US3426756A - Disposable diaper - Google Patents

Description

Feb. 11, 1969 G. A. ROMANEK I 3,426,756

DISPOSABLE DIAPER Filed June 16, 1965 sheet Tlclb.

INVENTOR.

i ATTORNEY Feb. 11, 1969 G. A. ROMANEK 3,426,756

DI SPOSABLE DIAPER Filed June 16, 1965 sheet 2 @f2 INVENTOR.

United States Patent O 3,426,756 DISPOSABLE DIAPER Gerald A. Romanek, East Brunswick, NJ., assignor to Johnson & Johnson, a corporation of New Jersey Filed June 16, 1965, Ser. No. 464,454 U.S. Cl. 128-287 5 Claims Int. Cl. A61f .I3/16, 5/44; A611 15/00 ABSTRACT OF THE DISCLOSURE A disposable rectangular diaper defined by an absorbent pad covered `by a liquid absorbent facing sheet constructed and positioned to provide greater widthwise diaper strength and a liquid impervious backing sheet secured to said absorbent pad, said diaper having its widthwise edges specifically closed to preclude fiber dusting and the lengthwise edges extending beyond the absorbent pad and engulfed by said backing sheet to provide a repellent dam effect therealong.

A disposable diaper is constructed as an inexpensive article which is to be used once and then thrown away. It must, of necessity for commercial reasons, be made of inexpensive materials; however, these materials must be serviceable and they must be functionally arranged to provide a construction which is practical in all respects.

In disposa-ble diapers the use of ground wood pulp as a filler or as the disposable pad is very desirable since it is highly absorbent, adds softness and it is inexpensive. Our present day disposable diaper manufacturers are attempting to utilize absorbent pads of ground wood pulp. They have encountered several undesirable features which have not, to date, been satisfactorily overcome. One of these features is that the ground Wood pulp of the absorbent pad is easily displaced within the diaper, leaving voids and the other is that some -forrn of sealing for the four ends of the diaper must be undertaken to avoid pulp dusting. This latter factor creates the problem of pro viding soft, conforming, nonmigrating seals for the edges. Finally, virtually al1 present day disposable diapers of this character lack pinning strength, or have low tear strength, in the pinning direction.

These and other undesirable features have been overcome -by the instant invention which provides a disposable diaper comprising a flat absorbent pad sandwiched between a facing sheet and a plastic backing sheet, said sheets having their their machine direction commonly aligned in widthwise direction, said sheets being secured together along all common edges and said diaper being characterized by improved pinning strength, uniform softness throughout and improved wet strength.

More particularly, the instant invention provides a disposable rectangular diaper blank comprising an absorbent pad of ground wood pulp interposed between a facing sheet and a polyolefinic backing sheet, said sheets being secured together to preclude escape of pad material, the direction of the greatest strength of said sheets being commonly aligned in the pinning direction of said diaper and the two common edges offsaid sheets running in other than the pinning direction, both extending substantially uniformly beyond said pad along its length and being secured together and folded inward on said facing sheets to substantially preclude wicking along the lengthwise edges, said diaper being characterized by improved pinning strength, softness, wet strength, and pulp stability.

The term pinning direction will be used herein to define the direction of the diaper which runs parallel to the opposed edges which are to circumvent the babys waist and :be pinned or otherwise joined to each other in the area of the babys hips. In the usual case this repreice sents the widthwise direction of the normally rectangular diaper blank.

The diaper blank is to be defined as the unfolded diaper.

The absorbent pad of fibrous material is preferably of cellulose fibers, i.e., ground wood pulp, which have been disintegrated or fluffed to separate the individual fibers. Other fibrous moisture-absorbent materials, such as bleached cotton linters and Various grades of cotton waste produced by garnetting, etc., may also be used for the pad but the f'lutfed pulp is preferred because a pad made out of it is soft and flexible. The pad will have a weight within the range of from about 200 to about 700 grains for purely practical reasons, since too little absorbent material does not permit the accomplishment of its purpose while too much provides unwanted bulk and additional expense.

The backing sheet is so termed because it is not generally designed to be the skin-contacting face of the diaper. In the diaper construction of this invention, it functions to retain liquid within the diaper, i.e., to prevent liquids from penertrating the backing sheet. It also contributes a strength factor and it does possess elasticity.

The backing sheet is generally constructed from the thermoplastic resin and, in the instance of this invention, it is preferably a polyolefinic film. The latter would include films prepared from polymers of ethylene, propylene, l-butylene, etc. and higher homologs and copolymers of these monomers with ethylene. This is to be limited by the density of the film because low density film is preferred since it is not brittle and has greater .tear resistance. Functionally, high density backing film would introduce several undesirable properties. A film den-sity of up to about 0.94 grams/ cc. is preferred.

Most preferably this backing sheet is of polyethylene and is of a thickness within the range of from about 0.4 to about 1.5 mils, with 0.75 to 1.0 mil being preferred. It is important that this backing sheet have a thickness of at least about 0.4 mil. Below 0.4 mil the film has little or no integrity and adds little if anything in much needed strength to the diaper. l

Generally, all films have a machine and cross direction with the machine direction representing the direction of greater strength and generally a ratio of greater than 1:1 and 1:2 or 1:3 or better. The polyolefinic film used in the diaper of this invention is positioned such that its machine direction runs parallel to the pinning direction of the diaper. Additionally, the film may be embossed with a repeating pattern of closely spaced designs to reduce the harshness of the sheet material and to provide softness and a pleasing hand not unlike that of the facing sheet. This embossing also enhances the surface characteristics, the appearance and the gloss characteristics of the film making it look and act more like a textile fabric. It also reduces the noise level of the plastic film such that it will not crinkle. Generally, the film tends to liex and bend more readily and is therefore more adapted to this use.

The facing sheet utilized in this invention may be either of nonwoven construction or it may be a wet strength tissue or it may be a combination of plies of both. The facing sheet, quite generally, must permit liquids to pass through it since it is the skin-contacting member of the diaper, and it must also be soft throughout to insure that skin irritation is not induced. Additionally, this facing sheet must have integrity to insure that it will not readily fail when wetted and to insure that it will not fail during pinning as a result of the stress applied to certain areas either during the pinning process or after it is in position on the baby, i.e., in use.

When a nonwoven facing sheet constructed of individualized bers is utilized, care must be taken to insure mi that the binding material used to secure these fibers together in position in the fabric is not harsh and abrasive and thus cause irritation to the skin of the infant. The binder for the nonwoven fabric must be one that does not impart harshness to the fabric it binds and it must possess both a high wet strength and a high wet rub resistance to preclude fabric failure in the diaper which has absorbed liquid or has been wetted. The softness is a requisite characteristic of the binder since harshness will cause friction between the babys skin and the surface of the diaper with the resultant development of a skin rash. These requirements are satisfied by the general class of binders defined as cross-linked polyvinyl acetate, polyvinyl, chloride, acrylates and the like.

The nonwoven facing sheet utilized herein features highly individualized long-staple cellulose fibers which have been carded and then bonded together in either a regular repeating pattern of spaced binder areas or by over-all impregnation. Carding provides directional strength properties in the fabric creating a greater tensile strength in the machine direction of the fabric as opposed to the cross direction since the machine direction coincides with the direction of the fiber length in the carded fabric.

Alternatively, a wet strength tissue may be used in place of r in conjunction with, the nonwoven fabric. A noncreped tissue can be used, but generally, the rattle and stiffness inherent in that tissue, provided it is not softened with a humectant, renders it unsuitable for this purpose. A Wet-strength tissue having a crepe content of between and 25% is more suitable for use a diaper facing. The tissue selected should have a wet strength of at least of that of the dry strength. Typical chemical resins which impart this degree of wet strength are melamineformaldehyde, urea-formaldehyde and the like.

It is to be understood that a plurality of plies of wet strength tissue could be utilized in this invention and that in some instances where the total absorbent diaper is desired, it could be used to replace the plastic backing sheet as could the nonwoven fabric.

One of the major shortcomings of pulpfilled disposable diapers, as presently made, is the tendency for the pulp to shift in use and thereby leave voids of free space between pulp sections. Pulp dislocation can occur when a dry diaper is worn by the baby, but this condition is exaggerated when the diaper is soiled with urine. When this happens, capillarity in the pulp lay is greatly reduced, thereby restricting distribution of urine throughout the diaper, and the lumpiness which develops is uncomfortable to the baby. This invention teaches that the direction in which the facing sheet is placed on the diaper has a direct inuence on pulp stability.

Actually, the combination of features of the present invention preserve the diaper against: (l) failure of the facing sheet during use which would, among other things, permit the material of the absorbent pad to cling to the baby, and (2) separation of the absorbent pad during use which could cause leakage. Both of these problems normally occur in prior art diapers after short use and are caused by the oscillating movement of the babys buttocks, in a direction substantially common with the width of the diaper along the facing sheet. The combination, in the present invention, of the adhesive applied to the appropriate face of the backing sheet, where the adhesive acts to secure and stabilize the absorbent pad which is adhered to it, and the positioning of the facing sheet such that its machine direction runs in the pining direction of the diaper to provide the necessary cooperative elements which preclude such diaper failures during normal spans of use. In actuality the use of a multi-ply facing sheet provides even additional assurance against failure.

The purpose of the multi-ply facing is to provide additional stability to the pulp mat under actual use conditions. Generally, one ply of nonwoven and one ply of a wet-strength tissue are sufiicient to provide the required pulp stability. However, there are Certain diaper constructions, e.g., Extra Large and Toddler-size diapers which are used on large-size babies, which requires greater pulp stability than can be obtained with a two-ply facing. In such instances, it may be necessary to use three or more plies of the facing materials.

A further problem with pulp-filled disposable diapers is that of providing soft, conforming end seals which are strong and which prevent pulp dusting. It is common practice to seal at least two ends by embossing in one pattern or another. Embossing has several drawbacks. It is difficult to obtain a completely closed seal, which is necessary if pulp dusting is to be eliminated. Furthermore, embossed ends in which one of the components is ground wood pulp tend to be harsh and abrasive, they are low in tensile strength, and for all practical purposes, non-elastic. This invention teaches that embossing can be eliminated by employing a technique which provides an acceptable end-seal by folding the facing material around the edges of the pulp and inserting a short length of the facing between the pulp mat and the backing film. A light coating of adhesive on the backing film anchors the facing and holds it in place in use. The side seals along the length of the diaper are made by extending the backing film, containing a film of adhesive, and the facing materials beyond the end of the pulp mat. These sheeted materials are brought into contact and sealed by the application of a slight pressure. This sealed edge is then folded over on itself, an external adhesive applied in the fold, and pressure applied along the length of the fold. This provides a soft, dust-free seal which functions as a repellent dam in preventing spillage of urine onto babys clothing.

Elasticity, a factor of increasing importance, can be im parted to the diaper of this invention without reducing the newly imparted pinning strength and without subtracting from the improved over-all softness of the diaper or its increased wet strength or abrasion resistance. This is accomplished in the case of the nonwoven facing sheet by creping the fabric, for example, in accordance with the disclosure of U.S. 2,958,608. The thin backing sheet of polyethylene inherently `possesses elasticity and a crepe nonwoven facing sheet insures elasticity of 10% or at least about 11/2 inches in total in the pinning direction. This can be increased by replacing the nonwoven facing sheet with one or more plies of wet strength tissue which has also been creped, or by insuring that both the backing and facing sheets are of creped wet strength tissue. The machine direction of each component is kept in alignment with the pinning direction. Substitution of creped wet strength tissue will insure an extensibility of at least about 15% in the pinning direction.

For a better understanding 0f the invention, reference may be had to the accompanying drawings in which:

FIGURE l is a plan view of one embodiment of the diaper of this invention with parts broken away;

FIG. 2 is a sectional view on an enlarged scale taken along line 2 2 of FIG. 1;

FIG. 3a is a blown-up sectional view of one of the lengthwise or longitudinal edges of the diaper of FIG. 1 which has been finally folded and secured in position;

FIG. 3b is a sectional view on an enlarged scale of a widthwise edge of the diaper blank depicted in FIG. 1;

FIG. 4 shows the folded blank of FIG. 1 with the longitudinal edges folded as in FIG. 3a;

FIG. 5 shows the folded blank of FIG. 4 in position for use;

FIG. 6 is an enlarged cross-section taken along line 6--6 of FIG. 5;

FIG. 7 depicts an elastic embodiment of the diaper of this invention;

FIG. 8 shows the elasticity of the diaper blank of FIG. 7, and

FIG. 9 is a representative cross-section of yet another embodiment of this invention.

In FIGURE 1 the diaper blank 1 is constructed of a polyethylene backing sheet 2 and the nonwoven facin sheet 3 having interposed therebetween a pad 4 0f absorbent material. The pad extends in its intermediate position from one lateral or widthwise edge 5a or 5b of the polyethylene backing sheet 2 to the other edge and is secured in position by adhesive means applied to the inner face of the backing sheet 2. The absorbent pad 4 extends uniformly in the pinning direction or in the widthwise direction toward the opposed longitudinal edges 6a and 6b to a point shown by each of the dotted lines 7a and 7b in FIG. 1. The facing sheet 3 and the backing sheet 2 are secured to each other along the area between 6a and 7a and 6b and 7b by means of a wet-strength adhesive which permits excellent adhesion without sacrificing softness in the joinder area. Care must also be taken to insure that the adhesive used noes not react with body waste or does not inherently possess any features which would detract or destroy the functionality of the diaper. Securing these edges prevents loss of material from the pad 4 through edges 6a and 6b. Both the backing and the facing sheets are positioned in the diaper blank such that their direction of greatest strength, i.e., their machine direction, is parallel to the direction of pinning strength or in the widthwise direction represented by the arrow in FIG. 1.

FIG. 2 is a scross-section taken along line 2-2 of FIG. 1 and shows the absorbent pad 4 sandwiched between the facing sheet 3 and the backing sheet 2. Longitudinal edges 6a and 6b are plainly visable as are the longitudinal terminating points 7a and 7b of the pad 4 and the area between 6a and 7a and 6b and 7b where the facing sheet 3 and the backing sheet 2 are secured together. An adhesive 8 secures the backing sheet 2 to the absorbent pad 4 and the edges of the blank.

FIG. 3a is a blown-up cross-section of a longitudinal edge portion taken along line 2 2 of the diaper blank depicted in FIG. 1. The edge is folded over on the facing sheet 3 and secured in position as it would be in the final product. This would prevent wicking of liquids on the surface of the facing sheet 3 to edge 6a or 6b and onto the babys legs. This folding also insures that neither edge 6a nor 6b will cut the babys legs.

FIG. 3b is a blown-up cross-section of edge 5a taken along line 3b-3b of FIG. l showing the absorbent pad 4 extending to substantially the extremity of the backing sheet 2. The facing sheet 3 is seen to curl around and under the terminal portion of the pad 4 and is secured to the inner face of the backing sheet 2 by adhesive 8. This is mirrored along edge 5b and thus the material of pad 4 is fully contained within the diaper.

FIG. 4 depicts an optional feature which is disclosed and claimed in co-pending applic-ation Ser. No. 298,957. The diaper blank is folded along two longitudinal lines about one-quarter the total distance in from both longitudinal edges as is shown 'by the arrows in FIG. 4. The longitudinal edges, area 6a and 6b, have been folded in accordance with FIG. 3a, and each folded section of the diaper has been secured in position by a strategically located area of the adhesive 9a and 9b. Each area 9a and 9b of adhesive is located intermediate between width- 'wise edges of the diaper and a dist-ance removed sufiiciently from the longitudinal edges to permit each edge area to fold lback upon itself to expose in combination fthe facing sheet 3 and a portion of the pad 4 covered by it. This -is shown in F-IG. 5 which shows the diaper of FIG. 4 unfolded as is permitted by the adhesive 9a and 9b and in posi-tion to -be applied on the baby.

In FIG. 5, flared ends a and b are designed to cover the buttocks and stomach of the infant and a flared pocket is formed between points d and c which represents curved leg portions adapted to iit the babys legs. Note should be taken of the fact that at points 10 and 11 the longitudinal edges are folded back on the polyethylene backing sheet 2 and a portion of the facing sheet 3, having pad 4 thereunder, is exposed as the skin facing member in this area. The widthwise edges 5a and 5b are the edges which will be pinned around the midsection of the infant `and the direction of greatest strength for both `facing sheet 3 and the backing sheet 2 extend in the direction of the widthwise edge or in the pinning direction.

FIG. 6 is a cross-section taken along l-ine 6-6 of FIG. 5 showing .the details of the fold and the pocket formed thereby. The backing sheet 2, facing sheet 3 and absorb- -ent pad 4 are clearly visable as arerthe adhesive areas 9a and`9b. The folds at points 10 and 11 are also cleanly visable showing the exposure of facing sheet 3 covering .absorbent pad 4. Wicking along .the facing sheet 3 is prevented by the folds along the longitudinal edge of the diaper and liquid deposited on the facing sheet 2 must proceed into the pocket rather than escape.

FIG. 7 shows a diaper blank constructed of a two-ply facing sheet 3 and a polyethylene 'backing sheet 2 cont-aining an absorbent layer of ground wood pulp 4. The facing sheets 3 are creped with the creping .process having been .accomplished on the facing sheets 3 to provide extensibility of these sheets running from edge '6a to edge 6b which is also the machine `direction of the sheets 3. The facing sheets are constructed of wet strength tissue and the elasticity dened by the diaper blank have ,aft least 15% extensibility in the pinning direction, i.e., the directionextending parallel with the arrow,A and is at least 15% based on the original unextended dimension of the diaper in the pinning direction. This is represented in FIG. 8 which shows opposed forces A applied locally to opposed edges 6a and 6b (in the direction of each arrow) ofthe diaper blank of FIG. 7.

FIG. 9 represents a crosss section of yet another embodiment of a diaper of this invention where a wet strength tissue sheet 112 is interposed between the nonwoven facing sheet 3 and the absorbent pad 4. The backing sheet is of polyethylene and an adhesive 8 secures the plies and the ends in place.

While the preferred embodiments of the invention have been illustrated and described herein, it is to be understood that changes in the construction may be made within the scope of the appended claims 4without departing from the spirit of this invention.

I claim:

l1. A substantially rectangular disposable diaper comprising an absorbent pad of brolus material interposed between (a) an impermeable backing sheet of flexible synthetic material, said pad being adhesively secured to said backing sheet to ac-t to prevent pad separation, and (b) at least one liquid permeable facing sheet constructed of a member selected from the group consisting of nonwoven fabric and wet-strength tissue, said facing sheet being constructed such as to exhibit one direction of greater strength and being aligned in said diaper to position said direction of greater strength substantially parallel to the width of said diaper to prevent facing sheet Ifailuredue to directional stress applied thereto and resulting in direct contact between the wearer and the absorbent pad, the width-wise ends of said diaper being closed by having the facing sheet extend out and around the terminal edge of said absorbent pad therealong and being substan-tially continuously adhesively secured to ythe inner face of said backing sheet along said widthwise edges to preclude absorbent pad fiber dusting, and the lengthwise edge ends of said diaper sealed by the backing sheet and the facing sheet extend-ing beyond the terminal edge of said absorbent pad therealong with the backing sheet extending beyond and around the terminal edge of the facing sheet and adhesively secured to the inner `face of the facing sheet along said lengthwise edges short of the terminal edges of said .absonben't pad to preclude diber dusting from said absorbent pad and to act as a Irepellent dam to entrap Would-be escaping liquids.

2. The diaper of claim 1 wherein said backing sheet is of polyoleiin film and said diaper is constructed of multiple facing sheets selected from nonwoven fabric, creped -wet-strength tissue having a creped content between ve percent and twenty-tive percent and a wet-strength of at least about thirty percent of its dry strength and comb-inations thereof. l

3. A substantially rectangular disposable diper comprising an absorbent pad of a librous material interposed between (a) an impermeable backing sheet of exible synethet-ic material, said pad being adhesively secured to said backing sheet to act to prevent pad separation and (b) at least one facing sheet constructed of carded individualized bers bonded together by a means selected from the group consisting of spaced binder areas and overall irnpregnat-ion, said carding providing one direction of greater strength in said facing sheet and said facing sheet being aligned in said diaper to position the direction of greater strength substantially parallel to the pinning direction of ythe diaper and thereby act to prevent facing sheet failure :and direct con-tact between the wearer and the absorbent pad and to provide increased pinning strength for said diaper, the widthwise ends of said diaper being closed by having the facing sheet extend out and around the terminal edge of said absorbent pad therealong and being substantially continuously adhesively secured to the inner face of said backing sheet along said widthwise edges to preclude absorbent pad liber dusting, and the lengthwise edge ends of said diaper sealed by the backing sheet and the facing sheet extending beyond the terminal edge of said absorbent pad therealong with the backing sheet extending beyond and around the terminal edge of the facing sheet and adhesively secured to the inner face of the facing sheet along said lengthwise edges short of the terminal edges of said absorbent pad to preclude -ber dusting from said absorbent pad and to act as a repellent dam to entrap would-be escaping liquids.

4. The diaper of claim 3 wherein said backing sheet is polyethylene.

5. The diaper of claim 3 wherein said back-ing sheet is selected from a member of the group consisting of polyolen films.

References Cited UNITED STATES PATENTS Re. 26,151 1/1967 Duncan et a1 12S-284 2,560,332 7/195'1 Crane 12S-287 3,211,147 10/1965 Pherson et al. 12S-284 3,295,526 1/1967 Sabee 128-287 CHARLES F. ROSENB-AUN, Primary Examiner.

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