Surface crosslinked and surfactant coated absorbent resin particles and method of preparation

Claim 2

Particles according to Claim 1, wherein the absorbent resin is a hydrolyzate of a starch-acrylonitrile graft copolymer, a partially neutralized product of a starch-acrylic acid graft copolymer, a saponification product of a vinyl acetate acrylic ester copolymer, a hydrolyzate of an acrylonitrile copolymer, a crosslinked product of a hydrolyzate of an acrylonitrile copolymer, a hydrolyzate of an acrylamide copolymer, a crosslinked product of a hydrolyzate of an acrylamide copolymer, a partially neutralized product of polyacrylic acid, or a crosslinked product of partially neutralized polyacrylic acid.

Claim 3

Particles according to Claim 1 or Claim 2 wherein the polyhydroxy-containing compound is glycol, diethylene glycol, thiethylene glycol, polyethylene glycol, glycerol, polyglycerol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, propane diol butane diol, diethanolamine, triethanolamine, a hydroxy terminated polyoxyethylenepolyoxy-propylene block copolymer, a polyoxyethylene sorbitol derivative, a polyoxyethylene lanolin derivative, a sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, trimethylolpropane, pentaerythritol, sorbitol, mannitol, a sugar or a derivative of sugar.

Claim 4

Particles according to any one of Claims 1 to 3, wherein the resin is crosslinked at or near the surface of the particles with from 0.01 to about 10 parts by weight of the polyhydroxy compound per 100 parts of the water-absorbent resin; and the particles have coated on or bound to their surface from 0.01 to 2.0 parts by weight of the surfactant per 100 parts of the water-absorbent resin.

Claim 5

Particles according to any one of Claims 1 to 4, wherein the absorbent resin comprises a polymer of acrylic or methacrylic acid in which from 50 to 99% of the carboxyl moieties are neutralized; the polyhydroxy compound is glycerol or sorbitol; and the surfactant is a polyethoxylated sorbitol-lanolin derivative.

Claim 6

A process for the preparation of surface crosslinked absobent resin particles according to any one of Claims 1 to 5 which comprises A) contacting particles of a hydrogel of the water-absorbent resin with a composition comprising a polyhydroxy compound and a surfactant, or a polyhydroxy surfactant, optionally water and optionally a water miscible polar solvent, under conditions such that the polyhydroxy compound and surfactant, or the polyhydroxy surfactant, coat the water-absorbent resin particles without substantial penetration into the interior of the absorbent resin particles; B) drying the mixture of the hydrogel of the water-absorbent resin, and composition containing the polyhydroxy compound and surfactant, or polyhydroxy surfactant, under conditions such that the water, and optional solvent if present, are substantially removed and the polyhydroxy compound or polyhydroxy surfactant does not significantly react with the carboxyl moieties of the water absorbent resin; C) optionally, reducing the particle size of the dried coated absorbent resin by mechanical means; and D) heating the coated water-absorbent resin particles under conditions such that the polyhydroxy compound or the polyhydroxy surfactant reacts with the carboxy moieties of the water-absorbent resin so as to crosslink the surface of the absorbent resin particles.

Claim 7

A process according to Claim 6 wherein the composition containing the polyhydroxy compound and surfactant comprises i) from 0 to 99 parts by weight water; ii) from 0 to 99 parts by weight polar organic solvent; iii) from 0 to 99 parts by weight of surfactant; iv) from 1 to 99 parts by weight of polyhydroxy compound or polyhydroxy surfactant.

Claim 8

A process according to Claim 6 or Claim 7, wherein from 50 to 99.98 parts of water absorbent resin hydrogel by weight and from 0.02 to 50 parts by weight of the solution containing the polyhydroxy compound and surfactant, or polyhydroxy surfactant, are contacted.

Claim 9

A process according to any one of Claims 6 to 8 wherein A) the hydrogel of the water-absorbent resin and the composition comprising polyhydroxy compound and surfactant, or polyhydroxy surfactant, are contacted for a time of 0.5 minutes to 10 minutes at a temperature of from 20°C to 150°C; B) the mixture of the hydrogel of absorbent resin having coated thereon the composition comprising polyhydroxy compound and surfactant, or polyhydroxy surfactant, are dried at from 100 to 175°C for 10 to 60 minutes; C) the particle size of the dried coated absorbent resin particles is reduced to less than 2 mm; D) the coated absorbent resin particles are heated to a temperature of from 175 to 210°C for from 5 to 75 minutes such that the polyhydroxy compound or polyhydroxy surfactant reacts with the carboxyl moieties at or near the surface of the water-absorbent resin particles to crosslink the water-absorbent resin particles at or near the surface.

Claim 10

An absorbent structure comprising a woven or non-woven structure of paper, synthetic fibers, or natural fibers and surface crosslinked and surfactant coated water-absorbent resin particles according to one of Claims 1 to 5.