Patent ID: 6949208
Filing Date: 2005-09-27
Classification: B29C

Abstract:
1. An injection molding process for a thermoplastic resin molded article including the blowing agent incorporating step of supplying through a blowing agent supply opening a blowing agent to a resin melted by rotating a screw within a cylinder of an injection molding machine and mixing the blowing agent with the molten resin for incorporation, and the injection molding step of measuring out an amount of the blowing agent-incorporating molten resin obtained and thereafter injecting the measured-out resin into a mold cavity to prepare an expansion-molded article, the injection molding process being characterized in that the blowing agent is incorporated into the molten resin by supplying the blowing agent from a blowing agent inlet formed in a rear end portion of the screw to a blowing agent supply channel provided in the screw and then from the supply opening into an enlarged incorporating zone forming portion defined as having a deeper screw groove relative to a remaining portion of the screw, the enlarged incorporating zone portion having a portion not fed with the resin where the supply opening is located and positioned between front and rear screw flights and closer to the front flight and the enlarged incorporating zone forming portion being further defined by front and rear screw flights having an increased pitch relative to remaining ones of screw flights of the screw.