Gas barrier film, packaging film, and packaging bag

Abstract

To provide a gas barrier film which includes a polypropylene base and can achieve both favorable oxygen barrier performance and interlayer adhesion after heat sterilization treatment.SOLUTION: A gas barrier film includes, in this order, a base layer containing a polypropylene resin, a vapor deposition layer containing an inorganic oxide, and a gas barrier coating layer, wherein the base layer includes a first skin layer and a core layer, the vapor deposition layer is formed on the first skin layer side, the hardness of the first skin layer measured by a nano-indentation method is from 0.02 to 0.15 GPa, the hardness of the core layer is 0.07 GPa or more, and the hardness of the core layer is larger than the hardness of the first skin layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a gas barrier film, a packaging film, and a packaging bag.

Background Art

[0002] Gas barrier films are widely used as packaging materials for foods and pharmaceuticals that are subjected to heat sterilization treatments such as boiling treatment and retort treatment. When packaging contents such as foods and pharmaceuticals, it is important to reduce the oxygen transmission rate in order to suppress the deterioration and spoilage of the contents and maintain their quality. Therefore, conventionally, as a gas barrier film suitable for such applications, one using a polyethylene terephthalate film substrate having heat resistance and a low oxygen transmission rate has been used.

[0003] By the way, regarding packaging materials provided with a gas barrier film, in order to improve recyclability due to the increasing awareness of environmental problems, studies on packaging materials using a single material, so-called monomaterial packaging, are underway. Since polyolefin films such as polypropylene are generally used in packaging materials, in order to produce a monomaterial packaging, it is required to use a polyolefin film also as the substrate of the gas barrier film.

[0004] A polypropylene film as a polyolefin film is excellent in transparency, mechanical strength, heat resistance, etc. Therefore, using a polypropylene film as the substrate of a gas barrier film has been studied heretofore. For example, in Patent Document 1 below, a method of blending an ethylene-α-olefin copolymer with a polypropylene film has been proposed, and in Patent Documents 2 and 3, methods of laminating different polypropylene films have been proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in a conventional gas barrier film using a polypropylene film, it is difficult to achieve both good oxygen barrier properties and interlayer adhesion after heat sterilization treatment.

[0007] One aspect of the present disclosure aims to provide a gas barrier film that includes a polypropylene-based substrate and can achieve both good oxygen barrier properties and interlayer adhesion after heat sterilization treatment. One aspect of the present disclosure also aims to provide a packaging film and a packaging bag using the gas barrier film. [Means for Solving the Problems]

[0008] One aspect of the present disclosure provides a gas barrier film including a substrate layer containing a polypropylene-based resin, a vapor deposition layer containing an inorganic oxide, and a gas barrier coating layer, in this order. The substrate layer includes a first skin layer and a core layer. The vapor deposition layer is formed on the first skin layer side. The hardness of the first skin layer measured by the nanoindentation method is 0.02 to 0.15 GPa, the hardness of the core layer is 0.07 GPa or more, and the hardness of the core layer is greater than the hardness of the first skin layer.

[0009] Such a gas barrier film can achieve both good oxygen barrier properties and interlayer adhesion after heat sterilization treatment while including a polypropylene-based substrate.

[0010] In one embodiment, the first skin layer may include a propylene-α-olefin copolymer.

[0011] In one aspect, the ratio of the thickness of the first skin layer to the thickness of the core layer may be from 1 / 100 to 1 / 5.

[0012] In one aspect, the complex elastic modulus of the first skin layer measured by the nanoindentation method may be 1.2 to 2.5 GPa, and the complex elastic modulus of the core layer may be 2.0 GPa or more.

[0013] In one aspect, the inorganic oxide may include at least one of aluminum oxide and silicon oxide.

[0014] In one aspect, the gas barrier coating layer may be composed of a cured product of a composition containing a water-soluble polymer having a hydroxyl group and at least one selected from the group consisting of metal alkoxides, silane coupling agents, and their hydrolyzates.

[0015] In one aspect, the gas barrier film may further include an anchor coat layer between the base material layer and the vapor deposition layer.

[0016] In one aspect, the base material layer may include a first skin layer, a core layer, and a second skin layer in this order.

[0017] In one aspect, the second skin layer may include a propylene-α-olefin copolymer.

[0018] In one aspect, the hardness of the second skin layer measured by the nanoindentation method may be 0.02 to 0.15 GPa.

[0019] In one aspect, the thickness of the vapor deposition layer may be 5 nm or more and 80 nm or less.

[0020] Another aspect of the present disclosure provides a packaging film comprising the gas barrier film, a sealant layer overlapping the gas barrier coating layer, and an adhesive layer for adhering the gas barrier coating layer and the sealant layer, wherein after subjecting the packaging film to retort treatment, the hardness of the adhesive layer measured by nanoindentation is 0.1 MPa or more and less than 0.9 MPa.

[0021] In one aspect, before the retort treatment is carried out, the hardness of the adhesive layer measured by nanoindentation may be 1.0 MPa or more.

[0022] In one aspect, the thickness of the adhesive layer may be 0.5 μm or more and 10 μm or less.

[0023] In one aspect, each of the base material layer and the sealant layer is a polyolefin film, and the proportion of the total mass of the polyolefin in the packaging film may be 90% by mass or more.

[0024] In one aspect, the base material layer may be a stretched polypropylene film, and the sealant layer may be an unstretched polypropylene film.

[0025] In one aspect, the packaging film further comprises an outermost layer overlapping the base material layer and a second adhesive layer for adhering the outermost layer and the base material layer, the adhesive layer adheres the base material layer and the sealant layer, and the second adhesive layer may adhere the base material layer and the outermost layer.

[0026] In one aspect, after exposing the outermost layer at 120 °C for 15 minutes, the heat shrinkage rate in the MD direction of the outermost layer determined by the following formula (1) is 1% or more, and after subjecting the packaging film to retort treatment, the hardness of the second adhesive layer measured by nanoindentation may be 0.1 MPa or more and less than 0.9 MPa. Heat shrinkage rate in the MD direction (%) = (Length in the MD direction before heating - Length in the MD direction after heating) / Length in the MD direction before heating × 100 …(1)

[0027] One aspect of the present disclosure provides a packaging bag which is a product made of the above packaging film.

Advantages of the Invention

[0028] According to one aspect of the present disclosure, it is possible to provide a gas barrier film that has a polypropylene-based substrate and can achieve both good oxygen barrier properties and interlayer adhesion after heat sterilization treatment. Further, according to one aspect of the present disclosure, it is possible to provide a packaging film and a packaging bag using the gas barrier film.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0030] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, the present disclosure is not limited to the following embodiments.

[0031] [First Embodiment] <Gas barrier film> FIG. 1 is a schematic cross-sectional view showing a gas barrier film according to the first embodiment. As shown in FIG. 1, the gas barrier film 10a includes a base material layer 1, a vapor deposition layer 2, and a gas barrier coating layer 3 in this order. The base material layer 1 includes a first skin layer 11 and a core layer 12, and the vapor deposition layer 2 is formed on the first skin layer 11 side. That is, the vapor deposition layer 2 is formed on the first skin layer 11.

[0032] FIG. 2 is a schematic cross-sectional view showing a gas barrier film according to a modified example of the first embodiment. As shown in FIG. 2, the gas barrier film 10b includes a base material layer 1, a vapor deposition layer 2, and a gas barrier coating layer 3 in this order. The base material layer 1 includes a first skin layer 11, a core layer 12, and a second skin layer 13, and the vapor deposition layer 2 is formed on the first skin layer 11 side. That is, the vapor deposition layer 2 is formed on the first skin layer 11.

[0033] [Base material layer] The base material layer is a film (base film) serving as a support and contains a polypropylene-based resin. Examples of the polypropylene-based resin include homopolypropylene and propylene copolymers. Examples of the propylene copolymer include polypropylene-based copolymers such as propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer.

[0034] As the polypropylene-based resin, recycled resin may be used, or resin obtained by polymerizing raw materials derived from biomass such as plants may be used. These resins may be used alone, or these resins may be mixed with resins polymerized from ordinary fossil fuels and used.

[0035] The base material layer may be a stretched film or an unstretched film, but from the viewpoint of oxygen barrier properties, it may be a stretched film. Here, examples of the stretched film include a uniaxially stretched film and a biaxially stretched film, and the biaxially stretched film may improve heat resistance.

[0036] The base material layer is, for example, a polyolefin film. In this embodiment, the base material layer may contain a polypropylene film and may be made of a polypropylene film. The polypropylene film constituting the base material layer may be a stretched film or an unstretched film. However, from the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., the polypropylene film may be a stretched polypropylene film. Thereby, it is possible to suppress the heat fusion of the base material layer in the heat sealing process during bag making. Further, a gas barrier film can be more preferably used for applications subjected to heat treatment such as retort treatment and boiling treatment. The stretching method is not particularly limited, and any method may be used as long as a film with stable dimensions such as inflation stretching, uniaxial stretching, or biaxial stretching can be supplied.

[0037] The base material layer may contain known additives, for example, antioxidants, stabilizers, lubricants such as calcium stearate, fatty acid amides, erucic acid amide, organic additives such as antistatic agents, and inorganic additives such as particulate lubricants such as silica, zeolite, syloid, hydrotalcite, and silicon particles.

[0038] The thickness (total thickness) of the base material layer is not particularly limited, but may be, for example, 3 to 200 μm, or may be 6 to 50 μm.

[0039] From the viewpoint of the heat resistance of the gas barrier film, the polypropylene-based resin contained in the core layer may be crystalline polypropylene. From the viewpoint of further improving the heat resistance, the polypropylene-based resin contained in the core layer may be homopolypropylene which is a homopolymer of propylene. The polypropylene-based resin contained in the core layer may contain a mixture of homopolypropylene and a propylene-α-olefin random copolymer. The polypropylene-based resin contained in the core layer can contain 80% by mass or more of homopolypropylene, and may contain 100% by mass.

[0040] The first skin layer can relieve the difference between the shrinkage stress of the core layer and the shrinkage stress of the gas barrier coating layer due to heat sterilization treatment, and can prevent the occurrence of cracks in the gas barrier coating layer. An additional layer with an adhesive function, including acid-modified polyolefin, ethylene-vinyl alcohol copolymer, polyamide, etc., may be provided between the core layer and the first skin layer, or the core layer and the first skin layer may be in contact without an intervening layer.

[0041] In order to improve the adhesion between the base material layer and the vapor deposition layer, surface treatment such as plasma treatment or corona treatment may be performed on the first skin layer (the surface of the base material layer on the vapor deposition layer side).

[0042] The second skin layer can enhance the lamination strength with an adjacent layer (outer layer film or sealant layer). Similar to the above, other layers may be provided between the core layer and the second skin layer, or the core layer and the second skin layer may be in contact without an intervening layer.

[0043] In order to enhance the lamination strength with an adjacent layer without providing the second skin layer, surface treatment such as plasma treatment or corona treatment may be performed on the surface of the core layer, or an easy-adhesion coating layer may be provided.

[0044] From the perspective of improving the adhesion with the core layer, the polypropylene-based resin contained in each skin layer may include a propylene copolymer (a copolymer of propylene and other monomers). Examples of other monomers include α-olefins such as ethylene, 1-butene, and 1-hexene. Specifically, the propylene copolymer may be a propylene-ethylene random copolymer, a propylene-ethylene block copolymer, a propylene-α-olefin copolymer, etc. From the perspective of improving heat resistance, each skin layer may include a propylene-α-olefin copolymer.

[0045] From the perspective of improving heat resistance, the content of propylene monomer in the propylene copolymer can be 90 mol% or more, and may be 92 mol% or more, based on all monomers constituting the copolymer. From the perspective of imparting flexibility, the content of propylene monomer in the propylene copolymer can be 99.8 mol% or less, and may be 99.5 mol% or less, based on all monomers constituting the copolymer.

[0046] The hardness and complex elastic modulus of the core layer and each skin layer represent the hardness and complex elastic modulus measured by the nanoindentation method. The nanoindentation method is a measurement method in which a quasi-static indentation test is performed on the measurement object to obtain the mechanical properties of the sample. As the measurement device, Hysitron TI-Premier (trade name) manufactured by Bruker Japan Co., Ltd. can be used, and as the indenter, a Berkovich-type diamond indenter manufactured by Bruker Japan Co., Ltd. can be used.

[0047] The measurement by the nanoindentation method is performed in the displacement control mode. After pushing in to a depth of 30 nm at a pushing speed of 30 nm / second, it is held for 1 second at the maximum depth, and then unloaded at a speed of 30 nm / second.

[0048] The measurement is performed by acquiring the shape image of the sample cross-section by the shape measurement function of the measurement device that scans the sample surface with the indenter, and designating 20 points at intervals of 1 μm or more on the target layer from the shape image.

[0049] When calculating the hardness and complex elastic modulus, fused quartz as a standard sample is tested in advance to calibrate the relationship between the contact depth and the contact projected area of the indenter and the sample. Then, the unloading curve in the 60 - 95% region with respect to the maximum load during unloading is analyzed by the Oliver-Pharr method to calculate the hardness and complex elastic modulus.

[0050] The measurement by the nanoindentation method is carried out on the cross-section of the base material layer after embedding the base material layer in resin and then cutting it to expose the cross-section. When embedding in resin, corona treatment may be carried out as a surface treatment on the front and back surfaces of the base material layer to prevent peeling between the embedding resin and the base material layer. Note that the sample used for the measurement does not have to be in the state of only the base material layer, and a sample in the state of a gas barrier film or a packaging film may also be used.

[0051] The hardness of the core layer is 0.07 GPa or more. The core layer with hardness in this range is heat-resistant and can suppress the shrinkage of the base material layer during heat sterilization treatment. The hardness of the core layer may be 0.072 GPa or more, or 0.075 GPa or more. The upper limit of the hardness is not particularly limited, but since a polypropylene-based resin is used as the material, it can be 0.2 GPa or less.

[0052] The hardness of the first skin layer is in the range of 0.02 to 0.15 GPa. When the hardness of the first skin layer is 0.02 GPa or more, it is possible to suppress the first skin layer from becoming too soft, and it is difficult for problems such as a decrease in adhesion and a decrease in gas barrier properties to occur. When the hardness of the first skin layer is 0.15 GPa or less, it is possible to suppress the first skin layer from becoming too hard. As a result, the stress difference between the core layer and the gas barrier coating layer during heat sterilization treatment is relaxed, and it is difficult for the gas barrier property to decrease. Also, the adhesion strength between the core layer and the first skin layer is less likely to decrease. The hardness of the first skin layer may be 0.025 to 0.10 GPa, or 0.030 to 0.098 GPa.

[0053] The hardness of the second skin layer can be set in the same manner as the first skin layer 11. Thereby, not only can the lamination strength with the adjacent layer be increased, but also the adhesion strength with the core layer can be increased.

[0054] In order to reduce the shrinkage of the base material layer during heat sterilization treatment and maintain the adhesion strength between the layers, the hardness of the core layer in the base material layer is set to be the largest. That is, the hardness of the core layer is set to be greater than the hardness of the first skin layer and also greater than the hardness of the second skin layer. The hardness of the first skin layer and the second skin layer may be the same or different.

[0055] The complex elastic modulus of the core layer may be 2.0 GPa or more. Since the core layer with a complex elastic modulus in this range becomes stronger by heat, it becomes easier to suppress the shrinkage of the base material layer during heat sterilization treatment. The complex elastic modulus of the core layer may be 2.1 GPa or more, and may be 2.13 GPa or more. The upper limit of the complex elastic modulus is not particularly limited, but since a polypropylene-based resin is used as the material, it is 4.5 GPa or less.

[0056] The complex elastic modulus of the first skin layer may be in the range of 1.2 to 2.5 GPa. When the complex elastic modulus of the first skin layer is 1.2 GPa or more, it is suppressed that the first skin layer becomes too soft, and it is less likely to cause problems such as a decrease in adhesion and a decrease in gas barrier properties. When the complex elastic modulus of the first skin layer is 2.5 GPa or less, it is suppressed that the first skin layer becomes too hard. As a result, the stress difference between the core layer and the gas barrier coating layer during heat sterilization treatment is more easily relaxed, and the gas barrier property is less likely to decrease. Also, the adhesion strength between the core layer and the first skin layer is less likely to decrease. The complex elastic modulus of the first skin layer may be 1.22 to 2.48 GPa, or may be 1.25 to 2.45 GPa.

[0057] The complex elastic modulus of the second skin layer can be set in the same manner as the first skin layer. Thereby, not only can the lamination strength with the adjacent layer be further increased, but also the adhesion strength with the core layer can be further increased.

[0058] In order to make the shrinkage of the base material layer during heat sterilization treatment smaller and to easily maintain the adhesion strength between the layers, the composite elastic modulus of the core layer may be set to be the largest in the base material layer. That is, the composite elastic modulus of the core layer may be set to be larger than that of the first skin layer and also larger than that of the second skin layer. The composite elastic moduli of the first skin layer and the second skin layer may be the same or different.

[0059] The method for adjusting the hardness and composite elastic modulus of the core layer and each skin layer is not particularly limited. The adjustment of the hardness and composite elastic modulus of each layer containing a polypropylene-based resin can be performed, for example, by adjusting the type of resin constituting each layer, the mixing ratio when using a plurality of resins, the monomer ratio when using a copolymer, and the production method of each layer.

[0060] The thickness of each skin layer may be 0.1 μm or more. Thereby, the skin layer can be uniformly laminated on the core layer, and the variation in the thickness of the skin layer can be suppressed. Also, thereby, it is considered that the stress on the vapor deposition layer during heat sterilization treatment can be sufficiently relaxed, and the deterioration of the gas barrier property can be suppressed. From such a viewpoint, the thickness of each skin layer is, for example, 0.3 μm or more.

[0061] The upper limit of the thickness of each skin layer is not particularly limited, but from the viewpoint of more sufficiently ensuring the heat resistance of the entire base material layer, it is, for example, 2.0 μm or less, and may be 1.8 μm or less.

[0062] The ratio of the thickness of the first skin layer to the thickness of the core layer (thickness of the first skin layer / thickness of the core layer) may be 1 / 100 to 1 / 5, or may be 1 / 70 to 1 / 10. When the thickness ratio is within the above range, the heat resistance of the entire base material layer can be more sufficiently ensured, and the adhesion between the layers in the gas barrier film and the packaging film can be enhanced.

[0063] The ratio of the thickness of the second skin layer to the thickness of the core layer (thickness of the second skin layer / thickness of the core layer) may be from 1 / 100 to 1 / 5, or may be from 1 / 70 to 1 / 10. When the thickness ratio is within the above range, the heat resistance of the entire substrate layer can be more sufficiently ensured, and the adhesion between the layers in the gas barrier film and the packaging film can be further enhanced.

[0064] [Vapor deposition layer] The vapor deposition layer contains an inorganic oxide and is, for example, a layer provided on the substrate layer from the viewpoint of improving the gas barrier property against water vapor and oxygen. The vapor deposition layer may have transparency. Examples of the inorganic oxide include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or a mixture thereof. From the viewpoint of heat resistance during heat sterilization treatment, at least one of aluminum oxide and silicon oxide may be used as the inorganic oxide.

[0065] The thickness of the vapor deposition layer may be 5 to 300 nm. If the thickness of the vapor deposition layer is 5 nm or more, it is easy to make the layer thickness uniform and it is easier to ensure the function as a gas barrier film. Also, if the thickness of the vapor deposition layer is 300 nm or less, it is easy to impart flexibility to the vapor deposition layer, and it is difficult for cracks to occur in the vapor deposition layer even when external factors such as bending and pulling are applied after layer formation. From such a viewpoint, the thickness of the vapor deposition layer may be, for example, 6 nm or more, may be 150 nm or less, or may be 100 nm or less. The thickness of the vapor deposition layer may be 5 to 80 nm, or may be 20 to 40 nm.

[0066] The vapor deposition layer 2 can be formed by a normal vacuum deposition method. It is also possible to use other thin film formation methods such as a sputtering method, an ion plating method, or a plasma chemical vapor deposition method (CVD). However, considering productivity, the vacuum deposition method is excellent at present.

[0067] As the heating means for the vacuum deposition method, any one of an electron beam heating method, a resistance heating method, and an induction heating method may be used. Considering the wide range of selectivity of the evaporation material, the electron beam heating method may be used as the above heating means.

[0068] In order to improve the adhesion between the vapor deposition layer and the base material layer and the denseness of the vapor deposition layer, it is also possible to form the vapor deposition layer by using a plasma assist method or an ion beam assist method. Further, in order to increase the transparency of the vapor deposition layer, reactive vapor deposition in which various gases such as oxygen are blown in during vapor deposition may be used.

[0069] [Anchor coat layer] An anchor coat layer can be further provided between the base material layer and the vapor deposition layer. Thereby, the adhesion and gas barrier property of both layers after heat sterilization treatment can be further improved.

[0070] Examples of the coating agent for providing the anchor coat layer include acrylic resin, epoxy resin, acrylic urethane resin, polyester-based polyurethane resin, polyether-based polyurethane resin, etc. From the viewpoints of heat resistance and interlayer adhesion strength, acrylic urethane resin and polyester-based polyurethane resin may be the coating agent.

[0071] The thickness of the anchor coat layer may be 0.05 to 2 μm. If the thickness of the anchor coat layer is 0.05 μm or more, it is possible to further improve the adhesion between the base material layer and the vapor deposition layer. Also, if the thickness of the anchor coat layer is 2 μm or less, it is easy to impart flexibility to the anchor coat layer, and it is easy to maintain the gas barrier property even when external factors such as bending and pulling are applied after layer formation. From such a viewpoint, the thickness of the anchor coat layer may be, for example, 0.08 μm or more and 1 μm or less.

[0072] [Gas barrier coating layer] The gas barrier coating layer is provided for the purpose of protecting the vapor deposition layer and complementing the gas barrier property. The gas barrier coating layer may be composed of a cured product of a composition containing a water-soluble polymer having a hydroxyl group and at least one selected from the group consisting of metal alkoxides, silane coupling agents, and their hydrolyzates.

[0073] Examples of the water-soluble polymer having a salicylic acid group include polyvinyl alcohol, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, and the like. In particular, when polyvinyl alcohol (PVA) is used as a coating agent, the gas barrier property tends to be more excellent.

[0074] Examples of the metal alkoxide include compounds represented by the following general formula. M(OR 1 ) m (R 2 ) n-m In the above formula, R 1 is a monovalent organic group having 1 to 8 carbon atoms, and may be an alkyl group such as a methyl group or an ethyl group (OR 1 is a hydrolyzable group). R 2 is a monovalent organic group having 1 to 8 carbon atoms, and may be an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer of 1 to n. When there are a plurality of R 1 and R 2 , R 1 each other or R 2 each other may be the same or different.

[0075] Specific examples of the metal alkoxide include tetraethoxysilane [Si(OC2H5)4], triisopropoxyaluminum [Al(O-2'-C3H7)3], and the like. Tetraethoxysilane (TEOS) and triisopropoxyaluminum tend to be relatively stable in an aqueous solvent after hydrolysis.

[0076] Examples of the silane coupling agent include compounds represented by the following general formula. Si(OR 21 ) p (R 22 ) 3-p R 23 …(2) In the above formula, R 21 represents an alkyl group such as a methyl group or an ethyl group, and R 22represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or an alkyl group substituted with a methacryloxy group, and R 23 represents a monovalent organic functional group, and p represents an integer from 1 to 3. In addition, R 21 or R 22 When there are a plurality of them, R 21 each other or R 22 each other may be the same or different. As the monovalent organic functional group represented by R 23 there may be mentioned a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or a monovalent organic functional group containing an isocyanate group. Compounds obtained by using these silane coupling agents as multimers such as dimers and trimers may also be used.

[0077] Specific examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, 1,3,5-tris(3-methoxysilylpropyl)isocyanurate, and other silane coupling agents.

[0078] The gas barrier coating layer can be formed by coating the gas barrier coating layer-forming composition on the above vapor deposition layer and then heating and drying. The gas barrier coating layer-forming composition can be prepared by mixing at least one of a metal alkoxide and a silane coupling agent, or a hydrolyzed product thereof, with a water-soluble polymer dissolved in an aqueous solvent (such as water, a water / alcohol mixed solvent). In this composition (mixed solution), known additives such as isocyanate compounds, or dispersants, stabilizers, viscosity modifiers, colorants, etc. can be added as necessary within a range that does not impair the gas barrier properties.

[0079] When using PVA as the water-soluble polymer, the amount of PVA in the composition may be 20 to 70% by mass, or 25 to 60% by mass, based on the total solid content of the composition. When the amount of PVA is 20% by mass or more, the flexibility of the layer is maintained and it becomes easier to form a gas barrier coating layer. On the other hand, when the amount of PVA is 70% by mass or less, it becomes easier to impart sufficient gas barrier properties by the gas barrier film.

[0080] When using TEOS as the metal alkoxide, the amount of TEOS in the composition may be 30 to 80% by mass, or 40 to 75% by mass, based on the total solid content of the composition. When the amount of TEOS is 30% by mass or more, it becomes easier to exhibit high gas barrier properties. On the other hand, when the amount of TEOS is 80% by mass or less, it becomes easier to maintain the flexibility of the layer. The amount of TEOS is calculated in terms of SiO2.

[0081] When using isocyanurate silane as the silane coupling agent, it may be 1 to 20% by mass, or 5 to 15% by mass, based on the total solid content of the composition. If the amount of isocyanurate silane is 1% by mass or more, it is easy to obtain heat and water resistance and the adhesion strength is difficult to decrease. On the other hand, if the amount of isocyanurate silane is 20% by mass or less, the amount of other components in the composition does not become too low, and as a result, it is easy to obtain high gas barrier properties.

[0082] The thickness of the gas barrier coating layer may be 0.1 to 5 μm. When the thickness of the gas barrier coating layer is 0.1 μm or more, it becomes easier to exhibit high gas barrier properties. Also, when the thickness of the gas barrier coating layer is 5 μm or less, it is possible to suppress a decrease in gas barrier properties due to crack generation in the layer during coating. From such a viewpoint, the thickness of the gas barrier coating layer may be, for example, 0.2 μm or more and 1 μm or less.

[0083] <Packaging film> FIG. 3 is a schematic cross-sectional view showing the packaging film according to the first embodiment. The packaging film 20 shown in FIG. 3 has a structure in which a sealant layer 23 is laminated on the gas barrier coating layer 3 of the gas barrier film 10a via an adhesive layer 24.

[0084] FIG. 4 is a schematic cross-sectional view showing the packaging film according to a modification of the first embodiment. The packaging film 30 shown in FIG. 4 has a sealant layer 23 laminated on the second skin layer 13 of the gas barrier film 10b via an adhesive layer 24, and an outer layer film (outermost layer) 22 laminated on the gas barrier coating layer 3 of the gas barrier film 10b via a second adhesive layer 25. In the packaging film 30 shown in FIG. 4, the orientation of the gas barrier film 10b may be reversed. That is, an outer layer film (second base material layer) 22 may be laminated on the second skin layer 13 of the gas barrier film 10b via a second adhesive layer 25, and a sealant layer 23 may be laminated on the gas barrier coating layer 3 of the gas barrier film 10b via an adhesive layer 24.

[0085] (Outer layer film) The outer layer film is a layer provided for the purpose of enhancing the rigidity as a packaging bag. Therefore, the outer layer film can be referred to as the second base material layer. In order to make the packaging film a single-material packaging material, the outer layer film contains a polyolefin-based resin. Examples of the polyolefin-based resin include polyethylene and polypropylene, and polypropylene may be used from the viewpoint of retort treatment resistance. Here, the polypropylene may be homopolypropylene or a propylene copolymer, and homopolypropylene may be used from the viewpoint of heat resistance.

[0086] The outer layer film may be a stretched film or an unstretched film, and may be a stretched film from the viewpoint of oxygen barrier properties.

[0087] The thickness of the outer layer film is not particularly limited, and can be, for example, 15 to 200 μm.

[0088] (Sealant layer) The sealant layer contains a polyolefin resin. Specifically, as the polyolefin resin, ethylene-based resins such as low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-(meth)acrylic acid copolymer, homopolypropylene resin (PP), polypropylene-based resins such as propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-α-olefin copolymer, or a mixture thereof can be used. The material of the sealant layer can be appropriately selected from the above-mentioned thermoplastic resins according to the intended use and temperature conditions such as boiling treatment and retort treatment.

[0089] The sealant layer may also be a polyolefin film similar to the base material layer. The sealant layer has, for example, a single-layer structure and is a resin layer mainly made of polypropylene, but is not limited thereto. The sealant layer may contain a polypropylene film and may be made of a polypropylene film.

[0090] The thermoplastic resin constituting the sealant layer may or may not be stretched. From the viewpoint of lowering the melting point and facilitating heat sealing, it may not be stretched. The polypropylene film constituting the sealant layer may be an unstretched polypropylene film from the viewpoint of enhancing the sealing property by heat sealing.

[0091] The thickness of the sealant layer is not particularly limited, but can be, for example, 15 to 200 μm.

[0092] (Adhesive layer) The subsequent layer adheres the films to each other. Examples of the adhesive constituting the adhesive layer include polyurethane resins obtained by reacting a bifunctional or higher isocyanate compound with a main agent such as polyester polyol, polyether polyol, acrylic polyol, and carbonate polyol. The various polyols may be used alone or in combination of two or more. From the viewpoint of heat resistance (retort treatment resistance) during heat sterilization, a two-component curable urethane-based adhesive may be used.

[0093] For the purpose of promoting adhesion, the above-mentioned polyurethane resin may be blended with a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent, etc. From the viewpoint of environmental consideration, an adhesive whose polymer component is derived from biomass or an adhesive having biodegradability may be used as the adhesive. Further, the adhesive may be a barrier adhesive.

[0094] The coating amount of the adhesive may be, for example, 0.5 to 10 g / m 2 from the viewpoint of obtaining desired adhesive strength, followability, workability, etc.

[0095] The thickness of the adhesive layer is, for example, 0.5 μm or more and 10 μm or less. When the thickness of the adhesive layer is 0.5 μm or more, peeling between the gas barrier coating layer and the sealant layer can be favorably suppressed. When the thickness of the adhesive layer is 10 μm or less, the packaging film can be easily made into a single material (details will be described later). The thickness of the adhesive layer may be 1 μm or more, 2 μm or more, 8 μm or less, 6 μm or less, or 5 μm or less.

[0096] (Second Adhesive Layer) The second adhesive layer is a layered member that adheres the gas barrier film and the outer layer film. The material of the adhesive contained in the second adhesive layer is the same as the material of the adhesive contained in the adhesive layer. Therefore, the description of the materials and the like contained in the second adhesive layer will be omitted. The thickness of the second adhesive layer is the same as the thickness of the adhesive layer, and is, for example, 0.5 μm or more and 10 μm or less.

[0097] (Polyolefin content) The proportion of the total mass of polyolefin (in this embodiment, polypropylene) in the packaging film is 90% by mass or more. As a result, the packaging film can be said to be a (monomaterial) packaging material made of a single material and has excellent recyclability. From the viewpoint of further improving recyclability, the polyolefin content in the packaging film may be 92.5% by mass or more, or 95% by mass or more based on the total amount of the packaging film.

[0098] (Heat shrinkage rate of the base material layer) After exposing the base material layer to 120°C for 15 minutes (hereinafter simply referred to as "after heating"), the heat shrinkage rate of the base material layer in the MD direction obtained by the following formula (1) is 1% or more. For example, after heating the base material layer or the gas barrier film including the base material layer in an oven at 120°C for 15 minutes, the heat shrinkage rate of the base material layer in the MD direction obtained by the following formula (1) is 1% or more. From the viewpoints of reducing deformation during bag making and suppressing peeling between the gas barrier film and the sealant layer, the above heat shrinkage rate in the MD direction is, for example, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, or 7% or less. Note that, for example, the biaxially oriented polypropylene film has the above heat shrinkage rate of 1% or more, while the PET film has the above heat shrinkage rate of less than 1%. Heat shrinkage rate in the MD direction (%) = (Length in the MD direction before heating - Length in the MD direction after heating) / Length in the MD direction before heating × 100 …(1)

[0099] After the above heating, the heat shrinkage rate of the base material layer in the TD direction obtained by the following formula (2) is not particularly limited, but is, for example, 1% or more. From the viewpoints of reducing deformation during bag making and suppressing peeling between the gas barrier film and the sealant layer, the above heat shrinkage rate in the TD direction is, for example, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, or 7% or less. Heat shrinkage rate in the TD direction (%) = (Length in the TD direction before heating - Length in the TD direction after heating) / Length in the TD direction before heating × 100 …(2)

[0100] (Hardness of the adhesive layer) Based on the heat shrinkage rate of the above-described base material layer, in this embodiment, after subjecting the packaging film to retort treatment, the hardness of the adhesive layer is 0.1 MPa or more and less than 0.9 MPa. In this case, the adhesive layer can favorably follow the expansion and contraction of the base material layer accompanying heat treatment such as retort treatment and boiling treatment. Therefore, even when the above heat treatment is performed on the packaging film including the base material layer having the above-described heat shrinkage rate, peeling between the gas barrier film and the sealant layer is less likely to occur. In addition, generation of cracks in the adhesive layer during cooling after the above heat treatment and damage to the gas barrier film (at least one of the vapor deposition layer and the gas barrier coating layer) accompanying the generation of the cracks are suppressed. The hardness of the adhesive layer before the retort treatment is not particularly limited, but is, for example, 1.0 MPa or more.

[0101] The hardness of the adhesive layer can be controlled by the material of the adhesive, the amount of the curing agent, the aging time, etc. The closer the distance between the molecular chains of the adhesive, the harder the adhesive layer tends to be. The bulkier the adhesive, the softer the adhesive layer tends to be. The hardness of an aliphatic adhesive layer tends to be harder than that of an alicyclic or aromatic adhesive layer. The hardness of an alicyclic adhesive layer tends to be harder than that of an aromatic adhesive layer. The greater the amount of the curing agent contained in the adhesive layer, the harder the adhesive layer tends to be. The longer the aging time, the harder the adhesive layer tends to be.

[0102] The hardness of the adhesive layer in the packaging film is obtained by measuring the hardness of the portion exposed from the sealant layer (exposed portion). Removal of the sealant layer for exposing the adhesive layer is performed, for example, using an oblique cutting device. In this embodiment, the hardness of the adhesive layer is obtained by being measured by the nanoindentation method. The hardness of a sample such as the adhesive layer is calculated, for example, by the following method. First, fused quartz as a standard sample is tested in advance to calibrate the relationship between the contact depth and the contact projected area of the indenter and the sample. Then, the hardness of the sample is calculated by analyzing the unloading curve in the 20 to 95% region with respect to the maximum load during unloading by the Oliver-Pharr method.

[0103] (Hardness of the outer layer film) After exposing the outer layer film at 120°C for 15 minutes, the heat shrinkage rate of the outer layer film in the MD direction obtained by the above formula (1) is 1% or more. For example, after heating the outer layer film, or a laminate of the outer layer film and the gas barrier film 10b in an oven at 120°C for 15 minutes, the heat shrinkage rate of the outer layer film in the MD direction obtained by the following formula (1) is 1% or more. The following heat shrinkage rate in the MD direction is, for example, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, or 7% or less.

[0104] After the above heating, the heat shrinkage rate of the outer layer film in the TD direction obtained by the above formula (2) is not particularly limited, but is, for example, 1% or more and 12% or less.

[0105] (Hardness of the second adhesive layer) In this modified example, after performing a retort treatment on the packaging film, the hardness of the second adhesive layer is 0.1 MPa or more and less than 0.9 MPa. In this case, the second adhesive layer can follow well the expansion and contraction of the outer layer film accompanying heat treatments such as retort treatment and boiling treatment. Therefore, even when the above heat treatment is performed on the packaging film including the second adhesive layer having the above-described heat shrinkage rate, peeling between the gas barrier film and the outer layer film is less likely to occur. In addition, generation of cracks in the second adhesive layer during cooling after the above heat treatment, and damage to the gas barrier film (at least one of the vapor deposition layer and the gas barrier coating layer) accompanying the generation of the cracks are suppressed. The hardness of the second adhesive layer before the retort treatment is not particularly limited, but is, for example, 1.0 MPa or more.

[0106] The hardness of the second adhesive layer can be controlled by the material of the adhesive, the amount of the curing agent, the aging time, etc. The closer the distance between the molecular chains of the adhesive is, the harder the second adhesive layer tends to be. The bulkier the adhesive is, the softer the second adhesive layer tends to be. The hardness of the second adhesive layer that is aliphatic tends to be harder than that of the second adhesive layer that is alicyclic or aromatic. The hardness of the second adhesive layer that is alicyclic tends to be harder than that of the second adhesive layer that is aromatic. The larger the amount of the curing agent contained in the second adhesive layer is, the harder the second adhesive layer tends to be. The longer the aging time is, the harder the second adhesive layer tends to be.

[0107] <Packaging bag> The packaging bag is formed by making a bag from the above-described packaging film. The packaging bag can contain contents such as food and pharmaceuticals.

[0108] The packaging bag may be formed into a bag shape by folding a single packaging film in half with the sealant layers facing each other and then heat-sealing three sides, or by overlapping two packaging materials with the sealant layers facing each other and then heat-sealing four sides. Further, the packaging bag may have a shape having a bent portion (folded portion) such as a standing pouch. The packaging bag according to the present embodiment can maintain high gas barrier properties even when having a shape with a bent portion.

[0109] [Second Embodiment] <Laminate> FIG. 5(a) is a schematic plan view of a laminate according to an embodiment, and FIG. 5(b) is a schematic cross-sectional view showing the laminate according to an embodiment. The laminate 35 shown in FIGS. 5(a) and 5(b) is a sheet-like member having gas barrier properties (gas barrier laminate), and is a sheet-like packaging material used for manufacturing, for example, a packaging bag. The laminate 35 can be suitably used for applications that are subjected to heat treatments such as retort treatment and boiling treatment. The laminate 35 may correspond to the packaging film of the first embodiment.

[0110] Retort processing is generally a method of sterilizing microorganisms such as molds, yeasts, and bacteria under pressure to preserve foods, pharmaceuticals, and the like. Usually, a packaging bag containing food or the like is subjected to a pressure sterilization treatment under the conditions of 105 to 140 °C and 0.15 to 0.30 MPa for 10 to 120 minutes. Retort apparatuses include a steam type that uses heating steam and a hot water type that uses pressurized heated water, and they are appropriately selected according to the sterilization conditions of foods and the like that are the contents. Boiling treatment is a method of moist heat sterilization to preserve foods, pharmaceuticals, and the like. Usually, although it depends on the contents, a packaging bag containing food or the like is subjected to a moist heat sterilization treatment under the conditions of 60 to 100 °C and atmospheric pressure for 10 to 120 minutes. Boiling treatment is usually performed at 100 °C or lower using a hot water tank. As methods, there are a batch type in which it is immersed in a hot water tank at a constant temperature, treated for a certain period of time, and then taken out, and a continuous type in which it is passed through the hot water tank in a tunnel type for treatment.

[0111] The laminate 35 includes a barrier layer 40, a sealant layer 50, and an adhesive layer 60. The barrier layer 40 and the sealant layer 50 are laminated with each other and adhered by the adhesive layer 60. In the laminate 35, the barrier layer 40, the adhesive layer 60, and the sealant layer 50 are laminated in this order. Hereinafter, as shown in Fig. 5(a), the MD direction is defined as the flow direction (longitudinal direction) of the laminate 35, and the TD direction is defined as the width direction (lateral direction) of the laminate 35. Also, the direction orthogonal to both the MD and TD directions is defined as the lamination direction of the members included in the laminate 35.

[0112] [Barrier layer 40] The barrier layer 40 functions as a member that supports the laminate 35 and exhibits gas barrier properties against gases such as water vapor and oxygen. The barrier layer 40 may correspond to the gas barrier film of the first embodiment. As shown in FIG. 5, the barrier layer 40 includes a base material 41, an adhesion layer 42, a vapor deposition layer 43, and a barrier coat 44. In the barrier layer 40, the base material 41, the adhesion layer 42, the vapor deposition layer 43, and the barrier coat 44 are laminated in this order. For this reason, the adhesion layer 42 and the vapor deposition layer 43 are positioned between the base material 41 and the barrier coat 44 in the lamination direction, and the adhesion layer 42 is positioned between the base material 41 and the vapor deposition layer 43. In the present embodiment, the barrier coat 44 of the barrier layer 40 is the closest to the adhesive layer 60 in the lamination direction. For this reason, the base material 41 of the barrier layer 40 is the farthest from the adhesive layer 60 in the lamination direction.

[0113] [Base material 41] The base material 41 is a plastic member (base material layer) that functions as the outermost layer in the laminate 35. The thickness of the base material 41 is not particularly limited. Depending on the application, the thickness can be 6 to 200 μm, but from the perspective of reducing material usage for environmental load reduction, and from the perspective of obtaining excellent heat resistance, impact resistance, and excellent gas barrier properties, it may be 9 to 50 μm, it may be 12 to 38 μm, or it may be 18 to 30 μm.

[0114] From the perspective of recyclability of the laminate 35, etc., the base material 41 is, for example, a polyolefin film. In the present embodiment, the base material 41 may include a polypropylene film and may be made of a polypropylene film. The polypropylene film may be an acid-modified polypropylene film obtained by graft-modifying polypropylene using an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, etc. Further, as the polypropylene, polypropylene-based resins such as homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-α olefin copolymer, etc. can be used.

[0115] Various additives such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a light stabilizer, a tackifier, and an antistatic agent may be added to the polypropylene film constituting the base material 41.

[0116] The polypropylene film constituting the base material 41 may be a stretched film or an unstretched film. However, from the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., the polypropylene film may also be a stretched polypropylene film. Thereby, it is possible to suppress the heat fusion of the base material 41 in the heat seal step during bag making. In addition, the laminate 35 can be more preferably used for applications that are subjected to heat treatments such as retort treatment and boiling treatment. The stretching method is not particularly limited, and any method may be used as long as a film with stable dimensions can be supplied, such as stretching by inflation, or uniaxial stretching or biaxial stretching.

[0117] The base material 41 may be subjected to various pretreatment such as corona treatment, plasma treatment, and flame treatment within a range that does not impair the barrier performance on its laminated surface, or a coating layer such as an easy adhesion layer may be provided.

[0118] [Adhesion layer] The adhesion layer 42 functions as a layer (anchor coat layer) that can improve the adhesion performance of the vapor deposition layer 43 on the base material 41 and is provided directly above the base material 41. For this reason, the adhesion layer 42 is located between the base material 41 and the vapor deposition layer 43. By providing the adhesion layer 42, the smoothness of the surface on which the vapor deposition layer 43 is provided in the barrier layer 40 can be improved. Note that by improving the smoothness, it becomes easier to form the vapor deposition layer 43 uniformly without defects, and it is easier to exhibit high barrier properties. The adhesion layer 42 can be formed, for example, using an anchor coat agent.

[0119] Examples of the anchor coat agent include polyester-based polyurethane resin and polyether-based polyurethane resin. From the viewpoints of heat resistance and interlayer adhesion strength, a polyester-based polyurethane resin can be used as the anchor coat agent.

[0120] The thickness of the adhesion layer 42 is not particularly limited, but may be in the range of 0.01 to 5 μm, may be in the range of 0.03 to 3 μm, or may be in the range of 0.05 to 2 μm. When the thickness of the adhesion layer 42 is equal to or greater than the above lower limit value, sufficient interlayer adhesion strength tends to be obtained. On the other hand, when it is equal to or less than the above upper limit value, the desired gas barrier property tends to be easily exhibited.

[0121] As a method for coating the adhesion layer 42 on the substrate 41, known coating methods can be used without particular limitation, including dipping method; methods using spray, coater, printing machine, brush, etc. Further, as the types of coaters and printing machines used in these methods and their coating methods, there are gravure coaters such as direct gravure method, reverse gravure method, kiss reverse gravure method, offset gravure method, etc., reverse roll coater, micro gravure coater, chamber doctor combined coater, air knife coater, dip coater, bar coater, comma coater, die coater, etc.

[0122] The coating amount of the adhesion layer 42 is such that the mass per 1 m 2 after coating and drying the anchor coating agent may be 0.01 to 5 g / m 2 and may also be 0.03 to 3 g / m 2 After coating and drying the anchor coating agent, when the mass per 1 m 2 is equal to or greater than the above lower limit, film formation tends to be sufficient. On the other hand, when it is equal to or less than the above upper limit, it tends to dry sufficiently and it is difficult for the solvent to remain.

[0123] The method for drying the adhesion layer 42 is not particularly limited, and examples include drying by natural drying, drying in an oven set at a predetermined temperature, and using a dryer attached to the coater, such as an arch dryer, floating dryer, drum dryer, infrared dryer, etc. Further, the drying conditions can be appropriately selected according to the drying method. For example, in the method of drying in an oven, it may be dried at a temperature of 60 to 100 °C for about 1 second to 2 minutes.

[0124] As the contact layer 42, instead of the above polyurethane resin, a polyvinyl alcohol-based resin can be used. The polyvinyl alcohol-based resin may be any resin having vinyl alcohol units formed by saponifying vinyl ester units. For example, polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH) can be mentioned.

[0125] Examples of PVA include resins obtained by polymerizing vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate alone and then saponifying them. PVA may be a copolymer-modified or post-modified modified PVA. Modified PVA can be obtained, for example, by copolymerizing a vinyl ester and an unsaturated monomer copolymerizable with the vinyl ester and then saponifying. Examples of unsaturated monomers copolymerizable with vinyl esters include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxy group-containing α-olefins such as 3-buten-1-ol, 4-pentyn-1-ol, and 5-hexen-1-ol; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid; nitriles such as acrylonitrile and methacrylonitrile; amides such as diacetoneacrylamide, acrylamide, and methacrylamide; olefin sulfonic acids such as ethylenesulfonic acid, allylsulfonic acid, and methallylsulfonic acid; vinyl compounds such as alkyl vinyl ether, dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, and 3,4-diacetoxy-1-butene; vinylidene chloride, 1,4-diacetoxy-2-butene, and vinylene carbonate.

[0126] The degree of polymerization of PVA is, for example, from 300 to 3000. If the degree of polymerization is less than 300, the barrier property is likely to decrease. If it exceeds 3000, the viscosity is too high and the coatability is likely to decrease. The saponification degree of PVA may be 90 mol% or more, 95 mol% or more, or 99 mol% or more. Also, the saponification degree of PVA may be 100 mol% or less, or 99.9 mol% or less. The degree of polymerization and saponification degree of PVA can be measured according to the method described in JIS K 6726 (1994).

[0127] EVOH is generally obtained by saponifying a copolymer of ethylene and a vinyl ester such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprylate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl versatate, etc.

[0128] The degree of polymerization of EVOH is, for example, from 300 to 3000. If the degree of polymerization is less than 300, the barrier property is likely to decrease. If it exceeds 3000, the viscosity is too high and the coatability is likely to decrease. The saponification degree of the vinyl ester component of EVOH may be 90 mol% or more, 95 mol% or more, or 99 mol% or more. Also, the saponification degree of EVOH may be 100 mol% or less, or 99.9 mol% or less. The saponification degree of EVOH is determined from the peak area of hydrogen atoms contained in the vinyl ester structure and the peak area of hydrogen atoms contained in the vinyl alcohol structure by performing nuclear magnetic resonance (1H-NMR) measurement.

[0129] The ethylene unit content of EVOH is, for example, 10 mol% or more, and may be 15 mol% or more, 20 mol% or more, or 25 mol% or more. Also, the ethylene unit content of EVOH may be 65 mol% or less, 55 mol% or less, or 50 mol% or less. When the ethylene unit content is 10 mol% or more, the gas barrier property or dimensional stability under high humidity can be maintained well. On the other hand, when the ethylene unit content is 65 mol% or less, the gas barrier property can be enhanced. The ethylene unit content of EVOH can be determined by the NMR method.

[0130] When a polyvinyl alcohol - based resin is used as the adhesion layer 42, examples of the method for forming the adhesion layer 42 include coating using a polyvinyl alcohol - based resin solution, multi - layer extrusion, and the like.

[0131] [Vapor deposition layer 43] The vapor deposition layer 43 is a layer (gas barrier layer) that exhibits gas barrier properties against water vapor and oxygen, and contains at least one of a metal and an inorganic oxide. The vapor deposition layer 43 is provided immediately above the adhesion layer 42. The vapor deposition layer 43 may have a single - layer structure or a laminated structure. Therefore, the vapor deposition layer 43 contains at least one of a metal vapor deposition layer and an inorganic oxide layer. When the vapor deposition layer 43 includes a metal vapor deposition layer, examples of the metal contained in the metal vapor deposition layer include aluminum, stainless steel, and the like. When the vapor deposition layer 43 includes an inorganic oxide layer, examples of the inorganic oxide contained in the inorganic oxide layer include aluminum oxide, silicon oxide, magnesium oxide, tin oxide, and the like. From the viewpoints of transparency and barrier properties, the inorganic oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Also, from the viewpoint of excellent tensile stretchability during processing, the inorganic oxide layer may be a layer using silicon oxide. By using the inorganic oxide layer, a very thin layer within a range that does not affect the recyclability of the laminate 35 can provide high barrier properties.

[0132] When the vapor deposition layer 43 is an inorganic oxide layer using silicon oxide, the O / Si ratio of the inorganic oxide layer is desirably 1.7 or more. When the O / Si ratio is 1.7 or more, the content ratio of metallic Si is suppressed and good transparency is easily obtained. Further, the O / Si ratio may be 2.0 or less. When the O / Si ratio is 2.0 or less, it is possible to prevent the crystallinity of SiO from becoming high and the inorganic oxide layer from becoming too hard, and good tensile resistance can be obtained. Thereby, it is possible to suppress the occurrence of cracks in the inorganic oxide layer when the barrier coat 44 is laminated. Further, even after being formed into a packaging bag, the base material 41 may shrink due to heat during boiling or retort processing. However, when the O / Si ratio is 2.0 or less, the inorganic oxide layer easily follows the above shrinkage, and a decrease in barrier properties can be suppressed. From the viewpoint of obtaining these effects more sufficiently, the O / Si ratio of the inorganic oxide layer may be 1.75 or more and 1.9 or less, or may be 1.8 or more and 1.85 or less.

[0133] When the vapor deposition layer 43 is an inorganic oxide layer using silicon oxide, the O / Si ratio of the inorganic oxide layer can be determined by X-ray photoelectron spectroscopy (XPS). For example, the measuring apparatus can be measured with an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., trade name: JPS-90MXV) using a non-monochromatized MgKα (1253.6 eV) as the X-ray source and an X-ray output of 100 W (10 kV - 10 mA). For quantitative analysis to obtain the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p can be used.

[0134] The thickness of the vapor deposition layer 43 is, for example, 5 nm or more and 80 nm or less. When the thickness of the vapor deposition layer 43 is 5 nm or more, sufficient water vapor barrier properties can be obtained. Further, when the thickness of the vapor deposition layer 43 is 80 nm or less, it is possible to suppress the occurrence of cracks due to deformation caused by internal stress of the thin film and suppress a decrease in water vapor barrier properties. When the thickness of the vapor deposition layer 43 exceeds 80 nm, the cost tends to increase due to an increase in the amount of material used and a longer film formation time, etc., which is not preferable from an economic viewpoint. From the same viewpoint as above, the thickness of the vapor deposition layer 43 may be 20 nm or more and 40 nm or less.

[0135] The vapor deposition layer 43 can be formed, for example, by vacuum deposition. In vacuum deposition, a physical vapor deposition method or a chemical vapor deposition method can be used. Examples of the physical vapor deposition method include, but are not limited to, vacuum evaporation method, sputtering method, ion plating method, etc. Examples of the chemical vapor deposition method include, but are not limited to, thermal CVD method, plasma CVD method, photo CVD method, etc.

[0136] In the above-mentioned vacuum deposition, a resistance heating type vacuum evaporation method, an EB (Electron Beam) heating type vacuum evaporation method, an induction heating type vacuum evaporation method, a sputtering method, a reactive sputtering method, a dual magnetron sputtering method, a plasma chemical vapor deposition method (PECVD method), etc. may be used. However, considering productivity, at present, the vacuum evaporation method may be the most excellent. As the heating means of the vacuum evaporation method, any one of an electron beam heating method, a resistance heating method, and an induction heating method may be used.

[0137] [Barrier coat 44] The barrier coat 44 is a coating layer (gas barrier coating layer) having gas barrier properties and is provided on the base material 41. The barrier coat 44 is, for example, a layer formed using a gas barrier coating layer forming composition (hereinafter also referred to as a coating agent) containing at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and their hydrolyzates.

[0138] From the viewpoint of more sufficiently maintaining the gas barrier property after heat water treatment such as retort treatment, the coating agent may contain at least a silane coupling agent or its hydrolyzate, and may contain at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, and their hydrolyzates, and may contain a hydroxyl group-containing polymer compound or its hydrolyzate, a metal alkoxide or its hydrolyzate, and a silane coupling agent or its hydrolyzate. The coating agent can be prepared, for example, by mixing a solution in which a hydroxyl group-containing polymer compound, which is a water-soluble polymer, is dissolved in an aqueous (water or water / alcohol mixture) solvent with a metal alkoxide and a silane coupling agent that have been directly or previously hydrolyzed and the like.

[0139] Each component contained in the coating agent for forming the barrier coat 44 will be described in detail. Examples of the hydroxyl group-containing polymer compound used in the coating agent include polyvinyl alcohol, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, and the like. Among these, when polyvinyl alcohol (PVA) is used in the coating agent of the barrier coat 44, the gas barrier property tends to be particularly excellent.

[0140] From the viewpoint of obtaining excellent gas barrier property, the barrier coat 44 may be formed from a composition containing at least one selected from the group consisting of the metal alkoxide represented by the general formula (I) shown in the above embodiment and its hydrolyzate.

[0141] Specific examples of the metal alkoxide include tetraethoxysilane [Si(OC2H5)4], triisopropoxyaluminum [Al(O-2'-C3H7)3], and the like. Tetraethoxysilane and triisopropoxyaluminum tend to be relatively stable in an aqueous solvent after hydrolysis.

[0142] Examples of the silane coupling agent include the compounds represented by the general formula (II) shown in the above embodiment.

[0143] Specific examples of the silane coupling agent include silane coupling agents such as vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

[0144] Further, the silane coupling agent may be a polymer obtained by polymerizing the compound represented by the general formula (II). The polymer may be a trimer or 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate. This is a polycondensate of 3-isocyanatealkylalkoxysilane. It is known that 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate loses its chemical reactivity at the isocyanate part, but retains its reactivity due to the polarity of the nurate part. Generally, it is added to adhesives and the like in the same manner as 3-isocyanatealkylalkoxysilane and is known as an adhesion improver. Therefore, by adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to a hydroxyl group-containing polymer compound, the water resistance of the gas barrier coating layer can be improved by hydrogen bonding. 3-Isocyanatealkylalkoxysilane has high reactivity and low liquid stability, while 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is not water-soluble due to the polarity of the nurate part, but is easily dispersed in an aqueous solution and can keep the liquid viscosity stable. Also, the water resistance performance is equivalent to that of 3-isocyanatealkylalkoxysilane and 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate.

[0145] 1,3,5-Tris(3-trialkoxysilylalkyl) isocyanurate may be produced by thermal condensation of 3-isocyanatopropylalkoxysilane, and may contain 3-isocyanatopropylalkoxysilane as a raw material, but there is no particular problem. 1,3,5-Tris(3-trialkoxysilylpropyl) isocyanurate may also be used, or 1,3,5-tris(3-trimethoxysilylpropyl) isocyanurate may be used. Since this methoxy group has a high hydrolysis rate and those containing a propyl group can be obtained at a relatively low cost, 1,3,5-tris(3-trimethoxysilylpropyl) isocyanurate is advantageous in practice.

[0146] In addition, to the coating agent, within a range that does not impair the gas barrier property, it is also possible to add an isocyanate compound or known additives such as a dispersant, a stabilizer, a viscosity modifier, and a colorant as necessary.

[0147] The thickness of the barrier coat 44 may be 50 to 1000 nm, or may be 100 to 500 nm. When the thickness of the barrier coat 44 is 50 nm or more, there is a tendency to obtain a more sufficient gas barrier property, and when it is 1000 nm or less, there is a tendency to retain sufficient flexibility.

[0148] The coating liquid for forming the barrier coat 44 can be applied, for example, by dipping method, roll coating method, gravure coating method, reverse gravure coating method, air knife coating method, comma coating method, die coating method, screen printing method, spray coating method, gravure offset method, or the like. The coating film formed by applying this coating liquid can be dried, for example, by hot air drying method, hot roll drying method, high frequency irradiation method, infrared irradiation method, UV irradiation method, or a combination thereof.

[0149] When drying the above coating film, the temperature can be, for example, 50 to 150°C, or may be 70 to 100°C. By setting the temperature during drying within the above range, the occurrence of cracks in the vapor deposition layer 43 and the barrier coat 44 can be further suppressed, and excellent barrier properties can be exhibited.

[0150] The barrier coat 44 may be formed using a coating agent containing a polyvinyl alcohol-based resin and a silane compound. Acid catalysts, alkali catalysts, photoinitiators, etc. may be added to the coating agent as necessary.

[0151] The polyvinyl alcohol-based resin is as described above. Examples of the silane compound include silane coupling agents, polysilazanes, siloxanes, etc., and specifically, tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, hexamethyldisilazane, etc. can be mentioned.

[0152] [Printing layer] The laminate 35 may include a printing layer. The printing layer can be provided, for example, on at least one surface of the base material 41. The printing layer is provided at a position visible from the outside of the laminate 35 for the purpose of displaying information about the contents, identifying the contents, improving concealment, or enhancing the design of the packaging bag. The printing method and printing ink are not particularly limited and are appropriately selected from known printing methods and printing inks in consideration of printability on the film, design properties such as color tone, adhesion, and safety as a food container. As the printing method, for example, gravure printing, offset printing, gravure offset printing, flexographic printing, inkjet printing, etc. can be used. Among them, the gravure printing method is likely to be used from the viewpoints of productivity and high definition of the pattern.

[0153] To enhance the adhesion of the printing layer, various pretreatments such as corona treatment, plasma treatment, and frame treatment may be performed on the surface of the layer where the printing layer is provided, or a coat layer such as an easy-adhesion layer may be provided.

[0154] [Sealing layer 50] The sealing layer 50 is a layer that imparts heat-sealing properties in the laminate 35. From the perspective of recyclability of the laminate 35 and the like, the sealing layer 50 is a polyolefin film like the base material 41. In this embodiment, the sealing layer 50 has a single-layer structure and is a resin layer mainly made of polypropylene, but it is not limited thereto. The sealing layer 50 may contain a polypropylene film and may be made of a polypropylene film.

[0155] The polypropylene film may be an acid-modified polypropylene film obtained by graft-modifying polypropylene with an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, or the like. Also, as the polypropylene, polypropylene-based resins such as homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer can be used.

[0156] The polypropylene film constituting the sealing layer 50 may be an unstretched polypropylene film from the perspective of enhancing the heat-sealing property.

[0157] Various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, an adhesion promoter, and an antistatic agent may be added to the polypropylene film constituting the sealing layer 50.

[0158] The thickness of the sealing layer 50 is determined by the mass of the content, the shape of the packaging bag, etc., but may generally be a thickness of 30 to 150 μm and may be a thickness of 50 to 80 μm.

[0159] As a method for forming the sealant layer 50, a dry lamination method in which a film-like sealant layer made of the above-mentioned polypropylene is bonded with an adhesive such as a one-component curable or two-component curable urethane-based adhesive, a non-solvent dry lamination method in which a film-like sealant layer is bonded using a solvent-free adhesive, an extrusion lamination method in which the above-mentioned polypropylene is heated and melted, extruded in a curtain shape, and bonded, etc. can all be formed by known lamination methods.

[0160] Among the above formation methods, the dry lamination method has high resistance to retort treatment, especially high-temperature hot water treatment at 120°C or higher. On the other hand, if it is used for applications where the packaging bag is treated at a temperature of 85°C or lower, the lamination method is not particularly limited.

[0161] [Adhesive layer 60] The adhesive layer 60 is a layered member that bonds the barrier layer 40 and the sealant layer 50. As the material of the adhesive contained in the adhesive layer 60, for example, polyester-isocyanate-based resins, urethane resins, polyether-based resins, etc. can be used. To use the packaging bag for retort applications, a two-component curable urethane-based adhesive with retort resistance can be used. From the perspective of environmental consideration, the adhesive may not contain 3-glycidoxypropyltrimethoxysilane (GPTMS). The adhesive layer 60 may not contain chlorine. In this case, coloring of the adhesive forming the adhesive layer 60, recycled resin after recycling, and generation of odor due to heat treatment can be suppressed. The adhesive layer 60 may be formed of biomass materials and may not contain solvents from the perspective of environmental consideration.

[0162] The thickness of the adhesive layer 60 is 0.5 μm or more and 10 μm or less. When the thickness of the adhesive layer 60 is 0.5 μm or more, peeling between the barrier layer 40 and the sealant layer 50 can be well suppressed. When the thickness of the adhesive layer 60 is 10 μm or less, the laminate 35 can be easily made into a single material (details will be described later). The thickness of the adhesive layer 60 may be 1 μm or more, 2 μm or more, 8 μm or less, 6 μm or less, or 5 μm or less.

[0163] [Content of polyolefin] In the laminate 35, the proportion of the total mass of polyolefin (in this embodiment, polypropylene) is 90% by mass or more. Thus, the laminate 35 can be said to be a packaging material made of a single material (monomaterial) and is excellent in recyclability. From the viewpoint of further improving recyclability, the content of polyolefin in the laminate 35 may be 92.5% by mass or more, or 95% by mass or more based on the total amount of the laminate 35.

[0164] [Thermal shrinkage rate of the base material 41] After exposing the base material 41 to 120°C for 15 minutes (hereinafter simply referred to as "after heating"), the thermal shrinkage rate in the MD direction of the base material 41 obtained by the above formula (1) described in the first embodiment is 1% or more. For example, after heating the base material 41 or the barrier layer 40 containing the base material 41 in an oven at 120°C for 15 minutes, the thermal shrinkage rate in the MD direction of the base material 41 obtained by the following formula (1) is 1% or more. From the viewpoints of reducing deformation during bag making and suppressing peeling between the barrier layer 40 and the sealant layer 50, the thermal shrinkage rate in the MD direction is, for example, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, or 7% or less. Note that, for example, the biaxially stretched polypropylene film has a thermal shrinkage rate of 1%, while the PET film has a thermal shrinkage rate of less than 1%.

[0165] After the above heating, the thermal shrinkage rate in the TD direction of the base material 41 obtained by the above formula (2) described in the first embodiment is not particularly limited, but is, for example, 1% or more. From the viewpoints of reducing deformation during bag making and suppressing peeling between the barrier layer 40 and the sealant layer 50, the thermal shrinkage rate in the TD direction is, for example, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, or 7% or less.

[0166] [Hardness of the adhesive layer 60] Based on the heat shrinkage rate of the above-described base material 41, in this embodiment, after subjecting the laminate 35 to a retort treatment, the hardness of the adhesive layer 60 is 0.1 MPa or more and less than 0.9 MPa. In this case, the adhesive layer 60 can favorably follow the expansion and contraction of the base material 41 accompanying heat treatments such as retort treatment and boiling treatment. For this reason, even when the above heat treatment is performed on the laminate 35 including the base material 41 having the above-described heat shrinkage rate, peeling between the barrier layer 40 and the sealant layer 50 is less likely to occur. In addition, crack generation in the adhesive layer 60 during cooling after the above heat treatment and damage generation in the barrier layer 40 (at least one of the adhesion layer 42, the vapor deposition layer 43, and the barrier coat 44) accompanying the crack generation are suppressed. The hardness of the adhesive layer 60 before the retort treatment is not particularly limited, but is, for example, 1.0 MPa or more.

[0167] The hardness of the adhesive layer 60 can be controlled by the material of the adhesive, the amount of the curing agent, the aging time, etc. The closer the distance between the molecular chains of the adhesive, the harder the adhesive layer 60 tends to be. The bulkier the adhesive, the softer the adhesive layer 60 tends to be. The hardness of the adhesive layer 60 that is aliphatic tends to be harder than that of the adhesive layer 60 that is alicyclic or aromatic. The hardness of the adhesive layer 60 that is alicyclic tends to be harder than that of the adhesive layer 60 that is aromatic. The greater the amount of the curing agent contained in the adhesive layer 60, the harder the adhesive layer 60 tends to be. The longer the aging time, the harder the adhesive layer 60 tends to be.

[0168] The hardness of the adhesive layer 60 in the laminate 35 is obtained by measuring the hardness of the portion (exposed portion) exposed from the sealant layer 50. The removal of the sealant layer 50 for exposing the adhesive layer 60 is performed using, for example, an oblique cutting device. In the present embodiment, the hardness of the adhesive layer 60 is obtained by being measured by the nanoindentation method. The nanoindentation method is a measurement method for obtaining the mechanical properties of a sample by performing a quasi-static indentation test using an indenter on the target measurement object (sample). The hardness of a sample such as the adhesive layer 60 is calculated by, for example, the following method. First, fused quartz as a standard sample is tested in advance to calibrate the relationship between the contact depth and the contact projected area of the indenter and the sample. Then, the hardness of the sample is calculated by analyzing the unloading curve in the range of 20 to 95% with respect to the maximum load during unloading by the Oliver-Pharr method.

[0169] <Packaging bag> Hereinafter, with reference to FIG. 6, an example of a packaging bag which is a bag-shaped product of the laminate 35 will be described. FIG. 6 is a schematic plan view of an example of the packaging bag. The packaging bag 100 shown in FIG. 6 is formed into a bag shape by sealing, for example, the ends of the laminate 35 folded in half so as to sandwich the contents.

[0170] The packaging bag 100 is a three-sided bag having a main body portion 101 for containing the contents, a seal portion 102 located at an end of the main body portion 101, and a bent portion 103 where the laminate 35 is bent. The shape of the main body portion 101 is not particularly limited, and for example, it exhibits a rectangular shape when viewed from a predetermined direction. At least a part of the outer surface of the main body portion 101 may be printed. In the main body portion 101, for example, in addition to the contents, a specific gas such as nitrogen may be contained. The seal portion 102 is a portion where a part and another part of the sealant layer 50 provided in the laminate 35 are bonded together. In the seal portion 102, a part and another part of the sealant layer 50 provided in the laminate 35 are in close contact with each other. The seal portion 102 is formed, for example, by heating and compressing (i.e., heat-sealing) a part and another part of the sealant layer 50 provided in the laminate 35, but is not limited thereto. For example, the seal portion 102 may be formed by cold sealing or the like. In the packaging bag 100, the bent portion 103 constitutes one side of the main body portion 101, and the seal portion 102 constitutes the remaining three sides of the main body portion 101. Both ends of the bent portion 103 and the seal portion 102 overlap.

[0171] After performing a retort treatment on the laminate 35 according to the present embodiment described above, the hardness of the adhesive layer 60 measured by the nanoindentation method is 0.1 MPa or more and less than 0.9 MPa. Thus, even if the base material 41 having a heat shrinkage rate in the MD direction of 1% or more undergoes expansion and contraction due to the retort treatment, the adhesive layer 60 follows well. For this reason, it is possible to suppress the occurrence of damage to the barrier coat 44 due to the generation of cracks in the adhesive layer 60. Therefore, it is possible to provide a laminate 35 that can exhibit good gas barrier properties (particularly, oxygen permeation prevention performance) even after the retort treatment.

[0172] In one example, the barrier layer 40 has an adhesion layer 42 and a vapor deposition layer 43 located between the base material 41 and the barrier coat 44, and the adhesion layer 42 is located between the base material 41 and the vapor deposition layer 43. For this reason, the gas barrier properties of the laminate 35 can be improved as compared with the case where the barrier layer has only the base material 41 and the barrier coat 44.

[0173] In one example, the thickness of the vapor deposition layer 43 may be 5 nm or more and 80 nm or less. In this case, while preventing cracking of the vapor deposition layer 43, the gas barrier property can be improved.

[0174] In one example, the thickness of the adhesive layer 60 may be 0.5 μm or more and 10 μm or less. In this case, while suppressing peeling between the barrier layer 40 and the sealant layer 50 well, the laminate 35 can be easily made into a single material.

[0175] In one example, each of the base material 41 and the sealant layer 50 is a polyolefin film, and the proportion of the total mass of the polyolefin in the laminate 35 may be 90% by mass or more. In this case, single materialization is achieved.

[0176] In one example, the base material 41 may be a stretched polypropylene film, and the sealant layer 50 may be an unstretched polypropylene film. In this case, the laminate 35 is excellent in heat resistance against retort treatment and the like.

[0177] Next, with reference to FIG. 7, a modification of the second embodiment will be described. Hereinafter, descriptions overlapping with the above embodiment will be omitted, and parts different from the above embodiment will be described. That is, within a technically possible range, the descriptions of the above embodiment may be appropriately used for the modification.

[0178] FIG. 7 is a schematic cross-sectional view showing a laminate according to a modified example. As shown in FIG. 7, the laminate (packaging film) 35A has, in addition to the barrier layer 40, the sealant layer 50, and the adhesive layer 60, an outermost layer 70 that overlaps the barrier layer 40 and a second adhesive layer 60A that adheres the outermost layer 70 and the barrier layer 40. In this modified example, the sealant layer 50, the adhesive layer 60, the barrier layer 40, the second adhesive layer 60A, and the outermost layer 70 are laminated in this order. Further, the adhesive layer 60, the base material 41, the adhesion layer 42, the vapor deposition layer 43, the barrier coat 44, the second adhesive layer 60A, and the outermost layer 70 are laminated in this order. Therefore, the adhesive layer 60 adheres the base material 41 and the sealant layer 50, and the second adhesive layer 60A adheres the barrier coat 44 and the outermost layer 70. In this modified example, the barrier layer 40 functions as an intermediate layer in the laminate 35A.

[0179] [Outermost layer 70] The outermost layer 70 is a plastic member that functions as the outermost member in the laminate 35A. The outermost layer 70 has the same functions and performance as the base material 41. For example, the thickness of the outermost layer 70 is about the same as the thickness of the base material 41. From the viewpoint of recyclability suitability of the laminate 35A, etc., the outermost layer 70 is, for example, a polyolefin film. From the viewpoint of heat resistance, the outermost layer 70 may contain a polypropylene film and may be made of a polypropylene film.

[0180] In this modified example, after the outermost layer 70 is exposed to 120° C. for 15 minutes, the heat shrinkage rate in the MD direction of the outermost layer 70 obtained by the above formula (1) is 1% or more. For example, after the outermost layer 70, or the laminate of the outermost layer 70 and the barrier layer 40 is heated in an oven at 120° C. for 15 minutes, the heat shrinkage rate in the MD direction of the outermost layer 70 obtained by the above formula (1) is 1% or more. The heat shrinkage rate in the MD direction is, for example, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, or 7% or less.

[0181] After the above heating, the heat shrinkage rate in the TD direction of the outermost layer 70 obtained by the above formula (2) is not particularly limited, but is, for example, 1% or more and 12% or less.

[0182] [Second Adhesive Layer 60A] The second adhesive layer 60A is a layered member that adheres the barrier layer 40 and the outermost layer 70. The material of the adhesive contained in the second adhesive layer 60A is the same as the material of the adhesive contained in the adhesive layer 60. The thickness of the second adhesive layer 60A is the same as the thickness of the adhesive layer 60, and is 0.5 μm or more and 10 μm or less. In this modification, after subjecting the laminate 35A to retort treatment, the hardness of the second adhesive layer 60A is 0.1 MPa or more and less than 0.9 MPa. In this case, the second adhesive layer 60A can favorably follow the expansion and contraction of the outermost layer 70 accompanying heat treatments such as retort treatment and boiling treatment. Therefore, even when the above heat treatment is performed on the laminate 35A including the second adhesive layer 60A having the above-described thermal shrinkage rate, peeling between the barrier layer 40 and the outermost layer 70 is less likely to occur. In addition, generation of cracks in the second adhesive layer 60A during cooling after the above heat treatment and damage to the barrier layer 40 (at least one of the adhesion layer 42, the vapor deposition layer 43, and the barrier coat 44) accompanying the generation of such cracks are suppressed. The hardness of the second adhesive layer 60A before the retort treatment is not particularly limited, but is, for example, 1.0 MPa or more.

[0183] The hardness of the second adhesive layer 60A can be controlled by the material of the adhesive, the amount of the curing agent, the aging time, etc. The closer the distance between the molecular chains of the adhesive, the harder the second adhesive layer 60A tends to be. The bulkier the adhesive, the softer the second adhesive layer 60A tends to be. The hardness of the second adhesive layer 60A that is aliphatic tends to be harder than that of the second adhesive layer 60A that is alicyclic or aromatic. The hardness of the second adhesive layer 60A that is alicyclic tends to be harder than that of the second adhesive layer 60A that is aromatic. The greater the amount of the curing agent contained in the second adhesive layer 60A, the harder the second adhesive layer 60A tends to be. The longer the aging time, the harder the second adhesive layer 60A tends to be.

[0184] Also in the above-described modification, the same operational effects as those of the second embodiment are exhibited. In addition, the barrier layer 40 can be protected by the outermost layer 70.

[0185] The gas barrier film, packaging film, and packaging bag according to one aspect of the present disclosure are as described in, for example, the following [1] to

[19] , and these are described in detail based on the above embodiments and the above modification examples. [1] It includes a base material layer containing a polypropylene-based resin, a vapor deposition layer containing an inorganic oxide, and a gas barrier coating layer, in this order. The base material layer includes a first skin layer and a core layer, and the vapor deposition layer is formed on the first skin layer side. The gas barrier film, wherein the hardness of the first skin layer measured by nanoindentation is 0.02 to 0.15 GPa, the hardness of the core layer is 0.07 GPa or more, and the hardness of the core layer is greater than the hardness of the first skin layer. [2] The gas barrier film according to [1], wherein the first skin layer contains a propylene-α-olefin copolymer. [3] The gas barrier film according to [1] or [2], wherein the ratio of the thickness of the first skin layer to the thickness of the core layer is 1 / 100 to 1 / 5. [4] The gas barrier film according to any one of [1] to [3], wherein the complex elastic modulus of the first skin layer measured by nanoindentation is 1.2 to 2.5 GPa, and the complex elastic modulus of the core layer is 2.0 GPa or more. [5] The gas barrier film according to any one of [1] to [4], wherein the inorganic oxide contains at least one of aluminum oxide and silicon oxide. [6] The gas barrier film according to any one of [1] to [5], wherein the gas barrier coating layer is composed of a cured product of a composition containing a water-soluble polymer having a hydroxyl group and at least one selected from the group consisting of metal alkoxides, silane coupling agents, and their hydrolyzates. [7] The gas barrier film according to any one of [1] to [6], further comprising an anchor coat layer between the base material layer and the vapor deposition layer. [8] The gas barrier film according to any one of [1] to [7], wherein the base material layer includes the first skin layer, the core layer, and a second skin layer, in this order. [9] The gas barrier film according to [8], wherein the second skin layer contains a propylene-α-olefin copolymer.

[10] The gas barrier film according to [8] or [9], wherein the hardness of the second skin layer measured by nanoindentation is 0.02 to 0.15 GPa.

[11] The gas barrier film according to any one of [1] to

[10] , wherein the thickness of the vapor deposition layer is 5 nm or more and 80 nm or less.

[12] A packaging film comprising the gas barrier film according to any one of [1] to

[11] , a sealant layer overlapping the gas barrier coating layer, and an adhesive layer that adheres the gas barrier coating layer and the sealant layer and contains a two-component curable urethane-based adhesive. After subjecting the packaging film to retort treatment, the hardness of the adhesive layer measured by nanoindentation is 0.1 MPa or more and less than 0.9 MPa. The packaging film according to

[12] , wherein the hardness of the adhesive layer measured by nanoindentation before the retort treatment is 1.0 MPa or more.

[13] The packaging film according to

[12] or

[13] , wherein the thickness of the adhesive layer is 0.5 μm or more and 10 μm or less.

[14] Each of the base material layer and the sealant layer is a polyolefin film, and the proportion of the total mass of polyolefin in the packaging film is 90% by mass or more. The packaging film according to any one of

[12] to

[14] . The packaging film according to any one of

[12] to

[15] , wherein the base material layer is a stretched polypropylene film and the sealant layer is an unstretched polypropylene film.

[16] The base material layer is a stretched polypropylene film, The packaging film according to any one of

[12] to

[15] , wherein the sealant layer is an unstretched polypropylene film.

[17] A outermost layer overlapping the base material layer, and a second adhesive layer that adheres the outermost layer and the base material layer. The packaging film further comprises, and the adhesive layer adheres the base material layer and the sealant layer. The second adhesive layer is the packaging film according to any one of

[12] to

[16] , which adheres the base material layer and the outermost layer.

[18] After exposing the outermost layer at 120°C for 15 minutes, the heat shrinkage rate in the MD direction of the outermost layer obtained by the following formula (1) is 1% or more, After performing a retort treatment on the packaging film, the hardness of the second adhesive layer measured by the nanoindentation method is 0.1 MPa or more and less than 0.9 MPa, which is the packaging film according to

[17] . Heat shrinkage rate in the MD direction (%) = (Length in the MD direction before heating - Length in the MD direction after heating) / Length in the MD direction before heating × 100 …(1)

[19] A packaging bag, which is a bag made of the packaging film according to any one of

[12] to

[18] .

[0186] However, one aspect of the present disclosure is not limited to the above embodiments, the above modified examples, and the above [1] to

[19] . One aspect of the present disclosure can be further modified without departing from the gist thereof.

[0187] In the second embodiment and its modified example, the proportion of the total mass of polypropylene in the laminate may be 90% by mass or more. Therefore, for example, in the laminate according to the above modified example, the mass ratio of polypropylene in one of the base material and the outermost layer may be less than 90% by mass. Alternatively, in the laminate, the mass ratio of polypropylene in the barrier layer may be less than 90% by mass.

[0188] In the second embodiment and its modified example, an anchor coat layer and a vapor deposition layer are provided on the base material, but it is not limited thereto. For example, a vapor deposition layer may be provided on the sealant layer. In this case, an anchor coat layer may be provided between the sealant layer and the vapor deposition layer. At this time, the sealant layer and the anchor coat layer may be coextruded layers. Alternatively, the base material may include an anchor coat layer and a vapor deposition layer, and a vapor deposition layer may be provided on the sealant layer. Alternatively, the anchor coat layer may not be provided.

Examples

[0189] Hereinafter, the present disclosure will be described in more detail by way of examples, but the present disclosure is not limited to these examples. First, Examples 1 to 38, Comparative Examples 1 to 3, and Reference Examples 1 to 3 will be described.

[0190] <Production of Gas Barrier Film> (Example 1) Ethylene-1-butene-propylene random copolymer resin (ethylene content: 2.5 mol%, 1-butene content: 3.5 mol%) was prepared as the material for the skin layer, and homopolypropylene resin was prepared as the material for the core layer. After co-extruding these resins, a base film (base layer) with a total thickness of 20 μm was produced by biaxial stretching. The thickness of the skin layer was 0.7 μm, and the thickness of the core layer was 19.3 μm.

[0191] An acrylic primer solution was applied onto the skin layer of the base layer by gravure coating and dried to form an anchor coat layer with a thickness of 0.1 μm. Next, reactive vapor deposition by high-frequency excited ion plating was performed in an oxygen atmosphere under reduced pressure, and a thin film of silicon oxide with a thickness of 30 nm was deposited onto the anchor coat layer to form a vapor deposition layer made of an inorganic oxide.

[0192] Tetraethoxysilane (hereinafter referred to as "TEOS"), methanol, and 0.1N hydrochloric acid were mixed so that the mass ratio was 45 / 15 / 40 to obtain a TEOS hydrolysis solution. This solution was mixed with a 5 mass% aqueous solution of polyvinyl alcohol (hereinafter referred to as "PVA") and a solution of 1,3,5-tris(3-methoxysilylpropyl)isocyanurate diluted so that the solid content was 5 mass% in a water / IPA (isopropyl alcohol) mass ratio of 1 / 1 (R 2 Si(OH)3 conversion) to prepare a coating liquid (composition for forming a gas barrier coating layer). The coating liquid contains the SiO2 solid content (converted value) of TEOS and the R of isocyanurate silane 2The liquid was adjusted so that the mass ratio of the solid content of Si(OH)3 (converted value) to the solid content of PVA was 40 / 5 / 55. After applying this coating liquid onto the vapor deposition layer by the gravure coating method, it was dried under the conditions of 80°C for 60 seconds to form a gas barrier coating layer with a thickness of 0.3 μm.

[0193] In this way, the gas barrier film of Example 1 having a laminated structure of gas barrier coating layer / vapor deposition layer / anchor coat layer / skin layer / core layer was obtained.

[0194] (Example 2) A gas barrier film was obtained in the same manner as in Example 1, except that an ethylene-propylene random copolymer resin (ethylene content: 5.0 mol%) was used as the material for the skin layer.

[0195] (Example 3) A gas barrier film was obtained in the same manner as in Example 1, except that an ethylene-propylene random copolymer resin (ethylene content: 3.2 mol%) was used as the material for the skin layer.

[0196] (Example 4) A gas barrier film was obtained in the same manner as in Example 1, except that an ethylene-propylene random copolymer resin (ethylene content: 7.5 mol%) was used as the material for the skin layer.

[0197] (Comparative Example 1) A gas barrier film was obtained in the same manner as in Example 1, except that a base film with only a core layer was used without forming a skin layer.

[0198] (Comparative Example 2) A gas barrier film was obtained in the same manner as in Example 1, except that an ethylene-1-butene-propylene random copolymer resin (ethylene content: 5 mol%, 1-butene content: 6 mol%) was used as the material for the skin layer.

[0199] (Comparative Example 3) A gas barrier film was obtained in the same manner as in Example 1, except that an ethylene-propylene random copolymer resin (ethylene content: 0.5 mol%) was used as the material for the skin layer.

[0200] <Production of Packaging Film> An unstretched polypropylene film with a thickness of 60 μm was laminated on the gas barrier coating layer side of the gas barrier film produced in each example by the dry lamination method via a two-component curable urethane-based adhesive. Thereby, a packaging film was obtained.

[0201] (Example 5) An ethylene-1-butene-propylene random copolymer resin (ethylene content: 2.5 mol%, 1-butene content: 3.5 mol%) was prepared as the material for the first skin layer, a homopolypropylene resin was prepared as the material for the core layer, and an ethylene-propylene random copolymer resin (ethylene content: 7.5 mol%) was prepared as the material for the second skin layer. After co-extruding these resins, a base film (base material layer) with a total thickness of 20 μm was produced by biaxial stretching. The thicknesses of both the first skin layer and the second skin layer were 0.7 μm, and the thickness of the core layer was 18.6 μm.

[0202] Subsequently, the same operations as in Example 1 were performed on the first skin layer of the base material layer to laminate each layer, thereby obtaining the gas barrier film of Example 5 having a laminated structure of gas barrier coating layer / vapor deposition layer / anchor coat layer / first skin layer / core layer / second skin layer.

[0203] (Example 6) A gas barrier film was obtained in the same manner as in Example 5, except that an ethylene-propylene random copolymer resin (ethylene content: 5.6 mol%) was used as the material for the second skin layer.

[0204] (Example 7) A gas barrier film was obtained in the same manner as in Example 1, except that the surface of the core layer opposite to the first skin layer laminated surface was subjected to corona treatment.

[0205] (Reference Example 1) A gas barrier film was obtained in the same manner as in Example 6, except that a homopolypropylene resin was used as the material for the second skin layer.

[0206] (Reference Example 2) A gas barrier film was obtained in the same manner as in Example 6, except that an ethylene-propylene random copolymer resin (ethylene content: 0.7 mol%) was used as the material for the second skin layer.

[0207] (Reference Example 3) A gas barrier film was obtained in the same manner as in Example 6, except that an ethylene-1-butene-1-propylene random copolymer resin (ethylene content: 5 mol%, 1-butene content: 6 mol%) was used as the material for the second skin layer.

[0208] (Production of Packaging Film) A 20-μm-thick stretched polypropylene film was laminated on the gas barrier layer side of the gas barrier film produced in each example by dry lamination using a two-component curable urethane-based adhesive. Also, a 60-μm-thick unstretched polypropylene film was laminated on the base material layer side of the gas barrier film by dry lamination using a two-component curable urethane-based adhesive. Thereby, a packaging film was obtained.

[0209] (Example 8) A gas barrier film was obtained in the same manner as in Example 1, except that an aqueous polyurethane resin (Takelac WPB-341, manufactured by Mitsui Chemicals, Inc.) was applied by gravure coating on the skin layer of the base material layer and dried to form an anchor coat layer with a thickness of 1.5 μm.

[0210] (Example 9) A gas barrier film was obtained in the same manner as in Example 1, except that the thickness of the skin layer was 0.3 μm and the thickness of the core layer was 19.7 μm.

[0211] (Example 10) A gas barrier film was obtained by the same operation as in Example 1, except that the thickness of the skin layer was 1.5 μm, the thickness of the core layer was 16.5 μm, and the thickness of the anchor coat layer was 1.1 μm.

[0212] (Example 11) A gas barrier film was obtained by the same operation as in Example 1, except that the material of the skin layer was a butene-propylene random copolymer resin (butene content: 2.5 mol%), the thickness of the skin layer was 0.7 μm, and the thickness of the anchor coat layer was 2.1 μm.

[0213] (Example 12) A gas barrier film was obtained by the same operation as in Example 1, except that the material of the skin layer was a butene-propylene random copolymer resin (butene content: 1.0 mol%), the thickness of the skin layer was 0.7 μm, and the thickness of the anchor coat layer was 3.1 μm.

[0214] (Example 13) A gas barrier film was obtained by the same operation as in Example 1, except that the thickness of the anchor coat layer was 4.1 μm, and the coating liquid (composition for forming a gas barrier coating layer) was adjusted so that the mass ratio of the SiO2 solid content (converted value) of TEOS, the R 2 Si(OH)3 solid content (converted value) of isocyanurate silane, and the PVA solid content was 45 / 10 / 45.

[0215] (Example 14) A gas barrier film was obtained by the same operation as in Example 1, except that the thickness of the anchor coat layer was 5.1 μm, and the coating liquid (composition for forming a gas barrier coating layer) was adjusted so that the mass ratio of the SiO2 solid content (converted value) of TEOS, the R 2 Si(OH)3 solid content (converted value) of isocyanurate silane, and the PVA solid content was 45 / 7 / 48.

[0216] (Production of Packaging Film) A 60-μm-thick unstretched polypropylene film was laminated on the gas-barrier layer side of the gas-barrier film produced in each example by the dry lamination method via a two-component curable urethane-based adhesive, thereby obtaining a packaging film.

[0217] <Evaluation> (Preparation of Samples for Nanoindentation Measurement) The front and back surfaces of the gas-barrier film produced in each example were corona-treated at 0.20 kW each (apparatus: Corona Treater CT-0212 manufactured by Kasuga Electric Co., Ltd.), and then the film was cut with scissors into a wedge shape with a base of 1.0 mm × a height of 5.0 mm.

[0218] The cut film was embedded in a photocurable resin and cured with a halogen lamp KTX-100R (manufactured by Kenko Tokina Co., Ltd.). D-800 manufactured by Toagosei Co., Ltd. was used as the photocurable resin.

[0219] The film-embedded resin after photocuring was fixed with an insert for an AFM sample holder, and the cross-section of the film was cut with a glass knife at room temperature (25°C). Then, at room temperature, final cross-section cutting was performed with a diamond knife at a cutting speed of 1.0 mm / s and a cutting layer thickness of 100 nm, and the cutting was terminated when a mirror surface was obtained. As the cross-section cutting apparatus, an ultramicrotome (EM UC7 manufactured by Leica) and a cryosystem (EM FC7 manufactured by Leica) were used. Also, the cutting direction of the knife was parallel to the layer interface.

[0220] (Nanoindentation Measurement) As the measurement apparatus, Hysitron TI-Premier (trade name) manufactured by Bruker Japan Co., Ltd. was used, and as the indenter, a Berkovich-type diamond indenter manufactured by Bruker Japan Co., Ltd. was used.

[0221] The measurement by the nanoindentation method was performed in the displacement control mode. After pushing in to a depth of 30 nm at a pushing-in speed of 30 nm / second, it was held for 1 second at the maximum depth and then unloaded at a speed of 30 nm / second.

[0222] The measurement was performed by acquiring the shape image of the sample cross-section using the shape measurement function of a measuring device that scans the sample surface with a piezoresistor, and designating 20 points at intervals of 1 μm or more on the target layer from the shape image.

[0223] When calculating the hardness and complex elastic modulus, fused quartz as a standard sample was tested in advance to calibrate the relationship between the contact depth and contact projected area of the piezoresistor and the sample. Then, the unloading curve in the 60 - 95% region with respect to the maximum load during unloading was analyzed by the Oliver-Pharr method to calculate the hardness and complex elastic modulus.

[0224] (Retort treatment) Using the packaging films prepared in each example, a packaging bag with sealed sides was fabricated. The packaging bag was filled with water as the content. Then, retort sterilization treatment was performed at 130 °C for 30 minutes.

[0225] (Oxygen permeability measurement) The oxygen permeability of the packaging film after retort treatment was measured. The measurement was carried out using an oxygen permeability measuring device (OXTRAN 2 / 20, manufactured by Modern Control) under the conditions of a temperature of 30 °C and a relative humidity of 70%. The measurement method complied with JIS K - 7126, Method B (isobaric method), and ASTM D3985 - 81, and the measured value was expressed in the unit [cm 3 (STP) / m 2 ·day·atm].

[0226] (Lamination strength measurement) The lamination strength between the gas barrier film and the unstretched polypropylene film of the packaging film after retort treatment was measured. The measurement complied with JIS K6854 and was carried out with a test width of 15 mm, a peeling speed of 300 mm / min, and a peeling angle of 180 degrees. The measured value was expressed in the unit [N / 15 mm]. In Examples 1 - 4 and Comparative Examples 1 - 3, the lamination strength between the first skin layer and the unstretched polypropylene film was measured. In Examples 5 - 7 and Reference Examples 1 - 3, the lamination strength between the second skin layer and the unstretched polypropylene film was measured.

[0227] The conditions of each example and the evaluation results of each example are shown in Tables 1 to 6. In each table, ethylene-1-butene-propylene random copolymer resin is denoted as "EBP", ethylene-propylene random copolymer resin is denoted as "EP", butene-propylene random copolymer resin is denoted as "BP", homopolypropylene resin is denoted as "HPP", acrylic primer solution is denoted as "acrylic", water-based polyurethane resin is denoted as "urethane", silicon oxide is denoted as "SiOx", aluminum oxide is denoted as "AlOx", and isocyanurate silane is denoted as "SC". When the core layer is subjected to corona treatment, it is denoted as "HPP (corona treatment)".

[0228] As is clear from the results shown in Tables 1 to 6, it was confirmed that the packaging film using the gas barrier film of the examples can keep the oxygen permeability low even after heat sterilization treatment and has excellent laminate strength between layers.

[0229] As is clear from the results shown in Tables 3 and 4, it was confirmed that providing a second skin layer on the core layer or performing corona treatment has the effect of increasing the laminate strength with the layer adjacent to the base material layer.

[0230] [Table 1]

[0231] [Table 2]

[0232] [Table 3]

[0233] [Table 4]

[0234] [Table 5]

[0235]

Table 6

[0236] (Example 15) A 60-μm-thick unstretched polypropylene film was laminated on the gas-barrier property coating layer side of the gas-barrier film prepared in Example 1 by the dry lamination method via a two-component curable urethane-based adhesive (a) to obtain a packaging film.

[0237] (Examples 16 to 20) Packaging films of Examples 16 to 20 were obtained in the same manner as in Example 15, except that two-component curable urethane-based adhesives (b) to (f) were used instead of the adhesive (a).

[0238] (Example 21) A 60-μm-thick unstretched polypropylene film was laminated on the gas-barrier property coating layer side of the gas-barrier film prepared in Example 2 by the dry lamination method via a two-component curable urethane-based adhesive (a) to obtain a packaging film.

[0239] (Examples 22 to 26) Packaging films of Examples 24 to 28 were obtained in the same manner as in Example 21, except that two-component curable urethane-based adhesives (b) to (f) were used instead of the adhesive (a).

[0240] (Example 27) A 60-μm-thick unstretched polypropylene film was laminated on the gas-barrier property coating layer side of the gas-barrier film prepared in Example 3 by the dry lamination method via a two-component curable urethane-based adhesive (a) to obtain a packaging film.

[0241] (Examples 28 to 32) Except for using two-component curable urethane adhesives (b) to (f) instead of the adhesive (a), packaging films of Examples 28 to 32 were obtained in the same manner as in Example 27.

[0242] (Example 33) A 60-μm-thick unstretched polypropylene film was laminated on the gas barrier coating layer side of the gas barrier film prepared in Example 4 by the dry lamination method via a two-component curable urethane adhesive (a) to obtain a packaging film.

[0243] (Examples 34 to 38) Except for using two-component curable urethane adhesives (b) to (f) instead of the adhesive (a), packaging films of Examples 34 to 48 were obtained in the same manner as in Example 33.

[0244] <Evaluation> (Retort treatment) Using the packaging films prepared in each example, a packaging bag with sealed sides was made. The packaging bag was filled with water as the contents. Then, retort sterilization treatment was carried out at 130°C for 60 minutes.

[0245] (Measurement of hardness of adhesive layer) In each of Examples 15 to 38, a part of the packaging film, which was a part of the packaging bag after retort treatment, was cut out. Then, an epoxy-based adhesive (manufactured by Konishi Co., Ltd., trade name: Bond E Set) was applied on the base material layer of the cut-out packaging film. And by attaching the packaging film to a glass plate via the epoxy-based adhesive, a sample having a packaging film smoothly fixed to the glass plate was formed.

[0246] After the epoxy-based adhesive hardened, a sample was placed on an oblique cutting device (manufactured by Daipla Wintersteiger Co., Ltd., product name: SAICAS DN-GS). Next, after a diamond cutting blade with a V-shaped tip was attached to the oblique cutting device, side cut lines were made on the surface of the sealant layer at 1 mm intervals. Next, a diamond knife with a blade width of 1 mm, a rake angle of 20 degrees, and a clearance angle of 10 degrees was brought into contact with the surface of the sealant layer under a load of 0.05 N, and then the sealant layer was obliquely cut under the conditions of a horizontal speed of 50 μm / s and a vertical speed of 1 μm / s. At this time, first, after the cutting depth reached 55 μm, cutting was performed horizontally for 10 mm. Next, finish cutting was performed at a cutting depth of 1 μm under the conditions of a horizontal speed of 50 μm / s and a vertical speed of 1 μm / s. The exposed surface after cutting was observed, and the number of finish cutting times was added as necessary until the exposed surface of the desired adhesive layer was obtained. Thus, the preliminary preparation (i.e., the preparation for exposing the adhesive layer) for measuring the hardness of the adhesive layer after retort treatment by the nanoindentation method was completed.

[0247] Next, as an apparatus for measuring the hardness of the adhesive layer by the nanoindentation method, Hysitron TI-Premier (trade name) manufactured by Bruker Japan Co., Ltd. was used. Also, as the indenter, a Berkovich-type diamond indenter manufactured by Bruker Japan Co., Ltd. was used. Then, after installing the sample with the adhesive layer exposed in the above apparatus, in the displacement control mode, the pushing-in speed was set to 100 nm / second and the test depth was set to 125 nm, and the indenter was pushed into the sample at room temperature (25°C). Subsequently, after holding for 2 seconds at the maximum displacement, unloading was performed at a speed of 50 nm / second. The surface load was 1 μN, and surface correction was performed using the software of TriboScan. The measurement locations were observed with an optical microscope image, and 30 points were specified at intervals of 30 μm or more on the sample surface, that is, the exposed surface of the adhesive layer (the location at a distance of 1 / 4 from the sealant side when the distance between the sealant layer and the base material layer was equally divided into four on the exposed surface), and measurement was performed by the nanoindentation method. The method for calculating the hardness of the adhesive layer was as follows: First, fused quartz as a standard sample was tested in advance to calibrate the relationship between the contact depth and the contact projected area of the indenter and the sample. Then, the unloading curve in the 20 - 95% region with respect to the maximum load during unloading was analyzed by the Oliver-Pharr method to calculate the hardness.

[0248] (Oxygen permeability) In the same manner as the above method, the oxygen permeability of the packaging film after retort treatment was measured.

[0249] (Lamination strength measurement) In the same manner as the above method, the lamination strength between the gas barrier film after retort treatment and the unstretched polypropylene film was measured.

[0250] The conditions of each example and the evaluation results of each example are shown in Table 7. As is clear from the results shown in Table 7, the higher the hardness of the adhesive layer, the higher the measurement result of the oxygen permeability. Also, it was confirmed that the lamination strength was excellent as in Examples 1 to 14.

[0251]

Table 7

[0252] Next, Examples 45 to 80 and Comparative Examples 5 to 24 will be described.

[0253] <Base material, outermost layer, and sealant layer> As the base material and the outermost layer, a biaxially stretched polypropylene (OPP) film (manufactured by Mitsui Chemicals Toagosei Co., Ltd., trade name: ME-1, thickness: 20 μm) was prepared. Also, as the sealant layer, an unstretched polypropylene (CPP) film (manufactured by Toray Film Processing Co., Ltd., trade name: Trephan ZK93KM, thickness: 60 μm) was prepared.

[0254] <Preparation of composition for forming adhesion layer> γ-Isocyanatopropyltrimethoxysilane and acrylic polyol were mixed and stirred at a ratio of 1:5 to produce a mixed solution. Subsequently, tolylene diisocyanate (TDI) was added to the above mixed solution such that the number of NCO groups of tolylene diisocyanate was equal to the number of OH groups of acrylic polyol. Then, the mixed solution was diluted with ethyl acetate to a concentration of 2% by mass. Thereby, a composition for forming an adhesion layer (anchor coating agent) was prepared.

[0255] <Preparation of coating liquid α for barrier coating> 10 g each of the following Liquid A, Liquid B, and Liquid C were prepared and mixed to prepare coating liquid α.

[0256] Liquid A: A hydrolysis solution with a solid content of 5% by mass (in terms of SiO2) obtained by adding 72.1 g of 0.1 N hydrochloric acid to 17.9 g of tetraethoxysilane (Si(OC2H5)4) and 10 g of methanol and stirring for 30 minutes for hydrolysis.

[0257] Liquid B: A 5% by mass aqueous / methanol solution of polyvinyl alcohol (mass ratio of water to methanol is 95:5).

[0258] Solution C: A hydrolyzed solution obtained by diluting 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate with a mixed solution of water / isopropyl alcohol (mass ratio of water:isopropyl alcohol is 1:1) to a solid content of 5% by mass.

[0259] <Preparation of Coating Liquid β for Barrier Coating> First, TEOS, methanol, and 0.1N hydrochloric acid were mixed so that the mass ratio was 45 / 15 / 40 to obtain a TEOS hydrolysis solution. This solution, a 5% by mass aqueous solution of polyvinyl alcohol (hereinafter referred to as "PVA"), and a solution obtained by diluting 1,3,5-tris(3-methoxysilylpropyl)isocyanurate as a silane coupling agent with a water / IPA (isopropyl alcohol) = 1 / 1 solution to a solid content of 5% (R 2 Si(OH)3 conversion) were mixed to prepare coating liquid β. Coating liquid β was adjusted so that the mass ratio of the SiO2 solid content (converted value) of TEOS, the R 2 Si(OH)3 solid content (converted value) of isocyanurate silane, and the PVA solid content was 40 / 5 / 55.

[0260] <Preparation of Coating Liquid γ for Barrier Coating> Coating liquid γ was prepared by blending the following "aqueous polyurethane resin": 40 - 75% by mass, "water-soluble polymer": 10 - 40% by mass, and "silane coupling agent": 5 - 20% by mass.

[0261] Aqueous polyurethane resin: An aqueous dispersion of an aqueous polyurethane resin containing an acid group-containing polyurethane resin and a polyamine compound, the aqueous polyurethane dispersion "Takelac (registered trademark) WPB-341" manufactured by Mitsui Chemicals, Inc., with a solid content ratio of 30%.

[0262] Water-soluble polymer: Polyvinyl alcohol with a saponification degree of 98 - 99% and a polymerization degree of 500 (trade name: Poval PVA-105, manufactured by Kuraray Co., Ltd.).

[0263] Silane coupling agent: 3-glycidoxypropyltriethoxysilane (trade name: KBE-403, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0264] (Example 45) Using a bar coater, the composition for forming an adhesion layer was applied to the substrate, and the composition for forming the adhesion layer was dried at 50 °C. As a result, an adhesion layer (anchor coat layer) with a thickness of 0.2 μm was formed. Next, a transparent vapor deposition layer (silica vapor deposition layer) made of silicon oxide with a thickness of 40 nm was formed by a vacuum vapor deposition apparatus using an electron beam heating method.

[0265] Next, using a bar coater, coating liquid α was applied onto the vapor deposition layer, and the coating liquid α was dried at 60 °C for 1 minute. As a result, a barrier coat with a thickness of 300 nm was formed on the vapor deposition layer. Thus, a barrier layer having a substrate, an adhesion layer, a vapor deposition layer, and a barrier coat was formed.

[0266] Next, a two-component curable urethane-based adhesive (a) was applied onto the barrier coat of the barrier layer to form an adhesive layer with a thickness of 3 μm. Next, a sealant layer was laminated by the dry lamination method through the adhesive layer. Thus, a laminate (gas barrier laminate) having a laminated structure of a substrate, an adhesion layer, a vapor deposition layer, a barrier coat, an adhesive layer, and a sealant layer was manufactured. The content of polypropylene in the obtained laminate was 90% by mass or more.

[0267] (Examples 46 to 50) Laminates of Examples 46 to 50 were each manufactured in the same manner as in Example 1, except that two-component curable urethane-based adhesives (b) to (f) were used instead of the adhesive (a).

[0268] (Examples 51 to 56) Laminates of Examples 51 to 56 were each manufactured in the same manner as in Examples 45 to 50, except that coating liquid β was used instead of coating liquid α.

[0269] (Examples 57 to 62) The laminates of Examples 57 to 62 were each produced in the same manner as in Examples 45 to 50, except that coating liquid γ was used instead of coating liquid α.

[0270] (Example 63) After forming a barrier layer in the same manner as in Example 45, a two-component curable urethane-based adhesive (a) was applied onto the barrier coat of the barrier layer to form an adhesive layer having a thickness of 3 μm. Next, the outermost layer was laminated via the adhesive layer by the dry lamination method. Next, a two-component curable urethane-based adhesive (a) was applied onto the substrate of the barrier layer to form an adhesive layer having a thickness of 3 μm. Next, the sealant layer was laminated via the adhesive layer by the dry lamination method. Thereby, a laminate (gas barrier laminate) having a laminated structure of an outermost layer, a second adhesive layer, a barrier coat, a vapor deposition layer, an adhesion layer, a substrate, an adhesive layer, and a sealant layer was produced. The content of polypropylene in the obtained laminate was 90% by mass or more.

[0271] (Examples 64 to 68) The laminates of Examples 64 to 68 were each produced in the same manner as in Example 63, except that two-component curable urethane-based adhesives (b) to (f) were used instead of adhesive (a).

[0272] (Examples 69 to 74) The laminates of Examples 69 to 74 were each produced in the same manner as in Examples 63 to 68, except that coating liquid β was used instead of coating liquid α.

[0273] (Examples 75 to 80) The laminates of Examples 75 to 80 were each produced in the same manner as in Examples 63 to 68, except that coating liquid γ was used instead of coating liquid α.

[0274] (Comparative Examples 5 to 7) The laminates of Comparative Examples 5 to 7 were each produced in the same manner as in Example 45, except that adhesives (g) to (i) were used instead of adhesive (a).

[0275] (Comparative Examples 8 to 10) Laminates of Comparative Examples 8 to 10 were each produced in the same manner as in Example 51, except that adhesives (g) to (i) were used instead of the adhesive (a).

[0276] (Comparative Examples 11 to 13) Laminates of Comparative Examples 11 to 13 were each produced in the same manner as in Example 57, except that adhesives (g) to (i) were used instead of the adhesive (a).

[0277] (Comparative Examples 14 to 16) Laminates of Comparative Examples 14 to 16 were each produced in the same manner as in Example 63, except that adhesives (g) to (i) were used instead of the adhesive (a).

[0278] (Comparative Examples 17 to 19) Laminates of Comparative Examples 17 to 19 were each produced in the same manner as in Example 69, except that adhesives (g) to (i) were used instead of the adhesive (a).

[0279] (Comparative Examples 20 to 22) Laminates of Comparative Examples 20 to 22 were each produced in the same manner as in Example 75, except that adhesives (g) to (i) were used instead of the adhesive (a).

[0280] (Comparative Example 23) A laminate of Comparative Example 19 was produced in the same manner as in Example 45, except that a PET film (thickness: 20 μm) was used instead of the OPP film as the base material.

[0281] (Comparative Example 24) A laminate of Comparative Example 20 was produced in the same manner as in Comparative Example 5, except that a PET film (thickness: 20 μm) was used instead of the OPP film as the base material.

[0282] (Method for Measuring Thermal Shrinkage Rate of Base Material) The thermal shrinkage rate of the base material contained in the barrier layer was measured according to the following procedure. The measurement results of the thermal shrinkage rate of the base materials in Examples 45 to 50 and Comparative Examples 5 to 7 are shown in Table 8 below. The measurement results of the thermal shrinkage rate of the base materials in Examples 51 to 56 and Comparative Examples 8 to 10 are shown in Table 9 below. The measurement results of the thermal shrinkage rate of the base materials in Examples 57 to 62 and Comparative Examples 11 to 13 are shown in Table 10 below. The measurement results of the thermal shrinkage rate of the base materials in Examples 63 to 68 and Comparative Examples 14 to 16 are shown in Table 11 below. The measurement results of the thermal shrinkage rate of the base materials in Examples 69 to 74 and Comparative Examples 17 to 19 are shown in Table 12 below. The measurement results of the thermal shrinkage rate of the base materials in Examples 75 to 80 and Comparative Examples 20 to 22 are shown in Table 13 below. The measurement results of the thermal shrinkage rate of the base materials in Comparative Examples 23 and 24 are shown in Table 14 below.

[0283] (a) As shown in FIG. 8, the base material to be measured was cut out into a 200 mm × 200 mm size to obtain a measurement sample 500. (b) As shown in FIG. 8, two straight lines L1 and L2 with a length of 120 mm or more parallel to the TD direction of the measurement sample 500 were drawn with an interval of 100 mm. (c) As shown in FIG. 8, two straight lines L3 and L4 with a length of 120 mm or more parallel to the MD direction of the measurement sample 500 were drawn with an interval of 100 mm. (d) As shown in FIG. 8, scale marks N1 to N7 were written at seven positions on the straight line L1 at intervals of 20 mm. Scale marks were also written on the straight lines L2 to L4 in the same manner. At this time, when the scale marks N1 to N7 on the straight line L1 and the scale marks N1 to N7 on the straight line L2 were connected by a straight line, the positions of the scale marks on the straight lines L1 and L2 were adjusted so that the straight line was parallel to the MD direction. Also, when the scale marks N1 to N7 on the straight line L3 and the scale marks N1 to N7 on the straight line L4 were connected by a straight line, the positions of the scale marks on the straight lines L3 and L4 were adjusted so that the straight line was parallel to the TD direction. (e) The measurement sample 500 placed on a Teflon (registered trademark) sheet was placed on a glass plate in an oven heated to a predetermined temperature (150 °C or 160 °C) and heated for 15 minutes. After heating, the measurement sample 500 was taken out of the oven and left at room temperature (25 °C) for 30 minutes. (f) The linear distance between the scale N1 of the straight line L1 (the intersection point of L1 and N1) and the scale N1 of the straight line L2 (the intersection point of L2 and N1) was measured before and after heating as the MD direction length, and the MD direction heat shrinkage rate was obtained by the following formula (1). Similarly, the MD direction heat shrinkage rates at the respective positions of the scales N1 to N7 were obtained, and their average value was taken as the MD direction heat shrinkage rate of the measurement sample 500. MD direction heat shrinkage rate (%) = (MD direction length before heating - MD direction length after heating) / MD direction length before heating × 100 …(1)

[0284] <Retort treatment> Using the laminates prepared in each of the examples and comparative examples, a packaging bag with sealed sides was produced. The packaging bag was filled with water as the contents. Then, retort sterilization treatment was carried out at 130 °C for 60 minutes.

[0285] <Measurement of the hardness of the adhesive layer> In each of Examples 45 to 62 and Comparative Examples 5 to 13, a laminate that was part of the packaging bag after retort treatment was cut out. Then, an epoxy-based adhesive (manufactured by Konishi Co., Ltd., trade name: Bond E Set) was applied onto the base material of the cut-out laminate. And by attaching the laminate to a glass plate via the epoxy-based adhesive, a sample having a laminate smoothly fixed to the glass plate was formed. In each of Examples 63 to 80 and Comparative Examples 14 to 22, an epoxy-based adhesive (manufactured by Konishi Co., Ltd., trade name: Bond E Set) was applied onto the outermost layer of the laminate after retort treatment to form a sample.

[0286] After the epoxy-based adhesive had cured, a sample was placed on an oblique cutting device (manufactured by Dipla-Wintec Co., Ltd., product name: SAICAS DN-GS). Next, after a diamond cutting blade with a V-shaped tip was attached to the oblique cutting device, side cut lines were made on the surface of the sealant layer at 1 mm intervals. Next, a diamond knife with a blade width of 1 mm, a rake angle of 20 degrees, and a clearance angle of 10 degrees was brought into contact with the surface of the sealant layer under a load of 0.05 N, and then the sealant layer was obliquely cut under the conditions of a horizontal speed of 50 μm / s and a vertical speed of 1 μm / s. At this time, first, after the cutting depth reached 55 μm, cutting was performed horizontally for 10 mm. Next, finish cutting was performed at a cutting depth of 1 μm under the conditions of a horizontal speed of 50 μm / s and a vertical speed of 1 μm / s. The exposed surface after cutting was observed, and the number of finish cutting operations was increased as necessary until the desired exposed surface of the adhesive layer was obtained. Thus, the preliminary preparation (i.e., the preparation for exposing the adhesive layer) for measuring the hardness of the adhesive layer after retort treatment by the nanoindentation method was completed.

[0287] Next, as an apparatus for measuring the hardness of the adhesive layer by the nanoindentation method, Hysitron TI-Premier (trade name) manufactured by Bruker Japan Co., Ltd. was used. Also, as the indenter, a Berkovich-type diamond indenter manufactured by Bruker Japan Co., Ltd. was used. After installing the sample with the exposed adhesive layer in the above apparatus, in the displacement control mode, the pushing speed was set to 100 nm / second and the test depth was set to 125 nm, and the indenter was pushed into the sample at room temperature (25°C). Subsequently, after holding for 2 seconds at the maximum displacement, unloading was performed at a speed of 50 nm / second. The surface load was 1 μN, and surface correction was performed using the software of TriboScan. The measurement locations were observed with an optical microscope image, and 30 points were specified at intervals of 30 μm or more on the sample surface, that is, the exposed surface of the adhesive layer (the location 1 / 4 of the distance from the sealant side when the distance between the sealant layer and the base material layer was equally divided on the exposed surface), and measurement by the nanoindentation method was performed. The method for calculating the hardness of the adhesive layer was as follows: First, fused quartz as a standard sample was tested in advance to calibrate the relationship between the contact depth and the contact projected area of the indenter and the sample. Then, the unloading curve in the 20 - 95% region with respect to the maximum load during unloading was analyzed by the Oliver-Pharr method to calculate the hardness. The measurement results of the hardness of the adhesive layer in each of Examples 45 to 80 and Comparative Examples 5 to 24 are shown in Tables 8 to 14 below.

[0288] (Oxygen Permeability Measurement) For the laminate after retort treatment, the oxygen transmission rate (OTR) was measured. The measurement was performed using an oxygen permeability measuring device (OXTRAN 2 / 20 manufactured by Modern Control) under the conditions of a temperature of 30°C and a relative humidity of 70%. The OTR measurement method complied with JIS K-7126, Method B (isobaric method), and ASTM D3985-81, and the measured value of OTR was expressed in the unit [cc / m 2 ·day·atm]. The OTR measurement results of each of Examples 45 to 80 and Comparative Examples 5 to 24 are shown in Tables 8 to 14 below.

[0289]

Table 8

[0290]

Table 9

[0291]

Table 10

[0292]

Table 11

[0293]

Table 12

[0294]

Table 13

[0295]

Table 14

[0296] In any of Tables 8 to 14, the higher the hardness of the adhesive layer, the higher the measurement result of the oxygen permeability. However, depending on whether the thermal shrinkage rate of the base material is 1% or more, the absolute value of the oxygen permeability varies greatly. Specifically, when a base material with a thermal shrinkage rate of 1% or more is used, as shown in Tables 8 to 13, the oxygen permeability when the hardness of the adhesive layer is 0.9 MPa or more is higher than that when the hardness of the adhesive is 0.8 MPa. In addition, the oxygen permeability when the hardness of the adhesive layer is 0.9 MPa or more is at least 3.5 or more. On the other hand, when a base material with a thermal shrinkage rate of less than 1% is used, as shown in Table 7, the difference between the oxygen permeability when the hardness of the adhesive layer is 0.9 MPa or more and the oxygen permeability when the hardness of the adhesive is 0.8 MPa can be said to be on the order of error.

[0297] In each of Tables 8 to 10 and Tables 11 to 13, the oxygen permeability of the examples and comparative examples using Coating Liquid β or Coating Liquid γ is lower than that of the examples and comparative examples using Coating Liquid α. Also, the oxygen permeability of the examples and comparative examples having an outermost layer is lower than that of the examples and comparative examples not having an outermost layer.

Explanation of Signs

[0298] 1…Base material layer, 2, 43…Vapor deposition layer, 3…Gas barrier coating layer, 10a, 10b…Gas barrier film, 11…First skin layer, 12…Core layer, 13…Second skin layer, 20, 30…Packaging film, 22…Outer layer film (outermost layer), 23, 50…Sealant layer, 24, 60…Adhesive layer, 25, 60A…Second adhesive layer, 35, 35A…Laminate (packaging film), 40…Barrier layer (gas barrier film), 41…Base material (base material layer), 44…Barrier coat (gas barrier coating layer), 70…Outermost layer, 100…Packaging bag.

Claims

1. A substrate layer containing a polypropylene-based resin, a vapor deposition layer containing an inorganic oxide, and a gas barrier coating layer in this order, The substrate layer includes a first skin layer and a core layer, and the deposition layer is formed on the first skin layer side. A gas barrier film, wherein the hardness of the first skin layer is 0.02 to 0.15 GPa, and the hardness of the core layer is 0.07 GPa or more, as measured by a nanoindentation method, and the hardness of the core layer is greater than the hardness of the first skin layer.

2. The gas barrier film of claim 1 , wherein the first skin layer comprises a propylene-α-olefin copolymer.

3. 3. The gas barrier film according to claim 1, wherein the ratio of the thickness of the first skin layer to the thickness of the core layer is from 1 / 100 to 1 / 5.

4. 3. The gas barrier film according to claim 1, wherein the first skin layer has a composite elastic modulus of 1.2 to 2.5 GPa, and the core layer has a composite elastic modulus of 2.0 GPa or more, as measured by a nanoindentation method.

5. The gas barrier film according to claim 1 or 2, wherein the inorganic oxide comprises at least one of aluminum oxide and silicon oxide.

6. 3. The gas barrier film according to claim 1, wherein the gas barrier coating layer comprises a cured product of a composition comprising a water-soluble polymer having a hydroxyl group and at least one member selected from the group consisting of a metal alkoxide, a silane coupling agent, and a hydrolysate thereof.

7. The gas barrier film according to claim 1 or 2, further comprising an anchor coat layer between the substrate layer and the deposition layer.

8. The gas barrier film according to claim 1 or 2, wherein the base layer comprises the first skin layer, the core layer, and a second skin layer in this order.

9. The gas barrier film of claim 8, wherein the second skin layer comprises a propylene-α-olefin copolymer.

10. 10. The gas barrier film according to claim 9, wherein the hardness of the second skin layer is 0.02 to 0.15 GPa as measured by a nanoindentation method.

11. The gas barrier film according to claim 1 or 2, wherein the vapor deposition layer has a thickness of 5 nm or more and 80 nm or less.

12. The gas barrier film according to claim 1 ; a sealant layer overlying the gas barrier coating layer; A packaging film comprising an adhesive layer that bonds the gas barrier coating layer and the sealant layer, A packaging film, wherein after the packaging film is subjected to a retort treatment, the hardness of the adhesive layer measured by a nanoindentation method is 0.1 MPa or more and less than 0.9 MPa.

13. The packaging film according to claim 12 , wherein the adhesive layer has a hardness of 1.0 MPa or more as measured by a nanoindentation method before the retort treatment.

14. The packaging film according to claim 12 or 13, wherein the adhesive layer has a thickness of 0.5 μm or more and 10 μm or less.

15. Each of the base material layer and the sealant layer is a polyolefin film, The packaging film according to claim 12 or 13, wherein the total mass ratio of polyolefins in the packaging film is 90 mass % or more.

16. The base layer is a stretched polypropylene film, 14. The packaging film of claim 12 or 13, wherein the sealant layer is a non-oriented polypropylene film.

17. an outermost layer overlying the base layer; a second adhesive layer that adheres the outermost layer and the base layer to each other; Further equipped with the adhesive layer bonds the base layer and the sealant layer; The packaging film according to claim 12 or 13, wherein the second adhesive layer bonds the substrate and the outermost layer.

18. After the outermost layer is exposed to 120° C. for 15 minutes, the heat shrinkage rate of the outermost layer in the MD direction calculated by the following formula (1) is 1% or more, The packaging film according to claim 17, wherein the hardness of the second adhesive layer measured by a nanoindentation method after the packaging film is subjected to a retort treatment is 0.1 MPa or more and less than 0.9 MPa. Heat shrinkage rate in MD direction (%) = (MD length before heating - MD length after heating) / MD length before heating × 100 ... (1)

19. A packaging bag made from the packaging film according to claim 12 or 13.

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