. "Z is a polyfunctional isocyanate residue, A is ##STR4## or --SO2 --, l is an integer of from 1 to 10, and m and n are integers of from 0 to 4 with the proviso that the sum of m and n is an integer of from 0 to 4, p is an integer of from 1 to 4, and q is an integer of from 2 to 3." . . .