JPH0124629B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present application relates to a multilayer oriented polyester bottle, and more particularly to a polyester bottle with excellent gas barrier properties, interlayer adhesion properties, and creep properties. <Prior Art> Polyester represented by biaxially oriented polyethylene terephthalate has excellent rigidity and transparency, and is widely used in films, containers, and the like. The polyester container is made by extrusion molding or injection molding, and the bottomless area is formed into a cylindrical body with a bottom, that is, a preform, and the polyester container is simultaneously stretched in the axial direction and expanded in the circumferential direction by blowing fluid. Alternatively, there is a molded container or bottle in which co-peripheral side walls are biaxially stretched and oriented by successive processes, and this oriented blow-molded bottle has excellent transparency, rigidity, impact resistance, etc. Due to its good safety and hygiene properties, it has come to be widely used as containers for beverages and seasonings. However, the permeability of oxygen gas and carbon dioxide gas is not necessarily sufficient, and further improvements are expected. Various measures have been proposed to improve this gas barrier property.
Multilayer bottles whose gas barrier layer is made of polyolefin-vinyl alcohol copolymer having excellent gas barrier properties are also known. However, when a polyolefin-vinyl alcohol copolymer is used as a gas barrier layer, its adhesion to the base polyester layer is insufficient, so it is essential to introduce an adhesive layer that can adhere to both layers. It has been desired to develop a gas barrier material that has good adhesion to polyester and does not require a layer. <Objective of the Invention> An object of the present invention is to provide a multilayer oriented polyester bottle with improved gas barrier properties and interlayer adhesion. <Structure of the Invention> The present invention is a multilayer oriented bottle, which comprises a layer of thermoplastic polyester mainly composed of ethylene terephthalate units, an olefin-vinyl alcohol copolymer, and a crystalline material having a melting point of 120°C or more and 250°C or less. A multilayer oriented polyester bottle characterized by comprising a multilayer structure consisting of at least two layers of a blend containing polyester and polyester in a weight ratio of 50:50 to 10:90. The thermoplastic polyester mainly composed of ethylene terephthalate units as used in the present invention usually contains an acid component.
80 mol% or more, preferably 90 mol% or more of terephthalic acid, 80 mol% or more of the glycol component,
Preferably, it means a polyester in which 90 mol% or more is ethylene glycol, and the remaining acid components include isophthalic acid, naphthalene 2,6-dicarboxylic acid, diphenyl ether 4,4'-dicarboxylic acid, adipic acid, Other glycol components include propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, 2,2-bis(4-hydroxyphenyl)propane, p-oxybenzoic acid, p-hydroxyethoxybenzoic acid, etc. Examples include polyesters. From the viewpoint of mechanical properties, such a polyester needs to have an intrinsic viscosity of at least 0.5 or more, preferably 0.6 or more, as measured in an orthochlorophenol solvent at 35°C. In the present invention, the olefin-vinyl alcohol copolymer refers to a copolymer obtained by saponifying a copolymer of olefin and a vinyl ester such as vinyl acetate. Those containing 10 to 50 mol%, especially 20 to 45 mol%, and having a degree of saponification of 90% or more are used. In the present invention, the crystalline polyester having a melting point of 120°C or more and 250°C or less uses dicarboxylic acid or its ester-forming derivative as the acid component,
The main target of the glycol component is a linear saturated polyester obtained using a glycol having 2 to 20 carbon atoms or an ester-forming derivative thereof.
The temperature must be above ℃ and below 250℃. Particularly desirable examples of such crystalline polyesters include copolymerized polyethylene terephthalate containing ethylene terephthalate as a main constituent and containing a dicarboxylic acid other than terephthalic acid and/or a glycol other than ethylene glycol as a copolymerization component. Examples of dicarboxylic acids to be copolymerized include aliphatic dicarboxylic acids such as malonic acid, succinic acid, and adipic acid; aromatic dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, and 4,4' diphenylene ether dicarboxylic acid. . In addition, the glycols to be copolymerized include propylene glycol, tetramethylene glycol,
Examples include hexamethylene glycol, neopentyl glycol, diethylene glycol, and the like.
Further, a desired crystalline polyester can also be obtained by copolymerizing p-oxybenzoic acid, p-hydroxyethoxybenzoic acid, etc. The intrinsic viscosity of such polyester is preferably in the range of 0.4 to 1.0. The polyester needs to have a melting point of 120°C or higher. That is, if the temperature is lower than 120°C, the gas barrier layer will not be sufficiently oriented during stretch blow molding, and the gas barrier effect will not be exhibited. The melting point of the polyester needs to be 250°C or lower, preferably 240°C or lower. That is, when polyester having a melting point exceeding 250°C is used, the olefin-vinyl alcohol copolymer portion undergoes severe thermal deterioration during the kneading and molding process with the olefin-vinyl alcohol copolymer, making it impossible to obtain a desirable bottle. . The weight ratio of the olefin-vinyl alcohol copolymer and the crystalline polyester having a melting point of 120°C to 250°C is in the range of 50:50 to 10:90, more preferably in the range of 50:50 to 20:80. is necessary. In other words, if the weight of the olefin-vinyl alcohol copolymer exceeds 50%, the adhesion between the mixture layer and the thermoplastic polyester layer mainly composed of the ethylene terephthalate layer will be insufficient, resulting in peeling between the two layers in the stretched bottle. occurs. On the other hand, if the weight of the olefin-vinyl alcohol copolymer is less than 10% by weight, the desired improvement in gas barrier properties is not sufficient. It is sufficient to mix the olefin-vinyl alcohol copolymer and crystalline polyester used in the present invention by heating and melting them using an extruder or injection molding machine when creating a multilayer preform, but it is sufficient to improve the uniformity in the obtained preform. In order to achieve this, it is desirable to melt and knead the mixture in advance using an extruder or the like. The kneading temperature needs to be 260°C or less, preferably 250°C or less, taking into account the thermal decomposition of the olefin-vinyl alcohol copolymer. In the multilayer polyester bottle of the present invention, the thickness ratio of the polyester layer and the gas barrier resin mixed layer is not particularly limited, but considering the rigidity, gas barrier properties, etc. of the resulting bottle, the ratio of the thicknesses of both layers is not particularly limited. is preferably in the range of 95:5 to 50:50, preferably in the range of 90:10 to 70:30. The multilayer polyester bottle of the present invention may have two, three or more layers. Such a multilayer oriented bottle can be obtained by first forming a multilayer preform and then subjecting this preform to stretch blowing in the same manner as the method for obtaining conventional polyester bottles. To form a multilayer preform, for example, first, a pipe-shaped laminate consisting of a polyester layer and the gas barrier resin mixed layer is cut into a certain length by multilayer coextrusion, and both ends are heated and formed into desired openings and bottoms. sell. As another molding method, a multilayer injection molding method can be used to sequentially form layers of the gas barrier resin on the inner surface, outer surface, or middle of a polyester parison by injection, thereby obtaining a preform with desired properties. The method of oriented blowing using this multilayer preform is usually to reheat the preform to a temperature that allows it to be stretched, transfer it into a mold having a desired bottle shape, and then stretch it in the axial direction with a stretching rod and apply a compressed fluid such as compressed air to the preform. A conventional stretch-blowing method is used in which the material is blown into the shape of the container. When the preform is stretched or expanded by blowing, the stretching ratio of the body of the bottle is an area ratio of 1.2 times or more, preferably 2 times or more. The multilayer oriented polyester referred to in the present invention is a thermoplastic polyester layer mainly composed of ethylene terephthalate units and the gas barrier resin layer structure, but layers made of other types of polymers may be present for other purposes. Examples of such polymer layers include, for example, ethylene-vinyl alcohol copolymers and polyamide resins for the purpose of further improving gas barrier properties, and polycarbonate, polyarylate resins, polyethylene naphthalate resins, and heat-resistant polystyrene resins for the purpose of improving heat resistance. For the purpose of improving rigidity, examples include glass fiber-containing polyethylene terephthalate and mica-containing polyester resin. The bottle according to the present invention may contain a colorant, an ultraviolet absorber, an antistatic agent, a thermal oxidative deterioration inhibitor, a lubricant, a nucleating agent, a thermoplastic resin other than the above, etc., as necessary, within a range that does not impair the purpose of the present invention. can do. <Examples> Hereinafter, the present invention will be explained in detail with reference to Examples. The methods for measuring the main characteristics measured in the present invention are shown below. (1) Intrinsic viscosity of polyester resin: Calculated from solution viscosity measured at 35°C using o-chlorophenol solvent. (2) Melting point of polyester resin: Seiko Electronics Co., Ltd.
The endothermic peak potential was measured using a DSC20 model manufactured by Co., Ltd. at a heating rate of 20°C/min, and the melting point was taken as the endothermic peak potential. (In addition, various polyester resins were heated and crystallized at 100 to 130℃ in a hot air dryer prior to measurement.) (3) Carbon dioxide permeation amount: GPM- manufactured by Lyssy in Switzerland.
The amount of permeation per 500 c.c. bottle was measured at 30°C using a 200 model gas permeability meter (cc/container - 24 hr - atm). (4) Adhesive strength: Using a tanzaku-shaped specimen with a width of 15 mm, T was measured with a Toyo Baldwin Tensilon at a chuck distance of 20 mm and a tensile speed of 50 mm/min.
A beer peel test was conducted. Examples 1 to 10 and Comparative Examples 1 to 9 The polyester shown in Table 1 and an ethylene-vinyl alcohol copolymer containing 44 mol% of ethylene component were
Cylinder temperature 230-240℃ using 30mmφ extruder
The mixture was melt-kneaded and then cooled to form pellets. The sample of Comparative Example 1 could not be extruded at the above temperature, so the temperature was raised to 260 DEG C., but the extrusion was discontinued because the ethylene-vinyl alcohol copolymer decomposed. A multilayer stretched polyester made by Nissei ASB Machinery Co., Ltd. with the obtained mixture as the outer layer and polyethylene terephthalate with an intrinsic viscosity of 0.75 as the inner layer.
Molding was performed using a 150D multilayer oriented blow molding machine.
The stretching ratio of the body of the multilayer bottle is approximately 2 times in the vertical direction and approximately 4 times in the horizontal direction, and the dimensions of the container are approximately 170 mm in height and 70 mm in diameter, and the wall thickness of the body is 0.05 to 0.07 mm for the outer layer and 0.07 mm for the inner layer.
It was 0.25 to 0.27 mm and had a volume of 500 c.c. Table 1 shows the amount of carbon dioxide gas permeation and the adhesive strength between both layers measured for the obtained polyester bottle, and it is clear that the multilayer polyester bottle of the present invention has excellent properties.

【table】

[Table] Shows the weight percentage in.
2) No melting point peak occurred in DSC measurement.
Example 11 Using an extruder for the inner and outer layers with a diameter of 40 mmφ, an extruder for the intermediate layer with a diameter of 30 mmφ, and a ring-shaped die for two types and three layers, in Example 2, the inner and outer layers were made of polyethylene terephthalate with an intrinsic viscosity of 0.95. The two types of three-layer pipes made of polyester and ethylene-vinyl alcohol copolymer used were extruded into water and cooled. This pipe has an outer diameter of 25 mm and an inner diameter of 18 mm, with a middle layer of 0.6 mm, an inner layer of 1.2 mm, and an outer layer of 1.7 mm. Cut this pipe to about 100mm and cut one end of the pipe to about 220mm.
A preform with a total length of 95 mm was prepared by heating to a temperature of 0.degree. This preform is heated to 110℃ and blown in a blow mold while being stretched vertically to the desired height.
A multilayer oriented bottle with a diameter of 170 mm, an outer diameter of 70 mm, and an inner volume of 500 c.c. was obtained. The carbon dioxide permeation rate of this bottle is at 30℃.
0.28 cc/24-hr-atm, and it was difficult to separate the intermediate layer from the outer layer or inner layer.

Claims (1)

[Claims] 1. A multilayer oriented polyester bottle, in which a layer of thermoplastic polyester mainly composed of ethylene terephthalate units, an olefin-vinyl alcohol copolymer, and a crystalline polyester having a melting point of 120°C or more and 250°C or less are mixed in a ratio of 50:50 to 10:1. A multilayer oriented polyester bottle characterized in that it consists of a multilayer structure consisting of layers of a blend containing a weight ratio of 90.