Water absorbing starch resins

• US 4,076,663 A
• Filed: 03/29/1976
• Issued: 02/28/1978
• Est. Priority Date: 03/27/1975
• Status: Expired due to Term

• Current Assignee: Sanyo Chemical Industries Limited
• Original Assignee: Sanyo Chemical Industries Limited
• Inventors: Nakamura, Akira, Masuda, Fusayoshi, Nishida, Kazuo
• Primary Examiner(s): Woodberry, Edward M.
• Application Number:
  US05/671,148
• Time in Patent Office: 701 Days
• Field of Search: 260/17.4 ST, 260/17.4 R, 260/17 R, 260/17.4 GC, 260/17.4 CL, 128/284, 128/285, 128/290
• US Class Current: 525/54.31
• 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
• CPC Class Codes: C08F 220/281 and containing only one oxygen, e.g. furfuryl (meth)acrylate or 2-methoxyethyl (meth)acrylate
• CPC Class Codes: C08F 220/34 Esters containing nitrogen , e.g. N,N-dimethylaminoethyl (meth)acrylate
• CPC Class Codes: C08F 220/56 Acrylamide; Methacrylamide
• CPC Class Codes: C08F 222/385 Monomers containing two or more (meth)acrylamide groups, e.g. N,N'-methylenebisacrylamide
• CPC Class Codes: C08F 251/00 Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
• CPC Class Codes: C08F 2810/20 leading to a crosslinking, either explicitly or inherently
• CPC Class Codes: C08F 8/12 Hydrolysis
• CPC Class Codes: C08F 8/44 Preparation of metal salts or ammonium salts
• CPC Class Codes: C08L 51/02 grafted on to polysaccharides

Abstract

A highly water-absorbent resin is produced by polymerizing (A) starch or cellulose, (B) at least one monomer having a polymerizable double bond which is water-soluble or becomes water-soluble by hydrolysis and (C) a crosslinking agent, and subjecting, if necessary, the resulting product to hydrolysis.

Claims

1. A process for producing a water-absorbing resin which comprises polymerizing (a) at least one of natural starch and α

starch, (b) at least one monomer having a single polymerizable double bond which is a water-soluble or becomes water-soluble by hydrolysis, and (c) a crosslinking agent, and if the monomer (b) is one which becomes water soluble by hydrolysis, thereafter subjecting the resulting product to hydrolysis.

2. The water-absorbing resin having a water-absorbence of at least 60 ml/g obtained by the process of claim 1.

3. The water-absorbing resin having a water-absorbence of from 100 to 500 ml/g obtained by the process of claim 1.

4. The process of claim 1, wherein the crosslinking agent (C) is selected from the group consisting of (1) a compound having at least two isolated polymerizable double bonds, (2) a compound having at least one polymerizable double bond and at least one functional group reactive with the monomer (B), (3) a compound having at least two functional groups reactive with the monomer (B), (4) a polyvalent metal compound which can form ionic crosslinkages and mixtures thereof.

5. The process of claim 4, wherein the compound having at least two isolated polymerizable double bonds is a di- or poly-ester of an unsaturated mono- or poly-carboxylic acid with a polyol.

6. The process of claim 4, wherein the compound having at least two polymerizable double bonds is a diester of (meth)acrylic acid with an alkylene(C₂ -C₆) glycol or polyoxyalkylene(C₂ -C₄)glycol having a molecular weight of less than 400.

7. The process of claim 4, wherein the compound having at least two polymerizable double bonds is a bis-(meth)acrylamide.

8. The process of claim 7, wherein the bis(meth)-acrylamide is an N,N-alkylene(C₁ -C₆)bis(meth)acrylamide.

9. The process of claim 4, wherein the polyvalent metal compound is an oxide, hydroxide or weak acid salt of a polyvalent metal.

10. The process of claim 9, wherein the polyvalent metal is an alkaline earth metal or zinc.

11. The process of claim 1, wherein the monomer (B) which is water-soluble is a monoethylenically unsaturated compound having at least one hydrophilic group selected from the group consisting of carboxyl, carboxylic acid anhydride, carboxylic acid salt, sulfonic acid, sulfonic acid salt, hydroxyl, ether, amide, amino and quaternary ammonium salt groups.

12. The process of claim 11, wherein the monoethylenically unsaturated compound is a monoethylenically unsaturated carboxylic acid, anhydride thereof or salt thereof.

13. The process of claim 12, wherein the monoethylenically unsaturated compound is (meth)acrylic acid, maleic acid, fumaric acid, a water-soluble salt of said acids or maleic anhydride.

14. The process of claim 11, wherein the monoethylenically unsaturated compound having an amide group is (meth)acrylamide or vinyl lactam.

15. The process of claim 11, wherein the monoethylenically unsaturated compound having a quaternary ammonium salt group is a quaternary (meth)acrylic ester, a quaternary (meth)acrylic amide or a quaternary vinyl compound.

16. The process of claim 1, wherein the monomer (B) which becomes water-soluble by hydrolysis is a monoethylenically unsaturated compound having at least one hydrolyzable group selected from the group consisting of ester and nitrile groups.

17. The process of claim 16 wherein the monomer (B) is (meth)arylonitrile, alkyl (C₁ -C₃) (meth)acrylate or alkyl (C₁ -C₃)vinyl ester.

18. The process of claim 1, wherein the weight ratio of (A) :

(B) ;

(C) is 100 ;

10-3,000 ;

0.0001-20.

19. The process of claim 1, wherein the weight ratio of (A) :

(B) ;

(C) is 100 ;

50-1,000 ;

0.001-10.

20. The process of claim 1, wherein the starch is changed into α

-type starch in a solvent at an elevated temperature before being used in the polymerization.

21. The process of claim 1, wherein the monomer (B) is a monomer having at least one free carboxyl, carboxylic acid anhydride or free sulfonic group, and said group is neutralized to form a salt after the polymerization.