Water-Absorbing Polymer Structure with Improved Absorption Properties

• US 20080221277A1
• Filed: 04/21/2006
• Published: 09/11/2008
• Est. Priority Date: 04/22/2005
• Status: Active Grant

• Current Assignee: Evonik Superabsorber GmbH
• Original Assignee: Evonik Degussa GmbH
• Inventors: Walden, Mirko, Furno, Franck, Schmidt, Harald
• Granted Patent: US 8,247,499 B2
• Time in Patent Office: Days
• US Class Current: 525/418
• CPC Class Codes: A61L 15/18 containing inorganic materials
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: B01J 20/26 Synthetic macromolecular compounds
• CPC Class Codes: B01J 2220/68 Superabsorbents
• CPC Class Codes: C08F 20/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 8/44 Preparation of metal salts or ammonium salts
• CPC Class Codes: C08J 2300/14 Water soluble or water swellable polymers, e.g. aqueous gels
• CPC Class Codes: C08J 3/24 Crosslinking, e.g. vulcanising, of macromolecules mechanical aspects B29C35/00; crosslinking agents C08K
• CPC Class Codes: C08J 7/12 Chemical modification
• CPC Class Codes: C08L 33/02 Homopolymers or copolymers of acids; Metal or ammonium salts thereof

Abstract

A water-absorbing polymer structure is disclosed, whose surface has been brought into contact with a combination of a metal salt and an oxide of a metal. The invention also relates to a process for treating the surface of water-absorbing polymer structures whereby the surface of water-absorbing polymer structures is brought into contact with a combination of a metal salt and an oxide of a metal at a temperature of from about 50 to about 300° C. The present invention further relates to the water-absorbing polymer structures obtainable by this process, a composite comprising a water-absorbing polymer structure and a substrate, chemical products such as foams and fibers comprising water-absorbing polymer structures or a composite, and the use of a combination of an oxide of a metal and of a metal salt for treatment of the surface of super-absorbing polymer structures.

Claims

1. A water-absorbing polymer structure, which is based at least to 50 wt. % on carboxylate groups containing monomers and whose surface has been brought into contact with a combination of a metal salt of a bivalent or trivalent metal cation and an oxide of a transition metal, wherein at least about 50 wt. % of the oxide of the transition metal have a particle size in a range of about 10 to about 5,000 nm.

4. The water-absorbing polymer structure according to claim 1 wherein the polymer structure has an R/L-ratio of at least about 2.00 g/g %.

5. The water-absorbing polymer structure according to claim 4 wherein the metal salt is a water soluble metal salt.

6. The water-absorbing polymer structure according to claim 5, wherein the metal salt is a sulfate.

9. The water-absorbing polymer structure according to claim 1 wherein the oxide of the metal is a zinc oxide.

10. A water-absorbing polymer structure according to claim 1 wherein the polymer structure has

an inner region and

an outer region surrounding the inner region

and wherein the outer region has a higher degree of crosslinking than the inner region.

19. A composite comprising a water-absorbing polymer structure according to claim 1 and a substrate.

22. Use of the water-absorbing polymer structure according to claim 1 in foams, formed bodies, fibers, sheets, films, cables, sealing materials, liquid-absorbing hygiene articles, carriers for plant and fungus growth regulating agents, packaging materials, soil additives, for controlled release of active substances, or in construction materials.

25. The water-absorbing polymer structure according to claim 1 wherein the polymer structure has an R/LA ratio of at least 2.00 g/g %.

26. The water-absorbing polymer structure according to claim 1 wherein the polymer structure has an R/LA ratio of at least 2.00 g/g %.

2-3. -3. (canceled)

11. A process for treatment of the surface of water-absorbing polymer structures, comprising the process steps:

i) providing an untreated water-absorbing polymer structure which is based to at least about 50 wt. % on carboxylate groups containing monomers;

ii) bringing into contact the surface of the untreated water-absorbing polymer structure with a combination of a metal salt of a bivalent or trivalent metal cation and an oxide of a transition metal at a temperature from about 100 to about 300°

C., wherein at least about 50 wt. % of the oxide of the transition metal have a particle size from about 10 to about 5,000 nm.

15. The process according to claim 11 wherein the metal salt and the oxide of the metal in the form of a fluid F₁ comprising a solvent, the metal salts and the oxide of the transition metal are brought into contact with the water-absorbing polymer structure.

16. The process according to claim 15, wherein the fluid F₁ additionally comprises a post-crosslinker which is capable of reacting in a condensation reaction with functional groups of the water-absorbing polymer structure.

17. The process according to claim 11 wherein the metal salt in an amount from about 0.001 to about 5 wt. % and the oxide of the transition metal in an amount from about 0.001 to about 5 wt. %, respectively based on the weight of the untreated water-absorbing polymer structure, are brought into contact with the untreated water-absorbing polymer structure.

18. The process according to claim 11 wherein the metal salt is a salt of aluminum and the oxide of the transition metal is a zinc oxide.

12-14. -14. (canceled)

20-21. -21. (canceled)

23. Use of a combination of an oxide of a transition metal and a metal salt of a bivalent or trivalent metal cation for the treatment of the surface of superabsorbing polymer structures, which are based to at least about 50 wt. % on carboxylate groups containing monomers, wherein at least about 50 wt % of the oxide of the transition metal have a particle size within the range of about 10 to about 5,000 nm.

24. (canceled)