JP2839648B2 - Plastic container - Google Patents

Description

Description: TECHNICAL FIELD 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,
The purpose is to obtain a plastic container having excellent gas barrier properties.

[Conventional technology]

In recent years, plastic molded containers using an olefin-based polymer (for example, a propylene-based polymer) as the inner and outer layers and a saponified ethylene-vinyl acetate copolymer as the gas barrier layer have extremely excellent gas barrier properties. Its use is now expanding as it is suitable for preserving food.

[Problems to be Solved by the Invention] However, after filling the contents (for example, soup) into a molded container body of this kind, which has been conventionally started, and sealing it, a retort heat sterilization treatment (for example, at a temperature of 125 ° C.) 30 minutes), the saponified ethylene-vinyl acetate copolymer in the intermediate layer absorbs moisture during the heat sterilization treatment, resulting in a significant decrease in gas barrier properties, causing decay, deterioration and discoloration of the contents. there were.

From the above, the present invention has these disadvantages (problems).
To obtain a container made of a thermoplastic resin not only having excellent gas barrier properties at the time of non-retort but also having no rot, deterioration, and discoloration of the contents immediately after retort heat sterilization treatment and even when stored for a long time. It is.

[Means and actions for solving the problem]

According to the present invention, these problems are mainly caused by 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. It is a multilayer plastic container formed of a laminate with inner and outer surface layers of a thermoplastic resin, and has 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 prevention layer of less than 24 hours, and between the water vapor diffusion prevention layer and the inner and outer surface layers and the outer surface layer, the heat of crystal fusion measured by a differential scanning calorimeter is less than 2.0 cal / g. And a plastic container characterized by being provided with a substantially amorphous polyamide layer having a glass transition point of 80 ° C. to 180 ° C. measured by the calorimeter. Hereinafter, the present invention will be described specifically.

(A) Propylene-based polymer In the present invention, the propylene-based polymer constituting the inner surface layer and the outer surface image is a propylene homopolymer or ethylene or other α-olefin containing at least 70% by weight of propylene, or a random or 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. The melt index of these propylene-based polymers (measured at 14 according to JIS K-7210, hereinafter referred to as `` MI
(1) "is 0.005 to 80 g / 10 minutes, and 0.01 to 60 g
/ 10 minutes is desirable, and a propylene polymer of 0.01 to 40 g / 10 minutes is particularly preferable. MI (1) 0.005g / 10
If the propylene-based polymer of less than 10 minutes is used, the moldability of obtaining the container is poor, a good container cannot be obtained, and if the propylene-based polymer exceeds 80 g / 10 minutes, the impact resistance of the container is reduced. It is weak and the container is not practical.

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 synthetic resin and rubber fields.

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 Japanese Patent Application No. 59-12.
No. 4481.

Of these inorganic fillers, the powdery one has a diameter of
Those having a size of 30 μm or less (preferably 10 μm or less) are preferred.
For fibrous materials, the diameter is 1 to 500 μm (preferably 1 to 300 μm
m) and a length of 0.1 to 6.0 mm (preferably 0.1 to 5 mm) is desirable. Further, the plate is preferably 30 μm or less (preferably 10 μm or less). 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 inorganic filler-containing propylene polymer is at most 70% by weight, preferably 5 to 65% by weight, and 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, the ethylene-vinyl alcohol copolymer constituting the intermediate layer interposed between the inner surface layer and the outer surface layer is ethylene-acetic acid as a starting material. The polymerization ratio of ethylene in the vinyl copolymer is 15 to 60 mol%,
15-55 mol% is preferred. In particular, the degree of saponification is 80% or more, preferably 85% or more, and particularly preferably 90% or more.

Furthermore, the melt index (according to JIS K-7210,
Measured at a temperature of 210 ° C and a load of 2.16 kg.
(2) ") is usually 0.1 to 50 g / 10 minutes, and 0.1 to 20 g
g / 10 minutes is desirable, especially 0.5 to 20 g / 10 minutes. 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, if an ethylene-vinyl alcohol copolymer exceeding 20 g / 10 minutes is used, the moldability is poor when producing a multilayer laminate, and a good laminate cannot be obtained.

(C) Polyamide Further, 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 is defined as a crystal heat of fusion measured by a differential scanning calorimeter. Is less than 2 cal / g. When the heat of crystal fusion exceeds 2 cal / g, the melting point of the amide resin is high, and when the molding temperature is increased to the melting temperature to mold this polyamide resin,
The propylene-based polymer and 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, the gas barrier property is greatly 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, as an acid, adipic acid, azelaic acid, terephthalic acid, isophthalic acid, cyclohexane-1,
1,6-hexamethylenediamine, trimethyl-1,6-hexamethylenediamine, 4,4'-diamino-dicyclohexylenemethane, 4,4'-diamino-3,3 '-Dimethyldicyclo-hexylenemethane, 4,4'-diamino-dicyclohexylenepropane, isophoronediamine, and lactams such as caprolactam and laurolactam, and as isocyanates 4,4'-diphenylmethane diisocyanate and tolylene diisocyanate It is obtained by polycondensation. 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 production of 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, various methods such as adding a phosphorus compound in a polymerization manner to prevent coloring and gelling, and performing a two-stage polymerization consisting of a pre-condensation step and a post-condensation step using terephthalic acid diester as a starting material, and the like. It is desirable to devise.

Further, as the solution polymerization method, a decarboxylation condensation reaction between diisocyanate and dicarboxylic acid may be used.

In producing the container of the present invention, the polyamide layer and the ethylene-vinyl alcohol copolymer layer (gas barrier layer) are used to prevent deterioration of the barrier property 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 between them as described below.

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

As the olefin polymer, a homopolymer of ethylene, ethylene and a carbon atom having at most 12 (preferably 3
To 8) α-olefin (copolymerization ratio of α-olefin is usually 20% by weight or less, desirably 15% by weight or less, preferably 10% by weight or less) and ethylene as a main component ( In general, a monomer having a polar group of 65% by weight or more, preferably 70% by weight or more (eg, vinyl acetate, (meth) acrylic acid or an alkyl ester thereof)
And the above-mentioned propylene-based polymers.

Melt index of a homopolymer of ethylene and a copolymer of ethylene and a monomer having an α-olefin or a polar group (hereinafter referred to as “ethylene polymer”) [JIS
According to K-7210, the measurement was carried out under conditions of 4, and hereinafter referred to as "MI (3)"] and MI (1) of the propylene-based polymer are generally 0.01 to 100 g / 10 min, and 0.02 to 50 g / min. A time of 10 minutes is desirable, and a time of 0.05 to 50 g / 10 minutes is particularly preferable. When a propylene-based polymer or an ethylene-based polymer having a lower limit of MI (1) or MI (3) 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 polymers of ethylene or propylene and other α-olefins are desirable. .

Unsaturated carboxylic acids used in producing this graft copolymer are roughly classified into monobasic unsaturated carboxylic acids and dibasic unsaturated carboxylic acids. The monobasic unsaturated carboxylic acid usually has at most 20 (preferably 15 or less) carbons, and typical examples thereof include acrylic acid and methacrylic acid. The carbon number of the dibasic unsaturated carboxylic acid is generally at most 40 (preferably 30 or less), and typical examples thereof 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 (preferably 15 or less) carbon atoms in the amide group and the imide group. In addition, the total number of carbon atoms in 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 typical 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, and monoethyl maleate. Ethyl 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-monoethylamide,
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-N-monobutylamide, fumaric acid Acid N-
N, N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate.

The decomposition temperature of the radical initiator used for the graft polymerization for one minute and half life is usually 100 ° C. or higher, and 105 ° C.
Those described above are preferred, and those having a temperature of 120 ° C. or more are particularly preferred. Representative examples of suitable radical initiators include dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (tert-butyl-peroxy) Organic peroxides such as hexane, 2,5-dimethyl-2,5-di (tertiary-butylperoxy) hexane-3, lauroyl peroxide, and tertiary-butylperoxybenzoate.

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 0.03 to 3.0 parts by weight, and particularly preferably 0.1 to 2.0 parts by weight. When the usage ratio of the unsaturated carboxylic acid and its derivative is less than 0.01 part by weight as the total amount thereof, the adhesion of the graft copolymer is insufficient. On the other hand, when the amount exceeds 5.0 parts by weight, not only the risk of decomposition or crosslinking reaction occurring at the time of producing the graft copolymer, but also the adhesiveness is lowered.

In the case of a radical initiator, the amount is 0.001 to 1.0 part by weight, preferably 0.01 to 1.0 part by weight, particularly 0.01 to 0.5 part by weight. If the use ratio of the radical initiator is less than 0.002 parts by weight, the effect of the modification is poor, and it takes a long time to complete the modification. On the other hand, if it exceeds 1.0 part by weight, it is not preferable because excessive decomposition or crosslinking reaction occurs.

The graft copolymer of the present invention is produced by a 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 deterioration 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 ℃, 150 ~ 350 ℃
And 150 to 300 ° C. is particularly preferable.

Furthermore, in the present invention, the water vapor permeability of this resin measured at a temperature of 40 ° C. by the method of ASTM F1249 is 60 g / m ² · 24 hr.
It is necessary to make it exist in such a thickness that it becomes less than. For 60g / m ² · 24hr or more steam excessively only become no vapor diffusion preventing layer, or if not provided water vapor diffusion barrier layer, after retort treatment and especially when stored at high temperature and high humidity, and trapped in the polyamide layer The water that was
It 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) 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 12 and sealed by a lid 14. Also,
FIG. 2 is a partially enlarged sectional view of the low wall portion 11 of the sectional view shown in FIG. The container body has a flange 10 as shown in FIG. The container body is an inner surface layer 1 and an outer surface layer 2 made of a propylene polymer, and a gas barrier layer 3 made of an ethylene-vinyl alcohol copolymer interposed between these layers. Further, between the inner surface layer 1 and the gas barrier layer 3, and between the outer surface layer 2 and the gas barrier layer 3, polyamide layers 4 and 5 are provided, respectively.
Exists. Further, the gas barrier layer 3 and the polyamide layer 4
And 5, there are water vapor diffusion preventing layers 7 and 8.

Further, adhesive layers 6, 9 may be provided between the inner surface layer 1 and the outer surface layer 2 and the polyamide layers 4 and 5 in order to improve the adhesiveness.

The gas barrier layer (ethylene-vinyl alcohol copolymer 3) generally has a thickness of 5 to 200 μm, and particularly preferably 10 to 180 μm, in order to maintain practical gas barrier properties in a normal state.

Further, the inner surface layer 1 and the outer surface layer have a thickness of 50 μm to 2.0 m.
m, and particularly preferably 60 μm to 1.9 mm. The thickness of the amorphous nylon layer interposed between the outer surface layer and the barrier layer and between the inner surface layer and the barrier layer is respectively
The thickness 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, and FIG. 2 is a partially enlarged sectional view of the sectional view.

In the container shown in FIG. 1, the thickness of the flange portion 10, the body wall portion 13 and the bottom wall portion 11 is generally 0.3 to 2.0 mm in order to prevent self-retention and deformation during retorting. is there.

In order to manufacture 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 general olefin polymers may be applied. 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 a contact 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 the contents 12 are filled in the container body thus manufactured, the lid portion 14 is heat-sealed to the flange portion 10 to perform sealing. The lid 14 is a laminate forming the molded container body, for example, a laminate in which the inner surface layer of the lid 14 has a metal foil (for example, aluminum foil) outside a resin that can be heat-sealed with the inner surface layer 1 of the container body. It may be composed of

The sealed container thus produced is subjected to a retort heat sterilization treatment (sterilization treatment with steam or heat) under conditions of the time and temperature necessary to ensure commercial complete sterilization of the contents 12 (for example, 30 minutes at a temperature of 125 ° C).

[Examples and Comparative Examples]

Hereinafter, the present invention will be described in more detail with reference to examples.

In Examples and Comparative Examples, the oxygen permeability of each sample was measured at 23 ° C. using an oxygen permeation measuring device (model OX-TRAN10 / 50, manufactured by Modern Control Co., USA).
The measurement was performed under the conditions that the relative humidity inside the container was 90% and the relative humidity outside the container was 60%.

The water vapor transmission rate of the water vapor diffusion prevention resin can be measured using a water vapor transmission measuring device [Model: PERMAT, manufactured by Modern Control (USA).
RAN-W TWIN] at a measurement temperature of 40 ° C and a relative humidity of 96% RH.
It measured on condition of.

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

[(A) Propylene polymer]

A propylene homopolymer (hereinafter referred to as “PP (A)”) in which MI (1) is 1.0 g / 10 minutes as a propylene-based polymer;
85 parts by weight of an ethylene-propylene block copolymer (hereinafter referred to as “PP (B)”) having an MI (1) of 0.5 g / 10 min and an ethylene copolymerization ratio of 18% by weight;
(3) 0.2 g / 10 min, density of 0.955 g / cm ³ Ethylene homopolymer [hereinafter referred to as “PE (1)”] 15 parts by weight using an extruder with a screw diameter of 65 mm Resin temperature
A composition manufactured by kneading at 220 ° C. [pellet, hereinafter referred to as “composition (I)”], 60 parts by weight of the PP (B), PE
(1) A composition (pellet, hereinafter referred to as “composition (II)”) produced by kneading 10 parts by weight and 30 parts by weight of mica having an average particle size of 5.0 μm and an aspect ratio of about 60 in the same manner. And a composition (pellet, hereinafter referred to as "composition (III)") produced by similarly melt-kneading 70 parts by weight of PP (B) and talc having an average particle size of 5.0 µm.

[(B) Ethylene-vinyl alcohol copolymer]

Further, as an ethylene-vinyl alcohol copolymer,
A saponified product obtained by saponifying an ethylene-vinyl acetate copolymer having a copolymerization ratio of ethylene of 38 mol% [a saponification degree of 99%, MI (2) 4.0 g / 10, hereinafter referred to as “EVO
H ”) was used.

[(C) Water vapor diffusion preventing resin]

Further, 100 parts by weight of propylene homopolymer, 0.3 parts by weight of maleic anhydride, and 0.2 parts by weight of benzoyl peroxide were dry-blended for 5 minutes using a Henschel Kimiser as MI (1) as a water vapor diffusion preventing resin. . Modified polypropylene [MI (1) 25 g / 01 min] obtained by melt-kneading the obtained mixture using a single screw extruder (diameter 40 mm) at a resin temperature of 220 ° C.
It was used.

Using a T-die type film forming machine having a screw diameter of 40 m / nφ and a die width of 400 mm, films having various thicknesses of 8 μm to 120 μm were formed at an extrusion temperature of 230 ° C., and the water vapor permeability was measured. The results are shown in Table 1.

[(D) Amorphous polyamide resin]

In addition, as an amorphous polyamide resin, a mixture of terephthalic acid, trimethylhexamethylenediamine and water is first heated to 110 ° C., a methyl alcohol is removed by removing the methyl alcohol, and the resulting aqueous solution is heated at a temperature of 240 ° C. The polymer was subjected to melt-condensation polymerization under pressure of 25 atm to obtain a low polymer as a precursor. The low polymer was subjected to polycondensation at 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. The heat of crystal fusion was 0.2 cal / g. Met. Further, the glass transition point was 148 ° C. PA (a) was used as the amorphous polyamide resin. For comparison, a polycapramide (glass transition point: 48 ° C., heat of crystal melting: 16 cal / g, hereinafter referred to as “PA (b)”) produced by ring-opening polymerization of ε-caprolactam was used.

Examples 1 to 9, Comparative Examples 1 to 8 As shown in FIG. 2, the types and thicknesses of the inner and outer surface layers are mainly composed of the propylene-based polymer shown in Table 2, and the thickness of the intermediate layer is as shown in FIG. Is a gas barrier layer (EVOH layer) composed of an ethylene-vinyl alcohol copolymer (EVOH) shown in Table 2, and the thickness and type are respectively between the inner surface layer and the EVOH layer and between the outer surface layer and the EVOH layer. Shown in Table 2, further provided a water vapor diffusion preventing layer between the EVOH layer and the polyamide layer, the thickness between the polyamide layer and the inner and outer surface layers as shown in Table 2. Sheets were formed using a five-type nine-layer multi-layer sheet manufacturing apparatus (manufactured by Toshiba Instruments Co., Ltd., feed block method, five extruders with a screw diameter of 40 mm) so as to provide a water vapor diffusion preventing resin layer (Table 2). The numerical value of each layer thickness is Thickness at the stage of the heating).

Each sheet having such a configuration was manufactured into a container having a diameter of 76.8 mm, a depth of 45 mm, and a capacity of 156 cc using a vacuum forming machine (Model: FLV441, manufactured by Asano Laboratories). Each container thus obtained is filled with water so that 5% of the total content becomes a space portion, and a propylene-based weight having a thickness of 60 μm on both sides is interposed with an aluminum foil having a thickness of 20 μm. The lid produced by the coalescence was subjected to ring sealing for 3 seconds at a temperature of 200 ° C. and a pressure of 2.5 kg / cm ² to produce a container filled with water. Each of the obtained containers was placed in a retort pot (manufactured by Daiwa Seikan Co., Ltd., pneumatic type, retort treatment device) and retorted at a temperature of 121 ° C. for 20 minutes. The retort processing capacity and the oxygen permeability of the unretorted vessel were measured by an oxygen permeation measuring device. The obtained result is the third
It is shown in the table. 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.

[Effect of the Invention] 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.

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 sectional view of a container manufactured in the example and the comparative example. FIG. 2 is a partially enlarged sectional view of FIG. 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 ... flange, 11 Bottom wall 12 Contents (water), 13 Body wall 14 Lid

Continuation of the front page (56) References JP-A-63-236646 (JP, A) JP-A-56-3638 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 1 / 00-35/00

Claims (1)

(57) [Claims] 1. A gas barrier layer substantially composed 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 multilayer plastic container formed of a laminate of 40 ° C., which is provided so as to be sandwiched in contact with the gas barrier layer.
In the water vapor diffusion barrier layer is present water vapor permeability as measured is less than 60g / m ² · 24hr, and, between the water vapor diffusion barrier layer and the inner surface layer and the outer surface layer, a differential scanning calorimeter The measured heat of crystal fusion 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. Plastic container.