JPH0586918B2 - - Google Patents

Description

[Detailed description of the invention]

A: Technical Field of the Invention The present invention relates to a multilayer packaging for foods, etc., which has excellent storage stability due to its high gas barrier properties, and has the following advantages: An unprecedented multilayer film packaging material for retort sterilization (hereinafter referred to as retort) containers,
In particular, it relates to retort lid materials or retort pouches. The present invention also includes a cup-shaped or tray-shaped container for a retort having a high gas barrier property. B. Prior art Lid materials for retort containers include laminate films of aluminum foil and polyolefin (especially polypropylene) film, and double-seam metal lids. Both have almost perfect gas barrier properties, but are opaque and the contents cannot be seen. There are drawbacks. Being able to see through the contents is necessary to stimulate consumers' desire to purchase, but it is also necessary to prevent the contents from spilling when opening the package, or to prevent the contents from spilling when opened, or by partially punching a hole in the lid and placing it in a microwave, etc. This function is also necessary for heating. However, currently available plastic film transparent lid materials are currently used only for limited purposes because they lack gas barrier properties, particularly oxygen gas barrier properties. That is, the typical gas barrier resin currently used as a lid material is polyvinylidene chloride polymer (mainly vinylidene chloride-vinyl chloride copolymer, hereinafter sometimes abbreviated as PVDC), and the outer layer is biaxially stretched. It is used in the form of a film made by laminating a nylon film (hereinafter sometimes abbreviated as ON) and a polypropylene (hereinafter sometimes abbreviated as PP) film as an inner layer as a sealing layer using a dry lamination method. Oxygen permeation rate of PVDC (hereinafter abbreviated as OTR)
is 3 to ^20c.c./m2・day・atm around 20μ.
In order to obtain food shelf life of 6 months under normal conditions, the OTR of packaging material is approximately 0.8cc/m ²・day・
Considering that ATM is required, PVDC requires a thickness of at least 75μ. however,
PVDC with a thickness of 75μ has a high haze and a strong yellowish tinge, so it is usually 15 to 30μ, but only about 50μ is used in some applications that require special barrier properties. The shelf life of the wood is not sufficient. In recent years, vinylidene chloride-acrylic acid ester copolymer films having particularly high gas barrier properties have been known as PVDC polymers. the
OTR is 1.2cc・20μ/m ²・day・atm. However, this polymer has the disadvantage that it becomes white and opaque when subjected to retort treatment, and its OTR is also high.
It cannot be used as a transparent lid material for retorts. Gas barrier resins other than PVDC that are used for lid materials include metaxylylene diamine-adipic acid condensate (MX-nylon), polyamide,
Alternatively, there are PVDC-coated polyamides, etc., but all of them have low oxygen gas barrier properties and are only used for a limited number of foods that undergo little oxidative deterioration, or for foods that are distributed at low temperatures. Furthermore, film packaging materials for retort containers, such as pouches, are under even harsher conditions. In other words, the lid material is a part of the container, whereas the transparent film packaging materials used for pouches, skin packs, shrink packaging, deep-draw packaging, rocket packaging, etc. constitute the entire container. Currently, there are no transparent film packaging materials for retorts that have sufficient gas barrier properties, and even those that have been sterilized in retorts are distributed at low temperatures. Ethylene-vinyl alcohol copolymer resin (hereinafter sometimes abbreviated as EVOH) is currently a thermoplastic resin with the highest gas barrier properties.
0.3 (60%RH) to 0.75 (80%RH) cc per 20μ
A general-purpose brand that shows an OTR of ^m2・day・atm is used (EVALF type manufactured by Kuraray Co., Ltd.). EVOH is widely used as a gas barrier material in retort containers such as cups and trays.
EVOH uses a multilayer structure in which the middle layer is made of PP with low moisture permeability for the inner and outer layers. Also,
PP layer and EVOH to further improve storage stability
A method of containing a desiccant in the adhesive resin layer between the layers (US Pat. No. 4,407,897) or a method of containing a desiccant in the EVOH layer itself (US Pat. No. 4,407,897)
4425410). Furthermore, Special Publication No. 61-24254 (British Patent No.
2006108) describes a food plastic bottle consisting of an outer layer made of polyamide, an intermediate layer made of gas barrier resin (e.g. EVOH), and an inner layer made of polyolefin or thermoplastic polyester. It is described that a blend consisting of /66 copolymerized nylon 50:50 (weight ratio) is used. However, as stated in the patent publication, polyamide (nylon) is 50wt%
If you use a blend with EVOH that contains
Not only does the gas barrier property deteriorate, but there is also a tendency for the multilayer package to retain a whitish tinge during storage after retort treatment. This is clear from Comparative Example 6, which will be described later. Furthermore, Special Publication No. 59-38103 (British Patent No.
1545096) has a moisture-resistant resin with low moisture permeability or a creep-resistant resin layer as the inner and outer layers, and a gas barrier resin blend layer (e.g., a blend of EVOH and polyamide at a weight ratio of 90:10 to 10:90).
It describes a container with an intermediate layer of
There is no mention of providing a resin layer with relatively high moisture permeability as the outer layer and a resin layer with low moisture permeability as the inner layer, and using a layer that is a blend of EVOH and polyamide in a relatively small amount as the intermediate layer. . C Problems to be Solved by the Present Invention Although EVOH produces excellent retort containers when sandwiched with thick PP layers as inner and outer layers, and therefore used as hard containers such as cups and trays, Materials used for flexible film packaging such as wood and pouches cannot be used for retort packaging. This is because the resin in the inner and outer layers must be made thinner in order to be used as a film packaging material, so a high amount of water enters the EVOH layer during retort, resulting in a marked decrease in gas barrier properties and a cloudy EVOH layer. This is because there are serious problems such as the formation of wavy wrinkles and patterns, and the appearance of the material makes it unsuitable for practical use as a gas barrier film packaging material. D. Means for Solving the Problems The present inventors have discovered that the mechanism by which the gas barrier properties of the EVOH layer decreases due to retort processing, and the generation of cloudiness and wavy wrinkle patterns occurs during retort processing.
Along with the water absorption of the EVOH layer, the
The state of water inside the EVOH layer, and even during storage
We hypothesized that the behavior of water, which decreases from the EVOH layer through the outer layer, is significantly related, and based on this hypothesis, we conducted extensive studies on the effects of the EVOH composition and the influence of the inner and outer layer resins. As a result, instead of using EVOH as the interlayer, EVOH55-97% by weight and polyamide (less than
A composition consisting of 3 to 45% by weight of at least one resin selected from polyolefin, polyester, and polycarbonate (sometimes abbreviated as PA), polyolefin, polyester, and polycarbonate is used as the outer layer, and the moisture permeability of the outer layer (40
℃, 90% RH) of 40 g/m ² ·day or more, for example, an outer layer mainly composed of at least one resin selected from PA, polyester and polycarbonate, in particular PA. In addition, when a hydrophobic thermoplastic resin with a lower moisture permeability than the outer layer is used as the inner layer, especially a resin with a low moisture permeability such as PP, it does not cause appearance defects such as cloudiness, wrinkles, or patterns.
Equipped with EVOH's original advanced gas barrier properties,
Moreover, it is possible to obtain a highly practical transparent film packaging material for boiling sterilization or retort sterilization that does not cause blocking between packaging bodies, and in particular, exhibits excellent performance as lid material and pouches, which is the conventional wisdom regarding EVOH. The present invention was completed by confirming the surprising fact that PA etc. as a modifier in the interlayer composition
Even though it is distributed as an island component in the EVOH layer, it has a large influence on the behavior of the EVOH component in the matrix during retort. Although it was a conventional method to use a resin with as low moisture permeability as possible, it was found that it is effective to place a resin with high moisture permeability in the outer layer, which was finally adopted in the present invention. The methods used were completely different from the general understanding and expectations at the time the study began. Ethylene-vinyl alcohol copolymer (EVOH), which is one of the resins forming the composition of the intermediate layer (B) of the present invention, is a product obtained by hydrolyzing vinyl acetate units in a copolymer of ethylene and vinyl acetate. In particular, the content of ethylene units is 20 to 50 mol%, especially 27 to 40 mol%, and the degree of saponification of vinyl acetate units is 96%. Above all, those with 99% or more are mentioned, and the melt index (190℃,
2160g) is exemplified in the range of 0.2 to 60g/10 minutes. Further, EVOH referred to in the present invention may be modified with a copolymerizable monomer in a range of 5 mol% or less, and such modifying monomers include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, , acrylic ester, methacrylic ester, maleic acid, fumaric acid, itaconic acid, higher fatty acid vinyl ester, alkyl vinyl ether, N-(2-dimethylaminoethyl) methacrylamide or its quaternized product, N-vinylimidazole, or Its quaternary compound, N-
Examples include vinylpyrrolidone, N,N-butoxymethylacrylamide, vinyltrimethoxysilane, vinylmethyldimethoxysilane, and vinyldimethylmethoxysilane. In addition, as the polyamide resin (PA) which is one of the other resins forming the composition of the intermediate layer (B), polycapramide (nylon-6), poly-
ω-aminoheptanoic acid (nylon-7), poly-
ω-aminononanoic acid (nylon-9), polyundecaneamide (nylon-11), polylauryllactam (nylon-12), polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-1) 4,6), polyhexamethylene adipamide (nylon-6,6),
Polyhexamethylene sebamide (nylon-6,
10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon-10,6), polydecamethylene sebacamide ( Nylon-10,8), caprolactam/lauryllactam copolymer (nylon-
6/12), caprolactam/ω-aminononanoic acid copolymer (nylon-6/9), caprolactam/hexamethylene diammonium adipate copolymer (nylon-6/6,6), lauryl lactam/hexamethylene diammonium adipate copolymer (nylon-12/6,6), hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer (nylon-
6,6/6,10), ethylene diammonium adipate/hexamethylene diammonium adipate copolymer (nylon-2,6/6,6), caprolactam/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer Combined (nylon-6/6, 6/6, 10),
Examples include polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, hexamethylene isophthalamide/terephthalamide copolymer, and the like. Among these PAs, the most suitable for the present invention is caprolactam/lauryllactam copolymer, ie, nylon-6/12. The composition of the 6th and 12th components in Nylon-6/12 is not particularly limited, but the 12th component is 5 to 60% by weight,
More preferably, it is 10 to 50% by weight. Further, its relative viscosity is in the range of 2.0 to 3.6, more preferably 2.2 to 3.2. Polyether diamines and dicarboxylic acids (dimer acid, etc.) may be added during the condensation of these PAs, especially nylon-6/12, to form a polyamide having polyether bonds in the polymer chain.
There are also polyamides in which the amount of carboxyl end groups in the polyamide is reduced by adding aliphatic amines such as hexamethylene diamine or lauryl amine or aromatic amines such as metaxylylene diamine or methylbenzyl amine during condensation. preferable. In that case, it is preferable that the amino terminal group is 8×10 ⁻⁵ equivalent/g or more, and the carboxyl terminal group is 3×10 ⁻⁵ equivalent/g or less. Even though PA in the composition is often distributed as an island component within the EVOH layer, it has a significant effect on the sensitivity of EVOH to water during retorting, especially in preventing whitening, waving, and streaking. It is surprising that it has an effect. The detailed mechanism leading to such remarkable effects is not necessarily clear.
PA is the best modifier to be added to EVOH, but polyolefins, polyesters, and polycarbonates can also be used. Considering that even if polyolefin, polyester, polycarbonate, etc. are blended with EVOH instead of PA, some effect can be obtained in preventing the occurrence of wave patterns and stripes after retorting at 120℃. It is believed that a high resin blend will have such an effect. For purposes of retort or boil sterilization where the heating temperature is lower (for example, 105 to 115°C), a blend of medium density polyethylene and low density polyethylene also has some effect on the generation of wavy and striped patterns. However, PP, PP modified with maleic anhydride,
Blends of polyethylene, polyester resin, and EVOH have the disadvantage of inferior transparency compared to PA and EVOH blends, so PA blends are preferred for film packaging materials such as lids where transparency is important. For cups, trays, etc. that do not require transparency, blends of the resins mentioned above, such as PP, can be used. Here, the polyolefins include high density,
Medium density or low density polyethylene, vinyl acetate, acrylic ester, polyethylene copolymerized with α-olefins such as butene, hexene, 4-methyl-1-pentene, ionomer resin, polypropylene homopolymer, ethylene graft copolymer Polymerized polypropylene, or ethylene, butene, hexene, 4-methyl-1-
Polypropylene copolymerized with α-olefins such as pentene, poly-1-butene, and poly-4-methyl-1-pentene can be used. As polyolefins with improved compatibility with EVOH, maleic acid, acrylic acid, methacrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, citraconic anhydride,
Ethyl acrylate, methyl methacrylate, ethyl maleate, 2-ethylhexyl acrylate,
Modified polyolefins containing carbonyl groups at a concentration of 10 to 1400 mmol/100 g of polymer, particularly 30 to 1200 mmol/100 g of polymer, which have been modified by the action of acrylamide, methacrylamide, coconut oil aliphatic amide, maleimide, etc. Modified polypropylene can be used more preferably. Representative examples of polyester (saturated polyester resin) include poly(ethylene terephthalate), poly(butylene terephthalate), poly(ethylene terephthalate/isophthalate), and poly(ethylene glycol/cyclohexanedimethanol/terephthalate). Furthermore, these polymers may contain diols such as ethylene glycol, butylene glycol, cyclohexanedimethanol, neopentyl glycol, and pentanediol as copolymerization components, or isophthalic acid, benzophenonedicarboxylic acid, diphenylsulfonedicarboxylic acid, and diphenylmethane. Dicarboxylic acid, propylene bis(phenylcarboxylic acid), diphenyl oxide dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,
Those containing dicarboxylic acids such as sebacic acid and diethylsuccinic acid can be used. The composition ratio of EVOH and PA forming the composition of the intermediate layer (B) is 55 to 97% by weight: 45 to 3% by weight,
More preferably 65-85% by weight: 15-35% by weight. If components such as PA are low, defects in appearance such as wrinkles and patterns tend to appear when multilayer packaging is subjected to retort processing. On the other hand, if the content of components such as PA is too large, not only the gas barrier properties will be lowered, but also a tendency for the multilayer package to remain whitish when stored after retort processing is undesirable. In addition, the composition of the intermediate layer (B) may contain other polymers, antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants,
Colorants, fillers, etc. can be added. Examples of other polymers include polystyrene resins, polyvinyl chloride resins, acrylic resins, polyvinylidene chloride resins, and polyurethane resins. Among these, ethylenically unsaturated monomers (e.g., olefins such as ethylene and propylene) containing 2 to 25 mol% of at least one component unit selected from vinyl acetate, acrylic esters and methacrylic esters It is possible to impart flexibility to the laminated structure by blending a polymer or a saponified product thereof. Further, specific examples of additives other than polymers include the following. Stabilizers: Calcium acetate, calcium stearate, hydrotalcites, metal salts of ethylenediaminetetraacetic acid, etc. Antioxidants: 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'-hydroxyphenyl)propionate, 4,4'-thiobis-( 6-t-butylphenol) etc. 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, etc. Plasticizers: Dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate esters, etc. Antistatic agents Pentaerythritol monostearate, sorbitan monopalmitate, sulfated oleic acid, polyethylene oxide, carbo wax, etc. Lubricants: ethylene bisstearamide, butyl stearate, etc. Coloring agent: carbon black, phthalocyanine,
Quinacridone, indoline, azo pigments, titanium oxide, red iron oxide, etc. Fillers: Glass fiber, asbestos, mica, sericite, talc, glass flakes, ballastonite, calcium silicate, aluminum silicate, calcium carbonate, etc. In particular, 95 to 60% by weight of fillers selected from mica, sericite, talc and glass flakes and the above compositions (compositions of EVOH and PA, etc.)
When a composition with 40% by weight is used as an intermediate layer,
It is preferable that gas barrier properties are improved. This is mainly applicable to containers such as cups and trays. The blending method used to obtain the composition includes melt extrusion using a single or twin screw extruder (in the same direction or in different directions), an intensive mixer, a continuous intensive mixer, etc., followed by pelletizing while cooling. . In the multilayer packaging of the present invention, the above composition plays the role of a gas barrier material, and in particular, its thickness directly affects the barrier performance. The thickness of the intermediate layer is selected from a range of 10 to 250μ, usually from a range of 20 to 100μ. Next, the resin used for the outer layer in the multilayer package of the present invention will be described. The moisture permeability of the outer layer must be carefully selected because it affects the appearance and gas barrier properties of the multilayer packaging of the present invention, particularly the multilayer film packaging material, after retort treatment. In addition, when the multilayer packaging of the present invention is subjected to so-called boil sterilization treatment at temperatures below 100°C, resins with low heat resistance can be used; however, when the temperature exceeds 100°C, especially 105
When subjected to retort treatment carried out at a temperature of 135°C to 135°C, consideration must also be given to heat resistance. Furthermore, in the present invention, it has been found that the higher the moisture permeability of the outer layer, the better the appearance and gas barrier properties after retorting, resulting in better results. JIS-Z- is a method for evaluating moisture permeability.
The method shown in 0208 is to attach the film to a cup containing a moisture absorbent, seal it, fix it, and then leave it in a constant temperature and humidity device adjusted to 40℃ and 90% relative humidity to control the rate of weight increase. A convenient method is to obtain it by measurement. It is preferable to select the material so that the water vapor permeability (unit: g/m ² ·day) measured by this method shows a value of 40 or more, particularly 100 or more, and more preferably 200 or more. If an appearance with a value lower than 40 is used, recovery of gas barrier properties during storage after retort treatment is slow. In the present invention, the resin for the outer layer (A) that is preferably used is PA, polyester, or polycarbonate, and the resin for the outer layer that is preferably used is
It's a PA. Examples include the various types mentioned above.
PA, but especially nylon-6, nylon-6,6, nylon-6/6,6
etc. are preferred. The moisture permeability of this resin per 10 μm of thickness is 900 to 1100 g/m ² ·day for an unstretched product and approximately 390 g/m ² ·day for a biaxially stretched product. Therefore, if unstretched nylon is used, the thickness is 275μ or less, especially 110μ or less, and more preferably 15 to 40μ. Biaxially stretched nylon can be used in a thickness of 97μ or less, especially 39μ or less, more preferably 10 to 20μ. Other resins include polycarbonate resin (moisture permeability of 10μ thickness is 120-150g/m ²・day)
It is preferable to use the film in a thickness range of 10 to 38μ. Polyester resins may also be employed for the purposes of the present invention. Especially for polyethylene terephthalate resin, the moisture permeability of the stretched film is around 10 μm in thickness.
Since it is 60g/m ² ·day, it is used at 15μ or less. Other resins used for the outer layer that can be used for the purpose of the present invention and their moisture permeability per 10μ (indicated in the box) are shown below. Polyetherketone (143), polysulfone (490), polyethersulfone (500), polyetherimide (218), polyimide (208), polyarylate (510). On the other hand, polyvinyl chloride and polystyrene have high moisture permeability, making them suitable for constructing the multilayer packaging of the present invention, but their low heat resistance limits them to special uses such as low-temperature sterilization. Further, polypropylene has low moisture permeability (14 to 35 g/m ² ·day per 10 μm), so its use is usually difficult. Polyethylene is also not suitable because it has low moisture permeability and low heat resistance. The moisture permeability of the resin used for the outer layer can be measured by the moisture permeability of a single layer film, and if these are laminated by dry lamination, the value of the moisture permeability of the single layer film can be measured. The effect on the moisture permeability of the adhesive in dry lamination is small and is not considered. For multilayer packages that are already laminated (laminated products or coextruded products), the moisture permeability of the single layer resin film used for the outer layer is determined by the moisture permeability of the outer layer of the multilayer package. Can be substituted. When the outer layer is composed of two or more layers, the water vapor permeability of the multilayer outer layer can be determined by a conventional method from the water vapor permeability of a single layer film for each of the constituent resins. This concept of moisture permeability can also be applied to the inner layer described below. In the multilayer package of the present invention, it is important that the inner layer has a lower moisture permeability than the outer layer. There are no particular restrictions on the hydrophobic thermoplastic resin used for the inner layer, but
Depending on the purpose, excellent packaging materials can be obtained by considering moisture permeability, heat resistance, heat sealability, transparency, etc. First, generally speaking, the lower the moisture permeability of the inner layer, the higher the oxygen gas barrier properties 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. The above-mentioned moisture permeability is preferably 20 g/m ² ·day or less, more preferably 10 g/m ² ·day or less, for example, polypropylene 50 μ (moisture permeability 7
Suitable results are obtained by using (g/m ² ·day). Polypropylene can also provide satisfactory results in terms of heat resistance, heat sealability, and transparency. Although polypropylene is the preferred resin for the inner layer for many purposes, other thermoplastic resins can also be used. Examples include polyolefin resins other than polypropylene, polyamide resins, polyester resins, polystyrene resins, polyvinyl chloride resins, acrylic resins, polyvinylidene chloride resins, polyacetal resins, polycarbonate resins, etc. These resins may be used alone or in a stack. Making the moisture permeability of the inner layer lower than that of the outer layer can be achieved by selecting a resin or adjusting the thickness ratio of the inner layer and the outer layer. Also,
When the laminated structure of the present invention is produced by coextrusion, a common technique is employed in which the main resins of the intermediate layer and inner layer are laminated with adhesive resin sandwiched therebetween. Adhesive resins include polypropylene, polyethylene,
Alternatively, a resin modified by adding maleic anhydride or the like to a polyolefin such as a copolymer of ethylene and a monomer copolymerizable with ethylene (vinyl acetate, acrylic ester, etc.) may be used. Additives such as antioxidants, colorants, fillers, and the like 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 lamination methods. These include a coextrusion method, a dry lamination method, a sand lamination method, an extrusion lamination method, a coextrusion lamination method, and the like. In the coextrusion method, when PA is used for the outer layer, an adhesive resin layer may not be required between the outer layer and the intermediate layer, which is advantageous in terms of the process. When an adhesive resin layer is provided, it is preferable to make sure that the combined moisture permeability of the outer layer and the adhesive resin layer is as high as possible, particularly 40 g/m ² ·day or more. Dry lamination is generally performed by bonding three or more types of films, an outer layer, an intermediate layer, and an inner layer, using an adhesive. Commercially available films can be used for the outer layer, and non-oriented nylon film (CN), biaxially oriented nylon film (ON), biaxially oriented polyethylene terephthalate film (PET), polycarbonate film, etc. are suitable. In particular, biaxially stretched films, and more particularly biaxially stretched nylon films, are best. In addition to nylon film (CN or ON), suitable films for the inner layer include non-oriented polypropylene film (CCP), biaxially oriented polypropylene film (OPP), polyethylene film, polyvinylidene chloride film, etc. When retortability and heat sealability are important, it is desirable to use an unstretched polypropylene film for the innermost layer.
Good results can also be obtained by laminating the intermediate layer and inner layer by coextrusion, and then laminating films such as ON and CN by dry lamination. The characteristics of the multilayer packaging body of the present invention are best exhibited when it is used as a film packaging material, particularly as a film packaging material for retorts. Applications of film packaging materials include lid materials, pouches, vacuum packaging, skin packs, deep drawing packaging, and rocket packaging. The lid material is preferably sealed by a heat sealing method on a container mainly made of polypropylene laminated with a gas barrier material. The lid material of the present invention has high retention properties, excellent transparency, and no yellowish tinge, increasing commercial value, and has the advantage that the lid can be opened while checking the contents. Pouches are used in the form of three-sided seals, four-sided seals, pillows, gazettes, standing pouches, etc. It can also be used in bag-in-box form. The multilayer packaging body of the present invention exhibits excellent performance not only as a film packaging but also as a cup or tray type container. In this case, the resin for the inner layer is made of polypropylene, high-density polyethylene, heat-resistant polyester, etc., and is thicker than the film material by 200 to 1200 μm. The method for molding this container is to co-extrude and laminate the nylon outer layer and the composition for the intermediate layer onto a thick sheet of resin for the inner layer;
Alternatively, a method is adopted in which a laminate of a nylon film and a film of the composition (by dry lamination or coextrusion method) is laminated on an inner layer resin sheet by dry lamination or sand lamination method, and then deep drawing is performed using a vacuum-pressure forming machine. . Containers using the multilayer packaging of the present invention in the form of lids, pouches, trays, and cups are subjected to retort treatment or boil sterilization treatment, but these treatments include known hot water heating treatment methods and conditions. Can be adopted. Various methods are used for retort processing, such as a recovery method, a displacement method, a steam method, a shower method, and a spray method. Immediately after retorting, the packaging material of the present invention tends to become white and opaque. For example, among the multilayer packaging bodies of the present invention, suitable examples of film packaging materials include unstretched nylon-6 film (30μ, moisture permeability 300g/m ² ·day) as the outer layer;
The middle layer is a film (50μ) of a composition of 80:20 parts by weight of EVOH and nylon 6/12, and the inner layer is a film (50μ) of unstretched polypropylene, moisture permeability 7g/
This film is laminated using the dry lamination method (120°C, 30°C ⁾ using this film as a lid material or pouch.
When processed, it becomes white and opaque immediately after retort processing. However, if this container is subjected to a dehydrator and dried in a dryer in the same manner as a normal retort container to remove the water adhering to the surface of the container, it becomes transparent within about one hour under normal conditions. OTR also reaches its equilibrium value within 12 hours. In order to more reliably achieve transparency and OTR recovery, drying conditions that are stronger than usual may be used. The drying conditions are preferably dry heat treatment (usually in air), and the drying temperature and drying time preferably satisfy the following equation. -1/2x+43≦y≦-x+115 {However, 30℃≦x≦100℃, 0.5 minutes≦y≦85 minutes, x is drying temperature (℃), y is drying time (minutes)
shows. } As an example, in the case of 50°C, the conditions are 25 to 65 minutes, preferably 30 to 60 minutes, and in the case of 80°C, the conditions are 5 to 35 minutes, preferably 5 to 30 minutes. If temporary opacity after retort processing is not desired for the packaging material of the present invention, the moisture permeability of the outer layer may be reduced.
40-100g/m ²・day, inner layer moisture permeability 10g/m2・day
This can be achieved by setting it to less than m ² ·day. The outer layer is polyethylene terephthalate (approx. 12μ),
Alternatively, polycarbonate (15 to 30μ) may be used, and the inner layer may be polypropylene (50μ or more). The film packaging material with this configuration is
It does not become white and opaque under normal retort conditions (120℃, 30 minutes). However, with this configuration, OTR recovery tends to be slower than when a nylon film is used as the outer layer as described above. In order to speed up OTR recovery, stronger drying conditions,
For example, it is desirable to use the conditions at 80°C for 60 minutes. After the multilayer packaging of the present invention described above is filled with food, the interior is degassed by known means if necessary, or the interior is replaced with an inert gas such as nitrogen gas or carbon dioxide gas, and then heat-sealed. The container is sealed using a method such as the following, and then sterilized by boiling or retort treatment. Suitable foods include cooked or semi-cooked foods that can be eaten as is or heated prior to consumption. The following is an example of food. Cooked curry, cooked hash, beef stew, borscht, meat sauce, sweet and sour pork, sukiyaki, Chinese bean paste, eight treasure vegetables, meatballs, oden, boiled asparagus, sweet corn, matsushi room, tuna cream boil, consommé, potajiyu Various types of soups such as miso soup, pork soup, kenchin soup, rice, sekihan, kamameshi, fried rice, pilaf, porridge, spa detei, soba, udon, ramen, noodles, kamameshi base, Chinese soba base, and other accompanying foods; Boiled azuki, zenzai, anmitsu, meat dumplings, hamburgers, beef steaks, roast pork, pork sauté, corned beef, ham, sausage, grilled fish, yakiniku, yakitori, roast chicken, pork ketchup, fish meat dumplings, bacon, kamaboko, pudding, jelly, yokan , various pet foods. In addition, the multilayer packaging of the present invention can be used for fruit products such as mandarin oranges, peaches, binut pulls, cherries, and olives, soybean oil, sauces, etc.
Seasonings such as vinegar, mirin, dressing, mayonnaise, ketchup, edible oil, miso, lard, tofu, jam, butter, margarine, fruit juice, vegetable juice, beer, cola, lemonade, sake, shochu, fruit liquor, wine, whisky,
Also excellent as a container for brandy, etc. In addition, pharmaceuticals such as Ringer's solution, pesticides, cosmetics, detergents, benzene, toluene, xylene, acetone,
It can also be used as a container for organic liquid chemicals such as methyl ethyl ketone, normal hexane, cyclohexane, carbon tetrachloride, gasoline, kerosene, petroleum benzine, thinner, and grease. E Examples Example 1, Comparative Examples 1 and 2 The content of ethylene monomer units as EVOH
80 parts of resin pellets with a saponification degree of 28 mol%, a saponification degree of 99.8%, and a melt index (190°C, 2160 g) of 1.2 g/10 min, and PA-6/12 copolymer as PA [constituent units of caprolactam and lauryllactam] After dry blending 20 parts of 80/20 weight ratio with constituent units, melting point 196℃, relative viscosity 2.5], diameter 30mm.
Blend pellets were obtained by melt extrusion using a codirectional twin-screw extruder (die temperature: 230°C). After drying this blend pellet, film formation was performed using an extruder equipped with a full flute screw with a diameter of 40 mm and a coat hanger die with a width of 500 mm (temperature 230 ° C.).
A transparent film of the composition with a thickness of 50μ was obtained. Next, a film of the above composition was used as an intermediate layer, and a commercially available biaxially stretched nylon-6 film (Unitika Emblem ON, thickness 15μ, moisture permeability 260g/m ² .
day), and the inner layer is a commercially available unstretched polypropylene film (Tocello CP, thickness 50μ, moisture permeability 7g/ ^m2 .
Dry lamination was carried out as a day) to obtain a three-layer transparent film. As an adhesive for dry lamination, Takerakku A-385 (Takeda Pharmaceutical Co., Ltd.)
Takenate A-50 (manufactured by Takeda Pharmaceutical Co., Ltd.) was used as the hardening agent, and after lamination,
Cure for 3 days. This film was used as a lid material and was thermally bonded to a polypropylene cup-shaped container containing water using a heat sealer, with an inner surface of an unstretched polypropylene layer. This was subjected to retort treatment at 120° C. for 30 minutes using a retort device (manufactured by Hisaka Seisakusho Co., Ltd., high temperature and high pressure cooking sterilization tester, RCS-40RTGN). Immediately after retort processing, the film on the lid was whitish. After the retort treatment, the film was dried at 80° C. for 5 minutes, and the film became transparent and had a good appearance without any wave pattern. Immediately after drying, the outer layer (stretched nylon side) of the film used for the lid material was adjusted to 65% RH, the inner layer (unstretched polypropylene side) to 100% RH, and the temperature was adjusted to 20% RH.
The temperature and humidity are controlled to ℃ and the oxygen transmission rate (OTR) is
Measurement was performed using OXTRAN-10/50A (MOCON). Immediately after drying, the OTR was 1.1 cc/m ² ·day · atm, but after that, the OTR rapidly decreased to 0.3 cc/m ² ·day · atm after 12 hours, indicating high oxygen gas barrier properties. This oxygen gas barrier property shows that the OTR of the retort container lid material (Comparative Example 1) using 50μ of polyvinylidene chloride resin is 1.3cc/ ^m2 .
day・atm, and a multilayer film lid material (Comparative Example 2) using two layers of high barrier type polyvinylidene chloride film (SARAN-UB, manufactured by Asahi Chemical Industry Co., Ltd., thickness 25μ) had a temperature of 0.8 cc/ ^m2・
It can be seen that the lid material of the present invention exhibits significantly superior performance even when compared with the OTR of day/atm. Further, curry was placed in the cup-shaped container of Example 1, and retort treatment was performed under the same conditions as in Example 1.

[Table] *3 Weight ratio *4 ON: Biaxially stretched nylon film, PET:
Biaxially oriented polyethylene terephthalate film, CN: Unoriented nylon film OPP: 2
Axial oriented polypropylene film, CPP: Unoriented polypropylene film *5 g/m ²・day (40℃, 90%RH)
*6 cc・20μ/m ²・day・atm (12 hours later)
Examples 2 to 7 When the thickness of the biaxially stretched nylon film of the outer layer was increased in Example 1 (Examples 2 and 3), or instead of the EVOH and PA composition of Example 1, the composition of Table 1 was used. EVOH and PA shown in Examples 2-6
Alternatively, an unstretched nylon film (Example 4) or a polyethylene terephthalate film (Example 7) was used in place of the biaxially stretched nylon film. In the same manner as in Example 1, a laminate film was produced and subjected to retort treatment.
Table 1 shows the OTR measurement results and appearance evaluation.
All of these examples of the present invention exhibit good transparency and high oxygen gas barrier properties. Comparative Examples 3 to 5 A laminate film was prepared in the same manner as in Example 1 except that an EVOH film was used instead of the composition film for the intermediate layer in Example 1, and retort treatment was performed. Comparative example 3 in the table
and 4. OTR is 0.3~0.4cc/ ^m2・day・atm
Although it showed high oxygen gas barrier properties, the entire surface of the lid material had wrinkles and wavy patterns, making it unsuitable for practical use. In addition, the same procedure as in Example 1 was used except that a biaxially stretched polypropylene film (moisture permeability 7 g/m ² ·day, Comparative Example 5) was used instead of the biaxially stretched nylon film used for the outer layer in Example 1. A laminate film was produced and retorted. Although the film was transparent, it had a high OTR value and was not suitable as a barrier lid material. Example 8 The same multilayer film used in Examples 1 to 7 was heat-sealed into a pouch shape, water was poured into the pouch, and the opening was heat-sealed. Example 1
Retort treatment was carried out at 120°C for 30 minutes in the retort pot shown in . After the retort treatment, the surface of the pouch was whitish. When this was left in a hot air dryer at 80°C for 15 minutes, it became completely transparent and had a good appearance with no wave pattern. Example 9 In Example 1, a polycarbonate film (Teijin Panlite Film, thickness 20μ, moisture permeability 195g/m ² ) was used instead of the nylon film for the outer layer.
A three-layer film was obtained in the same manner as in Example 1, except that 3-layer film was used. This was used as a lid material and subjected to retort treatment in the same manner as in Example 1. The appearance of the film after retort treatment was good, and the OTR after 12 hours was 0.7 cc/m ² ·day · atm, indicating high gas barrier properties. Example 10 The film of the composition used in Example 1 was used as the intermediate layer, the outer layer was a commercially available unstretched nylon film (thickness 30 μm, moisture permeability 300 g/m ² day), and the inner layer was a polypropylene sheet (thickness 450 μm, moisture permeability 300 g/m 2 day). 0.78g/ ^m2・
Dry lamination was carried out in the same manner as in Example 1 to obtain a three-layer laminate sheet. This laminate sheet was made into a 140mm long sheet using a vacuum-pressure forming machine (manufactured by Asano Seisakusho Co., Ltd.).
A square tray container with a width of 83 mm and a height of 19 mm was molded. The average thickness of this container starts from the outer layer: nylon (20μ, moisture permeability 480g/m ² day), composition (33μ), polypropylene (296μ, moisture permeability 1.2g/m 2 day),
^m2・day). This tray was purged with nitrogen gas, filled with 5 ml of water, and the lid material shown in Example 1 was heat-sealed, followed by retort treatment at 120° C. for 30 minutes. After taking it out from the retort pot, it was dried at 80°C for 15 minutes, and after being stored at 20°C and 65% RH for 6 months, the oxygen concentration in the container was measured and found to be 0.4%. This concentration is low enough to protect many foods from deterioration due to oxygen. Example 11 A coextruded multilayer film consisting of four layers was produced using a feedblock type coextrusion apparatus having four extruders and a T-shaped die. The composition is polyamide-6 (Novamit 1020 manufactured by Mitsubishi Chemical Industries, Ltd.) from the outside, thickness
20μ), the blend composition used in Example 1 (thickness
50μ), adhesive resin (Mitsubishi Yuka Co., Ltd. Modelix P)
-300F, thickness 20μ) and polypropylene (Mitsubishi Noblen MA-6 manufactured by Mitsubishi Yuka Co., Ltd., thickness 60μ). The moisture permeability of the outer layer is 450 g/m ² ·day based on the moisture permeability measured with a single-layer film of the same thickness. On the other hand, the moisture permeability of the inner layer is 4.6 based on the moisture permeability measured with a two-layer film of 60μ polypropylene and 20μ adhesive resin.
g/m ²・day. This multilayer film was used as a lid material in the same manner as in Example 1, and
After performing retort treatment for 5 minutes, hot air drying treatment was performed at 80° C. for 5 minutes. The lid material film has good transparency and no wave patterns, and the OTR measured after 5 hours of retort processing is 0.9cc/m ²・day・atm.
OTR measured after 1 day was 0.4cc/m ²・day・atm
It was hot. Example 12 Four extruders and T similar to those used in Example 11
A coextruded multilayer sheet consisting of four layers was prepared using a feedblock type coextrusion apparatus having a die. The composition is polyamide-6 (Mitsubishi Chemical Industries, Ltd.) from the outside.
Nobamitsu 1020 (manufactured by Co., Ltd., thickness 54μ), blend composition used in Example 1 (thickness 135μ), adhesive resin (Admer QF-500, thickness 27μ), polypropylene (Mitsubishi Noblen X manufactured by Mitsubishi Yuka Co., Ltd.) −1B, thickness
1350μ). Using this multilayer sheet and a vacuum-pressure forming machine (manufactured by Asano Seisakusho Co., Ltd.), the bottom surface has a radius of 33 mm.
A cup-shaped container with a circular top surface of 37 mm and a height of 37 mm was molded. The composition of this container is polyamide-6 (average thickness 20μ), blend composition (50μ), adhesive resin (10μ), and polypropylene (500μ) from the outer layer, and the moisture permeability of the outer layer is 450g/
m ² ·day, and the moisture permeability of the inner layer is 0.7g/m ² ·day. This cup was purged with nitrogen gas, filled with 5 ml of water, and the lid material shown in Example 1 was heat-sealed, followed by retort treatment at 120° C. for 30 minutes.
After taking it out from the retort pot, it was dried with hot air at 80°C for 15 minutes, and after being stored for one year at 20°C and 65% RH, the oxygen concentration in the container was 0.35%. This concentration is low enough to protect many foods from deterioration due to oxygen. Example 13 A three-layer transparent film was obtained by dry lamination using the same materials and method as in Example 1. The non-stretched polypropylene film layer of this film was used as the inner surface, and the three sides were thermally bonded using a heat sealer to prepare four containers. Next, Ringer's solution, dialysis solution for artificial kidneys/solution A (aqueous electrolyte solution), dialysis solution for artificial kidneys/solution B (aqueous sodium bicarbonate solution), dialysis solution for artificial kidneys (electrolyte, aqueous sodium acetate solution), artificial kidney Fill with replenisher for
The remaining one was similarly heat-bonded and sealed. This was subjected to steam sterilization (autoclave sterilization) at 121°C for 30 minutes. Immediately after sterilization, the container had a whitish tinge, but when left at room temperature, 30
After about a minute, the container became transparent and had a good appearance. Furthermore, when stored for one year at room temperature and protected from light, no change was observed in the appearance or composition ratio of the contents, and no deterioration or degeneration was observed, indicating good storage stability. F. Effects of the Invention The multilayer packaging body of the present invention is mainly useful as a transparent film packaging material, especially as a transparent film packaging material for retorts, and particularly when used as a lid material for retort containers or a retort pouch, it has excellent transparency and It has high oxygen gas barrier properties not found in conventional film packaging materials for retorts. In other words, traditional
While the PVDC film packaging material had an OTR (1.3cc/ ^m2・day・atm) that gave a shelf life of about 4 months at the most, the transparent film packaging material of the present invention easily has a shelf life of about 6 months or 1 year. Required for storage stability of
The impact it will have on the food and medical retort packaging fields will be immeasurable in that OTR (0.2 to 0.8 cc/ ^m2・day・atm) can be obtained. Furthermore, the technology of the present invention can also be applied to cup- or tray-type retort containers.
EVOH has traditionally been used in these fields, but it is known that the moisture that permeates during retorting reduces the gas barrier properties of EVOH, and as mentioned above, the use of a desiccant has been proposed. There is. However, by applying the multilayer packaging of the present invention, it is possible to exhibit the high gas barrier properties inherent to EVOH without using a desiccant.

Claims (1)

[Claims] 1. Moisture permeability (measured at 40°C, 90% RH) is 40g/
resin outer layer (A) having a value of m ² ·day or more, 55 to 97% by weight of an ethylene-vinyl alcohol copolymer resin containing 20 to 50 mol% of ethylene monomer units, and at least one selected from polyamide, polyolefin, polyester, and polycarbonate. a kind of resin
An inner layer of a hydrophobic thermoplastic resin having a moisture permeability lower than that of the intermediate layer (B) and the outer layer (A) of the composition consisting of 45 to 3% by weight.
A gas barrier multilayer packaging body consisting of (C). 2. The multilayer packaging according to claim 1, wherein the polyamide used in the composition of the intermediate layer (B) is a caprolactam-lauryllactam copolymer. 3. A multilayer film packaging material for boil sterilization or retort sterilization, comprising the multilayer packaging body according to claim 1 or 2. 4. A lid for a boil sterilization or retort sterilization container comprising the multilayer packaging according to claim 1 or 2. 5. A pouch for boil sterilization or retort sterilization comprising the multilayer package according to claim 1 or 2. 6. A cup-shaped or tray-shaped container for boil sterilization or retort sterilization comprising the multilayer packaging according to claim 1 or 2. 7. A method for producing a content-filled package, which comprises filling the multilayer package according to any one of claims 1 to 8 with content, sterilizing it by retort, and then drying it under conditions that satisfy the following formula. -1/2x+43≦y≦-x+115 {However, 30℃≦x≦100℃≦, 0.5 minutes≦y≦85 minutes, x is drying temperature (℃), y is drying time (minutes)
shows. } 8. A pharmaceutical packaging material comprising the multilayer packaging body according to claim 1 or 2.