Preform extrusion molding apparatus, method for extrusion molding, and preform

Abstract

The present invention addresses the problem of controlling with high productivity and high precision the lamination state of an intermediate layer in the bottom portion of a preform during injection molding of the preform, the preform having a second resin layer laminated into a main material layer. The primary means of the present invention for addressing this problem is a method for injection-molding a test-tube-shaped preform with a second resin layer laminated into a main material layer as an intermediate layer, wherein a main-material resin is supplied for a designated amount of time at a designated supply speed from an outer flow channel and an inner flow channel to a combined flow channel; a second resin is supplied at the same time at a designated supply speed from a middle flow channel to the combined flow channel at a set time within the designated time range when the main-material resin is supplied; a shut-off pin is slid before the second resin is supplied, or after a designated time has elapsed from the start of the supply at least until the supply of the second resin is completed; the tip is placed in a designated location near the open end of the inner flow channel toward the combined flow channel; the opening of the open end is adjusted; and the supply speed of the main-material resin from the inner flow channel to the combined flow channel is reduced to a designated supply speed.

Description

technical field [0001] The present invention relates to an injection molding device, an injection molding method and Preform. Background technique [0002] The bottle body (PET bottle) made of polyethylene terephthalate (PET) resin obtained by biaxial stretch blow molding of a test tube-shaped preform formed by injection molding has excellent Transparency, mechanical strength, gas barrier properties, etc., and are used in various fields such as beverages, foods, and cosmetics. [0003] For applications that require more gas barrier properties such as oxygen in order to suppress the deterioration of the content liquid, in many cases, a nylon resin with high gas barrier properties is laminated on a main material layer made of PET resin that forms the main body. After forming the middle layer, two kinds of three-layer laminated structures are obtained. [0004] Furthermore, a PET bottle having such a laminated structure can also be obtained by biaxial stretch blow molding of...

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Problems solved by technology

[0020] However, if in Figure 12 At time point F of the injection molding mode, that is, when the injection of the barrier resin ends, if the flow of the barrier resin to the cavity 4 is not stopped instantaneously, it will become a so-called "defective cut" state, and the barrier resin layer 101b will be on the bottom 106 On the bottom wall part of the bottle body, it is laminated in a state where multiple layers are laminated and the fragments of the barrier resin layer 101b, that is, so-called scales, are laminated unevenly. stability, and reduced mechanical strength

[0021] In addition, there is a problem that scales of the barrier resin Rb remain at the front end of the multilayer nozzle 11, and the scales are mixed into the PET resin Ra in the next injection.

[0022] Additionally, if Figure 10 As shown in (b), according to the molding method capable of encapsulating the bottom, although the barrier resin layer 101b can be continuously laminated on the bottom 106 without breaking into a thin film, there is still the following problem: The size of the gate mark in the center of the base bottom 106 is unstable, the formability is unstable, and the PET resin layer 101a on the inner surface side is punctured when stretched longitudinally with a stretching rod.

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