Process for preparing highly reactive, water-absorptive resin

Claim 2

A process for preparing a highly reactive, water-absorptive resin, which comprises the steps of: mixing (1) an aqueous solution containing a water-soluble polymerization initiator, a crosslinking agent and a hydrophilic, polymerizable, monomer having a reactive functional group in the molecule, said reactive functional group being selected from the group consisting of amino groups and hydroxyl groups, with (2) a dispersion of fine particles of a highly water-absorptive resin dispersed in an organic liquid, said highly water-absorptive resin being capable of absorbing water in an amount of from 10 to 1500 times the weight of said resin, said resin being selected from the group consisting of polymers of acrylic acid, alkali metal salts of acrylic acid, methacrylic acid and alkali metal salts of methacrylic acid, said resin having a water content of 50 percent by weight or lower, whereby said fine particles are impregnated with said monomer and said crosslinking agent, the amount of said monomer being in the range of from 1 to 100% of the amount of said resin, and polymerizing said monomer to form a polymer on the surfaces of said fine particles so that the reactive functional groups of said polymer are present on the surfaces of said fine particles whereby said fine particles become highly reactive and remain highly water-absorptive.

Claim 3

A process for preparing a highly reactive, water-absorptive resin, which comprises the steps of: mixing (1) an aqueous solution containing a water-soluble crosslinking agent and a hydrophilic polymer having reactive functional groups in the molecule, said reactive functional groups being selected from the group consisting of amino groups and hydroxyl groups, with (2) a dispersion of fine particles of a highly water-absorptive resin dispersed in an organic liquid, said highly water-absorptive resin being capable of absorbing water in an amount of from 10 to 1500 times the weight of said resin, said resin being selected from the group consisting of polymers of acrylic acid, alkali metal salts of acrylic acid, methacrylic acid and alkali metal salts of methacrylic acid, said resin having a water content of 50 percent by weight or lower, whereby said fine particles are impregnated with said polymer, the amount of said polymer being in the range of from 1 to 100% of the amount of said resin and, crosslinking said polymer to form crosslinked polymer on the surfaces of said fine particles so that the reactive functional groups of said polymer are present on the surfaces of said fine particles whereby said fine particles become highly reactive and remain highly water-absorptive.

Claim 4

A process for preparing a highly reactive, water-absorptive resin, which comprises the steps of: mixing (1) an aqueous solution containing a water-soluble crosslinking agent and a hydrophilic polymer having reactive functional groups in the molecule, said reactive functional groups being selected from the group consisting of amino groups and hydroxyl groups, with (2) a dispersion of fine particles of a highly water-absorptive resin dispersed in an organic liquid, said highly water-absorptive resin being capable of absorbing water in an amount of from 10 to 1500 times the weight of said resin, said resin being selected from the group consisting of polymers of acrylic acid, alkali metal salts of acrylic acid, methacrylic acid and alkali metal salts of methacrylic acid, said resin having a water content of 50 percent by weight or lower, whereby said fine particles are impregnated with said polymer, the amount of said polymer being in the range of from 1 to 100% of the amount of said resin and, crosslinking said polymer to form crosslinked polymer on the surfaces of said fine particles so that the reactive functional groups of said polymer are present on the surfaces of said fine particles whereby said fine particles become highly reactive and remain highly water-absorptive.

Claim 5

A process for preparing a highly reactive, water-absorptive resin, which comprises the steps of mixing (A) an aqueous phase consisting essentially of a polymerizable, water-soluble, first monomer selected from the group consisting of acrylic acid, methacrylic acid and alkali metal salts thereof, and a water-soluble, polymerization initiator dissolved in water, with (B) an oil phase comprising a non-polar organic liquid, to form a water-in-oil suspension and polymerizing said monomer to obtain a dispersion of particles of a highly water-absorptive resin and containing water, said particles being dispersed in said non-polar organic liquid, said resin containing carboxyl or alkali metal carboxylate groups and being capable of absorbing an amount of water in the range of from 10 to 1500 times the weight of said resin; removing water from said dispersion so that said resin has a water content of 50 percent by weight or less; then mixing (1) said dispersion in which said resin has a water content of 50 percent by weight or less, with (2) an aqueous solution of a hydrophilic, polymerizable, second monomer having a reactive functional group in the molecule, a crosslinking agent and a water-soluble initiator, said reactive functional group being selected from the group consisting of hydroxy and amino, the amount of said second monomer being from 1 to 100% of the weight of said resin; polymerizing said second monomer to form a polymer of said second monomer on the surfaces of said resin particles so that said reactive functional groups of the polymer of said second monomer are present on the surfaces of said resin particles whereby said resin particles become highly reactive and remain highly water-absorptive; and then removing said organic liquid to obtain particles of said resin.

Claim 6

A process for preparing a highly reactive, water-absorptive resin, which comprises the steps of mixing (A) an aqueous phase consisting essentially of a polymerizable, water-soluble, first monomer selected from the group consisting of acrylic acid, methacrylic acid and alkali metal salts thereof, and a water-soluble, polymerization initiator dissolved in water, with (B) an oil phase comprising a non-polar organic liquid, to form a water-in-oil suspension and polymerizing said monomer to obtain a dispersion of particles of a highly water-absorptive resin and containing water, said particles being dispersed in said non-polar organic liquid, said resin containing carboxyl or alkali metal carboxylate groups and being capable of absorbing an amount of water in the range of from 10 to 1500 times the weight of said resin; removing water from said dispersion so that said resin has a water content of 50 percent by weight or less; then mixing (1) said dispersion in which said resin has a water content of 50 percent by weight or less, with (2) an aqueous solution of a hydrophilic, polymerizable, second monomer having a reactive functional group in the molecule, a crosslinking agent and a water-soluble initiator, said reactive functional group being selected from the group consisting of hydroxy and amino, the amount of said second monomer being from 1 to 100% of the weight of said resin; polymerizing said second monomer to form a polymer of said second monomer on the surfaces of said resin particles so that said reactive functional groups of the polymer of said second monomer are present on the surfaces of said resin particles whereby said resin particles become highly reactive and remain highly water-absorptive; and then removing said organic liquid to obtain particles of said resin.

Claim 7

A process for preparing a highly reactive, water-absorptive resin, which comprises the steps of mixing (A) an aqueous phase consisting essentially of a polymerizable, water-soluble, first monomer selected from the group consisting of acrylic acid, methacrylic acid and alkali metal salts thereof, and a water-soluble, polymerization initiator dissolved in water, with (B) an oil phase comprising a non-polar organic liquid, to form a water-in-oil suspension and polymerizing said monomer to obtain a dispersion of particles of a highly water-absorptive resin and containing water, said particles being dispersed in said non-polar organic liquid, said resin containing carboxyl or alkali metal carboxylate groups and being capable of absorbing an amount of water in the range of from 10 to 1500 times the weight of said resin; removing water from said dispersion so that said resin has a water content of 50 percent by weight or less; then mixing (1) said dispersion in which said resin has a water content of 50 percent by weight or less, with (2) an aqueous solution of a hydrophilic polymer having a reactive functional group in the molecule and a water-soluble crosslinking agent, said reactive functional group being selected from the group consisting of hydroxy and amino, the amount of said polymer being from 1 to 100% of the weight of said resin; cross-linking said polymer and coating the surfaces of said resin particles with the resulting cross-linked polymer so that said reactive functional groups of said polymer are present on the surfaces of said resin particles whereby said resin particles become highly reactive and remain highly water-absorptive; and then removing said organic liquid to obtain particles of said resin.

Claim 8

A process for preparing a highly reactive, water-absorptive resin, which comprises the steps of mixing (A) an aqueous phase consisting essentially of a polymerizable, water-soluble, first monomer selected from the group consisting of acrylic acid, methacrylic acid and alkali metal salts thereof, and a water-soluble, polymerization initiator dissolved in water, with (B) an oil phase comprising a non-polar organic liquid, to form a water-in-oil suspension and polymerizing said monomer to obtain a dispersion of particles of a highly water-absorptive resin and containing water, said particles being dispersed in said non-polar organic liquid, said resin containing carboxyl or alkali metal carboxylate groups and being capable of absorbing an amount of water in the range of from 10 to 1500 times the weight of said resin; removing water from said dispersion so that said resin has a water content of 50 percent by weight or less; then mixing (1) said dispersion in which said resin has a water content of 50 percent by weight or less, with (2) an aqueous solution of a hydrophilic polymer having a reactive functional group in the molecule and a water-soluble crosslinking agent, said reactive functional group being selected from the group consisting of hydroxy and amino, the amount of said polymer being from 1 to 100% of the weight of said resin; cross-linking said polymer and coating the surfaces of said resin particles with the resulting cross-linked polymer so that said reactive functional groups of said polymer are present on the surfaces of said resin particles whereby said resin particles become highly reactive and remain highly water-absorptive; and then removing said organic liquid to obtain particles of said resin.

Claim 9

A process as claimed in claim 1 or claim 2, wherein said water-absorptive resin is a hydrophilic polymer prepared by the reversed-phase suspension polymerization of an aqueous solution of a hydrophilic monomer selected from the group consisting of acrylic acid, methacylic acid and alkali metal salts thereof, said aqueous solution containing a water-soluble initiator.

Claim 10

A process as claimed in claim 1, claim 2, claim 3 or claim 4, wherein said highly water-absorptive resin is a polymer or a copolymer of acrylic acid or an alkali metal acrylate.

Claim 11

A process as claimed in claim 1, claim 2, claim 3 or claim 4, wherein the water content of said highly water-absorptive resin is in the range of from 1 to 50% by weight.

Claim 12

A process as claimed in claim 1, claim 2, claim 3 or claim 4, wherein the water content of said highly water-absorptive resin is in the range of from 10 to 40% by weight.

Claim 13

A process as claimed in claim 2 or claim 4, wherein said hydrophilic polymer is selected from the group consisting of a polymer or copolymer of (meth)acrylamide, N,N-dimentylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, vinylpyridine, vinylpyrrolidone, allylamine, 2-hydroxyethyl (meth)acrylate, polyethylene glycol (meth)acrylate, vinylsulfonate, styrene sulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid; polyethyleneimine; polyacrolein; polyethylene glycol and Hofmann degradation product of polyacrylamide.

Claim 14

A process as claimed in claim 2 or claim 4, wherein said crosslinking agent is polyglycidyl ether, halo-epoxy compound, polyaldehyde, polyol or polyamine.

Claim 15

A process as claimed in claim 1 or claim 3, wherein said hydrophilic monomer is selected from the group consisting of acylamide, methacrylamide, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, vinylpyridine, vinylpyrrolidone, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, polyethylene glycol(meth)acrylate, vinylsulfonate, styrene-sulfonic acid, acrylonitrile and methacrylonitrile.

Claim 16

A process as claimed in claim 1, claim 2, claim 3 or claim 4 in which said highly water-absorptive resin is a homopolymer of acrylic acid, alkali metal salt of acrylic acid, methacrylic acid or alkali metal salt of methacrylic acid.

Claim 17

A process as claimed in claim 1, claim 2, claim 3 or claim 4 in which said highly water-absorptive resin is a homopolymer of sodium acrylate.