Method for production of hydrophilic resin

• US 20020161132A1
• Filed: 03/29/2002
• Published: 10/31/2002
• Est. Priority Date: 06/10/1992
• Status: Active Grant

• Current Assignee: Katsuhiro Kajikawa, Kunihiko Ishizaki, Takumi Hatsuda, Yoshio Irie
• Original Assignee: Katsuhiro Kajikawa, Kunihiko Ishizaki, Takumi Hatsuda, Yoshio Irie
• Inventors: Ishizaki, Kunihiko, Irie, Yoshio, Kajikawa, Katsuhiro, Hatsuda, Takumi
• Granted Patent: US 6,998,447 B2
• Time in Patent Office: Days
• US Class Current: 525/329.7
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: C08F 20/04 Acids, Metal salts or ammonium salts thereof
• CPC Class Codes: C08L 33/02 Homopolymers or copolymers of acids; Metal or ammonium salts thereof

Abstract

In the production of an acrylate polymer by the steps of preparing a water-soluble unsaturated monomer having a ratio of neutralization in the range of 30 to 100 mol % and containing 50 to 100 mol % of an acrylate and then polymerizing the monomer, a method for the production of a hydrophilic resin which comprises using a water-soluble unsaturated monomer having a β-hydroxy propionic acid (salt) content of not more than 1,000 ppm. The hydrophilic resin obtained by this method exhibits excellent physical properties and has only a small residual monomer content. Further, a residual monomer content neither occurs nor increases in any using conditions.

Claims

1. A method for the production of a hydrophilic resin which comprises polymerizing a water-soluble unsaturated monomer containing 50 to 100 mol % of an acrylate having a ratio of neutralization in the range of 30 to 100 mol % and not more. than 1,000 ppm of β

-hydroxy propionic acid (salt).

2. A method according to claim 1, wherein said water-soluble unsaturated monomer contains 50 to 0 mol % of at least one unsaturated monomer selected from the group consisting of hydrophilic unsaturated monomers and hydrophobic unsaturated monomers.

3. A method according to claim 2, wherein said water-soluble unsaturated monomer contains not more than 300 ppm of β

-hydroxy propionic acid (salt).

4. A method according to claim 1, wherein said acrylate is at least one member selected from the group consisting of alkali metal salts and ammonium salts.

5. A method according to claim 4, wherein said alkali metal salt is at least one member selected from the group consisting of sodium salts and potassium salts.

6. A method according to claim 1, wherein said hydrophilic resin has a cross-linked structure.

7. A method according to claim 6, wherein said acrylate is an alkali metal salt and an ammonium salt and said absorbent polymer or a dry product thereof has been subjected to a heat treatment.

8. A method according to claim 7, wherein an ammonium salt accounts for 10 to 40 mol % of the acid group in said absorbent resin.

9. A method according to claim 7, wherein the temperature of said heat treatment is in the range of 150°

to 250°

C.

10. A method according to claim 4, wherein said heat treatment is carried out at the step of drying said absorbent resin.

11. A method for the production of a hydrophilic resin which comprises polymerizing a water-soluble unsaturated monomer containing 50 to 100 mol % of an acrylate having a ratio of neutralization in the range of 30 to 100 mol % and not more than 1,000 ppm of β

-hydroxy propionic acid (salt) and then cross-linking the surface region of the resultant acrylate polymer by treating said polymer with a second cross-linking agent having at least two groups capable of reacting with the functional group within the molecular unit of said polymer.

12. A method according to claim 11, wherein said water-soluble unsaturated monomer contains 50 to 0 mol % of at least one unsaturated monomer selected from the group consisting of hydrophilic unsaturated monomers and hydrophobic unsaturated monomers.

13. A method according to claim 12, wherein said water-soluble unsaturated monomer contains not more than 300 ppm of β

-hydroxy propionic acid (salt).

14. A method according to claim 11, wherein said acrylate is at least one member selected from the group consisting of alkali metal salts and ammonium salts.

15. A method according to claim 14, wherein said alkali metal salt is at least one member selected from -the group consisting of sodium salts and potassium salts.

16. A method according to claim 11, wherein said hydrophilic resin has a cross-linked structure.

17. A method according to claim 11, wherein said second cross-linking agent is at least one member selected from the group consisting of polyhydric alcohols, polyepoxy compounds, polyamines, polyaziridines, polyaldehydes, polyisocyanates, polyoxazolines, alkylene carbonates, and polyvalent metals.

18. A method according to claim 16, wherein said acrylate is an alkali metal salt and an ammonium salt and said absorbent polymer or the dry product thereof has undergone a heat treatment.

19. A method according to claim 18, wherein an ammonium salt accounts for 10 to 40 mol % of the acid group in said absorbent resin.

20. A method according to claim 18, wherein the temperature of said heat treatment is in the range of 1500 to 250°

C.

21. A method according to claim 18, wherein said heat treatment is carried out at the step of drying said absorbent resin.

23. A composition according to claim 21, wherein neutralization ratio of carboxyl group is 30 to 100 mol%.

22. An acrylic acid salt polymer composition which contains 1 to 1000 ppm of β

-hydroxy propionic acid (salt) and not more than 100 ppm of a residual monomer.

24. A composition according claim 23, wherein said acrylic acid salt polymer is an absorbent resin.

25. A composition according to claim 22, wherein a content of β

-hydroxy propionic acid (salt) is 1 to 100 ppm.