JP2000094547A - Multilayer container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sterilize at a high temperature under a high pressure and charge a content at a high temperature with excellent heat resistance and gas barrier properties, by forming it of a thermoplastic polyester layer containing an ethylene terephthalate unit as a main body and a polyamide layer reinforced by a silicate layer. SOLUTION: The multilayer container comprises (A) a thermoplastic polyester layer containing an ethylene terephthalate unit as a main body, and (B) a polyamide layer reinforced by a silicate layer. An intrinsic viscosity of the polyester is preferably 0.5 to 1.5 of a value measured at 35 deg.C by using a mixed refrigerant of phenol/tetrachloroethane=60/40 (by weight). The polyamide is obtained by using a monomer for forming the polyamide such as a lactam, an aminocarboxylic acid, a diamine and a dicarboxylic acid (including a pair of salts of them) or the like by melt polymerization (or melt polycondensation) or a solid state polymerization. An amount of the silicate layer is preferably 0.1 to 30 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multilayer container.
More specifically, the present invention relates to a novel multilayer container which is excellent in heat resistance and gas barrier properties and enables high-temperature filling of contents and high-temperature sterilization under pressure.

[0002]

2. Description of the Related Art Conventionally, polyethylene terephthalate (PET) has been attracting attention as a plastic container material due to its excellent mechanical and chemical properties. It is the main material of the container.

[0003] However, PET has a glass transition temperature.
It is around 70 ° C, and the heat resistance is not always high.
In addition, since it includes a large molding distortion generated during processing such as vacuum molding or stretch blow molding, it is also unsatisfactory in that deformation occurs during high-temperature filling and sterilization of contents. For example, filling a beverage at a high temperature of 65 ° C. or more causes problems such as deformation of the container. At present, the heat resistance has been improved to about 85 ° C due to the development of heat setting technology and crystallization technology for the container plug. , And the accompanying cost increase is a problem.

[0004] In addition, containers having improved heat resistance by the above-mentioned post-treatment are also effective only for high-temperature filling under normal pressure, and are not suitable for high-temperature filling under pressure or high-temperature sterilization of beverages containing a large amount of carbon dioxide gas. There is a problem that it causes deformation and cannot be used for such purposes.

Further, the gas barrier properties of PET are superior to polyolefins, but inferior to those of polyvinyl chloride and polyvinylidene chloride. Therefore, its use has been limited particularly to beverage containers requiring barrier properties of oxygen and carbon dioxide gas.

On the other hand, it has been pointed out that polyvinyl chloride and polyvinylidene chloride have insufficient heat resistance and also have a problem of environmental pollution due to containing halogen atoms.
It is not suitable as a material for plastic containers.

[0007] As described above, in reality, there is almost no material that can be used for plastic containers, while having both sufficient heat resistance and high gas barrier properties. Further, the effect of the post-treatment of the above-mentioned container is not always sufficient. Therefore,
A multilayer container comprising a PET layer and a layer made of a different kind of material having heat resistance or gas barrier properties has been proposed.

For example, JP-A-59-204552 discloses that P
There has been proposed a multilayer container comprising an ET layer and a layer of a polyarylate resin composition having excellent heat resistance. Also, Plastic Age, 1986, Vol. 11, pp. 191 proposes a multilayer container comprising a PET layer and a polymeta-xylylene adipamide layer having excellent gas barrier properties. However, these multilayer containers did not simultaneously satisfy both heat resistance and gas barrier properties.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a novel property which is excellent in heat resistance and gas barrier properties and enables high-temperature filling of contents and high-temperature sterilization under pressure. It is intended to provide a multilayer container.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when a polyamide layer reinforced with a specific reinforcing material is used for at least one layer of a multilayer container, heat resistance is increased. It has been found that the properties and gas barrier properties can be simultaneously improved, and the present invention has been achieved.

That is, the gist of the present invention is as follows. (1) A multilayer container comprising a layer (A) of a thermoplastic polyester mainly composed of ethylene terephthalate units and a layer (B) of a polyamide reinforced with a silicate layer. (2) The multilayer container according to the above (1), wherein the amount of the silicate layer in the layer (B) is 0.1 to 30% by weight. (3) The multilayer container according to the above (1), wherein the ratio of the layer (B) in the multilayer container is 1 to 99% by weight. (4) The multilayer container according to the above (1), which is stretched in at least one direction.

Hereinafter, the present invention will be described in detail.

The thermoplastic polyester mainly composed of ethylene terephthalate units used in the layer (A) of the present invention means that the main repeating unit is composed of ethylene terephthalate, and phthalic acid and isophthalic acid are contained in a proportion of not more than 20 mol% of the total acid components. Acid, hexahydrophthalic acid, naphthalenedicarboxylic acid, adipic acid, dicarboxylic acid components such as sebacic acid, etc .; polyvalent carboxylic acid components such as trimellitic acid and pyromellitic acid; or 20 mol% or less of all alcohol components. , 2-propanediol, 1,3-propanediol, 1,
Glycol components such as 4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol and cyclohexane dimethanol, and polyhydric alcohol components such as trimethylolpropane, triethylolpropane and pentaerythritol, or acid components An oxyacid component such as p-oxybenzoic acid or lactic acid is contained in a proportion of 20 mol% or less of all components including the alcohol component and the alcohol component. Such a thermoplastic polyester is produced by a combination of melt polycondensation or solid phase polymerization by a conventional method.

The intrinsic viscosity of the thermoplastic polyester is as follows:
Although not particularly limited, phenol / tetrachloroethane = 60/40 in consideration of the molding and performance of the container.
(Weight ratio) using a mixed solvent at a temperature of 25 ° C
It is preferably in the range of 0.5 to 1.5.

The polyamide used for the layer (B) of the present invention is obtained by melting a polyamide-forming monomer such as lactam, aminocarboxylic acid, or diamine and dicarboxylic acid (including a pair of salts thereof) by a conventional method. It is produced by using polymerization (or melt polycondensation) or solid phase polymerization in combination.

Specific examples of such a polyamide-forming monomer include lactams such as ε-caprolactam, ω-undecyl lactam and ω-laurolactam. Examples of the aminocarboxylic acid include 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and p-aminomethylbenzoic acid. Further, as the diamine, tetramethylene diamine, hexamethylene diamine, nonamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4 / 2,4,
4-trimethylhexamethylenediamine, 5-methylnonamethylenediamine, 2,4-dimethyloctamethylenediamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1-amino-3- Aminomethyl-3,5,5-trimethylcyclohexane, 3,8-bis (aminomethyl) tricyclodecane, bis (4-aminocyclohexyl) methane, bis (3-methyl-4
-Aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminopropyl) piperazine, aminoethylpiperazine and the like. Dicarboxylic acids include adipic acid, suberic acid, azelaic acid, sebacic acid, dodecadicarboxylic acid, terephthalic acid,
Examples include isophthalic acid, naphthalenedicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5-naphthaliumsulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, and diglycolic acid.

Specific examples of the polyamide used in the present invention include polycaproamide (nylon 6), polyundecamide (nylon 11), polydodecamide (nylon 12), polytetramethylene adipamide (nylon 46) and polyhexamethylene adipate. Amide (nylon 66), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polyundecamethylene adipamide (nylon 116), polytrimethylhexamethylene adipamide (nylon TMHT / 6), polyhexamethylene terephthalamide (nylon 6T), polyhexamethylene isophthalamide (nylon 6I), polynonamethylene terephthalamide (nylon 9T), poly [bis (4-aminocyclohexyl) methanedodecamide] (nylon PACM
12), poly [bis (3-methyl-4-aminocyclohexyl) methandodecamide] (nylon DMPACM12), polymethaxylylene adipamide (nylon MDX6), polyundecamethylene terephthalamide (nylon 11T), polyundeca Examples include methylene hexahydroterephthalamide, a copolymer thereof, or a mixture thereof. Of these, nylon 6, nylon 66, nylon 11, nylon 12, and copolymers or mixtures thereof are preferred, and nylon 6 and this copolymer are particularly preferred because of the balance between cost and performance.

Although the relative viscosity of the above polyamide is not particularly limited, it is measured at a temperature of 25 ° C. and a concentration of 1 g / dl using a 96% concentrated sulfuric acid solvent as a solvent in consideration of molding and performance of the container. It is preferable that the calculated value is in the range of 1.5 to 6.0.

The silicate layer used for the layer (B) of the present invention comprises:
A basic unit constituting the layered silicate, which is obtained by cleaving the swellable layered silicate,
In the polyamide, each side has a length of 0.002 to 1 μm and a thickness of 6 to 20 °. Such a swellable layered silicate may be a natural or synthetic one, and specific examples thereof include smectite-based minerals such as montmorillonite, beidellite, saponite, hectorite, and sauconite, and vermiculite. Vermiculite-based minerals, muscovite, biotite, paragonite, levitrite, swellable fluoromica, etc., mica-based minerals such as margarite, clintonite, anandite, etc., dombasite, sodoite,
Examples include chlorite-based minerals such as cocoaite, clinochlore, chamosite, and niemite, and hydrous inosilicate-based minerals such as sepiolite. Among these, swellable fluoromica-based minerals represented by the following formula (hydroxy group of mica) Is particularly preferable in terms of dispersibility in a polyamide resin and whiteness. α (MF) · β (aMgF ₂ · bMgO) · γSiO ₂ (where M represents sodium or lithium, α,
β, γ, a and b represent counts, respectively, and 0.1 ≦ a ≦ 2, 2
≦ β ≦ 3.5, 3 ≦ γ ≦ 4, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, a
+ B = 1).

As a method for producing such swellable fluorine mica, for example, silicon oxide, magnesium oxide and various fluorides are mixed, and the mixture is heated in an electric furnace or a gas furnace at a temperature of 1400 to 1500 ° C. There is a so-called melting method of completely melting and growing fluorine mica in a reaction vessel during the cooling process. Also, using talc as a starting material,
There is a method of obtaining fluorine mica by intercalating an alkali metal ion (Japanese Patent Application Laid-Open No. 2-149415). In this method, talc is mixed with an alkali silicofluoride or an alkali fluoride, and then mixed in a porcelain crucible for 700 to 12 hours.
Heat treatment at 00 ° C. for a short time makes it possible to obtain swellable fluoromica.

The method for obtaining the polyamide (B) reinforced with a silicate layer in the present invention is described in, for example, JP-A-6-2481.
There is a method of obtaining a swellable layered silicate and a polyamide-forming monomer by polymerization based on the method described in Japanese Patent No. 76-76. Further, there is a method according to Japanese Patent Application Laid-Open No. 63-221125, in which a swellable phyllosilicate is first subjected to an organic treatment in advance to obtain a composite, and then the composite and a monomer forming a polyamide are obtained by polymerization.

When such a method is used, the silicate layer is dispersed at the molecular level in the polyamide, and a material having an excellent reinforcing effect can be obtained. The dispersion state at the molecular level can be specifically confirmed by performing wide-angle X-ray measurement. That is, in the raw material state, diffraction originating from the interlayer distance of the layered silicate in the c-axis direction (usually 8 to 20 ° under moist heat) is observed, but the silicate layer is dispersed in the polyamide resin at the molecular level. In this case, it can be confirmed that each layer of the layered silicate peels off and takes a random direction, and as a result, a peak derived from the crystal structure of the layered silicate is not observed. It can also be confirmed by observing the approximate size of the silicate layer in the polyamide by electron micrograph observation.

The amount of the silicate layer in the layer (B) of the present invention is preferably from 0.1 to 30% by weight, more preferably from 0.2 to 15% by weight. 0.1% by weight
If it is less than 30%, it is difficult to obtain a multilayer container satisfying both heat resistance and gas barrier properties at the same time.
When it exceeds, it becomes difficult to mold a multilayer container.

Next, the multilayer container of the present invention will be described. In the multilayer container of the present invention, the layer configuration such as the number of layers and the layer arrangement is not particularly limited, and at least the layer (A) and the layer
(B) may be included in one or more layers, and the layer configuration can be appropriately selected according to the use of the container. Also, layer (A)
The weight ratio between the layer and the layer (B) can also be appropriately selected according to the application,
In order to sufficiently exhibit the effects of the present invention, the ratio of the layer (B) in the multilayer container is preferably in the range of 1 to 99% by weight, and more preferably in the range of 5 to 80% by weight. . Furthermore, an adhesive layer and other functional layers can be interposed as needed.

The multilayer container of the present invention can be obtained, for example, by heating the co-extruded multilayer sheet having the above-mentioned structure, and then performing deep drawing such as vacuum molding or compression molding. Moreover, it can also be obtained by direct blow molding by co-extrusion. Further, it can also be obtained by obtaining a multilayer preform by co-injection molding and then biaxially stretching it. Furthermore, after cutting the co-extruded multilayer pipe to a fixed length, both ends are heated, and a multilayer preform obtained by performing mouth formation and bottom fusion by compression molding is obtained and biaxially stretched. You can also get.

The multilayer container obtained by the above method is
It may be used without being stretched, or may be stretched in a uniaxial direction or a multiaxial direction. The presence or absence of stretching and the conditions thereof can be appropriately selected according to the application.

[0027]

〔Measuring method〕

(a) Relative viscosity of polyamide Polyamide was dissolved in 96% concentrated sulfuric acid to a concentration of 1 g / dl, and the flow time was measured at a temperature of 25 ° C using an Ubbelohde viscometer. The value obtained by dividing the flowing time of the sample solution by the flowing time of the solvent was defined as the relative viscosity of the sample. When adjusting the concentration of the polyamide sample solution to 1 g / dl, the concentration of the polyamide excluding the silicate layer was adjusted to 1 g / dl in consideration of the concentration of the silicate layer contained in advance. (b) Intrinsic viscosity of PET Using a mixed solvent of phenol / tetrachloroethane = 60/40 (weight ratio), using an Ubbelohde viscometer at a temperature of 25 ° C.
Was measured. (c) Dispersibility of silicate layer in polyamide (1) Measurement of polyamide pellets reinforced with silicate sheet using a wide-angle X-ray diffractometer (Rigaku, RAD-rB type) The dispersibility of the silicate layer inside was evaluated. When no peak in the c-axis direction derived from the layered structure observed in the raw material swellable fluoromica-based mineral was observed, it was considered that the silicate layer was dispersed at the molecular level in the polyamide matrix. (d) Dispersibility of silicate layer in polyamide (2) A polyamide pellet reinforced with a silicate layer was cut into small pieces, embedded in an epoxy resin, and cut into ultrathin sections with a diamond knife. The ultrathin section was observed with a transmission electron microscope (JEM-200CX, manufactured by JEOL Ltd., accelerating voltage: 100 kV) under an electron microscope photograph to evaluate the dispersibility of the silicate layer in the polyamide. (e) The content of the silicate layer in the polyamide The polyamide pellets reinforced with the silicate layer were precisely weighed in a porcelain crucible, and then incinerated (ashed) in an electric furnace maintained at 500 ° C for 15 hours. Was determined by measuring the amount of ash. Content of silicate layer (% by weight) = [(weight of ash) / (weight of sample)] x 100 (f) Oxygen or carbon dioxide gas permeability coefficient MOCONOX gas permeability measurement device manufactured by Modern Control
Using -TRAN-100A, the permeation amount of oxygen or carbon dioxide gas of the sheets having various thicknesses was measured according to ASTM D-3985-81. The measurement is performed at 23 ° C., 100% RH and 1 atm.
The oxygen or carbon dioxide gas permeability coefficient was determined by the following equation. Oxygen permeability coefficient (ml · mm / m ² · 24 hrs · atm) = oxygen permeability (ml / m ² · 24 hrs · atm) × thickness (mm) Carbon dioxide gas permeability coefficient (ml · mm / m ² · 24hrs · atm) = Carbon dioxide permeation amount (ml / m ² · 24 hrs · atm) × thickness (mm) Note that this value is an index of gas barrier properties, and the smaller the value, the better the gas barrier properties.

Reference Example 1 Preparation of Polyamide (P-1) Reinforced with Silicate Layer 10 kg of ε-caprolactam, 1 kg of water and a swellable fluoromica-based mineral (Somasif “ME-100” manufactured by Corp Chemical Co., Ltd.) The interlayer distance of the silicate layer measured by wide-angle X-ray is 9.6Å
12.5Å) 200 g was mixed and placed in a reaction vessel having a content of 30 liters, and a polyamide (P-1) reinforced with a silicate layer was prepared by the following method. In other words, the contents of the reactor were heated to 260 ° C while stirring, and while gradually releasing water vapor,
The pressure was increased from 4 kg / cm ² to 15 kg / cm ² . After that, the pressure was kept at 15 kg / cm ² and the temperature at 260 ° C for 1 hour.
While gradually releasing water vapor over time, the pressure was released to normal pressure, and then polymerization was carried out at 260 ° C. for 1 hour. At the time of completion of the polymerization, the reaction product was discharged from the reaction vessel, cooled, and cut into pellets. Next, the obtained pellets were refined with hot water at 95 ° C. for 3 hours, and dried to obtain a polyamide reinforced with a silicate layer. The relative viscosity of this polyamide (P-1) was 2.8. The polyamide (P-1) pellets were subjected to wide-angle X-ray diffraction measurement. As a result, no peak derived from the layered structure observed in the raw material swellable fluoromica-based mineral was observed, and the silicate layered structure was not observed. Was cleaved and found to be dispersed at the molecular level in the polyamide matrix. Further, when the polyamide (P-1) pellets were observed with a transmission electron microscope photograph, it was confirmed that the silicate layers were separated and dispersed at the molecular level in the polyamide matrix. In addition, polyamide (P-1) by ash measurement
The content of the silicate sheet therein was 2.1% by weight.

Reference Example 2 Preparation of polyamide (P-2) reinforced with silicate layer 8 kg of ε-caprolactam, 2 kg of 12-aminododecanoic acid,
Reference Example 1 except that 1 kg of water and 300 g of swellable fluoromica-based mineral (Somasif "ME-100" manufactured by Corp Chemical) were used.
Polyamide (P) reinforced with silicate sheet
-2) was prepared. The relative viscosity of this polyamide (P-2) is
3.0. The polyamide (P-2) pellet was subjected to wide-angle X-ray diffraction measurement. As a result, no peak derived from the layered structure observed in the raw material swellable fluoromica-based mineral was observed, and the silicate layered structure was not observed. Was cleaved and found to be dispersed at the molecular level in the polyamide matrix. Further, when the polyamide (P-2) pellet was observed with a transmission electron microscope photograph,
It was confirmed that the silicate layer was separated and dispersed at the molecular level in the polyamide matrix. The content of the silicate layer in the polyamide (P-2) by ash measurement was 2.8% by weight.

Example 1 and Comparative Example 1 Using PET having an intrinsic viscosity of 1.0 and polyamide (P-1) reinforced with a silicate layer of Reference Example 1, these materials were sufficiently dried by heating and vacuum drying. Extruded at 270 ° C using an extruder equipped with a multilayer die.
A sheet having a three-layer structure of ET / P-1 / PET = 340/80/340 (unit: μm) and a width of 800 mm was obtained. P-1 in this sheet
Was 9% by weight. Next, put this sheet at 150 ° C
After heating for 5 seconds, vacuum forming to 100mm diameter
A 270 μm, 40 mm deep cup was molded. This cup was uniformly stretched. For comparison, PE
A similar cup was molded using a single-layer sheet of T (760 μm in thickness) (Comparative Example 1). 95 ° C for these two cups
When the hot water was poured, the cup made of PET alone largely deformed and shrunk, but no deformation was observed in the cup of the present invention. Further, when the oxygen and carbon dioxide gas permeability coefficients were measured by the Mocon method using a sheet (thickness: 270 μm) cut out from the cup, as shown in Table 1, the gas permeability of the container of the present invention was higher than that of the container of PET alone as shown in Table 1. The barrier properties were greatly improved. Table 1 Gas barrier properties of containers (cups) Example 1 Comparative example 1 Oxygen permeability coefficient 1.1 2.0 Carbon dioxide gas permeability coefficient 4.2 8.0 (Note) Unit: ml ・ mm / m ²・ 24hrs ・ atm

Example 2 and Comparative Example 2 Using PET having an intrinsic viscosity of 1.0 and polyamide (P-2) reinforced with a silicate layer of Reference Example 2, these materials were sufficiently dried by heating under vacuum. Above, using a multilayer injection molding machine, molding at a temperature of 280 ℃, length 131mm, outer diameter 25m
m, and a preform having an average thickness of 4 mm was formed. This multilayer preform has a layer thickness configuration of PET / P-2 / PET =
It had a three-layer structure of 1.75 / 0.5 / 1.75 (unit: mm). The proportion of P-2 in this preform was 15% by weight. Next, the preform was transferred to a biaxial stretching blow machine, heated until the surface temperature reached 100 ° C., and subjected to biaxial stretching blow molding to obtain a biaxial stretching bottle. The dimensions of this bottle are 308mm in height, 91.5mm in outer diameter, 370μm in thickness, and the inner volume is
1.5 liters. For comparison, a similar biaxially stretched bottle was molded using a PET single-layer preform (thickness: 4.0 mm) (Comparative Example 2). For these two types of bottles
When 95 ° C. hot water was poured, the bottle made of PET alone was greatly deformed and shrunk, but no deformation was observed in the bottle of the present invention. Further, when the oxygen and carbon dioxide gas transmission coefficients were measured by the Mocon method using a sheet (thickness: 370 μm) cut out from the bottle, as shown in Table 2, the gas barrier in the container of the present invention was higher than that in the container of PET alone as shown in Table 2. The quality was greatly improved. Table 2 Gas barrier properties of containers (bottles) Example 1 Comparative Example 1 Oxygen permeability coefficient 1.2 2.3 Carbon dioxide gas permeability coefficient 4.8 9.2 (Note) Unit: ml ・ mm / m ²・ 24hrs ・ atm

[0032]

According to the present invention, there can be obtained a multilayer container which is excellent in heat resistance and gas barrier properties and enables high-temperature filling of contents and high-temperature sterilization under pressure.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masatake Yoshikawa 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Laboratory (72) Inventor Koji Fujimoto 23 Uji Kozakura Uji City, Kyoto Prefecture Unitika Research Center Institution (72) Inventor Sachiko Kokuryo 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Laboratory F-term (reference) DA01 EH20 GB16 JB16A JB16C JC00 JD02 JJ03 YY00B

Claims (4)

[Claims] 1. A multilayer container comprising a layer (A) of a thermoplastic polyester mainly composed of ethylene terephthalate units and a layer (B) of a polyamide reinforced with a silicate layer. 2. The amount of the silicate layer in the layer (B) is from 0.1 to
The multilayer container according to claim 1, which is 30% by weight. 3. The multilayer container according to claim 1, wherein the proportion of the layer (B) in the multilayer container is 1 to 99% by weight. 4. The film according to claim 1, wherein the film is stretched in at least one direction.
A multilayer container as described.