Method for the secondary crosslinking of hydrogels with bicyclic amide acetals

• US 20060211828A1
• Filed: 07/07/2004
• Published: 09/21/2006
• Est. Priority Date: 07/28/2003
• Status: Active Grant

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Oehsen, Ubbo von, Riegel, Ulrich, Massonne, Klemens, Daniel, Thomas, Elliott, Mark, Exner, Kai Michael
• Granted Patent: US 7,754,822 B2
• Time in Patent Office: Days
• US Class Current: 525/330.300
• CPC Class Codes: C08F 20/00 Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
• CPC Class Codes: C08F 8/30 Introducing nitrogen atoms or nitrogen-containing groups
• 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: Y10S 493/96 Toilet article

Abstract

A process for postcrosslinking a water-absorbing polymer comprises said polymer being treated with a postcrosslinker and, during or after said treating, being postcrosslinked and dried by temperature elevation, said postcrosslinker being a compound of the formula I
where R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are each independently hydrogen, C₁-C₁₂-alkyl, C₂-C₁₂-alkenyl or C₆-C₁₂-aryl, wherein C₁-C₁₂-alkyl, C₂-C₁₂-alkenyl or C₆-C₁₂-aryl may be halogen substituted. The liquid-absorbing polymers are useful in hygiene articles and packaging materials.

Claims

1. A process for postcrosslinking a water-absorbing polymer, which process comprises treating said polymer with a postcrosslinker and, during or after said treating, postcrosslinking and drying by temperature elevation, said postcrosslinker being a compound of a formula (I)

2. The process of claim 1 wherein said postcrosslinker is of the formula (I) wherein R¹ is C₁-C₆-alkyl, C₂-C₆-alkenyl, or C₆-C₇-aryl, R², R⁴, R⁶, and R⁸ are each independently hydrogen, and R³, R⁵, R⁷, and R⁹ are each independently hydrogen, C₁-C₄-alkyl, or C₂-C₄-alkenyl, wherein C₁-C₄-alkyl or C₂-C₄-alkenyl may be fluorine substituted.

3. The process of claim 1 wherein said postcrosslinker is 1-aza-4,6-dioxabicyclo[3.3.0]octane.

4. The process claim 1 wherein said polymer to be postcrosslinked contains structural units derived from acrylic acid or acrylic esters or is obtained by graft copolymerization of acrylic acid or acrylic esters onto a water-soluble polymeric matrix.

5. The process of claim 1 wherein said postcrosslinker is a surface postcrosslinker which is used as a solution in an inert solvent.

6. The process of claim 5 wherein said inert solvent comprises an aqueous solution of glycerol, methanol, ethanol, isopropanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, or mixtures thereof.

7. The process of claim 5 wherein said inert solvent is water or a mixture of water with a mono- or a polyfunctional alcohol which has an alcohol content in the range from 10% to 90% by weight.

8. The process of claim 1 wherein said postcrosslinker is used in an amount from 0.01% to 5% by weight, based on the weight of said polymer.

9. A water-absorbing polymer prepared by the process of claim 1.

10. A water-absorbing polymer of claim 8 characterized by an absorbency under load (AUL) at 0.7 psi (4830 Pa) of at least 15 g/g.

12. A hygiene article comprising a water-absorbing polymer prepared by the process of claim 1.

13. A packaging material comprising a water-absorbing polymer prepared by the process of claim 1.

11. (canceled)