Water-absorbing agent and process for producing the same

• US 6,809,158 B2
• Filed: 10/02/2001
• Issued: 10/26/2004
• Est. Priority Date: 10/20/2000
• Status: Active Grant

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Ikeuchi, Hiroyuki, Masuda, Yoshihiko, Harada, Nobuyuki
• Primary Examiner(s): Lipman, Bernard
• Application Number:
  US09/968,514
• Publication Number:
  US 20020072471A1
• Time in Patent Office: 1,120 Days
• Field of Search: 525/375, 525/383
• US Class Current: 525/375
• CPC Class Codes: C08J 2300/14 Water soluble or water swellable polymers, e.g. aqueous gels
• CPC Class Codes: C08J 3/245 Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
• CPC Class Codes: C08K 5/1535 Five-membered rings
• CPC Class Codes: C08K 5/353 Five-membered rings

Abstract

The present invention provides: a process for producing a water-absorbing agent at low temperature in a short time, wherein the water-absorbing agent has excellent balance between the absorption capacity without load and the absorption capacity under a load, high fluidity under a hygroscopic atmosphere, and excellent safety; and a novel water-absorbing agent and a novel crosslinking agent particularly suitable for crosslinking water-absorbent resins. The water-absorbing agent, having excellent balance between the absorption capacity without load and the absorption capacity under a load, high fluidity under a hygroscopic atmosphere, and excellent safety, can be obtained by using an oxetane compound and/or an imidazolidinone compound for a water-absorbent resin.

Claims

1. A process for producing a water-absorbing agent, which is characterized by comprising the step of blending an oxetane compound and/or an imidazolidinone compound with a water-absorbent resin, where said water-absorbent resin is selected from the group consisting of crosslinked poly(acrylic acids) and partially or entirely neutralized product thereof;

hydrolyzed copolymers of starch-acrylonitrile, neutralized graft polymers of starch-acrylic acid, saponified copolymers of vinyl acetate-acrylic acid ester, hydrolyzed copolymers of acrylonitrile or acrylamide, crosslinked polymers of hydrolyzed copolymers of acrylonitrile or acrylamide, crosslinked polyvinyl alcohols having a carboxyl group, and copolymers of crosslinked isobutylene-maleic anhydride.

2. A process for producing a water-absorbing agent according to claim 1, wherein the oxetane compound is represented by the following structural formula (1),

wherein the structural formula (1) is:

where;

R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group, or a substituted aromatic group.

3. A process for producing a water-absorbing agent according to claim 1, wherein the imidazolidinone compound is represented by the following structural formula (5),

wherein the structural formula (5) is:

where;

R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group, or a substituted aromatic group.

4. A process for producing a water-absorbing agent according to claim 1, which is characterized by comprising the steps of

blending the oxetane compound and/or the imidazolidinone compound with the water-absorbent resin;

and

heating the resultant mixture.

5. A process for producing a water-absorbing agent according to claim 2, which is characterized by comprising the steps of:

blending the oxetane compound and/or the imidazolidinone compound with the water-absorbent resin; and

heating the resultant mixture.

6. A process for producing a water-absorbing agent according to claim 3, which is characterized by comprising the steps of:

blending the oxetane compound and/or the imidazolidinone compound with the water-absorbent resin; and

heating the resultant mixture.

7. A process for producing a water-absorbing agent according to claim 1, which is characterized in that the water-absorbent resin is obtained after drying.

8. A process for producing a water-absorbing agent according to claim 2, which is characterized in that the water-absorbent resin is obtained after drying.

9. A process for producing a water-absorbing agent according to claim 3, which is characterized in that the water-absorbent resin is obtained after drying.

10. A process for producing a water-absorbing agent according to claim 4, which is characterized in that the water-absorbent resin is obtained after drying.

11. A process for producing a water-absorbing agent according to claim 5, which is characterized in that the water-absorbent resin is obtained after drying.

12. A process for producing a water-absorbing agent according to claim 6, which is characterized in that the water-absorbent resin is obtained after drying.

22. A process for producing a water-absorbing agent according to claim 1, wherein said water-absorbent resin is a water-swellable crosslinked poly(acrylic acid) or salt thereof.

23. A process for producing a water-absorbing agent according to claim 1, wherein said water-absorbent resin is a polymer obtained by polymerizing and crosslinking monomers comprising acrylic acid, acrylic acid salt or mixture thereof as a major component.

30. A process for producing a water-absorbing agent according to claim 1, wherein said water-absorbent resin is a water-insoluble crosslinked polymer.

31. A process for producing a water-absorbing agent according to claim 1, wherein said water-absorbent resin has a water-extractable content of not more than 40 wt %.

32. A process for producing a water-absorbing agent according to claim 1, wherein said water-absorbing resin is in the form of particles.

13. An absorbing agent, which comprises:

an oxetane compound and/or an imidazolidinone compound; and

a water-absorbent resin, where said water-absorbent resin is selected from the group consisting of crosslinked poly(acrylic acids) and partially or entirely neutralized product thereof, hydrolyzed copolymers of starch-acrylonitrile, neutralized graft polymers of starch-acrylic acid, saponified copolymers of vinyl acetate-acrylic acid ester, hydrolyzed copolymers of acrylonitrile or acrylamide, crosslinked polymers of hydrolyzed copolymers of acrylonitrile or acrylamide, crosslinked polyvinyl alcohols having a carboxyl group, and copolymers of crosslinked isobutylene-maleic anhydride.

33. A process for producing a water-absorbing agent according to claim 13, wherein said water-absorbing resin is a water-insoluble crosslinked polymer.

34. An absorbing agent according to claim 13, wherein said water-absorbing resin has a water-extractable content of not more than 40 wt %.

35. An absorbing agent according to claim 13, wherein said absorbing agent is in the form of particles.

14. An absorbing agent, which comprises a water-absorbent resin crosslinked with an oxetane compound and/or an imidazolidinone compound, where said water-absorbent resin is selected from the group consisting of crosslinked poly(acrylic acids) and partially or entirely neutralized product thereof, hydrolyzed copolymers of starch-acrylonitrile, neutralized graft polymers of starch-acrylic acid, saponified copolymers of vinyl acetate-acrylic acid ester, hydrolyzed copolymers of acrylonitrile or acrylamide, crosslinked polymers of hydrolyzed copolymers of acrylonitrile or acrylamide, crosslinked polyvinyl alcohols having a carboxyl group, and copolymers of crosslinked isobutylene-maleic anhydride.

15. An absorbing agent according to claim 14, wherein the surface neighborhood of the water-absorbent resin is treated with the oxetane compound and/or the imidazolidinone compound, and the absorption capacity under a load for a physiological saline solution of 0.9 weight % is at least 20 g/g at 2.07 kPa.

16. An absorbing agent according to claim 14, which is characterized in that the fluidity under a hygroscopic atmosphere is not less than 60% after being left for 20 minutes in a condition such that the temperature is 40°

C. and the relative humidity is 75%.

17. An absorbing agent according to claim 15, which is characterized in that the fluidity under a hygroscopic atmosphere is not less than 60% after being left for 20 minutes in a condition such that the temperature is 40°

C. and the relative humidity is 75%.

18. An absorbent article, which comprises the water-absorbing agent as recited in claim 14.

19. An absorbent article, which comprises the water-absorbing agent as recited in claim 15.

20. An absorbent article, which comprises the water-absorbing agent as recited in claim 16.

21. An absorbent article, which comprises the water-absorbing agent as recited in claim 17.

24. A process for producing a water-absorbing agent comprising:

crosslinking a water-absorbent resin with a crosslinking agent, said crosslinking agent comprising at least one compound selected from the group consisting of an oxetane compound having at least one oxetane skeleton per molecule, an imidazolidinone compound having at least one imidazolidinone skeleton per molecule, and mixtures thereof, where said water-absorbent resin is selected from the group consisting of crosslinked poly(acrylic acids) and partially or entirely neutralized product thereof, hydrolyzed copolymers of starch-acrylonitrile, neutralized graft polymers of starch-acrylic acid, saponified copolymers of vinyl acetate-acrylic acid ester, hydrolyzed copolymers of acrylonitrile or acrylamide, crosslinked polymers of hydrolyzed copolymers of acrylonitrile or acrylamide, crosslinked polyvinyl alcohols having a carboxyl group, and copolymers of crosslinked isobutylene-maleic anhydride.

25. A process for producing a water-absorbing agent according to claim 24, wherein said water-absorbent resin is a polyacrylic acid or salt thereof.

26. A process for producing a water-absorbing agent according to claim 24, wherein said water-absorbent resin is a polymer obtained by polymerizing and crosslinking monomers comprising acrylic acid, acrylic acid salts, or mixtures thereof as a major component.

27. A process for producing a water-absorbing agent according to claim 24, comprising surface crosslinking said resin with said crosslinking agent.

28. A process for producing a water-absorbing agent according to claim 24, wherein said oxetane has the structural formula (1):

where R¹, R², R³, R⁴, R⁵, and R⁶ each independently represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl groop, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group, or a substituted aromatic group.

29. A process for producing a water-absorbing agent according to claim 24, wherein said imidazolidinone compound has the structural formula (5):

where R¹, R², R³, R⁴, R⁵, and R⁶ each independently represent a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group, or a substituted aromatic group.