Polyester resin lamination vessel and molding method therefor

Abstract

A multilayer preform having at least a medium or intermediate gas barrier layer is prepared in advance by the injection molding of this preform in a predetermined shape that corresponds to the shape of a finished molded product. The body portion of this preform is heated to a blow moldable temperature. The heated preform is set in a primary blow mold (12), and is blow molded in the biaxial orientation to give a primary molded intermediate (5). The primary intermediate (5) is then heated to deform it forcibly by thermal shrinkage and thereby to give the secondary molded intermediate (6). The shrunken secondary intermediate (6) is set in a secondary blow mold (13), and is subjected to the secondary blow molding in the biaxial orientation to obtain a finished molded product, which is fixed thermally to give heat history to the PET resin. As a result, the PET resin layers are given a high degree of crystallization, which serves to complement the function of the gas barrier layer or layers in such a way that the container has high and effective gas barrier properties.

Description

technical field [0001] The present invention relates to a polyester resin laminated container and a forming method thereof, in particular, in a biaxially oriented container composed of thermoplastic polyester mainly composed of polyethylene terephthalate, for which the polyester resin layer The polyester resin laminated container and its forming method are laminated with a transparent film layer rich in air barrier properties and endowed with air barrier properties. Background technique [0002] Thermoplastic polyester resins represented by polyethylene terephthalate resins (hereinafter referred to as PET resins) have stable physical properties, pollution-free properties, excellent transparency, and high mechanical strength. Various aspects are widely used to form bottles and other shapes of hollow containers formed by biaxial stretch blow molding. [0003] In particular, such containers do not contain additives such as plasticizers and stabilizers, so they are harmless to ...

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Problems solved by technology

[0008] However, the mechanical properties of MXD-6 nylon copolymerized with ethylene-vinyl alcohol copolymer, which has excellent gas barrier properties, are significantly reduced, and the transparency is deteriorated, so the transparency can only be ensured by taking the form of a thin layer. Under such constraints, Even if such a multi-layer preform is blow-molded, the air barrier properties of the resulting hollow container tend to be insufficient.

And in the resin layer with poor mechanical performance but superior gas barrier properties, cracks will occur

[0009] On the other hand, it has been pointed out that in the above-mentioned three-layer structure, there is such a disadvantage that it is difficult to make the gas barrier resin layer thinner, and the gas blocked by the thermoplastic polyester resin layer for the gas barrier resin layer will deteriorate over time. It remains between the thermoplastic polyester resin and the gas barrier resin to cause delamination. Therefore, it is proposed in JP-A-60-240409 and JP-A-5-79494 that when forming a preform, the PET resin, MX nylon resin, and PET resin are sequentially injected into the same molding mold to form the inner and outer layers and the center layer are made of PET resin, and the outer layer and the inner layer and between the inner layer and the center layer are all MD A multilayer container with a 5-layer structure that alternately overlaps nylon resin layers

[0016] However, any multi-layer preform in the above-mentioned 3-layer and 5-layer structure adopts a common biaxial stretch blow molding machine, heats it in a stretchable humidity range, and then expands it in a blown metal mold. Stretching into a biaxially oriented container, rupture of the air barrier layer in the aforementioned three-layer structure cannot be prevented even in a five-layer structure, and overall reliability cannot be obtained due to such a phenomenon, and it is practically impossible fully practical

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