Copolymer obtainable by polymerization of a) at least one a) α, β-ethylenically unsaturated monomer of the general formula I ** Formula ** in which R14 and R15 are independently selected from each other from the group consisting of hydrogen, C1 alkyl -C8 straight or branched chain, methoxy, ethoxy, 2-hydroxyethoxy, 2-methoxyethoxy and 2-ethoxyethyl, R17 is hydrogen or methyl, R18 is alkylene or hydroxyalkylene with 1 to 24 C atoms, optionally substituted by alkyl, preferably C2H4 , C3H6, C4H8, CH2-CH (OH) -CH2, g is 0 or 1, Z is nitrogen when g>； = 1 or oxygen when g>； = 0, R25 or R26 are in each case and independently of each other chosen from the group consisting of hydrogen, straight or branched chain C1-C40 alkyl, formyl, straight or branched chain C1-C10 acyl, N, N-dimethylaminoethyl, 2-hydroxyethyl, 2-methoxyethyl, 2-ethoxyethyl, hydroxypropyl, methoxypropyl, ethoxypropyl or benzyl, in which at least 60% of a) exhibits an atom d and quaternary nitrogen, b) at least one monomer b) α, β ethylenically unsaturated of the general formula II ** Formula ** in which R1 to R3 independently mean one another hydrogen, C1-C4 alkyl or phenyl； c) at least one monomer c) α, β ethylenically unsaturated of the general formula III ** Formula ** in which one of the radicals R4 to R6 represents a group of the formula CH2>； = CR7- with R7>； = H or C1-C4 alkyl and the remaining R4 to R6 radicals independently represent each other H, alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl, in which R4 and R5 together with the amido group to which they are attached, may also represent a lactam with 5 to 8 ring atoms, in which R5 and R6 together with the nitrogen atom to which they are attached, can also represent a five to seven member heterocycle d) where appropriate at least one other d) monomer that can form polymers by radicals, different from a), b) and c).Copolímero obtenible mediante polimerización de a) al menos un monómero a) α, ß etilénicamente insaturado de la fórmula
