JP3032311B2 - Plastic container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic container useful for food. More specifically, the present invention relates to a plastic container provided with a gas barrier layer substantially composed of an ethylene-vinyl alcohol copolymer as an intermediate layer, and to provide a plastic container having excellent gas barrier properties.

[0002]

2. Description of the Related Art In recent years, plastic molded containers using an olefin polymer (for example, a propylene polymer) as an inner layer and an outer layer and a saponified ethylene-vinyl acetate copolymer as a gas barrier layer have a gas barrier property. Due to its excellence, its use is currently expanding as being suitable for preserving food.

[0003]

However, after the contents (eg, soup) of this type of molded container, which has been conventionally started, are filled and sealed, a retort heat sterilization treatment (eg, at a temperature of 125 ° C.) is performed. If the heat treatment is performed for 30 minutes, the saponified product of the ethylene-vinyl acetate copolymer in the intermediate layer absorbs moisture during the heat sterilization treatment, the gas barrier property is remarkably reduced, and the contents are spoiled, deteriorated and discolored. there were.

[0004] From the above, the object of the present invention is to eliminate these drawbacks (problems), that is, not only to have excellent gas barrier properties at the time of non-retort, but also to store immediately after retort heat sterilization and for a long time. As a result, a container made of a thermoplastic resin free from decay, deterioration and discoloration of the contents is obtained, and further, 20% by weight during thermoforming or blow molding.
It is to effectively reuse scraps such as punching loss and burrs generated at about 50% by weight.

[0005] According to the present invention, the object is to provide a gas barrier layer substantially composed of an ethylene-vinyl alcohol copolymer and a propylene-based polymer provided so as to sandwich the gas barrier layer. A multilayer plastic container formed of a laminate with inner and outer surface layers of a thermoplastic resin, and having a water vapor permeability of 60 g / m ² ··· measured at 40 ° C. provided so as to be sandwiched in contact with the gas barrier layer. There is a water vapor diffusion preventing layer of less than 24 hours, and between the water vapor diffusion preventing layer and the inner surface layer and the outer surface layer, the heat of crystal fusion measured with a differential scanning calorimeter is less than 2.0 cal / g. And a substantially amorphous polyamide layer having a glass transition point of 80 ° C. to 180 ° C. measured by the calorimeter is provided. Between the layer and the outer surface layer, the gas barrier resin is a thermoplastic resin layer containing a propylene-based polymer as a main component, wherein the propylene-based polymer is at least 45% by weight or more, and the gas barrier resin is 1 to The problem can be solved by a plastic container provided with a mixture layer of 55% by weight and a polyamide resin of 30% by weight or less. Hereinafter, the present invention will be described specifically.

(A) Propylene Polymer In the present invention, the propylene polymer constituting the inner surface layer and the outer surface layer may be propylene homopolymer or ethylene or other α-olefin containing at least 70% by weight of propylene. When a container is obtained by thermoforming, for example, vacuum forming, a good product can be obtained by mixing 1.0 to 50% by weight of an ethylene-based polymer with a propylene-based polymer. can get. The melt index of these propylene polymers (measured under the conditions of 14 in accordance with JIS K-7210, hereinafter referred to as "MI (1)") is 0.005 to 80 g.
/ 10 minutes, preferably from 0.01 to 60 g / 10 minutes, and particularly preferably a propylene-based polymer from 0.01 to 40 g / 10 minutes. If a propylene-based polymer having an MI (1) of less than 0.005 g / 10 min is used, the moldability of obtaining a container is poor, a good container cannot be obtained, and the propylene-based polymer exceeding 80 g / 10 min. When used, the impact resistance of the container is weak, and the container is not suitable for practical use.

[0007] As the propylene-based polymer in the present invention, a polymer to which an inorganic filler described below is added may be used.
In this case, when molding into a container and filling the container with food, from the viewpoint of food hygiene, a propylene-based polymer containing no inorganic filler further inside the inorganic filler-containing propylene-based polymer of the inner layer. Is preferably provided.

The inorganic filler is generally widely used in the fields of synthetic resin and rubber. As these inorganic fillers, those which do not react with oxygen and water and which do not decompose during kneading and molding are preferably used. Examples of the inorganic filler include oxides of metals such as aluminum, copper, iron, lead, nickel, magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony, and titanium, and hydrates (hydroxides) thereof. Compounds such as sulfates, carbonates, silicates, double salts thereof, and mixtures thereof are roughly classified. A typical example of the inorganic filler is disclosed in Japanese Patent Application No. 59-124481.
It is described in the specification.

Among these inorganic fillers, the powdery ones having a diameter of 30 μm or less (preferably 10 μm or less) are preferable. In the case of a fibrous material, the diameter is 1 to 500.
μm (preferably 1 to 300 μm) and a length of 0.1
It is desirably about 6.0 to 6.0 mm (preferably 0.1 to 5 mm). Further, the thickness of the plate is 30 μm or less (preferably 1 μm).
0 μm or less) is preferable. Among these inorganic fillers, those in the form of a plate (flake) and those in the form of powder are particularly preferred.

The composition ratio (content ratio) of the inorganic filler in the propylene polymer containing the inorganic filler is at most 7%.
0% by weight, preferably 5 to 65% by weight, more preferably 5 to 60% by weight. When the composition ratio of the inorganic filler in the propylene polymer containing the inorganic filler exceeds 70% by weight, the impact resistance of the obtained container is remarkably reduced, and only a container which is not suitable for practical use is obtained.

(B) Ethylene-vinyl alcohol copolymer Further, in the present invention, it is a starting material of an ethylene-vinyl alcohol copolymer constituting an intermediate layer interposed between the inner surface layer and the outer surface layer. The ethylene copolymerization ratio of the ethylene-vinyl acetate copolymer is 15 to 60 mol%, preferably 15 to 55 mol%. In particular, the degree of saponification is 80% or more, preferably 85% or more, and particularly preferably 90% or more.

Further, a melt index [JIS K
According to −7210, the temperature is 210 ° C. and the load is 2.1
6 kg, hereinafter referred to as "MI (2)"].
It is 50 g / 10 min, preferably 0.1 to 20 g / 10 min, and particularly preferably 0.5 to 20 g / 10 min. When an ethylene-vinyl alcohol copolymer having an MI (2) of less than 0.1 g / 10 minutes is used, the moldability is not good when producing the multilayer laminate described below. On the other hand, when an ethylene-vinyl alcohol copolymer exceeding 20 g / 10 minutes is used, moldability is poor when a multilayer laminate is produced, and a good laminate cannot be obtained.

(C) Polyamide The substantially amorphous polyamide used between the gas barrier layer and the inner surface layer and / or the outer surface layer in the present invention was measured by a differential scanning calorimeter. The heat of crystal fusion is less than 2 cal / g. Heat of crystal fusion is 2 cal /
If the amount exceeds g, the melting point of the amide resin is high, and when the molding temperature is increased to the melting temperature for molding the polyamide resin, the propylene-based polymer or the ethylene-vinyl alcohol copolymer may be thermally degraded. . It is important that the glass transition point measured by the calorimeter is 80 ° C to 180 ° C. When a polyamide resin having a glass transition point of less than 80 ° C. is used, barrier properties are significantly reduced when the plastic container of the present invention is subjected to heat treatment for retort heat sterilization or the like. On the other hand, when the temperature exceeds 180 ° C., the moldability is significantly reduced.

The polyamide is adipic acid,
Azelaic acid, terephthalic acid, isophthalic acid, cyclohexane-1,4-dicarboxylic acid and the like; and amines such as 1,6-hexamethylenediamine and trimethyl-
1,6-hexamethylenediamine, 4,4′-diamino-dicyclohexylenemethane, 4,4′-diamino-
3,3 ′ dimethyl dicyclo-hexylenemethane, 4,
4′-diamino-dicyclohexylenepropane, isophoronediamine, and also as a lactam, caprolactam,
Laurolactam, and as an isocyanate, 4,
It is obtained by polycondensing 4'-diphenylmethane diisocyanate and tolylene diisocyanate.
This polyamide resin is produced by subjecting these polycondensation components to melt polymerization and solution polymerization, respectively. The solution polymerization method is basically a pressure melt polymerization method as in the case of ordinary nylon-6 or nylon-66, but in the case of the polyamide resin, an aromatic dicarboxylic acid is used as a raw material dicarboxylic acid. In addition, since the polymerization temperature is relatively high, there is a problem that the polymer formed during the melt polymerization tends to be colored or gelled. Therefore, a phosphorus-based compound is added at the time of polymerization to prevent coloring and gelation, and various processes such as performing a two-stage polymerization comprising a pre-condensation step and a post-condensation step using terephthalic acid diester as a starting material, It is desirable to devise.
Further, as the solution polymerization method, a decarboxylation condensation reaction between diisocyanate and dicarboxylic acid may be used.

In manufacturing the container of the present invention, a polyamide layer and an ethylene-vinyl alcohol copolymer layer (gas barrier layer) are used in order to prevent deterioration of the barrier properties after long-term storage of about 2 to 18 months after the retort treatment. )
It is necessary to interpose the water vapor diffusion preventing layers as described below.

(D) Water Vapor Diffusion Prevention Resin In the present invention, the water vapor diffusion prevention resin used for preventing barrier properties during long-term storage and bonding the barrier layer and the polyamide layer to each other is an olefin-based resin. It is obtained by graft-polymerizing an unsaturated carboxylic acid or a derivative thereof to the union. The graft polymerization is generally carried out in the presence of a radical initiator described below.

As the olefin polymer, a homopolymer of ethylene, an ethylene and an α-olefin having a carbon number of at most 12 (preferably 3 to 8) (copolymerization ratio of the α-olefin is usually 20% by weight or less, desirably 1
5% by weight or less, preferably 10% by weight or less) and a monomer having a polar group containing ethylene as a main component (generally 65% by weight or more, preferably 70% by weight or more) Vinyl acetate, (meth) acrylic acid or an alkyl ester thereof] and the propylene-based polymer.

Ethylene homopolymer and ethylene and α
-Melt index of a copolymer with an olefin or a monomer having a polar group (hereinafter referred to as "ethylene-based polymer") [measured under condition 4 in accordance with JIS K-7210,
Hereinafter referred to as "MI (3)"] and MI (1) of the propylene-based polymer.
Minute, preferably from 0.02 to 50 g / 10 minutes,
In particular, those having a concentration of 0.05 to 50 g / 10 minutes are suitable.
When a propylene-based polymer or an ethylene-based polymer having MI (1) or MI (3) less than the lower limit is used, it is difficult to uniformly perform a graft reaction. On the other hand, if the amount exceeds the upper limit, the strength of the obtained adhesive resin is poor, and the adhesive strength is not good.

Among these olefin polymers, low- and high-density ethylene homopolymers, propylene homopolymers, copolymers of ethylene and propylene, and copolymers of ethylene or propylene with other α-olefins Coalescing is preferred.

The unsaturated carboxylic acids used for producing the graft copolymer are roughly classified into monobasic unsaturated carboxylic acids and dibasic unsaturated carboxylic acids. The carbon number of the monobasic unsaturated carboxylic acid is usually at most 20 (preferably 15 or less), and typical examples thereof include acrylic acid and methacrylic acid. Further, the carbon number of the dibasic unsaturated carboxylic acid is generally at most 40 (preferably 30 or less),
Representative examples include maleic acid, itaconic acid, nadecic acid and fumaric acid. Further, derivatives include esters, acid anhydrides, amides, imides and metal salts of these monobasic unsaturated carboxylic acids and dibasic unsaturated carboxylic acids. Among these derivatives, amides and imides usually have at most 20 carbon atoms (preferably 1
5 or less). Further, the total number of carbon atoms of the ester is generally at most 40, and desirably 30 or less. Further, the metal of the metal salt generally includes an alkali metal and a metal of Group 2 of the periodic table, and representative examples thereof include sodium, potassium, zinc, magnesium and calcium. Representative examples of these derivatives include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, glycidyl acrylate, glycidyl methacrylate,
Maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, acrylamide, methacrylamide, maleic monoamide, maleic diamide, maleic acid-N-mono Ethylamide, maleic acid-N, N-
Diethylamide, maleic acid-N-monobutylamide,
Maleic acid-N, N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monoethylamide, fumaric acid-N, N-diethylamide, fumaric acid-
Examples include N-monobutylamide, fumaric acid N-N, N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, and potassium methacrylate.

The decomposition temperature of the radical initiator used in the graft polymerization for a half-life of 1 minute is usually 100 ° C. or higher, preferably 105 ° C. or higher, particularly preferably 120 ° C.
The above is preferred. Representative examples of suitable radical initiators include dicumyl peroxide, benzoyl peroxide, di-tertiary-butyl peroxide, 2,2
5-dimethyl-2,5-di (tert-butyl-peroxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane-3, lauroyl peroxide, tertiary And organic peroxides such as tert-butyl peroxybenzoate.

The ratio of the unsaturated carboxylic acid and its derivative and the radical initiator to 100 parts by weight of the olefin polymer is usually as follows. For unsaturated carboxylic acids and derivatives thereof, the total amount thereof is 0.01 to 5.0 parts by weight, preferably 0.05 to 3.0 parts by weight, particularly preferably 0.1 to 2.0 parts by weight. It is. If the proportion of the unsaturated carboxylic acid and its derivative used is less than 0.01 parts by weight in total, the adhesiveness of the graft copolymer will be insufficient. On the other hand, when the amount exceeds 5.0 parts by weight, not only the decomposition or crosslinking reaction may occur at the same time when the graft copolymer is produced, but also the adhesiveness is lowered. In the radical initiator, 0.0
0.01 to 1.0 part by weight, preferably 0.01 to 1.0 part by weight, particularly 0.01 to 0.5 part by weight. When the use ratio of the radical initiator is less than 0.001 part by weight,
The effect of denaturation is poor, and it takes a long time to complete denaturation. On the other hand, if it exceeds 1.0 part by weight, it is not preferable because excessive decomposition or crosslinking reaction occurs.

The production of the graft copolymer of the present invention is carried out by known means for producing this type of graft copolymer. As a typical production method, xylene, an aromatic hydrocarbon compound such as toluene, hexane, an aliphatic hydrocarbon compound such as heptane in the solvent such as the olefin polymer, unsaturated carboxylic acid or its derivative and radical initiation And an olefin polymer, an unsaturated carboxylic acid or a derivative thereof and a radical initiator are preliminarily mixed under conditions that do not substantially crosslink, and the resulting mixture is mixed with a screw extruder, a Banbury. Mixing, kneaders and other kneading machines commonly used in the field of synthetic resins may be used for melt-mixing, but the latter method is preferred from the viewpoint of operation and economy. . In the latter case, the temperature conditions for the modification are appropriately selected in consideration of the degradation of the olefin polymer, the decomposition of the unsaturated carboxylic acid or its derivative, the decomposition temperature of the organic peroxide, and the like. ~ 350 ° C and 1
50-350 ° C is desirable, especially 150-300 ° C
Is preferred.

Further, in the present invention, this resin is
It must be present in such a thickness that the water vapor permeability measured at a temperature of 40 ° C. by the method of STM F1249 is less than 60 g / m ² · 24 hr. 60g / m ² · 24
In the case of a water vapor diffusion prevention layer with water vapor permeability of hr or more, or without a water vapor diffusion prevention layer, after retort treatment, especially when stored under high temperature and high humidity,
Moisture trapped in the polyamide layer diffuses into the barrier layer, resulting in poor barrier properties. On the other hand, the resin used for the water vapor diffusion preventing layer may be interposed between the inner surface and the polyamide and between the outer surface and the polyamide for the purpose of improving adhesion.

(E) Mixed Resin The mixed resin used in the present invention comprises at least a thermoplastic resin containing the ethylene-vinyl alcohol copolymer and a propylene polymer as main components. The composition ratio of the thermoplastic resin in the total amount thereof is usually 45 to 45.
It is 99% by weight, preferably 50 to 98% by weight, particularly preferably 55 to 97% by weight. When the composition ratio of the propylene-based polymer in the total amount of these is less than 45% by weight, the drop strength of the container is remarkably reduced, and the multi-layer sheet moldability,
In particular, it is difficult to stabilize the layer state. On the other hand, 9
If the content exceeds 9% by weight, the loss of burrs, burrs and the like generated during molding of the container of the present invention and during molding of a barrier sheet or a barrier film of a general ethylene-vinyl alcohol copolymer and a propylene-based polymer. The proportion of the propylene-based resin must be increased by blending the propylene-based polymer with the resin, and the recycled resin to be reused cannot be effectively used. Further, the effect of retaining the barrier property after the retort treatment by inserting the recycled resin into the position of the layer constitution of the present invention is reduced.

The proportion of the ethylene-vinyl alcohol copolymer in the total amount is usually 1 to 55% by weight.
And preferably 2 to 30% by weight, and particularly preferably 3 to 25% by weight. If the composition ratio of the ethylene-vinyl alcohol copolymer in the total amount is less than 1% by weight,
When molding the container of the present invention, and a barrier sheet of a general ethylene-vinyl alcohol copolymer and a propylene-based polymer, a punching loss generated during molding of the barrier film, a propylene-based resin or the like as a recycled resin such as burrs. It is necessary to reduce the composition ratio of the ethylene-vinyl alcohol copolymer by blending, and the recycled resin cannot be effectively used. Further, the effect of retaining the barrier property after the retort treatment by inserting the recycled resin into the position of the layer constitution of the present invention is reduced. On the other hand, if it exceeds 55% by weight, the drop strength of the container is significantly reduced.

The composition ratio of the polyamide in the total amount is usually preferably 30% by weight or less, and more preferably less than 25% by weight. If it exceeds 30% by weight, the drop strength of the container is significantly reduced.

(F) Container and Manufacturing Method Thereof Hereinafter, the container of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a cross-sectional view of a typical container body of the present invention filled with contents 14 and sealed by a lid 16.
FIG. 2 is a partially enlarged sectional view of the bottom wall portion 13 in the sectional view shown in FIG. The container body has a flange portion 12 as shown in FIG. The container body includes an inner surface layer 1 and an outer surface layer 2 made of a propylene-based polymer, and a gas barrier layer 3 made of an ethylene-vinyl alcohol copolymer interposed between these layers. Further, there are water vapor diffusion preventing layers 7 and 8 provided so as to be sandwiched in contact with the gas barrier layer. Further, there are polyamide layers 4 and 5 provided so as to be sandwiched in contact with the water vapor diffusion preventing layers 7 and 8,
Mixture layers 10, 11 exist between the polyamide layer and the inner and outer surface layers. Further, the mixture layer 1
Adhesive layers 6, 9 may be provided between 0, 11 and the polyamide layers 4 and 5 to improve the adhesion.

The gas barrier layer (ethylene-vinyl alcohol copolymer layer 3) generally has a thickness of 5 to 200 in order to maintain practical gas barrier properties under normal conditions.
μm, and particularly preferably 10 to 180 μm. Also,
The inner surface layer 1 and the outer surface layer have a thickness of 0.1 mm to 2.0 mm, particularly preferably 0.1 mm to 1.8 mm. The thickness of each of the polyamide layers 4 and 5 interposed between the outer surface layer and the barrier layer and between the inner surface layer and the barrier layer is 10 to 300 μm, and particularly preferably 20 to 200 μm.

FIG. 1 is a sectional view of the plastic container of the present invention.
FIG. 2 shows a partially enlarged sectional view of the sectional view. FIG.
In the container shown in FIG.
And the thickness of the bottom wall portion 13 is generally 0.3 to 2.0 mm in order to prevent self-shaping and deformation during retort processing.
It is.

In order to produce the container of the present invention, a molding method (a method obtained from a sheet, a method obtained from an injection molding, a method obtained from a hollow molding, etc.) practiced in the field of a general olefin polymer is applied. I just need. As a typical example of the molding method, an inner surface layer, a gas barrier layer, an outer surface layer, a water vapor diffusion preventing layer, or a thin material (film, sheet) of these layers and an adhesive resin layer is used in these fields. A laminated sheet is manufactured by forming a sheet or film in advance using a forming machine and bonding these thin materials. Next, a container may be manufactured from this sheet by a vacuum forming method, a pressure forming method or a press forming method. Further, the sheet may be produced by coextrusion sheet molding of an inner surface layer, a gas barrier layer, an outer surface layer, a water vapor diffusion preventing layer, or a polymer (resin) constituting these layers and an adhesive resin layer.

As shown in FIG. 1, after filling the contents 14 into the container body manufactured in this way, the lid 16 is heat-sealed to the flange 12 to seal. The lid part 16 is a laminated body forming a molded container main body, for example, a laminated body in which the inner surface layer of the lid part 16 has a metal foil (for example, aluminum foil) on the outside of a resin heat-sealable with the inner surface layer 1 of the container main body. It may be composed of The sealed container thus produced is subjected to a retort heat sterilization treatment (sterilization treatment by steam or heat) under conditions of the time and temperature necessary to ensure commercial complete sterilization of the contents 14 (for example, At a temperature of 125 ° C., 3
0 minutes).

[0033]

The present invention will be described in more detail with reference to the following examples. In Examples and Comparative Examples, the oxygen permeability of each sample was measured using an oxygen permeation measuring device [model OX-TRAN 10/5 manufactured by Modern Control Company (USA)].
0] was measured under the conditions of a measurement temperature of 23 ° C., a relative humidity inside the container of 90%, and a relative humidity outside the container of 60%.

The water vapor transmission rate of the water vapor diffusion preventing resin was measured using a water vapor transmission measurement device [Modern Control Co., USA]
PERMATRAN-WTWIN] was measured at a measurement temperature of 40 ° C. and a relative humidity of 96% RH.

The propylene polymers, ethylene-vinyl alcohol copolymers used in the Examples and Comparative Examples,
The types, production methods, physical properties, etc. of the water vapor diffusion preventing resin and the amorphous polyamide are shown below.

[(A) Propylene polymer] A propylene homopolymer (hereinafter referred to as "PP (A)") having a MI (1) of 1.0 g / 10 minutes as a propylene polymer,
85 parts by weight of an ethylene-propylene block copolymer (hereinafter referred to as “PP (B)”) in which (1) is 0.5 g / 10 min and the copolymerization ratio of ethylene is 18% by weight; ) Is 0.2 g / 10 min and the density is 0.965 g
/ Cm ³ of ethylene homopolymer [hereinafter referred to as “PE (1)”
15 parts by weight using an extruder having a screw diameter of 65 mm and kneading at a resin temperature of 220 ° C. while kneading the resin (pellet, hereinafter referred to as “composition (I)”); ) 60 parts by weight, 10 parts by weight of PE (1), an average particle size of 5.0 μm, and an aspect ratio of about 60
A composition prepared by kneading 30 parts by weight of mica in the same manner [pellet, hereinafter referred to as “composition (II)”]
And 70 parts by weight of PP (B) and an average particle size of 5.0.
A composition (pellet, hereinafter referred to as "composition (III)") produced by similarly melt-kneading talc having a particle size of .mu.m was used.

[(B) Ethylene-vinyl alcohol copolymer] The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer having a copolymerization ratio of ethylene of 38 mol%. Saponified (99% saponification, MI (2) 4.0 g / 10
Min., Hereinafter referred to as “EVOH”).

[(C) Water vapor diffusion preventing resin] Further, as a water vapor diffusion preventing resin, 100 parts by weight of a propylene homopolymer having an MI (1) of 0.5 g / 10 min, 0.3 parts by weight of maleic anhydride and Dry blending of 0.2 parts by weight of benzoyl peroxide was performed in advance using a Henschel mixer for 5 minutes. The resulting mixture was melt-kneaded at a resin temperature of 220 ° C. using a single screw extruder (diameter 40 mm) to use modified polypropylene [MI (1) 25 g / 10 min]. Screw diameter 4
Using a T-die film forming machine having a diameter of 0 mm and a die width of 400 mm, films having various thicknesses from 8 μm to 120 μm were formed at an extrusion temperature of 230 ° C., and the water vapor transmission rate was measured.
Table 1 shows the results.

[0039]

[Table 1] Table 1

[(D) Amorphous polyamide resin] A mixture of terephthalic acid, trimethylhexamethylenediamine and water was first used as an amorphous polyamide resin.
The resulting aqueous solution was heated to 240 ° C. and subjected to pressure melt-condensation polymerization at 25 ° C. under a pressure of 25 atm to obtain a low polymer as a precursor. The low polymer was subjected to polycondensation at a temperature of 260 ° C. under reduced pressure using an extruder. The obtained polymer [hereinafter referred to as “PA (a)”] was measured using dimethylformaldehyde as a solvent at a temperature of 25 ° C., and had a particle size average molecular weight of about 20,000.
It was 2 cal / g. The glass transition point was 148 ° C. PA (a) was used as an amorphous polyamide resin. For comparison, polycapramide produced by ring-opening polymerization of ε-caprolactam [glass transition point 48 ° C., heat of crystal fusion 16 cal / g;
(B) ").

[(E) Mixed resin] P as an inner and outer surface layer
A layer having a thickness of 0.6 mm using P (A), a barrier layer having a thickness of 40 μm using the above-described EVOH, a polyamide resin layer being PA (a), and a thickness of 100 μm each.
Furthermore, the thickness of the water vapor diffusion preventing layer is 40 μm each.
Was molded using a five-type, nine-layer multilayer sheet molding apparatus. Approximately 5mm
Pulverize into corners and pull the vent with a single screw extruder with L / D = 32, screw diameter 65mmφ, and set the die outlet temperature to 240.
C., pelletized and used as a resin mixture.

Examples 1 to 9 and Comparative Examples 1 to 8 As shown in FIG. 2, the type and thickness of the inner and outer surface layers are as shown in Table 2, and the layers are mainly composed of propylene-based polymer. The gas barrier layer (EVOH layer) composed of an ethylene-vinyl alcohol copolymer (EVOH) shown in Table 2 has a thickness and a type between the inner surface layer and the EVOH layer and between the outer surface layer and the EVOH layer. Provided a polyamide layer, and further provided a water vapor diffusion preventing layer between the EVOH layer and the polyamide layer,
A 30 μm adhesive layer is sandwiched between the inner and outer surface layers of both polyamide layers, and a mixture layer having a thickness shown in Table 2 is provided between the adhesive layer and the inner and outer surface layers. The sheet was formed using a seed 11-layer multilayer sheet manufacturing apparatus (manufactured by Toshiba Machine Co., Ltd., feed block method, four extruders with a screw diameter of 40 mm, and two extruders with a 65 mm diameter) (however, the thickness of each layer in Table 2) The thickness value indicates the thickness at the stage of the multilayer sheet).

Using a vacuum forming machine (model: FLV441, manufactured by Asano Laboratories), each sheet having such a configuration is 76.8 mm in diameter, 45 mm in depth and 156 cc in capacity.
Was manufactured. Each container thus obtained was filled with water so that 5% of the total content was in the space, and the thickness of both surfaces was 6 mm with an aluminum foil having a thickness of 20 μm interposed.
A lid made of a propylene polymer having a thickness of 0 μm was subjected to ring sealing at a temperature of 200 ° C. and a pressure of 2.5 kg / cm ² for 3 seconds to produce a container filled with water.
Each of the obtained containers was put into a retort pot (manufactured by Daiwa Seikan Co., Ltd., retort treatment device), and retort treatment was performed at a temperature of 121 ° C for 20 minutes. The oxygen permeability of the retort-treated container and the unretorted container was measured by an oxygen permeation measuring device (OX-TRAN 10/50, manufactured by Modern Control). Table 3 shows the obtained results. From Table 3, it is clear from Table 3 that not only the barrier property before and after the retort treatment hardly changed, but also the barrier property hardly changed even after long-term storage under high humidity. In addition, it was found that a large amount of loss generated during sheet molding or thermoforming can be reused, and by reusing the loss, it is possible to further prevent the deterioration of barrier properties.

[0044]

[Table 2]

[0045]

[Table 3] Table 3 1) cc / oxygen 1 atm, 24hr / piece 2) Measured after storage at 30 ° C, 90% RH for 3 months

[0046]

The plastic container of the present invention exhibits the following effects. That is, the container is made of a thermoplastic resin having not only excellent gas barrier properties but also no decay, deterioration or denaturation of the contents even when stored for a long time after the retort heat sterilization treatment. In addition, a large amount of loss and the like generated during sheet molding and thermoforming can be reused, and by reusing, a container made of a thermoplastic resin having a more excellent gas barrier property after retort heat sterilization treatment. The container obtained by the method of the present invention can be used in various fields to exhibit the above-mentioned effects. Representative applications are shown below. (1) Various processed seasoning food containers (2) Various liquid food containers (3) Various food containers (4) Various industrial chemical containers

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of containers manufactured in Examples and Comparative Examples.

FIG. 2 is a partially enlarged sectional view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner surface layer 2 Outer surface layer 3 Gas barrier layer 4, 5 Polyamide resin layer 6, 9 Adhesive resin layer 7, 8 Water vapor diffusion prevention layer 10 Mixture layer 11 Mixture layer 12 Flange 13 Bottom wall part 14 Contents (water) 15 Body wall 16 Lid

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-111541 (JP, A) JP-A-2-299836 (JP, A) JP-A-1-269528 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 B65D 1/00-1/48

Claims (1)

(57) [Claims] 1. A gas barrier layer consisting essentially of an ethylene-vinyl alcohol copolymer, and an inner / outer surface layer of a thermoplastic resin containing a propylene-based polymer as a main component and provided so as to sandwich the gas barrier layer. A multi-layer plastic container formed of a laminate of (4), provided so as to be sandwiched in contact with the gas barrier layer.
Water vapor permeability measured at 0 ° C. is 60 g / m ² · 24 hr
Is less than 2.0 cal / g between the water vapor diffusion preventing layer and the inner surface layer and the outer surface layer, as measured by a differential scanning calorimeter.
Is less than 80 ° C. and the glass transition point measured by the calorimeter is 80 ° C.
And a substantially amorphous polyamide layer having a temperature of about 180 ° C. is provided. Further, the gas barrier resin and the propylene-based polymer are mainly provided between the polyamide layer and the inner surface layer and the outer surface layer. a thermoplastic resin layer as a component, flop
At least 45% by weight or more of a propylene-based polymer;
1 to 55% by weight of rear resin and 3 of polyamide resin
A plastic container provided with a mixture layer of 0% by weight or less .