Patent ID: 7511096

Claim:
A method for the manufacture of cross-linked polyvinylacetals, said method comprising, in any sequence: (i) reacting a polymer (A1) which contains in relation to its total weight (a) 1.0 to 99.9 wt % structural units of formula (I) where R 1 represents hydrogen or methyl, (b) 0 to 99.0 wt % structural units of formula (2) wherein R 2 represents hydrogen or an alkyl group with 1 to 6 carbon atoms, (c) 0 to 70.0 wt % of structural units of formula (3) wherein R 3 , R 4 , R 5 and R 6 , are in each case groups independent of each other with a molecular weight in the range from 1 to 500 g/mol, and (d) 0.00001 to 30.0 wt % structural units of formula (4a) wherein R 7 is a linkage, an alkylene group with 1 to 10 carbon atoms optionally substituted by one or more COOH groups, or an optionally substituted arylene group with 6 to 12 carbon atoms, and R 8 is hydrogen, COOH, an alkyl group with 1 to 10 carbon atoms and optionally substituted by one or more COOH groups, or an optionally substituted aryl group with 6 to 12 carbon atoms, with at least one polyaldehyde of formula (5), R 9 (CHO) n (5) wherein R 9 represents a linkage or a group having 1 to 40 carbon atoms, and n is a whole number greater than 2; and (ii) at least partially esterifying groups of formula (1) and formula (4a) of polymer (A1) with each other.