INJECTION FOAMING METHOD AND FOAMED MOLDING

PROBLEM TO BE SOLVED: To provide an injection foaming method which can effectively prevent the occurrence of jetting in a molten thermoplastic resin injected into a cavity. SOLUTION: In the injection foaming method using a resin plasticating/melting means for plasticating/melting the thermoplastic resin and a mold assembly having a plug movable in the cavity, the molten thermoplastic resin in which gas is dissolved by the resin plasticating/melting means is injected into the cavity, the movement of the plug from a forward moving end toward a backward moving end is started simultaneously with the start of the injection, and the plug is positioned at the backward moving end simultaneously with the completion of the injection. Next, the molten thermoplastic resin in the cavity is cooled/solidified. When the pressure of the molten thermoplastic resin in the cavity is PR, and a pressure to make the molten thermoplastic resin in the cavity start foaming is PE, and when the plug is positioned at the backward moving end, PRis made larger than PE. When the thermoplastic resin in the cavity is cooled/solidified, PRis made smaller than PE. COPYRIGHT: (C)2006,JPO&NCIPI