Absorbent structures with gelling agent and absorbent articles containing such structures

Claim 2

A liquid-absorbent structure comprising a web having a density of from 0.06 to 0.3 g/cm 3 , said web comprising from 40% to 95% by weight of hydrophilic fibres and from 5% to 600/o by weight of nonfibrous particles of hydrogel-forming gelling agent thoroughly dispersed among the hydrophilic fibres in the web, which polymeric gelling agent has an equilibrium gel volume of at least 20 grams of synthetic urine per gram of gelling agent, characterised in that when dispersed as aforesaid among the hydrophilic fibres in the web the said particles are descrete non-agglomerated particles having a mass median particle size in the range from 400 to 1680 microns with the result that the effective equilibrium absorbent capacity of the said particles when in the said structure is greater than the corresponding effective equilibrium absorbent capacity of the particles in a comparative structure differing in composition and construction from the first above-mentioned only in that the particles in the said comparative structure have a mass median particle size less than 400 microns.

Claim 3

A liquid-absorbent structure comprising a web having a density of from 0.06 to 0.3 g/cm 3 , said web comprising from 40% to 950/o by weight of hydrophilic fibres and from 5% to 60% by weight of nonfibrous particles of hydrogel-forming gelling agent thoroughly dispersed among the hydrophilic fibres in the web, which polymeric gelling agent has an equilibrium gel volume of at least 20 grams of synthetic urine per gram of gelling agent, characterised in that when dispersed as aforesaid among the hydrophilic fibres in the web the said particles are nonfragile agglomerated particles having a mass median particle size in the range from 400 to 1680 microns with the result that the effective equilibrium absorbent capacity of the said particles when in the said structure is greater than the corresponding effective equilibrium absorbent capacity of the particles in a comparative structure differing in composition and construction from the first above-mentioned only in that the particles in the said comparative structure have a mass median particle size less than 400 microns.

Claim 4

A liquid-absorbent structure comprising a web having a density of from 0.06 to 0.3 g/cm 3 , said web comprising from 40% to 950/o by weight of hydrophilic fibres and from 5% to 60% by weight of nonfibrous particles of hydrogel-forming gelling agent thoroughly dispersed among the hydrophilic fibres in the web, which polymeric gelling agent has an equilibrium gel volume of at least 20 grams of synthetic urine per gram of gelling agent, characterised in that when dispersed as aforesaid among the hydrophilic fibres in the web the said particles are nonfragile agglomerated particles having a mass median particle size in the range from 400 to 1680 microns with the result that the effective equilibrium absorbent capacity of the said particles when in the said structure is greater than the corresponding effective equilibrium absorbent capacity of the particles in a comparative structure differing in composition and construction from the first above-mentioned only in that the particles in the said comparative structure have a mass median particle size less than 400 microns.

Claim 5

A liquid-absorbent structure according to claim 1 or claim 2 characterised in that the said nonfibrous particles of gelling agent, when dispersed among the hydrophilic fibres in the web, (a) have a mass median particle size in the range 400 to 1190 microns, with no more than 160/ 0 by weight of these particles having a particle size less than 200 microns, and no more than 16% by weight of those particles having a particle size greater than 1410 microns; or (b) have a mass median particle size in the range of 400 microns to 700 microns with no more than 16 0 /o by weight of these particles having a particle size less than 200 microns, and no more than 16% by weight of those particles having a particle size greater than 1200 microns; or (c) have a mass median particle size in the range 410 to 650 microns with no more than 16% by weight of those particles having a particle size less than 210 microns and no more than 160/o by weight having a particle size greater than 1000 microns; or (d) have a mass median particle size in the range 420 to 600 microns with no more than about 16% by weight of the particles having a particle size less than 220 microns and no more than 16% by weight having a particle size greater than 900 microns.

Claim 6

A liquid-absorbent structure according to any of claims 1 to 3 characterised in that the said web comprises from 70% to 900/o by weight of the said hydrophilic fibres and from 10% to 30% by weight of the said nonfibrous particles of gelling agent.

Claim 7

A liquid-absorbent structure according to any of claims 1 to 4 characterised in that the hydrophilic fibres are cellulosic fibres

Claim 8

A liquid-absorbent structure according to any of claims 1 to 5 characterised in that the hydrophilic fibres are wood pulp fibres and the hydrogel-forming polymeric gelling agent has a gel volume of 25 to 60 grams of synthetic urine per gram of gelling agent.

Claim 9

A liquid-absorbent structure according to any of claims 1 to 6 characterised in that the hydrophilic fibres are stiffened, twisted, curled cellulose fibres and the hydrogel-forming polymeric gelling agent has a gel volume of from 20 to 35 grams of synthetic urine per gram of gelling agent.

Claim 10

A liquid-absorbent structure according to any of claims 1 to 7 characterised in that the hydrogel-forming polymeric gelling agent is a slightly cross-linked, partially neutralised polymer selected from polyacrylates and acrylic acid grafted starch, said gelling agent having and equilibrium extractable polymer content in synthetic urine of no more than about 17% by weight.

Claim 11

A liquid-absorbent article comprising: A. a liquid impervious backing sheet; B. a liquid pervious top sheet; and C. a liquid absorbent core positioned between said backing sheet and said top sheet, characterised in that said absorbent core comprises a liquid-absorbent structure according to any of claims 1 to 8.

Claim 12

In a process for the manufacture of liquid absorbent structures comprising a web having a density of from 0.06 to 0.03 g/cm 3 , said web comprising from 40% to 950/o by weight of hydrophilic fibres and from 50/o to 60% by weight of nonfibrous particles of hydrogel-forming polymeric gelling agent having a equilibrium gel volume of at least 20 grams of synthetic urine per gram of gelling agent, which process includes a step wherein particles of the said gelling agent are fed, from a source thereof which is periodically restocked, to be thoroughly dispersed among the said hydrophilic fibres and the said web is laid down from the resultant thorough mixture of fibres and particles, the improvement comprising controlling the supply of the said particles at or from the said source thereof such that the particles are discrete non-agglomerated particles having nonfragile mass median particle size in the range of 400 to 1680 microns, with the result that the effective equilibrium absorbent capacity of the said particles when in the said structure is greater than the corresponding equilibrium absorbent capacity of the particles in a comparative structure differing in composition and construction from the first above-mentioned only in that the particles in the said comparative structure have a mass median particle size less than 400 microns.

Claim 13

In a process for the manufacture of liquid absorbent structures comprising a web having a density of from 0.06 to 0.03 g/cm 3 , said web comprising from 40% to 950/o by weight of hydrophilic fibres and from 50/o to 60% by weight of nonfibrous particles of hydrogel-forming polymeric gelling agent having a equilibrium gel volume of at least 20 grams of synthetic urine per gram of gelling agent, which process includes a step wherein particles of the said gelling agent are fed, from a source thereof which is periodically restocked, to be thoroughly dispersed among the said hydrophilic fibres and the said web is laid down from the resultant thorough mixture of fibres and particles, the improvement comprising controlling the supply of the said particles at or from the said source thereof such that the particles are discrete non-agglomerated particles having nonfragile mass median particle size in the range of 400 to 1680 microns, with the result that the effective equilibrium absorbent capacity of the said particles when in the said structure is greater than the corresponding equilibrium absorbent capacity of the particles in a comparative structure differing in composition and construction from the first above-mentioned only in that the particles in the said comparative structure have a mass median particle size less than 400 microns.

Claim 14

In a process for the manufacture of liquid absorbent structures comprising a web having a density of from 0.06 to 0.03 g/cm 3 , said web comprising from 400/o to 95% by weight of hydrophilic fibres and from 5% to 60% by weight of nonfibrous particles of hydrogel-forming polymeric gelling agent having an equilibrium gel volume of at least 20 grams of synthetic urine per gram of gelling agent, which process includes a step wherein particles of the said gelling agent are fed, from a source thereof which is periodically restocked, to be thoroughly dispersed among the said hydrophilic fibres and the said web is laid down from the resultant thorough mixture of fibres and particles, the improvement comprising controlling the supply of the said particles at or from the said source thereof such that the particles are nonfragile agglomerate particles having a mass median particle size in the range of 400 to 1680 microns, with the result that the effective equilibrium absorbent capacity of the said particles when in the said structure is greater than the corresponding equilibrium absorbent capacity of the said particles in a comparative structure differing in composition and construction from the first abovementioned only in that the particles in the said comparative structure have a mass median particle size less than 400 microns.

Claim 15

In a process for the manufacture of liquid absorbent structures comprising a web having a density of from 0.06 to 0.03 g/cm 3 , said web comprising from 400/o to 95% by weight of hydrophilic fibres and from 5% to 60% by weight of nonfibrous particles of hydrogel-forming polymeric gelling agent having an equilibrium gel volume of at least 20 grams of synthetic urine per gram of gelling agent, which process includes a step wherein particles of the said gelling agent are fed, from a source thereof which is periodically restocked, to be thoroughly dispersed among the said hydrophilic fibres and the said web is laid down from the resultant thorough mixture of fibres and particles, the improvement comprising controlling the supply of the said particles at or from the said source thereof such that the particles are nonfragile agglomerate particles having a mass median particle size in the range of 400 to 1680 microns, with the result that the effective equilibrium absorbent capacity of the said particles when in the said structure is greater than the corresponding equilibrium absorbent capacity of the said particles in a comparative structure differing in composition and construction from the first abovementioned only in that the particles in the said comparative structure have a mass median particle size less than 400 microns.

Claim 16

A process improvement according to Claim 10 or Claim 11 characterised in that the supply of said nonfibrous particles of gelling agent from the said source is controlled such that the said particles: (a) have a mass median particle size in the range 400 to 1190 microns, with no more than 16% by weight of these particles having a particle size less than 200 microns, and no more than 160/0 by weight of those particles having a particle size greater than 1410 microns; or (b) have a mass median particle size in the range of 400 microns to 700 microns with no more than 16% by weight of these particles having a particle size less than 200 microns, and no more than 16% by weight of those particles having a particle size greater than 1200 microns; or (c) have a mass median particle size in the range 410 to 650 microns with no more than 16% by weight of those particles having a particle size less than 210 microns and no more than 16% by weight having a particle size greater than 1000 microns; or (d) have a mass median particle size in the range 420 to 600 microns with no more than about 16% by weight of the particles having a particle size less than 220 microns and no more than 16% by weight having a particle size greater than 900 microns.

Claim 17

A composition especially suitable for use as an absorbent gelling agent in fibrous absorbent web structures, said composition comprising a plurality of nonfibrous, discrete non-agglomerated particles of a substantially water-insoluble, slightly crosslinked, partially neutralized, hydrogel-forming polymeric gelling agent material wherein: (A) said polymeric gelling agent material comprises: (i) from about 50 mole percent to 99.999 mole percent of polymerized unsaturated, polymerizable, acid group containing monomers; and (ii) from about 0.001 mole percent to 5 mole percent of a crosslinking agent; said polymeric gelling agent material having a degree of neutralization of at least about 50% and a gel volume of at least about 20 grams of synthetic urine per gram of gelling agent material; and (B) said plurality of particles has a mass median particle size ranging from about 400 to 1680 microns.

Claim 18

A composition especially suitable for use as an absorbent gelling agent in fibrous absorbent web structures, said composition comprising a plurality of nonfibrous, discrete non-agglomerated particles of a substantially water-insoluble, slightly crosslinked, partially neutralized, hydrogel-forming polymeric gelling agent material wherein: (A) said polymeric gelling agent material comprises: (i) from about 50 mole percent to 99.999 mole percent of polymerized unsaturated, polymerizable, acid group containing monomers; and (ii) from about 0.001 mole percent to 5 mole percent of a crosslinking agent; said polymeric gelling agent material having a degree of neutralization of at least about 50% and a gel volume of at least about 20 grams of synthetic urine per gram of gelling agent material; and (B) said plurality of particles has a mass median particle size ranging from about 400 to 1680 microns.

Claim 19

A composition especially suitable for use as an absorbent gelling agent in fibrous absorbent web structures, said composition comprising a plurality of nonfibrous, discrete nonfragile agglomerated particles of a substantially water-insoluble, slightly crosslinked, partially neutralized, hydrogel-forming polymeric gelling agent material wherein: (A) said polymeric gelling agent material comprises: (i) from about 50 mole percent to 99.999 mole percent of polymerized unsaturated, polymerizable, acid group containing monomers; and (ii) from about 0.001 mole percent to 5 mole percent of a crosslinking agent; said polymeric gelling agent material having a degree of neutralization of at least about 50 0 / o and a gel volume of at least about 20 grams of synthetic urine per gram of gelling agent material; and (B) said plurality of particles has a mass median particle size ranging from about 400 to 1680 microns.

Claim 20

A composition especially suitable for use as an absorbent gelling agent in fibrous absorbent web structures, said composition comprising a plurality of nonfibrous, discrete nonfragile agglomerated particles of a substantially water-insoluble, slightly crosslinked, partially neutralized, hydrogel-forming polymeric gelling agent material wherein: (A) said polymeric gelling agent material comprises: (i) from about 50 mole percent to 99.999 mole percent of polymerized unsaturated, polymerizable, acid group containing monomers; and (ii) from about 0.001 mole percent to 5 mole percent of a crosslinking agent; said polymeric gelling agent material having a degree of neutralization of at least about 50 0 / o and a gel volume of at least about 20 grams of synthetic urine per gram of gelling agent material; and (B) said plurality of particles has a mass median particle size ranging from about 400 to 1680 microns.

Claim 21

A composition according to Claim 13 or Claim 14 wherein (A) the polymeric gelling agent material is selected from polyacrylates and acrylic acid grafted starch and has an equilibrium extractable poiymer content in synthetic urine of no more than about 17% by weight; and (B) the plurality of gelling agent particles has a mass median particle size ranging from about 400 to 1190 microns with no more than about 16% by weight of said particles having a particle size less than 200 microns and no more than about 16% by weight of said particles having a particle size greater than 1410 microns.

Claim 22

A composition according to Claim 15 wherein said polymer gelling agent material has a gel volume of from about 25 to 60 grams of synthetic urine per gram of gelling agent and wherein said plurality of gelling agent particles has a mass median particle size ranging from about 400 to 700 microns with no more than about 16 0 /o by weight of said particles having a particle size less than 200 microns and no more than about 16% by weight of said particles having a particle size greater than about 1200 microns.

Claim 23

A composition according to Claim 15 wherein said plurality of gelling agent particles has the following particle size distribution as determined bv ASTM analvsis on U.S. Sieve Series screens:

Claim 24

A composition according to Claim 15 wherein the gelling agent particles are in the form of agglomerates.