PURPOSE: To achieve a good scattering ability of metal hydroxide by forming a coating layer by extrusion in one continuous process while kneading granulated material of a specified metal hydroxide by an extruder.

CONSTITUTION: Granulated material, 50-300wt.%, of a metal hydroxide of a grain size of 1-10mm and a compression strength of 0.1-5kg is mixed with 100wt.% polyolefine, and it is kneaded and extruded to form a coating layer in one continuous process by a single extruder or a biaxial extruder. For polyolefine, ethylene propylene copolymer, polyethylene, etc., is used. One or more than two of these can be used. The granulated material of the metal hydroxide consists of aluminum hydroxide, magnesium hydroxide, hydrotarsite, etc., compressed or granulated using binder of wax, lubricant, plasticizer, softening agent, etc.