The invention relates to the use of compositions which contain A) one or more copolymers, said copolymers containing one or more structural units resulting from a) 19.9 to 75.9 wt.-% of glycerin, b) 0.1 to 30 wt.-% of at least one dicarboxylic acid, and c) 24 to 80 wt.-% of at least one monocarboxylic acid according to formula (I): R