CA1149103A

CA1149103A - Absorbent structure containing superabsorbent

Info

Publication number: CA1149103A
Application number: CA000390146A
Authority: CA
Inventors: Dennis C. Holtman
Original assignee: Johnson and Johnson Baby Products Co
Current assignee: Johnson and Johnson Professional Inc
Priority date: 1980-11-17
Filing date: 1981-11-16
Publication date: 1983-07-05
Also published as: ZA817934B; PT73993A; ES267711Y; BR8107129A; MY8500942A; GB2087731A; DE3145400C2; ES267712Y; ES267711U; AU549283B2; NZ198896A; GB2087731B; ES267713Y; ES269736Y; GR68170B; AU7750981A; ES269736U; DE3145400A1; ES267712U; US4333463A

Abstract

Absorbent Structure Containing Superabsorbent Abstract of the Disclosure The present invention provides an absorbent structure for body fluids comprising a moisture-impermeable backing, an absorbent batt superimposed thereon and a moisture-permeable cover covering at least the side of the batt opposite the backing sheet. The absorbent batt contains a reservoir capable of receiving at least 75% of the discharge of body fluid in one second.
The reservoir is located in the void zone, is formed by compression of the fibers and contains superabsorbent deposited therein.

Description

Absorbent Structure Containinq Superabsorbent B grouncl of the Invention Disposable absorbent structures such as clisposable diapers, sanitary napkins and incontinence pads have met with increased commercial acceptance in recent years primarily because of their convenience. Many different constructions have been proposed and used and some have ' met with wide-spread commercial success in spite of certain inadequacies in functional propertie.s.

One of the most serious prior art problems has been the inability to provide a suitable construction that can accept alarge void of body fluids. This is particularly true of the incontinent whether the incontinent be active and working or ill and bedridden. Various attempts have been made to provide special structures to absorb a large body fluid void. These include U.S. Patent 3,441,024 to H. J. Ralph, U.S. Patent 3,747,602 to H. J.
Ralph, U.S. Patent 3,968,798 to H. C. Hokanson and U.S.
Patent 4,067,366 to R. L. Johnson. While these various constructions were designed to assist the adult incontinent, the problem of providing an overall absorbent structure which will handle a full volume discharge of urine without leakage and retain the discharge still remains.

Whether the incontinent be an adult or infant, disposable structures generally have not accepted and held a full volume discharge of urine without leakage onto clothing.
Similarly, the sanitary napkin shown in the art will not necessarily hold a full volume discharge of menstrual fluid. The present invention provides an absorbent ~,~

-2- JBP 19 structure ~hich may be used as an infant diaper, an adult incontinence device, a sanitary napkin, an incontinence pad, or the like.

Summary of the Invention The present invention provides ~n absorbent structure to receive and contain body fluids comprising a loosely-compacted, cellulosic fibrous batt having a moisture-impermeable backing sheet on one side and a fabric coverwhich covers at least the side of the absorbent batt opposite the backing sheet on the o~her side. The absorbent batt is provided ~ith a reservoir which has a capacity to hold at least 75~ of the body ~luid discharged in one second. Tlle reservoir is situated in the void zone, is formed by compression of the cellulosic fibers in that zone, and contains a dry solid water-swellable, water-insoluble absorbent composition.

The absorbent structure may be incorporated in a disposable diaper such as or an infant or in an adult diaper l~ith a larger liquid holding capaci~y. Furthermore, the absorbent structure may be incorporated in a sanitary - napkin as well as in an incontinence pad. In each instance, the opening of the reservoir is placed in the void zone allowing immediate acceptance by the reservoir of the body fluid discharge. Cenerally the discharge capacity of the reservoir will be a~ least 10 cc.

The reservoir is created by compression of the loosely-compacted, cellulosic fibers in the reservoir area. The compaction may be carried out by application of pressure

-3- JBP 194 in the sllape desired or tlle reservoir. This may be done by a stamping-type operation or by an embossing roll or ; the like.

Brie~ Description of the Drawings FIG. 1 is a perspective view of one embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line 2--2 of the embodiment of FIG. l;

FIG. 3 is a top vie~ of another embodiment of the present invention;
FIG. 4 is a ~op view of still another embodiment of tlle present invention;

FIG. 5 is a perspective view of a disposable di~per 2U utili7.ing the absorbent structure of the present invention;

FIG 6 is a perspective vie~ of a sanitary napkin incorpor-ating the absorbent structure of the presen~ invention;

FIG. 7 is a cross-sectional vie~l taken along line 7--7 of FIG. 6.

D _ ailed Description of the Invention l~hile this invention is susceptible of embodiment in many different forms, there is sho~n in the drawings,and herein ~ill be described in detail, preferred embodiments of tlle invention and modifications thereof. It is understood that ~ - JBP 194 the presen~ disclosure is to be considered as an exemplifi-cation of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. The scope of tlle invention ~ill be pointed out in the appended claims.

Reerring to the drawings,and particularly to FIG. 1, an absorbent structure 10 is provided with a reservoir 12 lyin~ below the cover 13. The cover is a moisture-permeable non-~oven abric. PIG. 2 shows the absorbent structure of FIG. 1 in cross-sectional viel~ along line 2--~. The moisture-permeable e~terior cover 18 completely wra~s the absorbent structure. A moisture barrier 16 which is a moisture-impermeable backing sheet covers the lS bottom areas as well as both sides of the structure.
Immediately adjacent the cellulosic batt 22 is a wrap of tissue 14~ It may not be necessary to llave a tissue ~rapping the cellulosic batt, but if the cellulosic batt is quite thick, such as an inch or more, it may be desirable to provide a tissue wrap to assist with mainten-ance of the desired sh~pe of the absorbent structure.
The cellulosic fibrous batt 22 is provided l~ith a reservoir 20 and a densified fibrous region 24. The reservoir 20 contains a water-swellable, water-insoluble absorbent composition 28. The surface of the fibrous batt containing the opening of the reservoir 20 is placed toward the wearer with the opening in the void ~one.
A re'ease liner 26 is removed to expose adhesive so as t~
secure Lhe structure to the underwear of the l~earer.
FIGS. 3 and 4 are top views of typical cellulosic batts used in the absorbent structure of the invention. The cellulosic batt 30 contains ~ reservoir 32 having the ~9~3 shape of a rectangle. The reservoir may be located nearer one end of the cellulosic batt 30~ e.g., one-third of the way or bet~een the center and end to assist in location in the void zone of the wearer. In FIG. 4, a cellulosic b~tt 40 is provided with the res~rvoir 42 having an oval shape. Any desired shape and si7e may be used so long as the reservoir covers at least one square inch of surface and contains at least 10 cc in volume.

Referring now to FIG. 5, a disposable diaper 50 is sho~n having a mois~ure-impermeable backing sl~eet 52. Super-imposed upon the backing sheet 52 is a loosely-compac~ed cellulosic ~ibrous batt 54. The fibrous batt contains a reservoir 56 created by compression or compac~ion of the fibers in that region. ~ithin the reservoir are contained particles of a superabsorbent 28. The cellulosic batt 54 is covered by a moisture-permeable facing 58 Qf non-woven fabric. The facing and backing are adhered in the margin region. In addition glue lines 57 are used to secure the fibrous ~att to the backing. Tape tabs 59 are provided to secure the diaper~about the wearer.

Referring now to FIGS. 6 and 7, a sanitary napkin 60 is depicted. The cover 6? shown in FIG. 6 is a moisture-permeable non-woven fabric. FIG. 7 is a cross-sectional view taken along lines 7--7 of FIG. 6. A cellulosic fibrous batt 64 is partially surrounded by a moisture barrier 70. The entire structure is wrapped in the moisture-permeable cover 72. The cellulosic batt 64 contains a reservoir 66. Withill the reser~oir 66 are superabsorbent particles 67. At the bottom o~ the reservoir is a dense fibrous area 68. The dense fibrous area 6S is created when ~he reservoir 66 is formed.

!

The loosely-compacted, cellulosic fibrous batt used in the absorbent structure of the present invention is formed from wood pulp fibers J rayon fibers, or cot~on lin~ers, or mi~tures thereof. The bat~ is primarily held together by S interfiber bonds requiring no added adhesive. In some instances, the batt may con~ain synthetic fusible fibers, such as polyethylene, polypropylene and the like. The batt is a low bulX density coherent web of loosely-compac~ed, cellulosic fibers preferably comminuted wood pulp fibers in the form of so-called "fluf." The reservoir in the cellulosic batt is created by compressing the portion o t~le batt which it is desired to become a reservoir. The compression should be suf~icient to create a reservoir, suf~icient depth to hold a~ least 10 cc.
The base of the reservoir is a densified fibrous region wherein the fibers are compacted. The densi~ied region quic'.~ly absorbs the body fluid and commences distribution of the flui~ to other parts of the cellulosic batt.
In addition, it may be desirable to provide a paper-like densified layer on the side of the batt opposite the reservoir which receives the original discharge. The paper-like densified layer is formed by a slight moistening of the surface of the batt followed by li.ght compaction using the application of pressure. U. S. Patent 3,017,304, Burgeni, provides such a densified layer in a loosely-compacted, cellulosic fibrous batt.

The cover or facing provided on the absorbent structure of the present invention is a non-woven fabric having a high degree o~ moisture-permeability. For e~ample, the fabric may be polyester, polyet}~ylene, polypropylene~ nylon, rayon or the lik~. Preferably the fabric used for the cover is a light~ei~ht fabric in the range of 0.3 - 5.0 oz. per square yard and Wit}l a density l~ss than ~9~3 0.2 gms/cc. The most suitable fabrics have unusually high elongation, lo~t~ softness and drape characteris~ics.
Though the cover is moisture-permeable, it is preferably of the type which after permeation o the moisture, prevents strike-back of the body fluid when the absorbent structure is approaching saturation.

The body of the cellulosic fibrous batt is substantially more wettable than the cover and tends to draw liquid a~ay from the facing layer. Thus the void occurs and the cover is permeated and the liquid deposi~ed in the reser~oir. The individual fibers of the batt are extremely wettable and thus draw the liquid into the fibrous batt.
The base of the reservoir is a densified fibrous region wherein the capillary radius is quite small. Thus the capillary pressure is increased and the liquid is rapidly distributed to por~ions of the cellulosic batt. The densified fibrous region a~ the base of the reser~oir provides Lhe ma~imum capillary pressure because it combines the very lo~ contact angle of the fibers of the batt with the high density of the densified fibers.

The individual fibers of the batt are e~tremely wettable, generally having liquid-fiber contact angles below about 15 and approaching zero in the optimum embodiment.
The wickability or preferential absorptivity of the body of the batt for water is limited, however, by its low density which results in large effective capillary radius for the capillaries be~ween adjacent fibers.

-8- J~P 194 The pressure causin~ a liquid to enter a cylindrical capillary is expressed by the equation 2~ cos P = r wherein P is the capillary pressure~
~-is the surface tension o~ the liquid, ~ is the liquid-fiber contact angle, and r is the capillary radius.

~iith a given liquid, tlle pressure (capillary force) increases -~ith the cosine of the liquid-fiber contact angle ~reaching a ma~imum where the angle is zero) and increases with narrower capillary radii so that narrower capillaries will dra~ liquid from wider ones.

The relative wickability between the cover layer and the body of the fibrous batt is affected by both the rela~ive densities of the layers and the relative wet~ability of the individual fibers in each layer. The individual fibe~rs of the batt ha~e substantially smaller liquid-- fiber contact angles than those of the cover layer overcoming the density difference and providing a substantial overall increase in c~pillary pressure to 2S absorb liquid into the body of the batt.

A densified fiber layer such as that at the base of the reser~oir provides the ma~imum capillary pressure because it combines the very lo~ contact angle of the fibers of the batt ~ith the hiah density ~small capillary radius) of the densified fibers.

9 JBP 19~
Thus ~hen urine is voide~ in~o an area in the cover layer, it partially wets a small portion of the cover layer and is passed through the covcr layer almost instantaneously to the first reservoir. In the first reservoir, the - 5 liquid comes into contact with ~lle body of the ba~t and the densifie~ reaion surro~lndin~ the reservoir. It- is preferentially absorbed into ,he densi~led region because of its small capillary structure and then into the body of the batt because of the enhanced wettability of the walls of the reservoir. The body fluid then passes througll the d~nsified region and into the second reservoir whereupon the superabsorbent particles begin ~heir absorption of the liquid. The absorbent structure performs in t~le s~ne manner ~hether the body fluid is urine, a menstr~lal fluid, or other liquid e~udate.

The superabsorbent particles are generally a dry solid water-s~ellable, ~ater-insoluble absorbent composition such as an ionic complex of a water-soluble anionic poly-electrolyte and a polyvalent metal cation. Typical super-absorbent compositions are illustrated in U. S. Patent

4,090,013 to S. H. Gansla~ et al and U. S. Pa~ent 4,0~,957 to S. H. Gansla~ et al. The superabsorbent may be in the form of individual particles or strips of ~ilm to l-~hich superabsorbent is adhered ~o other kno~n superabsorbent compositions. The superabsorbent may be affi~ed to the base o~ the superabsorbent reservoir or may si~ply lie independently ~iithin the reser~roir.

It ~ill be understood by those skilled in the art that variations and modifications of ~he specific embodiments described above may be employed without ~eparting from the spirit and scope of the inv~ntion as defined in the appended claims.

Claims

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

1. An absorbent structure suitable for absorption of body fluids comprising a moisture-impermeable backing sheet; an absorbent, loosely-compacted cellulosic fibrous batt, superimposed on said backing sheet; and a moisture-permeable fabric cover, covering at least the side of said absorbent batt opposite said backing sheet, said absorbent batt being provided with a reservoir having a capacity sufficient to hold at least 75% of the body fluid discharged in one second and containing deposited wherein a water-swellable, water-insoluble absorbent composition, said reservoir being situated in the void zone and being formed by the compression of the cellulosic fibrous batt.

2. The absorbent structure of Claim 1 wherein the reservoir is created by a depression in the fibrous batt and has a capacity of at least 10 cc.

3. The absorbent structure of Claim 1 wherein the base of the reservoir is a densified region of the fibers of the fibrous batt.

4. The absorbent structure of Claim 1 wherein the reservoir is located between the center and one transverse end of the absorbent structure.

5. The absorbent structure of Claim 1 wherein the capacity of the reservoir is sufficient to hold at least 90% of the body fluid discharged in one second.

6. An adult incontinence device substantially rectangular in shape comprising a moisture-impermeable backing sheet;

an absorbent,loosely-compacted cellulosic fibrous batt superimposed on said backing sheet; and a moisture-permeable fabric cover, covering at least the side of said absorbent batt opposite said backing sheet, said absorbent batt being provided with a reservoir covering at least one square inch of the surface of the batt and having a capacity of at least 10 cc and containing deposited therein a water-swellable, water-insoluble absorbent composition, said reservoir being situated in the void zone and being formed by compression of the cellulosic fibrous batt.

7. The adult incontinence device of Claim 6 wherein said backing sheet is provided with an adhesive strip for securement of the device when worn.

8. A disposable diaper comprising a moisture-impermeable backing sheet; an absorbent, loosely-compacted cellulosic fibrous batt, superimposed on said backing sheet; and a moisture-permeable facing superimposed on the side of the fibrous batt opposite said backing sheet, said absorbent batt being provided with a reservoir having capacity sufficient to hold at least 75% of the body fluid discharged in one second and contained deposited therein a water-swellable, water-insoluble absorbent composition, said reservoir being situated in the void zone and being formed by compression of the cellulosic fibrous batt.

9. The disposable diaper of Claim 8 wherein the reservoir has as its base a densified region and has a capacity of at least 10 cc.

10. A sanitary napkin containing a moisture-permeable outer layer containing an absorbent, loosely-compacted cellulosic fibrous batt, said absorbent batt being provided with a reservoir having a capacity sufficient to hold at least 75% of the body fluid discharged in one second and containing deposited therein a water-swellable, water-insoluble absorbent composition, said reservoir being situated in the void zone and being formed by compression of the cellulosic fibrous batt.

11. The sanitary napkin of Claim 10 wherein the base of the reservoir is a densified region of the fibers of the fibrous batt.