Gas barrier laminate and packaging bag

Abstract

A gas barrier laminate comprising, in this order, a paper base material, a layer containing a polyvinyl alcohol-based resin, a vapor-deposited layer, and a layer containing a polyolefin having a polar group.

Description

Technical Field

[0001] This invention relates to gas barrier laminates and packaging bags. Background Technology

[0002] Packaging materials are used in various sectors, including food, beverages, pharmaceuticals, and chemicals, to address the specific contents of each product. These materials must be able to prevent the permeation of substances that could cause spoilage, such as oxygen and water vapor (gas barrier properties).

[0003] In recent years, with the rise of environmental awareness, starting with issues such as marine plastic waste, the opportunity to move away from plastics has increased. From the perspective of reducing the use of plastic materials, the use of paper to replace plastic materials is being explored in various fields. For example, Patent Document 1 discloses a gas barrier laminate in which barrier layers are stacked on paper.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2020-69783 Summary of the Invention

[0005] The technical problem that the invention aims to solve Paper is easy to process due to its crease retention (also known as dead crease retention). However, according to the research of the inventors, there is still room for improvement in terms of cracking in the barrier layer and reduced gas barrier properties when making packaging bags with sharper creases (pillow bag packaging, three-side seal packaging, and gusseted bag packaging).

[0006] Furthermore, from the perspective of the Resource Effective Utilization Promotion Law, it is also required to reduce the amount of plastic materials used in gas barrier laminates.

[0007] The present invention was made in view of the above facts, and its object is to provide a gas barrier laminate having crease retention characteristics as paper, sufficient gas barrier properties even after bending, and contributing to the reduction of plastic material usage, as well as a packaging bag comprising the gas barrier laminate.

[0008] Means for solving technical problems The present invention provides a gas barrier laminate comprising, in sequence, a paper substrate, a layer comprising a polyvinyl alcohol resin, a vapor-deposited layer, and a layer comprising a polyolefin having polar groups.

[0009] Polyolefins having polar groups may have at least one selected from carboxyl groups, carboxyl salts, carboxylic anhydrides, and carboxylic esters.

[0010] The aforementioned polyolefins with polar groups can be copolymers of acrylates and maleic anhydride.

[0011] The aforementioned polyolefins with polar groups can be ethylene-vinyl acetate copolymers.

[0012] The aforementioned polyolefins with polar groups can be ethylene-glycidyl methacrylate copolymers.

[0013] The thickness of the layer containing polyvinyl alcohol resin can be greater than 1 μm and less than 5 μm.

[0014] The thickness of the vapor-deposited layer can be above 30nm and below 100nm.

[0015] The thickness of the layer containing the polyolefin with polar groups can be greater than 2 μm and less than 10 μm.

[0016] The thickness of the paper substrate can be 30μm or more and 100μm or less, and the thickness of the paper substrate is more than 70% of the overall thickness of the gas barrier laminate.

[0017] The weight of the paper, based on the gas barrier laminate as a whole, can be more than 50% by mass.

[0018] The present invention also provides a packaging bag comprising the gas barrier laminate of the present invention described above.

[0019] The aforementioned packaging bags may have a bend.

[0020] Invention Effects According to the present invention, it is possible to provide a gas barrier laminate having crease retention characteristics as paper, sufficient gas barrier properties even after bending, and contributing to the reduction of plastic material usage, as well as a packaging bag comprising the gas barrier laminate. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view illustrating a gas barrier laminate according to an embodiment of the present invention.

[0022] Figure 2 This is a perspective view of a packaging bag according to an embodiment of the present invention. Detailed Implementation

[0023] The following is a reference to the appendix, depending on the circumstances. Figure 1 The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments.

[0024] <Gas Barrier Laminate> Figure 1 This is a schematic cross-sectional view showing a gas barrier laminate according to one embodiment. The gas barrier laminate 10 according to one embodiment sequentially includes a paper substrate 1, a layer 2 containing a polyvinyl alcohol-based resin, a vapor-deposited layer 3, and a layer 4 containing a polyolefin having polar groups.

[0025] [Paper substrate] There are no particular restrictions on the paper substrate 1, as long as it is appropriately selected according to the intended use of the packaging bag for which the gas barrier laminate 10 is applied. There are no particular restrictions if the paper is made primarily of plant-derived pulp. Specific examples of paper substrate 1 include high-grade paper, specialty high-grade paper, coated paper, art paper, cast-coated paper, molded paper, kraft paper, and glassine paper. The thickness of paper substrate 1 can be, for example, 30 μm or more and 100 μm or less, or 30 μm or more and 70 μm or less. Furthermore, the thickness of the paper substrate can be 70% or more of the overall thickness of the gas barrier laminate. If the thickness of the paper substrate is 70% or more of the overall thickness of the gas barrier laminate, then its environmental adaptability is considered excellent.

[0026] A coating layer can also be provided on at least the side of the paper substrate 1 that contacts the layer 2 containing the polyvinyl alcohol resin (described later). By providing the coating layer, not only can the layer 2 containing the polyvinyl alcohol resin be prevented from penetrating into the paper, but it also acts as a filler to fill the unevenness of the paper, allowing for a defect-free and uniform film formation of the layer containing the polyvinyl alcohol resin. In the coating layer, the adhesive resin can be, for example, various copolymers such as styrene-butadiene, styrene-acrylic, and ethylene-vinyl acetate copolymers, polyvinyl alcohol resins, cellulose resins, paraffin wax (WAX), etc., and the filler can include, for example, clay, kaolin, calcium carbonate, talc, mica, etc.

[0027] There are no particular limitations on the thickness of the coating; for example, it can be 1~10μm or 3~8μm.

[0028] The weight of the paper, based on the gas barrier laminate as a whole, is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. When the weight of the paper is 50% by mass or more based on the gas barrier laminate as a whole, the amount of plastic material used can be significantly reduced, and the gas barrier laminate as a whole can be said to be made of paper, while also having excellent reusability.

[0029] [Layer containing polyvinyl alcohol resin] Layer 2, containing a polyvinyl alcohol-based resin, is disposed on the surface of the paper substrate to improve the adhesion between the paper substrate 1 and the vapor-deposited layer 3 (described later), or to improve the gas barrier properties (especially oxygen barrier properties) of the gas barrier laminate. Polyvinyl alcohol-based resins include, for example, fully saponified polyvinyl alcohol resin, partially saponified polyvinyl alcohol resin, modified polyvinyl alcohol resin, and ethylene-vinyl alcohol copolymer resin. Furthermore, the degree of polymerization of the polyvinyl alcohol-based resin is preferably 300 or higher and 1700 or lower. If the degree of polymerization is 300 or higher, the barrier properties or flexural strength of the gas barrier laminate become better; if the degree of polymerization is 1700 or lower, the viscosity of the polyvinyl alcohol-based resin coating solution (described later) decreases, and the coatability becomes better.

[0030] As a method for setting layer 2 containing polyvinyl alcohol resin, it can be obtained by coating a paper substrate 1 with a coating solution containing the aforementioned polyolefin polyvinyl alcohol resin and solvent and then drying it. Examples of solvents included in the coating solution include water, methanol, ethanol, isopropanol, n-propanol, n-butanol, n-pentanol, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide; a mixture of water and alcohols such as methanol, ethanol, and isopropanol is particularly preferred. Furthermore, the coating solution may also contain additives such as surfactants or preservatives, preservation stabilizers, silane coupling agents, and organotitanate esters.

[0031] This layer 2, which contains polyvinyl alcohol resin, has excellent flexibility. When bent, it can suppress cracking of the vapor-deposited layer described later, suppress the deterioration of gas barrier properties, and improve the adhesion between the vapor-deposited layer and the layer containing polyvinyl alcohol resin.

[0032] The thickness of layer 2, which contains polyvinyl alcohol-based resin, can be, for example, 1 μm or more, 2 μm or more, or 5 μm or less. If the thickness is 1 μm or more, the unevenness of the paper substrate can be efficiently filled, allowing the vapor-deposited layer to be uniformly stacked. Furthermore, if the thickness is 5 μm or less, the vapor-deposited layer can be uniformly stacked while reducing costs.

[0033] [Vapor Deposition Layer] The vapor-deposited layer 3 is a layer containing a metal or inorganic compound deposited on it. As a vapor-deposited layer, it can be a layer obtained by vapor-depositing aluminum, and may also contain aluminum oxide (Al₂O₃). x ), silicon dioxide (SiO) x )wait.

[0034] The thickness of the vapor-deposited layer 3 can be appropriately set according to the application, preferably 30 nm or more, but can also be 50 nm or more, or less than 100 nm or less than 80 nm. By making the thickness of the vapor-deposited layer 3 30 nm or more, it is easy to make the continuity of the vapor-deposited layer 3 sufficient, and by making it less than 100 nm, the occurrence of curling or cracking can be effectively suppressed, and sufficient gas barrier performance and flexibility can be easily achieved.

[0035] From the viewpoint of oxygen barrier performance or film uniformity, the vapor-deposited layer 3 is preferably formed by vacuum deposition. Known methods include vacuum deposition, sputtering, and chemical vapor deposition (CVD). Vacuum deposition is preferred due to its fast deposition speed and high productivity. Furthermore, in vacuum deposition, methods utilizing electron beam heating are particularly effective because the deposition rate can be easily controlled by adjusting the irradiation area or electron beam current, and the heating and cooling of the deposition material can be performed in a short time.

[0036] [A layer containing polyolefins with polar groups] A layer 4 containing a polyolefin with polar groups is disposed on the surface of the vapor-deposited layer 3 in a manner that it contacts the vapor-deposited layer 3, and the layer contains a polyolefin with polar groups. By using a polyolefin with polar groups, the water vapor barrier properties are improved due to the crystallinity of the polyolefin, and the bending resistance is improved due to the flexibility of the polyolefin. In addition, by introducing polar groups, the adhesion with the vapor-deposited layer is improved, resulting in a water-based coating in which polyolefin is dispersed in water, which is beneficial to the environment.

[0037] Polyolefins containing polar groups may include polyolefins having at least one selected from carboxyl groups, carboxyl salts, carboxylic anhydrides, and carboxylic esters.

[0038] Polyolefins with polar groups can be polyolefins copolymerized with ethylene or propylene, such as unsaturated carboxylic acids (such as acrylic acid and methacrylic acid) or unsaturated carboxylic acid esters, as well as salts formed by neutralizing carboxylic acids with alkaline compounds. In addition, polyolefins copolymerized with vinyl acetate, epoxy compounds, chlorinated compounds, urethane compounds, polyamide compounds, etc., can also be used.

[0039] As polyolefins with polar groups, specific examples include copolymers of acrylates and maleic anhydride, ethylene-vinyl acetate copolymers, and ethylene-glycidyl methacrylate copolymers.

[0040] This layer 4, containing a polyolefin with polar groups, exhibits excellent flexibility, suppressing cracking of the vapor-deposited layer after bending, and also provides excellent adhesion to the vapor-deposited layer. Furthermore, by including the aforementioned polyolefin, a gas barrier laminate with excellent water vapor barrier properties can be obtained. In addition, by providing the aforementioned layer containing a polyolefin with polar groups, it can also serve as a heat-sealing layer, thus eliminating the need for a separate heat-sealing layer.

[0041] In addition to the polyolefins mentioned above, layer 4, which contains polyolefins with polar groups, may also contain other components. Examples of such other components include silane coupling agents, organotitanates, polyacrylic acid, polyesters, polyurethanes, polycarbonates, polyureas, polyamides, polyolefin emulsions, polyimides, melamine, and phenol.

[0042] The content of the polyolefin in layer 4, which contains a polyolefin with polar groups, may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0043] The thickness of layer 4, which contains polyolefins with polar groups, can be, for example, 2 μm or more, 3 μm or more, 10 μm or less, 8 μm or less, or 5 μm or less. If the thickness of layer 4, which contains polyolefins with polar groups, is 2 μm or more, it can fully perform its function as a heat-sealing layer. Furthermore, if the thickness of layer 4, which contains polyolefins with polar groups, is 10 μm or less, it can effectively maintain adhesion or barrier properties with the vapor-deposited layer while reducing costs.

[0044] As a method for setting layer 4 containing a polyolefin having polar groups, it can be obtained by coating a vapor-deposited layer with a coating solution containing the aforementioned polyolefin and a solvent and then drying it. Examples of solvents included in the coating solution include water, methanol, ethanol, isopropanol, n-propanol, n-butanol, n-pentanol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. One of these solvents can be used alone, or two or more can be used in combination. From a performance perspective, methanol, ethanol, isopropanol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Furthermore, from an environmental perspective, methanol, ethanol, isopropanol, and water are preferred.

[0045] The gas barrier laminate of this embodiment maintains sufficient gas barrier properties even after bending. In this specification, gas barrier properties refer to sufficiently low water vapor permeability and oxygen permeability.

[0046] In this embodiment, the gas barrier laminate is folded with the paper substrate as the outer side, rolled once on a 600g roller, and the water vapor permeability at 40°C and 90%RH is preferably 3g / m after the crease is opened. 2 For oxygen permeability below / d, at 30℃ and 70%RH, a minimum oxygen permeability of 3cc / m is preferred. 2 / d / atm or less. Furthermore, the water vapor transmission rate at 40°C and 90%RH, measured after rolling a 600g roller once over the paper substrate with the crease removed, is preferably 3g / m. 2For oxygen permeability below / d, at 30℃ and 70%RH, a minimum oxygen permeability of 3cc / m is preferred. 2 / d / atm and below.

[0047] <Packaging Bags> Figure 2 This is a perspective view of a gusseted bag 20 formed by a gas barrier laminate 10. The bag is manufactured by sealing the opening at the top of the gusseted bag 20. The gusseted bag 20 has bent portions (bending portions B1 and B2) of the gas barrier laminate 10. Bending portion B1 is the portion where the gas barrier laminate 10 is folded when viewed from the innermost layer, while bending portion B2 is the portion where the gas barrier laminate 10 is folded when viewed from the innermost layer.

[0048] The packaging bag can be made by folding a gas barrier laminate in two, bending it appropriately to form the desired shape, and then heat-sealing it, or by overlapping two gas barrier laminates in four-sided arrangement and then heat-sealing them, thereby forming the bag shape.

[0049] In the packaging bag of this embodiment, the heat seal strength can be 2N or higher, or even 4N or higher. Furthermore, there is no particular limitation on the upper limit of the heat seal strength; for example, it can be 10N or lower.

[0050] Here, the heat seal strength is determined as follows: two gas barrier laminates 10 are overlapped with the polyolefin containing polar groups in the opposite direction as layer 4, and heat-sealed using a heat sealer at 120°C, 0.2 MPa, and 1 second. Then, a 15 mm wide strip is cut from it, and the maximum load when performing T-shaped peeling at a peeling speed of 300 mm / min is measured.

[0051] The packaging bag can hold food, medicine, and other contents. It is especially suitable for storing snacks and other food items. Even with a bent shape, the packaging bag of this embodiment maintains high gas barrier properties.

[0052] Furthermore, while an accordion bag is cited as an example of a packaging bag in this embodiment, other types of bags, such as pillow bags, three-side seal bags, or stand-up pouches, can also be made using the gas barrier laminate of this embodiment.

[0053] Example The present invention will be described in more detail below through examples, but the present invention is not limited to these examples.

[0054] <Fabrication of Gas Barrier Laminates> (Example 1) A coating solution containing polyvinyl alcohol resin with a saponification degree of 98% and a polymerization degree of 500, was dissolved in a water / IPA (IPA) solution at a concentration of 10% by mass and a water / IPA ratio of 8 / 2 on the clay-coated surface of paper (paper thickness: 50 μm, clay coating thickness: 5 μm). This solution was dried in an oven to form a layer containing polyvinyl alcohol resin with a thickness of 3 μm. Next, Al vapor deposition was performed on the polyvinyl alcohol resin layer using vacuum evaporation. The Al vapor deposition layer had a thickness of 50 nm. Then, a coating solution containing carboxyl salts (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied to the vapor deposition layer using a bar coater and dried in an oven to form a layer containing polyolefins with polar groups, thus obtaining a gas barrier laminate. The thickness of the polyolefin layer containing polar groups was 3 μm. The weight of paper in the gas barrier laminate was 82% by mass.

[0055] (Example 2) Except that the thickness of the layer containing polyvinyl alcohol resin is 1 μm, the gas barrier laminate is obtained by the same procedure as in Example 1. The paper in the gas barrier laminate weighs 85% by mass.

[0056] (Example 3) Except for setting the thickness of the polyvinyl alcohol resin layer to 5 μm, the gas barrier laminate was obtained through the same procedures as in Example 1. The paper in the gas barrier laminate weighed 79% by mass.

[0057] (Example 4) Except for setting the thickness of the vapor-deposited layer to 30 nm, a gas barrier laminate was obtained through the same procedures as in Example 1. The paper in the gas barrier laminate weighed 82% by mass.

[0058] (Example 5) Except for setting the thickness of the vapor-deposited layer to 100 nm, a gas barrier laminate was obtained through the same procedures as in Example 1. The paper in the gas barrier laminate weighed 82% by mass.

[0059] (Example 6) Except that the thickness of the layer containing the polyolefin with polar groups is 2 μm, the gas barrier laminate is obtained by the same procedure as in Example 1. The weight of the paper in the gas barrier laminate is 83% by mass.

[0060] (Example 7) Except that the thickness of the layer containing the polyolefin with polar groups is 10 μm, a gas barrier laminate is obtained by the same procedure as in Example 1. The weight of the paper in the gas barrier laminate is 73% by mass.

[0061] (Example 8) As the clay-coated paper, a paper thickness of 30 μm and a clay coating thickness of 5 μm were used. Otherwise, a gas barrier laminate was obtained through the same operation as in Example 1. The weight of the paper in the gas barrier laminate was 73% by mass.

[0062] (Example 9) As the clay-coated paper, a paper thickness of 100 μm and a clay coating thickness of 5 μm were used. Otherwise, a gas barrier laminate was obtained through the same operation as in Example 1. The weight of the paper in the gas barrier laminate was 90% by mass.

[0063] (Example 10) Except that the vapor-deposited layer is silicon dioxide and the thickness of the vapor-deposited layer is 30 nm, a gas barrier laminate was obtained through the same operation as in Example 1. The weight of the paper in the gas barrier laminate is 82% by mass.

[0064] (Example 11) Except that the vapor-deposited layer is aluminum oxide and the thickness of the vapor-deposited layer is 30 nm, a gas barrier laminate was obtained through the same operation as in Example 1. The weight of the paper in the gas barrier laminate is 82% by mass.

[0065] (Example 12) As the polyvinyl alcohol-based resin, a polyvinyl alcohol-based resin with a saponification degree of 98% and a polymerization degree of 1000 was used. Otherwise, a gas barrier laminate was obtained by the same operation as in Example 1.

[0066] (Example 13) The polyvinyl alcohol resin used in Example 1 was replaced with a modified polyvinyl alcohol resin (trade name: Exceval AQ4104, manufactured by Kuraray). Otherwise, a gas barrier laminate was obtained by the same operation as in Example 1.

[0067] (Example 14) A coating solution containing ethylene-vinyl acetate copolymer resin (trade name: Chemipearl V300, manufactured by Mitsui Chemicals) was applied using a bar coater and dried using an oven to form a layer of polyolefin containing polar groups. Otherwise, a gas barrier laminate was obtained by the same operation as in Example 1.

[0068] (Example 15) A coating solution containing a polyolefin resin (trade name: Bondine HX-8290, manufactured by Arkema) comprising carboxyl groups, carboxyl salts, carboxylic anhydrides, and carboxylic esters was applied using a bar coater. The solution was then dried in an oven to create a coating layer formed of polyolefin. Otherwise, a gas barrier laminate was obtained through the same procedures as in Example 1. The coating solution containing the polyolefin resin was prepared as follows.

[0069] An aqueous dispersion of polyolefin resin was prepared by mixing polyolefin resin (trade name: Bondine HX-8290, manufactured by Arkema) formed by ethylene, ethyl acrylate, and maleic anhydride in a mass ratio of 20 / 20 / 1 / 59, isopropanol, triethylamine, and distilled water, and heating and stirring.

[0070] (Example 16) A coating solution containing polyolefin resin was prepared by applying a coating solution of ethylene-glycidyl methacrylate copolymer (trade name: Sepolsion G515, manufactured by Sumitomo Chemical) using a bar coater and drying it in an oven. Otherwise, a gas barrier laminate was obtained by the same operation as in Example 1.

[0071] (Example 17) A coating solution containing carboxyl-containing salts (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied to the clay coating surface of paper (clay-coated paper, paper thickness: 50 μm, clay coating thickness: 5 μm) using a bar coater. The solution was then dried in an oven to form a layer containing polyolefins with polar groups. The layer thickness was 3 μm. Next, a coating solution containing polyvinyl alcohol resin with a saponification degree of 98% and a polymerization degree of 500 dissolved in a water / IPA (8 / 2) solution at a solids concentration of 10% by mass was applied to the polyolefin layer using a bar coater. This solution was then dried in an oven to form a layer containing polyvinyl alcohol resin. The layer thickness was 1 μm. Finally, Al vapor deposition was performed on the polyvinyl alcohol resin layer using a vacuum evaporation method. The Al vapor deposition layer thickness was 50 nm. Next, a coating solution containing carboxyl-containing salts (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied to the vapor-deposited layer using a bar coater, and then dried in an oven to form a layer containing polyolefins with polar groups, thus obtaining a gas barrier laminate. The thickness of the polyolefin layer containing polar groups was 3 μm. The weight of paper in the gas barrier laminate was 81% by mass.

[0072] (Example 18) A coating solution containing carboxyl-containing salts (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied to the clay coating surface of paper (clay-coated paper, paper thickness: 50 μm, clay coating thickness: 5 μm) using a bar coater. The solution was then dried in an oven to form a layer containing a polyolefin with polar groups. The layer thickness was 3 μm. Next, Al was deposited onto the polyolefin layer using vacuum evaporation. The Al deposition layer thickness was 50 nm. Then, a coating solution containing polyvinyl alcohol resin with a saponification degree of 98% and a polymerization degree of 500, dissolved in a water / IPA (8 / 2) solution at a solids concentration of 10% by mass, was applied onto the deposited layer using a bar coater. This solution was dried in an oven to form a layer containing polyvinyl alcohol resin. The layer thickness was 3 μm. Finally, Al was deposited onto the polyvinyl alcohol resin layer using vacuum evaporation. The Al deposition layer thickness was 50 nm. Next, a coating solution containing carboxyl-containing salts (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied to the vapor-deposited layer using a bar coater, and then dried in an oven to form a layer containing polyolefins with polar groups, thus obtaining a gas barrier laminate. The thickness of the polyolefin layer containing polar groups was 3 μm. The paper weight in the gas barrier laminate was 78% by mass.

[0073] (Example 19) A coating solution containing a polyolefin resin with carboxyl groups, carboxyl salts, carboxylic anhydride groups, and carboxylic esters (preparation of the coating solution is described in Example 15) was applied to the clay coating surface of paper (clay-coated paper, paper thickness: 50 μm, clay coating thickness: 5 μm) using a bar coater. The solution was then dried in an oven to form a layer containing a polyolefin with polar groups. The layer thickness was 2 μm. Next, a coating solution containing polyvinyl alcohol resin with a saponification degree of 98% and a polymerization degree of 500 dissolved in a water / IPA = 8 / 2 solution was applied to the polyolefin layer using a bar coater. This solution was dried in an oven to form a layer containing polyvinyl alcohol resin. The layer thickness was 1 μm. Finally, Al vapor deposition was performed on the polyvinyl alcohol resin layer using a vacuum evaporation method. The Al vapor deposition layer thickness was 50 nm. Next, a coating solution containing carboxyl-containing salts (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied to the vapor-deposited layer using a bar coater, and then dried in an oven to form a layer containing polyolefins with polar groups, thus obtaining a gas barrier laminate. The thickness of the polyolefin layer containing polar groups was 3 μm. The weight of paper in the gas barrier laminate was 82% by mass.

[0074] (Example 20) Except for changing the polyvinyl alcohol resin to a modified polyvinyl alcohol resin (trade name: Exceval AQ4104, manufactured by Kuraray), the gas barrier laminate was obtained by the same operation as in Example 19.

[0075] (Comparative Example 1) Except for the absence of a vapor-deposited layer, a gas barrier laminate was obtained through the same procedures as in Example 1. The paper in the gas barrier laminate weighed 82% by mass.

[0076] (Comparative Example 2) A coating solution containing acrylic alkyd resin was applied to the surface of paper (clay-coated paper, paper thickness: 50 μm, clay coating thickness: 5 μm) using a bar coater, and dried in an oven to form a layer containing acrylic alkyd resin. The layer thickness was 4 μm. Next, Al vapor deposition was performed on this layer. The Al vapor deposition layer thickness was 50 nm. Then, a coating solution containing polyvinyl alcohol resin and TEOS was applied to the Al vapor deposition layer using a bar coater, and dried in an oven to form a layer containing polyvinyl alcohol resin and TEOS. The layer thickness was 0.4 μm. Next, a coating solution containing carboxyl salts (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied using a bar coater, and dried in an oven to form a layer containing polyolefins with polar groups, obtaining a gas barrier laminate. The thickness of the polyolefin layer containing polar groups was 3 μm. The weight of paper in the gas barrier laminate was 80% by mass.

[0077] (Comparative Example 3) A coating solution containing carboxyl groups (trade name: Chemipearl S100, manufactured by Mitsui Chemicals) was applied to the surface of paper (clay-coated paper, paper thickness: 50 μm, clay coating thickness: 5 μm) using a bar coater. The coating was then dried in an oven to form a layer of polyolefin with polar groups. The layer thickness was 3 μm. Next, Al vapor deposition was performed on the polyolefin layer containing polar groups. The Al vapor deposition layer thickness was 50 nm. Subsequently, a coating solution containing carboxyl groups (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied to the vapor deposition layer using a bar coater and dried in an oven to form a layer of polyolefin with polar groups, thus obtaining a gas barrier laminate. The polyolefin layer containing polar groups had a thickness of 3 μm. The paper weight in the gas barrier laminate was 82% by mass.

[0078] (Comparative Example 4) Except that a coating solution containing ethylene-vinyl acetate copolymer resin (trade name: Chemipearl V300, Mitsui Chemicals) was used instead of a coating solution containing polyvinyl alcohol resin, a gas barrier laminate was obtained by the same operation as in Example 1. The weight of paper in the gas barrier laminate was 82% by mass.

[0079] (Comparative Example 5) Except that a coating solution containing urethane-curing acrylic resin was used instead of a coating solution containing polyvinyl alcohol resin, a gas barrier laminate was obtained by the same procedure as in Example 1. The weight of paper in the gas barrier laminate was 82% by mass.

[0080] (Comparative Example 6) A coating solution containing carboxyl groups (trade name: Chemipearl S100, manufactured by Mitsui Chemicals) was applied to the surface of paper (clay-coated paper, paper thickness: 50 μm, clay coating thickness: 5 μm) using a bar coater. The coating was then dried in an oven to form a layer containing a polyolefin with polar groups. The layer thickness was 3 μm. Next, Al vapor deposition was performed on the polyolefin layer containing polar groups. The Al vapor deposition layer thickness was 50 nm. Then, a coating solution containing polyvinyl alcohol resin was applied to the Al vapor deposition layer using a bar coater and dried in an oven to form a layer containing polyvinyl alcohol resin. The layer thickness was 1 μm. Finally, a coating solution containing carboxyl groups (trade name: Chemipearl S500, manufactured by Mitsui Chemicals) was applied using a bar coater and dried in an oven to form a layer containing a polyolefin with polar groups, thus obtaining a gas barrier laminate. The polyolefin layer containing polar groups had a thickness of 3 μm. The weight of the paper in the gas barrier laminate is 81% by mass.

[0081] (Comparative Example 7) Instead of using a bar coater to apply a coating containing polyvinyl alcohol resin, drying it in an oven to form a layer containing polyvinyl alcohol resin, a bar coater to apply a coating containing polyvinyl alcohol resin and TEOS, drying it in an oven to form a layer containing polyvinyl alcohol resin and TEOS, a gas barrier laminate was obtained through the same operation as in Comparative Example 6. The thickness of this layer is 1 μm.

[0082] <Determination of Water Vapor Transmission> The water vapor transmission rate of the gas barrier laminates in the examples and comparative examples was determined using the MOCON method. The measurement conditions were a temperature of 40°C and a relative humidity of 90%. A 600g roller was rotated at a speed of 300 mm / min while creases were applied to the gas barrier laminate; the water vapor transmission rate of the unfolded gas barrier laminate was also measured in the same manner. Furthermore, in Tables 1-8, "inner fold" indicates a gas barrier laminate with a mountain fold when viewed from the paper substrate side, and "outer fold" indicates a gas barrier laminate with a valley fold when viewed from the paper substrate side. The units in Tables 1-8 are [g / m³]. 2 ·day] indicates the result.

[0083] <Determination of Oxygen Permeability> The oxygen permeability of the gas barrier laminates of the examples and comparative examples was determined using JIS K7126, Method B (isobaric method). The measuring apparatus was an OXTRAN 2 / 20 (MOCON), and measurements were taken at 30°C and 70% relative humidity. Tables 1-8 use units [cc / m³]. 2 [ / d / atm] indicates the result.

[0084] <Determination of heat seal strength> Two gas barrier laminates were overlapped with the polyolefin containing polar groups facing each other. The laminates were then heat-sealed at 120°C, 0.2 MPa, and 1 second using a heat sealer. A 15 mm wide strip was then cut from the laminate, and the maximum load during T-shaped peeling at a peeling speed of 300 mm / min was measured. Results are expressed in Tables 1-8 using the unit [N / 15 mm].

[0085] Symbol Explanation 1 Paper substrate, 2 Layer containing polyvinyl alcohol resin, 3 Evaporated layer, 4 Layer containing polyolefin with polar groups, 10 Gas barrier laminate, 20 Accordion bag, B1, B2 Bending section.

Claims

1. A gas barrier laminate, comprising, in sequence: Paper substrate; A layer containing polyvinyl alcohol-based resin; Evaporated coating; and Heat seal layer, The vapor-deposited layer is formed on the layer containing polyvinyl alcohol-based resin. The heat-sealing layer is disposed on the surface of the vapor-deposited layer in a manner that it contacts the vapor-deposited layer. The heat-sealing layer comprises a polyolefin having polar groups, wherein the polyolefin having polar groups is a salt of a carboxyl group. The polyolefin content in the heat-sealing layer is 50% by mass or more. The thickness of the heat-sealing layer is greater than 2 μm and less than 10 μm.

2. The gas barrier laminate according to claim 1, wherein, The thickness of the layer containing polyvinyl alcohol resin is more than 1 μm and less than 5 μm.

3. The gas barrier laminate according to claim 1 or 2, wherein, The thickness of the vapor-deposited layer is above 30 nm and below 100 nm.

4. The gas barrier laminate according to claim 1 or 2, wherein, The thickness of the paper substrate is 30 μm or more and 100 μm or less, and the thickness of the paper substrate is more than 70% of the overall thickness of the gas barrier laminate.

5. The gas barrier laminate according to claim 1 or 2, wherein, The weight of the paper is at least 50% by mass, based on the gas barrier laminate as a whole.

6. A packaging bag comprising the gas barrier laminate according to any one of claims 1 to 5.

7. The packaging bag according to claim 6, wherein it has a bent portion.

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