Patent ID: 7713464
Filing Date: 2010-05-11
Classification: B29B,B29C,B29K,B32B,B65D,Y02W

Abstract:
1. A multilayer container production process comprising the steps of co-injecting at least polyglycolic acid and a thermoplastic polyester resin to form a bottomed multilayer preform, and then subjecting said multilayer preform to biaxial stretch blow molding, thereby producing a multilayer container having a heat resistance sufficient to withstand hot-filling at 93° C. for 20 seconds, wherein a body of the multilayer container is formed of layers having a total thickness of 150 μm-3 mm and has a haze value not exceeding 50% and wherein: (I) said polyglycolic acid is a gas baffler resin that contains a repeating unit represented by formula (1) at a proportion of at least 60% by weight, has a melt viscosity (η Formula (1) and said thermoplastic polyester resin is at least one thermoplastic aromatic polyester resin selected from the group consisting of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and has an inherent viscosity of 0.6 to 1.0 dl/g and a melt viscosity (η (II) in the co-injecting step, a molding machine equipped with a plurality of injection cylinders is used to co-inject resin melts through one gate into a single preform mold cavity by successive or concurrent molding in one clamping operation, wherein the polyglycolic acid resin temperature upon co-injection molding is in the range of 225 to 260° C., wherein (a) when the multilayer preform is prepared by successive molding, respective molten resins are injected through associated cylinders at such varied timings that said molten resins are continuously and alternately injected so that a previously injected thermoplastic polyester resin is formed into the inner and outer layers and a subsequently injected polyglycolic acid is formed into the intermediate layer, and (b) when the multilayer preform is prepared by concurrent molding, respective molten resins are injected through the associated cylinders at such varied timings that the thermoplastic polyester resin is first injected, during which the polyglycolic acid is injected at some point so that both resins are concurrently and continuously injected to form the thermoplastic polyester resin into the inner and outer layers and the polyglycolic acid into the intermediate layer, thereby making a bottomed, multilayer preform comprising (A) an inner layer and an outer layer, each composed of a thermoplastic polyester resin layer, (B) an intermediate layer comprising at least one polyglycolic acid layer and embedded in the thermoplastic polyester resin layers without interleaving an adhesive layer between the polyglycolic acid layer and the thermoplastic polyester resin layers, (C) an end of an opening formed of a thermoplastic polyester resin layer alone, and (D) the rest comprising a three- or multi-layer construction at least including an inner layer and an outer layer each composed of a thermoplastic polyester resin layer and an intermediate layer comprising at least one polyglycolic acid layer embedded in the thermoplastic polyester resin layers, whereby the outer layers of thermoplastic polyester resin in which the intermediate polyglycolic acid layer is embedded protect the polyglycolic acid from hydrolysis, (III) when the thermoplastic polyester resin is a polyethylene terephthalate (PET), the end of the opening in the multilayer preform is heat treated to crystallize the thermoplastic polyester resin layer, and (IV) after being regulated to a temperature at which stretch is possible, the multilayer preform is inserted into a blow mold cavity where the multilayer preform is blow molded while a pressurized fluid is blown thereinto, and, when the thermoplastic polyester resin is a polyethylene terephthalate (PET), while the mold has been heated to a temperature of 100 to 165° C., a biaxially oriented body of the multilayer container is thermally fixed simultaneously with stretch blow molding.