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 and medical drugs that undergo heat sterilization, such as boiling and retort treatments. In packaging these contents, it has been particularly important to reduce oxygen permeability. As barrier films used for packaging materials that undergo such heat sterilization, polyethylene terephthalate film, which has high heat resistance, is generally used as the base material.

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

[0004] Polypropylene films are widely used as packaging materials and the like because of their excellent transparency, mechanical strength, and heat resistance. However, unlike polyethylene terephthalate and the like, polypropylene is insufficient in secondary processability, such as metal deposition property, adhesion to other resins, and printability. To solve these problems, various methods have been proposed. 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] JP 2020-40257 A [Patent Document 2] JP 2021-20391 A [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 it impossible to keep oxygen permeability low after heat sterilization treatment, but the adhesion strength between films (layers) after heat sterilization treatment is low, so that 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 is capable of keeping oxygen permeability low even after heat sterilization treatment and that is capable of maintaining sufficient adhesion strength between films (layers) even after heat sterilization treatment, and 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 a base layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer, in this order, 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 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.

[0009] According to the above barrier film, the substrate layer has a first skin layer, a core layer, and a second skin layer each having a softening temperature in the above specific range, so that the adhesive strength between the substrate layer and each layer constituting the barrier film is increased, and it is possible to keep the oxygen permeability low even after heat sterilization treatment, and to provide sufficient adhesive strength between the films (layers) even after heat sterilization treatment. In addition, when the above barrier film is laminated with a sealant layer, or with a sealant layer and a second substrate layer to form a laminate, it is possible to increase the adhesive strength between the barrier film and the sealant layer and / or the second substrate layer. Therefore, by using the above 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 treatment, and can provide sufficient adhesive strength between the films (layers) even after heat sterilization treatment.

[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 present in the range of 120° C. to 170° C. In this case, the barrier film can suppress the oxygen permeability to a lower level even after heat sterilization treatment, and can provide 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 present in the range of 120° C. to 160° C. In this case, the barrier film can suppress the oxygen permeability to a lower level even after heat sterilization treatment, and can provide 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, in which case the barrier film can suppress the oxygen permeability to a lower level even after heat sterilization treatment, and can provide sufficient adhesive strength between the films even after heat sterilization treatment.

[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 the first skin layer and the second skin layer, in which case the barrier film can maintain 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 of the second skin layer. In this case, the barrier film can further reduce oxygen permeability even after heat sterilization. In addition, 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, in which case the barrier film can suppress oxygen permeability to a lower level even after heat sterilization, and can provide sufficient adhesive strength between films even after heat sterilization.

[0016] In the barrier film, the vapor deposition layer may contain at least one selected from the group consisting of aluminum oxide and silicon oxide, in which case the barrier film can suppress oxygen permeability to a lower level even after heat sterilization treatment, and can provide sufficient adhesive strength between films even after heat sterilization treatment.

[0017] In the above-mentioned barrier film, the above-mentioned gas barrier layer may contain at least one selected from the group consisting of a water-soluble polymer having a hydroxyl group, a metal alkoxide, a silane coupling agent, and hydrolysates thereof. In this case, the barrier film can suppress the oxygen permeability to a lower level even after heat sterilization treatment, and can provide sufficient adhesion strength between the films even after heat sterilization treatment.

[0018] In the barrier film, the 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 have an anchor coat layer between the first skin layer and the deposition layer. The barrier film having the above configuration can further improve the adhesion strength between the first skin layer and the deposition layer. Therefore, the barrier film can suppress the oxygen permeability to a lower level even after heat sterilization treatment, and can provide sufficient adhesion strength between the 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 to the sealant layer, the second substrate layer comprising a polyolefin. Since the laminate uses the barrier film of the present disclosure, it is possible to keep the oxygen permeability low even after heat sterilization treatment, and it is possible to provide sufficient adhesive strength between the 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, and can maintain sufficient adhesive strength between films even after heat sterilization. The packaging bag is also useful as a mono-material packaging material.

[0021] (Second aspect) The present disclosure provides a barrier film comprising a substrate layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer, in this order, wherein the substrate layer is composed 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 between 115°C and 170°C, and the core layer has at least one softening temperature of 190°C or higher.

[0022] According to the barrier film, since the base layer includes the skin layer and the core layer having a softening temperature in the specific range, the adhesive strength between the films is increased, and it is possible to keep the oxygen permeability low even after heat sterilization treatment, and to provide sufficient adhesive strength between the films even after heat sterilization treatment. 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 treatment, and can provide sufficient adhesive strength between the films even after heat sterilization treatment.

[0023] In the barrier film, the skin layer may contain a copolymer of propylene and an α-olefin, which can suppress the oxygen permeability of the barrier film to a lower level even after heat sterilization and can provide sufficient adhesive strength between the films even after heat sterilization.

[0024] In the barrier film, the skin layer may contain an ethylene-1-butene-propylene random copolymer, in which case the barrier film can 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 suppress oxygen permeability to a lower level even after heat sterilization treatment, and can provide sufficient adhesion 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 suppress the oxygen permeability to a lower level even after heat sterilization treatment, and can provide sufficient adhesive strength between films even after heat sterilization treatment.

[0027] In the barrier film, the vapor deposition layer may contain at least one selected from the group consisting of aluminum oxide and silicon oxide, in which case the barrier film can suppress oxygen permeability to a lower level even after heat sterilization treatment, and can provide sufficient adhesive strength between films even after heat sterilization treatment.

[0028] In the above-mentioned barrier film, 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, R 2 is an organic functional group.) or a hydrolyzate thereof, and a water-soluble polymer having a hydroxyl group. In this case, the barrier film can suppress the oxygen permeability to a lower level even after heat sterilization, and can provide sufficient adhesion strength between the films even after heat sterilization.

[0029] The barrier film may have an anchor coat layer between the skin layer and the vapor deposition layer. The barrier film having the above configuration can further improve the adhesion strength between the skin layer and the vapor deposition layer. Therefore, the barrier film can suppress the oxygen permeability to a lower level even after heat sterilization treatment, and can provide sufficient adhesion strength between the 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 to the sealant layer, the second substrate layer comprising a polyolefin. Since the laminate uses the barrier film of the present disclosure, it is possible to keep the oxygen permeability low even after heat sterilization treatment, and it is possible to provide sufficient adhesive strength between the 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, and can maintain sufficient adhesive strength between films even after heat sterilization. The packaging bag is also useful as a mono-material packaging material. Effect of the Invention

[0032] According to the present disclosure, it is possible to provide a barrier film that can maintain low oxygen permeability even after heat sterilization treatment and can maintain sufficient adhesion strength between films (layers) even after heat sterilization treatment, as well as a laminate and a packaging bag using the same. [Brief description 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. [Diagram 2] FIG. 1 is a schematic cross-sectional view showing a barrier film according to an embodiment of the present disclosure. [Diagram 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. [Diagram 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 PREFERRED EMBODIMENTS

[0034] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings where necessary. 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 deposition layer containing an inorganic oxide, and a gas barrier layer, wherein the base 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 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 in the range of 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 between 120°C and 160°C. [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 the above [1] to [3], wherein, when the softening temperatures of each layer of the base material layer are measured by LTA, the core layer has a softening temperature higher than the softening temperatures of any of the first skin layer and the second skin layer. [6] The barrier film according to any one of the above [1] to [5], wherein, when the softening temperatures of each layer of the base material layer are measured by LTA, the first skin layer has a softening temperature higher than any softening temperature of the second skin layer. [7] The barrier film according to any one of the above [1] to [6], wherein the first skin layer and the second skin layer each have a thickness of 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 hydrolysate 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 deposition layer.

[12] A barrier film comprising, in this order, a base layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer, wherein the base layer consists of two layers, namely, a skin layer and a core layer, from the vapor deposition layer side, and 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 of 190°C or higher.

[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 a ratio of a thickness of the skin layer to a 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, 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] , further comprising an anchor coat layer between the skin layer and the deposition layer.

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

[19] above and a sealant layer, the sealant layer comprising a polyolefin.

[21] The laminate according to

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

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

[20] or

[21] above.

[0036] <Barrier film according to the first aspect> The barrier film according to a first aspect comprises a base layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer, in that order, 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 that order, and 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.

[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 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) serving as a support, and contains polypropylene. The substrate layer 1a is a multilayered 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 may be a film oriented uniaxially or biaxially by forming polypropylene into a sheet and stretching the sheet by a conventional means. The stretching may be performed on the multilayered film. The substrate layer 1a may contain known additives, such as organic additives such as antioxidants, stabilizers, lubricants such as calcium stearate, fatty acid amides, and erucic acid amide, antistatic agents, and inorganic additives such as particulate lubricants such as silica, zeolite, syloid, hydrotalcite, and silicon particles, 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 having at least one softening temperature of 190° C. or higher when the softening temperature is measured from a film cross section by local thermal analysis (LTA) described later. The at least one softening temperature may be 195° C. or higher, or may be 198° C. or higher and 220° C. or lower. The softening temperature is a temperature measured at the center of the thickness direction of the core layer 12. When the at least one softening temperature is 190° C. or higher, the heat resistance of the base layer 1a can be increased, and the base layer 1a is resistant to heat during heat sterilization treatment, and the base layer 1a can be prevented from shrinking during heat sterilization treatment, making it impossible to use the base layer 1a 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 conditions.

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

[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. Between the core layer 12 and the first skin layer 11a, a layer other than the two may be provided, or the core layer 12 and the first skin layer 11a may be in contact with each other without any other layer being interposed therebetween. Between the core layer 12 and the second skin layer 13, a layer other than the two may be provided, or the core layer 12 and the second skin layer 13 may be in contact with each other without any other layer being interposed therebetween.

[0043] The first skin layer 11a is a layer having 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) 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 a temperature measured at the center of the thickness direction of the first skin layer 11a. When the at least one softening temperature is 120° C. or higher, the heat resistance of the first skin layer 11a is not too low, and there is little risk that the first skin layer 11a will soften during heat sterilization treatment, causing a decrease in adhesion and a deterioration in barrier properties. In addition, when the at least one softening temperature is 170° C. or lower, the flexibility of the first skin layer 11a can be suppressed from decreasing, 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 may be a layer having multiple softening temperatures. When the first skin layer 11a has a plurality of softening temperatures, at least one of the softening temperatures needs to satisfy 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) described later. The at least one softening temperature may be 120° C. or more and 160° C. or less, or 122° C. or more and 155° C. or less. The softening temperature is a temperature measured at the center of the thickness direction of the second skin layer 13. When the at least one softening temperature is 160° C. or less, the flexibility of the second skin layer 13 can be suppressed from decreasing, and the adhesive strength between the second skin layer 13 and the core layer 12 can be increased. Furthermore, when the at least one softening temperature is 120° C. or more, the heat resistance of the second skin layer 13 is not too low, and there is little risk that the second skin layer 13 will soften during heat sterilization treatment, causing a decrease in adhesiveness or a deterioration in barrier properties. The second skin layer 13 may be a layer having one softening temperature, or may be a layer having multiple softening temperatures. When the second skin layer 13 has a plurality of softening temperatures, at least one of the softening temperatures needs to satisfy 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 films generally have a three-layer structure of an outer layer film (second substrate layer) / barrier film / sealant layer to enhance the stiffness and self-supporting ability of the packaging bag. In the substrate layer 1a of the barrier film 10a of this embodiment, a second skin layer 13 is provided on the surface opposite to the barrier forming surface (the surface on which the 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 less. When the second skin layer 13 has a softening temperature of 160° C. or less, the flexibility of the second skin layer 13 is increased, and good adhesive strength with the core layer 12 is obtained.

[0047] The softening temperature of each layer is preferably set to be the highest in the core layer 12 in order to reduce the shrinkage of the base layer 1a during the heat sterilization treatment and maintain the adhesive strength between each layer. In other words, it is preferable that the core layer 12 has a softening temperature higher than any of the softening temperatures present in the first skin layer 11a and the second skin layer 13. In addition, it is preferable that the softening temperature of the first skin layer 11a is higher than that of the second skin layer 13, since it is easy to maintain a balance between the barrier properties after the heat sterilization treatment and the adhesiveness between each layer. In other words, it is preferable that the first skin layer 11a has a softening temperature higher than any of the softening temperatures present in 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, the shrinkage of the base material layer 1a during the heat sterilization treatment can be made smaller, 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, the shrinkage of the base material layer 1a during the heat sterilization treatment can be made smaller, 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 is no particular limitation on the method for adjusting the softening temperature 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, and the manufacturing method of each layer.

[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 the 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 the variation in the thickness of the first skin layer 11a and the second skin layer 13 can be suppressed. In addition, it is considered that the stress on the deposition layer during the heat sterilization treatment can be sufficiently alleviated, and the deterioration of the barrier property can be suppressed. From this viewpoint, 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, the upper limit value of the thickness of the first skin layer 11a and the second skin layer 13 is not particularly limited, but from the viewpoint of more sufficiently ensuring the heat resistance of the entire base layer 1a, it is preferably 2.0 μm or less, 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 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 mixed with resins polymerized from ordinary fossil fuels.

[0058] [Method of processing cross-section of sample for softening temperature measurement] 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 the front and back surfaces of the substrate layer in order 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 state of the substrate layer alone, and may be in the state of a barrier film or a laminate.

[0059] After the front and back surfaces of the base layer are treated, the base layer is cut into a rectangular or wedge shape with a razor and embedded. A photocurable resin is used as the embedding resin, and is hardened by light irradiation after embedding. For example, D-800 (trade name) manufactured by Toa Gosei Co., Ltd. can be used as the photocurable resin. Next, the hardened sample embedding resin is fixed with an insert for AFM sample holder, and trimming and cross-cutting of the base layer are performed with a glass knife at room temperature (25°C), and then cross-cutting is performed with a diamond knife at a low temperature (-140°C) until a mirror surface is obtained. Cross-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 being fixed with an insert for AFM sample holder. For example, an ultramicrotome EM UC7 (trade name) or a cryosystem EM FC7 (trade name) manufactured by Leica can be used as the cross-section cutting device. 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 exhibits softening behavior. In this embodiment, the softening temperature is evaluated by local thermal analysis (LTA) using an atomic force microscope, and the sample is heated by applying a voltage to a cantilever having a heater. In local thermal analysis (LTA), after the shape of the measurement sample is measured, a constant force (contact pressure) is applied to the sample surface with a cantilever at a predetermined location of the sample, and the sample is heated while maintaining the contact pressure constant. The temperature at which the height position (Z displacement) of the cantilever changes due to the change in hardness of the sample surface before and after heating is calculated as the softening temperature. The change in the height position of the cantilever refers to the change due to the vertical position rise of the cantilever due to the thermal expansion of the sample surface and the vertical position drop of the cantilever due to the softening of the sample surface. By converting the voltage applied to the heater of the cantilever when such a change in the height position of the cantilever occurs into a temperature, the softening temperature can be known locally in the nanoscale region and near the surface.

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

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

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

[0064] In Ztherm, the contact pressure of the cantilever (change in the deflection of the cantilever) is controlled to a constant value for measurement. However, the deflection of the cantilever changes with the applied voltage even without contacting the sample, so the contact pressure must be controlled after subtracting the deflection of the cantilever due to the applied voltage. Ztherm has a Detrend correction function that obtains the change in the deflection of the cantilever with respect to the applied voltage, and applies the maximum applied voltage used for measurement to the cantilever without the cantilever contacting the sample surface, and performs Detrend correction. In this embodiment, after shape measurement, Detrend correction is performed at the maximum applied voltage used for measurement and a voltage application rate (temperature rise rate) of 0.5 V / sec before measuring the softening temperature, 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 the softening temperature, a calibration curve of the applied voltage and the melting point (melting peak temperature) is created. For the calibration samples, samples whose melting points (melting peak temperature) have already been measured using a differential scanning calorimeter (DSC) are used, and the softening temperature is 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 (melting peak temperature) with a cubic function using the least squares method, and this is used as the calibration curve. 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), and cross-sectional samples prepared in an environment below the glass transition temperature are used for each. To prepare cross-sectional samples, an ultramicrotome and a cryosystem are used, and cross-sections are cut in an environment of -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 to obtain the softening temperature.

[0069] [Vapour-deposited layer] The deposition layer is provided on the base layer from the viewpoint of improving the gas barrier property against water vapor and oxygen, and is preferably transparent. The deposition 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. Considering the resistance to heat sterilization, it is more preferable to use at least one selected from aluminum oxide and silicon oxide, from the viewpoint of suppressing oxygen permeability to a lower level even after heat sterilization treatment and from the viewpoint of providing sufficient adhesive strength between films even after heat sterilization treatment.

[0070] The thickness of the deposition layer may be 5 to 300 nm. If the thickness of the deposition layer is 5 nm or more, a film with a uniform and sufficient thickness is easily obtained, and the function as a gas barrier film can be fully fulfilled. If the thickness of the deposition layer is 300 nm or less, flexibility can be imparted to the deposition layer, and cracks are unlikely to occur in the deposition layer even if external factors such as bending or pulling are applied after film formation. From this viewpoint, the thickness of the deposition 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 deposition layer can be formed by a normal vacuum deposition method. In addition, it is also possible to use other thin film formation methods such as sputtering, ion plating, and plasma vapor deposition (CVD). However, in terms of productivity, the vacuum deposition method is currently the most superior. As a heating means for the vacuum deposition method, it is preferable to use any of the electron beam heating method, resistance heating method, and induction heating method, but in consideration of the wide range of selectivity of the evaporation material, it is more preferable to use the electron beam heating method. In addition, in order to improve the adhesion between the deposition layer and the base layer and the denseness of the deposition layer, it is also possible to perform deposition using a plasma assist method or an ion beam assist method. In addition, in order to increase the transparency of the deposition film, reactive deposition in which various gases such as oxygen are blown in during deposition may be used.

[0072] In order to improve the adhesion between the substrate layer and the deposition layer, the substrate layer may be subjected to a surface treatment such as plasma treatment or corona treatment on the deposition layer side surface, and an anchor coat layer (not shown) may be provided between the substrate layer and the deposition layer. By providing an anchor coat layer, the adhesion and barrier properties after heat sterilization treatment can be further improved. Examples of coating agents for providing an 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 deposition layer and complementing the barrier property. 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. 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 a hydroxyl group 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 preferable because it has 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, R 2 is an organic functional group. It is preferable that the organic functional 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 the metal alkoxide 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, R 11 Friends 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] The silane coupling agent includes 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, R 21 Friends 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 mixing a water-soluble polymer dissolved in water or a water / alcohol mixed solvent with a silicon compound, a metal alkoxide, a silane coupling agent, etc., either directly or after being hydrolyzed in advance, and coating the mixture on the deposition layer, followed by heating and drying. It is also possible to add known additives such as an isocyanate compound, a dispersant, a stabilizer, a viscosity adjuster, and a colorant to this solution as necessary, within the range that does not impair the gas barrier properties.

[0081] When PVA is used as the water-soluble polymer, the ratio 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 ratio 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 ratio 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> The barrier film according to a second aspect is a barrier film comprising a substrate layer containing polypropylene, a vapor deposition layer containing an inorganic oxide, and a gas barrier layer, in that order, the substrate layer being composed of two layers, a skin layer and a core layer, in that order from the vapor deposition layer side, and in which, 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] 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, a barrier film 10b according to the present embodiment includes a base layer 1b, a 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) serving 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 deposition layer side. The substrate layer 1b may be a film made of polypropylene, or may be a film oriented uniaxially or biaxially by forming polypropylene into a sheet and stretching the sheet by a conventional means. The stretching may be performed on the multilayer film. The substrate layer 1b may contain known additives, such as organic additives such as antioxidants, stabilizers, lubricants such as calcium stearate, fatty acid amides, and erucic acid amide, antistatic agents, and inorganic additives such as particulate lubricants such as silica, zeolite, syloid, hydrotalcite, and silicon particles, depending on the purpose.

[0086] The thickness (total thickness) of the base layer 1b 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.

[0087] The skin layer 11b is a layer having 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) described later. The at least one softening temperature may be 120°C or more, 125°C or more, or 130°C or more from the viewpoint of improving heat resistance, and may be 165°C or less or 160°C or less from the viewpoint of imparting flexibility. The softening temperature is a temperature measured at the center in the thickness direction of the skin layer 11b. When the at least one softening temperature is 115°C or more, the heat resistance of the skin layer 11b is not too low, and there is little risk that the skin layer 11b will soften during heat sterilization treatment, causing a decrease in adhesion and a deterioration in barrier properties. In addition, when the at least one softening temperature is 170°C or less, the flexibility of the skin layer 11b can be suppressed from decreasing, and the adhesion strength between the skin layer 11b and the core layer 12 can be increased. 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 in the skin layer 11b may contain a copolymer of propylene and another monomer from the viewpoint of improving the adhesion with 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 skin layer 11b may contain a copolymer of propylene and an α-olefin. The copolymer may be a random copolymer. The polypropylene used in the skin layer 11b may contain a random copolymer of propylene and two or more kinds of α-olefins, or may contain an ethylene-1-butene-propylene random copolymer, from the viewpoint of suppressing the oxygen permeability to a lower level even after heat sterilization treatment and from the viewpoint of providing sufficient adhesion strength between the films even after heat sterilization treatment.

[0089] The ethylene 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 keeping oxygen permeability low even after heat sterilization treatment, and from the viewpoint of providing sufficient adhesion strength between films even after heat sterilization treatment, and may be 7 mass% or less, 6 mass% or less, 5 mass% or less, 4 mass% or less, or 3.5 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, and may be 5 mass% or less, 4 mass% or less, or 3.5 mass% or less, based on the total amount of polypropylene, in order to maintain low oxygen permeability even after heat sterilization treatment.

[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. In addition, it is possible to suppress the oxygen permeability to a lower level even after the heat sterilization treatment, and it is possible to provide a sufficient adhesive strength between the films even after the heat sterilization treatment. From this viewpoint, the thickness of the skin layer 11b is preferably 0.3 μm or more. On the other hand, the upper limit of the thickness of the skin layer 11b is not particularly limited, but from the viewpoint of more sufficiently ensuring the heat resistance of the entire base 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 film cross section by local thermal analysis (LTA) 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, and may be 220° C. or lower, 215° C. or lower, or 210° C. or lower. The softening temperature is a temperature measured at the center in the thickness direction of the core layer 12. By having the at least one softening temperature of 190° C. or higher, the heat resistance of the base layer 1b can be increased, and the base layer 1b is resistant to heat during heat sterilization treatment, and the base layer 1b can be prevented from shrinking during heat sterilization treatment, making it impossible to use the base layer 1b 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 conditions.

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

[0094] The softening temperature of the core layer 12, which is at least 190° C., may be at least 20° C. higher, at least 40° C. higher, or at least 50° C. higher than the softening temperature of the skin layer 11b, which is at least 115° C. and at most 170° C. In this case, the shrinkage of the base material layer 1b during the heat sterilization treatment can be made smaller, 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 the skin layer 11b to the thickness of the core layer 12 (thickness of the skin layer 11b / thickness of the 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 the entire base layer 1b can be more sufficiently ensured, the oxygen permeability can be further suppressed even after heat sterilization treatment, and sufficient adhesive strength can be maintained between the films even after heat sterilization treatment.

[0097] The base layer 1b is composed 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 between them. 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 manufacturing method of each layer (e.g., stretching conditions), etc.

[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 mixed with resins polymerized from ordinary fossil fuels.

[0100] The softening temperature of the base layer in this embodiment is measured in the same manner as in the softening temperature measurement described in the first aspect above.

[0101] [Vapour-deposited layer] The deposition layer of this embodiment may have the same configuration as the 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, the 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, the 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] In order to make the laminates 20a, 30a, 20b, 30b into mono-material packaging materials, polyolefin is used as the material for the second base material layer 22 and the sealant layer 23, but it is preferable to use polypropylene as in the base material layers 1a, 1b of the barrier films 10a, 10b. As the polypropylene used for the second base material layer 22, for example, a film obtained by stretching homopolypropylene to provide heat resistance can be used. As the sealant layer 23, for example, a stretched or unstretched polypropylene film may be used.

[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 the adhesive 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 alone 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 described above. The amount of adhesive to be applied in the adhesive layer 24 is, for example, 0.5 to 10 g / m from the viewpoint of obtaining the desired adhesive strength, followability, and processability. 2 From the viewpoint of environmental consideration, the adhesive layer 24 may be made of a polymer component derived from biomass or a biodegradable material. Also, the adhesive layer 24 may be made of an adhesive having a barrier property.

[0109] <Packaging bag> The packaging bag can be produced using the laminate described above. The packaging bag may be a bag shape obtained by folding one packaging material in half so that the sealant layers face each other, and then heat sealing three sides, or a bag shape obtained by stacking two packaging materials so that the sealant layers face each other, and then heat sealing four sides. The packaging bag can contain food, medicine, and other contents. 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 in a shape having a bent portion. EXAMPLES

[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 applied by gravure coating onto the first skin layer of the base material layer, and dried to form an anchor coat layer with a thickness of 0.1 μm. Next, a thin film of silicon oxide with a thickness of 30 nm was deposited on the anchor coat layer by reactive deposition using high-frequency excited ion plating in an oxygen atmosphere under reduced pressure, forming a 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 the three solutions: TEOS diluted with SiO2 solids (converted value) and isocyanurate silane R 2 The liquid was prepared so that the mass ratio of the Si(OH)3 solid content (converted value) to the PVA solid content was 40 / 5 / 55. This coating liquid was applied onto the deposition layer by gravure coating, and then dried under conditions of 80°C and 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 having a laminated structure of gas barrier layer / deposition layer / anchor coat layer / first skin layer / core layer / second skin layer was obtained.

[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] <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, 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] <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.

[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 had 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 had 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] [Laminated body production] 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 by dry lamination using a two-component curing urethane adhesive. Then, the second skin layer side of the barrier film was bonded to a 60 μm-thick unstretched polypropylene film by dry lamination using a two-component curing urethane adhesive to produce a three-layer laminate.

[0123] [evaluation] (Softening temperature measurement) The softening temperature of each layer constituting the base 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. A corona treatment machine (product name: CT-0212) manufactured by Kasuga Electric Co., Ltd. was used for the corona treatment.

[0124] After corona treatment on the front and back surfaces of the sample, the sample was cut into a wedge shape with a base of 1.0 mm and a height of 5.0 mm (the triangular surfaces with the above base and height are the front and back surfaces of the sample, and the bottom and side surfaces are the cross-section of the sample) with a razor. The cut sample was embedded in a photocurable resin and cured with a halogen lamp (Kenko Tokina, product name: KTX-100R). D-800 (product name) manufactured by Toa Gosei was used as the photocurable resin. The sample embedding resin after photocuring was fixed with an insert for an AFM sample holder, and the cross-section of the sample was cut with a glass knife at room temperature (25°C), and then the final cross-section was cut with a diamond knife at a low temperature (-140°C) with a cutting speed of 1.0 mm / s and a cutting film thickness of 100 nm. Cutting was completed when the surface became mirror-like. The cross-section cutting devices used were an ultramicrotome (manufactured by Leica, product name: EM UC7) and a cryosystem (manufactured by Leica, product name: EM FC7). 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 with an insert for the 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 (trade name) manufactured by Oxford Instruments Co., Ltd., a Ztherm system with a local thermal analysis option, and an AN2-200 (trade name) cantilever manufactured by Anasys Instruments Co., Ltd. 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 constitutes the base material layer.

[0126] When the sample surface was heated after Detrend correction with the cantilever contact pressure (change in cantilever deflection) set to 0.2 V, the voltage application rate (heating rate) set to 0.5 V / sec, and the maximum applied voltage set to 6.0 V, the sample surface expanded and the cantilever position rose. When the sample surface was further heated, it softened, 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 performed again.

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

[0128] A calibration curve was created to calculate the softening temperature of the sample. Four types of 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 voltage during detrend correction was 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 (temperature rise rate) was 0.5 V / sec. The calibration sample was measured 20 times at different measurement positions, and 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 base layer was converted to temperature, and the softening temperature was determined. The results are shown in Table 1.

[0130] (retort processing) Packaging bags with four sealed sides were produced 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 performed 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 treatment, 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). The 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-shaped peel angle. The measured 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 occurs 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 area 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 keep oxygen permeability low even after heat sterilization, and had excellent laminate strength between the layers. Note that the reason why the oxygen permeability after heat sterilization was high in Comparative Examples 1-1 and 1-3 is because cracks occurred in the vapor deposition layer during the heat sterilization. Also, the reason why the laminate strength between the OPP / barrier was low in Comparative Example 1-4 is 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 skin layer with a thickness of 0.7 μm and a core layer with a thickness of 19.3 μm. The thicknesses of the skin layer and the core layer were measured by the thickness method described below. The softening temperatures of each layer are shown in Table 2.

[0136] Next, an acrylic primer solution was applied by gravure coating onto the skin layer of the base material layer, and dried to form an anchor coat layer with a thickness of 0.1 μm. Next, a thin film of silicon oxide with a thickness of 30 nm was deposited on the anchor coat layer by reactive deposition using high-frequency excited ion plating in an oxygen atmosphere under reduced pressure, forming a deposition layer made of an 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 the three solutions: TEOS diluted with SiO2 solids (converted value) and isocyanurate silane R 2 The liquid was prepared so that the mass ratio of the Si(OH)3 solid content (converted value) to the PVA solid content was 43 / 10 / 47. This coating liquid was applied onto the deposition layer by gravure coating, and then dried under conditions of 80°C and 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 / 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 had 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 base film (base 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 had 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] [Laminated body production] 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) A barrier film made of photocurable resin was embedded to prepare a block, and the block was then cut using a diamond knife on an ultramicrotome (EM UC7, manufactured by Leica Microsystems). The cut-out portion of the block was observed using a scanning electron microscope (SU8020, manufactured by Hitachi High-Technologies Corporation) at magnifications of 5000 to 20000 times, and the thickness was measured from the observed image.

[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 produced 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 performed 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 If the oxygen permeability was 1.0 MPa or less, the laminate was judged to have a low oxygen permeability even after retort treatment. The results are shown in Table 2.

[0150] (Laminate strength measurement) The laminate strength between the barrier film and the unstretched polypropylene film was measured for the laminate after retort treatment. The measurement was performed in accordance with JIS K6854, with a test width of 15 mm, a peel speed of 300 mm / min, and a T-shaped peel angle. The measured 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 the core layer *3: Peeled off at the surface of the base film (base layer) [Industrial Applicability]

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

[0153] Reference Signs List: 1a, 1b...base material 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 material 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 is composed of two layers, a skin layer and a core layer, in that order from the vapor deposition layer side; A barrier film, 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 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 and 220°C or lower.

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

3. 10. The barrier film of claim 1, wherein the skin layer comprises an ethylene-1-butene-propylene random copolymer.

4. 2. The barrier film according to claim 1, wherein the thickness of the skin layer is 0.2 μm or more and 2.0 μm or less.

5. 2. The barrier film of claim 1, wherein the ratio of the thickness of the skin layer to the thickness of the core layer is 1 / 100 to 1 / 5.

6. 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.

7. 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.

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

9. A laminate comprising the barrier film according to any one of claims 1 to 8 and a sealant layer, wherein the sealant layer comprises a polyolefin.

10. 10. The laminate of claim 9, further comprising a second substrate layer on a side of the barrier film opposite the sealant layer, the second substrate layer comprising a polyolefin.

11. A packaging bag produced by producing the laminate according to claim 9.

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