US3547930A - Disposable sheet diaper and process for making the same - Google Patents

Description

Dec. 15, 1970 ,q, v, BLOM wST ETAL 3,547,930

DISPOSABLE SHEET DIAPER AND PROCESS FOR MAKING THE SAME Filed June 2, 1967 United States Patent 3,547,930 DISPOSABLE SHEET DIAPER AND PROCESS FOR MAKING THE SAME Nils Verner Blomqvist, Ornskoldsvik, Ingemar Liss-Alhin Croon, Alfredshem, and Gustav Harry Sundell, Jarnforsen, Sweden, assignors to M0 och Domsjo Aktiebolag, Ornskoldsvik, Sweden, a limited company of Sweden Filed June 2, 1967, Ser. No. 643,082 Claims priority, application Sweden, June 9, 1966, 7,920/ 66 Int. Cl. A611. 13/ 16' US. Cl. 128-284 11 Claims ABSTRACT OF THE DISCLOSURE Disposable sheet diapers are provided comprising as the absorbent portion cellulose fluff fibers enclosed between supporting sheets of moisture-pervious cellulosic material and interleavingly folded to form three strata or layers of absorbent cellulose fluff fibers separated by the enclosing sheets of cellulosic material. The interleaved layered composite is enclosed in a protective moisture-resistant but moisture-pervious sheet of a woven or nonwoven material.

A process is also provided for manufacturing the abovedescribed disposable sheet diapers in which a composite sheet material comprising a pair of supporting sheets of cellulosic material enclosing a layer of absorbent fibers, such as cellulose fluff fibers therebetween, is formed, by laying down cellulose fluff fibers on a supporting sheet of cellulosic material, such as cellulose wadding or paper, and a second sheet of like material placed on top, and the composite sheet material is folded by folding over the sides of the sheet toward each other and interleaving the folds to form three layers. Each layer contains absorbent material retained between sheets of cellulosic material, and each layer of absorbent material has two sheets of supporting material therebetween, providing excellent reinforcement for each layer. The folded composite material is then enclosed in a protective moistureresistant moisture-pervious woven or nonwoven fibrous sheet material.

This invention relates to disposable sheet diapers, and to a process for making the same, and more particularly, to disposable sheet diapers having an absorbent portion comprising an interleavingly folded composite having three thin parallel layers, each layer of which has inner and outer facing layers of cellulosic sheet material, enclosing an absorbent layer of cellulose fluff fibers therebetween, and a protective moisture-resistant moisturepervious Wrapper enclosing the interleaved layered composite.

Many efforts have been made to develo practicable disposable diapers, but the diapers that have been made available have not received wide consumer acceptance. Despite the burdensome nuisance of collecting and Washing cloth diapers for reuse, these are still preferred by most mothers, partly because of the relatively high cost of the available disposable diapers, and partly because these disposable diapers have not been able to match the absorbency of cloth diapers.

The problem is nicely summarized in US. Pat. No. 2,788,786, patented Apr. 16, 1957, to Dexter. Dexter points out that the available disposable diapers have not provided sufficient absorbency without sacrificing characteristics considered necessary to facilitate their disposability. Because of the limited capacity of ordinary waste disposal channels, Dexter accordingly designed his diaper so that it could be easily disposed of by dumping the absorbent material through household plumbing channels.

Various types of disposable diaper constructions have been suggested. Le Bolt, US. Pat. No. 2,649,858, patented Aug. 25, 1953, describes a two-ply diaper composed of an inner ply of soft, nonirritating material, such as paper, and an outer ply composed of absorbent material, such as cellulose wadding, preferably in several layers secured together. The entire diaper is formed of this material. A three-ply structure is also described, in which the outer sheet is composed of a water-proof or water-resistant material.

McGraW, US. Pat. No. 2,290,110, patented July 14, 1942, describes a disposable diaper made of soft paper, with a seat and crotch of absorbent material such as cotton.

US. Pat. No. 2,627,858 to Miller, patented Feb. 10, 1953, provides a diaper composed of an inner sheet of thin sheet material, such as tissue paper or rayon pulp cloth, an outer sheet made of a material such as a wetproof paper that prevents moisture from escaping from the inside of the diaper, and a filler made of cellulose or similar pulp material interposed between the inner and outer sheets. The filler layer extends throughout the diaper, but a supplemental filler layer of cellulose material similar to the main layer is interposed at the crotch portion of the diaper to provide extra padding and absorbent filler material Where it is most needed.

These various types of diapers are bulky, as pointed out by Dexter, because of the relatively low absorbency of the absorbent material employed. Dexter provides a diaper having an outer layer of water-repellent material, an inner layer of water-absorbent material, and an open pocket in the central portion of the diaper for a removable multilayered pad of high absorbent material, which can be dumped from the pocket in. disposing of the diaper, and thus greatly reduce the bulk of the material being disposed of.

US. Pat. No. 2,560,332 to Crane, patented July 10, 1951, describes a disposable diaper composed of a thin flexible moisture-absorbent abrasion-resistant fabric, such as a thin woven fabric, a thin flexible film of a moisture- ,impervious plastic material, and a moisture-absorbent pad disposed between the moisture-absorbent sheet and the thin flexible film, preferably made of cellulosic fibers and of sheet material, which is principally alpha cellulose which has been disintegrated or fiuffed to separate the individual fibers.

Reissue Pat. No. 26,151 to Duncan et al., dated Jan. 31, 1967, provides a disposable diaper composed of a thin flexible water-proof sheet having an absorbent pad superimposed thereon. The pad and the water-proof sheet are formed into a box pleat configuration by means of a multiplicity of longitudinal folds.

U.S. Pat. No. 2,788,003 to Morin, patented Apr. 9, 1957, describes a disposable absorbent pad consisting of a layer of flocky absorbent material, such as fluffed Wood pulp, covered with a facing sheet of moisture-permeable nonwoven fabric, the absorbent material being stabilized and anchored to the facing sheet through a pattern of spaced compressed strips of the absorbent material. The facing sheet contains a thermoplastic adhesive intermittently arranged on the sheet. The layer of absorbent material adheres to the adhesive and thereby to the sheet Whenever the pattern of compressed strips intersects the intermittently bonded area of the facing sheet.

US. Pat. No. 2,890,700 to Lonberg-Holm, patented June 16, 1959, discloses a contoured disposable diaper containing inner and outer sheets of moisture-absorbent material and a plurality of layers of moisture-absorbent material which can be tissue paper or pulp, preferably creped to enhance the flockiness and the absorbent capacity, disposed Within the inner and outer sheets of moisture-absorbent material. The sheets are sealed together by a close pattern embossing, and the various layers of moisture-absorbent material disposed between the inner and outer sheets are joined together by spot embossing.

U.S. Pat. No. 2,019,842 to Bussing et al., patented Nov. 5, 1935, relates to a diaper composed of a pad containing an outer layer of water-resistant fibrous material, an inner layer of soft fibrous tissue and a layer of cellulose wadding disposed between the inner and outer layers. The pad is held together by stitches of thread running through the inner and outer layers and the layer of cellulose wadding.

U.S. Pat. No. 3,295,526 to Sabee, patented Jan. 3, 1967, describes a disposable diaper containing a liquid-permeable facing sheet, a liquid-impervious cover sheet and a liquid-absorbent filler disposed between the two sheets. The facing sheet side margins extend over and bear against the filler side edges. The liquid-impervious cover sheet is bonded to the facing sheet margins by means of a bonding agent, such as a thermoplastic resin. The edges of the diaper are folded inwardly toward the childs body when the diaper is in use so that double thickness is provided about the legs of the child wearing the diaper, with all the absorbent material turned inward. The use of the folded over strips increases absorptive capacity of the diaper.

In accordance with the invention, a disposable sheet diaper is provided having a relatively high absorbency, compared to previously available disposable diapers, and a substantial resistance to penetration of fluids therethrough. This disposable diaper comprises as the absorbent portion cellulose fluff fibers enclosed between supporting sheets of cellulosic material, and interleavingly folded to form three strata or layers of absorbent cellulose fluff fibers separated by the enclosing sheets of cellulosic material. The interleaved layered composite is enclosed in a protective moisture-resistant but moisture-pervious layer of a woven or nonwoven material.

The cellulose fluff fibers provide the diaper with a high absorbency. In fact, the absorbency of fluff fibers is considerably higher than other cellulose fibers, such as tissue fibers. However, because of their small size and short length, fluff fibers are more difficult to form into mats or layers of considerable thickness that retain their shape and prevent penetration of fluids therethrough. It is for this reason that reinforcement of the fluff fibers by embossing as in U.S. Pat. No. 2,788,003 to Morin, dated Apr. 9, 1957, and U.S. Pat. No. 2,699,170 to Morin, dated Jan. 11, 1955 has been used. The construction of the invention avoids this problem. Since the cellulose fluff fibers are laid out in narrow strata or layers, held between supporting sheets, by folding the composite sheet material, they are well retained in a manner that reduces or prevents formation of channels therein, due to the cellulose fluff fibers clumping into separate masses of fibers within the composite which would allow for passage of liquids through the diaper. Even if the cellulose fluff should separate into clumps in one layer, it is most improbable that any clumping in the next layer would take place in the same place to form a passage through both layers. Thus, the possibility of fluid penetrating through the entire diaper without being absorbed in one layer at least is practically eliminated.

In addition, the two supporting layers of cellulosic sheet material in each of the three interleaved folded layers impart a high strength to the diaper, making it stronger than conventional cotton-wool diapers or sanitary napkins. The diaper of the invention has excellent absorption properties, and has been found to have approximately a higher absorption capacity than diapers constructed of the same volume of cellulose fluff in a single mass, enclosed between sheets of cellulosic material and a protective moisture-resistant but moisturepervious layer of woven or nonwoven fibrous sheet material.

The invention also provides a process for manufacturing disposable sheet diapers in which the absorbent portion is composed of an interleavingly folded composite having three thin parallel layers, each layer of which has inner and outer facing layers of cellulosic sheet material, enclosing an absorbent layer of cellulosic fluff fibers there between, and is enclosed within a protective moistureresistant but moisture-pervious wrapper of woven or nonwoven material. This process is capable of producing a long or endless strip of disposable diapers, arranged end to end. The disposable diapers can be cut off the strip in whatever length required. In one preferred embodiment, the boundaries between abutting ends of the disposable diapers on the strip are perforated or otherwise weakened to facilitate tearing, and the disposable diapers can then be separated from the strip, one at a time, much as in the manner of paper toweling.

In the diaper-making process of the invention, a composite sheet material comprising a pair of supporting sheets of cellulosic material enclosing an absorbent layer, such as cellulose fluff fibers, therebetween is formed, by laying down cellulose fluff fibers on a supporting sheet of cellulosic material, such as cellulose wadding or paper, and a second sheet of like material placed on top, and the composite sheet material is folded, for example, by folding over the sides of the composite sheet towards each other, and interleaving the folds to form three layers. Each layer thereby comprises absorbent material retained between sheets of cellulosic material, and each layer of absorbent material has two sheets of supporting material therebetween, providing excellent reinforcement for each layer. The folded composite material is then enclosed within a protective sheet of a woven or nonwoven fibrous sheet material. The sheet forming the protective layer can be folded over the absorbent composite with the sheet edges overlapped and bonded together by means of a binder or adhesive, or they can be sealed under heat and pressure, if they are made of or contain thermoplastic material.

The drawings illustrate preferred embodiments of the invention.

FIG. 1 represents a cross-section of one form of disposable diaper in accordance with the invention.

FIG. 2 represents a side view of apparatus for form ing a disposable diaper of the type shown in FIG. 1.

FIG. 3 represents a perspective view of the folding means employed in the apparatus of FIG. 2.

The disposable diaper illustrated in FIG. 1 is composed of an absorbent portion comprising three parallel thin layers 1, each from 3 to 4 mm. thick, and 300 to 360 mm. wide, composed of cellulose fluff fibers retained between sheets 2, 2 of cellulosic material, such as cellulose wadding or soft paper.

It is evident that the composite sheet comprising facing sheets 2, 2 and interposed fluff fiber layer 1 is folded over twice in three approximately equal panels, with panel or fold A laid down first, and panel or fold B laid down next, over A, leaving the central panel C at the bottom.

The composite of folded layer 1 and sheets 2, 2' is enclosed in a sheet 3 of nonwoven material, such as cellulose acetate, or high wet strength paper. The lapped ends 4, 4' of the sheet 3 are bonded together at their interface by a thermoplastic binder 5.

Although the diaper shown in FIG. 1 is elongated, with relatively narrow panels, in fact the diaper can be formed in any desired shape, such as square, rectangular, trapezoidal, elliptical, circular, triangular, or in any polygonal shape. For instance, any of the shapes of U.S. Pat. Nos. 2,788,786, 2,627,858, 2,290,110 and 2,649,858 can be employed, if desired. Other shapes and configurations will be apparent to those skilled in this art.

Such a diaper can be made by hand-folding. However, it is readily obtained as a continuous strip of disposable diapers arranged end-to-end by employing the apparatus shown in FIGS. 2 and 3. The apparatus as shown in FIG.

2 includes storage supply rolls 6, 14 of fiber supporting sheet material 2, 2, respectively, such as cellulosic wadding or soft paper, a storage roll 17 of protective covering material 3, such as a cellulose acetate web or mat of high wet strength or soft paper containing a thermoplastic binder therein, and a hood 13 and suction box 12 for airdeposition of absorbent fibers, in this case, cellulose fluff fibers, on the supporting sheet 2 from supply roll 6.

For support of the sheet 2' during laydown of absorbent fibers thereon, an endless band 30 of wire mesh is provided. This is rotated clockwise about guide rolls 7, 8, by drive roll 9, and is held taut by tensioning roller 11. Guide roll 31 directs the supporting sheet material 2 from roll 6 upon the belt 30. Suction box 12, which is disposed between rolls 7 and 8 beneath the belt 30, draws absorbent cellulose fluff fibers fed through hood 13 down onto the cellulosic material 2', and holds it there. Guide roll 15 directs the cellulosic sheet material 2 from roll 14 into place on top of the cellulose fluff fibers which are on top of the sheet 2 of cellulosic material from roll 6, thus forming the composite absorbent sheet.

The first folder 16 is provided for interleaving the composite sheet into folds A, B, C. The folder has a base 34 having converging flared wing sides 36 and 38. These converge from the point D where they first engage the composite sheet to the other end B of the folder 16 (see FIG. 3). Side 38 converges more closely to the base 34 than does side 36, and more rapidly, i.e., over a shorter distance, than does side 36. Consequently, the end of the composite sheet proceeding beneath side 38 is folded first, as fold A, onto the central portion C of the sheet, and the end of the composite sheet proceeding beneath side 36 is folded second, as fold B, on top of fold A proceeding beneath side 38, thus interleaving the two folds on top of the central portion C. The folded composite then passes beneath pressure roll 18, where the folds are brought smartly together with the supporting facing sheets 2, 2' of each fold in contact.

Guide rolls 17a and 17b direct the covering sheet 3 of cellulose acetate from roll 17 to the second folder 23. The folder 23 is essentially in the same form as folder 16 and is provided for folding the sides of the sheet 3 over the outside surfaces of the absorbent composite so that the ends 4, 4 overlap, as shown in FIG. 1. Endless conveyor belt 19, operated over rolls 19, 19", is provided for advancing the composite enclosed in the sheet 3 to and supporting the composite during heat sealing of the sheet ends 4, 4' by heated pressure roll 20. Cutting roller 21 is provided for cutting the endless folded composite diaper into desired lengths.

In operation, a web of cellulosic material 2, such as cellulose wadding from supply roll 6, is fed around guide roll 31 forward to endless mesh belt 30, driven by roll 9 over rolls 7, 8 and 10. Cellulose fluff fibers are fed through hood 13 and dispensed in an even layer on top of the web 2' of cellulose wadding, over the suction box 12. A second sheet 2 of cellulose wadding is fed from supply roll 14 and is placed on top of the formed cellulose fluff fiber layer 1, which is compressed between the sheets 2, 2' by means of pressure and guide roll 15. The formed absorbent composite sheet, which is now comprised of a lower 2 and an upper 2 cellulose wadding sheet and an intermediate layer 1 of cellulose fluff, is introduced into the folder 16, which raises and interleaves the sides of the composite sheet in panels or folds A, B, C. Next, a protective sheet 3, such as a bonded web of rayon fibers or soft paper having high wet strength is introduced from supply roll 17 over guide rollers 17a and 17b below the folding means 16. The center portion of the web 3 of nonwoven material is brought into contact With the underside of panel C of the three-layered folded composite by means of pressure roll 18, and the side portions, folds A, B of the composite, are compressed against the bottom panel C by the pressure roll 18. The folder 23 folds the sheet 3 over the top surface of the three-layered composite sheet in a manner such that the end portions 4, 4' overlap. The so-formed diaper is then advanced by means of endless conveyor 19, and the overlapping portions 4, 4 of the sheet 3 are heat sealed by means of the heated pressure roll 20, completing the package. The diaper is cut into desired lengths of for example, 250 to 400 mm., by means of a cutting roller 21.

The lapped ends 4, 4 can be bonded by a thermoplastic binding material incorporated in the sheet 3, or by a strip or filament or layer of thermoplastic material placed between the overlapping portions after which the material is heated to soften the strip or filament or layer and effect bonding. The panels or folds A, B, C of the finished diaper can be held together also by embossing at the time the diaper is cut into the desired lengths.

Instead of cutting, it is possible to apply weakening lines, such as score lines or perforations, across the finished strip of diapers, in the pattern or shape of the diaper to be cut from it, and wind up the finished strip of disposable diapers in a roll. The disposable diapers can readily be separated from the roll, when needed, by tearing along these lines by the housewife or mother.

The process of the invention is best used in the preparation of the disposable sheet diapers of the invention. However, it can also be used in the preparation of any type of disposable interleaviugly folded sheet diaper, napkin or sanitary napkin, having an absorbent layer enclosed between inner and outer facing sheets of water-pervious or water-impervious sheet material, and enclosed within a protective sheet of moisture-pervious moistureresistant material. In such composites, the absorbent material need not be cellulose fluff fibers. Other types of absorbent material can be used, such as cotton wadding, cotton fibers, cellulose pulp fibers, cellulose tissue fibers, and other types of absorbent fibers. These can be confined in a certain area, or can be distributed throughout the space between the inner and outer facing layers of the diaper, as shown in FIG. 1.

A very desirable diaper in accordance with the invention has a total weight within the range from about 10 to about 50 g., and preferably from about 20 to about 40 g. The cellulose flufl fibers and supporting cellulosic sheet material are in a weight ratio of fluff to cellulosic sheet material within the range from about 0.521 to about 3:1, and preferably about 2:1.

In order to form a diaper of desired thickness and width and without undue bulkness, the layer of cellulose fluff fibers in the composite sheet of cellulosic materialcellulose fluff fibers-cellulosic material, prior to folding, should have a thickness within the range from about 2 to about 6 mm., and preferably within the range from about 3 to about 4 mm., and a width within the range from about 200 to about 500 mm., and preferably within the range from about 300 to about 360 mm. Suitable dimensions for the diaper are from about 200 to about 450 mm. long, from about to about 160 mm. wide and from about 8 to about 16 mm. thick. A preferred diaper sheet before folding is from about 250 to about 400 mm. long, from about to about mm. wide, and from about 8 to about 14 mm. thick.

Cellulose flufl fibers are cellulose pulp fibers less than 5 mm. in length, and preferably less than about 3 mm. in length. The shorter the fibers, the denser and more relatively noncompressible the absorbent layer is. Also, the fibers are then less subject to breaking under wet conditions, and therefore give a stronger structure. For maximum density and nonswellability at least 20% by weight of the fibers should be less than about 0.8 mm. in length.

Cellulose fluff fibers are obtained by the disintegration of wood pulp in sheet or flash-dried form, using mechanical disintegrating apparatus. Such processes are well known and form no part of the instant invention. The

process and apparatus must be of the type that separates the fibers in an efficient way, without cutting the fiber too much. Overcutting the pulp fibers results in cellulose flour, which is unsuitable for the absorbent layer of the invention, and the proportion of cellulose fiour accordingly is held to a minimum.

As the source of cellulose fluff fibers there can be used any pulping wood, such as spruce wood, pine wood, hemlock wood, fir wood, birch wood, and other types of coniferous and hard woods.

The cellulose fluff fibers that are preferred for use in the invention are obtained by disintegrating chemical cellulose bleached or unbleached pulp, prepared by the sulfate or sulfite method or by semichemical methods, in such a way that the fibers are set free from the pulp while at the same time avoiding the formation of fiber bundles or knots and cutting of the fibers. This disintegration can be carried out in an apparatus such as a shredder or hammer mill or a disk refiner or a set of circular sawblades mounted on a rotating axis, or a combination of these. For instance, the chemical pulp in the form of sheets can be first roughly dry-disintegrated in a shredder or hammer mill and then further disintegrated in a disk refiner. If the pulp is in the form of rolls, it is possible to disintegrate it directly in one step in a hammer mill. It is not necessary, and in fact it is undesirable, to materially shorten the fibers of the cellulose pulp after such disintegration, and therefore the disintegration technique and apparatus used should be specially adapted to avoid this, using the known techniques.

It is preferred that the cellulose fibers fall within the following ranges of fiber length distribution.

TABLE I Fiber length range:

Less than 5 mm. but more than 0.833 mm. 30-60 Less than 0.833 mm. but more than 0.417

mm. 10-40 Less than 0.417 mm. but more than 0.208

mm. 10-40 Less than 0.208 mm. but more than 0.104

mm. 10-40 Less than 0.104 mm. 20

In fluff, the proportion of the median fraction of the fibers is somewhat greater than in ordinary chemical pulp. As a result of this difference, small as it is, in the distribution of fibers, fluff fibers have a higher bulk and a greater absorption than ordinary chemical pulp fibers.

Fluff fibers are rather different in physical nature from tissue fibers, which are also obtained from cellulose pulp, but are prepared by a different process. Tissue fibers are obtained by placing sheets or bales of chemical or mechanical cellulose pulp in hollanders, where the pulp is beaten with Water. The suspension obtained can then be stored and is next transported to heaters, after dilution to a pulp concentration of 0.5 to 1.5%. The heater can be a disk refiner, or a Jordan mill employing a rotating cone, and the beating is mild. After the heating, water is removed from the suspension in an uptaking machine, The fiber length distribution of the resulting tissue fibers is similar to that of fluff fibers, but the product is paper-like, and not bulky. The absorption capacity of tissue fibers is from /3 to A that of fluff fibers.

Consequently, tissue fibers are not as desirable as the absorbent material in the diapers in accordance with the invention, because of their low absorption capacity, but they can be used in the process of the invention.

Cotton cellulose fibers differ materially from cellulose pulp fibers. They are materially longer, greatly exceeding 5 mm. in length. Because of their length, they are subject to breakage and rupture, and give diapers which are not as strong as those obtained using cellulose pulp fibers. Moreover, they are more expensive. Consequently, they are not preferred for the diapers of the invention, but they can be employed in the process of the invention.

Percent distribution In preparing the cellulose fluff fibers, the pulp can, if desired, be treated with substances which provide crosslinkages between the cellulose molecules, thus improving the absorbent properties of the pulp. Such cross-linking agents may comprise epihalohydrins, such as, for instance, epichlorohydrin; polyepoxides, for instance, butadiene dioxide, epoxidized triglycerides as epoxidized glycerol trioleate and epoxidized glycerol trilinoleate, the monoacetate of epoxidized glycerol dioleate,

1 ,4-bis (2,3 -epoxypropoxy benzene,

1,3-bis 2,3-epoxypropoxy benzene,

4,4-bis 2,3-epoxypropoxy diphenyl ether,

1, 8-bis 2,3-epoxypropoxy octane,

1,4-bis 2,3-epoxypropoxy cyclohexane,

4,4-bis (2-hydroxy-3,4-epoxybutoxy diphenyldimethylmethane,

1,3-bis 4,5 -epoxypentoxy -5 -chlorobenzene,

1,4-bis 3 ,4-epoxybutoxy) -2-chlorocyclohexane,

1,3-bis 2-hydroxy-3,4-epoxybutoxy) benzene,

1,4-bis and (2-hydroxy-4,S-epoxypentoxy) benzene;

polyhalides, for instance, 1,3-dichloropropane, etc.

The supporting cellulosic material can be any cellulosic sheet material that is pervious to water, such as, for example, cellulose wadding or soft paper, having a weight per unit area of from about 10 to about 60 g. per m? per ply, and preferably within the range from about 20 to about 40 g. material per ply. Cellulose Wadding suitable for use herein can be produced from bleached sulfite or sulfate pulp or mixtures thereof, and should have a Weight per unit area within the range from about to about 40 g./m. per ply, and preferably from about to about g./m. Soft paper suitable for use herein can be produced from bleached sulfite, sulfate or semichemical pulp or mixtures thereof, and should have a Weight per unit area within the range from about 10 to about 50 g./m. per ply, and preferably from about 20 to about g./ rn. per ply. The cellulosic sheet material serves the dual function of retaining the cellulose fluff fibers, and strengthening the diaper. Several plies can be used together in each of the cellulosic sheet material layers, the number being in no way critical, so long as the overall thickness of the cellulosic sheet material is not such that the material is no longer soft and flexible and the finished diaper is not unduly bulky. Each layer of cellulosic sheet material containing one or more plies can have a thickness within the range from about 0.01 mm. to about 10 mm., and preferably within the range from about 0.1 mm. to about 5 mm.

The protective enclosing layer can comprise one or more plies of any water-pervious water-resistant woven or nonwoven sheet material that has a high wet strength. By high wet strength according to the present invention is meant from 3 to 6 kg. per mm. strip in the length direction, and from 0.3 to 1 kg. per 50 mm. strip in the transverse direction, as measured according to TAPPI 456 M-49. These materials can be made of any type of Water-resistant synthetic fiber, such as acetate rayon, nylon, polyacrylamides, polyvinyl chloride, polyvinylidene chloride, terephthalic acid-ethylene glycol polymers (Dacron), polyacrylonitrile (Orlon and Vinyon N), polyethylene, and polypropylene, or of natural fibers impregnated or coated with a suflicient amount of such materials to render them nonabsorbent, or of high wet modulus viscose rayon fibers. Especially preferred are nonwoven materials made from fibrilled rayon fibers, or rayon fibers having a length of from 5 to about 30 mm., mixed with fibers of sulfite, sulfate or semichemical pulps or corresponding cross-linked pulps or soft paper having high wet strength.

For greatest strength and resistance to disintegration in use, the fibers of the water-pervious sheet material are preferably bonded at their points of crossing by a synthetic resin binder material, such as a thermoplastic or thermosetting resin. The amount of binder that is employed should not materially reduce the porosity of the material, nor should the resiliency thereof be greatly affected, since an unduly rigid sheet material is hard to fold and wrap around the baby. Flexibility of the sheet material is very desirable and has very little effect on the strength of the final product. Relative non-compressibility can be obtained because of the nature of the cellulose fiber layer. This layer can be laid down and compacted very tightly, and consequently makes possible a relatively low bulk for its absorbency of the diapers of the invention, as compared to the known products.

Among the binder materials that can be used are polyvinyl chloride, polyethylene, polypropylene, nylon, polyacrylonitrile, ethylene glycol-terephthalic acid copolymers, polyvinyl acetate, copolymers of vinyl acetate and vinyl chloride, polyvinyl butyral, polytrifluorochloroethylene, urea-formaldehyde, melamine-formaldehyde, phenolformaldehyde, and alkyd resins. It is very suitable to use a binder comprising the same material as the fibers. These can be formulated into binder compositions of conveng tional type, including plasticizers, pigments, and fillers. Such compositions are well known, and form no part of the instant invention. In all cases, however, the binder composition should be resistant to and insoluble in body fluids.

The lapped end portions of the sheath or wrapper can be bonded together by use of an adhesive or binder. Any of those referred to above as binders for the fibers of the protective sheet material can be employed. It is preferred, however, that the sheet material be at least in part of thermoplastic material, so that the lapped ends can be bonded together by application of heat and pressure, sufiicient to soften and fuse the ends together. This greatly facilitates manufacture of the diaper, using, for example, the process of the invention. If the material of the sheet is solvent-softenable in whole or in part, a solvent can also be employed to effect bonding therebetween.

The following example in the opinion of the inventors represents a preferred embodiment of their invention.

EXAMPLE Employing the apparatus of FIGS. 2 and 3, a dis posable diaper as shown in FIG. 1 was prepared as follows:

Cellulose Wadding produced from bleached sulfite pulp having a weight per unit area of 25 g. per m was fed from supply roll 6 onto endless mesh belt 30. Sulfate pine wood pulp cellulose fluff fibers were fed through hood 13 and onto the cellulose wadding to form a layer of fluff fibers 3 mm. thick. Another layer of cellulose wadding was fed from supply roll 14 onto the top of the fluff layer, to form a composite of cellulose wadding-cellulose fluff fibers-cellulose wadding, The composite material was introduced into the folder 16 which raised and folded over the sides of the composite, interleaving the folds A and B to form three thin parallel layers, as shown in FIG. 1. A layer of nonwoven sheet material, comprising to 30 mm. rayon fibers mixed with sulfite pulp fibers and containing polyvinyl butyral as a thermoplastic binding agent was brought beneath the three layered composite, and the panels or folds A, B, C were compressed by the pressure roll 18. The ends of the nonwoven sheet were then folded over the top surface of the composite by means of folding means 23 in a manner such that they were overlapping. The lapped ends of the nonwoven material were passed beneath heated roll to seal them together, and complete the wrapping of the composite material in the nonwoven ma terial. The endless sheet diaper that was formed was 120 mm. wide and 11 mm. thick, and was cut into diapers 350 mm. long.

The absorption properties of the cut sections of the diaper were determined by hanging the diaper by its ends 1G to form an arc, whereupon 300 cm. of water from a pipe was allowed to flow slowly onto the diaper immediately above the lowermost portion of the arc. The rate of feed was slow enough to avoid spilling any. The amount of liquid which penetrated through the diaper was then measured.

As a control, a diaper of the same dimensions comprising a single ll mm. thick layer of cellulose fluff fibers, disposed between a pair of layers of the same cellulose wadding, and enclosed in a sheet of the same nonwoven material was prepared, and the absorption properties of this diaper were determined as above.

The diaper in accordance with the instant invention was found to have a 15% greater Water absorption capacity than the diaper comprised of a single 11 mm. thick layer of cellulose fluff fibers.

Having regard to the foregoing: disclosure, the following is claimed as the incentive and patentable embodiments thereof:

1. A disposable sheet diaper having a relatively high absorbency and a substantial resistance to peneration of fluids therethrough, consisting essentially of an absorbent portion comprising a substantially uniform layer comprising highly absorbent cellulose fluff fibers less than 5 mm. long enclosed between supporting sheets of waterpervious absorbent cellulosic material on each side of the layer of cellulose fluff fibers, the supporting sheets retaining the cellulose fluif fibers under compression to inhibit channeling or clumping of the cellulose fluff fibers, and interleavingly folded to form three strata of cellulose fluff fibers, each separated by one or two sheets of cellulosic material, the interleaved composite being enclosed within a protective nonabsorbent moisture-resistant moisture-pervious fibrous sheet material.

2. A disposable sheet diaper as claimed in claim 1, wherein the cellulose fluff fibers are selected from the group consisting of disintegrated, bleached or unbleached sulfite, sulfate and semicheznical pulp.

3. A disposable sheet diaper as claimed in claim 2, wherein the disintegrated pulp contains a cross-linking agent.

4. A disposable sheet diaper as claimed in claim 1, wherein the supporting sheets of cellulosic material are wadding produced from a pulp selected from the group consisting of bleached sulfite pulp, bleached sulfate pulp, and mixtures of bleached sulfite pulp and bleached sulfate pulp, having a weight per unit area Within the range from about 15 to about g./m. per ply.

5. A disposable sheet diaper as claimed in claim 1, wherein the supporting sheets of cellulosic material comprise soft paper produced from a pulp selected from the group consisting of bleached sulfite pulp, bleached sulfate pulp and semichemical pulp and mixtures thereof having a weight per unit area within the range from about 10 to about g./m. per ply.

6. A disposable sheet diaper as claimed in claim 1, wherein the protective moisture-resistant but moisturepervious fibrous sheet material comprises nonwoven fibrilled rayon fibers of 5 to 30 mm. in length, mixed with fibers obtained from pulp selected from the group consislting of sulfite pulp, sulfate pulp, and semichemical pu p.

7. A disposable sheet diaper as in claim 1, wherein the protective moisture-resistant moisture-pervious fibrous sheet material comprises soft paper having a high wet strength.

8. A disposable sheet diaper as claimed in claim 1, werein the protective moisture-resistant moisture-pervious fibrous sheet material is folded over the interleaved layered composite with the sheet edges overlapped and bound together.

9. A disposable sheet diaper as claimed in claim 8, wherein the overlapped edges of the sheet are bound together by a thermoplastic binder.

10. A disposable sheet diaper as claimed in claim 1 1 1 1 2 in the form of an endless strip of diapers, arranged end 3,067,747 12/1962 Wolterding et a1. 128-296 to end. 3,183,910 5/1965 Patterson 128-290 11. A disposable sheet diaper as claimed in claim 10, 3,211,147 10/1965 Pherson et al. 128284 wherein the boundaries between abutting ends of the 3,241,553 3/1966 Steiger 128-290 diapers on the endless strip are perforated. r 3,315,676 4/1967 Cooper 128-287 0 3,356,092 12/1967 Ioa 128-287 References Cited 2,788,003 4/1957 Morin 128-284 C1,

2,952,259 9/1960 Burgeni 128 -29O 10 2,999,038 9/1961 Drennen et al. 128284X 156204

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