WO1986002543A1

WO1986002543A1 - Multi-layered absorbent products

Info

Publication number: WO1986002543A1
Application number: PCT/US1985/002178
Authority: WO
Inventors: James G. Mitchell; Winalee G. Mitchell; Robert E. Strauss; Richard L. Jacobs
Original assignee: Tranquility Products International, Inc.
Priority date: 1984-11-02
Filing date: 1985-11-01
Publication date: 1986-05-09
Also published as: EP0200784A1

Abstract

A multi-layered disposable product (10, Fig. 1) comprises, in combination, a liquid-pervious body-contacting layer (11), a tissue layer (19), a layer (18) of a liquid-absorbing layer, a fluff layer (17), and a water impervious layer (16). The fluff layer (17) and the liquid absorbent layer (18) are disposed between the tissue layer (19) and the water impervious layer (16). The layer (18) of liquid-absorbent composition comprises means (represented by dots on the layer (18)) comprising a cross-linked acrylic polymer or a cross-linked acrylic copolymer which is operable to absorb at least 20 ml per g of a 1 percent by weight aqueous NaCl solution and is positioned between the fluff layer (17) and the tissue layer (19).

Description

I

MULTI-LAYERED ABSORBENT PRODUCTS

1. Cross Reference to Related Application

This is a continuation in part of United St ates application Se rial No . 667 , 811 , f iled November 2 , 1984 , for "MULTI-LAYERED ABSORBENT PRODUCTS" Definition

The terms "percent" and "parts " , as used he rein and in the appended claims , ref e r to percent and parts by weight , unless otherwise indicated .

2. Field of the Invention

This invention relates to multi-layered absorbent products, for example, diapers, which contain a superabsorbent composition. The absorbent product comprises a liquid pervious body-contacting layer, a liquid impervious layer and one or more liquid absorbent layers therebetween.

3. Description of the Prior Art

U.S. Patent No. 4,144,886, granted March 20, 1979 to Arno Hoist et al. discloses an absorbent laminate comprising a first absorbent layer, preferably, a cellulose flock layer, and a tissue layer which has a coating of an absorbent carbohydrate derivative on at least one surface and a body-contacting layer comprising fleece. The tissue layer is positioned between the fleece and the cellulose flock layer. According to the reference, the ' carbohydrate derivative comprises cross-linked cellulose ethers or starch grafted with acrylonitrile and subsequently saponified.

U.S. Patent No. 3,888,256, granted June 20, 1975 to Hanβ Studinger discloses a layered absorbent pad compris ing an absorbent layer disposed between upper and lower surface layers. According to the reference , the absorbent layer may comprise -a particulate swelling . subs tance adhered to a liquid-pervious carrier or support sheet;. The only swelling substances disclosed by the reference are- polyacrylamide and sulfonated polystyrene. An essential feature of the invention disclosed by this reference is that the particles of swelling substance are distributed on the carrier sheet such that they are spaced from one another a distance less than one-half the increase in diameter which occurs upon swelling thereof .

A coramercllly available diaper which was sold under the trade designation "Depends" prior to November 2, 1984, comprised a water imp ervious layer which , in lite, was positioned away from the wearer' s body, a layer of tissue which carried a water swellable substance and a fluff layer, in the recited order . The diaper further comprised an envelope composed of a water pervious , non- woven material. A more recent diaper sold under the indicated trade designation comprises a water impervious layer which, in use, is positioned away from the wearer' s body and a fluff layer which , on its s ide adjacent the water impervious layer -'.as as s embled in the f inal product, is impregnated with - -water swellable substance. SUMMARY OF THE INVENTION The instant invention is based upon the discovery of an improved multi-layered disposable product comprising a liquid pervious body-contacting layer, a fluff layer, at least one layer of a tissue having a liquid-absorbent composition thereon and a water impervious layer. According to the invention, the tissue layer is positioned between the body-contacting layer and the fluff layer. Also in accordance with the instant invention, the liquid-absorbent composition is a superabsorbent polymer or copolymer consisting of a cross-linked acrylic polymer, a cross- linked acrylic copolymer or a carboxymethyl cellulose polymer. A preferred superabsorbent is a water-absorbing resin produced by polymerizing (1) at least one unsaturated monomer which has a single polymerizable double bond and which is water soluble or becomes water soluble by hydrolysis, and (2) a cross-linking agent, and, if the unsaturated monomer (1) is one which becomes water soluble by hydrolysis, thereafter subjecting the resulting product to hydrolysis. Another preferred superabsorbent is a water-absorbing resin produced by polymerizing (1) at least one of natural starch and alpha starch, (2) at least one monomer which has a single polymerizable double bond and which is water soluble or becomes water soluble by hydrolysis, and (3) a cross-linking agent, and, if the monomer (2) is one which becomes water soluble by hydrolysis, thereafter subjecting the resulting product to hydrolysis. A particularly preferred, superabsorbent comprises a blend of water-absorbing resins consisting of at least one cross- linked acrylic polymer and at least one cross-linked copolymer

Improved absorbent products according to the instant invention surpass by; far known absorbent products in terms of absorbency, rate of absorbtion, capacity for retaining absorbed liquid under pressure, and feeling of "dryness" to a wearer.

Accordingly, it is an object of the instant invention to provide an improved multi-layer absorbent product.

It is a further object of the Instant invention to provide a multi-layer absorbent product which will retain under pressure liquids absorbed therein.

It is another object of the invention to provide a multi¬ layer absorbent product which feels "dry" to a wearer.

It is yet a further object of the invention to provide a multi-layer absorbent product which contains at least one superabsorbent polymer or copolymer which is operable to absorb at least 20 ml per gram of an aqueous solution containing 1 percent by weight of sodium chloride.

It is still another object of the invention to provide an improved liquid absorbent composition which includes means comprising a cross-linked acrylic polymer and a cross-linked acrylic-starch graft copolymer.

It is yet another object of the invention to provide an improved multi-layer aabsorbent product including a layerof an improved liquid absorbent composition which includes means comprising a cross-linked acrylic polymer and a cross-linked acrylic-starch graft copolymer.

Other objects and advantages of the invention will be apparent from the description which follows, referrence being made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a cross-sectional view of a multi-layer absorbent pad in accordance with the instant invention.

Figure 2 is a cross-sectional view of a second embodiment of a multi-layer absorbent pad according to the instant invention.

Figure 3 is a cross-sectional view of a third embodiment of a multi-layer absorbent pad according to the instant invention.

Figure 4 is a plot of experimentally determined absorbtion ranges for two different polymers and blends of the two.

DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, an embodiment of an absorbent pad according to the instant invention is indicated generally at 10. On the exterior of the absorbent pad 10 is a non-woven water- pervious cover 11, which may be formed from a flat sheet of a non- woven material which is folded around the other components of the absorbent pad 10. There is a bond at 12 between overlapping edges 13 and 14 of the water-pervious cover. The bond at 12 is on a side 15 of the absorbent pad 10, which, in use, would be positioned away from the body of the user.

The absorbent pad 10 further comprises a cover layer 16 composed of water impervious material, a fluf-f layer 17 and one or more layers of a superabsorbent laminate 18 which is enveloped by a cover 19 composed of tissue. The fluff layer 17 is bonded to the water impervious layer 16 by an adhesive indicated generally at 20. Suitable adhesives are available from Ecomelt A.G. as "adhesives for the sanitary industry." Hot melt, multi-bead formulations are preferred, for example ones available from Ecomelt under the designations H-101, H-110, H-115, H-201, H-210, H-301, H-310 and H-312.

According to the instant invention, the laminate 18 comprises a tissue with particles of a superabsorbent carboxymethyl cellulose polymer, cross-linked acrylic polymer, or cross-linked acrylic copolymer fixed on the surface thereof. The laminate 18, as shown in Figure 1, can be pleated. It has been found that pleating increases the rate of absorbency exhibited by the laminate 18. It will be appreciated, however, that the laminate 18 can be in the form of a flat sheet or sheets. Preferably, as shown in Figure 1, flaps 21 are partially punched out of the laminate 18 to produce openings 22 therein. It has been found that the provision of openings 22 increases the rate at which liquids are absorbed by the pad 10. The tissue portion of the laminate 18 can be a high wet-strength tissue or a low wet- strength tissue; the former is_^ preferred unless the pad 10 is to be flushable in which case the tissue should be of the low wet- strength type.

The second embodiment of the Instant invention is a pad indicated generally at 30 in Figure 2. In this embodiment, a water-pervious non-woven layer 31 is provided on a side 32 of the absorbent pad 30. Edges 33 and 34 of the water-pervious layer 31 are adhered to edges 35 and 36 of a water impervious layer 37« The superabsorbent laminate 18 surrounded by the covering of tissue 19, substantially as described hereinabove with reference to Figure 1, is incorporated in the absorbent pad 30. Adjacent to the water impervious layer 37, there is a tissue layer 38. Between the superabsorbent laminate 18 and the tissue layer 38, there is a fluff layer 39. Preferably, the tissue layer 38 is adhesively bonded to the water impervious layer 37 by an adhesive layer 40. The fluff layer 39 is bonded to the tissue, layer 38 by adhesive indicated generally at 41.

A third embodiment of the instant invention is an absorbent pad indicated generally at 0 (Figure 3), and comprising a water- pervious non-woven cover 51, a water impervious layer 52 and a fluff layer 53. A side 54 of the fluff layer 53 is impregnated with particles of at least one superabsorbent polymer or copolymer which is further described hereinafter. The fluff layer with the particles is enveloped by a sheet 55 of wet-strength tissue and the absorbent pad 50 is assembled so that the superabsorbent particles are positioned away from the water impervious layer 52. ό

As is shown in Figure 3, the non-woven water-pervious layer 51 can completely surround the rest of the absorbent pad 50. Alternatively, the non-woven water-pervious layer can be bonded to the water impervious- layer 52 as described above in connection with the absorbent pad ^'30 (Figure 2). Similarly, the non-woven water-pervious cover 11 (Figure 1) can be bonded to the water impervious layer 16.

The covers (Figures 1 and 2) composed of tissue need not completely envelope the superabsorbent laminate 18. However, in accordance with the invention, at least one layer of tissue, preferably wet-strength, is provided between the superabsorbent laminate 18 and a portion of the water-pervious cover 11 (Figure 1) and 31 (Figure 2), which portion, in use, would contact the body of the user. This layer of tissue is essential to facilitate wicking of fluids deposited in one place on the pad 10 (Figure 1) and 30 (Figure 2). Such wicking enables full utilization of the absorbent capacity of the superabsorbent laminate 18 by carrying luids to portions thereof remote from the place where they (the fluids) are deposited.

As indicated above, the laminate 18 comprises a tissue with particles of at least one superabsorbent polymer fixed on the surface thereof. In general, the polymer is one which is capable of absorbing at least 20 ml of a 1 percent by weight aqueous sodium chloride solution per gram of polymer. Preferably, one gram of the polymer is operable to absorb at least 40 ml of a 1 percent by weight aqueous sodium chloride solution.

In accordance with the instant invention, the polymer is a carboxymethyl cellulose polymer, a cross-linked acrylic polymer or a cross-linked acrylic-starch graft copolymer having the absorbtion capacity recited above. Compounds suitable for cross- linking acrylic compounds are well known in the chemical arts and are disclosed in U.S. patent Nos. 3,332,901, 3,224,986 and 2,926,154. Suitable cross-linked acrylic polymers and copolymers and methods for producing them are disclosed in U.S. patent Nos. 4,117,184 and 4,076,673_* Such polymers and copolymers are all suitable in structures according to the instant invention, provided that they have the Indicated absorbtion capacity.

A preferred polymer is a cross-linked acrylic polymer produced by polymerizing (1) at least one unsaturated monomer which has a single polymerizable double bond and which is water soluble or becomes water soluble by hydrolysis, and (2) a cross- linking agent, and, if the unsaturated monomer (1) is one which becomes water soluble by hydrolysis, thereafter subjecting the resulting product to hydrolysis. The polymer is one which is operable to absorb at least 40 ml of a 1 percent by weight aqueous sodium chloride solution per gram of polymer and which is further operable to absorb at least 9 ml per gram of polymer per minute of a 1 percent by weight aqueous sodium chloride solution. One such preferred acrylic polymer is commercially available from Grain Processing Corporation, Muscatine, Iowa 52761 under the trade designation J-550. This acrylic polymer has a total absorbency, measured by a test that is subsequently described herein, of 59 ml per g ( illileters per gram).

Another preferred- polymer is a cross-linked acrylic-starch graft copolymer produced by polymerizing (1) at least one σf a natural starch and alpha starch, (2) at least one monomer which has a single polymerizable double bond and which is water soluble or becomes water soluble by hydrolysis, and (3) a cross-linking agent, and, if the monomer (2) is one which becomes water soluble by hydrolysis, thereafter subjecting the resulting product to hydrolysis. The copolymer is one. hich is operable to absorb at least 40 ml of a 1 percent by weight aqueous sodium chloride solution per gram of copolymer. Polymers produced as described in U.S. patent No. 4,076,673 are representative of this preferred cross-linked acrylic-starch graft copolymer for use according to the instant invention. One such preferred acrylic-starch graft copolymer is commercially available from Sanyo Chemical Industries, Limited, 11-1, Ikkyo Nomoto-cho, Higashlyama-Ku, Kyoto 605, Japan under the trade designation Sanwet IM-1000. This polymer has a total absorbency, measured by the subsequently described test, of 52.

A particularly preferred superabsorbent for use in accordance with the instant invention comprises a blend of at least one cross-linked acrylic polymer which is operable to absorb at least 50 ml of a 1 percent by weight aqueous sodium chloride solution per gram of polymer and which is further operable to absorb at least 10 ml per gram of polymer per minute of a 1 percent by weight aqueous sodium chloride solution and at least one cross- linked acrylic-starch graf copolymer which is operable to absorb at least 50 ml of a 1- percent by weight aqueous sodium chloride solution per gram of polymer. In this blend, the cross-linked acrylic polymer constitutes from 5 percent to 50 percent, based upon the weight of the acrylic polymer and the acrylic-starch copolymer; preferrably. the cross-linked acrylic polymer constitutes from 10 percent to 35 percent; more preferrably from 15 percent to 30 percent on the indicated basis, in both cases.

It has been found that certain blends of at least one cross- linked acrylic polymer having the indicated absorbtion capacities and at least one cross-linked acrylic-starch graft copolymer having the indicated absorbtion capacity, exhibit absorbtion capacities substantially greater than would be expected on the basis of those exhibited by the two components of the blends. Absorbtion capacities in one minute for 0.2 gram portions of polymer (or blend) were determined using a capillary absorbency test proceedure which comprised: (1) attaching one end of a length of flexible vinyl tubing to a platform of acrylic sheet material constructed to opperably receive it such that the end of the tubing is flush with the platform; (2) attaching the other end of the vinyl tubing to a stopcock which comprises the tip of a graduated burette; (3) securing the platform and the burette in an adjustable stand so that the platform is at essentially the same height or slightly lower than the burette zero ; ( 4 ) filling the burette and the vinyl tubing with a 1 percent by weight sodium chloride solution; (5) closing the burette stopcock and adjusting the liquid level to zero; (6) placing 0.2 g of polymer (or blend) on a Whatman #1 (4.25 cm) filter paper and placing the filter paper on the platform; ( 7 ) opening the burette stopcock for one minute and thereafter recording the liquid level in the burette . In the test , the polymer ( o r blend) draws the salt solution through the filter paper against a decreasing negative head . Absorbency is expressed as ml/g where ml is volume of 1% by weight NaCl solution absorbed in milliliters and g is the weight of the sample in grams . Tests conducted as described above on various blends of J-550 and Sanwet IM-1000 resulted in the absorbencles presented in Table 1 , whe rein the rat ios compris ing column headings are percent J-550/percent IM-1000

TABLE 1 100/0 90/10 80/20 0/30 60/40 50/50

2.09 2.40 1.86 2.01 2.09 1.78

1.90 2.19 1.88 2.05 1.89 1.87

2.35 1.^'96 2.00 2.05 1.80 2.00

2.10 2.30 2.21 1.90 1.83 1.82

2.21 2.55 1.98 2.19 1.80 1.98

2.07

2.08

2.20 ^•

1.98

2.02

TABLE 1 (continued) 40/60 30/70 20/80 10/90 Q/100

1.40 1.62 1.30 1.37 1.09

1.54 1.60 1.82 1.00 0.88

1.65 1.69 1.49 1.19 0.80

1.40 1.70 1.65 1.10 0.98

1.58 1.70 1.49 1.13 0.93 0.80 0.98

0.93 0.84 0.78 The experimental results reported in Table 1 were subjected to statistical analysis. For each polymer (or blend) the average experimental absorbency and the standard deviation were calculated. Because of- the limited number of experimental values obtained for each polymer (or blend), a t-value corresponding to a 95 percent level of certainty was selected from the t-Distribution table for each sample in accordance with that sample's degrees of freedom [d.f.» (sample size)-l]. A range of experimental absorbencies was determined for each polymer (or blend) using the formula R - A +_ (t-value)S where R * range, A « average experimental absorbency and S * standard deviation. The results of these calculations are presented in Table 2.

TABLE 2

% J-550 / Average Standard % IM-1000 Absorbency Deviation t-value Range

100/0 2.10 0.13 2.262 1.81 to 2.39

90/10 2.28 0.22 2.776 1.67 to 2.89

80/20 1.99 0.14 2.776 1.60 to 2.38

70/30 2.04 0.10 2.776 1.76 to 2.32

60/40 1.88 0.12 2.776 1.55 to 2.21

50/50 1.89 0.10 2.776 1.61 to 2.17

40/60 1.51 0.11 2.776 1.20 to 1.82

30/70 1.66 0.05 2.776 1.52 to 1.80

20/80 1.55 0.20 2.776 0.99 to 2.11

10/90 1.16 0.14 2.776 0.77 to 1.55

0/100 0.90 0.10 2.262 .0.67 to 1.13

With reference to Figure 4, minimum, maximum and average absorbencies of 1.81, 2.39 and 2.10 reported in Table 2 for the J- 550 naterial are plotted at 60, 61 and 62. Similarly, the minimum, maximum and average absorbencies for the Sanwet IM-1000 material and for the several blends tested are set forth in Table 3, together with the reference numerals used to indicate the several points in Figure 4.

TABLE 3

% J-550 / Min. Ref. Max. Ref. Avg. Ref. % IM-1000 Abs. Num. Abs. Num. Abs. Num.

90/10 1.67 66 2.89 67 2.28 68

80/20 1.60 ^: 69 2.38 70 1.99 71

70/30 1.76 72 2.32 73 2.04 74

60/40 1.55 75 2.21 76 1.88 77

50/50 1.61 78 2.17 79 1.89 80

40/60 1.20 81 1.82 82 1.51 83

30/70 1.52 84 1.80 85 1.66 86

20/80 0.99 87' 2.11 88 1.55 89

10/90 0.77 90 1.55 91 1.16 92

0/100 0.67 93 1.13 94 0.90 95

In Figure 4, the line connecting points 62 and 65 represents the theoretical average absorbencies of varying blends of the two polymers based on the average absorbency of each when measured alone. In every instance, the experimental average absorbency calculated for each of the blends tested is substantially greater than the theoretical average absorbency for that blend. Similarly, the line between points 61 and 64 in Figure 4 represents the theoretical maximum absorbencies of varying blends. For six of the nine blends tested, the experimental average absorbency is greater than the theoretical maximum absorbency. For the blend comprising 30 percent of the J-550 material and 70 percent of the Sanwet IM-1000 material the entire experimental I? range of absorbencies (calculated to a 95 percent level of certainty) exceeds the maximum theoretical absorbency of that blend.

Tests were conducted on various blends of other superabsorbent polymers. Economically, both in terms of cost -and of handlability,it has been found to bedesirable for such blends to comprise as small of a percentage of cross-linked acrylic polymer as is operable to exhibit signif igant ly improved absorbency, specificly, improved rate of absorbency. Blends in accordance with the instant invention comprise from 5 percent to 50 percent cross-linked acrylic polymer based on the weight of the acrylic polymer and the acrylic-starch coplymer, preferably from 10 percent to 35 percent cross-linked acrylic polymer, more preferably from 15 percent to 30 percent cross-linked acrylic polymer on the indlcayed basis, in both cases.

Other commercially available polymers that have been investigated in blends are identified in Table 4.

TABLE 4

Polymer Trade Type Designation Source carboxymethyl cellulose Akucell 3019 Enka Industrial Colloids

Postbus 60

6800 AB Arnhem Holland acrylic Favor SAB-901 Stockhausen, Inc. P.O. Box 16025 2408 Doyle Street Greensboro, NC 27406 acrylic Arasorb Arakwa Chemical

Industries, Limited

1-21,

Hiranomachi Higashi-ku

Osaka 541, Japan acrylic-starch A-100 Grain Processing Corp. Muscatine , Iowa 52761

The total absorbencies , ml per g, of the foregoing materials were Akucell 3019 33, Favor SAB-901 56 , Arasorb C 47 and A-100 37. The absorbencies , ml per g per minute , were 9 _* 15 , Favor SAB-901 5.40, Arasorb C 9 - 85 and A-100 4.95.

Capillary absorbency tests conducted on the blends identified in Table 5 , below, indicated that the blends had substantially the absorbencies that would be expected from those of the individual polymers of the blends :

TABLE 5

Blend Ratios Tested

J-550/Akucell 3019 100/0, 67/33, 33/67, 0/100 J-550/Favor SAB-901 100/0, 67/33, 33/67, 0/100 IM-1000/Akucell 3019 100/0, 95/5, 80/20, 65/35, 0/100. Arasorb C/IM-1000 100/0, 90/10, 80/20, 70/30, 60/40, 50/50,

40/60, 30/70, 20/80, 10/90, 0/100

IM-1000/A-lOO 100/0, 67/33, 33/67, 0/100

Total absorbencies, as reported herein, were determined by placing one gram portions of the polymer under investigation in a beaker containing 100 ml 1 percent by weight aqueous sodium chloride solution, gravity filtering solids from the material in the beaker after thirty minutes of standing under ambient conditions, about 20 degrees C, with periodic stirring, and weighing the filter paper and the precipitate thereon. Filtration was through a previously weighed Whatman #1 filter paper. Total absorption was the weight of the filter paper and the precipitate thereon minus the sum of nine and the original weight of the filter paper, it having been found that the filter paper retains nine ml of the aqueous sodium chloride solution.

It will be appreciated from the foregoing discussion and data that certain blends of a cross-linked acrylic polymer and a cross- linked starch-acrylic graft copolymer show unexpectedly high rates of absorbency, and that the acrylic polymers of such blends must have a total absorbency of at least 50.ml per g and an absorbency rate of at least 10 ml per g per minute, while the starch acrylic graft must have a total absorbency of at least 50 ml pe r g . Ideally , the blend is of a cross-linked acrylic polymer having a total absorbency of substantially 59 ml pe r g and a rate of absorbency of substantially 10.5, and of a cross-linked, starch- acrylic graft copolymer having a total absorbency of substantially 52. In any event, both the acrylic polymer and the starch graft must be non-toxic when used in personal care products; this is true of the J-550 and of the IM-1000 materials.

Claims

WE CLAIM:

1. A multi-layered disposable absorbent product comprising, in combination, a liquid-pervious body-contacting layer, a tissue layer, a layer of liquid-absorbent composition, a fluff layer, and a water impervious layer, said fluff layer and said liquid-absorbent layer being disposed between said tissue layer and said water impervious layer, said layer of a liquid-absorbent composition including means comprising a carboxymethyl cellulose polymer, a cross-linked acrylic polymer, or a cross-linked acrylic copolymer which is operable to absorb at least 20 ml per g of a 1 percent by weight aqueous NaCl solution positioned between said fluff layer and said tissue layer.

2. A multi-layered disposable absorbent product as claimed in claim 1 wherein the liquid absorbent composition includes a cross-linked acrylic polymer produced by polymerizing (a) at least one unsaturated monomer which has a single polymerizable double bond and which is water soluble and (b) a cross-linking agent.

3. A multi-layered disposable absorbent product as claimed in claim 1 wherein the liquid absorbent composition includes a cross-linked acrylic polymer produced by polymerizing (a) at least one unsaturated monomer which has a single polymerizable double bond and which becomes water soluble by hydrolysis and (b) a cross-linking agent, and thereafter subjecting the resulting product to hydrolysis.

4. A multi-layered disposable absorbent product as claimed in claim 1 wherein the liquid-absorbent composition includes a cross-linked acrylic-starch graft copolymer produced by polymerizing (a) natural starch, (b) at least one monomer which has a single polymerizable double bond and which is water soluble, and (c) a cross-linking agent.

5. A multi-layered disposable absorbent product as claimed in claim 1 wherein the liquid-absorbent composition includes a cross-linked acrylic-starch graft copolymer produced by polymerizing (a) an alpha starch, (b) at least one monomer which has a single polymerizable double bond and which is water soluble, and (c) a cross-linking agent.

6. A multi-layered disposable absorbent product as claimed in claim 1 wherein the liquid-absorbent composition includes a cross-linked acrylic-starch graft copolymer produced by polymerizing (a) natural starch, (b) at least one monomer which has a single polymerizable double bond and which becomes water soluble by hydrolysis, and (c) a cross-linking agent, and thereafter subjecting the resulting product to hydrolysis.

7. A multi-layered disposable absorbent product as claimed in claim 1 wherein the liquid-absorbent composition includes a cross-linked acrylic-starch graft copolymer produced by polymerizing (a) an alpha starch, (b) at least one monomer which has a single polymerizable double bond and which becomes water soluble by hydrolysis, and (c) a cross-linking agent, and thereafter subjecting the resulting product to hydrolysis.

8. A multi-layered disposable absorbent product as claimed in claim 1 wherein the liquid-absorbent composition comprises a cross-linked acrylic polymer or a cross-linked acrylic copolymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

9. A. multi-layered disposable absorbent product as claimed in claim 2 wherein the liquid-absorbent composition comprises a cross-linked acrylic polymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

10. A multi-layered disposable absorbent product as claimed in claim 3 wherein the liquid-absorbent composition comprises a cross-linked acrylic polymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

11. A multi-layered disposable absorbent product as claimed in claim 4 wherein the liquid-absorbent composition comprises a cross-linked acrylic-starch graft copolymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

12. A multi-layered disposable absorbent product as claimed in claim 5 wherein the liquid-absorbent composition comprises a cross-linked acrylic-starch graft copolymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

13. A multi-layered disposable absorbent product as claimed in claim 6 wherein the liquid-absorbent composition comprises a cross-linked acrylic-starch graft copolymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

14. A multi-layered disposable absorbent product as claimed in claim 7 wherein the liquid-absorbent composition comprises a cross-linked acrylic-starch graft copolymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

15. A multi-layered disposable absorbent product as claimed in claim 8 wherein the' liquid-absorbent composition includes both a cross-linked acrylic polymer and a cross-linked acrylic-starch graft copolymer, wherein the polymer and the copolymer both are operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution and wherein the acrylic polymer is operable to absorb at least 9 ml per g per minute of a 1 percent by weight aqueous NaCl solution, said acrylic polymer constituting from 5 percent to 50 percent, based upon the weight of the acrylic polymer and the acrylic-starch copolymer in the absorbent product.

16. A multi-layered disposable absorbent product as claimed in claim 15 wherein the acrylic polymer constitutes from 10 percent to 35 percent, based upon the weight of the acrylic polymer and the acrylic-starch copolymer.

17. A multi-layered disposable absorbent product as claimed in claim 15 wherein the acrylic polymer constitutes from 15 percent to 30 percent, based upon the weight of the acrylic polymer and the acrylic-starch copolymer.

18. A layer of a liquid-absorbent composition, said composition including means comprising a cross-linked acrylic polymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution and which is operable to absorb at least 9 ml- per -g per minute of a 1 percent by weight aqueous NaCl solution- and a cross-linked acrylic-starch graft copolymer which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution, said acrylic polymer, constituting from 5 percent to 50 percent, based upon the weight of the acrylic polymer and the acrylic-starch copolymer.

19. A layer of a liquid-absorbent composition as claimed in claim 18 wherein the acrylic polymer constitutes from 10 percent to 35 percent, based upon the weight of the acrylic polymer and the acrylic-starch copolymer.

20. A layer of a liquid-absorbent composition as claimed in claim 18 wherein the acrylic polymer constitutes from 15 percent to 30 percent, based upon the weight of the acrylic polymer and the acrylic-starch copolymer.

21. A layer of a liquid-absorbent composition as claimed in claim 18 wherein the acrylic polymer has a total absorbency of substantially 59 ml 1 percent aqueous sodium chloride solution and is operable to absorb, per gram per minute, substantially 10.5 ml 1 percent aqueous sodium chloride solution, the cross-linked acrylic-starch graft copolymer has a total absorbency of substantially 52 ml 1 percent by weight aqueous sodium chloride solution, and both the acrylic polymer and the starch-graft copolymer are non-toxic when used in health care products.

22. A multi-layered disposable absorbent product as claimed in claim 1 wherein the liquid-absorbent layer is a laminate comprising the acrylic polymer or copolymer and a tissue sheet.

23. A multi-layered disposable absorbent product as claimed in claim 22 wherein the liquid-absorbent composition includes an acrylic-starch graft produced by polymerizing (a) natural starch, (b) at least one monomer which has a single polymerizable double bond and which is water soluble, and (c) a cross-linking agent.

24. A multi-layered disposable absorbent product as claimed in claim 22 wherein the liquid-absorbent composition includes an acrylic-starch graft produced by polymerizing (a) an alpha starch, (b) at least one monomer which has a single polymerizable double bond and which is water soluble, and (c) a' cross-linking agent.

25. A multi-layered disposable absorbent product as claimed in claim 22 wherein the liquid-absorbent composition includes an acrylic-starch graft produced by polymerizing (a) natural starch, (b-); .at ' least one monomer which has a single polymerizable double - bond and which becomes water soluble by hydrolysis, and (c) a cross-linking agent, and thereafter subjecting the resulting product to hydrolysis.

26. A multi-layered disposable absorbent product as claimed in claim 22 wherein the liquid-absorbent composition includes an acrylic-starch graft produced by polymerizing (a) an alpha starch, (b) at least one monomer which has a single polymerizable double bond and which becomes water soluble by hydrolysis, and (c) a cross-linking agent, and thereafter subjecting the resulting product to hydrolysis.

27. A multi-layered disposable absorbent product as claimed in claim 22 wherein the liquid-absorbent composition comprises a cross-linked acrylic polymer or a cross-linked acrylic copolymer whis is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

28. A multi-layered disposable absorbent product as claimed in claim 23 wherein the liquid-absorbent composition comprises an acrylic-starch graft which is operable to absorb at least 40 ml ,per g of a 1 percent by weight aqueous NaCl solution.

29. A multi-layered disposable absorbent product as claimed in claim 24 wherein the liquid-absorbent composition comprises an acr lic starch graft which is operable to absorb at least 40 ml pe g of a 1 percent by weight aqueous NaCl solution.

30. A multi-layered disposable absorbent product as claimed in claim 25 wherein the liquid-absorbent composition comprises an acrylic-starch graft which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.

31. A multi-layered disposable absorbent product as claimed in claim 26 wherein the liquid-absorbent composition comprises an acrylic-starch graft which is operable to absorb at least 40 ml per g of a 1 percent by weight aqueous NaCl solution.