Multilayer film for vacuum heat insulator, vapor deposited multilayer film for vacuum heat insulator, multilayer structure for vacuum heat insulator, vacuum packaging bag, and vacuum heat insulator

Abstract

Provided is a multilayer film for a vacuum heat insulator, which comprises an ethylene-vinyl alcohol copolymer layer (A), an adhesive layer (B) and a thermoplastic resin layer (C) in the stated order. The ethylene-vinyl alcohol copolymer layer (A) contains an ethylene-vinyl alcohol copolymer (a) having an ethylene unit content of 20-30 mol% as a primary component. The adhesive layer (B) contains an adhesive resin (b) as a primary component. The thermoplastic resin layer (C) contains polyethylene (c) as a primary component and is stretched at a stretching ratio of 3-12 times in at least one axial direction. The multilayer film can reduce the defect ratio when a vacuum heat insulator is produced and reduce the defect ratio after a vacuum heat insulator is bent.

Description

Multilayer film for vacuum insulation material, vapor-deposited multilayer film for vacuum insulation material, multilayer structure for vacuum insulation material, vacuum packaging bag and vacuum insulation material

[0001] The present invention relates to a multilayer film for a vacuum heat insulating material, a vapor-deposited multilayer film for a vacuum heat insulating material, a multilayer structure for a vacuum heat insulating material, a vacuum packaging bag, and a vacuum heat insulating material.

[0002] Traditionally, polyurethane foam insulation has been used as insulation for refrigerators, insulation panels for residential walls, and hot water tanks. Vacuum insulation materials, which are composed of a laminate film that has gas barrier properties even under high humidity conditions and a core material such as glass fiber with low thermal conductivity, have begun to be used as an alternative and more superior material. Aluminum foil is primarily used as a gas barrier material, but because aluminum is a good thermal conductor, a large amount of heat passes through the aluminum portion of the film, resulting in a decrease in insulation performance. To overcome this drawback, high-gas barrier films, such as polyester films with a thin aluminum-vapor-deposited layer or ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) films, have been considered as an alternative to aluminum foil.

[0003] These high gas barrier films may have a reduced gas barrier property due to bending. For example, Patent Document 1 describes a method for suppressing the reduction in gas barrier property due to bending, in which a vapor-deposited film including a substrate film containing a polyvinyl alcohol-based polymer and a metal vapor-deposited layer laminated on the substrate film, wherein the metal vapor-deposited layer has an average particle size of 150 nm or less as measured by an electron microscope, can suppress the reduction in gas barrier property due to bending. Furthermore, Patent Document 2 describes another method, in which a multilayer structure including a biaxially stretched polyvinyl alcohol-based resin film, an inorganic vapor-deposited layer, and an overcoat layer containing modified polyvinyl alcohol, has excellent flex resistance.

[0004] Furthermore, when aluminum is vapor-deposited onto the EVOH layer, the EVOH layer may heat shrink, resulting in wrinkles and sagging due to heat shrinkage during vapor deposition. As a means for solving such problems, Patent Document 3 describes that co-extrusion of polypropylene and ethylene-vinyl alcohol copolymer followed by biaxial stretching reduces wrinkles and sagging due to heat shrinkage during vapor deposition, thereby confirming an improvement in lamination film productivity.

[0005] International Publication No. WO 2013 / 125564 International Publication No. WO 2021 / 039646 JP 2019-135094

[0006] However, when the above-mentioned conventional high gas barrier films are used as materials for vacuum insulation materials, there is room for improvement in the rate at which a decrease in gas barrier property occurs during the production of the vacuum insulation material or when the vacuum insulation material is bent, i.e., in the defect rate, and further improvement in yield has been desired. The present invention has been made based on these circumstances, and an object of the present invention is to provide a multilayer film for vacuum insulation materials that can reduce the defect rate during the production of the vacuum insulation material and the defect rate after the vacuum insulation material is bent.

[0007] According to the present invention, the above object can be achieved by providing: [1] a multi-layer film for a vacuum insulation material, comprising an EVOH layer (A), an adhesive layer (B), and a thermoplastic resin layer (C) in this order, wherein the EVOH layer (A) contains, as a main component, EVOH (a) having an ethylene unit content of 20 mol% or more and 30 mol% or less, the adhesive layer (B) contains, as a main component, an adhesive resin (b), and the thermoplastic resin layer (C) contains, as a main component, polyethylene (c), and the multi-layer film is stretched at least uniaxially by a factor of 3 or more and 12 or less; [2] the multi-layer film for a vacuum insulation material of [1], wherein the EVOH layer (A) has an average thickness of 10 μm or less; [3] the multi-layer film for a vacuum insulation material of [1] or [2], wherein the melt flow rate of the EVOH (a) measured at 210°C under a load of 2,160 g as determined in accordance with the method described in ISO1133-1:2011 is 1 g / 10 min or more and 10 g / 10 min or less; [4] The multilayer film for a vacuum insulation material according to any one of [1] to [3], wherein the EVOH layer (A) does not contain EVOH having an ethylene unit content of more than 30 mol%; [5] The multilayer film for a vacuum insulation material according to any one of [1] to [4], wherein the EVOH layer (A), the adhesive layer (B), and the thermoplastic resin layer (C) are co-extruded; [6] The multilayer film for a vacuum insulation material according to any one of [1] to [5], wherein the multilayer film for a vacuum insulation material has an inorganic vapor deposition layer (D) on the surface opposite to the surface on which the adhesive layer (B) of the EVOH layer (A) is laminated; [7] The inorganic vapor deposition layer (D) is mainly composed of aluminum, and has an aluminum oxide layer (D1) and an aluminum layer (D2) successively in this order from the surface in contact with the EVOH layer (A), and in elemental analysis of the aluminum oxide layer (D1) in the depth direction, the maximum molar ratio of oxygen to aluminum (O / Al) measured with a scanning X-ray photoelectron spectrometer ＭＡＸ is 0.5 or more and 2.0 or less, and in an elemental analysis of the aluminum layer (D2) in the depth direction, the minimum value of the molar ratio of oxygen element to aluminum element (O / Al) measured by a scanning X-ray photoelectron spectrometer ＭＩＮ[8] a multilayer structure for a vacuum insulation material, obtained by laminating a thermoplastic resin layer (E) to the multilayer film for a vacuum insulation material or the vapor-deposited multilayer film for a vacuum insulation material of any of [1] to [7]; [9] the multilayer structure for a vacuum insulation material of [8], in which the thermoplastic resin layer (E) comprises at least one selected from the group consisting of polyamide, polyester, polyethylene, and polypropylene;

[10] the multilayer structure for a vacuum insulation material of [8] or [9], in which an adhesive layer is provided between the multilayer film for a vacuum insulation material or the vapor-deposited multilayer film for a vacuum insulation material and the thermoplastic resin layer (E);

[11] a vacuum packaging bag, comprising the multilayer structure for a vacuum insulation material of any of [8] to

[10] ;

[12] a vacuum insulation material, comprising the vacuum packaging bag of

[11] and a core material disposed inside the vacuum packaging bag, and in which the inside of the vacuum packaging bag is reduced in pressure.

[0008] According to the present invention, it is possible to provide a multilayer film for vacuum insulation material, which can reduce the defect rate during the production of vacuum insulation material and the defect rate after bending the vacuum insulation material, as well as a vapor-deposited multilayer film for vacuum insulation material, a multilayer structure for vacuum insulation material, a vacuum packaging bag, and a vacuum insulation material using said multilayer film.

[0009] In this specification, "gas barrier properties" primarily refers to oxygen barrier properties. The property of low thermal conductivity after flexed storage is sometimes referred to as "flexible storage properties." "Main component" refers to the component with the highest content by mass. When describing a layer structure, " / " indicates direct lamination, and " / / " indicates lamination either directly or via an adhesive layer. The term "outermost layer" does not refer to the layer present on the front side, distinguishing between the front and back sides. That is, a multilayer film, vapor-deposited multilayer film, or multilayer structure consisting of two or more layers has two outermost layers: one on one side and the other on the other side. In addition, in structures with a distinction between the inside and outside, such as a bag or container, the inner outermost layer is sometimes referred to as the innermost layer, and the outermost layer is sometimes referred to as the outermost layer. "Average thickness" refers to the average thickness measured at any five locations. The multilayer film for vacuum insulation materials of the present invention may also be referred to simply as a "multilayer film."

[0010] <Multilayer film for vacuum insulation material> The multilayer film for vacuum insulation material of the present invention comprises an EVOH layer (A), an adhesive layer (B), and a thermoplastic resin layer (C) in this order, wherein the EVOH layer (A) contains, as a main component, EVOH (a) having an ethylene unit content of 20 mol% or more and 30 mol% or less, the adhesive layer (B) contains, as a main component, an adhesive resin (b), and the thermoplastic resin layer (C) contains, as a main component, polyethylene (c), and the multilayer film is stretched at least uniaxially by a factor of 3 or more and 12 or less. Here, "comprising an EVOH layer (A), an adhesive layer (B), and a thermoplastic resin layer (C) in this order" means that as long as the EVOH layer (A), the adhesive layer (B), and the thermoplastic resin layer (C) are laminated in this order, there may be other layers between each layer, but it is preferable that the layers are directly laminated, i.e., the EVOH layer (A), the adhesive layer (B), and the thermoplastic resin layer (C) are directly laminated in this order. The use of such a multilayer film reduces the defective rate during the production of the vacuum insulation material and the defective rate after bending the vacuum insulation material. Although the reason for this is not clear, the following reason is presumed.

[0011] One cause of defects during the production of vacuum insulation materials and when they are bent is the breakage of the core material, such as glass fiber, through the multilayer film. The multilayer film for vacuum insulation materials of the present invention has good puncture strength because it comprises the EVOH layer (A), the adhesive layer (B), and the thermoplastic resin layer (C) in this order, and therefore tends to prevent the core material from breaking through, which is thought to improve yield. Furthermore, because the multilayer film for vacuum insulation materials of the present invention has such a layer structure, when attempting to reduce the average thickness of the EVOH layer (A) to reduce costs, for example, it can be made thinner to a level that cannot be achieved with a single EVOH layer, and further, sufficient puncture strength can be maintained even when the EVOH layer (A) is thinned, so that in one embodiment of the present invention, high yield can be achieved while reducing costs.

[0012] Furthermore, even in the multilayer film using polypropylene described in Patent Document 3, although penetration of the core material can be suppressed to some extent, polypropylene has a high hardness, so that the vapor deposition layer at the edge of the vacuum insulation material is likely to suffer damage such as cracks during production and bending of the vacuum insulation material, making it difficult to achieve a high level of yield improvement. On the other hand, the multilayer film of the present invention has a thermoplastic resin layer (C) containing polyethylene (c) as a main component, and therefore the flexibility of the multilayer film is improved compared to polypropylene, and it is thought that the defect rate during production of the vacuum insulation material and the defect rate after bending the vacuum insulation material will tend to be reduced.

[0013] Furthermore, by stretching the multilayer film of the present invention at least uniaxially by 3 times or more and 12 times or less, thermal shrinkage of the EVOH layer (A) can be suppressed, tending to reduce the defect rate during the production of the vacuum insulation material. Furthermore, even in a multilayer film having an EVOH layer (A), an adhesive layer (B), and a thermoplastic resin layer (C) containing polyethylene (c) as a main component, in this order, and stretched at least uniaxially by 3 times or more and 12 times or less, if the ethylene unit content of the EVOH contained in the EVOH layer (A) exceeds 30 mol%, the defect rate during the production of the vacuum insulation material and when the vacuum insulation material is bent has been found to be a unique effect observed in the configuration applied to the multilayer film of the present invention, which is not observed, for example, when the EVOH layer is used as a single layer. Although the reason for this is not clear, it is thought that in the layer structure of the multilayer film of the present invention, slight differences in the resin properties (such as puncture strength) of the EVOH layer (A) have a significant impact on the reject rate, and slight differences in the adhesive strength with the inorganic vapor deposition layer (D), which will be described later, have a significant impact on the reject rate. For the above reasons, the multilayer film of the present invention, by using EVOH (a) having a relatively low ethylene unit content of 20 mol % or more and 30 mol % or less as the main component, tends to exhibit the surprising effect of reducing the reject rate during production of the vacuum insulation material and when the vacuum insulation material is bent.

[0014] (EVOH Layer (A)) The EVOH layer (A) contains, as a main component, EVOH (a) having an ethylene unit content of 20 mol% or more and 30 mol% or less. By using EVOH (a) as a main component, the pin puncture strength of the multilayer film is improved, and the adhesion between the EVOH layer (A) and the inorganic vapor deposition layer (D) described below is improved. As a result, the defect rate of the vacuum insulation material and the defect rate after bending are reduced. Furthermore, the thermal conductivity of the obtained vacuum insulation material after bending storage is also reduced. One or more types of EVOH can be used as the EVOH constituting EVOH (a).

[0015] EVOH (a) can usually be obtained by saponifying an ethylene-vinyl ester copolymer. The production and saponification of the ethylene-vinyl ester copolymer can be carried out by known methods. A typical vinyl ester is vinyl acetate, but other fatty acid vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate may also be used.

[0016] The ethylene unit content of EVOH (a) is 20 mol% or more, preferably 22 mol% or more, more preferably 23 mol% or more, and may be 25 mol% or more. The ethylene unit content of EVOH (a) is 30 mol% or less, preferably 28 mol% or less. When the ethylene unit content of EVOH (a1) is 20 mol% or more, the flexibility is improved, thereby reducing damage to the inorganic vapor deposition layer (D) described below when bent, and the defect rate of the vacuum insulation material after bending tends to be lower. When the ethylene unit content is 30 mol% or less, the pin puncture strength of the multilayer film tends to be higher. Furthermore, the defect rate of the vacuum insulation material tends to be lower both before and after bending. Furthermore, the thermal conductivity of the vacuum insulation material after bending and storage also tends to be further reduced. The ethylene unit content of EVOH can be determined by nuclear magnetic resonance (NMR) spectroscopy.

[0017] The saponification degree of EVOH (a) (the ratio (mol %) of vinyl alcohol units to the total of vinyl alcohol units and vinyl ester units) is preferably 90 mol % or more, more preferably 98 mol % or more, and even more preferably 99 mol % or more. On the other hand, the saponification degree may be 100 mol % or less. The saponification degree of EVOH can be determined by nuclear magnetic resonance (NMR) spectroscopy. When the saponification degree is within the above range, the gas barrier property of the multilayer film under high humidity conditions tends to be improved.

[0018] EVOH (a) may contain units derived from other monomers other than ethylene, vinyl esters, and saponified products thereof, provided that the objectives of the present invention are not impaired. When EVOH (a) contains such other monomer units, the content of such other monomer units relative to the total structural units of EVOH (a) is preferably 30 mol% or less, more preferably 15 mol% or less, even more preferably 5 mol% or less, and particularly preferably 1 mol% or less. EVOH (a) may not contain any other monomer units. When EVOH (a) contains units derived from such other monomers, the lower limit may be 0.05 mol% or more, or even 0.1 mol% or more. When EVOH (a) contains units derived from such other monomers, the pin puncture strength tends to decrease, which may increase the defective rate during the production of vacuum insulation panels. Therefore, it is preferable that EVOH (a) does not contain any units derived from such other monomers. Examples of the other monomers include alkenes such as propylene, butylene, pentene, and hexene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, and 4-acyloxy-3-methyl 1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methyl nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid or salts thereof; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, and vinylidene chloride.

[0019] The EVOH (a) may be post-modified by a technique such as urethanization, acetalization, cyanoethylation, or oxyalkylenation.

[0020] The melt flow rate of EVOH (a) measured at 210°C under a load of 2,160 g in accordance with the method described in ISO 1133-1:2011 is preferably 1 g / 10 min or more and 10 g / 10 min or less, more preferably 1 g / 10 min or more and 8 g / 10 min or less.

[0021] The EVOH layer (A) may contain other components, such as antiblocking agents, processing aids, resins other than EVOH (a), carboxylic acid compounds, phosphoric acid compounds, boron compounds, metal salts, stabilizers, antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, surfactants, desiccants, crosslinking agents, reinforcing agents such as various fibers, etc., as long as the effects of the present invention are not impaired. The content of the other components in the EVOH layer (A) may be 5% by mass or less, 3% by mass or less, 1% by mass or less, or 0.5% by mass or less.

[0022] It is preferable that the EVOH layer (A) does not contain, as a resin other than the EVOH (a), an EVOH having an ethylene unit content of more than 30 mol%. Furthermore, the EVOH (a) may contain two or more types of EVOH having different ethylene unit contents, but it is preferable that the EVOHs constituting the EVOH (a) have the same ethylene unit content, from the viewpoint of reducing thickness unevenness during stretching and, as a result, suppressing an increase in thermal conductivity after bending and storage of the vacuum insulator.

[0023] The proportion of EVOH (a) in the resin constituting the EVOH layer (A) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 99% by mass or more, and the resin constituting the EVOH layer (A) may be substantially composed of EVOH (a) alone, or may be composed of EVOH (a) alone. The proportion of EVOH (a) in the EVOH layer (A) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 99% by mass or more.

[0024] The lower limit of the average thickness of the EVOH layer (A) is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 0.7 μm or more, even more preferably 1.5 μm or more, and may be 2 μm or more or 2.5 μm or more. When the average thickness of the EVOH layer (A) is at least the above-mentioned lower limit, the puncture strength of the multilayer film tends to be further increased. Furthermore, the defect rate of the vacuum insulation material before and after bending also tends to be further reduced. Furthermore, the thermal conductivity of the vacuum insulation material after bending and storage also tends to be further reduced. The upper limit of the average thickness of the EVOH layer (A) is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, particularly preferably 5 μm or less, and most preferably 4 μm or less. When the average thickness of the EVOH layer (A) is at most the above-mentioned upper limit, the defect rate of the vacuum insulation material before and after bending also tends to be reduced. Furthermore, by thinning the EVOH layer (A), the amount of EVOH (a) used can be reduced, thereby reducing costs. In particular, the average thickness of the EVOH layer (A) of 10 μm or less can only be achieved by stretching a multilayer film having an adhesive layer (B) and a thermoplastic resin layer (C) described below, and it is difficult to achieve an average thickness of the EVOH layer of 10 μm or less, for example, by stretching a single EVOH layer. Note that the average thickness of the EVOH layer (A) means the average thickness after stretching.

[0025] The EVOH layer (A) may consist of a single layer or multiple layers. When the EVOH layer (A) consists of multiple layers, it is preferable that the total average thickness is within the above range.

[0026] (Adhesive layer (B)) The adhesive layer (B) contains an adhesive resin (b) as a main component. This tends to improve the interlayer adhesion of the multilayer film for vacuum insulation materials. The content of the adhesive resin (b) in the adhesive layer (B) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 95% by mass or more, 99% by mass or more, or 99.9% by mass or more. The content of the adhesive resin (b) in the adhesive layer (B) may be 100% by mass or less, or may be 99.99% by mass or less.

[0027] As the adhesive resin (b), polyethylene having a carboxy group, a carboxylic anhydride group or an epoxy group is preferred, and polyethylene having a carboxylic anhydride group is more preferred.

[0028] Examples of polyethylene containing carboxyl groups include polyethylene copolymerized with acrylic acid or methacrylic acid. In this case, all or part of the carboxyl groups contained in the polyethylene may be present in the form of a metal salt, as typified by ionomers. Examples of polyethylene containing carboxylic acid anhydride groups include polyethylene graft-modified with maleic anhydride or itaconic acid. Examples of polyethylene containing epoxy groups include polyethylene copolymerized with glycidyl methacrylate. Among these, polyethylene containing carboxylic acid anhydride groups such as maleic anhydride can be preferably used.

[0029] The adhesive resin (b) preferably has a melt flow rate of 0.1 to 20 g / 10 min, more preferably 1 to 10 g / 10 min, at 210°C under a load of 2,160 g, measured in accordance with the method described in ISO 1133-1: 2011. When the adhesive resin (b) has a melt flow rate within the above range, the film formation stability tends to be improved.

[0030] The average thickness of the adhesive layer (B) is preferably 0.1 to 20 μm, more preferably 0.3 to 10 μm, and even more preferably 0.5 to 5 μm, from the viewpoints of industrial productivity and quality stability. The average thickness of the adhesive layer (B) means the average thickness after stretching.

[0031] (Thermoplastic resin layer (C)) The thermoplastic resin layer (C) contains polyethylene (c) as a main component. By using polyethylene (c) as a main component, the puncture strength of the multilayer film is improved, thereby reducing the defect rate of the vacuum insulation material both before and after bending. In addition, the stretching ratio can be increased while maintaining the performance of the multilayer film, allowing for thinner films and reducing costs. The content of polyethylene (c) in the thermoplastic resin layer (C) is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may be 95% by mass or more, 99% by mass or more, or 99.9% by mass or more. The content of polyethylene (c) in the thermoplastic resin layer (C) may be 100% by mass or less, or may be 99.99% by mass or less.

[0032] The polyethylene (c) is preferably at least one selected from linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), and more preferably at least one selected from linear low-density polyethylene and low-density polyethylene, or a mixture of at least one selected from linear low-density polyethylene and low-density polyethylene with high-density polyethylene.

[0033] The linear low-density polyethylene may be an ethylene polymer or ethylene copolymer polymerized using a metallocene catalyst. The ethylene polymer or ethylene copolymer polymerized using a metallocene catalyst is an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, produced by polymerizing ethylene or copolymerizing ethylene and the α-olefin in the presence of a catalyst formed from a compound of a transition metal of Group 4 of the periodic table, preferably zirconium, having at least one ligand having a cyclopentadienyl skeleton, an organoaluminum oxy compound, and various other components added as needed.

[0034] The polyethylene (c) preferably has a melt flow rate of 0.1 to 20 g / 10 min, more preferably 0.1 to 10 g / 10 min, even more preferably 0.1 to 5 g / 10 min, and may even have a melt flow rate of 0.1 to 3 g / 10 min, at 210°C and under a load of 2,160 g, as measured in accordance with the method described in ISO 1133-1: 2011. When the polyethylene (c) has a melt flow rate within the above range, the film formation stability tends to be improved.

[0035] The average thickness of the thermoplastic resin layer (C) is preferably 5 to 200 μm, more preferably 7 to 100 μm, and even more preferably 10 to 50 μm. The average thickness of the thermoplastic resin layer (C) means the average thickness after stretching.

[0036] In the multilayer film of the present invention, the thermoplastic resin layer (C) may be a single layer or multiple layers. When multiple thermoplastic resin layers (C) are provided, if the thermoplastic resin layers (C) are continuously laminated and made of the same material, they are considered to be a single layer. For example, if the EVOH layer (A) is "A," the adhesive layer (B) is "B," and the thermoplastic resin layer (C) is "C," then in a C / C / C / B / A multilayer film, if the thermoplastic resin layers (C) are all made of the same material, the multilayer film is considered to be a C / B / A multilayer film, and the average thickness of each thermoplastic resin layer (C) is the sum of the average thicknesses of the three layers. On the other hand, if the thermoplastic resin layers (C) are made of different materials in the above example, they are considered to be independent layers.

[0037] (Others) The multilayer film for vacuum insulation materials of the present invention has an EVOH layer (A), an adhesive layer (B), and a thermoplastic resin layer (C) in this order, and preferably has a configuration in which the EVOH layer (A), the adhesive layer (B), and the thermoplastic resin layer (C) are directly laminated in this order. Specific examples of the layer configuration of the multilayer film of the present invention include C / B / A, C / B / A / B / A, A / B / C / B / A, C / B / A / B / C / B / A, C / C / B / A, and C / C / C / B / A. Among these, C / B / A, C / C / B / A, and C / C / C / B / A are preferred from the viewpoint of industrial productivity. When multiple thermoplastic resin layers (C) are included, a preferred embodiment is one in which an HDPE layer, an LDPE layer or an LLDPE layer, and a layer containing HDPE and LDPE or LLDPE are laminated.

[0038] The overall average thickness of the multilayer film of the present invention can be appropriately set depending on the application of the vacuum insulation material. The overall average thickness is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. An overall average thickness of 10 μm or more tends to improve industrial productivity and mechanical properties. Furthermore, the overall average thickness is preferably 300 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. An overall average thickness of 300 μm or less tends to improve industrial productivity and economic efficiency. The overall average thickness of the multilayer film means the average thickness after stretching.

[0039] The method for producing the multilayer film of the present invention is not particularly limited, but a conventional coextrusion method in which each resin is extruded through a separate die or a common die and laminated is preferred. The coextrusion method allows for a high level of balance among film properties such as gas barrier property and flexibility, processability (reduction of film thickness unevenness), and economy (easiness to achieve the desired structure (e.g., thinning of the EVOH layer (A)) with fewer steps). Therefore, the multilayer film of the present invention preferably includes a structure in which the EVOH layer (A), adhesive layer (B), and thermoplastic resin layer (C) are coextruded. Examples of coextrusion methods include coextrusion cast molding, coextrusion inflation molding, and coextrusion coating molding. Among these, inflation molding using a circular die is preferred. Inflation molding is also preferred from the standpoint of cost. When inflation molding is used to produce the multilayer film of the present invention, known inflation molding methods can be used.

[0040] The multilayer film of the present invention is stretched at least uniaxially by 3 to 12 times. If the multilayer film of the present invention is stretched less than 3 times, thickness unevenness due to stretching and gas barrier properties tend to deteriorate. On the other hand, if the multilayer film of the present invention is stretched more than 12 times, the film surface after stretching tends to deteriorate. The multilayer film of the present invention is preferably stretched at least uniaxially by 4 times or more, more preferably by 5 times or more. Furthermore, the multilayer film of the present invention is preferably stretched at least uniaxially by 10 times or less, more preferably by 8 times or less. The multilayer film of the present invention may be stretched uniaxially or biaxially, but is preferably uniaxially stretched, and particularly preferably uniaxially stretched in the longitudinal direction (MD). In this case, it is preferable that the film is not substantially stretched in the width direction (TD). Furthermore, even when the multilayer film of the present invention is biaxially stretched, it is preferably stretched mainly in the machine direction (MD direction), and the ratio of the stretching ratio in the machine direction (MD direction) to the stretching ratio in the width direction (TD direction) (MD / TD) is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. The stretching ratio ratio (MD / TD) may also be 12 or less.

[0041] The stretching method for the multilayer film is not particularly limited, and examples thereof include tenter stretching, tubular stretching, and roll stretching. In the case of uniaxial stretching, roll stretching or the like can be employed. The temperature employed during uniaxial stretching is generally in the range of 50 to 130°C. In the case of biaxial stretching, tenter stretching or the like can be employed. In the case of simultaneous biaxial stretching, a temperature range of 70 to 100°C can be used to obtain a biaxially stretched film with little stretching unevenness. In the case of sequential biaxial stretching, a temperature range of 70 to 100°C can be used for stretching in the machine direction (MD) and a temperature range of 80 to 120°C can be used for stretching in the width direction (TD), to obtain a biaxially stretched film with little stretching unevenness.

[0042] The puncture strength of the multilayer film measured in accordance with JIS Z 1707:2019 is preferably 2.7 N or more, more preferably 3.3 N or more. If the puncture strength is 2.7 N or more, the defective rate of the vacuum insulation material tends to decrease. The puncture strength may be 12 N or less.

[0043] <Vapor-deposited multilayer film for vacuum insulation material> The vapor-deposited multilayer film for vacuum insulation material of the present invention has an inorganic vapor-deposited layer (D) on the surface of the EVOH layer (A) of the multilayer film opposite to the surface on which the adhesive layer (B) is laminated.

[0044] (Inorganic Vapor Deposition Layer (D)) The inorganic vapor deposition layer (D) is a layer that has barrier properties against oxygen and water vapor. By including the inorganic vapor deposition layer (D), the vapor-deposited multilayer film of the present invention has good gas barrier properties and tends to maintain a high vacuum state for a long period of time. The inorganic vapor deposition layer (D) can be formed by vapor-depositing an inorganic substance, and is preferably laminated directly on the surface of the EVOH layer (A). This tends to further improve the adhesion between the multilayer film and the inorganic vapor deposition layer (D). Examples of inorganic substances contained as a main component include metals (e.g., aluminum), metal oxides (e.g., silicon oxide, aluminum oxide), metal nitrides (e.g., silicon nitride), metal nitride oxides (e.g., silicon oxynitride), and metal carbonitrides (e.g., silicon carbonitride). Among these, inorganic vapor deposition layers (D) whose main component is aluminum, aluminum oxide, silicon oxide, magnesium oxide, or silicon nitride are preferred from the viewpoint of industrial productivity, and inorganic vapor deposition layers (D) whose main component is aluminum are more preferred.

[0045] The inorganic vapor-deposited layer (D) containing aluminum as a main component has an aluminum oxide layer (D1) and an aluminum layer (D2) successively arranged in this order from the surface side in contact with the EVOH layer (A), and in elemental analysis of the aluminum oxide layer (D1) in the depth direction, the maximum molar ratio of oxygen element to aluminum element (O / Al) measured with a scanning X-ray photoelectron spectrometer is ＭＡＸ is 0.5 or more and 2.0 or less, and in an elemental analysis of the aluminum layer (D2) in the depth direction, the minimum value of the molar ratio of oxygen element to aluminum element (O / Al) measured by a scanning X-ray photoelectron spectrometer ＭＩＮ is preferably less than 0.5.

[0046] There is no clear interface between the aluminum oxide layer (D1) and the aluminum layer (D2). Furthermore, the elemental composition of the aluminum oxide layer (D1) and the aluminum layer (D2) is usually not constant. The oxygen content gradually decreases from the aluminum oxide layer (D1) to the aluminum layer (D2). In other words, in the inorganic vapor deposition layer (D), the oxygen content of the intermediate layer portion (aluminum layer (D2)) is relatively low. In the inorganic vapor deposition layer (D), the oxygen content of the region (aluminum oxide layer (D1)) extending to a predetermined thickness from the surface of the inorganic vapor deposition layer (D) in contact with the EVOH layer (A) is relatively higher than that of the intermediate layer portion (aluminum layer (D2)). An aluminum oxide layer (D3) having a relatively higher oxygen content than that of the intermediate layer portion (aluminum layer (D2)) may be formed in a region extending to a predetermined thickness from the surface of the inorganic vapor deposition layer (D) opposite to the surface in contact with the EVOH layer (A). When the aluminum oxide layer (D3) is formed, the maximum value of the molar ratio of oxygen element to aluminum element (O / Al) in the aluminum oxide layer (D1) ＭＡＸ and the molar ratio of oxygen to aluminum (O / Al) in the aluminum oxide layer (D3), either of them may be larger. That is, the maximum molar ratio of oxygen to aluminum (O / Al) in the aluminum oxide layer (D1) ＭＡＸ is the maximum value in the aluminum oxide layer (D1) and does not necessarily coincide with the maximum value in the inorganic vapor deposition layer (D).

[0047] In elemental analysis of the aluminum oxide layer (D1) in the depth direction, the maximum value of the molar ratio of oxygen element to aluminum element (O / Al) measured by a scanning X-ray photoelectron spectrometer ＭＡＸ is 0.5 or more and 2.0 or less, preferably 0.8 or more and 1.8 or less, and more preferably 1.1 or more and 1.5 or less. ＭＡＸWhen the thickness is within the above range, the adhesion of the inorganic vapor deposition layer (D) to the EVOH layer (A) tends to be further improved, the defect rate of the vacuum insulation material before and after bending tends to be further reduced, and the bending storage stability of the vacuum insulation material tends to be further improved.

[0048] The maximum molar ratio of oxygen to aluminum (O / Al) in elemental analysis of the aluminum oxide layer (D1) in the depth direction ＭＡＸ is observed preferably in the range of 0 nm to 20 nm, more preferably 0 nm to 15 nm, from the surface in contact with the EVOH layer (A).

[0049] In elemental analysis of the aluminum layer (D2) in the depth direction, the minimum value of the molar ratio of oxygen element to aluminum element (O / Al) measured by a scanning X-ray photoelectron spectrometer ＭＩＮ The minimum molar ratio (O / Al) of oxygen element (O) to aluminum element (Al) in the aluminum layer (D2) is less than 0.5, preferably 0.001 or more and less than 0.5, more preferably 0.003 or more and less than 0.2, even more preferably 0.005 or more and less than 0.10, and even more preferably 0.01 or more and less than 0.06. ＭＩＮ When the thickness is within the above range, the gas barrier properties of the vapor-deposited multilayer film tend to be improved. The defective rate of the vacuum insulation material before and after bending also tends to be further reduced. Furthermore, the flexural storage properties of the vacuum insulation material also tend to be further improved.

[0050] The average thickness of the inorganic vapor deposition layer (D) is preferably 30 nm or more and 100 nm or less. The lower limit of the average thickness is more preferably 35 nm or more, and even more preferably 45 nm or more. When the average thickness of the inorganic vapor deposition layer (D) is equal to or greater than the above lower limit, the gas barrier properties of the vapor-deposited multilayer film tend to be improved. In addition, the defect rate of the vacuum insulation material before and after bending tends to be further reduced. Furthermore, the flexural storage properties of the vacuum insulation material tend to be further improved. The upper limit of the average thickness of the inorganic vapor deposition layer (D) is more preferably 90 nm or less, and may be 80 nm or less, 70 nm or less, or 60 nm or less.

[0051] The method for forming the inorganic vapor deposition layer (D) is not particularly limited, and examples thereof include physical vapor deposition methods such as vacuum deposition (e.g., resistance heating deposition, electron beam deposition, molecular beam epitaxy, etc.), sputtering, and ion plating; and chemical vapor deposition methods such as thermal chemical vapor deposition (e.g., catalytic chemical vapor deposition), photochemical vapor deposition, plasma chemical vapor deposition (e.g., capacitively coupled plasma, inductively coupled plasma, surface wave plasma, electron cyclotron resonance, dual magnetron, atomic layer deposition, etc.), and metalorganic chemical vapor deposition.

[0052] The inorganic vapor deposition layer (D) having the aluminum oxide layer (D1) and the aluminum layer (D2) can be effectively formed, for example, by using a vacuum vapor deposition method. For example, when vacuum vapor deposition of aluminum is performed on the surface of the EVOH layer (A) of the multilayer film, the deposition is performed while supplying a small amount of oxygen gas toward the multilayer film. As a result, aluminum elements are laminated in the form of aluminum oxide on the surface of the EVOH layer (A), forming the aluminum oxide layer (D1). The maximum molar ratio (O / Al) of oxygen elements (O) to aluminum elements (Al) in the aluminum oxide layer (D1) is ＭＡＸ can be controlled by the amount of oxygen gas supplied to the multilayer film. The amount of oxygen gas supplied to the multilayer film can be, for example, 20 mL / min to 180 mL / min. However, the suitable amount of oxygen gas supplied is appropriately adjusted depending on the aluminum deposition rate, etc. In addition, when a vapor-deposited multilayer film is provided with an inorganic vapor-deposited layer (D) having an aluminum oxide layer (D1) and an aluminum layer (D2) by a vacuum deposition method, an oxide film is usually formed on the surface of the inorganic vapor-deposited layer (D) by exposure to an air atmosphere, and this oxide film can become an aluminum oxide layer (D3).

[0053] Before vapor deposition, the surface of the EVOH layer (A) may be subjected to a plasma treatment. The plasma treatment may be performed by a known method, and atmospheric pressure plasma treatment is preferred. Examples of discharge gases used in atmospheric pressure plasma treatment include nitrogen gas, helium, neon, argon, krypton, xenon, and radon.

[0054] (Layer Structure, etc.) The layer structure of the vapor-deposited multilayer film is not particularly limited as long as the inorganic vapor-deposited layer (D) is provided on the surface of the EVOH (A) opposite to the surface on which the adhesive layer (B) is laminated, and examples thereof include C / B / A / D, C / B / A / B / A / D, A / B / C / B / A / D, C / B / A / B / C / B / A / D, C / C / B / A / D, and C / C / C / B / A / D. Among these, C / B / A / D, C / C / B / A / D, and C / C / C / B / A / D are preferred from the viewpoint of industrial productivity.

[0055] The overall average thickness of the vapor-deposited multilayer film can be appropriately set depending on the application of the vacuum insulation material. The overall average thickness is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. When the overall average thickness is 10 μm or more, industrial productivity and mechanical properties tend to be improved. Furthermore, the overall average thickness is preferably 300 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. When the overall average thickness is 300 μm or less, industrial productivity and economic efficiency tend to be improved.

[0056] <Multilayer structure for vacuum insulation material> The multilayer film or the vapor-deposited multilayer film may be further laminated with a thermoplastic resin layer (E) to be used as a multilayer structure for vacuum insulation material. This can impart properties depending on the type of thermoplastic resin constituting the thermoplastic resin (E) layer, such as heat sealability and mechanical strength. The thermoplastic resin layer (E) is laminated directly or via another layer on at least one surface of the multilayer film or the vapor-deposited multilayer film.

[0057] (Thermoplastic Resin Layer (E)) Examples of thermoplastic resins used in the thermoplastic resin layer (E) include polyolefins such as polyethylenes such as linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene, ethylene-vinyl acetate copolymers, ionomers, ethylene-propylene (block or random) copolymers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester copolymers, polypropylene, propylene-α-olefin copolymers, polybutene, and polypentene, as well as polyolefins obtained by graft-modifying these with unsaturated carboxylic acids or esters thereof; polyesters; polyamides (including copolymerized polyamides); polyvinyl chloride; polyvinylidene chloride; acrylic resins; polystyrene; polyvinyl esters; polyester elastomers; polyurethane elastomers; chlorinated polystyrene; chlorinated polypropylene; aromatic polyketones or aliphatic polyketones, and polyalcohols obtained by reducing these; polyacetals; and polycarbonates. Among these, the thermoplastic resin layer (E) preferably contains at least one selected from the group consisting of polyamide, polyester, polyethylene, and polypropylene, and more preferably contains at least one selected from the group consisting of polyamide, polyester, and polyethylene.

[0058] The content of the thermoplastic resin in the thermoplastic resin layer (E) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more. The thermoplastic resin layer (E) may be composed essentially of a thermoplastic resin, or may be composed of only a thermoplastic resin.

[0059] When the thermoplastic resin layer (E) is a polyolefin layer containing a polyolefin, this layer may be an unstretched layer or a stretched layer. In the multilayer structure of the present invention, when the innermost layer is a polyolefin layer in the form of a bag, these layers are preferably unstretched layers in terms of good heat sealability. In the multilayer structure of the present invention, when the outermost layer is a polyolefin layer in the form of a bag, these layers are preferably stretched in terms of good mechanical strength. As the polyolefin layer used as the thermoplastic resin layer (E), a polyethylene layer containing polyethylene and a polypropylene layer containing polypropylene are preferred.

[0060] When the thermoplastic resin layer (E) is a polyamide layer containing polyamide, the polyamide layer is preferably at least one outermost layer in the multilayer structure. In the multilayer structure of the present invention, the layer that becomes the outermost layer when formed into a bag shape may be a polyamide layer. In one embodiment of the multilayer structure of the present invention, one outermost layer may be a polyethylene layer, and the other outermost layer may be a polyamide layer. The polyamide layer may be a non-stretched layer or a stretched layer.

[0061] The thermoplastic resin layer (E) may be laminated directly onto the multilayer film or the vapor-deposited multilayer film, or may be laminated via another layer.

[0062] Examples of other layers include an adhesive layer. That is, the multilayer structure may include an adhesive layer between the multilayer film or the vapor-deposited multilayer film and the thermoplastic resin layer (E). Examples of the adhesive layer include a layer made of a curing adhesive (such as a two-component reactive polyurethane adhesive). The average thickness of the adhesive layer is preferably 0.1 μm or more and 10 μm or less, more preferably 0.3 μm or more and 5 μm or less, and even more preferably 0.5 μm or more and 3 μm or less. By setting the average thickness of the adhesive layer within the above range, it is possible to achieve a reduction in the weight of the multilayer structure while exhibiting sufficient adhesiveness.

[0063] The average thickness per layer of the thermoplastic resin layer (E) is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and may be 20 μm or more, 30 μm or more, or 40 μm or more. The upper limit of the average thickness per layer of the thermoplastic resin layer (E) is preferably 200 μm or less, more preferably 100 μm or less, and may be 60 μm or less. When the average thickness per layer of the thermoplastic resin layer (E) is within the above range, the functions required of the thermoplastic resin layer (E) tend to be exhibited. Furthermore, when the average thickness per layer of the thermoplastic resin layer (E) is below the above upper limit, it is possible to reduce the thickness of the multilayer structure, etc.

[0064] The multilayer structure of the present invention may further include another inorganic vapor deposition layer, in addition to the inorganic vapor deposition layer (D) of the vapor-deposited multilayer film, laminated to the multilayer film or the vapor-deposited multilayer film directly or via another layer. Such an inorganic vapor deposition layer may be provided, for example, by using the thermoplastic resin layer (E) as a substrate. That is, such an inorganic vapor deposition layer may be provided by laminating another vapor-deposited film obtained by vapor-depositing an inorganic material onto a resin film forming the thermoplastic resin layer (E) with the multilayer film or the vapor-deposited multilayer film. Examples of inorganic materials constituting such an inorganic vapor deposition layer include those described above as constituting the inorganic vapor deposition layer (D). A specific example is polyethylene terephthalate (PET) having an inorganic vapor deposition layer (D) that is preferably laminated.

[0065] The multilayer structure of the present invention may include two or more of the multilayer films or vapor-deposited multilayer films, in which case the multilayer films or vapor-deposited multilayer films may be the same or different.

[0066] (Other Layers) The multilayer structure of the present invention may have layers other than the multilayer film, the vapor-deposited multilayer film, the thermoplastic resin layer (E), the adhesive layer, and the other inorganic vapor-deposited layer. Examples of the other layers include a paper layer and a metal foil layer.

[0067] (Layer structure, etc.) Examples of layer structures of the multilayer structure of the present invention include: MLF / / PO MLF / / MLF / PO PO / / MLF / / PO PO / / MLF / / PO / / PO PA / / MLF / / PO PO / / MLF / / PO / / PO PA / / MLF / / PA / / PO PO / / MLF / / MLF / / PO PA / / MLF / / MLF / / PO PET / / MLF / / PO M-PET / / M-PET / / MLF / / PO PA / / PET / / MLF / / PO PA / / M-PET / / MLF / / PO PA / / VLF / / M-PET / / PO Examples include PA / / M-PET / / VLF / / M-PET / / PO, M-PET / / VLF / / M-PET / / PO, PA / / M-PET / / M-PET / / MLF / / PO, and PO / / M-PET / / M-PET / / MLF / / PO. Note that "MLF" refers to the multilayer film or vapor-deposited multilayer film, "PO" refers to the polyolefin layer, "PA" refers to the polyamide layer, "PET" refers to the PET layer, and "M-PET" refers to the PET layer with inorganic vapor deposition. In the layer configurations exemplified above, a structure in which another layer is disposed at any position is also an example of the multilayer structure of the present invention. Furthermore, the orientation of the multilayer film or vapor-deposited multilayer film is not particularly limited. For example, when the layer structure "MLF / / PO" of the multilayer structure (1) above includes a multilayer film having a layer structure of "A / B / C," it may have a layer structure of "A / B / C / / PO" or a layer structure of "C / B / A / / PO." However, when it has an inorganic vapor deposition layer (D), "MLF / / PO" preferably has a layer structure of "D / A / B / C / / PO." Furthermore, M-PET may have a structure of either "inorganic vapor deposition layer / PET" or "PET / inorganic vapor deposition layer," but it is preferable that the inorganic vapor deposition layer faces the "MLF" side, and the inorganic vapor deposition layer of M-PET is preferably an aluminum oxide layer or a silicon oxide layer.

[0068] The average thickness of the multilayer structure of the present invention (average thickness of the entire multilayer structure) is preferably 10 μm or more, and may be 20 μm or more, 30 μm or more, or 50 μm or more. When the average thickness of the multilayer structure is equal to or greater than the above lower limit, the defect rate of the vacuum insulation material before and after bending tends to be further reduced. In addition, the bending storage properties of the vacuum insulation material tend to be further improved. The average thickness of the multilayer structure is preferably 1,000 μm or less, and may be 500 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less. When the average thickness of the multilayer structure is equal to or less than the above upper limit, weight reduction and moldability can be achieved.

[0069] The method for producing the multilayer structure of the present invention is not particularly limited. For example, a multilayer structure can be obtained by laminating a resin film forming the thermoplastic resin layer (E), another vapor-deposited film, or the like, onto the multilayer film or the vapor-deposited multilayer film by a known means such as dry lamination. Alternatively, a multilayer structure can be obtained by laminating a thermoplastic resin layer (E), or the like, onto the multilayer film or the vapor-deposited multilayer film by, for example, melt extrusion.

[0070] <Vacuum Packaging Bag> The vacuum packaging bag of the present invention includes a packaging bag containing the multilayer structure for vacuum insulation material of the present invention, and the interior of the packaging bag is decompressed. The vacuum packaging bag is used as an exterior packaging material for a vacuum insulation material. Such a vacuum packaging bag suppresses deterioration in gas barrier property after bending and after bending storage, and can maintain a high vacuum state for a long period of time. From the viewpoint of heat sealability, etc., the multilayer structure used in the vacuum packaging bag preferably has a configuration in which a polyethylene layer is used as the innermost layer of the thermoplastic resin layer (E). In this case, it is preferable that the polyethylene layer is not stretched. Furthermore, in cases where high mechanical strength is required, it is preferable that the thermoplastic resin layer (E) has a polyamide layer. From the viewpoint of further suppressing deterioration in gas barrier property after bending storage, it is preferable that the inorganic vapor deposition layer (D) is disposed outside the EVOH layer (A). The vacuum packaging bag (outer packaging material) is formed, for example, by heat-sealing the multilayer structure.

[0071] <Vacuum insulation material> The vacuum insulation material of the present invention comprises the vacuum packaging bag and a core material disposed therein. In the vacuum insulator, the vacuum packaging bag is also referred to as an outer packaging material. The vacuum insulation material is used for applications requiring cold or warm insulation. Examples of the core material include glass fiber and polyurethane foam. In the vacuum insulation material, the core material is sealed in a vacuum state within the vacuum packaging bag (outer packaging material).

[0072] The vacuum insulation material of the present invention exhibits suppressed deterioration in gas barrier properties after bending treatment and bending storage, and can maintain high thermal insulation effects for a long period of time. The vacuum insulation material can be used as an insulation material for home appliances such as refrigerators, hot water supply systems, and rice cookers; as a residential insulation material used in walls, ceilings, attics, floors, etc.; as a vehicle roofing material; and as an insulation panel for vending machines, etc.

[0073] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples in any way.

[0074] [Evaluation Method] (1) Average Thickness of Vapor-Deposited Multilayer Film The vapor-deposited multilayer films obtained in the Examples and Comparative Examples were cut using a microtome to prepare slices for cross-sectional observation. The prepared slices were fixed to a sample holder with carbon tape and subjected to platinum ion sputtering at an accelerating voltage of 30 kV for 30 seconds. The cross section of the vapor-deposited multilayer film was observed at five points using a field-emission transmission electron microscope [device: SU8000 manufactured by Hitachi High-Technologies Corporation], and the average value was used as the average thickness of each layer of the vapor-deposited multilayer film. The measurement conditions were an accelerating voltage of 1 kV and a magnification of 20,000x.

[0075] (2) Molar Ratio of Oxygen to Aluminum in Inorganic Vapor Deposited Layer (D) (O / Al) The molar ratio of oxygen to aluminum (O / Al) was measured for the inorganic vapor deposition layer (D) of the vapor-deposited multilayer films obtained in the Examples and Comparative Examples while sputtering with argon in the thickness (depth) direction using a scanning X-ray photoelectron spectrometer "PHI Quntera SXM" manufactured by ULVAC-PHI, Inc. The X-ray source was AlKα (1486.6 eV), the X-ray beam diameter was 100 μmφ (25 W, 15 kV), the measurement range was 300 μm horizontal × 300 μm vertical, the signal acquisition angle was 45°, and the vacuum degree was 1×10 -６ The measurement was carried out under the condition of 100 Pa. The molar ratio of oxygen to aluminum at the measurement point where the molar ratio of oxygen observed on the EVOH layer (A) side (i.e., observed in the aluminum oxide layer (D1)) was maximum was defined as (O / Al). ＭＡＸ The molar ratio of oxygen to aluminum at the measurement point where the molar ratio of oxygen is minimum (i.e., the aluminum layer (D2)) is defined as (O / Al). ＭＩＮ It was decided.

[0076] (3) Puncture Strength Puncture strength was measured in accordance with JIS Z 1707:2019. Specifically, the multilayer films obtained in the examples and comparative examples were conditioned for one week under conditions of 23°C / 50% RH, and then cut into a circle with a diameter of 10 cm. The test specimen was fixed using a jig, and a semicircular needle with a diameter of 1.0 mm and a tip radius of 0.5 mm was pierced at a rate of 50 mm / min using an AUTOGRAPH AGS-H (manufactured by Shimadzu Corporation). The maximum stress until the needle penetrated was measured and evaluated according to the following criteria: A: 3.3 N or more B: 3.0 N or more but less than 3.3 N C: 2.7 N or more but less than 3.0 N D: less than 2.7 N

[0077] (4) Defective Rate of Vacuum Insulation Materials The multilayer structures obtained in the Examples and Comparative Examples were cut to 20 cm x 40 cm to prepare two covering materials, and these two covering materials were overlapped with the LLDPE layers facing each other, and three sides were heat-sealed 10 mm wide to prepare three-sided packaging bags. Glass fiber dried for 4 hours in an atmosphere of 160°C as a low thermal conductive core material and a small bag containing calcium oxide as an adsorbent were filled into the opening of the obtained packaging bag, and the packaging bag was sealed at a temperature of 20°C and an internal pressure of 1.0 Pa using a vacuum insulation panel manufacturing device (KT-500RD model, manufactured by NPC Corporation). 300 vacuum insulation materials were produced and stored at 23°C and 50% RH for one week. Using a thermal conductivity measuring device (FOX314 model, manufactured by Eiko Seiki Co., Ltd.), the thermal conductivity (mW / (m·k)) of the vacuum insulation material was measured with one side of the vacuum insulation material at 38°C and the other side at 12°C. Products with a value of more than 3.0 mW / m·K were deemed defective, and the defect rate for 300 pieces was calculated and evaluated according to the following criteria: A: Defect rate 1% or less B: Defect rate 1% or more and 3% or less C: Defect rate 3% or more and 5% or less D: Defect rate greater than 5%

[0078] (5) Defective rate of vacuum insulation material after bending Among the vacuum insulation materials obtained by the above evaluation method (4), those with a thermal conductivity of less than 3.0 mW / m·K were bent into a semi-arc shape along an R150 iron plate and then stored at 23 ° C. and 50% RH for one week. The semi-arc-shaped vacuum insulation material was pressed against a flat plate to flatten it, and the thermal conductivity (mW / (m·k)) of the vacuum insulation material was measured using a thermal conductivity measuring device in the same manner as above. Products with a defect rate of more than 3.0 mW / m·K were deemed defective, and the defect rate for 300 pieces was calculated and evaluated according to the following criteria: A: Defective rate 1% or less B: Defective rate 1% or more and 3% or less C: Defective rate 3% or more and 5% or less D: Defective rate greater than 5%

[0079] (6) Thermal conductivity of vacuum insulation material after bending storage Among the vacuum insulation materials obtained by the above evaluation method (5) after bending, those with a thermal conductivity of less than 3.0 mW / m·K were stored for 120 days in a thermo-hygrostat at 30 ° C. and 85% RH. After storing at 23 ° C. and 50% RH for one week, the semi-arc-shaped vacuum insulation material was pressed against a flat plate and flattened, and then the thermal conductivity was measured using a thermal conductivity measuring device in the same manner as above. The evaluation was performed twice, and the average value of the two evaluation results was used as the thermal conductivity before the test. The difference before and after the storage test (after the storage test - before the storage test) was calculated and evaluated according to the following criteria. A: 3.0 mW / m·K or less B: 3.0 mW / m·K or more and 4.0 mW / m·K or less C: 4.0 mW / m·K or more and 5.0 mW / m·K or less D: Greater than 5.0 mW / m·K

[0080] [Materials Used] EVOH (a) EVOH1: EVOH (ethylene unit content (Et) 27 mol%, saponification degree 99.99%, MFR 4.0 g / 10 min (210°C, 2160 g load), containing 200 ppm of sodium, 10 ppm of phosphoric acid, 500 ppm of boric acid, and 200 ppm of acetic acid) EVOH2: EVOH (ethylene unit content (Et) 29 mol%, saponification degree 99.99%, MFR 3.8 g / 10 min (210°C, 2160 g load), containing 200 ppm of sodium, 10 ppm of phosphoric acid, 700 ppm of boric acid, and 200 ppm of acetic acid) EVOH3: EVOH (ethylene unit content (Et) 24 mol%, saponification degree 99.99%, MFR 2.2 g / 10 min (210°C, 2160 g load), containing 200 ppm of sodium, 10 ppm of phosphoric acid, and 200 ppm of acetic acid) EVOH (a') EVOH4: EVOH (ethylene unit content (Et) 44 mol%, saponification degree 99.99%, MFR 3.3 g / 10 min (210°C, 2160 g load), containing 200 ppm of sodium acetate (calculated as sodium ions), 10 ppm of phosphoric acid, 1000 ppm of boric acid, and 200 ppm of acetic acid) Adhesive resin (b) MAhPE: "ADMER™ NF528" (maleic anhydride modified polyethylene, manufactured by Mitsui Chemicals, Inc., MFR (210°C, under a load of 2160 g) 2.9 g / 10 min, density 0.91 g / cm ３MAhPP: "Admer™ QF500" (maleic anhydride modified polypropylene, manufactured by Mitsui Chemicals, Inc., MFR (210°C, under a load of 2160 g) 2.2 g / 10 min, density 0.91 g / cm ３ Thermoplastic resin (c) PE: "Lumicene (trademark) Supertough 40ST05" (polyethylene, manufactured by Total, MFR (210 ° C, under a load of 2160 g) 0.6 g / 10 min), density 0.94 g / cm ３ Thermoplastic resin (c') PP: "Novatec (trademark) FL203D" (manufactured by Japan Polypropylene Corporation, MFR (210 ° C, under a load of 2160 g) 2.0 g / 10 min), density 0.90 g / cm ３ ) Thermoplastic resin layer (E) VM-PET: "VM-PET1510" (aluminum vapor-deposited PET film (average thickness 12 μm), manufactured by Toray Industries, Inc.). When describing the layer structure, VM is written on the side where the aluminum vapor-deposited layer is present. For example, when describing the layer structure of a PET / Al vapor-deposited layer, it is written as PET-VM. OPA: "EMBLEM (registered trademark) ONM15" (biaxially oriented polyamide film (average thickness 15 μm), manufactured by Unitika Ltd.) LLDPE: "UNILAX (registered trademark) LS760C" (LLDPE film (average thickness 50 μm), manufactured by Idemitsu Unitech Co., Ltd.)

[0081] [Example 1] A cylindrical multilayer film was produced using EVOH1 as the material for the EVOH layer (A), MAhPE as the material for the adhesive layer (B), and PE as the material for the thermoplastic resin layer (C) in an inflation extrusion molding machine under the following conditions: Three thermoplastic resin (C) layers were laminated with an average thickness of 50 μm, resulting in one thermoplastic resin (C) layer with an average thickness of 150 μm.

[0082] <Conditions for producing multilayer film> Layer structure of multilayer film: [Inner surface side] EVOH layer (A) / adhesive layer (B) / thermoplastic resin layer (C)=18 μm / 6 μm / 150 μm (total average thickness 174 μm) Apparatus: 5-type 5-layer inflation extrusion molding machine (manufactured by Dr Collin) Die temperature: 220° C. Blow-up ratio: 2.7 Take-up speed: 4 m / min Film folded diameter width: 25 cm <Conditions for EVOH layer (A) extruder> Extruder: 30φ single-screw extruder (manufactured by Dr Collin) Rotation speed: 24 rpm. Extrusion temperature: feeding section / compression section / metering section = 190°C / 220°C / 220°C <Conditions for adhesive layer (B) extruder> Extruder: 20φ single screw extruder (manufactured by Dr Collin) Rotation speed: 20 rpm Extrusion temperature: feeding section / compression section / metering section = 170°C / 190°C / 210°C <Conditions for thermoplastic resin layer (C) extruder 1> Extruder: 30φ single screw extruder (manufactured by Dr Collin) Rotation speed: 90 rpm Extrusion temperature: feeding section / compression section / metering section = 170°C / 190°C / 210°C. <Conditions for thermoplastic resin layer (C) extruder 2> Extruder: 20φ single screw extruder (manufactured by Dr Collin) Rotation speed: 70 rpm Extrusion temperature: feeding section / compression section / metering section = 170°C / 190°C / 210°C. <Conditions of Extruder 3 for Thermoplastic Resin Layer (C)> Extruder: 20φ single screw extruder (manufactured by Dr Collin) Rotation speed: 70 rpm Extrusion temperature: feeding section / compression section / metering section=170°C / 190°C / 210°C

[0083] The obtained cylindrical multilayer film was cut into a flat multilayer film, and then, using a stretching device (SDR-506WK) manufactured by Eto Corporation, it was uniaxially stretched to 5 times its original size in the machine direction (MD direction) at 120°C, and then heat-treated at 100°C for 1 second to obtain a stretched multilayer film (EVOH layer (A) / adhesive layer (B) / thermoplastic resin layer (C) = 3.0 μm / 1.0 μm / 25 μm). The puncture strength of the obtained stretched multilayer film was measured according to the method described in the above evaluation method (3). The results are shown in Table 1.

[0084] An aluminum vapor-deposited layer was formed as the inorganic vapor-deposited layer (D) on the resulting stretched multilayer film using a winding-type vacuum vapor deposition apparatus "EWA-105" manufactured by Japan Vacuum Engineering Co., Ltd., which has a transfer chamber and a vapor deposition chamber, by the following method. The "EWA-105" has an unwinder and a winder on the transfer chamber side, and a crucible for heating aluminum and a cooling can for cooling the film while transporting it inside the vapor deposition chamber, and the film is transported along the cooling can. The cooling can was cooled to -30°C, and the resulting stretched multilayer film was positioned so that a vapor-deposited layer was formed on the EVOH layer (A) side, and then transported at a transport speed of 150 m / min. Furthermore, a nozzle was installed in the deposition chamber to spray oxygen directly onto the stretched multilayer film before deposition (nozzle gap 2 mm, nozzle width 21 cm, film-to-nozzle distance 2 cm, angle to the film 30 degrees). Aluminum was vacuum-deposited while spraying oxygen at 80 mL / min, producing a vapor-deposited multilayer film in which an aluminum vapor-deposited layer with an average thickness of 50 nm was formed on the EVOH layer (A) of the stretched multilayer film. The average thickness of the aluminum vapor-deposited layer was adjusted by appropriately controlling the voltage applied to the crucible. The molar ratio of oxygen to aluminum (O / Al) was calculated for the vapor-deposited layer of the resulting vapor-deposited multilayer film according to the method described in Evaluation Method (2) above. The results are shown in Table 2.

[0085] A two-component urethane adhesive (Mitsui Chemicals, Inc.'s "Takelac™ A-520" and "Takenate™ A-50") was applied to the aluminum vapor-deposited layer side of VM-PET to an average dry thickness of 1.0 μm and dried to form an adhesive layer (Ad). This was then laminated to the aluminum vapor-deposited layer side of the resulting multilayer film to produce a laminate (PET-VM / Ad / aluminum vapor-deposited layer / EVOH layer (A) / adhesive layer (B) / thermoplastic resin layer (C)). Adhesive layers (average thickness 1.0 μm) were also formed on one side of OPA and LLDPE in the same manner as above, and OPA was laminated to the PET side and LLDPE to the thermoplastic resin layer (C) side to produce a multilayer structure (OPA / Ad / PET-VM / Ad / aluminum vapor-deposited layer / EVOH layer (A) / adhesive layer (B) / thermoplastic resin layer (C) / Ad / LLDPE). The obtained multilayer structure was evaluated according to the methods described in the above evaluation methods (4) to (6). The results are shown in Table 1.

[0086] [Examples 2 to 5] Multilayer films, vapor-deposited multilayer films, and multilayer structures were produced and evaluated in the same manner as in Example 1, except that in producing the multilayer films, the rotation speed of the EVOH layer (A) extruder was adjusted to change the average thickness of the EVOH layer (A) as shown in Table 1. The results are shown in Table 1. Evaluation by the above evaluation method (2) was not performed.

[0087] [Examples 6 and 7] Multilayer films, vapor-deposited multilayer films, and multilayer structures were produced and evaluated in the same manner as in Example 2, except that the type of EVOH was changed as shown in Table 1. The results are shown in Table 1. The evaluation by the above evaluation method (2) was not performed.

[0088] Comparative Example 1 A multilayer film, a vapor-deposited multilayer film, and a multilayer structure were produced and evaluated in the same manner as in Example 3, except that the type of EVOH was changed as shown in Table 1. The results are shown in Table 1. The evaluation by the above evaluation method (2) was not performed.

[0089] Comparative Example 2 A multilayer film, a vapor-deposited multilayer film, and a multilayer structure were produced and evaluated in the same manner as in Example 1, except that the extruders for the EVOH layer (A) and the adhesive layer (B) were stopped and the EVOH layer (A) and the adhesive layer (B) were not provided. The results are shown in Table 1. The evaluation by the above evaluation method (2) was not performed.

[0090] Comparative Example 3 A multilayer film, a vapor-deposited multilayer film, and a multilayer structure were produced and evaluated in the same manner as in Example 1, except that the materials for the adhesive layer (B) and the thermoplastic resin layer (C) were changed as shown in Table 1. The results are shown in Table 1. The evaluation by the above evaluation method (2) was not performed.

[0091] Comparative Example 4 A multilayer film, a vapor-deposited multilayer film, and a multilayer structure were produced and evaluated in the same manner as in Comparative Example 3, except that the material for the EVOH layer (A) was changed as shown in Table 1 and the rotation speeds of the EVOH layer (A) extruder and the thermoplastic resin layer (C) extruders 1 to 3 were adjusted to change the average thicknesses of the EVOH layer (A) and the thermoplastic resin layer (C) as shown in Table 1. The results are shown in Table 1. Evaluation by the above evaluation method (2) was not performed.

[0092] Examples 8 to 11 Multilayer films, vapor-deposited multilayer films, and multilayer structures were prepared and evaluated in the same manner as in Example 1, except that the amount of oxygen supplied during deposition was changed as shown in Table 2. The results are shown in Table 2.

[0093]

[0094]

Claims

1. A multilayer film for vacuum insulation material comprising an ethylene-vinyl alcohol copolymer layer (A), an adhesive layer (B) and a thermoplastic resin layer (C) in this order, the ethylene-vinyl alcohol copolymer layer (A) containing as its main component an ethylene-vinyl alcohol copolymer (a) having an ethylene unit content of 20 mol% or more and 30 mol% or less, the adhesive layer (B) containing as its main component an adhesive resin (b), and the thermoplastic resin layer (C) containing as its main component polyethylene (c), the multilayer film being stretched at least 3 times and no more than 12 times in one axial direction.

2. The multi-layer film for vacuum insulation according to claim 1, wherein the average thickness of the ethylene-vinyl alcohol copolymer layer (A) is 10 μm or less.

3. The multilayer film for vacuum insulation materials according to claim 1, wherein the ethylene-vinyl alcohol copolymer (a) has a melt flow rate of 1 g / 10 min or more and 10 g / 10 min or less under a load of 2160 g, as measured in accordance with the method described in ISO 1133-1:2011.

4. The multi-layer film for vacuum insulation materials according to claim 1, wherein the ethylene-vinyl alcohol copolymer layer (A) does not contain an ethylene-vinyl alcohol copolymer having an ethylene unit content of more than 30 mol %.

5. The multilayer film for vacuum insulation materials according to claim 1, wherein the ethylene-vinyl alcohol copolymer layer (A), the adhesive layer (B) and the thermoplastic resin layer (C) are coextruded.

6. A vapor-deposited multilayer film for vacuum insulation materials according to claim 1, comprising an inorganic vapor-deposited layer (D) on the surface of the ethylene-vinyl alcohol copolymer layer (A) opposite to the surface on which the adhesive layer (B) is laminated.

7. The inorganic vapor deposition layer (D) is mainly composed of aluminum, and has an aluminum oxide layer (D1) and an aluminum layer (D2) successively arranged in this order from the surface side in contact with the ethylene-vinyl alcohol copolymer layer (A), and in elemental analysis of the aluminum oxide layer (D1) in the depth direction, the maximum molar ratio of oxygen element to aluminum element (O / Al) measured by a scanning X-ray photoelectron spectroscopy analyzer is ＭＡＸ is 0.5 or more and 2.0 or less, and in an elemental analysis of the aluminum layer (D2) in the depth direction, the minimum molar ratio of oxygen element to aluminum element (O / Al) measured by a scanning X-ray photoelectron spectrometer ＭＩＮ The vapor-deposited multilayer film for vacuum insulation materials according to claim 6, wherein the value is less than 0.

5.

8. A multilayer structure for vacuum insulation materials, comprising the multilayer film for vacuum insulation materials or the vapor-deposited multilayer film for vacuum insulation materials according to any one of claims 1 to 7, and a thermoplastic resin layer (E) laminated thereon.

9. The multi-layer structure for vacuum insulation materials according to claim 8, wherein the thermoplastic resin layer (E) contains at least one material selected from the group consisting of polyamide, polyester, polyethylene and polypropylene.

10. The multilayer structure for vacuum insulation materials according to claim 8, further comprising an adhesive layer between the multilayer film for vacuum insulation materials or the vapor-deposited multilayer film for vacuum insulation materials and the thermoplastic resin layer (E).

11. A vacuum packaging bag comprising the multi-layer structure for vacuum insulation material according to claim 8.

12. A vacuum insulation material comprising the vacuum packaging bag according to claim 11 and a core material disposed inside the vacuum packaging bag, the inside of the vacuum packaging bag being reduced in pressure.