantially water-insoluble by crosslinking, and having
from about 25 to about 72 percent of its molecular structure
composed of hydrophilic groups, said hydrocolloidal compositions
being further defined as providing a gelatinous agglomerate of
liquid-swollen particulate members in the presence of a quantity of
body exudate, as capable of absorbing at least about fifteen times
its weight in body exudate, as capable of retaining said absorbed
exudate when exposed to pressure sufficient to deform said
agglomerate and as having a degree of cross-linking within the
range of the degrees of crosslinking obtained by copolymerizing a
mono-olefinic monomer with from about 0.05 to about 0.5 percent by
weight of a divinyl compound.
11. The dressing of claim 10 wherein said hydrocolloidal
composition is selected from the group consisting of
polyacrylamide, alkali metal salts of hydrolyzed polyacrylamides
and the free acid and alkali metal salts of polystyrene sulfonates.
Description
The present invention relates generally to absorbent dressings and,
more particularly, to diapers, to sanitary napkins, to catamenial
tampons, and to absorbent wound dressings, e.g., surgical
dressings, which are characterized by the use therein as the main
absorbent medium of a particulate hydrocolloidal composition which
is substantially aqueous insoluble at ambient temperatures and is
capable (1) of absorbing body exudates such as urine, menstrual
discharge and wound exudates in amounts of from at least 15 times
to about 70 times its weight, and (2) of holding these amounts of
absorbed exudate against release during normal flex and pressure as
a result of activity of the wearer, (3) while maintaining its
particulate integrity, albeit swollen grossly because of its
absorption and retention of body exudate.
As a result of the nature of the absorption of the body exudate by
the particulate hydrocolloidal component used in the absorbent
dressings of the invention, i.e., imbibing with concomitant
swelling so that particulate body form is maintained, the surface
of the wet dressing has a dry-to-the-touch feel. This coupled with
the unusual retention of the absorbed liquid even during normal
activity of the wearer makes the absorbent dressings of the
invention of substantial importance for all the intended uses, and
especially for diapers, particularly those of the so-called
"throw-away" type, and for catamenial tampons, where the articles
are relatively small with respect to the quantity of liquid body
exudate, urine and menstrual fluid, respectively, they are called
upon to handle.
Test results show in the case of a diaper in accordance with the
invention, that it will "hold" absorbed liquid in amounts of 30 and
more times the weight of the particulate hydrocolloidal component,
under a pressure of up to 2.5 p.s.i.
It may be that during actual use of the diaper of the invention the
movements of the child may be such as to apply a temporary
extraordinary pressure here and there, sufficient to disgorge some
absorbed urine from swollen particulates containing the same. Be
that as it may, if some absorbent particulates in the diaper have
absorbed their full capacity considering the pressure applied,
other surrounding absorbent particulates which have not absorbed up
to their capacities, are capable of absorbing additional urine,
with the result that the diaper feels substantially dry to the
touch at substantially all times during a normal time interval of
use.
In use in an absorbent dressing in accordance with the invention,
the substantially water-insoluble particulate hydrocolloid
absorbent material, of a particle size suitably in the range of
from about 1 micron to about 2 millimeters, is spread as uniformly
as possible onto and/or into a carrier sheet commonly used in
making an absorbent dressing, so that the carrier sheet and the
applied particulate layer can be fashioned by conventional
procedures into an absorbent dressing in accordance with the
invention. Preferably, the particulate absorbent material is
sandwiched between a pair of carrier sheets and then incorporated
by conventional procedures into an absorbent dressing according to
the invention, thus insuring that the desired discrete particulate
hydrocolloid layer is maintained in the final structure. In the
case of a catamenial tampon, this can be accomplished by first
spreading the hydrocolloid particles as a layer over a conventional
layer of absorbent fibers and then winding the latter on itself
into the form of a roll so that the hydrocolloid particles are
trapped between the windings.
The hydrocolloidal absorbent material used in accordance with this
invention may be in solid form such as, for example, a fiber, thin
film, or a cellular structure, all of which provide a large surface
area; however, it is preferred that it be in particulate form such
as a flake or granule, since these forms provide the largest
surface area for absorption and insure that maximum surface area is
available for absorbency. There should be at least about 5 percent
by weight, preferably 10 to 15 percent by weight, of hydrocolloidal
absorbent material based on the total weight of absorbent materials
in the dressing. In the case of a diaper or wound dressing the
total absorbent component may be the hereinabove described
hydrocolloid absorbent material.
Depending upon the end absorbent dressing desired, the carrier
sheet for the particulate hydrocolloid layer in the product may be
an absorbent mass or pad of textile fibers, wood pulp fibers,
cotton linters and mixtures of such fibers, one or more sheets of
bonded textile fibers, either synthetic or natural fibers, or a
mixture thereof. The term "carrier sheet" also includes a composite
of layers of absorbent tissue, e.g., creped tissue, paper sheets
and water impermeable films and fibrous sheets, perforated, if
desired, to allow liquids to pass therethrough freely, if desired.
As already indicated, the carrier sheets which may be used to make
the absorbent dressing of the invention may be those which are
commonly used in making absorbent dressings of conventional
construction.
Water-insoluble particulate hydrocolloid compounds of the type
herein contemplated are presently known materials, but their uses
in the past have not been related to that herein contemplated,
i.e., as an absorbent material in absorbent dressings, wherein the
absorbent material maintains its particulate character as it
imbibes and absorbs many times its weight of surrounding liquid,
and in doing so swells. As previously indicated, the absorbent,
water-insoluble particulate hydrocolloid contemplated herein is
capable of absorbing from about 15 to 70 times its weight of water,
urine and other body exudates. In doing so each individual
absorbent particle swells or enlarges several hundred percent times
its individual parameter without destruction of its initial
particulate integrity. As the particulate, water-insoluble
hydrocolloid accepts liquid it substantially immobilizes the same
therein, and the resulting particulate, liquid-swollen structure is
gelatinous.
The mass of swollen particulate water-insoluble hydrocolloid
particles within the body of the sanitary dressing define an
aciniform structure since each individual absorbent particle is a
greatly enlarged particle, having become liquid-swollen or
grape-like or acinus in form due to the water, urine or other
liquid it has absorbed. The individual, swollen, hydrocolloid
particles are tacky and hence within the absorbent dressing they
are in a clustered mass of liquid-swollen particles. The particles
remain in this aciniform state even in the presence of liquid in
excess of their ability to absorb.
The liquid-swollen hydrocolloid particles bind their absorbed water
tightly, as already indicated, but upon drying the particles are
dehydrated and return more or less to their original size. At this
time they can again operate more or less as before to absorb and
bind liquids, and hence in the case of an emergency the diaper of
the invention lends itself for re-use.
The water-insoluble hydrocolloid absorbent particles used in
accordance with the present invention are presently known
materials, generally being a hydrocolloid polymer material having
from about 25 to 72 percent of its molecular structure composed of
hydrophilic groups, and whose polymeric network has been
crosslinked to introduce a limited water insolubility into the
molecule. Suitable water-insoluble hydrocolloid absorbent material
in accordance with the invention have a minimum average molecular
weight per crosslinkage of about 13,000 and a maximum molecular
weight per crosslinkage of about 276,000. In general, the extent of
crosslinking is contained so that the polymeric network of the
hydrocolloid is not soluble in water, urine and the like, yet
remains flexible and swells as water and other liquid is absorbed
within its structure. As the hydrocolloid swells it maintains the
approximate shape and geometry it had before contact with liquid,
but the dimensions thereof are greatly enlarged to provide for the
binding of the liquid absorbed therein.
It is evident that absorbent dressings containing water-insoluble
hydrocolloid absorbent particles in accordance with the invention
are distinguishable from the prior art absorbent dressings which
may have had incorporated in their structure natural and/or
synthetic water soluble hydrocolloid materials to increase the
viscosity of, i.e., to thicken, the liquid absorbed into the
absorbent dressing structure.
For the present invention the crosslinked, water-insoluble
particulate hydrocolloids of the invention are not the equivalent
of known natural soluble hydrocolloids such as agar, karaya and the
water-soluble gums (tragacanth, arabic, locust beam, and guar), or
of synthetic hydrocolloids such as carboxymethyl cellulose and
carboxyethyl cellulose. These soluble hydrocolloids serve only to
increase viscosity of liquids and in the presence of an added
liquid excess, lose their power to retain the viscosity they had
previously achieved. In contrast as exemplified by diaper use, the
crosslinked hydrocolloid absorbent material within the diaper of
the invention swells upon absorption of liquid and retains the
absorbed liquid so that it does not flow back on the child. The
swollen hydrocolloid remains essentially locked in position within
the diaper structure and does not penetrate the diaper facings.
Liquid taken into the swollen structure is retained well under the
pressures encountered in use. And with any excess of liquid the
discrete, separate, liquid-swollen hydrocolloid entity maintains
its maximum swollen form.
The water-insoluble hydrocolloid absorbent material which may be
used in accordance with the present invention preferably is a
crosslinked polyacrylamide or a crosslinked sulfonated polystyrene
or a mixture of these acrylamides and polystyrenes.
The preferred hydrocolloid absorbent material is a hydrolyzed
crosslinked polyacrylamide which has the following values for the
variables identified in the general formula set forth immediately
below: n=28, m=72, Z=19 and Y=Na. This preferred material is
described in U.S. Pat. No. 3,229,769, patented Jan. 18, 1966.
The preferred hydrolyzed polyacrylamide hydrocolloid absorbent
materials of the invention suitably are compounds having the
following structural formula: ##SPC1##
where
Y is a hydrogen, ammonium or an alkali metal ion,
m is a number from 1 to 100,
n is a number from 0 to 100 and defines the degree of
hydrolysis,
m plus n is equal to 100, and
Z is a number from 1 to 30, where Z times 100 is equal to the
number of mer units between crosslinks.
The crosslinked polyacrylamide hydrocolloid material of the
invention may be prepared by known techniques, e.g., by
crosslinking a linear polyacrylamide (or by copolymerizing an
acrylamide) with a non-conjugated divinyl compound such as
methylene bis acrylamide. In the latter case, the polymerization
may be run by any of the standard methods including the use of
peroxide catalysts, or by photo polymerization with riboflavin
activator. The crosslinking compound may be present in an amount of
from about 500 to about 5,000 parts per million of
polymerizate.
Other examples of non-conjugated divinyl crosslinking compounds are
1,4-divinyl benzene; N,N-diallylacrylamide; diallylamine;
diallylmethacrylamide; 2,5-dimethyl-1,7-octadiene;
p,p'-diisopropenylbenzene; 2,8-dimethyl-1,8-nonadiene and
diethylene glycol divinyl ether.
The preferred polyacrylamides are those in the above general
formula that are hydrolyzed and wherein Y is sodium or potassium, n
is equal to a number in the range of 10 to 70 and Z is a number in
the range of 2 to 20. Most preferably, Y is sodium, n and Z are
numbers within the ranges 20 to 40 and 4 to 15, respectively.
Crosslinked polystyrene sulfonate hydrocolloid absorbent materials
which may be used in accordance with the invention preferably are
those which have been crosslinked with non-conjugated divinyl
compounds as above set forth. These polystyrene sulfonates are
known materials and have the following general structural formula:
##SPC2##
where
Z is a number from 100 to 3,000 and defines the number of mer units
between cross links, and
Y is a hydrogen, ammonium or an alkali metal ion.
These crosslinked polystyrene sulfonates are prepared by known
procedures, e.g., by copolymerizing styrene with a non-conjugated
divinyl compound such as divinyl benzene in the presence of a
polymerization catalyst such as benzoyl peroxide. It is customary
to add a suspension stabilizer (such as gelatin or polyvinyl
alcohol) so that small polymer beads in the range of from about 1
micron to about 2 millimeters will be formed during the
polymerization. The resultant polymer is sulfonated, for example,
by heating it in the presence of concentrated sulfuric acid at a
temperature of about 100.degree. C.
The mechanism whereby water or liquid is lead through the outer
covering sheet or through the facing sheet of the absorbent
dressing to the hydrocolloid absorbent medium incorporated into the
structure of the dressing is generally termed "wicking". Wicking is
effected generally by fibers either in the covering or facing sheet
or within the absorbent medium. These fibers act as channels to
direct the liquids deposited on the surface of the absorbent
dressing into the contained hydrocolloid absorbent medium. In the
present invention both means may be utilized simultaneously or
individually depending upon the desired composition of the facing
or covering sheet and whether the hydrocolloid is the sole
absorbent medium or whether it is combined with a fibrous absorbent
mass.
The hydrocolloid absorbent medium used in accordance with this
invention may be constructed of a blend of the hydrocolloid with a
mass or pad of fibers or a composite of layers of absorbent tissue,
e.g., creped tissue.
The invention will be described in detail in connection with
illustrative embodiments, e.g., a diaper, a surgical dressing, and
catamenial devices, specifically a tampon and a sanitary napkin, in
the accompanying drawings, wherein:
FIG. 1 is a perspective view of a diaper or surgical dressing of
the invention with a portion thereof cut away;
FIG. 2 is a cross section taken along 2 -- 2 of FIG. 1;
FIG. 3 is the same cross section as FIG. 2 after use and during
which absorption of body exudates has taken place;
FIG. 4 is a perspective view of another embodiment of a diaper or
surgical dressing of this invention, with portions thereof cut
away;
FIG. 5 is a cross section taken along 5 -- 5 of FIG. 4;
FIG. 6 is the same cross section as FIG. 5 after use and during
which absorption has taken place;
FIG. 7 is a perspective view of a sanitary napkin embodying the
invention, shown partially open to illustrate the same;
FIG. 8 is a perspective view of a catamenial tampon embodying the
invention, shown partially open to illustrate the same;
FIG. 9 is a cross section taken along line 9 -- 9 of FIG. 8,
FIGS. 10 and 11 are planar views of other embodiments of a tampon
construction before the same are formed into tampons;
FIG. 12 is a view of a tampon constructed from the embodiment shown
in FIG. 11, portions being broken away to show details; and
FIG. 13 is a cross section of an absorbent dressing used for
testing to illustrate the efficiency of this invention.
With specific reference to FIG. 1 which depicts a disposable diaper
1, the facing sheet 3 is a porous non-woven fabric made of
individualized fibers bonded together in a pattern of spaced binder
areas. The backing sheet 4 is a moisture-resistant sheet, e.g., a
thin gauge polyethylene film. The facing sheet 3 and the backing
sheet 4 are adhered together along common edges 6 by a selected
adhesive. A fibrous layer 9 constructed of absorbent fibers 7,
e.g., cellulosic, having incorporated therein, in random manner,
the aforedefined hydrocolloidal absorbent composition 8, provides
the absorptive medium of this diaper. The facing sheet 3 and the
backing sheet 4 are the "carriers" in this diaper construction.
The facing sheet 3 may be a sheet of soft, absorbent paper, a
lightweight intermittently bonded or overall impregnated nonwoven
fabric, a thin perforated plastic film or any such material which
will readily pass liquids therethrough and which present a smooth
and soft surface for contacting the wearer's body.
It is preferred that the layer of absorbent material 9 have a
backing sheet 4 constructed of a waterproof material such as a
layer of waterproof paper, a thin water-repellent film, etc. The
facing sheet 3 and the backing sheet 4 are secured to each other
along their longitudinal edges to prevent movement of the layers
with respect to each other. The sheets 3 and 4 may be secured by
any method known in the art, such as by glue, embossing the edges,
etc.
The hydrocolloidal absorbent composition 8, in particulate form,
may be applied to the fibrous layer 9 by sprinkling or dusting the
hydrocolloid absorbent into the absorbent pad.
Of course, the absorbent pad 9 may be constructed of a plurality of
sheets of absorbent material, and in such a case the hydrocolloidal
absorbent 8 may be adhesively secured to the surface of one or more
of the sheets. In point of fact, the fibrous material composing the
absorbent pad 9 may be constructed of any known absorbent material
such as fluffed wood pulp, woven cloth, cotton linters, a plurality
of plies of creped tissue, and the like.
Yet another means for securing the hydrocolloid in place with any
diaper or absorbent dressing, is to emboss the surface of the
absorbent pad 9 to provide cavities such as parallel ribbon-like
channels, diamond patterns, etc., that will contain the absorbent
hydrocolloid 8 to insure substantially uniform distribution.
FIG. 2 is a cross section taken along line 2 -- 2 of FIG. 1 and
shows the absorbent pad 9 constructed of absorbent fibers 7 and
having particles of the hydrocolloid absorbent material 8 attached
or secured to, or mechanically intermixed with the fibers. The
facing sheet 3, which may be singular or plural, and the
water-repellent backing sheet 4, engulf and entrap the absorbent
pad 7. The sheets 3 and 4 are joined along their common edges 6 by
an adhesive 10.
FIG. 3 shows the same cross section as is shown in FIG. 2 but after
use, and thus after absorption has taken place. Note the swollen
nature of the hydrocolloid absorbent which takes on an acinuous
form 11 in that in the swollen state it retains its particulate
integrity. The fibers 7 comprising the absorbent pad 9 aid in
retaining the gelatinous mass of liquid-swollen hydrocolloid
absorbent 11 in substantially uniform distribution throughout the
length and width of the diaper. Of course, the need for the
absorbent pad 9 can be obviated by techniques such as embosing
whereby the substantially uniform positioning of the hydrocolloid
absorbent is virtually insured. In that case the hydrocolloid of
the aforegiven definition does form essentially the total of the
absorbent medium, and in fact, will be the entire absorbent medium
if absorbent carriers are not utilized.
Another absorbent dressing, and more specifically a second diaper
12, encompassing this invention, is shown via FIG. 4. The facing
and backing sheets, 3 and 4 respectively, are as defined in FIG. 1;
however, the absorbent medium is defined by a layer of hydrocolloid
absorbent 5 in fine flake form in this instance. The absorbent
flakes 5 are substantially uniformly dispersed along the inner face
of the backing sheet 4 and kept in position by an adhesive layer
14, first applied to the inner surface of the backing sheet 4. In
this instance a thin wood pulp underlay 13 is secured uniformly to
the inner surface of the facing sheet 3 to provide wicking action
in the diaper 12. The cross section of FIG. 5 taken along 5 -- 5 of
FIG. 4 defines the diaper more particularly. Note the bottom most
layer of the hydrocolloidal absorbent composition 5 secured by
adhesive 14 to the inner surface of the backing sheet 4. The pulp
underlay 13 helps to keep the hydrocolloid absorbent in position to
provide an absorbent core. The pulp underlay 13 is clearly seen
secured to the inner surface of the facing sheet 3.
FIG. 6 depicts the same cross section as shown in FIG. 5 but after
the diaper 12 has been used for its intended purpose and has had a
quantity of body exudate absorbed in it. The hydrocolloidal
absorbent 16 is liquid swollen and is of the characteristic
gelatinous aciniform structure. The gelatinous mass 16, which is
virtually a continuous layer spanning the length and the width of
the diaper, is retained in a relatively flat position by depressed
sites 15 (formed by embossing techniques) spaced through the diaper
in a substantially uniform pattern. With the use of an adhesive 14
the backing sheet 4 and the facing sheet 3 become attached at these
sites 15 to provide means by which a reasonable flatness is
maintained, and the tendency of the gelatinous absorbent mass 16 to
ball in the center of the pad is precluded. The pulp underlay also
contributes substantially to maintain the position of the
gelatinous mass such that substantial flatness of the diaper is
maintained.
The diapers shown via FIGS. 1 - 6 could also represent surgical
dressings or other absorbent patches or bandages. The size of the
dressing need simply to be reduced accordingly since the dressing
would continue to function to absorb and retain body exudate.
In FIG. 7, a sanitary napkin 40 incorporating the invention
includes a relatively thick absorbent core 18 enclosed within a
liquid pervious fibrous wrapper 12 whose ends extend beyond the
ends of the absorbent core 18 to provide the usual attachment tab
13. The absorbent core 18 can be about 8 inches long, 2 1/2 inches
wide and one-fourth to one-half inch thick and in this instance
consists of a layer of the aforedefined particulate hydrocolloidal
absorbent composition 19 interposed between several layers of
fibrous material 15 such as cotton webs, air-layered cellulosic
fiber webs, non-woven or textile fibrous webs, wood pulp batts,
tissue pulp or like materials which are highly absorbent. The
entire core assembly is enclosed within the liquid pervious wrapper
12. As an alternative the hydrocolloidal absorbent 14 may be
randomly interspersed throughout the absorbent core 18.
Referring to FIGS. 8 and 9, there is illustrated a catamenial
tampon 21 incorporating the invention, and which includes the
elongated cylindrical core 22 of densely packed absorbent fibers
enclosed with a liquid pervious wrapper 23. Secured at one end of
the tampon are a pair of withdrawal strings 24 by which the tampon
can be withdrawn subsequent to use. The absorbent fibrous core has
about 12 percent by weight, based on the total weight, of the
aforedescribed hydrocolloidal absorbent composition 20 dispersed
therein.
FIG. 9 is an enlarged cross section taken along line 9 -- 9 of FIG.
8 and shows the particulate hydrocolloid 20 impregnated in the
fibrous absorbent core 22 which is encased by the liquid pervious
wrapper 23.
FIGS. 10 and 11 are planar views of other tampon constructions
before the same are formed into tampons. In both Figures an
absorbent covering sheet 30 forms the base for the layer 31 of the
aforedefined hydrocolloidal absorbent and the absorbent
positioning-sheet 32. Both sheets 30 and 32 are of nonwoven
construction and are liquid permeable; however, other liquid
absorbent mediums could be utilized, i.e., paper or woven textiles,
etc., and it is conceivable that apertured or foraminous
nonabsorbent sheets, e.g., apertured polyethylene film, could be
substituted for one or the other.
The tampon construction of FIG. 10 is formed by turning either of
the longitudinal edges over on itself and continuing to so roll the
edge to provide a cylindrical tampon. The cylindrical tampon is
then compressed and the free longitudinal edge adhesively secured.
The same applies to the tampon of FIG. 11, and in each instance the
arrows describe the method of forming. Each tampon has withdrawal
strings 33 secured by stitching 34 or other suitable means to the
composite.
A tampon formed of the embodiment shown in FIG. 11 is given in FIG.
12. The center portion of the tampon is cut away to show the
distribution and positioning of materials.
The absorbent dressings of the instant invention exhibit greatly
improved absorption and retention of liquids. To establish the
improved absorbency and retention of liquids, sample dressings were
prepared as follows: A plurality of 10 .times. 10 inch test
absorbent dressings were constructed by superimposing in congruent
relationship, layers of nonwoven fabric 26, fluffed wood pulp 27
and a hydrocolloidal composition 28 as is shown in cross section in
FIG. 13. Each sheet of nonwoven fabric weighed 1 gram, each layer
of pulp weighed 3.3 grams and each layer of hydrocolloidal
absorbent composition weighted 0.5 grams. A control dressing
similarly constructed contained no hydrocolloidal absorbent
composition.
Each dressing or pad was saturated with 500 milliliters of
deionized water. Each pad was inclined at an angle of about
45.degree. for 3 minutes and the water that escaped from each pad
or dressing was separately collected and measured.
After allowing 5 minutes for the escape of the water, a planar
pressure of 1.25 psi was applied to each pad. The water forced from
each pad or dressing by this pressure was separately collected and
measured. The amount of absorption was determined by calculating
the difference between the amount of water added and the amount of
water collected under these conditions. The results are shown in
Table I where the letters n, Z and Y are those utilized in defining
the polyacrylamides of this invention and the crosslinking agent
was methylene bis acrylamide. ##SPC3##
The absorbent dressing of this invention also maintains a reduced,
or minimal, surface wetness on the facing sheet, i.e., the sheet of
textile or paper-like material positioned contiguous to the skin of
the user, or in the alternative the sheet of the dressing exposed
directly to the source of the liquid which the dressing is intended
to absorb. This feature is dramatically established by the
following test utilizing two diapers of identical construction.
Each diaper measured 10 .times. 10 inches and the weight of the
absorbent facing and backing sheets was 200 grains per square yard.
Each diaper had a layer of fluffed wood pulp in an amount of 12
grams; however, only one diaper had 1.5 grams of a crosslinked
hydrolyzed polyacrylamide dispersed within the absorbent fibrous
layer. The values for n, m, Z and Y of this crosslinked hydrolyzed
polyacrylamide were 28, 72, 10 and Na respectively (which apply to
the structural formula on page 4) and the crosslinking agent was
methylene bis acrylamide. 150 ml of deionized water was added to
each of the horizontally positioned diapers. Diaper A contained the
hydrocolloidal composition and diaper B did not.
In the first test, identical thin sheets of preweighed paper
toweling were placed in facewise engagement with the facing sheets
of both diapers and a thin flat metal plate weighing 13 pounds was
placed upon each of these laminates. After 5 minutes the plate and
the paper toweling were removed from each diaper and was re-weighed
to determine the water pickup. The ratio of surface water pickup of
the conventional diaper B without the absorbent compound, i.e., the
crosslinked hydrolyzed polyacrylamide, to the diaper A containing
the absorbent was 4 to 1.
In another test, the facing sheet of each diaper was carefully
removed and weighed to determine its liquid content. The ratio of
the wetness of the facing sheets of the conventional diaper B
without the absorbent to that of the diaper A containing the
hydrocolloidal absorbent, was 3 1/2 to 1.
Another very important feature that is characteristic of the
absorbent dressing of this invention is the reduced internal spread
of absorbed liquid that it exhibits. To illustrate this feature,
diapers constructed in accordance with FIG. 1 of this invention
were prepared. Several contained the absorbent hydrocolloid defined
herein (specifically in this instance the methylene bis acrylamide
crosslinked hydrolyzed polyacrylamide bearing the values n=28,
m=72, Z=10 and Y=Na) while several were prepared without this
hydrocolloid. Fifty cubic centimeters (cc) of colored water was
introduced onto the center of each of these diapers constructed in
accordance with FIG. 1. The diapers contained either 0 percent, 16
percent or 31 percent by weight, based on the total weight of the
diaper, of absorbent hydrocolloid. The results are expressed in
terms of percent decrease of spread area based on the diaper that
did not contain any of the absorbent hydrocolloid.
% Wt. Water % Decrease Hydrocolloid Feed Rate in Spread in Pulp
(cc/sec.) Area from 0% Pulp
__________________________________________________________________________
0 1.6 0 16 1.6 46 31 1.6 72 0 8.3 0 16 8.3 36 31 8.3 45
__________________________________________________________________________
These results also show that at lower feed rates, the diaper of
this invention has more of an opportunity to absorb the water
before it flows past, thus decreasing the percent spread area.
In describing the present invention, certain embodiments have been
used for purposes of illustration; however, other embodiments and
modifications within the spirit and scope of the invention will
readily occur to those skilled in the art after a reading of this
disclosure. The invention is accordingly not to be limited to the
specific embodiments illustrated but only in accordance with the
appended claims.
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