that a+b is in the range from 1.8 to 3.0; (B) a second organopolysiloxane having at least two amino groups in a molecule represented by the average unit formula ##STR3## in which R3 is a hydrogen atom, a hydroxy group or a monovalent organic group having 1 to 9 carbon atoms each R3 independently from the others, R4 is a 3-aminopropyl group of the formula NH2 --CH2)3 or a 3-(2-aminoethylamino)propy