CA1242551A

CA1242551A - Reinforced batt for disposable absorbent article

Info

Publication number: CA1242551A
Application number: CA000470202A
Authority: CA
Inventors: Morris K. Swieringa
Original assignee: Personal Products Co
Current assignee: Personal Products Co
Priority date: 1983-12-19
Filing date: 1984-12-14
Publication date: 1988-10-04
Also published as: MX159490A; JPH0671472B2; GB8431948D0; GB2151548A; PT79696A; JPS60151302A; AU3686084A; BR8406440A; GB2151548B; AU578439B2; NZ210620A

Abstract

Abstract The present invention provides an absorbent article of manufacture having a first layer of a moisture-impervious backing sheet, a second layer of a multi-layer absorbent pad and a third layer of a moisture-pervious facing sheet overlying the multi-layer pad. The pad contains a moisture-pervious reinforcement sheet and a pair of cellulosic fibrous batts positioned on opposite sides of the moisture-pervious reinforcement sheet. The moisture-pervious reinforcement sheet contains an expandable section providing added flexibility while maintaining structural integrity of the absorbent article of manufacture.

Description

~L~4~:55~

REINFORCED BATT FOR DISPOSABLE ABSORBENT ARTICLE
Technical Field of the Invention This invention relates to a reinforced batt or panel for a disposable absorbent article, such as a disposable diaper. ~ore particularly, this invention relates to a multi-layer batt which includes between two batt layers a liquid permeable reinforcing sheet.
Background of the Invention Disposable diapers provide substantial advantages and convenience over diapers intended to be laundered and reused, and in recent years disposable diapers have met with increased success in the marketplaçe. Typical disposable diaper structures include a moisture retaining layer of relatively high liquid holding capacity sandwiched between a moisture pervious facing layer and a moisture impervious plastic backing sheet to confine moisture within the moisture retaining layer. Such diapers are shown in U.S. Patent No. 3,612,055 to Mesek et al. and in U.S. Patent No. Re: 26,151 to Duncan et al.
The moisture retaining layers of prior art diapers have typically been comprised of a batt of loosely compacted cellulosic fibers. It has been known to provide such absorbent batts with an integrally formed densified paper-like layer or skin, and U.S. Patent Nos. 3,017,304 to Burgeni and 3,612,055 to Mesek et al. are typical of such constructions. It i~ also known to provide absorbent batts having a continuous densified paper-like layer or skin with longitudinally extending thickened densified regions for directing moisture in a lengthwise direction of the batt, and ~epke U.S.
Patent No. 3,938,522 is typical of such constructions.

,~

~242551.

In addition to providing a wicking mechanism ~or directing liquid away from an initially wetted area and into remote regions of the diaper, such densi~ied layers and regions have added a degree of stability and strength to the batt. In spite of this bene~icial effect, lack of adequate panel stability is a longstanding problem in the disposable absorbent article art and which remains to be solved.
Prior art attempts to solve this problem have centered about the incorporation of a moisture impervious ~ilm or sheet into or adjacent to the absorbent batt to reinforce the same, and providing such sheets with apertures BO that liquid could pass therethrough. While such sheets or films havé
contributed to improved batt stability, they have done so at the expense of batt absorption, since ~uch films, or sheets, in effect form a liquid barrier adjacent to or within the batt. U.S. Patent Nos.
3,654,060 to Goldman; 3,890,974 to Kozak; 4,014,341 20 to Karami; and 4,282,874 to Mesek are typical of such prior art disclosures.
It is apparent that it would be desirable to provide a reinforced batt for an absorbent article, such as a disposable diaper, without impairing the ability of the batt to absorb liquid wetted thereon.
Summary of the Invention In accordance with the present invention, a moisture pervious reinforcement sheet is incorporated within an absorbent batt to not only add strength and stability to the batt, but also to contribute to wicking within the batt, while not impeding the ability o~ the batt to absorb liquid wetted thereon.
More particularly, the batt of the present invention includes a pair of batt layers having a moisture ~242551 pervious fabric reinforcing sheet interposed therebetween.
Stability is imparted to each of the batt layers adjacent to the reinforcing sheet because of the interfiber frictional engagement therebetween.
In essence, the reinforcing sheet acts as a locking or anchoring means which prevents the batt layers from moving relative to the reinforcing sheet and relative to one another.
The reinforcing sheet is preferably a nonwoven fabric formed of polyester or the like, which sheet may be generally coextensive in external dimensions with the batt layers between which it is interposed. The batt layers are substantially less dense than the reinforcing sheet, and liquid wetted onto the absorbent batt tends to wick preferentially along the reinforcing sheet. Being pervious to liquids, the reinforcing sheet presents substantially no impediment to the rate or amount of liquid absorption in the batt. In fact, because the reinforcing sheet adds strength and stability to the batt, increased liquid storage capacity can be provided by using heavier weight batt layers.
In accordance with another aspect of the invention, expansion means is provided internally of the reinforcing sheet to accommodate flexure and stretching of the facing, backing and batt layers with which the reinforcing sheet is associated. More specifically, the central portion of the reinforcing sheet is provided with a pattern of slits, which enable the reinforcing sheet to expand upon stretching to form a grid-like configuration without tearing or rupturing of the reinforcing sheet. The reinforcing sheet will contract upon retraction and assume its original unexpanded configuration. The ~24~51.

slits are par-tially opened when the diaper is manufactured t.o accommodt.e some shrinkage or contraction that can take place during the manufacturing process.
According to a furt.her broad aspect of the present invention there is provi.ded an absorbent article comprising a first outer layer in -the form of a moisture impervious backing sheet. A second layer is also provided in the form of a mult.ilayer absorbent pad means. The pad means is smaller than the first outer layer and spaced i.nwardly from the sides thereof. The pad means comprises a first cellu-losic fi.brous batt positioned in superposed relationship wi.th respect to the first outer layer. A moist.ure pervious nonwoven fabri.c is positioned in superposed relati.onshi.p with respect to the fi.rst batt. A second cellulosi.c fibrous batt is positioned in superposed relati.onship with respect to the moi.sture pervi.ous nonwoven fabric. The moisture pervi.ous nonwoven fabri.c is adapted t.o provi.de reinforcement and structural integrity to the two layers of cellulosic fi.brous batt between which it i.s disposed. A third layer is provided i.n the form of a moisture pervious facing sheet and overlyi.ng the mult.i.layer absorbent pad means.
Accordi.ng to a further broad aspec-t of the present i.nvent.ion the absorbent article, above described, is a disposable diaper and wherei.n the moisture i.mpervious back-ing sheet and moisture pervi.ous facing sheet are substan-tially rectangular. The pad means has a substantially ~t~ngular confi.gurat.i.on and is disposed substantially symmetrically wi.th respect to the backing sheet and facing sheet.

~242S51 - 4a -.
_ ief Desciption of the Drawing_ Fig. 1 is a perspective view of a disposable diaper formed in accordance with the teachings of the present invention, with certain portions broken away to illustrate details of internal construction;
Fig. 2 is an enlarged cross-sectional view taken generally along line 2-2 of Fig.. l;
Fig. 3 is a perspective view of the diaper of the present invention as applied to an infant and Figs. 4 and 5 are enlarged fragmenting plan views of the reinforcing sheet of the present invention in unexpanded and expanded conditions, respectively.
Descri~tion of the Preferred Embodiment , While this invention i8 susceptible of embodiment in many different forms, there is shown in the drawing and will herein be described in detail a preferred embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.
Referring now to the drawings, the disposable diaper 10 of the present invention includes a facing layer 12 formed of a moisture pervious material, and adapted to be positioned adjacent to the infant's skin. Diaper 10 further includes a moisture impervious outer layer 16 sustantially coextensive in external dimension with facing layer 12. Sandwiched between outer layers 12 ~2~255~

and 16 is an absorbent unit 14 which is smaller in external dimension than outerlayers 12 and 16, and which is disposed symmetrically with respect thereto. Absorbent unit 14 may be secured to backing sheet 16 by spaced, parallel glue lines, and layers 12 and 16 may be secured to one another outwardly of batt 14 by such glue line, as is well understood by those skilled in the art.
Securement means is provided for releasably attaching the diaper 10 about the perineal area of the wearer, and such securement means may take the form of tape tabs 18 secured to backing sheet 16 at one end thereof, as is also well known to those skilled in the art.
Absorbent unit 14 includes a first, or lower, batt layer 20 positioned in surface-to-surface juxtaposition with backing sheet 16, and secured thereto by the aforementioned glue lines. Batt layer 20 may include an integral paper-like densified skin on its lower surface, as taught by U.S. Patent No.
3,612,055 to Mesek et al., and such a skin may be thickened in selected regions as taught by U.S.
Patent No. 3,938,522 to Repke.
Absorbent unit 14 includes an intermediate layer in the form of a reinforcing sheet 24, which is illustrated as being substantially coextensive in external dimension with batt layer 20 and which is positioned in surface-to-surface juxtaposition with respect thereto. Reinforcing sheet 24 need not be coextensive in external dimension with the facing and backing layer, and may be shorter or sli~htly longer than such layers. ~owever, it is important that the reinforcing sheet, and particularly the expansion means thereof, be present in the central portion of the diaper, as will hereafter appear.

Sheet 24 is a nonwoven fabric, and the fibers at the lower surface thereof and the fibers at the upper surface of batt layer 20 cooperate through interfiber frictional engagement to lock reinforcing sheet 24 in place relative to batt layer 20.
Reinforcing sheet 24 is a liquid pervious fabric, such as a spun-bonded polyester fabric. While fabric weight is not critical to the present invention, spun-bonded polyester fabrics having a fabric weight of about .7 oz/yd. have been found satisfactory for purposes of the present invention. The reinforcing sheet may be formed of other polymeric materials, such as polyethylene, so long as such a sheet is moisture pervious. The term ~moisture pervious" as used herein refers to those fabrics which do not provide a substantial impediment to transmission of moisture from batt layers 22 through the moisture pervious reinforcing sheet into an underlying batt layer. The reinforcing sheet preferably has a density greater than the adjacent batt layers to provide a wicking mechanism within the absorbent unit.
Absorbent unit 14 includes a second batt layer 22 positiGned in superposed relationship with respect to reinforcing sheet 24. Batt layer 22 has substantially the same external dimensions as batt layer 20 and reinforcing sheet 24 and is substantially coterminous with reinforcing sheet 24.
Batt 22 is retained against movement relative to reinforcing sheet 24 and hence relative to batt layer 20, by the cooperative action of the interfiber frictional engagement of the fibers at the contacting surfaces of batt layer 22 and reinforcing sheet 24.
Several different types of materials may be used for facing layer 12, for example, the material ~'4255~

may be a nonwoven web made of a mixture of fibers consisting predominantly of inexpensive, short, cellulosic fibers suGh as short wood pulp fibers or cotton linters in amounts of 75 percent to 98 S percent, the balance being texti]e length fibers such as rayon as described in ~.S. Patent No. 3,663,348 to Liloia, et al.
Nonwoven materials suitable for use in the forming of facing layers of diapers of this invention can have fabric weights in the range of from about 0.5 to 5 ounces per square yard and densities of less than 0.15 g/cc., generally in the range of 0.05 to about 0.1 g/cc. the dry strength of the material for a fabric having a weight of about 1.5 ounces per square yard is at least 0.15 lbs. per inch of width in the machine direction and at least 0.1 lb. per inch of width in the cross direction. Such fabrics have good elongation, loft, softness, and drape characteristics.
Facing~ may also be made of an apertured nonwoven fabric which is formed, for example, in accordance with the teachings of commonly assigned U.S. Pat. Nos. 2,862,251; 3,081,514; and 3,081,515.
Furthermore, facings may also be made from other types of fabric such as those disclosed and described in U.S. Patent No. 3,485,706 to Evans. Such facings can be made of naturally occurring fibers, synthetic fibers or blends thereof. Typical diaper facings made of polyester type fibers may have a weight of about 0.7S ounces per square yard.
The facing may be the same size as, and coterminous with, the backing; or alternately, the facing may be wider than the backing and have its side edges inwardly folded so that the facing is coterminous wi~h the backing, as is shown in Fig. 3 ~242551 of U.S. Pat. NoO 3,612,055. In addition, facings may be made from non-apertured materials such as nonwoven isotropic webs or apertured polyolefin or polyester films having the desired moisture permeability. In all of the aforementioned facings, the materials should be relatively hydrophobic so as to retard wicking within the facing.
A suitable material for backing 16 of the diaper of the present invention can be an opaque polyolefin; for example, polyethylene about 0 001 inch thick. Another s~itable material for this purpose is polyethylene terephthalate having a thickness of about 0.005 inch.
Batt layers 20 and 22 are formed of loosely compacted short cellulose fibers, such as wood pulp fibers or cotton linters, or mixtures thereof which are primarily held together by interfibrous bonds requiring no added adhesive, as is known in the art.
Briefly, these batts are a low bulk density coherent web of loosely compacted cellulose fibers preferably comminuted wood pulp fiber in the form of so-called n f luf f n .
The term "short f ibers", as used herein refers to fibers less than about 1/4 inch in length, in contrast to "long fibers", or ~textile length fibers" which are longer than about 1/4 inch in length and generally between 1/2 and 2-1/2 inches in length.
Batt layers 20 and 22 may be formed as separate layers, and thereafter positioned in the above described relationship with respect to one another and with respect to reinforcing sheet 24.
Alternatively, batt layer 22 can be formed by direct fiber deposition on reinforcing sheet 24. In either event, the resulting composite laminate may be

2~51 lightly compacted to enhance the interfiber frictional engagement between the fibers of reinforcing sheet 24 and the fibers on the contacting surfaces of batt layers 20 and 22.
Reinfoecing sheet 24 includes expansion means 26 in the central portion thereof for accommodating expansion and contraction of the backing, facing and batt layers which occurs during application and wearing of the diaper 10. The expansion means 26 is located medially of the reinforcing sheet between solid end portions 28, 30.
Expansion means 26 is defined by a plurality or parallel rows of elongate slits 32 which are disposed perpendicularly with respect to the sides of the reinforcing sheet. When the diaper is initially manufactured, the reinforcing sheet 24 is stretched so as to partially open the slits 32. This accommodates shrinkage or contraction of the reinforcing sheet, which may occur during further manufacturing steps due to heat and/or moisture.
As is clear from Fig. 4, the slits 32 in adjacent rows are positioned in staggered, overlapping relationship with respect to one another. As a consequence, when the reinforcing sheet is extended, the expansion means 26 will form an open grid-llke structure defined by generally diamond shaped openings 34. The unslit fabric portion between openings 34 provide a multiplicity of hinges, which enable the sheet to flex and follow the movement of the facing, backing and batt layers.
Expansion of the sheet 24 will take place without tearing or r~pturing thereof, 60 that the sheet will continue to perform its reinforcing function. When the expanding force (indicated by directional arrow F
in Fig. 5) is released, the reinforcing sheet will ~24,255~

contract and return to the original unexpanded position of Fig. 4 where the slits are open about 25%
of the size of the fully expanded openings 34 shown in Fig. 5.
While the disposable diaper 10 illustrated in the drawing does not include elastic elements at opposite sides thereof, such diapers are well known for providing improved fit and sealing about the infant's legs. The reinforced panel with expansion means of the present invention is particularly adapted for use with such so-called "fitted diapersn. In use, the disposable diaper is applied to the baby by laying out the diaper on a single flat surface and placing the baby thereon. The waist underlying end of the diaper is that end having the fastener means and the other end of the diaper extends downwardly between the baby's legs. Next, the downwardly extending edge of the diaper is brought up between the baby's legs to a position covering the perineum and contiguous ~ith the front portion of the baby's waist. The diaper thereafter is secured to the baby by placing the corners of the waist portion of the abdomen covering end as far around the baby's waist as they will go and by bringing the corners of the underlying end of the diaper into an overlapping relationship with the aforementioned corners so that the diaper snugly encircles the baby's waist and provides a custom fit. The adhesive tape fasteners are then prepared for use and the diaper is secured in a desired position by simply urging the pressure-sensitive adhesive surface of the tape tab in contact with the adjacent outer surfaces of the opposite corner of the diaper.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An absorbent article comprising a first outer layer in the form of a moisture impervious backing sheet;
a second layer in the form of a multilayer absorbent pad means, said pad means being smaller than said first outer layer and spaced inwardly from the sides thereof, the pad means comprising a first cellulosic fibrous batt positioned in superposed relationship with respect to said first outer layer, a moisture pervious nonwoven fabric positioned in superposed relationship with respect to said first batt, and a second cellulosic fibrous batt positioned in superposed relationship with respect to said moisture pervious nonwoven fabric, said moisture pervious nonwoven fabric being adapted to provide reinforcement and structural integrity to the two layers of cellulosic fibrous batt between which it is dis-posed; and a third layer in the form of a moisture pervious facing sheet overlying the multilayer absorbent pad means.

2. The absorbent article of claim 1 wherein the mois-ture pervious nonwoven fabric includes means for expansion thereof when the moisture impervious backing sheet and the moisture pervious facing sheet are flexed, whereby the structural integrity of the two layers of cellulosic fibrous batt is maintained.

3. The absorbent article of claim 2 wherein the mois-ture pervious nonwoven fabric has said expansion means located centrally thereof.

4. The absorbent article of claim 3 wherein the expan-sion means comprises a plurality of openings such that when the ends of the moisture pervious reinforcement sheet are extended a reticulated grid type formation forms in the center portion of the reinforcement sheet.

5. The absorbent article of claim 4 wherein said expansion means comprises a plurality of uniform slits within the central portion of the moisture pervious nonwoven fabric, said slits being disposed in rows extending from side to side of said nonwoven fabric.

6. The absorbent article of claim 1 wherein the absor-bent article is a disposable diaper and wherein said moisture impervious backing sheet and moisture pervious facing sheet are substantially rectangular, the pad means having a substan-tially rectangular configuration and being disposed substan-tially symmetrically with respect to the backing sheet and facing sheet.

7. A substantially rectangular multilayer disposable diaper comprising a first outer layer in the form of a mois-ture impervious backing sheet; a first absorbent batt posi-tioned in superposed relationship with respect to the backing sheet and forming a second layer smaller than the backing sheet and spaced inwardly from the longitudinal side edges thereof; a third layer in the form of an expandable moisture pervious sheet means positioned in superposed confronting relationship with respect to the first batt layer on the side opposite the backing sheet, the expandable sheet means layer having generally the same dimensions as the first batt layer; a fourth layer in the form of a second absorbent batt positioned in superposed confronting relationship with respect to the expandable sheet means layer on the opposite side of the batt of the second layer, the second batt of the fourth layer having generally the same dimensions as the expandable sheet means; and a fifth outer layer in the form of a moisture pervious facing sheet positioned in superposed confronting relation with respect to the second batt of the fourth layer on the side opposite the expandable sheet means, the facing sheet having generally the same dimensions as the moisture impervious backing sheet, thereby providing marginal side portions around the perimeter of the diaper in which the backing sheet and the facing sheet are in contact with and secured to each other.

8. The disposable diaper of claim 7 wherein the expandable sheet means comprises non-woven material having expansion means located centrally of the longitudinal dimension thereof.

9. The disposable diaper of claim 8 wherein the expansion means comprises a plurality of openings such that when the ends of the expandable non-woven sheet are extended along the longitudinal dimension of the sheet, a grid-type formation forms in the center portion of the expandable non-woven sheet.

10. The disposable diaper of claim 9 wherein the expansion means comprises a plurality of uniform slits within the central portion of the expandable sheet means, said slits being disposed in rows spanning the transverse dimension thereof such that the slits of alternating rows are displaced defining a reticulated grid type formation including elongated six sided diamond apertures upon expansion of the ends of the expandable non-woven sheet in the longitudinal dimension.