US3400717A - Diapers - Google Patents

Description

Sept. 10, 1963 R. B. CUBITT ETAL 3,400,717

DIAPERS Filed May 21, 1965 FIG. 2

6 r 5m A w I 1,. {fitx United States Patent DIAPERS Robert Bruce Cubitt, Bound Brook, Herman Lowell Marder, Plainfield, and Werner Otto Tundermann, Colonia, N.J., assignors to Colgate-Palmolive Company, New York, N.Y., a corporation of Delaware Filed May 21, 1965, Ser. No. 457,762 14 Claims. (Cl. 128-284) ABSTRACT OF THE DISCLOSURE Absorbent articles such as diapers, sanitary napkins and the like comprising a core of highly absorbent material are provided with a surface web of high wet strength paper plasticized to give unusual softness and nonirritating characteristics thereto.

The present invention relates to disposable diapers and to paper suitable for use as the inner surface layer of a disposable diaper, that is, the surface layer intended to be placed in contact with the skin. In a broader sense the invention also relates to other absorbent articles, particularly suitable for absorbing body wastes (e.g., sanitary napkins and bed pads) using a core of highly absorbent material covered with a surface layer of paper.

Disposable diapers may be produced from an absorbent material such as layers of cellulose wadding, absorben tissue, blotter stock, or loose cellulose pulp, such as wood fluff, of suitable thickness (e.g., about /2 inch) surfaced with a layer of a wet-strength paper. While wet-strength papers of sufficient softness to be placed in contact with a babys skin, in the use of the diaper, are known to the art (as shown, for example, in US. Patent 2,046,763 of July 7, 1936), such papers have been found to be deficient in use. For example, on storage of disposable diapers having this surface layer of wet-strength paper, it has been found that the initially soft paper becomes rattly and harsh and irritating to the skin.

It is therefore an object of this invention to provide a disposable diaper having a surface layer of wet-strength paper which retains its softness on prolonged periods of storage under the varying conditions generally encountered during the shipment and stocking of products of this type.

Other objects of this invention will be apparent from the following detailed description and claims. In this description and claims, all proportions are by weight unless otherwise specified.

It has now been found that the change in the softness of the wet-strength paper on storage is due, in large part, to the migration of the softener from the surface layer of the diaper into the highly absorbent body of the diaper. When this occurs, the amount of softener in the wetstrength paper is diminished, making the paper harsher. This migration has now been found to be characteristic of such common paper-softening agents as glycerine and diethylene glycol, both of which are liquid, and urea, which is a crystalline solid, as Well as mixtures of urea and sodium nitrate.

' In accordance with one aspect of this invention, there is provided a diaper having a core of absorbent material and an inner surface layer of porous internally plasticized wet-strength paper having a zero plasticizer migration time, as defined herein, of at least three days at-120F. We have found it particularly advantageous to use as the internal plasticizer a polyethylene glycol having a number average molecular weight in the range of about 282-810, or an average number of oxyethylene units in the range of about 6-18,'provided that the weight fraction of molecules of molecular weight below about 282 or 6 oxyethylene Patented Sept. 10, 1968 "ice units is neglible (below 10%) since we have found that these will migrate. Since in practice it is very difiicult to obtain polyethylene glycols with a very narrow molecular weight distribution, the preferred average molecular Weight is about 600; commercial preparations of this material (e.g., Carbowa 600) have negligible amounts of glycols of molecular weight below 282, and contain less than about 10% of polyethylene glycols of less than 8 oxyethylene units (M.W., 370). It is within the scope of this invention, however, to employ sharper cuts of the polyethylene glycols than are now available commercially; one example is a polyethylene glycol with an average molecular weight of about 414 (average of 9 oxyethylene units) and no material having less than about 6 or more than about 13 oxyethylene units We have found that the use of the polyethylene glycols described above gives a wet-strength paper which is soft and pleasant to the touch ,over a wide range of humidities, which is nontoxic and safe in contact with the skin, and which retains its softness during storage of disposable diapers surfaced with such paper. In contrast the use of other polyethylene glycols, in place of those set forth above, gives a paper which is either too harsh or waxy initially or becomes too harsh during storage of the diapers.

The paper can be made of bleached cellulose stock, and may be of softwood or hardwood pulp. Papers made of cellulose fibers other than wood fibers have given excellent results; an example is a paper, similar to that used commercially for tea bags, made of hemp fibers. The wetstrength of the paper is generally attained, in a manner well known to the art, by the use of a small amount of a water-insoluble bonding agent, such as glue (as in US. Patents 2,035,024 and 2,046,763) or regenerated cellulose (as in US. Patent 2,048,293). The use of synthetic resins (e.g., cationic melamine-formaldehyde, modified urea-formaldehyde and polyamide resins) for imparting Wet-strength to paper is also Well known in the paper art; the wet-strength papers made with these resins are usually resistant to biodegradation in septic tank systems.

The papers previously mentioned are therefore more desirable, than those containing these synthetic resins, for making disposable diapers which are intended to be flushed down a toilet. They are also more desirable in that they show considerably better response to plasticization than the papers made with the more hydrophobic synthetic resins. Parchmentized papers made by treating paper with strong acid (e.g., strong sulfuric acid) have good wet strength, but usually do not have the porosity needed for use as an inner surface layer of a disposable diaper. The porosity and thus the desired permeability to liquids can be increased appreciably by perforating the parchmentized paper, e.g., with 6-10 perforations, of inch diameter, per square inch. More desirably, the necessary porosity can be attained by the use of an initially very porous paper, Which retains much its initial porosity on parchmentizing.

The porosity of the paper can be measured conveniently by a standard conventional Gurley PP porosity tester (which measures the rate of flow of air through porous paper). The porosity, so measured, should be such that no more than about 2 seconds, and preferably much less, is needed for 100 cc. of air to pass through the plasticised paper.

The wet-strength paper, before plasticization, is preferably not too stiff. When tested with the Handle-O- Meter, a device widely used in the textile and tissue paper industries for measuring the hand of fabric or paper, the total hand of the unplasticized paper should preferably be at most 100 (as measured in standard manner using a Thwing Albert Handle-O-Meter with a 10 mm. slot width on a 4" x 4" sample conditioned at 70 F. and RH, the value of hand being the sum of the four readings taken on both sides and in both directions of the sample). Best results thus far have been attained with papers thinner than mils in thickness.

The wet strength of the plasticized paper after thorough soaking in water should preferably be at least A1 pound/in. when measured in the weaker direction (cross-machine direction) under standard TAPPI conditions but more preferably about 1 pound/in, or more, in the weaker direction. It is preferred that the wet strength in the machine direction be at least 2 pounds/in. The presence of the plasticizer generally has little, if any, eflect on the wet strength.

It is convenient to apply the polyethylene glycol to the wet-strength paper by saturating the paper with an aqueous solution of the polyethylene glycol and then evaporating the water. This provides maximum penetration into the fibers with minimum surface coating.

The amount of the polyethylene glycol used in the paper may be varied in accordance with the degree of softening desired and the particular type of paper used. Generally, the percent pickup, i.e., the increase in weight (measured after conditioning at 70 F. and 65% RH.) as a result of the addition of the polyethylene glycol, will be above about 5% and well below 50%, preferably in the range of about -25%. It will be understood that variations in the type of furnish, type of pulp, porosity of the paper, etc., will affect the hand of the paper and its response to plasticization. With some papers, such as very thin paper made of hemp fibers and a regenerated cellulose binder, amounts at the lower end of the preferred range yield as soft a product as is obtained by the use of amounts at the upper end of this range with thicker papers made of wood pulp cellulose.

It is preferable to use an amount of polyethylene glycol which is insufficient to substantially affect the optical reflectance or porosity of the paper. For example, in one series of tests, using a wet-strength paper made of a wood pulp cellulose and in which the bonding agent was tanned glue, the presence of the polyethylene glycol at levels of percent pickup below about 30% had practically no effeet on the porosity (Gurley, seconds/300 cc.) or on the optical reflectance (photovolt, with trigreen filter using a standard black background; background alone giving a reading of 5, white standard giving a reading of 84). At about 30% pickup the porosity and reflectance changed sharply. For instance, the reading of porosity at pickup was within 10% of the reading for the unplasticized material while at about 33% pickup there was an average difference of about in those readings. Similarly, the photovolt reading, of brightness, at 25% pickup was on the average within about 10% of the reading for the unplasticized material while at about 33% pickup the brightness (reflectance) was only about half the brightness of the unplasticized material. It is believed that the plasticizer enters the void volume within the individual fibers of the paper and that the effects of excess plasticizer, described above, are due to surface coating of the fibers and filling of the spaces between them in addition to the filling of the void volume within the fiber. Such additional amounts are wasteful and are lost through migration.

The treated paper may be tested for loss of plasticizer in contact with a much thicker mass of absorbent cellulosic material in the following manner. A 4-inch by 8-inch sheet of the treated paper (previously conditioned to constant weight at 65% RH. and 70 F.) is placed on a 4" x 8%" sheet, weighing 4 grams, of blotter stock (sulphate pulp, 6913 Saturating Paper, of Crocker Hamilton Papers, Inc., having a caliper of 32-34 mils), previously separately conditioned to constant weight at 65 RH. and 70 F. The assembly is folded widthwise centrally to 4" x 4" to produce a sandwich of two layers of the wet-strength paper within upper and lower layers of blotter stock. The sandwich is placed in a polyethylone bag and then pressed with five similar bags of samples, one on top of another between two 4" x 4" pieces 4 of Masonite hardboard (with the smooth sides of the hardboard toward the samples), a /2 lb. weight is placed on the upper Masonite board and the whole assembly is placed in an oven at 120 F. At the end of three days, the samples are removed from the oven, reconditioned at RH. and F. and the paper and blotter are separately weighed and examined, after which each blotter sample is reassembled with its corresponding paper sample and the test repeated for additional 3-day intervals. The zero plasticizer migration time is the length of the test period during which substantially no loss of weight of plasticizer from the paper is evident.

The presence of the palsticizer is most noticeable in its effects on the rattliness, harshness, and smoothness of the paper. The unplasticized papers, even those exhibiting low Handle-O-Meter readings, are rattly and will make a harsh sound when a small piece of the paper is shaken by hand. The incorporation of the plasticizer not only reduces the Handle-O-Meter reading but greatly diminishes this rattling, makes the paper more limp, gives the paper a softer feel and in general makes it acceptable for application next to the skin.

The amount of nonmigrating plasticizer should be such that the total hand of the paper (as measured on the Handle-O-Meter) is less than below 30, and preferably below about 20 for best results. It will be understood that it is within the broader scope of this inven tion to have present small proportions of additional plasticizers, which may be of the migrating type, such as glycerine, for special purposes. The amount of the nonmigrating plasticizer employed in the practice of this invention should in itself be sufficient to reduce the hand of the paper to the values indicated above; for most purposes, therefore, the presence of a migratory plasticizer is wasteful and unnecessary.

The paper may also contain other additives such as perfumes and bacteriostatic agents, which are conveniently incorporated with the plasticizer, being added to the aqueous plasticizer solution. For example, a bacteriostatic quaternary ammonium compound may be used, such as para-diisobutyl-phenoxyethoxyethyl dimethyl benzyl ammonium chloride in amount of 0.016 lb. per 3000 square feet of paper. The perfume may, for instance, be of the coconut extract-synthetic vanillin type used in the amount of 0.01 lb. per 3000 square feet of paper.

Other suitable plasticizers, less preferred than the polyethylene glycol described above, are noncrystallizing sorbitols or sorbitol ethers (e.g., lower hydroxyalkyl ethers of sorbitol). We have found that in wet-strength paper these materials are highly effective as plasticizers which do not migrate to an adjacent cellulose absorbent core. Unlike sorbitol itself which, while substantially nonmigrating, crystallizes on storage giving the paper an undesirable feel, these polyhydric alcohols retain their noncrystalline character, in wet-strength paper, on long storage. These plasticizers are, however, less effective at low humidities than the preferred polyethylene glycols. The use of blends of the plasticizers is within the scope of this invention.

The absorbent core which constitutes the major part of the weight of the diaper preferably has no wet strength, so that when placed in a volume of water it will, with slight agitation (as occurs in the flushing of a conventional toilet bowl), disintegrate into a slurry of fibers or small segments. Examples of absorbent materials are water leaf multi-ply crepe wadding or sulfite cellulose fluff, or a defibered flock of bleached softwood kraft fibers, or degreased cotton linters, or combinations thereof. When the core is composed of tissue paper, it is preferably, in order to promote disintegration on immersion, subdivided into a number of sections; thus the core may be made up of two layers, each composed of abutting sections extending across the width of the layer, the sections of the upper layer being staggered with respect to those of the lower layer so that they overlie the abuttingedges of the sections of the lower layer. The core-will generally have a weight in the range of about 30 to 100 grams of cellulose per square foot of core; the diapers may have a core measuring, for example, about 6 x 12" and weighing about 15 to 50 grams.

Another feature of this invention relates particularly to plasticized wet-strength papers having proteinaceous bonding agents. We have found that the proteolytic enzymes in feces tend to attack the proteinaceous bonding agent, and thus decrease the effective wet strength of the paper diaper. Glycerine in plasticizing proportions inhibits this enzyme action, but is unsuitable because of its migrating tendency. Accordingly, we may incorporate an enzyme inhibitor such as a chelating agent, e.g., ethylene diamine tetracetic acid, in small amounts, say about to ,4 e.g., based on the weight of the paper to insure against attack on the proteinaceous bonding agent. a

It is within the broader scope of this invention to use the plasticizers describedhere with other wet-strength cellulose webs, such as the known wet-strength substantially structureless nonwoven webs, in place of wetstrength paper.

The following examples are given to illustrate this invention further.

EXAMPLE 1 A paper produced in accordance with U8. Patent 2,046,763 was leached thoroughly with water to remove all water-soluble materials and then dried. The resulting smooth paper which had a thickness of about 2 mils and a basis weight of about 13-15 pounds/ 3000 sq. ft., was similar'in feel to the usual onion skin paper; on crumpling it was rattly and noisy. Itswet tensile strength,

after soaking one hour in water at room temperature, was 2 lbs/in. in the machine direction and 1 /2 lbs/in. in the cross direction, while its wet Mullen Burst strength was about 6 lbs.

The paper was then conditioned (to constant weight) at 65% RH. and 70 F., then weighed and then padded with an aqueous 33% solution of Carbowax 600, which is a liquid polyethylene glycol, completely soluble in water at 20- C., having an average molecularweight in the range of 570630, a specific gravity of 1.127 20/20-C., a freezing range of 2025 C., a viscosity of 10.5 centistokes at 210 F., a refractive index n of 1.469, a surface tension of 44.5 dynes/cm. at 25 C., a comparative hygroscopicity (glycerol-100) of 40, a vapor pressure of about 5.2 10- mm. Hg at 100 C., and a flash point Y of about 475 F. (Cleveland open cup tester). The molecular weight distribution of this polyethylene glycol may be represented by a graph having the following approximate points.

Number of oxide units: Weight percent 6 The treated paper was dried, conditioned (to constant weight) at 65% RH. and 70 F. and then weighed. The percent pickup due to the treatment with softener was thus found to be 25%. (Percent pickup is where W is the conditioned weight before the softener solution is applied and W is the conditioned weight after the treatment with softener.) The softened paper was opaque, smooth, limp, had 'a soft pleasant hand and could be shaken or crumpled in the hand easily without crackling or rattling.

Disposable diapers made with outer layers of the treated paper (by enclosing a core of Wood fluff, wrapped in a thin layer of tissue paper having no wet strength, between two sheets of the treated paper, one on each face of the diaper) retain their desirable characteristics over long periods of storage at ambient temperatures including periods of exposure to hot summer temperatures; during storage the outer layers do not stiffen significantly or become rattly.

When tested for loss of plasticizer in contact with absorbent cellulose at 120 F., in the manner described above, the softened paper sample had lost none of its Weight after the first 3 days of test and was still soft and pliable. In contrast the original paper or the same leached paper similarly softened with glycerine lost of its original pickup after 3 days, the same leached paper softened with urea (28% pickup) lost 36% of its original pickup after 3 days, and the same leached paper softened with Carbowax 200 (polyethylene glycol of average molecular weight 190-210), at a percent pickup of 20%, lost 40% of its original pickup after 3 days.

After 9 days of testing papers carrying the Carbowax 600 still showed no loss of softener (Within the experimental accuracy; i.e., the weight change was not over 4 mg.) and retained substantially their original softness. In contrast, the same leached paper softened with Carbowax 1500 (a blend having an average molecular weight of 500-600 and made up of equal parts of polyethylene glycol of 285-315 average molecular weight and polyethylene glycol of 1300-1600 average molecular weight) at a 22.6% pickup, lost 12.7% of its original pickup after 3 days, while the same leached paper softened with another blend of polyethylene glycols of average molecular weight of 600 (made up of Carbowaxes 200 and 4000, which are polyethylene glycols of average molecular weights 190-210 and 3000-3700), at a 21.4% pickup, lost 20.8% of its original pickup after 3 days.

'A temperature of 120 F., used in the test described above, is not unusual for the interior of a freight car in the hot summer sun; the diapers of this invention can withstand shipment under such conditions.

The above-described paper softened with 25% of Carbowax 600 was also tested for stability in contact with absorbent cellulosic material at 65% RH. and 70 F. This test was similar to the accelerated test described above except that instead of placing the assembly of boards and bagged samples in an oven, the assembly was left in a room at 65% RH. and 70 F. After 30 days there was no loss of softener.

The molecular weights of the polyethylene glycols are determined by the known technique of end group analysis, in which the polymer is heated with a predetermined quantity of phthalic anhydride-pyridine reagent, and the mixture is then treated with a predetermined quantity of sodium hydroxide and then titrated with sodium hydroxide, as described in Bulletin F4772E of Union Carbide Co.

EXAMPLE 2 In this example the paper used is a cellulose wet-strength tea-bag type paper whose fibers are hemp having an average fiber length of about it-V2, and whose bonding agent is regenerated cellulose. The paper has a basis weight of 8.06 lbs/3000 sq. ft.; a caliper of 1.2 mils; a tensile strength of 5.8 lbs/in. (dry) and 1.6 lbs./in. (wet) in the machine direction, and 4.5 lbs/in. (dry) and 1.3 lbs/in. (wet) in the cross direction; a Mullen Burst strength of 6.0 lbs. (dry) and 4.5 lbs. (wet). After treatment with an aqueous solution of Carbowax 600 to give a percent pickup of the resulting soft treated paper is used as the cover of a disposable diaper as described in claim 1, with similar results.

The treated paper retains in large measure the strength of the unplasticized paper but is much softer, limper and less rattly.

The treated paper was tested for plasticizer migration in the manner described in Example 1. After 3 months, at either 70 F. or 120 F. there was no loss of'plasticizer from the treated paper. The following figures for total hand were obtained with the Handle-O-Meter (used in the manner previously described) on samples before and after such migration testing:

Test Temperature Hand before Test Hand after 3 mos.

of Test (a) The leached, dried paper employed in Example 1 was conditioned as in Example 1 and then padded with an aqueous solution of Atlas Arlex, an 83% aqueous solution of sorbitol mixed with sorbitol anhydrides and other polyhydric derivative of sorbitol. The Arlex is a liquid having an average molecular weight (on a dry solids basis) of 196, a viscosity at C. of about 1700 cps., a specific gravity at 25 C. of about 1.32, and a refractive index of about 1.48; it is soluble in water and methanol and insoluble in mineral spirits at 25 C.

(b) Example 3(a) was repeated except that the plasticizer was Atlas G2401 instead of Arlex. The 6-2401 is an 85% aqueous solution of hydroxypropylsorbitol. It is a liquid having a hydroxyl number of 1350- 1500, a specific gravity at 25 C. of about 1.27, a viscosity at 25 C. of about 2500 cps. and a refractive index of about 1.475. It is soluble in water and 5% aqueous solutions of sulfuric acid, sodium hydroxide, aluminum chloride or sodium sulfate; also soluble in ethanol, methanol, propylene glycol, ethylene glycol and B ethoxyethanol, but insoluble in acetone, mineral oil and mineral spirits.

The percent pickup in each of Examples 3(a) and 3(b) was about 2530%. The resulting plasticized papers performed well as surface layers for disposable diapers. Tests of the papers in contact with blotting paper, as in Examples 1 and 2, gave the following results:

8 EXAMPLE 4 Example 1 was repeated except that the percent pickup Was varied. The following results were obtained:

Migration Hand Percent Storage pickup Temp. days 3 mos. Before After the 3 Test mos. Test 9 days 3 mos.

A typical disposable diaper of this invention is shown in the drawing in which FIG. 1 is a perspective view of the diaper and FIG. 2 is a cross-sectional view along the line 22 of FIG. 1. In the drawing:

The absorbent material is a mass of wood fluff 2 which is the preponderant material by weight in the diaper (e.g., it may be about 6" x 12", about /2" thick and may weigh about 15 to 50 g.). To form the absorbent core the wood fluff is enclosed in a thin wrapping of one layer of no-wet-strength tissue paper 4 which keeps the wood fluff particles together. The absorbent core is dis posed between two cover layers 5 and 6 of the wetstrength paper. The layers 5 and 6 extend beyond the ends of the core (giving the diaper an area of, for example, 6" x 24"), providing tabs which may be tucked over the childs plastic pants and thereby act to retain the diaper in position on the child. Both edges of one layer 5 are lapped around the absorbent core and under the corresponding edges of the other layer 6 and are spot-bonded, as at 7, to the tissue paper 4, as by any suitable adhesive. The layer 6 which is intended for use next to the childs body, is similarly bonded, as at 8, to the tissue paper at points spaced from the overlapping edges. When the diaper is wet the overlapped edges are held together by the surface tension of the liquid therebetween. This force of the surface tension acts to preclude sliding or other relative movement between the overlapping edges. When it is desired to dispose of the used diaper, it is only necessary to grasp one extended end thereof and place the diaper within the confines of a toilet bowl. Before flushing, the diaper is dipped in the water in the customary manner, commonly used by mothers to remove the bulk soil from cloth diapers. As the cover layers 5, 6 are respectively secured to the absorbent core only, and not to each other, the action of the water, and the weight of the wet core, causes cover layer 6 to separate from the cover layer 5. As a result, the soil will be washed into the bowl and the absorbent core will fall into the toilet and disintegrate into a slurry of fibers or small segments. Thereupon, the cover layers may be allowed to drop into the bowl and the entire diaper may be flushed therethrough. Thus, the diaper and its contents is completely disposed of without soiling the hands of the person handling the same.

Diapers made in accordance with this invention can readily be stored for 18 months or more at ambient temperatures without significant changes in their properties, even when the wet-strength paper and the absorbent core are pressed firmly against each other, as occurs when the diapers are packed tightly together in a carton. They can be shipped in uninsulated freight cars exposed to extremes of weather, such as hot summer sun, without substantial detrimental effect.

Sanitary napkins may be prepared in the conventional manner using the plasticized webs of this invention in place of the nonwoven fabrics generally employed as outer wrappers for the sanitary napkins. For example an absorbent cellulose pad, such as is conventionally employed in such napkins (e.g., 7" x 2% x /a) may be wrapped with a 7" x 19" sheet of the plasticized paper, previously described, in such a manner that the two long edges of the sheet overlap and are bonded together, or to the pad, on the outer surface of the napkin, that is on that side of the napkin which is to be worn away from the body. At the inner surface of the napkin, which is to be in contact with the body, the paper wrapper forms a smooth unbroken layer. The ends of the wrapping sheet extend longitudinally from both ends of the pad to form attaching tabs, for attachment in the usual manner to the sanitary napkin gadget commonly worn by the user.

The plasticizers used in this invention are of course preferably nontoxic and nonirritating to the skin.

Although the present invention has been described with reference to particular embodiments and examples, it will be apparent to those skilled in the art that variations and modifications of this invention can be made and that equivalents can be substituted therefor without departing from the principles and spirit of the invention.

What is claimed is:

1. An absorbent article for absorbing body wastes comprising a core of highly absorbent material covered with a surface layer of wet-strength paper internally plasticized with 5 to 50% of a substantially nonmigratory plasticizer to reduce the hand and rattliness of said paper, said plasticizer in said amount exhibiting a zero plasticizer migration time at 120 F. of at least 3 days, said internally plasticized paper having a wet strength of at least A pound per inch in its weaker direction, a Gurley porosity such that it passes 100 cc. of air in less than 2 seconds, and a total hand of less than 30.

2. An article as set forth in claim 1 in which the article is a diaper and the absorbent core is a mass of cellulose fiber having substantially no wet strength.

3. An article as set forth in claim 1 in which the article is a sanitary napkin and the absorbent core is a mass of cellulose fiber having substantially no wet strength.

4. An article as set forth in claim 1 in which the article is a bed pad and the absorbent core is a mass of cellulose fiber having substantially no wet strength.

5. An absorbent article for absorbing body wastes comprising a core of highly absorbent material covered with a surface layer of thin wet-strength cellulose web carrying as a softener therefor 5 to of a polyethylene glycol having an average of about 6 to 18 oxyethylene units'and containing less than about 10% of polyethylene glycols of less than 6 oxyethylene units.

6. A diaper as set forth in claim 2 in which the wetstrength paper is plasticized with a polyethylene glycol having an average of about 6 to 18 oxyethylene unifs and containing less than about 10% of polyethylene glycols of less than 6 oxyethylene units.

7. A diaper as set forth in claim 2 in which the paper fibers are bonded with a regenerated cellulose bonding agent.

8. A diaper as set forth in claim 2 in which the paper fibers are bonded with a protein and the paper contains about to ethylene diamine tetraacetic acid.

9. A diaper as set forth in claim 2 in which the paper fibers are bonded by parchmentization.

10. A diaper as set forth in claim 2 in which the paper contains hemp fibers.

11. A diaper as set forth in claim 6 in which the paper contains hemp fibers and a regenerated cellulose bonding agent.

12. A diaper as set forth in claim 6 in which the percent pickup of plasticizer is about 15 to 25%.

13. A diaper as set forth in claim 2 in which the wet-strength paper is plasticized with hydroxypropyl sorbitol.

14. An absorbent article as set forth in claim 3 in which the wet-strength paper is plasticized with a nonirritating nontoxic plasticizer comprising a polyethylene glycol having an average of about 6 to 10 oxyethylene units and containing less than about 10% of polyethylene glycols of less than 6 oxyethylene units.

References Cited UNITED STATES PATENTS 2,046,763 7/1936 Asnes l17-156 2,486,805 11/1949 Seymour et al. l28284 2,776,913 1/1957 Anderson 1l7-154 2,849,000 8/ 1958 Lewing l28285 2,965,436 12/1960 Domenico et al 117155 3,306,293 2/1967 Marder et a1 l28284 Re. 26,151 1/1967 Duncan et al. l28284 CHARLES F. ROSENBAUM, Primary Examiner.

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