PREFORM EXTRUSION MOLDING APPARATUS, METHOD FOR EXTRUSION MOLDING, AND PREFORM

摘要

The present invention addresses the problem of controlling with high productivity and high precision the lamination state of an intermediate layer in the bottom portion of a preform during injection molding of the preform, the preform having a second resin layer laminated into a main material layer. The primary means of the present invention for addressing this problem is a method for injection-molding a test-tube-shaped preform with a second resin layer laminated into a main material layer as an intermediate layer, wherein a main-material resin is supplied for a designated amount of time at a designated supply speed from an outer flow channel and an inner flow channel to a combined flow channel; a second resin is supplied at the same time at a designated supply speed from a middle flow channel to the combined flow channel at a set time within the designated time range when the main-material resin is supplied; a shut-off pin is slid before the second resin is supplied, or after a designated time has elapsed from the start of the supply at least until the supply of the second resin is completed; the tip is placed in a designated location near the open end of the inner flow channel toward the combined flow channel; the opening of the open end is adjusted; and the supply speed of the main-material resin from the inner flow channel to the combined flow channel is reduced to a designated supply speed.