R7 is C2 -C12 alkylene which can be interrupted by 1, 2 or 3 of the groups --O-- or --N(R6)--, C6 -C14 cycloalkylene or cycloalkylenedialkylene and Y is a divalent group of the formula --O-- or --N(R6)--, and A and B independently of the other are a group of the formula R8 O-- or (R9)(R10)N--, wherein R8 is C1 -C12 alkyl, C3 -C7 alkenyl, cyclohexyl, benzyl, phenyl or C7 -C12 alkylphenyl, R9 is C1