Preform injection molding device, injection molding method, and synthetic resin bottle body

摘要

The present invention addresses the problem of creating an injection molding device and injection molding method for laminating a colored layer of predetermined thickness within a predetermined range onto a main material layer at high precision in a peripheral wall of a preform. An injection molding device for resolving this problem is configured to have a nozzle part for converging the flows of a main material resin and a second resin to form a converged resin body, such that an outer flow path through which the main material resin flows, an inner flow path through which the second resin flows, and a cylindrical converged flow path at which the main material resin and the second resin from the outer flow path and the inner flow path are converged, are disposed in the stated order from the outside. A first convergence part of the outer flow path going toward the converged flow path is disposed at a predetermined interval downstream of a second convergence part of the inner flow path going toward the converged flow path. A cylindrical shut-off pin is slidably inserted into and disposed in the converged flow path. In this configuration, the sliding position of the shut-off pin gives rise to a function whereby either the first convergence part or the second convergence part, or both of these, is either obstructed or opened.