MANUFACTURE OF SYNTHETIC RESIN FOAM

PROBLEM TO BE SOLVED: To enable existence of micro-bubbles stably at a high ratio by a method wherein a salt having water of crystallization and a composition containing a specific amount of a bubble adjustor are heated, melted, and kneaded in synthetic resin, and after injecting a vaporization foaming agent, which is foamed by extrusion in a low pressure area, and large and small bubbles of specific diameters are coexisted by dispersion. SOLUTION: A salt having crystallization water and a composition containing 0.01-5 pts.wt. of a foam adjustor are heated, melted, and kneaded in 100 pts.wt. of synthetic resin, a vaporization foaming agent is injected, then foamed by extrusion in a low pressure area, and a bubble of 0.25 mm or under bubble diameger princially and a bubble of 0.35-1 mm bubble diameter are made to coexist by dispersion. The synthetic resin is excellent in thermal insulation property, rich in rigidity, and further can be favorably applied to a foam of polystyrene resin. Further, salts having crystallization water, are mineral and organic hydrated salts having water under ordinary temperature and ordinary pressure. Furthermore, as the foam adjustor, for example, a talc agent, calcium carbonate power, etc., are independently or two or more kinds are used by mixing.