Quaternized copolymer

A process for preparing a quaternized copolymer, which comprises:

• (A) copolymerizing one or more straight-chain, branched or cyclic, ethylenically unsaturated C2 to C100 hydrocarbons (monomer M1), which may bear one or more oxygen- or nitrogen-functional substituents which cannot be reacted with amines to give amides or imides or with alcohols to give esters, with one or more ethylenically unsaturated C3- to C12-carboxylic acids or C3- to C12-carboxylic acid derivatives (monomer M2), which bear one or two carboxylic acid functions and can be reacted with amines to give amides or imides or with alcohols to give esters, to give a copolymer (CP) with a number-average molecular weight Mn of 500 to 20 000;
• (B) performing partial or full amidation or imidation or esterification of the carboxylic acid functions of the (M2) units in the copolymer (CP) by reacting them with one or more oligoamines (OA) having 2 to 6 nitrogen atoms or alcoholamines (AA), each of which comprises at least one primary or secondary nitrogen atom or at least one hydroxyl group and at least one quaternizable tertiary nitrogen atom;
• (C) partially or full quaternizing the at least one tertiary nitrogen atom in the OA or AA units with at least one quaternizing agent (QM), wherein the at least one quaternizing agent (QM) is at least one alkylene oxide;
• where the sequence of steps (B) and (C) may also be reversed, such that the partial or full amidation or imidation of esterification of the carboxylic acid functions of the (M2) units in the copolymer (CP) can be effected by reacting with the oligoamines (OA) or alcoholamines (AA) already quaternized in reaction step (C).