"al types A N X and B which are connected by methylene groups, in which A-N X is a radical of a compound of one of the general formulae NXandR R-R-R (3 1 2 Z wherein seven to 12 carbon atoms, and aryl with six to 12 carbon atoms, R is an arylene group having six to 12 carbon atoms, Y- is one of the groups NH-, and O p is a number from 1 to 3, and B is a radical of a compound selected from the group" . . . .