| 摘要 |
PURPOSE:To provide a method which can crystallize a neck piece by utilizing potential heat at the time of injection molding and does not generate a thermal deformation in the crystallizing step. CONSTITUTION:A PET resin material partly containing a resin material which has at least 100ppm or more of water content is charged in a hopper 26. The PET resin material is plasticized by pressure and heat of a screw 30 of an injection molding unit 20, and injected in a mold clamping unit 24 having an injection mold. The resin filled in a cavity of the unit 24 is cooled with refrigerant to be circulated to the mold, and slowly cooled in the mold. In this case, the material containing low water content is hydrolyzed in the case of plasticizing, and its molecular weight is reduced. Accordingly, its crystallizing speed is accelerated due to the reduction in the molecular weight, and the piece is crystallized in the mold within a practical cooling time. |
