INJECTION MOLDING APPARATUS AND PREFORM

摘要

PROBLEM TO BE SOLVED: To provide a method for controlling with high productivity and high accuracy a lamination aspect of an intermediate layer in a bottom of a preform in injection molding of the preform where a second resin layer is laminated in the main material layer.SOLUTION: An injection molding method of a test tube-like preform where a second resin layer 101b is laminated in a main material layer 101a as the intermediate layer includes: supplying main material resin from an outer flow path and an inner flow path to a confluent flow path at a prescribed supply speed for a prescribed time; simultaneously supplying second resin 101b from a middle flow path to the confluent flow path at a prescribed supply speed in a fixed time within a prescribed time when the main material resin is supplied; sliding a shut-off pin before the second resin 101b is supplied or until at least supply of the second resin 101b is finished from after a prescribed time from starting supply; arranging the tip thereof on a prescribed position near an opening end of the inner flow path to the confluent flow path; adjusting an aperture of the opening end; and reducing a supply speed of the main material resin from the inner flow path to the confluent flow path to a prescribed speed.