Gas barrier film, laminated film and packaging bag

Abstract

To provide an aluminum-free gas barrier film capable of suppressing the decrease in tear strength and interlayer adhesion strength under high humidity conditions.SOLUTION: There is provided a gas barrier film having an intermediate layer, a first layer laminated on one surface of the intermediate layer and a second layer laminated on the other surface of the intermediate layer, wherein each of the first layer and the second layer contains a liquid crystal polymer having a melting point of 230°C or less or an isophthalic acid-modified polyethylene terephthalate modified with isophthalic acid, the intermediate layer contains a polyester resin, the polyester resin is a polycondensate of a polycarboxylic acid component and a polyhydric alcohol component comprising a diethylene glycol component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas barrier film, a laminated film, and a packaging bag. [Background technology]

[0002] Conventionally, packaging bags made of a laminate film in which multiple layers are laminated on the inner surface of a base layer made of film, paper, etc. have been widely used as packaging bags for containing contents such as food, medicine, etc. The laminate film used in such packaging bags generally has gas barrier properties that block the entry of gases that deteriorate the contents, such as water vapor and oxygen, in order to prevent deterioration and spoilage of the contents and to maintain their functions and properties.

[0003] For example, Patent Document 1 discloses a packaging bag made by laminating a base layer / first adhesive layer / gas barrier layer / second adhesive layer / sealant layer in that order to form a sealed portion by sealing a laminated film with the sealant layer as the inner surface. It also discloses that the gas barrier layer is a polyester film vapor-deposited with aluminum or an inorganic oxide, which provides excellent gas barrier properties and enables the quality of the fragrance to be maintained for a long time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-5013 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional laminate films, the gas barrier layer is often an aluminum-deposited polyester film or aluminum foil. Such aluminum-containing laminate films generate large amounts of CO2 during production and disposal, and are difficult to separate and recover during disposal. To address this issue, a liquid crystal polymer with excellent gas barrier properties could be used as the gas barrier layer. However, liquid crystal polymer films lack tear strength, and using a liquid crystal polymer-containing gas barrier layer would result in a decrease in the tear strength of the laminate film. Furthermore, if the adhesive layer is made of a material that is susceptible to moisture degradation, the adhesive strength between the gas barrier layer and the adhesive layer may decrease, particularly in high-humidity environments, potentially leading to delamination between the adhesive layer and the gas barrier layer.

[0006] In view of the above, one aspect of the present invention provides an aluminum-free gas barrier film that can suppress a decrease in tear strength and interlayer adhesive strength in a high-humidity environment. [Means for solving the problem]

[0007] A gas barrier film according to one embodiment of the present invention comprises an intermediate layer, a first layer laminated on one side of the intermediate layer, and a second layer laminated on the other side of the intermediate layer, wherein each of the first and second layers comprises a liquid crystal polymer having a melting point of 230°C or less, or the liquid crystal polymer and isophthalic acid-modified polyethylene terephthalate modified with isophthalic acid, and the intermediate layer comprises a polyester resin, which is a polycondensate of a polycarboxylic acid component and a polyhydric alcohol component including a diethylene glycol component. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to provide an aluminum-free gas barrier film that can suppress a decrease in tear strength and interlayer adhesive strength in a high-humidity environment. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a schematic diagram showing a cross section of a gas barrier film according to one embodiment. [Figure 2] 1 is a schematic diagram showing a cross section of a laminated film according to one embodiment. [Figure 3] 1 is a schematic diagram of a packaging bag according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification, unless otherwise specified, the symbol "to" indicating a range of values ​​means that the range includes the values ​​before and after it as the lower and upper limits.

[0011] (gas barrier film) 1 is a schematic diagram showing a cross section of a gas barrier film 1 according to one embodiment. The gas barrier film 1 of this embodiment has an intermediate layer 2, a first layer 3 laminated on one side of the intermediate layer 2, and a second layer 4 laminated on the other side of the intermediate layer 2. That is, the gas barrier film 1 has a configuration in which the intermediate layer 2 is sandwiched between the first layer 3 and the second layer 4.

[0012] The first layer 3 and the second layer 4 each contain a liquid crystal polymer (A) having a melting point of 230°C or lower, or a liquid crystal polymer (A) and an isophthalic acid-modified polyethylene terephthalate (B) modified with isophthalic acid, and the intermediate layer 2 contains a polyester resin (C). The polyester resin (C) is a polycondensate of a polycarboxylic acid component and a polyhydric alcohol component containing a diethylene glycol component. This configuration allows the gas barrier film 1 to block the intrusion of gas from the outside and exhibit gas barrier properties. In this specification, gas barrier properties refer to the property of blocking gases, and include water vapor barrier properties that block water vapor and oxygen barrier properties that block oxygen.

[0013] The polyhydric alcohol component containing a diethylene glycol component improves the flexibility of the polyester resin (C) in the gas barrier film 1, thereby preventing a decrease in tear strength and interlayer adhesive strength in a high-humidity environment. Furthermore, because one side and the other side of the intermediate layer 2 are covered by the first layer 3 and the second layer 4, it is thought that moisture is less likely to penetrate into the intermediate layer 2 from the outside, even in a high-humidity environment, and deterioration of the intermediate layer 2 containing the polyester resin (C) is therefore prevented. From this perspective, it is thought that a decrease in adhesive strength between the intermediate layer 2 and each of the first layer 3 and the second layer 4 can be prevented.

[0014] In this specification, the tear strength refers to a value measured as follows: In accordance with JIS K 7128-1, a sample of gas barrier film 1 was cut to 150 mm x 50 mm, a 75 mm long slit was made in the center, and the tear strength in the machine direction was measured using a chuck width of 50 mm and a pulling speed of 200 mm / min using the trouser tear method.

[0015] In this specification, the adhesive strength refers to a value measured as follows: A sample of gas barrier film 1 cut to a size of 25.4 mm x 200 mm is subjected to the ring method, and the adhesive strength in the machine direction is measured by clamping the first layer 3 or the second layer 4 with a gripper at a peel distance of 30 mm and a peel rate of 5 mm / min.

[0016] Because the gas barrier film 1 is aluminum-free (does not contain aluminum), CO2 emissions can be reduced during the manufacturing and disposal processes. Furthermore, when the gas barrier film 1 is discarded, it can be disposed of as plastic waste, allowing for easy separation and collection. Furthermore, when the first layer 3 and the second layer 4 each contain a liquid crystal polymer (A) and an isophthalic acid-modified polyethylene terephthalate (B) modified with isophthalic acid, the liquid crystal polymer (A) and the isophthalic acid-modified polyethylene terephthalate (B) have good affinity and can be uniformly mixed, so they can be mixed without the addition of, for example, a reactive compatibilizer. Therefore, the gas barrier film 1 of this embodiment has excellent recyclability. Furthermore, because the gas barrier film 1 is aluminum-free, it can be used in production lines that use metal detectors to detect metallic foreign matter.

[0017] Examples of polycarboxylic acid components constituting the polyester resin (C) contained in the intermediate layer 2 include one or more selected from terephthalic acid, isophthalic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, adipic acid, sebacic acid, and the like.

[0018] The polyhydric alcohol component constituting the polyester resin (C) preferably contains 1 mol % to 5 mol % of a diethylene glycol component, which can further improve the flexibility of the polyester resin (C), thereby increasing the adhesive strength between the intermediate layer 2 and each of the first layer 3 and the second layer 4.

[0019] Examples of the polyhydric alcohol component constituting the polyester resin (C), other than diethylene glycol, include one or more selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexamethylenediol, cyclopentane dimethanol, cyclohexane dimethanol, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 2,2-dipropyl-1,3-propanediol, 2-propyl-2-methyl-1,3-propanediol, 2-propyl-2-ethyl-1,3-propanediol, 2-isopropyl-2-methyl-1,3-propanediol, 2-isopropyl-2-ethyl-1,3-propanediol, 2-butyl-2-methyl-1,3-propanediol, and 2-butyl-2-ethyl-1,3-propanediol. The polyester resin (C) is non-liquid crystal and is different from the liquid crystal polymer (A).

[0020] The polyester resin (C) is preferably a modified polyethylene terephthalate composed of a dicarboxylic acid component made of terephthalic acid and a diol component containing an ethylene glycol component and a 1,4-butanediol component, which can increase the adhesive strength between the intermediate layer 2 and each of the first layer 3 and the second layer 4.

[0021] The glass transition temperature of the polyester resin (C) is preferably from −10° C. to 40° C., and more preferably from 10° C. to 30° C. When the glass transition temperature of the polyester resin (C) is from −10° C. to 40° C., the flexibility of the polyester resin (C) can be further improved, and the adhesive strength between the intermediate layer 2 and each of the first layer 3 and the second layer 4 can be increased.

[0022] The melting point of the liquid crystal polymer (A) constituting each of the first layer 3 and the second layer 4 is preferably 220°C or lower. When the melting point of the liquid crystal polymer (A) is 220°C or lower, the molding temperature can be kept relatively low, and the polyester resin (C) of the intermediate layer 2 can be prevented from changing due to thermal decomposition or the like. Furthermore, when each of the first layer 3 and the second layer 4 contains the liquid crystal polymer (A) and an isophthalic acid-modified polyethylene terephthalate (B) modified with isophthalic acid, the molding temperature can be kept relatively low, and the isophthalic acid-modified polyethylene terephthalate (B) can be prevented from changing due to thermal decomposition or the like. Therefore, the gas barrier film 1 can further suppress a decrease in tear strength in a high-humidity environment.

[0023] Examples of monomers constituting the liquid crystal polymer (A) include one or more selected from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid hydroquinone, resorcinol, 2,6-dihydroxynaphthalene, 4,4'-biphenol, p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4-aminobenzoic acid, 4-aminophenol, 1,4-phenylenediamine, and the like.

[0024] The liquid crystal polymer (A) preferably contains a p-hydroxybenzoic acid component and a 6-hydroxy-2-naphthoic acid component as monomer components constituting the liquid crystal polymer (A). When the liquid crystal polymer (A) contains a p-hydroxybenzoic acid component and a 6-hydroxy-2-naphthoic acid component as monomer components, the gas barrier film 1 can exhibit better gas barrier properties and can further suppress a decrease in tear strength in a high-humidity environment. From the viewpoint of improving gas barrier properties, the liquid crystal polymer (A) more preferably contains a p-hydroxybenzoic acid component and a 6-hydroxy-2-naphthoic acid component as main monomer components. Here, "main component" means that the liquid crystal polymer (A) contains 50 mol % or more of the monomer components constituting the liquid crystal polymer (A).

[0025] The liquid crystal polymer (A) preferably further contains a terephthalic acid component and a hydroquinone component as monomer components constituting the liquid crystal polymer (A), thereby enabling the gas barrier film 1 to exhibit even better gas barrier properties and further suppress a decrease in tear strength in a high-humidity environment.

[0026] The monomer component constituting the liquid crystal polymer (A) is preferably an aromatic compound, which allows the gas barrier film 1 to exhibit superior gas barrier properties and also has excellent tear strength.

[0027] Examples of the liquid crystal polymer (A) include VECTORA (registered trademark) and ZENITE (registered trademark) manufactured by Celanese, LAPEROS (registered trademark) manufactured by Polyplastics, XYDAR (registered trademark) manufactured by ENEOS, Sumikasuper LCP (registered trademark) manufactured by Sumitomo Chemical, and UENO LCP (registered trademark) manufactured by Ueno Pharmaceuticals.

[0028] When the first layer 3 and the second layer 4 each contain a liquid crystal polymer (A) and an isophthalic acid-modified polyethylene terephthalate (B) modified with isophthalic acid, the isophthalic acid-modified polyethylene terephthalate (B) used in the first layer 3 and the second layer 4 is a linear polyester resin obtained by condensation polymerization of a dicarboxylic acid component and a diol component, in which the dicarboxylic acid component is primarily terephthalic acid and further contains isophthalic acid, and the diol component is primarily ethylene glycol. Here, the term "major component" refers to the component with the highest content. Note that the isophthalic acid-modified polyethylene terephthalate (B) is non-liquid crystal and is not included in the liquid crystal polymer (A).

[0029] The copolymerization ratio of the isophthalic acid component in the dicarboxylic acid component constituting the isophthalic acid-modified polyethylene terephthalate (B) can be, for example, 3 mol % to 30 mol %. Here, the copolymerization ratio of the isophthalic acid component in the dicarboxylic acid component refers to the proportion (mol percentage) of the isophthalic acid component in the dicarboxylic acid component.

[0030] The intrinsic viscosity (IV) of the isophthalic acid-modified polyethylene terephthalate (B) is preferably 0.60 dL / g to 1.0 dL / g. Here, the intrinsic viscosity is a value measured in accordance with JIS K 7367-5 in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (1 / 1 by mass) at 30°C. When the intrinsic viscosity is 0.60 dL / g or more, the gas barrier film 1 of this embodiment can exhibit excellent gas barrier properties. Furthermore, when the intrinsic viscosity is 1.0 dL / g or less, the first layer 3 and the second layer 4 can be easily extruded, improving the processability of the gas barrier film 1.

[0031] When each of the first layer 3 and the second layer 4 contains a liquid crystal polymer (A) and an isophthalic acid-modified polyethylene terephthalate (B) modified with isophthalic acid, the content of the liquid crystal polymer (A) in each of the first layer 3 and the second layer 4 is preferably 78 parts by mass to 99 parts by mass, and the content of the isophthalic acid-modified polyethylene terephthalate (B) in each of the first layer 3 and the second layer 4 is preferably 1 part by mass to 22 parts by mass. When the contents of the liquid crystal polymer (A) and the isophthalic acid-modified polyethylene terephthalate (B) are within the above ranges, the gas barrier film 1 can exhibit superior gas barrier properties and tear strength. More preferably, the content of the liquid crystal polymer (A) in each of the first layer 3 and the second layer 4 is 80 parts by mass to 90 parts by mass, and the content of the isophthalic acid-modified polyethylene terephthalate (B) in each of the first layer 3 and the second layer 4 is 10 parts by mass to 20 parts by mass.

[0032] The composition of the material constituting the first layer 3 and the composition of the material constituting the second layer 4 may be the same or different.

[0033] The ratio of the thickness of the first layer 3 to the thickness of the intermediate layer 2 to the thickness of the second layer 4 is preferably 0.8-4.5:1:0.8-4.5, and more preferably 2-2.7:1:2-2.7. When the ratio of the thickness of the first layer 3 to the thickness of the intermediate layer 2 to the thickness of the second layer 4 is 2-2.7:1:2-2.7, the gas barrier film 1 can exhibit better gas barrier properties and can further suppress a decrease in tear strength in a high-humidity environment.

[0034] When the total thickness of the gas barrier film 1 is 100 μm, the thickness of each of the first layer 3 and the second layer 4 may be 30 μm to 45 μm, and the thickness of the intermediate layer 2 may be 10 μm to 40 μm. When the thickness of each of the first layer 3 and the second layer 4 is 30 μm to 45 μm and the thickness of the intermediate layer 2 is 10 μm to 40 μm, the gas barrier film 1 can exhibit better gas barrier properties and can further suppress a decrease in tear strength in a high-humidity environment. Furthermore, the gas barrier film 1 can be particularly suitably used for packaging bags.

[0035] After being left for 30 days in an environment at a temperature of 40°C and a relative humidity of 90%, it is preferable that the rate of decrease in tear strength of the gas barrier film 1 is 1% or less, and the rate of decrease in adhesive strength between each of the first layer 3 and the second layer 4 and the intermediate layer 2 is 2% or less. This makes it possible for the gas barrier film 1 to further suppress decreases in tear strength and interlayer adhesive strength in a high-humidity environment.

[0036] After being left for 90 days in an environment at a temperature of 40°C and a relative humidity of 90%, it is preferable that the rate of decrease in tear strength of the gas barrier film 1 is 3% or less, and the rate of decrease in adhesive strength between each of the first layer 3 and the second layer 4 and the intermediate layer 2 is 2% or less. This makes it possible for the gas barrier film 1 to further suppress decreases in tear strength and interlayer adhesive strength in a high-humidity environment.

[0037] The initial tear strength of the gas barrier film 1 (immediately after production) is preferably 0.5 N / 100 μm or more, and more preferably 0.8 N / 100 μm or more. When the gas barrier film 1 has a tear strength of 0.5 N / 100 μm or more, tearing of the gas barrier film 1 can be further suppressed even when a long gas barrier film 1 is continuously molded in a high-humidity environment and the long molded film is wound up after molding.

[0038] The first layer 3, the second layer 4, and the intermediate layer 2 are preferably formed into a film by coextrusion. That is, the gas barrier film 1 can be formed into a film by coextrusion, in which the material constituting the first layer 3, the material constituting the second layer 4, and the material constituting the intermediate layer 2 are simultaneously melt-extruded. This increases the adhesive strength between each of the first layer 3 and the second layer 4 and the intermediate layer 2, compared to when the first layer 3, the second layer 4, and the intermediate layer 2 are laminated by a lamination method. Therefore, the gas barrier film 1 can further suppress a decrease in adhesive strength in a high-humidity environment.

[0039] Furthermore, because the liquid crystal polymer (A) constituting each of the first layer 3 and the second layer 4 has a melting point of 230°C or less, the heating temperature during co-extrusion can be relatively low, and the polyester resin (C) constituting the intermediate layer 2 can be prevented from changing due to thermal decomposition or the like. Therefore, the gas barrier film 1 can further prevent a decrease in tear strength in a high-humidity environment. Even when a long gas barrier film 1 is continuously molded in a high-humidity environment and the long molded film is wound up after molding, the gas barrier film 1 can be prevented from tearing.

[0040] (Laminated film) Fig. 2 is a schematic diagram showing a cross section of a laminate film according to one embodiment. As shown in Fig. 2, a laminate film 6 according to this embodiment includes a gas barrier film 1 according to this embodiment and a sealant layer 5 laminated on the surface of the second layer 4 of the gas barrier film 1. In the example shown in Fig. 2, the sealant layer 5 is laminated on the surface of the second layer 4, but it may also be laminated on the surface of the first layer 3. The sealant layer 5 contains one or more of a polyethylene resin, a polypropylene resin, a polyester resin, and a cyclic olefin resin. This allows the laminate film 6 to suppress a decrease in tear strength and interlayer adhesive strength in a high-humidity environment.

[0041] The sealant layer 5 forms one outermost surface of the laminated film 6. Here, the sealant layer 5 is a layer used for heat sealing, and when the laminated film 6 is used as a packaging material, it is a layer disposed as the innermost layer that comes into contact with the contents. The first layer 3 or the second layer 4 and the sealant layer 5 may be bonded via an adhesive layer or an anchor agent layer, but are preferably bonded directly. The sealant layer 5 is preferably a resin film that has excellent heat resistance, mechanical properties, and printability.

[0042] When the laminated film 6 is used as a packaging material, the gas barrier film 1 is positioned outside the sealant layer 5 that comes into contact with the contents, thereby blocking the intrusion of gas from the outside, and the laminated film 6 of this embodiment can exhibit excellent gas barrier properties.

[0043] The sealant layer 5 preferably contains isophthalic acid-modified polyethylene terephthalate modified with isophthalic acid. The isophthalic acid-modified polyethylene terephthalate contained in the sealant layer 5 may be the same as the isophthalic acid-modified polyethylene terephthalate (B) contained in the first layer 3 or the second layer 4 described above. When the sealant layer 5 is made of isophthalic acid-modified polyethylene terephthalate, the laminate film 6 of this embodiment can exhibit even better gas barrier properties. Furthermore, the laminate film 6 can improve the initial adhesion between the sealant layer 5 and the first layer 3 or the second layer 4.

[0044] The copolymerization ratio of the isophthalic acid component in the dicarboxylic acid component constituting the isophthalic acid-modified polyethylene terephthalate is preferably 3 mol% to 30 mol%, and more preferably 5 mol% to 25 mol%. Here, the copolymerization ratio of the isophthalic acid component in the dicarboxylic acid component refers to the proportion (mol percentage) of the isophthalic acid component in the dicarboxylic acid component. When the copolymerization ratio of the isophthalic acid component in the dicarboxylic acid component is 3 mol% or more, the laminate film 6 of this embodiment can exhibit superior gas barrier properties and tear strength. Furthermore, when the copolymerization ratio of the isophthalic acid component in the dicarboxylic acid component is 30 mol% or less, the laminate film 6 can be provided with heat resistance sufficient to withstand the heat generated when heat-sealing laminate films 6 together or between the laminate film 6 and another film, or heat resistance sufficient to withstand the heat of hot contents when a packaging bag or the like formed from the laminate film 6 is filled with hot contents.

[0045] The thickness of the sealant layer 5 depends on the application of the packaging material and is not particularly limited, but may be, for example, 10 μm to 50 μm.

[0046] The sealant layer 5 may contain additives as components other than the resin. The additives are not particularly limited, but examples thereof include antioxidants, lubricants, antiblocking agents, stabilizers, ultraviolet absorbers, flame retardants, antistatic agents, and colorants.

[0047] The laminate film 6 may have other layers provided on the opposite side of the sealant layer 5 with respect to the gas barrier film 1. As the other layers, for example, one or more layers can be appropriately selected from a reinforcing layer, a gas barrier layer, a light-shielding layer, a printed layer, etc. The other layers may include, for example, an adhesive layer, an anchor agent layer, etc.

[0048] The method for producing the laminated film 6 is not particularly limited, and examples thereof include extrusion lamination, dry lamination, coextrusion, and a combination of these. Furthermore, the strength and heat distortion resistance of the film can be improved by uniaxially or biaxially stretching the formed film before lamination.

[0049] (packaging bag) Fig. 3 is a schematic diagram of a packaging bag 10 according to one embodiment. The packaging bag 10 is formed using the laminate film 6 of this embodiment. As shown in Fig. 3, the packaging bag 10 has a bag-shaped body 11 formed from the laminate film 6 and a mouth 12 joined to at least one location on the periphery of the body 11. The shape of the body 11 is not particularly limited, and examples include a three-sided bag, a four-sided bag, a seamed bag, a gusset bag, and a stand-up pouch. The body 11 may also be a large packaging bag, such as an inner bag for a bag-in-box.

[0050] The material for the mouth portion 12 can be suitably used as long as it can be bonded to the sealant layer 5 of the laminate film 6 that constitutes the packaging bag 10 to ensure airtightness, but it is preferably a resin that can be heat-sealed to the sealant layer 5 of the laminate film 6. This allows the mouth portion 12 and the laminate film 6 to be bonded by heat sealing. For this reason, the material for the mouth portion 12 is preferably polyethylene terephthalate (PET), and more preferably isophthalic acid-modified PET. This allows the mouth portion 12 to be easily heat-sealed to the sealant layer 5 of the laminate film 6 and also improves the gas barrier properties of the packaging bag 10.

[0051] When heat-sealing the laminate film 6 and the mouth portion 12, the laminate films 6 may be overlapped with the sealant layer 5 on the inside, and the mouth portion 12 may be inserted between the overlapping sealant layers 5 and heat-sealed. Alternatively, a flange or a boat-shaped fusion base may be provided at one end of the mouth portion 12, and this flange or fusion base may be heat-sealed to the periphery of a hole provided in the laminate film 6 or to the inner surface of the opening of the packaging bag. [Example]

[0052] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0053] In Examples 1 to 4 and Comparative Example 4, the raw materials were blended and melted in the proportions shown in Table 1. The molten material for the first layer, the molten material for the intermediate layer, and the molten material for the second layer were then co-extruded using a T-die extruder to obtain a 100-μm-thick gas barrier film consisting of three layers: the first layer, the intermediate layer, and the second layer, laminated in that order. In Comparative Example 1, the raw materials shown in Table 1 were melted, and the molten material for the first layer was extruded using a T-die extruder to obtain a 100-μm-thick gas barrier film consisting of only the first layer. In Comparative Examples 2 and 3, the raw materials were blended and melted in the proportions shown in Table 1. The molten material for the first layer and the molten material for the intermediate layer were then co-extruded using a T-die extruder to obtain a 100-μm-thick gas barrier film consisting of two layers: the first layer and the intermediate layer, laminated in that order. The thicknesses of the first layer, the intermediate layer, and the second layer of the gas barrier films of Examples 1 to 4 and Comparative Examples 2 to 4 were as shown in Table 1. Details of each raw material are as follows:

[0054] (A) Liquid crystal polymer A-1: Low-melting-point liquid crystal polymer (product name "UENO LCP (registered trademark) A-8100", manufactured by Ueno Pharmaceutical Co., Ltd., density ρ = 1.40 g / cm 3 , melting point Tm=220℃)

[0055] (B) Isophthalic acid modified polyethylene terephthalate (isophthalic acid modified PET) B-1: Isophthalic acid modified polyethylene terephthalate (copolymerization ratio of isophthalic acid component in dicarboxylic acid component: 10 mol%, density ρ = 1.34 g / cm 3 , melting point Tm = 228 ° C, intrinsic viscosity IV = 0.85 dl / g) B-2: Isophthalic acid modified polyethylene terephthalate (copolymerization ratio of isophthalic acid component in dicarboxylic acid component: 5 mol%, density ρ = 1.34 g / cm 3 , melting point Tm = 240 ° C, intrinsic viscosity IV = 0.97 dl / g)

[0056] (C) Polyester resin C-1: Modified polyethylene terephthalate (trade name "PRIT30", manufactured by Bell Polyester Products, Inc., density ρ = 1.24 g / cm 3 , melting point Tm = 188 ° C, glass transition temperature Tg = 30 ° C, intrinsic viscosity IV = 0.75 dl / g) C-2: Polyester elastomer (copolymer of polybutylene terephthalate and polytetramethylene glycol, trade name "Pelprene (registered trademark) P-150M", manufactured by Toyobo Co., Ltd., density ρ = 1.21 g / cm 3 , melting point Tm = 166 ° C, melt flow rate (MFR) = 8.0 g / 10 min)

[0057] The liquid crystal polymer (A-1) contains p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, and hydroquinone as monomer components. The polyester resin (C-1) contains a dicarboxylic acid component consisting of terephthalic acid and a diol component consisting of diethylene glycol, ethylene glycol, and 1,4-butanediol.

[0058] The MFR is a value (g / 10 min) at a test temperature of 190°C and a nominal load of 2.16 kg. The intrinsic viscosity is a value (dl / g) measured at 30°C in a mixed solvent of phenol and 1,1,2,2-tetrachloroethane in a mass ratio of 1:1.

[0059] [Table 1]

[0060] Next, the obtained gas barrier films were evaluated as follows. For the gas barrier film of Comparative Example 1, evaluation was performed on all aspects except adhesive strength because no intermediate layer or second layer was provided. The evaluation results are shown in Tables 2 to 4.

[0061] (tear strength) The tear strength of each gas barrier film was measured as follows: initially (immediately after production of the gas barrier film), after leaving it in an environment of 40°C and 90% relative humidity for 30 days, and after leaving it for 90 days.

[0062] In accordance with JIS K 7128-1, a trouser tearing method was used to measure the tear strength in the machine direction by making a 75 mm long slit in the center of a gas barrier film sample cut to 150 mm x 50 mm, with a chuck width of 50 mm and a pulling speed of 200 mm / min.

[0063] The percentage decrease in tear strength after 30 days and after 90 days was calculated relative to the initial tear strength. A decrease in tear strength of 1% or less after 30 days was considered pass, and a decrease of 2% or more was considered fail.

[0064] (Adhesive strength) The adhesive strength between the first layer and the intermediate layer of each gas barrier film was measured as follows: initially (immediately after the gas barrier film was produced), after leaving it in an environment of 40°C and 90% relative humidity for 30 days, and after leaving it for 90 days.

[0065] Using the ring method, the adhesive strength in the machine direction was measured for a gas barrier film sample cut to 25.4 mm x 200 mm, with the first layer clamped between grippers at a peel distance of 30 mm and a peel rate of 5 mm / min.

[0066] The decrease in interlayer adhesive strength after 30 days and after 90 days was calculated relative to the initial adhesive strength. A decrease in interlayer adhesive strength of 2% or less after 30 days was considered acceptable, and a decrease of 3% or more was considered unacceptable.

[0067] The tear strength and adhesive strength in a high humidity environment were evaluated. If both the rate of decrease in tear strength after leaving for 30 days and the rate of decrease in interlayer adhesive strength after leaving for 30 days passed, the product was deemed usable for practical use. If either one failed, the product was deemed unusable for practical use.

[0068] (with or without blocking) Each long gas barrier film was wound into a roll, and then the rolled gas barrier film was unwound to check for the presence or absence of blocking. If there was no blocking and the gas barrier films could be peeled off and unwound, it was evaluated as no blocking, and if the gas barrier films were tightly attached and could not be unwound, it was evaluated as having blocking.

[0069] (oxygen gas permeability, water vapor permeability) The oxygen gas permeability and water vapor permeability of the produced gas barrier film were measured in accordance with JIS K 7126-2 and JIS K 7129-2.

[0070] [Table 2]

[0071] [Table 3]

[0072] [Table 4]

[0073] As shown in Tables 2 and 3, the gas barrier films of Examples 1 to 4 passed the tear strength and adhesive strength evaluations in a high-humidity environment, confirming that they are suitable for practical use. Furthermore, even after being left for 90 days, the gas barrier films of Examples 1 to 4 showed a decrease in tear strength of 3% or less and a decrease in interlayer adhesive strength of 2% or less. Furthermore, as shown in Table 4, the gas barrier films of Examples 1 to 4 were free of blocking and had excellent blocking resistance, and their oxygen permeability and water vapor permeability were at the same levels as those of the gas barrier film of Comparative Example 1, which was made solely of a liquid crystal polymer, confirming that they had excellent gas barrier properties.

[0074] The gas barrier film of Comparative Example 1 had excellent oxygen permeability and water vapor permeability, but had low initial tear strength and was therefore unsuitable for practical use. The gas barrier films of Comparative Examples 2 and 3 passed the test for the rate of decrease in interlayer adhesive strength after being left for 30 days, but failed the test for the rate of decrease in tear strength after being left for 30 days. The gas barrier film of Comparative Example 4 failed both the rate of decrease in tear strength and the rate of decrease in interlayer adhesive strength after being left for 30 days. Furthermore, the gas barrier films of Comparative Examples 2 to 4 had a rate of decrease in tear strength and interlayer adhesive strength of more than 10% after being left for 90 days. Furthermore, blocking was observed in the gas barrier films of Comparative Examples 2 and 3.

[0075] Furthermore, using the raw materials of Example 1 shown in Table 1 and isophthalic acid-modified PET as the raw material for the sealant layer, a four-layer laminate film was produced by coextrusion molding, in which a first layer of 40 μm in thickness, a middle layer of 20 μm in thickness, a second layer of 40 μm in thickness, and a sealant layer of 50 μm in thickness were laminated in that order. A three-pack sealed bag was then produced at a heat sealing temperature of 170°C, a sealing pressure of 0.2 MPa, and a sealing time of 1 sec, and it was confirmed that the packaging bag could be produced without any problems.

[0076] (Aspects of the present invention) The present invention includes the following aspects. <Aspect 1> an intermediate layer, a first layer laminated on one surface of the intermediate layer, and a second layer laminated on the other surface of the intermediate layer; each of the first layer and the second layer contains a liquid crystal polymer having a melting point of 230°C or less, or the liquid crystal polymer and isophthalic acid-modified polyethylene terephthalate modified with isophthalic acid; the intermediate layer contains a polyester resin, The polyester resin is a gas barrier film that is a polycondensation product of a polycarboxylic acid component and a polyhydric alcohol component containing a diethylene glycol component. <Aspect 2> In the gas barrier film according to embodiment 1, the polyhydric alcohol component contains 1 mol % to 5 mol % of a diethylene glycol component. <Aspect 3> In the gas barrier film according to aspect 1 or 2, the glass transition temperature of the polyester resin is from -10°C to 40°C. <Aspect 4> In the gas barrier film according to any one of Aspects 1 to 3, the polyester resin is a modified polyethylene terephthalate composed of a dicarboxylic acid component consisting of a terephthalic acid component and a diol component containing a diethylene glycol component, an ethylene glycol component, and a 1,4-butanediol component. <Aspect 5> In the gas barrier film according to any one of Aspects 1 to 4, the liquid crystal polymer contains a p-hydroxybenzoic acid component and a 6-hydroxy-2-naphthoic acid component as monomer components constituting the liquid crystal polymer. <Aspect 6> Aspect 6. The gas barrier film according to any one of aspects 1 to 5, wherein the ratio of the thickness of the first layer to the thickness of the intermediate layer to the thickness of the second layer is 2-3:1:2-3. <Aspect 7> 7. The gas barrier film according to any one of aspects 1 to 6, wherein the thickness of the intermediate layer is 10 μm to 30 μm. <Aspect 8> A gas barrier film according to any one of aspects 1 to 7, wherein, after being left in an environment of 40°C temperature and 90% relative humidity for 30 days, the rate of decrease in tear strength is 1% or less, and the rate of decrease in adhesive strength between the first layer and the second layer and the intermediate layer is 2% or less. <Aspect 9> Aspect 9. The gas barrier film according to any one of aspects 1 to 8, wherein the first layer, the second layer, and the intermediate layer are formed into a film shape by coextrusion molding. <Aspect 10> A gas barrier film according to any one of aspects 1 to 9; a sealant layer laminated on a surface of the first layer or the second layer, The sealant layer is a laminated film containing at least one of a polyethylene resin, a polypropylene resin, a polyester resin, and a cyclic olefin resin. <Aspect 11> Aspect 11 is the laminate film according to aspect 10, wherein the sealant layer contains isophthalic acid-modified polyethylene terephthalate modified with isophthalic acid. <Aspect 12> A packaging bag formed using the laminated film according to aspect 10 or 11. [Explanation of symbols]

[0077] 1. Gas barrier film 2. Middle class 3 1st layer 4 2nd layer 5 Sealant Layer 6. Laminated film 10 packaging bags 11 Torso 12 Mouth

Claims

1. an intermediate layer, a first layer laminated on one surface of the intermediate layer, and a second layer laminated on the other surface of the intermediate layer; each of the first layer and the second layer contains a liquid crystal polymer having a melting point of 230°C or less, or the liquid crystal polymer and isophthalic acid-modified polyethylene terephthalate modified with isophthalic acid; the intermediate layer contains a polyester resin, The polyester resin is a polycondensate of a polycarboxylic acid component and a polyhydric alcohol component containing a diethylene glycol component.

2. 2. The gas barrier film according to claim 1, wherein the polyhydric alcohol component contains 1 mol % to 5 mol % of a diethylene glycol component.

3. 3. The gas barrier film according to claim 2, wherein the glass transition temperature of the polyester resin is from -10°C to 40°C.

4. 4. The gas barrier film according to claim 3, wherein the polyester resin is a modified polyethylene terephthalate comprising a dicarboxylic acid component comprising a terephthalic acid component and a diol component comprising a diethylene glycol component, an ethylene glycol component, and a 1,4-butanediol component.

5. 5. The gas barrier film according to claim 4, wherein the liquid crystal polymer contains a p-hydroxybenzoic acid component and a 6-hydroxy-2-naphthoic acid component as monomer components constituting the liquid crystal polymer.

6. 6. The gas barrier film according to claim 5, wherein the ratio of the thickness of the first layer to the thickness of the intermediate layer to the thickness of the second layer is 2-3:1:2-3.

7. 7. The gas barrier film according to claim 6, wherein the thickness of the intermediate layer is 10 μm to 30 μm.

8. 8. The gas barrier film according to claim 7, wherein, after being left in an environment at a temperature of 40°C and a relative humidity of 90% for 30 days, the rate of decrease in tear strength is 1% or less, and the rate of decrease in adhesive strength between the first layer and the second layer and between the intermediate layer and the first layer and the second layer is 2% or less.

9. The gas barrier film according to claim 8 , wherein the first layer, the second layer, and the intermediate layer are formed into a film by coextrusion molding.

10. The gas barrier film according to any one of claims 1 to 9, a sealant layer laminated on a surface of the first layer or the second layer, The sealant layer is a laminated film containing at least one of a polyethylene resin, a polypropylene resin, a polyester resin, and a cyclic olefin resin.

11. The laminated film according to claim 10, wherein the sealant layer comprises isophthalic acid-modified polyethylene terephthalate modified with isophthalic acid.

12. A packaging bag formed using the laminated film according to claim 10.

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