Bend-resistance agent and laminate

Abstract

The present invention provides: a bend-resistance agent for making a decrease in functional layer performance less likely to occur after bending in a laminate in which various functional layers are provided to a paper substrate; and a laminate. The bend-resistance agent for forming satisfies the following conditions 1-3 and forms a bend-resistant layer in a laminate in which a paper substrate layer, the bend-resistant layer, and a functional layer are layered in this order (excluding a case where the bend-resistance agent is OKS-1009 and the functional layer is an active energy ray-curable ink composition layer). Condition 1: The bend-resistance agent contains a resin and a medium, and the content of the resin (in terms of solid content) is 70-100 mass%. Condition 2: The degree of elongation of the bend-resistant layer in a tensile test is not less than 200%. Condition 3: The shape restoration degree of the bend-resistant layer is not less than 80%.

Description

Bending-resistant materials and laminates

[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.

[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 Sustainable Development Goals (SDGs). In response to these demands, paper packaging materials with barrier properties (moisture-proof properties) have been studied (for example, Patent Documents 1 and 2).

[0003] JP 2002-220494 A JP 2009-155780 A

[0004] However, when packaging materials are produced using the paper laminates described in Patent Documents 1 and 2, there is a problem in that the functionality of the functional layer (such as moisture resistance) is reduced when the package 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.

[0006] As a result of intensive research to solve the above problems, the inventors discovered that the above problems could be solved by providing a folding-resistant layer between the paper base layer and the functional layer, and thus completed the present invention.

[0007] That is, a folding-resistant agent according to one embodiment of the present invention that solves the above-mentioned problems is a folding-resistant agent for forming a folding-resistant layer in a laminate in which a paper substrate layer, a folding-resistant layer, and a functional layer are laminated in this order, and satisfies the following conditions 1 to 3 (excluding cases in which the folding-resistant agent is OKS-1009 and the functional layer is an active energy ray-curable ink composition layer). (Condition 1) The folding-resistant agent includes a resin and a medium, and the content of the resin (converted into solid content) in the folding-resistant agent is 70 to 100 mass%. (Condition 2) The degree of elongation of the folding-resistant layer in a tensile test calculated by the following formula is 200% or more: Elongation (%) = 100 × (Lb - L0) / L0, where Lb refers to the gauge length at break, and L0 refers to the gauge length before the tensile test. The tensile test is performed in accordance with JIS K 6251. (Condition 3) The shape recovery of the fold-resistant layer, calculated by the following formula, is 80% or more: Shape recovery (%) = 100 × (L1 - L2) / (L1 - L0), where 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 those that cannot be elongated to 100%, it is the limit gauge length without breakage. L2 is the gauge length of the fold-resistant layer when the external force is removed after the tensile test, and the tensile test is a tensile test conducted in accordance with JIS K 6251.

[0008] Furthermore, one aspect of the laminate of the present invention that solves the above problem is 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 above-mentioned folding-resistant agent.

[0009] <Bending-resistant agent> The folding-resistant agent of one embodiment of the present invention is used to form a folding-resistant layer in a laminate in which a paper substrate layer, a folding-resistant layer, and a functional layer are laminated in this order. However, this does not apply when the folding-resistant agent is OKS-1009 and the functional layer is an active energy ray-curable ink composition layer. The folding-resistant agent satisfies the following conditions 1 to 3. Note that the folding-resistant agent of this embodiment may be configured such that the paper substrate layer, the folding-resistant layer, and the functional layer are laminated in this order, and other layers may be provided before, after, or between them. (Condition 1) The folding-resistant agent includes a resin and a medium, and the resin content (in terms of solids content) is 70 to 100 mass% in the folding-resistant agent. (Condition 2) The folding-resistant layer has an elongation of 200% or more in a tensile test calculated using the following formula: Elongation (%) = 100 × (Lb - L0) / L0, where Lb is the gauge length at break, and L0 is the gauge length before the tensile test. The tensile test is conducted in accordance with JIS K 6251. (Condition 3) The shape recovery of the fold-resistant layer, calculated by the following formula, is 80% or more. Shape recovery (%) = 100 × (L1 - L2) / (L1 - L0), where L0 is the gauge length before the tensile test. L1 is the gauge length at 100% elongation in the tensile test, and for those that cannot be elongated to 100%, it is the limit gauge length without breakage. L2 is the gauge length of the fold-resistant layer when the external force is removed after the tensile test, and the tensile test is conducted in accordance with JIS K 6251. Each of these is explained below.

[0010] (Regarding Condition 1) Resin The resin is not particularly limited. For example, the resin preferably includes at least one selected from the group consisting of polyurethane resin, acrylic resin, polyester resin, polyvinyl alcohol resin, styrene-butadiene resin, vinyl chloride resin, ethylene-vinyl acetate copolymer resin, and polyolefin resin. From the standpoint of solid content and viscosity, the resin is more preferably an emulsion of polyurethane resin, acrylic resin, styrene-butadiene resin, vinyl chloride resin, ethylene-vinyl acetate copolymer resin, or polyolefin resin. As a result, the folding-resistant agent is applied to a laminate having various functional layers provided on a paper substrate to form a folding-resistant layer containing the resin between the paper substrate and the functional layer. The resulting laminate exhibits less degradation of the functionality of the functional layer before and after folding.

[0011] The polyurethane resin is not particularly limited, and an example thereof is a polyurethane resin obtained by reacting a diisocyanate compound, a diol compound, and optionally, a chain extender and a reaction terminator.

[0012] The diisocyanate compound is not particularly limited. Examples of the diisocyanate compound include aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate; alicyclic diisocyanate compounds such as isophorone diisocyanate and hydrogenated xylylene diisocyanate; and aromatic diisocyanate compounds such as xylylene diisocyanate, α,α,α',α'-tetramethylxylylene diisocyanate, toluylene diisocyanate, and diphenylmethane diisocyanate.

[0013] The diol compound is not particularly limited. Examples of the diol compound include low molecular weight diols such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, and triethylene glycol; and high molecular weight diols such as polyester diol compounds, polyether diol compounds, polycarbonate diol compounds, and polybutadiene glycol compounds.

[0014] The polyurethane resin may have various skeletons, such as polyether polyurethane resin, polyester polyurethane resin, polyester-polyether polyurethane resin, and polycarbonate polyurethane resin.

[0015] The polyester resin is not particularly limited. For example, the polyester resin can be obtained by an esterification reaction using a polycarboxylic acid and a polyhydric alcohol as raw materials.

[0016] The polycarboxylic acid is not particularly limited. Examples of the polycarboxylic acid include 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, and the like, and acid anhydrides thereof.

[0017] The polyhydric alcohol is not particularly limited. Examples of polyhydric alcohols include glycols and trihydric or higher polyhydric alcohols. 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, and 3,3-diethyl-1,5-pentanediol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and dipentaerythritol.

[0018] The acrylic resin is not particularly limited, and examples thereof include polyester-modified acrylic resin, polyurethane-modified acrylic resin, and a copolymer of versatate vinyl ester and an acrylic monomer, which is a copolymer of versatate vinyl ester and an acrylic monomer.

[0019] The polyvinyl alcohol-based resin is not particularly limited. For example, the polyvinyl alcohol-based resin may be polyvinyl alcohol, or a derivative or modified product of polyvinyl alcohol.

[0020] The degree of polymerization of the polyvinyl alcohol resin is preferably 100 to 5000, more preferably 500 to 3000. When the degree of polymerization of the polyvinyl alcohol resin is within the above range, the folding-resistant agent has excellent film strength and handling suitability.

[0021] The saponification degree of the polyvinyl alcohol-based resin is preferably 60 mol % or more, more preferably 75 mol % or more. When the saponification degree of the polyvinyl alcohol-based resin is within the above range, the bending-resistant agent has excellent film strength and water resistance.

[0022] The polyvinyl alcohol derivative is a polyvinyl alcohol derivative in which up to about 40 mol % of the hydroxyl groups are acetalized.

[0023] The modified polyvinyl alcohol includes those obtained by copolymerizing a carboxyl group-containing monomer, an amino group-containing monomer, a sulfonic group-containing monomer, an acetoacetyl group-containing monomer, butenediol, etc.

[0024] Examples of polyvinyl alcohol resins include Poval and Exeval (both manufactured by Kuraray Co., Ltd.), Gohsenol and Nichigo G Polymer (both manufactured by Mitsubishi Chemical Corporation).

[0025] 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-based monomer, butadiene, and, as necessary, other monomers copolymerizable with the styrene-based monomer and butadiene.

[0026] The styrene monomers include styrene, α-methylstyrene, β-methylstyrene, 2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, 4-methoxystyrene, vinyltoluene, and divinylbenzene.

[0027] Other monomers copolymerizable with styrene-based monomers and butadiene include (meth)acrylic acid alkyl ester 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; (meth)acrylic acid hydroxyalkyl ester monomers such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; and carboxyl group-containing monomers such as itaconic acid, maleic acid, and (meth)acrylic acid. The styrene-butadiene-based resin emulsion is preferably a carboxy (carboxy group)-modified styrene-butadiene-based resin emulsion.

[0028] From the viewpoint of improving blocking properties and leveling properties, the styrene-butadiene resin emulsion preferably has a glass transition temperature of −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 from the midpoint of the temperature range in which the glass transition occurs.

[0029] Examples of styrene-butadiene resin emulsions include Nipol SX1105A, Nipol LX407S12, and Nipol LX435 (all manufactured by Nippon Zeon Co., Ltd.).

[0030] 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.

[0031] 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.

[0032] 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. Examples of 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.

[0033] The polymer other than the vinyl chloride copolymer is not particularly limited as long as it can be graft-copolymerized with vinyl chloride.

[0034] Examples of vinyl chloride resins include Vinyblan (manufactured by Nisshin Chemical Industry Co., Ltd.) and Sumikaflex (manufactured by Sumika Chemtex Co., Ltd.).

[0035] 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.

[0036] The ethylene-vinyl acetate copolymer resin is Sumikaflex (manufactured by Sumika Chemtex Co., Ltd.) or the like.

[0037] The polyolefin resin is not particularly limited, and examples of the polyolefin resin include polyethylene resin, polypropylene resin, polybutylene resin, and a resin emulsion in which a polyolefin resin obtained by copolymerizing two or more of ethylene, propylene, and butylene is dispersed in water.

[0038] 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.

[0039] 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.).

[0040] 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.

[0041] 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, water-miscible organic solvents include alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and propylene glycol, and alkyl ether derivatives thereof, esters such as ethyl formate, methyl acetate, and ethyl acetate, and ketones such as acetone.

[0042] Further, 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.

[0043] When the bending-resistant agent is solvent-based, from an environmental perspective, the medium is preferably a mixed solvent of an ester-based organic solvent, an alcohol-based organic solvent, and a ketone-based organic solvent, or a mixed solvent of an ester-based organic solvent and an alcohol-based organic solvent, which is more environmentally friendly.

[0044] The content of the medium is not particularly limited. For example, the content of the medium in the flex-resistant agent is preferably 40% by mass or more, more preferably 45% by mass or more. Furthermore, the content of the medium in the flex-resistant agent is preferably 80% by mass or less. By having the content of the medium within the above range, the flex-resistant agent can optimize its storage stability, printability, and application amount.

[0045] Optional Components The folding-resistant agent of the present embodiment may contain optional components in addition to the resin and medium. The optional components are not particularly limited. Examples of optional components include wax, antifoaming agent, inorganic filler, release agent, thickener, surface conditioner, surfactant, plasticizer, polymerization inhibitor, UV absorber, light stabilizer, antioxidant, etc.

[0046] (Condition 2) The folding-resistant agent of the present embodiment is an agent for forming a folding-resistant layer in a laminate in which a paper base layer, a folding-resistant layer, and a functional layer are laminated in this order.

[0047] Regarding condition 2, the flex-resistant layer obtained using the flex-resistant agent of this embodiment has an elongation of 200% or more in a tensile test. The elongation is expressed by the following formula: Elongation (%) = 100 × (Lb - L0) / L0, where Lb is the gauge length at break, and L0 is the gauge length before the tensile test. The tensile test is conducted in accordance with JIS K 6251.

[0048] The degree of elongation of the fold-resistant layer is sufficient as long as it is 200% or more, and preferably 250% or more. If the degree of elongation of the fold-resistant layer is less than 200%, the fold-resistant layer is unlikely to maintain the function of the functional layer before and after folding the laminate, and the function is likely to deteriorate. In this embodiment, the degree of elongation of the fold-resistant layer can be measured by the following method.

[0049] -Method for measuring the elongation of the folding-resistant layer A folding-resistant agent is applied to a substrate such as glass, dried, and peeled off to prepare a JIS K 6251 Tensile Type 3 dumbbell-shaped test piece (film thickness 300 μm). Next, the elongation of each test piece is measured when it is pulled to break using the following tester under the following conditions: Tensile tester: AGS-X, manufactured by Shimadzu Corporation, Elongation speed: 300 mm / min, Temperature: 23°C, Humidity: 50%

[0050] (Regarding Condition 3) Regarding Condition 3, the shape recovery rate of the fold-resistant layer is 80% or more. The shape recovery rate may be 80% or more, preferably 90% or more, and more preferably 95% or more. If the shape recovery rate is less than 80%, the fold-resistant layer will have difficulty maintaining the function of the functional layer.

[0051] In this embodiment, the degree of shape recovery can be evaluated by carrying out a tensile test carried out in accordance with JIS K 6251. The tensile test for evaluating the degree of shape recovery can be carried out under the following conditions using the following testing machine.

[0052] - Method for Evaluating the Shape Recovery of the Bending-Resistant Layer A bending-resistant agent is applied to any substrate, such as glass, dried, and peeled off to form a test specimen. Using the obtained test specimen, a JIS K 6251 Tensile Type 3 dumbbell-shaped specimen (film thickness 300 μm) is prepared. Next, each test specimen is stretched using the following test machine under the following conditions and held in that state for 5 minutes. The test specimen is then removed from the test machine, and its length is measured after 3 hours. Tensile test machine: AGS-X, manufactured by Shimadzu Corporation. Stretching speed: 50 mm / min. Temperature: 23°C. Humidity: 50%. The shape recovery is calculated using the following formula: Shape recovery (%) = 100 × (L1 - L2) / (L1 - L0), where 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.

[0053] Returning to the explanation of the folding-resistant agent as a whole, the laminate to which the folding-resistant agent is applied is a laminate in which a paper base layer, a folding-resistant layer, and a functional layer are laminated in this order.

[0054] (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 containing plant-derived pulp as the main component, 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 containing pulp as the main component, which is easily dispersible in water by mechanical disintegration.

[0055] 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 substrate layer is more preferably 300 g / m or more. 2 Preferably, the weight 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.

[0056] (Bending-resistant layer) The bending-resistant layer is a layer formed by applying the bending-resistant agent of the present embodiment.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] (Functional Layer) The functional layer is a layer for imparting various functions to the paper substrate. The laminate of this embodiment has 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.

[0061] 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 makes it difficult for the functions of the various functional layers (moisture-proof property, gas barrier property, oil resistance, water resistance, or water-repellent property) to deteriorate before and after folding of the obtained laminate.

[0062] When the functional layer is a moisture-proof layer, the moisture-proof layer is provided by applying a moisture-proof coating agent, for example, the moisture-proof coating agent contains an anionic binder resin, an inorganic layered compound, and an aqueous medium.

[0063] 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 copolymer, because of its good water resistance, good elongation, and resistance to cracking of the functional layer due to folding.

[0064] 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, and other compounds copolymerizable therewith. The aromatic vinyl compound is preferably styrene, etc. The conjugated diene compound is preferably 1,3-butadiene.

[0065] 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 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 sulfoethyl sodium salt, and methacrylate sulfopropyl sodium salt; and other compounds copolymerizable therewith. The aromatic vinyl compound is preferably styrene or the like. The unsaturated carboxylic acid monomer and unsaturated sulfonic acid monomer or their salts are preferably acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and the like.

[0066] Olefin-unsaturated carboxylic acid copolymers are copolymers obtained by emulsion polymerization of an olefin, particularly an α-olefin such as ethylene or propylene, with a monomer consisting of an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, or butenetricarboxylic acid; an unsaturated polycarboxylic acid alkyl ester having at least one carboxyl group, such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, or maleic acid monobutyl ester; an unsaturated sulfonic acid monomer or its salt, such as acrylamidopropanesulfonic acid, acrylate sulfoethyl sodium salt, or methacrylate sulfopropyl sodium salt; or other compounds copolymerizable therewith. The olefin is preferably an α-olefin, particularly ethylene. The unsaturated carboxylic acid monomer or 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 an olefin-unsaturated carboxylic acid copolymer, an aqueous dispersion of an ammonium salt of an ethylene-acrylic acid copolymer is commercially available as Zaixen AC, Zaixen A, etc. (manufactured by Sumitomo Seika Chemicals Co., Ltd.), and can be easily obtained and used.

[0067] 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, even 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. Furthermore, the content of the anionic binder resin is preferably 95% by mass or less, more preferably 85% by mass or less, based on the total solid content of the moisture-proof coating agent. By having the content of the anionic binder resin within the above range, the resulting functional layer (moisture-proof layer) can exhibit high moisture resistance.

[0068] 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 of these. 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. Synthetic products include synthetic hectorite (sodium magnesium silicate), synthetic bentonite, synthetic saponite, and synthetic mica. 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, and synthetic mica, synthetic hectorite, and synthetic bentonite. Furthermore, from the viewpoint of improving barrier properties, the inorganic layered compound is more preferably montmorillonite, synthetic mica, or synthetic hectorite. Inorganic layered compounds may be used in combination.

[0069] 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, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less, based on the total solid content of 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 of 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 resistance.

[0070] The aqueous medium is not particularly limited. For example, the aqueous medium may be water alone, or may be a mixture of water and a water-miscible organic solvent such as an alcohol (e.g., methanol, ethanol, or propanol), a polyhydric alcohol (e.g., ethylene glycol or propylene glycol) or an alkyl ether derivative thereof, an ester (e.g., ethyl formate, methyl acetate, or ethyl acetate), or a ketone (e.g., acetone).

[0071] The moisture-proof coating agent may contain at least one selected from amino acids and cationic resins to further improve moisture resistance. The amino acids and cationic resins are not particularly limited. Examples of amino acids include glycine, alanine, leucine, valine, phenylalanine, proline, serine, threonine, lysine, arginine, aspartic acid, glutamic acid, polylysine, polyglutamic acid, and other amino acids, amino acid polymers, and amino acid derivatives. The amino acids may be copolymers of amino acids. The amino acids are preferably copolymers or polymers of amino acids, as these provide better moisture resistance.

[0072] Examples of the cationic resin include polyalkylene polyamines, polyamide compounds, polyamidoamine-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, polyamidoamine polyurea-epihalohydrin or formaldehyde condensation reaction products, polyamide polyurea compounds, polyamine polyurea compounds, polyamidoamine polyurea compounds, polyamidoamine compounds, polyethyleneimine, polyvinylpyridine, amino-modified acrylamide compounds, polyvinylamine, and polydiallyldimethylammonium chloride.

[0073] The moisture-proof coating agent may contain additives as needed. The additives are not particularly limited. Examples of additives include dispersants, surfactants, antifoaming agents, wetting agents, dyes, color adjusters, and thickeners.

[0074] The method for producing 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 optionally amino acids, a cationic resin, and additives, and thoroughly stirring and mixing the mixture at room temperature.

[0075] 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. Furthermore, 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 obtained laminate has excellent moisture resistance.

[0076] When the functional layer is a gas barrier layer, the gas barrier layer is formed by applying a gas barrier coating agent, for example, the gas barrier coating agent includes an aqueous polymer, an inorganic layered compound, and an aqueous medium.

[0077] The aqueous polymer is not particularly limited. Examples of the aqueous polymer include polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives, cellulose derivatives, polyvinylpyrrolidone, polyacrylonitrile resins, polyamide resins, polyester resins, urethane resins, polyacrylic acid and its salts, casein, and polyethyleneimine. Among these, the aqueous polymer is preferably fully saponified or partially saponified polyvinyl alcohol or modified polyvinyl alcohol, in view of being able to impart better 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.

[0078] 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, and more preferably 70% by mass or more, of the total solid content of the gas barrier coating agent.

[0079] The inorganic layered compound is the same as the inorganic layered compound described above in relation to the moisture-proof layer. From the viewpoint of improving gas barrier properties, the inorganic layered compound is preferably at least one selected from the group consisting of mica, bentonite, and kaolin.

[0080] 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, relative to 100 parts by mass of the aqueous polymer of the gas barrier coating agent. Furthermore, the content of the inorganic layered compound is preferably 20 parts by mass or less, more preferably 50 parts by mass or less, relative to 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 resulting functional layer (gas barrier layer) has excellent gas barrier properties under high humidity conditions.

[0081] The aqueous medium may be water alone, or may be an aqueous medium obtained by mixing water with 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, or an alkyl ether derivative thereof, an ester such as ethyl formate, methyl acetate, or ethyl acetate, or a ketone such as acetone.

[0082] 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 thoroughly stirring and mixing the mixture at room temperature.

[0083] 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. Furthermore, 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.

[0084] When the functional layer is an oil-resistant layer, the oil-resistant layer is formed by applying an oil-resistant coating agent. For example, the oil-resistant coating agent may contain a pigment, a styrene-butadiene copolymer, polyvinyl alcohol, and an aqueous medium, or a styrene-acrylic copolymer, wax, and an aqueous medium.

[0085] An oil-resistant coating agent containing a pigment, a styrene-butadiene copolymer, polyvinyl alcohol, and an aqueous medium will be described.

[0086] The pigment is not particularly limited. Examples of pigments include inorganic and organic pigments. Inorganic pigments include kaolins such as kaolin, structural kaolin, delaminated kaolin, and calcined kaolin, as well as 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, and minerals such as smectite. Among these, kaolin is preferred because it can impart excellent oil resistance and water resistance. Furthermore, kaolin provides excellent transparency and gloss when the density of the greaseproof paper is increased.

[0087] When the pigment is kaolin, the average particle size of the kaolin is preferably 0.5 μm or more, more preferably 1 μm or more. Also, the average particle size of the kaolin is preferably 20 μm or less, more preferably 10 μm or less. When the average particle size of the kaolin is within the above range, the resulting functional layer (oil-resistant layer) has excellent oil resistance.

[0088] 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.

[0089] 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.

[0090] The styrene-butadiene copolymer is blended to impart excellent water resistance (water repellency) to the functional layer. The 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 of the styrene-butadiene copolymer is "A6160" commercially available from Asahi Kasei Corporation.

[0091] 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 obtained oil-resistant layer can exhibit excellent film-forming ability and excellent water- and oil-repellency.

[0092] The average particle size of the styrene-butadiene copolymer is preferably 0.01 μm or more, more preferably 0.03 μm or more. The average particle size of the styrene-butadiene copolymer is preferably 1.0 μm or less, more preferably 0.5 μm or less. When the average particle size of the styrene-butadiene copolymer is within the above range, the styrene-butadiene copolymer has excellent water dispersibility.

[0093] 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, and more preferably 25% by mass or more, of the total solid content of the oil-resistant coating agent. Furthermore, the content of the styrene-butadiene copolymer is preferably 50% by mass or less, and more preferably 45% by mass or less, of 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 on the paper substrate that is excellent in not only oil resistance but also water resistance (water repellency).

[0094] The polyvinyl alcohol is not particularly limited. For example, the polyvinyl alcohol may be a polyvinyl alcohol-based resin such as unmodified fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, or modified polyvinyl alcohol. Modified polyvinyl alcohol may be ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, or diacetone-modified polyvinyl alcohol. Among these, unmodified fully saponified polyvinyl alcohol, ethylene-modified polyvinyl alcohol, and carboxy-modified polyvinyl alcohol are preferred because they can impart excellent oil resistance. Furthermore, ethylene-modified polyvinyl alcohol can suppress thickening of the oil-resistant coating agent. This provides the oil-resistant coating agent with excellent coatability. Furthermore, the resulting oil-resistant layer has excellent coated surface condition.

[0095] 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, based on the total solid content of the oil-resistant coating agent. Furthermore, the content of the polyvinyl alcohol-based resin is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total solid content of the oil-resistant coating agent. By having the polyvinyl alcohol-based resin content within the above range, the resulting oil-resistant layer can exhibit superior oil resistance. Furthermore, the polyvinyl alcohol-based resin can suppress thickening of the oil-resistant coating agent. This allows the oil-resistant coating agent to suppress the occurrence of coating defects.

[0096] The aqueous medium may be water alone, or may be an aqueous medium obtained by mixing water with 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, or an alkyl ether derivative thereof, an ester such as ethyl formate, methyl acetate, or ethyl acetate, or a ketone such as acetone.

[0097] Next, an oil-resistant coating agent containing a styrene-acrylic copolymer, a wax, and an aqueous medium will be described.

[0098] Examples of the styrene-acrylic copolymer include styrene-acrylic copolymers obtained by copolymerizing styrene or a styrene derivative with acrylic acid (methacrylic acid), alkyl acrylate esters such as methyl acrylate, ethyl acrylate, and butyl acrylate, and alkyl methacrylate esters such as methyl methacrylate, and the like, and a styrene-acrylic copolymer emulsion is preferred.

[0099] Examples of waxes include polyolefin waxes such as paraffin wax, carboxyl group-containing paraffin wax, microcrystalline wax, polyethylene wax, carboxyl group-containing polyethylene wax, polypropylene wax, and ethylene-propylene copolymer wax, candelilla wax, rice wax, montan wax, fatty acids such as stearic acid, fatty acid amides such as stearic acid amide, stearic acid bisamide, oleic acid amide, and palmitic acid amide, and fatty acid metal salts such as zinc stearate and calcium stearate. The wax content is preferably 1.5 to 20% by mass of the total solids content of the oil-resistant coating agent.

[0100] The aqueous medium may be water alone, or may be an aqueous medium obtained by mixing water with 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, or an alkyl ether derivative thereof, an ester such as ethyl formate, methyl acetate, or ethyl acetate, or a ketone such as acetone.

[0101] 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 then thoroughly stirring and mixing the mixture at room temperature.

[0102] 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. Furthermore, 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.

[0103] 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 contain a styrene-acrylic copolymer, a wax, and an aqueous medium.

[0104] The styrene-acrylic copolymer is not particularly limited. For example, the styrene-acrylic copolymer is a styrene-acrylic copolymer obtained by copolymerizing styrene and a styrene derivative with acrylic acid (methacrylic acid), alkyl acrylate esters such as methyl acrylate, ethyl acrylate, and butyl acrylate, or alkyl methacrylate esters such as methyl methacrylate. Among these, the styrene-acrylic copolymer is preferably a styrene-acrylic copolymer emulsion.

[0105] The wax is not particularly limited. Examples of waxes include polyolefin waxes such as paraffin wax, carboxyl group-containing paraffin wax, microcrystalline wax, polyethylene wax, carboxyl group-containing polyethylene wax, polypropylene wax, and ethylene-propylene copolymer wax; candelilla wax, rice wax, montan wax; fatty acids such as stearic acid; fatty acid amides such as stearic acid amide, stearic acid bisamide, oleic acid amide, and palmitic acid amide; and fatty acid metal salts such as zinc stearate and calcium stearate. The wax content is preferably 1.5 to 20 mass% of the total solids content of the water-resistant coating agent.

[0106] The aqueous medium may be water alone, or may be an aqueous medium obtained by mixing water with 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, or an alkyl ether derivative thereof, an ester such as ethyl formate, methyl acetate, or ethyl acetate, or a ketone such as acetone.

[0107] The method for producing 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, a wax, and an aqueous medium, and thoroughly stirring and mixing the mixture at room temperature.

[0108] 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. Furthermore, 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 resulting laminate has excellent water resistance.

[0109] When the functional layer is a water-repellent layer, the water-repellent layer is formed 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.

[0110] The water repellent is not particularly limited. Examples of the water repellent include a water-based coating agent containing a paraffin hydrocarbon (e.g., Brightone FC-350 manufactured by Sakata Inx Corporation), a wax-based water repellent (e.g., Celestall 40R manufactured by Lion Specialty Chemicals Corporation), and the like. The water repellent is not limited to a paraffin-based agent. The water repellent may also contain a microcrystalline wax, a polyethylene wax, a modified wax component such as a maleated petroleum resin, or the like. The wax-based component may also contain a rosin-based resin, an unsaturated higher alcohol, or the like.

[0111] The aqueous medium may be water alone, or may be an aqueous medium obtained by mixing water with 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, or an alkyl ether derivative thereof, an ester such as ethyl formate, methyl acetate, or ethyl acetate, or a ketone such as acetone.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] <Laminate and manufacturing method of laminate> A laminate according to one embodiment of the present invention is a laminate comprising a paper substrate layer, a folding-resistant layer, and a functional layer laminated in this order. The folding-resistant layer is a layer formed by applying the folding-resistant agent described above.

[0116] 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.

[0117] 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 may be applied separately and then dried, or both may be applied and then dried together.

[0118] 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. 2 The coating amount of the fold-resistant layer (in terms of solid content) is preferably 30 g / m or more. 2 It is preferable that the weight 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.

[0119] When the functional layer is a moisture-proof layer, the coating amount of the moisture-proof coating agent (in terms of 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 moisture-proof coating agent (in terms of solid content) is preferably 30 g / m or more. 2 It is preferable that the weight 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.

[0120] When the functional layer is a gas barrier layer, the coating amount of the gas barrier coating agent (in terms of solid content) 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 preferably 10 g / m or more. 2 Preferably, it is 5 g / m or less. 2When the coating amount of the gas barrier coating agent is within the above range, the laminate exhibits excellent gas barrier properties.

[0121] When the functional layer is an oil-resistant layer, the coating amount of the oil-resistant coating agent (in terms of 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.

[0122] When the functional layer is a water-resistant layer, the coating amount of the water-resistant coating agent (in terms of 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 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.

[0123] When the functional layer is a water-repellent layer, the coating amount of the water-repellent coating agent (in terms of 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 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.

[0124] 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.

[0125] An embodiment of the present invention has been described above. The present invention is not particularly limited to the above embodiment. Note that the above embodiment mainly describes an invention having the following configuration.

[0126] (1) In a laminate in which a paper base layer, a folding-resistant layer, and a functional layer are laminated in this order, 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 folding-resistant agent includes a resin and a medium, and the content of the resin (converted to solid content) in the folding-resistant agent is 70 to 100 mass %. (Condition 2) The degree of elongation of the folding-resistant layer in a tensile test calculated by the following formula is 200% or more: Elongation (%) = 100 × (Lb - L0) / L0, where Lb refers to the gauge length at break, and L0 refers to the gauge length before the tensile test. The tensile test is performed in accordance with JIS K 6251. (Condition 3) The shape recovery of the fold-resistant layer, calculated by the following formula, is 80% or more: Shape recovery (%) = 100 × (L1 - L2) / (L1 - L0), where 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 those that cannot be elongated to 100%, it is the limit gauge length without breakage. L2 is the gauge length of the fold-resistant layer when the external force is removed after the tensile test, and the tensile test is a tensile test conducted in accordance with JIS K 6251.

[0127] According to this configuration, in a laminate in which various functional layers are provided on a paper substrate, the fold-resistant agent is applied to form a fold-resistant layer 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 folding.

[0128] (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.

[0129] 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.

[0130] (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.

[0131] 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 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.

[0132] (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).

[0133] With this configuration, the function of the functional layer in the obtained laminate is less likely to deteriorate before and after bending.

[0134] The present invention will be described 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."

[0135] The raw materials used are as follows: <Paper base> OK Blizzard (basis weight 70 g / m 2 , manufactured by Oji Materia Co., Ltd.)

[0136] <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.

[0137] <Oil-Resistant Coating Agent> INXKote WB FLEXO FDA GREASE RES AC4551 was used as the oil-resistant coating agent.

[0138] <Bending resistance additive> Polyurethane resin 1 (Superflex 460S, Dai-ichi Kogyo Seiyaku Co., Ltd.) Polyurethane resin 2 (Superflex 210, Dai-ichi Kogyo Seiyaku Co., Ltd.) Acrylic resin 1 (DXA.4081, VANORA) Acrylic resin 2 (Neocryl A-1125, Covestro) Polyvinyl alcohol resin 1 (OKS-1009, Mitsubishi Chemical Corporation) Polyvinyl alcohol resin 2 (BVE8049Q, Mitsubishi Chemical Corporation) Polyvinyl alcohol resin 3 (OKS-8118, Mitsubishi Chemical Corporation) Styrene-butadiene resin 1 (Smartex VA-1015, Nippon A&L Co., Ltd.) Styrene-butadiene resin 2 (Nipol LX407S12, manufactured by Nippon Zeon Co., Ltd.) 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 (Arrowbase SD-1010, manufactured by Unitika Ltd.)

[0139] <Method for Producing Folding-Resistant Agents> 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 solids content of 30% to obtain folding-resistant agents 1 to 3, 8, and 9. The undiluted acrylic resin 2 was used as folding-resistant agent 4. Polyvinyl alcohol resins 1 to 3 were dissolved in a solvent (ion-exchanged water) to obtain solutions with a solids content of 10%, to obtain folding-resistant agents 5 to 7. Ethylene-vinyl acetate copolymer resins 1 and 2 were diluted with a medium (ion-exchanged water) to a solids content of 30%, to obtain folding-resistant agents 10 and 11. Polyolefin resins 1 and 2 were diluted with a medium (ion-exchanged water) to a solids content of 30%, to obtain folding-resistant agents 12 and 13.

[0140]

[0141] Example 1: The folding resistance agent 1 was applied to one side of a paper substrate in an amount of 3 g / m after drying. 2 After coating with a bar coater, the layer was dried with a dryer at 60°C to form a folding-resistant layer. An oil-resistant agent was then applied thereon in an amount of 6 g / m after drying. 2 After applying the coating with a bar coater so that the coating was as shown in the figure, the coating was dried with air from a dryer at 60°C to form an oil-resistant layer, thereby producing a laminate for evaluating oil resistance of Example 1.

[0142] Examples 2 to 14 Laminates for evaluating oil resistance or laminates for evaluating moisture proofness were prepared in the same manner as in Example 1, except that folding resistance agents 1, 3, 5, 6, 8, 10, and 12 were used for the oil-resistant layer and the moisture-proof layer in the combinations shown in Table 2 below.

[0143] <Comparative Examples 1 and 2> Each functional layer was coated on one side of a paper substrate in an amount of 6 g / m after drying. 2 After applying the coating with a bar coater so that the coating was as shown in the figure, the coating was dried with air from a dryer at 60°C to form an oil-resistant layer, thereby producing laminates for evaluating oil resistance or laminates for evaluating moisture proofness of Comparative Examples 1 and 2.

[0144] Comparative Examples 3 to 12 Laminates for evaluating oil resistance and laminates for evaluating moisture proofness were prepared in the same manner as in Example 1, except that folding resistance agents 2, 4, 7, 9, 11, and 13 were used for the oil-resistant layer and the moisture-proof layer in the combinations shown in Table 2 below.

[0145] The degree of elongation and the degree of shape restoration of the fold-resistant layer were evaluated by the following evaluation methods. The results are shown in Table 2.

[0146] The resulting laminates were also evaluated for moisture resistance and oil resistance depending on the type of functional layer. These evaluations were performed before and after bending as described below. The results are shown in Table 2.

[0147] (Method for measuring elongation of fold-resistant layer) A fold-resistant agent was applied to a glass substrate, dried, and peeled off to prepare a JIS K 6251 tensile No. 3 dumbbell-shaped test piece (film thickness 300 μm). Next, the elongation of each test piece was measured when pulled to break using the following tester under the following conditions: Tensile tester: AGS-X, manufactured by Shimadzu Corporation, Extension speed: 300 mm / min, Temperature: 23°C, Humidity: 50%. The elongation was calculated using the following formula: Elongation (%) = 100 × (Lb - L0) / L0, where Lb is the gauge length at break, and L0 is the gauge length before the tensile test. The tensile test was performed in accordance with JIS K 6251.

[0148] (Method for Evaluating the Degree of Shape Recovery of Folding Resistant Agent) The degree of shape recovery was evaluated by conducting a tensile test in accordance with JIS K 6251. The tensile test to evaluate the degree of shape recovery was conducted using the following tester under the following conditions. The folding 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 tester under the following conditions and held in that state for 5 minutes. Thereafter, the test piece was removed from the tester, and the length of the test piece after 3 hours was measured. Tensile tester: AGS-X, manufactured by Shimadzu Corporation, Elongation speed: 50 mm / min, Temperature: 23°C, Humidity: 50%. The degree of shape recovery was calculated using the following formula. Shape recovery rate (%) = 100 x (L1 - L2) / (L1 - L0) where 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 at which the specimen will not break. L2 is the gauge length when the external force is removed after the tensile test.

[0149] (Folding method) A 4000 g roller was rolled over the laminate 10 times at a speed of 30 cm / sec to make the first crease in the laminate. The laminate with the crease was opened, and a second crease was made in the same manner as the first crease, perpendicular to the first crease. The laminate was folded so that the side coated with the coating agent was on the inside.

[0150] (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 sample). After 90 minutes, the area of ​​the salad oil seeping out 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 2 In addition, in all the examples and comparative examples, when no creases were made in the laminate, there was absolutely no bleeding to the back surface.

[0151] (Moisture Proofing Property) The laminate obtained above was measured for water vapor transmission rate (WVTR value, g / m) in accordance with JIS Z 0208-1976. 2The temperature and humidity conditions were a temperature of 40±0.5°C and a relative humidity of 90±2%. The degradation values ​​of the water vapor transmission rate were calculated before and after folding, and the extent to which the degradation value had decreased was evaluated compared to when no folding-resistant layer was provided. In the case where no folding-resistant layer was provided (Comparative Example 2), the water vapor transmission rate before folding was 25.6 g / m 2 / day, water vapor permeability after folding was 56.6 g / m 2 / day, and the degradation value was 31.0 g / m 2 / day.

[0152]

[0153] As shown in Table 2, it was found that the laminates obtained using the folding resistance additives of Examples 1 to 14 of the present invention were less likely to have their functional layer performance deteriorated before and after folding.

Claims

1. A laminate in which a paper base layer, a folding-resistant layer, and a functional layer are laminated in this order, the following conditions 1 to 3 are satisfied, and a folding-resistant agent for forming the folding-resistant layer is used (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 folding-resistant agent includes a resin and a medium, and the content of the resin (converted into solid content) in the folding-resistant agent is 70 to 100 mass %. (Condition 2) The degree of elongation of the folding-resistant layer in a tensile test calculated by the following formula is 200% or more. Elongation (%) = 100 x (Lb - L0) / L0, where Lb refers to the length between the gauge marks at break, 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 of the fold-resistant layer calculated by the following formula is 80% or more. Shape recovery (%) = 100 x (L1 - L2) / (L1 - L0), where 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 those that cannot be elongated to 100%, it is the limit gauge length at which the layer does not break. L2 refers to the gauge length of the fold-resistant layer when the external force is removed after the tensile test, and the tensile test is a tensile test performed in accordance with JIS K 6251.

2. The bending-resistant agent according to claim 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.

3. The folding-resistant agent according to claim 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.

4. A laminate comprising a paper base layer, a folding-resistant layer, and a functional layer laminated in this order, the folding-resistant layer being a layer formed by applying the folding-resistant agent according to claim 1 or 2.

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