Patent ID: 7250481
Filing Date: 2007-07-31
Classification: A61L,C07C,C08G

Abstract:
1. A process for preparing a crosslinked hydrogel, which comprises a) reacting at least one polyalcohol A with at least one ethylenically unsaturated carboxylic acid B in the presence of at least one esterification catalyst C and of at least one polymerization inhibitor D and also optionally of a water-azeotroping solvent E to form an ester F, b) optionally removing some or all of the water formed in a) from the reaction mixture during and/or after a), f) optionally neutralizing the reaction mixture, h) optionally removing any solvent E by distillation and/or i) stripping with a reaction-inert gas, k) polymerizing the reaction mixture from one of a) to i), in the presence of at least one radical initiator K and of optionally at least one grafting base L, with optionally at least one additional monoethylenically unsaturated compound bearing no acid groups N and also optionally at least one further copolymerizable hydrophilic monomer M, wherein ester F acts as a crosslinker, whereby a crosslinked hydrogel is formed, l) optionally postcrosslinking the reaction mixture obtained from k), m) drying the reaction mixture obtained from k) or l), and n) optionally grinding and/or sieving the reaction mixture obtained from k), l) or m), wherein said ethylenically unsaturated carboxylic acid B is present in a molar excess to said polyalcohol A per hydroxyl group to be esterified in A of at least 2.5:1, and the optionally neutralized carboxylic acid B in the reaction mixture obtained after step i) substantially remains in said reaction mixture.