Barrier film, laminate and packaging bag

Abstract

To provide a barrier film which can keep oxygen permeability low even after heat sterilization treatment and has sufficient adhesion strength between films (between layers) even after heat sterilization treatment.SOLUTION: There is provided a barrier film which comprises a base material layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer in that order, wherein the base material layer has a multilayer structure comprising at least three layers: a first skin layer, a core layer, and a second skin layer in this order, when the softening temperature of each layer of the base material layer is measured by local thermal analysis (LTA), the first skin layer has at least one softening temperature 120°C or more, the core layer has at least one softening temperature 190°C or more and the second skin layer has at least one softening temperature 160°C or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to barrier films, laminates, and packaging bags. [Background technology]

[0002] Barrier films are widely used as packaging materials for foods, medical drugs, and other items that undergo heat sterilization, such as boiling and retort treatments. When packaging these contents, it has been particularly important to reduce oxygen permeability. Barrier films used in packaging materials that undergo heat sterilization generally use polyethylene terephthalate film, which has high heat resistance, as the base material.

[0003] However, in recent years, with growing awareness of environmental issues, there has been growing interest in packaging materials made from a single material, so-called monomaterial packaging, in order to make packaging materials recyclable. Since olefin-based films such as polypropylene are generally used as sealant layers for packaging materials, in order to produce monomaterial packaging using such sealant layers, it is necessary to use polypropylene as the substrate for the barrier film as well. For example, Patent Documents 1 and 2 listed below propose monomaterial packaging materials using polypropylene.

[0004] Polypropylene films are widely used as packaging materials due to their excellent transparency, mechanical strength, and heat resistance. However, unlike polyethylene terephthalate and the like, polypropylene lacks sufficient secondary processability, such as metal vapor deposition properties, adhesion to other resins, and printability. Various methods have been proposed to solve these problems. For example, Patent Document 3 proposes a polypropylene-based film formed from a blend of polypropylene and an ethylene-α-olefin copolymer, and Patent Document 4 proposes a polypropylene-based film having a layer formed from a blend of polypropylene and an ethylene-α-olefin copolymer and a layer formed from a polypropylene-based resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-40257 [Patent Document 2] Patent Publication No. 2021-20391 [Patent Document 3] Japanese Patent Application Publication No. 63-291929 [Patent Document 4] Japanese Patent Application Publication No. 63-290743 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with conventional barrier films and laminate structures, not only are they unable to maintain low oxygen permeability after heat sterilization, but the adhesion strength between films (layers) after heat sterilization is low, which causes problems when used as a pouch filled with contents: the pouch has low tear strength and is easily broken by impact, such as being dropped.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a barrier film that can keep oxygen permeability low even after heat sterilization treatment and that can maintain sufficient adhesive strength between films (layers) even after heat sterilization treatment, as well as a laminate and a packaging bag using the same. [Means for solving the problem]

[0008] (First aspect) The present disclosure provides a barrier film comprising, in this order, a substrate layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer, wherein the substrate layer has a multilayer structure comprising at least three layers, in this order, a first skin layer, a core layer, and a second skin layer, and when the softening temperatures of each layer of the substrate layer are measured by local thermal analysis (LTA), the first skin layer has at least one softening temperature of 120°C or higher, the core layer has at least one softening temperature of 190°C or higher, and the second skin layer has at least one softening temperature of 160°C or lower.

[0009]

[0013] According to the above-mentioned barrier film, the substrate layer comprises a first skin layer, a core layer, and a second skin layer each having a softening temperature within the above-mentioned specific range, thereby increasing the adhesive strength between the substrate layer and the layers constituting the barrier film, making it possible to keep the oxygen permeability low even after heat sterilization, and to maintain sufficient adhesive strength between the films (layers) even after heat sterilization. Furthermore, when the above-mentioned barrier film is laminated with a sealant layer, or with a sealant layer and a second substrate layer, to form a laminate, the adhesive strength between the barrier film and the sealant layer and / or the second substrate layer can be increased. Therefore, by using the above-mentioned barrier film, it is possible to obtain a laminate and a packaging bag using the same that can keep the oxygen permeability low even after heat sterilization, and that can maintain sufficient adhesive strength between the films (layers) even after heat sterilization.

[0010] In the barrier film, when the softening temperature of the first skin layer is measured by LTA, at least one softening temperature may be in the range of 120° C. to 170° C. In this case, the barrier film can further reduce oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0011] In the barrier film, when the softening temperature of the second skin layer is measured by LTA, at least one softening temperature may be in the range of 120° C. to 160° C. In this case, the barrier film can further reduce oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0012] In the barrier film, the first skin layer and the second skin layer may contain a copolymer of propylene and an α-olefin, which allows the barrier film to have a lower oxygen permeability even after heat sterilization and to have sufficient adhesive strength between films even after heat sterilization.

[0013] In the barrier film, when the softening temperatures of the layers of the base layer are measured by LTA, the core layer may have a softening temperature higher than the softening temperatures of both the first skin layer and the second skin layer, which allows the barrier film to maintain a low oxygen permeability even after heat sterilization.

[0014] In the barrier film, when the softening temperatures of each layer of the base layer are measured by LTA, the first skin layer may have a softening temperature higher than any softening temperature present in the second skin layer. In this case, the barrier film can maintain a low oxygen permeability even after heat sterilization. Furthermore, when the barrier film is laminated with a sealant layer, or with the sealant layer and the second base layer to form a laminate, the adhesive strength between the barrier film and the sealant layer and / or the second base layer can be further increased.

[0015] In the barrier film, the first skin layer and the second skin layer may each have a thickness of 2.0 μm or less, which allows the barrier film to maintain a low oxygen permeability even after heat sterilization and to maintain sufficient adhesive strength between films even after heat sterilization.

[0016] In the barrier film, the vapor-deposited layer may contain at least one selected from the group consisting of aluminum oxide and silicon oxide, which makes it possible to further reduce the oxygen permeability of the barrier film even after heat sterilization treatment, and to maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0017] In the barrier film, the gas barrier layer may contain a water-soluble polymer having a hydroxyl group and at least one selected from the group consisting of a metal alkoxide, a silane coupling agent, and a hydrolyzate thereof. In this case, the barrier film can further reduce oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0018] In the barrier film, the vapor deposition layer may be formed on the surface of the first skin layer opposite to the core layer. In this case, the barrier film may also have an anchor coat layer between the first skin layer and the vapor deposition layer. A barrier film having the above configuration can further improve the adhesive strength between the first skin layer and the vapor deposition layer. Therefore, the barrier film can further reduce oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0019] The present disclosure also provides a laminate comprising the barrier film of the present disclosure and a sealant layer, the sealant layer comprising a polyolefin. The laminate may further comprise a second substrate layer on the surface of the barrier film opposite the sealant layer, the second substrate layer comprising a polyolefin. Because the laminate uses the barrier film of the present disclosure, it is possible to keep oxygen permeability low even after heat sterilization treatment, and it is also possible to maintain sufficient adhesive strength between films even after heat sterilization treatment. The laminate is also useful as a mono-material packaging material.

[0020] The present disclosure also provides a packaging bag produced by manufacturing the laminate of the present disclosure. The packaging bag uses the laminate of the present disclosure, and therefore can maintain low oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment. The packaging bag is also useful as a mono-material packaging material.

[0021] (Second aspect) The present disclosure provides a barrier film comprising, in this order, a substrate layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer, wherein the substrate layer consists of two layers, a skin layer and a core layer, in that order from the vapor deposition layer side, and wherein, when the softening temperatures of each layer of the substrate layer are measured by local thermal analysis (LTA), the skin layer has at least one softening temperature of 115°C or higher and 170°C or lower, and the core layer has at least one softening temperature of 190°C or higher.

[0022] According to the barrier film, the base layer includes the skin layer and the core layer, each having a softening temperature within the specific range, thereby increasing the adhesive strength between the films, making it possible to keep the oxygen permeability low even after heat sterilization, and to maintain sufficient adhesive strength between the films even after heat sterilization. Therefore, by using the barrier film, it is possible to obtain a laminate and a packaging bag using the same, which can keep the oxygen permeability low even after heat sterilization, and can maintain sufficient adhesive strength between the films even after heat sterilization.

[0023] In the barrier film, the skin layer may contain a copolymer of propylene and an α-olefin, which makes it possible to further reduce the oxygen permeability of the barrier film even after heat sterilization treatment, and to maintain sufficient adhesive strength between the films even after heat sterilization treatment.

[0024] In the barrier film, the skin layer may contain an ethylene-1-butene-propylene random copolymer, which allows the barrier film to maintain a low oxygen permeability even after heat sterilization.

[0025] In the barrier film, the skin layer may have a thickness of 0.2 μm or more and 2.0 μm or less, in which case the barrier film can further reduce oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0026] In the barrier film, the ratio of the thickness of the skin layer to the thickness of the core layer may be 1 / 100 to 1 / 5, in which case the barrier film can further reduce oxygen permeability even after heat sterilization treatment, and can also maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0027] In the barrier film, the vapor-deposited layer may contain at least one selected from the group consisting of aluminum oxide and silicon oxide, which makes it possible to further reduce the oxygen permeability of the barrier film even after heat sterilization treatment, and to maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0028] In the barrier film, the gas barrier layer is Si(OR 1 )4 and R 2 Si(OR 3 )3(OR 1 and OR 3 are each independently a hydrolyzable group, and R 2 is an organic functional group.) and a water-soluble polymer having a hydroxyl group. In this case, the barrier film can further reduce the oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0029] The barrier film may include an anchor coat layer between the skin layer and the vapor deposition layer. A barrier film having the above configuration can further improve the adhesive strength between the skin layer and the vapor deposition layer. Therefore, the barrier film can further reduce oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment.

[0030] The present disclosure also provides a laminate comprising the barrier film of the present disclosure and a sealant layer, the sealant layer comprising a polyolefin. The laminate may further comprise a second substrate layer on the surface of the barrier film opposite the sealant layer, the second substrate layer comprising a polyolefin. Because the laminate uses the barrier film of the present disclosure, it is possible to keep oxygen permeability low even after heat sterilization treatment, and it is also possible to maintain sufficient adhesive strength between films even after heat sterilization treatment. The laminate is also useful as a mono-material packaging material.

[0031] The present disclosure also provides a packaging bag produced by manufacturing the laminate of the present disclosure. The packaging bag uses the laminate of the present disclosure, and therefore can maintain low oxygen permeability even after heat sterilization treatment, and can maintain sufficient adhesive strength between films even after heat sterilization treatment. The packaging bag is also useful as a mono-material packaging material. [Effects of the Invention]

[0032] According to the present disclosure, it is possible to provide a barrier film that can keep oxygen permeability low even after heat sterilization treatment and that can maintain sufficient adhesive strength between films (layers) even after heat sterilization treatment, as well as a laminate and a packaging bag using the same. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a barrier film according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic cross-sectional view showing a barrier film according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a schematic cross-sectional view showing a laminate according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a schematic cross-sectional view showing a laminate according to an embodiment of the present disclosure. [Figure 5] FIG. 1 is a schematic cross-sectional view showing a laminate according to an embodiment of the present disclosure. [Figure 6] FIG. 1 is a schematic cross-sectional view showing a laminate according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, embodiments of the present disclosure will be described in detail, with reference to the drawings as needed. However, the present disclosure is not limited to the following embodiments.

[0035] The present disclosure provides the following barrier films, laminates, and packaging bags. [1] A barrier film comprising, in this order, a base layer containing polypropylene, a vapor-deposited layer containing an inorganic oxide, and a gas barrier layer, wherein the base layer has a multilayer structure comprising at least three layers, namely a first skin layer, a core layer, and a second skin layer, in this order, and wherein, when the softening temperatures of each layer of the base layer are measured by local thermal analysis (LTA), the first skin layer has at least one softening temperature of 120°C or higher, the core layer has at least one softening temperature of 190°C or higher, and the second skin layer has at least one softening temperature of 160°C or lower. [2] The barrier film according to [1] above, wherein, when the softening temperature of the first skin layer is measured by LTA, at least one softening temperature is 120°C or higher and 170°C or lower. [3] The barrier film according to [1] or [2] above, wherein, when the softening temperature of the second skin layer is measured by LTA, at least one softening temperature is 120°C or higher and 160°C or lower. [4] The barrier film according to any one of the above [1] to [3], wherein the first skin layer and the second skin layer contain a copolymer of propylene and an α-olefin. [5] The barrier film according to any one of [1] to [3] above, wherein, when the softening temperatures of the layers of the base material layer are measured by LTA, the core layer has a softening temperature higher than the softening temperatures of both the first skin layer and the second skin layer. [6] The barrier film according to any one of [1] to [5] above, wherein, when the softening temperatures of the layers of the base material layer are measured by LTA, the first skin layer has a softening temperature higher than any softening temperature present in the second skin layer. [7] The barrier film according to any one of the above [1] to [6], wherein the thickness of each of the first skin layer and the second skin layer is 2.0 μm or less. [8] The barrier film according to any one of the above [1] to [7], wherein the vapor-deposited layer contains at least one selected from the group consisting of aluminum oxide and silicon oxide. [9] The barrier film according to any one of the above [1] to [8], wherein the gas barrier layer comprises a water-soluble polymer having a hydroxyl group, and at least one selected from the group consisting of a metal alkoxide, a silane coupling agent, and a hydrolyzate thereof.

[10] The barrier film according to any one of the above [1] to [9], wherein the vapor deposition layer is formed on the surface of the first skin layer opposite to the core layer.

[11] The barrier film according to

[10] above, further comprising an anchor coat layer between the first skin layer and the vapor deposition layer.

[12] A barrier film comprising, in this order, a base layer containing polypropylene, a vapor-deposited layer containing an inorganic oxide, and a gas barrier layer, wherein the base layer consists of two layers, a skin layer and a core layer, in that order from the vapor-deposited layer side, and wherein, when the softening temperatures of each layer of the base layer are measured by local thermal analysis (LTA), the skin layer has at least one softening temperature between 115°C and 170°C, and the core layer has at least one softening temperature between 190°C and 190°C.

[13] The barrier film according to

[12] above, wherein the skin layer comprises a copolymer of propylene and an α-olefin.

[14] The barrier film according to

[12] or

[13] above, wherein the skin layer comprises an ethylene-1-butene-propylene random copolymer.

[15] The barrier film according to any one of the above

[12] to

[14] , wherein the thickness of the skin layer is 0.2 μm or more and 2.0 μm or less.

[16] The barrier film according to any one of the above

[12] to

[15] , wherein the ratio of the thickness of the skin layer to the thickness of the core layer is 1 / 100 to 1 / 5.

[17] The barrier film according to any one of the above

[12] to

[16] , wherein the vapor-deposited layer contains at least one selected from the group consisting of aluminum oxide and silicon oxide.

[18] The gas barrier layer is made of Si(OR 1 )4 and R 2 Si(OR 3 )3(OR 1 and OR 3 are each independently a hydrolyzable group, and R 2 is an organic functional group.) and a water-soluble polymer having a hydroxyl group.

[19] The barrier film according to any one of the above

[12] to

[18] , which comprises an anchor coat layer between the skin layer and the vapor deposition layer.

[20] A laminate comprising the barrier film according to any one of the above [1] to

[19] and a sealant layer, wherein the sealant layer contains a polyolefin.

[21] The laminate according to

[20] , further comprising a second substrate layer on the surface of the barrier film opposite the sealant layer, the second substrate layer comprising a polyolefin.

[22] A packaging bag produced by producing the laminate described in

[20] or

[21] above.

[0036] <Barrier film according to the first aspect> A barrier film according to a first aspect comprises a substrate layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer, in this order; the substrate layer has a multilayer structure comprising at least three layers, namely a first skin layer, a core layer, and a second skin layer, in this order; and when the softening temperatures of each layer of the substrate layer are measured by local thermal analysis (LTA), the first skin layer has at least one softening temperature of 120°C or higher, the core layer has at least one softening temperature of 190°C or higher, and the second skin layer has at least one softening temperature of 160°C or lower.

[0037] Fig. 1 is a schematic cross-sectional view showing a barrier film according to a first aspect of the present embodiment. As shown in Fig. 1, a barrier film 10a according to the present embodiment includes a base layer 1a, a vapor deposition layer 2, and a gas barrier layer 3, in this order.

[0038] [Base material layer] The substrate layer 1a is a film (base film) that serves as a support and contains polypropylene. The substrate layer 1a is a multilayer film including at least three layers: a first skin layer 11a, a core layer 12, and a second skin layer 13. The substrate layer 1a may be a film made of polypropylene, or the polypropylene may be formed into a sheet and stretched by conventional means to form a uniaxially or biaxially oriented film. Stretching may be performed on a multilayer film. Known additives, such as organic additives such as antioxidants, stabilizers, lubricants such as calcium stearate, fatty acid amides, and erucic acid amide, and antistatic agents, and inorganic additives such as particulate lubricants such as silica, zeolite, syloid, hydrotalcite, and silicon particles, may be added to the substrate layer 1a depending on the purpose.

[0039] The thickness (total thickness) of the base layer 1a is not particularly limited, and may be, for example, 3 μm or more and 200 μm or less, 6 μm or more and 50 μm or less, or 10 μm or more and 30 μm or less.

[0040] The core layer 12 is a layer that has at least one softening temperature of 190°C or higher when the softening temperature is measured from a cross section of the film by local thermal analysis (LTA), which will be described later. The at least one softening temperature may be 195°C or higher, or may be 198°C to 220°C. The softening temperature is measured at the center of the core layer 12 in the thickness direction. Having the at least one softening temperature of 190°C or higher can improve the heat resistance of the base layer 1a, making it resistant to heat during thermal sterilization treatment and preventing problems such as the base layer 1a shrinking during thermal sterilization treatment and becoming unusable as a packaging material. The core layer 12 may be a layer having one softening temperature or a layer having multiple softening temperatures. When the core layer 12 has multiple softening temperatures, it is sufficient that at least one of the softening temperatures satisfies the above-mentioned condition.

[0041] The polypropylene used in the core layer 12 may be crystalline polypropylene from the viewpoint of enhancing the heat resistance of the base layer 1a, or may be homopolypropylene, which is a homopolymer of propylene, from the viewpoint of further improving the heat resistance for heat sterilization treatment. However, a random copolymer of propylene and an α-olefin, or a mixture of such a copolymer with homopolypropylene, may also be used as long as it does not significantly impair the effects of the present disclosure.

[0042] A first skin layer 11a is provided on one surface of the core layer 12, and a second skin layer 13 is provided on the other surface. Both surfaces of the base layer 1a may be formed by the first skin layer 11a and the second skin layer 13. A layer other than the core layer 12 and the first skin layer 11a may be provided between them, or the core layer 12 and the first skin layer 11a may be in contact with each other without an intervening layer. A layer other than the core layer 12 and the second skin layer 13 may be provided between them, or the core layer 12 and the second skin layer 13 may be in contact with each other without an intervening layer.

[0043] The first skin layer 11a has at least one softening temperature of 120°C or higher when the softening temperature is measured from a cross section of the film by local thermal analysis (LTA), which will be described later. The at least one softening temperature may be 120°C or higher and 170°C or lower, or 125°C or higher and 168°C or lower. The softening temperature is measured at the center of the first skin layer 11a in the thickness direction. When the at least one softening temperature is 120°C or higher, the heat resistance of the first skin layer 11a is not excessively reduced, and there is little risk that the first skin layer 11a will soften during heat sterilization, resulting in a decrease in adhesion or a deterioration in barrier properties. Furthermore, when the at least one softening temperature is 170°C or lower, a decrease in the flexibility of the first skin layer 11a can be suppressed, and the adhesion strength between the first skin layer 11a and the core layer 12 can be increased. The first skin layer 11a may be a layer having one softening temperature or a layer having multiple softening temperatures. When the first skin layer 11a has a plurality of softening temperatures, it is sufficient that at least one of the softening temperatures satisfies the above-mentioned condition.

[0044] The second skin layer 13 is a layer having at least one softening temperature of 160°C or less when the softening temperature is measured from a cross section of the film by local thermal analysis (LTA), which will be described later. The at least one softening temperature may be 120°C or higher and 160°C or lower, or 122°C or higher and 155°C or lower. The softening temperature is measured at the center of the second skin layer 13 in the thickness direction. Having the at least one softening temperature of 160°C or lower prevents a decrease in the flexibility of the second skin layer 13 and increases the adhesive strength between the second skin layer 13 and the core layer 12. Having the at least one softening temperature of 120°C or higher prevents the heat resistance of the second skin layer 13 from decreasing too much, reducing the risk of the second skin layer 13 softening during heat sterilization, resulting in a decrease in adhesiveness or a deterioration in barrier properties. The second skin layer 13 may be a layer having one softening temperature or a layer having multiple softening temperatures. When the second skin layer 13 has a plurality of softening temperatures, it is sufficient that at least one of the softening temperatures satisfies the above-mentioned condition.

[0045] The polypropylene used in the first skin layer 11a and the second skin layer 13 may contain a copolymer of propylene and another monomer from the viewpoint of improving adhesion to the core layer 12. As the other monomer, for example, an α-olefin such as ethylene, 1-butene, or 1-hexene may be used. The copolymer may be a random copolymer.

[0046] Monomaterial packaging materials using polypropylene film generally have a three-layer structure of an outer layer film (second substrate layer), a barrier film, and a sealant layer to enhance the stiffness and self-standing ability of the packaging bag. In the barrier film 10a of this embodiment, the substrate layer 1a has a second skin layer 13 on the surface opposite the barrier-forming surface (the surface on which the vapor deposition layer and gas barrier layer are formed) for the purpose of enhancing the laminate strength with the adjacent layer (second substrate layer or sealant layer). The second skin layer 13 has a softening temperature of 160°C or lower. Having a softening temperature of 160°C or lower improves the flexibility of the second skin layer 13, resulting in good adhesive strength with the core layer 12.

[0047] The softening temperature of each layer is preferably set highest for the core layer 12 in order to minimize shrinkage of the base layer 1a during heat sterilization and maintain the adhesive strength between the layers. In other words, the core layer 12 preferably has a softening temperature higher than either of the first skin layer 11a or the second skin layer 13. Furthermore, the softening temperatures of the first skin layer 11a and the second skin layer 13 are preferably set higher than the softening temperature of the second skin layer 13, since this makes it easier to maintain a balance between the barrier properties and the adhesiveness between the layers after heat sterilization. In other words, the first skin layer 11a preferably has a softening temperature higher than either of the second skin layer 13.

[0048] The softening temperature of the core layer 12, which is 190° C. or higher, may be 10° C. or higher, or 20° C. or higher, than the softening temperature of the first skin layer 11a, which is 120° C. or higher. In this case, shrinkage of the base material layer 1a during the heat sterilization treatment can be reduced, and the adhesive strength between the layers after the heat sterilization treatment can be more sufficiently maintained.

[0049] The softening temperature of the core layer 12, which is 190°C or higher, may be 35°C or higher, or 45°C or higher than the softening temperature of the second skin layer 13, which is 160°C or lower. In this case, shrinkage of the base material layer 1a during the heat sterilization treatment can be reduced, and the adhesive strength between the layers after the heat sterilization treatment can be more sufficiently maintained.

[0050] The softening temperature of first skin layer 11a, which is 120°C or higher, may be 5°C or higher, or 15°C or higher, than the softening temperature of second skin layer 13, which is 160°C or lower. In this case, it is easier to maintain a sufficient balance between the barrier properties and the adhesion between the layers after heat sterilization treatment.

[0051] There are no particular limitations on the method for adjusting the softening temperatures of the first skin layer 11a, the core layer 12, and the second skin layer 13. The softening temperature of each layer can be adjusted, for example, by adjusting the type of resin constituting each layer, the mixing ratio of multiple resins when multiple resins are used, the monomer ratio when a copolymer is used, the manufacturing method of each layer, etc.

[0052] The thickness of each of the first skin layer 11a and the second skin layer 13 may be 0.1 μm or more. If this thickness is 0.1 μm or more, the first skin layer 11a, the core layer 12, and the second skin layer 13 can be uniformly laminated, and thickness variations in the first skin layer 11a and the second skin layer 13 can be reduced. Furthermore, it is believed that stress on the vapor deposition layer during heat sterilization treatment can be sufficiently alleviated, and deterioration of barrier properties can be suppressed. From this perspective, the thickness of the first skin layer 11a and the second skin layer 13 is preferably 0.3 μm or more. On the other hand, there is no particular upper limit on the thickness of the first skin layer 11a and the second skin layer 13, but from the perspective of more sufficiently ensuring the heat resistance of the entire base material layer 1a, it is preferably 2.0 μm or less, and more preferably 1.8 μm or less.

[0053] The thickness of the core layer 12 may be 2 μm or more, 10 μm or more, or 15 μm or more, and may be 150 μm or less, 50 μm or less, or 20 μm or less.

[0054] The ratio of the thickness of the first skin layer 11a to the thickness of the core layer 12 (thickness of the first skin layer 11a / thickness of the core layer 12) may be 1 / 100 to 1 / 5, or 1 / 70 to 1 / 10. When the thickness ratio is within the above range, the heat resistance of the entire base material layer 1a can be more sufficiently ensured, and the adhesion between the layers in the barrier film and the laminate can be further improved.

[0055] The ratio of the thickness of the second skin layer 13 to the thickness of the core layer 12 (thickness of the second skin layer 13 / thickness of the core layer 12) may be 1 / 100 to 1 / 5, or 1 / 70 to 1 / 10. When the thickness ratio is within the above range, the heat resistance of the entire base material layer 1a can be more sufficiently ensured, and the adhesion between the layers in the barrier film and the laminate can be further improved.

[0056] The thickness of the first skin layer 11a and the thickness of the second skin layer 13 may be the same or different. The thickness of the first skin layer 11a may be equal to or less than the thickness of the second skin layer 13. The ratio of the thickness of the first skin layer 11a to the thickness of the second skin layer 13 (thickness of the first skin layer 11a / second skin layer 13) may be 1 / 5 to 1 / 0.5, or 1 / 3 to 1 / 1. When the thickness ratio is within the above range, the heat resistance of the entire base layer 1a can be more sufficiently ensured, and the adhesion between the layers in the barrier film and the laminate can be further improved.

[0057] The polypropylene (including copolymers of propylene and other monomers) used in the base layer 1a may be a recycled resin, or a resin obtained by polymerizing raw materials derived from biomass such as plants. When using these resins, they may be used alone or in combination with resins polymerized from ordinary fossil fuels.

[0058] [Cross-section processing method for softening temperature measurement sample] In the softening temperature measurement of the substrate layer in this embodiment, the softening temperature of each layer is measured from the cross section of the substrate layer. The substrate layer may be subjected to a corona treatment as a surface treatment on both the front and back surfaces to prevent peeling between the embedding resin and the substrate layer after embedding. The sample used for the softening temperature measurement does not have to be in the form of the substrate layer alone, and may be in the form of a barrier film or a laminate.

[0059] After surface treatment of the front and back surfaces of the base layer, the base layer is cut into strips or wedges with a razor and embedded. A photocurable resin is used as the embedding resin, which is cured by light irradiation after embedding. Examples of photocurable resins that can be used include D-800 (product name) manufactured by Toa Gosei Co., Ltd. Next, the cured sample embedding resin is fixed in an AFM sample holder insert, and trimming and cross-section cutting of the base layer are performed with a glass knife at room temperature (25°C). Subsequently, cross-section cutting is performed with a diamond knife at a low temperature (-140°C) until a mirror finish is obtained. Cross-section cutting with a diamond knife can be performed, for example, at a cutting speed of 1.0 mm / s and a cutting film thickness of 100 nm. The cross-sectioned sample is used for softening temperature measurement while fixed in an AFM sample holder insert. Examples of cross-section cutting devices that can be used include an Ultramicrotome EM UC7 (product name) or a Cryosystem EM FC7 (product name) manufactured by Leica. The cutting direction is parallel to the layer interface.

[0060] [Softening temperature measurement method] The softening temperature is the temperature at which a material such as a resin begins to soften. In this embodiment, the softening temperature is evaluated using local thermal analysis (LTA) using an atomic force microscope. The sample is heated by applying a voltage to a cantilever equipped with a heater. In LTA, the shape of the sample is measured, and then a constant force (contact pressure) is applied to the sample surface with the cantilever at a predetermined location. The sample is heated while maintaining this constant contact pressure. The softening temperature is calculated as the temperature at which the cantilever height (Z displacement) changes due to changes in the hardness of the sample surface before and after heating. The change in cantilever height refers to the vertical rise of the cantilever due to thermal expansion of the sample surface and the vertical fall of the cantilever due to softening of the sample surface. By converting the voltage applied to the cantilever heater when such a change in cantilever height occurs into temperature, the softening temperature can be determined locally in the nanoscale region, near the surface.

[0061] The equipment used is an atomic force microscope (AFM) MFP-3D-SA (trade name) manufactured by Oxford Instruments, with the local thermal analysis option Ztherm. AC mode (tapping mode) is used for shape measurement, and contact mode is used for softening temperature measurement.

[0062] The cantilever used is an AN2-200 (trade name) manufactured by Anasys Instruments, with a spring constant of 0.5 to 3.5 N / m.

[0063] The voltage application rate (temperature rise rate) of the cantilever in measuring the softening temperature is set to 0.5 V / sec.

[0064] Ztherm measures by controlling the cantilever's contact pressure (change in cantilever deflection) at a constant level. However, because cantilever deflection changes with applied voltage even without contact with the sample, it is necessary to control the contact pressure after subtracting the cantilever deflection due to the applied voltage. Ztherm has a detrend correction function that acquires the change in cantilever deflection with applied voltage. The maximum voltage used for measurement is applied to the cantilever without the cantilever contacting the sample surface, and detrend correction is performed. In this embodiment, after shape measurement, detrend correction is performed at the maximum voltage used for measurement and a voltage application rate (heating rate) of 0.5 V / s before softening temperature measurement, and then measurement is performed. The contact pressure is set to 0.2 V.

[0065] The set value for the downward displacement of the cantilever to stop the measurement is 30 nm.

[0066] The softening point is determined as the point where the vertical height (Z displacement) of the cantilever is maximum, and the applied voltage at this point is read.

[0067] To convert the applied voltage of the cantilever heater into a softening temperature, a calibration curve of applied voltage and melting point (peak melting temperature) is created. For the calibration samples, samples whose melting points (peak melting temperatures) have already been measured using a differential scanning calorimeter (DSC) are used. The softening temperatures are measured at different measurement positions for each calibration sample. A calibration curve is created by approximating the average applied voltage at the softening point and the melting point (peak melting temperature) with a cubic function using the least squares method. The calibration samples are polycaprolactone pellets (melting point: 60°C), low-density polyethylene pellets (melting point: 112°C), polypropylene pellets (melting point: 166°C), and biaxially stretched polyethylene terephthalate film (melting point: 255°C). Cross-sectional samples prepared below the glass transition temperature are used. An ultramicrotome and cryosystem are used to prepare cross-sectional samples, and cross-sections are cut at -80°C for polycaprolactone, -140°C for low-density polyethylene, -40°C for polypropylene, and room temperature 25°C for polyethylene terephthalate.

[0068] Using this calibration curve of applied voltage and melting point (melting peak temperature), the applied voltage at the softening point is converted into a temperature, which is taken as the softening temperature.

[0069] [Vapour-deposited layer] The vapor-deposited layer is provided on the substrate layer from the viewpoint of improving gas barrier properties against, for example, water vapor and oxygen, and is preferably transparent. The vapor-deposited layer contains an inorganic oxide, and examples of the inorganic oxide that can be used include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, and mixtures thereof. In consideration of resistance to heat sterilization, it is more preferable to use at least one selected from aluminum oxide and silicon oxide, from the viewpoint of further reducing oxygen permeability even after heat sterilization treatment and maintaining sufficient adhesive strength between films even after heat sterilization treatment.

[0070] The thickness of the vapor-deposited layer may be 5 to 300 nm. When the thickness of the vapor-deposited layer is 5 nm or more, a film with a uniform and sufficient thickness is easily obtained, and the film can fully function as a gas barrier film. Furthermore, when the thickness of the vapor-deposited layer is 300 nm or less, flexibility can be imparted to the vapor-deposited layer, and the vapor-deposited layer is less likely to crack even when subjected to external factors such as bending or pulling after film formation. From this perspective, the thickness of the vapor-deposited layer is preferably 6 nm or more, more preferably 8 nm or more, and preferably 150 nm or less, more preferably 100 nm or less.

[0071] The vapor deposition layer can be formed by a conventional vacuum deposition method. Other thin film formation methods, such as sputtering, ion plating, and plasma vapor deposition (CVD), can also be used. However, considering productivity, vacuum deposition is currently the most advantageous method. The heating method for vacuum deposition is preferably one of electron beam heating, resistance heating, and induction heating, but electron beam heating is more preferable considering the wide range of evaporation material options. Furthermore, to improve the adhesion between the vapor deposition layer and the substrate layer and the density of the vapor deposition layer, plasma-assisted or ion-beam-assisted deposition can also be used. Furthermore, to increase the transparency of the vapor deposition film, reactive vapor deposition, in which various gases such as oxygen are blown into the vapor deposition, may be used.

[0072] To improve adhesion between the substrate layer and the vapor deposition layer, the surface of the substrate layer facing the vapor deposition layer may be subjected to a surface treatment such as plasma treatment or corona treatment, or an anchor coat layer (not shown) may be provided between the substrate layer and the vapor deposition layer. By providing an anchor coat layer, adhesion and barrier properties after heat sterilization can be further improved. Examples of coating agents for providing the anchor coat layer include acrylic resins, epoxy resins, acrylic urethane resins, polyester polyurethane resins, and polyether polyurethane resins. Among these coating agents, acrylic urethane resins and polyester polyurethane resins are preferred from the viewpoints of heat resistance and interlayer adhesive strength.

[0073] [Gas barrier layer] The gas barrier layer is provided for the purpose of protecting the vapor deposition layer and complementing the barrier properties. The gas barrier layer may be formed from a coating liquid containing a silicon compound or a hydrolyzate thereof and a water-soluble polymer having a hydroxyl group. Alternatively, the gas barrier layer may be formed from a coating liquid containing a water-soluble polymer having a hydroxyl group and at least one selected from the group consisting of a metal alkoxide, a silane coupling agent, and hydrolyzates thereof.

[0074] Examples of water-soluble polymers having hydroxyl groups include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, etc. In particular, when polyvinyl alcohol (PVA) is used as a coating agent, it is preferred because it provides better gas barrier properties.

[0075] Examples of silicon compounds include Si(OR 1 )4 and R 2 Si(OR 3 )3(OR 1 and OR 3 are each independently a hydrolyzable group, and R 2 is an organic functional group. It is preferable that the group is at least one selected from Si(OR 1 As R, it is preferable to use tetraethoxysilane [Si(OC2H5)4]. Tetraethoxysilane is preferably used because it is relatively stable in aqueous solvents after hydrolysis. 2 Si(OR 3 )R in 3 2 is preferably selected from the group consisting of a vinyl group, an epoxy group, a methacryloxy group, a ureido group, and an isocyanate group.

[0076] Examples of metal alkoxides include compounds represented by the following general formula: M(OR 11 ) m (R 12 ) n-m…(1) In the above formula (1), R 11 and R 12 are each independently a monovalent organic group having 1 to 8 carbon atoms, and are preferably 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 from 1 to n. 11 and R 12 If there are multiple 11 Comrades or R 12 They may be the same or different.

[0077] Specific examples of metal alkoxides include tetraethoxysilane [Si(OC2H5)4], triisopropoxyaluminum [Al(O-2'-C3H7)3], etc. Tetraethoxysilane and triisopropoxyaluminum are preferred because they are relatively stable in aqueous solvents after hydrolysis.

[0078] 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 (2), R 21 represents an alkyl group such as a methyl group or an ethyl group, and R 22 represents 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 of 1 to 3. 21 or R 22 If there are multiple 21 Comrades or R 22 R may be the same or different. 23Examples of the monovalent organic functional group represented by the formula (I) include a monovalent organic functional group containing a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or an isocyanate group. Compounds obtained by converting these silane coupling agents into polymers such as dimers and trimers may also be used.

[0079] Specific examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

[0080] The gas barrier layer can be formed by dissolving a water-soluble polymer in water or a water / alcohol mixed solvent, mixing it with a silicon compound, metal alkoxide, silane coupling agent, etc., either directly or after being pre-treated by hydrolysis, and coating the resulting mixture on the vapor-deposited layer, followed by heating and drying. Known additives such as isocyanate compounds, dispersants, stabilizers, viscosity modifiers, and colorants can also be added to this solution as needed, provided that the gas barrier properties are not impaired.

[0081] When PVA is used as the water-soluble polymer, the proportion of PVA in the mixed solution is preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 40% by mass or less, based on the total solid content of the mixed solution. When the proportion of PVA is 20% by mass or more, the flexibility of the film is maintained and it becomes easier to form a gas barrier layer. On the other hand, when the proportion of PVA is 50% by mass or less, sufficient gas barrier properties can be imparted to the barrier film.

[0082] The thickness of the gas barrier layer may be 0.05 μm or more, or 0.1 μm or more, and may be 10 μm or less, or 1 μm or less.

[0083] <Barrier film according to the second aspect> A barrier film according to a second aspect comprises a substrate layer containing polypropylene, a vapor-deposited layer containing an inorganic oxide, and a gas barrier layer, in this order; the substrate layer is composed of two layers, a skin layer and a core layer, in that order from the vapor-deposited layer side; and when the softening temperatures of each layer of the substrate layer are measured by local thermal analysis (LTA), the skin layer has at least one softening temperature of 115°C or higher and 170°C or lower, and the core layer has at least one softening temperature of 190°C or higher.

[0084] Fig. 2 is a schematic cross-sectional view showing a barrier film according to a second aspect of the present embodiment. As shown in Fig. 2, the barrier film 10b according to the present embodiment includes a base layer 1b, a vapor deposition layer 2, and a gas barrier layer 3 in this order.

[0085] [Base material layer] The substrate layer 1b is a film (base film) that serves as a support and contains polypropylene. The substrate layer 1b is a multilayer film consisting of two layers, a skin layer 11b and a core layer 12, in that order from the vapor deposition layer side. The substrate layer 1b may be a film made of polypropylene, or the polypropylene may be formed into a sheet and the sheet stretched by conventional means to form a uniaxially or biaxially oriented film. Stretching may be performed on a multilayer film. Known additives, such as organic additives such as antioxidants, stabilizers, lubricants such as calcium stearate, fatty acid amides, and erucic acid amide, and antistatic agents, and inorganic additives such as particulate lubricants such as silica, zeolite, syloid, hydrotalcite, and silicon particles, may be added to the substrate layer 1b depending on the purpose.

[0086] The thickness (total thickness) of the base layer 1b is not particularly limited, but may be, for example, 3 μm or more and 200 μm or less, 6 μm or more and 50 μm or less, or 10 μm or more and 30 μm or less.

[0087] The skin layer 11b is a layer that has at least one softening temperature between 115°C and 170°C when the softening temperature is measured from a cross section of the film by local thermal analysis (LTA), which will be described later. The at least one softening temperature may be 120°C or higher, 125°C or higher, or 130°C or higher from the viewpoint of improving heat resistance, or 165°C or lower or 160°C or lower from the viewpoint of imparting flexibility. The softening temperature is measured at the center of the skin layer 11b in the thickness direction. Having the at least one softening temperature of 115°C or higher prevents the heat resistance of the skin layer 11b from decreasing too much, reducing the risk of the skin layer 11b softening during heat sterilization treatment, resulting in a decrease in adhesion and a deterioration in barrier properties. Having the at least one softening temperature of 170°C or lower can prevent a decrease in the flexibility of the skin layer 11b and increase the adhesion strength between the skin layer 11b and the core layer 12. The skin layer 11b may be a layer having one softening temperature or a layer having multiple softening temperatures. When the skin layer 11b has multiple softening temperatures, it is sufficient that at least one of the softening temperatures satisfies the above-mentioned condition.

[0088] The polypropylene used for the skin layer 11b may contain a copolymer of propylene and another monomer from the viewpoint of improving adhesion to the core layer 12. Examples of other monomers that may be used include α-olefins such as ethylene, 1-butene, and 1-hexene. The skin layer 11b may contain a copolymer of propylene and an α-olefin. The copolymer may be a random copolymer. The polypropylene used for the skin layer 11b may contain a random copolymer of propylene and two or more α-olefins, or may contain an ethylene-1-butene-propylene random copolymer, from the viewpoint of further reducing oxygen permeability even after heat sterilization and maintaining sufficient adhesive strength between films even after heat sterilization.

[0089] The ethylene content in the polypropylene used for the skin layer 11b may be 1% by mass or more, 1.5% by mass or more, or 2% by mass or more, based on the total amount of polypropylene, from the viewpoint of keeping oxygen permeability lower even after heat sterilization treatment and from the viewpoint of providing sufficient adhesive strength between films even after heat sterilization treatment, and may be 7% by mass or less, 6% by mass or less, 5% by mass or less, 4% by mass or less, or 3.5% by mass or less.

[0090] The 1-butene content in the polypropylene used for the skin layer 11b may be 1 mass% or more, 1.5 mass% or more, or 2 mass% or more, based on the total amount of polypropylene, from the viewpoint of further reducing oxygen permeability even after heat sterilization treatment, and may be 5 mass% or less, 4 mass% or less, or 3.5 mass% or less.

[0091] The thickness of the skin layer 11b may be 0.2 μm or more. If the thickness of the skin layer 11b is 0.2 μm or more, the skin layer 11b and the core layer 12 can be laminated uniformly. Furthermore, it is possible to further reduce oxygen permeability even after heat sterilization treatment, and to maintain sufficient adhesive strength between the films even after heat sterilization treatment. From these perspectives, the thickness of the skin layer 11b is preferably 0.3 μm or more. On the other hand, there is no particular upper limit to the thickness of the skin layer 11b, but from the perspective of ensuring sufficient heat resistance of the entire base material layer 1b, it is preferably 2.0 μm or less, and more preferably 1.8 μm or less. The thickness of the skin layer 11b may be 0.2 μm or more and 2.0 μm or less, or 0.3 μm or more and 1.8 μm or less.

[0092] The core layer 12 is a layer having at least one softening temperature of 190°C or higher when the softening temperature is measured from a cross section of the film by local thermal analysis (LTA), which will be described later. The at least one softening temperature may be 195°C or higher, 200°C or higher, 205°C or higher, or 210°C or higher, or 220°C or lower, 215°C or lower, or 210°C or lower. The softening temperature is measured at the center of the core layer 12 in the thickness direction. Having at least one softening temperature of 190°C or higher can improve the heat resistance of the base layer 1b, making it resistant to heat during heat sterilization treatment and preventing problems such as the base layer 1b shrinking during heat sterilization treatment and becoming unusable as a packaging material. The core layer 12 may be a layer having one softening temperature or multiple softening temperatures. When the core layer 12 has multiple softening temperatures, it is sufficient that at least one of the softening temperatures satisfies the above-mentioned condition.

[0093] The polypropylene used in the core layer 12 may be crystalline polypropylene from the viewpoint of enhancing the heat resistance of the base layer 1b, or may be homopolypropylene, which is a homopolymer of propylene, from the viewpoint of further improving the heat resistance for heat sterilization treatment. However, a random copolymer of propylene and an α-olefin, or a mixture of such a copolymer with homopolypropylene, may also be used as long as it does not significantly impair the effects of the present disclosure.

[0094] The softening temperature of the core layer 12, which is 190° C. or higher, may be 20° C. or higher, 40° C. or higher, or 50° C. or higher than the softening temperature of the skin layer 11b, which is 115° C. or higher and 170° C. or lower. In this case, shrinkage of the base material layer 1b during the heat sterilization treatment can be reduced, and the adhesive strength between the layers after the heat sterilization treatment can be more sufficiently maintained.

[0095] The thickness of the core layer 12 may be 2 μm or more, 10 μm or more, or 15 μm or more, and may be 150 μm or less, 50 μm or less, or 20 μm or less.

[0096] The ratio of the thickness of skin layer 11b to the thickness of core layer 12 (thickness of skin layer 11b / thickness of core layer 12) may be 1 / 100 to 1 / 5, 1 / 80 to 1 / 8, or 1 / 70 to 1 / 10. When the thickness ratio is within the above range, the heat resistance of base layer 1b as a whole can be more sufficiently ensured, the oxygen permeability can be further reduced even after heat sterilization treatment, and sufficient adhesive strength can be maintained between films even after heat sterilization treatment.

[0097] The base layer 1b is made up of only two layers: a skin layer 11b and a core layer 12. The skin layer 11b and the core layer 12 are in contact with each other without any other layer interposed therebetween. Both surfaces of the base layer 1b are formed by the skin layer 11b and the core layer 12.

[0098] There is no particular limitation on the method for adjusting the softening temperature of the skin layer 11b and the core layer 12. The softening temperature of each layer can be adjusted, for example, by adjusting the type of resin constituting each layer, the mixing ratio of multiple resins when multiple resins are used, the monomer ratio (e.g., ethylene content) when a copolymer is used, and the production method of each layer (e.g., stretching conditions).

[0099] The polypropylene (including copolymers of propylene and other monomers) used in the base layer 1b may be a recycled resin, or a resin obtained by polymerizing raw materials derived from biomass such as plants. When using these resins, they may be used alone or in combination with resins polymerized from ordinary fossil fuels.

[0100] The softening temperature of the substrate layer of this embodiment is measured by the same method as that described in the first aspect above.

[0101] [Vapour-deposited layer] The vapor deposition layer of this embodiment may have the same configuration as the vapor deposition layer described in the first aspect above.

[0102] [Gas barrier layer] The gas barrier layer of this embodiment may have the same configuration as the gas barrier layer described in the first aspect above.

[0103] <Laminate> 3 and 4 are schematic cross-sectional views showing a laminate according to a first aspect of this embodiment. As shown in Fig. 3 and Fig. 4, laminates 20a and 30a according to this embodiment have a structure in which a second base material layer (outer layer film) 22 and a sealant layer 23 are laminated on both sides of the above-mentioned barrier film 10a via an adhesive layer 24. In the laminate 20a shown in Fig. 3, the second base material layer 22 is laminated on the gas barrier layer 3 of the barrier film 10a, and the sealant layer 23 is laminated on the second skin layer 13 of the barrier film 10a. In the laminate 30a shown in Fig. 4, the second base material layer 22 is laminated on the second skin layer 13 of the barrier film 10a, and the sealant layer 23 is laminated on the gas barrier layer 3 of the barrier film 10a.

[0104] 5 and 6 are schematic cross-sectional views showing a laminate according to a second aspect of this embodiment. As shown in Fig. 5 and Fig. 6, laminates 20b and 30b according to this embodiment have a structure in which a second base material layer (outer layer film) 22 and a sealant layer 23 are laminated on both sides of the above-mentioned barrier film 10b via an adhesive layer 24. In the laminate 20b shown in Fig. 5, the second base material layer 22 is laminated on the gas barrier layer 3 of the barrier film 10b, and the sealant layer 23 is laminated on the core layer 12 of the barrier film 10b. In the laminate 30b shown in Fig. 6, the second base material layer 22 is laminated on the core layer 12 of the barrier film 10b, and the sealant layer 23 is laminated on the gas barrier layer 3 of the barrier film 10b.

[0105] To make the laminates 20a, 30a, 20b, and 30b into mono-material packaging materials, polyolefin is used as the material for the second base material layer 22 and the sealant layer 23. However, it is preferable to use polypropylene, as with the base material layers 1a and 1b of the barrier films 10a and 10b. The polypropylene used for the second base material layer 22 may be, for example, a film obtained by stretching homopolypropylene to impart heat resistance. The sealant layer 23 may be, for example, a stretched or unstretched polypropylene film.

[0106] The thickness of the second base layer 22 is not particularly limited, but may be, for example, 15 μm or more and 200 μm or less.

[0107] The thickness of the sealant layer 23 is not particularly limited, but may be, for example, 15 μm or more and 200 μm or less.

[0108] The adhesive layer 24 bonds the films together. Examples of adhesives constituting the adhesive layer 24 include polyurethane resins in which a bifunctional or higher isocyanate compound is reacted with a base material such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol. The various polyols may be used singly or in combination of two or more. For the purpose of promoting adhesion, the adhesive layer 24 may contain a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent, or the like blended with the polyurethane resin. The amount of adhesive to be applied to the adhesive layer 24 is, for example, 0.5 to 10 g / m, from the viewpoint of obtaining the desired adhesive strength, followability, processability, and the like. 2 From the viewpoint of environmental consideration, the adhesive layer 24 may be made of a polymer component derived from biomass or biodegradable. Also, the adhesive layer 24 may be made of an adhesive having barrier properties.

[0109] <Packaging bag> A packaging bag can be produced using the laminate described above. The packaging bag may be formed into a bag shape by folding one sheet of packaging material in half so that the sealant layers face each other and then heat-sealing three sides, or may be formed into a bag shape by stacking two sheets of packaging material so that the sealant layers face each other and then heat-sealing four sides. The packaging bag can contain contents such as food, medicine, etc. The packaging bag may also have a shape with a bent portion (folded portion) such as a standing pouch. The packaging bag according to this embodiment can maintain high gas barrier properties even in a shape with a bent portion. [Example]

[0110] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0111] <Example 1-1> The first skin layer was made of ethylene-1-butene-propylene random copolymer resin, the core layer was made of homopolypropylene resin, and the second skin layer was made of ethylene-propylene random copolymer resin. These resins were co-extruded and then biaxially stretched to produce a substrate film (substrate layer) with a total thickness of 20 μm. The thicknesses of the first and second skin layers were both 0.7 μm, and the core layer was 18.6 μm. The softening temperatures of each layer are shown in Table 1.

[0112] Next, an acrylic primer solution was gravure coated onto the first skin layer of the base material layer and dried to form a 0.1 μm thick anchor coat layer. Next, a 30 nm thick silicon oxide thin film was deposited onto the anchor coat layer by reactive deposition using radio frequency excited ion plating in an oxygen atmosphere under reduced pressure to form a vapor deposition layer made of inorganic oxide.

[0113] Next, tetraethoxysilane (hereinafter referred to as "TEOS"), methanol, and 0.1N hydrochloric acid were mixed in a mass ratio of 45 / 15 / 40 to obtain a TEOS hydrolysis solution. This solution, a 5 mass% aqueous solution of polyvinyl alcohol (hereinafter referred to as "PVA"), and a 1 / 1 solution of 1,3,5-tris(3-methoxysilylpropyl) isocyanurate in water / IPA (isopropyl alcohol) at a solid content of 5 mass% (R 2 The coating solution was prepared by mixing three solutions: a solution diluted with SiO2 solids (equivalent) of TEOS and R of isocyanurate silane. 2 A solution was prepared so that the mass ratio of Si(OH)3 solid content (converted value) to PVA solid content was 40 / 5 / 55. This coating solution was applied to the vapor deposition layer by gravure coating and then dried at 80°C for 60 seconds to form a gas barrier layer with a thickness of 0.3 μm. In this way, the barrier film of Example 1-1 was obtained, which had a laminated structure of gas barrier layer / vapor deposition layer / anchor coat layer / first skin layer / core layer / second skin layer.

[0114] <Example 1-2> A barrier film was obtained in the same manner as in Example 1-1, except that an ethylene-1-butene-propylene random copolymer resin was used as the material for the first skin layer, a homopolypropylene resin was used as the material for the core layer, and an ethylene-1-butene-propylene random copolymer resin was used as the material for the second skin layer, so that each layer had a softening temperature as shown in Table 1.

[0115] <Examples 1-3> A barrier film was obtained in the same manner as in Example 1-1, except that an ethylene-propylene random copolymer resin was used as the material for the first skin layer, a homopolypropylene resin was used as the material for the core layer, and an ethylene-propylene random copolymer resin was used as the material for the second skin layer, so that each layer had a softening temperature as shown in Table 1.

[0116] <Examples 1-4> A barrier film was obtained in the same manner as in Example 1-1, except that an ethylene-1-butene-propylene random copolymer resin was used as the material for the first skin layer, a homopolypropylene resin was used as the material for the core layer, and an ethylene-propylene random copolymer resin was used as the material for the second skin layer, so that each layer had a softening temperature as shown in Table 1.

[0117] <Comparative Example 1-1> A barrier film was obtained in the same manner as in Example 1-1, except that homopolypropylene resin was used as the material for the first skin layer, core layer, and second skin layer so that each layer had a softening temperature as shown in Table 1.

[0118] <Comparative Example 1-2> A barrier film was obtained in the same manner as in Example 1-1, except that an ethylene-1-butene-propylene random copolymer resin was used as the material for the first skin layer, and a homopolypropylene resin was used as the material for both the core layer and the second skin layer, so that each layer would have a softening temperature as shown in Table 1.

[0119] <Comparative Example 1-3> A barrier film was obtained in the same manner as in Example 1-1, except that an ethylene-propylene random copolymer resin was used as the material for the first skin layer and the second skin layer, and a homopolypropylene resin was used as the material for the core layer, so that each layer would have a softening temperature as shown in Table 1.

[0120] <Comparative Example 1-4> A barrier film was obtained in the same manner as in Example 1-1, except that an ethylene-1-butene-propylene random copolymer resin was used as the material for the first skin layer, a homopolypropylene resin was used as the material for the core layer, and an ethylene-propylene random copolymer resin was used as the material for the second skin layer, so that each layer had a softening temperature as shown in Table 1.

[0121] <Comparative Example 1-5> A barrier film was obtained in the same manner as in Example 1-1, except that an ethylene-propylene random copolymer resin was used as the material for the first skin layer, a homopolypropylene resin was used as the material for the core layer, and an ethylene-propylene random copolymer resin was used as the material for the second skin layer, so that each layer had a softening temperature as shown in Table 1.

[0122] [Laminate fabrication] A 20 μm thick stretched polypropylene film was bonded to the gas barrier layer side of the barrier film produced in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-5 using a two-component curing urethane adhesive by dry lamination. Then, the second skin layer side of the barrier film was bonded to a 60 μm thick unstretched polypropylene film using a two-component curing urethane adhesive by dry lamination to produce a three-layer laminate.

[0123] [evaluation] (Softening temperature measurement) The softening temperature of each layer constituting the substrate layer was measured by the method described below. The laminates made of the barrier films made in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-5 were used as measurement samples, and corona treatment was performed on the front and back surfaces of the samples at 0.20 kW using a corona treatment machine (product name: CT-0212) manufactured by Kasuga Electric Co., Ltd.

[0124] After corona treatment of the front and back surfaces of the sample, the sample was cut with a razor into a wedge shape with a base of 1.0 mm and a height of 5.0 mm (the triangular surface with the base and height described above represents the front and back surfaces of the sample, and the bottom and side surfaces represent the cross-section of the sample). The cut sample was embedded in a photocurable resin and cured using a halogen lamp (Kenko Tokina, product name: KTX-100R). The photocurable resin used was a D-800 (product name) from Toa Gosei Co., Ltd. After photocuring, the sample embedding resin was fixed in an AFM specimen holder insert. The sample was cross-sectioned with a glass knife at room temperature (25°C), followed by a final cross-section cut with a diamond knife at a low temperature (-140°C) at a cutting speed of 1.0 mm / s and a cutting film thickness of 100 nm. Cutting was completed when a mirror surface was obtained. An ultramicrotome (Leica, product name: EM UC7) and a cryosystem (Leica, product name: EM FC7) were used as cross-section cutting devices. The cutting direction of the knife was parallel to the layer interface. Cutting was performed from the apex of the wedge shape. The cross-sectioned sample was fixed in an insert for an AFM sample holder and used for softening temperature measurement.

[0125] The softening temperature and shape measurements were performed using an atomic force microscope (AFM) MFP-3D-SA (manufactured by Oxford Instruments) with a Ztherm system local thermal analysis option and an Anasys Instruments AN2-200 (manufactured by Anasys Instruments) with a spring constant of 0.5 to 3.5 N / m. The softening temperature measurements were performed at the center of the thickness direction of each layer (first skin layer, core layer, and second skin layer) that make up the substrate layer.

[0126] When the sample surface was heated after detrend correction with a cantilever contact pressure (change in cantilever deflection) of 0.2 V, a voltage application rate (heating rate) of 0.5 V / s, and a maximum applied voltage of 6.0 V, the sample surface expanded and the cantilever position rose. Further heating of the sample surface softened it, and the measurement was terminated when the cantilever position dropped 30 nm. If the Z-displacement did not drop 30 nm from the change point and reached the maximum applied voltage, the maximum applied voltage during detrend correction and measurement was increased by 0.5 V and the measurement was repeated.

[0127] The voltage applied at the point where the vertical height (Z displacement) of the cantilever was maximum was taken as the voltage applied at the softening point, and the voltage value was read.

[0128] A calibration curve was created to calculate the softening temperature of each sample. Four calibration samples were used: polycaprolactone (melting point: 60°C), low-density polyethylene (LDPE, melting point: 112°C), polypropylene (PP, melting point: 166°C), and polyethylene terephthalate (PET, melting point: 255°C). The maximum applied voltages during detrend correction were 3.5 V for polycaprolactone, 5.5 V for low-density polyethylene, 6.7 V for polypropylene, and 7.9 V for polyethylene terephthalate. The cantilever contact pressure (change in cantilever deflection) was 0.2 V, and the voltage application rate (heating rate) was 0.5 V / s. Measurements were performed 20 times at different measurement positions on the calibration sample. A calibration curve was created by approximating the average applied voltage at the softening point and the melting point with a cubic function using the least-squares method.

[0129] Using a calibration curve of applied voltage and melting point (melting peak temperature), the applied voltage at the softening point of each layer (first skin layer, core layer, and second skin layer) constituting the substrate layer was converted into a temperature, which was taken as the softening temperature. The results are shown in Table 1.

[0130] (retort processing) Packaging bags with four sealed sides were made using the laminates produced in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-5, and filled with water, followed by retort sterilization at 130°C for 30 minutes.

[0131] (Oxygen permeability measurement) The oxygen permeability of the laminate after retort treatment was measured. The measurement was carried out using an oxygen permeability measuring device (OXTRAN 2 / 20, manufactured by Modern Control) under conditions of a temperature of 30°C and a relative humidity of 70%. The measurement method complies with JIS K-7126, Method B (constant pressure method) and ASTM D3985-81, and the measurement value is expressed in units of cm 3 (STP) / m 2 The results are shown in Table 1.

[0132] (Laminate strength measurement) After retort processing, the laminate strength was measured between the stretched polypropylene film and the barrier film (referred to as "OPP / barrier" in the table) and between the barrier film and the unstretched polypropylene film (referred to as "barrier / CPP" in the table). Measurements were performed in accordance with JIS K6854, with a test width of 15 mm, a peel speed of 300 mm / min, and a T-type peel angle. Measurement values ​​were expressed in units of [N / 15 mm]. The results are shown in Table 1.

[0133] [Table 1] *1: The film breaks without peeling at the interface *2: Peeling at the interface between the first skin layer and the core layer *3: Peeling at the interface between the core layer and the second skin layer *4: Peeling off at the surface of the second skin layer *5: The peeling point moves to the interface between the core layer and the second skin layer.

[0134] As is clear from the results shown in Table 1, it was confirmed that the packaging bags using the barrier films of Examples 1-1 to 1-4 were able to maintain low oxygen permeability even after heat sterilization, and also had excellent laminate strength between each layer. Note that the oxygen permeability after heat sterilization in Comparative Examples 1-1 and 1-3 was high because cracks occurred in the vapor-deposited layer during the heat sterilization. Furthermore, the laminate strength between the OPP and barrier film in Comparative Example 1-4 was low because the peeling location shifted to the interface between the core layer and the second skin layer.

[0135] <Example 2-1> The skin layer was made of ethylene-1-butene-propylene random copolymer resin (ethylene content: 2.5 mol%, 1-butene content: 3.5 mol%), and the core layer was made of homopolypropylene resin. These resins were co-extruded and then biaxially stretched to produce a substrate film (substrate layer) with a total thickness of 20 μm, including a 0.7 μm thick skin layer and a 19.3 μm thick core layer. The thicknesses of the skin layer and core layer were measured using the thickness method described below. The softening temperatures of each layer are shown in Table 2.

[0136] Next, an acrylic primer solution was gravure coated onto the skin layer of the substrate layer and dried to form a 0.1 μm thick anchor coat layer. Next, a 30 nm thick silicon oxide thin film was deposited onto the anchor coat layer by reactive deposition using radio frequency excited ion plating in an oxygen atmosphere under reduced pressure, forming a vapor deposition layer made of inorganic oxide.

[0137] Next, tetraethoxysilane (hereinafter referred to as "TEOS"), methanol, and 0.1N hydrochloric acid were mixed in a mass ratio of 45 / 15 / 40 to obtain a TEOS hydrolysis solution. This solution, a 5 mass% aqueous solution of polyvinyl alcohol (hereinafter referred to as "PVA"), and a 1 / 1 solution of 1,3,5-tris(3-methoxysilylpropyl) isocyanurate in water / IPA (isopropyl alcohol) at a solid content of 5 mass% (R 2The coating solution was prepared by mixing three solutions: a solution diluted with SiO2 solids (equivalent) of TEOS and R of isocyanurate silane. 2 A solution was prepared so that the mass ratio of Si(OH)3 solid content (converted value) to PVA solid content was 43 / 10 / 47. This coating solution was applied to the vapor deposition layer by gravure coating and then dried at 80°C for 60 seconds to form a gas barrier layer with a thickness of 0.3 μm. In this way, the barrier film of Example 2-1, having a laminated structure of gas barrier layer / vapor deposition layer / anchor coat layer / skin layer / core layer, was obtained.

[0138] <Example 2-2> A barrier film was obtained in the same manner as in Example 2-1, except that an ethylene-1-butene-propylene random copolymer resin (ethylene content: 2.0 mol %, 1-butene content: 2.0 mol %) was used as the material for the skin layer so that each layer had a softening temperature as shown in Table 2, and a substrate film having a skin layer with a thickness of 0.8 μm and a core layer with a thickness of 19.2 μm was prepared.

[0139] <Example 2-3> A barrier film was obtained in the same manner as in Example 2-1, except that an ethylene-propylene random copolymer resin (ethylene content: 5.0 mol%) was used as the material for the skin layer so that each layer had a softening temperature as shown in Table 2, and a substrate film having a skin layer with a thickness of 0.8 μm and a core layer with a thickness of 19.2 μm was prepared.

[0140] <Example 2-4> A barrier film was obtained in the same manner as in Example 2-1, except that an ethylene-propylene random copolymer resin (ethylene content: 3.2 mol%) was used as the material for the skin layer so that each layer had a softening temperature as shown in Table 2, and a substrate film having a skin layer with a thickness of 1.5 μm and a core layer with a thickness of 18.5 μm was prepared.

[0141] <Example 2-5> A barrier film was obtained in the same manner as in Example 2-1, except that an ethylene-propylene random copolymer resin (ethylene content: 3.2 mol%) was used as the material for the skin layer so that each layer would have a softening temperature as shown in Table 2, and a substrate film having a total thickness of 18 μm and including a skin layer with a thickness of 0.3 μm and a core layer with a thickness of 17.7 μm was prepared.

[0142] <Comparative Example 2-1> A barrier film was obtained in the same manner as in Example 2-1, except that a substrate film (substrate layer) having a total thickness of 20 μm was produced from only the material for the core layer.

[0143] <Comparative Example 2-2> A barrier film was obtained in the same manner as in Example 2-1, except that an ethylene-1-butene-propylene random copolymer resin (ethylene content: 3.2 mol %, 1-butene content: 5.0 mol %) was used as the material for the skin layer so that each layer would have a softening temperature as shown in Table 2.

[0144] <Comparative Example 2-3> A barrier film was obtained in the same manner as in Example 2-1, except that an ethylene-propylene random copolymer resin (ethylene content: 0.7 mol%) was used as the material for the skin layer so that each layer had a softening temperature as shown in Table 2, and a substrate film having a skin layer with a thickness of 0.8 μm and a core layer with a thickness of 19.2 μm was prepared.

[0145] [Laminate fabrication] A 60 μm thick unstretched polypropylene film was bonded to the gas barrier layer side of each of the barrier films produced in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-3 by dry lamination using a two-component curing urethane adhesive to produce a two-layer laminate.

[0146] [evaluation] (Measurement of skin and core thickness) The specimens were embedded in a barrier film made using a photocurable resin, and then cut into blocks. These were then cross-sectioned using a diamond knife on an ultramicrotome (Leica Microsystems EM UC7). The cross-sections were then observed under a scanning electron microscope (Hitachi High-Tech SU8020) at magnifications of 5,000 to 20,000 times, and the thickness was measured from the images.

[0147] (Softening temperature measurement) The softening temperatures of the layers (skin layer and core layer) constituting the base layer in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-3 were measured in the same manner as in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-5. The results are shown in Table 2.

[0148] (retort processing) Packaging bags with four sealed sides were made using the laminates produced in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-3, and filled with water, followed by retort sterilization at 130°C for 30 minutes.

[0149] (Oxygen permeability measurement) The oxygen permeability of the laminate after retort treatment was measured. The measurement was carried out using an oxygen permeability measuring device (OXTRAN 2 / 20, manufactured by Modern Control) under conditions of a temperature of 30°C and a relative humidity of 70%. The measurement method complies with JIS K-7126, Method B (constant pressure method) and ASTM D3985-81, and the measurement value is expressed in units of cm 3 (STP) / m 2 The oxygen permeability is 2.0 cm 3 (STP) / m 2 The results are shown in Table 2.

[0150] (Laminate strength measurement) The laminate strength between the barrier film and unstretched polypropylene film was measured for the laminate after retort processing. Measurements were performed in accordance with JIS K6854, with a test width of 15 mm, a peel speed of 300 mm / min, and a T-type peel angle. Measurement values ​​were expressed in units of [N / 15 mm]. The results are shown in Table 2.

[0151] [Table 2] *1: The barrier film and unstretched polypropylene film do not peel off at the interface, but the film breaks. *2: Peeling between the skin layer and core layer *3: Peels off from the surface of the base film (base layer) [Industrial Applicability]

[0152] Packaging bags using the barrier film according to the present disclosure can be used as packaging materials with little deterioration in barrier properties and adhesion even when subjected to heat sterilization treatments such as boiling treatment, retort treatment, etc. Furthermore, as mono-material packaging materials, gas barrier packaging materials suitable for recycling can be provided. [Explanation of symbols]

[0153] 1a, 1b...base layer, 2...vapor deposition layer, 3...gas barrier layer, 10a, 10b...barrier film, 11a...first skin layer, 11b...skin layer, 12...core layer, 13...second skin layer, 20a, 20b, 30a, 30b...laminate, 22...second base layer, 23...sealant layer, 24...adhesive layer.

Claims

1. a substrate layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer in this order; the substrate layer has a multilayer structure including at least three layers, namely, a first skin layer, a core layer, and a second skin layer, in this order; the core layer and the first skin layer are in contact with each other without any other layer therebetween, the core layer and the second skin layer are in contact with each other without any other layer therebetween, the vapor deposition layer is formed on a surface of the first skin layer opposite to the core layer, the first skin layer, the second skin layer, and the core layer all comprise polypropylene; The thickness of the core layer is 2 μm or more and 150 μm or less, a ratio of the thickness of the first skin layer to the thickness of the core layer is 1 / 100 to 1 / 5; the ratio of the thickness of the second skin layer to the thickness of the core layer is 1 / 100 to 1 / 5; A barrier film, wherein, when the softening temperatures of each layer of the substrate layer are measured by local thermal analysis (LTA), the first skin layer has at least one softening temperature only at 120°C or higher, the core layer has at least one softening temperature only at 190°C or higher and 220°C or lower, and the second skin layer has at least one softening temperature only at 160°C or lower.

2. 2. The barrier film according to claim 1, wherein, when the softening temperature of the first skin layer is measured by LTA, at least one softening temperature is present only in the range of 120°C or higher and 170°C or lower.

3. 2. The barrier film according to claim 1, wherein, when the softening temperature of the second skin layer is measured by LTA, at least one softening temperature is present only in the range of 120°C or higher and 160°C or lower.

4. 10. The barrier film of claim 1, wherein the first skin layer and the second skin layer comprise a copolymer of propylene and an α-olefin.

5. 2. The barrier film according to claim 1, wherein, when the softening temperatures of the layers of the base layer are measured by LTA, the core layer has a softening temperature higher than the softening temperatures of the first skin layer and the second skin layer.

6. 2. The barrier film according to claim 1, wherein, when the softening temperatures of the layers of the base layer are measured by LTA, the first skin layer has a softening temperature higher than any softening temperature of the second skin layer.

7. 2. The barrier film according to claim 1, wherein the first skin layer and the second skin layer each have a thickness of 2.0 μm or less.

8. 2. The barrier film according to claim 1, wherein the vapor-deposited layer comprises at least one selected from the group consisting of aluminum oxide and silicon oxide.

9. 2. The barrier film according to claim 1, wherein the gas barrier layer comprises a water-soluble polymer having a hydroxyl group, and at least one selected from the group consisting of a metal alkoxide, a silane coupling agent, and a hydrolyzate thereof.

10. 10. The barrier film of claim 1, further comprising an anchor coat layer between the first skin layer and the vapor deposition layer.

11. A laminate comprising the barrier film according to any one of claims 1 to 10 and a sealant layer, wherein the sealant layer comprises a polyolefin.

12. 12. The laminate of claim 11, further comprising a second substrate layer on a side of the barrier film opposite the sealant layer, the second substrate layer comprising a polyolefin.

13. A packaging bag produced by producing the laminate according to claim 11.

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