A crosslinkable polymer according to claim 16, wherein the units containing a crosslinkable group are units of the formula III ##STR47## in which R is alkylene having up to 12 carbon atoms, R1 is hydrogen or lower alkyl, p has the value zero or one, q has the value zero or one, R4 is an olefinically unsaturated, crosslinkable radical having 2 to 8 carbon atoms, and R5 and R6, independently of one