Patent ID: 7312275

Claim:
A crosslinked polyvinyl acetal, characterized in that it can be obtained from at least one polyvinyl acetal (I), which can be obtained by reacting at least one polymer (A), which contains a) 1.0 to 99.9 wt. % structural units of formula (1) wherein R 1 denotes hydrogen or methyl, b) 0 to 99.0 wt. % structural units of formula (2) wherein R 2 represents hydrogen or an alkyl radical with 1 to 6 carbon atoms, c) 0 to 70.0 wt. % structural units of formula (3) wherein R 3 , R 4 , R 5 and R 6 are, in each case independently of one another, radicals with a molecular weight in the range from 1 to 500 g/mol, d) 0.0001 to 30.0 wt. % structural units of formula (4) wherein R 7 and R 8 represent, in each case independently of one another, hydrogen, a carboxyl group or an alkyl group with 1 to 10 carbon atoms, which can optionally have one or more COOH groups as substituents, related in each case to the total weight of polymer (A), with at least one compound (B) of formula (5), wherein R 9 and R 10 are, in each case independently of one another, hydrogen, COOH, an alkyl group with 1 to 10 carbon atoms or an optionally substituted aryl group with 6 to 12 carbon atoms, whereby groups of formula (1) and of formula (4) are, at least in part, esterified with one another wherein the polyvinyl acetal is thermally crosslinked at temperatures in the range from 120° C. to 280° C.