US 3777759 A
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.
Description (OCR text may contain errors)
United States Patent 1 Oehmke et al. I
[ 51 Dec. 11, 1973 i 54 i ENZYME-D ISPERSIBLE BANDAGE  Inventors: Richard W. Oehmke, Hudson, Wis.;
Ronald F. Ofstead, Maplewood,
 Assignee: Minnesota Mining and Manufacturing Company, St. Paul, Minn.
221 Filed: Sept. 25, 1972 21 Appl. No.: 291,659
Primary Examiner-Charles F. Rosenbaum Attorney-Kinney, Alexander, Sell, Steldt & Delahunt  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 dryand wet-strength, wet-strength being conferred on the materials by a binder vlhich isessentially unaffected over periods of serveial 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.
6 Claims, 2 Drawing Figures l ENZYME-DISPERSIBLE BANDAGE 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. I
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 dis posable after a single'use, which possess good wetstr'ength so as to provide structural integrity during condition of use withoutthe 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 drystrength and can be folded or otherwise handled in that condition, without weakening them. I
Broadly speaking, the multi-ply pad of the invention consists essentially of an inner body-contacting, selfsupporting, 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, watersoluble 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 presentin effective amount-ranging from about 0.3 percent to about equal amounts by weight of said fiber insaid 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 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 wetstrength; and an outer lamina of a self-supporting, nonwoven 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 mul'ti-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 multiply 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 wetstrength in water in the absence of enzymes of about 0.7 to 50 kg./cm 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, watersoluble 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,,) 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 substitue'nt 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 preselected shape or size, according to the purpose for which they are desired. Usefully, the nonwoven 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 US. Pat. No. 3,507,661, and 400 parts of distilled water. Several 46 X 36 cm. paperlike, non-woven sheets of basis weight 24 g./cm of viscose rayon fiber are saturated with the solution and allowed to air dry. These sheets are then cured at 100 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 I00 parts of water by weight, and dried on a paper dryer at 65 C. if desired a small amount of starch, e.g., 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 63-65 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 multiply 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, l0 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 nonwoven 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, enzymedegradable, 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 nonwoven web. Enough binder is used to give the nonwoven web wet-strength in water, in the absence of enzyme, of about 1 to 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 fiuids 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 but 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 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 ethylenemethacrylate 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 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.
What is claimed is:
l. 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 waterinsoluble, 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 waterrepellent 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 naturallyoccurring material of the binder is gelatin.
4. Pad according to claim 1, in which the waterrepellent 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.