Copolymers having unsaturated side chains produced through an esteracid interchange of polyvinyl ester

Claim 1

A PROCESS FOR PREPARING POLYMERIZABLE ESTER POLYMERS HAVING PENDANT ETHYLENICALLY UNSATURATED ACYL GROUPS, WHICH COMPRISES, THROUGH AN ESTER-ACID INTERCHANGE REACTION REPLACING SATURATED ACYL SIDE CHAINS OF A VINYL ALCOHOL-SATURATED ORGANIC ACID ESTER POLYMER WITH POLYMERIZABLE UNSATURATED ALIPHATIC ACYL SIDE CHAINS, EACH ACYL GROUP HAVING NOT OVER FOUR CARBON ATOMS, SAID ESTERACID INTERCHANGE BEING ACCOMPLISHED BY HEATING (A) A SOLUTION OF THE ESTER POLYMER WITH (B) A POLYMERIZABLE A,B-MONOETHYLENICALLY UNSATURATED MONOCARBOXYLIC ACID HAVING NOT MORE THAN FOUR CARBON ATOMS IN CONTACT WITH, AS A CATALYST, AN AMOUNT NOT EXCEEDING TWO WEIGHT PERCENT BASED ON (A) AN (B), SUFFICIENT TO CATALYZE THE REACTION, OF A STRONG ACID, AND AT AN ELEVATED TEMPERATURE BELOW THE POLYMERIZATION TEMPERATURE OF SAID UNSATURATED ACID, AND THE NUMBER OF MOLS OF ALPHA, BETA-UNSATURATED ACID BEING APPROXIMATELY EQUAL TO THE NUMBER OF ESTER GROUPS TO BE REPLACED.