U.S. patent number 3,777,759 [Application Number 05/291,659] was granted by the patent office on 1973-12-11 for enzyme-dispersible bandage.
This patent grant is currently assigned to Minnesota Mining and Manufacturing Company. Invention is credited to Richard W. Oehmke, Ronald F. Ofstead.
United States Patent |
3,777,759 |
Oehmke , et al. |
December 11, 1973 |
ENZYME-DISPERSIBLE BANDAGE
Abstract
A readily disposable, multi-ply pad for contacting the body and
absorbing body wastes consists of multiple plys of non-woven,
fibrous material of good dry- and wet-strength, wet-strength being
conferred on the materials by a binder which is essentially
unaffected over periods of serveral hours or more by aqueous body
wastes, but which is rapidly degraded by exposure to aqueous media
containing enzymes; one or moreof the interior plys can be plain,
untreated, non-woven fibrous material in the form of an absorbent
pad; the whole pad being readily dispersed and disposable in
domestic waste disposal systems by the addition of enzyme to the
disposal receptacle together with the used pad, and such disposal
having the advantage that even long-continued disposal of numerous
pads has little or no deleterious effect upon domestic disposal
systems.
Inventors: |
Oehmke; Richard W. (Hudson,
WI), Ofstead; Ronald F. (Maplewood, MN) |
Assignee: |
Minnesota Mining and Manufacturing
Company (St. Paul, MN)
|
Family
ID: |
23121252 |
Appl.
No.: |
05/291,659 |
Filed: |
September 25, 1972 |
Current U.S.
Class: |
604/366; 604/372;
604/370; 604/381 |
Current CPC
Class: |
A61F
13/15211 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A41b 013/02 () |
Field of
Search: |
;128/284-288,290,296 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Rosenbaum; Charles F.
Claims
What is claimed is:
1. A readily disposable, multi-ply pad for contacting the body and
absorbing body wastes and the like, which comprises an inner
body-contacting, self-supporting, water-absorbent lamina composed
of a non-woven composite web consisting essentially of relatively
short fibers having substantially no wet-strength in the absence of
binder and in combination therewith a water-insoluble, normally
solid, enzyme-degradable binder which consists of a polymer of at
least one ethylenically unsaturated monomer covalently bonded with
a naturally-occurring, enzyme-degradable, water-soluble polymeric
material, said polymer having a molecular weight of at least about
10,000 and a degree of polymerization of at least about 50, and
said binder being present in effective amount ranging from about
0.3 percent to about equal amounts by weight of said fiber in said
non-woven web, and sufficient to impart to said non-woven web
wet-strength in aqueous milieu in the absence of enzyme of from
about 0.7 to 50 kg. per square centimeter, and to permit dispersion
of said non-woven web in a period ranging from about 5 to 30
minutes in aqueous milieu containing enzyme capable of degrading
said water-soluble polymeric material to disintegrate said binder
and render said web readily dispersible; an intermediate lamina of
non-woven, highly moisture-absorbent fibers containing no binder
and having substantially no wet-strength; and an outer lamina of a
self-supporting, non-woven composite web of material the same as
said body-contacting web, having over and supported upon not more
than one surface thereof a thin, flexible adherent coating of
water-repellent material which is frangible when unsupported, said
laminae being contiguous and said inner and outer laminae being
approximately equal in area and larger than said intermediate
lamina; whereby the said pad when in use absorbs body waste liquids
without permitting penetration thereof through said outer layer,
and said pad when disposed of by placing it in aqueous milieu
containing enzyme capable of degrading the binder in said inner and
outer laminae is rendered completly dispersible and devoid of
wet-strength.
2. Pad according to claim 1, in which the fibers are
cellulosic.
3. Pad according to claim 1, in which the naturally-occurring
material of the binder is gelatin.
4. Pad according to claim 1, in which the water-repellent coating
comprises microcrystalline wax.
5. Pad according to claim 1, in which the non-woven webs of the
inner and outer laminae contain a paper softener.
6. Pad according to claim 1, of a size adapted for use as a diaper
for infants.
Description
This invention relates to readily disposable, multi-ply sanitary
devices such as diapers and the like, for contacting the human body
and absorbing body wastes, which are designed to be disposed of by
flushing them in an ordinary water closet in the usual domestic
waste disposal systems.
Many attempts have been made to provide disposable sanitary items
such as diapers, and a certain measure of commercial success has
been attained. Thus, for example, the devices described in U.S.
Pat. Nos. 3,636,952; 3,480,016; 3,070,095; 3,214,323; 3,406,688, as
well as others, have described so-called disposable sanitary
products.
Disadvantages of the prior art materials, it is believed, have
limited their use or required disagreeable or difficult handling in
disposal or the like so as to discourage their acceptance. Some
approaches have involved using materials of low wet-strength, so as
to make them easily dispersed, but this entails obvious
disadvantages in use or requires external, non-disposable
supporting fabrics.
Possibly the nearest approach to a practical product of this type
is shown in U.S. Pat. No. 3,480,016, in which non-woven sheets
bound with a binder which is degraded by the addition of acidic or
basic material to the aqueous media in which the multi-ply products
are to be disposed, is described. However, because the materials
which are to be added to the disposal system are strong acids, or
bases, it is believed that long-continued use of these substances
for disposal purposes would entail serious ultimate damage to home
or domestic type sewage disposal systems such as septic tanks and
the like. Possibly, widespread use of such acidic or basic
materials in municipal sewage disposal systems would also be
disadvantageous. Moreover, the handling of strong acids or bases
entails hazards to the persons who come in contact with such
materials, particularly children, and of course the association of
such materials with the use of diapers for small children must be a
distinct disadvantage.
This invention contemplates provision of diapers and other sanitary
products which are inexpensive and disposable after a single use,
which possess good wet-strength so as to provide structural
integrity during condition of use without the need for
reinforcement by woven fabrics, yet which are readily and safely
disposed of in domestic disposal systems with the aid of materials
which cause no harm to or interference with the efficiency of such
sewage disposal systems.
While the products of the invention, having good wet-strength, are
readily handled in that condition and it is understood that they
also have excellent dry-strength and can be folded or otherwise
handled in that condition, without weakening them.
Broadly speaking, the multi-ply pad of the invention consists
essentially of an inner body-contacting, self-supporting,
water-absorbent lamina composed of a non-woven composite web
consisting essentially of relatively short fibers having
substantially no wet-strength in the absence of binder and in
combination therewith a water-insoluble, normally solid,
enzyme-degradable binder which consists of a polymer of at least
one ethylenically unsaturated monomer covalently bonded with a
naturally-occurring enzyme-degradable, water-soluble polymeric
material, said polymer having a molecular weight of at least about
10,000 and a degree of polymerization at least about 50, and said
binder being present in effective amount ranging from about 0.3
percent to about equal amounts by weight of said fiber in said
non-woven web, and sufficient to impart to the said non-woven web
wet-strength in aqueous milieu in the absence of enzyme of from
about 0.7 to 50 kg. per square centimeter, and to permit dispersion
of said non-woven web in a period ranging from about 5 to about 30
minutes in aqueous milieu containing enzyme capable of degrading
said water-soluble polymeric material to disintegrate said binder
and render said web readily dispersible; one or more intermediate
laminae of non-woven, highly moisture-absorbent fibers containing
no binder and having substantially no wet-strength; and an outer
lamina of a self-supporting, non-woven composite web of material
the same as said body-contacting web, having over and supported
upon not more than one surface thereof an adherent coating of
frangible, water-repellent material, said laminae being contiguous
and said inner and outer laminae being approximately equal in area
and larger than said intermediate lamina or laminae. It will be
apparent that the multi-ply structure in use is so placed that the
innermost layer contacts the body, and body waste liquids are
absorbed in and passed therethrough into the interior lamina or
laminae, and are absorbed therein. The water-repellent material
prevents passage of moisture all the way through the pad. After
use, the entire multi-ply pad is placed in, e.g., a domestic flush
toilet and an amount of enzyme is added to the water therein. The
non-woven plys rapidly disintegrate and can be flushed down the
toilet in the usual way, without fear of stoppage. The enzymes do
not interfere with the function or efficiency of the domestic
sewage disposal system, even with repeated use.
The non-woven web which is employed to make the inner and outer
laminae of the multi-ply product of the invention is that described
in the copending application of George H. Crawford, Charles F.
Nawrot and Ronald F. Ofstead, Ser. No. 285,084, filed Aug. 30,
1972.
Generally speaking, the self-supporting, non-woven webs of that
application, which are employed here as laminae in the multi-ply
product of the present invention, consist of non-woven webs of
short fibers of cellulosic or synthetic fibers and the like, e.g.,
viscose rayon, cotton, wool, silk, cellulosics, linen, hemp, wood
fibers, regenerated cellulose, nylon, polyesters, etc. Preferably,
they are natural fibers which are ultimately biodegradable. They
are combined with a water-insoluble, normally solid
enzyme-disintegratable binder which is sufficient to impart to the
non-woven web a wet-strength in water in the absence of enzymes of
about 0.7 to 50 kg./cm.sup.2. They are bound with a binder which
consists of a water-insoluble polymer of at least one ethylenically
unsaturated monomer, covalently bonded with a naturally-occurring,
enzyme-degradable, water-soluble polymeric material. Exemplary of
such binders are reaction products with gelatin disclosed in U.S.
Pat. No. 3,507,661. The ethylenically unsaturated polymers which
are reacted with gelatin in these binders have a molecular weight
of at least about 10,000 and a degree of polymerization of at least
50, and preferably are of a molecular weight such that they have
glass transition temperature (T.sub.g) which is substantially
independent of the molecular weight of the polymer. In these
binders, the ethylenically unsaturated polymer can also be termed a
vinyl polymer, and is required to have substituent groups, either
pendant or terminal, which are reactive with the water-soluble
naturally-occurring polymers. These vinyl polymers can also be
termed polymers and copolymers of addition-polymerizable vinyl
monomers which have substituent groups reactive with compounds
having active hydrogen.
The enzymes which are employed for disposal of the multi-ply
product of the invention can be any of the well-known classes of
enzymes such as hydrolases, oxidases, reductases, transferases and
isomerases, which catalyze chemical processes of hydrolysis,
oxidation, reduction, group transfer, isomerization, etc. It may be
necessary to buffer the aqueous medium in which they are employed,
to obtain the maximum catalytic effect. More complete descriptions
of enzymes, their structure and catalytic action, which will
characterize the enzymes employable in connection with the
multi-ply products of this invention, are well-known to the art,
as, for example, the series of publications entitled "The Enzymes,"
edited by Paul D. Boyer, Academic Press, New York; or reference may
also be had to U.S. Pat. No. 3,386,441, which discloses various
proteolytic, mucolytic or amylolytic enzymes, therein used for a
purpose different than here employed but also in connection with
absorbent sanitary pads.
Preferably, cellulose or cellulosic fibers are employed for making
the multi-ply structures of the invention.
The absorbent, multi-ply devices of the invention are made from
sheets of non-woven materials which are pre-cut in a pre-selected
shape or size, according to the purpose for which they are desired.
Usefully, the non-woven material is prepared in the form of a roll,
and one or more rolls of the material are associated with dies or
cutting devices so as to facilitate manufacture in a continuous
fashion, in which the webs are drawn from the rolls continuously,
brought together in overlying fashion with two or more laminae in
contact, and then cut into the preselected, appropriate size and
shape. Adhesive may be applied to hold the laminae together, or
portions of the multi-ply product, e.g., edges or corners, may be
pressed together for this purpose, if desired. Thereafter, the
multi-ply sheets can be folded, wrapped or packaged in any desired
way for convenient handling and sale.
A diaper having the property of being dispersible in enzyme
solution may be constructed in the following manner.
A binder solution is first prepared from 21 parts of hide glue, 7.5
parts of a polymer latex containing 30 percent solids by weight of
a copolymer of 90 parts ethylacrylate and 10 parts of glycidyl
methacrylate prepared as described in U.S. Pat. No. 3,507,661, and
400 parts of distilled water. Several 46 .times. 36 cm. paperlike,
non-woven sheets of basis weight 24 g./cm.sup.2 of viscose rayon
fiber are saturated with the solution and allowed to air dry. These
sheets are then cured at 100.degree. C. for 3 to 5 minutes in an
oven.
After curing, the sheets are desirably treated with a softening
agent, such as glycerol. For this purpose, they are saturated with
a mixture of 120 parts of glycerol and 100 parts of water by
weight, and dried on a paper dryer at 65.degree. C. If desired a
small amount of starch, e.g., 10 grams, can be added to the
softener. Half of the sheets are then brush coated with molten
microcrystalline wax (available under the trademark Shellmax 500)
at a temperature of 63.degree.- 65.degree. C. to form a thin,
flexible, water-repellent coating. The temperature must be high
enough to make the wax coatable, yet low enough to prevent
significant penetration of the web.
A sheet of wax-coated material is laid wax side up on a flat
surface, and about 25 to 35 g. of wood pulp fluff is evenly spread
upon all but about a 6 cm. border around the edge. One of the
unwaxed sheets is then placed on the top of this, and the edges are
heat-sealed with a warm iron.
A diaper of this construction can be folded appropriately and
fastened about an infant using safety pins or other fastening
means. After being soiled, the diaper is placed into an ordinary
domestic flush toilet bowl along with 2 to 3 grams of a proteolytic
enzyme (available under the trademark Protease 62). After 5 to 10
minutes the diaper is essentially completely dispersed and may be
completely flushed away without danger of clogging the sewer
system.
The invention will be further illustrated by the accompanying
drawing, in which:
FIG. 1 is a perspective view of a disposable pad according to the
invention, one corner of which has been separated into its
component plies (a part of the coating on one of these being broken
away) to illustrate the relationship of the parts, and
FIG. 2 is a partial view in cross-section of the multi-ply pad of
FIG. 1 along the line 2--2.
Referring to the drawings, in FIG. 1 a diaper of the invention is
shown in flat, unfolded position. A corner of the diaper is peeled
back to disclose the three plies of which it is composed. In this
figure, 10 designates the diaper in the condition in which all
plies are approximated, the non-woven material thereof being soft
and of low resilience and having an uncalendered surface so as to
cause the respective plies to cling together when pressed together
along the edges sufficiently to withstand normal handling and
folding without separating. Inner, body-contacting ply 12 is
composed of a non-woven web of relatively short cellulose fibers
having sustantially no wet-strength in the absence of binder, and
which has an enzyme-degradable, normally solid, water-insoluble
binder therein which consists of a polymer of at least one
ethylenically unsaturated monomer covalently bonded with a
naturally-occurring, enzyme-degradable, water-soluble polymeric
material having a molecular weight of at least about 10,000 and a
degree of polymerization of at least about 50, which is present in
effective amount ranging from about 0.3 percent to about equal
amounts by weight of said fiber in the non-woven web. Enough binder
is used to give the non-woven web wet-strength in water, in the
absence of enzyme, of about 1 to 100 psi. Desirably, the web is
dispersible in aqueous milieu containing enzyme in about 5 to 30
minutes.
The intermediate ply 14 consists of non-woven web which is
substantially without wet-strength, or which has binder as
described for the inner ply 12. This ply is preferably of lower
density, or higher loftiness, and is highly absorbent of body
fluids when in use, i.e., it has a wicking action and the ability
to absorb and hold 100 to 300 ml. of fluid. The size of this
intermediate ply is preferably made smaller in all dimensions than
the inner and outer plies, so as to be overlapped by them on all
sides. A useful material for the purpose is creped tissue paper or
a similar bat of cellulosic fibers.
Outer ply 15, made of the same material as inner ply 12, has on its
surface a flexible coating 16 about 25 to 125 microns in thickness
of wax having tensile strength from about 0.5 to 25 kg./cm.sup.2.
Typical waxes useful for the purpose include microcrystalline wax,
ozokerite, paraffin wax, beeswax, tallow and waxy polyvinyl esters
of fatty acids which have been modified by the incorporation of up
to 25 percent of a flexible modifier to provide suitable
flexibility and tensile strength to the wax. Typical flexibility
modifiers include petrolatum and low molecular weight polymers and
copolymers such as polyvinylacetate, polyethylene and
ethylene-methacrylate copolymer. Thin films and coatings of such
waxy materials have little strength or film-forming properties when
unsupported. The function of this coating is to prevent passage of
body fluids through the outermost layer, while withstanding a
reasonable amount of folding and bending. The coating is made thin
so that it will not flake off. The coating does not penetrate the
thickness of the ply to any material extent, so that when the
uncoated surface of the outer ply is contacted with aqueous enzyme
solution, the web disintegrates and disperses from that side,
leaving the water-repellent coating unsupported. In this condition
it readily fractures and disperses with slight agitation. Such
frangible coatings are preferred.
It will of course be apparent that the water-repellent coating can
alternatively be placed on the outer side of outer ply 15 with
similar results.
The assembly of plies has been pressed together as indicated at 17,
to cause the laminae to adhere sufficiently to withstand normal
handling while in dry condition.
FIG. 2 shows the multi-ply pad of FIG. 1, in which the inner,
body-contacting ply 12, absorbent intermediate ply 14 and outer ply
15, with water-repellent coating 16, are shown in cross-section.
The materials are compressed together at 17.
In both of the figures of the drawing, the thicknesses of the plies
are exagggerated for clarity. Typical thickness for each ply are as
follows: inner ply, 0.1 mm.; absorbent ply, 5 mm.; outer ply, 0.15
mm., including the coating of waxy material. Obviously these can be
made thicker or thinner as required for any specific use.
* * * * *