ting of methyl, ethyl and propyl groups, and the subscript n is zero or 1, or a partial hydrolyzate thereof, (A-4) from 0.01 to 10 parts by weight of an organosilane or organopolysiloxane compound having, in a molecule, at least one substituted or unsubstituted guanidino group represented by the general formula --N═C(NR4 2)2, in which R4 is a hydrogen atom or a monovalent hydrocarbon group,