Injection-expansion molded, thermoplastic resin product and production process thereof

摘要

Disclosed is a process for the production of an injection-expansion molded, thermoplastic resin product. The process comprises a gas dissolving step, a cooling step, a metering and injection step, and an expansion controlling step. Specifically, a thermoplastic resin is molten in a continuous plasticator (1), supercritical carbon dioxide and/or nitrogen is added as a blowing agent, and the blowing agent and the thermoplastic resin are formed into a mutually-dissolved state. The resultant molten resin composition is cooled within the plasticator while maintaining a pressure equal to or higher than a critical pressure of the blowing agent. The thus-cooled molten resin composition is metered by an injector (7) and is filled in a mold (8). An internal pressure of the mold is lowered beyond the critical pressure of the blowing agent to produce cell nuclei, whereby the cell diameter is controlled. The blowing agent is maintained in a supercritical state up to the metering and injection step.