Method for production of absorbent resin

• US 5,532,323 A
• Filed: 03/04/1993
• Issued: 07/02/1996
• Est. Priority Date: 03/05/1992
• Status: Expired due to Term

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Yano, Kazutaka, Irie, Yoshio, Kajikawa, Katsuhiro, Nagasuna, Kinya
• Primary Examiner(s): Nagumo, Mark
• Application Number:
  US08/026,407
• Time in Patent Office: 1,216 Days
• Field of Search: 526/240, 526/318.41, 526/320, 526/73, 525/384, 528/481
• US Class Current: 525/384
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: C08F 220/04 Acids; Metal salts or ammonium salts thereof

Abstract

An absorbent resin exhibiting a high absorption ratio, having only a small water-soluble component content, and have excellent gel stability to withstand the effect of aging is produced. The production of the absorbent resin comprises a step of polymerizing a water-soluble monoethylenically unsaturated monomer by using, in a proportion of 0.01-0.3 mol % based on the amount of the water-soluble monoethylenically unsaturated monomer, a cross-linking agent having at least one group of the following formula I: ##STR1## wherein R¹ is an alkylene group of 2 to 4 carbon atoms interposed between two polymerizing unsaturated groups in the molecular unit thereof and then heat-treating the resin produced by the polymerization at a temperature in the range of from 160° to 230° C.

Claims

1. A method for producing an absorbent resin comprising polymerizing a water-soluble monoethylenically unsaturated monomer in the presence of a cross-linking agent, said cross-linking agent possessing at least two polymerizable unsaturated groups and between said two polymerizable unsaturated groups at least one unit represented by the formula V:

##STR10## wherein R² and R³ are independently a hydrogen atom or a methyl group and n is a number in the range of from 2 to 100, said cross-linking agent is used in a proportion in the range of from 0.01 to 0.3 mol % based on the amount of said water-soluble monoethylenically unsaturated monomer, and heat-treating the resultant polymer at a temperature in the range of from 160°

to 230°

C. in the presence of another cross-linking agent having at least two reacting groups capable of reacting with functional groups of said polymer.

2. A method according to claim 1, wherein said cross-linking agent of formula (V) is used in a proportion in the range of from 0.03 to 0.2 mol % based on the amount of said water-soluble monoethylenically unsaturated monomer.

3. A method according to claim 1, wherein said water-soluble monoethylenically unsaturated monomer contains 50% by weight or more of at least one member selected from the group consisting of acrylic acid and alkali metal salts and amine salts.

4. A method according to claim 1, wherein said heat treatment of said polymer is carried out at a temperature in the range of from 180°

to 200°

C.

5. A method according to claim 1, wherein said another cross-linking agent is a polyalcohol.

6. A method according to claim 1, wherein the amount of said another cross-linking agent is in the range of 0.005 to 5% by weight based on the amount of said polymer.