Gas barrier film
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOPPAN HOLDINGS INC
- Filing Date
- 2025-03-24
- Publication Date
- 2026-06-25
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a gas barrier film.
Background Art
[0002] Packaging materials used for packaging foods, pharmaceuticals, etc. are required to have the property of preventing the entry of gases (water vapor, oxygen, etc.) that can modify the contents in order to suppress the deterioration and spoilage of the contents and maintain their functions and quality (gas barrier property). In addition, since the packaging material may be subjected to heat sterilization treatment such as boiling treatment, excellent heat resistance is required. Therefore, a laminate (gas barrier film) having gas barrier property and heat resistance is used for these packaging materials.
[0003] As the gas barrier film, a film in which a gas barrier layer made of a material having gas barrier property is provided on the surface of a resin base material is known. As the gas barrier layer, a metal foil, a metal vapor deposition film, a film formed by a wet coating method, etc. are known. As the resin base material, a polyolefin film such as a polyethylene film is known. For example, Patent Document 1 describes an aluminum vapor deposition polyethylene film characterized by having an aluminum vapor deposition film on the surface of an unstretched polyethylene film having a thickness of less than 30 μm made of linear low density polyethylene produced by using a metallocene catalyst.
[0004] In addition, improving the characteristics of the gas barrier film by making the resin base material into a laminate having a plurality of resin layers has been studied. For example, Patent Document 2 describes, as a film capable of suppressing the occurrence of wrinkles, a resin layer including a first surface and a second surface, and a vapor deposition layer provided on the second surface of the resin layer. The resin layer has a first layer constituting the first surface, and at least one hard layer having a density higher than the density of the first layer and having a density of 0.934 g / cm 3 and having the above density, and the total thickness of the hard layers is 60% or more of the total thickness of the resin layer.
Prior Art Documents
Patent Document
[0005]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0006] By the way, in recent years, due to the increasing environmental awareness triggered by problems such as marine plastic waste, there has been a demand for further improving the efficiency of the separation, recovery, and recycling of plastic materials. In the case of packaging materials as well, there has been a growing demand for monomaterialization.
[0007] However, when the inventors studied the monomaterialization of gas barrier films, it was found that depending on the type of polyethylene resin constituting each layer of the polyethylene film, wrinkles may occur on the surface of the polyethylene film, making it difficult to form a gas barrier layer, or it may be difficult to impart sufficient transparency and heat resistance.
[0008] Therefore, one aspect of the present invention aims to provide a gas barrier film having excellent processing stability when providing a gas barrier layer, excellent transparency, and excellent heat resistance capable of maintaining gas barrier properties even after heat sterilization treatment.
Means for Solving the Problems
[0009] One aspect of the present invention includes the following [1] to [6]. [1] A gas barrier film having a laminated structure including a multilayer polyethylene film and a gas barrier layer, wherein the multilayer polyethylene film has a surface layer, an intermediate layer, and a back layer in this order, and the surface layer is provided between the intermediate layer and the gas barrier layer, The surface layer is made of medium-density polyethylene resin or high-density polyethylene resin having a density of 0.926 g / cm 3 or more, and the composite elastic modulus of the surface layer and the back layer is 1.45 GPa or more and less than 1.90 GPa, and the composite elastic modulus of the intermediate layer is 1.80 GPa or more and less than 2.50 GPa, the ratio of the thickness of the intermediate layer to the total thickness of the surface layer and the back layer is 0.5 or more, the temperature indicated by the maximum value of the melting peak observed in the differential scanning calorimetry of the multilayer polyethylene film is more than 129 °C and less than 136 °C, the gas barrier layer is a gas barrier film having at least one of an inorganic oxide layer and a gas barrier coating layer. [2] The density of the multilayer polyethylene film is 0.940 g / cm 3 or more, and the gas barrier film according to [1]. [3] The gas barrier layer has the inorganic oxide layer, and the inorganic oxide layer contains at least one of aluminum oxide and silicon oxide, and the gas barrier film according to [1] or [2]. [4] The gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer contains at least one selected from the group consisting of a water-soluble polymer and at least one selected from the group consisting of a metal alkoxide, a hydrolyzate thereof, and reaction products thereof, and the gas barrier film according to any one of [1] to [3]. [5] The gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer contains at least one selected from the group consisting of a silane coupling agent, a hydrolyzate thereof, and reaction products thereof, and the gas barrier film according to any one of [1] to [4]. [6] The gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer contains a polyvalent metal salt of a carboxylic acid, and the gas barrier film according to any one of [1] to [5]. [Advantages of the Invention]
[0010] According to one aspect of the present invention, it is possible to provide a gas barrier film having excellent processing stability when providing a gas barrier layer, excellent transparency, and excellent heat resistance capable of maintaining gas barrier properties even after heat sterilization treatment.
Brief Description of the Drawings
[0011]
Figure 1
Figure 2
Figure 3
Modes for Carrying Out the Invention
[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the drawings are schematic, and for example, the relationship between the thickness and the planar dimensions, and the ratio of the thicknesses of the respective layers are different from the actual ones. Further, the embodiments shown below are examples of configurations for embodying the technical idea of the present disclosure, and the technical idea of the present disclosure is not limited to the materials, shapes, structures, etc. of the constituent parts being as described below.
[0013] [Gas Barrier Film] FIG. 1 is a cross-sectional view of a gas barrier film according to an embodiment of the present invention. The gas barrier film 100 has a laminated structure including at least a multilayer polyethylene film 10 and a gas barrier layer 20.
[0014] The content of the polyethylene resin in the gas barrier film 100 may be 90% by mass or more, or 95% by mass or more based on the total amount of the gas barrier film 100 from the viewpoint of realizing monomaterialization and excellent recyclability.
[0015] The thickness of the gas barrier film 100 may be 5 μm or more, 10 μm or more, or 15 μm or more from the viewpoint of easily achieving excellent heat resistance and easily manufacturing stably, and may be 100 μm or less, 60 μm or less, or 40 μm or less from the viewpoint of cost.
[0016] <Multi-layer polyethylene film> The multi-layer polyethylene film 10 includes a surface layer 11, an intermediate layer 12, and a back layer 13 in this order. The surface layer 11 is provided between the intermediate layer 12 and the gas barrier layer 20. The surface layer 11 and the back layer 13 are the outermost layers of the multi-layer polyethylene film 10, respectively.
[0017] The content of the polyethylene resin in the multi-layer polyethylene film 10 may be 90% by mass or more, or 95% by mass or more based on the total amount of the multi-layer polyethylene film 10 from the viewpoint of realizing single materialization and having excellent recyclability.
[0018] The density of the multi-layer polyethylene film 10 is 0.935 g / cm 3 or more, 0.940 g / cm 3 or more, 0.945 g / cm 3 or more, 0.950 g / cm 3 or more, or 0.955 g / cm 3 or more from the viewpoint that wrinkles are less likely to occur, the processing stability is more excellent, the gas barrier property and the adhesion are more easily maintained even after heat sterilization treatment, and the heat resistance is more excellent. The density of the multi-layer polyethylene film 10 is 0.980 g / cm 3 or less, 0.975 g / cm 3 or less, 0.970 g / cm 3 or less, 0.965 g / cm 3 or less, or 0.960 g / cm 3 or less.
[0019] The multilayer polyethylene film 10 may be unstretched. When the multilayer polyethylene film 10 is unstretched, it means that the absolute value of the molecular orientation degree of the multilayer polyethylene film is less than 1.07. Since the multilayer polyethylene film 10 is unstretched (the absolute value of the molecular orientation degree is less than 1.07), it becomes difficult for the gas barrier layer 20 to peel off near the surface layer 11 of the multilayer polyethylene film 10, and there is a tendency for the adhesion with the gas barrier layer 20 to be excellent. The absolute value of the molecular orientation degree means the absolute value of the molecular orientation degree of the molecular chains in the plane of the multilayer polyethylene film measured by rotating the multilayer polyethylene film in a microwave polarized electric field using a microwave method molecular orientation meter (for example, MOA-5012A manufactured by Oji Scientific Instruments Co., Ltd.).
[0020] The thickness of the multilayer polyethylene film 10 is not particularly limited and can be appropriately determined according to costs and applications while considering the suitability as a packaging material and the lamination suitability with other layers. The thickness of the multilayer polyethylene film 10 may be 3 μm or more, 5 μm or more, 6 μm or more, or 10 μm or more, and may also be 200 μm or less, 120 μm or less, 100 μm or less, or 40 μm or less.
[0021] (Surface layer) The surface layer 11 is a layer composed of a medium-density polyethylene resin or a high-density polyethylene resin of 0.926 g / cm 3 or more. Since the surface layer 11 is composed of a medium-density polyethylene resin or a high-density polyethylene resin of 0.926 g / cm 3 or more, the heat resistance of the multilayer polyethylene film 10 is excellent. In this specification, the high-density polyethylene resin means a polyethylene resin having a density of 0.942 g / cm 3 or more. Hereinafter, the polyethylene resin constituting the surface layer 11 is also referred to as the first polyethylene resin.
[0022] The content of the first polyethylene resin in the surface layer 11 may be 90% by mass or more, 95% by mass or more, or 98% by mass or more, based on the total amount of the surface layer 11, and may also be 100% by mass (in the aspect where the surface layer 11 consists essentially of the first polyethylene resin). When the surface layer 11 is composed of a plurality of polyethylene resins (for example, a plurality of polyethylene resins having different average molecular weights, densities, etc.), a mixture of the plurality of polyethylene resins is regarded as the first polyethylene resin.
[0023] The surface layer 11 may be composed of a first polyethylene resin having a density in the following range from the viewpoints that wrinkles are less likely to occur, the processing stability is more excellent, and the gas barrier property is more easily maintained even after heat sterilization treatment and the heat resistance is more excellent. The density of the first polyethylene resin is 0.930 g / cm 3 or more, 0.935 g / cm 3 or more, or 0.940 g / cm 3 or more. The density of the first polyethylene resin is 0.970 g / cm 3 or less, 0.965 g / cm 3 or less, or 0.960 g / cm 3 or less. In particular, when the density of the first polyethylene resin is 0.960 g / cm 3 or less, it is possible to suppress the roughening of the surface of the multilayer polyethylene film 10 and the generation of resin powder, and it is easier to achieve an excellent gas barrier property.
[0024] The complex elastic modulus of the surface layer 11 is 1.45 GPa or more and less than 1.90 GPa. Since the complex elastic modulus of the surface layer 11 is 1.45 GPa or more and less than 1.90 GPa, the transparency and gas barrier property of the multilayer polyethylene film 10 are excellent. The complex elastic modulus of the surface layer 11 can be measured by the nanoindentation method, and specifically, it can be measured by the method described in the following examples.
[0025] The complex elastic modulus of the surface layer 11 may be 1.50 GPa or more, 1.55 GPa or more, or 1.60 GPa or more, and may be 1.85 GPa or less, 1.80 GPa or less, or 1.75 GPa or less.
[0026] The melt flow rate MFR1 of the first polyethylene resin at 190 ° C and a load of 2.16 kg is not particularly limited and can be appropriately adjusted according to the method for producing the first polyethylene resin. The melt flow rate MFR1 of the first polyethylene resin at 190 ° C and a load of 2.16 kg may be 5 g / 10 min or less, 3 g / 10 min or less, or 1.5 g / 10 min or less. The MFR1 of the first polyethylene resin may be 0.1 g / 10 min or more or 0.3 g / 10 min or more. In this specification, the melt flow rate means a value measured in accordance with JIS K6921-2.
[0027] The thickness of the surface layer 11 is not particularly limited and can be appropriately determined according to the cost and application while considering the suitability derived from the manufacturing method and apparatus and the lamination suitability with other layers. From a practical point of view, the thickness of the surface layer 11 may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, and may be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less.
[0028] (Intermediate layer) The intermediate layer 12 is a layer containing a polyethylene resin. Hereinafter, the polyethylene resin constituting the intermediate layer 12 is also referred to as the second polyethylene resin. The content of the second polyethylene resin in the intermediate layer 12 may be 90% by mass or more, 95% by mass or more, or 98% by mass or more based on the total amount of the intermediate layer 12, and may be 100% by mass (a mode in which the intermediate layer 12 consists substantially of the second polyethylene resin). When the intermediate layer 12 is composed of a plurality of polyethylene resins (for example, a plurality of polyethylene resins having different average molecular weights, densities, etc.), a mixture of the plurality of polyethylene resins is used as the second polyethylene resin.
[0029] The intermediate layer 12 may be composed of a second polyethylene resin having a density in the following range from the viewpoints that wrinkles are less likely to occur and the processing stability is more excellent, that the gas barrier property is more easily maintained even after heat sterilization treatment, and that the heat resistance is more excellent. The density of the second polyethylene resin is 0.940 g / cm 3 or more, 0.945 g / cm 3 or more, or 0.950 g / cm 3 or more. The density of the second polyethylene resin is 0.980 g / cm 3 or less, 0.975 g / cm 3 or less, 0.970 g / cm 3 or less, or 0.965 g / cm 3 or less.
[0030] The complex elastic modulus of the intermediate layer 12 is 1.80 GPa or more and less than 2.50 GPa. When the complex elastic modulus of the intermediate layer 12 is 1.80 GPa or more and less than 2.50 GPa, wrinkles are less likely to occur in the multilayer polyethylene film 10, and the transparency and gas barrier property are excellent. The complex elastic modulus of the intermediate layer 12 can be measured by the nanoindentation method, specifically, it can be measured by the method described in the examples below.
[0031] The complex elastic modulus of the intermediate layer 12 may be 1.90 GPa or more, 2.00 GPa or more, 2.05 GPa or more, 2.10 GPa or more, or 2.15 GPa or more, and may be 2.40 GPa or less, 2.35 GPa or less, or 2.30 GPa or less.
[0032] The melt flow rate MFR2 of the second polyethylene resin at 190 °C and a load of 2.16 kg is not particularly limited and can be appropriately adjusted according to the method for producing the second polyethylene resin. The melt flow rate MFR2 of the second polyethylene resin at 190 °C and a load of 2.16 kg may be 5 g / 10 min or less, 3 g / 10 min or less, 2 g / 10 min or less, or 1.5 g / 10 min or less. The MFR2 of the second polyethylene resin may be 0.1 g / 10 min or more, 0.5 g / 10 min or more, or 0.8 g / 10 min or more.
[0033] The thickness of the intermediate layer 12 is not particularly limited and can be appropriately determined according to costs and applications while considering the suitability derived from the manufacturing method and apparatus, and the lamination suitability with other layers. From a practical perspective, the thickness of the intermediate layer 12 may be 5 μm or more, 8 μm or more, 10 μm or more, 12 μm or more, or 15 μm or more, and may also be 80 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less.
[0034] From the perspective of easily maintaining gas barrier properties even after heat sterilization treatment and having excellent heat resistance, the ratio of the thickness of the intermediate layer 12 to the total thickness of the surface layer 11 and the back layer 13 (thickness of the intermediate layer / (thickness of the surface layer + thickness of the back layer)) is 0.5 or more. The ratio of the thickness of the intermediate layer 12 to the total thickness of the surface layer 11 and the back layer 13 may be 1 or more, 1.2 or more, 1.4 or more, or 1.5 or more. The ratio of the thickness of the intermediate layer 12 to the total thickness of the surface layer 11 and the back layer 13 may be 3 or less, 2.5 or less, or 2 or less.
[0035] The greater the thickness of the intermediate layer 12, the more excellent heat resistance can be achieved. From the perspective that the gas barrier property can be more easily maintained even after heat sterilization treatment and the heat resistance is more excellent, the thickness of the intermediate layer 12 may be greater than the thickness of the surface layer 11 and / or the thickness of the back layer 13. From the perspective that the gas barrier property can be more easily maintained even after heat sterilization treatment and the heat resistance is more excellent, the thickness of the intermediate layer 12 may be 1 times or more, 1.5 times or more, 2 times or more, 2.5 times or more, or 3 times or more the thickness of the surface layer 11 and / or the thickness of the back layer 13. The thickness of the intermediate layer 12 may be 8 times or less, 7 times or less, 6.5 times or less, or 6 times or less the thickness of the surface layer 11 and / or the thickness of the back layer 13.
[0036] (Back layer) The back layer 13 is a layer containing a polyethylene resin. Hereinafter, the polyethylene resin constituting the back layer 13 is also referred to as the third polyethylene resin. The content of the third polyethylene resin in the back layer 13 may be 90% by mass or more, 95% by mass or more, or 98% by mass or more based on the total amount of the back layer 13, and may be 100% by mass (the mode in which the back layer 13 consists substantially of the third polyethylene resin). When the back layer 13 is composed of a plurality of polyethylene resins (for example, a plurality of polyethylene resins having different average molecular weights, densities, etc.), a mixture of the plurality of polyethylene resins is used as the third polyethylene resin.
[0037] The back layer 13 may be composed of a third polyethylene resin having a density in the following range from the perspective that wrinkles are less likely to occur and the processing stability is more excellent, and from the perspective that the gas barrier property and adhesion can be more easily maintained even after heat sterilization treatment and the heat resistance is more excellent. The density of the third polyethylene resin is 0.920 g / cm 3 or more, 0.926 g / cm 3 or more, 0.930 g / cm 3 or more, 0.935 g / cm 3 or more, or 0.940 g / cm 3 or more. The density of the third polyethylene resin is 0.970 g / cm 3 or less, 0.965 g / cm 3 or less, or 0.960 g / cm3 The following may be applicable. When the density of the third polyethylene resin is 0.960 g / cm 3 or less, roughening of the surface of the multilayer polyethylene film 10 and generation of resin powder can be suppressed. By suppressing the generation of resin powder, when the multilayer polyethylene film 10 is wound up in a roll, adhesion of resin powder to the surface on the surface layer 11 side of the multilayer polyethylene film 10 can be suppressed, and it becomes easier to realize excellent gas barrier properties.
[0038] The complex elastic modulus of the back layer 13 is 1.45 GPa or more and less than 1.90 GPa. When the complex elastic modulus of the back layer 13 is 1.45 GPa or more and less than 1.90 GPa, the transparency and gas barrier properties of the multilayer polyethylene film 10 are excellent. The complex elastic modulus of the back layer 13 can be measured by the nanoindentation method, and specifically, it can be measured by the method described in the examples below.
[0039] The complex elastic modulus of the back layer 13 may be 1.50 GPa or more, 1.55 GPa or more, or 1.60 GPa or more, and may be 1.85 GPa or less, 1.80 GPa or less, or 1.75 GPa or less.
[0040] The melt flow rate MFR3 of the third polyethylene resin at 190 °C and a load of 2.16 kg is not particularly limited and can be appropriately adjusted according to the method of manufacturing the third polyethylene resin. The melt flow rate MFR3 of the third polyethylene resin at 190 °C and a load of 2.16 kg may be 5 g / 10 min or less, 3 g / 10 min or less, or 1.5 g / 10 min or less. The MFR3 of the third polyethylene resin may be 0.1 g / 10 min or more or 0.3 g / 10 min or more.
[0041] The thickness of the inner layer 13 is not particularly limited and can be appropriately determined according to costs and applications while considering the suitability derived from the manufacturing method and apparatus and the lamination suitability with other layers. From a practical perspective, the thickness of the inner layer 13 may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, and may also be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less.
[0042] The inner layer 13 may have the same configuration as the surface layer 11. That is, the multilayer polyethylene film 10 may have a symmetric structure with respect to the intermediate layer 12. By having a symmetric structure, curling during the production of the multilayer polyethylene film 10 can be suppressed, and the multilayer polyethylene film 10 can be stably produced.
[0043] The surface layer 11, the intermediate layer 12, and the inner layer 13 may each contain a resin other than polyethylene resin as appropriate within a range that does not impair recyclability. Examples of such resins include ethylene-vinyl acetate copolymers (EVA), ethylene-α-olefin copolymers, ethylene-(meth)acrylic acid copolymers, homopolypropylene resins (PP), propylene-ethylene random copolymers, propylene-ethylene block copolymers, propylene-α-olefin copolymers, olefin resins such as polybutene, polyamides, polyethylene vinyl alcohol, polyesters, and various modifying resins. Also, each may independently contain one or more additives. Examples of additives include crosslinking agents, antioxidants, antiblocking agents, lubricants (slip agents), ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, and pigments.
[0044] The intermediate layer 12 may be a single layer or may be formed of a plurality of layers. For example, as shown in FIG. 2, the multilayer polyethylene film 30 in the gas barrier film 200 has a surface layer 31, an intermediate layer 32, and a back layer 33, and the intermediate layer 32 has resin layers 32a, 32b, and 32c. At this time, the resin layers 32a, 32b, and 32c all have the same composition. The fact that the intermediate layer 32 has a plurality of layers can be confirmed by observing the cross section of the multilayer polyethylene film 30 with an optical microscope or an electron microscope.
[0045] The multilayer polyethylene film 10 may be provided with layers other than the three layers of the surface layer 11, the intermediate layer 12, and the back layer 13. For example, as shown in FIG. 3, the multilayer polyethylene film 40 in the gas barrier film 300 has a surface layer 41, an intermediate layer 42, and a back layer 43, has a resin layer 44 between the surface layer 41 and the intermediate layer 42, and has a resin layer 45 between the intermediate layer 42 and the back layer 43. The resin layer 44 contains, for example, a polyethylene resin and has a composition different from that of the surface layer 41 and the intermediate layer 42. The resin layer 45 contains, for example, a polyethylene resin and has a composition different from that of the intermediate layer 42 and the back layer 43. The multilayer polyethylene film may be, for example, three layers, five layers, seven layers, or more.
[0046] The temperature indicated by the maximum value of the melting peak observed in the differential scanning calorimetry of the multilayer polyethylene film 10 is more than 129°C and less than 136°C. Since the temperature indicated by the maximum value of the melting peak is more than 129°C and less than 136°C, the processing stability is excellent. When there are a plurality of melting peaks, the temperature indicated by the maximum value of any melting peak is within the above range. The temperature indicated by the maximum value of the melting peak means the value measured by the method described in the examples below.
[0047] Each layer of the multilayer polyethylene film 10 may be composed of a polyethylene resin having a density in the following range from the viewpoint that wrinkles are less likely to occur and the processing stability is more excellent, and from the viewpoint that the gas barrier property is more easily maintained even after heat sterilization treatment and the heat resistance is more excellent. The density of the polyethylene resin is 0.940 g / cm3 945 g / cm³ or more 3 or 950 g / cm³ or more 3 It may be so. The density of the polyethylene resin is 980 g / cm³ or less, 3 975 g / cm³ or less, 3 970 g / cm³ or less, 3 or 965 g / cm³ or less. 3 It may be so.
[0048] The method for manufacturing the multilayer polyethylene film 10 is not particularly limited, and it can be manufactured by known methods such as the air-cooled inflation method, the water-cooled inflation method, and the T-die casting method. From the perspective of versatility, the multilayer polyethylene film 10 may be manufactured by the inflation method or the air-cooled inflation method. The air-cooled inflation method is a method in which a mold having an annular lip called a ring die (or a crosshead die) is installed at the tip of an extruder, and the material is extruded in a tube shape and continuously molded. More specifically, an air hole is installed in the center of the ring die, compressed air is blown in from the air hole to expand the tube, and the multilayer polyethylene film 10 can be manufactured by cooling while pulling with a roller called a pinch roll and winding up the film.
[0049] The obtained multilayer polyethylene film 10 may be subjected to a surface modification treatment to improve the suitability of subsequent processes as necessary. For example, the surface of the multilayer polyethylene film 10 may be subjected to a modification treatment to improve printing suitability or lamination suitability during lamination. Examples of the modification treatment include treatments that generate functional groups by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and flame treatment, and modification treatments by wet processes that form an easy-adhesion layer by coating.
[0050] <Gas barrier layer> The gas barrier layer 20 is a layer provided on the multilayer polyethylene film 10 from the viewpoint of improving the gas barrier properties against water vapor and oxygen. The gas barrier layer 20 is preferably a layer having transparency. The gas barrier layer 20 has an inorganic oxide layer 21 and a gas barrier coating layer 22. The gas barrier layer 20 may have both the inorganic oxide layer 21 and the gas barrier coating layer 22, or may have only one of the inorganic oxide layer 21 and the gas barrier coating layer 22.
[0051] (Inorganic oxide layer) The inorganic oxide layer 21 contains an inorganic oxide. Examples of the inorganic oxide include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, and mixtures thereof. From the viewpoints of more easily maintaining the gas barrier properties even after heat sterilization treatment, having more excellent heat resistance, and having more excellent transparency, the inorganic oxide layer 21 may contain at least one selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide.
[0052] The thickness of the inorganic oxide layer 21 may be 5 to 150 nm. If the thickness of the inorganic oxide layer 21 is 5 nm or more, it is easy to form a layer having a uniform and sufficient film thickness, and sufficient gas barrier properties can be realized. If the thickness of the inorganic oxide layer 21 is 150 nm or less, flexibility can be imparted to the inorganic oxide layer 21, and even if an external load such as bending or pulling is applied after forming the inorganic oxide layer 21, cracking of the inorganic oxide layer 21 can be suppressed. The thickness of the inorganic oxide layer 21 may be 6 nm or more, or 8 nm or more, and may be 100 nm or less, or 50 nm or less.
[0053] The inorganic oxide layer 21 can be formed by a normal vacuum deposition method. It can also be formed by other thin film formation methods such as sputtering method, ion plating method, plasma chemical vapor deposition method (CVD), etc. From the viewpoint of excellent productivity, the inorganic oxide layer 21 may be formed by a vacuum deposition method.
[0054] As the heating means for the vacuum evaporation method, any one of an electron beam heating method, a resistance heating method, and an induction heating method can be used. From the viewpoint of the wide range of selectivity of the evaporation material, the electron beam heating method may be used for the vacuum evaporation method. From the viewpoints of improving the adhesion between the multilayer polyethylene film 10 and the inorganic oxide layer 21 and the denseness of the inorganic oxide layer 21, deposition may be performed by a plasma assist method, an ion beam assist method, or the like. From the viewpoint of improving the transparency of the inorganic oxide layer 21, deposition may be performed by reactive evaporation.
[0055] (Gas barrier coating layer) The gas barrier coating layer 22 is a layer provided for the purpose of protecting the multilayer polyethylene film 10 or the inorganic oxide layer 21 and complementing the gas barrier property. The gas barrier coating layer 22 may contain a water-soluble polymer and at least one selected from the group consisting of a metal alkoxide, its hydrolyzate, and reaction products thereof. The gas barrier coating layer 22 may contain at least one selected from the group consisting of a silane coupling agent, its hydrolyzate, and reaction products thereof.
[0056] Examples of the water-soluble polymer include polyvinyl alcohol, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, and the like. From the viewpoint of excellent gas barrier property, the water-soluble polymer may be polyvinyl alcohol (PVA).
[0057] 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. R 11 and R 12Each may independently be an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer from 1 to n. Note that R 11 and R 12 When there are a plurality of them, R 11 may be the same as or different from each other, and R 12 may be the same as or different from each other.
[0058] Examples of the metal alkoxide include tetraethoxysilane [Si(OC2H5)4], triisopropoxyaluminum [Al(O-2’-C3H7)3], and the like. From the viewpoint of being relatively stable in an aqueous solvent after hydrolysis, the metal alkoxide may be tetraethoxysilane or triisopropoxyaluminum.
[0059] 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, 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 from 1 to 3. Note that when there are a plurality of R 21 or R 22 , R 21 may be the same as or different from each other, and R 22 may be the same as or different from each other. Examples of the monovalent organic functional group represented by R 23 include a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, and a monovalent organic functional group containing an isocyanate group. The silane coupling agent may be a multimer such as a dimer or trimer of the above-described silane coupling agent.
[0060] Examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and the like.
[0061] The gas barrier coating layer 22 can be formed by dissolving a water-soluble polymer in water or a water / alcohol mixed solvent, then mixing it with a metal alkoxide, a silane coupling agent, or a hydrolyzate thereof to obtain a mixed solution, and applying the mixed solution to the surface of the inorganic oxide layer 21 (or the multilayer polyethylene film 10 when the inorganic oxide layer 21 is not present), followed by heating and drying. Additives such as isocyanate compounds, dispersants, stabilizers, viscosity modifiers, and colorants may be added to the mixed solution.
[0062] When the water-soluble polymer is PVA, the content of PVA in the mixed solution may be 20 to 50% by mass or 25 to 40% by mass based on the total solid content of the mixed solution. When the content of PVA is 20% by mass or more, it becomes easier to form the gas barrier coating layer 22. When the content of PVA is 50% by mass or less, the gas barrier property is excellent.
[0063] The gas barrier coating layer 22 may be a coating film (a polyvalent metal salt coating film of a polycarboxylic acid) that is a reaction product of a carboxy group of a polycarboxylic acid polymer and a polyvalent metal compound. The polyvalent metal salt coating film of a polycarboxylic acid can be formed by applying a mixed solution of a polycarboxylic acid polymer and a polyvalent metal compound to the surface of the inorganic oxide layer 21 (when there is no inorganic oxide layer 21, the multilayer polyethylene film 10) and heating and drying it. Further, after applying and drying a coating liquid mainly composed of a polycarboxylic acid polymer to the surface of the inorganic oxide layer 21 (when there is no inorganic oxide layer 21, the multilayer polyethylene film 10) to form a coating film, a coating liquid mainly composed of a polyvalent metal compound is applied and dried on the coating film to form a coating film, and a crosslinking reaction is carried out between these coating films to form a polyvalent metal salt coating film of a polycarboxylic acid.
[0064] A polycarboxylic acid polymer is a polymer having two or more carboxy groups in the molecule. Examples of the polycarboxylic acid polymer include polymers of ethylenically unsaturated carboxylic acids; copolymers of ethylenically unsaturated carboxylic acids and other ethylenically unsaturated monomers; acidic polysaccharides having a carboxyl group in the molecule, such as alginic acid, carboxymethyl cellulose, and pectin.
[0065] Examples of the ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, etc. Examples of the ethylenically unsaturated monomer copolymerizable with the ethylenically unsaturated carboxylic acid include saturated carboxylic acid vinyl esters such as ethylene, propylene, and vinyl acetate, alkyl acrylates, alkyl methacrylates, alkyl itaconates, vinyl chloride, vinylidene chloride, styrene, acrylamide, acrylonitrile, etc. The polycarboxylic acid polymer may be one kind or two or more kinds.
[0066] As the polymer of an ethylenically unsaturated carboxylic acid, from the viewpoint of excellent gas barrier properties, it is preferably a polymer containing a structural unit derived from at least one monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, itaconic acid, fumaric acid, and crotonic acid, and more preferably a polymer containing a structural unit derived from at least one monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid.
[0067] In the polymer of an ethylenically unsaturated carboxylic acid, the proportion of the structural unit derived from at least one monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid is preferably 80 mol% or more, more preferably 90 mol% or more, based on the total amount of monomers of the polymer.
[0068] The number average molecular weight of the polycarboxylic acid-based polymer is preferably from 2,000 to 10,000,000, more preferably from 5,000 to 1,000,000. When the number average molecular weight is 2,000 or more, the gas barrier film has sufficient water resistance, and it is possible to suppress the deterioration of gas barrier properties, transparency, and the occurrence of whitening due to moisture. When the number average molecular weight is 10,000,000 or less, the viscosity of the coating liquid when forming the gas barrier coating layer 22 does not become too high, and it becomes easy to form a film.
[0069] When forming a coating film by applying and drying a coating liquid containing a polycarboxylic acid-based polymer as a main component and then forming a coating film of a coating liquid containing a polyvalent metal compound as a main component, a part of the carboxyl groups of the polycarboxylic acid-based polymer may be neutralized in advance with a basic compound. By neutralizing a part of the carboxyl groups of the polycarboxylic acid-based polymer in advance, the water resistance and heat resistance can be further improved. The basic compound may be at least one basic compound selected from the group consisting of a polyvalent metal compound, a monovalent metal compound, and ammonia. Examples of the polyvalent metal compound include the compounds exemplified as the polyvalent metal compound described later. Examples of the monovalent metal compound include sodium hydroxide and potassium hydroxide.
[0070] The coating liquid containing a polycarboxylic acid-based polymer as a main component may contain additives such as a crosslinking agent, a curing agent, a leveling agent, an antifoaming agent, an antiblocking agent, an antistatic agent, a dispersant, a surfactant, a softening agent, a stabilizer, a film-forming agent, and a thickening agent.
[0071] The solvent used for the coating liquid containing a polycarboxylic acid-based polymer as a main component is preferably an aqueous medium. Examples of the aqueous medium include water, a water-soluble or hydrophilic organic solvent, and a mixture thereof. The aqueous medium mainly contains water. The water content in the aqueous medium may be 70% by mass or more, or 80% by mass or more. Examples of the water-soluble or hydrophilic organic solvent include alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; nitriles such as acetonitrile; cellosolves, carbitols, and the like.
[0072] The polyvalent metal compound is not particularly limited as long as it reacts with the carboxyl groups of the polycarboxylic acid-based polymer to form a polyvalent metal salt of the polycarboxylic acid, and examples thereof include zinc oxide, magnesium oxide, magnesium methoxide, copper oxide, calcium carbonate, and the like. The polyvalent metal compound may be zinc oxide from the viewpoint of excellent gas barrier properties. One kind or two or more kinds of the polyvalent metal compound may be used.
[0073] Zinc oxide is an inorganic material having ultraviolet absorption performance. When zinc oxide is in the form of particles, the average particle diameter of the zinc oxide particles may be 5 μm or less, 1 μm or less, or 0.1 μm or less from the viewpoints of gas barrier property, transparency, and film forming property.
[0074] When applying and drying a coating solution mainly composed of a polyvalent metal compound to form a film, the coating solution may contain, in addition to the polyvalent metal compound (for example, zinc oxide particles), a solvent, a resin soluble or dispersible in the solvent, a dispersant, a softening agent, a stabilizer, a film forming agent, a thickening agent, etc.
[0075] Examples of the resin soluble or dispersible in the solvent include alkyd resin, melamine resin, acrylic resin, urethane resin, polyester resin, phenol resin, amino resin, fluororesin, epoxy resin, isocyanate resin, etc. By the coating solution containing these resins, the coatability and film forming property are improved.
[0076] As the dispersant, an anionic surfactant or a nonionic surfactant can be used. Examples of the surfactant include (poly) carboxylate, alkyl sulfate ester salt, alkylbenzene sulfonate, alkylnaphthalene sulfonate, alkyl sulfosuccinate, alkyl diphenyl ether disulfonate, alkyl phosphate, aromatic phosphate ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester, alkyl allyl sulfate ester salt, polyoxyethylene alkyl phosphate ester, sorbitan alkyl ester, glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan alkyl ester, polyoxyethylene alkyl allyl ether, polyoxyethylene derivative, polyoxyethylene sorbitol fatty acid ester, polyoxy fatty acid ester, polyoxyethylene alkylamine, etc. These surfactants may be used alone or in combination of two or more.
[0077] When the coating liquid containing a polyvalent metal compound as the main component contains an additive, the mass ratio of the polyvalent metal compound to the additive (polyvalent metal compound: additive) may be 30:70 to 99:1, or 50:50 to 98:2.
[0078] Examples of the solvent used in the coating liquid containing a polyvalent metal compound as the main component include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, butyl acetate, and the like. From the viewpoint of coatability, the solvent may be at least one selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water. From the viewpoint of film-forming property, the solvent may be at least one selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, and water. One or more solvents may be used.
[0079] Examples of the coating method of the coating liquid include a casting method, a dipping method, a roll coating method, a gravure coating method, a screen printing method, a reverse coating method, a spray coating method, a kit coating method, a die coating method, a metering bar coating method, a combined chamber doctor coating method, a curtain coating method, and the like.
[0080] The above-described gas barrier coating layer 22 can maintain excellent gas barrier properties even after heat sterilization treatment. Therefore, when a laminate provided with a sealant layer on the gas barrier film 100 is used as a packaging material for heat sterilization treatment, the packaging material has excellent gas barrier properties even after heat sterilization treatment. Further, the above-described gas barrier coating layer 22 has sufficient transparency, bending resistance, and stretch resistance, and is preferable because there is no risk of generating harmful substances such as dioxin.
[0081] From the perspective of excellent gas barrier properties, the thickness of the gas barrier coating layer 22 may be 0.05 μm or more, or 0.1 μm or more. From the perspectives of easily forming a uniform coating surface, reducing the load due to drying, and manufacturing cost, the thickness of the gas barrier coating layer 22 may be 1 μm or less, or 0.5 μm or less.
[0082] (Undercoat layer) From the perspective of improving the adhesion between the multilayer polyethylene film 10 and the gas barrier layer 20, an undercoat layer (not shown) may be provided between the multilayer polyethylene film 10 and the gas barrier layer 20. By providing the undercoat layer, it becomes easier to maintain the gas barrier properties and adhesion even after heat sterilization treatment.
[0083] The undercoat layer can be formed, for example, from a coating solution containing a resin such as an acrylic resin, an epoxy resin, an acrylic urethane resin, a polyester-based polyurethane resin, or a polyether-based polyurethane resin. From the perspectives of heat resistance and interlayer adhesion strength, the undercoat layer may be formed from a coating solution containing an acrylic urethane resin or a polyester-based polyurethane resin.
[0084] The method of applying the coating solution for forming the undercoat layer may be a known coating method, including dipping method; methods using spray, coater, printing machine, brush, etc. Also, as for the types of coaters and printing machines used in these methods and their coating methods, there are gravure coaters such as direct gravure method, reverse gravure method, kiss reverse gravure method, offset gravure method, reverse roll coater, micro gravure coater, chamber doctor combined coater, air knife coater, dip coater, bar coater, comma coater, die coater, etc.
[0085] As a method for drying the undercoat layer, it is not particularly limited, and examples thereof include a method by natural drying, a method of drying in an oven set at a predetermined temperature, and a method using a dryer attached to a coater, such as an arch dryer, a floating dryer, a drum dryer, an infrared dryer, etc. The drying conditions can be appropriately selected according to the drying method. For example, in the method of drying in an oven, it may be dried at 60 to 100 °C for about 1 second to 2 minutes.
[0086] From the viewpoint of easily obtaining sufficient adhesion between layers, the thickness of the undercoat layer may be 0.01 μm or more, 0.03 μm or more, or 0.05 μm or more. From the viewpoint of excellent gas barrier properties, the thickness of the undercoat layer may be 5 μm or less, 3 μm or less, or 2 μm or less.
[0087] <Packaging material> The gas barrier film 100 can be used as a packaging material constituting a packaging bag. Specifically, after providing a sealant layer on the gas barrier film 100 to form a laminate, it can be used as a packaging material such as a flat bag, a three-side bag, a clasp bag, a gusset bag, a standing pouch, a pouch with a spout, a pouch with a beak, etc.
[0088] In addition to packaging materials, the gas barrier film 100 can be used as a film for electronic devices, a film for solar cells, a film for fuel cells, a substrate film, etc.
Examples
[0089] Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited only to the following examples.
[0090] <Polyethylene resin> · Resin A: density 0.963 g / cm 3 , MFR 1.35 g / 10 min, DSC melting point 134 °C. · Resin B: density 0.944 g / cm 3 , MFR 0.45 g / 10 min, DSC melting point 131 °C. · Resin C: density 0.950 g / cm 3 , MFR 1.1 g / 10 min, DSC melting point 130 °C. · Resin D: density 0.958 g / cm 3 , MFR 1 g / 10 min, DSC melting point 133 °C. · Resin E: density 0.960 g / cm 3 , MFR 1 g / 10 min, DSC melting point 135 °C. · Resin F: density 0.920 g / cm 3 , MFR 0.85 g / 10 min, DSC melting point 124 °C. · Resin G: density 0.941 g / cm 3 , MFR 1.3 g / 10 min, DSC melting point 129 °C. · Resin H: density 0.962 g / cm 3 , MFR 0.85 g / 10 min, DSC melting point 134 °C. · Resin I: density 0.926 g / cm 3 , MFR 0.85 g / 10 min, DSC melting point 123 °C.
[0091] <Production of polyethylene film> (Examples 1 to 26, Comparative Examples 1 to 11) The resins shown in Tables 1 to 6 were respectively charged into an extruder as the resins constituting the surface layer, the intermediate layer, and the back layer, melt-kneaded at 190 °C, and then polyethylene resin was introduced from a three-layer die, and a multilayer polyethylene film was produced by the air-cooled inflation method. The thickness of the entire multilayer polyethylene film produced in each example and each comparative example was in the range of 25 to 40 μm. The content of the polyethylene resin in the multilayer polyethylene film produced in each example and each comparative example was 90% by mass or more.
[0092] <Production of gas barrier film> On the surface of the surface layer side of the multilayer polyethylene films prepared in each example and each comparative example, an undercoat layer, an inorganic oxide layer, and a gas barrier coating layer were formed to have the configurations shown in Tables 1 to 6, and a gas barrier film laminated in the order of multilayer polyethylene film / undercoat layer / inorganic oxide layer / gas barrier coating layer was produced. The undercoat layer, adhesive layer, inorganic oxide layer, and gas barrier coating layer were each formed by the methods described below. The content of the polyethylene resin in the gas barrier films prepared in each example and each comparative example was 90% by mass or more in all cases.
[0093] <Undercoat layer> An acrylic polyol (manufactured by DIC Corporation, Acridic CL-1000) and an isocyanate compound (manufactured by Tosoh Corporation, TDI type curing agent Coronate 2030) were mixed so that the solid content mass ratio was 6:4. Next, ethyl acetate was added and diluted so that the solid content became 2% by mass to obtain a coating solution for forming the undercoat layer. After one-sided corona treatment was performed on the surface of the surface layer side of the multilayer polyethylene films of each example and each comparative example, the coating solution for forming the undercoat layer was applied to the surface subjected to corona treatment using a gravure printing machine to form a coating film, and a 0.1 μm-thick undercoat layer was formed by drying in an oven at 60°C for 10 seconds.
[0094] <Inorganic oxide layer> When the inorganic oxide was silicon oxide, a transparent inorganic oxide layer (silicon oxide film) made of 30 nm-thick silicon oxide was formed by a vacuum deposition apparatus using an electron beam heating method. The silicon oxide film had an O / Si ratio of 1.8. When the inorganic oxide was aluminum oxide, a transparent inorganic oxide layer (aluminum oxide film) made of 15 nm-thick aluminum oxide was formed by a vacuum deposition apparatus using an electron beam heating method. The aluminum oxide film had an O / Al ratio of 1.5.
[0095] <Gas barrier coating layer> (Organic-inorganic composite film) An aqueous solution in which polyvinyl alcohol resin (PVA, Poval PVA-105 manufactured by Kuraray Co., Ltd., saponification degree 98-99%, degree of polymerization 500) was dissolved, tetraethoxysilane (TEOS), and γ-glycidoxypropyltrimethoxysilane (GPTMS, KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd.) were each hydrolyzed with 0.02 mol / L hydrochloric acid to prepare an aqueous solution. Next, three aqueous solutions were mixed so that the mass ratio of PVA:TEOS:GPTMS was 40:50:10 in the mass ratio before hydrolysis of PVA, TEOS, and GPTMS. Next, isopropyl alcohol was added to the mixed aqueous solution and diluted so that the mass ratio of water to isopropyl alcohol was 90:10, and a coating liquid for forming an organic-inorganic composite film (solid content: 5% by mass) was obtained. On the inorganic oxide layer, using a gravure printing machine, the following mixed liquid for an organic-inorganic composite film was coated to form a coating film, and dried in an oven at 60 °C for 10 seconds to form a gas barrier coating layer composed of an organic-inorganic composite film with a thickness of 0.3 μm.
[0096] (Multivalent metal salt film of polycarboxylic acid) 58.9 parts by mass of distilled water was added to 20 parts by mass of an aqueous solution of polyacrylic acid (Aron A-10H manufactured by Toagosei Co., Ltd., number average molecular weight 200,000, solid content concentration 25% by mass) and diluted. Next, 0.44 parts by mass of aminopropyltrimethoxysilane (APTMS, manufactured by Aldrich) was added and stirred to obtain a uniform mixed liquid for A film mainly composed of a polycarboxylic acid-based polymer. 100 parts by mass of a zinc oxide fine particle aqueous dispersion (ZE143 manufactured by Sumitomo Osaka Cement Co., Ltd.) and 2 parts by mass of a curing agent (Liofol HAERTER UR 5889-21 manufactured by Henkel) were mixed to obtain a mixed liquid for B film mainly composed of a multivalent metal compound. On the inorganic oxide layer, using a gravure printing machine, the following mixed liquid for A film was coated to form a coating film, and dried in an oven at 60 °C for 10 seconds to form an A film with a thickness of 0.2 μm. Further, using a gravure printing machine, the mixed liquid for B film was coated to form a coating film, and dried in an oven at 60 °C for 10 seconds to form a B film with a thickness of 0.2 μm. Thereby, an oxygen barrier film composed of a multivalent metal salt film of polycarboxylic acid was formed.
[0097] <Adhesive layer> (Urethane-based adhesive) To 100 parts by mass of Tacklac A525 (manufactured by Mitsui Chemicals, Inc.), 11 parts by mass of Takenate A52 (manufactured by Mitsui Chemicals, Inc.) and 84 parts by mass of ethyl acetate were mixed to obtain a urethane-based adhesive.
[0098] (Epoxy-based adhesive) To 23 parts by mass of a solvent obtained by mixing ethyl acetate and methanol in a mass ratio of 1:1, 16 parts by mass of Maxceleb C93T (manufactured by Mitsubishi Gas Chemical Company, Inc.) and 5 parts by mass of Maxceleb M-100 (manufactured by Mitsubishi Gas Chemical Company, Inc.) were mixed to obtain an epoxy-based adhesive.
[0099] <Complex elastic modulus> The multilayer polyethylene film was embedded in the visible light curable resin D-800. Then, using an ultramicrotome Leica EM UC7 and a diamond knife Microstar LH, the multilayer polyethylene film was cut perpendicular to the lamination direction. Finish processing was performed on the exposed cross-section under the conditions of a cutting thickness Feed of 100 nm and a cutting speed Speed of 1 mm / s to obtain a measurement sample. For the measurement, Hysitron TI-Premier (trade name) manufactured by Bruker Japan Co., Ltd. was used as the measuring device, and a Berkovich type diamond indenter manufactured by Bruker Japan Co., Ltd. was used as the indenter. The measurement conditions were as follows. Temperature: room temperature (25 °C). Mode: load control mode. Pushing-in and unloading: After pushing in to a load of 15 μN at a pushing-in speed of 1.5 μN / second, it was held for 5 seconds at the maximum load and then unloaded at a speed of 1.5 μN / second. Measurement location: Using the shape measurement function of the measuring device that scans the sample surface with the indenter, the shape image of the cross-section of the measurement sample was obtained, and 20 points were specified at intervals of 1 μm or more on the cross-section of the measurement sample from the shape image. When calculating the complex elastic modulus, fused quartz was used as a standard sample, and the relationship between the contact depth and the contact projected area of the indenter and the sample was calibrated in advance. Then, the unloading curve in the range of 60 - 95% of the maximum load during unloading was analyzed by the Oliver-Pharr method to calculate the complex elastic modulus of the measured sample. The measurement results are shown in Tables 1 - 6.
[0100] <Melting peak temperature> For the prepared multilayer polyethylene film, differential scanning calorimetry was performed using a differential scanning calorimeter (manufactured by Hitachi, Ltd., trade name DSC7020) in accordance with JIS K7121 - 1987 under the conditions of a measurement temperature of 20 - 200°C and a heating rate of 10°C / min, and the temperature at the maximum value of the melting peak of the obtained curve was read. The results are shown in Tables 1 - 6. If there is no maximum value of the melting peak within the range exceeding 129°C and less than 136°C, it is indicated as "-" in the table.
[0101] [Evaluation] <Processing stability> After forming the gas barrier coating layer (for examples and comparative examples without forming the gas barrier coating layer, after forming the inorganic oxide layer), the appearance of the gas barrier film was visually confirmed, and the processing stability was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 1 - 6. A: No wrinkles were observed in the appearance of the gas barrier film. B: Slight wrinkles were observed in the appearance of the gas barrier film. C: Many wrinkles were observed in the appearance of the gas barrier film.
[0102] <Transparency> The haze of the prepared multilayer polyethylene film was measured in accordance with JIS K7136 using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH - 20), and the transparency was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 1 - 6. A: Haze is less than 20% B: Haze is 20% or more and less than 35% C: Haze is 35% or more
[0103] <Oxygen barrier property> For the gas barrier films prepared in each example and each comparative example, after dry laminating the above-mentioned urethane-based adhesive or the above-mentioned gas barrier adhesive using a multi-coater TM-MC (manufactured by HIRANO TECSEED), it was cured at 40 °C for 3 days to form an adhesive layer. After curing, LLDPE (polyethylene film, manufactured by Mitsui Chemicals Toagosei Co., Ltd., TUX MC-S, thickness 60 μm) was laminated on the adhesive layer to produce a laminate in which the gas barrier film / adhesive / LLDPE was laminated in this order. Using an oxygen permeability measuring device (product name OXTRAN-2 / 20, manufactured by MOCON), in accordance with the JIS K-7126-2 B method, in an atmosphere of 30 °C and 70% RH, the oxygen permeability (cm 3 / (m 2 ·day·atm)) of the produced laminate was measured, and the oxygen barrier property was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 1 to 6. A+: The oxygen permeability is less than 2 cm 3 / (m 2 ·day·atm). A: The oxygen permeability is 2 cm 3 / (m 2 ·day·atm) or more and less than 5 cm 3 / (m 2 ·day·atm). A-: The oxygen permeability is 5 cm 3 / (m 2 ·day·atm) or more and less than 10 cm 3 / (m 2 ·day·atm). B+: The oxygen permeability is 10 cm 3 / (m 2 ·day·atm) or more and less than 20 cm 3 / (m 2 ·day·atm). B: The oxygen permeability is 20 cm 3 / (m 2 ·day·atm) or more and less than 50 cm 3 / (m 2 ·day·atm). B-: The oxygen permeability is 50 cm 3 / (m 2 ·day·atm) or more.
[0104] <Oxygen barrier property after boiling treatment> Two sheets of the produced laminate were cut out to a size of 15 cm × 10 cm, and the two cut-out laminates were overlapped so that their sealant layers faced each other, and three sides were impulse-sealed into a pouch shape. 150 mL of water was put into the pouch as the content, and the remaining one side was impulse-sealed to produce a pouch (packaging bag) with four sides sealed. The produced pouch was subjected to boiling treatment at 95 °C for 30 minutes in a boiling treatment apparatus. After the boiling treatment, the pouch was opened to remove the content, and after being sufficiently dried, the oxygen permeability was measured by the method described above to evaluate the oxygen barrier property. The evaluation results are shown in Tables 1 to 6.
[0105]
Table 1
[0106]
Table 2
[0107]
Table 3
[0108]
Table 4
[0109]
Table 5
[0110]
Table 6
Explanation of symbols
[0111] 10, 30, 40... multi-layer polyethylene film, 11, 31, 41... surface layer, 12, 32, 42... intermediate layer, 13, 33, 43... inner layer, 20... gas barrier layer, 21... inorganic oxide layer, 22... gas barrier coating layer, 100, 200, 300... gas barrier film.
Claims
1. A gas barrier film having a laminated structure comprising a multilayer polyethylene film and a gas barrier layer, The multilayer polyethylene film has a surface layer, an intermediate layer, and a back layer in this order, and the surface layer is provided between the intermediate layer and the gas barrier layer. The combined modulus of the surface layer and the back layer is 1.45 GPa or more and less than 1.90 GPa, and the combined modulus of the intermediate layer is 1.80 GPa or more and less than 2.50 GPa. A gas barrier film in which the gas barrier layer has at least one of an inorganic oxide layer and a gas barrier coating layer.
2. The gas barrier film according to Claim 1, wherein the thickness of the multilayer polyethylene film is 10 μm or more and 120 μm or less.
3. The gas barrier film according to claim 1, wherein the thickness of the surface layer is 1 μm or more and 50 μm or less.
4. The gas barrier film according to claim 1, wherein the thickness of the intermediate layer is 5 μm or more and 80 μm or less.
5. The gas barrier layer has the inorganic oxide layer, The gas barrier film according to claim 1, wherein the inorganic oxide layer comprises at least one of aluminum oxide and silicon oxide.
6. The gas barrier layer has the gas barrier coating layer, The gas barrier film according to claim 1, wherein the gas barrier coating layer comprises a water-soluble polymer and at least one selected from the group consisting of metal alkoxides, their hydrolysates, and reaction products thereof.
7. The gas barrier layer has the gas barrier coating layer, The gas barrier film according to claim 1, wherein the gas barrier coating layer comprises at least one selected from the group consisting of a silane coupling agent, its hydrolysate, and reaction products thereof.
8. The gas barrier layer has the gas barrier coating layer, The gas barrier film according to claim 1, wherein the gas barrier coating layer contains a polyvalent metal salt of a carboxylic acid.