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

An injection molding apparatus that injection molds a test-tube-shaped preform that is subjected to biaxial stretch blow molding, the preform including a circumferential wall having a longitudinal strip-shaped portion that is made of a B resin and that is formed in a longitudinal strip shape in a circumferentially predetermined position in the circumferential wall over a predetermined height range, a remaining portion of the circumferential wall excluding the longitudinal strip-shaped portion being made of an A resin, the injection molding apparatus comprising:

• a nozzle portion that supplies the A resin and the B resin which are molten along a circumferential direction;
• and
• a mold that is located in a front end of the nozzle portion, wherein
• the nozzle portion includes:
• a cylindrical inner mandrel;
• an outer mandrel that is arranged coaxially with the inner mandrel;
• and a columnar shut-off pin that is inserted and arranged in the inner mandrel and that serves to release and shut off flows of the molten resins in a front end portion of the nozzle portion, and wherein
• between the inner mandrel and the outer mandrel, a cylindrical flow path and a reduced-diameter flow path are formed in the stated order in a direction toward a downstream side, the reduced-diameter flow path being configured by a cylindrical flow path tapered to have a reduced diameter toward downstream, and on downstream of the reduced-diameter flow path, a columnar joining flow path is formed in which the molten resins in cylindrical forms join into a columnar form, and a longitudinal groove flow path is further formed to interrupt the cylindrical flow path and the reduced-diameter flow path in a circumferential direction,
• the longitudinal groove flow path has a flow path width that is reduced on a downstream side below a predetermined position than on an upper stream side thereof and a flow path depth that is increased on the downstream side below the predetermined position than on the upper stream side thereof,
• the molten B resin is supplied to the longitudinal groove flow path, and the molten A resin is supplied to the cylindrical flow path excluding the longitudinal groove flow path and the molten resins that have joined into the columnar form are injected and filled into a cavity of the mold via the joining flow path of the nozzle portion and a pin gate located in a position of the cavity of the mold that corresponds to a middle of a bottom wall of a bottom portion of the preform.