A description if given of novel siloxane copolymers producible by (a) reacting in a first step organopolysiloxanes (1) which comprise per molecule at least one Si-bound hydrogen atom with substantially linear oligomeric or polymeric compounds (2) of the general formula R1-(A-CnH2n) m-A1-H (I), wherein R1 is a monovalent substituted or unsubstituted hydrocarbon moiety to which Si-H groups can be added in a hydrosilylation reaction, A is a divalent, polar organic moiety selected from the group -O-, -C(O)-O-, -O-C(O)-, -O-C(O)-O-, -C(O)- NH-, -NH-C(O)-, urethane moiety and urea moiety, A1 is a divalent, polar organic moiety selected from the group -O-, -NH- and -NR'- (wherein R' is a monovalent hydrocarbon moiety having 1 to 18 carbon atoms), n is an integer from 1 to 20 and m is O or a positive integer, (b) reacting in a second step the resultant H-A1 group-bearing intermediates (4); with organic compounds (5) which comprise per molecule at least two isocyanate groups, wherein the reaction takes place in the presence of further organic compounds (6) and (7) which are reactive toward isocyanate groups, with the proviso that the compounds (6) contain at least one tertiary amine group and that the compounds (7) are those which can be eliminated again from the siloxane copolymer in a temperature range from 50 DEG C to 250 DEG C, wherein free isocyanate groups are again formed in the siloxane copolymer, and (c) partially or completely quaternizing in a third step the amine-containing intermediates (8) from step (b) with an alkylating agent (9).