To improve physical characteristics, tear resistance in particular, of a molded article by an extrusion molding method using principally a chemical foaming agent.
The extrusion molding method comprises the steps of adding a thermally expandable microsphere 4 including a liquefied gas in a polymer shell in addition to a chemical foaming agent 3 convertible into a gas by pyrolysis to a base resin material 2, heating and kneading the mixture and extruding it to obtain the molded article 5. The molded article 5 has a constitution where bubbles 5a formed from the chemical foaming agent 3, bubbles 5b formed from the expanded thermally expandable microsphere 4 and bubbles 5c formed from unexpanded thermally expandable microsphere 4 are dispersed in the base resin material.
SHINADA HITOSHI
NOMURA MAKOTO
Nobuyuki Kaneda
Katsuhiro Ito
Ishibashi Masayuki