Abstract: Polymers essentially comprising units of the formula I ##STR1## in which R.sup.1 and R.sup.2 are hydrogen or methyl andR.sup.3 is hydrogen, C.sub.1 -C.sub.18 -alkyl, C.sub.5 -C.sub.12 -cycloalkyl, C.sub.6 -C.sub.10 -aryl or C.sub.6 -C.sub.10 -aryl-C.sub.1 -C.sub.4 -alkyl, it being possible for these radicals, with the exception of the C.sub.1 -C.sub.18 -alkyl radicals, to be up to trisubstituted by radicals selected from the group consisting of C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy and halogen, are prepared by reacting a polymer based on C.sub.1 -C.sub.20 -alkyl esters of acrylic acid, methacrylic acid or mixtures thereof with ammonia or a primary amine in an extruder, by mixing the ammonia or the primary amine by mixing intensively with a melt of the polymer to be reacted, at at most 250.degree. C., before the imidation is carried out, and are used for producing thermoplastic moldings, films or fibers.