JPH0852845A - Multi-layered structure and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the resistance to retort by constituting a compound or compounds of one kind or more selected out of an ethylene-vinyl acetate copolymer saponified material, adjusted terminal adjustment polyamide resin, a hindered phenol compound, aliphatic carboxylic acid alkaline earth metal salt and higher fatty acid metal salt and the like and specifying the percentage of respective components to be selected. CONSTITUTION:A multi-layer structure is constituted of a compound or compounds (e) selected out of an ethylene-vinyl acetate copolymer saponified material (a), adjusted terminal adjustment polyamide (b), a hindered phenol compound (c), aliphatic carboxylic acid alkaline earth metal salt (d) and higher aliphatic salt and the like. A resin composition II of oxygen gas barrier properties, having the weight ratio of a:b being (70:30)-(96:4), and the blend ratio of (c) to the total amount of (a) and (b) is 0.01wt.%, while the blend ratio of (d) to the total amount of (a) and (b) is 0.5-15mumol/g in terms of metal, and the blend ratio of (e) to the total amount of (a) and (b) is 0.01-1wt.%, is formed and further a thermoplastic resin layer provided with permeability lower than that of a thermoplastic resin layer I is formed as an innermost layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer structure using a resin composition containing a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) and a specific polyamide resin. A multi-layer structure having excellent oxygen gas barrier properties before and after retort sterilization treatment and appearance of the film, and useful for applications such as a multi-layer film packaging material for retort sterilization treatment, a container for retort sterilization treatment, a lid material for retort sterilization treatment, and the like. Regarding manufacturing method.

[0002]

2. Description of the Related Art As a food package using a multilayer structure, especially a multilayer film, contents are filled in a bag (pouch),
After resealing, there is a retort packaging material that requires high-temperature heat sterilization to have the same storage effect as canned food. As the packaging material, there are generally a type including aluminum foil and a transparent type including vinylidene chloride.

However, the aluminum foil has a drawback that the contents cannot be confirmed because it is opaque, and the vinylidene chloride requires a thickness of 60 to 80 μm to obtain a desired oxygen gas barrier property. As a result, the packaging material becomes yellowish and the transparency is lowered, so that it is usually used at about 15 to 30 μm, and there is a problem that sufficient oxygen gas barrier property is not obtained. There is.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 62-62
In JP-A-202735, the ethylene content is 20 to 6
On one side of a base material having a polyolefin resin layer on both sides of an EVOH resin layer of 0 mol% and a saponification degree of 90 mol% or more,
Disclosed is a laminate for retort sterilization treatment provided with an EVOH layer having an ethylene content of 20 to 60 mol% and a saponification degree of 90 mol% or more.

Further, Japanese Patent Laid-Open No. 1-308628 discloses that
EVOH 55-9 with an ethylene content of 20-50 mol%
7% by weight of polyamide resin, polyolefin resin,
An oxygen gas barrier multi-layered package characterized by using a layer of a composition of 45 to 3% by weight of a resin selected from polyester resins and polycarbonate resins as an outermost layer and using a low humidity thermoplastic resin as an inner layer. Is disclosed.

[0006]

However, the technique disclosed in Japanese Patent Laid-Open No. 62-202735 has some effect on the boil treatment, but in the retort sterilization treatment, the outer EVOH layer is formed during the retort treatment. It absorbs water and swells, and at the same time, melts and flows, and cannot be used as a retort packaging material. Further, the EVOH layer sandwiched between the polyolefin layers absorbs water during the retort treatment, and the oxygen gas barrier property after the retort sterilization treatment becomes worse than that before the retort sterilization treatment.

In the technique disclosed in JP-A-1-308628, although the recovery rate of the oxygen gas barrier property after the retort sterilization treatment is improved, the oxygen gas barrier property at room temperature and normal humidity and after the retort sterilization treatment is improved. It is still inadequate, and in the technology disclosed in the publication, gel value or fish eye may be generated in the molded product during long-term operation, which may significantly lower the commercial value, probably because the polyamide-based resin and EVOH have a large chemical reactivity. , The processability such as stretching becomes poor, and the recovery rate of the oxygen gas barrier property at room temperature and normal humidity and the oxygen gas barrier property after retort sterilization is good, and the oxygen gas barrier before and after retort sterilization is good. There has been a demand for the appearance of a multilayer structure having a good film appearance with little change in sex and without the generation of gels, fish eyes and the like.

[0008]

Means for Solving the Problems In order to solve the above problems, the inventors of the present invention have diligently studied and found that the water vapor permeability (40 ° C.,
Measured under 90% RH) is 10 to 500 g / m ² · day
On both sides of the thermoplastic resin layer (I) having a value, saponified ethylene-vinyl acetate copolymer (a) having an ethylene content of 20 to 60 mol% and a saponification degree of 90 mol% or more; Number of terminal COOH groups (x) and terminal CONR
R'group (provided that R is a hydrocarbon group having 1 to 22 carbon atoms, R '
Is the number of hydrogen or a hydrocarbon group having 1 to 22 carbon atoms (y)
Is adjusted to satisfy 100 × y / (x + y) ≧ 5, a terminal-adjusted polyamide resin (b), a hindered phenol compound (c), an aliphatic carboxylic acid alkaline earth metal salt (d) and ethylene. At least one compound (e) selected from bis fatty acid amides, higher fatty acid metal salts, polymer esters, fatty acid esters, and hydrocarbon compounds
And the weight ratio of (a) :( b) is 70: 30-9.
6: 4, the mixing ratio of (c) to the total amount of (a) and (b) is 0.01 to 1% by weight, and the mixing ratio of (d) to the total amount of (a) and (b) is 0.5 to 15 in terms of metal
An oxygen gas barrier resin composition layer (II) having a proportion of (e) with respect to the total amount of (a) and (b) of 0.01 to 1 wt% at μmol / g is formed. Water vapor permeability lower than the thermoplastic resin layer (I) as an inner layer (40 ℃,
Thermoplastic resin layer (measured under 90% RH) (III)
By providing a multi-layered structure with little change in oxygen gas barrier properties before and after retort sterilization treatment and without generation of gels or fish eyes, good retort resistance can be obtained. In particular, pouches, lid materials, etc. boil or retort The inventors have found that they are suitable for film packaging materials for sterilization treatment and completed the present invention.

The present invention will be described in detail below. Water vapor permeability (40 ° C., 90 ° C.) used for the intermediate layer of the multilayer structure of the present invention.
% Thermoplastic resin layer (I) having a value of 10 to 500 g / m ² · day is measured at 40 ° C. and 90% RH.
The layer is not particularly limited as long as it is a layer using a thermoplastic resin having a moisture permeability of 10 to 500 g / m ² · day below, and specific examples of the thermoplastic resin include nylon 6 and nylon 6
・ 12, Nylon 6.66, Nylon 6.9, Nylon 6/12, Nylon 12, Nylon 6.4, Polyamide resins such as amorphous polyamide, high density, medium density, low density polyethylene, vinyl acetate, acrylic Acid ester or polyethylene copolymerized with α-olefins such as butene, hexene, 4-methyl-1-pentene, ionomer resin, polypropylene homopolymer, polypropylene graft copolymerized with ethylene, or ethylene, hexene, 4-methyl Polypropylene copolymerized with α-olefins such as -1-pentene, polyolefin resins such as poly-1-butene and poly-4-methyl-1-pentene, polyvinyl chloride resins, acrylic resins, polyvinylidene chloride resins Resin, polyacetal resin, polyester resin, poly Carbonate resins, polystyrene resins, and the like can be used, and these resins can be used alone or in combination of two or more, and are preferably nylon 6, a blend of nylon 6 and an amorphous polyamide, nylon 6. A blend of 66 and amorphous polyamide is used, and in particular, a blend of nylon 6 and amorphous polyamide is preferably used because it shows good stretchability and film strength.

In the present invention, the moisture permeability of the thermoplastic resin layer (I) using the above-mentioned thermoplastic resin is 40 ° C., 9
It is important to be in the range of 10 to 500 g / m ² · day under 0% RH, and the water vapor permeability of the resin layer (I) is 10 g.
If it is less than / m ² · day, there is a problem that the recovery rate of oxygen gas barrier property after retort sterilization treatment is slow, and if it is more than 500 g / m ² · day, the oxygen gas barrier resin layer located on the inner layer side ( II) absorbs moisture from the outside air, resulting in a problem of insufficient oxygen gas barrier property at room temperature and normal humidity, preferably 15 to 450 g /
m ² · day, more preferably 20 to 400 g / m ² · d
ay. Further, if the thermoplastic resin layer (I) satisfies the above moisture permeability, it is also possible to employ a multilayer laminate in which two or more layers of the above thermoplastic resin are laminated.

As a method of defining the water vapor transmission rate of the present invention,
The method specified in JIS Z 0208, that is, the film is attached to a cup containing a hygroscopic agent, sealed, fixed, and then left in a thermo-hygrostat controlled at 40 ° C. and 90% relative humidity to increase the weight. It depends on the method of obtaining by measuring the speed. In the multilayer structure of the present invention, the oxygen gas barrier resin composition layer (II) disposed on both sides of the thermoplastic resin layer (I) means EVOH (a), end-adjusting polyamide resin (b), hinder. At least one compound selected from dephenolic compound (c), aliphatic carboxylic acid alkaline earth metal salt (d) and ethylenebis fatty acid amide, higher fatty acid metal salt, polymer ester, fatty acid ester, hydrocarbon compound ( EVOH (a) has an ethylene content of 20 to 6
It is used in an amount of 0 mol% (preferably 25 to 55 mol%) and a vinyl acetate unit having a saponification degree of 90 mol% or more (preferably 95 mol% or more, more preferably 98 mol% or more). When the ethylene content is less than 20 mol%, the melt moldability is deteriorated, while when the ethylene content exceeds 60 mol%, the oxygen gas barrier property is deteriorated and the saponification degree is 9%.
If it is less than 0 mol%, the hot water resistance is poor and unsuitable.

[0012] EVOH (a), if a small amount,
It may be "copolymer-modified" with other comonomers such as α-olefin, unsaturated carboxylic acid compound, unsaturated sulfonic acid compound, (meth) acrylonitrile, (meth) acrylamide, vinyl ether, vinyl chloride and styrene. . Further, within the range that does not impair the gist of the present invention,
"Post-modification" such as urethanization, acetalization, cyanoethylation, etc. may be performed.

As the terminal-adjusting polyamide resin (b), the number of terminal COOH groups (x) and terminal CONRR 'groups (wherein R is a hydrocarbon group having 1 to 22 carbon atoms and R'is hydrogen) are used as the terminal-adjusting polyamide resin. Alternatively, a terminal-adjusted polyamide-based resin is used in which the number (y) of hydrocarbon groups having 1 to 22 carbon atoms) is adjusted to satisfy 100 × y / (x + y) ≧ 5. Such a terminal-adjusted polyamide resin (b) is produced by polycondensing a polyamide raw material in the presence of a monoamine having 1 to 22 carbon atoms or a monocarboxylic acid having 2 to 23 carbon atoms.

As the polyamide raw material, lactams (ε-caprolactam, enantolactam, capryllactam, lauryllactam, α-pyrrolidone, α-piperidone, etc.), ω-amino acids (6-aminocaproic acid, 7-aminoheptane) are used. Acid, 9-aminononanoic acid, 11
-Aminoundecanoic acid, etc.), dibasic acid (adipic acid, glutaric acid, pimelic acid, speric acid, azelaic acid, sebacic acid, undecanedioic acid, dodecadioic acid, hexadecanedioic acid, eicosadiendioic acid, diglycolic acid, 2,2,4-trimethyladipic acid, xylene dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,
(Terephthalic acid, isophthalic acid, etc.), diamines (hexamethylenediamine, tetramethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4 (or 2,2,4-) trimethylhexamethylenediamine , Bis- (4,4′-aminocyclohexyl) methane, metaxylenediamine and the like).

Examples of monoamines having 1 to 22 carbon atoms include aliphatic monoamines (methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, undecylamine. , Dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, octadecylamine, eicosylamine, docosylamine), alicyclic monoamines (cyclohexylamine,
Methylcyclohexylamine, etc.), aromatic monoamines (benzylamine, β-phenylethylamine, etc.), symmetrical secondary amines (N, N-dibutylamine, N, N-dihexylamine, N, N-dioctylamine, N, N- Didecylamine, etc.), mixed secondary amine (N-methyl-N-
Ethylamine, N-methyl-N-butylamine, N-methyl-N-dodecylamine, N-methyl-N-octadecylamine, N-ethyl-N-hexadecylamine, N
-Ethyl-N-octadecylamine, N-propyl-N
-Hexadecylamine, N-methyl-N-cyclohexylamine, N-methyl-N-benzylamine, etc.) and the like.

Here, as the monocarboxylic acid having 2 to 23 carbon atoms, aliphatic monocarboxylic acids (acetic acid, propionic acid,
Butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid,
Capric acid, pelargonic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, myritoleic acid, palmitic acid, stearic acid, oleic acid, linoleic acid,
Arachidic acid, behenic acid, etc.), alicyclic monocarboxylic acids (cyclohexanecarboxylic acid, methylcyclohexanecarboxylic acid, etc.), aromatic monocarboxylic acids (benzoic acid, toluic acid, ethylbenzoic acid, phenylacetic acid, etc.) and the like. .

If necessary, in addition to the above monoamine or the monocarboxylic acid, an aliphatic diamine (ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, decamethylene). Diamine, dodecamethylenediamine, 2, 2, 4 (or 2,
4,4-) trimethylhexamethylenediamine) etc.),
Alicyclic diamine (cyclohexanediamine, bis-
(4,4′-aminocyclohexyl) methane, etc., aromatic diamine (xylenediamine, etc.), aliphatic dicarboxylic acid (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid) , Dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, octadecenedioic acid, eicosadionic acid, eicosendioic acid, docosanedioic acid, 2,2,4-trimethyladipic acid, etc.), alicyclic dicarboxylic acid Diamines and dicarboxylic acids such as (1,4-cyclohexanedicarboxylic acid) and aromatic dicarboxylic acids (terephthalic acid, isophthalic acid, xylenedicarboxylic acid, etc.) can be made to coexist.

In producing the end-adjusted polyamide resin (b), the above polyamide raw materials may be used and the reaction may be started according to a conventional method. The carboxylic acid and amine start the reaction under reduced pressure from the start of the reaction. Can be added at any stage up to. Further, the carboxylic acid and the amine may be added simultaneously or separately.

The amount of carboxylic acid and amine used is 2 to 20 meq / mol, preferably 3 as the carboxyl group and the amount of amine, per 1 mol of the polyamide raw material (monomer constituting the repeating unit or 1 mol of monomer unit). .About.19 meq / mol (the equivalent of amino group is 1 equivalent of the amount of amino group that reacts with 1 equivalent of carboxylic acid in a ratio of 1: 1 to form an amide bond). If this amount is too small, it becomes impossible to produce a polyamide-based resin having the effect of the present invention. On the contrary, if it is too large, it becomes difficult to produce a polyamide having a high viscosity, and the physical properties of the polyamide-based resin are adversely affected. become.

The reaction pressure is preferably 400 Torr or less, preferably 300 Torr or less at the end of the reaction. If the pressure at the end of the reaction is high, the desired relative viscosity cannot be obtained. The low pressure is not particularly inconvenient. The reduced pressure reaction time is preferably 0.5 hours or longer, usually about 1 to 2 hours.

The hydrocarbon group represented by R or R'in the -CONRR 'group at the terminal of the terminal-adjusting polyamide resin (b) is an aliphatic hydrocarbon group (methyl group,
Ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, dodecyl group,
Tridecyl group, tetradecyl group, tetradecylene group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, eicosyl group, docosyl group, etc., alicyclic hydrocarbon group (cyclohexyl group, methylcyclohexyl group, cyclohexylmethyl group, etc.), aromatic Examples thereof include group hydrocarbon groups (phenyl group, toluyl group, benzyl group, β-phenylethyl group, etc.).

Terminal-adjusting terminal of polyamide-based resin (b)
The conversion ratio of the COOH group to the -CONRR 'group is adjusted by the presence of an amine or a carboxylic acid with the amine during the production of the polyamide resin. In the present invention, the degree of this conversion depends on the number of terminal -COOH groups ( x) and the end-
The relationship with the number of CONRR 'groups (y) is 100 × y /
(X + y) ≧ 5, preferably 100 × y / (x + y) ≧
10 is satisfied, the -COOH group is -CONRR '
The amount of unconverted —COOH groups is preferably 50 μeq / g · polymer or less, preferably 40 μeq / g · polymer or less, and particularly preferably 20 μeq / g · polymer or less. Is desirable. If the degree of conversion is small, the effect of the present invention cannot be expected, and on the contrary, increasing the degree of conversion does not cause any inconvenience from the viewpoint of physical properties, but since it becomes difficult to manufacture, the amount of unmodified terminal carboxyl group is 1 μeq. It is a good idea to limit the amount to / g · polymer.

The hydrocarbon group represented by -CONRR 'can be measured by gas chromatography after hydrolyzing the polyamide resin with hydrochloric acid. -C
The OOH group can be measured by dissolving a polyamide resin in benzyl alcohol and titrating with 0.1N caustic soda. As the terminal group of the polyamide resin, the above-mentioned
In addition to the CONRR ′ group, there are —COOH group and —NH ₂ group derived from the above polyamide raw material.

The terminal amino group may or may not be modified, but it is preferably modified with the above hydrocarbon group since it has good fluidity and melt heat stability. Also, as a polyamide raw material,
[Epsilon] -caprolactam is particularly preferable in that better boiling resistance and retort resistance can be obtained.

The hindered phenol compound (c) is N, N'-hexamethylenebis (3,5-di-t).
-Butyl-4-hydroxyhydrocinnamide), 1,
1,3-tris (2-methyl-4-hydroxy-5-t
-Butylphenyl) butane, 1,3,5-trimethyl-
2,4,6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis [methylene-
3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate], n-octadecyl-β-
(4'-hydroxy-3 ', 5'-di-t-butylphenyl) propionate, 2,2'-methylenebis (4-
Methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol),
4,4'-thiobis (6-t-butyl-m-cresol), 4,4'-thiobis (3-methyl-6-t-butylphenol), pentaerythrityl-tetrakis [3
-(3,5-di-t-butyl-4-hydroxyphenyl) propionate] and the like, preferably N,
N'-hexamethylenebis (3,5-di-t-butyl-
4-hydroxyhydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, pentaerythrityl-tetrakis [3- ( 3,5-di-t-butyl-4
-Hydroxyphenyl) propionate].

Examples of the aliphatic carboxylic acid alkaline earth metal salt (d) include acetic acid, propionic acid, butyric acid, valeric acid,
Examples thereof include beryllium salts, magnesium salts, calcium salts, strontium salts and barium salts of aliphatic carboxylic acids having about 1 to 9 carbon atoms such as caproic acid and capric acid, and especially magnesium salts of aliphatic carboxylic acids having 2 to 4 carbon atoms. And calcium salts are important.

Examples of the compound (e) include ethylene bis fatty acids such as ethylene bis-stearyl amide (having 16 to 16 carbon atoms).
18) Higher fatty acid metal salts such as amide, zinc stearate, aluminum stearate, calcium stearate and magnesium stearate, adipate condensate of polypropylene glycol, sebacate condensate of polypropylene, polymer ester [eg, spalm aceti Made), Hoechst wax-E (made by Hoechst Japan), lytol (made by Sanwa Yushi), wood wax (made by Noda wax)], fatty acid ester [for example, butyl stearate, Nissan caster wax-A (made by NOF Corporation), TB-121 (manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.)], a low molecular weight polyolefin such as polyethylene having a molecular weight of 900 to 30,000 by the viscosity method, a molecular weight of 1,000 to the viscosity method.
Examples thereof include low molecular weight polyolefins such as modified polyethylene and modified polypropylene having an acid value of 20,000 in the range of 5 to 100, and preferably ethylene bis fatty acid (having 16 carbon atoms).
-18) Amide, zinc stearate, lead stearate, calcium stearate, magnesium stearate, modified polyethylene having a molecular weight of 1000 to 20000 by a viscosity method and an acid value of 5 to 100, and modified polypropylene are mentioned, and particularly preferably. , Zinc stearate, calcium stearate.

The oxygen gas barrier resin composition layer (II) of the present invention comprises the EVOH (a), the end-adjusted polyamide resin (b), the hindered phenol compound (c) and the aliphatic carboxylic acid alkali as described above. It consists of an earth metal salt (d) and at least one compound (e) selected from ethylene bis fatty acid amide, higher fatty acid metal salt, polymer ester, fatty acid ester, and hydrocarbon compound. The mixing ratio with (b) is 70: by weight.
When the blending ratio of the terminal-adjusted polyamide resin (b) is less than the above weight ratio, the effect of improving boil resistance and retort resistance is not sufficiently exerted, If it is too large, the oxygen gas barrier property of EVOH (a) is impaired. Preferably 80: 20-9
It is 0:10.

The blending ratio of the hindered phenol compound (c) is 0.01 to the total amount of (a) and (b).
It must be in the range of 1% by weight. When the blending ratio of the hindered phenolic compound (c) is less than the above range, the antioxidant property is insufficient, so that an oxidizing gel or a die retention product is likely to occur during molding, or the aliphatic carboxylic acid shown above. The synergistic effect with the alkaline earth metal salt (d) and the compound (e) is reduced, and a multilayer structure having an excellent film appearance cannot be obtained. On the other hand, even if the mixing ratio is more than the above range, the suppressing effect of the high temperature oxidizing gel and the synergistic effect with the aliphatic carboxylic acid alkaline earth metal salt (d) and the compound (e) are not improved beyond a certain limit. Also, it is disadvantageous in terms of cost, and is preferably 0.05 to 0.8% by weight, more preferably 0.1 to 0.5% by weight.

Furthermore, the compounding ratio of the aliphatic carboxylic acid alkaline earth metal salt (d) is 0.5 to 15 μmol / g, preferably 1 in terms of metal, based on the total amount of (a) and (b). ~ 9 μmol / g, 0.5μ
If it is less than mol / g, the melt viscosity is increased, and conversely 15μ.
If it exceeds mol / g, gel formation or foaming may occur during molding, or the oxygen gas barrier resin composition layer (II) may be colored or the moldability may become unstable, which is not suitable.
Further, the compounding ratio of the compound (e) is required to be 0.01 to 1% by weight based on the total amount of (a) and (b), and if it is less than 0.01% by weight, an extruder or a die is used. If the amount exceeds 1% by weight, the surging phenomenon increases during molding and a stable multilayer structure cannot be obtained, which is unsuitable, and preferably 0.1 to 1% by weight.

The oxygen barrier resin composition layer (II) contains a plasticizer, a filler, an antiblocking agent, a coloring agent,
Additives such as antistatic agents can be appropriately added. Further, as the thermoplastic resin layer (III) used as the innermost layer of the multilayer structure of the present invention, any known thermoplastic resin for sealant (heat seal) used for heat sealing of resin containers or bags may be used. It can be used, but in order to obtain the effect of the present invention, it must be a low moisture-permeable thermoplastic resin having a lower moisture permeability than the thermoplastic resin layer (I). When the water vapor permeability of the thermoplastic resin layer (III) is higher than that of the thermoplastic resin layer (I), the oxygen barrier resin composition (II) absorbs moisture in the contents to lower the oxygen barrier property. Is inappropriate.

Specific examples of the thermoplastic resin used in the thermoplastic resin layer (III) of the present invention include polypropylene homopolymer, polypropylene graft-polymerized with ethylene, high density polyethylene, low density polyethylene based on the polypropylene, Examples include linear low-density polyethylene, blends of ethylene-vinyl acetate copolymer, polyolefin resins such as high-density polyethylene other than polypropylene, copolyester, etc., which are heat sealability, transparency and retort fields. Considering that, polypropylene homopolymer, polypropylene graft-polymerized with ethylene, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer blended with the polypropylene as a base. Particularly suitably used.

In manufacturing the multilayer structure of the present invention,
Known methods such as a co-extrusion method such as a T-die method and an inflation method, a blow molding method, and a co-injection method can be adopted, and the method is not particularly limited, but a co-extrusion method is used as an example of the production method. The method for manufacturing the multilayer structure will be described below.

When the multilayer structure of the present invention is produced by the coextrusion method, the oxygen gas barrier resin layer (II), the thermoplastic resin layer (I) and the oxygen gas barrier resin layer (II) are used.
For the thermoplastic resin layer (III) and the thermoplastic resin layer (III), an ordinary method of laminating with an adhesive resin interposed therebetween is adopted. As the adhesive resin, a resin obtained by modifying a polyolefin-based resin such as polypropylene, polyethylene, or a copolymer of ethylene and a monomer copolymerizable with ethylene (vinyl acetate, acrylic ester, etc.) by adding maleic anhydride or the like is used. , The resin temperature of the oxygen gas barrier resin layer (II) is 235 to 260 ° C.,
Preferably, the temperature is 240 to 250 ° C., and the appearance of the film is evaluated by a coextrusion molding apparatus of 4 types and 7 layers of (II) / adhesive resin / (I) / adhesive resin / (II) / adhesive resin / (III) A good multilayer structure is obtained.

Further, the above-mentioned multilayer structure can be obtained by using a dry lamination method, an extrusion lamination method or the like. That is, (I) and (I
(I), (III) Each layer is preformed by a twin-screw extruder or the like, and each layer is dry-laminated with an adhesive resin such as urethane resin, or coextrusion-molded as described above (II)
Examples include a method of dry laminating (III) to a laminate of / adhesive resin / (I) / adhesive resin / (II).
Incidentally, the above-mentioned layer structure is described by omitting the adhesive resin layer, and the adhesive resin as described above can be adopted as necessary at the time of interlayer adhesion, but as the thermoplastic resin layer (I), polyamide is used. When a system resin is used, the adhesive resin may not be required for the adhesion with the oxygen gas barrier resin layer (II).

In such a multilayer structure, the thickness of each layer cannot be generally stated depending on the type of the laminate (multilayer structure).
When used as a film packaging material for boil sterilization or retort sterilization, (II) is 5 to 250 μm, preferably 1
It is 0 to 100 μ, and more preferably 10 to 80 μ. Further, the thicknesses of the (I) and (III) layers are not particularly limited because they are defined by the moisture permeability. The multilayer structure of the present invention exerts its characteristics most when used as a film packaging material, particularly a film packaging material for boil sterilization or retort sterilization treatment. Examples of uses of the film packaging material include lid materials, pouches, vacuum packaging, skin packaging, deep drawing packaging, and rocket packaging.

The lid material of the present invention is preferably heat-sealed by a heat-sealing method in a container made of a thermoplastic resin such as polypropylene laminated with an oxygen gas barrier resin. The lid material of the present invention has excellent transparency and can be opened while confirming the contents. The pouches of the present invention are used in the form of three-way seals, four-way seals, pillows, gussets, standing pouches and the like.

The multi-layer structure of the present invention can exhibit excellent characteristics as a container such as a cup or tray in addition to the above film packaging. As a method for molding a container, a sheet is molded by coextrusion molding, heated and softened, and then molded into a predetermined container by a vacuum molding method, a plug assist molding method, a pressure molding method, a CD method, or an injection molding method. And any other method is used. Further, the multilayer structure of the present invention can be formed into a tube or bottle by blow molding.

A container using the multilayer structure of the present invention in the form of a lid material, pouch, tray, cups or bottle, or tube can be subjected to retort sterilization treatment or hot water heating treatment known as boil sterilization treatment. . For the retort treatment, various methods such as a recovery method, a substitution method, a steam method, a shower method, and a spray method are adopted. Lid material, pouch, tray, cups or bottles comprising the multilayer structure of the present invention,
The retort sterilization treatment can be carried out in a state in which a container such as a tube is filled with food such as soup, pork juice, meat sauce, oden, pilaf, udon, vinegared pork, hamburger steak, cooked curry.

[0040]

[Working] The multi-layer structure of the present invention has good recoverability of oxygen barrier property at room temperature and normal humidity and oxygen gas barrier property after retort sterilization, and oxygen gas barrier property after retort sterilization is retort sterilization. The same as before treatment is obtained, and it is very useful to obtain a multi-layer film packaging material for retort sterilization treatment, a container for retort sterilization treatment, and a lid material for retort sterilization treatment, which has a good film appearance without generation of gel, fish eyes, etc. In producing the multilayer structure, the oxygen gas barrier resin layer is extruded at 235 to 260 ° C. to enable coextrusion with a resin having a relatively high melting point and also improve long-run formability. .

[0041]

EXAMPLES The present invention will be described in more detail below with reference to examples. The following (a) to (e) were prepared. EVOH (a) a-1: ethylene content 32 mol%, degree of saponification 99.5
Mol%, MI (melt index) = 3.0 (210
(° C, 2160 g load) a-2: ethylene content 38 mol%, saponification degree 99.5.
Mol%, MI = 8.0 (same as above)

Terminal-adjusting polyamide resin (b) b-1: Nylon 6 Terminal COOH group: 9 μeq / g Polymer 100 × y / (x + y) = 87, MI = 2.5 (230
° C, 2160 g) b-2: Nylon 6/66 (Nylon 66 component 20
% By weight) Terminal COOH group: 3 μeq / g · polymer 100 × y / (x + y) = 94, MI = 11.2 (same as above) b-3: Nylon 6 Terminal COOH group: 20 μeq / g · polymer 100 × y / ( x + y) = 60, MI = 3.6 (same as above)

Hindered Phenol Compound (c) c-1: N, N'-hexamethylenebis (3,5-di-)
t-Butyl-4-hydroxyhydrocinnamide) (“Irganox 1098” manufactured by Ciba-Gayky) c-2: 1,3,5-trimethyl-2,4,6-tris (3,5-di-) t-butyl-4-hydroxybenzyl)
Benzene (“Irganox 1330” manufactured by Ciba-Gayky) c-3: Pentaerythrityl-tetrakis [3- (3,
5-di-t-butyl-4-hydroxyphenyl) propionate] (“Irganox 1010” manufactured by Ciba-Gayky)

Aliphatic carboxylic acid alkaline earth metal salt
(D) d-1: magnesium acetate tetrahydrate d-2: calcium propionate d-3: magnesium butyrate

Compound (e) e-1: ethylene bis-stearyl amide e-2: polyethylene (molecular weight 3200 by viscosity method,
Acid value 20 KOHmg / g) e-3: Zinc stearate e-4: Magnesium stearate e-5: Zinc stearate: Calcium stearate =
1: 0.5 (weight ratio) e-6: Zinc stearate: Aluminum stearate = 1: 0.7 (weight ratio)

Example 1 As shown in Table 1, the above components (a) to (d) were blended, melt-extruded by a twin-screw extruder, cooled and pelletized, and the pelletized product was made into an oxygen gas barrier resin composition. Layer (II), while a polyamide resin containing 90% by weight of nylon-6 resin and 10% by weight of amorphous polyamide was used as the thermoplastic resin layer (I) and the temperature was set to 250 ° C.
Co-extruded from a die so as to have a layer structure of (II) / (I) / (II) and cooled by a chill roll in which cooling water circulates to produce a flat three-layer laminated film. The resin temperature of the oxygen gas barrier resin composition layer (II) was 247 ° C.

Next, a commercially available non-stretched polypropylene film (manufactured by Tohcello Chemical Co., Ltd., trade name: Tocello CP) was dry-laminated as the thermoplastic resin layer (III) on the above three-layer laminated film. Adhesive for dry lamination (Toyo Morton Co., Ltd., Adcoat AD-335A / CAT-
10) was used, and after curing, the laminate was cured at 40 ° C. for 1 day to obtain a multilayer structure having the following layer structure, and the following evaluation was performed. Oxygen gas barrier resin composition layer (II) 20μ Thermoplastic resin layer (I) 35μ, moisture vapor transmission rate 140g / m ² · day Oxygen gas barrier resin composition layer (II) 10μ Thermoplastic resin layer (III) 50μ, Water vapor transmission rate 6g / m ² · day

[Evaluation content] Formability A three-layer laminate of the above (II) / (I) / (II) was formed under the same conditions.
Long-run molding was performed for one day, and the appearance of the laminate was visually evaluated. The criteria are as follows. ○ --- No foreign matter, gel or surging is generated even after 7 days from the start of film formation. Δ --- Foreign matter, gel, or surging occurred 3 to 6 days after the start of film formation. × −−− Foreign matter, gel, or surging occurred within 3 days after the start of film formation.

Retort resistance (1) The multi-layer structure obtained above is retorted by a retort device (Yamato Scientific Co., Ltd. ).
121 ° C using an autoclave SM-31 manufactured by Co., Ltd.
After performing retort sterilization treatment in a steam atmosphere for 30 minutes, the appearance of the multilayer structure after standing for 30 minutes at room temperature was visually observed. The criteria are as follows. ○ −−− Transparent and no discoloration was observed. × −−− Discoloration was observed due to haze or whitening. Retort resistance (2) In the evaluation of the above retort resistance (1), the oxygen permeability of the multilayer structure before the retort sterilization treatment and after 3 hours after the retort sterilization treatment is measured by an oxygen permeability measuring device (OXTRAN-10).
/ 50A, manufactured by MOCON), and the recoverability after retort sterilization treatment was examined by the following formula. A = oxygen permeability after 3 hours after retort sterilization treatment / oxygen permeability before retort sterilization treatment The criteria are as follows. ◯ −−− A <3 Δ −−− 3 ≦ A ≦ 5 × −−− 5 <A

Examples 2 to 6 and Comparative Examples 1 to 11 Evaluations were made in the same manner as in Example 1 except that the gas barrier resin layer (II) shown in Tables 1 to 5 was used. The evaluation results are also shown in Tables 1 to 5. In addition, the numbers of the components (c) and (e) shown in Tables 1 to 5 represent the respective blending ratios with respect to the total amount of (a) and (b) in ppm value,
The numerical value after the metal name of the component (d) represents the compounding amount (μmol / g) of the metal with respect to the total amount of the components (a) and (b).

[0051]

Table 1 Example 1 Example 2 Example 3 Example 4 (a) Component a-1 90 parts a-1 80 parts a-1 70 parts a-2 70 parts (b) Component b-1 10 parts b -1 20 parts b-1 30 parts b-1 30 parts (c) Component c-1 4000ppm c-3 4000ppm c-2 8000ppm c-1 4000ppm (d) Component d-1 Mg 3.5 d-1 Mg 2.0 d- 3 Mg 2.3 d-2 Ca 6.0 (e) component e-6 1700ppm e-5 1500ppm e-3 1300ppm e-4 1500ppm Moldability ○ ○ ○ ○ Retort resistance (1) ○ ○ ○ ○ Retort resistance (2) ○ ○ ○ ○

[0052]

Table 2 Example 5 Example 6 Comparative Example 1 Comparative Example 2 (a) component a-1 90 parts a-2 90 parts a-1 90 parts a-1 90 parts (b) component b-2 10 parts b −3 10 parts b−1 10 parts b−1 10 parts (c) component c−1 1000 ppm c−3 − c−1 4000 ppm (d) component d−1 Mg 2.0 d−1 − d−1 Mg 3.5 (e ) Component e-2 5000ppm e-1 − − Moldability ○ ○ × △ Retort resistance (1) ○ ○ − ○ Retort resistance (2) ○ ○ − ○ Note) Comparative Example 1 has poor moldability (large amount of gel is generated) Therefore, a satisfactory multilayer structure could not be obtained, and the retort resistance was not evaluated.

[0053]

Table 3 Comparative Example 3 Comparative Example 4 Comparative Example 5 (a) Component a-1 90 parts a-2 90 parts a-1 98 parts (b) Component b-1 10 parts b-3 10 parts b-12 Part (c) Component-c-1 4000ppm c-1 4000ppm (d) Component d-1 Mg 3.5-d-1 Mg 3.5 (e) Component e-6 1700ppm e-6 1700ppm e-6 1700ppm Formability △ △ ○ Retort resistance (1) ○ ○ × Retort resistance (2) ○ ○ ×

[0054]

Table 4 Comparative Example 6 Comparative Example 7 Comparative Example 8 (a) Component a-1 65 parts a-1 90 parts a-1 90 parts (b) Component b-1 35 parts b-1 10 parts b-1 10 Part (c) Component c-1 4000ppm c-1 4000ppm c-1 4000ppm (d) Component d-1 Mg 3.5 d-1 Mg 18 d-1 Mg 0.3 (e) Component e-6 1700ppm e-6 1700ppm e- 6 1700ppm Moldability △ × △ Retort resistance (1) ○ − ○ Retort resistance (2) ○ − ○ Note) In Comparative Example 7, a satisfactory multilayer structure was obtained because of poor moldability (surge generation). No evaluation was performed on the retort resistance.

[0055]

Table 5 Comparative Example 9 Comparative Example 10 Comparative Example 11 (a) Component a-1 90 parts a-1 90 parts a-1 90 parts (b) Component b-1 10 parts b-1 10 parts b-1 10 Part (c) Component c-1 4000ppm c-1 4000ppm c-1 4000ppm (d) Component d'Na 3.0 d-1 Mg 3.5 d-1 Mg 3.5 (e) Component e-6 1700ppm e-6 50ppm e-6 15000ppm Moldability × △ × Retort resistance (1)- ○○ Retort resistance (2)- ○○ Note) d'is sodium acetate Comparative Example 9 has poor moldability (large amount of gel), so a satisfactory multilayer structure The body was not obtained and the retort resistance was not evaluated.

Comparative Example 12 A thermoplastic resin layer (I) having a thickness of 30 μm and a moisture permeability of 9 g
The evaluation was carried out in accordance with Example 1 except that polypropylene of / m ² · day was used.

Comparative Example 13 Evaluation was carried out according to Example 1 except that the following multilayer structure (total thickness 105 μm) was used. Thermoplastic resin layer (I) 35μ, water vapor transmission rate 140g / m ² · day Oxygen gas barrier resin composition layer (II) 30μ Thermoplastic resin layer (III) 50μ, water vapor transmission rate 6g / m ² · day Comparative Example 12 and The evaluation results of 13 are shown in Table 6.

[0058]

[Table 6]

Example 7 Using the same multilayer structure as that used in Examples 1 to 6 as a lid material, a cup-shaped container made of polypropylene containing water was heat-bonded with a non-stretched polypropylene layer as an inner surface by a heat sealer. . This was subjected to retort sterilization treatment at 121 ° C. for 30 minutes using the retort device shown in the above-mentioned Examples and Comparative Examples. Immediately after the retort treatment, the lid film was transparent and had a good appearance with no wavy pattern.

Example 8 The same multilayer structure as that used in Examples 1 to 6 was heat-sealed into a pouch, and water was put thereinto to heat-seal the mouth. This was subjected to retort sterilization treatment at 121 ° C. for 30 minutes using the retort device shown in the above-mentioned Examples and Comparative Examples. Immediately after the retort treatment, the pouch was transparent and had a good appearance with no wavy pattern.

Example 9 Dry lamination similar to that of Example 1 was carried out using the same oxygen gas barrier resin as that used in Examples 1 to 6 to obtain the following multilayer structure. Oxygen gas barrier resin composition layer (II) 180μ Thermoplastic resin layer (I) 315μ, moisture vapor transmission rate 16g / m ² · day Oxygen gas barrier resin composition layer (II) 90μ Thermoplastic resin layer (III) 450μ, Water vapor transmission rate 0.7 g / m ² · day (polypropylene sheet) This multilayer structure is 100 m in length by using a vacuum pressure molding machine (manufactured by Asano Manufacturing Co., Ltd.).
A square tray container having m, width 80 mm, and height 50 mm was formed. The average thickness of this container is (II) / (I) / (II)
/ (III) = 40/75 (water vapor transmission rate 67g / m ² · day)
/ 25/110 (water vapor transmission rate 3 g / m ² · day) (μ). After replacing the tray with nitrogen gas, 5 ml of water was enclosed and the retort sterilization treatment was performed at 121 ° C. for 30 minutes using the retort device shown in the above-mentioned Examples and Comparative Examples. Immediately after the retort treatment, the container was transparent and had a good appearance. After this container was left at 20 ° C. and 65% RH for 12 months, the oxygen concentration in the container was measured and found to be about 1 ppm.

Comparative Examples 14 and 15 In Example 1, the oxygen gas barrier resin composition layer (I
The resin temperature at the time of extrusion of I) was 230 ° C. (Comparative Example 14) and 270 ° C. (Comparative Example 15).
Occurred, and a good laminated film could not be obtained.

[0063]

INDUSTRIAL APPLICABILITY The multilayer structure of the present invention is excellent in oxygen gas barrier property at room temperature and normal humidity and in recoverability of oxygen gas barrier property after retort sterilization treatment, and oxygen gas barrier property after retort sterilization treatment. A multi-layer film packaging material for retort sterilization treatment, which is equivalent to that before retort sterilization treatment and has a good film appearance without the occurrence of gel, fish eyes, etc.
A container for retort sterilization treatment and a lid material for retort sterilization treatment are obtained, which is very useful. In producing the multilayer structure, an oxygen gas barrier resin layer is extruded at 235 to 260 ° C. to have a relatively high melting point. It also has the effect of enabling high co-extrusion with a resin and improving long-run moldability.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B32B 27/36 8413-4F 102 8413-4F B65D 81/34 Z // C08L 23/08 LDF LDK

Claims (13)

[Claims] 1. Water vapor transmission rate (measured at 40 ° C. and 90% RH)
Having an ethylene content of 20 to 60 mol% and a saponification degree of 90 mol% or more on both sides of the thermoplastic resin layer (I) having a value of 10 to 500 g / m ² · day. Compound (a), terminal COO by terminal modifier
The number (x) of H groups and a terminal CONRR 'group (where R is a hydrocarbon group having 1 to 22 carbon atoms, R'is hydrogen or 1 to 2 carbon atoms).
The number (y) of 2 hydrocarbon groups is 100 × y / (x +
y) end-adjusted polyamide-based resin (b) adjusted so as to satisfy ≧ 5, hindered phenol-based compound (c),
An aliphatic carboxylic acid alkaline earth metal salt (d) and at least one compound (e) selected from ethylene bis fatty acid amide, higher fatty acid metal salt, polymer ester, fatty acid ester, and hydrocarbon compound, (a) ):
The weight ratio of (b) is 70:30 to 96: 4, and the mixing ratio of (c) to the total amount of (a) and (b) is 0.01 to.
1% by weight, the compounding ratio of (d) to the total amount of (a) and (b) is 0.5 to 15 μmol / g in terms of metal,
An oxygen gas barrier resin composition layer (II) having a compounding ratio of (e) to the total amount of (a) and (b) of 0.01 to 1% by weight is formed, and a thermoplastic resin is further used as the innermost layer. A multilayer structure provided with a thermoplastic resin layer (III) having a moisture permeability lower than that of the layer (I) (measured at 40 ° C. and 90% RH). 2. The multilayer structure according to claim 1, wherein the thermoplastic resin layer (I) is any one of a polyamide resin, a polyolefin resin, a polyester resin and a polycarbonate resin. 3. The multilayer structure according to claim 1, wherein the thermoplastic resin layer (I) is a polyamide resin made of nylon-6 and amorphous polyamide. 4. The hindered phenol compound (c) is N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxyhydrocinnamide), 1,3,5-
Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate], the multilayer structure according to any one of claims 1 to 3. 5. The multilayer according to claim 1, wherein the aliphatic carboxylic acid alkaline earth metal salt (d) is a magnesium salt of an aliphatic carboxylic acid having 2 to 4 carbon atoms. Structure. 6. The compound (e) has an ethylene bis fatty acid amide having 16 to 18 carbon atoms, zinc stearate, lead stearate, calcium stearate, magnesium stearate, a molecular weight of 1000 to 20,000 and an acid value of 5 by the viscosity method. The multilayer structure according to any one of claims 1 to 5, which is at least one selected from low molecular weight polyolefins in the range of 100. 7. The multilayer structure according to claim 1, wherein the polyamide raw material of the end-adjusted polyamide resin (b) is ε-caprolactam. 8. The multilayer structure according to claim 1, wherein the thermoplastic resin layer (III) is made of a polyolefin thermoplastic resin. 9. The multilayer structure according to claim 1, which is used for a multilayer film for boil sterilization or retort sterilization. 10. The multilayer structure according to claim 1, which is used for a container for boiling sterilization or retort sterilization. 11. The multilayer structure according to any one of claims 1 to 9, which is used in a pouch for boil sterilization or retort sterilization. 12. The multilayer structure according to claim 1, which is used as a lid material for boil sterilization or retort sterilization. 13. The method for producing the multilayer structure according to claim 1, wherein the oxygen gas barrier resin composition layer (II) is extruded at a resin temperature of 235 ° C. to 260 ° C. And a method for manufacturing a multilayer structure.