Bending-resistant materials and laminates

Abstract

The present invention provides a folding resistance agent and a laminate in which various functional layers are provided on a paper base material, which makes it difficult for the functional layers to deteriorate before and after folding. [Solution] A laminate in which a paper base layer, a folding-resistant layer, and a functional layer are laminated in this order, and a folding-resistant agent for forming the folding-resistant layer satisfies the following conditions 1 to 3 (excluding the case where the folding-resistant agent is OKS-1009 and the functional layer is an active energy ray-curable ink composition layer). (Condition 1) The fold-resistant agent contains a resin and a medium, and the content of the resin (in terms of solid content) in the fold-resistant agent is 70 to 100 mass %. (Condition 2) The bending-resistant layer has an elongation of 200% or more in a tensile test. (Condition 3) The shape recovery rate of the folding-resistant layer is 80% or more.

Description

[Technical Field]

[0001] The present invention relates to a folding-resistant agent and a laminate. More specifically, the present invention relates to a folding-resistant agent and a laminate that make it difficult for the functional layers to deteriorate before and after folding in a laminate in which various functional layers are provided on a paper base material. [Background technology]

[0002] In recent years, there has been a demand for eliminating plastic and aluminum in the food industry in order to respond to environmental concerns and the demands of the SDGs (Sustainable Development Goals). In response to these demands, paper packaging materials with barrier properties (moisture-proof properties) have been studied (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-220494 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-155780 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when packaging materials are produced using the paper laminates described in Patent Documents 1 and 2, the packaging has a problem in that the functionality of the functional layer (for example, moisture resistance) is reduced when the packaging material is folded.

[0005] The present invention has been made in consideration of these conventional problems, and aims to provide a folding-resistant agent and a laminate that are less likely to experience a decrease in the functionality of the functional layers before and after bending in a laminate in which various functional layers are provided on a paper base material. [Means for solving the problem]

[0006] As a result of intensive studies to solve the above problems, the inventors of the present invention have found that the above problems can be solved by providing a bend-resistant layer between the paper base material layer and the functional layer, and have completed the present invention. That is, the bend-resistant agent and laminate of the present invention for solving the above problems mainly include the following configurations.

[0007] (1) In a laminate in which a paper base material layer, a bend-resistant layer, and a functional layer are laminated in this order, the following conditions 1 to 3 are satisfied, and a bend-resistant agent for forming the bend-resistant layer (however, except when the bend-resistant agent is OKS-1009 and the functional layer is an active energy ray-curable ink composition layer). (Condition 1) The bend-resistant agent contains a resin and a medium, The content (in terms of solid content) of the resin is 70 to 100% by mass in the bend-resistant agent. (Condition 2) The elongation in the tensile test determined by the following formula for the bend-resistant layer is 200% or more. Elongation (%) = 100 × (Lb - L0) / L0 However, Lb refers to the length between the gauge marks at the time of breakage, and L0 refers to the length between the gauge marks before the tensile test. The tensile test is a tensile test carried out in accordance with JIS K 6251. (Condition 3) The shape recovery degree determined by the following formula for the bend-resistant layer is 80% or more. Shape recovery degree (%) = 100 × (L1 - L2) / (L1 - L0) However, L0 refers to the length between the gauge marks before the tensile test. L1 refers to the length between the gauge marks at 100% elongation in the tensile test, and for those that cannot be elongated to 100%, it is the length between the gauge marks at the limit without breakage. L2 refers to the length between the gauge marks of the bend-resistant layer when the external force is removed after the tensile test. The tensile test is a tensile test carried out in accordance with JIS K 6251.

[0008] According to such a configuration, the bend-resistant agent is applied to form a bend-resistant layer between the paper base material and the functional layer in a laminate in which various functional layers are provided on the paper base material. The obtained laminate is less likely to have a decrease in the function of the functional layer before and after bending.

[0009] (2) The bending-resistant agent according to (1), wherein the resin comprises at least one selected from the group consisting of polyurethane resins, acrylic resins, polyester resins, polyvinyl alcohol resins, styrene-butadiene resins, vinyl chloride resins, ethylene-vinyl acetate copolymer resins, and polyolefin resins.

[0010] According to this configuration, in a laminate having various functional layers provided on a paper substrate, the fold-resistant agent is applied to form a fold-resistant layer containing the resin between the paper substrate and the functional layer, and the function of the functional layer in the obtained laminate is less likely to deteriorate before and after bending.

[0011] (3) The folding-resistant agent according to (1) or (2), wherein the functional layer includes at least one layer selected from the group consisting of a moisture-proof layer, a gas barrier layer, an oil-resistant layer, a water-resistant layer, and a water-repellent layer.

[0012] According to this configuration, the folding-resistant agent is applied to a laminate having various functional layers provided on a paper substrate so as to form a folding-resistant layer between the paper substrate and the functional layers, and the resulting laminate is less likely to lose the functions (moisture resistance, gas barrier properties, oil resistance, water resistance, or water repellency) of the various functional layers before and after folding.

[0013] (4) A laminate in which a paper base layer, a folding-resistant layer, and a functional layer are laminated in this order, and the folding-resistant layer is a layer formed by applying the folding-resistant agent described in any one of (1) to (3).

[0014] With this configuration, the function of the functional layer in the obtained laminate is less likely to deteriorate before and after bending. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a folding resistance agent and a laminate in which various functional layers are provided on a paper base material, which makes it difficult for the functional layers to deteriorate before and after folding. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Flexural strength agent> The flexural strength agent according to an embodiment of the present invention is a flexural strength agent for forming a flexural strength layer in a laminate in which a paper base material layer, a flexural strength layer, and a functional layer are laminated in this order. However, it excludes the case where the flexural strength agent is OKS-1009 and the functional layer is an active energy ray-curable ink composition layer. The flexural strength agent satisfies the following Conditions 1 to 3. Note that the flexural strength agent of the present embodiment only needs to have a configuration in which the paper base material layer, the flexural strength layer, and the functional layer are laminated in this order, and other layers may be provided before, after, or in the middle thereof. (Condition 1) The flexural strength agent contains a resin and a medium, The content of the resin (in terms of solid content) is 70 to 100% by mass in the flexural strength agent. (Condition 2) The elongation in the tensile test of the flexural strength layer determined by the following formula is 200% or more. Elongation (%) = 100×(Lb - L0) / L0 However, Lb refers to the length between gauge marks at the time of breakage, and L0 refers to the length between gauge marks before the tensile test. The tensile test is a tensile test conducted in accordance with JIS K 6251. (Condition 3) The shape recovery degree of the flexural strength layer determined by the following formula is 80% or more. Shape recovery degree (%) = 100×(L1 - L2) / (L1 - L0) However, L0 refers to the length between gauge marks before the tensile test. L1 refers to the length between gauge marks at 100% elongation in the tensile test, and for those that cannot be elongated to 100%, it is the length between gauge marks at the limit without breakage. L2 refers to the length between gauge marks of the flexural strength layer when the external force is removed after the tensile test. The tensile test is a tensile test conducted in accordance with JIS K 6251. Each will be described below.

[0017] (Regarding Condition 1) ·Resin The resin is not particularly limited. For example, the resin preferably contains at least one selected from the group consisting of polyurethane resins, acrylic resins, polyester resins, polyvinyl alcohol resins, styrene-butadiene resins, vinyl chloride resins, ethylene-vinyl acetate copolymer resins, and polyolefin resins. From the viewpoints of solid content and viscosity, the resin is more preferably an emulsion of a polyurethane resin, an acrylic resin, a styrene-butadiene resin, a vinyl chloride resin, an ethylene-vinyl acetate copolymer resin, or a polyolefin resin. Thereby, the flex resistance agent is applied to form a flex resistance layer containing the above resin between the paper base material and the functional layer in a laminate in which various functional layers are provided on the paper base material. In the obtained laminate, the functions of the functional layer are less likely to deteriorate before and after folding.

[0018] The polyurethane resin is not particularly limited. For example, the polyurethane resin is a polyurethane resin obtained by reacting a diisocyanate compound, a diol compound, and optionally a chain extender or a reaction terminator.

[0019] The diisocyanate compound is not particularly limited. For example, the diisocyanate compound is an aliphatic diisocyanate compound such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate; an alicyclic diisocyanate compound such as isophorone diisocyanate and hydrogenated xylylene diisocyanate; an aromatic diisocyanate compound such as xylylene diisocyanate, α,α,α’,α’-tetramethylxylylene diisocyanate, toluylene diisocyanate, and diphenylmethane diisocyanate.

[0020] The diol compound is not particularly limited. For example, the diol compound is a low molecular weight diol such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, and triethylene glycol; a high molecular weight diol such as a polyester diol compound, a polyether diol compound, a polycarbonate diol compound, and a polybutadiene glycol compound.

[0021] In addition, the polyurethane resin may have various skeletons. For example, the polyurethane resin may be a polyether-based polyurethane resin, a polyester-based polyurethane resin, a polyester-polyether-based polyurethane resin, a polycarbonate-based polyurethane resin, or the like.

[0022] The polyester resin is not particularly limited. For example, the polyester resin can be obtained by an esterification reaction using a polyvalent carboxylic acid and a polyhydric alcohol as raw material components.

[0023] The polyvalent carboxylic acid is not particularly limited. For example, the polyvalent carboxylic acid includes phthalic acid, isophthalic acid, tetrahydrophthalic acid, tetrahydroisophthalic acid, hexahydrophthalic acid, hexahydroterephthalic acid, trimellitic acid, adipic acid, sebacic acid, succinic acid, azelaic acid, fumaric acid, maleic acid, itaconic acid, pyromellitic acid, etc., and acid anhydrides thereof.

[0024] The polyhydric alcohol is not particularly limited. For example, the polyhydric alcohol includes glycols and polyhydric alcohols having three or more valences. Examples of glycols include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, neopentyl glycol, hexylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, methylpropanediol, cyclohexanedimethanol, 3,3-diethyl-1,5-pentanediol, etc. Examples of polyhydric alcohols having three or more valences include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, etc.

[0025] The acrylic resin is not particularly limited. For example, the acrylic resin may be a polyester-modified acrylic resin, a polyurethane-modified acrylic resin, or a copolymer of vinyl versatate and an acrylic monomer, which is a copolymer of vinyl versatate and an acrylic monomer.

[0026] The polyvinyl alcohol resin is not particularly limited. For example, the polyvinyl alcohol resin may be polyvinyl alcohol, or a derivative or modified product of polyvinyl alcohol.

[0027] The polyvinyl alcohol resin preferably has a degree of polymerization of 100 to 5000, more preferably 500 to 3000. When the degree of polymerization of the polyvinyl alcohol resin is within the above range, the flexure-resistant agent has excellent film strength and handling suitability.

[0028] The saponification degree of the polyvinyl alcohol resin is preferably 60 mol% or more, more preferably 75 mol% or more. When the saponification degree of the polyvinyl alcohol resin is within the above range, the flexure-resistant agent has excellent film strength and water resistance.

[0029] The derivative of polyvinyl alcohol is a polyvinyl alcohol derivative in which about 40 mol% of the hydroxyl groups are acetalized.

[0030] The modified product of polyvinyl alcohol is a modified product of polyvinyl alcohol obtained by copolymerizing a carboxyl group-containing monomer, an amino group-containing monomer, a sulfone group-containing monomer, an acetoacetyl group-containing monomer, butanediol, etc.

[0031] Examples of the polyvinyl alcohol resin include Poval, Exceval (both manufactured by Kuraray Co., Ltd.), Gosenol, and Nitgo G Polymer (both manufactured by Mitsubishi Chemical Corporation).

[0032] The styrene-butadiene resin is not particularly limited. For example, the styrene-butadiene resin is a resin emulsion obtained by emulsion polymerization or solution polymerization of a monomer composition containing a styrene monomer, butadiene, and, if necessary, other monomers copolymerizable with the styrene monomer and butadiene.

[0033] The styrene monomers are styrene, α-methylstyrene, β-methylstyrene, 2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, 4-methoxystyrene, vinyltoluene, divinylbenzene, etc.

[0034] Other monomers copolymerizable with the styrene monomer and butadiene are alkyl (meth)acrylate monomers such as methyl (meth)acrylate and butyl (meth)acrylate; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; amide group-containing monomers such as (meth)acrylamide and N,N-dimethyl(meth)acrylamide; hydroxyalkyl (meth)acrylate monomers such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; carboxyl group-containing monomers such as itaconic acid, maleic acid, and (meth)acrylic acid, etc. The styrene-butadiene resin emulsion is preferably a carboxy (carboxyl group)-modified styrene-butadiene resin emulsion.

[0035] From the viewpoint of improving blocking properties and leveling properties, the glass transition temperature of the resin of the styrene-butadiene resin emulsion is preferably -20°C or higher, more preferably -10°C or higher. The glass transition temperature is determined by differential scanning calorimetry (DSC) and is usually calculated by the midpoint of the temperature range where the glass transition occurs.

[0036] The styrene-butadiene resin emulsion is Nipol SX1105A, Nipol LX407S12, Nipol LX435 (manufactured by Zeon Corporation, Japan), etc.

[0037] The vinyl chloride resin is not particularly limited. Examples of the vinyl chloride resin include a vinyl chloride homopolymer, a copolymer of vinyl chloride with a monomer copolymerizable with vinyl chloride, and a graft copolymer in which vinyl chloride is graft-copolymerized with a polymer other than the copolymer of vinyl chloride with a monomer copolymerizable with vinyl chloride. Among these, the vinyl chloride resin is preferably a vinyl chloride resin or a vinyl chloride resin emulsion.

[0038] The method for producing the vinyl chloride resin is not particularly limited. For example, the vinyl chloride resin can be produced by any known method, such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization.

[0039] The vinyl chloride copolymerizable monomer constituting the copolymer of vinyl chloride and a copolymerizable monomer is not particularly limited as long as it has a reactive double bond in the molecule. Such monomers include α-olefins such as ethylene, propylene, and butylene, vinyl esters such as vinyl acetate and vinyl propionate, vinyl ethers such as butyl vinyl ether and cetyl vinyl ether, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, acrylic or methacrylic acid esters such as methyl acrylate, ethyl methacrylate, and phenyl methacrylate, aromatic vinyls such as styrene and α-methylstyrene, vinyl halides such as vinylidene chloride and vinyl fluoride, and N-substituted maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide.

[0040] The polymer other than the vinyl chloride copolymer is not particularly limited as long as it can be graft-copolymerized with vinyl chloride.

[0041] Examples of vinyl chloride resins include Vinyblan (manufactured by Nisshin Chemical Industry Co., Ltd.) and Sumikaflex (manufactured by Sumika Chemtex Co., Ltd.).

[0042] The ethylene-vinyl acetate copolymer resin is not particularly limited. For example, the ethylene-vinyl acetate copolymer resin is a resin emulsion obtained by emulsion polymerization of a monomer composition containing ethylene and vinyl acetate monomer. In this case, the mass ratio of ethylene to vinyl acetate monomer (ethylene / vinyl acetate monomer) blended during copolymerization is preferably 10 / 90 to 70 / 30.

[0043] Examples of ethylene-vinyl acetate copolymer resins include Sumikaflex (manufactured by Sumika Chemtex Co., Ltd.).

[0044] The polyolefin resin is not particularly limited, and examples of the polyolefin resin include polyethylene resin, polypropylene resin, polybutylene resin, and resin emulsions in which polyolefin resins obtained by copolymerizing two or more of ethylene, propylene, and butylene are dispersed in water.

[0045] The polyolefin resin may also be a modified polyolefin resin in which an amino group, a carboxyl group, a hydroxyl group, an acryloyl group, or other polymer chain is introduced into the polyolefin chain; an oxidized polyolefin resin in which a portion of the polyolefin chain is oxidized; or a halogenated polyolefin resin in which a portion of the polyolefin chain is treated with a halogen.

[0046] Examples of polyolefin resins include Arrowbase (manufactured by Unitika Ltd.), Chemipearl (manufactured by Mitsui Chemicals, Inc.), and Superchron (manufactured by Nippon Paper Industries Co., Ltd.).

[0047] The resin content (solid content equivalent) in the solid content of the flexure-resistant agent is not particularly limited. For example, the resin content in the flexure-resistant agent may be 70% by mass or more, and preferably 80% by mass or more. The resin content in the flexure-resistant agent may be 100% by mass or less. By having the resin content within the above range, the flexure-resistant agent can achieve both coatability and coating film properties.

[0048] ·Medium The medium is not particularly limited as long as it satisfies conditions 1 to 3. For example, when the folding-resistant agent is aqueous, the medium may be water alone, or may be an aqueous medium containing a mixture of water and a water-miscible organic solvent. The water-miscible organic solvent is not particularly limited. For example, the water-miscible organic solvent may be alcohols such as methanol, ethanol, and propanol; polyhydric alcohols such as ethylene glycol and propylene glycol; alkyl ether derivatives thereof; esters such as ethyl formate, methyl acetate, and ethyl acetate; and ketones such as acetone.

[0049] In addition, when the folding-resistant agent is a solvent, the medium may be an alcohol-based solvent such as methanol, ethanol, isopropyl alcohol, normal propanol, butanol, isobutanol, or tert-butanol; an aromatic hydrocarbon-based solvent such as toluene or xylene; an aliphatic hydrocarbon-based solvent such as hexane, cyclohexane, methylcyclohexane, or ethylcyclohexane; a ketone-based solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone; an ester-based solvent such as ethyl acetate, n-propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, or tert-butyl acetate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, or ethylene glycol monomethyl ether. Glycol solvents such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether, and esterified products thereof, and the esterified products thereof are preferably mainly acetated products, such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate.

[0050] When the flexing agent is solvent-based, the medium is preferably a mixed solvent of an ester-based organic solvent, an alcohol-based organic solvent, and a ketone-based organic solvent from an environmental perspective, or a mixed solvent of an ester-based organic solvent and an alcohol-based organic solvent that is more environmentally friendly, etc.

[0051] The content of the medium is not particularly limited. For example, the content of the medium is preferably 40% by mass or more, more preferably 45% by mass or more in the flexing agent. Also, the content of the medium is preferably 80% by mass or less in the flexing agent. By having the content of the medium within the above range, the flexing agent can optimize storage stability, printing suitability, and coating amount.

[0052] ·Optional components The flexing agent of the present embodiment may appropriately contain optional components in addition to the above resin and medium. The optional components are not particularly limited. For example, the optional components are wax, defoaming agent, inorganic filler, release agent, thickening agent, surface conditioner, surfactant, plasticizer, polymerization inhibitor, ultraviolet absorber, light stabilizer, antioxidant, etc.

[0053] (Regarding Condition 2) The flexing agent of the present embodiment is a flexing agent for forming a flexing layer in a laminate in which a paper base material layer, a flexing layer, and a functional layer are laminated in this order.

[0054] Regarding Condition 2, the elongation in the tensile test of the flexing layer obtained using the flexing agent of the present embodiment is 200% or more. The elongation is represented by the following formula. Elongation (%) = 100×(Lb - L0) / L0 However, Lb refers to the length between the gauge marks at the time of breakage, and L0 refers to the length between the gauge marks before the tensile test. The tensile test is a tensile test conducted in accordance with JIS K 6251.

[0055] The elongation of the flexure-resistant layer should be 200% or more, preferably 250% or more. When the elongation of the flexure-resistant layer is less than 200%, it is difficult for the flexure-resistant layer to maintain the function of the functional layer before and after folding the laminate, and the function is likely to deteriorate. In the present embodiment, the elongation of the flexure-resistant layer can be measured by the following method.

[0056] · Method for measuring the elongation of the flexure-resistant layer Apply a flexure-resistant agent on an arbitrary substrate such as glass, dry it, peel it off, and produce a test piece in the shape of a dumbbell according to JIS K 6251 Type 3 tensile test piece (film thickness 300 μm). Next, measure the elongation when each test piece is pulled until it breaks using the following test machine under the following conditions. Tensile testing machine: AGS-X, manufactured by Shimadzu Corporation Elongation rate: 300 mm / min Temperature: 23 °C Humidity: 50%

[0057] (Regarding Condition 3) Regarding Condition 3, the shape restoration degree of the flexure-resistant layer is 80% or more. The shape restoration degree should be 80% or more, preferably 90% or more, and more preferably 95% or more. When the shape restoration degree is less than 80%, it is difficult for the flexure-resistant layer to maintain the function of the functional layer.

[0058] In the present embodiment, the shape restoration degree can be evaluated by conducting a tensile test performed in accordance with JIS K 6251. The tensile test for evaluating the shape restoration degree can be carried out using the following test machine under the following conditions.

[0059] · Method for evaluating the shape restoration degree of the flexure-resistant layer Apply a flexure-resistant agent on an arbitrary substrate such as glass, dry it, peel it off, and make it into a test piece shape. Using the obtained test piece, produce a dumbbell shape according to JIS K 6251 Type 3 tensile test piece (film thickness 300 μm). Next, under the following conditions, use the following test machine to stretch each test piece and hold it in that state for 5 minutes. Then, remove the test piece from the test machine and measure the length of the test piece after 3 hours. Tensile testing machine: AGS-X, manufactured by Shimadzu Corporation Stretching speed: 50mm / min Temperature: 23℃ Humidity: 50% The degree of shape restoration is calculated using the following formula: Shape recovery rate (%) = 100 × (L1-L2) / (L1-L0) Here, L0 refers to the gauge length before the tensile test. L1 refers to the gauge length at 100% elongation in the tensile test, and for specimens that cannot be elongated to 100%, it is the limit gauge length without breakage. L2 is the gauge length when the external force is removed after the tensile test.

[0060] Returning to the explanation of the folding endurance agent as a whole, the laminate to which the folding endurance agent is applied is a laminate in which a paper base layer, a folding endurance layer, and a functional layer are laminated in this order.

[0061] (Paper base layer) The paper base layer is not particularly limited. For example, the paper constituting the paper base layer is not particularly limited. For example, the paper may be any commonly used paper whose main component is plant-derived pulp, such as bleached or unbleached kraft paper, fine paper, paperboard, liner paper, coated paper, single-side glazed paper, glassine paper, graphene paper, etc. Among these, the paper is preferably paper whose main component is pulp that is easily dispersible in water by mechanical disintegration.

[0062] The basis weight and thickness of the paper base layer are not particularly limited. For example, the basis weight of the paper base layer is 30 g / m 2 It is preferable that the weight is 50 g / m or more. 2 The thickness of the paper base layer is more preferably 300 g / m or more. 2 Preferably, it is 250 g / m or less. 2 It is more preferable that the thickness and basis weight of the paper base layer are within the above ranges, so that the folding endurance agent can easily maintain the function of the functional layer.

[0063] (bending resistant layer) The folding-resistant layer is a layer formed by applying the folding-resistant agent of this embodiment.

[0064] The method for applying the fold resistance agent to the paper substrate is not particularly limited, and examples thereof include a method using a blade coater, a bar coater, an air knife coater, a slit die coater, a gravure coater, a gravure reverse coater, a microgravure coater, a gate roll coater, or the like.

[0065] The applied fold-resistant agent is dried. The drying method for drying the fold-resistant agent is not particularly limited. For example, known drying equipment may be used for the drying method, such as a hot air dryer, an infrared dryer, a gas burner, or a hot plate.

[0066] The thickness of the fold-resistant layer is not particularly limited. For example, the thickness of the fold-resistant layer is preferably 1 μm or more, more preferably 3 μm or more. Furthermore, the thickness of the fold-resistant layer is preferably 30 μm or less, more preferably 20 μm or less. When the thickness of the fold-resistant layer is within the above range, the function of the functional layer in the obtained laminate is less likely to deteriorate before and after bending.

[0067] (functional layer) The functional layer is a layer for imparting various functions to the paper substrate. The laminate of this embodiment includes a fold-resistant layer formed by adding the above-mentioned fold-resistant agent. As a result, the functions imparted by the functional layer of the laminate are less likely to be lost before and after folding.

[0068] The functional layer is not particularly limited. The functional layer can be appropriately selected depending on the desired application. Specifically, the functional layer preferably includes at least one layer selected from the group consisting of a moisture-proof layer, a gas barrier layer, an oil-resistant layer, a water-resistant layer, and a water-repellent layer. This prevents the functions of the various functional layers (moisture-proof property, gas barrier property, oil resistance, water resistance, or water-repellent property) from deteriorating before and after folding of the obtained laminate.

[0069] When the functional layer is a moisture-proof layer The moisture-proof layer is provided by applying a moisture-proof coating agent, which may contain, for example, an anionic binder resin, an inorganic layered compound, and an aqueous medium.

[0070] The anionic binder resin is not particularly limited. Examples of the anionic 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, the anionic binder resin is preferably at least one selected from the group consisting of styrene-butadiene copolymers, styrene-acrylic copolymers, and olefin-unsaturated carboxylic acid copolymers, and more preferably an olefin-unsaturated carboxylic acid copolymers, because of its good water resistance, good elongation, and resistance to cracking of the functional layer due to folding.

[0071] Styrene-butadiene copolymers are copolymers obtained by emulsion polymerization of aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, pt-butylstyrene, and chlorostyrene with 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 with these. The aromatic vinyl compound is preferably styrene. The conjugated diene compound is preferably 1,3-butadiene.

[0072] The styrene-acrylic copolymer is a copolymer obtained by emulsion polymerization of a monomer composed of an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, p-t-butylstyrene, chlorostyrene, etc., an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, butenetricarboxylic acid, etc., an unsaturated polycarboxylic acid alkyl ester having at least one carboxyl group such as monoethyl itaconate, monobutyl fumarate and monobutyl maleate, an unsaturated sulfonic acid monomer or its salt such as acrylamidopropanesulfonic acid, sodium acrylate sulfonatoethyl salt, sodium methacrylate sulfopropyl salt, etc., and other compounds copolymerizable therewith. The aromatic vinyl compound is preferably styrene or the like. The unsaturated carboxylic acid monomer, the unsaturated sulfonic acid monomer or its salt is preferably acrylic acid, methacrylic acid, itaconic acid, fumaric acid or the like.

[0073] The olefin-unsaturated carboxylic acid copolymer is a copolymer obtained by emulsion polymerization of monomers consisting of olefins, especially α-olefins such as ethylene and propylene, and 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 monoethyl itaconate, monobutyl fumarate, and monobutyl maleate, unsaturated sulfonic acid monomers or their salts such as acrylamidopropanesulfonic acid, sodium acrylate sulfonylethyl salt, and sodium methacrylate sulfopropyl salt, and other compounds copolymerizable therewith. The olefin is preferably an α-olefin, especially ethylene or the like. The unsaturated carboxylic acid monomer, unsaturated sulfonic acid monomer or its salt is preferably acrylic acid, methacrylic acid, itaconic acid, fumaric acid or the like. As a specific example of the olefin-unsaturated carboxylic acid copolymer, an aqueous dispersion of an ethylene-acrylic acid copolymer ammonium salt is commercially available as Zeicen AC, Zeicen A, etc. (manufactured by Sumitomo Seika Chemicals Co., Ltd.) and can be easily obtained and used.

[0074] The content of the anionic binder resin is not particularly limited. For example, the content of the anionic binder resin is preferably 20% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and particularly preferably 70% by mass or more based on the total solid content of the moisture-proof coating agent. Also, the content of the anionic binder resin is preferably 95% by mass or less, more preferably 85% by mass or less in the total solid content of the moisture-proof coating agent. When the content of the anionic binder resin is within the above range, the resulting functional layer (moisture-proof layer) can exhibit high moisture-proof properties.

[0075] The inorganic layered compound is not particularly limited. For example, the inorganic layered compound may be either a natural product or a synthetic product, or a mixture thereof. Natural products include smectite-based clay minerals such as montmorillonite, kaolinite (kaolin mineral), pyrophyllite, talc, beidellite, nontronite, saponite, hectorite, sauconite, stevensite, etc., and mica-based clay minerals such as bentonite, pure mica, brittle mica, etc. Synthetic products include synthetic hectorite (sodium magnesium silicate), synthetic bentonite, synthetic saponite, synthetic mica, etc. Among these, from the viewpoint of improving dispersibility, the inorganic layered compound is preferably at least one selected from the group consisting of water-swellable montmorillonite, bentonite, synthetic mica, synthetic hectorite, and synthetic bentonite. Also, from the viewpoint of improving barrier properties, the inorganic layered compound is more preferably montmorillonite, synthetic mica, or synthetic hectorite. The inorganic layered compounds may be used in combination.

[0076] The content of the inorganic layered compound is not particularly limited. For example, the content of the inorganic layered compound is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 30% by mass or less, and particularly preferably 20% by mass or less, based on the total solid content in the moisture-proof 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, based on the total solid content in the moisture-proof coating agent. When the content of the inorganic layered compound is within the above range, the resulting functional layer (moisture-proof layer) can exhibit high moisture-proof properties.

[0077] The aqueous medium is not particularly limited. For example, the aqueous medium may be water alone, or an aqueous medium mixed with water and water-miscible organic solvents such as alcohols like methanol, ethanol, propanol, polyhydric alcohols like ethylene glycol, propylene glycol and their alkyl ether derivatives, esters like ethyl formate, methyl acetate, ethyl acetate, and ketones like acetone.

[0078] The moisture-proof coating agent may contain at least one selected from amino acids and cationic resins in order to further improve moisture-proof properties. Amino acids and cationic resins are not particularly limited. For example, amino acids include amino acids such as glycine, alanine, leucine, valine, phenylalanine, proline, serine, threonine, lysine, arginine, aspartic acid, glutamic acid, polylysine, polyglutamic acid, polyglutamic acid, polymers of amino acids, amino acid derivatives, etc. Amino acids may be copolymers of amino acids. From the viewpoint of better moisture-proof properties, amino acids are preferably copolymers or polymers of amino acids.

[0079] Cationic resins include polyalkylene polyamines, polyamide compounds, polyamideamine-epihalohydrin or formaldehyde condensation reaction products, polyamine-epihalohydrin or formaldehyde condensation reaction products, polyamide polyurea-epihalohydrin or formaldehyde condensation reaction products, polyamine polyurea-epihalohydrin or formaldehyde condensation reaction products, polyamideamine polyurea-epihalohydrin or formaldehyde condensation reaction products, polyamide polyurea compounds, polyamine polyurea compounds, polyamideamine polyurea compounds and polyamideamine compounds, polyethyleneimine, polyvinylpyridine, amino-modified acrylamide-based compounds, polyvinylamine, polydiallyldimethylammonium chloride, etc.

[0080] The moisture-proof coating agent may be appropriately blended with additives as necessary. Additives are not particularly limited. For example, additives include dispersants, surfactants, defoaming agents, wetting agents, dyes, color adjusters, thickeners, etc.

[0081] The production method of the moisture-proof coating agent is not particularly limited. For example, the moisture-proof coating agent can be prepared by mixing an anionic binder resin, an inorganic layered compound, an aqueous medium and, as appropriate, amino acids, cationic resins, and additives, and stirring and mixing them sufficiently at room temperature.

[0082] When the functional layer is a moisture-proof layer, the thickness of the moisture-proof layer is not particularly limited. For example, the thickness of the moisture-proof layer is preferably 3 μm or more, more preferably 5 μm or more. Also, the thickness of the moisture-proof layer is preferably 30 μm or less, more preferably 20 μm or less. When the thickness of the moisture-proof layer is within the above range, the resulting laminate has excellent moisture-proof properties.

[0083] · When the functional layer is a gas barrier layer The gas barrier layer is provided by applying a gas barrier coating agent. For example, the gas barrier coating agent contains an aqueous polymer, an inorganic layered compound, and an aqueous medium.

[0084] The aqueous polymer is not particularly limited. For example, the aqueous polymer is polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives, cellulose derivatives, polyvinyl pyrrolidone, polyacrylonitrile-based resin, polyamide-based resin, polyester-based resin, urethane-based resin, polyacrylic acid and its salts, casein, polyethyleneimine, etc. Among these, the aqueous polymer is preferably completely saponified or partially saponified polyvinyl alcohol, or modified polyvinyl alcohol, from the viewpoint of imparting more excellent 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, diacetone-modified polyvinyl alcohol, etc.

[0085] The content of the aqueous polymer is not particularly limited. For example, the content of the aqueous polymer is preferably 50% by mass or more, more preferably 70% by mass or more, based on the total solid content of the gas barrier coating agent.

[0086] The inorganic layered compound is the same as the inorganic layered compound described above in relation to the moisture-proof layer. The inorganic layered compound is preferably at least one selected from the group consisting of mica, bentonite, and kaolin, from the viewpoint of improving the gas barrier properties.

[0087] The content of the inorganic layered compound is not particularly limited. For example, the content of the inorganic layered compound is preferably 1 part by mass or more, more preferably 30 parts by mass or more, based on 100 parts by mass of the aqueous polymer of the gas barrier coating agent. Further, the content of the inorganic layered compound is preferably 20 parts by mass or less, more preferably 50 parts by mass or less, based on 100 parts by mass of the aqueous polymer of the gas barrier coating agent. When the content of the inorganic layered compound is within the above range, the obtained functional layer (gas barrier layer) has excellent gas barrier properties under high humidity conditions.

[0088] The aqueous medium may be only water, or an aqueous medium in which water is mixed with water-miscible organic solvents such as alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and propylene glycol and their alkyl ether derivatives, esters such as ethyl formate, methyl acetate, and ethyl acetate, and ketones such as acetone.

[0089] The method for producing the gas barrier coating agent is not particularly limited. For example, the gas barrier coating agent can be prepared by mixing an aqueous polymer, an inorganic layered compound, and an aqueous medium and sufficiently stirring and mixing them at room temperature.

[0090] When the functional layer is a gas barrier layer, the thickness of the gas barrier layer is not particularly limited. For example, the thickness of the gas barrier layer is preferably 0.1 μm or more, more preferably 0.5 μm or more. Further, the thickness of the gas barrier layer is preferably 10 μm or less, more preferably 5 μm or less. When the thickness of the gas barrier layer is within the above range, the obtained laminate has excellent gas barrier properties.

[0091] · When the functional layer is an oil-resistant layer The oil-resistant layer is provided by applying an oil-resistant coating agent. For example, as the oil-resistant coating agent, an oil-resistant coating agent containing a pigment, a styrene-butadiene copolymer, polyvinyl alcohol, and an aqueous medium, a styrene-acrylic copolymer, a wax, and an aqueous medium can be used.

[0092] An oil-resistant coating agent containing a pigment, a styrene-butadiene copolymer, polyvinyl alcohol, and an aqueous medium will be described.

[0093] The pigment is not particularly limited. For example, the pigment is various pigments such as inorganic pigments and organic pigments. The inorganic pigments are kaolins such as kaolin, structural kaolin, delamica kaolin, and calcined kaolin, synthetic mica, heavy calcium carbonate, light calcium carbonate, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, aluminum hydroxide, magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, calcium silicate, white carbon, bentonite, zeolite, sericite, smectite, and other minerals. Among these, kaolin is preferable because it can impart excellent oil resistance and water resistance. Also, kaolin has excellent transparency and gloss when the density of the oil-resistant paper is increased.

[0094] When the pigment is kaolin, the average particle size of kaolin is preferably 0.5 μm or more, more preferably 1 μm or more. Also, the average particle size of kaolin is preferably 20 μm or less, more preferably 10 μm or less. When the average particle size of kaolin is within the above range, the resulting functional layer (oil-resistant layer) has excellent oil resistance.

[0095] Examples of organic pigments include solid, hollow, or through-hole particles of polydienes such as polyisoprene, polyneoprene, and polybutadiene; polyalkenes such as polybutene, polyisobutylene, and polypropylene; polymers or copolymers of vinyl monomers such as vinyl acetate, styrene, (meth)acrylic acid, (meth)acrylic acid alkyl esters, (meth)acrylamide, and methyl vinyl ether; polyurethane resins, polyester resins, polyamide resins, urea resins, melamine resins, and benzoguanamine resins.

[0096] The pigment content is not particularly limited. For example, the pigment content is preferably 20% by mass or more, more preferably 40% by mass or more, of the total solid content of the oil-resistant coating agent. Furthermore, the pigment content is preferably 70% by mass or less, more preferably 65% by mass or less, of the total solid content of the oil-resistant coating agent. When the pigment content is within the above range, the obtained oil-resistant layer has excellent oil resistance and water resistance.

[0097] Styrene-butadiene copolymer is blended to impart excellent water resistance (water repellency) to the functional layer. Styrene-butadiene copolymer is obtained by copolymerizing styrene and butadiene as monomers. When a water-insoluble copolymer is used, the copolymer may be used in the form of a latex. The styrene-butadiene copolymer of this embodiment is not particularly limited. One example is "A6160" commercially available from Asahi Kasei Corporation.

[0098] The glass transition temperature (Tg) of the styrene-butadiene copolymer is preferably 30°C or lower, more preferably 20°C or lower, and even more preferably 0°C or lower. The Tg of the styrene-butadiene copolymer is preferably -40°C or higher, more preferably -30°C or higher, and even more preferably -20°C or higher. When the Tg of the styrene-butadiene copolymer is within the above range, the resulting oil-resistant layer can exhibit excellent film-forming ability and excellent water and oil repellency.

[0099] The average particle diameter of the styrene-butadiene copolymer is preferably 0.01 μm or more, more preferably 0.03 μm or more. Further, the average particle diameter of the styrene-butadiene copolymer is preferably 1.0 μm or less, more preferably 0.5 μm or less. When the average particle diameter of the styrene-butadiene copolymer is within the above range, the styrene-butadiene copolymer has excellent water dispersibility.

[0100] The content of the styrene-butadiene copolymer is not particularly limited. For example, the content of the styrene-butadiene copolymer is preferably 20% by mass or more, more preferably 25% by mass or more, based on the total solid content of the oil-resistant coating agent. Further, the content of the styrene-butadiene copolymer is preferably 50% by mass or less, more preferably 45% by mass or less, based on the total solid content of the oil-resistant coating agent. When the content of the styrene-butadiene copolymer is within the above range, the oil-resistant coating agent can form an oil-resistant layer excellent in water resistance (water repellency) in addition to oil resistance on the paper substrate.

[0101] The polyvinyl alcohol is not particularly limited. For example, the polyvinyl alcohol is a polyvinyl alcohol-based resin such as unmodified fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, or modified polyvinyl alcohol. Modified polyvinyl alcohol includes ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diacetone group-modified polyvinyl alcohol, and the like. Among these, unmodified fully saponified polyvinyl alcohol, ethylene-modified polyvinyl alcohol, and carboxy-modified polyvinyl alcohol are preferable because they can impart excellent oil resistance. Further, ethylene-modified polyvinyl alcohol can suppress the thickening of the oil-resistant coating agent. Thereby, the oil-resistant coating agent has excellent coating applicability. Further, the obtained oil-resistant layer has an excellent state of the coated surface.

[0102] The content of the polyvinyl alcohol-based resin is not particularly limited. For example, the content of the polyvinyl alcohol-based resin is preferably 0.5% by mass or more, more preferably 3% by mass or more, in the total solid content of the oil-resistant coating agent. Further, the content of the polyvinyl alcohol-based resin is preferably 20% by mass or less, more preferably 10% by mass or less, in the total solid content of the oil-resistant coating agent. When the content of the polyvinyl alcohol-based resin is within the above range, the obtained oil-resistant layer can exhibit more excellent oil resistance. In addition, the polyvinyl alcohol-based resin can suppress the thickening of the oil-resistant coating agent. Thereby, the oil-resistant coating agent can suppress the occurrence of coating defects.

[0103] The aqueous medium may be only water, or an aqueous medium in which water is mixed with water-miscible organic solvents such as alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and propylene glycol and their alkyl ether derivatives, esters such as ethyl formate, methyl acetate, and ethyl acetate, and ketones such as acetone.

[0104] Next, an oil-resistant coating agent containing a styrene-acrylic copolymer, a wax, and an aqueous medium will be described.

[0105] Examples of the styrene-acrylic copolymer include styrene-acrylic copolymers obtained by copolymerizing styrene and styrene derivatives with acrylic acid (methacrylic acid) and alkyl acrylates such as methyl acrylate, ethyl acrylate, and butyl acrylate, and alkyl methacrylates such as methyl methacrylate. Preferably, it is a styrene-acrylic copolymer emulsion.

[0106] The waxes include polyolefin waxes such as paraffin wax, carboxyl group-containing paraffin wax, microcrystalline wax, polyethylene wax, carboxyl group-containing polyethylene wax, polypropylene wax, ethylene-propylene copolymer wax, etc., candelilla wax, rice wax, montan wax, fatty acids such as stearic acid, fatty acid amides such as stearic acid amide, bis-stearic acid amide, oleic acid amide, palmitic acid amide, etc., and fatty acid metal salts such as zinc stearate and calcium stearate. The content of the wax is preferably 1.5 to 20% by mass in the total solid content of the oil-resistant coating agent.

[0107] The aqueous medium may be only water, or an aqueous medium obtained by mixing water with water-miscible organic solvents such as alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and propylene glycol and their alkyl ether derivatives, esters such as ethyl formate, methyl acetate, and ethyl acetate, and ketones such as acetone.

[0108] The method for producing the oil-resistant coating agent is not particularly limited. For example, the oil-resistant coating agent can be prepared by mixing a pigment, a styrene-butadiene copolymer, polyvinyl alcohol, and an aqueous medium, or by mixing a styrene-acrylic copolymer, a wax, and an aqueous medium, and sufficiently stirring and mixing at room temperature.

[0109] When the functional layer is an oil-resistant layer, the thickness of the oil-resistant layer is not particularly limited. For example, the thickness of the oil-resistant layer is preferably 1 μm or more, more preferably 3 μm or more. Also, the thickness of the oil-resistant layer is preferably 20 μm or less, more preferably 10 μm or less. When the thickness of the oil-resistant layer is within the above range, the obtained laminate has excellent oil resistance.

[0110] · When the functional layer is a water-resistant layer The water-resistant layer is provided by applying a water-resistant coating agent. The water-resistant coating agent is not particularly limited. For example, the water-resistant coating agent may be a styrene-acrylic copolymer, wax, a water-resistant coating agent containing an aqueous medium, or the like.

[0111] The styrene-acrylic copolymer is not particularly limited. For example, the styrene-acrylic copolymer may be a styrene-acrylic copolymer obtained by copolymerizing styrene and styrene derivatives with acrylic acid (methacrylic acid) and alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, and alkyl methacrylates such as methyl methacrylate. Among these, the styrene-acrylic copolymer is preferably a styrene-acrylic copolymer emulsion.

[0112] The wax is not particularly limited. For example, the wax may be a paraffin wax, a carboxyl group-containing paraffin wax, a microcrystalline wax, a polyethylene wax, a carboxyl group-containing polyethylene wax, a polypropylene wax, an ethylene-propylene copolymer wax, or other polyolefin waxes, a candelilla wax, a rice wax, a montan wax, a fatty acid such as stearic acid, a fatty acid amide such as stearic acid amide, bis-stearic acid amide, oleic acid amide, palmitic acid amide, or a fatty acid metal salt such as zinc stearate, calcium stearate. The content of the wax is preferably 1.5 to 20% by mass in the total solid content of the water-resistant coating agent.

[0113] The aqueous medium may be only water, or a water-based medium obtained by mixing water with water-miscible organic solvents such as alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and propylene glycol and their alkyl ether derivatives, esters such as ethyl formate, methyl acetate, and ethyl acetate, and ketones such as acetone.

[0114] The manufacturing method of the water-resistant coating agent is not particularly limited. For example, the water-resistant coating agent can be prepared by mixing a styrene-acrylic copolymer, wax, and an aqueous medium, and sufficiently stirring and mixing at room temperature.

[0115] When the functional layer is a water-resistant layer, the thickness of the water-resistant layer is not particularly limited. For example, the thickness of the water-resistant layer is preferably 1 μm or more, more preferably 3 μm or more. Also, the thickness of the water-resistant layer is preferably 20 μm or less, more preferably 10 μm or less. When the thickness of the water-resistant layer is within the above range, the obtained laminate has excellent water resistance.

[0116] · When the functional layer is a water-repellent layer The water-repellent layer is provided by applying a water-repellent coating agent. For example, the water-repellent coating agent contains a water-repellent agent, an aqueous medium, and, if necessary, an inorganic pigment.

[0117] The water-repellent agent is not particularly limited. For example, the water-repellent agent is an aqueous coating agent containing a paraffinic hydrocarbon (e.g., Brightone FC-350 manufactured by Sakata Inx Corporation), a wax-based water-repellent agent (e.g., Celestar 40R manufactured by Lion Specialty Chemicals Co., Ltd.), etc. The water-repellent agent is not limited to paraffinic. The water-repellent agent may contain modified wax components such as microcrystalline wax, polyethylene wax, and maleated petroleum resin. Also, the wax-based component may contain a rosin-based resin or an unsaturated higher alcohol, etc.

[0118] The aqueous medium may be only water, or an aqueous medium mixed with water and water-miscible organic solvents such as alcohols like methanol, ethanol, and propanol, polyhydric alcohols like ethylene glycol and propylene glycol and their alkyl ether derivatives, esters like ethyl formate, methyl acetate, and ethyl acetate, and ketones like acetone.

[0119] There are no particular limitations on the method for producing the water-repellent coating agent. For example, the water-repellent coating agent can be prepared by mixing the water-repellent agent and an aqueous medium, and thoroughly stirring and mixing them at room temperature.

[0120] When the functional layer is a water-repellent layer, the thickness of the water-repellent layer is not particularly limited. For example, the thickness of the water-repellent layer is preferably 1 μm or more, more preferably 3 μm or more. Furthermore, the thickness of the water-repellent layer is preferably 20 μm or less, more preferably 10 μm or less. When the thickness of the water-repellent layer is within the above range, the resulting laminate has excellent water repellency.

[0121] Returning to the explanation of the folding-resistant agent, the folding-resistant agent of this embodiment is applied to a laminate in which various functional layers are provided on a paper substrate so as to form a folding-resistant layer between the paper substrate and the functional layer. The obtained laminate is less likely to lose function of the functional layer before and after folding.

[0122] <Laminate and method for manufacturing the laminate> The laminate of one embodiment of the present invention is a laminate in which a paper substrate layer, a folding-resistant layer, and a functional layer are laminated in this order. The folding-resistant layer is a layer formed by applying the above-mentioned folding-resistant agent.

[0123] The paper substrate layer, the folding-resistant layer, and the functional layer that constitute the laminate are as described above in relation to the embodiment of the folding-resistant agent.

[0124] The method for producing the laminate is not particularly limited. For example, the laminate can be produced by applying a folding resistance agent to a paper substrate layer, and then applying various functional coating agents (moisture-proof coating agent, gas barrier coating agent, oil-resistant coating agent, water-resistant coating agent, water-repellent coating agent). The folding resistance agent and the functional coating agent applied may be dried separately or both may be applied and then dried together.

[0125] The coating amount of the folding-resistant layer (solid content equivalent) is 1 g / m 2 It is preferable that the content is 3 g / m or more. 2The coating amount of the fold-resistant layer (solid content equivalent) is preferably 30 g / m or more. 2 Preferably, it is 20 g / m or less. 2 When the coating amount of the fold-resistant layer is within the above range, the resulting laminate exhibits excellent fold resistance.

[0126] When the functional layer is a moisture-proof layer, the coating amount of the moisture-proof coating agent (converted to solid content) is 1 g / m 2 It is preferable that the content is 3 g / m or more. 2 It is more preferable that the coating amount of the moisture-proof coating agent (in terms of solid content) is 30 g / m or more. 2 Preferably, it is 20 g / m or less. 2 When the coating amount of the moisture-proof coating agent is within the above range, the laminate exhibits excellent moisture-proof properties.

[0127] When the functional layer is a gas barrier layer, the coating amount of the gas barrier coating agent (solid content equivalent) is 0.1 g / m 2 It is preferable that the content is 0.5 g / m or more. 2 The coating amount (solid content equivalent) of the gas barrier coating agent is more preferably 10 g / m or more. 2 Preferably, it is 5 g / m or less. 2 When the coating amount of the gas barrier coating agent is within the above range, the laminate exhibits excellent gas barrier properties.

[0128] When the functional layer is an oil-resistant layer, the coating amount of the oil-resistant coating agent (converted to solid content) is 1 g / m 2 It is preferable that the content is 3 g / m or more. 2 The coating amount of the oil-resistant coating agent (in terms of solid content) is preferably 20 g / m or more. 2 Preferably, it is 10 g / m or less. 2 When the coating amount of the oil-resistant coating agent is within the above range, the laminate exhibits excellent oil resistance.

[0129] When the functional layer is a water-resistant layer, the coating amount of the water-resistant coating agent (solid content equivalent) is 1 g / m 2 It is preferable that the content is 3 g / m or more. 2 The coating amount of the water-resistant coating agent (in terms of solid content) is preferably 20 g / m or more. 2 Preferably, it is 10 g / m or less. 2 When the coating amount of the water-resistant coating agent is within the above range, the laminate exhibits excellent water resistance.

[0130] When the functional layer is a water-repellent layer, the coating amount of the water-repellent coating agent (solid content equivalent) is 1 g / m 2 It is preferable that the content is 3 g / m or more. 2 The coating amount of the water-repellent coating agent (in terms of solid content) is preferably 20 g / m or more. 2 Preferably, it is 10 g / m or less. 2 When the coating amount of the water-repellent coating agent is within the above range, the laminate exhibits excellent water repellency.

[0131] As described above, according to this embodiment, in a laminate in which various functional layers are provided on a paper substrate, a fold-resistant layer containing the above-mentioned fold-resistant agent is formed between the paper substrate and the functional layer, so that the function of the functional layer in the resulting laminate is less likely to deteriorate before and after folding. [Example]

[0132] The present invention will be explained in more detail below with reference to examples. The present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass." The figures for the amounts of each material in the tables are "parts by mass."

[0133] The raw materials used are shown below. <Paper base material> OK Blizzard (grammage 70g / m 2 , manufactured by Oji Materia Co., Ltd.)

[0134] <Moisture-proof coating agent> To 60.0 parts of anionic binder (Zaixen A, solids content 25%, manufactured by Sumitomo Seika Chemicals Co., Ltd.), 25.0 parts of an inorganic layered compound (Somasif ME300B-4T, solids content 8%, manufactured by Katakura Co-op Agri Co., Ltd.) was added under stirring, and 2.0 parts of a modified amide resin (Sumirez (registered trademark) Resin SPI-203(50)H, manufactured by Taoka Chemical Co., Ltd.) as a dispersant and 13 parts of ion-exchanged water were further added and stirred to obtain a moisture-proof coating agent.

[0135] <Oil-resistant coating agent> The oil-resistant coating agent used was INXKote WB FLEXO FDA GREASE RES AC4551.

[0136] <Bending resistance agent> Polyurethane resin 1 (Superflex 460S, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Polyurethane resin 2 (Superflex 210, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Acrylic resin 1 (DXA.4081, manufactured by VANORA) Acrylic resin 2 (Neocryl A-1125, manufactured by Covestro) Polyvinyl alcohol resin 1 (OKS-1009, manufactured by Mitsubishi Chemical Corporation) Polyvinyl alcohol resin 2 (BVE8049Q, manufactured by Mitsubishi Chemical Corporation) Polyvinyl alcohol resin 3 (OKS-8118, manufactured by Mitsubishi Chemical Corporation) Styrene-butadiene resin 1 (Smartex VA-1015, manufactured by Nippon A&L Co., Ltd.) Styrene-butadiene resin 2 (Nipol LX407S12, manufactured by Zeon Corporation) Ethylene-vinyl acetate copolymer resin 1 (Sumikaflex S-201HQ, manufactured by Sumika Chemtex Co., Ltd.) Ethylene-vinyl acetate copolymer resin 2 (Sumikaflex SDX-5100, manufactured by Sumika Chemtex Co., Ltd.) Polyolefin resin 1 (Arrowbase SE-1030N, manufactured by Unitika Ltd.) Polyolefin resin 2 (Arrow base SD-1010, manufactured by Unitika Ltd.)

[0137] <Method for producing flexure-resistant agent> As shown in Table 1, polyurethane resins 1 and 2, acrylic resin 1, and styrene-butadiene resins 1 and 2 were diluted with a medium (ion-exchanged water) to a solid content of 30% to obtain flexure-resistant agents 1 to 3, 8, and 9. For acrylic resin 2, the undiluted solution was used as flexure-resistant agent 4. Also, polyvinyl alcohol resins 1 to 3 were dissolved in a solvent (ion-exchanged water) to obtain a 10% solid content solution as flexure-resistant agents 5 to 7. Ethylene-vinyl acetate copolymer resins 1 and 2 were diluted with a medium (ion-exchanged water) to a solid content of 30% to obtain flexure-resistant agents 10 and 11. Polyolefin resins 1 and 2 were diluted with a medium (ion-exchanged water) to a solid content of 30% to obtain flexure-resistant agents 12 and 13.

[0138]

Table 1

[0139] <Example 1> On one surface of the paper substrate, flexure-resistant agent 1 was applied with a bar coater so that the dry coating amount would be 3 g / m 2 and then dried with a dryer air at 60°C to form a flexure-resistant layer. Further, an oil-resistant agent was applied with a bar coater so that the dry coating amount would be 6 g / m 2 and then dried with a dryer air at 60°C to form an oil-resistant layer, thereby producing a laminate for oil resistance evaluation of Example 1.

[0140] <Examples 2 to 14> Using the combinations shown in Table 2 below, laminates for oil resistance evaluation or laminates for moisture resistance evaluation were produced in the same manner as in Example 1, except that flexure-resistant agents 1, 3, 5, 6, 8, 10, and 12 were used for the oil-resistant layer and the moisture-proof layer.

[0141] <Comparative Examples 1 and 2> On one surface of the paper substrate, each functional layer was applied with a dry coating amount of 6 g / m 2After coating with a bar coater so as to obtain the above, it was dried with a dryer air at 60°C to form an oil-resistant layer, thereby producing a laminate for oil resistance evaluation or a laminate for moisture resistance evaluation of Comparative Examples 1 and 2.

[0142] <Comparative Examples 3 to 12> Using the combinations shown in Table 2 below, laminates for oil resistance evaluation or laminates for moisture resistance evaluation were produced in the same manner as in Example 1, except that bending resistance agents 2, 4, 7, 9, 11, and 13 were used for the oil-resistant layer and the moisture-proof layer.

[0143] The elongation of the bending-resistant layer and the shape restoration degree of the bending-resistant layer were evaluated by the following evaluation methods. The results are shown in Table 2.

[0144] In addition, for the obtained laminates, moisture resistance and oil resistance were evaluated according to the types of the produced functional layers. These evaluations were performed before and after the following bending. The results are shown in Table 2.

[0145] (Measurement method of elongation of bending-resistant layer) A bending resistance agent was applied on a glass substrate, dried, and peeled off to produce a test piece in the shape of a dumbbell No. 3 for tension of JIS K 6251 (film thickness: 300 μm). Next, the elongation when each test piece was pulled until it broke was measured using the following testing machine under the following conditions. Tensile testing machine: AGS-X, manufactured by Shimadzu Corporation Extension rate: 300 mm / min Temperature: 23°C Humidity: 50% The elongation is obtained by the following formula. Elongation (%) = 100×(Lb - L0) / L0 However, Lb refers to the length between gauge marks at the time of fracture, and L0 refers to the length between gauge marks before the tensile test. The tensile test is a tensile test performed in accordance with JIS K 6251.

[0146] (Evaluation method of shape restoration degree of bending resistance agent) The degree of shape recovery was evaluated by conducting a tensile test according to JIS K 6251. The tensile test for evaluating the degree of shape recovery was carried out using the following test machine under the following conditions. A bending resistance agent was applied to a glass substrate, dried, and peeled off to prepare a JIS K 6251 tensile type 3 dumbbell-shaped test piece (film thickness 300 μm). Next, each test piece was stretched using the following test machine under the following conditions and held in that state for 5 minutes. Thereafter, the test piece was removed from the test machine, and the length of the test piece was measured after 3 hours. Tensile testing machine: AGS-X, manufactured by Shimadzu Corporation Stretching speed: 50mm / min Temperature: 23℃ Humidity: 50% The degree of shape restoration is calculated using the following formula: Shape recovery rate (%) = 100 × (L1-L2) / (L1-L0) Here, L0 refers to the gauge length before the tensile test. L1 refers to the gauge length at 100% elongation in the tensile test, and for specimens that cannot be elongated to 100%, it is the limit gauge length without breakage. L2 is the gauge length when the external force is removed after the tensile test.

[0147] (Bending method) A 4000g roller was rolled over the laminate 10 times at a speed of 30cm / s to create the first crease in the laminate. The laminate was then opened, and a second crease was made in the same manner as the first, perpendicular to the first crease. The laminate was folded so that the side coated with the coating agent was facing inward.

[0148] (Oil resistance) 0.03 g of salad oil was dropped onto the coated surface of the laminate (on the intersection of the folds for the folded samples). After 90 minutes, the area of the salad oil seeping to the backside was measured, and the extent to which the stain area had been reduced compared to when the folding-resistant layer was not provided was evaluated. Note that when the folding-resistant layer was not provided (Comparative Example 1), the stain area was 12.4 cm 2It was. Also, when no crease was made on the laminate in all the examples and comparative examples, there was no bleeding to the back surface at all.

[0149] (Moisture resistance) The laminate obtained above was measured for water vapor transmission rate (WVTR value, g / m 2 / day) in accordance with JIS Z 0208-1976. The temperature and humidity conditions were 40 ± 0.5°C and 90 ± 2% relative humidity. The deterioration value of the water vapor transmission rate before and after bending was calculated, and it was evaluated how much the deterioration value was reduced compared to the case where the anti-bending layer was not provided. The water vapor transmission rate before bending in the case where the anti-bending layer was not provided (Comparative Example 2) was 25.6 g / m 2 / day, and the water vapor transmission rate after bending was 56.6 g / m 2 / day, and the deterioration value was 31.0 g / m 2 / day.

[0150]

Table 2

[0151] As shown in Table 2, it was found that the laminates obtained using the anti-bending agents of Examples 1 to 14 of the present invention were less likely to have the functions of the functional layer degraded before and after bending.

Claims

1. In a laminate in which a paper base material layer, a fold-resistant layer, and a functional layer are laminated in this order, the following Conditions 1 to 3 are satisfied, the functional layer includes at least one of a moisture-proof layer, a gas barrier layer, an oil-resistant layer, a water-resistant layer, or a water-repellent layer, when the functional layer includes an oil-resistant layer, the oil-resistant layer is a layer to which an oil-resistant coating agent is applied, when the functional layer includes a water-resistant layer, the water-resistant layer is a layer to which a water-resistant coating agent is applied, a fold-resistant agent for forming the fold-resistant layer (however, excluding the case where the fold-resistant agent is OKS-1009, and the functional layer is an active energy ray-curable ink composition layer, and the case where a film mainly composed of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is used as the heat-sealing layer). (Condition 1) The fold-resistant agent includes a resin and a medium, the resin includes at least one selected from the group consisting of an ethylene-vinyl acetate copolymer resin and a polyolefin resin, the content (in terms of solid content) of the resin is 70 to 100% by mass in the fold-resistant agent. (Condition 2) The elongation in the tensile test determined by the following formula of the fold-resistant layer is 200% or more. Elongation (%) = 100×(Lb - L0) / L0 However, Lb refers to the length between the gauge marks at the time of breakage, and L0 refers to the length between the gauge marks before the tensile test. The tensile test is a tensile test carried out in accordance with JIS K 6251. (Condition 3) The shape recovery degree determined by the following formula of the fold-resistant layer is 80% or more. Shape recovery degree (%) = 100×(L1 - L2) / (L1 - L0) However, L0 refers to the length between the gauge marks before the tensile test. L1 refers to the length between the gauge marks at 100% elongation in the tensile test, and for those that cannot be elongated up to 100%, it is the length between the gauge marks at the limit without breakage. L2 refers to the length between the gauge marks of the fold-resistant layer when the external force is removed after the tensile test. The tensile test is a tensile test carried out in accordance with JIS K 6251.

2. A laminate in which a paper base material layer, a fold-resistant layer, and a functional layer are laminated in this order, wherein the fold-resistant layer is a layer formed by applying the fold-resistant agent according to Claim 1.

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