Laminate

Abstract

Provided is a laminate excellent in water vapor barrier properties both in a state of not having been folded at all and a state after folding. A laminate has a substrate, a resin layer (1), and a resin layer (2). The resin layer (1) and the resin layer (2) are adjacent to each other. The resin layer (1) contains a water-dispersible polymer and wax. The resin layer (2) contains a vinyl alcohol polymer and polyalkyleneimine.

Description

Laminate

[0001] The present invention relates to a laminate.

[0002] Paper packaging materials have traditionally been used as packaging materials for foods, medical products, electronic components, etc. As one such packaging material, Patent Document 1 describes grease-resistant paper obtained by applying a coating agent containing a carboxyl group-containing polyvinyl alcohol-based polymer to a paper substrate. However, the grease-resistant paper of Patent Document 1 has insufficient gas barrier properties (particularly water vapor barrier properties and oxygen barrier properties). As paper packaging materials for improving gas barrier properties, Patent Documents 2 and 3 describe paper packaging materials in which a water vapor barrier layer, a gas barrier layer, and a sealant layer are laminated on a paper substrate, and the gas barrier layer contains a vinyl alcohol-based polymer (hereinafter, the vinyl alcohol-based polymer will also be referred to as "PVOH").

[0003] International Publication No. 2022 / 202997 Japanese Patent Application Laid-Open No. 2020-163675 Japanese Patent Application Laid-Open No. 2021-20398

[0004] Further improvements in the water vapor barrier property are also required for conventional laminates having a structure in which a water vapor barrier layer and a gas barrier layer are laminated on a substrate. In particular, the water vapor barrier property of such laminates is likely to deteriorate when they are folded, so it is also important to improve the water vapor barrier property even after folding.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a laminate that has excellent water vapor barrier properties both in an unfolded state and in a folded state.

[0006] The problem is solved by the following: [1] a laminate having a substrate, a resin layer (1) and a resin layer (2), the resin layer (1) and the resin layer (2) being adjacent to each other, the resin layer (1) containing a water-dispersible polymer and a wax, and the resin layer (2) containing a vinyl alcohol-based polymer and a polyalkyleneimine; [2] the laminate of [1], in which the content of the polyalkyleneimine in the resin layer (2) is 30 parts by mass or less per 100 parts by mass of the vinyl alcohol-based polymer; [3] the laminate of [1] or [2], in which the number-average molecular weight of the polyalkyleneimine is 30,000 or more; [4] the laminate of any of [1] to [3], in which the water-dispersible polymer is at least one selected from the group consisting of an olefin-based polymer and a styrene-based polymer; [5] the laminate of any of [1] to [4], in which the content of the wax in the resin layer (1) is 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the water-dispersible polymer; [6] the laminate of any of [1] to [5], wherein the wax is at least one selected from the group consisting of paraffin wax, microcrystalline wax, and carnauba wax; [7] the laminate of any of [1] to [6], wherein the resin layer (1) is the outermost layer; [8] the laminate of any of [1] to [7], wherein the resin layer (1) is substantially free of a layered inorganic material; [9] the laminate of any of [1] to [8], wherein the substrate is paper;

[10] the laminate of [9], wherein, with respect to the water vapor transmission rate measured under conditions of a temperature of 40°C and a relative humidity of 90%, the ratio of the water vapor transmission rate in a folded state to the water vapor transmission rate in a never-folded state is 1.10 or less.

[0007] According to the present invention, it is possible to provide a laminate that has excellent water vapor barrier properties both in an unfolded state and in a folded state.

[0008] <Laminate> A laminate according to one embodiment of the present invention has a substrate, a resin layer (1) and a resin layer (2), the resin layer (1) and the resin layer (2) being adjacent to each other, the resin layer (1) containing a water-dispersible polymer and a wax, and the resin layer (2) containing a vinyl alcohol-based polymer and a polyalkyleneimine.

[0009] A laminate according to one embodiment of the present invention has excellent water vapor barrier properties both in a state where it has never been folded and in a state where it has been folded. The reason for this is unclear, but the following is thought to be the reason. By incorporating wax into the resin layer (1) and polyalkyleneimine into the resin layer (2), the wax and polyalkyleneimine interact between adjacent resin layers (1) and (2). This enhances the interaction between the resin layer (1) and the resin layer (2), improving interlayer adhesion. As a result, it is presumed that the laminate has excellent water vapor barrier properties both in a state where it has never been folded and in a state where it has been folded. Hereinafter, the water vapor barrier properties in a state where it has never been folded and the water vapor barrier properties in a state where it has been folded may be collectively referred to simply as water vapor barrier properties. Details of each layer, etc. are described below.

[0010] (Substrate) The substrate may be the outermost layer on one side of the laminate. That is, no other layer may be laminated on one side of the substrate. Other layers may be laminated on both sides of the substrate. The substrate may be printed or the like.

[0011] In this specification, the outermost layer refers to a layer having one exposed surface. The term "outermost layer" does not distinguish between the inner surface and the outer surface of the laminate. That is, the laminate has two outermost layers. For example, when the laminate is formed into a bag shape, both the innermost layer and the outermost layer are outermost layers.

[0012] The material of the substrate is not particularly limited, and substrates made of various materials can be used. Examples of substrates that can be used include resin films such as thermoplastic resin films and thermosetting resin films, fiber aggregates such as paper and fabric, and metal foils. The resin film may be a stretched film or a non-stretched film. Among these, the substrate is preferably a fiber aggregate, and more preferably paper. When the substrate is paper, the processability of the laminate can be improved. The substrate may be a single layer or a multilayer. In the case of a multilayer substrate, each layer may be made of a different material, such as a multilayer substrate formed by laminating a resin film on paper.

[0013] The base paper can be a general paper whose main component is plant-derived pulp. In this specification, the term "main component" refers to the component with the highest content by mass. The base paper is also referred to as a paper base material. In addition to pulp, the paper base material may contain sizing agents, fillers, paper strength agents, retention aids, pH adjusters, drainage aids, waterproofing agents, softeners, antistatic agents, antifoaming agents, slime control agents, dyes, pigments, etc.

[0014] Examples of paper substrates include kraft paper, bleached kraft paper, fine paper, medium-quality paper, alkaline paper, paperboard, glassine paper, semi-glassine paper, and parchment paper, with kraft paper or bleached kraft paper being preferred.

[0015] The basis weight (mass per unit area) of the paper base material is 20 g / m ２ More than 500g / m ２ Preferably, 30 g / m or less ２ More than 300g / m ２ More preferably, 40 g / m or less ２ More than 200g / m ２ More preferably, 50 g / m or less ２ More than 100g / m ２ Even more preferred are the following:

[0016] The density of the paper base material is 0.5 g / cm ３ 1.2g / cm or more ３ Preferably, 0.6 g / cm or less ３1.0g / cm or more ３ The following is more preferred:

[0017] The paper substrate can be produced by a conventionally known method, and commercially available paper substrates can also be used.

[0018] The average thickness of the substrate (paper substrate and other substrate) may be, for example, in the range of 1 μm to 1000 μm, in the range of 3 μm to 400 μm, in the range of 5 μm to 100 μm, or in the range of 7 μm to 50 μm.

[0019] (Resin Layer (1)) The resin layer (1) contains a water-dispersible polymer and a wax. The resin layer (1) may be a layer having a resin content of 50% by mass or more and 100% by mass or less. The resin layer (1) may be a layer formed by coating (coated layer). The resin layer (1) is a layer that mainly exhibits water vapor barrier properties.

[0020] (Water-Dispersible Polymer) The resin layer (1) can exhibit good water vapor barrier properties by containing a water-dispersible polymer. The water-dispersible polymer may be, for example, a polymer having structural units derived from a hydrocarbon-based monomer, or a copolymer having structural units derived from a hydrocarbon-based monomer and other structural units. Examples of hydrocarbon-based monomers include olefins and styrene-based compounds, which will be described later. The ratio of structural units derived from hydrocarbon-based monomers to all structural units in the water-dispersible polymer may be, for example, 40 mol% to 100 mol%, 50 mol% to 99 mol%, or 60 mol% to 95 mol%. The water-dispersible polymer may be a polymer that is substantially unnecessary in water but is dispersible in water. The solubility of the water-dispersible polymer in water at 20°C may be, for example, 1 g / 100 g or less, 0.1 g / 100 g or less, or 0.01 g / 100 g or less. Examples of water-dispersible polymers include olefin-based polymers, styrene-based polymers, and polyester-based polymers. The water-dispersible polymer may be the main component of the resin layer 1. One or more types of water-dispersible polymers may be used.

[0021] (Olefin-Based Polymer) The olefin-based polymer is a polymer containing an olefin as a monomer. The olefin-based polymer may be a polyolefin, which is a polymer of one or more olefins, or a copolymer of one or more olefins with one or more other monomers other than olefins.

[0022] Examples of the olefin include α-olefins such as ethylene, propylene, n-butene, and isobutylene.

[0023] Examples of the monomer other than the olefin that constitutes the olefin polymer include an unsaturated carboxylic acid compound, a diene compound, a vinyl ester, a vinyl ether, a vinyl halide, a vinylidene halide, and an allyl compound. An unsaturated carboxylic acid compound or a vinyl ester is preferred, and an unsaturated carboxylic acid compound is more preferred.

[0024] The unsaturated carboxylic acid compound refers to an unsaturated carboxylic acid or a compound in which the hydrogen atom of the carboxy group constituting the unsaturated carboxylic acid is substituted with another atom or another group. That is, the unsaturated carboxylic acid compound includes not only unsaturated carboxylic acid but also unsaturated carboxylic acid esters, unsaturated carboxylic acid salts, etc. The unsaturated carboxylic acid compound is preferably a monomer having a carboxy group or a salt thereof.

[0025] Examples of unsaturated carboxylic acid compounds include unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; unsaturated carboxylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, itaconic acid monoethyl ester, and fumaric acid monobutyl ester; and unsaturated carboxylic acid salts such as sodium (meth)acrylate. Note that "(meth)acrylic acid" means acrylic acid and methacrylic acid.

[0026] Examples of vinyl esters include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc. Of these, vinyl acetate is preferred.

[0027] The olefin polymer is preferably a polyolefin, an olefin-vinyl ester copolymer, or an olefin-unsaturated carboxylic acid copolymer, and more preferably an olefin-unsaturated carboxylic acid copolymer. The olefin-vinyl ester copolymer refers to a copolymer of one or more olefins and one or more vinyl esters. The olefin-unsaturated carboxylic acid copolymer refers to a copolymer of one or more olefins and one or more unsaturated carboxylic acid compounds.

[0028] Examples of the olefin-vinyl ester copolymer include ethylene-vinyl formate copolymer, ethylene-vinyl acetate copolymer, and ethylene-vinyl propionate copolymer, among which ethylene-vinyl acetate copolymer is preferred. These copolymers may further be copolymerized with other monomers copolymerizable with the olefin and vinyl ester.

[0029] Examples of olefin-unsaturated carboxylic acid copolymers include ethylene-(meth)acrylic acid copolymer, ethylene-methyl(meth)acrylate copolymer, ethylene-ethyl(meth)acrylate copolymer, ethylene-butyl(meth)acrylate copolymer, and ethylene-maleic acid copolymer. The olefin-unsaturated carboxylic acid copolymer is preferably an olefin-unsaturated carboxylic acid copolymer, which is a copolymer of one or more olefins and one or more unsaturated carboxylic acids (e.g., ethylene-(meth)acrylic acid copolymer, ethylene-maleic acid copolymer, etc.). The olefin-unsaturated carboxylic acid copolymer is also preferably a copolymer of ethylene and an unsaturated carboxylic acid compound. A particularly preferred example of the olefin-unsaturated carboxylic acid copolymer is ethylene-(meth)acrylic acid copolymer. These copolymers may further be copolymerized with other monomers copolymerizable with the olefin and the unsaturated carboxylic acid compound.

[0030] (Styrene-based polymer) A styrene-based polymer is a polymer containing a styrene-based compound as a monomer. The styrene-based compound refers to styrene and a compound in which the hydrogen atoms of styrene are substituted with other atoms or other groups. Examples of the styrene-based compound include styrene, α-methylstyrene, vinyltoluene, and chlorostyrene, with styrene being preferred.

[0031] Examples of the styrene polymer include polystyrene, styrene-acrylic copolymers, and styrene-butadiene copolymers.

[0032] A styrene-acrylic copolymer is a copolymer of the above-mentioned styrene compound and an acrylic compound. The acrylic compound refers to (meth)acrylic acid and a compound in which the hydrogen atom of the carboxy group constituting (meth)acrylic acid is substituted with another atom or another group. Examples of the acrylic compound include (meth)acrylic acid, (meth)acrylic acid esters, and (meth)acrylic acid salts. Examples of the (meth)acrylic acid esters include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate and ethyl (meth)acrylate. Examples of the (meth)acrylic acid salts include sodium (meth)acrylate.

[0033] Examples of styrene-acrylic copolymers include styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid ester copolymers, styrene-(meth)acrylate copolymers, etc. The styrene-acrylic copolymers may be further copolymerized with other monomers.

[0034] The styrene-butadiene copolymer is a copolymer of the above-mentioned styrene compound and a butadiene compound. The butadiene compound refers to butadiene and compounds in which the hydrogen atoms of butadiene have been substituted with other atoms or other groups. Examples of the butadiene compound include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, with 1,3-butadiene being preferred.

[0035] The styrene-butadiene copolymer is preferably a styrene-butadiene copolymer, which may be further copolymerized with other monomers.

[0036] As the styrene polymer, a styrene-acrylic copolymer and a styrene-butadiene copolymer are preferred, and a styrene-acrylic copolymer is more preferred.

[0037] (Polyester-based polymer) A polyester-based polymer is a polymer in which one or more types of monomers are polymerized via an ester bond. Examples of the polyester-based polymer include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyglycolic acid, and aromatic liquid crystal polyester.

[0038] From the viewpoint of water vapor barrier properties, the water-dispersible polymer is preferably at least one selected from the group consisting of olefin-based polymers and styrene-based polymers, and more preferably a styrene-based polymer.

[0039] The lower limit of the content of the water-dispersible polymer in the resin layer (1) is preferably 50% by mass, more preferably 60% by mass, and may be 70%, 80%, 90%, or 95% by mass. By setting the content of the water-dispersible polymer in the resin layer (1) to be equal to or greater than the lower limit, the water vapor barrier property of the laminate can be further improved. On the other hand, the upper limit of this content is preferably 99.9% by mass, more preferably 99% by mass, and may be 98%, 96%, 94%, 90%, or 80% by mass.

[0040] (Wax) The wax may be, for example, an organic substance having an alkyl group that is solid or semi-solid at room temperature (e.g., 20°C) and melts in the temperature range from room temperature to 100°C (i.e., has a melting point of 20°C or higher and 100°C or lower). The melting point of the wax may be 40°C or higher and 90°C or lower, or 50°C or higher and 80°C or lower. The wax may be an ester of a fatty acid and an alcohol.

[0041] Examples of waxes include natural waxes such as animal- or plant-derived waxes (e.g., beeswax, carnauba wax, etc.), mineral waxes (e.g., microcrystalline wax, etc.), and petroleum wax; and synthetic waxes such as polyethylene wax, paraffin wax, and polyester wax. The wax is preferably at least one selected from the group consisting of paraffin wax, microcrystalline wax, and carnauba wax. Use of such waxes can further enhance the water vapor barrier properties of the laminate. One or more waxes can be used.

[0042] Commercially available waxes can be used. Commercially available carnauba waxes include "Cellosol 524" manufactured by Chukyo Yushi Co., Ltd. and "ML160RPH" manufactured by Michelman Co., Ltd. Commercially available paraffin waxes include "Hydrin L-700" manufactured by Chukyo Yushi Co., Ltd. and "Paraffin WAX-155" manufactured by Nippon Seiro Co., Ltd. Commercially available dispersions containing a water-dispersible polymer and a wax may also be used to form the resin layer (1). Commercially available dispersions of this type include "XP-8829" manufactured by Seiko PMC Co., Ltd. and "Joncryl 4130" manufactured by BASF Co., Ltd.

[0043] The lower limit of the wax content in the resin layer (1) is preferably 0.1 parts by mass, and may be 0.5 parts by mass, 1 part by mass, 2 parts by mass, 3 parts by mass, 5 parts by mass, 7 parts by mass, or 10 parts by mass, relative to 100 parts by mass of the water-dispersible polymer. By setting the wax content to be equal to or greater than the lower limit, it is possible to further improve the water vapor barrier properties of the laminate. On the other hand, the upper limit of the content is preferably 20 parts by mass, and may be 15 parts by mass, 10 parts by mass, 8 parts by mass, 6 parts by mass, or 5 parts by mass. By setting the wax content to be equal to or less than the upper limit, it is possible to improve the heat sealability when the resin layer (1) is the outermost layer, the adhesion to other layers when other layers are laminated on the surface of the resin layer (1), and the printability when printing is performed on the surface of the resin layer (1), while the laminate fully exhibits water vapor barrier properties.

[0044] (Other Components, etc.) The resin layer (1) may further contain components other than the water-dispersible polymer and wax. Examples of the other components include resins other than the water-dispersible polymer, layered inorganic materials, dispersants, surfactants, antifoaming agents, dyes, thickeners, etc.

[0045] It is preferable that the resin layer (1) is substantially free of a layered inorganic material. A layered inorganic material is usually contained in the resin layer as a component for enhancing barrier properties. However, if the resin layer (1) contains an excessive amount of a layered inorganic material, the layered inorganic material may interact with the wax, causing aggregation, etc. In such cases, the layered inorganic material may not be dispersed uniformly in the resin layer (1), and the water vapor barrier properties of the layered inorganic material may not be fully exhibited. Furthermore, if the resin layer (1) contains a layered inorganic material, the layered inorganic material may crack when the laminate is folded, resulting in a decrease in water vapor barrier properties. In contrast, the laminate of this embodiment can exhibit excellent water vapor barrier properties due to the interaction between the wax and the polyalkyleneimine, etc., even if the resin layer (1) does not contain a layered inorganic material, and the decrease in water vapor barrier properties due to folding can be suppressed. Furthermore, if the resin layer (1) is the outermost layer, the presence of the layered inorganic material in the resin layer (1) may affect heat sealability. For these reasons, the upper limit of the content of the layered inorganic material in the resin layer (1) is preferably 10% by mass, more preferably 3% by mass, and even more preferably 1% by mass, and may be 0.5%, 0.1%, or 0.01% by mass. The lower limit of the content of the layered inorganic material in the resin layer (1) may be 0% by mass. The resin layer (1) may not contain a layered inorganic material.

[0046] The total content of the water-dispersible polymer and wax in the resin layer (1) may be 90% by mass or more, 95% by mass or more, 99% by mass or more, or substantially 100% by mass.

[0047] The lower limit of the mass per unit area of ​​one resin layer (1) is 1 g / m ２ is preferred, and 3 g / m ２ More preferably, 5 g / m ２ More preferably, 7 g / m ２Even more preferably, 10 g / m ２ When the mass per unit area of ​​one resin layer (1) is equal to or greater than the lower limit, the water vapor barrier properties of the laminate can be further improved. Furthermore, when the resin layer (1) is the outermost layer, when the mass per unit area of ​​one resin layer (1) is equal to or greater than the lower limit, the resin layer (1) can function as a sufficiently good sealant layer. The upper limit of the mass per unit area of ​​one resin layer (1) is 100 g / m ２ is preferred, and 40 g / m ２ More preferably, 20 g / m ２ More preferably, 15 g / m ２ When the mass per unit area of ​​one resin layer (1) is equal to or less than the upper limit, it is possible to reduce the thickness of the laminate.

[0048] (Resin Layer (2)) The resin layer (2) contains a vinyl alcohol polymer and a polyalkyleneimine. The resin layer (2) may be a layer having a resin content of 50% by mass or more and 100% by mass or less. The resin layer (2) may be a layer formed by coating (coated layer). The resin layer (2) is a layer that mainly exhibits oxygen barrier properties.

[0049] (Vinyl alcohol polymer) The vinyl alcohol polymer is a polymer having a vinyl alcohol unit (—CH ２ Vinyl alcohol polymers are generally obtained by saponifying vinyl ester polymers. One or more vinyl alcohol polymers can be used.

[0050] The viscosity-average degree of polymerization of the vinyl alcohol-based polymer is preferably 200 or more and 5,000 or less. The lower limit of the viscosity-average degree of polymerization may be 300, 400, 500, or 800. On the other hand, the upper limit of the viscosity-average degree of polymerization may be 3,000, 2,500, 2,000, 1,200, 1,000, 700, or 500. When the viscosity-average degree of polymerization of the vinyl alcohol-based polymer is within the above range, the water vapor barrier property, oxygen barrier property, etc. of the laminate can be improved, and the coatability and strength of the formed layer, etc. can also be optimized.

[0051] The viscosity-average degree of polymerization of a vinyl alcohol polymer is measured in accordance with JIS K 6726:1994. Specifically, the intrinsic viscosity [η] (liters / g) of the vinyl alcohol polymer is measured in water at 30°C, and the viscosity-average degree of polymerization P is calculated using the value of the intrinsic viscosity [η] according to the following formula. When the saponification degree of the vinyl alcohol polymer is less than 99.5 mol%, the polymer is saponified to a saponification degree of 99.5 mol% or more, and then the intrinsic viscosity [η] is measured. P = ([η] x 10 ４ / 8.29) （１／０．６２）

[0052] The lower limit of the saponification degree of the vinyl alcohol polymer is preferably 70 mol%, more preferably 80 mol%, more preferably 90 mol%, even more preferably 95 mol%, and may be 96 mol%, 97 mol%, 98 mol%, or 99 mol%. A saponification degree equal to or greater than the lower limit can improve the water vapor barrier property, oxygen barrier property, and the like of the laminate. On the other hand, the upper limit of the saponification degree may be 100 mol% or 99.9 mol%. The saponification degree of the vinyl alcohol polymer is measured in accordance with JIS K 6726:1994.

[0053] The vinyl alcohol polymer may have a monomer unit derived from a monomer other than the vinyl alcohol unit and the vinyl ester unit. Examples of such other monomers include α-olefins such as ethylene, propylene, n-butene, and isobutylene; (meth)acrylic acid and its salts; (meth)acrylic acid esters; (meth)acrylamide; (meth)acrylamide derivatives such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, (meth)acrylamidopropanesulfonic acid and its salts, (meth)acrylamidopropyldimethylamine and its salts or quaternary salts thereof, and N-methylol(meth)acrylamide and its derivatives; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, and i-propyl vinyl ether. Examples of suitable vinyl ethers include vinyl ethers such as n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids and salts or esters thereof such as maleic acid, itaconic acid, and fumaric acid; vinyl silyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; 1,4-diacetoxybutene; 3,4-diacetoxy-1-butene; vinylformamide; and vinylpyrrolidone. In this specification, a vinyl alcohol polymer that is substantially free of monomer units derived from other monomers than vinyl alcohol units and vinyl ester units is also referred to as polyvinyl alcohol.

[0054] The other monomer is preferably an α-olefin, and more preferably ethylene. That is, the vinyl alcohol polymer may be an α-olefin-vinyl alcohol copolymer or an ethylene-vinyl alcohol copolymer (ethylene-modified polyvinyl alcohol). Use of such a vinyl alcohol polymer can further improve the water vapor barrier properties of the laminate.

[0055] The lower limit of the content of α-olefin units relative to all monomer units in the α-olefin-vinyl alcohol copolymer is preferably 0.1 mol%, more preferably 0.5 mol%, even more preferably 1 mol%, and may be 2 mol%, 3 mol%, 4 mol%, or 5 mol%. On the other hand, the upper limit of this content is preferably 20 mol%, more preferably 15 mol%, even more preferably 13 mol%, and may be 10 mol%, 8 mol%, 6 mol%, or 5 mol%. The lower limit of the content of ethylene units relative to all monomer units in the ethylene-modified polyvinyl alcohol (hereinafter sometimes referred to as the ethylene modification amount) is preferably 0.1 mol%, more preferably 0.5 mol%, even more preferably 1 mol%, and may be 2 mol%, 3 mol%, 4 mol%, or 5 mol%. On the other hand, the upper limit of this content is preferably 20 mol%, more preferably 15 mol%, even more preferably 13 mol%, and may be 10 mol%, 8 mol%, 6 mol%, or 5 mol%.

[0056] The total content of vinyl alcohol units, vinyl ester units, and any α-olefin units relative to all monomer units in the vinyl alcohol polymer is preferably 95 mol% or more, more preferably 99 mol% or more, and may be 100 mol%.

[0057] The lower limit of the content of the vinyl alcohol-based polymer in the resin layer (2) is preferably 60% by mass, more preferably 70% by mass, even more preferably 80% by mass, even more preferably 90% by mass, and may be 91%, 92%, 93%, or 94% by mass. On the other hand, the upper limit of the content of the vinyl alcohol-based polymer in the resin layer (2) is preferably 99% by mass, and may be 98% by mass, or may be 96%, 94%, 92%, or 90% by mass. By setting the content of the vinyl alcohol-based polymer in the resin layer (2) within the above range, the water vapor barrier property, oxygen barrier property, etc. of the laminate can be improved.

[0058] (Polyalkyleneimine) The polyalkyleneimine is preferably a polyalkyleneimine having an alkylene unit having 2 to 5 carbon atoms. Examples of the polyalkyleneimine include polyethyleneimine and polypropyleneimine, and polyethyleneimine is preferred. The polyalkyleneimine may be linear or branched. One or more types of polyalkyleneimine can be used.

[0059] The lower limit of the number average molecular weight of the polyalkyleneimine is preferably 30,000, more preferably 50,000, and may be 70,000, 100,000, or 200,000. When the number average molecular weight of the polyalkyleneimine is equal to or greater than the lower limit, the interaction with the wax in the resin layer (1) is enhanced, and the water vapor barrier properties of the laminate are further improved. The upper limit of the number average molecular weight of the polyalkyleneimine may be, for example, 3,000,000, or may be 2,000,000, 1,000,000, 800,000, 500,000, 300,000, or 200,000. The number average molecular weight of the polyalkyleneimine is a value measured by dissolving the polyalkyleneimine in a solvent capable of dissolving it and using gel permeation chromatography (GPC).

[0060] The lower limit of the polyalkyleneimine content in the resin layer (2) is preferably 0.3 parts by mass, more preferably 0.5 parts by mass, even more preferably 1 part by mass, even more preferably 3 parts by mass, and may even be 5 parts by mass, relative to 100 parts by mass of the vinyl alcohol-based polymer. By setting the polyalkyleneimine content at or above this lower limit, the interaction with the wax in the resin layer (1) is further enhanced, and the water vapor barrier properties of the laminate are further improved. On the other hand, the upper limit of the content is preferably 30 parts by mass, more preferably 20 parts by mass, even more preferably 10 parts by mass, and in some cases even more preferably 8 parts by mass, 7 parts by mass, or 6 parts by mass. By setting the polyalkyleneimine content at or below this upper limit, the water vapor barrier properties of the laminate can be further improved. It is believed that the wax contained in the resin layer (1) exhibits good water vapor barrier properties when it is sufficiently present on the surface opposite to the interface with the resin layer (2). By setting the content of polyalkyleneimine in the resin layer (2) to the above upper limit or less, the strength of the interaction between the polyalkyleneimine and the wax becomes appropriate, and the wax in the resin layer (2) is prevented from being unevenly distributed only on the interface side with the resin layer (1). In such a case, the wax can be sufficiently present on the surface of the resin layer (2) opposite to the resin layer (1), allowing the laminate to exhibit better water vapor barrier properties.

[0061] (Other Components, etc.) The resin layer (2) may further contain components other than the vinyl alcohol polymer and the polyalkyleneimine. Examples of the other components include resins other than the vinyl alcohol polymer and the polyalkyleneimine, layered inorganic materials, dispersants, surfactants, antifoaming agents, dyes, preservatives, fillers, interlayer adhesives, thickeners, etc.

[0062] Examples of layered inorganic materials include micas, mica, talc, montmorillonite, kaolinite, vermiculite, smectite, hectorite, taeniolite, and acid clay, with mica being preferred. The layered inorganic materials may be natural or synthetic. One or more types of layered inorganic materials may be used.

[0063] The average particle size of the layered inorganic material is preferably from 1 μm to 50 μm, more preferably from 4 μm to 30 μm. The average particle size is the average value of the particle sizes (longest diameter) of 20 randomly selected particles in a magnified image obtained by atomic force microscopy.

[0064] The aspect ratio of the layered inorganic material can be, for example, 20 or more, 100 or more, or 300 or more, but is preferably 500 or more. The aspect ratio may be, for example, 10,000 or less, 7,000 or less, 3,000 or less, or 2,000 or less. The aspect ratio refers to the average major diameter relative to the average thickness of flat particles. The average thickness and average major diameter are the average values ​​of the thickness and major diameter (longest diameter) of any 20 particles in an enlarged image obtained by atomic force microscopy.

[0065] In one embodiment, the resin layer (2) may not contain a layered inorganic material. The upper limit of the content of the layered inorganic material in the resin layer (2) may be, for example, 40% by mass, and may be 30%, 20%, 10%, 3%, 1%, 0.5%, 0.1%, or 0.01% by mass. When the content of the layered inorganic material in the resin layer (2) is equal to or less than the upper limit, deterioration of the water vapor barrier property due to bending can be suppressed. The lower limit of the content of the layered inorganic material in the resin layer (2) may be 0% by mass or 1% by mass.

[0066] The total content of the vinyl alcohol polymer and the polyalkyleneimine in the resin layer (2) is preferably 90% by mass or more, more preferably 95% by mass or more or 99% by mass or more. When the total content of the vinyl alcohol polymer and the polyalkyleneimine in the resin layer (2) is equal to or more than the lower limit, the water vapor barrier properties of the laminate tend to be further improved.

[0067] The lower limit of the mass per unit area of ​​one resin layer (2) is 0.3 g / m ２ is preferred, and 0.5 g / m ２ More preferably, 1 g / m ２ More preferably, 1.5 g / m ２ or 2 g / m ２When the mass per unit area of ​​one resin layer (2) is equal to or greater than the lower limit, the water vapor barrier property, oxygen barrier property, etc. can be improved. The upper limit of the mass per unit area of ​​one resin layer (2) is 15 g / m ２ is preferred, and 10 g / m ２ More preferably, 6 g / m ２ More preferably, 4 g / m ２ When the mass per unit area of ​​one resin layer (2) is equal to or less than the upper limit, the thickness of the laminate can be reduced.

[0068] (Other Layers) The laminate according to one embodiment of the present invention may further include layers other than the substrate, the resin layer (1), and the resin layer (2). Examples of the other layers include other resin layers, vapor-deposited layers, and metal foil layers.

[0069] The laminate according to one embodiment of the present invention preferably has a filler layer as another layer. Typically, the filler layer is a layer that is directly laminated on the substrate. The filler layer may be a layer formed by coating (a coating layer), or may be a layer containing a resin as a main component. The filler layer may also be called an undercoat layer, a precoat layer, or the like.

[0070] Examples of resins used in the filling layer include olefin polymers, styrene polymers, polyester polymers, urethane polymers, and vinyl alcohol polymers. Examples of the olefin polymers, styrene polymers, and polyester polymers include those exemplified as the water-dispersible polymers contained in the resin layer (1). Urethane polymers are typically polymers obtained by reacting polyisocyanate with polyol, and conventionally known polymers can be used. Examples of the vinyl alcohol polymers include those exemplified as the vinyl alcohol polymers contained in the resin layer (2). A cationic resin can also be used in combination with such a resin in the filling layer.

[0071] Among these, a vinyl alcohol polymer is preferred as the resin used in the filling layer. The preferred form of the vinyl alcohol polymer used as the resin in the filling layer is the same as the preferred form of the vinyl alcohol polymer contained in the resin layer (2). For example, the vinyl alcohol polymer used in the filling layer is preferably an α-olefin-vinyl alcohol copolymer, and more preferably an ethylene-vinyl alcohol copolymer (ethylene-modified polyvinyl alcohol).

[0072] When the filling layer contains a vinyl alcohol-based polymer, the filling layer may further contain a polyalkyleneimine, similar to the resin layer (2), or may not contain a polyalkyleneimine. In one embodiment, it is preferable that the filling layer does not substantially contain a polyalkyleneimine. When the filling layer contains a vinyl alcohol-based polymer, the content of the polyalkyleneimine in the filling layer relative to 100 parts by mass of the vinyl alcohol-based polymer in the filling layer may be, for example, less than 1 part by mass, less than 0.5 parts by mass, or less than 0.1 parts by mass.

[0073] The lower limit of the resin content in the filling layer is preferably 50% by mass, more preferably 60% by mass, and may be 70%, 80%, or 90% by mass, while the upper limit of this content may be 100%, 99%, 95%, 90%, or 80% by mass.

[0074] The lower limit of the content of the vinyl alcohol polymer in the filling layer is preferably 50% by mass, more preferably 60% by mass, and may be 70%, 80%, or 90% by mass, while the upper limit of this content may be 100%, 99%, 95%, 90%, or 80% by mass.

[0075] The filling layer may further contain a layered inorganic material. On the other hand, the filling layer may not contain a layered inorganic material. The upper limit of the content of the layered inorganic material in the filling layer can be, for example, 40 mass%, and may be 30 mass%, 20 mass%, 10 mass%, 3 mass%, 1 mass%, 0.5 mass%, 0.1 mass%, or 0.01 mass%. The lower limit of the content of the layered inorganic material in the filling layer may be 0 mass% or 1 mass%.

[0076] The filling layer may further contain components other than the resin and the layered inorganic material, such as a dispersant, a surfactant, an antifoaming agent, a dye, and a thickener.

[0077] The lower limit of the mass per unit area of ​​one filling layer is 0.1 g / m ２ is preferred, and 0.3 g / m ２ More preferably, 0.5 g / m ２ When the mass per unit area of ​​one filling layer is equal to or greater than the lower limit, the water vapor barrier property and the like can be further improved. The upper limit of the mass per unit area of ​​one filling layer is 10 g / m ２ is preferred, and 5 g / m ２ More preferably, 2 g / m ２ When the mass per unit area of ​​one filling layer is equal to or less than the upper limit, it is possible to reduce the thickness of the laminate.

[0078] The laminate according to one embodiment of the present invention may have a sealant layer other than the resin layer (1). When the resin layer (1) is the outermost layer, the resin layer (1) may function as a sealant layer. The sealant layer may be referred to as a heat seal layer or the like. The sealant layer is usually the outermost layer of the laminate. The outermost layer on one side of the laminate may be a sealant layer, or the outermost layers on both sides may both be sealant layers. The sealant layer may be a layer formed by coating (coating layer).

[0079] The sealant layer is usually composed mainly of a polymer. The polymer used in the sealant layer may be at least one selected from the group consisting of olefin-based polymers and styrene-based polymers. The sealant layer may further contain other components in addition to the polymer. Examples of other components include dispersants, surfactants, antifoaming agents, dyes, and thickeners.

[0080] When the laminate according to one embodiment of the present invention has a vapor-deposited layer, it can exhibit excellent water vapor barrier properties, oxygen barrier properties, etc. The vapor-deposited layer is a layer formed by vapor deposition, and is preferably a layer formed by vapor deposition of an inorganic substance (inorganic vapor-deposited layer).

[0081] Examples of materials constituting the vapor-deposited layer include inorganic materials such as metals (e.g., aluminum), metal oxides (e.g., silicon oxide, aluminum oxide, magnesium oxide), metal nitrides (e.g., silicon nitride), metal nitride oxides (e.g., silicon oxynitride), and metal carbonitrides (e.g., silicon carbonitride). Among the examples of inorganic materials listed above, silicon is considered to be included in the metals. The vapor-deposited layer may be composed of an organic material, or may be composed of both an organic material and an inorganic material. From the viewpoints of barrier properties, industrial productivity, and the like, the material constituting the vapor-deposited layer is preferably aluminum, aluminum oxide, silicon oxide, magnesium oxide, or silicon nitride, more preferably aluminum or aluminum oxide, and even more preferably aluminum.

[0082] The lower limit of the average thickness of one vapor-deposited layer is preferably 5 nm, more preferably 10 nm, even more preferably 20 nm, and even more preferably 30 nm. By setting the average thickness of the vapor-deposited layer to the above lower limit or more, it is possible to improve the barrier properties, etc. On the other hand, the upper limit of the average thickness of one vapor-deposited layer is preferably 200 nm, more preferably 150 nm, even more preferably 100 nm, and may be 80 nm or 60 nm. By setting the average thickness of the vapor-deposited layer to the above upper limit or less, cracking of the vapor-deposited layer during bending, etc., can be suppressed, and deterioration of the water vapor barrier properties and oxygen barrier properties after bending can be reduced. The average thickness of the vapor-deposited layer is the average value of the thicknesses at any 10 points on the cross section of the vapor-deposited layer measured using an electron microscope.

[0083] In one embodiment of the present invention, the laminate may not have any layers other than the substrate, the resin layer (1), the resin layer (2), and any filler layer. For example, the laminate may not have a vapor-deposited layer. Furthermore, the laminate may use a substrate provided with a filler layer as the substrate. Examples of such substrates include coated paper.

[0084] (Layer Structure, etc.) In the laminate according to one embodiment of the present invention, the resin layer (1) and the resin layer (2) are adjacent to each other. The resin layer (1) and the resin layer (2) may be in direct contact with each other.

[0085] In the laminate according to one embodiment of the present invention, the resin layer (1) is preferably the outermost layer. When the resin layer (1) is the outermost layer, the wax in the resin layer (1) can be sufficiently present on the outermost surface of the laminate, thereby exhibiting particularly excellent water vapor barrier properties. Furthermore, when the resin layer (1) is the outermost layer, the resin layer (1) can function as a sealant layer.

[0086] In the laminate, it is preferable that the substrate, the resin layer (2) and the resin layer (1) are directly laminated in this order, or that the substrate, the filling layer, the resin layer (2) and the resin layer (1) are directly laminated in this order.

[0087] In a laminate according to one embodiment of the present invention, the substrate, the resin layer (1), and the resin layer (2) may each be only one layer or two or more layers. In a laminate according to one embodiment of the present invention, the substrate, the resin layer (1), and the resin layer (2) each preferably have only one layer. When there are two or more layers of the substrate, the resin layer (1), and the resin layer (2), their compositions, thicknesses, etc. may be the same or different. Furthermore, when there are two or more layers of either the resin layer (1) or the resin layer (2), there may be a resin layer (1) or a resin layer (2) that is not adjacent to the other of the resin layer (1) and the resin layer (2). That is, it is sufficient that at least one pair of the resin layer (1) and the resin layer (2) is adjacent to each other.

[0088] Examples of the layer structure of the laminate according to one embodiment of the present invention are as follows: 1 represents the resin layer (1), 2 represents the resin layer (2), A represents the filling layer, and B represents the sealant layer. Substrate / 1 / 2 Substrate / 2 / 1 Substrate / A / 1 / 2 Substrate / A / 2 / 1 Substrate / A / 1 / 2 / B 2 / 1 / substrate / 1 / 2 1 / 2 / substrate / 2 / 1 1 / 2 / A / substrate / A / 2 / 1 B / substrate / 2 / 1 B / substrate / A / 2 / 1 B / A / substrate / A / 2 / 1

[0089] The laminate according to one embodiment of the present invention can be suitably used as greaseproof paper, gas barrier paper, flavor barrier paper, packaging material, etc. When the outermost layer of the laminate is the resin layer (1) or another sealant layer, the laminate can be used in a state where it is formed into a predetermined shape (for example, a bag shape) by heat-sealing the outermost layers together. The heat-sealing method is not particularly limited, and known methods can be used, such as a hot plate heat sealer, impulse sealer, ultrasonic sealer, frictional heat sealer, dielectric heating sealer, etc.

[0090] With respect to the water vapor permeability of a laminate according to one embodiment of the present invention, measured under conditions of a temperature of 40°C and a relative humidity of 90%, the ratio of the water vapor permeability after folding to the water vapor permeability before folding is preferably 1.10 or less, more preferably 1.05 or less. Such a laminate is less likely to lose its water vapor barrier property even after folding, and is excellent in processability, handleability, etc. In particular, when the substrate is paper, the water vapor barrier property generally tends to decrease when folded. Therefore, a laminate having the ratio equal to or less than the upper limit is particularly useful when the substrate is paper. The lower limit of the ratio may be 1.00 or 1.01. For example, in a laminate according to one embodiment of the present invention, the ratio can be suitably achieved when the resin layer (1) is substantially free of a layered inorganic material, and more suitably achieved when both the resin layer (1) and the resin layer (2) are substantially free of a layered inorganic material. When the resin layer (1) or the like does not contain a layered inorganic material, the flexibility of the layer is increased, and the layered inorganic material is prevented from cracking due to bending, which would otherwise cause a decrease in barrier properties, and therefore the ratio can be a low value.

[0091] The water vapor permeability of the laminate in an unfolded state and the water vapor permeability of the laminate in a folded state are specifically measured by the method described in the examples below.

[0092] <Method for manufacturing laminate> The method for manufacturing a laminate according to one embodiment of the present invention is not particularly limited, but it can typically be manufactured by providing a resin layer (1) and a resin layer (2) on a substrate by coating. The order of coating for providing the resin layer (1) and the resin layer (2) is not particularly limited, but it is preferable to provide the resin layer (2) and the resin layer (1) on the substrate in this order by coating. In the case of a laminate having a filling layer, the filling layer can also be provided by coating. For example, it is preferable to provide the filling layer, the resin layer (2), and the resin layer (1) on the substrate in this order by coating.

[0093] For example, resin layer (1), resin layer (2), etc. can be provided by applying a coating liquid for forming each layer and drying it. Drying does not need to be performed after each coating liquid, and a simultaneous multi-layer coating method may be employed. Each coating liquid can be applied by a conventionally known method. Coating can be performed using, for example, a blade coater, flexo coater, comma coater, metering rod size press, two-roll size press, shim sizer, bar coater, air knife coater, slit die coater, gravure coater, reverse gravure coater, microgravure coater, gate roll coater, curtain coater, etc.

[0094] The method for drying the applied coating liquid is not particularly limited, and can be carried out using, for example, a hot air dryer, an infrared dryer, a gas burner, a hot plate, or the like.

[0095] The solvent or dispersion medium for the coating liquid for forming each layer is not particularly limited, and water or an organic solvent (ethanol, isopropyl alcohol, methyl ethyl ketone, toluene, etc.) can be used, with water being preferred.

[0096] <Grease-resistant paper> Grease-resistant paper including the laminate according to one embodiment of the present invention is also a suitable embodiment of the present invention. The grease-resistant paper according to one embodiment of the present invention may be made of the laminate according to one embodiment of the present invention.

[0097] The greaseproof paper has excellent water vapor barrier properties and oxygen barrier properties, and is suitable for use as packaging for oily foods such as French fries and fried chicken, packaging for wrapping butter, and cooking paper for baking bread, cakes, and the like.

[0098] The oil resistance (KIT value) of the greaseproof paper is preferably at least grade 5, and more preferably at least grade 6 or at least grade 7. This oil resistance is a value measured on the surface by a kit test based on TAPPI No. T559cm-02.

[0099] <Gas barrier paper> A gas barrier paper comprising a laminate according to one embodiment of the present invention is also a suitable embodiment of the present invention. The gas barrier paper according to one embodiment of the present invention may be made of the laminate according to one embodiment of the present invention.

[0100] The gas barrier paper has excellent water vapor barrier properties and oxygen barrier properties and is suitable for use as packaging material for food, pesticides, pharmaceuticals, cosmetics, medical supplies, electronic components, clothing, and the like.

[0101] The oxygen permeability of the gas barrier paper is 100 cc / atm / m ２ / day or less is preferable, and 30cc / atm / m ２ / day or less is more preferable, and 10cc / atm / m ２ / day or less is more preferable, and 3 cc / atm / m ２ The oxygen permeability is a value measured under conditions of 20°C and 65% RH.

[0102] <Packaging Material> A packaging material including a laminate according to one embodiment of the present invention is also a suitable embodiment of the present invention. The packaging material according to one embodiment of the present invention may be made of the laminate according to one embodiment of the present invention, the greaseproof paper according to one embodiment of the present invention, or the gas barrier paper according to one embodiment of the present invention.

[0103] The packaging material has excellent water vapor barrier properties and oxygen barrier properties and is suitable for use as packaging for, for example, food, agricultural chemicals, pharmaceuticals, cosmetics, medical products, electronic components, clothing, and the like.

[0104] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples in any way.

[0105] (Evaluation of Water Vapor Barrier Property of Laminate Before Bending) The water vapor transmission rate (WVTR) of the laminate before folding (a laminate that had never been folded) was measured with the coated side facing inward by the cup method in accordance with JIS Z 2080. In this measurement, the temperature was 40°C and the relative humidity was 90% for Examples 1 to 12 and Comparative Examples 1 to 6, and the temperature was 23°C and the relative humidity was 85% for Example 13 and Comparative Example 7.

[0106] (Evaluation of the water vapor barrier properties of the folded laminate) The laminate was folded in half with the coated surface facing outward, pressed to create a complete crease, and then unfolded. The laminate was further folded with the coated surface facing inward, with the crease perpendicular to the original crease, and pressed to create a complete crease. The water vapor transmission rate (WVTR) of the folded laminate was then measured with the coated surface facing inward by the cup method in accordance with JIS Z 2080. The measurements were carried out at a temperature of 40°C and a relative humidity of 90% for Examples 1 to 12 and Comparative Examples 1 to 6, and at a temperature of 23°C and a relative humidity of 85% for Example 13 and Comparative Example 7.

[0107] The materials used in producing the laminates of the Examples and Comparative Examples are as follows: (Vinyl alcohol-based polymers) PVOH-1: ethylene-modified polyvinyl alcohol having a viscosity-average degree of polymerization of 790, a degree of saponification of 98.6 mol%, and an ethylene-modified amount of 7.7 mol% PVOH-2: polyvinyl alcohol having a viscosity-average degree of polymerization of 660 and a degree of saponification of 98.5 mol% PVOH-3: ethylene-modified polyvinyl alcohol having a viscosity-average degree of polymerization of 1,190, a degree of saponification of 99.2 mol%, and an ethylene-modified amount of 6.3 mol% PVOH-4: ethylene-modified polyvinyl alcohol having a viscosity-average degree of polymerization of 1,970, a degree of saponification of 96.1 mol%, and an ethylene-modified amount of 3.8 mol% PVOH-5: vinyl alcohol-based polymer ("BVE8049Q" manufactured by Mitsubishi Chemical Corporation)

[0108] (Dispersions containing water-dispersible polymers) St-Acryl Em-1: Dispersion of styrene-acrylic copolymer containing wax ("XP-8829" manufactured by Seiko PMC) St-Acryl Em-2: Dispersion of styrene-acrylic copolymer containing wax ("Joncryl 4130" manufactured by BASF) St-Acryl Em-3: Dispersion of styrene-acrylic copolymer not containing wax ("Joncryl 4110" manufactured by BASF) PO Em: Dispersion of ethylene-acrylic copolymer not containing wax ("Zaixen AC" manufactured by Sumitomo Seika Chemicals)

[0109] (Polyalkyleneimine, etc.) PEI-1: Polyethyleneimine having a number average molecular weight of 70,000 ("Epomin P-1000" manufactured by Nippon Shokubai) PEI-2: Polyethyleneimine having a number average molecular weight of 100,000 ("Epomin P-3000" manufactured by Nippon Shokubai) PEI-3: Polyethyleneimine having a number average molecular weight of 750,000 ("Loxanol M16730" manufactured by BASF) PU: Polyurethane ("NeorezR670XP" manufactured by Covestro AG)

[0110] Example 1 St-Acryl Em-1 (a dispersion of a styrene-acrylic copolymer containing wax) was prepared as a coating solution (1) for forming a resin layer (1). A coating solution (2) for forming a resin layer (2) was prepared by mixing a polyalkyleneimine, PEI-1, with an aqueous solution of a vinyl alcohol polymer, PVOH-1. The content of the polyalkyleneimine in the coating solution (2) was 2.5 parts by mass per 100 parts by mass of the vinyl alcohol polymer.

[0111] Basis weight as base material: 80 g / m ２ The coating weight after drying was 3 g / m on bleached kraft paper. ２ The coating solution (2) was applied using a reverse gravure coater so that the coating amount after drying was 13 g / m. ２ The coating liquid (1) was applied using a wire bar so that the thickness of the resin layer (1) was 100° C. and the applied coating liquid (1) was dried for 5 minutes at 100° C. Thus, a laminate (substrate / resin layer (2) / resin layer (1)) of Example 1 was obtained.

[0112] The water vapor barrier property (WVTR) of the obtained laminate of Example 1 before folding was 20.2 cc / m ２ / day, the water vapor barrier property (WVTR) after bending is 21.5cc / m ２ / day.

[0113] Example 2 An aqueous solution of PVOH-1, a vinyl alcohol polymer, was prepared as a coating liquid for forming a filling layer. St-Acryl Em-1 (a dispersion of a styrene-acrylic copolymer containing wax) was prepared as a coating liquid (1) for forming a resin layer (1). A coating liquid (2) for forming a resin layer (2) was prepared by mixing PEI-1, a polyalkyleneimine, with an aqueous solution of PVOH-1, a vinyl alcohol polymer. The content of the polyalkyleneimine in coating liquid (2) was 2.5 parts by mass relative to 100 parts by mass of the vinyl alcohol polymer.

[0114] Basis weight as base material: 80 g / m ２ The coating amount after drying was 1 g / m on bleached kraft paper. ２ The coating solution for forming the filler layer was applied using a reverse gravure coater so that the coating amount after drying was 3 g / m. ２ The coating solution (2) was applied using a reverse gravure coater so that the coating amount after drying was 13 g / m. ２ The coating liquid (1) was applied using a wire bar so as to form a resin layer (1), and the coating liquid (1) was dried at 100° C. for 5 minutes, thereby obtaining a laminate of Example 2 (substrate / filler layer / resin layer (2) / resin layer (1)).

[0115] The water vapor barrier property (WVTR) of the obtained laminate of Example 2 before folding was 15.5 cc / m ２ / day, the water vapor barrier property (WVTR) after bending is 16.2cc / m ２ / day.

[0116] [Examples 3 to 12, Comparative Examples 1 to 6] Each laminate (substrate / filler layer / resin layer (2) / resin layer (1)) of Examples 3 to 12 and Comparative Examples 1 to 6 was obtained in the same manner as in Example 2, except that the type of coating liquid (1) (dispersion containing a water-dispersible polymer), the type of vinyl alcohol-based polymer in coating liquid (2), the type and content (content relative to 100 parts by mass of the vinyl alcohol-based polymer) of polyalkyleneimine or the like (polyalkyleneimine or polyurethane), and the coating amount of each coating liquid were changed as shown in Table 1. The water vapor barrier properties (WVTR) of each obtained laminate were evaluated before and after bending. The evaluation results are shown in Table 1.

[0117]

[0118] Example 13 An aqueous solution of PVOH-1, a vinyl alcohol polymer, was prepared as a coating liquid for forming a filling layer. 20 parts by mass of polyethylene wax (Mitsui Chemicals' "Chemipearl S100") was added to 100 parts by mass of PO Em (a dispersion of a wax-free ethylene-acrylic copolymer) and mixed to prepare a coating liquid (1) for forming a resin layer (1). A polyalkyleneimine, PEI-1, was mixed with an aqueous solution of PVOH-1, a vinyl alcohol polymer, to prepare a coating liquid (2) for forming a resin layer (2). The content of the polyalkyleneimine in coating liquid (2) was 2.5 parts by mass relative to 100 parts by mass of the vinyl alcohol polymer.

[0119] Basis weight as base material: 80 g / m ２ The coating amount after drying was 1 g / m on bleached kraft paper. ２ The coating solution for forming the filler layer was applied using a reverse gravure coater so that the coating amount after drying was 3 g / m. ２ The coating solution (2) was applied using a reverse gravure coater so that the coating amount after drying was 13 g / m. ２The coating liquid (1) was applied using a wire bar so as to form a resin layer (1), and the coating liquid (1) was dried at 100° C. for 5 minutes, thereby providing a resin layer (1). In this way, a laminate (substrate / filler layer / resin layer (2) / resin layer (1)) of Example 13 was obtained.

[0120] The water vapor barrier property (WVTR) of the obtained laminate of Example 13 before folding was 69.4 cc / m ２ / day, the water vapor barrier property (WVTR) after bending is 71.1cc / m ２ / day.

[0121] [Comparative Example 7] A laminate (substrate / filler layer / resin layer (2) / resin layer (1)) of Comparative Example 7 was obtained in the same manner as in Example 13, except that PO Em (a dispersion of an ethylene-acrylic copolymer containing no wax) was used as is as the coating liquid (1) for forming the resin layer (1). The water vapor barrier properties (WVTR) of the obtained laminate were evaluated before and after bending. The evaluation results are shown in Table 2.

[0122]

[0123] Each of the laminates of Examples 1 to 13, in which the resin layer (1) contained a wax and the resin layer (2) contained a polyalkyleneimine, had excellent water vapor barrier properties before and after folding. On the other hand, even if the resin layer (1) contained a wax, when the resin layer (2) did not contain a polyalkyleneimine as in Comparative Examples 1 and 2, or when polyurethane was contained instead of a polyalkyleneimine as in Comparative Example 3, the water vapor barrier property was not excellent. Furthermore, as shown by a comparison between Comparative Example 4 and Comparative Example 5, when the resin layer (1) did not contain a wax, the effect of improving the water vapor barrier property was low even when the resin layer (2) contained a polyalkyleneimine. In contrast, as shown by a comparison between Comparative Example 1 and Example 2, when the resin layer (1) contained a wax, the water vapor barrier property was greatly improved by including a polyalkyleneimine in the resin layer (2).

[0124] The laminate of the present invention can be suitably used as a packaging material such as greaseproof paper, gas barrier paper, and flavor barrier paper.

Claims

1. A laminate having a substrate, a resin layer (1) and a resin layer (2), wherein the resin layer (1) and the resin layer (2) are adjacent to each other, the resin layer (1) contains a water-dispersible polymer and a wax, and the resin layer (2) contains a vinyl alcohol-based polymer and a polyalkyleneimine.

2. The laminate according to claim 1, wherein the content of the polyalkyleneimine in the resin layer (2) is 30 parts by mass or less per 100 parts by mass of the vinyl alcohol polymer.

3. The laminate according to claim 1 or 2, wherein the polyalkyleneimine has a number average molecular weight of 30,000 or more.

4. The laminate according to claim 1 or 2, wherein the water-dispersible polymer is at least one selected from the group consisting of olefin-based polymers and styrene-based polymers.

5. A laminate according to claim 1 or 2, wherein the content of the wax in the resin layer (1) is 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the water-dispersible polymer.

6. The laminate according to claim 1 or 2, wherein the wax is at least one selected from the group consisting of paraffin wax, microcrystalline wax, and carnauba wax.

7. The laminate according to claim 1 or 2, wherein the resin layer (1) is the outermost layer.

8. The laminate according to claim 1 or 2, wherein the resin layer (1) is substantially free of layered inorganic materials.

9. The laminate according to claim 1 or 2, wherein the substrate is paper.

10. The laminate described in claim 9, wherein the ratio of the water vapor permeability measured under conditions of a temperature of 40°C and a relative humidity of 90% after folding to the water vapor permeability when not folded is 1.10 or less.

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