Process for producing water-absorbent resin

• US 5,281,683 A
• Filed: 12/14/1992
• Issued: 01/25/1994
• Est. Priority Date: 12/18/1991
• Status: Expired due to Fees

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Irie, Yoshio, Yano, Kazutaka
• Primary Examiner(s): Schofer, Joseph L.
• Assistant Examiner(s): SAROFIM, NABIL F
• Application Number:
  US07/989,658
• Time in Patent Office: 407 Days
• Field of Search: 526/323.2, 526/320
• US Class Current: 526/323.2
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 290/062 Polyethers

Abstract

A water-absorbent resin having high absorption capacity and a slight amount of water-soluble ingredients is produced by a process, which includes polymerizing a water-soluble monoethylenic unsaturated monomer in the presence of a crosslinking agent, and using a bifunctional compound represented by the following general formula 1 as the crosslinking agent; ##STR1## wherein R¹ and R² are a hydrogen atom or a methyl group independently, and --(X)-- is a divalent organic group combined in a straight chain type by an optional arrangement of a structural unit (A) of --(CO--CH═CH--CO--O)_L -- and l=1-5, a structural unit (B) of --(CH₂ CH₂ O)_m -- and m=2-100, and a structural unit (C) of --(R³ O)_n -- and n=0-20, in which R³ is a C₃ -C₄ alkylene.

Claims

1. A process for producing a water-absorbent resin, comprising polymerizing a water-soluble monoethylenic unsaturated monomer in the presence of a crosslinking agent, wherein said crosslinking agent is a compound represented by the following formula ##STR9## wherein R¹ and R² denote a hydrogen atom or a methyl group independently;

X denotes a divalent, straight chain organic group comprising structural units A, B and optionally C, wherein

A is 1 to 5 units of --CO--CH═

CH--CO--O--,

B is 2 to 100 units of --CH₂ CH₂ O--, and

C is 0 to 20 units of --R³ O--, wherein R³ is a branched or straight chain C₃ -C₄ alkylene, with the provisos (i) that B should be located on both sides of structural unit A when X includes structural units A and B, but not C, and (ii) that at least one of B and C may be located on both sides of structural unit A when X includes A, B and C.

2. A process for producing a water-absorbent resin as claimed in claim 1, wherein the crosslinking agent is used in a proportion of from 0.01 to 1 mole % based on the water-soluble monoethylenic unsaturated monomer.

3. A process for producing a water-absorbent resin as claimed in claim 1 or 2, wherein a polymerization reaction is carried out by using an aqueous monomer solution containing a water-soluble monoethylenic unsaturated monomer as a main component.

4. A process for producing a water-absorbent resin as claimed in claim 3, wherein the concentration of the water-soluble monoethylenic unsaturated monomer in the aqueous monomer solution is in a range of from 20% by weight up to a concentration of saturation.