CA1185051A

CA1185051A - Absorbent structure with reservoir

Info

Publication number: CA1185051A
Application number: CA000390029A
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: 1981-11-13
Publication date: 1985-04-09
Also published as: ES267716Y; ZA817932B; MY8600143A; AR242710A1; AU7750781A; ES269737Y; PT73994A; ES267715U; NZ198895A; ES267714U; ES267715Y; GR68172B; ES269737U; GB2087730A; AU549282B2; BR8107160A; GB2087730B; ES267716U; DE3145398A1; ES267714Y

Abstract

Absorbent Structure with Reservoir Abstract of the Disclosure The present invention provides an absorbent structure comprising a moisture-impermeable backing, an absorbent batt and a moisture-permeable cover covering at least the side opposite the moisture-impermeable backing. The absorbent batt is of loosely-compacted, cellulosic fibers and contains a reservoir capable of receiving at least about 75%
of the body fluid discharged in one second. The reservoir is formed by compression of the fibers in the reservoir zone.

Description

s~

~bsorbent Struc e with Reservoir Background of the Invention Disposable absorbent structures such as disposable 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 ~lith wide-spread commercial success in spite of certain inadequzcies in functional properties.
One of the most serious prior art problems has been the inability to provide a suitable construction that can accept a large void of body fluids. This is particularly true of the adult incontinent whether the incontinent be active and l~orking 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 3,968,79~ to ~. C. Hokanson, and U. S Patent 4,067,366 to R. L. Johnson. I~'hile these various constructions were designed to assist the adult incontinent, the problem of providing an overall absorbent structure which ~ill handle a full volume discharge of urine without leakage s,ill remains.
Whether the incontinent be an adult or an infant, disposable structures generally have not accepted and held a full volume discharge of urine without leakage onto clothingr Similarly, the sanitary nap~ins known in the art will no~
necessarily hold a full volume dischar~e o F menstrual fluid. The present invention provides an absorbent structure which may be used as an infant diaper, an adult incontinence device, a sanitary napkin, an incontinence pad, or the like.

~ummary o the Invention The present invention provides, froln one of its broad S aspects, an absorbent structure suitable for absorption of body fluids and comprising a moisture-impermeable backing sheet. An absorbent, loosely-compacted, cellulosic fibrous bat-t is su~erimposed on the backing sheet. A moisture-permeable fabric ~over covers at least the side of the absorben-t batt opposite the backing sheet. The absorbent batt is provided with a reservoir having a capacity of at least 10 cc and covers at least one square inch of surface.
The reservoir is situated in a void zone between the center and one transverse end and ls formed by compression of -the cellulosic fibrous batt.

The absorbent structure may be incorporated in a disposable diaper such as for an infant or in an adult diaper with a larger liquid holding capacity. 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.
Generally, the discharge capacity of the reservoir will be at 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 in the shape desired for the reservoir. This may be done by a stam,oing-type operation or by an embossing roll or the like.

35~

-i- JBP 191 rief Descrip~ion of the Drawings FI~. 1 is a perspective view of one embodiment o~ 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 view of another embodiment of the present ln invention;

FIG. 4 is a top view o still another embodiment of the present invention;

FI~. 5 is a perspective view of a disposable diaper utilizing the absorbent structure of the present invention;

FIG. 6 is a perspecti~e view of a sanitary napkin incorpor-ating the absorbent structure of the present invention; and FIG. 7 is a cross-sectional view taken along line 7--7 of ~IG. 6.

Detailed Description of the Invention l~ile this invention is susceptible of embodiment in many different forms, there is shown in the dra-~in~s, and herein will be described in detail~ preferred embodiments of ~he invention and modifications thereof. I~ is understood th;t the present disclosure is to be considered as an e~emplifi-cation of the principles of the invention and is not in~ended to limit the invention to the embodiments illustrated. The scope of the invention will be pointed out in the appended claims.

5~S~L

Referrin~ to the dra~ings and particularly to FIG. 1, an absorben-t structure 10 is provided with a reservoir 12 lying belo~ the cover 13. The cover is a moisture-permeable non--~oven fabric. FIG. 2 shows the absorbent S structure of FIG. 1 in cross-sectional vie~ along line 2--2.
The moisture-per~eable exterior cover 18 completely ~raps the absorben~ structure. A moisture barrier 16 ~hich is a moisture-impermeable backing sheet, covers the bottom area 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 have a tissue wrapping 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 maintenance of the desired shape of the absorbent structure. The cellulosic fibrous batt 22 is provided with a reservoir 20 and a densified fibrous region 24. the surface of the fibrous ba~t containing the opening of the reservoir 20 is placed toward the wearer with the opening in the void zone.
release liner 26 is re~oved to expose adhesive so as to secure the structure to the underwear of the ~earer.

FIGS. 3 and 4 are top views of typical cellulosic bat~s used in the absorbent structure of the invention. The cellulosic batt ~0 contains a reservoir 32 having the shape of a rectangle. The reservoir may be located nearer one end of the cellulosic batt sO, e.g., one-ti~ird of the way, or between the center and end, to assist in location in the ~oid 70ne of the wearer. In FIG. 4 a cellulosic batt 40 is provided with a reservoir ~2 having an oval sllape. Any desired shape and size may be used so long as the reservoir covers at least one square inch of surface and contains at least 10 cc in volume.

5 ~
-5- J~P 191 Referrin~ now to FIG. 5, a disposable diaper 50 is shown ha~ing a moisture-impermeable backing sheet 52. Super-imposed upon the backing sheet 52 is a loosely-compacted, cellulosic fibrous batt 54. The fibrous batt contains a reservoir 56 created by compression or compaction of the fibers in ehat re~ion. The cellulosic batt 54 is covered by a moisture-permeable facing 58 of non-woven fabric.
The facin~ and the backing are adhered in the margin regions. In addition, glue lines 57 are used to secure the fibrous batt to the backing. Tape tabs S9 are provided to secure the diaper abowt the wearer.

Referring now to ~IGS. 6 and 7, a sanitary napkin 60 is depicted. The cover 62 shown in FIG. 6 is a moisture-permeable non-woven fabric. FIG. 7 is a cross-sectional view taken along line 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 6~
contains a reservoir 66. At the bottom of the reservoir is a dense fibrous area 6S. The dense fibrous area 68 is created when the reser~oir 66 is formed.

The loosely-compacted, cellulosic fibrous batt uscd in the absorbent structure of the present invention is formed from wood pulp fibers, rayon fibers, or cotton linters, or mixtures thereof. The batt is primarily held together by interfiber bonds requirin~ no added adhesive. In some instances, the batt may contain synthetic fusible fibers, such as polyethylene, polypropylene and the like. The batt is a low bulk density coheren~ web of loosely-compac~ed - cellulosic fibers pre~erably comminuted wood pulp fibers in the form of so-called '7fluff."

x~

lhe reservoir in the ccllulosic batt is creatcd by compressing the portion of the batt ~hich it is desired become a reservoir. The compression should be sufficient to create a reservoir of suEficient depth to hold at least 10 cc. The base of the reservoir is a densified fibrous region l~herein the fibers are compacted. The densified region quickly absorbs the body fluid and commences distribution of the fluid 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. The paper-like densified layer is formed by a slight moistening of the surface of the batt follo~ed by light 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 provided on the absorbent structure of the present invention is a non-woven fabric having a high degree of moisture permeability. For e~ample, the fabric may be polyester, polyethylene, polypropylene, nylon~
rayon, or the like. Preferably, the fabric used for the cover is a light~eight fabric in the range of 0.3 to 5.0 oz. per square yard and ~ith a density less than 0.2 gms/cc. The most suitable fabrics have unusually high elongation, loft, softness and drape characteristics.
Though the cover is moisture^permeable, it is preferably of ~he type which after permeation of the moisture, prevents strike-bac~ of the body fluid when the absorbent structure is approachina saturation.

5(~S~

The body of the ce~ losic Eibrous ba~t is substantially more wettable than the cover and tends to draw liquid away from the facing layer. Thus the void occurs and the cover is permeated and the liquid deposi~ed in the reservoir. 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 wher~n the capillary radius is quite small. Thus the capillary pressure is increased and ~he liquid is rapidly distributed to portions of ~he cellulosic batt. The densified fibrous region at the base of the reservoir provides the ma~imum capillary pressure because it combines the very low contact angle of the fibers of the batt with the high density of the densified fibers.
The individual fibers of the batt are extremely wettable, generally having liquid-fiber contact angles below about 15 and approaching zero in the optimum embodiment. The wickability or preferential absorptivi~y of the body of the ba~t for water is limited, however, by its low density which results in large effective capillary radius for the capillaries between a~jacent fibers.

The pressure causing a liquid to enter a cylindrical capillary is e~pressed by the equation

2~cos p _ r wherein P is the capillary pressure, 30 ~' 3.5 the surface tension of the liquid, ~ is the liquid-fiber contact angle, and r is the capillary radius.

^LI ~S~5il l~ith a given liquid, the pressure (capillary force) increases with thc cosine of the liquid-fiber contact angle (reaching a ma~imum where thc angle is zero) and increases with narrower capillary radii so that narrower capillaries will draw liquid from wider ones.

The relative wickability be~ een the cover layer and the body of the fibrous batt is affected b;- both the relative densities of the layers and the relative wettability of the individual fibers in each layer. The individual fibers of the batt have substantially smaller liquid-fiber contact angles than those of the cover layer overcoming the density difference and providing a substantial overall increase in capillary pressure to absorb liquid into the body of the batt.

A densified fiber layer such as that at the base of the reservoir provides the maximum capillary pressure because it combines the very low contact angle of the fibers of the batt with the high density (small capillary radius) of the densified fibers.

Thus when urine is voided into an area in the cover layer, it partially wets a small portion of the cover layer and is passed through the cover layer, almost instantaneously, to the reservoir. It then comes into contact Wit]l the body of the batt surrounding the reservoir and is preferentially absorbed into the body of the batt because of the enhanced wettability of the reservoir and particularly the base of the reservoir. The same is true when the body fluid is a menstrual Lluid or other liquid exudate.

It .~ill be understood by those s~illed in the art that variations and modifications of the speciEic embodiments described above may be employed without departin~ from the spirit and scope of the invention as defined in the S appended claims.

SUPPLEMENTARY DISCLOSURE

In the principal disclosure there is described and claimed an absorbent structure wherein an absorbent batt of loosely-compacted, cellulosic fibers is provided with a reservoir having a discharge capacity of at least 10 cc. It has now been found that in a preferred embodiment of the present invention the reservoir should not cover more than 25% of the surface of the absorbent batt and should have a depth of more than one-half the thickness of the absorbent batt.

The reservoir of the present invention is formed by compres-sion of the fibers in the reservoir ~one and is located so that the product, when worn, re-tains the proper shape. The absorbent structure receives and contains body fluids, particularly urine.

In one of its embodiments the absorbent batt is substan-tially rectangular in shape and is provided with a reservoir which (1) has a capacity of at least 10 cc, (2) which covers at least one square inch of surface, (3) which is situated between the center and one transverse end of the substan-tially rectangular absorbent batt, (4) which covers less than about 25% of the surface area of the absorbent batt, and (5) is formed by compression OI the cellulosic fibrous batt so that the depth of the reservoir is more than half the thickness of the absorbent batt.

In U.S. Patent No. 4,184,498, there is provided a sanitary napkin which by its appearance would seem to be a structure which might be used for the deposit of urine and the containment thereof. It has been found, however, that a single depression such as is provided by the patent extend-ing substantially the length of the structure does not contain a substantial discharge of urine when being worn in place. This is because the structure folds on the depression the entire length of the structure and fails to provide a substantial reservoir whic'n retains its shape and consequently high volume of discharge. The single reservoir provided by the present invention does not permit the folding or collapse of the central portion behind the reservoir in such a way that liquid could leak. Instead, the reservoir of the present invention, as it is defined above, provides an absorbent structure which retains the reservoir substantially in its originally shaped state when the product is being used so that the entire absorbent structure is available for proper use without collapsing or folding to permit leakage. The absorbent structure of the present invention, when utilized either in a diaper-type structure or in a simple pad-type structure when worn between the legs of the wearer, attains a boat-like shape due to the compression on each side near -the reservoir caused by the legs of the wearer. This boat-like shape keeps the reservoir available for substantially all of its holding capacity and keeps the ends and sides of the pad in a position such that leakage does not occur.

According to a broad aspect of the present invention there is provided an absorbent structure suitable for absorbtion of body fluids comprising a moisture-impermeable backing sheet. An absorbent, loosely-compacted, cellulosic fibrous batt is superinposed on the backing sheet. A moisture-permeable fabric cover covers at least the side of the absorbent batt opposite the backing sheet. The absorbent batt is provided with a reservoir having a capacity of at least 10 cc and covers at least one square inch but does not cover more than 25% of the surface of the absorbent batt. The reservoir is situated between the center and one transverse end and is fonned by compression of the cellulo~
sic fibrous batt such that the depth of the reservoir is more than one-half the thickness of the absorbent batt.

Generally, -the discharge capaci-ty of the reservoir is sufficient to hold at least 75% of the urine discharged in one second.

In the drawings supported by the Supplem~ntary Disclosure FIGURE 8 is a cross-section view taken across the reser-voir provided with an absorbent batt.

As can be seen in Figure 8, there is shown an absorbent batt 22 provided with a reservoir 20 therein. A moisture-permeable exterior cover 18 completely wraps the absorbent structure. A moisture barrier 16, which is a moisture-impermeable backing sheet, covers the bottom area 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 have a tissue wrapping 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 maintenance of the desired shape of the absorbent structure. The cellulosic fibrous batt 22 is provided with a reservoir 20 and a densified fibrous region 24. The surface of the fibrous batt containing the opening of the reservoir 20 is placed toward the wearer with the opening in the void zone. A release liner 26 is removed to expose adhesive so as to secuxe the structure to the underwear of the wearer. The reservoir does not cover more than 25% of the sur~ace and the depth thereof is more than one-half the thickness of the uncom~ressed batt. This structure may be used as a urine pad or an incontinence pad.

It is also pointed out that the cover provided on the absorbent structure may also be a film ~lich is perforated or non-continuous. Also, the individual fibers of the batt are extremely wettable and may have liquid-fiber contact angle~ below about 30 and approaching 20 in the optimum embodiment. The wickability or preferential absorptivity of the body of the batt for water is limited, however, by lts low density which results in large effective capi-llary radii for the capillaries bet~een adjacent fibers.

Claims

The embodiments of the invention in which an exclusive property or privilege 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 of at least 10 cc and covering at least one square inch of surface, said reservoir being situated in a void zone between the center and one transverse end and being formed by compression of the cellulosic fibrous batt.

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

3. An adult incontinence device substantially rect-angular 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 capa-city of at least 10 cc, said reservoir being situated in a void zone between the center and one transverse end and being formed by compression of the cellulosic fibrous batt.

4. The adult incontinence device of claim 3 wherein said backing sheet is provided with an adhesive layer which functions as an adhesive strip for securement of the device when worn.

5. 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 a capacity of at least 10 cc and covering at least one square inch of surface, said reservoir being situated in a void zone between the center and one transverse end and being formed by compression of the cellulosic fibrous batt.

6. A sanitary napkin comprising a moisture-permeable outer layer containing an absorbent loosely-compacted cellulosic fibrous batt, said absorbent batt being provided with a reservoir having a capacity of at least 10 cc and covering at least one square inch of surface, said reservoir being situated in a void zone between the center and one transverse end and being formed by compression of the cellu-losic fibrous batt.

7. The sanitary napkin of claim 6 wherein the base of the reservoir is a densified region of the fibers of the fibrous batt.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

SD8. 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 of at least 10 cc, covers at least one square inch but does not cover more than 25% of the surface of said absorbent batt, said reservoir being situated between the center and one trans-verse end and being formed by compression of the cellulosic fibrous batt such that the depth of said reservoir is more than one-half the thickness of said absorbent batt.

SD9. The absorbent structure of claim 8 wherein the base of said reservoir is a densified region of the fibers of the fibrous batt.

SD10. An adult incontinence device substantially rect-angular 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 but not more than 25% of the surface and having a capacity of at least 10 cc, said reservoir being situated between the center and one transverse end of the absorbent batt and being formed by compression of the cellulosic fibrous batt to provide a depth more than one-half the thickness of the absorbent batt.

SD11. The adult incontinence device of claim 10 wherein said backing sheet is provided with an adhesive layer which functions as an adhesive strip for securement of the device when worn.

SD12. A disposable diaper comprising a moisture-imper-meable 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 covering at least one square inch of the surface of the batt but not more than 25%
of the surface and having a capacity of at least 10 cc, said reservoir being situated between the center and one trans-verse end of the absorbent batt and being formed by compres-sion of the cellulosic fibrous batt to provide a depth in the reservoir of more than one-half the thickness of the absorbent batt.

SD13. The disposable diaper of claim 12 wherein the reservoir has as its base a densified fibrous region.