SYNTHETIC RESIN BOTTLE HAVING A GRADATION PATTERN, AND PROCESS FOR INJECTION MOLDING THE PREFORM FOR USE IN SUCH A BOTTLE

摘要

The technical problem to be solved is to change the thickness of the colored resin layer of the preform gradually in the upward or downward direction, by utilizing a tendency of gradual decrease in the thickness of the colored resin layer caused by the flow of the main resin inside the preform mold when the main resin and the colored resin are injected into the mold. This involves adjusting the injection pattern including the time of starting and ending the supply of the main resin and the colored resin, and pressure or velocity profiles, reducing the thickness of the colored resin layer gradually upstream or downstream, injection-molding the preform in which a color-gradated portion associated with the thickness of the colored resin layer has been formed, and biaxially drawing and blow molding this preform into a bottle having a color-gradated portion.

主权项

1. A process for injection molding a preform in a shape of a test tube, comprising:
flowing molten synthetic resins through at least three layer-forming channels comprising a cylindrical inner flow channel, a middle flow channel, and a cylindrical outer flow channel; flowing the molten synthetic resins through a confluence disposed downstream of the at least three layer-forming channels and through a joined flow channel; passing the molten synthetic resins through a gate disposed at a position opposed to a center of a bottom of a preform to be molded; and injecting the molten synthetic resins into a mold to form the preform; supplying each of the inner flow channel and the outer flow channel with a supply of a main resin for the preform from at least one first loader at a time span, pressure, or velocity; supplying the middle flow channel with a supply of a colored resin from a second loader at a pressure and/or velocity during a time within the time span; allowing the colored resin to join the main resin from the inner flow channel and the main resin from the outer flow channel at the confluence in such a manner that a layer of the colored resin is sandwiched between two layers of the main resin; forming a multi-layered molten resin fluid having an intermediate layer of the colored resin between the two layers of the main resin within the joined flow channel over a certain span of time; adjusting an injection pattern including at least one of a time of starting and ending the supply of the colored resin, pressure and velocity profiles; and gradually reducing a thickness of the intermediate layer at a downstream point of flow in a downstream direction so as to form a color-gradated portion caused by a change in the thickness.