Gas barrier laminate, packaging material and vacuum insulation material using the same

Abstract

A gas barrier laminate according to the present disclosure has a laminated structure comprising a polyolefin-based substrate layer, a first polyvinyl alcohol-based resin layer, a vapor deposition layer, and a second polyvinyl alcohol-based resin layer in this order, wherein the vapor deposition layer directly contacts the first polyvinyl alcohol-based resin layer and the second polyvinyl alcohol-based resin layer, and a pressing hardness measured with a nanoindenter in a cross-section of the second polyvinyl alcohol-based resin layer is not more than 0.5 GPa.

Description

Technical Field

[0001] The present disclosure relates to a gas barrier laminate, a packaging material using the same, and a vacuum heat insulating material.

Background Art

[0002] A gas barrier laminate combining a plastic film base material and a vapor deposition layer is widely used as a packaging material for articles that require blocking of various gases such as water vapor and oxygen. Various improvements have been studied for the gas barrier laminate for the purpose of preventing a decrease in gas barrier properties and further improving the barrier properties. For example, Patent Document 1 discloses a gas barrier laminate characterized by having a base material having a polyethylene naphthalate layer, a layer composed of a composition containing an acrylic polyol and an isocyanate compound, and an inorganic thin film layer in this order.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in recent years, due to the increasing environmental awareness starting from problems such as marine plastic waste, there has been a growing demand for more efficient separation, collection, and recycling of plastic materials. That is, even in packaging materials that have conventionally been made more performance-oriented by combining various different materials, there has been a growing demand for single-materialization.

[0005] The inventor selected a polyolefin resin as a material excellent in recyclability. However, it became clear from the study of the inventor that there is room for improvement in the barrier properties after bending when attempting to achieve single-materialization using a polyolefin resin.

[0006] The present disclosure provides a gas barrier laminate including a polyolefin-based substrate layer and having excellent gas barrier properties even after being bent. The present disclosure also provides a packaging material and a vacuum insulation material using this gas barrier laminate. **Means for Solving the Problems**

[0007] In order to solve the above problems, the present disclosure provides the following gas barrier laminate, packaging material, and vacuum insulation material. [1] A gas barrier laminate having a laminated structure including a polyolefin-based substrate layer, a first polyvinyl alcohol-based resin layer, a vapor deposition layer, a second polyvinyl alcohol-based resin layer, in this order, and the vapor deposition layer is in direct contact with the first polyvinyl alcohol-based resin layer and the second polyvinyl alcohol-based resin layer, and the indentation hardness of the second polyvinyl alcohol-based resin layer measured by nanoindentation in cross-section is 0.5 GPa or less. [2] The gas barrier laminate according to [1], wherein the ratio (S2 / S1) of the indentation hardness (S2) of the second polyvinyl alcohol-based resin layer measured by nanoindentation in cross-section to the indentation hardness (S1) of the first polyvinyl alcohol-based resin layer measured by nanoindentation in cross-section is 3 to 10. [3] The gas barrier laminate according to [1] or [2], wherein the thickness of the first polyvinyl alcohol-based resin layer is 0.5 to 2.5 μm. [4] The gas barrier laminate according to any one of [1] to [3], wherein the second polyvinyl alcohol-based resin layer contains Si. [5] The gas barrier laminate according to any one of [1] to [4], wherein the second polyvinyl alcohol-based resin layer contains a silane coupling agent. [6] The gas barrier laminate according to any one of [1] to [5], wherein the vapor deposition layer contains aluminum or silicon oxide. [7] The gas barrier laminate according to any one of [1] to [6], wherein the polyolefin-based substrate layer and the first polyvinyl alcohol-based resin layer are coextruded layers. [8] A packaging material comprising the gas barrier laminate according to any one of [1] to [7]. [9] The packaging material according to [8], which is used for a package subjected to vacuum treatment.

[10] The packaging material according to [8], which is used for a package subjected to freezing treatment.

[11] A vacuum heat insulating material comprising the packaging material according to [8].

Advantages of the Invention

[0008] According to the present disclosure, there is provided a gas barrier laminate including a polyolefin-based substrate layer and having excellent gas barrier properties even after being bent. According to the present disclosure, there are provided a packaging material and a vacuum heat insulating material using this gas barrier laminate.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, the present disclosure is not limited to the following embodiments.

[0011] The gas barrier laminate according to this embodiment has a laminated structure including a polyolefin-based substrate layer, a first polyvinyl alcohol-based resin layer, a vapor deposition layer, and a second polyvinyl alcohol-based resin layer in this order. The vapor deposition layer is in direct contact with the first polyvinyl alcohol-based resin layer and the second polyvinyl alcohol-based resin layer, and the indentation hardness of the second polyvinyl alcohol-based resin layer measured by nanoindentation in cross-section is 0.5 GPa or less.

[0012] According to the above gas barrier laminate, the gas barrier property is excellent even after bending. The reason for such an effect is speculated by the present inventor as follows. That is, since the vapor deposition layer is hard but brittle, it is easily damaged by bending. In the above gas barrier laminate, the vapor deposition layer is in direct contact with the first and second polyvinyl alcohol-based resin layers. Further, the indentation hardness of the second polyvinyl alcohol-based resin layer measured by nanoindentation in cross-section is 0.5 GPa or less. Due to these, the polyvinyl alcohol-based resin layer serves as a flexible layer to prevent the expansion of cracks in the vapor deposition layer and as a gas barrier layer to fill defects in the vapor deposition layer. Therefore, the above gas barrier laminate has excellent gas barrier property even after bending.

[0013] For example, when another layer is provided between the first and second polyvinyl alcohol-based resin layers and the vapor deposition layer, the gas passing through the defects in the vapor deposition layer from the other layer will escape.

[0014] Since the above gas barrier laminate uses a polyolefin-based substrate layer as the substrate, it has better slipperiness and is more excellent in transportability compared with the case where EVOH is used as the substrate. Further, since the above gas barrier laminate uses a polyolefin-based substrate layer as the substrate and is less affected by heat, moisture, etc., it has a tendency to be excellent in processability.

[0015] FIG. 1 is a schematic cross-sectional view showing a gas barrier laminate according to an embodiment. The gas barrier laminate 100 shown in FIG. 1 includes a polyolefin-based substrate layer 10, a first polyvinyl alcohol-based resin layer 11, a vapor deposition layer 12, and a second polyvinyl alcohol-based resin layer 13, in this order.

[0016] (Polyolefin-based substrate layer) The polyolefin-based substrate layer (hereinafter, also simply referred to as "substrate layer") is a film that serves as one of the supports and contains a polyolefin-based resin.

[0017] Examples of the polyolefin-based resin include polyethylene (PE), polypropylene (PP), polybutene (PB), cycloolefin polymer, etc. Further, examples of the polyolefin-based resin include acid-modified polyolefin obtained by graft-modifying polyolefin with an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, etc. As raw material monomers during polypropylene synthesis, a small amount of second or third components such as ethylene or butene may be used. Since the polyolefin-based resin has high flexibility, it is difficult to break the bag even when containing liquid heavy objects, and when used as a packaging material subjected to vacuum treatment, it is easy to follow regardless of the contents and tends to be less likely to deteriorate in gas barrier properties. Therefore, polyethylene is preferable. From the viewpoint of excellent heat resistance, a homopolymer film of propylene can be used as the substrate layer.

[0018] Polyethylene is, for example, low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (L·LDPE), ethylene-vinyl acetate copolymer (EVA), or ethylene·α-olefin copolymer.

[0019] The film constituting the base material layer may be a stretched film or an unstretched film. However, from the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., the film constituting the base material layer may be a stretched film. The stretching method is not particularly limited, and any method may be used as long as a film with stable dimensions can be supplied, such as inflation stretching, uniaxial stretching, or biaxial stretching. From the viewpoint of excellent tearability regardless of the tearing direction, a biaxial stretched film is preferable.

[0020] The thickness of the base material layer is not particularly limited, but from the viewpoints of obtaining excellent impact resistance and excellent gas barrier properties, it can be 9 to 100 μm and may be 15 to 30 μm.

[0021] The film constituting the base material layer may be subjected to various pretreatment such as corona treatment, plasma treatment, and frame treatment, or a coating layer such as an easy adhesion layer may be provided on its laminated surface within a range that does not impair the barrier performance.

[0022] The film constituting the base material layer may contain additives such as an antistatic agent, an ultraviolet absorber, a plasticizer, and a lubricant as necessary.

[0023] The content of the polyolefin resin in the base material layer may be 70% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass based on the total amount of the base material layer.

[0024] (First polyvinyl alcohol resin layer) The polyvinyl alcohol resin may be any resin having a vinyl alcohol unit formed by saponifying a vinyl ester unit. For example, polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH) can be mentioned. From the viewpoints of heat resistance and gas barrier properties, EVOH can be preferably used.

[0025] Examples of the PVA include resins obtained by polymerizing a vinyl ester such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprylate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl versatate, etc. alone and then saponifying the polymerized product.

[0026] The PVA may be a modified PVA modified by copolymerization or post-modification. The copolymerization-modified PVA can be obtained, for example, by copolymerizing a vinyl ester and an unsaturated monomer copolymerizable with the vinyl ester and then saponifying the copolymer. The post-modified PVA can be obtained by copolymerizing an unsaturated monomer in the presence of a polymerization catalyst with the PVA obtained by polymerizing a vinyl ester and then saponifying the polymerized product. From the viewpoint of exhibiting sufficient gas barrier properties, the amount of modification in the modified PVA can be less than 50 mol%, and from the viewpoint of obtaining the effect of modification, it can be 10 mol% or more.

[0027] Examples of the above unsaturated monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene; hydroxy group-containing α-olefins such as 3-buten-1-ol, 4-pentin-1-ol, 5-hexen-1-ol; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, undecylenic acid; nitriles such as acrylonitrile, methacrylonitrile; amides such as diacetoneacrylamide, acrylamide, methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid; vinyl compounds such as alkyl vinyl ether, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, 3,4-diacetoxy-1-butene; vinylidene chloride, 1,4-diacetoxy-2-butene, vinylene carbonate, polyoxypropylene, polyoxypropylene vinylamine, etc. From the viewpoint of gas barrier properties, the unsaturated monomer can be an olefin, particularly ethylene.

[0028] Examples of the polymerization catalyst include radical polymerization catalysts such as azobisisobutyronitrile, benzoyl peroxide, and lauryl peroxide. The polymerization method is not particularly limited, and bulk polymerization, emulsion polymerization, solution polymerization, etc. can be employed.

[0029] The degree of polymerization of PVA is preferably from 300 to 3000. When the degree of polymerization is 300 or more, there is a tendency for better barrier properties, and when it is 3000 or less, there is a tendency for better coating suitability. The saponification degree of PVA is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 98 mol% or more. Also, the saponification degree of PVA may be 100 mol% or less, or 99.9 mol% or less. The degree of polymerization and saponification degree of PVA can be measured according to the method described in JIS K 6726 (1994).

[0030] EVOH is generally obtained by saponifying a copolymer of ethylene and a vinyl ester such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprylate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate.

[0031] The ethylene unit content of EVOH is 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, and particularly preferably greater than 35 mol%. Also, the ethylene unit content of EVOH is preferably 65 mol% or less, more preferably 55 mol% or less, and even more preferably less than 50 mol%. When the ethylene unit content is 10 mol% or more, the gas barrier properties or dimensional stability under high humidity can be maintained well. On the other hand, when the ethylene unit content is 65 mol% or less, the gas barrier properties can be enhanced. The ethylene unit content of EVOH can be determined by the NMR method.

[0032] Saponification can be carried out with an alkali or an acid, but an alkali can be used from the viewpoint of saponification rate. Examples of the alkali include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal alkoxides such as sodium ethylate, potassium ethylate, and lithium methylate.

[0033] The thickness of the first polyvinyl alcohol-based resin layer is not particularly limited, but from the viewpoints of barrier properties and processability, it can be 0.05 to 5 μm, may be 0.5 to 2.5 μm, and may be 0.3 to 1.5 μm.

[0034] The mass per unit area of the first polyvinyl alcohol-based resin layer can be 0.1 to 10 g / m 2 This mass can be 0.1 g / m 2 If it is 2 or more, even if the smoothness of the surface of the base material layer is insufficient, the surface of the first polyvinyl alcohol-based resin layer can be formed sufficiently smoothly, and a vapor deposition layer excellent in gas barrier properties can be formed on the surface. On the other hand, if this mass is 10 g / m 2 or less, it is advantageous in terms of realizing a single material of the packaging material and reducing the material cost.

[0035] The indentation hardness by a nanoindenter in the cross section of the first polyvinyl alcohol-based resin layer may be 0.05 to 0.1 GPa. The indentation hardness is measured by the method described in the examples below.

[0036] (Vapor deposition layer) The vapor deposition layer is a layer (gas barrier layer) that exhibits gas barrier properties against water vapor and oxygen. The vapor deposition layer may contain at least one of a metal and an inorganic oxide. The vapor deposition layer may have a single-layer structure or a laminated structure. The vapor deposition layer includes at least one of a metal vapor deposition layer and an inorganic oxide layer. When the vapor deposition layer includes a metal vapor deposition layer, examples of the metal contained in the metal vapor deposition layer include aluminum and stainless steel. When the vapor deposition layer includes an inorganic oxide layer, examples of the inorganic oxide contained in the inorganic oxide layer include aluminum oxide, silicon oxide, magnesium oxide, tin oxide, etc. From the viewpoints of transparency and barrier properties, the inorganic oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Also, from the viewpoint of excellent tensile drawability during processing, it is preferable to use a layer using silicon oxide as the inorganic oxide layer. By using the inorganic oxide layer, a very thin layer within a range that does not affect the recyclability of the gas barrier laminate can provide high barrier properties.

[0037] The layer thickness of the vapor deposition layer can be 5 to 80 nm. When the layer thickness is 5 nm or more, it becomes easier to obtain sufficient gas barrier properties. Also, when the layer thickness is 80 nm or less, the generation of cracks due to deformation by the internal stress of the thin film is suppressed, and a decrease in gas barrier properties is likely to be suppressed. From the above viewpoints, the layer thickness of the vapor deposition layer may be 10 to 50 nm, or may be 20 to 40 nm.

[0038] (Second polyvinyl alcohol-based resin layer) Regarding the polyvinyl alcohol-based resin constituting the second polyvinyl alcohol-based resin layer, reference can be made to the content described in the section of the first polyvinyl alcohol-based resin layer.

[0039] The indentation hardness by nano-indentation in the cross-section of the second polyvinyl alcohol-based resin layer is 0.5 GPa or less, and since it is further excellent in gas barrier properties after bending, it is preferably less than 0.5 GPa, more preferably 0.4 GPa or less, and still more preferably 0.3 GPa or less. The indentation hardness of the second polyvinyl alcohol-based resin layer may be 0.05 GPa or more. The indentation hardness is measured by the method described in the examples below.

[0040] The ratio (S2 / S1) of the indentation hardness (S2) by nano-indentation in the cross-section of the second polyvinyl alcohol-based resin layer to the indentation hardness (S1) by nano-indentation in the cross-section of the first polyvinyl alcohol-based resin layer is preferably 3 to 10 because it is further excellent in gas barrier properties after bending.

[0041] The second polyvinyl alcohol-based resin layer may contain Si. Specifically, the second polyvinyl alcohol-based resin layer may be a cured product of a raw material containing a polyvinyl alcohol-based resin and a silane compound. Examples of the silane compound include tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane, and silazanes such as hexamethyldisilazane. As the silane compound, a compound generally used as a silane coupling agent or a polysiloxane compound having a siloxane bond may also be used. Examples of the silane coupling agent include epoxy silane (such as glycidoxypropyltrimethoxysilane), (meth)acrylic silane (such as acryloxypropyltrimethoxysilane), amino silane, ureido silane, isocyanate silane, isocyanurate silane (such as tris(3-trialkoxysilylpropyl)isocyanurate), and mercapto silane.

[0042] When forming the second polyvinyl alcohol-based resin layer, the amount of the silane compound in the above raw materials can be adjusted according to the indentation hardness by a nanoindenter in the cross-section of the second polyvinyl alcohol-based resin layer, and since the resulting gas barrier laminate has excellent gas barrier properties after being bent, it can be 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, and more preferably 1 to 5 parts by mass with respect to 1 part by mass of the polyvinyl alcohol-based resin.

[0043] The thickness of the second polyvinyl alcohol-based resin layer is not particularly limited, but from the viewpoints of barrier properties and processability, it can be 0.05 to 2 μm, preferably 0.1 to 0.6 μm, and more preferably 0.2 to 0.5 μm.

[0044] <Method for manufacturing a gas barrier laminate> The gas barrier laminate can be manufactured, for example, by a manufacturing method including a step of forming a first polyvinyl alcohol-based resin layer on a base material layer, a step of forming a vapor deposition layer on the first polyvinyl alcohol-based resin layer, and a step of forming a second polyvinyl alcohol-based resin layer on the vapor deposition layer.

[0045] (Step of forming the first polyvinyl alcohol-based resin layer) In this step, a coating solution containing a polyvinyl alcohol-based resin and a liquid medium can be used. The coating solution can be obtained, for example, by dissolving a powder of a polyvinyl alcohol-based resin obtained by synthesis in a liquid medium. Examples of the liquid medium include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. From the viewpoint of reducing environmental load, water can be used as the liquid medium. In this case, a coating solution can be obtained by dissolving the powder of the polyvinyl alcohol-based resin in hot water (for example, 80 °C).

[0046] The content of the polyvinyl alcohol-based resin (solid content) in the coating liquid can be 3 to 20% by mass from the viewpoint of maintaining good coatability.

[0047] The coating liquid may contain additives such as isocyanate and polyethyleneimine to improve adhesion. Further, the coating liquid may contain additives such as preservatives, plasticizers, alcohols, and surfactants.

[0048] The coating liquid can be applied to the base material layer by any suitable method. The application of the coating liquid can be carried out by a wet film-forming method such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, or a die coater. The coating temperature and the drying temperature of the coating liquid are not particularly limited and can be, for example, 50°C or higher.

[0049] The first polyvinyl alcohol-based resin layer may be formed on the base material layer by an extrusion method. In the case of extrusion, multilayer extrusion using a T-die can be employed. Examples of the adhesive that can be used during extrusion include maleic anhydride-modified polypropylene resin.

[0050] After applying the above adhesive component onto the base material layer and drying it, an adhesive layer may be pre-formed on the base material layer.

[0051] The thickness of the adhesive layer can be 0.1 to 50 μm, and may be 0.5 to 20 μm, from the viewpoints of adhesiveness, followability, processability, etc.

[0052] The base material layer and the first polyvinyl alcohol-based resin layer may be a coextruded layer formed by a coextrusion method. When these layers are coextruded layers, the laminate tends to obtain good adhesion and is easy to maintain gas barrier properties.

[0053] (Step of forming a vapor deposition layer) The vapor deposition layer can be formed, for example, by vacuum deposition. In vacuum deposition, a physical vapor deposition method or a chemical vapor deposition method can be used. Examples of the physical vapor deposition method include, but are not limited to, vacuum evaporation, sputtering, ion plating, etc. Examples of the chemical vapor deposition method include, but are not limited to, thermal CVD, plasma CVD, photo CVD, etc.

[0054] In the above vacuum deposition, a resistance heating type vacuum evaporation method, an EB (Electron Beam) heating type vacuum evaporation method, an induction heating type vacuum evaporation method, sputtering, reactive sputtering, dual magnetron sputtering, plasma chemical vapor deposition (PECVD method), etc. are particularly preferably used. However, considering productivity, the vacuum evaporation method is the most excellent at present. As the heating means of the vacuum evaporation method, it is preferable to use any one of an electron beam heating method, a resistance heating method, and an induction heating method.

[0055] (Step of forming the second polyvinyl alcohol-based resin layer) In this step, a coating solution can be used in the same manner as in the step of forming the first polyvinyl alcohol-based resin layer. Regarding the coating solution, reference can be made to the content described in the section of the step of forming the first polyvinyl alcohol-based resin layer.

[0056] The coating solution for forming the second polyvinyl alcohol-based resin layer may contain a silane compound. The content of the silane compound in the coating solution may be adjusted so that a desired amount of the silane compound is contained with respect to the amount of the polyvinyl alcohol-based resin.

[0057] When the coating solution contains a silane compound, the coating solution may further contain an acid catalyst, an alkali catalyst, a photoinitiator, etc.

[0058] <Packaging material> The packaging material includes the above gas barrier laminate and a sealant layer provided on the surface of the gas barrier laminate. Examples of the sealant layer include a layer containing a polyolefin resin or a polyester resin. Examples of the polyolefin resin include polyethylene (PE), polypropylene (PP), polybutene (PB), cycloolefin polymer, etc. Further, examples of the polyolefin resin include acid-modified polyolefin obtained by graft-modifying polyolefin with an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, etc. As raw material monomers during the synthesis of polypropylene, a small amount of second or third components such as ethylene or butene may be used. Since the polyolefin resin has high flexibility, it is difficult to break the bag even when containing liquid heavy objects, and when used as a packaging material subjected to vacuum treatment, it is easy to follow regardless of the contents and tends to be less likely to deteriorate the gas barrier property. From this viewpoint, polyethylene is preferable. Polyethylene is, for example, low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (L·LDPE), ethylene-vinyl acetate copolymer (EVA) or ethylene-α-olefin copolymer. Figure 2 is a schematic cross-sectional view showing a packaging material according to an embodiment.

[0059] The packaging material 200 shown in FIG. 2 includes a gas barrier laminate 100 and a sealant layer 14 provided on the surface of the gas barrier laminate 100 opposite to the base material layer (on the surface of the second polyvinyl alcohol-based resin layer). For example, when both the base material layer 10 and the sealant layer 14 are made of a polyolefin resin, based on the total mass of the packaging material 200, the content of the polyolefin resin can be 90% by mass or more (preferably 95% by mass or more). Such a packaging material 200 can achieve a single material. The packaging material 200 is preferably used for a package to be subjected to a vacuum treatment. In the vacuum treatment, bending caused by the contents occurs in the packaging material. Since the packaging material 200 includes a gas barrier laminate that is excellent in gas barrier properties even after being bent, it is excellent in gas barrier properties even after the vacuum treatment. Further, the packaging material 200 is preferably used for a package to be subjected to a freezing treatment. Here, the package includes a packaging bag composed of the packaging material 200 and the contents accommodated in the packaging bag.

[0060] Examples of the contents include foods, liquids, pharmaceuticals, electronic components, and the heat insulating core material described later.

[0061] When both the base material layer 10 and the sealant layer 14 are made of polypropylene, based on the total mass of the packaging material 200, the content of polypropylene can be 90% by mass or more (preferably 95% by mass or more). Also, when both the base material layer 10 and the sealant layer 14 are made of polyethylene, based on the total mass of the packaging material 200, the content of polyethylene can be 90% by mass or more (preferably 95% by mass or more). Since the base material layer 10 and the sealant layer 14 are highly flexible, it is difficult to break the bag even when containing a liquid heavy object, and when used as a packaging material subjected to a vacuum treatment, it is easy to follow regardless of the contents and the gas barrier property tends to be less deteriorated, so it is preferable that both contain polyethylene.

[0062] The content of the polyolefin resin in the packaging material 200 is preferably 90% by mass based on the total amount of the packaging material 200.

[0063] The packaging material of the present disclosure is not limited to the above embodiments. For example, the packaging material 200 may further include a resin layer between the sealant layer and the gas barrier laminate. Examples of the material constituting such a resin layer include nylon, polyethylene terephthalate, and polyolefin.

[0064] Also, the packaging material of the present disclosure may further include a gas barrier laminate. The packaging material 300 shown in FIG. 3 includes a gas barrier laminate 100a, a resin layer 15, a gas barrier laminate 100b, and a sealant layer 14. The packaging material 300 is suitably used as a vacuum insulation material. The vacuum insulation material includes a packaging bag formed of the packaging material 300 and a heat insulating core material accommodated in the packaging bag. Examples of the heat insulating core material include glass fiber and rigid urethane.

[0065] In the vacuum insulation material, the pressure inside the packaging material 300 is 10 5 Pa or less, 10 2 Pa or less, 10 -1 Pa or less, 10 -5 Pa or less, or 10 -8 Pa or less, and may be 10 -8 Pa or more, 10 -5 Pa or more, 10 -1 Pa or more, or 10 2 Pa or more.

[0066] The vacuum insulation material can be used, for example, as a member that covers the outer surface of a cold storage device and a heat insulation device to maintain heat insulation, a member that covers the outer surface of a cold storage container and a heat insulation container to maintain heat insulation, and an outer wall material used in construction applications. Examples of the cold storage device and the heat insulation device include a vending machine, a refrigerator, a freezer, a jar pot, and a rice cooker. Examples of the cold storage device and the heat insulation device include a cooler box and a water cylinder. Examples of the building in which the outer wall material is used include a house and a cold storage warehouse.

[0067] In the packaging material 300, the gas barrier laminate 100b is arranged such that the second polyvinyl alcohol-based resin layer 13 becomes the resin layer side 15, but the base material layer 10 may be positioned on the resin layer 15 side.

Example

[0068] Hereinafter, the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to these examples.

[0069] The following materials were prepared. (Film) · CPP film: manufactured by Toray Industries, Inc., trade name "Trefan ZK207", thickness 60 μm · LLDPE film 1: manufactured by Mitsui Chemicals Toagosei Co., Ltd., trade name "TUX-MCS", thickness 60 μm · LLDPE film 2: manufactured by Mitsui Chemicals Toagosei Co., Ltd., trade name "FCS", thickness 40 μm · ONY film: manufactured by Unitika Ltd., trade name "Emblem ONM", thickness 15 μm (Adhesive) · Manufactured by Mitsui Chemicals SKC Polyurethane Co., Ltd., trade name "A525 / A52", two-component type (Coating liquid A) Polyvinyl alcohol (trade name: Kuraray Poval 60-98, manufactured by Kuraray Co., Ltd., hereinafter also referred to as "PVA") was prepared as an aqueous solution with a solid content of 5%. (Coating liquid B) Tetraethoxysilane (trade name: KBE04, solid content: 100%, manufactured by Shin-Etsu Chemical Co., Ltd., hereinafter also referred to as "TEOS"), methanol (Kanto Chemical), and 0.1N hydrochloric acid (Kanto Chemical) were mixed so that the weight ratio was 17 / 10 / 73 to prepare a hydrolysis solution with a solid content of 5% (in terms of weight ratio SiO2 conversion). (Coating liquid C) 1,3,5-Tris(3-methoxysilylpropyl) isocyanurate (silane coupling agent) was prepared as a hydrolysis solution with a solid content of 5% (in terms of weight ratio RSi(OH)3 conversion) in a water / IPA = 1 / 1 solution.

[0070] [First study] <Production of Gas Barrier Laminate> (Example 1) While forming an OPP film (polyolefin-based substrate layer) using a monomer resin of polypropylene, an EVOH layer (first polyvinyl alcohol-based resin layer) was formed on the surface of the OPP film by a coextrusion method. The mass per unit area of the EVOH layer was 0.97 g / m 2 .

[0071] Using a vacuum deposition apparatus with an electron beam heating method, silicon oxide was deposited on the surface of the first polyvinyl alcohol-based resin layer to form a SiO x deposition film (deposition layer, thickness: 50 nm).

[0072] A mixture of coating liquids A, B, and C was obtained. The mixing ratio of coating liquids A, B, and C was adjusted so that PVA / SiO2 / silane coupling agent (SC agent) had the solid content mass ratio shown in Table 1. The mixture was applied to the surface of the deposition layer opposite to the first polyvinyl alcohol-based resin layer to form a coating film, and the coating film was dried to form a second polyvinyl alcohol-based resin layer (thickness: 300 nm). Thereby, a gas barrier laminate was obtained.

[0073] (Example 2) SiO x Instead of the SiO deposition film, an AL deposition film (thickness: 50 nm) was formed by depositing AL on the surface of the first polyvinyl alcohol-based resin layer using a vacuum deposition apparatus with an electron beam heating method. A gas barrier laminate was obtained in the same manner as in Example 1 except for this.

[0074] (Example 3) A polypropylene film (manufactured by Mitsui Chemicals Toagosei Co., Ltd., trade name "ME-1", thickness: 20 μm) was prepared as the base material layer. An EVOH solution (manufactured by Mitsubishi Chemical Corporation, trade name: 16DX) was dissolved in a mixed solution of water and IPA to prepare a solution with a solid content of 5% by mass. The obtained solution was coated on the surface of the polypropylene film that had been subjected to corona treatment to form a coating film, and the coating film was dried to form a first polyvinyl alcohol-based resin layer (thickness: 0.8 μm). In the same manner as in Example 1, a vapor deposition layer was formed on the surface of the first polyvinyl alcohol-based resin layer, and a second polyvinyl alcohol-based resin layer was formed on the vapor deposition layer to obtain a gas barrier laminate.

[0075] (Example 4) A gas barrier laminate was obtained in the same manner as in Example 3, except that the mixing ratios (PVA / SiO2 / SC agent) of coating liquids A, B, and C were adjusted to the solid content mass ratios shown in Table 1.

[0076] (Example 5) A gas barrier laminate was obtained in the same manner as in Example 1, except that a biaxially oriented HDPE (BOPE: Biaxially Oriented Polyethylene) film was used instead of the OPP film as the polyolefin-based base material layer.

[0077] (Example 6) A gas barrier laminate was obtained in the same manner as in Example 2, except that a biaxially oriented HDPE film (thickness: 24.2 nm) was used instead of the OPP film as the polyolefin-based base material layer, and the thickness of the AL vapor deposition film was 75 nm.

[0078] (Example 7) A gas barrier laminate was obtained in the same manner as in Example 5, except that the mixing ratios (PVA / SiO2 / SC agent) of coating liquids A, B, and C were adjusted to the solid content mass ratios shown in Table 2.

[0079] (Example 8) A gas barrier laminate was obtained in the same manner as in Example 6, except that the mixing ratios (PVA / SiO2 / SC agent) of Coating Liquids A, B, and C were adjusted to the solid content mass ratios shown in Table 2.

[0080] (Comparative Example 1) A gas barrier laminate was obtained in the same manner as in Example 1, except that the mixing ratios of Coating Liquids A, B, and C were set to the solid content mass ratios shown in Table 1.

[0081] (Comparative Example 2) A biaxially stretched EVOH film (manufactured by Kuraray Co., Ltd., trade name "VM-XL") vapor-deposited with AL was used as the gas barrier laminate.

[0082] (Comparative Example 3) A gas barrier laminate was obtained in the same manner as in Example 1, except that the second polyvinyl alcohol-based resin layer was not formed.

[0083] (Comparative Example 4) A polypropylene film (thickness: 20 μm) was prepared as the base material layer. An anchor coat layer was formed on the surface of the base material layer. Using an electron beam heating type vacuum vapor deposition apparatus, silicon oxide was vapor-deposited on the surface of the anchor coat layer to form a SiO x vapor deposition film (vapor deposition layer, thickness: 50 nm). A mixture of Coating Liquids A, B, and C was obtained in the same manner as in Example 1. The mixture was applied to the surface of the vapor deposition layer opposite to the base material layer to form a coating film, and the coating film was dried to form a second polyvinyl alcohol-based resin layer (thickness: 300 nm). Thereby, a gas barrier laminate was obtained.

[0084] (Comparative Example 5) A gas barrier laminate was obtained in the same manner as in Example 5, except that the mixing ratios (PVA / SiO2 / SC agent) of Coating Liquids A, B, and C were adjusted to the solid content mass ratios shown in Table 2.

[0085] (Comparative Example 6) A gas barrier laminate was obtained in the same manner as in Example 5, except that the second polyvinyl alcohol-based resin layer was not formed.

[0086] (Comparative Example 7) A biaxially stretched HDPE film (thickness: 25 nm) with AL (thickness: 75 nm) vapor-deposited was used as the gas barrier laminate.

[0087] <Measurement of indentation hardness> The indentation hardness of the first and second polyvinyl alcohol-based resin layers of the gas barrier laminates obtained in each example and comparative example was measured. The indentation hardness was measured by the nanoindentation method. The nanoindentation method is a measurement method in which a quasi-static indentation test is performed on the target measurement object to obtain the mechanical properties of the sample.

[0088] The measurement sample (cross-sectional sample) was prepared as follows. That is, after corona treatment was performed on both sides of the gas barrier laminate, it was embedded in a visible light curable resin D-800. Then, using an ultramicrotome Leica EM UC7 and a diamond knife Microstar LH, the gas barrier laminate was cut perpendicular to the lamination direction. The exposed cross-section was finish-processed under the conditions of a cutting thickness Feed of 100 nm and a cutting speed Speed of 1 mm / s to obtain a measurement sample.

[0089] For the measurement, Hysitron TI-Premier (trade name) manufactured by Bruker Japan Co., Ltd. was used as the measurement device, and a Berkovich-type diamond indenter manufactured by Bruker Japan Co., Ltd. was used as the indenter. The measurement conditions were as follows.

[0090] Temperature: room temperature (25 °C). Mode: load control mode. Indentation and unloading: After indentation was performed at an indentation speed of 1.5 μN / second up to a load of 15 μN, it was held for 5 seconds at the maximum load and then unloaded at a speed of 1.5 μN / second. Measurement location: By using the shape measurement function of the measurement device that scans the sample surface with the indenter, the shape image of the cross-section of the second polyvinyl alcohol-based resin layer was obtained, and 20 points were specified at intervals of 1 μm or more on the cross-section of the second polyvinyl alcohol-based resin layer from the shape image.

[0091] When calculating the indentation hardness, fused quartz was used as a standard sample, and the relationship between the contact depth and the contact projected area of the indenter and the sample was calibrated in advance. Thereafter, the unloading curve in the range of 60 to 95% of the maximum load during unloading was analyzed by the Oliver-Pharr method to calculate the indentation hardness.

[0092] <Evaluation of the slipperiness of the gas barrier laminate> For the gas barrier laminates of each example and comparative example, the coefficient of kinetic friction between the main surface on the base material layer side and the main surface on the opposite side was measured. The measurement was carried out in accordance with JIS K7125, with a test width of 80 × 200 mm, a contact area of the sliding piece of 40 cm 2 , and a sliding speed of 100 mm / min. The measured values (unit: μD) were evaluated according to the following criteria. The results are shown in Tables 1 and 2.

[0093] (Criteria) A: The measured value is 1.0 μD or less B: The measured value exceeds 1.0 μD or the laminate is not slippery and zipperring occurs and the measurement cannot be performed

[0094] <Transportability> The first mother roll obtained by winding the gas barrier laminates (width: 500 mm) of each example and comparative example was prepared. The gas barrier laminate was fed out from the mother roll by roll-to-roll and wound up as the second mother roll. The feeding speed was 50 m / min. When wrinkles occurred in the second mother roll, the evaluation was "B", and when no wrinkles occurred, the evaluation was "A". The results are shown in Tables 1 and 2.

[0095] <Mass ratio of polyolefin resin> (Examples 1 to 4, Comparative Examples 1 to 4) The gas barrier laminates of each example and comparative example and a CPP film (sealant layer, manufactured by Mitsui Chemicals Toagosei Co., Ltd., trade name "TUX-MCS", thickness: 60 μm) were dry laminated with a two-component curable adhesive (manufactured by Mitsui Chemicals, trade names "A525" and "A50") having a thickness of 3 μm to obtain a laminated film. They were bonded so that the surface on the side opposite to the base material layer of the gas barrier laminate faced the CPP film.

[0096] The mass ratio of the polyolefin resin (polypropylene) in the laminate film was determined from the masses of the gas barrier laminate, the CPP film (thickness: 60 μm), and the adhesive (thickness: 3 μm). The results are shown in Table 1.

[0097] (Examples 5 to 8, Comparative Examples 5 to 7) The mass ratio of the polyolefin resin (polyethylene) in the laminate film was determined in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 4, except that LLDPE Film 1 was used instead of the CPP film as the sealant layer. The results are shown in Table 2.

[0098] <Oxygen Permeability Measurement (Initial)> (Examples 1 to 4, Comparative Examples 1 to 4) The gas barrier laminate and the CPP film (sealant layer) of each example and comparative example were dry-laminated with an adhesive to obtain a laminate film. They were bonded so that the surface of the gas barrier laminate opposite to the base material layer faced the CPP film. The oxygen permeability of the laminate film was measured. The measurement was carried out using an oxygen permeability measuring device (OXTRAN 2 / 20 manufactured by Modern Control) under the conditions of a temperature of 30°C and a relative humidity of 70%. The measurement method conformed to JIS K-7126, Method B (isobaric method), and ASTM D3985-81. The results are shown in Table 1. The measured values are expressed in the unit [cc / m 2 ·day·atm].

[0099] (Examples 5 to 8, Comparative Examples 5 to 7) The oxygen permeability was measured in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 4, except that LLDPE Film 1 was used instead of the CPP film as the sealant layer. The results are shown in Table 2.

[0100] <Water Vapor Permeability Measurement (Initial)> In the same manner as the oxygen permeability measurement (initial stage), laminate films were obtained using the gas barrier laminates of each example and comparative example. The water vapor permeability of the laminate films was measured. The measurement was carried out using an oxygen permeability measuring device (PERMATRAN 3 / 31, manufactured by Modern Control) under the conditions of a temperature of 40°C and a relative humidity of 90%. The measurement method complied with JIS K-7126, Method B (isobaric method), and ASTM D3985-81. The results are shown in Tables 1 and 2. The measured values were expressed in the unit [g / m 2 ·day].

[0101] <Laminate strength> In the same manner as the oxygen permeability measurement (initial stage), laminate films were obtained using the gas barrier laminates of each example and comparative example. For the laminate films, the laminate strength was measured. The measurement complied with JIS K6854 and was carried out with a test width of 15 mm, a peeling speed of 300 mm / min, and a peeling angle of 180°. The results are shown in Tables 1 and 2. The measured values were expressed in the unit [N / 15 mm].

[0102] <Bending test> In the same manner as the oxygen permeability measurement (initial stage), laminate films were obtained using the gas barrier laminates of each example and comparative example. A test piece of 210 mm × 297 mm was cut out from the laminate film. Both ends of the test piece were bonded together and rolled into a cylindrical shape. Both ends of the cylindrical test piece were held by a fixed head and a driving head. The following steps 1 to 4 were taken as one cycle, and 100 cycles were carried out at 25°C. The speed of performing the cycle was 40 cycles / min. The oxygen permeability after the bending test was measured in the same manner as the oxygen permeability measurement (initial stage). The water vapor permeability after the bending test was measured in the same manner as the water vapor permeability measurement (initial stage).

[0103] Step 1: While applying a 440-degree twist to the test piece, narrow the distance between the fixed head and the driving head from 7 inches to 3.5 inches. Step 2: While keeping the twist applied to the test piece, narrow the distance between the heads to 1 inch. Step 3: Widen the distance between the heads to 3.5 inches. Step 4: While returning the twist, widen the distance between the heads to 7 inches.

[0104]

Table 1

[0105]

Table 2

[0106] [Second Consideration] [Manufacture of Laminate Film] (Example 1A) A gas barrier laminate was obtained in the same manner as in Example 1 of the first consideration. The gas barrier laminate and a CPP film (sealant layer) were dry-laminated with an adhesive to obtain a laminate film. They were bonded so that the surface on the second polyvinyl alcohol-based resin layer side of the gas barrier laminate faced the CPP film.

[0107] (Example 1B) A laminate film was obtained in the same manner as in Example 1A, except that LLDPE film 1 was used instead of the CPP film.

[0108] (Example 1C) A gas barrier laminate was obtained in the same manner as in Example 1 of the first consideration. The gas barrier laminate and an ONY film were dry-laminated with an adhesive to obtain a laminate. They were bonded so that the surface on the second polyvinyl alcohol-based resin layer side of the gas barrier laminate faced the ONY film. Then, the surface on the ONY film side of the laminate and LLDPE film 1 were dry-laminated with an adhesive to obtain a laminate film.

[0109] (Comparative Example 3A) A laminate film was obtained in the same manner as in Example 1A, except that the gas barrier laminate of Comparative Example 3 was used instead of the gas barrier laminate of Example 1.

[0110] [Gas Barrier Property after Vacuum Treatment] The laminate films of each example and comparative example were cut into pieces with a size of 315 mm in length and 230 mm in width. These were folded in half and three sides were heat-sealed to produce a pouch having an opening. Glass beads with a diameter of 1 cm to 2 cm were placed in this pouch. Subsequently, a package subjected to vacuum treatment was obtained using a small chamber type vacuum packaging machine. The package was opened after 1 hour. For the opened packaging bag, the oxygen permeability and water vapor permeability were measured in the same manner as the oxygen permeability measurement (initial) and water vapor permeability measurement (initial). The results are shown in Table 3.

[0111] <Gas barrier properties after vacuum treatment and boiling treatment> The laminate films of each example and comparative example were cut into pieces with a size of 315 mm in length and 230 mm in width. These were folded in half and three sides were heat-sealed to produce a pouch having an opening. Glass beads with a diameter of 1 cm to 2 cm were placed in this pouch. Subsequently, a package subjected to vacuum treatment was obtained using a small chamber type vacuum packaging machine. The package was opened after 10 minutes, water was put in again, and the opening was heat-sealed to obtain a package. The package was subjected to boiling treatment at 90 °C for 3 minutes. For the packaging bag after boiling treatment, the oxygen permeability and water vapor permeability were measured in the same manner as the oxygen permeability measurement (initial) and water vapor permeability measurement (initial). The results are shown in Table 3.

[0112] <Presence or absence of discoloration of food after vacuum treatment and freezing treatment> The laminate films of each example and comparative example were cut into pieces with a size of 315 mm in length and 230 mm in width. These were folded in half and three sides were heat-sealed to produce a pouch having an opening. This pouch was filled with red-colored fish meat (amberjack) and subjected to vacuum treatment to obtain a package. The package was stored at -25 °C for 1 month. Photographs of the package before and after storage were visually compared. Those with no change in the color appearance of the red-colored fish meat were designated as "A", and those discolored to brown due to freezer burn were designated as "B". The results are shown in Table 3.

[0113]

Table 3

[0114] [Third Consideration] (Example 1D) In the same manner as in Example 1 of the first consideration, two gas barrier laminates were obtained. The second polyvinyl alcohol-based resin layer of the gas barrier laminate of the first Example 1 and the ONY film were dry laminated with an adhesive to obtain a first laminate. Next, the surface on the ONY film side of the first laminate and the surface on the second polyvinyl alcohol-based resin layer side of the second gas barrier laminate of Example 1 were dry laminated using an adhesive to obtain a second laminate. The surface on one base material layer side of the second laminate and the LLDPE film 2 were dry laminated with an adhesive to obtain a laminated film.

[0115] (Comparative Example 3B) A laminated film was obtained in the same manner as in Example 1D, except that the gas barrier laminate of Comparative Example 3 was used instead of the gas barrier laminate of Example 1.

[0116] <Evaluation of Vacuum Insulation Material> Vacuum insulation materials were manufactured from the laminated films of Example 1D and Comparative Example 3B. Specifically, two sheets of each laminated film (size: 300 mm × 300 mm) were prepared. By facing the laminated films and heat-sealing three sides, a packaging bag for accommodating a heat insulation core material with only one side open was obtained. As the heat insulation core material, glass fiber (290 × 290 mm) that had been subjected to a drying treatment (temperature: 120°C, time: 1 hour) was prepared. The glass fiber was accommodated in the packaging bag. After evacuating the internal space of the packaging bag to make the pressure inside the bag 1.0 Pa, the opening of the bag was heat-sealed and sealed. Thereby, a vacuum insulation material (thickness: 5 mm, length: 300 mm, width: 300 mm) was obtained.

[0117] The vacuum insulation material was stored at 60°C for two weeks. The thermal conductivity of the vacuum insulation material before and after storage was measured. The thermal conductivity was measured by the heat flow meter method using a thermal conductivity measuring device (manufactured by Eihong Seiki Co., Ltd., product name "HC-074") in accordance with JIS-A-1412-3. The thermal conductivity before storage of Example 1D and Comparative Example 3B was both 0.005 [W / M·K]. The thermal conductivity after storage of Example 1D remained unchanged from before storage at 0.005 [W / M·K]. On the other hand, the thermal conductivity after storage of Comparative Example 3B was a value greater than 0.005 [W / M·K].

Explanation of symbols

[0118] 10... base material layer, 11... first polyvinyl alcohol-based resin layer, 12... vapor deposition layer, 13... second polyvinyl alcohol-based resin layer, 100... gas barrier laminate, 200, 300... packaging material.

Claims

1. A polyolefin-based substrate layer, a first polyvinyl alcohol-based resin layer, a vapor deposition layer, a second polyvinyl alcohol-based resin layer, having a laminated structure comprising these in this order, wherein the vapor deposition layer is in direct contact with the first polyvinyl alcohol-based resin layer and the second polyvinyl alcohol-based resin layer, the indentation hardness by nanoindentation in the cross-section of the second polyvinyl alcohol-based resin layer is 0.5 GPa or less, the ratio (S2 / S1) of the indentation hardness (S2) by nanoindentation in the cross-section of the second polyvinyl alcohol-based resin layer to the indentation hardness (S1) by nanoindentation in the cross-section of the first polyvinyl alcohol-based resin layer is 3 to 10, a gas barrier laminate.

2. The gas barrier laminate according to Claim 1, wherein the thickness of the first polyvinyl alcohol-based resin layer is 0.5 to 2.5 μm.

3. The gas barrier laminate according to Claim 1, wherein the second polyvinyl alcohol-based resin layer contains Si.

4. The gas barrier laminate according to Claim 1, wherein the second polyvinyl alcohol-based resin layer contains a silane coupling agent.

5. The gas barrier laminate according to Claim 1, wherein the vapor deposition layer contains aluminum or silicon oxide.

6. The gas barrier laminate according to Claim 1, wherein the polyolefin-based substrate layer and the first polyvinyl alcohol-based resin layer are coextruded layers.

7. A packaging material comprising the gas barrier laminate according to any one of Claims 1 to 6.

8. The packaging material according to Claim 7, which is used for a package subjected to vacuum treatment.

9. The packaging material according to Claim 7, which is used for a package subjected to freezing treatment.

10. A vacuum insulation material comprising the packaging material according to Claim 7.

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