Disposable Diapers

Krusko March 20, 1

Patent Grant 3721242

U.S. patent number 3,721,242 [Application Number 05/023,752] was granted by the patent office on 1973-03-20 for disposable diapers. This patent grant is currently assigned to Scott Paper Company. Invention is credited to Evelyn H. Krusko.


United States Patent 3,721,242
Krusko March 20, 1973

DISPOSABLE DIAPERS

Abstract

Disposable diaper having a moisture absorbent fluff pad which is contoured in the crotch area and which is disposed between a facing sheet and a backing sheet, said facing sheet being adapted to contact the body of a child. Both the facing sheet and backing sheet have a basis weight in the range of approximately 1.0-2.0 ounces per square yard, and each are comprised of a batt of moisture-absorbent, self-sustaining, adhesively bonded, intermingled cellulosic fibers. The outer surface of the facing and backing sheets each have a pattern defined by ridges and valleys extending over substantially the entire surface of the batt, the density of the sheets in the regions of said valleys being greater than the density of the sheets in the regions of said ridges. A method for manufacturing the facing sheet and backing sheet of the disposable diaper by forming a randomly arranged, intermingled cellulosic fibrous batt having a basis weight of approximately 1.0 ounces per square yard, passing said batt through a nip defined between a patterned roll and a moistened rubber roll to provide a pattern in one surface of the batt and raise a nap on the other surface, spraying opposite surfaces of said batt with adhesive, drying said adhesive and setting said adhesive.


Inventors: Krusko; Evelyn H. (Philadelphia, PA)
Assignee: Scott Paper Company (Delaware County, PA)
Family ID: 21816991
Appl. No.: 05/023,752
Filed: March 30, 1970

Current U.S. Class: 604/365; 604/370; 604/375; 604/378; 604/380
Current CPC Class: A61F 13/15585 (20130101); A61F 13/533 (20130101); A61F 2013/15284 (20130101); A61F 2013/4958 (20130101); A61F 2013/51078 (20130101)
Current International Class: A61F 13/15 (20060101); A61f 013/16 ()
Field of Search: ;128/284,286,287,290,296

References Cited [Referenced By]

U.S. Patent Documents
3072123 January 1963 Davis
3612055 October 1971 Mesek et al.
2549982 April 1951 McKhann et al.
2788003 April 1957 Morin
2862251 December 1958 Kalwaites
3402715 September 1968 Liloia et al.
3426756 February 1969 Romanek
3439678 April 1969 Thomas
3444859 May 1969 Kalwaites
3523536 August 1970 Ruffo
Primary Examiner: Rosenbaum; Charles F.

Claims



What is claimed is:

1. A throw-away diaper having an elongate absorbent layer disposed between a facing sheet and a backing sheet, said facing sheet being soft and moisture pervious; said elongate absorbent layer having a transverse dimension defined by spaced, elongate said margins, at least a portion of said side margins being recessed to define a narrow crotch region adapted to be positioned in the perineal region of a wearer; said facing and backing sheets having side margins extending transversely beyond the spaced side margins of said absorbent layer and having a substantially uniform transverse dimension in the region of the diaper disposed in longitudinal alignment with the recessed portions of the side margins of said absorbent layer.

2. The throw-away diaper according to claim 1, wherein said absorbent layer is comprised of a fluff batt of wood pulp fibers.

3. The throw-away diaper according to claim 2, wherein said facing sheet and said backing sheet are substantially rectangular.

4. The throw-away diaper according to claim 3, wherein said elongate absorbent layer has a forward region and a rearward region disposed, respectively, on opposite sides of the crotch region, said forward and rearward regions having a greater transverse dimension than said crotch region.

5. The throw-away diaper according to claim 3, wherein said backing sheet is comprised of a thin plastic water repellent material.

6. A throw-away diaper according to claim 1, wherein said facing sheet comprises a moisture absorbent, self-sustaining, adhesively bonded, fibrous batt including randomly arranged, intermingled cellulosic fibers, said batt having a substantially uniform weight of fibers per unit area throughout substantially its entire extent, an embossed pattern providing a plurality of ridge regions and valley regions extending over substantially its entire extent, the density of said facing sheet in the regions of said valleys being greater than the density of said facing sheet in the regions of said ridges.

7. The throw-away diaper according to claim 6, wherein said backing sheet is comprised of a thin plastic water-repellant material.

8. A throw-away diaper according to claim 6, wherein said facing sheet comprises up to about 30 percent long reinforcing fibers, and the remainder of said facing sheet comprises relatively short cellulosic fibers.

9. The throw-away diaper according to claim 8, wherein the short cellulosic fibers of said facing sheet are wood pulp fibers.

10. The throw-away diaper according to claim 9, wherein said reinforcing fibers are rayon.

11. The throw-away diaper according to claim 10, wherein said adhesive is a cross-linkable acrylic latex.

12. The throw-away diaper according to claim 9, wherein said facing sheet has a basis weight up to about 2 ounces per square yard.

13. The throw-away diaper according to claim 12, wherein said facing sheet has a basis weight in the range of approximately 1.1-1.6 ounces per square yard.

14. The throw-away diaper according to claim 6, having a second embossed pattern in said facing sheet and underlying elongate absorbent layer, whereby the moisture absorption rate into and along said facing sheet and underlying absorbent layer is enhanced.

15. The throw-away diaper according to claim 14, wherein said backing sheet is comprised of a thin plastic water repellent material.

16. The throw-away diaper according to claim 14, wherein said second embossed pattern is comprised of spaced, continuous embossed lines in said facing sheet and elongate absorbent layer.

17. The throw-away diaper according to claim 16, comprising two sets of spaced, continuous embossed lines, one of said sets of embossed lines being disposed transversely to the other of said sets of embossed lines.

18. The throw-away diaper according to claim 17, wherein said backing sheet is water repellent.

19. A throw-away diaper according to claim 6, wherein said backing sheet is comprised of a self-sustaining, adhesively bonded, fibrous batt including randomly arranged, intermingled cellulosic fibers.

20. The throw-away diaper according to claim 19, wherein said backing sheet contains a water-repellant agent. 21. A throw-away diaper according to claim 1, wherein said elongate absorbent layer has a forward region and a rearward region disposed, respectively, on opposite sides of the crotch region, said forward and rearward regions having a greater transverse

dimension than said crotch region. 22. The throw-away diaper according to claim 1, wherein said backing sheet is comprised of a thin plastic water

repellent material. 23. A throw-away diaper or the like having an elongate, moisture-absorbent layer disposed between a backing sheet and a facing sheet, said facing sheet being a moisture absorbent, self-sustaining, adhesively bonded, fibrous batt including randomly arranged, intermingled cellulosic fibers, said batt having a substantially uniform weight of fibers per unit area throughout substantially its entire extent, a first embossed pattern disposed only in said fibrous batt providing a plurality of ridge regions and valley regions extending over substantially the entire extent of said facing sheet, the density of said facing sheet in the regions of said valleys being greater than the density of said facing sheet in the region of said ridges, and a second embossed pattern impressed into said facing sheet and underlying moisture-absorbent layer whereby the moisture absorption rate into and along said facing

sheet and moisture-absorbent layer is enhanced. 24. The throw-away diaper according to claim 23, wherein said facing sheet comprises up to about 30 percent long reinforcing fibers, and the remainder of said facing sheet

comprises relatively short cellulosic fibers. 25. The throw-away diaper according to claim 24, wherein said facing sheet has a basis weight of up

to about 2.0 ounces per square yard. 26. The throw-away diaper according to claim 25, wherein said facing sheet has a basis weight approximately in

the range of 1.1 - 1.6 ounces per square yard. 27. The throw-away diaper according to claim 24, wherein said short cellulosic fibers are wood pulp fibers. 28The throw-away diaper according to claim 27, wherein said long

reinforcing fibers are rayon fibers. 29. The throw-away diaper according to claim 28, wherein a cross-linkable acrylic latex bonds the fibers in

said facing sheet. 30. The throw-away diaper according to claim 28, wherein said elongate absorbent layer has a transverse dimension defined by spaced, elongate side margins, at least a portion of said side margins being recessed toward each other to define a narrow crotch region adapted

to be positioned in the perineal region of a wearer. 31. The throw-away diaper according to claim 24, wherein said elongate absorbent layer has a transverse dimension defined by spaced, elongate side margins, at least a portion of said side margins being recessed toward each other to define a narrow crotch region adapted to be positioned in the perineal region of

the wearer. 32. The throw-away diaper according to claim 23, wherein said backing sheet is comprised of a self-sustaining, adhesively bonded,

fibrous batt of randomly arranged, intermingled cellulosic fibers. 33. The throw-away diaper according to claim 23, wherein said backing sheet is

water repellent. 34. The throw-away diaper according to claim 23, wherein said second embossed pattern provides spaced, continuous compressed lines

in said facing sheet and said moisture-absorbent layer. 35. The throw-away diaper according to claim 23, wherein said second embossed pattern provides two sets of spaced, continuous embossed lines in said facing sheet and said moisture-absorbent layer, the embossed lines in one of said sets extending substantially transverse to the embossed lines in the other

of said sets. 36. The throw-away diaper according to claim 23, wherein said elongate absorbent layer has a transverse dimension defined by spaced, elongate side margins, at least a portion of said side margins being recessed toward each other to define a narrow crotch region adapted

to be positioned in the perineal region of a wearer. 37. A throw-away diaper according to claim 36, wherein said elongate absorbent layer has a forward region and a rearward region disposed, respectively, on opposite sides of the crotch region, said forward and rearward regions having a

greater transverse dimension than said crotch region. 38. The throw-away diaper according to claim 36, wherein said second embossed pattern is impressed into said facing sheet substantially only in regions overlying

said elongate absorbent layer. 39. The throw-away diaper according to claim 38, wherein said elongate absorbent layer is a fluff batt of cellulosic fibers.
Description



BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for manufacturing nonwoven cover sheets for a disposable diaper and to a disposable diaper formed from said cover sheets.

2. Description of the Prior Art

A demand exists for a disposable diaper of the non-flushable, throwaway type which is inexpensive and possesses the mechanical and physical properties to perform as well, or better, than conventional textile cloth diapers. A non-flushable, throwaway diaper which is intended to serve as a satisfactory replacement for the conventional textile cloth diaper should have sufficient strength in both the dry and wet condition to retain its shape, sufficient abrasion resistance to prevent the surface adjacent the baby from shredding or "pilling up" and sufficient flexibility to be worn comfortably. In addition, the disposable diaper should closely resemble a conventional textile cloth diaper in hand feel and appearance, and should be low cost to justify disposing of the diaper after each use.

Prior art non-flushable, throwaway diapers have not been commercially accepted to any substantial degree. This lack of acceptance is believed to be attributable to the inability of others to produce a product having the requisite mechanical and physical properties to replace conventional textile cloth diapers.

A representative prior art non-flushable throwaway diaper is disclosed in U.S. Pat. No. 3,402,715, issued to Liloia et al., taken in conjunction with abandoned application Ser. No. 515,874, which is referred to in the Liloia et al patent. This prior art diaper has an absorbent fluff pad sandwiched between a pair of non-woven fabrics formed predominately of short cellulosic fibers, such as wood pulp or cotton linters, and the remainder of the fibers are longer synthetic fibers such as rayon. This diaper does not possess sufficient dry tensile strength and wet tensile strength to perform satisfactorily unless an excessive quantity of adhesive is utilized. Excessive quantities of adhesive will impair flexibility and cause a reduction in the fluid retaining capacity of the cover material. Also, excessive adhesive application may impair the surface feel characteristics of the cover sheet.

SUMMARY OF THE INVENTION

The disposable diaper of this invention is comprised of a moisture absorbent pad sandwiched between a nonwoven facing sheet, and a backing sheet. In the preferred embodiment of the invention, the backing sheet is identical in construction to the facing sheet; however, the backing sheet could be a thin film of waterproof, flexible material such as polyethylene, vinyl plastic, etc. In the preferred embodiment of the invention the facing sheet and backing sheet are each defined by a substantially rectangular nonwoven, moisture-absorbent, self-sustaining, adhesively bonded, fibrous batt of randomly arranged, intermingled cellulosic fibers predominately consisting of short wood pulp fibers and the moisture absorbent pad is contoured to provide a reduced width in the crotch area. The outwardly facing surfaces of each nonwoven batt is provided with an embossed pattern therein defined by a plurality of ridges and valleys extending over substantially the entire surface area of the batt, the density of said batt in the regions of said valleys being greater than the density of said batt in the regions of said ridges. The embossed pattern is produced by passing said batt through a nip defined between a patterned roll and a substantially smooth-surfaced roll such as one made of rubber. Sufficient pressure is applied to the rolls to insure that the pattern is retained in the fibrous batt during subsequent operations. After the embossed pattern is formed in the batt an adhesive, such as an acrylic latex, is sprayed on opposed surfaces of said batt to enhance the strength and abrasion resistance of the batt, while not destroying the hand and flexibility thereof. By applying adhesive to the batt after embossing, the batt was approximately 30 percent stronger than a batt which was embossed after the adhesive was applied to opposed surfaces of said batt and cured. The embossing operation compresses the fibers of the batt into close proximity with respect to each other, and therefore, the adhesive is more effectively utilized to bond fibers together than when said adhesive is applied to an unembossed batt.

In the preferred embodiment of the invention, the patterned roll is provided with a terry cloth pattern, which is formed in the roll by a photoengraving process which utilizes the negative of a photograph of a terry cloth pattern. After embossing the fibrous batt has the physical appearance of a terry cloth woven product. In this embodiment, the extremely close pattern of ridges and valleys making up the terry cloth pattern provides excellent abrasion resistance to the fabric. Other patterns such as straight line regions of alternating ridges and valleys simulating a corduroy pattern can also be impressed into the fibrous batt.

The nonwoven facing and backing sheets of the disposable diaper of this invention are manufactured by forming a bonded batt of randomly arranged, intermingled fibers comprised of predominately short cellulosic fibers, such as wood pulp fibers, and the remainder of said batt is comprised of longer synthetic fibers, such as high tenacity rayon fibers. The batt is then passed through the nip defined between a patterned roll and a rubber roll, moisture being added to the surface of the rubber roll to moisten the fibrous batt as it passes through the nip. Applying moisture to the batt enhances the ability of the batt to retain the embossed pattern therein during subsequent operations, and also aids in releasing the batt from the rolls. The side of the batt which contains the rubber roll is provided with a loose fiber nap which is capable of mechanically interlocking with a loose fiber nap of a like batt, or with the fibers of the absorbent pad of the diaper. After the embossing operation the patterned batt passes adhesive-applying stations whereat an adhesive, such as an acrylic latex, is sprayed onto opposite surfaces of said batt. A vacuum assist is provided at each adhesive-applying station to insure that adequate adhesive penetration into the batt occurs, and to minimize back-splash and adhesive drift. After the adhesive has been sprayed on the opposed surfaces of the fibrous batt, the batt is transported through an oven wherein the batt is dryed and the adhesive is set. The finished nonwoven fabric is then wound into a roll for subsequent use in the manufacture of disposable diapers and the like.

It is an object of this invention to provide a disposable diaper of the throwaway type which has sufficient strength and abrasion resistance to serve as a replacement for conventional textile diapers.

It is a further object of this invention to provide a throwaway diaper having excellent hand feel and drape characteristics.

It is a further object of this invention to provide a throwaway diaper having a textile fabric appearance.

It is a further object of this invention to provide a throwaway diaper which is extremely absorbent.

It is a further object of this invention to provide a throwaway diaper having a moisture absorbent inner pad covered on at least one side thereof by a nonwoven, moisture absorbent facing sheet.

It is a further object of this invention to provide a throwaway diaper having a nonwoven facing sheet, one side of which is provided with an embossed pattern defined by a plurality of ridges and valleys, the density of the facing sheet in the regions of said valleys being greater than the density of the facing sheet in the regions of said ridges.

It is a further object of this invention to provide a throwaway diaper having a water repellent backing sheet.

It is a further object of this invention to provide a throwaway diaper having a nonwoven randomly arranged, intermingled cellulosic fiber batt as a backing sheet thereof, said backing sheet being chemically treated with a moisture repellent material.

It is a further object of this invention to provide a throwaway diaper having a facing sheet defined by a bonded fibrous batt of randomly arranged, intermingled cellulosic fibers, said batt being provided with an embossed relief pattern in its outer surface thereof, which extends over substantially the entire surface of the batt, and a second embossed pattern extending through said facing sheet and into a moisture absorbent pad over which said facing sheet is disposed to provide mechanical entanglement between the fibers of the facing sheet and the fibers of the moisture absorbent pad whereby fluid communication through said facing sheet into said pad, and also along said pad and facing sheet are enhanced.

It is a further object of this invention to provide a method for manufacturing a facing sheet of a throwaway diaper wherein an adhesive is applied to an embossed fibrous batt of randomly arranged, intermingled cellulosic fibers, and said adhesive is subsequently dried and set.

It is a further object of this invention to provide a method for manufacturing a facing sheet of a throwaway diaper wherein a fibrous batt is moistened by water sprayed upon the surface of a rubber roll which defines, in conjunction with a patterned embossing roll, a nip region through which said fibrous batt passes.

Other objects and advantages of this invention will be readily understood by referring to the detailed description which follows taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the sequential steps performed in manufacturing a nonwoven cover material for a throwaway diaper;

FIG. 2 is an enlarged sectional view along line 2--2 of FIG. 1 showing details of construction of the non-woven facing sheet utilized in the disposable diapers of this invention;

FIG. 3 is a perspective view of the disposable diaper of this invention; and

FIG. 4 is a sectional view taken along line 4--4 of FIG. 3, with the specific embossed pattern shown in FIG. 2 omitted for purposes of clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The method of manufacturing a moisture absorbent, nonwoven, self-sustaining, absorbent fabric suitable for use as a cover material in disposable diapers and the like can best be understood by referring to the schematic representation of the process shown in FIG. 1. A loosely compacted, randomly arranged, intermingled fibrous batt 10, comprised of approximately 75 percent wood pulp fibers and approximately 25 percent longer synthetic fibers, such as rayon, is formed by conventional web-forming equipment which does not form a part of the present invention but which will be discussed briefly for purposes of clarity. Baled rayon is opened by feeding it through a Rando Prefeeder and Rando Opener-Blender, both of which are manufactured by the Curlator Corporation of Rochester, New York. A continuous roll of pulp lap is fiberized by passing it through a fiberizer, such as the one manufactured by Joa, Inc. of North Wales, Fla. The opened rayon fibers and defibered wood pulp fibers are blended in a Rando Feeder, and are air-laid by a Rando Webber to form a randomly arranged, intermingled fibrous batt containing approximately 75 percent wood pulp fibers and 25 percent rayon fibers and having approximately 8 percent moisture regain. The Rando Feeder and Rando-Webber are manufactured by the Curlator Corporation. The wood pulp lap preferably is provided with a suitable debonding agent to insure that the pulp lap can be uniformly defibered in the fiberizer.

In the preferred embodiment of the invention, a high wet modulus rayon of 1.5 denier and 1 9/16 inch length is used; however, other synthetic fibers can be utilized. A high wet modulus rayon fiber can be purchased from FMC Corporation and is designated as FMC Fiber 410.

The fibrous batt can be formed with a basis weight up to about 2 ounces per square yard; however, in the preferred embodiment of the invention the fibrous batt, as initially formed by the Rando-Webber, has a basis weight in the range of approximately 0.9-1.1 ounces per square yard.

The fibrous batt formed by the web forming equipment is embossed on one surface 32 (FIG. 2) thereof by feeding said batt through a nip defined between an upper patterned roll 12 and a lower rubber roll 14. In the preferred embodiment of this invention, the upper pattern roll 12 is loaded by hydraulic cylinders to provide the necessary pressure to form the embossed pattern in the batt 10. Moisture is sprayed from a nozzle 16 onto the surface of rubber roll 14 just prior to the nip, whereby the moisture is transferred from the rubber roll to the batt 10 as the batt passes through the nip to insure that the pattern formed in said batt will be retained therein during subsequent operations and to aid in releasing the web from the rolls. In the event that the initially formed batt 10 has sufficient moisture to retain an embossed pattern therein during subsequent operations, the application of moisture prior to embossing can be eliminated.

In the preferred embodiment of the invention, a terry cloth pattern is formed on the surface of roll 12 by a photoengraving process well known in the art. It is understood that other patterns and other methods of applying a pattern to a roll can be utilized. The patterned embossing roll is heated by steam within the range of approximately 190.degree.F to 210.degree.F, and a pressure of the order of magnitude of 0.5 to 20 pounds per linear inch is applied at the nip of rollers 12 and 14.

The temperature of the embossing roll 12 can be varied depending upon the particular embossing pressure imposed on the batt 10, i.e., lower temperatures can be used with increasing pressures. In addition, various percentages of moisture add-on can be applied through nozzle 16, depending on the pressure-temperature parameters of the embossing step, i.e., lower percentages of moisture can be utilized by increasing the embossing pressure and/or temperature. The moisture level of the batt must be sufficient to insure that the batt will retain its embossed pattern during subsequent operations.

After the pattern has been embossed into the upper surface 32 of the web, the batt 10 is fed past successive adhesive-applying stations. At the first station, adhesive is applied to the lower surface of the web through an adhesive nozzle 18, and a vacuum assist 20 is provided from the opposite side of said batt to improve adhesive penetration and minimize backsplash and adhesive drift. At the second adhesive-applying station, the adhesive is sprayed onto the upper surface 32 of the batt 10 through an adhesive spray nozzle 22, and a vacuum assist 24 is provided from the opposite side of the batt for the same reason that the vacuum assist 20 is provided at the first adhesive-applying station.

In the preferred embodiment of this invention a self cross-linkable acrylic latex sold by Rohm & Haas under the trade name Rhoplex HA8 is utilized. The total adhesive solids add-on is approximately 8-12 percent by weight.

After the batt 10 has passed the second adhesive-applying station, it is fed through an oven 26 which is maintained at approximately 300.degree.F to dry the web, and subsequently at about 320.degree.F to cure said web. The web, as it enters the oven has approximately 200 percent moisture add-on by weight which resulted from the moisture application through nozzle 16 and the moisture application through adhesive nozzles 18 and 20. The dryed and cured batt is then rolled in a roll 28 for subsequent use as a nonwoven cover material for disposable diapers.

Although the self cross-linkable acrylic latices are preferred in the manufacture of the nonwoven fabric of this invention, other adhesives may be utilized, and when other adhesives are utilized the batt 10 will be subjected to an adhesive-setting process appropriate for the particular adhesive used.

It is highly desirable to utilize a predominate amount of wood pulp fibers in the nonwoven fabric of this invention, since wood pulp is relatively inexpensive as compared to the cost of longer textile fibers, such as rayon and cotton, and since wood pulp has excellent absorbency characteristics.

The nonwoven cover material formed according to the above-described method has a basis weight up to or about 2.0 ounces per square yard, but preferably is in the range of approximately 1.1 to approximately 1.6 ounces per square yard. Manufacturing a nonwoven fabric of predominately short cellulosic fibers, such as wood pulp, in the basis weight range referred to above, requires extreme care in handling during the fabrication thereof. This is particularly true prior to embossing at which time the formed batt 10 has relatively little integrity. By applying moisture from nozzle 16 onto the surface of rubber roll 14 for transfer to the batt 10, instead of applying moisture directly against the surface of the web, the batt is not physically disturbed, and therefore the chance of destroying the uniformity of the batt is reduced.

The fiber construction in the finished fabric is shown in FIG. 2. The finished fabric has an upper embossed surface 32 which is defined by the pattern contained in the outer periphery of pattern roll 12, and a lower, loose fiber nap surface 30 formed by its engagement with the periphery of rubber roll 14 during the embossing operation. The function of the loose fiber nap surface 30 will be described in detail with respect to the disposable diaper construction shown in FIGS. 3 and 4.

Referring to FIGS. 3 and 4, the diaper 40 of this invention is comprised of a moisture absorbent pad 46 extending longitudinally along the center of the diaper and adapted to fit between the legs of an infant in the crotch area. The pad 46 is preferably made of fluffed wood pulp fibers, and is contoured in the crotch area to define an hourglass configuration for reducing unneeded bulk to provide comfort for the baby. The absorbent pad is sandwiched between a facing sheet 42 adapted to be positioned against the skin of the baby, and a backing sheet 44. In the preferred embodiment of the invention, both the facing sheet 42 and the backing sheet 44 are comprised of randomly arranged intermingled cellulosic fibers manufactured according to the process described in detail, supra and both the facing and backing sheets are substantially rectangular as is shown in FIG. 3.

To prevent moisture strikethrough during use of the diaper, a fluid impermeable material, such as polyethylene can be placed between the absorbent fluff pad 46 and the backing sheet 44, or to retard the rate of moisture strikethrough, the backing sheet 44 may be coated or chemically treated in a suitable manner to render it substantially water impermeable. For example, a material such as an emulsion of wax and poly(vinyl acetate) sold by Du Pont under the trade name Nalan GN is extremely effective for retarding moisture strikethrough when applied to both surfaces of the backing sheet 44.

The outer surfaces of facing sheet 42 and backing sheet 44 are provided with the embossed pattern formed by embossing roll 12, and therefore, the loose fiber nap layer 30 of the facing sheet 42 faces the corresponding loose fiber nap surface 30 of the backing sheet 44. When the sheets are assembled to produce disposable diaper 40, the fibers of the loosely napped surfaces tend to mechanically interlock with each other and with the fibers of the absorbent fluff pad 46 to thereby provide a relatively stable product. In addition, any suitable adhesive, such as hot melt can be utilized to bond the facing sheet to the backing sheet, and to retain the fluff pad 46 in proper position therebetween.

To enhance the capillary flow characteristics between the facing sheet 42 and the absorbent pad 46, a substantially broad pattern is embossed into the absorbent pad 46 through the facing sheet 42, to define compressed lines 54, and high loft, bulk regions 52. This embossed pattern produces a continuous fiber network between the facing sheet 42 and the fluff in the compressed regions 54 to enhance the fluid distribution along lines 54 and into the fluff pad 46. As can be seen in FIG. 3, two sets of spaced, continuous embossed lines 54 are formed in the facing sheet and underlying absorptive layer 46. One of the sets of embossed lines 54 extends in the long direction of the diaper, and the second set of embossed lines extends substantially transverse to the first set of embossed lines.

In the preferred embodiment of the invention, the backing sheet 44 has a longitudinal length slightly in excess of the longitudinal length of facing sheet 42, and the end portions of the backing sheet 44 are folded over the upper surface of facing sheet 42 to provide strengthened regions 48 and 50 for receiving pins. Alternatively, the facing sheet and backing sheet can be manufactured of the same length, and a print bonded pattern can be applied to the longitudinally spaced edges of the diaper to provide the needed pin strength, or alternatively a gauze insert can be sandwiched between the sheets at the longitudinally spaced edges to provide the necessary pin strength.

* * * * *


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