Patent ID: 8658741

Claim:
A process for the preparation of a modified block copolymer comprising the steps a1) polymerizing in a first step ethylenically unsaturated monomers in the presence of at least one nitroxylether having the structural element wherein X represents a group having at least one carbon atom and is such that the free radical X. derived from X is capable of initiating polymerization; or a2) polymerizing in a first step ethylenically unsaturated monomers in the presence of at least one stable free nitroxyl radical and a free radical initiator; and in a second step b) modifying the block copolymer prepared under a1) or a2) by a transesterification reaction with a mono alcohol derived from ethylenoxide, propylenoxide or mixtures thereof with up to 100 C atoms, wherein a1) or a2) is carried out in two radical polymerization steps to form a block copolymer wherein in the first polymerization step the monomers are C 1 -C 6 alkyl esters of acrylic or methacrylic acid and in the second polymerization step the monomers are 4-vinylpyridine or pyridinium-ion, 2-vinylpyridine or pyridinium-ion, vinyl-imidazole or imidazolinium-ion, dimethylacrylamide, 3-dimethylaminopropylmethacrylamide or mixtures thereof.