Method for the secondary crosslinking of hydrogels with bicyclic amide acetals

• US 7,754,822 B2
• Filed: 07/07/2004
• Issued: 07/13/2010
• Est. Priority Date: 07/28/2003
• Status: Expired due to Fees

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Exner, Kai Michael, von Oehsen, Ubbo, Riegel, Ulrich, Massonne, Klemens, Daniel, Thomas, Elliott, Mark
• Primary Examiner(s): Jagannathan; Vasu
• Assistant Examiner(s): Boyle; Robert C
• Application Number:
  US10/565,050
• Publication Number:
  US 20060211828A1
• Time in Patent Office: 2,197 Days
• Field of Search: 525/330.3, 525/375, 525/383
• US Class Current: 525/375
• 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 of claim 1 wherein said polymer to be postcrosslinked (a) contains structural units derived from acrylic acid or acrylic esters or (b) 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.

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

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