. . . . "Preferred compounds for (A)(b) and (B)(b) are organosilicon compounds having the general formula ##STR3## wherein R5 denotes an alkyl or aryl group having up to 10 carbon atoms, R6 is a group R5 or a hydrogen atom, p has a value of from 0 to 20, q has a value of from 1 to 70, and there are at least 3 silicon-bonded hydrogen atoms present per molecule." .