JP2982972B2 - Multilayer structure and multilayer package - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Technical Field of the Invention The present invention relates to a multilayer structure and a multilayer package having a high gas barrier property and thus excellent preservability of foods and the like, and more particularly to a high gas barrier property. The present invention also relates to a retort disinfecting packaging material which has never been seen before in view of having both excellent transparency.

B. Conventional technology Transparent plastic-based packaging materials, especially film-based packaging materials, are widely used in retort or boil-sterilized foods, with the major characteristics that they are lightweight, can be heated by a microwave oven, and that the contents can be seen. Used in However, plastic films lack their gas barrier properties, especially oxygen gas barrier properties.
Currently, it is used only for limited applications.

Ethylene-vinyl alcohol copolymer resin (hereinafter referred to as EV
Sometimes abbreviated as OH. ) Is a well-known fact that it is currently the thermoplastic resin with the highest gas barrier properties. However, when this is applied to a film for retort, whiteness remains after retort treatment due to water absorption of the EVOH layer, There is a problem that appearance defects such as peeling occur. In contrast, Japanese Patent Application Laid-Open No. 1-253442 discloses a resin in which EVOH is blended with a polyamide resin or the like as an intermediate layer, a resin having a high moisture permeability is used for an outer layer material, and a resin having a lower moisture permeability than the outer layer material is used for an inner layer material. There is a description of a film having excellent retortable transparency and gas barrier properties, but there is no description of a combination with an inorganic film.

In addition, Japanese Unexamined Patent Publication (Kokai) No. 1-1171633 describes a multilayer film for retort using a barrier material such as EVOH and an inorganic film in combination. However, it does not disclose that an inorganic film is provided in a layer made of a blend of an EVOH-based polyamide and the like, and further that the inorganic film is disposed inside the EVOH.

C. Problems to be solved by the present invention The multilayer film described in JP-A-1-253442 has two disadvantages. One is that when the adhesive layer is used thinly, the retort easily causes interfacial peeling, and the other is that the barrier property in the retort is not sufficient.

It has been confirmed that when peeling occurs, not only the appearance becomes poor, but also the barrier property decreases. To solve this problem, a method of increasing the thickness of the adhesive layer is conceivable, but the adhesive is expensive and greatly affects the cost of the packaging material. There has been a demand for a method of preventing the occurrence of peeling with a normal use amount.

Next, the oxygen permeation in the retort will be described. During the retort, the plastic container and the film-based packaging material usually pressurize the inside of the retort treatment tank with air to prevent the container from being ruptured due to a temperature difference between the inside and outside of the container and the peeling off of the seal portion (1 atm of air is common). ). In this case, oxygen permeates into the container during the retort. Although the multilayer film described in JP-A-1-253442 recovers the barrier property immediately after retorting, it has not been sufficient in terms of oxygen permeation in the retort. This is because EVOH absorbs a large amount of water early in retort sterilization, and as a result, the barrier property decreases. This has not been considered at all as an essential disadvantage of EVOH-based films. Although the oxygen consumption rate in the retort differs depending on the content food, for example, meat and the like are fast and may change color during the retort, and thus improvement is required.

D. Means for Solving the Problems The present inventors have observed the state of interfacial delamination in detail, studied this improvement method, and in parallel,
Extensive studies were conducted on the effects of food on oxygen permeation in retorts. As a result, the inorganic film (B), in particular,
It is said that a combination of an inorganic vapor-deposited film and a layer (A) of a composition such as EVOH and polyamide (hereinafter sometimes abbreviated as PA) is effective in improving barrier properties, especially in retort. Very useful results have been found.

Regarding the provision of the inorganic film (B) in the layer (A) of the composition, two effects were expected at the beginning to improve the barrier property. One is that the barrier property in the retort is improved by the oxygen barrier property of the inorganic film itself, and the other is that the water permeability of the inorganic film is small, so that the increase in the water content of the composition layer (A) is suppressed to some extent. The purpose of the present invention is to reduce barrier property deterioration due to moisture absorption.

However, when the inorganic film is disposed only inside the composition layer (A), moisture permeation from the outer layer side is extremely large, and there is no effect in terms of barrier properties and interface adhesiveness. Was expected.

However, in practice, a multilayer packaging material comprising the EVOH composition (A), an outer layer material (such as a biaxially stretched polyamide film) and an inner layer material (such as an unstretched polypropylene film) and the composition (A)
When an inorganic film (B) is disposed inside and a multilayer packaging material in which an outer layer material and an inner layer material are similarly retorted at the same time, the water absorption rate during retort is almost the same for both, the latter multilayer packaging body The barrier property in the retort was surprisingly much higher than the barrier value arithmetically predicted from the barrier property of the former multilayer package alone and the barrier property of the inorganic film. This indicates that the inorganic film has an effect other than suppressing moisture permeation.

In understanding the effect of the barrier property, the result of the above-described another phenomenon, that is, the difficulty of peeling is considered to be an important hint. There are various states in the peeling of the EVOH-based film by the retort. One of the states is a phenomenon in which the EVOH layer is softened by water absorption, and in some cases, flows near the interface to cause peeling.

In the present invention, the EVOH composition layer (A) and the inorganic film (B)
It is thought that the inorganic film (B) acts like one skeleton and suppresses the flow of the EVOH composition layer (B) itself because of strong adhesion. As a result, it can be understood that remarkable improvements in peeling and barrier properties were developed. Therefore, in the present invention, the EVOH composition layer (A)
It is preferable that the inorganic film (B) is adjacent to the inorganic film (B). However, the inorganic film (B) may function as a skeleton to suppress the flow of the EVOH composition layer (A) to some extent. It is free to provide another layer between the layers (A) and (B).

The ethylene-vinyl alcohol copolymer (EVOH), which is one of the resins forming the composition layer (A), may be any resin as long as the vinyl acetate unit in the copolymer of ethylene and vinyl acetate is hydrolyzed. In particular, the content of ethylene units is 20 to
65 mol%, preferably 20-50 mol%, especially 27-45 mol%, the degree of saponification of vinyl acetate units is 96% or more, especially 99%
The above are listed as melt indexes (190 ° C, 2
Examples of the value of 160 g) include a range of 0.2 to 60 g / 10 minutes. The EVOH referred to in the present invention may be modified with a copolymer monomer in a range of 5 mol% or less. Examples of the modified monomer include propylene, 1-butene, 1-hexene, 4-methyl-1 pentene, acrylic Acid esters, methacrylic esters, maleic acid, fumaric acid, itaconic acid, higher fatty acid vinyl esters, alkyl vinyl ethers, N- (2-dimethylaminoethyl) methacrylamides or quaternized products thereof, N-vinylpyrrolidone, N,
Examples thereof include N-butoxymethylacrylamide, vinyltrimethoxysilane, vinylmethyldimethoxysilane, and vinyldimethylmethoxysilane.

As the resin forming the composition layer (A), polyamide is first mentioned. Examples of the polyamide resin (PA) include 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), polyhexamethylene adipamide (nylon-6,6), Polyhexamethylene sebacamide (nylon-6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon- 10,8) or caprolactam / lauryl lactam copolymer (nylon-6 / 1
2), caprolactam / ω-aminononanoic acid copolymer (nylon-6 / 9), caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,
6), lauryl lactam / hexamethylene diammonium adipate copolymer (nylon-12 / 6,6), hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon-6,6 / 6,1)
0), ethylene diammonium adipate / hexamethylene diammonium adipate copolymer (nylon-2,
6 / 6,6), caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon-6 / 6,6 / 6,10), polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, Hexamethylene isophthalamide / terephthalamide copolymer and the like. Those obtained by modifying these PAs with aromatic amines such as methylbenzylamine and meta-xylylenediamine are also preferable. Meta-xylylenediammonium adipate is also preferred.

These PAs can be used alone or in a mixture of two or more.

Among these PAs, the most preferable one for the present invention is a caprolactam / lauryl lactam copolymer, that is, one having nylon-6 / 12 as a main component. The composition of the six and twelve components in nylon-6 / 12 is not particularly limited, but the twelve components are 5 to 60% by weight, more preferably 5 to 50% by weight.
% Is preferred. The relative viscosity is 2.0 ~
4.0, more preferably in the range of 2.4 to 3.9.

A polyamide having a polyether bond in the polymer chain may be obtained by adding a polyether diamine and a dicarboxylic acid (such as dimer acid) at the time of polycondensation of these PAs, especially nylon-6 / 12. In addition, during condensation, NH _{3 and} also aliphatic amines such as monoamine, hexamethylenediamine and laurylamine and aromatic amines such as meta-xylylenediamine are added to reduce the amount of carboxyl end groups in the polyamide. Those that have been made are also preferred. In this case, the amino group is preferably at least 5 × 10 ⁻⁵ equivalent / g and the carboxyl terminal group is preferably at most 3 × 10 ⁻⁵ equivalent / g.

PA is the best resin for forming the resin composition layer (A), but polyolefin, polyester, or polycarbonate can be used in place of PA.

As described in Japanese Patent Application Laid-Open No. 1-253442, despite the fact that these resins are distributed as island components in EVOH, the sensitivity of EVOH to water during retort, especially generation of whiteness and wavy patterns. It is surprising that it has a great effect on prevention. This mechanism is not always clear,
It is believed that a resin blend with a melting point higher than the retort temperature acts on EVOH and exerts such an effect.

Here, as the polyolefin, high-density, medium-density or low-density polyethylene, vinyl acetate, or butene, hexene, polyethylene copolymerized with α-olefins such as 4-methyl-1-pentene, polypropylene homopolymer, Polypropylene copolymerized with ethylene, or polypropylene copolymerized with α-olefins such as butene, hexene, and 4-methyl-1-pentene, poly-1-butene, and poly-4-methyl-1-pentene can be used. As a further improvement in the compatibility with EVOH, the above polyolefins are added to maleic acid, acrylic acid, methacrylic acid, coutronic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, ethyl acrylate , Methyl methacrylate, ethyl maleate, 2-ethylhexyl acrylate, acrylamide, methacrylamide, coconut oil aliphatic amide, maleimide, etc. to modify, carbonyl group 10-1400 mmol / 100 g polymer, especially 30 ~ Modified polyolefin and bark-modified polypropylene which are contained at a concentration of 1200 mmol / 100 g polymer can be preferably used.

As polyester (saturated polyester resin),
Poly (ethylene terephthalate), poly (butylene terephthalate), poly (ethylene terephthalate / isophthalate), poly (ethylene glycol / cyclohexane dimethanol / terephthalate) and the like are mentioned as typical examples, and further, as a copolymer component in these copolymers. Diols such as ethylene glycol, butylene glycol, cyclohexane dimethanol, neopentyl glycol, and pentane diol; or isophthalic acid, benzophenone dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl methane dicarboxylic acid, propylene bis (phenyl carboxylic acid), diphenyl oxide Dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, That for the additional inclusion of dicarboxylic acids such as ethyl succinic acid.

The composition ratio of EVOH forming the composition layer (A) to at least one resin selected from PA, polyolefin, polyester, and polycarbonate is 55 to 97% by weight: 4
It is 5 to 3% by weight, preferably 65 to 85% by weight: 15 to 35% by weight. When the components such as PA are small, when the multilayer package is subjected to the retort treatment, defects such as wrinkles and patterns tend to appear, and the interfacial adhesion with the inorganic film is reduced.
Conversely, a large amount of components such as PA is not preferred because the gas barrier properties are reduced.

The composition layer (A) may contain another polymer or an antioxidant, an ultraviolet absorber, a plasticizer, an antistatic agent, a lubricant, a coloring agent, a filler, and the like as long as the object of the present invention is not impaired. It can also be added. Other polymers include polystyrene resin, polyvinyl chloride resin, acrylic resin, polyvinylidene chloride resin, polyurethane resin and the like. Further, ethylenically unsaturated monomers (eg, olefins such as ethylene and propylene) containing 2 to 25 mol% of at least one component unit selected from vinyl acetate, acrylates and methacrylates, copolymers Alternatively, it is also possible to impart flexibility to the laminated structure by blending the saponified product. Further, specific examples of the additives other than the polymer include the following.

Stabilizers: calcium acetate, calcium stearate, hydrotalcites, metal salts of ethylenediaminetetraacetic acid and the like.

Antioxidant: 2,5-di-t-butylhydroquinone, 2,6
-Di-t-butyl-p-cresol, 4,4-thiobis-
(6-t-butylphenol), 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), octadecyl-3- (3 ', 5'-di-t-butyl-4'-hydroxy Phenyl) propionate, 4,4'-thiobis- (6-t-butylphenol) and the like.

UV absorbers: ethyl-2-cyano-3,3'-diphenylacrylate, 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 agent: pentaerythritol monostearate, sorbitan monopalmitate, sulfated oleic acid, polyethylene oxide, carbon wax and the like.

Lubricants: ethylene bis stearamide, butyl stearate and the like.

Colorant: carbon black, phthalocyanine, quinacridone, indoline, azo-based face amount, titanium oxide, red iron oxide, etc.

Fillers: glass fiber, asbestos, mica, sericite, talc, glass flake, ballastonite calcium silicate, aluminum silicate, calcium carbonate, etc.

In particular, a composition comprising 5 to 60% by weight of a filler selected from mica, sericite, talc and glass flakes and 95 to 40% by weight of the above composition (composition of EVOH and PA) is used as a layer (A). When used, it is preferable because the gas barrier property is improved. This is mainly applicable to containers such as cups and trays.

As a blending method for obtaining the composition for forming the layer (A), melt extrusion using a single-screw or twin-screw extruder (in the same direction or in a different direction), an intensive mixer, a continuous intensive mixer, or the like is performed, followed by cooling. A method of pelletizing is used.

The composition thus obtained is subjected to non-stretching or stretching (uniaxial stretching or biaxial stretching) after melt molding to form a sheet or a film and used as the layer (A). The molding method and the stretching method are not particularly limited, but ordinary methods can be used.

In the multilayer structure of the present invention, the layer (A) plays a role of a gas barrier material, and its thickness directly affects the barrier performance. The thickness of the layer (A) is 10 to 250
It is selected from the range of μ, usually from 15 to 100 μ.

Next, the inorganic film (B) laminated on the layer (A) will be described. Here, the inorganic film is desirably a transparent inorganic film. In particular, an inorganic oxide film and a nitride film are desirable in terms of cost, film strength, and the like. For example, aluminum oxide (AlO _x )
, Silicon oxide (SiO _x ), boron oxide (abbreviated below BO _x )
, Zirconium oxides, titanium oxides, magnesium oxides, aluminum nitrides, silicon nitrides and the like. Other examples include fluorides, alkali or alkaline earth metal oxides, and a plurality of these compounds.

These inorganic films are typically laminated by a vapor deposition method, and may be laminated on only one side of the layer (A) of the composition, or may be laminated on both sides. In the case of laminating only on one side, particularly in the case of retort, it is preferable to provide it inside the layer (B) of the composition (the side of the contents to be filled in the package). Although the inorganic film is sufficient as a thin film, its thickness is 100 to 500, preferably 200 to 400.

Since the multilayer structure thus obtained is particularly useful as a package, the package will be described below.

Examples of the structure of the multilayer package include a structure in which the inorganic film (B) is provided inside the layer (A) described above or a structure in which the inorganic film (B) is provided on both surfaces of the layer (A). As a preferred embodiment, there is a layer in which a high moisture permeable thermoplastic resin layer (C) is provided in the outer layer and a low moisture permeable thermoplastic resin (D) is provided in the inner layer.

Careful selection is necessary because the moisture permeability of the outer layer (C) affects the appearance and gas barrier properties of the multilayer package of the present invention, particularly the multilayer film-based packaging material after retorting.
When the multilayer package of the present invention is subjected to a so-called boil sterilization treatment at 100 ° C. or less, a resin having low heat resistance can be used, but if it exceeds 100 ° C., particularly 105 to 135 ° C.
In the case of being subjected to the retort treatment performed in the above, consideration for heat resistance is also necessary. Further, in the present invention, it was found that the higher the moisture permeability of the outer layer, the better the results, such as the more favorable the appearance after retort and the gas barrier property are. As a method for evaluating moisture permeability, JIS-Z-0
208, that is, a film of an arbitrary thickness is attached to a cup containing a hygroscopic agent, sealed and fixed, and then left in a constant temperature and humidity apparatus controlled at 40 ° C. and a relative humidity of 90%, A convenient method is to determine the weight increase rate by measuring it. Moisture permeability measured by this method (unit
g / m ² · day) having a value of 35 or more, especially 50 or more, and more preferably 100 or more, results in rapid recovery of the barrier property upon storage after retort treatment.

In the present invention, the resin of the outer layer (C) preferably used is PA, polyester or polycarbonate, and the resin most preferably used for the outer layer is PA. Examples thereof include various PAs as described above, and particularly, nylon-6, nylon-6,6, nylon-6 / 6,6 and the like. The thickness of this resin is 900 to 1100 g / m ² · day for a non-stretched product having a moisture permeability per 10 μm. The moisture permeability is substantially proportional to the thickness of the resin layer (C). Therefore, it is preferable to use a thinner resin. However, depending on the resin, it may not be possible to form the thinner resin.

In the case of non-stretched nylon, it is used at 275 μm or less, particularly at 110 μm or less, and more preferably at 15 to 40 μm. If it is biaxially stretched nylon, it can be used with a thickness of 97 μm or less, particularly 39 μm or less, and more preferably 10 to 20 μm. As other resin, polycarbonate resin (10μ thickness moisture permeability 120
150150 g / m ² · day, and it is preferable to use in a thickness range of 10 to 38 μm.

Further, polyester-based resins can also be employed for the purpose of the present invention. In particular, the polyethylene terephthalate resin is preferably used at 15 μm or less because the moisture permeability of the stretched film is 60 g / m ² · day per 10 μ thickness.

In addition, the moisture permeability (indicated in parentheses) per 10 μm of the resin film used for the outer layer (C), which can be used for the purpose of the present invention, is shown. Polyetherketone (143), polysulfone (490), polyethersulfone (500), polyetherimide (218), polyimide (208), polyarylate (510). On the other hand, polyvinyl chloride and polystyrene have high moisture permeability, which is suitable for the structure of the multilayer package of the present invention. However, since they have low heat resistance, they are limited to special applications such as low-temperature sterilization. In addition, polypropylene is usually difficult to use because of low moisture permeability (14 to 35 g / m ² · day per 10 μ). Polyethylenes are also unsuitable because of their low moisture permeability and low heat resistance.

A commercially available film can be used as the outer layer (C), and a non-stretched nylon film (CN), a biaxially stretched nylon film (ON), a biaxially stretched polyethylene terephthalate film (O-PET), a polycarbonate film, and the like are preferable. Particularly, a biaxially stretched film is the best.

The moisture permeability of the resin used for the outer layer (C) can be determined by measuring the moisture permeability of the single-layer film, and when the resin is laminated by a dry lamination method, the moisture permeability value of the single-layer film can be used. The effect on the moisture permeability of the adhesive in dry lamination is small and is not considered. Multi-layer package already laminated (laminated product or co-extruded product)
With regard to (2), the moisture permeability of the film obtained by forming the resin used in the outer layer into a single layer can be substituted for the value of the moisture permeability of the outer layer of the multilayer package. When the outer layer is composed of two or more layers, the moisture permeability of the multilayer outer layer can be determined by a conventional method from the moisture permeability of a single-layered film for each of the constituent resins. This concept of moisture permeability can be applied to the inner layer described below.

In the multilayer package of the present invention, it is important that the inner layer (D) has a lower moisture permeability than the outer layer. There is no particular limitation on the low water-absorbing thermoplastic resin used for the inner layer, but depending on the purpose, it is possible to obtain an excellent packaging material by considering points such as moisture permeability, heat resistance, heat sealing property, and transparency. it can. First, generally, the lower the moisture permeability of the inner layer, the higher the oxygen gas barrier property of the obtained multilayer structure. This is believed to be because the lower the moisture permeability of the inner layer, the lower the relative humidity of the intermediate layer. 20 g / m ² with the above-mentioned moisture permeability
Day or less, more preferably 10 g / m ² · day or less, for example, polypropylene 60μ (moisture permeability 6 g / m 2
Suitable results are obtained by using ² · day). Polypropylene can provide satisfactory results in terms of heat resistance, heat sealing properties, and transparency. Polypropylene is the preferred resin for the inner layer for many purposes, but other thermoplastics can be used. For example,
Polyolefin resins other than polypropylene, polyamide resins, polyester resins, polystyrene resins,
Examples thereof include a polyvinyl chloride resin, an acrylic resin, a polyvinylidene chloride resin, a polyacetal resin, and a polycarbonate resin. These resins are used alone or in a laminated form.

The film used for the inner layer (D) is a nylon film (CN or ON), a non-oriented polypropylene film (CPP), a biaxially oriented polypropylene film (OP
P), a polyethylene film, a polyvinylidene chloride film and the like are suitable, but when importance is placed on retort properties and heat sealing properties, it is desirable to use an unstretched polypropylene film for the innermost layer.

The moisture permeability of the inner layer (D) can be made lower than that of the outer layer (D) by selecting a resin or adjusting the thickness ratio of the inner layer and the outer layer. In the case where some layers of the laminated structure of the present invention are formed by a co-extrusion method, a general technique of laminating an intermediate layer and an inner layer with an adhesive resin interposed therebetween is adopted. Examples of the adhesive resin include polypropylene, polyethylene, and a resin obtained by modifying a polyolefin such as a copolymer of ethylene and a copolymerizable monomer (such as vinyl acetate or acrylate) with addition of maleic anhydride or the like. Is used.

Additives such as antioxidants, coloring agents, and fillers as described above may be added to the resin used for the outer layer or the inner layer.

The multilayer structure of the present invention can be manufactured by the following various laminating methods. Coextrusion method, dry lamination method,
In the sand laminating method, extrusion laminating method, and co-extrusion method, when PA is used for the outer layer, an adhesive resin layer may not be required between the layer and the intermediate layer, which is advantageous in the process. If an adhesive resin layer is provided, the moisture permeability of the outer layer and the adhesive resin layer together should be as high as possible, especially at 35 g /
It is preferable to consider it to be m ² · day or more. Dry lamination is generally performed by laminating three or more films of an outer layer, an intermediate layer, and an inner layer. Therefore, if necessary, the inorganic film is laminated at a desired position by a vapor deposition method before bonding.

The following are typical examples of the layer structure of the multilayer structure and the multilayer package of the present invention. (A) /
(B), (B) / (A) / (B), (C) / (A) /
(B) / (D), (C) / (B) / (A) / (B) /
(D), (C) / (A) / (B) / (C) / (D),
(C) / (B) / (A) / (B) / (A) / (D).

It is free to provide an adhesive layer between these layers as necessary, and it is also possible to provide another layer, for example, a resin layer, between each layer. Examples of such a layer configuration include (C) / (A) / (B) / (B) / (D).

The multilayer package of the present invention exhibits its characteristics most when used as a film packaging material, especially for a retort film. Applications of the film packaging material include lid materials, pouches, vacuum packaging, skin packs, deep drawing packaging, and rocket packaging. As the lid material, a method of sealing and sealing by a heat sealing method in a container mainly composed of polypropylene laminated with a gas barrier material is preferable. The lid material of the present invention has the advantages that it has a high level of holding properties, is also excellent in transparency, has no yellowish tint, etc., enhances its commercial value, and can be opened while checking the contents. Pouches are used in the form of three-sided seals, four-sided seals, pillows, gussets, standing pouches and the like. It can also be used in the form of a bag-in-box. The multilayer package of the present invention exhibits excellent performance not only as a film package but also as a cup or tray type container. In this case, as the resin of the inner layer, use polypropylene, high-density polyethylene, heat-resistant polyester, etc., thicker than the film material, 200 to 1200
It is preferred to be μ. As a method of forming the container, a method of coextruding and laminating the composition of the outer layer nylon and the intermediate layer on a thick sheet of the inner layer resin, or a laminate of the nylon film and the composition film (by dry lamination or coextrusion) After laminating to the inner layer resin sheet by dry lamination or sand lamination method,
A method of deep drawing with a vacuum pressure molding machine is suitably adopted.

The container using the outer package of the present invention in the form of a cover material, a pouch, a tray, and cups is subjected to a retort treatment or a boil sterilization treatment.These treatment methods include known hot water heating treatment methods and conditions. Can be adopted. For the retort treatment, various methods such as a recovery method, a displacement method, a steam method, a shower method, and a spray method are employed. Immediately after the retort treatment is performed, the packaging material of the present invention tends to be white and opaque.

For example, in the multilayer package of the present invention, a non-stretched nylon-6 film (30 μm, moisture permeability 300 g / m ² · day) is preferably used for the outer layer, and EVOH and nylon-6 / 12 are used for the intermediate layer. 80:20 parts by weight of a film (50μ) of a composition, and a non-stretched polypropylene film (60μ, moisture permeability 6g / m ² · day) laminated by dry lamination as an inner layer However, when this film is used as a cover material or a pouch, when it is retorted (120 ° C., 30 minutes), it becomes white and opaque immediately after the retort treatment. However, when this is subjected to a dehydrator and dried in a drier in the same manner as a normal retort container to remove water adhering to the surface, it becomes transparent under normal conditions within about one hour. Oxygen gas permeability (OTR) also reaches its equilibrium value within 12 hours. In order to measure the transparency and the recovery of the OTR more reliably, it is only necessary to carry out drying that is stronger than usual. As an example, at 50 ° C., 25 to 65 minutes, preferably 30 to 60 minutes, 80
In the case of ° C, the conditions include 3 to 35 minutes, preferably 5 to 10 minutes.

In the case where temporary opacity for several hours after the retort treatment as described above is not desired in the packaging material of the present invention, it can be achieved by setting the moisture permeability of the outer layer to 35 to 100 g / m ² · day. As the outer layer, polyethylene terephthalate (about 12
μ) or polycarbonate (15-30μ)
A preferable configuration is that the inner layer is made of polypropylene (50 μ or more).

Film wrapping materials of this configuration can be used under normal retort conditions (12
(0 ° C, 30 minutes) does not cause white opacity. However,
In this configuration, the OTR recovery tends to be slower than when the nylon film is used for the outer layer. In order to speed up the recovery of the OTR, it is desirable to use more intensive drying conditions, for example, at 80 ° C. for 10 minutes.

The above-described multilayer package of the present invention is filled with food and then the inside is degassed by known means as necessary, or nitrogen gas, carbon gas or the like is replaced with an inert gas, and then heat sealing or other means is used. Seal and then boil or retort sterilize.

As food, cooked or semi-cooked foods that are eaten as they are or heated before eating are suitable. Next, examples of food will be described.

Cooked curry, cooked bean curd, beef stew,
Borscht, meat sauce, sweet and sour pork, sukiyaki, chinese bean paste,
Happo greens, meat and potatoes, oden, asparagus boiled, sweet corn, mushroom, tuna cream boiled, consommé, potage, etc., miso soup, pork juice, kenchin soup, rice, red rice, pot rice, fried rice, pilaf, porridge, Attached foods such as spaghetti, buckwheat, udon, ramen, noodles, kamamai-no-moto, Chinese buckwheat noodles, boiled red bean, zenzai, anmitsu, meat dumpling, hamburger, beef steak, roast pork, pork soy, corn beef, ham, Sausage, grilled fish, grilled meat, grilled chicken, roast chicken, pork ketchup, fish meat, bacon, kamaboko, pudding, jelly, yokan, various pet foods. Further, the multilayer package of the present invention is a confectionery product such as orange, peach, pineapple, cherry, olive, soy sauce, sauce, vinegar, mirin, dressing, mayonnaise, ketchup, edible oil, miso, seasoning such as lard, tofu, etc. It is also excellent as a container for jam, butter, margarine, confectionery juice, vegetable juice, beer, cola, lemonade, sake, shochu, confectionery, wine, whiskey and brandy. Also, medicines such as Ringer's solution, pesticides,
Cosmetics, detergents, benzene, toluene, xylene, acetone, methyl ethyl ketone, normal hexane, cyclohexane, carbon tetrachloride, gasoline, kerosene, petroleum benzene,
It can also be used as a container for organic liquid chemicals such as thinner and grease.

E. Examples Example 1, Comparative Examples 1 and 3 As EVOH, the content of ethylene monomer unit was 28 mol%,
99.8% saponification degree, melt index (190 ° C, 2160g)
80 parts of resin pellets of 1.2 g / 10 min and PA-6 / 12 copolymer as PA [caprolactam unit and lauryl lactam unit in weight ratio of 80/20, melting point of 196 ° C., relative viscosity of 2.5] 2
After 0 parts of dry blending, the mixture was melt-extruded with a coaxial twin-screw extruder having a diameter of 30 mm (die temperature: 230 ° C.) to obtain blend pellets. After drying the blend pellets, a film was formed using an extruder having a full flight screw having a diameter of 40 mm and a coat hanger die having a width of 500 mm (temperature: 230 ° C.)
A transparent film of the composition with a thickness of 15μ was obtained.

Next, using an electron beam evaporation apparatus, the degree of vacuum was 1.0 × 10
^{At -5} Torr, a 2000 Å silicon oxide film was deposited on one side of the film.

Next, a commercially available biaxially stretched nylon-6 film (Unitika Emblem ON, thickness 15μ, moisture permeability 260 g / m ² day) was used for the outer layer, using the vapor deposition surface of this film as the inner layer and the intermediate layer.
For the inner layer, a commercially available unstretched polypropylene film (TOCELLO)
Dry lamination was performed using a CP, a thickness of 60 μm, and a moisture permeability of 7 g / m ² · day) to obtain a three-layer transparent film. As an adhesive for dry lamination, Takelac A-385 (manufactured by Takeda Pharmaceutical Co., Ltd.) was used as a main agent, and Takenate A-10 (manufactured by Takeda Pharmaceutical Co., Ltd.) was used as a curing agent. The application amount of the adhesive was 2.3 g / m ² . After lamination, 40 ℃, 3
Curing was carried out for a day.

This film was used as a pouch sealed inside on all sides with a size of 10 × 10 cm. The contents were water, tomato sauce and beef (raw). Using a retort device (Hisaka Manufacturing Co., Ltd., high-temperature high-pressure cooking sterilization tester, RCS-40RTGN) at 120 ° C
A 30 minute retort treatment was performed.

After the retort treatment, the film became whitish, but the film became transparent about 2 hours after the retort treatment,
The appearance was good without any delamination.

Immediately after the retort, the color of the contents taken out of the bag showed very little discoloration. From this, it is clear that the oxygen permeation amount in the retort was small. Furthermore, the film was taken out from the pouch after retort, the outside of the film was humidified to 65% RH, and the inside (food side) was humidified to 100% RH, and the oxygen transmission rate (OTR) was adjusted to OXTRAN-10 / at 20 ° C.
50A was measured using a (MOCON Co.), immediately after the retort is ^{1.0cc / m 2 · day · atm} , 12 hours after 0.4cc / m ² · day · atm
showed that. This is a normal EVOH film (Kuraray Eval Film EF-
F15μ) is 65% RH on both sides and the value before retort is 0.5, which indicates that the storage performance is excellent.

Furthermore, the value of 0.4 does not include the silicon oxide film,
The value after retorting of the pouch using the above EVOH composition layer 1.
6 (Comparative Example 1 to be described later) and 1.1 (Comparative Example 3 to be described later) when the silicon oxide film alone and the barrier resin layer were not included were significantly larger than the value 0.7 calculated from each case alone.

Examples 2-3 When the silicon oxide film is disposed on both sides of the composition layer (transparent film) in Example 1 (Example 2), the effect is also obtained.
Furthermore, the OTR after retort was as small as 0.1. In Example 3, a silicon oxide film was deposited on biaxially stretched polyethylene terephthalate, and the deposited surface and the composition layer (transparent film) were used.
Was laminated, but surprisingly, this configuration had the same effect.

Examples 4 and 5 The same effect was obtained when the outer layer was changed as shown in Table 1 in Example 1.

Comparative Examples 1 and 2 In Example 1, when a silicon oxide film was not used and the adhesive layer was thin as in Example 1, delamination occurred between the films, and a large amount of adhesive was used as shown in Comparative Example 2. Needed to use. Further, in this case, oxygen permeation in the retort was large, and when the filled beef was taken out after the retort, the surface turned brown.

Comparative Examples 3 to 5 When a high barrier type vinylidene chloride resin (PVDC) is used in combination with a silicon oxide film (Comparative Example 5), the barrier effect is obtained when PVDC is used alone (Comparative Example 4) and when a silicon oxide film is used alone (Comparative Example 4). This is consistent with the value calculated from Comparative Example 3), and no peculiar effect is exhibited by the combined use.

Examples 6 to 8 and Comparative Examples 6 and 7 In Example 1, the case where the composition of the EVOH composition was changed is shown. Those having no PA content and conversely having too much PA caused poor appearance.

There was no significant difference when changing the types of EVOH and PA.

Comparative Example 8 In Example 1, when a film obtained by vapor-depositing a silicon oxide film on a composition layer was used as an intermediate layer with the vapor-deposited surface as an outer layer side,
The contents after retort had hardly changed,
The film was slightly whitened and the appearance was impaired.

 The above results are summarized in Tables 1 and 2.

Example 9 A film having a thickness of 150 μ was obtained in the same manner as in Example 1 except that the EVOH composition was used. Subsequently, the film was simultaneously stretched 3.3 times in length and 3.3 times in width at 80 ° C. using a film stretch tester × 6H type manufactured by Toyo Seiki, and heat-set at 150 ° C. The resulting film was 15μ. Thereafter, after vapor deposition in the same manner, the multilayer was formed and retorted.

The multilayer film after the retort had the same good appearance as in Example 1. The oxygen permeability coefficient measured at 12 hours after retort is 0.3, which is smaller than that in the case of no stretching. This is generally considered to be due to the same effect as the improvement of the barrier performance by biaxial stretching, that is, to the oriented crystallization of molecules.

Example 10 The film shown in Example 1 was used as a lid material, heat-sealed in a PP container, and retorted in the same manner as in Example 1. The appearance after retort was good. Also, the OTR was 0.4.

Example 11 A co-extruded multilayer film consisting of two layers was produced using a feed block type co-extrusion apparatus having two extruders and a T-die. The composition is outer polyamide (Mitsubishi Chemical Industries, Ltd.)
Novamid 1020, thickness 15μ), the inside is the composition used in Example 1 (thickness 15μ). An unstretched polypropylene film was dry-laminated as in Example 1 on the vapor-deposited side of the film in which an inorganic vapor-deposited film was formed on the composition side of this film as in Example 1. Using this film, retorting was performed in the same manner as in Example 1.

The outside of the film after the retort was good, there was almost no discoloration of the contents, and the OTR was 0.4, which was the same result as in Example 1.

Example 12 In Example 1, 20 parts of maleic anhydride-modified PP (Admer QF-500 manufactured by Mitsui Petrochemical Industries, Ltd., melting point 165 ° C.) was melt-blended in the same manner as in Example 1 except that the resin to be blended with EVOH was changed to PA. A blend pellet was obtained. Hereinafter, a single-layer film was obtained in the same manner. Although the film was slightly cloudy as compared with that of Example 1, the film was uniform. After depositing an inorganic film in the same manner as in Example 1, a multilayer film was obtained and retort treatment was performed. The appearance after the retort was the same transparency as before the retort, no delamination was observed, and there were no other abnormalities. The OTR after retort was 0.4.
Therefore, it is sufficiently applicable to a material that does not require transparency as much as the packaging material of Example 1.

Example 13 A film was obtained by blending 20 parts of polyethylene terephthalate (Kuraray KS750R manufactured by Kuraray Co., Ltd., melting point: 252 ° C.) in Example 1 with the exception that the resin to be blended with EVOH was changed to PA. The film had good transparency. However, a slight lumps were generated on the film during the long-term film-forming operation. This is thought to be due to the reaction between EVOH and polyethylene terephthalate. Thereafter, a sample was prepared and retorted in the same manner as in Example 1. The appearance was good and the OTR was 0.4.

F. Effects of the Invention The multilayer structure and the multilayer package of the present invention
An object of the present invention is to solve a major drawback of the OH-based retort packaging material, that is, a decrease in oxygen barrier property during retort.

Claims (7)

(57) [Claims] 1. An ethylene-vinyl alcohol copolymer resin containing 20 to 65 mol% of ethylene monomer units in an amount of 55 to 97% by weight.
And at least one resin 45 selected from polyamide, polyolefin, polyester and polycarbonate
A multilayer package having an inorganic film (B) inside a layer (A) of a composition comprising 3% by weight. 2. A layer (A) as an intermediate layer, an outer layer (C) of a highly moisture-permeable thermoplastic resin on the outside, an inorganic film (B) on the inside of the layer (A), and a low permeability on the inside. The multilayer package according to claim 1, which has an inner layer (D) of a wet thermoplastic resin. 3. The multilayer package according to claim 2, wherein the outer layer (C) is a resin layer having a moisture permeability (measured at 40 ° C. and 90% RH) of 35 g / m ² · day or more. 4. The multilayer package according to claim 2, wherein the inner layer (D) is a resin layer having a moisture permeability (measured at 40 ° C. and 90% RH) of 20 g / m ² · day or less. 5. A multilayer package for sterilizing boil or retort comprising the multilayer package according to any one of claims 1 to 4. 6. A food package obtained by filling the multilayer package according to any one of claims 1 to 4 with food and sterilizing by boiling or retort. 7. The multilayer package according to any one of claims 1 to 6, wherein the composition of the intermediate layer (A) is a composition of an ethylene-vinyl alcohol copolymer and a polyamide.