METHOD FOR INJECTION MOLDING AMORPHOUS THERMOPLASTIC

PROBLEM TO BE SOLVED: To reduce a viscosity of a molten resin and to enhance its flowability by cooling the molten resin at a glass transition temperature or higher of the surface of the resin which temperature is lowered due to dissolving of a carbon dioxide in a mold cavity in the surface of the resin during injection filling and a surface temperature of the mold lower than the transition temperature at a center of the resin. SOLUTION: When a resin is filled in a mold cavity after a carbon dioxide gas is fully filled in the cavity, the gas is dissolved in a resin surface layer, the dissolved gas is operated as a plasticizer, a glass transition temperature is lowered only at the surface of the resin or the viscosity of the molten resin is lowered. The gas dissolved in the surface layer is diffused in the resin as a time is elapsed, and a glass transition temperature of the surface layer is raised up to that substantially at a center of the resin. If the surface temperature of the mold is lower than the transition temperature of the center of the injected filled molten, the surface layer and the center are solidified within a normal resin cooling time to get a product. As a result, it can allow an upgraded mold surface transferability and high productivity to be compatible by setting a suitable temperature.