JP2021171941A - Multi-layer structure - Google Patents

Abstract

An object of the present invention is to provide an excellent multilayer structure in which an ethylene-vinyl alcohol copolymer layer is hardly affected by water intrusion even immediately after retort treatment, and the multilayer structure as a whole exhibits excellent gas barrier properties. [Solution] An ethylene-vinyl alcohol copolymer layer (A), an adhesive resin layer (B), and the ethylene-vinyl alcohol copolymer layer (A) via the adhesive resin (B). A multilayer structure comprising a cyclic olefin resin layer (C) laminated on the ethylene-vinyl alcohol copolymer layer (A) containing a desiccant (D). [Selection diagram] None

Description

The present invention relates to a multilayer structure including an ethylene-vinyl alcohol-based copolymer layer, an adhesive resin layer, and a cyclic olefin-based resin layer, and more particularly to a multilayer structure that exhibits excellent gas barrier properties immediately after retorting. It is a thing.

Conventionally, ethylene-vinyl alcohol-based copolymers (hereinafter sometimes abbreviated as "EVOH") are often used as packaging materials for foods because they have excellent gas barrier properties and transparency against oxygen, and most of them are used. It is used as a multi-layer structure in which functions such as water resistance and strength are added by being laminated with another resin layer via an adhesive resin layer.

Foods packaged using such a multilayer structure are often subjected to retort treatment (high temperature pressure sterilization treatment) or hot water treatment in order to enable long-term storage at room temperature. When these treatments are performed, hot water or water vapor may infiltrate the EVOH layer, causing whitening of the EVOH layer and deterioration of gas barrier properties. In order to prevent this, for example, it is laminated on the EVOH layer. It has been proposed to adjust the amount of water vapor permeation of the outer layer or the like to a specific value (see Patent Document 1).

Similarly, for the purpose of suppressing whitening of the EVOH layer and suppressing deterioration of gas barrier property, a cyclic olefin resin layer having low water vapor transmission rate is provided on at least one surface of the EVOH layer, and water reaches the EVOH layer during retort treatment. It has been proposed to prevent infiltration (see Patent Document 2).

JP-A-2018-62141 Japanese Unexamined Patent Publication No. 2016-7754

However, in the technique of Patent Document 1, the water vapor permeation amount of a specific layer including the outer layer is adjusted to prevent the infiltration of water during the retort treatment, while the water infiltrated into the EVOH layer is discharged to the outside after the retort treatment. It is characterized by letting it escape, and when looking at the entire multilayer structure, the water vapor permeability is relatively high, and it is not possible to completely prevent water from entering the EVOH layer, especially during retort treatment, so further improvement is required. ing.

On the other hand, in the technique of Patent Document 2, since the water vapor transmission rate of the cyclic olefin resin layer arranged outside the EVOH layer is extremely low, it is possible to effectively prevent the infiltration of water into the EVOH layer. However, if even a small amount of water infiltrates the EVOH layer during retort treatment or the like, there is a problem that it is difficult for water to escape from that state and it takes time to recover from the state in which the gas barrier property of the EVOH layer is lowered. Improvement is required.

Therefore, an object of the present invention is to provide an excellent multilayer structure in which the EVOH layer is not easily affected by the infiltration of water immediately after the treatment such as retort treatment and exhibits excellent gas barrier properties as the entire multilayer structure.

As a result of diligent studies to solve the above problems, the present inventors have applied the EVOH layer to a multilayer structure including an EVOH layer which is a gas barrier layer and a cyclic olefin resin layer which exhibits low water vapor permeability. We have found that the above-mentioned problems can be solved by containing a desiccant, and have arrived at the present invention.

That is, the present invention includes an EVOH layer (A), an adhesive resin layer (B), and a cyclic olefin resin layer (C), and the cyclic olefin resin layer (C) is the EVOH layer (A). ) Is a multilayer structure laminated via the adhesive resin layer (B) on at least one surface, and the EVOH layer (A) is a multilayer structure containing a desiccant (D). , The summary.

According to the multilayer structure of the present invention, a cyclic olefin resin layer (C) having a low water vapor transmission rate is formed on at least one surface of the EVOH layer (A), which is a gas barrier layer, via an adhesive resin (B). It is laminated and has excellent gas barrier properties against oxygen and water vapor. Moreover, even if water penetrates into the EVOH layer (A) during the retort treatment (including hot water treatment), the desiccant (D) contained in the EVOH layer (A) absorbs the water, so that the EVOH layer (A) The original gas barrier property is not impaired. Since the water remains absorbed by the desiccant (D) even after the retort treatment, the gas barrier property of the EVOH layer (A) does not deteriorate, and the gas barrier property immediately after the retort treatment is excellent. Shown, this is maintained for a long time.

As described above, those skilled in the art cannot easily recall that the EVOH layer (A) contains a desiccant and the desiccant absorbs the water that has penetrated into the multilayer structure. That is, when the moisture infiltrated during the retort treatment is absorbed by the desiccant (D) contained in the EVOH layer (A), the moisture is released from the desiccant (D) due to a change in the environment. The cyclic olefin resin layer (C) having a low water vapor permeability, which is laminated on the EVOH layer (A) via the adhesive resin layer (B), blocks the discharge of water to the outside, so that the adhesive resin There is a concern that water stays at the interface between the layer (B) and the cyclic olefin resin layer (C) to form water bubbles, which appear as granular swelling when viewed from the surface of the multilayer structure, resulting in poor appearance. Therefore, those skilled in the art do not intend to include the desiccant (D) in the EVOH layer (A) in which the cyclic olefin resin layer (C) is laminated via the adhesive resin layer (B). It is common sense.

On the other hand, the present inventors have broken through such common general knowledge and made the EVOH layer (A), the cyclic olefin resin layer (C) having low water vapor permeability, and the adhesive resin layer (B). When the desiccant (D) was contained in the EVOH layer (A) in the multilayer structure formed by laminating the layers, as described above, even if water penetrates into the EVOH layer (A) during the retort treatment, even if water penetrates into the EVOH layer (A). Not only does the desiccant (D) absorb this and the excellent gas barrier property does not deteriorate, but even if the environment changes after the retort treatment, water vapor swelling as a concern occurs and the appearance deteriorates. It was found that such a problem does not occur.

This is because, in the above configuration, even if water is released from the desiccant (D) due to an environmental change or the like, the water is dispersed and spread in the cyclic olefin resin layer (C) and localized. This is probably because swelling does not occur.

Hereinafter, embodiments for carrying out the present invention will be specifically described, but the present invention is not limited thereto.

The multilayer structure of the present invention is a cyclic olefin resin layer laminated on the EVOH layer (A) via the EVOH layer (A), the adhesive resin layer (B), and the adhesive resin layer (B). The EVOH layer (A) contains the desiccant (D). Hereinafter, each layer will be described in order.

[EVOH layer (A)]
The EVOH layer (A) constituting the multilayer structure of the present invention is formed of only EVOH or a resin composition composed of a resin containing EVOH as a main component (hereinafter, may be referred to as "EVOH-based resin composition"). It is a layer, and the desiccant (D) described later is contained in this layer. The EVOH is a resin usually obtained by saponifying an ethylene-vinyl ester-based copolymer, which is a copolymer of ethylene and a vinyl ester-based monomer, and is a water-insoluble thermoplastic resin. As the vinyl ester-based monomer, vinyl acetate is generally used from the economical point of view.

The polymerization method of the ethylene and the vinyl ester-based monomer can be carried out by using any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization, and generally, a solution using methanol as a solvent. Polymerization is used. The obtained ethylene-vinyl ester copolymer can also be saponified by a known method.

The EVOH produced in this manner is mainly composed of ethylene-derived structural units and vinyl alcohol structural units, and usually contains a small amount of vinyl ester structural units that remain without being saponified.

As the vinyl ester-based monomer, vinyl acetate is typically used because of its good marketability and high efficiency of impurity treatment during production. Examples of other vinyl ester-based monomers include vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versaticate and the like. Examples thereof include aliphatic vinyl esters and aromatic vinyl esters such as vinyl benzoate. Usually, aliphatic vinyl esters having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms are used. Can be done. These can be used alone or in combination of two or more.

The above EVOH usually uses petroleum-derived raw materials such as naphtha, but natural gas-derived raw materials such as shale gas, sugars and starches contained in sugar cane, tensai, corn, potatoes, etc., or components such as starch, or Plant-derived raw materials purified from components such as cellulose contained in plants such as rice, wheat, and potato may be used.

The content of the ethylene structural unit in the EVOH can be controlled by the pressure of ethylene when copolymerizing the vinyl ester-based monomer and ethylene, and is preferably 20 to 60 mol%. It is more preferably 25 to 50 mol%, and particularly preferably 25 to 35 mol%. If the content is too low, the gas barrier property and melt moldability under high humidity tend to decrease, and if the content is too high, the gas barrier property tends to decrease.
The content of the ethylene structural unit can be measured based on, for example, ISO14663.

The degree of saponification of the vinyl ester component in EVOH is the amount, temperature, and time of the saponification catalyst (usually, an alkaline catalyst such as sodium hydroxide is used) when saponifying the ethylene-vinyl ester copolymer. It can be controlled by, etc., and is usually 90 to 100 mol%, preferably 95 to 100 mol%, and particularly preferably 99 to 100 mol%. If the degree of saponification is low, the gas barrier property, thermal stability, moisture resistance, etc. tend to decrease, which is not preferable.
The degree of saponification of EVOH can be measured based on JIS K 6726 (however, EVOH is used as a solution uniformly dissolved in a water / methanol solvent).

The melt flow rate of EVOH (based on MFR, JIS K 7210) (210 ° C., load 2160 g) is usually 0.5 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, particularly preferably. 3 to 35 g / 10 minutes. If the MFR is too large, the moldability tends to be unstable, and if it is too small, the viscosity tends to be too high and melt extrusion becomes difficult.
The MFR is an index of the degree of polymerization of EVOH, and can be adjusted by the amount of the polymerization initiator when copolymerizing ethylene and the vinyl ester-based monomer and the amount of the solvent.

Further, EVOH may further contain structural units derived from the commonomers shown below as long as the effects of the present invention are not impaired (for example, 10 mol% or less of EVOH).
Examples of the comonomer include olefins such as propylene, 1-butene and isobutene, 3-butene-1-ol, 3-butene-1,2-diol, 4-pentene-1-ol and 5-hexene-1,2. Hydroxy group-containing α-olefins such as −diol and derivatives such as esterified products and allyl groups thereof; Hydroxyalkylvinylidenes such as 2-methylenepropane-1,3-diol and 3-methylenepentane-1,5-diol; Hydroxyalkyl vinylidene diacetates such as 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, 1,3-dibutyryloxy-2-methylenepropane; acrylic acid, methacrylic acid , Crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid and other unsaturated acids or salts thereof or mono- or dialkyl esters having 1 to 18 carbon atoms in the alkyl group; acrylamide, alkyl Acrylamides such as N-alkylacrylamide, N, N-dimethylacrylamide, 2-acrylamide propanesulfonic acid or a salt thereof, acrylamidepropyldimethylamine or an acid salt thereof or a quaternary salt thereof, which have 1 to 18 carbon atoms in the group; Acrylamide, N-alkylmethacrylate having 1 to 18 carbon atoms in the alkyl group, N, N-dimethylmethacrylate, 2-methacrylamide propanesulfonic acid or a salt thereof, methallylamide propyldimethylamine or an acid salt thereof or its 4 Methacrylates such as grade salts; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide; Vinyl cyanide such as acrylicnitrile and methacrylnitrile; Vinyl ethers such as alkyl vinyl ether, hydroxyalkyl vinyl ether, alkoxyalkyl vinyl ether; vinyl halide compounds such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide; vinyl silanes such as trimethoxyvinylsilane; Allyl halides such as allyl acetate and allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; trimethyl- (3-acrylamide-3-dimethylpropyl) -ammonium chloride, acrylamide-2-methylpropanesulfonic acid, etc. Comonomer can be mentioned. These can be used alone or in combination of two or more.

In particular, when EVOH having a primary hydroxyl group in the side chain is used as the EVOH used in the present invention, it is preferable in that the secondary moldability is improved while maintaining the gas barrier property, and among them, hydroxy group-containing α-olefins. EVOH obtained by copolymerizing the above is preferable, and EVOH having a 1,2-diol structure in a side chain is particularly preferable.

When EVOH having a primary hydroxyl group is used in the side chain, the content of the structural unit derived from the monomer having the primary hydroxyl group is usually 0.1 to 20 mol% of EVOH, and further 0.5 to 15 mol. %, Especially preferably 1 to 10 mol%.

Further, the EVOH used in the present invention may be "post-denatured" such as urethanization, acetalization, cyanoethylation, and oxyalkyleneization.

Further, the EVOH used in the present invention includes two or more types of EVOH, for example, those having different contents of ethylene structural units, those having different degrees of saponification, those having different degrees of polymerization, those having different copolymerization components, and the like. It may be a mixture.

When the EVOH layer (A) used in the multilayer structure of the present invention is formed of an EVOH-based resin composition containing EVOH as a base resin and another thermoplastic resin, the above-mentioned EVOH is contained in the entire resin component. The amount is usually 50 to 99% by weight, preferably 60 to 95% by weight, and particularly preferably 70 to 90% by weight. If the amount of EVOH is too small, the gas barrier property may be insufficient.

[Other thermoplastic resins]
In the above-mentioned EVOH-based resin composition, other thermoplastic resins that can be used together with the above-mentioned EVOH include, for example, specifically, linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, and ethylene-. Vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene-α-olefin (α-olefin with 4 to 20 carbon atoms) copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene-α- Olefin (α-olefin with 4 to 20 carbon atoms) copolymer, olefins such as polybutene and polypentene alone or copolymers, polycyclic olefins, or these olefins alone or copolymers are unsaturated carboxylic acids or their owns. Broadly defined polyolefin resins such as those graft-modified with esters, polystyrene resins, polyesters, polyamides, copolymer polyamides, polyvinyl chlorides, polyvinylidene chlorides, acrylic resins, vinyl ester resins, polyester elastomers, polyurethane elastomers, chlorine Examples thereof include copolymerized polyethylene and chlorinated polypropylene.

Petroleum-derived raw materials such as naphtha are usually used for the above-mentioned other thermoplastic resins, but like EVOH, they are contained in natural gas-derived raw materials such as shale gas, sugar cane, starch, corn, potatoes, and the like. You may use a plant-derived raw material purified from a component such as sugar and starch, or a component such as cellulose contained in plants such as rice, wheat and millet.

In particular, when the multilayer structure of the present invention is used as a packaging material for food, the EVOH of the EVOH layer (A) is prevented from being eluted at the end of the packaging material after the retort treatment of the packaging material. It is preferable to use an EVOH-based resin composition containing a polyamide-based resin. That is, the above-mentioned polyamide resin can form a network structure by the amide bond interacting with at least one of the OH group and the ester group of EVOH, thereby preventing the elution of EVOH during the retort treatment. be able to.

As the above-mentioned polyamide resin, known ones can be used.
For example, specifically, polycapramid (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecaneamide (nylon 11), polylauryl lactam (nylon 12). Homopolymers such as. Examples of the copolymerized polyamide resin include polyethylenediamine adipamide (nylon 26), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), and polyhexamethylene sebacamide (nylon 610). ), Polyhexamethylene dodecamide (nylon 612), polyoctamethylene adipamide (nylon 86), polydecamethylene adipamide (nylon 108), caprolactam / lauryllactam copolymer (nylon 6/12), caprolactam / ω-aminononanoic acid copolymer (nylon 6/9), caprolactam / hexamethylene diammonide adipate copolymer (nylon 6/66), lauryl lactam / hexamethylene diammonium adipate copolymer (nylon 12/66), ethylenediamine Adipamide / hexamethylene diammonide adipate copolymer (nylon 26/66), caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium sevacate copolymer (nylon 66/610), ethyleneammonium adipate / hexamethylene di Aliper polyamides such as ammonium adipate / hexamethylene diammonium sevacate copolymer (nylon 6/66/610), polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, polymethoxylylen adipamide, hexamethylene isophthalamide. / Terephthalamide copolymer, poly-p-phenylene terephthalamide, aromatic polyamide such as poly-p-phenylene 3-4'diphenyl ether terephthalamide, amorphous polyamide, these polyamide-based resins are methylenebenzylamine, Examples thereof include those modified with an aromatic amine such as a polymer amine and a polymer ammonium adipate. Alternatively, these terminal-modified polyamide-based resins may be used, and terminal-modified polyamide-based resins are preferable.

The terminal-modified polyamide-based resin is, for example, specifically, a terminal-modified polyamide-based resin modified with a hydrocarbon group having 1 to 22 carbon atoms, and a commercially available resin may be used. More specifically, for example, the number of terminal COOH groups [X] of the terminal modified polyamide resin and the terminal CONR ₁ R ₂ groups (where R ₁ is a hydrocarbon group having 1 to 22 carbon atoms and R ₂ is a hydrogen atom or A terminal-modified polyamide-based resin in which the number [Y] of (hydrocarbon groups having 1 to 22 carbon atoms) satisfies the following formula (1) is preferably used.
[Y / (X + Y)] × 100 ≧ 5… (1)

The terminal-modified polyamide-based resin is obtained by modifying the carboxy groups of a normal unmodified polyamide-based resin with an N-substituted amide with a terminal modifier, and is based on the total number of carboxy groups contained in the polyamide-based resin before modification. It is a polyamide resin modified by 5% or more. If the amount of modification is too small, a large number of carboxy groups will be present in the polyamide resin, and the carboxy groups will react with EVOH during melt molding to generate gel or the like, resulting in a poor appearance of the obtained multilayer structure. Tends to be easy. Such a terminally modified polyamide resin can be produced, for example, by the method described in JP8-19302.

As the terminal modifier, an amine capable of reacting with a carboxy group is used in order to reduce the amount of the carboxy group in the polyamide resin. Such amine is a mono-substituted amine represented by _{HNR 1} R _{2 (R 2} is a hydrogen atom) or a di-substituted amine. When at least one of R ₁ and R _{2 of HNR 1} R ₂ is an organic group, it may be a hydrocarbon group having no carboxy group, and a hydroxyl group, an amino group, or a carbonyl group as long as the gist of the present invention is not impaired. It may have other functional groups such as, but it is preferably an aliphatic hydrocarbon group. Specifically, R ₁ and R ₂ are hydrocarbon groups having 1 to 22 carbon atoms, preferably hydrocarbon groups having 5 to 20 carbon atoms. R ₁ and R ₂ may be the same group or different.

The content of the unmodified terminal carboxy group of the terminal-modified polyamide resin is preferably small. The above content can be determined as a value (molar equivalent to 1 g of polymer) calculated by dissolving this polyamide resin in benzyl alcohol and titrating it with a 0.1 mol / L sodium hydroxide aqueous solution, and is usually 0 to 0. It is 50 μeq / polymer 1 g, preferably 0 to 30 μeq / polymer 1 g, and particularly preferably 0 to 25 μeq / polymer 1 g. If such a value is too large, gel or the like will be generated during melt molding, and the appearance will be poor, and the retort property will tend to be deteriorated. If such a value is too small, there is no inconvenience in terms of physical properties, but productivity tends to decrease, so that it may remain to some extent. In this case, it is usually 5 to 50 μeq / polymer 1 g, more preferably 10 to 30 μeq / polymer 1 g, and particularly preferably 15 to 25 μeq / polymer 1 g.

_{Further, it is preferable that the two} terminal NH groups of the unmodified polyamide resin are also modified with a hydrocarbon group having 1 to 22 carbon atoms, as in the case of the terminal carboxy group. Therefore, as the terminal adjusting agent used at this time, a carboxylic acid capable of reacting with an amino group in order to reduce the amount of amino groups in the polyamide resin, specifically, a monocarboxylic acid represented by RCOOH ( In the formula, R is a hydrocarbon group having 1 to 22 carbon atoms).

The melting point of the terminal-modified polyamide resin as described above is usually 200 to 250 ° C., preferably 200 to 230 ° C.

When a polyamide resin is used as the other thermoplastic resin, the content ratio of the EVOH / polyamide resin is usually 99/1 to 70/30 in terms of weight ratio, preferably 97/3 to 75/25, particularly. It is preferably 95/5 to 85/15. If the proportion of the polyamide resin is too large, the long-run moldability and gas barrier property tend to be insufficient. If the ratio of the polyamide resin is too small, the effect of suppressing the elution of EVOH after hot water treatment tends to be insufficient.

[Desiccant (D)]
The desiccant (D) used in the present invention has an effect of preventing EVOH in the EVOH layer (A) from absorbing water and lowering the gas barrier property.

As the desiccant (D), generally known hygroscopic compounds and water-soluble desiccants can be used. It is preferably a water-soluble desiccant, more preferably a hydrate-forming metal salt. When a water-soluble desiccant, particularly a hydrate-forming metal salt, is used, it has the property of incorporating water molecules as water of crystallization. Therefore, the water that has penetrated into the resin composition layer by hot water treatment is used as water of crystallization. It is considered that it can be absorbed to prevent the breakdown of hydrogen bonds between molecules in EVOH, thereby suppressing the deterioration of the gas barrier performance of the EVOH layer (A).

Examples of the hygroscopic compound include silica gel, bentonite, synthetic zeolite (molecular sieve), and highly water-absorbent resin.

Examples of the water-soluble desiccant include sodium chloride, sodium nitrate, sugar, trilithium phosphate, sodium metaphosphate, sodium polyphosphate, and various hydrate-forming metal salts.
The hydrate-forming metal salt is a salt capable of absorbing water as water of crystallization, and the production method thereof is not limited. For example, a salt synthesized as a hydrate and dried and dehydrated may be used. can. It is preferable that the product is completely dehydrated (anhydride) by dry dehydration from the viewpoint of hygroscopicity, but it may be a partially dehydrated product (hydrate less than the saturated amount).

Examples of the metal constituting the hydrate-forming metal salt are monovalent, divalent or trivalent metals, and examples of the monovalent metal include alkali metals such as sodium and potassium. Examples of the divalent metal include alkaline earth metals such as beryllium, magnesium and calcium, and transition metals capable of forming divalent ions such as copper, zinc and iron. Further, examples of the trivalent metal include aluminum and iron. Of these, preferred metals are sodium and magnesium, and particularly preferred metals are magnesium.

Examples of the acid constituting the hydrate-forming metal salt include sulfuric acid, carboxylic acid, phosphoric acid, boric acid, nitric acid, carbonic acid, and sulfurous acid. Among these, preferred acids are sulfuric acid, carboxylic acid and phosphoric acid, and particularly preferable acids are sulfuric acid and carboxylic acid.

Specific examples of the hydrate-forming metal salt include chlorides such as cobalt chloride, calcium chloride, and magnesium chloride; monosodium dihydrogen phosphate, disodium monohydrogen phosphate, trisodium phosphate, and pyrophosphate. Phosphates such as sodium and calcium hydrogen phosphate; carboxylates such as disodium succinate, sodium tartrate, trisodium citrate, trimagnesium dicitrate; sulfates such as sodium sulfate, potassium sulfate and magnesium sulfate can be mentioned. .. Of these, sulfates and carboxylates such as succinate and citrate are preferable from the viewpoint of restoration of gas barrier property after retort treatment, and in particular, partial or complete dehydration of magnesium sulfate and trimagnesium dicitrate. The thing is preferably used.

The hydrate-forming metal salt as described above absorbs moisture to form a hydrate having water of crystallization. For example, as the metal sulfate having water of crystallization, such as sodium sulfate _{(Na 2 SO 4 · 10H 2} O), 1 -valent metal salts such as potassium sulfate _{(K 2 SO 4 · 1H 2} O); beryllium sulfate (beso ₄ · 4H ₂ O), magnesium sulphate _{(MgSO 4 · 7H 2 O)} , alkaline earth metal salts such as calcium sulfate _{(CaSO 4 · 2H 2 O)} ; copper sulfate _{(CuSO 4 · 5H 2 O)} , zinc sulfate (ZnSO ₄ · 7H ₂ O), iron sulfate (FeSO ₄ · 7H ₂ O) a transition metal salt and the like; aluminum sulfate _{(Al 2 (SO 4) 3} · 16H 2 O) and the like.

Specific examples of the carboxylic acid salt hydrate having crystalline water include sodium acetate (CH ₃ COONa · 3H ₂ O) and calcium acetate ((CH ₃ COO) ₂ Ca · H) as monovalent carboxylates. _{Acetates such as 2} O); lactates such as calcium lactate ((CH ₃ CH (OH) COO) ₂ Ca · 5H ₂ O); zinc gluconate ((CH ₂ (OH) CH (OH) CH (OH)) CH (OH) CH (OH) COO) ₂ Zn · 3H ₂ O), calcium gluconate ((CH ₂ (OH) CH (OH) CH (OH) CH (OH) CH (OH) COO) ₂ Ca · H ₂ O) gluconate and the like; magnesium benzoate _{((C 6 H 5 COO)} 2Mg · 4H 2 O), benzoates such as calcium benzoate _{((C 6 H 5 COO)} 2 Ca · 3H 2 O) Apple acid salts such as sodium malate (NaOOCCH (OH) CH ₂ COONa) 3H ₂ O), calcium malate (OOCCH (OH) CH ₂ COO) Ca · H ₂ O); Shu as a divalent carboxylic acid salt potassium acid _{((COONa) 2 · H 2} O), ammonium oxalate _{((COONH 4) 2 · H} 2 O) oxalate, etc .; disodium succinate _{((CH 2 COONa) 2 ·} 6H 2 O), succinate dipotassium _{((CH 2 COOK) 2 ·} 3H 2 O) succinate such as; L-glutamic acid potassium _{(HOOCCH (NH 2) CH 2} CH 2 COOK · H 2 O), L- glutamate sodium hydrogen ( Glutamines such as HOOCCH (NH ₂ ) CH ₂ CH ₂ COONa · H ₂ O), magnesium L-glutamate ((OOCCH (NH ₂ ) CH ₂ CH ₂ COO) Mg · 4H ₂ O); sodium L-aspartate ( Asparaginates such as HOOCCH ₂ CH (COOH) NH ₂ · H ₂ O); sodium hydrogen tartrate (HOOCCH (OH) CH (OH) COONa · H ₂ O), disodium L-tartrate (NaOCOCH (OH)) Tartrates such as CH (OH) COONa · 2H ₂ O); tripotassium citrate (KOCOCH ₂ C (OH) (COOK) CH ₂ COOK · H ₂ O), trisodium citrate (((OH) COOK · H 2 O) as trivalent carboxylic acid salts. _{C 3 H 5 O (COO)} 3) Na 3 · 2H 2 O), disuccinic trimagnesium _{((C 3 H 5 O (} COO) 3) 2Mg 3 · 14H 2 O), disuccinic tricalcium _{((C 3 H 5 O (} COO) 3) 2 Ca 3 · 4H 2 O ) citrate and the like; tetravalent carboxylate as calcium disodium ethylenediaminetetraacetic acid _{(Ca (OOCCH 2) 2NCH 2} CH 2 N (CH 2 COONa) 2 · 2H 2 O), disodium ethylenediaminetetraacetate ((HOOCCH _{2) 2NCH 2 CH 2 N (} CH 2 COONa) 2 · 2H 2 O) ethylenediaminetetraacetic acid salts such as and the like.

The chemical formula shown in parentheses is the chemical formula of the saturated hydrate of each metal salt. The hydrate-forming metal salt used as the desiccant (D) in the present invention is a partially dehydrated product or a completely dehydrated product capable of forming the above-mentioned hydrate. When the amount of water of crystallization contained in the saturated hydrate of the metal salt is 100% on a weight basis, the partially dehydrated product is a partially dehydrated water of crystallization of the saturated hydrate, and the amount of water of crystallization is usually 90. A hydrate of the metal salt having less than% water of crystallization is applicable. Since it is preferable to use a partially dehydrated product that allows the saturated hydrate to exist more stably at room temperature, it is preferable to use a partially dehydrated product that has been dehydrated to less than 70% of the amount of crystalline water, which is more preferable. Is a completely dehydrated product.

The melting point of the desiccant (D) is preferably 300 ° C. or higher from the viewpoint of water absorption effect. If the melting point is too low, the function as a desiccant may be deteriorated after melt molding. The desiccant (D) can be used alone or in combination of two or more.

The content of the desiccant (D) is usually preferably 1 to 50 parts by weight with respect to 100 parts by weight of EVOH in the EVOH-based resin composition for forming the EVOH layer (A), and among them, 3 It is more preferably ~ 25 parts by weight, further preferably 5 to 15 parts by weight, and particularly preferably 7 to 12 parts by weight. If the content of the desiccant (D) is too large with respect to EVOH, the transparency of the obtained EVOH layer (A) will be impaired, or the resin composition will aggregate during molding and the screen mesh of the molding machine will be blocked. It tends to be easier. On the other hand, if the content is too small, the effect of absorbing the water that has penetrated into the EVOH layer (A) tends to decrease, and the gas barrier property after the retort treatment tends to decrease.

[Plate-shaped inorganic filler]
The EVOH-based resin composition may further contain a plate-like inorganic filler. Examples of the plate-shaped inorganic filler include kaolin containing hydrous aluminum silicate as a main component and having plate-shaped particles, mica and smectite which are layered silicate minerals, and talc composed of magnesium hydroxide and silicate. Can be given. Of these, kaolin is preferably used. The type of kaolin is not particularly limited and may or may not be fired, but fired kaolin is preferable.

The addition of these plate-shaped inorganic fillers further improves the gas barrier property of the resin composition. Since the plate-shaped inorganic filler has a multi-layer structure, the plate-shaped surface of the plate-shaped filler is easily oriented in the plane direction of the resin composition layer, and the plate-shaped inorganic filler oriented in the plane direction is the resin composition layer. It seems that it contributes to oxygen blocking.

The amount of such a plate-shaped inorganic filler added is not particularly limited, but is usually 1 to 20 parts by weight, preferably 3 to 20 parts by weight, and more preferably 5 to 15 parts by weight with respect to 100 parts by weight of EVOH. It is a department.

[Oxygen absorber]
The EVOH-based resin composition used in the present invention may contain an oxygen absorber for the purpose of further improving the gas barrier property after the retort treatment. The oxygen absorber is a compound or compound system that captures oxygen faster than the packaged contents. Specific examples thereof include an inorganic oxygen absorber, an organic oxygen absorber, and a composite oxygen absorber used in combination with an inorganic catalyst and an organic compound.

Examples of the inorganic oxygen absorber include metals and metal compounds, which absorb oxygen by reacting with oxygen. As the metal, a metal having a higher ionization tendency than hydrogen (Fe, Zn, Mg, Al, K, Ca, Ni, Sn, etc.) is preferable, and iron is typical. These metals are preferably used in powder form. As the iron powder, conventionally known iron powders such as reduced iron powder, atomized iron powder, and electrolytic iron powder can be used without particular limitation. When iron is used, the iron may be iron that has been once oxidized and treated by reduction. The oxygen-deficient metal compound is preferable as the metal compound. Here, examples of the oxygen-deficient metal compound include cerium oxide (CeO ₂ ), titanium oxide (TiO ₂ ), zinc oxide (ZnO), and the like, and oxygen is released from the crystal lattice by reducing these oxides. It is extracted and becomes oxygen-deficient, and exhibits oxygen absorption ability by reacting with oxygen in the atmosphere. It is also preferable that the metal and the metal compound as described above contain a metal halide or the like as a reaction accelerator.

Examples of the organic oxygen absorber include a hydroxyl group-containing compound, a quinone-based compound, a double bond-containing compound, and an oxidizing resin. Oxygen can be absorbed by the reaction of oxygen with the hydroxyl groups and double bonds contained in these. As the organic oxygen absorber, a ring-opening polymer of cycloalkenes such as polyoctenylene, a conjugated diene polymer such as butadiene, and a cyclized product thereof are preferable.

The composite oxygen absorber refers to a combination of a transition metal catalyst and an organic compound, and absorbs oxygen by exciting oxygen with the transition metal catalyst and reacting the organic compound with oxygen. It is a compound system that captures and absorbs oxygen by reacting the organic compound in the composite oxygen absorber with oxygen faster than foods and the like that are the contents of the package. The transition metal constituting the transition metal-based catalyst is at least one selected from, for example, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, ruthenium, and palladium, and among them, with a resin. Cobalt is preferable in terms of compatibility, functionality as a catalyst, and safety. As the organic compound, a ring-opening polymer of cycloalkenes such as polyoctenylene which is an organic oxygen absorber, a conjugated diene polymer such as butadiene and a cyclized product thereof, etc. are preferable, and examples of other organic compounds include MXD nylon and the like. Nitrogen-containing resin, tertiary hydrogen-containing resin such as polypropylene, polyalkylene ether bond-containing resin such as block copolymer having a polyalkylene ether unit, and anthraquinone polymer are preferable.

The content of such an oxygen absorber is not particularly limited, but is usually 1 to 30 parts by weight, preferably 3 to 25 parts by weight, and more preferably 5 to 20 parts by weight with respect to 100 parts by weight of EVOH. Is.

When the transition metal catalyst and the organic compound are used in combination, the content ratio (weight ratio) is not particularly limited, but the transition metal catalyst is 0. It is contained in the range of 0001 to 5% by weight, more preferably 0.0005 to 1% by weight, and more preferably 0.001 to 0.5% by weight.

[Further other additives]
In addition to the above components, the EVOH-based resin composition used in the present invention contains, if necessary, ethylene glycol, as long as the effects of the present invention are not impaired (for example, less than 5% by weight of the entire resin composition). Plastics such as aliphatic polyhydric alcohols such as glycerin and hexanediol; saturated aliphatic amides (eg stearic acid amides), unsaturated fatty acid amides (eg oleic acid amides), bis fatty acid amides (eg ethylene bisstearic acid amides) Etc.), lubricants such as low molecular weight polyolefins (for example, low molecular weight polyethylene having a molecular weight of about 500 to 10000, or low molecular weight polypropylene); heat stabilizers; antiblocking agents; antioxidants; colorants; antistatic agents; ultraviolet absorbers; Antibacterial agents; insoluble inorganic salts (eg, hydrotalcite, etc.); fillers (eg, inorganic fillers, etc.); crystal nucleating agents (eg, talc, kaolin, etc.); surfactants, waxes; dispersants (eg, calcium stearate, stearic acid, etc.) Monoglyceride, etc.); Known additives such as conjugated polyene compounds and aldehyde compounds (for example, unsaturated aldehydes such as crotonaldehyde) can be appropriately blended.

The EVOH-based resin composition used for the EVOH layer (A) of the present invention is usually prepared by melt kneading or a mechanical mixing method (pellet dry blend) to prepare the EVOH, the desiccant (D), and EVOH. It is carried out by mixing with various optional components that can be used in combination with, preferably by a melt-kneading method.

The machine used for the above-mentioned melt-kneading is not particularly limited, and a known melt-kneader can be used. For example, a kneader ruder, a mixing roll, a Banbury mixer, a plast mill, an extruder and the like can be mentioned. Among them, in the case of an extruder, a single-screw or twin-screw extruder or the like can be mentioned, and it is also preferable to provide a vent suction device, a gear pump device, a screen device or the like, if necessary. The temperature in the melt-kneading is usually 150 to 300 ° C, preferably 170 to 250 ° C.

[Adhesive resin layer (B)]
Next, the adhesive resin layer (B) constituting the multilayer structure of the present invention will be described. The adhesive resin layer (B) is a layer for adhering the EVOH layer (A) and the cyclic olefin resin (C) described later, and can be obtained by using the following adhesive resin.

Examples of the adhesive resin include a modified polyolefin-based polymer containing a carboxy group obtained by chemically bonding an unsaturated carboxylic acid or an anhydride thereof to a polyolefin-based resin by an addition reaction, a graft reaction, or the like. be able to. Examples of the modified polyolefin polymer containing the carboxy group include maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene (block and random) copolymer, and maleic anhydride. Maleic anhydride-modified polymers such as graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, maleic anhydride-modified polycyclic olefin resin, and maleic anhydride graft-modified polyolefin resin can give.
These may be used alone or as a mixture of two or more kinds.

The adhesive resin is particularly conservative in that it contributes not only to the adhesiveness of the resin but also to the effect of suppressing gel generation during melt heating and the effect of suppressing the decrease in transparency. Maleic anhydride-modified polymers such as acid-modified ethylene-α-olefin copolymers are suitable.

The acid value of the maleic anhydride-modified polymer is usually 50 mgKOH / g or less, preferably 30 mgKOH / g or less, and particularly preferably 20 mgKOH / g or less. If the acid value is too high, the number of reaction points with the hydroxyl groups in EVOH increases, a highly polymerized product is generated in the melt-kneading process, the stability during extrusion processing decreases, and it tends to be difficult to obtain a good molded product. There is. The lower limit of the acid value is usually 1 mgKOH / g, preferably 2 mgKOH / g. The acid value is measured based on JIS K 0070.

When maleic anhydride-modified polyethylene is used as the maleic anhydride-modified polymer, the MFR (190 ° C., load 2160 g) is usually 0.01 to 150 g / 10 minutes, preferably 0.1 to 50 g / 10 minutes. It is more preferably 1 to 25 g / 10 minutes, and even more preferably 3 to 10 g / 10 minutes.

When a maleic anhydride-modified ethylene-α-olefin copolymer is used as the maleic anhydride-modified polymer, the MFR (230 ° C., load 2160 g) is usually 0.1 to 150 g / 10 minutes, preferably 0.1 to 150 g / 10 minutes. It is 0.5 to 100 g / 10 minutes, more preferably 1 to 50 g / 10 minutes, and even more preferably 5 to 35 g / 10 minutes. If the MFR is too large or too small, molding defects tend to occur when molding the multilayer structure, which is not preferable.

Any additive can be appropriately added to the adhesive resin as long as the effects of the present invention are not impaired. Examples of such additives include heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, neutralizers, rust inhibitors, pigments and the like.

Then, using the adhesive resin and any additive, a resin composition for obtaining the adhesive resin layer (B) constituting the present invention can be prepared. The preparation is carried out in the same manner as in the EVOH-based resin composition.

[Cyclic olefin resin layer (C)]
Next, in the multilayer structure of the present invention, the cyclic olefin resin layer (C) laminated on the EVOH layer (A) via the adhesive resin layer (B) will be described. The cyclic olefin resin layer (C) has a characteristic of low water vapor transmission rate, and has an effect of suppressing the infiltration of water into the inner EVOH layer (A).

The cyclic olefin resin layer (C) can be obtained by using a cyclic olefin resin which is a polymer having a cyclic olefin structure in at least one of a main chain and a side chain.

Examples of the polymer having the cyclic olefin structure in the main chain include the polymer represented by the following chemical formula (1). Examples of the polymer having the cyclic olefin structure in the side chain include the polymer represented by the following chemical formula (2).

The polymer represented by the chemical formula (1) can be obtained by polymerizing a monomer having an unsaturated bond in the cyclic olefin structure (for example, norbornene). Further, the polymer represented by the above chemical formula (2) can be obtained by polymerizing a monomer having an unsaturated bond outside the cyclic olefin structure (for example, vinyl norbornene).

Among them, a polymer having a cyclic olefin structure in the main chain is preferable from the viewpoint of weather resistance, moisture resistance and the like. The number of carbon atoms constituting the cyclic olefin structure is not particularly limited, but is preferably 4 to 30, more preferably 5 to 20, and even more preferably 5 to 15. If the number of carbon atoms is too large or too small, the moisture resistance and moldability tend to decrease.

Specifically, as the monomer having an unsaturated bond in the cyclic olefin structure, a bicyclo [2,2,1] hept-2-ene (norbornen) derivative and a tricyclo [4,3,0,12,5] deca- 3,7-Diene (common name: dicyclopentadiene) derivative, tricyclo [4.3.0.12.5] -3-decene derivative, tricyclo [4.3.0.12.5] -3-undecene derivative , Tetracyclo [4.4.0.12, 5.17, 10] -dodeca-3-ene (common name: tetracyclododecene) derivative, hexacyclo [6.6.1.13, 6.110, 13. 02, 7.09,14] -4-heptadecene derivative, octacyclo [8.8.0.12, 9.14, 7.111, 18.113, 16.03, 8.012, 17] -5-docosen Derivatives, pentacyclo [6.6.1.13, 6.02, 7.09,14] -4-hexadecene derivatives, heptacyclo-5-eicosene derivatives, heptacyclo-5-heneicosene derivatives, pentacyclo [6.5.1. 13,6.02,7.09,13] -4-pentadecene derivative, pentacyclo-4,10-pentadecadien derivative and the like can be mentioned.

Examples of the bicyclo [2,2,1] hept-2-ene (norbornene) derivative include bicyclo [2,2,1] hept-2-ene (common name: norbornene) and 5-methyl-bicyclo [2,2]. , 1] hept-2-ene, 5,5-dimethyl-bicyclo [2,2,1] hept-2-ene, 5-ethyl-bicyclo [2,2,1] hept-2-ene, 5-butyl -Bicyclo [2,2,1] hept-2-ene, 5-hexyl-bicyclo [2,2,1] hept-2-ene, 5-octyl-bicyclo [2,2,1] hept-2-ene , 5-Octadecyl-bicyclo [2,2,1] hept-2-ene, 5-ethylidene-bicyclo [2,2,1] hept-2-ene, 5-methylidene-bicyclo [2,2,1] hept -2-ene, 5-vinyl-bicyclo [2,2,1] hept-2-ene, 5-propenyl-bicyclo [2,2,1] hept-2-ene, 5-methoxycarbonyl-bicyclo [2, 2,1] hept-2-ene, 5-cyano-bicyclo [2,2,1] hept-2-ene, 5-methyl-5-methoxycarbonyl-bicyclo [2,2,1] hept-2-ene 5-methoxycarbonylbicyclo [2,2,1] hept-2-ene, 5-ethoxycarbonylbicyclo [2,2,1] hept-2-ene, 5-methyl-5-methoxycarbonylbicyclo [2,2] , 1] hept-2-ene, 5-methyl-5-ethoxycarbonylbicyclo [2,2,1] hept-2-ene, bicyclo [2,2,1] hept-5-enyl-2-methylpropio Nate, bicyclo [2,2,1] hept-5-enyl-2-methyloctaneate, 5-hydroxymethylbicyclo [2,2,1] hept-2-ene, 5,6-di (hydroxymethyl) bicyclo [2,2,1] hept-2-ene, 5-hydroxy-i-propylbicyclo [2,2,1] hept-2-ene, 5,6-dicarboxybicyclo [2,2,1] hept- 2-ene; 5-cyanobicyclo [2,2,1] hept-2-ene, bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acidimide; 5-cyclopentyl-bicyclo [2] , 2,1] hept-2-ene, 5-cyclohexyl-bicyclo [2,2,1] hept-2-ene, 5-cyclohexenylbicyclo [2,2,1] hept-2-ene, 5-phenyl -Bicyclo [2,2,1] hept-2-ene can be mentioned.

The tricyclo [4,3,0,12,5] deca-3,7-diene derivative includes tricyclo [4,3,0,12,5] deca-3,7-diene (common name: dicyclopentadiene). ), Tricyclo [4,3,0,12,5] deca-3-ene; tricyclo [4,3,0,12,5] undeca-3,7-diene; tricyclo [4,3,0,12, 5] Undeca-3,8-diene; Tricyclo [4,3,0,12,5] Undeca-3-ene can be mentioned.

The tricyclo [4.3.0.12.5] -3-decene derivatives include tricyclo [4.3.0.12.5] -3-decene and 2-methyl-tricyclo [4.3.0]. .12,5] -3-decene, 5-methyl-tricyclo [4.3.0.12.5] -3-decene, and tricyclo [4.3.0.12.5] -3-undecene. Examples of the derivative include tricyclo [4.3.0.12.5] -3-undecene and 10-methyltricyclo [4.3.0.12.5] -3-undecene.

Then, a tetracyclo [4.4.0.12,5.17,10] -dodeca-3-ene (common name: tetracyclododecene) derivative can be mentioned, and specifically, 8-methyltetracyclo [4]. 4.0.12, 5.17,10] -dodeca-3-ene, 8-ethyltetracyclo [4.4.0.12, 5.17,10] -dodeca-3-ene, 8-methi Redentetracyclo [4.4.0.12,5.17,10] -dodeca-3-ene, 8-ethylidenetetracyclo [4.4.0.12, 5.17,10] -dodeca-3-en En, 8-vinyltetracyclo [4.4.0.12,5.17,10] -dodeca-3-ene, 8-propenyl-tetracyclo [4.4.0.12,5.17,10]- Dodeca-3-ene, 8-methoxycarbonyltetracyclo [4.4.0.12,5.17,10] -dodeca-3-ene, 8-methyl-8-methoxycarbonyltetracyclo [4.4.0] .12,5.17,10] -Dodeca-3-ene, 8-hydroxymethyltetracyclo [4.4.0.12,5.17,10] -Dodeca-3-ene, 8-carboxytetracyclo [ 4.4.0.12,5.17,10] -dodeca-3-ene; 8-cyclopentyl-tetracyclo [4.4.0.12, 5.17,10] -dodeca-3-ene, 8- Cyclohexyl-tetracyclo [4.4.0.12,5.17,10] -dodeca-3-ene, 8-cyclohexenyl-tetracyclo [4.4.0.12, 5.17,10] -dodeca-3 -En, 8-phenyl-cyclopentyl-tetracyclo [4.4.0.12, 5.17, 10] -dodeca-3-ene can be mentioned.

Further, as the hexacyclo [6.6.1.13, 6.110, 13.02, 7.09, 14] -4-heptadecene derivative, hexacyclo [6.6.1.13, 6.110, 13. 02,7.09,14] -4-heptadecene, 12-methylhexacyclo [6.6.1.13, 6.110, 13.02.7.09,14] -4-heptadecene, 1,6 Examples thereof include 10-trimethyl-hexacyclo [6.6.1.13, 6.110, 13.02, 7.09, 14] -4-heptadecene and the like.

Octacyclo [8.8.0.12.9.14, 7.111, 18.113, 16.03, 8.012, 17] -5-Docosene derivatives include octacyclo [8.8.0.12]. 9.14, 7.111, 18.113, 16.03, 8.012, 17] -5-docosen, 15-methyl-octacyclo [8.8.0.12, 9.14, 7.111, 18 .113, 16.03, 8.012, 17] -5-docosen.

As a pentacyclo [6.6.1.13,6.02,7.09,14] -4-hexadecene derivative, pentacyclo [6.6.1.13, 6.02, 7.09, 14] -4 -Hexadecene, 1,3-dimethylpentacyclo [6.6.1.13, 6.02, 7.09,14] -4-hexadecene, 15,16-dimethylpentacyclo [6.66.113] 6.02, 7.09, 14] -4-hexadecene can be mentioned.
As a heptacyclo-5-eicosene derivative, heptacyclo- [8.7.0.12,9.14,7.111,17.03,8.012,16] -eicosene, and as a heptacyclo-5-heneicosene derivative, Heptacyclo- [8.8.0.12.9.14, 7.111, 18.03, 8.012, 17] -Heneikosen can be mentioned.

As a pentacyclo [6.5.1.13,6.02,7.09,13] -4-pentadecene derivative, pentacyclo [6.5.1.13, 6.02, 7.09, 13] -4 -Pentadecene, 1,3-dimethylpentacyclo [6.5.1.13, 6.02, 7.09,13] -4-Pentadecene, 1,6-dimethylpentacyclo [6.5.1.13] 6.02, 7.09,13] -4-pentadecene is mentioned, and the pentacyclo-4,10-pentadecadene derivative includes pentacyclo [6,5,1,13,6,02,7,09,13]. ] Pentadeca-4,10-diene can be mentioned.

Specific examples of the monomer having an unsaturated bond outside the cyclic olefin structure include vinyl norbornene and vinyl norbornene.

These cyclic olefin-based monomers may be used alone or in combination of two or more. Among these, the bicyclo [2,2,1] hept-2-ene (norbornene) derivative is preferable, and the bicyclo [2,2,1] hept-2-ene (norbornene) is particularly preferable from the viewpoint of market availability. Is.

When two or more of these cyclic olefin-based monomers are used in combination, the content of the bicyclo [2,2,1] hept-2-ene (norbornene) derivative with respect to the total cyclic olefin-based monomer is 10% by weight. The above is preferable from the viewpoint of weather resistance.

The cyclic olefin resin also includes homopolymers of cyclic olefin monomers and copolymers with other monomers copolymerizable with the cyclic olefin monomers described below. Also included is a hydrogenated polymer having a cyclic olefin structure in at least one of the main and side chains.

The other monomer copolymerizable with the cyclic olefin monomer is not particularly limited as long as it can be copolymerized with the cyclic olefin monomer.
Examples include acyclic olefins, specifically ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1. -Pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl -1-Hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, etc. have 2 to 20 carbon atoms.
Α-olefin; non-conjugated diene such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7-octadien and the like can be mentioned.
These copolymerizable monomers can be used alone or in combination of two or more.
Among them, an α-olefin having 2 to 20 carbon atoms is preferable, an α-olefin having 2 to 4 carbon atoms is more preferable, and ethylene is particularly preferable, from the viewpoint of reactivity and versatility.

When the cyclic olefin resin obtained by polymerizing such a monomer is a copolymer of such other copolymerizable monomers, the proportion of structural units having a cyclic olefin structure is usually 1 to 99 mol%. It is preferably 20 to 70 mol%, and particularly preferably 40 to 50 mol%. If the proportion of repeating units having a cyclic olefin structure is too small, weather resistance and heat resistance may be insufficient. On the other hand, if the amount is too large, the melt moldability tends to decrease.
That is, the content of the other copolymerizable monomer is usually 1 to 99 mol%, preferably 10 to 90 mol%, and particularly preferably 30 to 70 mol%.

In addition, some of the above-mentioned monomers have a double bond remaining, and when such a double bond remains, the cyclic olefin resin may be colored. Therefore, it is preferable to use the cyclic olefin resin by hydrogenating it.

When the cyclic olefin resin used in the present invention is hydrogenated and used, the polymer obtained as described above is obtained by a method of hydrogenating with hydrogen in the presence of a hydrogenation catalyst according to a conventional method. Can be done.
From the viewpoint of weather resistance and moisture resistance, the hydrogenation rate is usually more preferably 95% or more, 98% or more, and even more preferably 99% or more. Here, the hydrogenation rate is expressed as the ratio of the number of moles of hydrogenated ones to the total number of moles of carbon-carbon double bonds before hydrogenation.

The glass transition point (Tg) of the cyclic olefin resin indicates a value measured by JIS K 7121, and is usually 120 ° C. or higher, preferably 125 to 210 ° C., more preferably 130 to 180 ° C., particularly preferably. It is 130 to 150 ° C.
That is, if the glass transition temperature is too low, the resin tends to fuse during the retort treatment. On the other hand, if it is too high, the processing temperature tends to be high and it tends to be difficult to process.

The molecular weight of the cyclic olefin resin is appropriately selected according to the purpose of use, but is converted to polyisoprene measured by a gel permeation chromatograph method of a cyclohexane solution (toluene solution if the polymer resin is not dissolved). The weight average molecular weight is usually 5,000 to 5,000, 8,000 to 20,000, more preferably 5,000 to 100,000, and even more preferably 5,000 to 100,000. If the weight average molecular weight is too large, the processing temperature may be high and it may be difficult to process, and if it is too small, the strength of the multilayer structure tends to be insufficient.

The MFR (230 ° C., 2160 g load) of the cyclic olefin resin is usually 0.5 to 100 g / 10 minutes, more preferably 5 to 50 g / 10 minutes. If the MFR is too small, the molding temperature becomes higher and the molding tends to be defective. On the other hand, if it is too large, molding defects such as burrs tend to occur during molding.

The density of the cycloolefin resin (kg / m ^3), in the measurement based on ISO1183, usually 700~1300kg / m ^3, more preferably 900~1100kg / m ^3, particularly preferably at 950~1050kg / m ³ ..

These cyclic olefin resins can be used alone or in combination of two or more. However, it is desirable that the cyclic olefin resin contains a cyclic olefin resin having a glass transition point (Tg) of 120 ° C. or higher as a main component, and the content thereof is usually 60 to 60 to that of the entire cyclic olefin resin. It is 100% by weight, preferably 70 to 100% by weight, more preferably 80 to 100% by weight, and even more preferably 90 to 100% by weight. Most preferably, it is composed of only a cyclic olefin resin having a glass transition point (Tg) of 120 ° C. or higher.

Examples of commercially available products of such cyclic olefin-based resins include "ZEONEX" manufactured by Zeon Corporation, "TOPAS" manufactured by Polyplastics, and "Abel" manufactured by Mitsui Chemicals.

As the cyclic olefin resin used in the present invention, for example, an unsaturated carboxylic acid-modified cyclic olefin resin obtained by modifying the cyclic olefin resin with an unsaturated carboxylic acid or a derivative thereof by a known method may be used.

Examples of such modification include known methods such as a method of mixing an unsaturated carboxylic acid or a derivative thereof with a cyclic olefin resin to modify it, a method of copolymerizing and modifying it, and a method of graft modification.

Examples of the mixing method include a melt mixing method and a solution mixing method. As a copolymerization method, a method of copolymerizing the unsaturated carboxylic acid or a derivative thereof with a cyclic olefin resin by a known method is common. Further, as the above-mentioned graft modification method, for example, a method of dispersing or dissolving a cyclic olefin resin and an unsaturated carboxylic acid or a derivative thereof in an organic solvent and reacting by heating and stirring, or a cyclic olefin without using a solvent. There is a method in which a system resin and an unsaturated carboxylic acid or a derivative thereof are melt-kneaded with an extruder and reacted. The latter is simpler and more economically advantageous.

The unsaturated carboxylic acids include, for example, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid and TM nadic acid (endosys). -Unsaturated dicarboxylic acids such as bicyclo [2,2,1] hept-5-ene-2,3-dicarboxylic acid) can be mentioned.

Examples of the above-mentioned derivative of the unsaturated carboxylic acid include unsaturated carboxylic acid anhydrides, unsaturated carboxylic acid halides, unsaturated carboxylic acid amides, unsaturated carboxylic acid imides, and ester compounds of unsaturated carboxylic acids. .. Specific examples include maleyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, glycidyl maleate, glycidyl acrylate and glycidyl methacrylate. These unsaturated carboxylic acids or derivatives thereof may be used alone or in combination of two or more.

Among them, the unsaturated carboxylic acid or its derivative has a carbon number of usually 3 to 20, preferably 3 to 15, and particularly preferably 3 to 10 from the viewpoint of handleability. Further, the melting point of the unsaturated carboxylic acid or its derivative is usually 0 to 200 ° C., preferably 30 to 100 ° C., and particularly preferably 40 to 80 ° C. from the viewpoint of handleability.

Further, the cyclic olefin resin may contain, if necessary, another resin or various compounding agents in an amount of 10% by weight or less based on the total amount of the cyclic olefin resin.

Examples of various compounding agents include commonly used compounding agents, for example, antiaging agents, stabilizers, flame retardants, plasticizers, crystal nucleating agents, hydrochloric acid absorbers, antistatic agents, inorganic fillers, lubricants, antiblocking agents and the like. can give. Further, a colorant, an ultraviolet absorber (for example, a benzophenone type, a benzotriazole type, an acrylate type, a salicylate type, etc.) may be blended to provide a light-shielding property.

Then, a resin composition for obtaining the cyclic olefin resin layer (C) constituting the present invention can be prepared by using the cyclic olefin resin and any other resin or compounding agent. The preparation is carried out in the same manner as in the EVOH-based resin composition and the adhesive resin.

[Multi-layer structure]
Next, the multilayer structure of the present invention will be described.

The multilayer structure of the present invention has an EVOH layer (A), an adhesive resin layer (B), and a cyclic olefin resin layer laminated on the EVOH layer (A) via the adhesive resin layer (B). (C) is provided, and is a multi-layer structure including a laminating unit having this laminating structure.

In the multilayer structure of the present invention, at least one of the above laminated units may be contained, for example, a cyclic olefin resin is provided on one surface of the EVOH layer (A) via an adhesive resin layer (B). The cyclic olefin resin layer (C) was laminated on both sides of the structure (A / B / C) in which the layer (C) was laminated and the EVOH layer (A) via the adhesive resin layer (B), respectively. The structure (C / B / A / B / C) can be mentioned. Of course, the laminated unit may be formed in a repeatedly stacked form, and in that case, another resin layer may be interposed between the laminated unit and the laminated unit.

As a laminating method for obtaining the laminating unit, a known method can be used. For example, a method of melt-extruding and laminating an adhesive resin layer (B) and a cyclic olefin resin layer (C) on a film or sheet to be an EVOH layer (A), or conversely, an adhesive resin layer (B) or an annular layer. Examples thereof include a method of melt-extruding and laminating the resin composition to be the EVOH layer (A) on the olefin resin layer (C), or a method of co-extruding the three layers (A), (B) and (C). .. Another method is to apply a solution of the resin composition to be the EVOH layer (A) on the cyclic olefin resin layer (C) provided with the adhesive resin layer (B), and then remove the solvent. Be done. Among these, the coextrusion method is preferable from the viewpoint of cost and environment.

[Other layer (E)]
In the multilayer structure of the present invention, at least one other layer (E) is laminated on one surface or both sides of the laminated unit (the unit may be a single unit or a plurality of repeating units). You may be. Examples of the other layer (E) include a base material layer (E1) for adding strength to the laminated unit, a bonding between the base material layer (E1) and the laminated unit, or a bonding between the laminated units. The adhesive layer (E2) and the like can be mentioned.
<Base layer (E1)>
As the material used for the base material layer (E1), various thermoplastic resins (hereinafter referred to as "base material resins") are used. Further, a recycled resin obtained by remelt molding the end portion, defective product, etc. generated in the process of manufacturing the multilayer structure of the present invention may be used. Such recycled resins include a melt mixture of an EVOH layer (A), an adhesive resin layer (B), a cyclic olefin resin layer (C), and another layer (E).

The base resin used for the base layer (E1) includes linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, and ethylene-propylene (block and random) copolymer weight. Combined, polyethylene-based resins such as ethylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer and the like. Includes (unmodified) polyolefin-based resins such as polypropylene-based resins, polybutenes, and polypentenes, and modified olefin-based resins such as unsaturated carboxylic acid-modified polyolefin-based resins obtained by graft-modifying these polyolefins with unsaturated carboxylic acids or esters thereof. Broadly defined polyolefin resins, cyclic olefin resins, ionomers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, polyester resins, polyamide resins (including copolymerized polyamides) ), Polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorinated polyethylene, halogenated polyolefin such as chlorinated polypropylene, aromatic or aliphatic polyketones, etc. Be done.

<Adhesive layer (E2)>
As the adhesive used for the adhesive layer (E2) for bonding the base material layer (E1) and the laminated unit, known adhesives such as organic titanium compounds, isocyanate compounds, polyester compounds, and polyurethane compounds. Can be used, and may be appropriately selected depending on the type of the thermoplastic resin constituting the base material layer (E1). Further, as the layer for joining the base material layer (E1) and the laminated units or joining the laminated units, the adhesive resin layer (B) may be used in addition to the adhesive layer (E2).

The thermoplastic resin used for the base material layer (E1) and the adhesive used for the adhesive layer (E2) have a range that does not impair the gist of the present invention (for example, 30% by weight or less, preferably 10). In (% by weight or less), conventionally known plasticizers, fillers, clays (montmorillonite, etc.), colorants, antioxidants, antioxidants, lubricants, core materials, blocking inhibitors, ultraviolet absorbers, waxes, etc. Can be blended.

When the multilayer structure of the present invention contains at least one other layer (E) such as the base material layer (E1) and the adhesive layer (E2) as another layer, for example, the following production method Can be given.

(I) All by co-extruding the resin that becomes the laminated unit of the EVOH layer (A) / adhesive resin layer (B) / cyclic olefin resin layer (C) and the resin that becomes the other layer (E). Method of laminating layers:
(Ii) A method of forming a film, a sheet or the like to be another layer (E) separately formed by dry laminating with the above-mentioned lamination unit (A / B / C);
(Iii) By melt-coextruding the resin to be the lamination unit (A / B / C) on the surface of a film, sheet, etc. to be another layer (E) separately formed, or a laminate in which these are appropriately combined. How to laminate;
(Iv) A method of applying a solution of a resin to be another layer (E) to the laminated unit (A / B / C) and then removing the solvent;

Among them, from the viewpoint of productivity, the method (i) in which the resin to be the laminated unit (A / B / C) and the resin to be the other layer (E) are co-extruded is preferable.

Further, without using another layer (E), for example, a cyclic olefin resin layer (C) is laminated on both sides of the EVOH layer (A) via an adhesive resin layer (B) to form a three-kind five-layer structure. Also in the case of obtaining the same, as described above, a method of co-extruding these layers at once is preferable.

In the case of coextrusion molding, the extrusion molding temperature of the resin composition (barrel temperature of the extruder) is usually set appropriately in the range of 150 to 300 ° C. (further, 160 to 250 ° C.).

In the present invention, the barrel temperature of the extruder means the surface temperature of the barrel of the extruder. If the extruder barrel has multiple sections and the individual sections are set to different temperatures, the highest of these is taken as the barrel temperature.

The obtained multilayer structure may be subjected to (heating) stretching treatment, if necessary. The stretching treatment may be either uniaxial stretching or biaxial stretching, and in the case of biaxial stretching, it may be simultaneous stretching or sequential stretching. Further, as the stretching method, a roll stretching method, a tenter stretching method, a tubular stretching method, a stretching blow method, vacuum compressed air forming, or the like, which has a high stretching ratio, can also be adopted. The stretching temperature is a temperature in the vicinity of the multilayer structure, and is usually selected from the range of about 40 to 170 ° C., preferably about 60 to 160 ° C. If the stretching temperature is too low, the stretchability becomes poor, and if it is too high, it becomes difficult to maintain a stable stretched state.

Further, thermal fixing may be performed for the purpose of imparting dimensional stability after stretching. The heat treatment can be carried out by a well-known means. For example, the above-mentioned multilayer structure (in the form of a stretched film) is usually held at 80 to 180 ° C., preferably 100 to 165 ° C. for about 2 to 600 seconds while maintaining a tense state. Perform heat treatment.

In the multilayer structure of the present invention thus obtained, a cyclic olefin resin layer (C) having a low water vapor transmission rate is formed on at least one surface of the EVOH layer (A), which is a gas barrier layer, as an adhesive resin ( It is laminated via B) and has excellent gas barrier properties against oxygen and water vapor. Moreover, even if water penetrates into the EVOH layer (A) during the retort treatment, the desiccant (D) contained in the EVOH layer (A) absorbs the water, so that the EVOH layer (A) has the original gas barrier property. Is not impaired. Then, even after the retort treatment, the water remains absorbed by the desiccant (D), so that the gas barrier property of the EVOH layer (A) does not deteriorate. Therefore, it exhibits excellent gas barrier properties immediately after the retort treatment, does not cause any problems in appearance, and can maintain good quality for a long time.

The thickness of the multilayer structure (including the stretched one), and the thickness of the EVOH layer (A), the adhesive resin layer (B), and the cyclic olefin resin layer (C) constituting the multilayer structure are determined. Although it cannot be unequivocally determined depending on the layer structure, the type of resin of each layer, the application and packaging form, the required physical properties, etc., the thickness of the entire multilayer structure is usually 10 to 5000 μm, preferably 30 to 3000 μm, and particularly preferably 50 to. It is 2000 μm. The thickness of the EVOH layer (A) is usually 1 to 500 μm, preferably 3 to 300 μm, particularly preferably 5 to 200 μm, and the thickness of the adhesive resin layer (B) is usually 0.5 to 250 μm. It is preferably 1 to 150 μm, particularly preferably 3 to 100 μm. The thickness of the cyclic olefin resin layer (C) is usually 1 to 300 μm, preferably 5 to 200 μm, and particularly preferably 10 to 100 μm.

The ratio of the thickness of the EVOH layer (A) to the thickness of the adhesive resin layer (B) (both the thickness of a single layer) A / B is usually 1/10 to 10/1, preferably 1/5 to 1/5. It is 5/1, particularly preferably 1/3 to 3/1. If the A / B is too small, the gas barrier property may be insufficient, and if it is too large, the adhesiveness may be insufficient.

The ratio of the thickness of the EVOH layer (A) to the thickness of the cyclic olefin resin layer (C) (both the thickness of the single layer) A / C is usually 1/50 to 10/1, preferably 1/30. ~ 5/1, particularly preferably 1 / 10-3 / 1. If the A / C is too small, the recovery rate of the gas barrier property of the EVOH resin deteriorated by the retort treatment may decrease, and if it is too large, water tends to infiltrate into the multilayer structure during the retort treatment. It may cause a decrease in gas barrier property and adhesive strength.

[Use of multi-layer structure]
The multilayer structure of the present invention is used for general foods, seasonings such as mayonnaise and dressings, fermented foods such as miso, fats and oils foods such as salad oil, various packaging material containers for beverages, cosmetics, pharmaceuticals, and packaging. It can be suitably used as a gas barrier layer for packaging materials such as films.
In particular, the multilayer structure of the present invention is particularly useful as a packaging material for foods to be treated with hot water because it has excellent gas barrier properties after hot water treatment.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. Unless otherwise specified, the terms "part" and "%" below mean the weight standard.

Prior to the examples, the following ingredients were prepared.

<Resin composition for EVOH layer (A)>
A-1: EVOH [ethylene content 29 mol%, saponification degree 99.6 mol%, MFR 3.8 g / 10 minutes (210 ° C, load 2160 g), melt viscosity 2200 Pa · s (250 ° C, shear rate 25 / sec) ), Volatile content 0.2%] 90 parts and 10 parts of trimagnesium dicitrate anhydride (manufactured by Jungbunzer), which is a desiccant (D), are melted in a twin-screw extruder having two mixing zones. Kneaded EVOH resin composition A-2: EVOH [ethylene content 29 mol%, saponification degree 99.8 mol%, MFR 3.8 g / 10 minutes (210 ° C., load 2160 g)]

<Resin composition for adhesive resin layer (B)>
B-1: Maleic anhydride-modified polypropylene [Mitsui Chemicals, Inc., "Admer QF551", melting point 135 ° C., melt viscosity 926 Pa · s (210 ° C., shear rate 25 / sec)]

<Resin composition for cyclic olefin resin layer (C)>
C-1: Cyclic olefin polymer [Zeon Corporation, "ZEONEX 690R", glass transition temperature (Tg) 135 ° C, melt viscosity 1600 Pa · s (250 ° C, shear rate 25 / sec)]

[Examples 1 to 6, Comparative Examples 1 to 3]
Using each of the above components, coextrusion is carried out under the following conditions by a coextrusion multilayer structure molding apparatus having a three-kind five-layer feed block, a die for molding a multilayer structure, and a take-up machine, and the cooling water is circulated. A multilayer structure of 3 types and 5 layers cooled by chill roll (cyclic olefin resin layer (C) / adhesive resin layer (B) / EVOH layer (A) / adhesive resin layer (B) / cyclic olefin resin layer (C) film) was produced. The structure and thickness of each layer are as shown in Table 1 below.

<Extrusion molding conditions>
-Cyclic olefin resin layer (C): 40 mmφ single-screw extruder (barrel temperature: 240 ° C)
-EVOH layer (A): 40 mmφ single-screw extruder (barrel temperature: 240 ° C)
-Adhesive resin layer (B): 32 mmφ single-screw extruder (barrel temperature: 240 ° C)
・ Die: 4 types, 5 layers type feed block die (die temperature: 240 ° C)
-Cooling roll temperature: 80 ° C

Then, a test piece having a size of 10 cm × 10 cm was cut out from each of the obtained multilayer structures.
After retort treatment at 100 ° C. for 30 minutes using a high-temperature high-pressure cooking sterilizer (“Flavor Ace RCS-40RTGN” manufactured by Hisaka Works), the gas barrier properties (oxygen permeation) of each test piece are as follows. Degree) was evaluated.

<Evaluation of gas barrier property>
For each test piece after the retort treatment, immediately after taking it out from the apparatus, the moisture adhering to both surfaces is completely removed, and then an oxygen permeability measuring apparatus (“Ox-Tran2 / 21” manufactured by MOCON) is used. Te, the oxygen permeability of each specimen (cc / m ² .day.atm) was measured to evaluate the value of the 2 hours after the start of measurement. Therefore, in the present invention, "immediately after the retort treatment" means two hours after the retort treatment is completed.
The measurement conditions were 90% RH inside humidity, 50% RH outside humidity, and a temperature of 23 ° C. with respect to the test piece. Since the thickness of each test piece is different, the measured values were all converted to values at a thickness of 20 μm in order to eliminate the influence of the thickness.

These results are also shown in Table 1 below.

From the above results, it can be seen that all of the products of Examples 1 to 6 have lower oxygen permeability after the retort treatment than the products of Comparative Examples 1 to 6, and exhibit high gas barrier properties.

The present invention includes an EVOH layer (A) containing a desiccant (D) and a cyclic olefin resin layer (C) laminated on the EVOH layer (A) via an adhesive resin layer (B). It is a multi-layer structure and can be widely used as a packaging material or the like that exhibits excellent gas barrier properties immediately after retort treatment.

Claims (4)

The ethylene-vinyl alcohol-based copolymer layer (A), the adhesive resin layer (B), and the cyclic olefin-based resin layer (C) are provided, and the cyclic olefin-based resin layer (C) is the ethylene-vinyl. A multilayer structure laminated on at least one surface of the alcohol-based copolymer layer (A) via the adhesive resin layer (B), and the ethylene-vinyl alcohol-based copolymer layer (A). A multilayer structure comprising a desiccant (D). The multilayer structure according to claim 1, wherein the cyclic olefin resin layer (C) is made of a cyclic olefin resin having a glass transition temperature of 120 ° C. or higher. The multilayer structure according to 1 or 2, wherein the cyclic olefin resin layer (C) has a thickness of 10 μm or more. Oxygen permeability immediately after 30 minutes retorted at 100 ° C. has a thickness of the multilayer structure as 20μm, 16cc / m ^2. day. The resin composition according to any one of claims 1 to 3, wherein the resin composition is atm or less.