Water vapor barrier coating agent and laminate

Abstract

This water vapor barrier coating agent contains an anionic binder resin, amino acids, an inorganic layered compound, and an aqueous medium, and is characterized in that the ratio of the amino acids in the total solid content included in the water vapor barrier coating agent is 0.5-40.0 mass%. The water vapor barrier coating agent is highly safe and has excellent water vapor barrier properties.

Description

Water vapor barrier coating agent and laminate

[0001] The present invention relates to a water vapor barrier coating agent and a laminate.

[0002] Packaging materials based on paper and endowed with water vapor barrier properties or gas barrier properties (particularly oxygen barrier properties) have traditionally been used in packaging foods, medical products, electronic components, and the like to prevent deterioration of the contents.

[0003] A common method for imparting water vapor barrier properties or gas barrier properties to a paper substrate is to laminate a synthetic resin film or metal foil with excellent gas barrier properties onto paper as a support. However, materials in which a synthetic resin film or the like is laminated onto a paper substrate have environmental issues, such as the difficulty of recycling the paper or synthetic resin after use and the problem of microplastics. Therefore, development of water vapor barrier materials and gas barrier materials using paper as a substrate without using a synthetic resin film or the like has been progressing. For example, Patent Document 1 discloses a paper barrier material in which a water vapor barrier layer and a gas barrier layer are provided in this order on a paper substrate. The water vapor barrier layer contains a layered inorganic compound, a cationic resin, and an anionic binder resin.

[0004] Japanese Patent Application Laid-Open No. 2020-69783

[0005] In recent years, there has been a growing demand for water vapor barrier coating agents that use safer additives instead of safer cationic resins for food packaging materials. However, the cationic resin that forms the water vapor barrier layer described in Patent Document 1 is a non-edible material.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a water vapor barrier coating agent and a laminate that are highly safe and have excellent water vapor barrier properties.

[0007] That is, the present invention has the following configurations. [1] A water vapor barrier coating agent containing an anionic binder resin, amino acids, an inorganic layered compound, and an aqueous medium, wherein the proportion of the amino acids is 0.5% by mass or more and 40.0% by mass or less of the total solid content contained in the water vapor barrier coating agent. [2] The water vapor barrier coating agent according to [1], wherein the polymer that forms the backbone of the anionic binder resin is preferably at least one selected from the group consisting of a styrene-butadiene copolymer, a styrene-acrylic copolymer, and an olefin-unsaturated carboxylic acid copolymer. [3] The water vapor barrier coating agent according to [1] or [2], wherein the proportion of the anionic binder resin is 40% by mass or more and 95% by mass or less, and the proportion of the inorganic layered compound is 1% by mass or more and 30% by mass or less of the total solid content contained in the water vapor barrier coating agent. [4] A laminate obtained by coating a paper substrate with the water vapor barrier coating agent according to any one of [1] to [3].

[0008] The water vapor barrier coating agent and laminate of the present invention are highly safe and have excellent water vapor barrier properties. Amino acids are the building blocks of proteins in living organisms, and many of the essential and non-essential amino acids that make up proteins in the human body are approved as food additives, making them highly safe materials.

[0009] <Water Vapor Barrier Coating Agent> The water vapor barrier coating agent of the present invention contains an anionic binder resin, amino acids, an inorganic layered compound, and an aqueous medium.

[0010] <Anionic Binder Resin> The anionic binder resin has the function of dispersing inorganic layered compounds and is preferably a binder resin modified with a monomer containing an acid group such as carboxylic acid. Examples of polymers that form the backbone of the binder resin include styrene-butadiene copolymers, styrene-acrylic copolymers, methacrylate-butadiene copolymers, acrylonitrile-butadiene copolymers, olefin-unsaturated carboxylic acid copolymers, and acrylic ester polymers. Among these, at least one selected from the group consisting of styrene-butadiene copolymers, styrene-acrylic copolymers, and olefin-unsaturated carboxylic acid copolymers is preferred because of its good water resistance, good elongation, and resistance to cracking of the coating layer due to folding. An olefin-unsaturated carboxylic acid copolymer is more preferred. The anionic binder resin is preferably in the form of an aqueous dispersion from the viewpoint of handling.

[0011] Styrene-butadiene copolymers are copolymers obtained by emulsion polymerization of monomers consisting of aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, p-t-butylstyrene, and chlorostyrene, conjugated diene compounds such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, as well as other compounds copolymerizable therewith. Styrene is a preferred aromatic vinyl compound, and 1,3-butadiene is a preferred conjugated diene compound. Styrene-butadiene copolymers are commercially available under the trade name Nipol SX1105A (manufactured by Nippon Zeon Co., Ltd.), and are readily available and usable.

[0012] Styrene-acrylic copolymers are copolymers obtained by emulsion polymerization of aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, p-t-butylstyrene, and chlorostyrene with monomers such as unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, and maleic acid monobutyl ester; unsaturated sulfonic acid monomers or salts thereof such as acrylamidopropanesulfonic acid, acrylate sodium sulfoethyl salt, and methacrylate sulfopropyl sodium salt; and other compounds copolymerizable therewith. Styrene is a preferred aromatic vinyl compound, and acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and the like are preferred unsaturated carboxylic acid monomers and unsaturated sulfonic acid monomers or salts thereof. Styrene-acrylic copolymers are commercially available under the trade name of Joncryl PDX 7741 (manufactured by BASF Japan Ltd.), and are easily available and can be used.

[0013] Olefin-unsaturated carboxylic acid copolymers are copolymers obtained by emulsion polymerization of olefins, particularly α-olefins such as ethylene and propylene, with monomers consisting of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid, unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, and maleic acid monobutyl ester, unsaturated sulfonic acid monomers or their salts such as acrylamidopropanesulfonic acid, acrylate sodium sulfoethyl salt, and methacrylate sulfopropyl sodium salt, and other compounds copolymerizable with these. The olefin is preferably an α-olefin, particularly ethylene, and the unsaturated carboxylic acid monomer or unsaturated sulfonic acid monomer or its salt is preferably acrylic acid, methacrylic acid, itaconic acid, or fumaric acid. Specific examples of olefin-unsaturated carboxylic acid copolymers include aqueous dispersions of ammonium salt of ethylene-acrylic acid copolymer, which are commercially available under the trade names Zaixen AC and Zaixen A (manufactured by Sumitomo Seika Chemicals Co., Ltd.), and are easily available and can be used.

[0014] The content of the anionic binder resin is not particularly limited, and is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 60% by mass or more, of the total solid content contained in the water vapor barrier coating agent. Meanwhile, the content of the anionic binder resin is preferably 95% by mass or less, and more preferably 85% by mass or less, of the total solid content contained in the water vapor barrier coating agent. That is, the content of the anionic binder resin is preferably 20% by mass or more and 95% by mass or less, more preferably 40% by mass or more and 95% by mass or less, even more preferably 50% by mass or more and 85% by mass or less, and particularly preferably 60% by mass or more and 85% by mass or less, of the total solid content contained in the water vapor barrier coating agent.

[0015] <Amino acids> Many amino acids are approved as food additives, are highly safe, and have the ability to disperse inorganic layered compounds, thereby improving water vapor barrier properties. Examples of amino acids include valine, leucine, isoleucine, phenylalanine, tryptophan, lysine, histidine, methionine, threonine, glycine, alanine, proline, aspartic acid, glutamic acid, asparagine, glutamine, tyrosine, arginine, cysteine, and serine, as well as amino acid derivatives. The compound may also be a dipeptide such as carnosine, anserine, homoanserine, kyotorphin, balenine, aspartame, glorin, baletin, or pseudoproline; a tripeptide such as eisenin, glutathione, isoleucine-proline-proline, leupeptin, melanostatin, ophthalmic acid, or norophthalmic acid; or an oligopeptide such as amanitin, antipain, ceruletide, glutathione, netropsin, pepstatin, peptide T, phalloidin, teprotide, or tuftsin. The compound may also be a homopolymer of amino acids such as polyvaline, polyleucine, polyisoleucine, polyphenylalanine, polytryptophan, polylysine, polyhistidine, polyglycine, polyalanine, polyproline, polyaspartic acid, polyglutamic acid, polytyrosine, or polyarginine. Alternatively, the compound may be a copolymer of a combination of the above amino acids. From the standpoint of miscibility, the amino acid is preferably a monocarboxylic acid. The amino acids may be used alone or in combination.

[0016] The content of amino acids is from 0.5% by mass to 40.0% by mass of the total solid content contained in the water vapor barrier coating agent. The content of amino acids is preferably from 1.0% by mass to 30% by mass, more preferably from 2.0% by mass to 20% by mass, of the total solid content contained in the water vapor barrier coating agent. That is, the content of amino acids is preferably from 1.0% by mass to 30% by mass, more preferably from 2.0% by mass to 20% by mass, of the total solid content contained in the water vapor barrier coating agent.

[0017] <Inorganic Layered Compound> The inorganic layered compound may be either a natural product or a synthetic product, or a mixture of these. Examples of natural products include smectite clay minerals such as montmorillonite, kaolinite (kaolin mineral), pyrophyllite, talc, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite, and mica clay minerals such as bentonite, pure mica, and brittle mica. Examples of synthetic products include synthetic hectorite (sodium magnesium silicate), synthetic bentonite, synthetic saponite, and synthetic mica. Among these, at least one selected from the group consisting of water-swellable montmorillonite, bentonite, and synthetic mica, synthetic hectorite, and synthetic bentonite is particularly preferred from the viewpoint of improving dispersibility, and montmorillonite, synthetic mica, and synthetic hectorite are more preferred from the viewpoint of improving barrier properties. The inorganic layered compounds may be used alone or in combination.

[0018] The content of the inorganic layered compound is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 20% by mass or less, of the total solid content contained in the water vapor barrier coating agent. On the other hand, the content of the inorganic layered compound is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 5% by mass or more, of the total solid content contained in the water vapor barrier coating agent. In other words, the content of the inorganic layered compound is preferably 1% by mass or more and 40% by mass or less, more preferably 1% by mass or more and 30% by mass or less, even more preferably 2% by mass or more and 20% by mass or less, and particularly preferably 5% by mass or more and 20% by mass or less, of the total solid content contained in the water vapor barrier coating agent.

[0019] <Aqueous Medium> The aqueous medium may be water alone, or may be a mixture of water and a water-miscible organic solvent such as an alcohol such as methanol, ethanol, or propanol, a polyhydric alcohol such as ethylene glycol or propylene glycol, an alkyl ether derivative thereof, an ester such as ethyl formate, methyl acetate, or ethyl acetate, or a ketone such as acetone.

[0020] <Other Additives> If necessary, dispersants, surfactants, antifoaming agents, wetting agents, dyes, color adjusters, thickeners, etc. may be added to the water vapor barrier coating agent.

[0021] <Method for producing a water vapor barrier coating agent> The method for producing a water vapor barrier coating agent using the above-mentioned constituent materials is not particularly limited, and examples thereof include: (1) a method in which an inorganic layered compound (which may have been previously swollen and cleaved in a dispersion medium such as water), amino acids, and an aqueous medium are added to and mixed with an anionic binder resin solution, and the inorganic layered compound is dispersed using a stirrer or disperser; (2) a method in which an inorganic layered compound is swelled and cleaved in a dispersion medium such as water, and then an anionic binder resin solution, amino acids, and an aqueous medium are added to and mixed with the resulting dispersion (dispersion solution) using a stirrer or disperser; and (3) a method in which an inorganic layered compound is swelled and cleaved in a dispersion medium such as water, and then amino acids are added, and then an anionic binder resin solution and an aqueous medium are added to and mixed with the resulting dispersion (dispersion solution) using a stirrer or disperser.

[0022] The stirring device or dispersing device is not particularly limited as long as it is a conventional stirring device or dispersing device, and can be used to uniformly disperse the inorganic layered compound in the dispersion. However, it is preferable to use a high-pressure disperser, ultrasonic disperser, etc., in order to obtain a transparent and stable inorganic layered compound dispersion. Examples of high-pressure dispersers include Nanomizer (trade name, manufactured by Nanomizer Co., Ltd.), Microfluidizer (trade name, manufactured by Microfluidex Co., Ltd.), Ultimizer (trade name, manufactured by Sugino Machine Co., Ltd.), DeBEE (trade name, manufactured by BEE Co., Ltd.), and Niro Soavi Homogenizer (trade name, manufactured by Niro Soavi Co., Ltd.). It is preferable to perform the dispersion process under pressure conditions of these high-pressure dispersers of 100 MPa or less. If the pressure conditions exceed 100 MPa, the inorganic layered compound is more likely to be crushed, and the desired gas barrier properties may be reduced.

[0023] <Laminate> The laminate of the present invention has a water vapor barrier layer formed by applying a water vapor barrier coating agent to at least one surface of a paper substrate and drying the coating. Furthermore, when gas barrier properties are required, for example, a gas barrier layer can be formed by further applying a gas barrier coating agent on the water vapor barrier layer and drying the applied coating. Note that when a gas barrier layer is formed, a water vapor barrier coating agent may be applied and then a gas barrier coating agent may be applied on top of the applied coating without being completely dried.

[0024] <Paper substrate> The paper substrate used in the paper substrate layer is not particularly limited as long as it is a commonly used paper containing plant-derived pulp as the main component. Specific examples include bleached or unbleached kraft paper, fine paper, paperboard, liner paper, coated paper, semi-glossy paper, glassine paper, graphene paper, etc. The paper substrate is preferably paper containing pulp as the main component, which is easily dispersible in water by mechanical disintegration.

[0025] <Water vapor barrier layer> The water vapor barrier layer is obtained by applying a water vapor barrier coating agent and drying it. The thickness of the water vapor barrier layer is preferably 1 to 30 μm, and more preferably 3 to 20 μm. The coating amount of the water vapor barrier layer is 1 to 30 g / m2 in terms of solid content. ２ It is preferable that the density is 3 to 20 g / m ２ It is more preferable that:

[0026] <Gas Barrier Layer> The gas barrier layer is obtained by applying a gas barrier coating agent and drying it. The thickness of the gas barrier layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm. The coating amount of the gas barrier layer is 0.1 to 10 g / m2 in terms of solid content. ２ It is preferable that the density is 0.5 to 7 g / m ２ It is more preferable that:

[0027] <Gas Barrier Coating Agent> The gas barrier coating agent contains, for example, a water-soluble polymer and an aqueous medium, and may also contain an inorganic layered compound.

[0028] <Water-Soluble Polymer> Examples of water-soluble polymers include polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives, cellulose derivatives, polyvinylpyrrolidone, urethane-based resins, polyacrylic acid and its salts, casein, and polyethyleneimine. Among these, fully saponified or partially saponified polyvinyl alcohol or modified polyvinyl alcohol is preferred because of its superior gas barrier properties. Examples of modified polyvinyl alcohol include ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol. The water-soluble polymers may be used alone or in combination. The content of the water-soluble polymer is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, of the total solids content of the gas barrier coating agent.

[0029] <Inorganic layered compound> As with the water vapor barrier layer, the inorganic layered compounds described above in the water vapor barrier coating agent can be used as the inorganic layered compound. The inorganic layered compounds may be used alone or in combination. The content of the inorganic layered compound is not particularly limited, and is preferably about 1 to 40 parts by mass per 100 parts by mass of the water-soluble polymer in the gas barrier coating agent. From the viewpoint of improving barrier properties, the inorganic layered compound is preferably at least one type selected from the group consisting of mica, bentonite, and kaolin.

[0030] <Aqueous Medium> The aqueous medium may be water alone, or may be a mixture of water and a water-miscible organic solvent such as an alcohol such as methanol, ethanol, or propanol, a polyhydric alcohol such as ethylene glycol or propylene glycol, an alkyl ether derivative thereof, an ester such as ethyl formate, methyl acetate, or ethyl acetate, or a ketone such as acetone.

[0031] <Method for producing gas barrier coating agent> The method for producing the gas barrier coating agent is not particularly limited. For example, a gas barrier coating agent of a predetermined concentration can be prepared by mixing a water-soluble polymer, an inorganic layered compound, and an aqueous medium, and thoroughly stirring and mixing the mixture at room temperature.

[0032] <Coating Method> There are no particular limitations on the coating method for applying the water vapor barrier coating agent and the gas barrier coating agent, and known methods can be used. Examples of coating methods include a blade coater, a bar coater, an air knife coater, a slit die coater, a gravure coater, a microgravure coater, and a gate roll coater. In particular, for forming the water vapor barrier layer, a coater that scrapes the coating surface, such as a reverse gravure coater, a kiss reverse gravure coater, a blade coater, a bar coater, an air knife coater, or a slit die coater, is preferred because it promotes the orientation of the inorganic layered compound.

[0033] The drying equipment for drying the water vapor barrier coating agent and the gas barrier coating agent is not particularly limited, and known equipment can be used, such as a hot air dryer, an infrared dryer, a gas burner, and a hot plate.

[0034] <Sealant Layer> The laminate of the present invention has a water vapor barrier layer, or a water vapor barrier layer and a gas barrier layer, on at least one surface of the paper base layer, and may further have a sealant layer formed on at least one outermost layer of the laminate.

[0035] The sealant layer is a layer that melts and adheres by heating or ultrasonic waves, and can bond laminates together by heat sealing or the like. The sealant layer can be formed by laminating synthetic resins such as polyethylene, polypropylene, ethylene-vinyl acetate polymers, and polyvinyl acetate polymers using a melt extrusion lamination method or a dry lamination method. The sealant layer can also be formed by coating an emulsion dispersion of synthetic resins such as polyethylene, polypropylene, ethylene-vinyl acetate polymers, and polyvinyl acetate polymers. The thickness of the sealant layer is preferably 1 to 50 μm, and more preferably 3 to 30 μm. The amount of the sealant layer formed is 1 to 50 g / m2 in terms of solid content. ２ It is preferable that the density is 3 to 30 g / m ２ It is more preferable that:

[0036] The water vapor barrier coating agent and laminate of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. In the examples and comparative examples, "parts" and "%" refer to "parts by mass" and "% by mass", respectively, unless otherwise specified. The raw materials used in the examples and comparative examples are as follows:

[0037] <Paper base> OK Blizzard (basis weight 70 g / m ２, manufactured by Oji Materia Co., Ltd.) <Anionic binder resin> Ethylene-acrylic acid copolymer (trade name "Zaixen A", solid content 25% by mass, manufactured by Sumitomo Seika Chemicals Co., Ltd.) Styrene-acrylic copolymer (trade name "Joncryl PDX 7741", solid content 50% by mass, manufactured by BASF Japan Ltd.) Styrene-butadiene copolymer (trade name "Nipol SX1105A", solid content 45.5% by mass, manufactured by Zeon Corporation) <Inorganic layered compound> Synthetic mica (trade name "Somasif ME300B-4T", solid content 7.9% by mass, manufactured by Katakura Co-op Agri Co., Ltd.) Montmorillonite (trade name "Kunipia F", manufactured by Kunimine Industries Co., Ltd., dispersed in ion-exchanged water to a solid content of 4% was used) <Amino acids> L-valine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Leucine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Isoleucine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Phenylalanine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Tryptophan (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Lysine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Histidine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Methionine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Threonine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Glycine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Alanine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Proline (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Aspartic acid (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Glutamic acid (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Asparagine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Glutamine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Arginine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Cysteine ​​(solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Serine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) L-Citrulline (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) Diglycine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) Triglycine (solid content 100% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) ε-Polylysine (solid content 25% by mass, manufactured by JNC Corporation)

[0038] <Method for producing water vapor barrier coating agent> Anionic binder resin, inorganic layered compound, amino acids, and aqueous medium were mixed in proportions as shown in Tables 1 and 2, and stirred with a stirrer to produce water vapor barrier coating agents of Examples and Comparative Examples.

[0039] <Method of manufacturing laminate> The water vapor barrier coating agent obtained above was applied to one side of a paper substrate in an amount of 5 g / m2 after drying. ２ After coating with a bar coater so that the coating was as follows: After coating with a bar coater so that the coating was as follows:

[0040] <Evaluation Method> <Water Vapor Barrier Property> The laminate obtained above was measured for water vapor transmission rate (WVTR value, g / m) in accordance with JIS Z 0208-1976. ２ / day) was measured. The temperature and humidity conditions were a temperature of 40±0.5°C and a relative humidity of 90±2%. The following "◎" or "◯" was used as the pass criteria. [Evaluation criteria] ◎: The water vapor transmission rate decreased by 50% or more compared to when no amino acid was contained. ◯: The water vapor transmission rate decreased by 25% or more but less than 50% compared to when no amino acid was contained. △: The water vapor transmission rate decreased by more than 0% but less than 25% compared to when no amino acid was contained. ×: The water vapor transmission rate increased compared to when no amino acid was contained. Specifically, Examples 1 to 25 and Comparative Examples 5 and 6 were evaluated based on the water vapor transmission rate of Comparative Example 1 (636 g / m ２ / day), Example 26 is compared with Comparative Example 2 (517 g / m ２ / day), Example 27 is compared with Comparative Example 3 (120 g / m ２ / day), Example 28 is compared with Comparative Example 4 (230 g / m ２ / day).

[0041]

[0042]

Claims

1. A water vapor barrier coating agent containing an anionic binder resin, amino acids, an inorganic layered compound, and an aqueous medium, characterized in that the proportion of the amino acids in the total solid content contained in the water vapor barrier coating agent is 0.5 mass% or more and 40.0 mass% or less.

2. The water vapor barrier coating agent according to claim 1, characterized in that the polymer that forms the backbone of the anionic binder resin is at least one selected from the group consisting of styrene-butadiene copolymers, styrene-acrylic copolymers, and olefin-unsaturated carboxylic acid copolymers.

3. The water vapor barrier coating agent according to claim 1 or 2, characterized in that, of the total solid content contained in the water vapor barrier coating agent, the proportion of the anionic binder resin is 40 mass% or more and 95 mass% or less, and the proportion of the inorganic layered compound is 1 mass% or more and 30 mass% or less.

4. A laminate comprising a paper substrate coated with the water vapor barrier coating agent according to any one of claims 1 to 3.

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