Hydrolytically decomposable ionic copolymers

Hydrolytically degradable polyionic copolymerizates which are composed of

• a) 10 to 55 mol-% of a cyclic ketene acetal A,
• b) 4 to 90 mol-% of a methacrylic acid derivative B,
• c) 0 to 80 mol-% of a methacrylic acid derivative C,
• wherein the sum of the components A, B and C results in 100 mol-% and wherein the cyclic ketene acetal A is selected from
• wherein R1 and R2 stand independently of one another for a linear or branched alkyl group with 1 to 12 carbon atoms,
• and the methacrylic acid derivative B is selected from
• N,N-dimethylaminoethylmethacrylic acid (DMEAMA) according to formula (Xa)
• wherein 45% to 95% of the DMEAMA are available ionized in the form of a quaternary amine of the formula (Xb),
• in such a way that the polyionic copolymerizate is a cationic copolymerizate, wherein
• R3 stands for a linear or branched alkyl group with 1 to 12 carbon atoms or a benzyl group of the formula (VII)
• where n=0-12 and X− stands for fluorine, chloride or bromide,
• and wherein the methacrylic acid derivative C is selected of compounds according to formula (VIII)
• wherein R4 is selected from
• —OCH3, —N(CH3)2, an oligoethylene glycol of the general formula —O—(CH2—CH2—O)mH, an ω-methoxy-oligoethylene glycol of the general formula —O—(CH2—CH2—O)m—CH3, wherein m represents a natural number between 1 and 12, vinyl acetate, acrylonitrile, 2-hydroxyethyl methacrylate, N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylcaprolactame, N-vinylpyrrolidone, N-2-hydroxypropylmethacrylamide, N-3-hydroxpropylmethacrylamide, N,N-di methylacrylamide, styrene, N,N-dimethylaminostyrene.