Abstract: A film-forming polymer is prepared by polymerisation of: from 4 to 50 mol % of monomer units A selected from the group consisting of the trialkylsilyl esters of an ethylenically unsaturated carboxylic acid, and mixtures thereof; from 5 to 45 mol % of monomer units B selected from the group consisting of the N-vinyl lactam monomers of general formula CH2═CH—NR′″″—CO—R′|, the N-vinyl amides of general formula CH2═CH—N—CO—R″, the monomers of general formula CH2═CR′″—COO—R″″—NR′″″—CO—R′|, the monomers of general formula CH2═CR′″—COO—R″″—N—CO—R″, 2-pyrrolidone-1-isoprenyl ketone, and mixtures thereof, wherein R′ is a n-alkylidene radical having 2 to 8 carbon atoms, R″ is selected from the group consisting of alkyl, cycloalkyl, aryl, alkylaryl and arylalkyl radicals hav