Gas-barrier film, multilayer object, and packaging material

Abstract

Provided is a gas-barrier film comprising a multilayered polyethylene film and a gas-barrier layer, wherein the multilayered polyethylene film comprises at least three layers, which are a front layer, an interlayer, and a back layer formed in this order from the gas-barrier layer side. The interlayer has a probe descent temperature which is higher than the probe descent temperature of the front layer and is not lower than the probe descent temperature of the back layer. The front layer is made of a medium-density polyethylene resin having a density of 0.926 g / cm3 or higher or of a high-density polyethylene resin. The gas-barrier layer includes an inorganic oxide layer and / or a gas-barrier coating layer.

Description

Gas barrier film, laminate and packaging material

[0001] The present invention relates to a gas barrier film, a laminate, and a packaging material.

[0002] Packaging materials used for packaging foods, pharmaceuticals, etc. are required to have gas barrier properties that prevent the intrusion of gases (water vapor, oxygen, etc.) that denature the contents, in order to prevent deterioration and spoilage of the contents and maintain their function and quality. Furthermore, packaging materials are required to have excellent heat resistance, as they may be subjected to heat sterilization treatments such as boiling. Therefore, laminates (gas barrier films) that have gas barrier properties and heat resistance are used for these packaging materials.

[0003] Known gas barrier films include those in which a gas barrier layer made of a material having gas barrier properties is provided on the surface of a resin substrate. Known gas barrier layers include metal foils, metal vapor-deposited films, and coatings formed by wet coating. Known resin substrates include polyolefin films such as polyethylene films. For example, Patent Document 1 describes an aluminum-deposited polyethylene film, which is an unstretched polyethylene film having a thickness of less than 30 μm and made of linear low-density polyethylene produced using a metallocene catalyst, and which has an aluminum vapor-deposited film on the surface thereof.

[0004] Furthermore, studies have been conducted to improve the properties of gas barrier films by forming a resin substrate into a laminate having a plurality of resin layers. For example, Patent Document 2 describes a film capable of suppressing the occurrence of wrinkles, which comprises a resin layer having a first surface and a second surface, and a vapor deposition layer provided on the second surface of the resin layer, and the resin layer has a density higher than that of the first layer constituting the first surface and a density of 0.934 g / cm ３ and at least one hard layer having a density of at least 1000 MPa, wherein the total thickness of the hard layers is at least 60% of the total thickness of the resin layer.

[0005] JP 2001-179878 A JP 2018-24213 A

[0006] In recent years, growing environmental awareness stemming from issues such as marine plastic waste has led to calls for more efficient sorting and recovery of plastic materials and recycling, and there is also a growing demand for mono-material packaging materials.

[0007] However, in conducting research to develop mono-material gas barrier films, the inventors found that, depending on the type of polyethylene resin that constitutes each layer of the polyethylene film, wrinkles may occur on the surface of the polyethylene film, making it difficult to form a gas barrier layer or to impart sufficient heat resistance.

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

[0009] One aspect of the present invention includes the following [1] to

[14] . [1] A multilayer polyethylene film comprising a gas barrier layer, the multilayer polyethylene film having at least three layers, a surface layer, an intermediate layer, and a back layer, in this order on the gas barrier layer side, the intermediate layer having a probe drop temperature higher than that of the surface layer and equal to or higher than that of the back layer, the surface layer having a viscosity of 0.926 g / cm ３ [2] A gas barrier film comprising a medium-density polyethylene resin or a high-density polyethylene resin having a density of 0.942 g / cm or more, wherein the gas barrier layer has at least one of an inorganic oxide layer and a gas barrier coating layer. ３The gas barrier film according to [1], wherein the intermediate layer has a probe drop temperature of 125°C or higher. [3] The gas barrier film according to [1] or [2], wherein the intermediate layer has a probe drop temperature of 125°C or higher. [4] The gas barrier film according to any one of [1] to [3], wherein the thickness of the intermediate layer is 33% or more of the thickness of the multilayer polyethylene film. [5] The gas barrier film according to any one of [1] to [4], wherein the multilayer polyethylene film has an absolute value of a degree of molecular orientation of less than 1.07. [6] The gas barrier film according to any one of [1] to [5], wherein the gas barrier layer has the inorganic oxide layer, and the inorganic oxide layer contains at least one of aluminum oxide and silicon oxide. [7] The gas barrier film according to any one of [1] to [6], wherein the gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer contains a water-soluble polymer and at least one selected from the group consisting of a metal alkoxide, a hydrolysate thereof, and a reaction product thereof. [8] The gas barrier film according to any one of [1] to [7], wherein the gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer contains at least one selected from the group consisting of a silane coupling agent, a hydrolyzate thereof, and a reaction product thereof. [9] The gas barrier film according to [1] to [8], wherein the gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer contains a polyvalent metal salt of a carboxylic acid.

[10] A laminate comprising the gas barrier film according to any one of [1] to [9], an adhesive layer disposed on the surface of the gas barrier layer opposite the multilayer polyethylene film, and a sealant layer disposed via the adhesive layer.

[11] The laminate according to

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

[12] The laminate according to

[10] or

[11] , wherein the adhesive layer contains a gas barrier adhesive.

[13] The laminate according to any one of

[10] to

[12] , further comprising: a second adhesive layer disposed on the surface of the multilayer polyethylene film on the back layer side; and a substrate disposed via the second adhesive layer.

[14] A packaging material comprising the laminate according to any one of

[10] to

[13] .

[0010] According to one aspect of the present invention, there is provided a gas barrier film having excellent processing stability when a gas barrier layer is provided and excellent heat resistance that allows the gas barrier property to be maintained even after heat sterilization treatment. Also, according to another aspect of the present invention, there is provided a laminate having excellent recyclability, excellent processing stability when a gas barrier layer is provided, excellent heat resistance that allows the gas barrier property to be maintained even after heat sterilization treatment, and adhesion to a heat seal layer.

[0011] Fig. 1 is a cross-sectional view of a gas barrier film according to one embodiment of the present invention. Fig. 2 is a cross-sectional view of a gas barrier film according to another embodiment of the present invention. Fig. 3 is a cross-sectional view of a gas barrier film according to another embodiment of the present invention. Fig. 4 is a cross-sectional view of a laminate according to one embodiment of the present invention. Fig. 5 is a cross-sectional view of a laminate according to another embodiment of the present invention. Fig. 6 is a cross-sectional view of a laminate according to another embodiment of the present invention. Fig. 7 is a cross-sectional view of a laminate according to another embodiment of the present invention.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the drawings are schematic, and for example, the relationship between thickness and planar dimensions, and the thickness ratio of each layer may differ from the actual ones. Furthermore, the embodiments shown below exemplify configurations for embodying the technical idea of ​​the present disclosure, and the technical idea of ​​the present disclosure is not limited to the materials, shapes, structures, etc. of the components described below.

[0013] 1 is a cross-sectional view of a gas barrier film according to one embodiment of the present invention. The gas barrier film 100 comprises at least a multilayer polyethylene film 10 and a gas barrier layer 20.

[0014] The content of polyethylene resin in the gas barrier film 100 may be 90% by mass or more, or 95% by mass or more, based on the total amount of the gas barrier film 100, in order to achieve mono-materialization and excellent recyclability.

[0015] The thickness of the gas barrier film 100 may be 5 μm or more, 10 μm or more, or 15 μm or more from the viewpoint of easily achieving excellent heat resistance and easy stable production, and may be 100 μm or less, 60 μm or less, or 40 μm or less from the viewpoint of cost.

[0016] <Multilayer Polyethylene Film> The multilayer polyethylene film 10 has three layers, a surface layer 11, an intermediate layer 12, and a back layer 13, in this order on the gas barrier layer 20 side. The surface layer 11 and the back layer 13 are each the outermost layer of the multilayer polyethylene film 10.

[0017] The content of polyethylene resin in the multilayer polyethylene film 10 may be 90% by mass or more, or 95% by mass or more, based on the total amount of the multilayer polyethylene film 10, from the viewpoint of realizing mono-materialization and excellent recyclability.

[0018] The density of the multilayer polyethylene film 10 is set to 0.935 g / cm from the viewpoints of being less prone to wrinkles, being more stable in processing, and being more likely to maintain gas barrier properties and adhesion even after heat sterilization treatment and being more heat resistant. ３ Above, 0.940g / cm ３ Above, 0.945g / cm ３ Above, 0.950g / cm ３ or more, or 0.955 g / cm ３ The density of the multilayer polyethylene film 10 may be 0.980 g / cm or more from the viewpoints of wrinkles being less likely to occur, better processing stability, and gas barrier properties and adhesion being more likely to be maintained even after heat sterilization treatment, resulting in better heat resistance. ３ Below, 0.975g / cm ３ Below, 0.970g / cm ３ Below, 0.965g / cm ３ or less, or 0.960 g / cm ３ From these viewpoints, the density of the multilayer polyethylene film 10 may be 0.935 to 0.980 g / cm ３ , 0.940-0.975g / cm ３ , 0.945-0.970g / cm３ , 0.950-0.965g / cm ３ , or 0.955 to 0.960 g / cm ３ may be.

[0019] The multilayer polyethylene film 10 may be unstretched. The multilayer polyethylene film 10 being unstretched means that the absolute value of the molecular orientation degree of the multilayer polyethylene film is less than 1.07. When the multilayer polyethylene film 10 is unstretched (the absolute value of the molecular orientation degree is less than 1.07), the gas barrier layer 20 is less likely to peel off in the vicinity of the surface layer 11 of the multilayer polyethylene film 10, and the adhesion to the gas barrier layer 20 is excellent. The absolute value of the molecular orientation degree may be 1 or more, 1.02 or more, or 1.04 or more. From these viewpoints, the absolute value of the molecular orientation degree may be 1 or more but less than 1.07, 1.02 or more but less than 1.07, or 1.04 or more but less than 1.07. The absolute value of the molecular orientation degree means a value measured by the method described in the examples described later.

[0020] The thickness of the multilayer polyethylene film 10 is not particularly limited and can be appropriately determined according to cost and application, taking into consideration suitability as a packaging material and suitability for lamination with other layers. From the viewpoint of improving processability, the thickness of the multilayer polyethylene film 10 may be 3 μm or more, 5 μm or more, 6 μm or more, or 10 μm or more. From the viewpoint of reducing the thickness of the packaging material and improving heat resistance, the thickness of the multilayer polyethylene film 10 may be 200 μm or less, 120 μm or less, 100 μm or less, or 40 μm or less. From these viewpoints, the thickness of the multilayer polyethylene film 10 may be 3 to 200 μm, 5 to 120 μm, 6 to 100 μm, or 10 to 40 μm.

[0021] (Surface layer) The surface layer 11 has a density of 0.926 g / cm ３ The surface layer 11 is a layer made of the medium-density polyethylene resin or the high-density polyethylene resin having a density of 0.926 g / cm ３ By being made of the above medium-density polyethylene resin or high-density polyethylene resin, the multilayer polyethylene film 10 has excellent heat resistance. In this specification, high-density polyethylene resin means a polyethylene resin having a density of 0.942 g / cm ３Hereinafter, the polyethylene resin constituting the surface layer 11 will also be referred to as a first polyethylene resin.

[0022] From the viewpoints of realizing mono-materialization and excellent recyclability, the content of the first polyethylene resin in the surface layer 11 may be 90% by mass or more, 95% by mass or more, or 98% by mass or more, or may be 100% by mass (an embodiment in which the surface layer 11 is substantially composed of the first polyethylene resin), based on the total amount of the surface layer 11. When the surface layer 11 is composed of a plurality of polyethylene resins (for example, a plurality of polyethylene resins having different average molecular weights, densities, etc.), a mixture of the plurality of polyethylene resins is used as the first polyethylene resin.

[0023] From the viewpoints of being less prone to wrinkles, having better processing stability, and being more likely to maintain gas barrier properties even after heat sterilization treatment and having better heat resistance, the surface layer 11 may be made of a first polyethylene resin having a density in the following range: The density of the first polyethylene resin is 0.930 g / cm ３ Above, 0.935g / cm ３ or more, or 0.940 g / cm ３ The density of the first polyethylene resin may be 0.970 g / cm or more. ３ Below, 0.965g / cm ３ or less, or 0.960 g / cm ３ In particular, the density of the first polyethylene resin may be 0.960 g / cm or less. ３ By setting the density of the first polyethylene resin to 0.930 to 0.970 g / cm or less, it is possible to prevent the surface of the multilayer polyethylene film 10 from becoming rough and the generation of resin powder, and it is easy to achieve excellent gas barrier properties. ３ , 0.935-0.965g / cm ３ , or 0.940 to 0.960 g / cm ３ may be.

[0024] Melt flow rate (MFR) of the first polyethylene resin at 190°C and a load of 2.16 kg １is not particularly limited and can be appropriately adjusted depending on the method for producing the first polyethylene resin. １ The MFR of the first polyethylene resin may 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 wrinkles being less likely to occur and processing stability being more excellent, and gas barrier properties being more easily maintained even after heat sterilization treatment and heat resistance being more excellent. １ From the viewpoints of wrinkles being less likely to occur and processing stability being more excellent, and gas barrier properties being more likely to be maintained even after heat sterilization treatment and heat resistance being more excellent, the MFR of the first polyethylene resin may be 0.1 g / 10 min or more or 0.3 g / 10 min or more. １ The melt flow rate may be 0.1 to 5 g / 10 min, 0.1 to 3 g / 10 min, 0.1 to 1.5 g / 10 min, or 0.3 to 5 g / 10 min. In this specification, the melt flow rate refers to a value measured in accordance with JIS K6921-2.

[0025] The probe drop temperature of the surface layer 11 may be 120°C or higher, 125°C or higher, 130°C or higher, or 133°C or higher from the viewpoints of reducing wrinkles and improving processing stability, and of more easily maintaining gas barrier properties even after heat sterilization and improving heat resistance. The probe drop temperature of the surface layer 11 may be 160°C or lower, 155°C or lower, 150°C or lower, or 146°C or lower from the viewpoints of reducing wrinkles and improving processing stability. Having a probe drop temperature of 150°C or lower for the surface layer 11 can suppress surface roughening of the multilayer polyethylene film 10 and the generation of resin powder, making it easier to achieve excellent gas barrier properties. From these viewpoints, the probe drop temperature of the surface layer 11 may be 120 to 160°C, 125 to 155°C, 130 to 150°C, or 133 to 146°C.

[0026] The tip drop temperature is a parameter related to localized thermal analysis of materials using a probe and can be obtained by measuring the tip's rise and fall behavior. To measure the tip drop temperature, an atomic force microscope (AFM) equipped with a cantilever (probe) with a heating mechanism and a nanothermal microscope is used. The cantilever is placed in contact with the surface of a solid sample fixed to a sample stage. When a voltage is applied to the cantilever in contact mode to heat the sample, the sample surface thermally expands, causing the cantilever to rise. Further heating of the cantilever softens the sample surface, significantly changing its hardness. As a result, the cantilever descends and penetrates the sample surface. The point at which the sudden displacement detected at this time begins is the tip drop start point, and the voltage is converted to temperature to obtain the tip drop temperature. This method allows the tip drop temperature to be determined locally in the nanoscale region, near the surface.

[0027] Examples of AFMs that can be used include the MPF-3D-SA and Ztherm systems manufactured by Oxford Instruments, and the Nano Thermal Analysis series and nanoIR series manufactured by Bruker Japan. Measurements are also possible with AFMs from other manufacturers if a Nano Thermal Analysis is attached. An example of a cantilever is the AN2-200 manufactured by Anasys Instruments. Cantilevers other than those listed above can also be used, as long as they can sufficiently reflect laser light and allow voltage to be applied.

[0028] The temperature range for measuring the probe descent temperature varies depending on the material to be measured, but for example, the starting temperature can be about room temperature, 25° C., and the ending temperature can be about 400° C. In this specification, the temperature range for measuring the probe descent temperature can be from 25° C. to 300° C.

[0029] The spring constant of the cantilever may be 0.1 to 3.5 N / m, and is preferably 0.5 to 3.5 N / m for measurements in both tapping mode and contact mode. In AFM, the deflection of the cantilever is sometimes measured in units of voltage. In contact mode, the deflection of the cantilever changes before and after contact between the cantilever and the sample. By keeping this change within the range of 0.1 to 3.0 V, it is possible to prevent damage to the sample surface while keeping the cantilever in contact with the sample.

[0030] The temperature rise rate of the cantilever varies depending on the heating mechanism, etc., but may be 0.1 to 10 V / sec, and preferably 0.2 to 5 V / sec. When the sample surface softens, the tip of the cantilever sinks into the sample and descends. The amount of cantilever sinking affects the detection sensitivity of the peak top of the softening curve, and can be set to 3 to 500 nm. From the viewpoint of preventing damage to the cantilever, it is more preferable to set the amount of sinking to 5 to 100 nm.

[0031] To calculate the probe drop temperature, a calibration curve must be created. In the examples described below, calibration curves are created using polycaprolactone, low-density polyethylene, polypropylene, and polyethylene terephthalate as calibration samples. Details of the creation of the calibration curve will be described later. The materials of the calibration samples are not limited to those described above. Any material with a thermal conductivity not significantly different from that of a typical polymer, with at least one melting point near 60°C, one near 250°C, and one somewhere in between, may be used. For example, polypropylene may be omitted from the four calibration samples described above, leaving only polycaprolactone, low-density polyethylene, and polyethylene terephthalate as the calibration samples. To accurately measure the temperature of the sample, a calibration curve is created after sample measurement. Four types of calibration samples are used: polycaprolactone (melting point: 55°C), low-density polyethylene (LDPE, melting point: 110°C), polypropylene (PP, melting point: 164°C), and polyethylene terephthalate (PET, melting point: 235°C). Each measurement is taken twice at different measurement positions, and the average value is used as the probe descent temperature to create a calibration curve. Using this calibration curve, the voltage is used as the probe descent start point, and the temperature is converted to the probe descent temperature.

[0032] The thickness of the surface layer 11 is not particularly limited and can be appropriately determined according to cost and application, taking into consideration the suitability of the manufacturing method and equipment, and the suitability for lamination with other layers. From a practical standpoint, the thickness of the surface layer 11 may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more. From the standpoint of reducing the thickness of the packaging material, the thickness may be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. From these standpoints, the thickness of the surface layer 11 may be 1 to 50 μm, 2 to 30 μm, 3 to 20 μm, 4 to 10 μm, or 5 to 50 μm.

[0033] (Intermediate Layer) The intermediate layer 12 is a layer containing a polyethylene resin. Hereinafter, the polyethylene resin constituting the intermediate layer 12 is also referred to as the second polyethylene resin. From the viewpoint of realizing a mono-material structure and achieving excellent recyclability, the content of the second polyethylene resin in the intermediate layer 12 may be 90% by mass or more, 95% by mass or more, or 98% by mass or more, based on the total amount of the intermediate layer 12, or may be 100% by mass (an embodiment in which 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 the multiple polyethylene resins is used as the second polyethylene resin.

[0034] From the viewpoints of wrinkle resistance, superior processing stability, easier maintenance of gas barrier properties even after heat sterilization treatment, and superior heat resistance, the intermediate layer 12 may be composed of a second polyethylene resin having a density in the following range. The density of the second polyethylene resin is 0.940 g / cm ３ Above, 0.945g / cm ３ or more, or 0.950 g / cm ３ The density of the second polyethylene resin may be 0.980 g / cm or more. ３ Below, 0.975g / cm ３ Below, 0.970g / cm ３ or less, or 0.965 g / cm ３ From these viewpoints, the density of the second polyethylene resin may be 0.940 to 0.980 g / cm or less. ３ , 0.940-0.975g / cm ３ , 0.945-0.970g / cm ３ , 0.950-0.965g / cm ３ may be.

[0035] Melt flow rate (MFR) of the second polyethylene resin at 190°C and a load of 2.16 kg ２ is not particularly limited and can be appropriately adjusted depending on the method for producing the second polyethylene resin.２ The MFR of the second polyethylene resin may be 5 g / 10 min or less, 3 g / 10 min or less, 2 g / 10 min or less, or 1.5 g / 10 min or less, from the viewpoint of wrinkles being less likely to occur and processing stability being more excellent, and gas barrier properties being more easily maintained even after heat sterilization treatment and heat resistance being more excellent. ２ From the viewpoints of wrinkles being less likely to occur and processing stability being more excellent, and gas barrier properties being more likely to be maintained even after heat sterilization treatment and heat resistance being more excellent, the MFR of the second polyethylene resin may be 0.1 g / 10 min or more, 0.5 g / 10 min or more, or 0.8 g / 10 min or more. ２ may be 0.1 to 5 g / 10 min, 0.1 to 3 g / 10 min, 0.5 to 2 g / 10 min, or 0.5 to 1.5 g / 10 min.

[0036] The higher the probe drop temperature of the intermediate layer 12, the easier it is to achieve excellent heat resistance. The probe drop temperature of the intermediate layer 12 may be 125°C or higher, 130°C or higher, 135°C or higher, 138°C or higher, 140°C or higher, or 142°C or higher from the viewpoints of being less likely to wrinkle and achieving better processing stability, and of more easily maintaining gas barrier properties even after heat sterilization treatment and achieving better heat resistance. The probe drop temperature of the intermediate layer 12 may be 170°C or lower, 165°C or lower, 160°C or lower, 157°C or lower, or 155°C or lower from the viewpoints of being less likely to wrinkle and achieving better processing stability. From these viewpoints, the probe drop temperature of the intermediate layer 12 may be 125 to 170°C, 135 to 165°C, 140 to 157°C, or 142 to 155°C.

[0037] The probe drop temperature of the intermediate layer 12 is higher than the probe drop temperature of the surface layer 11 and equal to or higher than the probe drop temperature of the back layer 13. By having the probe drop temperature of the intermediate layer 12 higher than the probe drop temperature of the surface layer 11 and equal to or higher than the probe drop temperature of the back layer 13, wrinkles are less likely to occur, processing stability is more excellent, and excellent heat resistance that allows gas barrier properties to be maintained even after heat sterilization treatment can be achieved.

[0038] The difference between the probe drop temperature of the intermediate layer 12 and the probe drop temperature of the surface layer 11 and / or the back layer 13 may be 3°C or more, 5°C or more, or 8°C or more, from the viewpoints of reducing wrinkles and improving processing stability, and of making it easier to maintain gas barrier properties even after heat sterilization treatment and improving heat resistance. The difference between the probe drop temperature of the intermediate layer 12 and the probe drop temperature of the surface layer 11 and / or the back layer 13 may be 20°C or less, 15°C or less, or 13°C or less, from the viewpoints of reducing wrinkles and improving processing stability. From these viewpoints, the difference between the probe drop temperature of the intermediate layer 12 and the probe drop temperature of the surface layer 11 and / or the back layer 13 may be 3 to 20°C, 5 to 15°C, or 8 to 13°C.

[0039] The thickness of the intermediate layer 12 is not particularly limited and can be determined appropriately according to cost and application, taking into consideration the suitability of the manufacturing method and equipment, and the suitability for lamination with other layers. From a practical standpoint, the thickness of the intermediate layer 12 may be 5 μm or more, 8 μm or more, 10 μm or more, 12 μm or more, or 15 μm or more. From the standpoint of reducing the thickness of the packaging material, the thickness may be 80 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less. From these standpoints, the thickness of the intermediate layer 12 may be 5 to 80 μm, 8 to 50 μm, 10 to 40 μm, 12 to 30 μm, or 15 to 80 μm.

[0040] The greater the thickness of the intermediate layer 12, the better the heat resistance that can be achieved. From the viewpoints of more easily maintaining gas barrier properties and achieving better heat resistance even after heat sterilization treatment, the thickness of the intermediate layer 12 may 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. From the viewpoints of more effectively preventing wrinkles and achieving better processing stability, the thickness of the intermediate layer 12 may be 80% or less, 77% or less, or 75% or less of the thickness of the multilayer polyethylene film 10. From these viewpoints, the thickness of the intermediate layer 12 may be 30 to 80%, 33 to 80%, 40 to 77%, 50 to 77%, 55 to 75%, or 60 to 75% of the thickness of the multilayer polyethylene film 10.

[0041] The thickness of the intermediate layer 12 may be greater than the thickness of the surface layer 11 and / or the thickness of the back layer 13, from the viewpoint of more easily maintaining gas barrier properties even after heat sterilization and more excellent heat resistance. The thickness of the intermediate layer 12 may be 1 time or more, 1.5 times or more, 2 times or more, 2.5 times or more, or 3 times or more the thickness of the surface layer 11 and / or the back layer 13, from the viewpoint of more easily maintaining gas barrier properties even after heat sterilization and more excellent heat resistance. The thickness of the intermediate layer 12 may be 8 times or less, 7 times or less, 6.5 times or less, or 6 times or less the thickness of the surface layer 11 and / or the back layer 13, from the viewpoint of more unlikely occurrence of wrinkles and more excellent processing stability. From these viewpoints, the thickness of the intermediate layer 12 may be 1 to 8 times, 1 to 6 times, 1.5 to 7 times, 2 to 6.5 times, or 2.5 to 6 times the thickness of the surface layer 11 and / or the back layer 13.

[0042] (Back layer) The back layer 13 is a layer containing a polyethylene resin. Hereinafter, the polyethylene resin constituting the back layer 13 is also referred to as the third polyethylene resin. From the viewpoint of realizing a mono-material structure and achieving excellent recyclability, the content of the third polyethylene resin in the back layer 13 may be 90% by mass or more, 95% by mass or more, or 98% by mass or more, based on the total amount of the back layer 13, or may be 100% by mass (an embodiment in which the back layer 13 is substantially composed of the third polyethylene resin). When the back layer 13 is composed of multiple polyethylene resins (for example, multiple polyethylene resins with different average molecular weights, densities, etc.), a mixture of the multiple polyethylene resins is referred to as the third polyethylene resin.

[0043] The back layer 13 may be composed of a third polyethylene resin having a density in the following range, from the viewpoint of being less prone to wrinkles, having better processing stability, and being more likely to maintain gas barrier properties and adhesion even after heat sterilization treatment and having better heat resistance. The density of the third polyethylene resin is 0.920 g / cm ３ Above, 0.926g / cm ３ Above, 0.930g / cm ３ Above, 0.935g / cm ３ or more, or 0.940 g / cm ３The density of the third polyethylene resin may be 0.970 g / cm or more. ３ Below, 0.965g / cm ３ or less, or 0.960 g / cm ３ The density of the third polyethylene resin may be 0.960 g / cm or less. ３ By ensuring that the density of the third polyethylene resin is 0.920 to 0.970 g / cm or less, it is possible to prevent the surface of the multilayer polyethylene film 10 from becoming rough and the generation of resin powder. By preventing the generation of resin powder, it is possible to prevent the adhesion of resin powder to the surface of the outer layer 11 side of the multilayer polyethylene film 10 when the multilayer polyethylene film 10 is wound into a roll, and it becomes easier to achieve excellent gas barrier properties. From these viewpoints, the density of the third polyethylene resin is set to 0.920 to 0.970 g / cm ３ , 0.926-0.970g / cm ３ , 0.930-0.965g / cm ３ , 0.935-0.965g / cm ３ , or 0.940 to 0.960 g / cm ３ may be.

[0044] Melt flow rate (MFR) of the third polyethylene resin at 190°C and a load of 2.16 kg ３ is not particularly limited and can be appropriately adjusted depending on the method for producing the third polyethylene resin. ３ The MFR of the third polyethylene resin may 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 wrinkles being less likely to occur and processing stability being more excellent, and gas barrier properties being more easily maintained even after heat sterilization treatment and heat resistance being more excellent. ３ From the viewpoints of wrinkles being less likely to occur and processing stability being more excellent, and gas barrier properties being more likely to be maintained even after heat sterilization treatment and heat resistance being more excellent, the MFR of the third polyethylene resin may be 0.1 g / 10 min or more or 0.3 g / 10 min or more. ３may be 0.1 to 5 g / 10 min, 0.1 to 3 g / 10 min, or 0.3 to 1.5 g / 10 min.

[0045] The probe drop temperature of the back layer 13 may be 120°C or higher, 125°C or higher, 130°C or higher, or 133°C or higher, from the viewpoints of reducing wrinkles and improving processing stability, and of more easily maintaining gas barrier properties and adhesion even after heat sterilization and improving heat resistance. The probe drop temperature of the back layer 13 may be 160°C or lower, 155°C or lower, 150°C or lower, or 146°C or lower, from the viewpoints of reducing wrinkles and improving processing stability. Having a probe drop temperature of 160°C or lower for the back layer 13 can prevent the surface of the multilayer polyethylene film 10 from becoming rough and the generation of resin powder. By preventing the generation of resin powder, adhesion of resin powder to the surface of the front layer 11 side of the multilayer polyethylene film 10 can be prevented when the multilayer polyethylene film 10 is wound into a roll, making it easier to achieve excellent gas barrier properties. From these viewpoints, the probe drop temperature of the backing layer 13 may be 120 to 160°C, 125 to 155°C, 130 to 150°C, or 133 to 146°C.

[0046] The thickness of the back layer 13 is not particularly limited and can be determined appropriately according to cost and application, taking into consideration the suitability of the manufacturing method and equipment, and the suitability for lamination with other layers. From a practical standpoint, the thickness of the back layer 13 may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more. From the standpoint of reducing the thickness of the packaging material, the thickness of the back layer 13 may be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. From these standpoints, the thickness of the back layer 13 may be 1 to 50 μm, 2 to 30 μm, 3 to 20 μm, 4 to 10 μm, or 5 to 50 μm.

[0047] The back layer 13 may have the same configuration as the front layer 11. That is, the multilayer polyethylene film 10 may have a symmetrical structure with respect to the intermediate layer 12. When the multilayer polyethylene film 10 has a symmetrical structure, curling during production of the multilayer polyethylene film 10 can be suppressed, and the multilayer polyethylene film 10 can be produced stably.

[0048] The surface layer 11, intermediate layer 12, and back layer 13 may contain resins other than polyethylene resin as appropriate, as long as they do not impair recyclability. Examples of such resins include olefin-based resins such as ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-(meth)acrylic acid copolymer, homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-α-olefin copolymer, polybutene, polyamide, polyethylene vinyl alcohol, polyester, and various modifying resins. Each layer may also independently contain one or more additives. Examples of additives include crosslinkers, antioxidants, antiblocking agents, lubricants (slip agents), UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, and pigments.

[0049] The intermediate layer 12 may be a single layer or may be formed of multiple layers. For example, as shown in Figure 2, the multilayer polyethylene film 30 in the gas barrier film 200 has a surface layer 31, an intermediate layer 32, and a back layer 33, and the intermediate layer 32 has resin layers 32a, 32b, and 32c. In this case, the 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 with an optical microscope or an electron microscope.

[0050] The multilayer polyethylene film 10 may include layers other than the three layers of the surface layer 11, the intermediate layer 12, and the back layer 13. For example, as shown in FIG. 3 , the multilayer polyethylene film 40 in the gas barrier film 300 includes a surface layer 41, an intermediate layer 42, and a back layer 43, a resin layer 44 between the surface layer 41 and the intermediate layer 42, and a resin layer 45 between the intermediate layer 42 and the back layer 43. The resin layer 44 contains, for example, a polyethylene resin and has a different composition from the surface layer 41 and the intermediate layer 42. The resin layer 45 contains, for example, a polyethylene resin and has a different composition from the intermediate layer 42 and the back layer 43. The multilayer polyethylene film may have, for example, three layers, five layers, seven layers, or more layers.

[0051] Each layer of the multilayer polyethylene film 10 may be made of a polyethylene resin having a density in the following range, from the viewpoints of being less prone to wrinkles, having better processing stability, being more likely to maintain gas barrier properties even after heat sterilization treatment, and having better heat resistance. The density of the polyethylene resin is 0.930 g / cm ３ Above, 0.940g / cm ３ Above, 0.945g / cm ３ or more, or 0.950 g / cm ３ The density of the polyethylene resin may be 0.980 g / cm or more. ３ Below, 0.975g / cm ３ Below, 0.970g / cm ３ or less, or 0.965 g / cm ３ From these viewpoints, the density of the polyethylene resin may be 0.930 to 0.980 g / cm ３ , 0.940-0.975g / cm ３ , 0.945-0.970g / cm ３ , 0.950-0.965g / cm ３ may be.

[0052] The method for producing the multilayer polyethylene film 10 is not particularly limited, and the multilayer polyethylene film 10 can be produced by known methods such as an air-cooled inflation method, a water-cooled inflation method, and a T-die casting method. From the viewpoint of versatility, the multilayer polyethylene film 10 may be produced by either an inflation method or an air-cooled inflation method. The air-cooled inflation method is a method in which a mold with an annular lip called a ring die (or a crosshead die) is installed at the tip of an extruder, and material is extruded into a tubular shape to continuously form it. More specifically, an air hole is installed in the center of the ring die, and compressed air is blown through the air hole to expand the tube, and the tube is cooled while being pulled by rollers called pinch rolls, and the film is then wound up, thereby producing the multilayer polyethylene film 10.

[0053] The obtained multilayer polyethylene film 10 may be subjected to a surface modification treatment to improve suitability for subsequent processes, as necessary. For example, the surface of the multilayer polyethylene film 10 may be modified to improve printability or lamination suitability during lamination. Examples of modification treatments include treatments that generate functional groups by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and flame treatment, and wet process modification treatments that form an easy-adhesion layer by coating.

[0054] <Gas Barrier Layer> The gas barrier layer 20 is a layer provided on the multilayer polyethylene film 10 from the viewpoint of improving gas barrier properties against water vapor and oxygen. The gas barrier layer 20 is preferably a transparent layer. The gas barrier layer 20 has an inorganic oxide layer 21 and a gas barrier coating layer 22. The gas barrier layer 20 may have both the inorganic oxide layer 21 and the gas barrier coating layer 22, or may have only one of the inorganic oxide layer 21 and the gas barrier coating layer 22.

[0055] (Inorganic Oxide Layer) The inorganic oxide layer 21 contains an inorganic oxide. Examples of inorganic oxides include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, and mixtures thereof. From the viewpoints of more easily maintaining gas barrier properties and adhesion even after heat sterilization treatment, more excellent heat resistance, and transparency, the inorganic oxide layer 21 may contain at least one selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide.

[0056] The thickness of the inorganic oxide layer 21 may be 5 to 150 nm. If the thickness of the inorganic oxide layer 21 is 5 nm or more, it is easy to form a layer with a uniform and sufficient film thickness, and sufficient gas barrier properties can be achieved. If the thickness of the inorganic oxide layer 21 is 150 nm or less, flexibility can be imparted to the inorganic oxide layer 21, and even if an external load such as bending or pulling is applied to the inorganic oxide layer 21 after its formation, the occurrence of cracks in the inorganic oxide layer 21 can be suppressed. The thickness of the inorganic oxide layer 21 may be 6 nm or more, or 8 nm or more, or may be 100 nm or less, or 50 nm or less. From these viewpoints, the thickness of the inorganic oxide layer 21 may be 6 to 100 nm, or 8 to 50 nm.

[0057] The inorganic oxide layer 21 can be formed by a typical vacuum deposition method. It can also be formed by other thin film formation methods such as sputtering, ion plating, plasma chemical vapor deposition (CVD), etc. The inorganic oxide layer 21 may be formed by the vacuum deposition method from the viewpoint of excellent productivity.

[0058] The heating method for the vacuum deposition method can be any of electron beam heating, resistance heating, and induction heating. The vacuum deposition method may be electron beam heating in view of the wide range of evaporation material options. In view of improving the adhesion between the multilayer polyethylene film 10 and the inorganic oxide layer 21 and the density of the inorganic oxide layer 21, deposition may be performed by a plasma-assisted method, an ion-beam-assisted method, or the like. In view of improving the transparency of the inorganic oxide layer 21, deposition may be performed by reactive deposition.

[0059] (Gas Barrier Coating Layer) The gas barrier coating layer 22 is a layer provided for the purpose of protecting the multilayer polyethylene film 10 or the inorganic oxide layer 21 and complementing the gas barrier properties. The gas barrier coating layer 22 may contain a water-soluble polymer and at least one selected from the group consisting of a metal alkoxide, a hydrolyzate thereof, and a reaction product thereof. The gas barrier coating layer 22 may contain at least one selected from the group consisting of a silane coupling agent, a hydrolyzate thereof, and a reaction product thereof.

[0060] Examples of the water-soluble polymer include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, etc. The water-soluble polymer may be polyvinyl alcohol (PVA) from the viewpoint of excellent gas barrier properties.

[0061] Examples of metal alkoxides include compounds represented by the following general formula: M(OR １１ ) ｍ (R １２ ) ｎ－ｍ ... (1) In the above formula (1), R １１ and R １２ are each independently a monovalent organic group having 1 to 8 carbon atoms. １１ and R １２ may each independently be an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer from 1 to n. １１ and R １２ If there are multiple １１ Comrades or R １２ They may be the same or different.

[0062] The metal alkoxides include tetraethoxysilane [Si(OC ２ H ５ ) ４ ], triisopropoxyaluminum [Al(O-2'-C ３ H ７ ) ３ The metal alkoxide may be tetraethoxysilane or triisopropoxyaluminum, from the viewpoint that it is relatively stable in an aqueous solvent after hydrolysis.

[0063] Examples of the silane coupling agent include compounds represented by the following general formula: Si(OR ２１ ) ｐ (R ２２ ) ３－ｐ R ２３ ... (2) In the above formula (2), R ２１ represents an alkyl group such as a methyl group or an ethyl group, and R２２ represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or an alkyl group substituted with a methacryloxy group, and R ２３ represents a monovalent organic functional group, and p represents an integer of 1 to 3. ２１ or R ２２ If there are multiple ２１ Comrades or R ２２ R may be the same or different. ２３ Examples of the monovalent organic functional group represented by the formula (I) include a monovalent organic functional group containing a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, and an isocyanate group. The silane coupling agent may be a polymer such as a dimer or trimer of the above-mentioned silane coupling agent.

[0064] Examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

[0065] The gas barrier coating layer 22 can be formed by dissolving a water-soluble polymer in water or a water / alcohol mixed solvent, then mixing it with a metal alkoxide, a silane coupling agent, or a hydrolyzate thereof to obtain a mixed solution, applying the mixed solution to the surface of the inorganic oxide layer 21 (or the multilayer polyethylene film 10 if the inorganic oxide layer 21 is not present), and drying by heating. Additives such as an isocyanate compound, a dispersant, a stabilizer, a viscosity modifier, and a colorant may be added to the mixed solution.

[0066] When the water-soluble polymer is PVA, the content of PVA in the mixed solution may be 20 to 50 mass % or 25 to 40 mass % based on the total solid content of the mixed solution. A PVA content of 20 mass % or more facilitates the formation of the gas barrier coating layer 22. A PVA content of 50 mass % or less provides excellent gas barrier properties.

[0067] The gas barrier coating layer 22 may be a coating containing a polyvalent metal salt of polycarboxylic acid, which is a reaction product between a carboxy group of a polycarboxylic acid polymer and a polyvalent metal compound (a polyvalent metal salt coating of polycarboxylic acid). The polyvalent metal salt coating of polycarboxylic acid can be formed by applying a mixed solution of a polycarboxylic acid polymer and a polyvalent metal compound to the surface of the inorganic oxide layer 21 (or the multilayer polyethylene film 10 if the inorganic oxide layer 21 is not present) and drying the mixture. Alternatively, the polyvalent metal salt coating of polycarboxylic acid may be formed by applying a coating liquid containing a polycarboxylic acid polymer as a main component to the surface of the inorganic oxide layer 21 (or the multilayer polyethylene film 10 if the inorganic oxide layer 21 is not present) and drying the coating to form a coating, and then applying a coating liquid containing a polyvalent metal compound as a main component to the coating and drying the coating to form a coating, and then allowing a crosslinking reaction between the two coatings to form the polyvalent metal salt coating of polycarboxylic acid.

[0068] The polycarboxylic acid polymer is a polymer having two or more carboxyl groups in the molecule. Examples of the polycarboxylic acid polymer include polymers of ethylenically unsaturated carboxylic acids, copolymers of ethylenically unsaturated carboxylic acids with other ethylenically unsaturated monomers, and acidic polysaccharides having carboxyl groups in the molecule, such as alginic acid, carboxymethylcellulose, and pectin.

[0069] Examples of ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, etc. Examples of ethylenically unsaturated monomers copolymerizable with ethylenically unsaturated carboxylic acids include saturated carboxylic acid vinyl esters such as ethylene, propylene, and vinyl acetate, alkyl acrylates, alkyl methacrylates, alkyl itaconates, vinyl chloride, vinylidene chloride, styrene, acrylamide, and acrylonitrile. The polycarboxylic acid polymer may be one type or two or more types.

[0070] From the viewpoint of excellent gas barrier properties, the ethylenically unsaturated carboxylic acid polymer is preferably a polymer containing a structural unit derived from at least one monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, itaconic acid, fumaric acid, and crotonic acid, and more preferably a polymer containing a structural unit derived from at least one monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid.

[0071] In the polymer of ethylenically unsaturated carboxylic acid, the proportion of constitutional units derived from at least one monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid is preferably 80 mol % or more, and more preferably 90 mol % or more, based on the total amount of monomers in the polymer.

[0072] The number-average molecular weight of the polycarboxylic acid polymer is preferably 2,000 to 10,000,000, and more preferably 5,000 to 1,000,000. When the number-average molecular weight is 2,000 or more, the gas barrier film has sufficient water resistance, and deterioration of gas barrier properties and transparency and whitening due to moisture can be suppressed. When the number-average molecular weight is 10,000,000 or less, the viscosity of the coating liquid when forming the gas barrier coating layer 22 does not become too high, making it easier to form a coating.

[0073] When a coating liquid containing a polycarboxylic acid polymer as a main component is applied and dried to form a film, and then a coating liquid containing a polyvalent metal compound as a main component is formed, some of the carboxy groups of the polycarboxylic acid polymer may be neutralized in advance with a basic compound. By neutralizing some of the carboxy groups of the polycarboxylic acid polymer in advance, water resistance and heat resistance can be further improved. The basic compound may be at least one basic compound selected from the group consisting of a polyvalent metal compound, a monovalent metal compound, and ammonia. Examples of polyvalent metal compounds include compounds exemplified as polyvalent metal compounds described below. Examples of monovalent metal compounds include sodium hydroxide, potassium hydroxide, etc.

[0074] The coating liquid containing a polycarboxylic acid polymer as a main component may contain additives such as a crosslinking agent, a curing agent, a leveling agent, an antifoaming agent, an antiblocking agent, an antistatic agent, a dispersant, a surfactant, a softener, a stabilizer, a film-forming agent, and a thickener.

[0075] The solvent used in the coating liquid containing a polycarboxylic acid polymer as a main component is preferably an aqueous medium. Examples of the aqueous medium include water, water-soluble or hydrophilic organic solvents, and mixtures thereof. The aqueous medium contains water as a main component. The water content in the aqueous medium may be 70% by mass or more, or 80% by mass or more. Examples of the water-soluble or hydrophilic organic solvent include alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; nitriles such as acetonitrile; cellosolves, carbitols, and the like.

[0076] The polyvalent metal compound is not particularly limited as long as it is a compound that reacts with a carboxyl group of a polycarboxylic acid polymer to form a polyvalent metal salt of a polycarboxylic acid, and examples thereof include zinc oxide, magnesium oxide, magnesium methoxide, copper oxide, and calcium carbonate. From the viewpoint of excellent gas barrier properties, the polyvalent metal compound may be zinc oxide. One or more types of polyvalent metal compounds may be used.

[0077] Zinc oxide is an inorganic material having ultraviolet absorbing properties. When zinc oxide is in the form of particles, the zinc oxide particles may have an average particle size of 5 μm or less, 1 μm or less, or 0.1 μm or less, from the viewpoints of gas barrier properties, transparency, and coating film formability.

[0078] When a coating film is formed by applying and drying a coating liquid containing a polyvalent metal compound as a main component, the coating liquid may contain, in addition to the polyvalent metal compound (e.g., zinc oxide particles), a solvent, a resin soluble or dispersible in the solvent, a dispersant, a softener, a stabilizer, a film-forming agent, a thickener, and the like.

[0079] Examples of resins that are soluble or dispersible in a solvent include alkyd resins, melamine resins, acrylic resins, urethane resins, polyester resins, phenolic resins, amino resins, fluororesins, epoxy resins, isocyanate resins, etc. When the coating liquid contains these resins, the coating properties and film-forming properties are improved.

[0080] As the dispersant, anionic surfactants and nonionic surfactants can be used. Examples of surfactants include (poly)carboxylates, alkyl sulfates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylsulfosuccinates, alkyldiphenyletherdisulfonates, alkylphosphates, aromatic phosphates, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, alkylallyl sulfates, polyoxyethylene alkylphosphates, sorbitan alkyl esters, glycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene alkylallyl ethers, polyoxyethylene derivatives, polyoxyethylene sorbitol fatty acid esters, polyoxy fatty acid esters, and polyoxyethylene alkylamines. These surfactants may be used alone or in combination.

[0081] When a coating liquid containing a polyvalent metal compound as a main component contains an additive, the mass ratio of the polyvalent metal compound to the additive (polyvalent metal compound:additive) may be 30:70 to 99:1, or 50:50 to 98:2.

[0082] Examples of solvents used in coating liquids containing a polyvalent metal compound as a main component include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. From the viewpoint of coatability, the solvent may be at least one selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water, or from the viewpoint of film-forming properties, may be at least one selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, and water. One or more solvents may be used.

[0083] Examples of methods for applying the coating liquid include casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metalling bar coating, chamber doctor combined coating, and curtain coating.

[0084] The gas barrier coating layer 22 described above can maintain excellent gas barrier properties even after heat sterilization. Therefore, when a laminate in which a sealant layer is provided on the gas barrier film 100 is used as a packaging material for heat sterilization, the packaging material has excellent adhesion even after heat sterilization. In addition, the gas barrier coating layer 22 described above is preferable because it has sufficient transparency, flex resistance, and stretch resistance, and there is no risk of generating harmful substances such as dioxins.

[0085] The thickness of the gas barrier coating layer 22 may be 0.05 μm or more, or 0.1 μm or more, from the viewpoint of excellent gas barrier properties. The thickness of the gas barrier coating layer 22 may be 1 μm or less, or 0.5 μm or less, from the viewpoint of easily forming a uniform coated surface, reducing the load due to drying, and production costs. From these viewpoints, the thickness of the gas barrier coating layer 22 may be 0.05 to 1 μm, or 0.1 to 0.5 μm.

[0086] (Undercoat layer (anchor coat layer)) From the viewpoint of improving the adhesion between the multilayer polyethylene film 10 and the gas barrier layer 20, an undercoat layer (anchor coat layer, not shown) may be provided between the multilayer polyethylene film 10 and the gas barrier layer 20. By providing an undercoat layer (anchor coat layer), the gas barrier properties and adhesion can be more easily maintained even after heat sterilization treatment.

[0087] The undercoat layer (anchor coat layer) can be formed from a coating liquid containing a resin such as an acrylic resin, an epoxy resin, an acrylic urethane resin, a polyester polyurethane resin, a polyether polyurethane resin, etc. From the viewpoints of heat resistance and interlayer adhesive strength, the undercoat layer (anchor coat layer) may be formed from a coating liquid containing an acrylic urethane resin or a polyester polyurethane resin.

[0088] The method for applying the coating liquid for forming the undercoat layer (anchor coat layer) may be a known coating method, and examples thereof include an immersion method (dipping method), and methods using a spray, a coater, a printer, a brush, etc. In addition, examples of the types of coaters and printers used in these methods and the coating methods thereof include gravure coaters such as direct gravure, reverse gravure, kiss reverse gravure, and offset gravure, reverse roll coaters, microgravure coaters, coaters combined with a chamber doctor, air knife coaters, dip coaters, bar coaters, comma coaters, and die coaters.

[0089] The method for drying the undercoat layer (anchor coat layer) is not particularly limited, but examples thereof include natural drying, drying in an oven set at a predetermined temperature, and using a dryer attached to a coater, such as an arch dryer, floating dryer, drum dryer, infrared dryer, etc. Drying conditions can be appropriately selected depending on the drying method, and for example, in a method of drying in an oven, drying may be performed at 60 to 100°C for about 1 second to 2 minutes.

[0090] The thickness of the undercoat layer (anchor coat layer) may be 0.01 μm or more, 0.03 μm or more, or 0.05 μm or more, from the viewpoint of easily obtaining sufficient adhesion between layers. The thickness of the undercoat layer (anchor coat layer) may be 5 μm or less, 3 μm or less, or 2 μm or less, from the viewpoint of excellent gas barrier properties. From these viewpoints, the thickness of the undercoat layer (anchor coat layer) may be 0.01 to 5 μm, 0.03 to 3 μm, or 0.05 to 2 μm.

[0091] <Laminate> The gas barrier film 100 can be used as a material for constituting a laminate. Fig. 4 is a cross-sectional view of a laminate according to one embodiment of the present invention. The laminate 400 comprises the gas barrier film 100, an adhesive layer 130, and a sealant layer 140. It can also be said that the laminate 400 comprises a multilayer polyethylene film 10, an inorganic oxide layer 21, a gas barrier coating layer 22, the adhesive layer 130, and the sealant layer 140. That is, another embodiment of the present invention is a laminate comprising the above-mentioned gas barrier film, an adhesive layer disposed on the surface of the gas barrier layer opposite the multilayer polyethylene film, and a sealant layer disposed via the adhesive layer.

[0092] The content of polyethylene resin in the laminate 400 may be 90% by mass or more, or 95% by mass or more, based on the total amount of the laminate 400, from the viewpoint of realizing mono-materialization and excellent recyclability.

[0093] The thickness of the laminate 400 is not particularly limited and can be determined appropriately depending on the cost and application. The thickness of the laminate 400 may be 50 μm or more, 60 μm or more, or 70 μm or more, or may be 300 μm or less, 250 μm or less, or 200 μm or less. From these viewpoints, the thickness of the laminate 400 may be 50 to 300 μm, 60 to 250 μm, or 70 to 200 μm.

[0094] (Adhesive Layer) The adhesive layer 130 is a layer containing at least one type of adhesive, and is provided between the gas barrier layer 20 and the sealant layer 140 to bond them together. The adhesive layer 130 can be formed using a known adhesive. The adhesive may be, for example, a dry lamination adhesive. The dry lamination adhesive is not particularly limited, and examples thereof include ester-based adhesives, ether-based adhesives, and urethane-based adhesives. These adhesives may be one-component curing types or two-component curing types.

[0095] From the viewpoint of excellent gas barrier properties, the adhesive layer 130 may be formed using a gas barrier adhesive. Furthermore, even if minute cracks occur in the inorganic oxide layer 21 or the gas barrier coating layer 22, the gas barrier adhesive can fill in the cracks and fill in the gaps, thereby preventing a decrease in the gas barrier properties of the laminate 400.

[0096] A gas barrier adhesive is an adhesive that can 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 "Maxieve" manufactured by Mitsubishi Gas Chemical Company, Inc. and "Paslim" manufactured by DIC Corporation.

[0097] The oxygen permeability of the gas barrier adhesive is, for example, 150 cc / m ２ ·day·atm or less, and 100cc / m ２ ·day·atm or less is more preferable, and 80cc / m ２ It is more preferable that the viscosity is 50 cc / m or less. ２When the oxygen permeability is within the above range, the gas barrier properties of the laminate 400 can be sufficiently improved.

[0098] The adhesive layer 130 can be formed by applying an adhesive by, for example, bar coating, dipping, roll coating, gravure coating, reverse coating, air knife coating, comma coating, die coating, screen printing, spray coating, gravure offset, or the like to form a coating film, and then drying and curing the coating film. From the viewpoint of suppressing cracking of 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 applying an adhesive directly on the surface of the inorganic oxide layer 21 or the gas barrier coating layer 22, followed by drying and curing.

[0099] The temperature at which the coating film is dried may be, for example, 30 to 200° C., and preferably 50 to 180° C. The temperature at which the coating film is cured may be, for example, 20 to 70° C., and preferably 30 to 60° C. By setting the drying and curing temperatures within the above ranges, it is possible to suppress the occurrence of cracks in the inorganic oxide layer 21 and the adhesive layer 130, and it is possible to sufficiently improve the gas barrier properties of the laminate 400.

[0100] 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, cushioning properties that absorb external impacts can be obtained, making it easier to prevent the inorganic oxide layer 21 from cracking and further improving the gas barrier properties of the laminate 400. When the thickness of the adhesive layer is 20 μm or less, the flexibility of the laminate 400 tends to be sufficiently maintained.

[0101] The thickness of the adhesive layer 130 is preferably 50 times or more the thickness of the inorganic oxide layer 21. By making the thickness of the adhesive layer 130 50 times or more the thickness of the inorganic oxide layer 21, cushioning properties that absorb external impacts can be obtained, making it easier to prevent the inorganic oxide layer 21 from cracking 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 making the thickness of the adhesive layer 130 300 times or less the thickness of the inorganic oxide layer 21, the flexibility and processability of the laminate 400 are excellent and costs can be reduced. From these perspectives, the thickness of the adhesive layer 130 may be 50 to 300 times the thickness of the inorganic oxide layer 21.

[0102] (Sealant Layer) The sealant layer 140 is a layer made of, for example, a polyethylene resin. The sealant layer 140 is a layer that is bonded by heat sealing when the laminate 400 is used to form a packaging material such as a packaging bag. The polyethylene resin that makes up the sealant layer 140 may be a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), or a very low-density polyethylene resin (VLDPE) from the viewpoint of excellent heat sealing properties. From the viewpoint of environmental impact, the sealant layer 140 may be made of a biomass-derived polyethylene resin or a recycled polyethylene resin. The sealant layer 140 may be made of, for example, a non-oriented polyethylene film.

[0103] Low density polyethylene has a density of 0.900 g / cm ３ 0.925g / cm or more ３ As the linear low density polyethylene, polyethylene having a density of 0.900 g / cm3 or less can be used. ３ 0.925g / cm or more ３ As the ultra-low density polyethylene, polyethylene having a density of 0.900 g / cm3 or less can be used. ３ Less than 100% polyethylene can be used.

[0104] The sealant layer 140 may contain a resin other than polyethylene resin. Examples of resins other than polyethylene resin include olefin-based resins such as ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-(meth)acrylic acid copolymer, homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-α-olefin copolymer, and polybutene. The sealant layer 140 may contain additives such as antioxidants, lubricants, antiblocking agents, and antistatic agents.

[0105] The thickness of the sealant layer 140 may be, for example, 20 μm or more, 40 μm or more, or 50 μm or more. A thickness of 20 μm or more of the sealant layer 140 can achieve sufficient heat seal strength. The thickness of the sealant layer 140 may be, for example, 200 μm or less, 170 μm or less, or 150 μm or less. A thickness of 200 μm or less of the sealant layer 140 can provide excellent processability. From these viewpoints, the thickness of the sealant layer 140 may be 20 to 200 μm, 40 to 170 μm, or 50 to 150 μm.

[0106] 5, 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 a back layer 53, and the intermediate layer 52 has resin layers 52a, 52b, and 52c. In this case, the 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 a cross section of the multilayer polyethylene film 50 with an electron microscope or an optical microscope.

[0107] As shown in Figure 6, when the multilayer polyethylene film has layers other than the three layers of a surface layer, an intermediate layer, and a back layer, the multilayer polyethylene film 60 in the laminate 600 has a surface layer 61, an intermediate layer 62, and a back layer 63, a resin layer 64 between the surface layer 61 and the intermediate layer 62, and a resin layer 65 between the intermediate layer 62 and the back layer 63. The resin layer 64 is, for example, a layer containing a polyethylene resin and having a different composition from the surface layer 61 and the intermediate layer 62. The resin layer 65 is, for example, a layer containing a polyethylene resin and having a different composition from the intermediate layer 62 and the back layer 63. The multilayer polyethylene film may have, for example, three layers, five layers, seven layers, or more layers.

[0108] As shown in FIG. 7 , the laminate 700 may include a second adhesive layer 170 on the surface of the multilayer polyethylene film 10 opposite the sealant layer 140, and a substrate 180 disposed via the second adhesive layer 170.

[0109] (Second Adhesive Layer) The second adhesive layer 170 is a layer containing at least one type of adhesive, and is provided between the multilayer polyethylene film 10 and the substrate 180 to bond them together. The adhesive used for the second adhesive layer 170 may be a one-component curing adhesive or a two-component curing adhesive. Examples of the adhesive include a urethane-based adhesive, an epoxy-based adhesive, and a silicone-based adhesive. The second adhesive layer may be the same adhesive used to form the adhesive layer 130 described above.

[0110] The thickness of the second adhesive layer 170 may be, for example, 0.5 μm or more, 0.8 μm or more, or 1 μm or more, and may be 6 μm or less, 5 μm or less, or 4.5 μm or less. From these viewpoints, the thickness of the second adhesive layer 170 may be 0.5 to 6 μm, 0.8 to 5 μm, or 1 to 4.5 μm.

[0111] (Substrate) The substrate 180 is the outermost layer of the laminate 700 and is a layer provided for the purpose of protecting the laminate 700. The substrate 180 may be, for example, a layer containing a polyethylene resin, or may be a polyethylene film. In addition to the polyethylene resin, the substrate 180 may also contain additives such as an antioxidant, a lubricant, an antiblocking agent, and an antistatic agent.

[0112] The difference in heat fusion temperature between the substrate 180 and the sealant layer 140 may be 10° C. or more. When the difference in heat fusion temperature between the substrate 180 and the sealant layer 140 is 10° C. or more, a packaging bag can be easily formed when the laminate 700 is used as a packaging material to produce the packaging bag.

[0113] The thickness of the substrate 180 may be, for example, 10 μm or more, 20 μm or more, or 30 μm or more, or 200 μm or less, 150 μm or less, or 100 μm or less. From these viewpoints, the thickness of the substrate 180 may be 10 to 200 μm, 20 to 150 μm, or 30 to 100 μm.

[0114] The laminate 400 may further include a printed layer (not shown). The printed layer is provided at a position visible from the outside of the laminate 400 for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. The printed layer may be provided, for example, on the surface of the inorganic oxide layer 21, the surface of the gas barrier coating layer 22, or the surface of the sealant layer 140 of the laminate 400.

[0115] The method for forming the printed layer is not particularly limited, and known printing methods and printing inks can be applied. The printing method and printing ink are appropriately selected in consideration of, for example, printability for each layer of the laminate 400, design such as color tone, adhesion, safety as a food container, and the like.

[0116] 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 viewpoints of productivity and high definition of the image.

[0117] In order to improve the adhesion of the printing layer, the surface of the layer forming the printing layer may be subjected to pretreatment such as corona treatment, plasma treatment, or flame treatment, or a coating layer such as an easy-adhesion layer may be provided.

[0118] <Packaging Materials> The gas barrier films 100, 200, 300 and the laminates 400, 500, 600, 700 can each be used as packaging materials for forming packaging bags. Specifically, the gas barrier films 100, 200, 300 are provided with a sealant layer to form a laminate, which can then be used as packaging materials for flat bags, three-sided bags, palm-shaped bags, gusseted bags, standing pouches, pouches with spouts, pouches with beaks, and the like.

[0119] The gas barrier films 100, 200, 300 and the laminates 400, 500, 600, 700 can be used as films for electronic devices, solar cells, fuel cells, substrate films, etc. in addition to packaging materials.

[0120] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0121] <Polyethylene resin> Resin A: Density 0.950 g / cm ３ , MFR1.1g / 10min. ・Resin B: Density 0.958g / cm ３ , MFR1g / 10min. ・Resin C: Density 0.949g / cm ３ , MFR0.3g / 10min. ・Resin D: Density 0.960g / cm ３ , MFR1g / 10min. ・Resin E: Density 0.944g / cm ３ , MFR0.45g / 10min. ・Resin F: Density 0.926g / cm ３ , MFR0.85g / 10min. ・Resin G: Density 0.941g / cm ３ , MFR1.3g / 10min. ・Resin H: Density 0.962g / cm ３ , MFR0.85g / 10min. ・Resin I: Density 0.920g / cm ３ , MFR0.85g / 10min.

[0122] <Preparation of Polyethylene Films> (Examples 1 to 26A, Comparative Examples 1 to 10A) The resins shown in Tables 1 to 6 constituting the surface layer, intermediate layer, and back layer were each charged into an extruder and melt-kneaded at 190°C. After that, the polyethylene resin was introduced through a three-layer die, and multilayer polyethylene films were produced by an air-cooled inflation method. The overall thickness of the multilayer polyethylene films produced in each Example and Comparative Example was within the range of 25 to 40 μm. The polyethylene resin content in the multilayer polyethylene films produced in each Example and Comparative Example was 90 mass% or more.

[0123] Example 27A The resins shown in Table 6 constituting Layers 1 to 5 were each charged into an extruder and melt-kneaded at 190°C. Then, polyethylene resin was introduced through a five-layer die, and a multilayer polyethylene film was produced by air-cooling inflation extrusion, in which Layers 1 and 2 were surface layers, Layer 3 was an intermediate layer, and Layers 4 and 5 were back layers. The polyethylene resin content in the produced multilayer polyethylene film was 90% by mass or more.

[0124] Example 28A The resins shown in Table 6 constituting Layers 1 to 7 were each charged into an extruder and melt-kneaded at 190°C. Then, polyethylene resin was introduced through a 7-layer die, and a multilayer polyethylene film was produced by air-cooling inflation extrusion, in which Layers 1 and 2 were surface layers, Layers 3 to 5 were intermediate layers, and Layers 6 and 7 were back layers. The polyethylene resin content in the produced multilayer polyethylene film was 90% by mass or more.

[0125] Example 29A The resins shown in Table 6 constituting Layers 1 to 7 were each charged into an extruder and melt-kneaded at 190°C. Then, polyethylene resin was introduced through a 7-layer die, and a multilayer polyethylene film was produced by air-cooling inflation extrusion, in which Layer 1 was the surface layer, Layers 2 to 6 were the middle layers, and Layer 7 was the back layer. The polyethylene resin content in the produced multilayer polyethylene film was 90% by mass or more.

[0126] Example 30A The resins shown in Table 6 constituting Layers 1 to 7 were each charged into an extruder and melt-kneaded at 190°C. Then, polyethylene resin was introduced through a 7-layer die, and a multilayer polyethylene film was produced by air-cooling inflation extrusion, in which Layers 1 and 2 were surface layers, Layers 3 to 5 were intermediate layers, and Layers 6 and 7 were back layers. The polyethylene resin content in the produced multilayer polyethylene film was 90% by mass or more.

[0127] <Probe Drop Temperature> The probe drop temperature (softening point) of each layer of the multilayer polyethylene film was measured using an atomic force microscope equipped with a nanothermal microscope consisting of a cantilever (probe) with a heating mechanism. First, the multilayer polyethylene film was embedded in a visible light curing resin to obtain a measurement sample. Next, in a -140°C environment, the measurement sample was cross-sectioned in a direction parallel to the TD direction using a diamond knife of a cryo-ultramicrotome. After measuring the thickness of each layer from the cross section of the multilayer polyethylene film, the probe drop temperature of the multilayer polyethylene film was measured as follows.

[0128] The atomic force microscope used was an Oxford Instruments MPF-3D-SA, the nanothermal microscope equipped with the atomic force microscope was an Oxford Instruments Ztherm, and the cantilever was an Anasys Instruments AN2-200 (trade name). After measuring the shape of the sample with a 10 μm field of view in AC mode, the cantilever was separated from the sample by 5 to 10 μm in the Z direction (normal to the sample surface). In this state, the detrend correction function of the device was performed in contact mode with a maximum applied voltage of 6 V and a heating rate of 0.5 V / s to correct for changes in the cantilever deflection due to applied voltage. Then, in contact mode, the cantilever was brought into contact with the sample so that the change in deflection before and after contact between the cantilever and the sample was 0.2 V. While maintaining a constant deflection value, a voltage was applied to the cantilever at a maximum applied voltage of 6 V and a heating rate of 0.5 V / s to heat the sample. The displacement of the cantilever in the Z direction at this time was recorded, and the measurement was stopped when the Z displacement changed from rising to falling and fell 50 nm from the change point. If the Z displacement reached the maximum applied voltage without falling 50 nm from the change point, the maximum applied voltage during detrend correction and measurement was increased by 0.5 V and the measurement was repeated. The applied voltage at which the recorded Z displacement was maximized was converted into temperature. This measurement was performed at 10 points within a 10 μm field of view, and the average of the 10 points was taken as the probe drop temperature. The probe drop temperatures for each layer of the multilayer polyethylene film are shown in Tables 1 to 6.

[0129] A calibration curve was used to convert the applied voltage to temperature. Polycaprolactone (melting point 60°C), low-density polyethylene (melting point 112°C), polypropylene (melting point 166°C), and polyethylene terephthalate (melting point 255°C) were measured as calibration samples, and a calibration curve of applied voltage vs. temperature was created. Here, the melting point was the melting peak temperature measured using a differential scanning calorimeter (DSC) at a heating rate of 5°C / min. The measurement method for the calibration samples was the same as that for the sample measurements, but the maximum applied voltage during Detrend correction and measurement was set to 3.5 V if the sample was polycaprolactone, 5.5 V if the sample was low-density polyethylene, 6.5 V if the sample was polypropylene, and 7.8 V if the sample was polyethylene terephthalate. The relationship between the applied voltage at which the Z displacement was maximized when measuring each calibration sample and the melting point was approximated by a cubic function using the least squares method to create a calibration curve.

[0130] <Preparation of Gas Barrier Film> An undercoat layer, an inorganic oxide layer, and a gas barrier coating layer were formed on the outer surface of the multilayer polyethylene film prepared in each Example and Comparative Example, so as to have the configurations shown in Tables 1 to 6, and gas barrier films were prepared by laminating the layers in the following order: multilayer polyethylene film / undercoat layer / inorganic oxide layer / gas barrier coating layer. The undercoat layer, adhesive layer, inorganic oxide layer, and gas barrier coating layer were each formed by the methods described below. The polyethylene resin content in the gas barrier films prepared in each Example and Comparative Example was 90% by mass or more.

[0131] <Undercoat Layer> An acrylic polyol (Acrydic CL-1000, manufactured by DIC Corporation) and an isocyanate compound (TDI-type curing agent Coronate 2030, manufactured by Tosoh Corporation) were mixed at a solids mass ratio of 6:4. Ethyl acetate was then added to dilute the mixture to a solids content of 2% by mass, yielding a coating liquid for forming an undercoat layer. One side of the outer layer side of the multilayer polyethylene film of each Example and Comparative Example was subjected to a corona treatment, and then the coating liquid for forming an undercoat layer was applied to the corona-treated surface using a gravure printing machine to form a coating film, which was then dried in an oven at 60°C for 10 seconds to form an undercoat layer with a thickness of 0.1 μm.

[0132] <Inorganic Oxide Layer> When the inorganic oxide was silicon oxide, a transparent inorganic oxide layer of silicon oxide having a thickness of 30 nm was formed using a vacuum deposition apparatus with electron beam heating. When the inorganic oxide was aluminum oxide, a transparent inorganic oxide layer of aluminum oxide having a thickness of 15 nm was formed using a vacuum deposition apparatus with electron beam heating.

[0133] <Gas Barrier Coating Layer> (Organic-Inorganic Composite Coating) An aqueous solution of polyvinyl alcohol resin (PVA, Poval PVA-105 manufactured by Kuraray Co., Ltd., saponification degree 98-99%, polymerization degree 500), tetraethoxysilane (TEOS), and γ-glycidoxypropyltrimethoxysilane (GPTMS, KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd.) was hydrolyzed with 0.02 mol / L hydrochloric acid to prepare an aqueous solution. Next, the three aqueous solutions were mixed so that the mass ratio of PVA:TEOS:GPTMS was 40:50:10, which was the mass ratio of the PVA, TEOS, and GPTMS before hydrolysis. Next, the mixed aqueous solution was diluted with isopropyl alcohol so that the mass ratio of water to isopropyl alcohol was 90:10, to obtain a coating liquid for forming an organic-inorganic composite coating (solid content: 5% by mass). A gravure printing press was used to apply the organic-inorganic composite coating mixture described below to the inorganic oxide layer to form a coating film, which was then dried in an oven at 60°C for 10 seconds to form a gas barrier coating layer consisting of an organic-inorganic composite coating with a thickness of 0.3 μm. (Polycarboxylic acid polyvalent metal salt coating) 20 parts by weight of an aqueous polyacrylic acid solution (Aron A-10H, manufactured by Toagosei Co., Ltd., number average molecular weight 200,000, solids concentration 25% by weight) was diluted with 58.9 parts by weight of distilled water. Next, 0.44 parts by weight of aminopropyltrimethoxysilane (APTMS, manufactured by Aldrich) was added and stirred to obtain a uniform coating mixture A composed primarily of a polycarboxylic acid polymer. 100 parts by mass of a zinc oxide fine particle aqueous dispersion (ZE143, manufactured by Sumitomo Osaka Cement Co., Ltd.) and 2 parts by mass of a curing agent (Liofol HAERTER UR 5889-21, manufactured by Henkel) were mixed to obtain a B coating mixture containing a polyvalent metal compound as a main component. The A coating mixture described below was applied onto the inorganic oxide layer using a gravure printer to form a coating, and the coating was dried in an oven at 60°C for 10 seconds to form a 0.2 μm thick A coating. Furthermore, the B coating mixture was applied using a gravure printer to form a coating, and the coating was dried in an oven at 60°C for 10 seconds to form a 0.2 μm thick B coating. This resulted in the formation of an oxygen barrier coating consisting of a polyvalent metal salt of polycarboxylic acid.

[0134] <Adhesive Layer> (Urethane-Based Adhesive) A urethane-based adhesive was obtained by mixing 100 parts by mass of Takelac A525 (manufactured by Mitsui Chemicals), 11 parts by mass of Takenate A52 (manufactured by Mitsui Chemicals), and 84 parts by mass of ethyl acetate.

[0135] (Gas barrier adhesive) A gas barrier adhesive was obtained by mixing 23 parts by mass of a solvent prepared by mixing ethyl acetate and methanol in a mass ratio of 1:1 with 16 parts by mass of Maxieve C93T (manufactured by Mitsubishi Gas Chemical Company, Inc.) and 5 parts by mass of Maxieve M-100 (manufactured by Mitsubishi Gas Chemical Company, Inc.).

[0136] [Evaluation] <Processing Stability> After forming the gas barrier coating layer (after forming the inorganic oxide layer in the examples and comparative examples in which the gas barrier coating layer was not formed), the appearance of the gas barrier film was visually inspected, and the processing stability was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 1 to 6. A: No wrinkles were observed on the appearance of the gas barrier film. B: Slight wrinkles were observed on the appearance of the gas barrier film. C: Many wrinkles were observed on the appearance of the gas barrier film.

[0137] <Gas Barrier Properties> The gas barrier films produced in each Example and Comparative Example were dry-laminated with the above-mentioned urethane adhesive or the above-mentioned gas barrier adhesive using a multicoater TM-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 Tohcello, TUX MC-S, thickness 60 μm) was bonded to the adhesive layer to produce a laminate in which gas barrier film / adhesive / LLDPE were laminated in this order. The oxygen permeability (cm ) of the produced laminate was measured using an oxygen permeability measuring device (trade name OXTRAN-2 / 20, manufactured by MOCON) in an atmosphere of 30°C and 70% RH. ３ / (m ２ The gas barrier properties were evaluated based on the following criteria. The evaluation results are shown in Tables 1 to 6. A+: Oxygen permeability is 2 cm or less. ３ / (m ２ A: Oxygen permeability is less than 2 cm ３ / (m ２・day・atm) or more, 5cm ３ / (m ２ A-: Oxygen permeability is less than 5 cm ３ / (m ２ ・day・atm) or more, 10cm ３ / (m ２ B+: Oxygen permeability is less than 10 cm ３ / (m ２ ・day・atm) or more, 20cm ３ / (m ２ B: Oxygen permeability is less than 20 cm ３ / (m ２ ・day・atm) or more, 50cm ３ / (m ２ B-: Oxygen permeability is less than 50 cm ３ / (m ２ ・day・atm) or more.

[0138] <Gas Barrier Properties After Boiling Treatment> The laminate was cut into two pieces measuring 15 cm x 10 cm, and the two cut-out laminates were stacked with the sealant layers facing each other, and three sides were impulse sealed to form a pouch. 150 mL of water was placed in the pouch as the contents, and the remaining side was impulse sealed to produce a pouch (packaging bag) with four sides sealed. The produced pouch was boiled at 95°C for 30 minutes in a boiling treatment device. After boiling, the pouch was opened to remove the contents and thoroughly dried, and then the oxygen permeability was measured using the method described above to evaluate the gas barrier properties. The evaluation results are shown in Tables 1 to 6.

[0139] <Molecular orientation degree> Using a microwave molecular orientation meter (Oji Keisokuki Co., Ltd., product name MOA-5012A), the degree of molecular orientation of molecular chains in the plane of the multilayer polyethylene film was measured by rotating the multilayer polyethylene film in a microwave polarized electric field. The absolute value of the degree of molecular orientation of the multilayer polyethylene films produced in each Example and Comparative Example was all less than 1.07. Furthermore, when the multilayer polyethylene film was stretched in the MD direction and the degree of molecular orientation of the stretched multilayer polyethylene film was measured, the absolute value of the degree of molecular orientation was 1.30.

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146] <Preparation of Polyethylene Films> (Examples 1 to 20B, Comparative Examples 1 to 8B) The resins shown in Tables 7 to 11 constituting the surface layer, intermediate layer, and back layer were each charged into an extruder and melt-kneaded at 190°C. The polyethylene resin was then introduced through a three-layer die, and multilayer polyethylene films were prepared by air-cooling inflation. The overall thickness of the multilayer polyethylene films prepared in each Example and Comparative Example was within the range of 25 to 40 μm. The polyethylene resin content of the multilayer polyethylene films prepared in each Example and Comparative Example was 90 mass% or more.

[0147] (Example 21B) The resins shown in Table 12 constituting Layers 1 to 5 were each charged into an extruder and melt-kneaded at 190°C. After that, polyethylene resin was introduced through a five-layer die, and a multilayer polyethylene film was produced by air-cooling inflation extrusion, in which Layers 1 and 2 were surface layers, Layer 3 was an intermediate layer, and Layers 4 and 5 were back layers. The polyethylene resin content of each of the produced multilayer polyethylene films was 90% by mass or more.

[0148] (Example 22B) The resins shown in Table 12 constituting Layers 1 to 7 were each charged into an extruder and melt-kneaded at 190°C. After that, polyethylene resin was introduced through a 7-layer die, and multilayer polyethylene films were produced by air-cooling inflation extrusion, in which Layers 1 and 2 were surface layers, Layers 3 to 5 were intermediate layers, and Layers 6 and 7 were back layers. The polyethylene resin content of each of the produced multilayer polyethylene films was 90% by mass or more.

[0149] (Example 23B) The resins shown in Table 12 constituting Layers 1 to 7 were each charged into an extruder and melt-kneaded at 190°C. After that, polyethylene resin was introduced through a 7-layer die, and a multilayer polyethylene film was produced by air-cooling inflation extrusion, in which Layer 1 was the surface layer, Layers 2 to 6 were the middle layers, and Layer 7 was the back layer. The polyethylene resin content of each of the produced multilayer polyethylene films was 90% by mass or more.

[0150] (Example 24B) The resins shown in Table 12 constituting Layers 1 to 7 were each charged into an extruder and melt-kneaded at 190°C. Then, polyethylene resin was introduced through a 7-layer die, and multilayer polyethylene films were produced by air-cooling inflation extrusion, in which Layers 1 and 2 were surface layers, Layers 3 to 5 were intermediate layers, and Layers 6 and 7 were back layers. The polyethylene resin content of each of the produced multilayer polyethylene films was 90% by mass or more.

[0151] <Preparation of Laminates> The surface of the outer layer side of the multilayer polyethylene films prepared in Examples 1 to 20B and Comparative Examples 1 to 8B was subjected to a corona treatment. Next, an anchor coat layer, an inorganic oxide layer, a gas barrier coating layer, an adhesive layer, and a sealant layer were formed on the surface of the multilayer polyethylene film by the method described below so as to have the configurations shown in Tables 7 to 11. The multilayer polyethylene film / anchor coat layer / inorganic oxide layer / gas barrier coating layer / adhesive layer / sealant layer were laminated in this order, and then aged at 40°C for 4 days to obtain a laminate. The polyethylene resin content in the laminates prepared in each Example and Comparative Example was 90% by mass or more.

[0152] The surface of the back layer side of the multilayer polyethylene films produced in Examples 21 to 24B was subjected to a corona treatment. Next, an anchor coat layer, an inorganic oxide layer, a gas barrier coating layer, an adhesive layer, and a sealant layer were formed on the surface of the multilayer polyethylene film by the method described below, so as to have the configurations shown in Table 6. Next, "LA7735" (trade name, polyisocyanate component) manufactured by Henkel Japan Co., Ltd. and "LA6159" (trade name, polyol component) manufactured by Henkel Japan Co., Ltd. were mixed in a two-component mixing and supplying device at a mass ratio of 100:45 to obtain a two-component curing urethane adhesive. The urethane adhesive was applied in a solventless adhesive laminator at a processing speed of 100 m / min, with doctor roll and coating roll temperatures of 60°C, to a coating amount of 2.1 g / m. ２ The adhesive layer was coated on the surface opposite the sealant layer of the multilayer polyethylene film so that the adhesive layer was 100% by mass. Next, unstretched polyethylene (HDPE film, product name: HS31, manufactured by Tama Poly) was attached to the coated adhesive layer, and aged at 40°C for 1 day to obtain a laminate. The polyethylene resin content in the laminates produced in each Example and Comparative Example was 90% by mass or more.

[0153] <Anchor Coat Layer> Acrylic polyol and tolylene diisocyanate were mixed so that the number of NCO groups in tolylene diisocyanate was equal to the number of OH groups in the acrylic polyol, and the mixture was diluted with ethyl acetate to a total solids content (total amount of acrylic polyol and tolylene diisocyanate) of 5% by mass. β-(3,4-epoxycyclohexyl)trimethoxysilane was added to the diluted mixture in an amount of 5 parts by mass per 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and the mixture was mixed to prepare a composition for forming an anchor coat layer (anchor coating agent). The anchor coat layer was formed by applying the composition for forming an anchor coat layer to the surface of a corona-treated multilayer polyethylene film by gravure coating and drying. The coating amount of the polyester resin in the anchor coat layer was 0.1 g / m ２ It was.

[0154] <Inorganic Oxide Layer> When the inorganic oxide was silicon oxide, a transparent inorganic oxide layer of silicon oxide having a thickness of 30 nm was formed using a vacuum deposition apparatus with electron beam heating. When the inorganic oxide was aluminum oxide, a transparent inorganic oxide layer of aluminum oxide having a thickness of 15 nm was formed using a vacuum deposition apparatus with electron beam heating.

[0155] <Gas barrier coating layer> A gas barrier coating agent was prepared by mixing the following liquids A, B, and C in a mass ratio of 70 / 20 / 10, respectively. The gas barrier coating agent was applied by gravure coating and dried to form a gas barrier coating layer with a thickness of 0.3 μm. Liquid A: tetraethoxysilane (Si(OC ２ H ５ ) ４ 17.9 g of SiO 2 , 10 g of methanol, and 72.1 g of 0.1N hydrochloric acid were added and stirred for 30 minutes to obtain a hydrolyzed solid content of 5% by mass (SiO ２ Solution B: A mixed solution of 5% by mass of polyvinyl alcohol, water, and methanol in a mass ratio of 95:5. Solution C: A hydrolyzed solution of 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate diluted with a mixed solution of water and isopropyl alcohol (mass ratio of water:isopropyl alcohol 1:1) to a solids content of 5% by mass.

[0156] <Adhesive Layer> Either of the following urethane adhesives or gas barrier adhesives was applied by dry lamination and dried to form a 3 μm thick adhesive layer. (Urethane Adhesive) A urethane adhesive was obtained by mixing 100 parts by mass of Takelac A525 (manufactured by Mitsui Chemicals, Inc.), 11 parts by mass of Takenate A52 (manufactured by Mitsui Chemicals, Inc.), and 84 parts by mass of ethyl acetate.

[0157] (Gas barrier adhesive) A gas barrier adhesive was obtained by mixing 23 parts by mass of a solvent prepared by mixing ethyl acetate and methanol in a mass ratio of 1:1 with 16 parts by mass of Maxieve C93T (manufactured by Mitsubishi Gas Chemical Company, Inc.) and 5 parts by mass of Maxieve M-100 (manufactured by Mitsubishi Gas Chemical Company, Inc.).

[0158] <Sealant Layer> A 60 μm thick unstretched film made of linear low density polyethylene resin (LLDPE) (manufactured by Mitsui Chemicals Tocello, Inc., trade name: TUX-MCS) was used as the sealant layer.

[0159] [Evaluation] <Processing stability> The multilayer polyethylene film after the formation of the gas barrier layer was visually inspected and the processing stability was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 7 to 12. A: No wrinkles were observed in the appearance or rolled shape of the multilayer polyethylene film. B: Slight wrinkles were observed in either the appearance or rolled shape of the multilayer polyethylene film. C: Many wrinkles were observed in either the appearance or rolled shape of the multilayer polyethylene film.

[0160] <Gas Barrier Properties> The laminates produced in each of the Examples and Comparative Examples were measured for oxygen permeability (cm) in an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name OXTRAN-2 / 20, manufactured by MOCON Corporation). ３ / (m ２ The gas barrier properties were evaluated based on the following criteria. The evaluation results are shown in Tables 7 to 12. A+: Oxygen permeability is 2 cm or less. ３ / (m ２ A: Oxygen permeability is less than 2 cm ３ / (m ２ ・day・atm) or more, 5cm ３ / (m ２ A-: Oxygen permeability is less than 5 cm ３ / (m ２ ・day・atm) or more, 10cm ３ / (m ２ B+: Oxygen permeability is less than 10 cm ３ / (m ２ ・day・atm) or more, 20cm ３ / (m ２ B: Oxygen permeability is less than 20 cm ３ / (m ２ ・day・atm) or more, 50cm ３ / (m ２ B-: Oxygen permeability is less than 50 cm ３ / (m ２ ・day・atm) or more, 100cm ３ / (m ２ C: Oxygen permeability is less than 100 cm ３ / (m ２ ・day・atm) or more.

[0161] <Gas Barrier Properties After Boiling Treatment> The laminates prepared in each Example and Comparative Example were cut into two pieces measuring 15 cm x 10 cm, and the two cut-out laminates were stacked with their sealant layers facing each other, and three sides were impulse sealed to form a pouch. 150 ml of water was placed in the pouch as the contents, and the remaining side was impulse sealed to produce a pouch (packaging bag) with four sides sealed. The produced pouches were boiled at 95°C for 30 minutes using a boiling treatment device. After the boiling treatment, the pouches were opened to remove the contents and thoroughly dried. The oxygen permeability of the boiled pouches was measured using the method described above to evaluate their gas barrier properties. The evaluation results are shown in Tables 7 to 12.

[0162] <Gas Barrier Property After Bending> The laminates prepared in each Example and Comparative Example were cut into a size of 295 mm length x 210 mm width to prepare evaluation samples. The evaluation samples were formed into cylindrical shapes with a diameter of 87.5 mm x 210 mm and attached to the fixed head of a Gelbo Flex Tester (manufactured by Tester Sangyo Co., Ltd., product name: BE-1005). Both ends of the evaluation sample were held with an initial gripping distance of 175 mm, and a 440° twist was applied with a stroke of 87.5 mm. This operation was repeated 10 times at a speed of 40 times / min to bend the evaluation sample. Next, the oxygen permeability of the evaluation sample after bending was measured using the method described above, and the gas barrier property was evaluated. The evaluation results are shown in Tables 7 to 12.

[0163] <Adhesion> A 15 mm wide strip test piece was cut out from the laminate produced in each Example and Comparative Example, and the laminate strength between the multilayer polyethylene film and the heat seal layer was measured using an Orientec Tensilon universal testing machine RTC-1250 in accordance with JIS Z1707. The laminate strength was measured using a T-peel test under normal conditions. The evaluation results are shown in Tables 7 to 12.

[0164] <Adhesion after Boiling Treatment> The laminates prepared in each Example and Comparative Example were cut into two pieces measuring 15 cm x 10 cm, and the two cut-out laminates were stacked with the sealant layers facing each other and impulse-sealed on three sides to form a pouch. 200 ml of water was placed in the pouch as the contents, and the remaining side was impulse-sealed to produce a pouch (packaging bag) with four sealed sides. The prepared pouches were subjected to a boiling treatment at 95°C for 30 minutes using a boiling treatment device. After the boiling treatment, the pouches were opened, the contents were removed, and the pouches were thoroughly dried. After that, 15 mm-wide strip-shaped test pieces were cut from the pouches. The laminate strength between the multilayer polyethylene film and the heat-seal layer was measured in accordance with JIS Z1707 using an Orientec Tensilon universal testing machine RTC-1250. The laminate strength was measured using a T-peel test under normal conditions. The evaluation results are shown in Tables 7 to 12.

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[0171] 10, 30, 40, 50, 60... multilayer polyethylene film, 11, 31, 41, 51, 61... surface layer, 12, 32, 42, 52, 62... intermediate layer, 13, 33, 43, 53, 63... back layer, 20... gas barrier layer, 21... inorganic oxide layer, 22... gas barrier coating layer, 100, 200, 300... gas barrier film, 130... adhesive layer, 140... sealant layer, 170... second adhesive layer, 180... substrate, 400, 500, 600, 700... laminate.

Claims

1. A multilayer polyethylene film and a gas barrier layer, the multilayer polyethylene film having at least three layers, a surface layer, an intermediate layer, and a back layer, in this order on the gas barrier layer side, the probe drop temperature of the intermediate layer being higher than the probe drop temperature of the surface layer and equal to or higher than the probe drop temperature of the back layer, the surface layer having a viscosity of 0.926 g / cm ３ 1. A gas barrier film comprising a medium density polyethylene resin or a high density polyethylene resin having a density of at least 1000 nm, and the gas barrier layer comprises at least one of an inorganic oxide layer and a gas barrier coating layer.

2. The density of the multilayer polyethylene film is 0.942 g / cm ３ The gas barrier film according to claim 1 .

3. The gas barrier film according to claim 1, wherein the intermediate layer has a probe drop temperature of 125° C. or higher.

4. The gas barrier film according to claim 1, wherein the thickness of said intermediate layer is 33% or more of the thickness of said multilayer polyethylene film.

5. The gas barrier film according to claim 1, wherein the multilayer polyethylene film is unstretched.

6. The gas barrier film according to claim 1, wherein the gas barrier layer has an inorganic oxide layer, and the inorganic oxide layer contains at least one of aluminum oxide and silicon oxide.

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

8. The gas barrier film according to claim 1, wherein the gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer contains at least one member selected from the group consisting of a silane coupling agent, a hydrolysate thereof, and a reaction product thereof.

9. The gas barrier film according to claim 1, wherein the gas barrier layer has a gas barrier coating layer, and the gas barrier coating layer contains a polyvalent metal salt of a carboxylic acid.

10. A laminate comprising: a gas barrier film according to any one of claims 1 to 9; an adhesive layer disposed on the surface of said gas barrier layer opposite said multilayer polyethylene film; and a sealant layer disposed via said adhesive layer.

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

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

13. The laminate according to claim 10, further comprising: a second adhesive layer disposed on the surface of the back layer side of the multilayer polyethylene film; and a substrate disposed via the second adhesive layer.

14. A packaging material comprising the laminate of claim 10.

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