"taining the solid product (I); thereafter mixing (A) said solid product (I), (B) a chain or cyclic siloxane polymer expressed by the general formula ##STR2## (wherein n represents 3-10,000, and R1 and R2 represent same or different kinds of hydrogen, alkyl group, aryl group, halogen, alkoxy group, aryloxy group, or fatty acid residual group), and (C) a halide, an oxyhalide, an alcoholate, an alkox" . . . . .