US3777758A

US3777758A - Disposable diaper

Info

Publication number: US3777758A
Application number: US00198381A
Authority: US
Inventors: L May; N Schiff; W Strickel; G Liloia; F Mesek; R Shepherd
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-05-16
Filing date: 1971-11-12
Publication date: 1973-12-11
Anticipated expiration: 1990-12-11

Abstract

A disposable multi-layer diaper is disclosed in which a first layer to be brought into contact with an infant''s skin, is a through bonded non-woven fabric of predominantly short length fibers mixed with long, i.e., textile length, fibers. The fabric is treated with a rewetting agent so as to have the desired degree of wettability and absorbency. A second layer, in juxtaposition to the facing layer, is a highly absorbent pad of short length fibers. The final layer, positioned on the side of said pad opposite said facing layer, is also through bonded nonwoven fabric of predominantly short length fibers in admixture with long or textile length fibers. In each of the layers of the diaper the short length fibers are naturally occurring cellulosic fibers, e.g., wood pulp fibers and cotton linters having a length not exceeding about one-quarter inch.

Description

United States Patent 1191 Mesek et al.

[ Dec. 11, 1973 1 DISPOSABLE DIAPER [22] Filed: Nov. 12, 1971 [21] Appl. No.:=l98,38l

Related US. Application Data [63] Continuation-impart of Ser. No. 729,784, May 16, 1968, Pat. No. 3,663,348, which is a continuation-in-part of Ser. No. 515,874, Dec. '23, 1965, abandoned.

[52] US. Cl. 128/284 [51] Int. Cl. A6lf 13/16 [58] Field of Search 128/284, 286, 287, 128/290, 296

[56] References Cited UNITED STATES PATENTS 2,696,819 Lovekin 128/284 Primary Examiner-Charles F. Rosenbaum Attorney-Michael Q. Tatlow et al.

[57] ABSTRACT A disposable multi-layer diaper is disclosed in which a first layer to be brought into contact with an infants skin, is a through bonded non-woven fabric of predominantly short length fibers mixed with long, i.e., textile length, fibers. The fabric is treated with a rewetting agent so as to have the desired degree of wettability and absorbency. A second layer, in juxtaposition to the facing layer, is a highly absorbent pad of short length fibers. The final layer, positioned on the side of said pad opposite said facing layer, is also through bonded non-woven fabric of predominantly short length fibers in admixture with long or textile length fibers. In each of the layers of the diaper the short length fibers are naturally occurring cellulosic fibers, e-gwood pulp fibers and cotton linters having a length not exceeding about one-quarter inch.

16 Claims, 10 Drawing Figures 1 DHSPOSABLE manna CROSS-REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION Disposable diapers have met with widespread com-' mercial acceptance in the recent past, primarily because of their convenience. Even though such diapers are functionally inadequate in certain respects, and more expensive to use than cloth diapers, consumers have exhibited an increased tendency to accept these deficiencies as part of the price for convenience."

Typical disposable diapers include a fabric facing layer to be placed adjacent an infants skin, an absorbent pad or batt, and a moisture-impervious backing sheet. I

One of the problems of the prior art has been the inability to provide a suitable lightweight, inexpensive facing material, i.e., one which would be pliable, soft, comfortable and non-irritating to an infants skin, while at the same time having adequate strength, dimensional stability, and loft; and the desired degree of water-wettability and absorbency. Since cost is a vital factor in disposable diapers, it is essential that the foregoing properties be obtained in a facing fabric made of low cost fibers.

Cost savings in a diaper facing fabric can be realized by using short length fibers, such as the fibers of wood pulp or cotton linters, and because of this it has been a desideratum in the manufacture of facing layer fabrics and fabriclike materials to use such fibers as com,- pared to the generally used longer fibers of one-half inch or more in length. However, prior to this invention, it has not been possible to utilize such short length cellulosic fibers in a diaper facing fabric having desired loft and strength characteristics, since short length fibers as conventionally used interlock to form a coherent layer of relatively high density. Such relatively high density layers have been used as diaper facing materials, but the use has not been entirely successful because they do not have the loft which is required in a facing material to help in keeping an infants skin relatively dry.

Another problemthat has confronted the disposable diaper industry is the inability to provide a relatively short length, naturally occurring cellulosic fibers. in admixture with a small proportion of textile length fibers, with the resulting layer being bonded throughout its thickness with a cross-linked bonding agent, (2) a highly absorbent pad formed of short length, naturally occurring cellulosic fibers positioned in juxtaposed relationship with respect to said facing layer, and (3) a backing layer on the side of the pad opposite of said facing layer, and also consisting predominantly of short length, naturally occurring cellulosic fibers in admixture with a small proportion of textile length fibers, and

,also bonded throughout its thickness with a crosslinked bonding agent.

inexpensive backing member having adequate water repellency from naturally occurring cellulosic fibers. It is conventional to use a plastic moisture-impervious sheet, such as a polyethylene sheet, as a backing member in a disposable diaper to provide the desired water repellency, but while such diapers are satisfactory as a single use item, they are not truly disposable, since the entire diaper structure is not completely biodegradable. In addition, a plastic'sheet tends to impart stiffness and clamminess to the diaper.

SUMMARY OF-THE INVENTION In accordance with the present invention a multilayer diaper is provided which includes (I) an absorbent facing layer to be brought into contact with the infants skin and consisting predominantly of low cost,

' The textile length fibers in the facing layer cooperate with the short fibers to give the facing layer loft and strength, which loft is more or less maintained, and which strength is augmented, by a binder. The resulting layer is of relatively low density, and in addition to having high loft and strength, the layer is soft and conformable, thus making it ideally well suited for use as a diaper facing.

In a preferred embodiment of the invention, the fibers of the facing layer are in uniform admixture throughout the thickness of the layer, and the fibers are held in their lofted state by a binder, such as those of the self-curing acrylic latex family, the urethane family, or other binders which can be utilized in low viscosity solutions or suspensions. The binder add-on is in the range of from about 1 percent to about 30 percent of the weight of the fibers on a dry solids basis. While such binder materials'have the effect of interferring with the normal water-absorbency of the mixture of fibers constituting the facing layer, because the binder coats the individual fibers, in accordance with the present invention the facing layer including the binder is madeabsorbent by treatment of the layer with a rewetting agent (surfactant). Hence, urine may pass through the facing layer and be absorbed in the absorbent pad, thus, desirably carrying the urine away from the skin of the infant. The ability of urine to pass through the lofted mixture of fibers, bonded as described above, and into the absorbent pad, is an important feature of the diaper of the present invention. Without treating the bonded facing layer, the binder component could interfere with the normal water-absorbent characteristics of the fibers, and the facing layer would not adequately serve for use in accordance with the present invention.

In the backing layer, water repellency is desired and the wetting agent is preferably omitted from its binder, so that the backing layer is sufficiently water repellent to prevent urine absorbed in the pad from striking through the diaper.

The overall combination provides a diaper in which all components are fibrous, and therefore, has the desirable feel and drape qualities of a cloth diaper. Since all the layers of the diaper are formed of cellulosic fibers, the diaper is disposable in the true sense of the word.

BRIEF DESCRIPTION OF THE DRAWINGS FIG, 1 is a schematic view of a production line showing the preparation of a fabric used as facing or backing in the diaper of the present invention;

FIG. 2 is a perspective view illustrating a swatch of fabric used as facing or backing in the diaper of the present invention;

FIG. 3 is a perspective view illustrating a modification of the fabric used as facing or backing in thediaper of the present invention;

FIG. 4 is a perspective view illustrating a further modification of the fabric used as facing or backing in the diaper of the present invention;

FIG. 5 is a schematic view of a production line showing the preparation of a modified fabric used as facing or backing in the diaper of the present invention;

FIG. 6 is a perspective view illustrating a swatch of fabric prepared in the manner of FIG; 5;

FIG. 7 is a perspective view of an open unfolded diaper of the present invention, with a portion of the top layer broken away to illustrate the internal construction;

FIG. 8 is a cross-sectional view taken along line 88 of FIG. 7; and

FIG. 9 is a perspective view, partly in phantom, illustrating the manner in which the diaper of FIGS. 7 and 8 is folded.

FIG. 10 is a fragmentary perspective view, with a portion of the top layer broken away to show an internal end reinforcement.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, a diaper of simple inexpensive construction is illustrated in FIGS. 7, 8 and 9. The diaper is formed of a top fabric sheet 29 and a bottom fabric sheet 30, the

fabric sheets

29 and 30 being made in the manner hereinafter described. Between

fabric sheets

29 and 30 is an absorbent pad 31 formed of wood pulp, or other highly absorbent material. The absorbent pad 31 is substantially narrower in width than the top and

bottom fabric sheets

29 and 30 and is spaced from the edges of

sheets

29 and 30 to lie along the center portion of the diaper, i.e., the portion which would, in use, be positioned at the crotch of the infant. The bottom fabric sheet 30 may be longer than the top fabric sheet 29, the extending

ends

32 and 33 being folded over to form reinforced

areas

34 and 35 for receiving safety pins and the like when applying the a diaper. However, if desired, the top and bottom sheets may be of substantially the same length and a strip of gauze or other woven fabric, 41 in FIG. 10, inserted be tween the two sheets at each end to reinforce the diaper in these areas. I r

As is hereinafter explained,

fabric sheets

29 and 30 are both comprised of a mixture of short and long fibers that are through bonded by a bonding agent that tends to make the sheets water repellent. The water repellency may be modified, or overcome, by use of a rewetting agent. In forming the diaper, both the top fabric sheet 29 and the bottom fabric sheet 30 may be formed of a readily wettable and highly absorbent fabric, i.e., one which contains a rewetting agent, or the diaper may be formed with only the top fabric 29 and the absorbent filler 31 being absorbent while the bottom fabric 30 is nonabsorbent as hereinafter described, the same having been prepared without being rendered readily wettable and highly absorbent through the inclusion of a rewetting agent, also as hereinafter described. I

The fabrics used as facing sheets and backing sheets in the diaper of the present invention have a fiber content which is predominantly short fibers. By way of definition, short fibers," as used herein, means wood pulp, cotton linters or the like where the fiber lengths are less than one-fourth inch in length. Between 75 percent and 98 percent of the total fiber content in the fabrics of this invention are such short fibers. Both wood pulp and cotton linters are substantially less expensive than the textile length cellulosic fibers of cotton and rayon generally employed in making both woven and non-woven cellulosic fabrics. In the preferred embodiments, the wood pulp fibers and the second cut cotton linters generally have a length not exceeding about one-fourth inch with the average length being from about one-sixteenth to three-sixteenths inch. Accordingly, the fabrics of the present invention have a fiber content in which between 75 percent and 98 percent of the fibers are less than onefourth inch in length.

Textile length fibers or long fibers in this specification means fibers at least three-fourths inch in length, and in the preferred forms of the invention the long fibers are all of substantially the same length, preferably produced synthetically and preferably at least 1 inch long. In one preferred embodiment made in accordance with Example I, 1.5 denier rayon longfibers were used which were uniformly cut to about 1% inch lengths and homogeneously and randomly dispersed with the short fibers. Surprisingly high tensile strengthsare thereby attainable provided the short fibers are thoroughly and efficiently separated and the short and long fibers are carefully and thoroughly blended and intermixed.

The fabrics used in the diaper of the present invention have fabric weights in the range of l to 8 oz./yd."; a density of less than 0.15 gm./cc., the density generally being in the range of 0.100 gm./cc. to 0.050 gm./cc.; and for a fabric having a weight of about 1.5 oz./yd. a dry strength of at least 0.15 lbs./in. of width in machine direction and 0.10 lbs./in. of width in the cross direction. The fabrics have unusually good elongation, loft, softness and drape characteristics when compared with prior products incorporating any substantial amount of short fibers.

The fabrics are prepared by first forming a web of randomly laid dry fibers, the web when laid having a density of about 0.09 gmJcc. to 0.025 gm./cc. measured by ASTM Method D-l777 at 0.l6'lbs./sq.in.

(test procedure set forth in the manual of The American Society for Testing Materials). Where wood pulp fibers are used, the same are generally obtained in the form of a fiberboard of fairly dense construction from which the fibers must be separated. These wood pulp fibers generally have a fiber length ranging from a fine dust to about one-fourth inch.

Short-length fibers are best classified by the Clark Classification procedure described in the test manual of The Technical Association of Pulp and Paper Industry (TAPPI-T233 SU64). In this procedure a water slurry of the fibers is passed through a series of graded screens. Using this technique, which avoids grinding the fibers, second cut cotton linters are found to have the following composition:

30 percent retained by a 12 mesh screen 22 percent retained by an 18 mesh screen 14 percent retained by a 30 mesh screen 16 percent retained by a 50 mesh screen 18 percent passed through 50 mesh screen In making the short fiber fabrics used in the diapers of the present invention a web of dry fibers is first formed. In the preferred method of manufacture, the web is then impregnated with a binder fluid by flowing a solution or dispersion of the binder through the web. The impregnated web is then subjected to suction to remove excess binder fluid and assure uniform distribution of binder fluid throughout the fiber web. This impregnation by binder fluid followed by suction is hereinafter referred to as suction-bonding. The fiber web at this point has, in one embodiment on a solids basis, 4 percent to 6 percent dry solids add-on by weight of the web. Depending upon the strength requirements of the web, the loft and the softness desired in the end product, the range of dry solids added on may vary over the range of about ll percent to about 30 percent. The web so formed is then dried and heated to cure the binder. This can be done simultaneously by passing into a drying oven heated to a temperature of about 310F. to 320F. where the same is dried and the binder cured. The preferred binders areof the self-curing acrylic latex family, the urethane family, or other binders which can be utilized in low viscosity solutions or suspensions.

The diaper of this invention has especial advantages by virtue of the facing and backing layers being formed of lightweight, low density, lofty, and soft fabrics. The especially useful range of fabric densities in accordance with this invention is from about'0.05 gm./cc. to about 0.15 gm./cc. By the use of the teachings set forth herein, and specifically the combination of fibers and other parameters, it has been found possible to manufacture lightweight I fabrics, that is, fabrics having weights of less than 8oz./sq.yd. and handle the product, air blown or otherwise assembled dry, during further processing. Thereby unusually desirable weights, densities and other physical characteristics are obtained rendering the fabrics particularly useful in the diaper of the present invention.

The preparation of predominantly short fiber fabrics for use in the diaper of the present invention is illustrated schematically, for example, in FIG. 1. Referring to FIG. 1, a web 10 of mixed randomly disposed short fibers ill and long fibers 119 is deposited from fiberlaying equipment'll2 onto a foraminous moving screen or belt 13. The fiber-laying equipment'lZ is preferably of the air deposition type such as a modified RANDQ WEBBER made by the Curlator Co. The low density fiber web it) is moved by belt 13 below a screen containing a weir box Mof binder in fluid form, i.e., in solution or aqueous dispersion. The binder fluid is flowed onto and through the web 10 in quantities substantially in excess of the ultimate amount to be deposited on the fibers completely impregnating the web. The web 10, immediately after impregnation withthe binder fluid, passes over, a suction box 15 where excess binderfluid is removed. The impregnated web 10 is conveyed by belt 13 through a dryer to. The fabric is then removed from belt 13 and collected, for example, on fabric roll I 17. A section of fabric so formed is illustrated, for example in FIG. 2 of the drawings showing a very small percentage of long fibers 19. An alternate construction with a larger percentage of long fibers 19 is shown diagrammatically in H6. 3. The binder fluid should be of the low viscosity type to maintain the features of the invention described. A low viscosity binder is generally one having the desired adhesive qualities and having, in fluid form, a viscosity less than 5 centipoises.

The binder fluid, in the preferred method of manufacture, is flowed onto the fabric from the weir box M and a major proportion thereof is withdrawn in the sucduce products that would notbe satisfactory for use in the diaper of this invention.

It has been found that the elongation characteristics I are enhanced in fabrics made in accordance with the teachings set'forth above. ()ne set of samples was constructed with about 2% oz./yd. of fiber weightand utilizing wood pulp as the short fibers and about 1 inch 1.5 denier rayon staple as the long fibers. In the set, the percentage of long fibers was varied, and the elongationtests were performed on the unbonded web. Over the range of interest, the percentage of elongation varied from about percent to 94 percent. The elongation was measured by stretching a sample of the fabric between two clamped ends and measuring the percentage increase in length before the two ends separated.

Based on the samples tested, a fabric made of 98 percent short fibers has about a 60 percent elongation, both in the machine direction and in the cross direction. Samples made of percent short fibers with 15 percent long fibers exhibited an elongation of about 88 percent, and samples containing 75 percent short fibers showed an elongation of about 94 percent. it has been found that there is a substantial increase in elongation characteristics with the addition of about 2 percent of long fibers to an otherwise short fiber fabric. The percentage of elongation rises very rapidly with the addition of long fibers up to about 2 percent and continues to increase for increases in long fibers up to 10 percent at a diminishing rate. As the percentage of long fibers is increased from about 10 percent to about 25 percent, the elongation characteristics improve rather consistently and more gradually. However, it has been found that additional long fibers in excess of about 25 percent do not increase the elongation characteristics at the 7 same rate and actually reduce the elongation in some cases. A sample made of percent long fibers and no short fibers showed an elongation in both directions of approximately 60 percent and a sample made of 100 percent short fibers exhibited an elongation of 28 percent.

lt is extremely difficult tohandle a web of randomly disposed dry fibers of predominantly short fiber length in webs of 8 oz./yd. or less through the bonding equipment and subsequently through the drying apparatus. In fact, handling of fabrics having weights of less than 2 oz./yd. had heretofore been considered unworkable. It has been found'that this problem can be overcome through use of the teachings contained herein.

Referring to FIG. 5, a means is schematically shown for manufacturing a fabric having two distinctly different surface characteristics. A relatively thin web 21 of dry, mixed fibers 11 and 19 is first laid down, superimposing on the same is a loose weave fabric 22 such as a low count gauze, cotton scrim, or the like. A second relatively thin web 23 of dry fibers iii and 119 is then deposited onto the loose weave fabric 22. The dry laminate so formed is suction-bonded, dried, and cured in the manner previously described. The laminate is then split into two

fabrics

24 and 25, the laminate separating at the point of intersection of the loose weave fabric. The loose weave fabric 22 is removed and the

fabrics

24 and 25 wound on

separate rolls

26 and 27. Other methods of splitting may be employed with or without an actual dividing web 22.

By first forming and then splitting the web, fabrics having unique surface characteristics are formed including short fibers, the fabrics having excellent drape, loft and elongation characteristics. A section of fabric formed by the split web technique is illustrated in FIG. 6. The fabric is quite similar to that of FIG. 2 differing primarily in that the fibers 28, on the surface previously adjacent the loose weave fabric 22, have substantially more loft than the fibers on the other surface of the fabric. The apparatus of FIG. 5 is schematically illustrated as in FIG. 1, 12' indicating fiber-layer equipment, 13' a moving belt, 14 a binder container and dispenser, 15 a suction box, and 16' heating and drying apparatUS.

In some constructions, it is desirable to have even greater drapability than would result from the construction features already described. Increased drape can be attained without significant loss of loft, softness or strength by embossing the fabric after completion of the processes shown in FIGS. 1 and 5. This produces a fabric such as shown in FIG. 4 where the fibers l1 and 19 have been subjected to embossing pressure along the lines 20.

The fabrics so far described are not in and of themselves water absorbent as the bonding agent appears to sufficiently coat the individual fibers as to interfere with their normal water-absorbent characteristics. Absorbent fabrics can be made, however, by treating the fabric with a rewetting agent such, for example, as an anionic sulfonated alkyl ester. In the preferred practice of making facing fabrics for the diapers of the present invention, the rewetting agent is included in the impregnating solution or suspension together with the binder. By including the rewetting agent at this step in the manufacture of the fabrics, the same are found to be readily wettable and highly absorbent.

The preparation of fabrics for the diapers of the present invention are further illustrated by the following examples. The examples are given for the purpose of illustration only, and the invention is not limited thereto.

EXAMPLE I A fibrous web composed of approximately 15 percent textile length fibers such as uniformly cut 1% inch 1.5 denier rayon fibers and 85 percent fibers of individualized second cut cotton linters is made on a web laying device to a weight of 2 oz./yd. This web is then conveyed into a bonder as heretofore described using a preferred bonding agent such as a self-cross-linkin'g acrylic emulsion. The composition of the binder suspension and the amount of suction at the suction slot is controlled so as to give the fabric a dry solids add-on of 4.75 percent based on the fabric weight. The wet -web is conveyed into a drying oven having a temperature of 310-320F. where it is dried and the resin binder cured. The resultant material has a density of 0.05 to 0.07 gm./cc., a dry strength of about 1.4 lbs.lin. of width in the machine direction and about 0.8 lbs/in. of width in the cross direction. The wet strengths are about 0.9 lbs.lin. of width in the machine direction and about 0.5 lbs/in. of width in the cross direction. The fabric has excellent hand or feel and drape.

EXAMPLE II A fibrous web composed of approximately 25 percent textile length fibers such as uniform 1.5 denier 1 inch rayon fibers and percent fibers of ground up douglas fir bleached kraft pulp is made on a web laying device to a weight of 1.5 to 2 oz./yd. The web is then conveyed into a suction bonder heretofore described using the bonding agent HYCAR 2,600 X 120. The composition of the binder suspension and the amount of suction at the suction slot is controlled to give the fabric a dry solids add-on of about 25 percent based on the fiber weight. The wet web is conveyed into a drying oven having a temperature of 310-320F. where it is dried and the resin binder:cured. The resultant web has a density of 0.08 gm./cc.; a dry strength of about 7 lbs.lin. of width and a wet strength of about 2.2 lbs.lin. of width in the machine direction.

EXAMPLE III A fibrous web composed of approximately 10 percent textile length fibers such as uniform 1.5 denier 1% inch rayon fibers and percent douglas fir pulp is made to a weight of 1.5 oz./yd. The web is then passed through a suction bonder and receives thorough impregnation wity HYCAR 2,600 X 120. The composition and viscosity of the binder suspension and amount of suction are controlled to give the fabric a dry solids add-on of about 1 percent. based on the fiber weight.

The wet web is conveyed into a drying ove'n having a temperature of 310 to 320F. where it is dried and the resin cured. The resultant fabric has a density of 0.06 gm./cc., a dry tensile strength of 0.18 lbs.lin. in the machine direction and 0.13 lbs.lin. in the cross direction, and the bonded fabric shows an elongation of 50 percent before separation.

EXAMPLE IV A fibrous web composed of approximately 13 percent textile Iength fibers such as uniform 1.5 denier 1% inch rayon fibers and 87 percent douglas fir pulp is made to a weight of 8 oz./yd. The web is then passed through a suction bonder and receives thorough impregnation with IIYCAR 2600 X 120. The composition and viscosity of the binder suspension and amount of suction are controlled to give the fabric a dry solids add-on of about 1.5 percent based on the fiber weight.

The wet web is conveyed into a drying oven having a temperature of 310 to 320F. where it is dried and the resin cured. The resultant fabric has a density of 0.09 gm./cc., a dry tensile strength of 1.9 lbs.lin. in the machine direction and 1.4 lbs.lin. in the cross direction, and the bonded fabric shows an elongation of 70 percent before separation.

EXAMPLE V A fibrous web composed of approximately 5 percent textile length fibers such as uniform 1.5 denier 1% inch rayon fibers and percent douglas fir pulp is made to a weight of 2.3 oz./yd. The web is then passed through a suction bonder and receives thorough impregnation with IIYCAR 2600 X 120. The composition and viscosity of the binder suspension and amount of suction are controlled to give the fabric a dry solids add-on of about 2 percent based on the fiber weight.

The wet web is conveyed into a drying oven having a temperature of 310 to 320F. where it is dried and the resin cured. The resultant fabric has a density of 0.07 gm./cc., a dry tensile strength of0.56 lbs/in. in the machine direction and 0.40 lbs./in. in the cross direction, and the bonded fabric shows an elongation of 46 percent before separation.

The excellent hand, feel and drape qualities of the fabrics given diapers made therefrom much the same feel and handling qualities as diapers formed of woven fabrics. However, the use of the short textile fibers, such as wood pulp and cotton linters, permits the same to be manufactured at a price substantially below that of woven fabrics or the conventional non-woven fabrics thus keeping the cost of the final diaper well within a price such that the same can be disposed of after use. Where the

fabrics

29 and 30 of the diaper are made through the split web technique heretofore described, the side of each fabric sheet which was in the inner portion of the web prior to splitting has appreciably more fiber loft-than the other side of the fabric. This loft is quite beneficial in forming a several ply construction such as the diaperconstruction just described. The loft sides of the fabrics are placed in face-to-face contact with each other on either side of the filler or absorbent pad 31-. The loft fibers tend to interlock when the surfaces are pressed together. The

fabrics

29 and 30 are thus mechanically united along their edges on each side of the absorbent pad 31 to give the appearance and feel of a single fabric. This also prevents the absorbent pad 31 from shifting its position. The side edges 36 and 37 of the diaper may or may not be further secured through spot bonding along the edge to prevent an initial separation of the

fabrics

29 and 30 along such edges if desired.

As the fibers of

fabrics

29 and 30 are through bonded, there is no problem with fraying edges and the like so that heins or other structure for prevention of edge fraying is not necessary. Because of its simple construction, the whole diaper can be assembled relatively easily.

In order to improve the ease with which the diaper is applied, the portions extending along each side of absorbent pad 31 are folded in towards the center of the diaper and then back on themselves to form'two double folds 38 and 39, one along each side of the diaper. This is'illustrated in FIG. 9. The double fold along each side is stabilized by adhesive ll!) and 41 being applied near the center portion of each double fold as measured from the diaper ends. This may either be a permanent or temporary adhesive as the primary purpose of the adhesive is to hold the center portion of the folds in place while the end portions of the folds are opened in applying the diaper.

As is evident from the above description, the present invention provides a unique diaper construction wherein all of the layers of the diaper are comprised entirely of cellulosic fibers. The facing and backing layers, despite their low density and despite the fact that they are comprised predominantly of short fibers, are heldtogether as a lofty assemblage of fibers by the inclusion of a minor proportion of textile length fibers and a binder. Furthermore, the fibers of the facing material have the desired degree of wettability and absorbency, by virtue of the fabric having been treated with a rewetting agent, which counteracts the interfering effect that the binder has upon the normal waterabsorbent characteristics of the fibers. As a result,

urine can readily pass through the facing layer and into m the highly absorbent pad in juxtaposition therewith. The backing layer of the diaper is not treated with a rewetting agent, and thus the backing layer tends to repel urine and prevent urine absorbed in the pad from striking through the diaper.

lllustratively, the facing layer may be prepared in accordance with Example I, as set forthabove, except that a rewetting agent is included in the impregnating solution, thus imparting to the facing layer the desired degree of wettability and absorbency. The backing layer may be prepared in accordance with Example ll, also set forth above; however, there is no rewetting agent in the impregnating solution for the backing layer.

It is believed that one of the factors that enables the facing layer of the diaper of the present invention to keep liquid away from the infant's skin isthat the fibers of the pad have greater wettability for water than the fibers of the facing layer. it is thought that since the pad is substantially more water-wettable than the facing layer, it tends to draw liquid preferentially away from the facing layer and into the pad. It is also thought that the bonding agent, in addition to retaining the fibers of the facing layer in their lofted relationship, serves the further function, in cooperation with the rewetting agent, of giving the facing layer a controlled amount of water absorbency, so that urine that has passed through the facing layer and into the absorbent pad is preferentially retained therein rather than soaking back into the facing layer. The backing layer, by virtue of not being treated with a rewetting agent, resists any tendency for urine to strike through the diaper, and causes urine to spread out and soak into unwetted portions of the pad.

A particular embodiment of the invention has been used to illustrate the same. The invention, however, is not limited to the specific embodiment. In view of the foregoing disclosure, variations or modifications thereof will be apparent, and it is intended to include within the invention all such variations and modifications except as do not come within the scope of the appended claims.

What is claimed is:

11. A multi-layerdiaper comprising: a facing layer; a highly absorbent pad disposed in face-to-face juxtaposition to said facing layer; and a backing layer on the side of said pad opposite said facing layer, said facing layer comprising a through bonded non-woven fabric of mixed short and long fibers, said fabric having a short fiber content of at least about percent by weight of the fabric, said short fibers having a length less than one-fourth inch and said long fibers having a length greater than three-fourths inch, said fibers being bonded by a cross-linked binder applied throughout said fabric in an amount between about 1 percent and about 30 percent of the weight of the fibers on a dry solids basis, said fabric having a weight of less than 8 oz./yd. and a density of 0.05 to 0.15 gm./cc.

2. The diaper of claim 1 wherein both said facing layer and said backing layer are formed of said through bonded non-woven fabric.

3. The diaper of claim 2 wherein said facing layer is treated with a rewetting agent to make it waterwettable.

4. The diaper of claim 1 wherein said facing layer and said backing layer are rectangular and substantially coextensive, said pad is substantially rectangular, narrower than said facing layer and said backing layer and centrally disposed with respect thereto to provide marginal portions of saiddiaper in which said facing layer and said backing layer are in direct contact with each other.

5. The diaper of claim 4 wherein said marginal portions of said facing layer and said backing layer are adhered to one another.

6. The diaper of claim 2 in which the through-bonded fabric of said facing layer and the through-bonded fabric of said backing layer each have one surface in which the fiber loft is substantially greater than the fiber loft of the other surface, the surfaces of greater fiber loft of said fabrics facing one another to mechanically interlock said facing layer and said backing layer at least in part through the interlocking of fibers on the surfaces of greater fiber loft.

7. The diaper of claim 6 in which a strip of open mesh fabric is placed between said facing layer and said backing layer at opposite ends of the diaper to reinforce the diaper in these areas.

8. The diaper of claim 1 wherein the short fiber content of the facing layer is in the range of about 75 to about 98 percent by weight of the fabric.

9. The diaper of claim 1 wherein said short and long fibers are randomly disposed and uniformly distributed.

10. A multi-layer diaper comprising: a waterwettable facing layer adapted to be positioned adjacent the skin of an infant; a highly absorbent pad disposed in face-to-face juxtaposition to said facing layer; and a backing layer on the side of said pad opposite said facing layer, said backing layer comprising a through bonded non-woven fabric of mixed short and long fibers, said fabric having a short fiber content of at least about 75 percent by weight of the fabric, said short fibers having a length less than one-fourth inch and said long fibers having a length greater than three-fourths inch, said fibers being bonded by a cross-linked binder applied throughout said fabric in an amount between about 1 percent and about 30 percent of the weight of the fibers on a dry solids basis, said fabric having a weight of less than 8 oz./yd. and a density of 0.05 to 0.15 gm./cc.

11. The diaper of claim 10 wherein both said facing layer and said backing layer are formed of said through bonded non-woven fabric, said facing layer being treated with a rewetting agent to make it waterwettable.

12. The diaper of claim 10 wherein said facing layer and said backing layer are rectangular and substantially coextensive, said pad is substantially rectangular, narrower than said facing layer and said backing layer and centrally disposed with respect thereto to provide marginal portions of said diaper in which said facing layer and said backing layer are in direct contact with each other. g

13.A multi-layer diaper comprising: a facing layer; a highly absorbent fibrous pad disposed in face-to-face juxtaposition to said facing layer; and a backing layer on the side of said pad opposite said facing layer, said facing layer comprising a nonwoven fabric of mixed short and long fibers having one surface in which the fiber loft is substantially greater'than the fiber loft of the other surface, the surface of greater fiber loft facing inwardly and in direct contact with a surface of said pad, the fibers in said contacting surfaces being mechanically interlocked with each other.

14. The diaper of claim 13 wherein said facing layer is embossed on at least the outer surface thereof, whereby the drape characteristics of the diaper are enhanced.

15. The diaper of claim 13 wherein said facing layer and said backing layer are rectangular and substantially coextensive, said pad is substantially rectangular, narrower than said facing layer and said backing layer and centrally disposed with respect thereto to provide marginal portions of said diaper in which said facing layer and said backing layer are in direct contact with each other, said backing layer comprising a nonwoven fabric of mixed short and long fibers having one surface in which the fiber loft is substantially greater than the fiber loft of the other surface, the surface of greater fiber loft in said backing layer facing inwardly and in direct contact in said marginal portions with the surface of greater fiber loft of said facing layer, the fibers on said contacting surfaces in said marginal portions being interlocked with each other.

16. The diaper of claim 1 wherein said facing layer is embossed on at least the outer surface thereof whereby the drape characteristics of the diaper are enhanced.

Claims

2. The diaper of claim 1 wherein both said facing layer and said backing layer are formed of said through bonded non-woven fabric.
3. The diaper of claim 2 wherein said facing layer is treated with a rewetting agent to make it water-wettable.
4. The diaper of claim 1 wherein said facing layer and said backing layer are rectangular and substantially co-extensive, said pad is substantially rectangular, narrower than said facing layer and said backing layer and centrally disposed with respect thereto to provide marginal portions of said diaper in which said facing layer and said backing layer are in direct contact with each other.
5. The diaper of claim 4 wherein said marginal portions of said facing layer and said backing layer are adhered to one another.
6. The diaper of claim 2 in which the through-bonded fabric of said facing layer and the through-bonded fabric of said backing layer each have one surface in which the fiber loft is substantially greater than the fiber loft of the other surface, the surfaces of greater fiber loft of said fabrics facing one another to mechanically interlock said facing layer and said backing layer at least in part through the interlocking of fibers on the surfaces of greater fiber loft.
7. The diaper of claim 6 in which a strip of open mesh fabric is placed between said facing layer and said backing layer at opposite ends of the diaper to reinforce the diaper in these areas.
8. The diaper of claim 1 wherein the short fiber content of the facing layer is in the range of about 75 to about 98 percent by weight of the fabric.
9. The diaper of claim 1 wherein said short and long fibers are randomly disposed and uniformly distributed.
10. A multi-layer diaper comprising: a water-wettable facing layer adapted to be positioned adjacent the skin of an infant; a highly absorbent pad disposed in face-to-face juxtaposition to said facing layer; and a backing layer on the side of said pad opposite said facing layer, said backing layer comprising a through bonded non-woven fabric of mixed short and long fibers, said fabric having a short fiber content of at least about 75 percent by weight of the fabric, said short fibers having a length less than one-fourth inch and said long fibers having a length greater than three-fourths inch, said fibers being bonded by a cross-linked binder applied throughout said fabric in an amount between about 1 percent and about 30 percent of the weight of the fibers on a dry solids basis, said fabric having a weight of less than 8 oz./yd.2 and a density of 0.05 to 0.15 gm./cc.
11. The diaper of claim 10 wherein both said facing layer and said backing layer are formed of said through bonded non-woven fabric, said facing layer being treated with a rewetting agent to make it water-wettable.
12. The diaper of claim 10 wherein said facing layer and said backing layer are rectangular and substantially coextensive, said pad is substantially rectangular, narrower than said facing layer and said backing layer and centrally disposed with respect thereto to provide marginal portions of said diaper in which said facing layer and said backing layer are in direct contact with each other.
13. A multi-layer diaper comprising: a facing layer; a highly absorbent fibrous pad disposed in face-to-face juxtaposition to said facing layer; and a backing layer on the side of said pad opposite said facing layer, said facing layer comprising a nonwoven fabric of mixed short and long fibers having one surface in which the fiber loft is Substantially greater than the fiber loft of the other surface, the surface of greater fiber loft facing inwardly and in direct contact with a surface of said pad, the fibers in said contacting surfaces being mechanically interlocked with each other.
14. The diaper of claim 13 wherein said facing layer is embossed on at least the outer surface thereof, whereby the drape characteristics of the diaper are enhanced.
15. The diaper of claim 13 wherein said facing layer and said backing layer are rectangular and substantially coextensive, said pad is substantially rectangular, narrower than said facing layer and said backing layer and centrally disposed with respect thereto to provide marginal portions of said diaper in which said facing layer and said backing layer are in direct contact with each other, said backing layer comprising a nonwoven fabric of mixed short and long fibers having one surface in which the fiber loft is substantially greater than the fiber loft of the other surface, the surface of greater fiber loft in said backing layer facing inwardly and in direct contact in said marginal portions with the surface of greater fiber loft of said facing layer, the fibers on said contacting surfaces in said marginal portions being interlocked with each other.
16. The diaper of claim 1 wherein said facing layer is embossed on at least the outer surface thereof whereby the drape characteristics of the diaper are enhanced.