Surface treated absorbent polymers

Claim 3

A method as claimed in claim 1, characterised in that the water-absorbent resin possesses anionic or pseudo-anionic character.

Claim 4

A method as claimed in either claim 1 or claim 2, characterised in that the water-absorbent resin contains neutralized carboxyl, neutralized sulfonate, neutralized sulfate, neutralized phosphate, amide or nitrile functionalities.

Claim 5

A method as claimed in claim 3, characterised in that the water-absorbent resin contains neutralized carboxyl functionalities.

Claim 8

A process for preparing a solid water-absorbent resin with improved water absorbing properties comprising mixing a monomer solution of (A) acrylic acid, neutralized 70-100 mole percent; (B) styrene and/or methyl methacrylate in an amount of 0% to 25% based on the weight of acrylic acid and (C) a water-miscible to water-soluble polyvinyl monomer in a combined concentra­tion of (A), (B) and (C) of at least 30 wt. %; with water to form a mixed monomer solution wherein the monomers of the mixed monomer solution consist essen­tially of (A) and (B) and (C) and initiating polymeriza­tion of said monomers such that during polymerization, the exothermic heat of reaction is substantially the only heat energy used to accomplish polymerization, cross-­linking and to drive off sufficient water to obtain a solid cross-linked resin having a water content of 15 percent by weight or less; and thereafter contacting said resin with a polyquaternary amine.

Claim 9

A process for preparing a solid water-absorbent resin with improved water absorbing properties comprising mixing a monomer solution of (A) acrylic acid, neutralized 70-100 mole percent; (B) styrene and/or methyl methacrylate in an amount of 0% to 25% based on the weight of acrylic acid and (C) a water-miscible to water-soluble polyvinyl monomer in a combined concentra­tion of (A), (B) and (C) of at least 30 wt. %; with water to form a mixed monomer solution wherein the monomers of the mixed monomer solution consist essen­tially of (A) and (B) and (C) and initiating polymeriza­tion of said monomers such that during polymerization, the exothermic heat of reaction is substantially the only heat energy used to accomplish polymerization, cross-­linking and to drive off sufficient water to obtain a solid cross-linked resin having a water content of 15 percent by weight or less; and thereafter contacting said resin with a polyquaternary amine.

Claim 10

A process as claimed in claim 7, characterised in that the combined concentration of the monomers (A), (B) and (C) is at least 30 wt. % and less than 70 wt. %.

Claim 11

A process as claimed in either claim 7 or claim 8, characterised in that the mixed monomer solution has a temperature of 20 to 85°C. prior to polymerization.

Claim 12

A process as claimed in any one of claims 7 to 9, characterised in that monomer (C) is N,N-methylenebis­acrylamide or N,N,-methylenebismethacrylamide.

Claim 13

A process as claimed in any one of claims 7 to 10, characterised in that the mixed monomer solution contains 1 to 10 wt. % of an organic solvent based on the weight of monomers (A), (B) and (C).

Claim 14

A process as claimed in any one of claims 7 to 11, characterised in that the polymer retains 0.1% to 5.0% polyamine based on the total weight of the treated polymer.

Claim 15

A process as claimed in any one of claims 7 to 12, characterised in that the solid cross-linked resin is treated with from about 0.25% to 2.0% by dry weight of a polyquaternary amine based on the weight of said resin.

Claim 16

A process as claimed in any one of claims 7 to 13, characterised in that the polyquaternary amine has a molecular weight from 200 to 5000, preferably from 300 to 4000.

Claim 17

A process as claimed in any one of claims 7 to 14, characterised in that the polyquaternary amine is a condensation product of hexamethylenediamine, dimethylamine and epichlorohydrin; a condensation product of dimethyl­amine and epichlorohydrin; or quaternized polyethylene­imine.

Claim 18

A process as claimed in any one of claims 7 to 15, characterised in that the polyquaternary amine is dispersed in a non-aqueous solvent from about 0.1% to about 20% by weight before contacting the solid water-­absorbent resin.

Claim 19

A process as claimed in claim 16, characterised in that the non-aqueous solvent is methanol, isopropyl alcohol, acetone, methyl ethyl ketone or mixtures thereof.

Claim 20

A process as claimed in any one of claims 7 to 17, characterised by the step of adjusting the temperature of the monomer mixture to a temperature of 25 to 85°C. prior to initiating polymerization of said monomer mixture.

Claim 21

A process as claimed in any one of claims 7 to 18, characterised in that a polymerization initiator is added in an amount of at least 0.5% total weight of monomers (A), (B) and (C).

Claim 22

A process as claimed in any one of claims 7 to 19, characterised by the step of pulverizing said cross-­linked resin to form a powder prior to contacting said powder with a polyquaternary amine in an amount of about 0.1% to 5.0% based on the weight of said cross-linked resin copolymer.

Claim 23

A process as claimed in any one of claims 7 to 20, characterised in that it comprises depositing said monomer mixture including an initiator onto a support surface in sheet form for polymerization and cross-­linking, followed by pulverizing the resultant cross-­linked resin to form a powder, and thereafter contacting said powder with a polyquaternary amine in an amount of from about 0.1% to 5.0% based on the weight of said powder.