Also, typical examples of the hydrolyzable group X are, for instance, a halogen atom such as fluorine, chlorine, bromine or iodine atom; a group of the general formula: --OZ wherein Z is a group having 1 to 18 carbon atoms selected from the group consisting of an alkenyl group, a saturated or unsaturated hydrocarbon group, a halogenated hydrocarbon group, a hydrocarbon group containing ether bond,