Gas barrier film, laminate, and packaging material

Abstract

The gas barrier film is provided with a multilayer polyethylene film and a gas barrier layer, the multilayer polyethylene film has a surface layer, an intermediate layer, and an inner layer in this order, the surface layer is provided between the intermediate layer and the gas barrier layer, and the surface layer is composed of a medium-density polyethylene resin or a high-density polyethylene resin having a density of 0.926 g / cm3 or more. The composite elastic modulus of the surface layer and the inner layer is 1.45 GPa or more and less than 1.90 GPa, 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 inner layer is 0.5 or more, the temperature indicated by the maximum value of the melting peak of the multilayer polyethylene film exceeds 129 DEG C and less than 136 DEG C, and the thickness of the intermediate layer is 0.5 or more. The gas barrier layer has at least one of an inorganic oxide layer and a gas barrier coating layer.

Description

Technical Field

[0001] This invention relates to gas barrier films, laminates, and packaging materials. Background Technology

[0002] For packaging materials used in the packaging of food, pharmaceuticals, and other products, in order to prevent spoilage and deterioration of the contents and maintain their function and quality, properties that prevent the entry of gases (water vapor, oxygen, others) that would denature the contents are required (gas barrier properties). Furthermore, packaging materials are sometimes subjected to heat sterilization treatments such as boiling, thus requiring excellent heat resistance. Therefore, these packaging materials utilize laminates with both gas barrier and heat resistance properties (gas barrier films).

[0003] As a gas barrier film, a gas barrier film having a gas barrier layer made of a gas barrier material on the surface of a resin substrate is known. As a gas barrier layer, metal foil, metal vapor-deposited film, and film formed by wet coating are known. As a resin substrate, polyolefin films such as polyethylene films are known. For example, Patent Document 1 describes an aluminum vapor-deposited polyethylene film, characterized by having an aluminum vapor-deposited film on the surface of an unstretched polyethylene film with a thickness of less than 30 μm, made of linear low-density polyethylene manufactured using a metallocene catalyst.

[0004] Furthermore, the properties of gas barrier films were studied by constructing the resin substrate as a laminate having multiple resin layers. For example, Patent Document 2 describes a film capable of suppressing wrinkle formation, comprising: a resin layer including a first surface and a second surface; and a vapor-deposited layer disposed on the second surface of the resin layer, wherein the resin layer comprises: a first layer constituting the first surface; and at least one rigid layer having a density higher than that of the first layer and having a density of 0.934 g / cm³. 3 The above density and the thickness of the hard layer together account for more than 60% of the total thickness of the resin layer.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2001-179878 Patent Document 2: Japanese Patent Application Publication No. 2018-24213 Summary of the Invention

[0006] The problem that the invention aims to solve Furthermore, in recent years, with the increasing environmental awareness brought about by issues such as marine plastic waste, there is a growing demand for more efficient classification, recycling, and reuse of plastic materials, and packaging materials are increasingly required to be made of single materials.

[0007] However, in the process of promoting the single materialization of gas barrier membranes, the inventors found that, depending on the type of polyethylene resin that constitutes each layer of the polyethylene membrane, wrinkles sometimes occur on the surface of the polyethylene membrane, making it difficult to form a gas barrier layer, and sometimes it is difficult to impart sufficient transparency and heat resistance.

[0008] Therefore, one aspect of the present invention is to provide a gas barrier film having excellent processing stability when a gas barrier layer is provided, excellent transparency, and excellent heat resistance that maintains gas barrier properties even after heat sterilization treatment.

[0009] Solution for solving the problem One aspect of the present invention includes the following [1] to

[15] .

[0010] [1] A gas barrier membrane, comprising a laminated structure, the laminated structure comprising multiple layers of polyethylene film and a gas barrier layer, the multiple layers of polyethylene film comprising a surface layer, an intermediate layer and an inner layer in sequence, the surface layer being disposed between the intermediate layer and the gas barrier layer, the surface layer being composed of a gas barrier layer having a gas barrier layer density of 0.926 g / cm³. 3 The material is composed of medium-density polyethylene resin or high-density polyethylene resin of the above-mentioned density, wherein the composite elastic modulus of the outer layer and the inner layer is 1.45 GPa or more and less than 1.90 GPa, the composite elastic modulus of the middle layer is 1.80 GPa or more and less than 2.50 GPa, and the gas barrier layer has at least one of an inorganic oxide layer and a gas barrier coating layer.

[0011] [2] According to the gas barrier membrane described in [1], wherein the density of the multilayer polyethylene film is 0.940 g / cm³. 3 above.

[0012] [3] The gas barrier membrane according to [1] or [2], wherein the gas barrier layer has the inorganic oxide layer, the inorganic oxide layer comprising at least one of aluminum oxide and silicon oxide.

[0013] [4] A gas barrier membrane according to any one of [1] to [3], wherein the gas barrier layer has the gas barrier coating layer, the gas barrier coating layer comprising a water-soluble polymer and at least one selected from the group consisting of metal alkoxides, hydrolysates of metal alkoxides and their reaction products.

[0014] [5] A gas barrier membrane according to any one of [1] to [4], wherein the gas barrier layer has the gas barrier coating layer comprising at least one selected from the group consisting of silane coupling agents, hydrolysates of silane coupling agents and their reaction products.

[0015] [6] A gas barrier membrane according to any one of [1] to [5], wherein the gas barrier layer has the gas barrier coating layer comprising a polyvalent metal salt of carboxylic acid.

[0016] [7] The gas barrier membrane according to any one of [1] to [6], wherein the ratio of the thickness of the intermediate layer to the total thickness of the surface layer and the inner layer is 0.5 or more.

[0017] [8] A gas barrier membrane according to any one of [1] to [8], wherein the thickness of the intermediate layer is 33% or more of the thickness of the multilayer polyethylene film.

[0018] [9] A gas barrier membrane according to any one of [1] to [8], wherein the temperature indicated by the maximum value of the melting peak observed in differential scanning calorimetry of the multilayer polyethylene membrane is greater than 129°C and less than 136°C.

[0019]

[10] A laminate comprising: a gas barrier membrane as described in any one of [1] to [9]; an adhesive layer disposed on the surface of the gas barrier layer opposite to the multilayer polyethylene membrane; and a sealing layer disposed by means of the adhesive layer, wherein the absolute value of the molecular orientation degree of the multilayer polyethylene membrane is less than 1.07.

[0020]

[11] According to the laminate of

[10] , wherein the content of polyethylene resin in the laminate is 90% by mass or more, based on the total amount of the laminate.

[0021]

[12] The laminate according to

[10] or

[11] , wherein a gas barrier coating is further provided on the surface of the inorganic oxide layer on the sealing layer side.

[0022]

[13] The laminate according to any one of

[10] to

[12] , wherein the adhesive layer comprises a gas barrier adhesive.

[0023]

[14] The laminate according to any one of

[10] to

[13] further comprises: a second adhesive layer disposed on the surface of the inner layer side of the multilayer polyethylene film; and a substrate disposed by means of the second adhesive layer.

[0024]

[15] A packaging material comprising a laminate as described in any one of

[10] to

[14] .

[0025] Invention Effects According to one aspect of the present invention, a gas barrier film can be provided that has excellent processing stability when a gas barrier layer is provided, excellent transparency, and excellent heat resistance that maintains gas barrier properties even after heat sterilization treatment. Attached Figure Description

[0026] Figure 1 This is a cross-sectional view of a gas barrier membrane according to one embodiment of the present invention.

[0027] Figure 2 This is a cross-sectional view of a gas barrier membrane according to another embodiment of the present invention.

[0028] Figure 3 This is a cross-sectional view of a gas barrier membrane according to another embodiment of the present invention.

[0029] Figure 4 This is a cross-sectional view of a laminated body according to one embodiment of the present invention.

[0030] Figure 5 This is a cross-sectional view of a laminated body according to another embodiment of the present invention.

[0031] Figure 6 This is a cross-sectional view of a laminated body according to another embodiment of the present invention.

[0032] Figure 7 This is a cross-sectional view of a laminated body according to another embodiment of the present invention. Detailed Implementation

[0033] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that the drawings are schematic; for example, the relationship between thickness and planar dimensions, and the ratio of thicknesses of each layer, differ from reality. Furthermore, the embodiments shown below illustrate configurations used to concretize the technical concept of the present disclosure; the materials, shapes, structures, etc., of the constituent components are not limited to those described below.

[0034] [Gas barrier membrane] Figure 1 This is a cross-sectional view of a gas barrier membrane according to one embodiment of the present invention. The gas barrier membrane 100 has a laminated structure, which includes at least multiple layers of polyethylene film 10 and gas barrier layers 20.

[0035] From the perspective of achieving single materialization and excellent recyclability, based on the total amount of gas barrier membrane 100, the content of polyethylene resin in gas barrier membrane 100 can be more than 90% by mass or more than 95% by mass.

[0036] From the viewpoints of easily achieving excellent heat resistance and easy and stable manufacturing, the thickness of the gas barrier membrane 100 can be 5 μm or more, 10 μm or more, or 15 μm or more. From the viewpoint of cost, the thickness of the gas barrier membrane 100 can be less than 100 μm, less than 60 μm, or less than 40 μm. From these viewpoints, the thickness of the gas barrier membrane 100 can be 5–100 μm, 10–60 μm, or 15–40 μm.

[0037] <Multilayer polyethylene film> The multilayer polyethylene film 10 sequentially comprises a surface layer 11, an intermediate layer 12, and an inner layer 13. The surface layer 11 is disposed between the intermediate layer 12 and the gas barrier layer 20. The surface layer 11 and the inner layer 13 are the outermost layers of the multilayer polyethylene film 10.

[0038] From the perspective of achieving single materialization and excellent recyclability, based on the total amount of multilayer polyethylene film 10, the content of polyethylene resin in multilayer polyethylene film 10 can be more than 90% by mass or more than 95% by mass.

[0039] From the perspectives of being less prone to wrinkles, having superior processing stability, and maintaining gas barrier properties, airtightness, and heat resistance even after heat sterilization, the density of multilayer polyethylene film 10 can be 0.935 g / cm³. 3 Above, 0.940 g / cm 3 Above, 0.945 g / cm 3 Above, 0.950 g / cm 3 Above, or 0.955 g / cm 3 The above. From the perspectives of being less prone to wrinkles, having superior processing stability, and maintaining gas barrier properties and airtightness even after heat sterilization, as well as superior heat resistance, the density of multilayer polyethylene film 10 can be 0.980 g / cm³. 3 Below, 0.975g / cm 3 Below, 0.970 g / cm 3 Below, 0.965g / cm 3 Below, or 0.960 g / cm 3 Based on these viewpoints, the density of the multilayer polyethylene film 10 can be 0.935–0.980 g / cm³. 3 0.940~0.975g / cm 3 0.945~0.970g / cm 3 0.950~0.965g / cm 3 Or 0.955~0.960g / cm 3 .

[0040] The multilayer polyethylene film 10 can be unstretched. Unstretched multilayer polyethylene film 10 means that the absolute value of the molecular orientation degree of the multilayer polyethylene film is less than 1.07. With the multilayer polyethylene film 10 unstretched (absolute value of molecular orientation degree less than 1.07), the gas barrier layer 20 is less likely to peel off near the surface layer 11 of the multilayer polyethylene film 10, exhibiting excellent adhesion to the gas barrier layer 20. The absolute value of the molecular orientation degree can be 1 or more, 1.02 or more, or 1.04 or more. From these perspectives, the absolute value of the molecular orientation degree can be 1 or more and less than 1.07, 1.02 or more and less than 1.07, or 1.04 or more and less than 1.07. The absolute value of the molecular orientation degree refers to the absolute value of the molecular chain orientation degree within the surface of the multilayer polyethylene film, measured by rotating the multilayer polyethylene film in a microwave polarized electric field using a microwave molecular orientation meter (e.g., MOA-5012A manufactured by Oji Measuring Instruments Co., Ltd.).

[0041] The thickness of the multilayer polyethylene film 10 is not particularly limited; its suitability as a packaging material and its compatibility with other layers can be considered, and it can be appropriately determined based on cost and intended use. From the viewpoint of improving processability, the thickness of the multilayer polyethylene film 10 can be 3 μm or more, 5 μm or more, 6 μm or more, or 10 μm or more. From the viewpoint of thinning the packaging material and considering heat resistance, the thickness of the multilayer polyethylene film 10 can be less than 200 μm, less than 120 μm, less than 100 μm, or less than 40 μm. From these viewpoints, the thickness of the multilayer polyethylene film 10 can be 3–200 μm, 5–120 μm, 6–100 μm, or 10–40 μm.

[0042] (surface layer) Surface layer 11 is composed of 0.926 g / cm³ 3 The above-mentioned layer is composed of medium-density polyethylene resin or high-density polyethylene resin. The surface layer 11 contains 0.926 g / cm³. 3 The multilayer polyethylene film 10, composed of medium-density polyethylene resin or high-density polyethylene resin, exhibits excellent heat resistance. In this specification, high-density polyethylene resin refers to resin with a density of 0.942 g / cm³. 3 The above-mentioned polyethylene resin. Hereinafter, the polyethylene resin constituting the surface layer 11 will also be referred to as the first polyethylene resin.

[0043] From the perspective of achieving single-material standardization and excellent recyclability, based on the total amount of surface layer 11, the content of the first polyethylene resin in surface layer 11 can be 90% by mass or more, 95% by mass or more, or 98% by mass or more, or 100% by mass (in the case where surface layer 11 is substantially composed of the first polyethylene resin). When surface layer 11 is composed of multiple polyethylene resins (e.g., multiple polyethylene resins with different average molecular weights, densities, etc.), a mixture of multiple polyethylene resins is designated as the first polyethylene resin.

[0044] From the perspectives of being less prone to wrinkling, having better processing stability, and maintaining gas barrier properties and heat resistance even after heat sterilization, the surface layer 11 can be composed of a first polyethylene resin with a density within the following range. The density of the first polyethylene resin can be 0.930 g / cm³. 3 Above, 0.935g / cm 3 Above, or 0.940 g / cm 3 The density of the first type of polyethylene resin can be 0.970 g / cm³. 3 Below, 0.965g / cm 3 Below, or 0.960 g / cm 3 The following is specific: The density of the first polyethylene resin is 0.960 g / cm³. 3 The following methods can suppress surface roughening and resin powder formation in the multilayer polyethylene film 10, easily achieving excellent gas barrier properties. From these perspectives, the density of the first polyethylene resin can be 0.930–0.970 g / cm³. 3 0.935~0.965g / cm 3 Or 0.940~0.960g / cm 3 .

[0045] The composite elastic modulus of the surface layer 11 is 1.45 GPa or higher and less than 1.90 GPa. Because the composite elastic modulus of the surface layer 11 is 1.45 GPa or higher and less than 1.90 GPa, the multilayer polyethylene film 10 exhibits excellent transparency and gas barrier properties. The composite elastic modulus of the surface layer 11 can be determined by nanoindentation, specifically by the method described in the examples below.

[0046] From the viewpoint of superior transparency and gas barrier properties, the composite elastic modulus of the surface layer 11 can also be 1.50 GPa or higher, 1.55 GPa or higher, or 1.60 GPa or higher. From the viewpoint of superior transparency and gas barrier properties, the composite elastic modulus of the surface layer 11 can also be 1.85 GPa or lower, 1.80 GPa or lower, or 1.75 GPa or lower. From these viewpoints, the composite elastic modulus of the surface layer 11 can also be 1.50–1.85 GPa, 1.55–1.80 GPa, or 160–1.75 GPa.

[0047] 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 by the method of manufacturing the first polyethylene resin. From the viewpoint of less wrinkling, better processing stability, and better maintenance of gas barrier properties, airtightness, and heat resistance even after heat sterilization, the melt flow rate (MFR1) of the first polyethylene resin at 190°C and a load of 2.16 kg can be 5 g / 10 min or less, 3 g / 10 min or less, or 1.5 g / 10 min or less. From the viewpoint of less wrinkling, better processing stability, and better maintenance of gas barrier properties, airtightness, and heat resistance even after heat sterilization, the MFR1 of the first polyethylene resin can be 0.1 g / 10 min or more, or 0.3 g / 10 min or more. From these viewpoints, the MFR1 of the first polyethylene resin can be 0.1–5 g / 10 min, 0.1–3 g / 10 min, or 0.3–1.5 g / 10 min. In this specification, melt flow rate refers to the value measured according to JIS K6921-2.

[0048] The thickness of the surface layer 11 is not particularly limited and can be determined appropriately based on factors such as the suitability of the manufacturing method and apparatus, as well as its compatibility with other layers, and according to cost and intended use. From a practical point of view, the thickness of the surface layer 11 can be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more. From the point of view of making the packaging material into a thin film, the thickness of the surface layer 11 can be less than 50 μm, less than 30 μm, less than 20 μm, or less than 10 μm. From these points of view, the thickness of the surface layer 11 can be 1–50 μm, 2–30 μm, 3–20 μm, 4–10 μm, or 5–50 μm.

[0049] (Intermediate layer) The intermediate layer 12 is a layer containing polyethylene resin. Hereinafter, the polyethylene resin constituting the intermediate layer 12 will also be referred to as the second polyethylene resin. From the viewpoint of achieving single-material standardization and excellent recyclability, based on the total amount of the intermediate layer 12, the content of the second polyethylene resin in the intermediate layer 12 can be 90% by mass or more, 95% by mass or more, or 98% by mass or more, or it can be 100% by mass (in the case where the intermediate layer 12 is substantially composed of the second polyethylene resin). When the intermediate layer 12 is composed of multiple polyethylene resins (e.g., multiple polyethylene resins with different average molecular weights, densities, etc.), a mixture of multiple polyethylene resins is designated as the second polyethylene resin.

[0050] From the perspectives of being less prone to wrinkling, having better processing stability, and maintaining gas barrier properties and heat resistance even after heat sterilization, the intermediate layer 12 can be composed of a second polyethylene resin with a density within the following range. The density of the second polyethylene resin can be 0.940 g / cm³. 3 Above, 0.945 g / cm 3 Above, or 0.950 g / cm 3 The density of the second type of polyethylene resin can be 0.980 g / cm³. 3 Below, 0.975g / cm 3 Below, 0.970 g / cm 3 Below, or 0.965 g / cm 3 Based on these viewpoints, the density of the second polyethylene resin can be 0.940–0.980 g / cm³. 3 0.945~0.975g / cm 3 Or 0.950~0.965g / cm 3 .

[0051] The composite elastic modulus of the interlayer 12 is 1.80 GPa or higher and less than 2.50 GPa. Because the composite elastic modulus of the interlayer 12 is 1.80 GPa or higher and less than 2.50 GPa, wrinkles are less likely to occur in the multilayer polyethylene film 10, and it exhibits excellent transparency and gas barrier properties. The composite elastic modulus of the interlayer 12 can be determined by nanoindentation, specifically by the method described in the examples below.

[0052] From the viewpoint of being less prone to wrinkling and having superior transparency and gas barrier properties, the composite elastic modulus of the interlayer 12 can also be 1.90 GPa or higher, 2.00 GPa or higher, 2.05 GPa or higher, 2.10 GPa or higher, or 2.15 GPa or higher. From the viewpoint of being less prone to wrinkling and having superior transparency and gas barrier properties, the composite elastic modulus of the interlayer 12 can also be 2.40 GPa or lower, 2.35 GPa or lower, or 2.30 GPa or lower. From these viewpoints, the composite elastic modulus of the interlayer 12 can also be 1.90–2.40 GPa, 2.00–2.40 GPa, 2.05–2.35 GPa, 2.10–2.35 GPa, or 2.15–2.30 GPa.

[0053] The melt flow rate (MFR2) of the second polyethylene resin at 190°C and 2.16 kg load is not particularly limited and can be appropriately adjusted by the method of manufacturing the second polyethylene resin. From the viewpoint of being less prone to wrinkling, having better processing stability, and being more likely to maintain gas barrier properties and airtightness, as well as better heat resistance, even after heat sterilization, the melt flow rate (MFR2) of the second polyethylene resin at 190°C and 2.16 kg load can be less than 5 g / 10 min, less than 3 g / 10 min, less than 2 g / 10 min, or less than 1.5 g / 10 min. From the viewpoint of being less prone to wrinkling, having better processing stability, and being more likely to maintain gas barrier properties and airtightness, as well as better heat resistance, even after heat sterilization, the MFR2 of the second polyethylene resin can be more than 0.1 g / 10 min, more than 0.5 g / 10 min, or more than 0.8 g / 10 min. Based on these viewpoints, the MFR2 of the second polyethylene resin can be 0.1–5 g / 10 min, 0.1–3 g / 10 min, 0.5–2 g / 10 min, or 0.8–1.5 g / 10 min.

[0054] The thickness of the intermediate layer 12 is not particularly limited and can be determined appropriately based on factors such as the suitability of the manufacturing method and apparatus, as well as its compatibility with other layers, and according to cost and intended use. From a practical point of view, the thickness of the intermediate layer 12 can be 5 μm or more, 8 μm or more, 10 μm or more, 12 μm or more, or 15 μm or more. From the point of view of making the packaging material into a thin film, the thickness of the intermediate layer 12 can be 80 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less. From these points of view, the thickness of the intermediate layer 12 can be 5–80 μm, 8–50 μm, 10–40 μm, 12–30 μm, or 15–80 μm.

[0055] From the viewpoint that it is easier to maintain gas barrier properties and superior heat resistance even after heat sterilization, the ratio of the thickness of the intermediate layer 12 to the total thickness of the surface layer 11 and the inner layer 13 (thickness of the intermediate layer / (thickness of the surface layer + thickness of the inner layer)) can be 0.5 or more. From the viewpoint that it is easier to maintain gas barrier properties and superior heat resistance even after heat sterilization, the ratio of the thickness of the intermediate layer 12 to the total thickness of the surface layer 11 and the inner layer 13 can also be 1 or more, 1.2 or more, 1.4 or more, or 1.5 or more. From the viewpoint that it is easier to maintain gas barrier properties and superior heat resistance even after heat sterilization, the ratio of the thickness of the intermediate layer 12 to the total thickness of the surface layer 11 and the inner layer 13 can be 3 or less, 2.5 or less, or 2 or less. From these viewpoints, the ratio of the thickness of the intermediate layer 12 to the total thickness of the surface layer 11 and the inner layer 13 can be 1 to 3, 1.2 to 2.5, 1.4 to 2, or 1.5 to 3.

[0056] The greater the thickness of the interlayer 12, the better the heat resistance can be achieved. From the viewpoint that it is easier to maintain gas barrier properties and achieves better heat resistance even after heat sterilization treatment, the thickness of the interlayer 12 can be 30% or more, 33% or more, 40% or more, 50% or more, 55% or more, or 60% or more of the thickness of the multilayer polyethylene film 10. Alternatively, the thickness of the interlayer 12 can be less than 80%, 77% or less, or 75% or less of the thickness of the multilayer polyethylene film 10. From these viewpoints, the thickness of the interlayer 12 can be 30%–80%, 33%–80%, 40%–77%, 50%–77%, 55%–75%, or 60%–75% of the thickness of the multilayer polyethylene film 10.

[0057] The greater the thickness of the intermediate layer 12, the better the heat resistance can be achieved. From the viewpoint that it is easier to maintain gas barrier properties and superior heat resistance even after heat sterilization, the thickness of the intermediate layer 12 can be greater than the thickness of the surface layer 11 and / or the thickness of the inner layer 13. From the viewpoint that it is easier to maintain gas barrier properties and superior heat resistance even after heat sterilization, the thickness of the intermediate layer 12 can be more than 1, 1.5, 2, 2.5, or 3 times the thickness of the surface layer 11 and / or the inner layer 13. From the viewpoint that it is easier to maintain gas barrier properties and superior heat resistance even after heat sterilization, the thickness of the intermediate layer 12 can be less than 8, 7, 6.5, or 6 times the thickness of the surface layer 11 and / or the inner layer 13. Based on these viewpoints, the thickness of the intermediate layer 12 can be 1 to 8 times, 1.5 to 7 times, 2 to 6.5 times, 2.5 to 6 times, or 3 to 8 times the thickness of the outer layer 11 and / or the inner layer 13.

[0058] (Inner layer) The inner layer 13 is a layer containing polyethylene resin. Hereinafter, the polyethylene resin constituting the inner layer 13 will also be referred to as the third polyethylene resin. From the viewpoint of achieving single-material standardization and excellent recyclability, based on the total amount of the inner layer 13, the content of the third polyethylene resin in the inner layer 13 can be 90% by mass or more, 95% by mass or more, or 98% by mass or more, or it can be 100% by mass (in a scheme where the inner layer 13 is substantially composed of the third polyethylene resin). When the inner layer 13 is composed of multiple polyethylene resins (e.g., multiple polyethylene resins with different average molecular weights, densities, etc.), a mixture of multiple polyethylene resins is designated as the third polyethylene resin.

[0059] From the perspectives of being less prone to wrinkles, having superior processing stability, and maintaining gas barrier properties, airtightness, and heat resistance even after heat sterilization, the inner layer 13 can be composed of a third polyethylene resin with a density within the following range. The density of the third polyethylene resin can be 0.920 g / cm³. 3 Above, 0.926 g / cm 3 Above, 0.930 g / cm 3 Above, 0.935g / cm 3 Above, or 0.940 g / cm 3 The density of the third type of polyethylene resin can be 0.970 g / cm³. 3 Below, 0.965g / cm 3 Below, or 0.960 g / cm 3 The density of the third-generation polyethylene resin is 0.960 g / cm³. 3 The following measures can suppress surface roughening and resin powder formation in the multilayer polyethylene film 10. By suppressing resin powder formation, resin powder can be prevented from adhering to the surface of the surface layer 11 of the multilayer polyethylene film 10 during roll winding, thus facilitating excellent gas barrier properties. From these perspectives, the density of the third polyethylene resin can be 0.920–0.970 g / cm³. 3 0.926~0.970g / cm 3 0.930~0.965g / cm 3 0.935~0.965g / cm 3 Or 0.940~0.960g / cm 3 .

[0060] The composite elastic modulus of the inner layer 13 is 1.45 GPa or higher and less than 1.90 GPa. Because the composite elastic modulus of the inner layer 13 is 1.45 GPa or higher and less than 1.90 GPa, the multilayer polyethylene film 10 exhibits excellent transparency and gas barrier properties. The composite elastic modulus of the inner layer 13 can be determined by nanoindentation, specifically by the method described in the examples below.

[0061] From the perspective of superior transparency and gas barrier properties, the composite elastic modulus of the inner layer 13 can also be 1.50 GPa or higher, 1.55 GPa or higher, or 1.60 GPa or higher. From the perspective of superior transparency and gas barrier properties, the composite elastic modulus of the inner layer 13 can also be 1.85 GPa or lower, 1.80 GPa or lower, or 1.75 GPa or lower. From these perspectives, the composite elastic modulus of the inner layer 13 can also be 1.50–1.85 GPa, 1.55–1.80 GPa, or 1.60–1.75 GPa.

[0062] 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 by the method of manufacturing the third polyethylene resin. From the viewpoint of less wrinkling, better processing stability, and better maintenance of gas barrier properties, airtightness, and heat resistance even after heat sterilization, the melt flow rate (MFR3) of the third polyethylene resin at 190°C and a load of 2.16 kg can be less than 5 g / 10 min, less than 3 g / 10 min, or less than 1.5 g / 10 min. From the viewpoint of less wrinkling, better processing stability, and better maintenance of gas barrier properties, airtightness, and heat resistance even after heat sterilization, the MFR3 of the third polyethylene resin can be greater than 0.1 g / 10 min or greater than 0.3 g / 10 min. From these viewpoints, the MFR3 of the third polyethylene resin can be 0.1–5 g / 10 min, 0.1–3 g / 10 min, or 0.3–1.5 g / 10 min.

[0063] The thickness of the inner layer 13 is not particularly limited and can be determined appropriately based on factors such as the suitability of the manufacturing method and apparatus, as well as its compatibility with other layers, and according to cost and intended use. From a practical point of view, the thickness of the inner layer 13 can be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more. From the point of view of making the packaging material into a thin film, the thickness of the inner layer 13 can be less than 50 μm, less than 30 μm, less than 20 μm, or less than 10 μm. From these points of view, the thickness of the inner layer 13 can be 1–50 μm, 2–30 μm, 3–20 μm, 4–10 μm, or 5–50 μm.

[0064] The inner layer 13 can also have the same structure as the outer layer 11. That is, the multilayer polyethylene film 10 can also have a symmetrical structure relative to the intermediate layer 12. By having a symmetrical structure, curling during the manufacture of the multilayer polyethylene film 10 can be suppressed, and the multilayer polyethylene film 10 can be manufactured stably.

[0065] The outer layer 11, middle layer 12, and inner layer 13 may also appropriately contain resins other than polyethylene resin, to the extent that they do not impair recyclability. Examples of such resins include: ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-(meth)acrylic acid copolymer, homopolymer polypropylene (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-α-olefin copolymer, polybutene, and other olefin-based resins; polyamide; polyvinyl alcohol; polyester; and various modified resins. Furthermore, one or more additives may be contained independently. Examples of additives include, for instance, crosslinking agents, antioxidants, anti-blocking agents, lubricants (slip agents), ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, and pigments.

[0066] The intermediate layer 12 can be a single layer or formed by multiple layers. For example, as shown... Figure 2 As shown, the multilayer polyethylene film 30 in the gas barrier membrane 200 has a surface layer 31, an intermediate layer 32, and an inner layer 33. The intermediate layer 32 has resin layers 32a, 32b, and 32c. In this case, resin layers 32a, 32b, and 32c all have the same composition. The fact that the intermediate layer 32 has multiple layers can be confirmed by observing the cross-section of the multilayer polyethylene film 30 using an optical microscope or an electron microscope.

[0067] The multilayer polyethylene film 10 may also have layers other than the three layers 11, 12, and 13. For example, Figure 3 As shown, the multilayer polyethylene film 40 in the gas barrier membrane 300 has a surface layer 41, an intermediate layer 42, and an inner layer 43. A resin layer 44 is provided between the surface layer 41 and the intermediate layer 42, and a resin layer 45 is provided between the intermediate layer 42 and the inner layer 43. The resin layer 44 is, for example, a layer containing polyethylene resin and having a composition different from that of the surface layer 41 and the intermediate layer 42. The resin layer 45 is, for example, a layer containing polyethylene resin and having a composition different from that of the intermediate layer 42 and the inner layer 43. The multilayer polyethylene film can be, for example, three-layer, five-layer, seven-layer, or more.

[0068] The temperature indicated by the maximum value of the melt peak observed in differential scanning calorimetry for the multilayer polyethylene film 10 can exceed 129°C and be lower than 136°C. With a temperature exceeding 129°C and lower than 136°C, the processing stability is excellent. In the presence of multiple melt peaks, the temperature indicated by the maximum value of any one melt peak is within the aforementioned range. The temperature indicated by the maximum value of the melt peak refers to the value measured by the method described in the examples below.

[0069] From the perspectives of being less prone to wrinkles, having superior processing stability, and maintaining gas barrier properties and heat resistance even after heat sterilization, each layer of the multilayer polyethylene film 10 can be composed of polyethylene resin with a density within the following range. The density of the polyethylene resin can be 0.930 g / cm³. 3 Above, 0.940 g / cm 3 Above, 0.945 g / cm 3 Above, or 0.950 g / cm 3 The density of polyethylene resin can be 0.980 g / cm³. 3 Below, 0.975g / cm 3 Below, 0.970 g / cm 3 Below, or 0.965 g / cm 3 Based on these viewpoints, the density of polyethylene resin can be 0.930–0.980 g / cm³. 3 0.940~0.975g / cm 3 0.945~0.970g / cm 3 Or 0.950~0.965g / cm 3 .

[0070] The method for manufacturing the multilayer polyethylene film 10 is not particularly limited, and it can be manufactured using known methods such as air-cooled blow-blowing, water-cooled blow-blowing, and T-die casting. From a general point of view, the multilayer polyethylene film 10 can be manufactured by blow-blowing or by air-cooled blow-blowing. Air-cooled blow-blowing refers to the following method: a die with an annular lip (or right-angle feed die) is set at the top of an extruder, and material is extruded into a tubular shape and continuously formed. More specifically, an air hole is provided in the center of the annular die, and compressed air is blown in through the air hole to expand the tube. The film is wound up while being pulled and cooled using rollers called pinch rollers, thereby manufacturing the multilayer polyethylene film 10.

[0071] The obtained multilayer polyethylene film 10 may also undergo surface modification treatment to improve its suitability for subsequent processes, as needed. For example, the surface of the multilayer polyethylene film 10 may be modified to improve its printability and lamination suitability during stacking. Examples of modification treatments include: corona discharge treatment, plasma treatment, flame treatment, and other treatments that generate functional groups by oxidizing the film surface; and modification treatments using wet processes that form an easy-to-adhere layer through coating.

[0072] <Gas Barrier Layer> The gas barrier layer 20 is a layer disposed 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 transparent layer. The gas barrier layer 20 comprises 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 it may have only either the inorganic oxide layer 21 or the gas barrier coating layer 22.

[0073] (Inorganic oxide layer) The inorganic oxide layer 21 comprises inorganic oxides. Examples of inorganic oxides include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, and mixtures thereof. From the viewpoints of better maintaining gas barrier properties and airtightness even after heat sterilization, superior heat resistance, and superior transparency, the inorganic oxide layer 21 may comprise at least one selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide.

[0074] The thickness of the inorganic oxide layer 21 can be 5–150 nm. If the thickness of the inorganic oxide layer 21 is 5 nm or more, it is easy to form a layer with uniform and sufficient film thickness, achieving sufficient gas barrier properties. If the thickness of the inorganic oxide layer 21 is less than 150 nm, it can impart flexibility to the inorganic oxide layer 21, suppressing cracking even when external loads such as bending or stretching are applied after the inorganic oxide layer 21 is formed. The thickness of the inorganic oxide layer 21 can also be 6 nm or more, or 8 nm or more, or less than 100 nm, or less than 50 nm. From these perspectives, the thickness of the inorganic oxide layer 21 can also be 6–100 nm, or 8–50 nm.

[0075] The inorganic oxide layer 21 can be formed by conventional vacuum evaporation. Alternatively, it can be formed by other thin film formation methods such as sputtering, ion plating, and plasma vapor deposition (CVD). From the viewpoint of superior productivity, the inorganic oxide layer 21 can be formed by vacuum evaporation.

[0076] As a heating method for vacuum evaporation, electron beam heating, resistance heating, and induction heating can all be used. From the viewpoint of broad selectivity of evaporation materials, electron beam heating is a suitable method for vacuum evaporation. From the viewpoint of improving the adhesion between the multilayer polyethylene film 10 and the inorganic oxide layer 21, as well as the density of the inorganic oxide layer 21, evaporation can be performed using plasma-assisted methods, ion beam-assisted methods, etc. From the viewpoint of improving the transparency of the inorganic oxide layer 21, reactive evaporation can be used.

[0077] (Gas barrier coating) The gas barrier coating 22 is a layer provided for the purpose of protecting the multilayer polyethylene film 10 or the inorganic oxide layer 21 and supplementing gas barrier properties. The gas barrier coating 22 may comprise at least one water-soluble polymer and at least one selected from the group consisting of metal alkoxides, hydrolysates of metal alkoxides, and their reaction products. The gas barrier coating 22 may also comprise at least one selected from the group consisting of silane coupling agents, hydrolysates of silane coupling agents, and their reaction products.

[0078] Examples of water-soluble polymers include polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), starch, methylcellulose, carboxymethylcellulose, and sodium alginate. From the perspective of excellent gas barrier properties, polyvinyl alcohol (PVA) is a suitable water-soluble polymer.

[0079] As metal alkoxides, for example, compounds represented by the following general formulas can be listed.

[0080] (1): M(OR) 11 ) m (R) 12 ) n－m In the above formula (1), R 11 and R 12 Each is an independent monovalent organic group having 1 to 8 carbon atoms. R 11 and R 12 Each can be an alkyl group, such as methyl or ethyl. M represents an n-valent metal atom, such as Si, Ti, Al, or Zr. m is an integer from 1 to n. It should be noted that when multiple R atoms exist... 11 and R 12 In the case of R 11 Each other or R 12 They can be the same or different.

[0081] Examples of metal alkoxides include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [Al(O-2'-C3H7)3]. From the perspective of their relative stability in aqueous solvents after hydrolysis, metal alkoxides can be either tetraethoxysilane or triisopropoxyaluminum.

[0082] As silane coupling agents, for example, compounds represented by the following general formulas can be listed.

[0083] (2): Si(OR) 21 ) p (R) 22 ) 3－p R 23 In the above formula (2), R 21 R represents alkyl groups such as methyl and ethyl. 22 R represents a monovalent organic group such as alkyl, aralkyl, aryl, alkenyl, alkyl substituted with acryloyloxy, or alkyl substituted with methacryloyloxy. 23 Let R represent a monovalent organic functional group, and p represent integers from 1 to 3. It should be noted that when multiple R exist... 21 or R 22 In the case of R 21 Each other or R 22 They can be the same or different. As R... 23 The monovalent organic functional groups shown can include glycidyloxy, epoxy, mercapto, hydroxyl, amino, alkyl groups substituted with halogen atoms, and monovalent organic functional groups containing isocyanate groups. Silane coupling agents can also be dimers, trimers, or other polymers of the above-mentioned silane coupling agents.

[0084] Examples of silane coupling agents include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-epoxypropoxypropylmethyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-methacryloyloxypropylmethyldimethoxysilane.

[0085] The gas barrier coating 22 can be formed by dissolving a water-soluble polymer in water or a water / alcohol mixture, mixing it with a metal alkoxide, a silane coupling agent, or their hydrolysates to obtain a mixed solution, coating the mixed solution onto the surface of an inorganic oxide layer 21 (or a multilayer polyethylene film 10 if an inorganic oxide layer 21 is not present), and then heating and drying. Additives such as isocyanate compounds, dispersants, stabilizers, viscosity modifiers, and colorants may also be added to the mixed solution.

[0086] When the water-soluble polymer is PVA, the PVA content in the mixed solution can be 20–50% by mass or 25–40% by mass, based on the total solid content of the mixed solution. When the PVA content is 20% by mass or higher, a gas-barrier coating layer 22 is easily formed. When the PVA content is 50% by mass or lower, excellent gas barrier properties are achieved.

[0087] The gas barrier coating 22 can also be a film containing a polycarboxylic acid polyvalent metal salt as a reaction product of the carboxyl groups of a polycarboxylic acid polymer and a polyvalent metal compound (polycarboxylic acid polyvalent metal salt film). The polycarboxylic acid polyvalent metal salt film can be formed by coating a mixed solution of a polycarboxylic acid polymer and a polyvalent metal compound onto the surface of an inorganic oxide layer 21 (or a multilayer polyethylene film 10 if an inorganic oxide layer 21 is not present), and then heating and drying it. Alternatively, the polycarboxylic acid polyvalent metal salt film can be formed by coating a coating solution mainly composed of a polycarboxylic acid polymer onto the surface of an inorganic oxide layer 21 (or a multilayer polyethylene film 10 if an inorganic oxide layer 21 is not present) and drying it to form a film, then coating a coating solution mainly composed of a polyvalent metal compound onto the film and drying it to form another film, and then subjecting these films to a crosslinking reaction.

[0088] Polycarboxylate polymers are polymers that have two or more carboxyl groups within their molecules. Examples of polycarboxylate polymers include: polymers of olefinically unsaturated carboxylic acids; copolymers of olefinically unsaturated carboxylic acids with other olefinically unsaturated monomers; and acidic polysaccharides such as alginate, carboxymethyl cellulose, and pectin that have carboxyl groups within their molecules.

[0089] Examples of olefinically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of olefinically unsaturated monomers that can copolymerize with olefinically unsaturated carboxylic acids include ethylene, propylene, vinyl acetate and other saturated carboxylic acid vinyl esters, alkyl acrylates, alkyl methacrylates, alkyl itaconic acid esters, vinyl chloride, vinylidene chloride, styrene, acrylamide, and acrylonitrile. Polycarboxylic acid polymers can contain one or more of these compounds.

[0090] From the viewpoint of excellent gas barrier properties, polymers of olefinic unsaturated carboxylic acids are preferably polymers containing constituent units 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. More preferably, polymers containing constituent units derived from at least one monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid are preferred.

[0091] In the polymer of olefinic unsaturated carboxylic acids, the proportion of constituent units derived from at least one monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid and itaconic acid, based on the total amount of monomers in the polymer, is preferably 80 mol% or more, more preferably 90 mol% or more.

[0092] The number average molecular weight of the polycarboxylate polymer is preferably 2,000 to 10,000,000, more preferably 5,000 to 1,000,000. With a number average molecular weight of 2,000 or higher, the gas barrier film will have sufficient water resistance, suppressing the deterioration of gas barrier properties and transparency, and preventing whitening caused by moisture. With a number average molecular weight of 10,000,000 or lower, the viscosity of the coating liquid when forming the gas barrier coating layer 22 will not become too high, facilitating film formation.

[0093] After coating a solution containing a polycarboxylate polymer as the main component and allowing it to dry to form a film, in the case of forming a film containing a polyvalent metal compound as the main component, a portion of the carboxyl groups of the polycarboxylate polymer can be pre-neutralized by an alkaline compound. By pre-neutralizing a portion of the carboxyl groups present in the polycarboxylate polymer, water resistance and heat resistance can be further improved. The alkaline compound can be at least one alkaline compound selected from the group consisting of polyvalent metal compounds, monovalent metal compounds, and ammonia. Examples of polyvalent metal compounds, described later, can be listed. Examples of monovalent metal compounds include sodium hydroxide and potassium hydroxide.

[0094] Coatings with polycarboxylate polymers as the main component may also contain additives such as crosslinking agents, curing agents, leveling agents, defoamers, anti-blocking agents, antistatic agents, dispersants, surfactants, softeners, stabilizers, film-forming agents, and thickeners.

[0095] For coatings containing polycarboxylate polymers as the main component, aqueous solvents are preferred. Examples of aqueous solvents include water, water-soluble or hydrophilic organic solvents, and mixtures thereof. An aqueous solvent is a medium containing water as its main component. The water content in an aqueous solvent can be 70% by mass or more, or 80% by mass or more. Examples of water-soluble or hydrophilic organic solvents include, for example: alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; nitriles such as acetonitrile; cellosols, carbitols, etc.

[0096] Polyvalent metal compounds are any compounds that react with the carboxyl groups of polycarboxylic acid polymers to form polycarboxylic acid polyvalent metal salts; there are no particular limitations. Examples include zinc oxide, magnesium oxide, magnesium methoxide, copper oxide, and calcium carbonate. From the viewpoint of excellent gas barrier properties, zinc oxide can be a suitable polyvalent metal compound. One or more polyvalent metal compounds can be used.

[0097] Zinc oxide is an inorganic material with ultraviolet absorption properties. When zinc oxide is in the form of particles, from the viewpoints of gas barrier properties, transparency, and coating formation, the average particle size of zinc oxide particles can be less than 5 μm, less than 1 μm, or less than 0.1 μm.

[0098] When a coating liquid with a polyvalent metal compound as the main component is applied and dried to form a film, the coating liquid may contain, in addition to the polyvalent metal compound (e.g., zinc oxide particles), solvents, resins soluble in or dispersible in solvents, dispersants, softeners, stabilizers, film-forming agents, thickeners, etc.

[0099] Examples of resins that are soluble or dispersible in solvents include alkyd resins, melamine resins, acrylic resins, urethane resins, polyester resins, phenolic resins, amino resins, fluororesins, epoxy resins, and isocyanate resins. By containing these resins in the coating solution, the coatability and film-forming properties are improved.

[0100] Anionic and nonionic surfactants can be used as dispersants. Examples of surfactants include (poly)carboxylates, alkyl sulfates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, alkyl phosphates, aromatic phosphates, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, alkyl allyl sulfates, polyoxyethylene alkyl phosphates, sorbitan alkyl esters, glycerol fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene fatty acid esters, and polyoxyethylene alkylamines. One or more of these surfactants can be used.

[0101] When a coating liquid with 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) can be 30:70 to 99:1 or 50:50 to 98:2.

[0102] Solvents used in coatings primarily composed of polyvalent metal compounds include, for example, water, methanol, ethanol, isopropanol, n-propanol, n-butanol, n-pentanol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. From the viewpoint of coating properties, the solvent can be at least one selected from the group consisting of methanol, ethanol, isopropanol, toluene, ethyl acetate, methyl ethyl ketone, and water. From the viewpoint of film formation properties, the solvent can be at least one selected from the group consisting of methanol, ethanol, isopropanol, and water. One or more solvents can be used.

[0103] Examples of coating methods for liquid coatings include casting, dipping, roller coating, gravure coating, screen printing, reverse coating, spraying, kit coating, die coating, metering bar coating, coating with a chamber doctor blade, and curtain coating.

[0104] The aforementioned gas barrier coating 22 maintains excellent gas barrier properties even after heat sterilization. Therefore, when a laminate with a sealing layer provided on the gas barrier film 100 is used as a packaging material for heat sterilization, the packaging material exhibits excellent gas barrier properties and airtightness even after heat sterilization. Furthermore, the aforementioned gas barrier coating 22 possesses sufficient transparency, flexural strength, and tensile strength, and poses no risk of generating harmful substances such as dioxins, making it preferable.

[0105] From the viewpoint of excellent gas barrier properties, the thickness of the gas barrier coating layer 22 can be 0.05 μm or more, or 0.1 μm or more. From the viewpoint of easily forming a uniform coating surface, reducing the load caused by drying, and reducing manufacturing costs, the thickness of the gas barrier coating layer 22 can be 1 μm or less, or 0.5 μm or less. From these viewpoints, the thickness of the gas barrier coating layer 22 can be 0.05 to 1 μm, or 0.1 to 0.5 μm.

[0106] (Primer coating (anchor coating)) From the viewpoint of improving the adhesion between the multilayer polyethylene film 10 and the gas barrier layer 20, a primer coating (anchor coating, not shown) can be provided between the multilayer polyethylene film 10 and the gas barrier layer 20. By providing a primer coating (anchor coating), gas barrier properties and adhesion are easily maintained even after heat sterilization treatment.

[0107] The base coat (anchor coat) can be formed, for example, from a coating liquid containing resins such as acrylic resin, epoxy resin, urethane acrylate resin, polyester polyurethane resin, and polyether polyurethane resin. From the viewpoint of heat resistance and interlayer adhesion strength, the base coat (anchor coat) can be formed from a coating liquid containing urethane acrylate resin or polyester polyurethane resin.

[0108] The method of applying the coating liquid to form the base coat (anchor coating) can be a known coating method, such as: dipping method; methods using sprayers, coating machines, printing machines, brushes, etc. Furthermore, the types of coating machines and printing machines used in these methods, and their coating methods, can include: gravure coating machines such as direct gravure, reverse gravure, kiss reverse gravure, and offset gravure; reverse roller coating machines; micro gravure coating machines; coating machines using chamber doctor blades; air knife coating machines; dip coating machines; bar coating machines; comma coating machines; and die coating machines, etc.

[0109] Methods for drying the primer coating (anchor coating) are not particularly limited and can include: natural drying; drying in an oven set to a specified temperature; and using a dryer attached to the coating machine (e.g., an arch dryer, floating dryer, drum dryer, infrared dryer, etc.). The drying conditions can be appropriately selected depending on the drying method; for example, in oven drying, drying can be performed at 60–100°C for approximately 1 second to 2 minutes.

[0110] From the viewpoint of easily achieving sufficient interlayer adhesion, the thickness of the primer layer (anchor layer) can 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 primer layer (anchor layer) can be 5 μm or less, 3 μm or less, or 2 μm or less. From these viewpoints, the thickness of the primer layer (anchor layer) can be 0.01–5 μm, 0.03–3 μm, or 0.05–2 μm.

[0111] <Layered Body> The gas barrier membrane 100 can be used as a material constituting a laminate. Figure 4This is a cross-sectional view of a laminate according to one embodiment of the present invention. The laminate 400 includes a gas barrier film 100, an adhesive layer 130, and a sealing layer 140. Alternatively, the laminate 400 may also include a multilayer polyethylene film 10, an inorganic oxide layer 21, a gas barrier coating layer 22, an adhesive layer 130, and a sealing layer 140. That is, another embodiment of the present invention is a laminate including the aforementioned gas barrier film, an adhesive layer disposed on the surface of the gas barrier layer opposite to the multilayer polyethylene film, and a sealing layer disposed by means of the adhesive layer.

[0112] From the perspective of achieving single materialization and excellent recyclability, based on the total amount of laminate 400, the content of polyethylene resin in laminate 400 can be above 90% by mass or above 95% by mass.

[0113] The thickness of the laminate 400 is not particularly limited and can be appropriately determined based on cost and application. The thickness of the laminate 400 can be 50 μm or more, 60 μm or more, or 70 μm or more, and can be less than 300 μm, 250 μm or less, or 200 μm or less. From these perspectives, the thickness of the laminate 400 can be 50–300 μm, 60–250 μm, or 70–200 μm.

[0114] (Adhesive layer) The adhesive layer 130 is a layer containing at least one adhesive, disposed between the gas barrier layer 20 and the sealing layer 140 to bond the two together. The adhesive layer 130 can be formed using known adhesives. The adhesive can be, for example, a dry lamination adhesive. Dry lamination adhesives are not particularly limited; examples include ester-based adhesives, ether-based adhesives, and urethane-based adhesives. These adhesives can be one-component curing types or two-component curing types.

[0115] From the viewpoint of excellent gas barrier properties, the adhesive layer 130 can be formed using a gas barrier adhesive. Furthermore, even if minute cracks are generated in the inorganic oxide layer 21 and the gas barrier coating layer 22, the gas barrier adhesive can enter the gaps in the cracks and fill them, thus suppressing the decrease in the gas barrier properties of the laminate 400.

[0116] Gas barrier adhesives are adhesives that exhibit gas barrier properties after curing. Examples of gas barrier adhesives include epoxy adhesives and polyester / polyurethane adhesives. Specific examples of gas barrier adhesives include "MAXIVE" manufactured by Mitsubishi Gas Chemical Co., Ltd., and "Paslim" manufactured by DIC Corporation.

[0117] The oxygen permeability of the gas barrier adhesive is preferably, for example, 150 cc / m 2·day·atm or less, preferably 100cc / m 2 For days and atm below, 80cc / m is further preferred. 2 For daily use below atm, 50cc / m is particularly preferred. 2 •day·atm and below. By ensuring that the oxygen permeability is within the above range, the gas barrier properties of the laminate 400 can be sufficiently improved.

[0118] The adhesive layer 130 can be formed, for example, by applying an adhesive using methods such as bar coating, dip coating, roller coating, gravure coating, reverse coating, air knife coating, comma coating, mold coating, screen printing, spraying, or gravure offset coating, followed by drying and curing the coating. From the viewpoint of suppressing cracks in the inorganic oxide layer 21, the adhesive layer 130 is preferably formed directly on the surface of the inorganic oxide layer 21 or the gas barrier coating layer 22. That is, the adhesive layer 130 is preferably formed by directly applying the adhesive to the surface of the inorganic oxide layer 21 or the gas barrier coating layer 22 and then drying and curing it.

[0119] The temperature for drying the coating film can be, for example, 30–200°C, preferably 50–180°C. The temperature for curing the coating film can be, for example, 20–70°C, preferably 30–60°C. By setting the drying and curing temperatures within the above ranges, cracks in the inorganic oxide layer 21 and the adhesive layer 130 can be suppressed, and the gas barrier properties of the laminate 400 can be sufficiently improved.

[0120] The thickness of the adhesive layer 130 is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm. When the thickness of the adhesive layer 130 is 0.1 μm or more, it provides cushioning against external impacts, thus easily suppressing cracks in the inorganic oxide layer 21 and further improving the gas barrier properties of the laminate 400. When the thickness of the adhesive layer is 20 μm or less, there is a tendency to sufficiently maintain the flexibility of the laminate 400.

[0121] The thickness of the adhesive layer 130 is preferably 50 times or more the thickness of the inorganic oxide layer 21. By having the adhesive layer 130 at least 50 times the thickness of the inorganic oxide layer 21, it provides cushioning against external impacts, thus easily suppressing cracks in the inorganic oxide layer 21 and further improving the gas barrier properties of the laminate 400. The thickness of the adhesive layer 130 is preferably 300 times or less the thickness of the inorganic oxide layer 21. By having the adhesive layer 130 at least 300 times the thickness of the inorganic oxide layer 21, the laminate 400 exhibits excellent flexibility and processability, and costs can be reduced. From these perspectives, the thickness of the adhesive layer 130 can be 50 to 300 times the thickness of the inorganic oxide layer 21.

[0122] (Sealing layer) The sealing layer 140 is, for example, a layer made of polyethylene resin. The sealing layer 140 is a layer joined by heat sealing when forming packaging materials such as packaging bags using the laminate 400. From the viewpoint of excellent heat-sealing properties, the polyethylene resin constituting the sealing layer 140 can be low-density polyethylene resin (LDPE), linear low-density polyethylene resin (LLDPE), or ultra-low-density polyethylene resin (VLDPE). From the viewpoint of environmental impact, the sealing layer 140 can be made of polyethylene resin derived from biomass or recycled polyethylene resin. The sealing layer 140 can, for example, be made of unstretched polyethylene film.

[0123] As a low-density polyethylene, a density of 0.900 g / cm³ can be used. 3 Above and less than 0.925 g / cm 3 Polyethylene. As a linear low-density polyethylene, a density of 0.900 g / cm³ can be used. 3 Above and less than 0.925 g / cm 3 Polyethylene. As ultra-low density polyethylene, it can be used with a density of less than 0.900 g / cm³. 3 Polyethylene.

[0124] The sealing layer 140 may also contain resins other than polyethylene resin. Examples of resins other than polyethylene resin include ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-(meth)acrylic acid copolymer, homopolymer polypropylene (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-α-olefin copolymer, polybutene, and other olefin-based resins. The sealing layer 140 may also contain additives such as antioxidants, lubricants, anti-blocking agents, and antistatic agents.

[0125] The thickness of the sealing layer 140 can be, for example, 20 μm or more, 40 μm or more, or 50 μm or more. Sufficient heat-sealing strength can be achieved when the thickness of the sealing layer 140 is 20 μm or more. The thickness of the sealing layer 140 can be, for example, 200 μm or less, 170 μm or less, or 150 μm or less. Excellent processability is achieved when the thickness of the sealing layer 140 is 200 μm or less. From these viewpoints, the thickness of the sealing layer 140 can be 20–200 μm, 40–170 μm, or 50–150 μm.

[0126] like Figure 5 As shown, when the intermediate layer is formed of multiple layers, the multilayer polyethylene film 50 in the laminate 500 has a surface layer 51, an intermediate layer 52, and an inner layer 53. The intermediate layer 52 has resin layers 52a, 52b, and 52c. In this case, resin layers 52a, 52b, and 52c all have the same composition. The fact that the intermediate layer 52 has multiple layers can be confirmed by observing the cross-section of the multilayer polyethylene film 50 using an optical microscope or an electron microscope.

[0127] like Figure 6 As shown, in the case where the multilayer polyethylene film has layers other than the three layers of a surface layer, an intermediate layer, and an inner layer, the multilayer polyethylene film 60 in the laminate 600 has a surface layer 61, an intermediate layer 62, and an inner layer 63. A resin layer 64 is provided between the surface layer 61 and the intermediate layer 62, and a resin layer 65 is provided between the intermediate layer 62 and the inner layer 63. The resin layer 64 is, for example, a layer containing polyethylene resin and having a composition different from that of the surface layer 61 and the intermediate layer 62. The resin layer 65 is, for example, a layer containing polyethylene resin and having a composition different from that of the intermediate layer 62 and the inner layer 63. The multilayer polyethylene film can have, for example, three, five, seven, or more layers.

[0128] like Figure 7 As shown, the laminate 700 may have a second adhesive layer 170 and a substrate 180 disposed by means of the second adhesive layer 170 on the surface of the multilayer polyethylene film 10 opposite to the sealing layer 140 side.

[0129] (Second adhesive layer) The second adhesive layer 170 is a layer containing at least one adhesive, disposed between the multilayer polyethylene film 10 and the substrate 180 to bond the two together. The adhesive used in the second adhesive layer 170 can be a one-component curing adhesive or a two-component curing adhesive. Examples of adhesives include urethane-based adhesives, epoxy-based adhesives, and silicone-based adhesives. The second adhesive layer can use the same adhesive used to form the adhesive layer 130 described above.

[0130] The thickness of the second adhesive layer 170 is, for example, 0.5 μm or more, 0.8 μm or more, or 1 μm or more, and can be 6 μm or less, 5 μm or less, or 4.5 μm or less. From these points of view, the thickness of the second adhesive layer 170 can be 0.5 to 6 μm, 0.8 to 5 μm, or 1 to 4.5 μm.

[0131] (Substrate) Substrate 180 is the outermost layer of laminate 700 and is provided for the purpose of protecting laminate 700. Substrate 180 may be a layer containing polyethylene resin or a polyethylene film. In addition to polyethylene resin, substrate 180 may also contain additives such as antioxidants, lubricants, anti-blocking agents, and antistatic agents.

[0132] The temperature difference between the substrate 180 and the sealing layer 140 can be 10°C or more. With a temperature difference of 10°C or more between the substrate 180 and the sealing layer 140, it is easy to form packaging bags when using the laminate 700 as packaging material.

[0133] The thickness of the substrate 180 can be, for example, 10 μm or more, 20 μm or more, or 30 μm or more, or less than 200 μm, less than 150 μm, or less than 100 μm. From these points of view, the thickness of the substrate 180 can be 10–200 μm, 20–150 μm, or 30–100 μm.

[0134] The laminate 400 may also include a printed layer (not shown). The printed layer is located in a position visible from the outside of the laminate 400 for the purpose of displaying information related to the contents, identifying the contents, or improving the design of the packaging bag. For example, the printed layer may be provided on the surface of the inorganic oxide layer 21 of the laminate 400, the surface of the gas barrier coating layer 22, or the surface of the sealing layer 140.

[0135] The method of forming the printed layers is not particularly limited, and known printing methods and inks can be used. For example, appropriate selection of printing methods and inks can be made considering factors such as the printability, color design, adhesion, and safety as a food container for each layer of the laminate 400.

[0136] Examples of printing methods include gravure printing, offset printing, gravure-offset printing, flexographic printing, and inkjet printing. Among these, gravure printing is preferred from the viewpoint of productivity and high image precision.

[0137] From the perspective of improving the adhesion of the printed layer, pretreatments such as corona treatment, plasma treatment, and flame treatment can be performed on the surface of the layer forming the printed layer, or coatings such as easy-to-adhere layers can be applied.

[0138] Packaging Materials Gas barrier films 100, 200, and 300, and laminates 400, 500, 600, and 700 can be used as packaging materials for making packaging bags. Specifically, based on the gas barrier films 100, 200, and 300 with a sealing layer to form a laminate, they can be used as packaging materials for flat bags, three-side seal bags, gusseted bags, corner-supported bags, stand-up pouches, spouted bags, and pointed-spout bags, etc.

[0139] Gas barrier membranes 100, 200, 300 and laminates 400, 500, 600, 700, in addition to packaging materials, can also be used as membranes for electronic devices, solar cells, fuel cells, substrates, etc.

[0140] [Example] The present invention will now be described in detail through examples. However, the present invention is not limited to the examples described below.

[0141] <Polyethylene Resin> • Resin A: Density 0.963 g / cm³ 3 MFR 1.35 g / 10 min, DSC melting point 134 ° C.

[0142] • Resin B: Density 0.944 g / cm³ 3 MFR 0.45 g / 10 min, DSC melting point 131 °C.

[0143] • Resin C: Density 0.950 g / cm³ 3 MFR 1.1 g / 10 min, DSC melting point 130 ° C.

[0144] • Resin D: Density 0.958 g / cm³ 3 MFR 1g / 10min, DSC melting point 133℃.

[0145] • Resin E: Density 0.960 g / cm³ 3 MFR 1g / 10min, DSC melting point 135℃.

[0146] • Resin F: Density 0.920 g / cm³ 3 MFR 0.85 g / 10 min, DSC melting point 124 °C.

[0147] • Resin G: Density 0.941 g / cm³ 3 MFR 1.3g / 10min, DSC melting point 129℃.

[0148] • Resin H: Density 0.962 g / cm³ 3MFR 0.85 g / 10 min, DSC melting point 134 ° C.

[0149] • Resin I: Density 0.926 g / cm³ 3 MFR 0.85 g / 10 min, DSC melting point 123 °C.

[0150] <Production of Polyethylene Film> (Examples 1A to 26A, Comparative Examples 1A to 11A) The resins listed in Tables 1-6, which constitute the outer, middle, and inner layers, were fed into an extruder and melt-blended at 190°C. Polyethylene resin was then introduced through a three-layer die, and a multilayer polyethylene film was produced by air-cooled inflation. The overall thickness of the multilayer polyethylene films produced in each example and comparative example was in the range of 25-40 μm. The polyethylene resin content in the multilayer polyethylene films produced in each example and comparative example was 90% by mass or more.

[0151] <Fabrication of Gas Barrier Membranes> In the various embodiments and comparative examples, the surface of the multilayer polyethylene film produced had a base coating layer, an inorganic oxide layer, and a gas barrier coating layer formed in a configuration shown in Tables 1 to 6, thus creating a gas barrier film stacked in the order of multilayer polyethylene film / base coating layer / inorganic oxide layer / gas barrier coating layer. It should be noted that the base coating layer, adhesive layer, inorganic oxide layer, and gas barrier coating layer were formed by methods described later. The polyethylene resin content in the gas barrier films produced in the various embodiments and comparative examples was 90% by mass or more.

[0152] <Undercoat> Acrylic polyol (ACRYDIC CL-1000, manufactured by DIC Corporation) and isocyanate compound (CORONATE 2030, a TDI-type curing agent manufactured by Tosoh Corporation) were mixed in a solids-to-weight ratio of 6:4. Then, ethyl acetate was added to dilute the mixture to a solids content of 2% by weight, resulting in a primer-forming solution. After subjecting the surface of the multilayer polyethylene film of each example and comparative example to single-sided corona treatment, the primer-forming solution was applied to the corona-treated surface using a gravure printing press to form a coating film. The film was then dried in an oven at 60°C for 10 seconds, thereby forming a primer layer with a thickness of 0.1 μm.

[0153] <Inorganic oxide layer> With silicon oxide as the inorganic oxide, a transparent inorganic oxide layer (silicon oxide film) with a thickness of 30 nm was formed by vacuum evaporation using an electron beam heating-based heating method. The O / Si ratio of the silicon oxide film was 1.8.

[0154] With aluminum oxide as the inorganic oxide, a transparent inorganic oxide layer (alumina film) with a thickness of 15 nm was formed by vacuum evaporation using an electron beam heating-based heating method. The O / Al ratio of the aluminum oxide film was 1.5.

[0155] <Gas Barrier Coating> (Organic-inorganic composite coating) An aqueous solution containing polyvinyl alcohol resin (PVA, Kuraray PVA-105, saponification degree 98%–99%, degree of polymerization 500) was prepared, along with aqueous solutions obtained by hydrolyzing tetraethoxysilane (TEOS) and γ-epoxypropoxypropyltrimethoxysilane (GPTMS, Shin-Etsu Chemical Co., Ltd. KBM-403) separately with 0.02 mol / L hydrochloric acid. Next, the three aqueous solutions were mixed in a PVA:TEOS:GPTMS mass ratio of 40:50:10 (before hydrolysis). Then, isopropanol was added to dilute the mixed aqueous solution at a water:isopropanol mass ratio of 90:10 to obtain a coating solution for forming an organic-inorganic composite film (solid content: 5% by mass).

[0156] A coating is formed by applying the organic-inorganic composite film mixture (described later) onto an inorganic oxide layer using a gravure printing press, and then drying it in an oven at 60°C for 10 seconds, thereby forming a gas barrier coating layer with a thickness of 0.3 μm composed of an organic-inorganic composite film.

[0157] (Polycarboxylic acid polyvalent metal salt coating) Diluted 20 parts by weight of an aqueous solution of polyacrylic acid (ARON A-10H, manufactured by Toa Synthetic Co., Ltd., number average molecular weight 200,000, solid content concentration 25% by mass) with 58.9 parts by weight of distilled water. Then, 0.44 parts by weight of aminopropyltrimethoxysilane (APTMS, manufactured by Aldrich) was added and stirred to obtain a homogeneous A-coating mixture with polycarboxylic acid polymers as the main component.

[0158] 100 parts by weight of zinc oxide microparticle aqueous dispersion (manufactured by Sumitomo Osaka Cement Co., Ltd., ZE143) and 2 parts by weight of curing agent (manufactured by Henkel Co., Ltd., Liofol HAERTER UR 5889-21) were mixed to obtain a B coating mixture with polyvalent metal compounds as the main components.

[0159] A coating film is formed by applying the A coating film mixture (described later) onto an inorganic oxide layer using a gravure printing press, and then drying it in an oven at 60°C for 10 seconds, thereby forming an A coating film with a thickness of 0.2 μm. Next, a B coating film is formed by applying a B coating film using a gravure printing press, and then drying it in an oven at 60°C for 10 seconds, thereby forming a B coating film with a thickness of 0.2 μm. Thus, an oxygen barrier coating film composed of a polycarboxylic acid polyvalent metal salt coating is formed.

[0160] <Adhesive layer> (Carbamate adhesives) A urethane-based adhesive was obtained by mixing 100 parts by weight of TAKELAC A525 (manufactured by Mitsui Chemicals) with 11 parts by weight of TAKELAC A52 (manufactured by Mitsui Chemicals) and 84 parts by weight of ethyl acetate.

[0161] (Epoxy adhesives) An epoxy adhesive was obtained by mixing 16 parts by mass of MAXIVE C93T (manufactured by Mitsubishi Gas Chemical Company) and 5 parts by mass of MAXIVE M-100 (manufactured by Mitsubishi Gas Chemical Company) into 23 parts by mass of a solvent prepared by mixing ethyl acetate and methanol in a mass ratio of 1:1.

[0162] <Composite elastic modulus> A multilayer polyethylene film was embedded in a visible-light curable resin, D-800. Then, using a Leica EM UC7 ultramicrotome with a MicroStar LH diamond scalpel, the multilayer polyethylene film was cut perpendicular to the stacking direction. The resulting cross-section was then finished at a cutting thickness of 100 nm and a cutting speed of 1 mm / s to prepare the test specimen.

[0163] In the measurement, the Hysitron TI-Premier (trade name) manufactured by Bruker Japan Co., Ltd. was used as the measuring device, and the Berkovich type diamond indenter manufactured by Bruker Japan Co., Ltd. was used as the indenter. The measurement conditions are as follows.

[0164] Temperature: Room temperature (25℃).

[0165] Mode: Load control mode.

[0166] Pressing and unloading: Press in at a pressing speed of 1.5 μN / s to reach a load of 15 μN, hold at the maximum load for 5 seconds, and then unload at a speed of 1.5 μN / s.

[0167] Measurement site: The shape measurement function of the measuring device is used to scan the surface of the sample by using the indenter to obtain the shape image of the sample cross section. Based on the shape image, 20 points are specified on the cross section of the sample at intervals of more than 1 μm.

[0168] In calculating the composite elastic modulus, fused silica was used as the standard specimen, and the relationship between the contact depth and the projected contact area between the indenter and the specimen was pre-calibrated. Then, the Oliver-Pharr method was used to analyze the unloading curve relative to the maximum load range of 60%–95% during unloading, and the composite elastic modulus of the specimen was calculated. The measurement results are shown in Tables 1–6.

[0169] <Melting Peak Temperature> For the fabricated multilayer polyethylene film, differential scanning calorimetry (DSC7020, manufactured by Hitachi, Ltd.) was used according to JIS K7121-1987. The temperature of the maximum melting peak was measured at a temperature of 20–200°C and a heating rate of 10°C / min. The results are shown in Tables 1–6. It should be noted that if there is no maximum melting peak in the range above 129°C but below 136°C, it is recorded as "-" in the table.

[0170] [evaluate] <Processing Stability> The appearance of the gas barrier film after the formation of the gas barrier coating (for examples without a gas barrier coating, and for comparative examples after the formation of an inorganic oxide layer) was visually confirmed, and the processing stability was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 1 to 6.

[0171] A: No wrinkles were observed on the appearance of the gas barrier membrane.

[0172] B: Slight wrinkles were observed on the appearance of the gas barrier membrane.

[0173] C: Numerous wrinkles were observed on the appearance of the gas barrier membrane.

[0174] <Transparency> The haze of the multilayer polyethylene film was measured using a haze meter (Nippon Denshoku Kogyo, NDH-20) according to JIS K7136, and the transparency was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 1 to 6.

[0175] A: Haze level is less than 20%.

[0176] B: Haze level is above 20% and below 35%.

[0177] C: Haze level is above 35%.

[0178] <Oxygen Barrier Properties> For the gas barrier membranes produced in each embodiment and comparative example, the aforementioned urethane-based adhesive or the aforementioned gas barrier adhesive was dry-laminated using Multi Coater™-MC (manufactured by HIRANO TECSEED), and then cured at 40°C for 3 days to form an adhesive layer. After curing, LLDPE (polyethylene film, manufactured by Mitsui Chemicals Tosel, TUX MC-S, 60 μm thick) was laminated onto the adhesive layer to produce a laminate consisting of gas barrier membrane / adhesive / LLDPE sequentially stacked. The oxygen permeability (cm²) of the laminate was measured using an oxygen permeability measuring device (trade name OXTRAN-2 / 20, manufactured by MOCON) according to JIS K-7126-2 B method at 30°C and 70% RH. 3 / (m 2 The oxygen barrier properties were evaluated based on the following evaluation criteria (day / atm). The evaluation results are shown in Tables 1-6.

[0179] A+: Oxygen permeability less than 2cm 3 / (m 2 ·day·atm).

[0180] A: Oxygen permeability is 2cm 3 / (m 2 (day / atm) or more and less than 5cm 3 / (m 2 ·day·atm).

[0181] A-: Oxygen permeability is 5cm 3 / (m 2 (day / atm) or more and less than 10cm 3 / (m 2 ·day·atm).

[0182] B+: Oxygen permeability is 10 cm⁻¹ 3 / (m 2 (day / atm) or more and less than 20cm 3 / (m 2 ·day·atm).

[0183] B: Oxygen permeability is 20cm 3 / (m 2 (day / atm) or more and less than 50cm 3 / (m 2 ·day·atm).

[0184] B-: Oxygen permeability is 50 cm⁻¹ 3 / (m 2 (day / atm) and above.

[0185] <Oxygen barrier properties after boiling treatment> The prepared laminated body was cut into two 15cm × 10cm pieces. These two pieces were then overlapped with their sealing layers facing each other, and three sides were pulse-sealed to form a bag. 150mL of water was placed inside the bag as the contents, and the remaining side was pulse-sealed to create a four-sided sealed bag (packaging bag). The bag was then boiled at 95°C for 30 minutes using a boiling treatment apparatus. After boiling, the bag was opened, the contents removed, and the bag was allowed to dry thoroughly. The oxygen permeability was then measured using the method described above to evaluate the oxygen barrier properties. The evaluation results are shown in Tables 1–6. <Production of Polyethylene Film> (Examples 1B-13B, 16B-22B, Comparative Examples 1B-10B) The resins listed in Tables 7, 8, and 10-12, which constitute the outer, middle, and inner layers, were fed into an extruder and melt-blended at 190°C. Polyethylene resin was then introduced through a three-layer die, and a multilayer polyethylene film was produced by air-cooled inflation. The overall thickness of the multilayer polyethylene films produced in each example and comparative example was in the range of 25-40 μm. The polyethylene resin content in the multilayer polyethylene films produced in each example and comparative example was 90% by mass or more.

[0186] (Example 14B) The resins listed in Table 9, which constitute layers 1 to 5, were fed into an extruder and melt-blended at 190°C. Then, polyethylene resin was introduced through a five-layer die, and a multilayer polyethylene film was produced using an air-cooled blowing method, with layer 1 as the surface layer, layers 2 to 4 as intermediate layers, and layer 5 as the inner layer. The polyethylene resin content in the produced multilayer polyethylene film was 90% by mass or more.

[0187] (Example 15B) The resins listed in Table 9, which constitute layers 1 to 7, were fed into an extruder and melt-blended at 190°C. Then, polyethylene resin was introduced through a die in all seven layers, and a multilayer polyethylene film was produced using an air-cooled blowing method, with layer 1 as the surface layer, layers 2 to 6 as intermediate layers, and layer 7 as the inner layer. The polyethylene resin content in the produced multilayer polyethylene film was 90% by mass or more.

[0188] <Creating Layered Bodies> The surface of the multilayer polyethylene film produced in each embodiment and comparative example was subjected to corona treatment. Next, using the method described later, an anchor coating layer, an inorganic oxide layer, a gas barrier coating layer, an adhesive layer, and a sealing layer were formed on the surface of the multilayer polyethylene film in the manner shown in Tables 7-12. After laminating in the order of multilayer polyethylene film / anchor coating layer / inorganic oxide layer / gas barrier coating layer / adhesive layer / sealing layer, the laminate was aged at 40°C for 4 days to obtain the laminate. The polyethylene resin content in the laminates produced in each embodiment and comparative example was 90% by mass or more.

[0189] The inner layer surface of the multilayer polyethylene film produced in Examples 19B to 22B was subjected to corona treatment. Next, using the method described later, an anchor coating, an inorganic oxide layer, a gas barrier coating, an adhesive layer, and a sealing layer were formed on the surface of the multilayer polyethylene film in the manner shown in Table 10. Next, a second adhesive layer was formed by applying any one of the following urethane-based or epoxy-based adhesives to the surface of the multilayer polyethylene film opposite to the sealing layer using a dry lamination method, or by applying a solvent-free adhesive to the surface of the multilayer polyethylene film opposite to the sealing layer using a solvent-free adhesive laminator. Next, unstretched polyethylene (30 μm thick) or stretched polyethylene (25 μm thick) serving as the surface substrate was laminated onto the second adhesive layer, and the laminate was aged at 40°C for 1 day. The polyethylene resin content in the laminates produced in each example and comparative example was 90% by mass or more.

[0190] Carbamate-based adhesive: A carbamate-based adhesive was obtained by mixing 100 parts by weight of TAKELAC A525 (manufactured by Mitsui Chemicals) with 11 parts by weight of TAKELAC A52 (manufactured by Mitsui Chemicals) and 84 parts by weight of ethyl acetate.

[0191] Epoxy adhesive: An epoxy adhesive was obtained by mixing 16 parts by mass of MAXIVE C93T (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 5 parts by mass of MAXIVE M-100 (manufactured by Mitsubishi Gas Chemical Co., Ltd.) into 23 parts by mass of a solvent prepared by mixing ethyl acetate and methanol in a mass ratio of 1:1.

[0192] Solvent-free adhesive: LA7735 (manufactured by Henkel Japan Co., Ltd.), as a polyisocyanate component, and LA6159 (manufactured by Henkel Japan Co., Ltd.), as a polyol component, were mixed in a two-component mixing and feeding device at a mass ratio of 100:45 to obtain a two-component curing type urethane adhesive. Application of the urethane adhesive: The solvent-free adhesive was applied using a laminator at a processing speed of 100 m / min, with the coating amount control roller and coating roller temperature at 60°C, resulting in an adhesive coating amount of 2.1 g / m³. 2 This is done in a certain way.

[0193] <Anchor Coating> Acrylic polyol (ACRYDIC CL-1000, manufactured by DIC Corporation) and isocyanate compound (CORONATE 2030, a TDI-type curing agent manufactured by Tosoh Corporation) were mixed in a solids-to-weight ratio of 6:4. Then, ethyl acetate was added to dilute the mixture to 2% by weight of solids, resulting in an anchor coating forming solution. After subjecting the surface of the multilayer polyethylene film of each example and comparative example to single-sided corona treatment, the anchor coating forming solution was applied to the corona-treated surface using a gravure printing press to form a coating film. The film was then dried in an oven at 60°C for 10 seconds, thereby forming an anchor coating with a thickness of 0.1 μm.

[0194] <Inorganic oxide layer> With silicon oxide as the inorganic oxide, a transparent inorganic oxide layer (silicon oxide film) with a thickness of 30 nm was formed by vacuum evaporation using an electron beam heating-based heating method. The O / Si ratio of the silicon oxide film was 1.8.

[0195] With aluminum oxide as the inorganic oxide, a transparent inorganic oxide layer (alumina film) with a thickness of 15 nm was formed by vacuum evaporation using an electron beam heating-based heating method. The O / Al ratio of the aluminum oxide film was 1.5.

[0196] <Gas Barrier Coating> (Organic-inorganic composite coating) An aqueous solution containing polyvinyl alcohol resin (PVA, Kuraray PVA-105, saponification degree 98%–99%, degree of polymerization 500) was prepared, along with aqueous solutions obtained by hydrolyzing tetraethoxysilane (TEOS) and γ-epoxypropoxypropyltrimethoxysilane (GPTMS, Shin-Etsu Chemical Co., Ltd. KBM-403) separately with 0.02 mol / L hydrochloric acid. Next, the three aqueous solutions were mixed in a PVA:TEOS:GPTMS mass ratio of 40:50:10 (before hydrolysis). Then, isopropanol was added to dilute the mixed aqueous solution at a water:isopropanol mass ratio of 90:10 to obtain a coating solution for forming an organic-inorganic composite film (solid content: 5% by mass).

[0197] A coating is formed by applying a mixture of organic and inorganic composite film to an inorganic oxide layer using a gravure printing press, and then drying it in an oven at 60°C for 10 seconds, thereby forming a gas barrier coating layer with a thickness of 0.3 μm composed of organic and inorganic composite film.

[0198] (Polycarboxylic acid polyvalent metal salt coating) Diluted 20 parts by weight of an aqueous solution of polyacrylic acid (ARON A-10H, manufactured by Toa Synthetic Co., Ltd., number average molecular weight 200,000, solid content concentration 25% by mass) with 58.9 parts by weight of distilled water. Then, 0.44 parts by weight of aminopropyltrimethoxysilane (APTMS, manufactured by Aldrich) was added and stirred to obtain a homogeneous A-coating mixture with polycarboxylic acid polymers as the main component.

[0199] 100 parts by weight of zinc oxide microparticle aqueous dispersion (manufactured by Sumitomo Osaka Cement Co., Ltd., ZE143) and 2 parts by weight of curing agent (manufactured by Henkel Co., Ltd., Liofol HAERTER UR 5889-21) were mixed to obtain a B coating mixture with polyvalent metal compounds as the main components.

[0200] A coating film is formed by applying the A coating film mixture (described later) onto an inorganic oxide layer using a gravure printing press, and then drying it in an oven at 60°C for 10 seconds, thereby forming an A coating film with a thickness of 0.2 μm. Next, a B coating film is formed by applying a B coating film using a gravure printing press, and then drying it in an oven at 60°C for 10 seconds, thereby forming a B coating film with a thickness of 0.2 μm. Thus, an oxygen barrier coating film composed of a polycarboxylic acid polyvalent metal salt coating is formed.

[0201] <Adhesive layer> (Carbamate adhesives) A urethane-based adhesive was obtained by mixing 100 parts by weight of TAKELAC A525 (manufactured by Mitsui Chemicals) with 11 parts by weight of TAKELAC A52 (manufactured by Mitsui Chemicals) and 84 parts by weight of ethyl acetate.

[0202] (Gas barrier adhesive) A gas barrier adhesive was obtained by mixing 16 parts by mass of MAXIVE C93T (manufactured by Mitsubishi Gas Chemical Company) and 5 parts by mass of MAXIVE M-100 (manufactured by Mitsubishi Gas Chemical Company) into 23 parts by mass of a solvent prepared by mixing ethyl acetate and methanol in a mass ratio of 1:1.

[0203] <Composite elastic modulus> A multilayer polyethylene film was embedded in a visible-light curable resin, D-800. Then, using a Leica EM UC7 ultramicrotome with a MicroStar LH diamond scalpel, the multilayer polyethylene film was cut perpendicular to the stacking direction. The resulting cross-section was then finished at a cutting thickness of 100 nm and a cutting speed of 1 mm / s to prepare the test specimen.

[0204] In the measurement, the Hysitron TI-Premier (trade name) manufactured by Bruker Japan Co., Ltd. was used as the measuring device, and the Berkovich type diamond indenter manufactured by Bruker Japan Co., Ltd. was used as the indenter. The measurement conditions are as follows.

[0205] Temperature: Room temperature (25℃).

[0206] Mode: Load control mode.

[0207] Pressing and unloading: Press in at a pressing speed of 1.5 μN / s to reach a load of 15 μN, hold at the maximum load for 5 seconds, and then unload at a speed of 1.5 μN / s.

[0208] Measurement site: The shape measurement function of the measuring device is used to scan the surface of the sample by using the indenter to obtain the shape image of the sample cross section. Based on the shape image, 20 points are specified on the cross section of the sample at intervals of more than 1 μm.

[0209] In calculating the composite elastic modulus, fused silica was used as the standard specimen, and the relationship between the contact depth and the projected contact area between the indenter and the specimen was pre-calibrated. Then, the Oliver-Pharr method was used to analyze the unloading curve relative to the maximum load range of 60%–95% during unloading, and the composite elastic modulus of the specimen was calculated. The measurement results are shown in Tables 7–12.

[0210] <Molecular Orientation Degree> The degree of molecular orientation of the molecular chains within the surface of the multilayer polyethylene film was determined by rotating the film in a microwave polarized electric field using a microwave molecular orientation meter (Oji Measurement Instrument Co., Ltd., trade name MOA-5012A). The measurement results are shown in Tables 7-12.

[0211] [evaluate] <Processing Stability> The appearance of the gas barrier film after the formation of the gas barrier coating (for examples without a gas barrier coating, and for comparative examples after the formation of an inorganic oxide layer) was visually confirmed, and the processing stability was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 7-12.

[0212] A: No wrinkles were observed on the appearance of the gas barrier membrane.

[0213] B: Slight wrinkles were observed on the appearance of the gas barrier membrane.

[0214] C: Numerous wrinkles were observed on the appearance of the gas barrier membrane.

[0215] <Transparency> Patterns were printed on the surface of the gas barrier coating layer of the gas barrier films produced in each embodiment and comparative example. The aforementioned urethane-based adhesive or the aforementioned gas barrier adhesive was dry-laminated using Multi Coater™-MC (manufactured by HIRANO TECSEED), and then cured at 40°C for 3 days to form an adhesive layer. After curing, LLDPE (polyethylene film, manufactured by Mitsui Chemicals Tosel, TUX MC-S, 60 μm thick) was laminated onto the adhesive layer to create a laminate of gas barrier film / adhesive / LLDPE sequentially stacked. The printed patterns were visually confirmed from the multilayer polyethylene film side, and the transparency was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 7-12.

[0216] A: The pattern is clear.

[0217] C: The pattern is not clear.

[0218] <Gas Barrier Properties> For the fabricated laminate, the oxygen transmission rate (cm³) was measured using an oxygen transmission rate measuring device (trade name OXTRAN-2 / 20, manufactured by MOCON) according to JIS K-7126-2 B method at 30°C and 70% RH. 3 / (m 2 The gas barrier properties were evaluated based on the following evaluation criteria (day / atm). The evaluation results are shown in Tables 7-12.

[0219] (Evaluation criteria for oxygen permeability) A+: Oxygen permeability less than 2cm 3 / (m 2 ·day·atm).

[0220] A: Oxygen permeability is 2cm 3 / (m 2 (day / atm) or more and less than 5cm 3 / (m 2 ·day·atm).

[0221] A-: Oxygen permeability is 5cm 3 / (m 2 (day / atm) or more and less than 10cm 3 / (m 2 ·day·atm).

[0222] B+: Oxygen permeability is 10 cm⁻¹ 3 / (m 2 (day / atm) or more and less than 20cm 3 / (m 2 ·day·atm).

[0223] B: Oxygen permeability is 20cm 3 / (m 2 (day / atm) or more and less than 50cm 3 / (m 2 ·day·atm).

[0224] B-: Oxygen permeability is 50 cm⁻¹ 3 / (m 2 (day / atm) or more and less than 100cm 3 / (m 2 ·day·atm).

[0225] C: Oxygen permeability is 100cm 3 / (m 2 (day / atm) and above.

[0226] <Gas Barrier Properties After Boiling> The prepared laminated body was cut into two 15cm × 10cm pieces. These two pieces were then overlapped with their sealing layers facing each other, and three sides were pulse-sealed to form a bag. 150mL of water was placed inside the bag as the contents, and the remaining side was pulse-sealed to create a four-sided sealed bag (packaging bag). The bag was then boiled at 95°C for 30 minutes using a boiling treatment apparatus. After boiling, the bag was opened, the contents removed, and the bag was allowed to dry thoroughly. The oxygen permeability was measured using the method described above to evaluate the gas barrier properties. The evaluation results are shown in Tables 7–12.

[0227] <Gas Barrier Properties After Bending> The prepared laminate was cut into pieces measuring 295 mm in length and 210 mm in width and used as evaluation samples. These samples were then fitted into a cylindrical shape (87.5 mm in diameter and 210 mm in width) onto the fixing head of a Gelvo FlexTester (trade name: BE-1005) manufactured by TESTER SANGYO. Holding the samples at both ends with an initial holding interval of 175 mm, a 440-degree twist was applied with a stroke of 87.5 mm, and this action was repeated 10 times at a speed of 40 times / minute to induce bending. The oxygen permeability of the bent samples was measured using the method described above to evaluate gas barrier properties. The evaluation results are shown in Tables 7-12.

[0228] <Seamless fit> 15mm wide strips of test material were cut from the fabricated laminate. The heat-sealable layer was peeled from the multilayer polyethylene film using an ORIENTEC TENSILON RTC-1250 universal testing machine, and the lamination strength was measured according to JIS Z1707. For the lamination strength measurement, in addition to 90° peel (normal 90° peel) and 180° peel (normal 180° peel), 90° peel (wet 90° peel) and 180° peel (wet 180° peel) were also performed with the peel interface moistened with water. The adhesion was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 7–12.

[0229] A: The lamination strength is 2N / 15mm or higher.

[0230] B: Lamination strength is less than 2N / 15mm. Explanation of reference numerals in the attached figures: 10, 30, 40, 50, 60: Multilayer polyethylene film; 11, 31, 41, 51, 61: Top layer; 12, 32, 42, 52, 62: Intermediate layer; 13, 33, 43, 53, 63: Inner layer; 20: Gas barrier layer; 21: Inorganic oxide layer; 22: Gas barrier coating layer; 100, 200, 300: Gas barrier film; 130: Adhesive layer; 140: Sealing layer; 170: Second adhesive layer; 180: Substrate; 400, 500, 600, 700: Laminate.

Claims

1. A gas barrier membrane, wherein, It has a layered structure. The laminated structure comprises multiple layers of polyethylene film and a gas barrier layer. The multilayer polyethylene film has a surface layer, an intermediate layer, and an inner layer in sequence, with the surface layer disposed between the intermediate layer and the gas barrier layer. The surface layer is composed of a material with a density of 0.926 g / cm³. 3 It is composed of medium-density polyethylene resin or high-density polyethylene resin with the above-mentioned density. The composite elastic modulus of the outer layer and the inner layer is greater than 1.45 GPa and less than 1.90 GPa. The composite elastic modulus of the intermediate layer is above 1.80 GPa and less than 2.50 GPa. The gas barrier layer has at least one of an inorganic oxide layer and a gas barrier coating layer.

2. The gas barrier membrane according to claim 1, wherein, The density of the multilayer polyethylene film is 0.940 g / cm³. 3 above.

3. The gas barrier membrane according to claim 1, wherein, The gas barrier layer has the inorganic oxide layer. The inorganic oxide layer comprises at least one of aluminum oxide and silicon oxide.

4. The gas barrier membrane according to claim 1, wherein, The gas barrier layer has the gas barrier coating. The gas barrier coating comprises a water-soluble polymer and at least one selected from the group consisting of metal alkoxides, hydrolysates of metal alkoxides, and their reaction products.

5. The gas barrier membrane according to claim 1, wherein, The gas barrier layer has the gas barrier coating. The gas barrier coating comprises at least one selected from the group consisting of silane coupling agents, hydrolysates of silane coupling agents, and their reaction products.

6. The gas barrier membrane according to claim 1, wherein, The gas barrier layer has the gas barrier coating. The gas barrier coating contains a multivalent metal salt of carboxylic acid.

7. The gas barrier membrane according to claim 1, wherein, The ratio of the thickness of the intermediate layer to the combined thickness of the outer layer and the inner layer is 0.5 or more.

8. The gas barrier membrane according to claim 1, wherein, The thickness of the intermediate layer is more than 33% of the thickness of the multilayer polyethylene film.

9. The gas barrier membrane according to claim 1, wherein, The temperature indicated by the maximum melting peak observed in differential scanning calorimetry for the multilayer polyethylene film is above 129°C and below 136°C.

10. A layered body, wherein, have: Gas barrier membrane as described in any one of claims 1 to 9; An adhesive layer is disposed on the surface of the gas barrier layer opposite to the multilayer polyethylene film; and A sealing layer, configured with the adhesive layer, The absolute value of the molecular orientation degree of the multilayer polyethylene film is less than 1.

07.

11. The laminate according to claim 10, wherein, Based on the total amount of the laminate, the content of polyethylene resin in the laminate is 90% by mass or more.

12. The laminate according to claim 10, wherein, The surface of the inorganic oxide layer on the sealing layer side also has a gas barrier coating.

13. The laminate according to claim 10, wherein, The adhesive layer comprises a gas barrier adhesive.

14. The laminate according to claim 10, wherein, It also has: A second adhesive layer is disposed on the surface of the inner layer side of the multilayer polyethylene film; and The substrate is configured with the aid of the second adhesive layer.

15. A packaging material, wherein, It comprises the laminate as described in claim 10.

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