Container with synthetic resin window, preform and preform injection molding method

摘要

Abstract A method of injection molding a test tube-shaped preform for biaxial stretch blow molding, the method being performed with the use of an injection molding apparatus including a nozzle, the nozzle comprising three cylindrical flow paths disposed concentrically about the same axis, the method comprising supplying the major material resin from the outer flow path and the inner flow path to the combined flow path for a predetermined time period at a predetermined supplying rate; simultaneously supplying the intermediate layer resin from the middle flow path to the combined flow path at a predetermined supplying rate; injecting a columnar laminated molten resin into a cavity of a metal mold connected to a tip of the nozzle through a gate to fill the cavity, the columnar laminated molten resin being composed of the major material resin and the intermediate layer resin formed in the major material resin in a laminated manner that are combined into a columnar shape at the combined flow path, and the gate being disposed at a position in the cavity that corresponds to a center of a bottom wall of a bottom of the preform; and forming a non-laminated section, where the intermediate layer is not formed, that extends in a shape of a longitudinal strip along a central axis direction of the preform on a circumferential wall of the preform, by causing the shut-off longitudinal rib piece to circumferentially interrupt the intermediate layer resin in the middle flow path.