JP3235920B2 - Multi-layer package - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer package excellent in gas barrier properties and resistance to bending under high water content.

[0002]

2. Description of the Related Art Conventionally, in the case of packages for foods and medicines, metal cans, glass bottles, various plastic containers, and the like have been used as packaging containers.
2. Description of the Related Art Plastic containers are used as various types of packaging containers in terms of flexibility in form, impact resistance, and cost. Among them, ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) is a melt-moldable thermoplastic resin having extremely excellent gas barrier properties, oil resistance and fragrance retention properties as compared with other resins. In the field of packaging, it has been suitably used for a molded product such as a packaging film, particularly a food packaging film, sheet, or container.

However, while metal cans and glass bottles have zero oxygen permeation as material, plastic containers are particularly suitable for packaging such as pouches or lids for sterilizing boil or retort. Under the condition where heat and moisture act simultaneously, such as in hot water sterilization or steam sterilization, which has been spotlighted as a food distribution form in recent years, its gas barrier property, especially oxygen gas barrier property, is insufficient, Oxygen more than the permissible enters the container, the deterioration of the content food by oxygen occurs,
It becomes a problem in terms of preservability such as flavor and freshness of food, and is currently used only for limited applications.

[0004] That is, as a typical gas barrier resin used as a pouch or a lid material, there is a polyvinylidene chloride polymer, but it does not necessarily have a sufficient oxygen gas barrier property. It is not preferable from the viewpoint of global environmental problems (recycling is not possible, and decomposed substances caused by incineration are considered to cause acid rain). Also, EVOH, which is a representative of other gas barrier resins,
In order to prevent the above problems, a plastic container having a multilayer structure in which EVOH is laminated with a thermoplastic resin layer and an adhesive resin layer has been put on the market. At present, the performance as a food packaging container to be obtained has not been obtained.

In such a multilayer structure, EVOH
Shows good gas barrier properties under low humidity, but heat and moisture act simultaneously, especially in boil sterilization or retort sterilization, that is, when used under high temperature and high humidity, moisture passes through the outer layer to EVOH. Penetrate into the layer, and
It has been pointed out that the gas barrier property of the VOH layer is rapidly reduced. Further, particularly in the form of a multilayer film typified by a pouch or a lid material, a change in appearance due to heat shrinkage was also a major problem.

Further, in order to reduce the influence of moisture in boil sterilization or retort sterilization and to improve the disadvantage that the gas barrier property is reduced, a multilayer laminate provided with a protective layer containing a desiccant has been disclosed in Japanese Patent Application Laid-Open Publication No. Sho. 57-170748 and JP-B-62-6508. However, since the water that has entered the protective layer by the treatment comes into contact with the gas barrier layer, the water that has been adsorbed once migrates to the gas barrier layer, and there is a concern that the function of the gas barrier layer is reduced. Was also inadequate.

Japanese Patent Application Laid-Open Nos. 1-253422 and 4-
No. 131237 discloses a multilayer package comprising a composition comprising EVOH and a polyamide resin or a polyester resin as an intermediate layer, a high moisture permeable resin (eg, polyamide) as an outer layer, and a low moisture permeable resin (eg, polypropylene) as an inner layer. Has been described. However, although this package has a predetermined effect in the application of the sterilization treatment, there is a problem in that when an external force such as bending is applied to the film, "cracks" are generated in the composition layer and poor appearance occurs. there were. Specifically, there is a phenomenon in which a broken portion is formed in the film in a vacuum package or the like, and this portion is whitened after retort, and it appears that delamination has occurred. Further, even in the case of a pouch having water therein, the pressure may fluctuate greatly during the retort, and the pouch may repeatedly expand and contract, or may be bent when handled immediately after the retort.

[0008]

Due to the above-mentioned problems, the prior art has limited the use conditions and the use form. Accordingly, an object of the present invention is to provide a package which has excellent hot water resistance (retort resistance) and does not cause abnormal appearance due to bending during or immediately after retort with high water content.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have found that a layer containing an ethylene-vinyl alcohol copolymer (A) is an intermediate layer (2). In the body, a multilayer package containing at least one resin layer (3) adjacent to the layer (2) and containing a boron compound, in particular, the intermediate layer (2) is 51 to 98% by weight of an ethylene-vinyl alcohol copolymer (A) and at least one resin selected from polyamide, polyolefin, polyester and polycarbonate (B) 2 to 49% by weight
The composition (C) layer composed of
%), And the inner layer has a moisture permeability (40 ° C., 90% R) of 40 g / m ² · day or more.
It has been found that a multilayer package comprising a resin layer (4) having a value (measured under H) of 20 g / m ² · day or less can achieve the above object.

Hereinafter, the present invention will be described specifically. EVOH (A) contained in the intermediate layer is a saponified ethylene-vinyl ester copolymer, and preferably has an ethylene content of 20 to 60 mol%, more preferably 25 to 55 mol%. If the ethylene content is less than 20 mol%,
Water resistance, hot water resistance and moisture resistance are reduced, gas barrier properties under high humidity are impaired, stress cracking resistance is reduced, and it is difficult to maintain good melt processing characteristics. On the other hand, if it is more than 60 mol%, the water resistance, hot water resistance and moisture resistance are improved, but the originally excellent gas barrier properties are deteriorated. In any case, it becomes unsuitable as a material for packaging or the like. The degree of saponification of the vinyl ester component is 9
It must be at least 5 mol%, preferably 98%.
Mol%. When the saponification degree is less than 95 mol%, the thermal stability is deteriorated, a disadvantage that a gel is easily generated at the time of melt processing occurs, the gas barrier property and the oil resistance are reduced, and the original properties of EVOH cannot be maintained. It becomes difficult to enjoy the effect of. Here, as the vinyl ester, vinyl acetate is mentioned as a typical example, but other vinyl esters,
For example, lower or higher fatty acid vinyl esters (such as vinyl propionate and vinyl pivalate) can be used. The vinyl ester may be used alone or in combination of two or more.

In the present invention, EVOH (A) is a known one.
Polymerization is carried out in a solvent such as methanol, t-butanol or dimethyl sulfoxide by a known method using a polymerization initiator such as benzoyl peroxide or azobisisobutyronitrile under pressure, followed by catalysis with an acid or an alkali catalyst. It is a product obtained by Examples of the fatty acid vinyl ester include vinyl acetate, vinyl propionate, vinyl versatate, vinyl pivalate, and the like, and aromatic vinyl carboxylate can be used. However, vinyl pivalate is preferred from the viewpoint of gas barrier properties.

In addition, the melt index of EVOH (A) (at a temperature of 19 according to ASTM D1238 65T)
The value measured under the conditions of 0 ° C. and a load of 2160 g; hereinafter referred to as MI) is not particularly limited, but is 0.1 to 100 g / 10
(However, when the melting point is around 190 ° C. or higher, the temperature is measured at a plurality of higher temperatures, and the temperature is plotted on the semi-logarithmic graph with the horizontal axis and MI on the vertical axis, and extrapolated to 190 ° C.). Further, EVOH (A) referred to in the present invention may be modified with a small amount of a copolymer monomer as long as the object of the present invention is not hindered. Examples of the modifying monomer include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, acrylate, methacrylate,
Maleic acid, phthalic acid, itaconic acid, higher fatty acid vinyl ester, alkyl vinyl ether, N-vinylpyrrolidone, N-normal butoxymethyl acrylamide, N
-(2-Dimethylaminoethyl) methacrylamides or quaternary compounds thereof, N-vinylimidazole or quaternary compounds thereof can be exemplified.

In addition, EVOH (A) includes sodium,
Acetates and phosphates of alkali metals such as potassium or alkaline earth metals such as calcium and magnesium;
A small amount of derivatives such as acid salts, borates, chlorides, hydroxides and oxides of phosphoric acid and a small amount of acids such as acetic acid and phosphoric acid have better thermal stability during extrusion at high temperatures. Good and preferred.

In the present invention, the EVOH (A) has an ethylene content of 20 to 60 mol%, a saponification degree of 95 mol% or more, and a vinyl silane content of 0.0001 to 0.5.
Mole-% silicon-containing EVOH can also be used for the purposes of the present invention. As the olefinically unsaturated monomer containing silicon, a conventionally known monomer such as disclosed in JP-A-61-290046 can be used. For example, vinyl trimethoxy silane, vinyl triethoxy silane, vinyl methyl dimethoxy silane, vinyl triacetoxy silane, vinyl tripropionyloxy silane and the like can be mentioned. The silicon content is selected according to each purpose, but is preferably in the range of 0.0001 to 0.5 mol%, particularly preferably 0.001 to 0.1 mol%.

The resin (B) forming the composition (C) in the present invention is, for example, polyamide. The polyamide is a polyamide obtained by polycondensation of a lactam having three or more ring members, a polymerizable ω-amino acid, or a dibasic acid and a diamine. Specifically, polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-
9), polyundecaneamide (nylon-11), polylauryl lactam (nylon-12), polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexa Methylene adipamide (nylon-6, 6), polyhexamethylene sebacamide (nylon-6, 10), polyhexamethylene dodecamide (nylon-6, 12), polyoctamethylene adipamide (nylon-8, 6), polydecamethyleneamipamide (nylon-10, 8), or caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / ω-aminononanoic acid copolymer (nylon-6 / 9), Caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,6), Urirurakutamu / hexamethylene diammonium adipate copolymer (nylon-12 /
6, 6), hexamethylene diammonium adipate /
Hexamethylene diammonium sebacate copolymer (nylon-6,6 / 6,10), ethylenediammonium adipate / hexamethylenediammonium adipate copolymer (nylon-2,6 / 6,6), caprolactam / hexamethylene Diammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6 / 6,6 / 6,10), polyhexamethyleneisophthalamide (nylon-6, I), polyhexamethyleneterephthalamide (nylon-6, T) and hexamethylene isophthalamide / terephthalamide copolymer (nylon-6, I / 6, T). In these polyamides, 2,2,4-diamine is used as a diamine.
Alternatively, aliphatic diamines into which substituents such as 2,4,4-trimethylhexamethylenediamine or the like, aromatic amines such as methylbenzylamine and meta-xylylenediamine may be used, or the polyamide may be modified.
Further, 2,2,4- and 2,2 as dicarboxylic acids
Aliphatic dicarboxylic acids having substituents such as 4,4-trimethyladipic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, xylylenedicarboxylic acid phthalate, alkyl-substituted tere and isophthalic acids, Use of an aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or modification to polyamide may be performed.
These polyamides may be used alone or in a mixture of two or more.

Among these polyamides, the most effective ones for the present invention are caprolactam / laurolactam copolymer (nylon-6 / 12) and caprolactam / hexamethylene adipate copolymer (nylon-6 / 6,
6). In both cases, the copolymerization ratio of the caprolactam component is not particularly limited. In the case of nylon-6 / 12, the caprolactam component is 94 to 40% by weight, and in the case of nylon-6 / 6,6, the caprolactam component is 99 to 5%.
Those having 0% by weight are preferred because they have good compatibility with EVOH.
Further, the relative viscosity of the polyamide measured in 90% formic acid is from 2.0 to 4.2, preferably from 2.2 to 3.8.

These polyamides, especially nylon-6 /
12. Nylon-6 / 6,6 is copolymerized with polyetherdiamine or polyetherdicarboxylic acid in the polymer chain,
Polyamide having an ether bond may be used. Also,
Add laurylamine, methylbenzylamine, etc.,
Those having a reduced amount of carboxyl groups in the polyamide are also preferred. In this case, the amino terminal group is preferably 8 × 10 ^{-1 to} 5 equivalents / g or more, and the carboxyl terminal group is preferably 3 × 10 ^{-1 to} 5 equivalents / g or less.

As the resin (B) forming the composition (C) in the present invention, a polyamide is optimal, but a polyolefin, a polyester or a polycarbonate can be used instead of the polyamide.

The polyolefin forming the composition (C) includes high-, medium-, or low-density polyethylene, polypropylene, vinyl acetate, acrylate, and α such as butene, hexene, and 4-methyl-1-pentene. -Olefin copolymerized polyethylene, ionomer resin, polypropylene homopolymer,
Polypropylene graft copolymerized with ethylene, or polypropylene copolymerized with α-olefins such as ethylene, hexene and 4-methyl-1-pentene, poly-1-butene, poly-4-methyl-1-pentene, or Maleic acid, acrylic acid,
It contains modified polyolefins treated with itaconic acid, maleic anhydride, itaconic anhydride and the like. A modified polyolefin containing a carbonyl group at a concentration of 10 to 1400 mmol / 100 g polymer, particularly 30 to 1200 mmol / 100 g polymer, particularly a modified polypropylene, can be preferably used.

The polyester forming the composition (C) includes poly (ethylene terephthalate), poly (ethylene naphthalate), poly (butylene terephthalate),
A representative example is a saturated polyester resin represented by poly (ethylene terephthalate / isophthalate).

EVO forming the composition (C) in the present invention
The composition ratio of H (A) to at least one resin (B) selected from polyamide, polyolefin, polyester and polycarbonate is a composition comprising 51 to 98% by weight of EVOH (A) and 2 to 49% by weight of resin (B). Things. If the EVOH content is less than 51% by weight, sufficient gas barrier properties cannot be obtained. On the other hand, when the EVOH content is 98
If the content is more than 10% by weight, the hot water resistance (retort resistance) is poor. E
The mixing ratio of VOH (A) and resin (B) is EVOH 51-
98% by weight, preferably 60-97% by weight, more preferably 65-95% by weight, polyamide 2-49% by weight, preferably 3-40% by weight, more preferably 5-3% by weight.
5% by weight.

As a method of blending the EVOH (A) and the composition (C) comprising at least one resin (B) selected from polyamide, polyolefin, polyester and polycarbonate, the respective resins are dry-blended, uniaxially or uniaxially. A melt blending method is used in which melt extrusion is performed by a twin screw extruder (same direction or different direction), an intensive mixer, a continuous intensive mixer, and the like, and then pelletized under cooling.

Next, the resin layer (3) containing the boron compound necessary for the present invention will be described. The compound may "crack" in the resin layer (2) when subjected to bending in a retort under severe conditions or immediately after high water content, but the boron contained in the resin layer (3) in the retort may be reduced. It is considered that the compound migrates to the resin layer (2) and contributes to its prevention. That is, the reason why the effect of preventing cracks in the resin layer (2) is exerted is not necessarily clear, but the boron ions transferred into the resin layer (2) form strong ionic bonds with the EVOH molecules, and the cross-linking effect between the molecules occurs. It is presumed to cause this.

Examples of the resin forming the resin layer (3) include a polyolefin resin, a polyester resin, a polyamide resin, a polystyrene resin and a polycarbonate resin. Suitable resins include olefin resins and adhesive resins composed of olefin resins. Examples of the polyolefin resin include high-density, medium-density or low-density polyethylene, high-density, medium-density or low-density polypropylene, vinyl acetate, acrylate, and α such as butene, hexene, and 4-methyl-1-pentene. -Olefin copolymerized polyethylene, ionomer resin, polypropylene homopolymer,
Polypropylene graft copolymerized with ethylene, or polypropylene copolymerized with α-olefins such as ethylene, hexene and 4-methyl-1-pentene, poly-1-butene, poly-4-methyl-1-pentene, etc. can give. Among them, polypropylenes are suitable for the purpose of the present invention. The adhesive resin is not particularly limited as long as it does not cause delamination at a practical stage, and is not particularly limited. An unsaturated carboxylic acid or an anhydride thereof may be an olefin polymer (for example, polyethylene, polypropylene, polyolefin such as polybutene, It is obtained by chemically (e.g., addition reaction, graft reaction) bonding to an olefin-based copolymer). Modified olefin polymers containing a carboxyl group are exemplified. Specifically, one selected from maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer or Preferred are mixtures of the two. In addition, EVOH can be mixed with these adhesive resins within a range that does not impair the effects of the present invention. In the co-extrusion method, for the inner layer made of the moisture-resistant thermoplastic resin, scrap generated when the multilayer container of the present invention is produced can be used as a raw material. Also,
The scrap can also be used as a layer independent of the inner and outer layers.

The content of the boron compound in the resin layer (3) is not particularly limited, but the preferred range is 0.01 to 15% by weight, preferably 0.1 to 10% by weight, more preferably 0.1 to 10% by weight of the boron metal element. Preferably it is 0.2 to 7% by weight.

The method for obtaining the resin composition comprising the resin forming the resin layer (3) and the boron compound is not particularly limited, and may be a dry blend. Kneading method) is preferable in terms of uniform dispersibility of the resin and the boron compound. In this method, a resin powder or pellets and a boron compound are mixed in a conventional mixer, for example, a Henschel mixer or a super mixer, or a master is prepared by mixing a boron compound with an EVOH melt. There is a method in which the resin is mixed with a powder, a pellet, and a melt, and then the mixture is kneaded at a temperature equal to or higher than the melting point of the resin. The resin and the boron compound may be directly introduced into a kneader and kneaded without previously mixing the resin and the boron compound as described above. Continuous kneaders such as a continuous intensive mixer and a kneading-type twin-screw extruder (in the same direction or in different directions) are used as kneaders for obtaining a composition having a high degree of dispersion without agglomerates of boron compounds. However, a batch-type kneader such as a Banbury mixer, an intensive mixer, or a pressure kneader can also be used.

It is a necessary condition that the resin layer (3) is adjacent to the intermediate layer (2). Here, the term “adjacent” means a dry laminate having a thickness of 15 μ or less, preferably 10 μ or less, more preferably 5 μ or less. The case where the layer is formed between the resin layer (2) and the resin layer (3) is also considered to be adjacent. Further, the laminate layer may contain a boron compound. The boron compound content is not particularly limited, but the preferred range is 0.01 to 15% by weight, preferably 0.1 to 10% by weight, more preferably 0.1 to 10% by weight, based on the weight of the boron metal element.
2 to 7% by weight. The operation of containing the boron compound in the laminate layer is not particularly limited, and any method can be used as long as the boron compound is smoothly contained in the laminate layer. For example, a treatment agent obtained by dissolving and dispersing a boron compound in water is immersed in a multilayer film having a laminate forming layer as an outer layer, and air knife coating, mayer bar coating, discharge from a casting head, roll coating, doctor roll coating, and doctor Knife coating, contact treatment with the film by means of spraying, coating and swelling and dispersing a solution / dispersion containing the boron compound on the film, or dissolving / dispersing the boron compound in the dry lamination adhesive itself, A method in which lamination and the compounding of the boron compound into the laminate layer are performed at the same time may be mentioned.

Various boron compounds can be used, and examples thereof include boric acid and boric acid compounds represented by the following formula (I). ^{_{x 1 M 2 O · yB 2}} O 3 · zH 2 O (I) ( wherein, M is a metal, ¹ M ₂ is the title when M is a monovalent metal such as potassium, sodium, lithium , Calcium, magnesium, etc. y /
x is typically 1/3, 1/2, 1, 2, 5/2, 4 and each is an orthoborate, diborate, metaborate, tetraborate, pentaborate Among them, boric acid, disodium tetraborate and potassium borate are preferred, with boric acid being particularly preferred.

Even when the film comprising the multilayer package of the present invention is used, if it is still severely bent at the time of hot water boiling or retorting, it is rarely formed in the intermediate layer (2) layer to "crack" in the layer. Whitening may occur, and in the present invention, at least one resin (B) selected from polyamide, polyolefin, polyester and polycarbonate is used in an amount of 2 to 49% by weight and EVOH (A)
As an ethylene content of 20 to 60 mol%, preferably 20 to 45 mol%, more preferably 25 to 40 mol%,
A saponification degree of the vinyl ester component of at least 90 mol%, preferably at least 95 mol%, more preferably at least 98 mol%, of 50 to 97 wt% of EVOH (A-1), and an ethylene content of 30 to 65 mol%, and The ethylene content is at least 4 mol%, preferably at least 6 mol%, higher than EVOH (A-1), the degree of saponification of the vinyl ester component is at least 90 mol%,
Preferably 93 mol% or more, more preferably 95 mol%
It is more preferable to use a composition comprising 1 to 48% by weight of the EVOH (A-2) since whitening does not occur in the composition layer even in the case of severe bending during hot water boiling or retort. EVOH (A-1) and EV
The compounding ratio of OH (A-2) is EVOH (A-1) 50 to
97% by weight, preferably 60-97% by weight, more preferably 65-95% by weight, and EVOH (A-2) 1-48.
% By weight, preferably 2-45% by weight, more preferably 2% by weight.
３０30% by weight.

In addition, EVOH, polyamide, polyolefin, polyester, polycarbonate and the composition may contain an antioxidant, a coloring agent, an ultraviolet absorber, a slip agent, an antistatic agent, a plasticizer, boric acid as long as the present invention is not impaired. And various additives such as a crosslinking agent, an inorganic filler and an inorganic drying agent, and various resins such as a superabsorbent resin. For example, the following are exemplified.

Stabilizers: calcium stearate, metal salts of hydrotalcites and the like. Antioxidants: 2,5-di-t-butylhydroquinone,
2,6-di-tert-butyl-p-cresol, 4,4-thiobis (6-tert-butylphenol), 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol), octadecyl- 3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl), propionate,
4,4'-thiobis- (6-t-butylphenol),
Tris (2,4-di-tert-butylphenyl) phosphite, di (2,4-di-tert-butylphenyl) -pentaerythritol-diphosphite, 9.1
Phosphate antioxidants such as 0-dihydro-9-oxa-10 phosphaphenanthrene;
Thioether-based antioxidants such as 3,3'-thio-di-propionate;

UV absorber: ethyl-2-cyano-3,
3'-diphenyl acrylate, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2-
(2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy- 4-octoxybenzophenone and the like.

Plasticizer: dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate ester and the like.

Antistatic agents: pentaerythritol monostearate, sorbin monopalmitate, sulfated oleic acid, polyethylene oxide, carbon wax and the like. Lubricants: ethylene bisstearoid, butyl stearate and the like.

Coloring agents: carbon black, phthalocyanine, quinacridone, indoline, azo pigments, titanium oxide, red iron oxide, etc.

Filler: glass fiber, asbestos,
Mica, sericite, talc, glass flake, ballastonite, calcium silicate, aluminum silicate, montmorillonite, hectorite, beidellite, nontronite, saponite, sauconite, stevensite.

One of the important aspects of the present invention is that the resin material comprising the EVOH (A) or the composition (C) is used as the intermediate layer (2), and the outer layer has a moisture permeability of 40 g / m ^2.
A resin layer (1) having a thickness of at least day, and a resin layer (4) having a moisture permeability of 20 g / m ² · day or less at the inner layer. The aforementioned resin layer (3) is located between the resin layer (2) and the resin layer (4), or the resin layer (1) and / or the resin layer (4) also serves as the resin layer (3) itself. Good.
By adopting such a layer configuration, the gas barrier property after the retort is quickly recovered, and the gas barrier property after the recovery is excellent, and at the same time, appearance abnormalities such as delamination, wrinkles, partial whitening, and whitening due to bending are reduced. It is possible to obtain a multi-layer package having such a feature that it does not occur.

Here, the moisture permeability of the inner and outer layers is determined according to JIS-Z-0.
208, that is, the inner and outer layers are formed in a metal cup containing a hygroscopic agent, and the films are attached and sealed as lids, respectively, left at a temperature of 40 ° C. and a relative humidity of 90% RH to determine the weight increase. , The method of calculating from the increase speed is convenient.

In the case where the resin layer (1) having a moisture permeability of 40 (g / m ² · day) or more is provided in the outer layer, the barrier property can be recovered quickly and the transparency after retort can be sufficiently recovered. It is suitable. Further, even when the treatment is performed at a high temperature of 110 ° C. or more, there is no fusion blocking between outer layers, which is preferable. In this case, it is more preferable to use a resin layer having a moisture permeability of 100 or more. In the case of the outer layer having a value of 40 or less, not only the barrier property is slowly recovered but the storage performance is inferior, but also the transparency recovery property after retort is not sufficient.

Factors that affect the moisture permeability are the type of resin and its thickness. Suitable types of resin for the outer layer include polyamide (nylon-6, nylon-6 / 6,6, nylon-6 / 12, etc.), polyester (polyethylene terephthalate and its modified products, polybutylene terephthalate and its modified products, etc.) , Polystyrene resin,
Polystyrene-polybutadiene block copolymer resin and polycarbonate, which can be used alone or in combination. However, depending on the application, such as when used in a retort, it is necessary to consider heat resistance. In dry lamination, a non-stretched product or a biaxially stretched product can be selected.

Specifically, a commercially available biaxially stretched polyamide film (15 μ) or a biaxially stretched polyester film (12 μ) has a moisture permeability of 260 g / m ² · da, respectively.
y is 50 g / m ² · day, which is preferable as the outer layer material.

Another factor affecting moisture permeability is thickness. For example, polypropylene has a moisture permeability of 7 at 20μ, but this value increases in inverse proportion to the thickness, and becomes 70 at 2μ, which is the applicable range of the present invention. However, some of the general multi-layering methods described below are subject to manufacturing restrictions. For example, dry lamination has not been put into practical use due to problems such as the presence or absence of a commercially available single-layer film, the strength in handling, and the problem of product warpage. However, thinning as described above is possible by coextrusion or coextrusion lamination, and it is also possible to use a thin polypropylene resin outside the EVOH layer.

The inner layer has a moisture permeability of 20 g / m ² · day
It is important to use the following resin layer (4), and a multilayer package having a high barrier property can be obtained by using the inner layer having such moisture permeability. This is because the intermediate layer (2) has a low substantial humidity. In addition, the lower the moisture permeability of the multilayer package, the more the moisture content of the contents can be reduced, and the more the moisture absorption of the contents is prevented. In retort applications, the greater the difference in moisture permeability between the outer layer and the inner layer, the more preferable, because even if the composition absorbs moisture in the retort, water is scattered during storage and the barrier properties are quickly restored.

The moisture permeability of the inner layer is also related to the type and thickness of the resin.
The above is preferred.

As the types of resins, polyethylene (low density, high density, linear low density, etc.), polypropylene (homopropylene polymer, copolymer), polyvinyl acetate resin, And the like are preferable, but it is also possible to composite with the resin used for the outer layer.

Before the multi-layering, a deposited film of aluminum, silicon oxide, aluminum oxide or the like may be formed by a known method. In addition, it can be combined with another type of film on which a vapor-deposited film is formed.In this case, it is preferable to provide a vapor-deposited film or another type of film on which a vapor-deposited film is formed inside the resin layer of the present invention from the viewpoint of barrier properties. .

The method for forming the multilayer is not particularly limited, and examples thereof include coextrusion molding, coinjection molding, extrusion lamination, dry lamination, and wet lamination. Thereby, it is multi-layered with sheets, films, bottles, cups and tubes, and if necessary, shaped into a desired shape or stretched (uniaxially or biaxially stretched) for use.

In obtaining a multilayer package, it may be preferable to use an adhesive resin in order to improve the adhesiveness of each layer. Here, as the adhesive resin, an olefin polymer or copolymer modified (added, grafted, etc.) with an unsaturated carboxylic acid or its anhydride (such as maleic anhydride) な ど polyethylene (low-density polyethylene, linear low- Adhesive resin represented by density polyethylene), polypropylene ethylene-vinyl acetate copolymer, and ethylene-acrylate ester II can be used. However, when used on the outer layer side, it is necessary to limit the thickness in consideration of moisture permeability.

The thus obtained package of the present invention is excellent in gas barrier properties,
Because it has excellent hot water resistance that is not found in VOH, it is used for ordinary food packaging, especially for containers, bags, pouches, container lids and boilers, retort sterilized food packaging that is sealed by heat sealing. Useful as container material. It is also desirable for non-food packaging materials such as pharmaceuticals, pesticides, cosmetics, detergents, organic pesticides, audio components, stationery, and other non-food packaging materials.

In particular, the package of the present invention is useful as a container for sterilizing boil and retort. Here, ordinary methods and conditions can be adopted for sterilizing boil and retort. For the retort treatment, a method such as a recovery type, a steam type, a shower type, and a spray type can be adopted.

[0051]

【Example】

Example 1 EVOH having an ethylene content of 27 mol%, a saponification degree of a vinyl acetate component of 99.5 mol%, and a melt index (MI) extrapolated at 190 ° C. of 1.6 g / 10 min.
(A, described in A-1 in Table 1) was 80% by weight, and the polyamide resin (B) was a nylon-6 / 12 copolymer (caprolactam unit and lauryl lactam unit having a weight ratio of 90/10. With a melting point of 215 ° C. and a relative viscosity of 2.
5, MI extrapolated to 190 ° C. is 3.6 g / 10 min) 20
The weight percent mixture was melt extruded at 220 ° C. in a single screw extruder to give blended pellets. Subsequently, the resin was melted at a resin temperature of 230 ° C. by an extrusion film forming machine having a coat hanger die, and then cast on a cast roll at 98 ° C. to obtain a transparent non-stretched film {f} having a thickness of 15 μm.

On the film, a boric acid-containing adhesive resin (manufactured by Mitsui Petrochemical Industry Co., Ltd.)
MER) After adding boric acid to QF500 (polypropylene-based adhesive resin) (1 wt% as boron atom), blended and pelletized at 220 ° C. using a single screw extruder (｝) and polypropylene (Diapolymer Co., Ltd.)
Mitsubishi Polypropylene PY220 # is melted at 240 ° C., the thickness of the adhesive resin layer is set to 10 μm, the thickness of the polypropylene layer is set to 50 μm, and the boric acid-containing adhesive resin is positioned on the film f to form a co-extrusion coat at 20 m / min. Then, a laminate was obtained by co-extrusion coating of film f / boric acid-containing adhesive resin / polypropylene composition {moisture permeability of boric acid-containing adhesive resin / polypropylene composition 6 g / m ² · day}.

Next, a commercially available biaxially stretched nylon-6 film (trade name: emblem, thickness 15) manufactured by Unitika Ltd.
μ, moisture permeability of 260 g / m ² · day 選 び, and 4 g of A-385 / A-50 manufactured by Takeda Pharmaceutical Co., Ltd. as a solid content as an adhesive for dry lamination (two-part type, urethane-based). / M ² , and after evaporating the solvent at 80 ° C., laminating the above multilayer film and aging at 40 ° C. for 5 days to obtain a multilayer film 多層 biaxially stretched nylon-6 film / laminate layer / film f / hoe An acid-containing adhesive resin / polypropylene was obtained.

From this film, a bag heat-sealed on three sides was made, water was added, and the other piece was heat-sealed and sealed. The bag was folded in four and tied with a string to create a texture bend. This is a retort apparatus {High temperature and high pressure cooking sterilization tester, RCS-40RTGN} manufactured by Hisaka Manufacturing Co., Ltd.
Was used to perform a retort treatment at 125 ° C. for 30 minutes. After the retort treatment, the string was unraveled and stored in a room at 20 ° C. and 65% RH. Immediately after the retort, it was whitened, but about 30
It became completely transparent in minutes, and no other abnormalities in appearance were observed. Table 1 shows the above results.

Example 2 In Example 1, the same processing and evaluation as in Example 1 were carried out, except that after the retort treatment, the string was released and the bag was forcibly bent by hand (the bag was bent 20 times vertically and 20 times horizontally). Was done.
Table 1 shows the results.

Comparative Example 1 In Example 2, an adhesive resin containing no boric acid (Admer QF manufactured by Mitsui Petrochemical Industry Co., Ltd.)
The same processing and evaluation as in Example 2 were performed except that 500 (polypropylene adhesive resin) was used. The results are shown in Table 1 (when the cross section of the whitened portion was observed under a microscope, a crack was found in the blended EVOH layer.).

Example 3 In Example 2, as the EVOH used for the intermediate layer, the ethylene content was 27 mol%, the saponification degree of the vinyl acetate ester component was 99.5 mol%, and the MI extrapolated to 190 ° C. was 1.
75% by weight of EVOH (A-1) and ethylene content of 44 mol%, saponification degree of vinyl acetate component 99.5 mol%, MI of 190 ° C. of 5.5 g / 1 at 6 g / 10 min.
The same processing and evaluation as in Example 2 were carried out, except that a mixture of 5 minutes by weight of EVOH (A-2) for 0 minutes was used. Table 1 shows the results.

Comparative Example 2 In Example 3, an adhesive resin containing no boric acid (Admer QF5 manufactured by Mitsui Petrochemical Industries, Ltd.)
The same processing and evaluation as in Example 2 were performed except that 00 (polypropylene adhesive resin) was used. Table 1 shows the results
(When the cross section of the whitened portion was observed with a microscope, a crack was found in the blended EVOH layer.)

[0059]

[Table 1] In Table 1, * 1 A: Nylon-6 / 12 (copolymerization ratio nylon-
(6: 90% by weight) * 2 The appearance of the bag after retorting is as follows. Very good: no change. Good: Slightly cloudy, but practically no problem. Bending whitening: Many clear whitenings are observed in the bag.

[0060]

Industrial Applicability The multilayer package of the present invention has excellent hot water resistance, less appearance abnormality due to bending during and immediately after retort, and less deterioration of gas barrier property due to retort. Therefore, it is effective for food packaging, especially for retort food packaging.

Claims (5)

(57) [Claims] 1. A multilayer package comprising a layer containing an ethylene-vinyl alcohol copolymer (A) as an intermediate layer (2), a polyolefin resin, a polyolefin resin,
Steal resin, polyamide resin, polystyrene resin
And at least selected from polycarbonate resins
And a multilayer package comprising at least one resin layer (3) containing a boron compound. 2. On the side of the intermediate layer (2), a moisture permeability (40 ° C.,
Value measured under 90% RH) is 40 g / m ² · day or less.
The multilayer packaging according to claim 1, wherein the upper resin layer (1) is laminated.
body. 3. The resin layer (3) has a water vapor transmission rate (40 ° C.,
20 g / m ² · day or less (measured under 90% RH)
The resin layer according to claim 1 or 2, wherein a lower resin layer (4) is laminated.
Multilayer packaging. 4. An intermediate layer (2) comprising ethylene-vinyl alcohol.
51 to 98% by weight of a coal copolymer (A) and a polyamide,
Polyolefin, polyester and polycarbonate
At least one resin (B) selected from the group consisting of 2-49 weight
% Of the composition (C) comprising:
The multilayer package according to claim 1. 5. A multilayer according to any one of claims 1 to 4.
Boil-sterilized or retort-sterilized packaging material consisting of a package
Wood.