| 摘要 |
PROBLEM TO BE SOLVED: To provide a foam that has beautiful external appearances, exhibits high rigidity and has a uniform and large cell size without causing breakage of a cell wall or a void. SOLUTION: A master batch of a thermally expandable microcapsule is added to polypropylene and the resultant is fed to a heating barrel (1) of an injection molding machine through a hopper (3) and is mixed under pressure. Carbon dioxide in a supercritical state is injected into the heating barrel (1) through a gas injection port (2) provided in the middle of the heating barrel (1), and a resin composition is thereby caused to be impregnated with the carbon dioxide and to melt under pressure at an expansion initiation temperature of the thermally expandable microcapsule or a higher temperature. The thus-obtained foamable resin composition is injected into a cavity of a mold (7) and subsequently the movable mold (9) of the mold (7) is made to go back to a direction to enlarge the cavity thereby to decrease the pressure. Thus, the foam is obtained. COPYRIGHT: (C)2008,JPO&INPIT |
