JPH0464440A - Multilayer plastic vessel and its manufacture - Google Patents

Abstract

PURPOSE:To improve the barrier performance against gas such as oxygen, carbon dioxide, or the like, and water vapor by forming a multilayer vessel comprising at least two layers of thermoplastic polyester having a specified composition and polyolefin. CONSTITUTION:A perform is molded by injection molding, which comprises at least two layers of a thermoplastic layer containing an ethylene naphthalate unit of 80mol% as a repeated unit and a polyolefinic layer. It is then subjected to draw/blow molding in at least single axis direction at a temperature of 110-170 deg.C, to thereby form a multilayer vessel. The used polyolefin preferably contains a propylene unit of 70mol% as a repeated unit, and also may be a copolymer of olefin such as 1-octane of 30mol%. In order to enhance the transparency, and the barrier performance against gas such as oxygen, carbon dioxide or the like in the vessel, it is preferable to effect the draw-molding in at least a single axis direction.

Description

Detailed Description of the Invention [Graduation Field of Application] The present invention provides a multilayer plastic container that is transparent and has excellent barrier properties against gases such as oxygen and carbon dioxide gas or water vapor, and barrier properties against ultraviolet rays. This relates to a manufacturing method.

[Prior art and problems to be solved by the invention] Polyethylene naclate ( P.E.
N) is attracting attention. PEN has barrier properties against gases such as oxygen and water vapor due to polyethylene terephthalate (
It can also block ultraviolet rays in the 320-380 nm range, which PET cannot block. In addition, it has the same stretchability as PET, and like PET, strong containers can be made by biaxial stretch blow molding.

However, PEN is very expensive due to the complicated manufacturing process of the raw material 286-naphthalene dicarboxylic acid or dimethyl 2,6-naphthalene dicarboxylate, and it is difficult to use PEN alone in general-purpose food packaging containers, for example. . Therefore, it would be a great advantage if containers could be made at low cost without reducing the performance of PEN.

One solution to this problem is multilayer molding using PEN. For example, Japanese Patent Application Laid-Open No. 61-279553 describes a PET/PEN multilayer hollow molded product and a method for manufacturing the same. However, if the water vapor barrier property is particularly desired to be improved, the PET/PEN combination requires a considerably thick PEN layer, which has little cost advantage.

Furthermore, the optimum stretching temperatures for PET and PEN are different, which makes it difficult to stretch and mold the preform uniformly.

[Means to solve the problem]

The present inventors have made extensive studies to solve the above problems, and have found that a layer of thermoplastic polyester containing 80 mol% or more of ethylene naphthalate units as repeating units;
A multilayer plastic container consisting of at least two layers including a polyolefin layer is transparent, has excellent barrier properties against gases such as oxygen and carbon dioxide, water vapor, and ultraviolet rays, and is easy to mold uniformly and at low cost. It was found that the invention had great advantages, and the present invention was completed.

That is, the present invention provides a multilayer plastic container comprising at least two layers: a layer of thermoplastic polyester containing 80 mol% or more of ethylene naphthalate units as repeating units and a layer of polyolefin, and the production of this multilayer plastic container. 8 as a repeating unit.
A preform consisting of at least two layers, a layer of thermoplastic polyester containing 0 mol% or more of ethylene naphthalate units and a layer of polyolefin, is molded by injection molding, and the preform is molded at a temperature range of 110°C to 170°C. The present invention provides a method for manufacturing a multilayer plastic container, which is characterized by stretch blow molding in at least one axial direction.

The thermoplastic polyester containing 80 mol% or more of ethylene naphthalate units as repeating units used in the present invention refers to a polymer in which 80 mol% or more of ethylene 2.6-naphthalate units are contained within a range of less than 20 mol%. It may also contain other ester repeating units. 2,
Dicarboxylic acid components other than 6-naphthalene dicarboxylic acid include 1,5-, L6-, 1.7-, and 2.7-naphthalene dicarboxylic acids, which are isomers of 2,6-naphthalene dicarboxylic acid, terephthalic acid, and isophthalic acid. Acid, phthalic acid, cyclohexane dicarboxylic acid, dibromoisophthalic acid, sodium sulfoisophthalic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, diphenoxyethane dicarboxylic acid, phenylene dioxydiacetic acid, etc. Aromatic dicarboxylic acids; Examples include aliphatic dicarboxylic acids such as adipic acid, sebacic acid, succinic acid, glutaric acid, piperic acid, schelic acid, azelaic acid, undecadionic acid, and dodecadionic acid, either singly or in a mixture of two or more.

In addition, diol components other than ethylene glycol include trimethylene glycol, tetramethylene glycol, pentamethylene glycol, xamethylene glycol, octamethylene glycol, decamethylene glycol, propylene glycol, neopentyl glycol,
Aliphatic glycols such as diethylene glycol and polyethylene glycol; cycloaliphatic glycols such as cyclohexane dimetatool; o, m, p xylylene glycol, 2,
Aromatic glycols such as 2-bis(4-hydroxyethoxyphenyl)propane may be used alone or as a mixture of two or more thereof.

The thermoplastic polyester in the present invention can be produced by known manufacturing methods such as a polycondensation reaction with the above dicarboxylic acid component and a diol component, or a transesterification reaction using a short chain alkyl ester (such as dimethyl ester) of the above dicarboxylic acid component and a diol component. It can be obtained by

Furthermore, hydroxycarboxylic acids such as hydroxybenzoic acid and hydroxynaphthoic acid; diphenols such as hydroquinone, redulcinol, dihydroxydiphenyl, and dihydroxydiphenyl ether may be copolymerized.

The intrinsic viscosity of the thermoplastic polyester containing 80 mol% or more of ethylene naphthalate units as repeating units used in the present invention (phenol/tetrachloroethane; weight ratio 6/4.25°C) is 0.3 a/g. The above is preferable; if it is less than 0.3 a/g, the mechanical properties of the obtained multilayer container will deteriorate, which is not preferable.

The polyolefin used in the present invention preferably contains 70 mol% or more of propylene units as repeating units, and 30 mol% or less of other olefins such as ethylene, 1-butene, 1-pentene, ■-hexene, and 1-octene. A copolymerized product may also be used. Moreover, in the case of a copolymer, a random copolymer or a bronc copolymer may be used.

In the present invention, adhesive resins, colorants, oxidation stabilizers, ultraviolet absorbers, antistatic agents, flame retardants, etc. may be added to either the thermoplastic polyester layer or the polyolefin layer to the extent that they do not impair stretchability. I can do it.

The multilayer plastic container of the present invention may have at least two layers, the thermoplastic polyester layer and the polyolefin layer. Inner layer and thermoplastic polyester outer layer 2
A 3N structure with polyolefin as the outer and inner layers and a thermoplastic polyester as the middle layer, a 3-layer structure with thermoplastic polyester as the outer and inner layers and polyolefin as the middle layer, etc., and an adhesive layer between each layer. It is also possible to provide

Further, in order to improve the transparency of the container and the barrier properties against scum such as oxygen and carbon dioxide gas and water vapor, it is preferable to stretch the container in at least one axial direction. For this purpose, the container of the present invention is made by injection molding a preform consisting of at least two layers, the thermoplastic polyester layer and the polyolefin layer.
It is produced by stretch blow molding in at least one axis at a temperature range of .

The optimal stretching temperature varies depending on the type of polyolefin used, but in the case of polypropylene homopolymers or Pronk copolymers of propylene and other monomers, it is 1.
30°C to 170'C, 1 for random copolymers
It is preferable to stretch at 10″C to 160°C.11
If the temperature is less than 0°C, both the polyolefin layer and the thermoplastic polyester layer have high elastic modulus and cannot be stretched uniformly. On the other hand, if the temperature exceeds 170'C, the thermoplastic polyester layer will crystallize, and even in this case, it will no longer be possible to stretch it uniformly.

〔Effect of the invention〕

The multilayer plastic container of the present invention is transparent and has excellent barrier properties against gases such as oxygen and carbon dioxide gas and water vapor, and barrier properties against ultraviolet rays, and is particularly suitable for use as a food packaging container. can.

[Examples] Hereinafter, the present invention will be explained in detail with reference to Examples, but these Examples are not intended to limit the present invention in any way.

The test methods used in Examples and Comparative Examples are as follows.

- Uniformity of wall thickness of the container The thickness of the body of the container was measured at several locations and evaluated based on the degree of variation from the average value.

○...Width of variation is less than 5% of the average value△...
・Width of variation is 5 to 50% of the average value × width of variation is 50% or more of the average value ・Oxygen permeability of container C1 The oxygen permeability coefficient of the container at normal pressure was measured. In order to compare the measured values of various containers, the oxygen permeability coefficient (unit: cffl ・mm/m2 ・24
hr-atm).

- Water vapor permeability of container The container filled with calcium chloride and sealed was left in a room at 40° C. and 90% relative humidity. The weight of the container was measured every other day to determine the weight increase per day. In order to compare the measurements of various containers, the water vapor permeability (unit: g-mm/m"-24hr) is calculated by dividing the surface area of each container and then multiplying by the average wall thickness of each container. did.

- A mouth sample was cut from the ultraviolet shielding container, and the wavelength of transmitted light was measured using a spectrophotometer 11V-265F produced by Shimadzu Corporation to evaluate the shielding properties.

Examples 1 to 3 A random copolymer of propylene and ethylene (ethylene content 14-5 mol%, melt flow rate 3.0 g/10 m1n) was used as the polyolefin, a homopolymer of PEN dried at 140°C for 4 hours as the thermoplastic polyester ( Polyolefin is the outermost layer and inner layer and PEN is the middle layer.
A three-layer preform of 7IITlI+, length 115, and wall thickness 3 mm was molded by injection molding.

The molding conditions at that time were: the set temperature of the cylinder of the kneader for polyolefin was 200 to 240°C, the set temperature of the cylinder of the kneader for PEN was 270 to 290°C, and the set temperature of the mold was 20 to 40°C. did.

Subsequently, biaxial stretch blow molding was performed at 130°C, and the capacity was 6.
00m1, body diameter 60 plates, height 220 values, mouth diameter 2
A heptavalent cylindrical container was molded. The molding machine used was an injection blow molding machine manufactured by Issei Niss Bee Machinery. As shown in Table 1, three types of containers having different thickness ratios of each layer were molded to give Examples 1 to 3.

The test results for each container are shown in Table 1.

Example 4 Polypropylene homopolymer (
A cylindrical container was molded in the same manner as in Example 1, except that biaxial stretch blow molding was performed at 145° C. using a melt flow rate of 9.5 g/10 m1n.

The test results for the container are shown in Table 1.

Comparative Examples 1 to 3 PET (intrinsic viscosity 0.75
dfl/g) in the same manner as in Examples 1 to 3 except that PET was used as the outermost layer and inner layer, PEN homopolymer (intrinsic viscosity 0.68a/g) was used as the middle layer, and each layer was formed as shown in Table 1. Three types of multilayer containers with different thickness ratios were molded.

The test results for each container are shown in Table 1.

Comparative Example 4 A random copolymer of propylene and ethylene (ethylene content: 4.5 mol%, melt flow rate: 3.0 g/10 m1) was used as the polyolefin, and biaxial stretch blow molding was performed at 130°C to form a single-layer container. did.

The test results for the container are shown in Table 1.

Comparative Example 5 A multilayer container was molded in the same manner as in Example 1 except that the stretching temperature was 100°C.

The test results for the container are shown in Table 1.

Comparative Example 6 A multilayer container was molded in the same manner as in Example 1 except that the stretching temperature was 180°C.

The test results for the container are shown in Table 1.

Claims (1)

[Scope of Claims] 1. A layer of thermoplastic polyester containing 80 mol% or more of ethylene naphthalate units as repeating units;
A multilayer plastic container consisting of at least two layers with a layer of polyolefin. 2. The multilayer plastic container according to claim 1, wherein the polyolefin contains 70 mol% or more of propylene units as repeating units. 3. A thermoplastic polyester layer containing 80 mol% or more of ethylene naphthalate units as repeating units;
A preform consisting of at least two layers including a polyolefin layer is molded by an injection molding method, and the preform is heated at 110°C to 1°C.
The method for manufacturing a multilayer plastic container according to claim 1, characterized in that stretch blow molding is carried out in at least one axial direction at a temperature range of 70°C.