R1, R2, R5 and R6 are each independently of the others hydrogen, ???SO2???(C1-C6)alkylphenyl, C1-C30alkyl, C1-C30alkyl???CO??? or a radical of the formula ???(CnH2n???O???)m???R8; R3 is hydrogen or ???SO2???(C1-C6)alkylphenyl; R4 and R7 are a C1-C30alkylene or a radical of the formula ???(CnH2n???O???)m???R8; Z is a divalent radical ???NH???CO???; R8 is a direct bond or C1-C12alkylene; n is an int