Coating material for imparting mineral oil resistance and multilayer body

Abstract

To provide a mineral-oil-resistance-imparting coating material capable of imparting an excellent mineral oil resistance, and a laminate including a coating layer composed of the mineral-oil-resistance-imparting coating material.SOLUTION: A mineral-oil-resistance-imparting coating material includes a copolymer of a monomer composition and an aqueous solvent in which the copolymer is dissolved and / or dispersed. The monomer composition contains a nitrile-group-containing unsaturated ethylenic monomer and a carboxy-group-containing unsaturated ethylenic monomer. Relative to the total amount of the monomer composition, the content ratio of the nitrile-group-containing unsaturated ethylenic monomer is 21 mass% or more and 70 mass% or less. Relative to the total amount of the monomer composition, the content ratio of the carboxy-group-containing unsaturated ethylenic monomer is 3 mass% or more and 10 mass% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a mineral oil-resistant coating material and a laminate.

Background Art

[0002] Mineral oil is contained in various materials. For example, recycled paper contains mineral oil derived from printing ink. Therefore, when recycled paper is used as a packaging material, the packaged product may be adhered to and impregnated with mineral oil. Therefore, it has been considered to laminate a mineral oil-resistant coating layer on a material containing mineral oil.

[0003] For example, a cardboard package including paper contaminated with mineral oil and a barrier layer has been proposed. In this cardboard package, the barrier layer is obtained by an aqueous polymer dispersion. The aqueous polymer dispersion contains a copolymer. The copolymer is obtained by emulsion polymerization of an alkyl (meth) acrylate, 0.1 to 5% by mass of an acid monomer, 0 to 20% by mass of acrylonitrile, and 0 to 10% by mass of other monomers (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In various industrial fields, further improvement in mineral oil resistance is required.

[0006] The present invention is a mineral oil-resistant coating material capable of imparting excellent mineral oil resistance, and a laminate including a coating layer of the mineral oil-resistant coating material.

Means for Solving the Problems

[0007] The present invention [1] includes a copolymer of a monomer composition containing a nitrile group-containing unsaturated ethylenic monomer and a carboxyl group-containing unsaturated ethylenic monomer, and an aqueous solvent for dissolving and / or dispersing the copolymer. The content ratio of the nitrile group-containing unsaturated ethylenic monomer is 21% by mass or more and 70% by mass or less, and the content ratio of the carboxyl group-containing unsaturated ethylenic monomer is 3% by mass or more and 10% by mass or less, based on the total amount of the monomer composition, and includes an oil-resistant mineral oil-imparting coating material.

[0008] The present invention [2] includes the oil-resistant mineral oil-imparting coating material according to [1] above, wherein the glass transition temperature of the copolymer is -30°C or more and 100°C or less.

[0009] The present invention [3] includes a laminate including recycled paper and a coating layer of the oil-resistant mineral oil-imparting coating material according to [1] or [2] above formed on at least one side of the recycled paper.

Effects of the Invention

[0010] The oil-resistant mineral oil-imparting coating material of the present invention contains a copolymer of a monomer composition containing a nitrile group-containing unsaturated ethylenic monomer and a carboxyl group-containing unsaturated ethylenic monomer in a predetermined ratio. Therefore, the oil-resistant mineral oil-imparting coating material of the present invention can form a coating layer excellent in oil resistance to mineral oil.

[0011] The laminate of the present invention includes the coating layer of the above oil-resistant mineral oil-imparting coating material. Therefore, the laminate of the present invention is excellent in oil resistance to mineral oil.

Modes for Carrying Out the Invention

[0012] The oil-resistant mineral oil-imparting coating material of the present invention contains a copolymer of a monomer composition and an aqueous solvent for dissolving and / or dispersing the copolymer.

[0013] The copolymer of the monomer composition is, for example, a (meth)acrylic polymer. Note that (meth)acrylic means acrylic and / or methacrylic (the same applies hereinafter).

[0014] The monomer composition contains a hard monomer as an essential component. The hard monomer is a monomer having a relatively high glass transition temperature of the homopolymer (calculated by the FOX equation (the same applies hereinafter)), for example, 20°C or higher, preferably 200°C or lower.

[0015] The hard monomer contains a nitrile group-containing unsaturated ethylenic monomer as an essential component. In other words, the monomer composition contains a nitrile group-containing unsaturated ethylenic monomer as an essential component.

[0016] Examples of the nitrile group-containing unsaturated ethylenic monomer include nitrile group-containing vinyl monomers. Examples of the nitrile group-containing vinyl monomer include (meth)acrylonitrile. Note that (meth)acrylonitrile is acrylonitrile and / or methacrylonitrile. These can be used alone or in combination of two or more. From the viewpoint of mineral oil resistance, the nitrile group-containing unsaturated ethylenic monomer is preferably a nitrile group-containing vinyl monomer, more preferably (meth)acrylonitrile, and even more preferably acrylonitrile.

[0017] The content ratio of the nitrile group-containing unsaturated ethylenic monomer is 21% by mass or more, preferably 24% by mass or more, based on the total amount of the monomer composition. If the content ratio of the nitrile group-containing unsaturated ethylenic monomer exceeds the above lower limit, more excellent mineral oil resistance can be obtained.

[0018] Also, the content ratio of the nitrile group-containing unsaturated ethylenic monomer is 70% by mass or less, preferably 65% by mass or less, more preferably 60% by mass or less, based on the total amount of the monomer composition. If the content ratio of the nitrile group-containing unsaturated ethylenic monomer is below the above upper limit, better mineral oil resistance can be obtained.

[0019] In particular, from the viewpoint of the mineral oil resistance of the coated surface in the unbending state, the content ratio of the nitrile group-containing unsaturated ethylenic monomer is more preferably 35% by mass or more, particularly preferably 40% by mass or more. Also, the content ratio of the nitrile group-containing unsaturated ethylenic monomer is preferably 60% by mass or less.

[0020] On the other hand, from the viewpoints of the blocking resistance of the coated surface and the flex resistance (crack resistance during bending and mineral oil resistance after bending) of the coated surface, the content ratio of the nitrile group-containing unsaturated ethylenic monomer is more preferably 34% by mass or less, still more preferably 30% by mass or less, particularly preferably 28% by mass or less. Also, the content ratio of the nitrile group-containing unsaturated ethylenic monomer is preferably 24% by mass or more.

[0021] Also, the content ratio of the nitrile group-containing unsaturated ethylenic monomer is, for example, 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, based on the total amount of the hard monomer.

[0022] Also, the content ratio of the nitrile group-containing unsaturated ethylenic monomer is, for example, 100% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less, based on the total amount of the hard monomer.

[0023] The hard monomer can contain a benzene ring-containing unsaturated ethylenic monomer as an optional component. In other words, the monomer composition can contain a benzene ring-containing unsaturated ethylenic monomer as an optional component.

[0024] Examples of the benzene ring-containing unsaturated ethylenic monomer include styrenic vinyl monomers. Examples of the styrenic vinyl monomers include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and chlorostyrene. These can be used alone or in combination of two or more. As the benzene ring-containing unsaturated ethylenic monomer, preferably, styrenic vinyl monomers are mentioned, and more preferably, styrene is mentioned.

[0025] When the monomer composition contains a benzene ring-containing unsaturated ethylenic monomer, the content ratio of the benzene ring-containing unsaturated ethylenic monomer is, from the viewpoint of the polymerizability of the nitrile group-containing unsaturated ethylenic monomer, for example, 1% by mass or more, preferably 2% by mass or more, more preferably 5% by mass or more, based on the total amount of the monomer composition.

[0026] Also, when the monomer composition contains a benzene ring-containing unsaturated ethylenic monomer, the content ratio of the benzene ring-containing unsaturated ethylenic monomer is, from the viewpoint of mineral oil resistance, for example, 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, based on the total amount of the monomer composition.

[0027] The hard monomer can contain methyl methacrylate as an optional component. In other words, the monomer composition can contain methyl methacrylate as an optional component.

[0028] When the monomer composition contains methyl methacrylate, the content ratio of methyl methacrylate is, from the viewpoint of mineral oil resistance, for example, 1% by mass or more, preferably 2% by mass or more, more preferably 5% by mass or more, based on the total amount of the monomer composition.

[0029] Also, when the monomer composition contains methyl methacrylate, the content ratio of methyl methacrylate is, from the viewpoint of mineral oil resistance, for example, 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, based on the total amount of the monomer composition.

[0030] The hard monomer preferably includes an unsaturated ethylenic monomer containing a nitrile group and methyl methacrylate. More preferably, the hard monomer consists of an unsaturated ethylenic monomer containing a nitrile group and methyl methacrylate, or preferably, the hard monomer consists of an unsaturated ethylenic monomer containing a nitrile group, an unsaturated ethylenic monomer containing a benzene ring, and methyl methacrylate.

[0031] From the viewpoint of mineral oil resistance, the content ratio of the hard monomer is, for example, 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, and still more preferably 55% by mass or more, based on the total amount of the monomer composition.

[0032] From the viewpoint of film-forming property, the content ratio of the hard monomer is, for example, 90% by mass or less, preferably 80% by mass or less, and more preferably 70% by mass or less, based on the total amount of the monomer composition.

[0033] In addition, the monomer composition can contain a soft monomer as an optional component. The soft monomer is a monomer having a relatively low glass transition temperature of the homopolymer (for example, less than 20°C, preferably 0°C or less).

[0034] Examples of the soft monomer include alkyl (meth)acrylates other than methyl methacrylate. Note that (meth)acrylate means acrylate and / or methacrylate (the same applies hereinafter).

[0035] Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having an alkyl moiety with 1 to 30 carbon atoms (excluding methyl methacrylate). More specifically, examples of the alkyl (meth)acrylate include methyl acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, neopentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, 1-methyltridecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, eicosyl (meth)acrylate, docosyl (meth)acrylate, tetracosyl (meth)acrylate, triacontyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. These can be used alone or in combination of two or more.

[0036] Preferred examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having an alkyl moiety with 2 to 10 carbon atoms, more preferably butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate, and even more preferably butyl acrylate and 2-ethylhexyl acrylate.

[0037] When the monomer composition contains a soft monomer, the content ratio of the soft monomer is, from the viewpoint of film-forming property, for example, 1% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more, based on the total amount of the monomer composition. That is, the monomer composition preferably contains a soft monomer from the viewpoint of mineral oil resistance.

[0038] Also, when the monomer composition contains a soft monomer, the content ratio of the soft monomer is, from the viewpoint of mineral oil resistance, for example, 60% by mass or less, preferably 55% by mass or less, more preferably 50% by mass or less, based on the total amount of the monomer composition.

[0039] The monomer composition also contains a copolymerizable monomer. The copolymerizable monomer is a monomer copolymerizable with a hard monomer and / or a soft monomer. Examples of the copolymerizable monomer include a copolymerizable essential monomer and a copolymerizable optional monomer.

[0040] The copolymerizable essential monomer is contained in the monomer composition as an essential component. Examples of the copolymerizable essential monomer include carboxy group-containing unsaturated ethylenic monomers. In other words, the monomer composition contains a carboxy group-containing unsaturated ethylenic monomer as an essential component.

[0041] Examples of the carboxy group-containing unsaturated ethylenic monomer include carboxy group-containing vinyl monomers. Examples of the carboxy group-containing vinyl monomers include α,β-unsaturated carboxylic acids and their salts. Examples of the α,β-unsaturated carboxylic acids include α,β-unsaturated monocarboxylic acids and α,β-unsaturated dicarboxylic acids. Examples of the α,β-unsaturated monocarboxylic acids include (meth)acrylic acid and crotonic acid. Examples of the α,β-unsaturated dicarboxylic acids include itaconic acid, maleic acid, fumaric acid, itaconic anhydride, maleic anhydride, and fumaric anhydride. Examples of the salts include sodium salts, potassium salts, and ammonium salts. These can be used alone or in combination of two or more. From the viewpoint of mineral oil resistance, the carboxy group-containing unsaturated ethylenic monomer preferably includes carboxy group-containing vinyl monomers, more preferably α,β-unsaturated monocarboxylic acids, still more preferably (meth)acrylic acid, and particularly preferably methacrylic acid.

[0042] From the viewpoint of mineral oil resistance, the content ratio of the carboxy group-containing unsaturated ethylenic monomer is 3% by mass or more, preferably 4% by mass or more, and more preferably 5% by mass or more based on the total amount of the monomer composition. If the content ratio of the carboxy group-containing unsaturated ethylenic monomer exceeds the above lower limit, better film-forming properties and mineral oil resistance can be obtained.

[0043] From the viewpoint of mineral oil resistance, the content ratio of the carboxy group-containing unsaturated ethylenic monomer is 10% by mass or less, preferably 8% by mass or less based on the total amount of the monomer composition. If the content ratio of the carboxy group-containing unsaturated ethylenic monomer is below the above upper limit, better film-forming properties and mineral oil resistance can be obtained.

[0044] The copolymerizable optional monomer is a copolymerizable monomer contained in the monomer composition as needed. Examples of the copolymerizable optional monomer include other functional group-containing copolymerizable monomers.

[0045] Other functional group-containing copolymerizable monomers are functional group-containing copolymerizable monomers other than carboxyl group-containing unsaturated ethylenic monomers. Examples of other functional group-containing copolymerizable monomers include hydroxyl group-containing vinyl monomers, amide group-containing vinyl monomers, glycidyl group-containing vinyl monomers, amino group-containing vinyl monomers, acetoacetoxy group-containing vinyl monomers, phosphate group-containing vinyl monomers, and sulfonic acid group-containing vinyl monomers.

[0046] Examples of hydroxyl group-containing vinyl monomers include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. Examples of amide group-containing vinyl monomers include (meth)acrylamide and methylenebis(meth)acrylamide. Examples of glycidyl group-containing vinyl monomers include glycidyl (meth)acrylate. Examples of amino group-containing vinyl monomers include 2-aminoethyl (meth)acrylate, 2-(N-methylamino)ethyl (meth)acrylate, and 2-(N,N-dimethylamino)ethyl (meth)acrylate. Examples of acetoacetoxy group-containing vinyl monomers include acetoacetoxyethyl (meth)acrylate. Examples of phosphate group-containing vinyl monomers include 2-(meth)acryloxyethyl acid phosphate. Examples of sulfonic acid group-containing vinyl monomers include allyl sulfonic acid, methallyl sulfonic acid, acrylamide t-butyl sulfonic acid, and styrene sulfonate. Examples of salts include sodium salts, potassium salts, and ammonium salts.

[0047] Other functional group-containing copolymerizable monomers can be used alone or in combination of two or more.

[0048] As other functional group-containing copolymerizable monomers, preferably, hydroxyl group-containing vinyl monomers, amide group-containing vinyl monomers, and N-substituted unsaturated carboxylic acid amides can be mentioned.

[0049] In addition, as copolymerizable optional monomers, further, for example, vinyl esters, N-substituted unsaturated carboxylic acid amides, heterocyclic-reduced vinyl compounds, vinylidene halide compounds, α-olefins, dienes, and crosslinkable vinyl monomers can be mentioned.

[0050] Examples of vinyl esters include vinyl acetate and vinyl propionate. Examples of N-substituted unsaturated carboxylic acid amides include N-methylol(meth)acrylamide. Examples of heterocyclic-reduced vinyl compounds include vinyl pyrrolidone. Examples of vinylidene halide compounds include vinylidene chloride and vinylidene fluoride. Examples of α-olefins include ethylene and propylene. Examples of dienes include butadiene. Examples of crosslinkable vinyl monomers include methylene bis(meth)acrylamide, divinylbenzene, polyethylene glycol chain-containing di(meth)acrylate, trimethylolpropane tetraacrylate, and pentaerythritol triacrylate and pentaerythritol tetraacrylate. These can be used alone or in combination of two or more.

[0051] The content ratio of the copolymerizable optional monomers is appropriately set according to the purpose and application.

[0052] For example, when the monomer composition contains a hydroxyl group-containing vinyl monomer, the content ratio of the hydroxyl group-containing vinyl monomer is, from the viewpoint of mineral oil resistance, for example, 0.5% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, based on the total amount of the monomer composition.

[0053] Further, for example, when the monomer composition contains a hydroxyl group-containing vinyl monomer, the content ratio of the hydroxyl group-containing vinyl monomer is, from the viewpoint of mineral oil resistance, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less.

[0054] Further, for example, when the monomer composition contains an amide group-containing vinyl monomer, the content ratio of the amide group-containing vinyl monomer is, based on the total amount of the monomer composition, from the viewpoint of mineral oil resistance, for example, 0.5% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more.

[0055] Further, for example, when the monomer composition contains an amide group-containing vinyl monomer, the content ratio of the amide group-containing vinyl monomer is, from the viewpoint of mineral oil resistance, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less.

[0056] Further, for example, when the monomer composition contains N-substituted unsaturated carboxylic acid amides, the content ratio of the N-substituted unsaturated carboxylic acid amides is, based on the total amount of the monomer composition, from the viewpoint of mineral oil resistance, for example, 0% by mass or more, preferably 0.5% by mass or more, more preferably 1.0% by mass or more.

[0057] Further, for example, when the monomer composition contains N-substituted unsaturated carboxylic acid amides, the content ratio of the N-substituted unsaturated carboxylic acid amides is, from the viewpoint of mineral oil resistance, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less.

[0058] The copolymerizable monomer preferably contains the essential copolymerizable monomer and does not contain the optional copolymerizable monomer. That is, the monomer composition preferably contains a hard monomer, a soft monomer, and an essential copolymerizable monomer. More preferably, the monomer composition consists of a hard monomer, a soft monomer, and an essential copolymerizable monomer.

[0059] The copolymer of the monomer composition is obtained by polymerizing the above monomer composition by a known method. More specifically, for example, the monomer composition and a polymerization initiator are blended in an aqueous solvent to polymerize the monomer composition.

[0060] The polymerization initiator is not particularly limited, and examples thereof include water-soluble initiators and oil-soluble initiators. Examples of the water-soluble initiator include potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, and organic hydroperoxides. Examples of the oil-soluble initiator include benzoyl peroxide and azobisisobutyronitrile. Further, known redox initiators are also included as the polymerization initiator. These can be used alone or in combination of two or more. As the polymerization initiator, a water-soluble initiator is preferable, and ammonium persulfate is more preferable.

[0061] The blending ratio of the polymerization initiator is, for example, 0.01 part by mass or more, preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, and still more preferably 0.25 part by mass or more with respect to 100 parts by mass of the monomer composition. Also, the blending ratio of the polymerization initiator is, for example, 3 parts by mass or less, preferably 2 parts by mass or less with respect to 100 parts by mass of the monomer composition.

[0062] Examples of the aqueous solvent include water and hydrophilic solvents. Examples of the hydrophilic solvents include alcohols, ketones, esters, ethers, ether alcohols, ether alcohol acetates, and nitriles. Examples of the alcohols include methanol and ethanol. Examples of the ketones include acetone. Examples of the esters include ethyl acetate and butyl acetate. Examples of the ethers include dioxane and tetrahydrofuran. Examples of the ether alcohols include cellosolve and carbitol. Examples of the ether alcohol acetates include cellosolve acetate and carbitol acetate. Examples of the nitriles include acetonitrile. These can be used alone or in combination of two or more. Preferred as the aqueous solvent is water.

[0063] When water is used as the aqueous solvent, preferably, an emulsifier is blended with the monomer composition, and the monomer composition undergoes emulsion polymerization in water.

[0064] Examples of the emulsifier include anionic surfactants and nonionic surfactants. Examples of the anionic surfactants include alkyl sulfate esters, aliphatic sulfonates, alkylbenzene sulfonates, and alkyl diphenyl ether sulfonates. Examples of the nonionic surfactants include alkyl esters of polyethylene glycol, alkyl phenyl ethers of polyethylene glycol, and alkyl ethers of polyethylene glycol. These can be used alone or in combination of two or more.

[0065] The blending ratio of the emulsifier is appropriately set according to the purpose and application. More specifically, the blending ratio of the emulsifier is, for example, 0.1 part by mass or more, preferably 0.3 part by mass or more, based on 100 parts by mass of the monomer composition. Also, the blending ratio of the emulsifier is, for example, 2.0 parts by mass or less, preferably 1.8 parts by mass or less, based on 100 parts by mass of the monomer composition.

[0066] Incidentally, the polymerization conditions are appropriately set according to the purpose and application. For example, the pressure condition is under normal pressure. Also, the polymerization temperature is, for example, 30°C or higher, preferably 50°C or higher. Further, the polymerization temperature is, for example, 95°C or lower, preferably 85°C or lower. Also, the polymerization time is, for example, 0.5 hours or longer, preferably 1.5 hours or longer. Further, the polymerization time is, for example, 20 hours or shorter, preferably 10 hours or shorter.

[0067] Also, in the polymerization, known additives can be blended in an appropriate ratio from the viewpoint of improving production stability. Examples of the additives include a pH adjuster, a sequestering agent, a molecular weight regulator, and a chain transfer agent. Incidentally, the additives may be added to the monomer composition before polymerization, may be added to the reaction solution during polymerization, or may be added to the reaction completion solution after polymerization.

[0068] Thereby, the monomer composition copolymerizes in the aqueous solvent, and a copolymer of the monomer composition is formed. As a result, an oil-resistant mineral oil-imparting coating material containing the aqueous solvent and the copolymer dissolved and / or dispersed in the aqueous solvent is obtained. More specifically, when water is used as the aqueous solvent, an oil-resistant mineral oil-imparting coating material is obtained as a resin emulsion in which the copolymer is dispersed in water.

[0069] Also, in the above polymerization, preferably, a neutralizing agent is blended in the reaction completion solution to adjust the pH. Examples of the neutralizing agent include ammonia. The neutralizing agent is preferably added to the reaction completion solution after polymerization. Also, if necessary, the reaction completion solution is held for a predetermined time. The pH of the reaction completion solution after blending the neutralizing agent is, for example, 5 or higher, preferably 7 or higher, more preferably 8 or higher. Also, the pH of the reaction solution is, for example, 11 or lower, more preferably 10 or lower. By the neutralizing agent, in the reaction completion solution, the copolymer is hydrated, swollen, and softened.

[0070] In the above polymerization, the monomer composition may be polymerized in one batch or may be polymerized in multiple stages. For example, by polymerizing the monomer composition in multiple stages, core-shell particles can be formed.

[0071] More specifically, first, a part of the monomer composition (primary composition) is polymerized to synthesize a primary polymer, and then, in the presence of the primary polymer, the remainder (secondary composition) with respect to a part of the monomer composition is polymerized to synthesize a secondary polymer (multi-stage polymerization). Thereby, core-shell particles of a copolymer containing a core composed of the primary polymer and a shell composed of the secondary polymer covering the primary polymer are obtained. Note that the reaction order of a part and the remainder of the monomer composition may be reversed from the above.

[0072] Preferably, the part of the monomer composition (primary composition) contains a nitrile group-containing unsaturated ethylenic monomer, a carboxy group-containing unsaturated ethylenic monomer, and a soft monomer. Further, the remainder (secondary composition) with respect to a part of the monomer composition preferably contains a functional group-containing copolymerizable monomer.

[0073] The above copolymer contains a repeating unit derived from a nitrile group-containing unsaturated ethylenic monomer and a repeating unit derived from a carboxy group-containing unsaturated ethylenic monomer.

[0074] In the above copolymer, the content ratio of the repeating unit derived from the nitrile group-containing unsaturated ethylenic monomer is the same as the content ratio of the nitrile group-containing unsaturated ethylenic monomer in the monomer composition.

[0075] That is, the content ratio of the repeating unit derived from the nitrile group-containing unsaturated ethylenic monomer is 21% by mass or more, preferably 24% by mass or more, based on the total amount of the copolymer. Also, the content ratio of the repeating unit derived from the nitrile group-containing unsaturated ethylenic monomer is 70% by mass or less, preferably 65% by mass or less, more preferably 60% by mass or less, based on the total amount of the copolymer. When the content ratio of the repeating unit derived from the nitrile group-containing unsaturated ethylenic monomer is within the above range, better mineral oil resistance can be obtained.

[0076] In particular, from the perspective of the mineral oil resistance of the coated surface in the unbent state, the content ratio of the repeating unit derived from the nitrile group-containing unsaturated ethylenic monomer is more preferably 35% by mass or more, particularly preferably 40% by mass or more, based on the total amount of the copolymer. Also, the content ratio of the repeating unit derived from the nitrile group-containing unsaturated ethylenic monomer is preferably 60% by mass or less, based on the total amount of the copolymer.

[0077] On the other hand, from the perspectives of the blocking resistance of the coated surface and the bending resistance (crack resistance during bending and mineral oil resistance after bending) of the coated surface, the content ratio of the repeating unit derived from the nitrile group-containing unsaturated ethylenic monomer is more preferably 34% by mass or less, more preferably 30% by mass or less, particularly preferably 28% by mass or less, based on the total amount of the copolymer. Also, the content ratio of the repeating unit derived from the nitrile group-containing unsaturated ethylenic monomer is preferably 24% by mass or more, based on the total amount of the copolymer.

[0078] Also, in the copolymer, the content ratio of the repeating unit derived from the carboxy group-containing unsaturated ethylenic monomer is the same as the content ratio of the carboxy group-containing unsaturated ethylenic monomer in the monomer composition.

[0079] That is, the content ratio of the repeating unit derived from the carboxy group-containing unsaturated ethylenic monomer is 3% by mass or more, preferably 4% by mass or more, more preferably 5% by mass or more, based on the total amount of the copolymer. Also, the content ratio of the repeating unit derived from the carboxy group-containing unsaturated ethylenic monomer is 10% by mass or less, preferably 8% by mass or less, based on the total amount of the copolymer. When the content ratio of the repeating unit derived from the carboxy group-containing unsaturated ethylenic monomer is within the above range, more excellent mineral oil resistance can be obtained.

[0080] In addition, the weight average molecular weight of the copolymer is, for example, 5,000 or more, preferably 10,000 or more, more preferably 30,000 or more. Also, the weight average molecular weight of the copolymer is, for example, 1,000,000 or less, preferably 800,000 or less, more preferably 500,000 or less. The weight average molecular weight is the polystyrene equivalent molecular weight determined by gel permeation chromatography.

[0081] In addition, from the viewpoints of mineral oil resistance and blocking resistance of the coated surface, the glass transition temperature of the copolymer is, for example, -50°C or higher, preferably -30°C or higher. Also, from the viewpoints of mineral oil resistance and film-forming property, the glass transition temperature of the copolymer is, for example, 200°C or lower, preferably 100°C or lower, more preferably 80°C or lower. The glass transition temperature is calculated by the FOX equation (the same applies hereinafter).

[0082] In particular, from the viewpoint of the mineral oil resistance of the coated surface in the unbent state, the glass transition temperature of the copolymer is more preferably -10°C or higher, even more preferably 0°C or higher, even more preferably 10°C or higher, and particularly preferably 20°C or higher. Also, the glass transition temperature of the copolymer is preferably 80°C or lower.

[0083] On the other hand, from the viewpoints of the blocking resistance of the coated surface and the flex resistance (crack resistance during bending and mineral oil resistance after bending), the glass transition temperature of the copolymer is more preferably 20°C or lower, still more preferably 10°C or lower, still more preferably 0°C or lower, and particularly preferably -10°C or lower. Also, the glass transition temperature of the copolymer is preferably -30°C or higher.

[0084] In the mineral oil resistance-imparting coating material, the solid content concentration of the copolymer is, for example, 3% by mass or more, preferably 5% by mass or more, and more preferably 10% by mass or more. Also, in the mineral oil resistance-imparting coating material, the solid content concentration of the copolymer is, for example, 50% by mass or less, preferably 30% by mass or less.

[0085] Note that in the mineral oil resistance-imparting coating material, the solid content concentration of the copolymer is appropriately adjusted as needed by adding or removing an aqueous solvent.

[0086] Also, the mineral oil resistance-imparting coating material can contain additives in an appropriate ratio as needed. Examples of the additives include crosslinking agents, inorganic pigments, organic pigments, fillers, antioxidants, ultraviolet absorbers, thermoplastic resins, thermosetting resins, lubricants, thickeners, wetting agents, defoaming agents, and pH adjusters. These can be used alone or in combination. Preferred examples of the additives include crosslinking agents and inorganic pigments.

[0087] Examples of the crosslinking agents include isocyanate-based crosslinking agents, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, and oxazoline-based crosslinking agents. These can be used alone or in combination of two or more. Preferred examples of the crosslinking agents include isocyanate-based crosslinking agents and carbodiimide-based crosslinking agents.

[0088] The blending ratio of the crosslinking agent is not particularly limited and is appropriately set according to the purpose and application. More specifically, the blending ratio of the crosslinking agent is, for example, 1 part by mass or more, preferably 3 parts by mass or more, based on 100 parts by mass of the total amount of the copolymer. Also, the blending ratio of the crosslinking agent is, for example, 30 parts by mass or less, preferably 20 parts by mass or less, based on 100 parts by mass of the total amount of the copolymer.

[0089] If the mineral oil resistance-imparting coating material contains a crosslinking agent, more excellent mineral oil resistance and film-forming properties can be obtained.

[0090] Examples of the inorganic pigment include calcium carbonate, talc, colloidal silica, clay, calcined kaolin, titanium oxide, zinc oxide, aluminum hydroxide, and clay minerals. Examples of the clay minerals include montmorillonite, saponite, hectorite, vermiculite, kaolinite, natural mica, and synthetic mica. These can be used alone or in combination of two or more. The blending ratio of the inorganic pigment is not particularly limited and is appropriately set according to the purpose and application.

[0091] If the mineral oil resistance-imparting coating material contains an inorganic pigment, more excellent mineral oil resistance can be obtained. Furthermore, if the mineral oil resistance-imparting coating material contains an inorganic pigment, the gloss of the coated surface can be controlled, and the heat resistance, water resistance, and gas barrier properties of the coated surface can be improved.

[0092] And the above-mentioned mineral oil resistance-imparting coating material contains a copolymer of a monomer composition containing a nitrile group-containing unsaturated ethylenic monomer and a carboxy group-containing unsaturated ethylenic monomer in a predetermined ratio. Therefore, the above-mentioned mineral oil resistance-imparting coating material can form a coating layer excellent in mineral oil resistance. Furthermore, in the above-mentioned mineral oil resistance-imparting coating material, since an aqueous solvent is used, the environmental load can be reduced compared with the case where an organic solvent is used. In addition, the coating layer formed from the above-mentioned mineral oil resistance-imparting coating material has excellent adhesion to a substrate containing mineral oil.

[0093] That is, the above-mentioned coating material for imparting mineral oil resistance can form a mineral oil-resistant layer with excellent adhesion as a coating layer while reducing the environmental load. Therefore, the above-mentioned coating material for imparting mineral oil resistance is preferably applied to a substrate containing mineral oil.

[0094] Examples of the mineral oil include saturated hydrocarbons derived from petroleum and aromatic hydrocarbons derived from petroleum. More specifically, examples of the mineral oil include hydrocarbon compounds having 6 to 30 carbon atoms, liquid paraffin, solid paraffin, wax, and petrolatum.

[0095] Examples of the substrate containing mineral oil include substrates containing printing ink, and more specifically, recycled paper.

[0096] The thickness of the substrate containing mineral oil is not particularly limited and is appropriately set according to the purpose and application. For example, the thickness of the substrate containing mineral oil is, for example, 1 μm or more, preferably 3 μm or more. Also, the thickness of the substrate containing mineral oil is, for example, 1000 μm or less, preferably 800 μm or less.

[0097] Then, the above-mentioned coating material for imparting mineral oil resistance is applied, for example, to one surface of a substrate containing mineral oil and dried by heating as necessary.

[0098] The method for applying the coating material for imparting mineral oil resistance is not particularly limited, and a known coating method is adopted. Examples of the coating method include the gravure coater method, the small-diameter gravure coater method, the reverse roll coater method, the transfer roll coater method, the kiss coater method, the dip coater method, the microgravure coating method, the knife coater method, the air doctor coater method, the blade coater method, the rod coater method, the squeeze coater method, the cast coater method, the die coater method, the screen printing method, and the spray coating method.

[0099] Also, the drying conditions are not particularly limited and are appropriately set according to the purpose and application. For example, the drying temperature is, for example, 40°C or higher. Also, the drying temperature is, for example, 200°C or lower. Also, the drying time is appropriately set according to the purpose and application.

[0100] Thereby, a coating layer of the mineral oil-resistant imparting coating material is formed on one surface of the base material containing mineral oil.

[0101] The thickness of the coating layer (after drying) is not particularly limited and is appropriately set according to the purpose and application. For example, the thickness of the coating layer (after drying) is, for example, 1 μm or more, preferably 3 μm or more. Also, the thickness of the coating layer (after drying) is, for example, 10 μm or less, preferably 8 μm or less.

[0102] As described above, a laminate including a base material containing mineral oil and the coating layer of the above-described mineral oil-resistant imparting coating material disposed on the surface thereof is obtained.

[0103] In particular, when recycled paper is selected as the base material containing mineral oil, a laminate including the recycled paper and the coating layer of the above-described mineral oil-resistant imparting coating material disposed on one surface of the recycled paper is obtained.

[0104] The thickness of the laminate is not particularly limited and is appropriately set according to the purpose and application. For example, the thickness (total thickness) of the laminate is, for example, 1 μm or more, preferably 3 μm or more. Also, the thickness (total thickness) of the laminate is, for example, 1000 μm or less, preferably 800 μm or less.

[0105] And the above laminate includes the coating layer of the above-described mineral oil-resistant imparting coating material. Therefore, the above laminate is excellent in mineral oil resistance. As a result, the above laminate is suitably used as a packaging material.

[0106] More specifically, when a base material without the above coating layer (preferably recycled paper) is used as a packaging material, mineral oil may seep out on the surface of the packaging material, and in the contact portion between the packaging material and the object to be packaged, the mineral oil contained in the base material may adhere to and impregnate the object to be packaged.

[0107] On the other hand, in the above laminate, a coating layer of the above mineral oil-resistant property-imparting coating material is formed on at least one side of a base material (preferably recycled paper) containing mineral oil.

[0108] Therefore, even when the packaging material comes into contact with the object to be packaged, the adhesion and impregnation of mineral oil to the object to be packaged can be suppressed by the coating layer of the above mineral oil-resistant property-imparting coating material.

[0109] In the above description, the coating layer of the mineral oil-resistant property-imparting coating material is disposed on one surface of the recycled paper. However, the coating layer of the above mineral oil-resistant property-imparting coating material can also be disposed on both surfaces of the recycled paper.

[0110] Also, in the above description, the coating layer of the mineral oil-resistant property-imparting coating material is disposed on one side or both sides of the recycled paper. However, for example, an arbitrary intermediate layer (undercoat layer) may be interposed between the recycled paper and the coating layer. Further, if necessary, a known topcoat layer (overcoat layer) may be laminated on the coating layer of the above mineral oil-resistant property-imparting coating material. Even in such a case, the adhesion and impregnation of mineral oil to the object to be packaged can be suppressed by the coating layer of the above mineral oil-resistant property-imparting coating material.

[0111] As described above, the mineral oil-resistant property-imparting coating material and the laminate are suitably used, for example, in the field of packaging materials.

[0112] In addition, the above-described coating material for imparting mineral oil resistance can also be used, for example, as an alternative material to a fluorine coating material. In such a case, the coating material for imparting mineral oil resistance is suitably used in various fields where conventional fluorine coating materials are used.

Examples

[0113] The specific numerical values such as the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values (numerical values defined as "below" and "less than") or lower limit values (numerical values defined as "above" and "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the above "Mode for Carrying Out the Invention". Also, unless otherwise specified in the following description, "parts" and "%" are based on mass.

[0114] 1. Preparation of Coating Material for Imparting Mineral Oil Resistance Example 1 A separable flask equipped with a stirrer and a reflux condenser was charged with 230 g of ion-exchanged water and 1.5 g of sodium dodecyl diphenyl ether disulfonate, and the inside of the flask was replaced with nitrogen gas. Next, the temperature inside the flask was raised to 75°C. Then, 0.5 g of potassium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 5 hours. The emulsion of the monomer composition contained 56 g of acrylonitrile, 5 g of styrene, 5 g of methyl methacrylate, 26 g of n-butyl acrylate, 8 g of methacrylic acid, 0.1 g of n-dodecyl mercaptan, 0.2 g of sodium dodecyl diphenyl ether disulfonate, and 56 g of ion-exchanged water.

[0115] Subsequently, the polymerization was completed by holding at the above temperature for 4 hours. Thereafter, aqueous ammonia was added to the flask to make it alkaline, and the temperature was held at that level for 2 hours. As a result, the copolymer was hydrated, swollen, and softened. Thereafter, the flask was cooled to room temperature, and deionized water was added to the flask. As a result, an oil-resistant coating material imparting resin emulsion of the copolymer with a solid content concentration of about 20% by mass was obtained.

[0116] Also, the glass transition temperature (Tg) of the copolymer was calculated by the following FOX equation (the same shall apply hereinafter). The glass transition temperature (Tg) of the copolymer is shown in Table 1 (the same shall apply hereinafter).

[0117] 1 / Tg = W1 / Tg1 + W2 / Tg2 + ··· + W n / Tg n (1) [In the formula, Tg is the glass transition temperature of the copolymer (unit: K), Tg i (i = 1, 2, ··· n) is the glass transition temperature (unit: K) when monomer i forms a homopolymer, W i (i = 1, 2, ··· n) represents the mass fraction of monomer i in all the monomers.]

[0118] Example 2 230 g of ion-exchanged water and 1.5 g of sodium dodecyl sulfate were charged into a separable flask equipped with a stirrer and a reflux condenser, and the inside of the flask was replaced with nitrogen gas. Subsequently, the temperature inside the flask was raised to 75°C. Next, 1.0 g of potassium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 5 hours. The emulsion of the monomer composition contained 45 g of acrylonitrile, 10 g of methyl methacrylate, 40 g of n-butyl acrylate, 5 g of methacrylic acid, 0.2 g of sodium dodecyl sulfate, and 56 g of ion-exchanged water.

[0119] Next, after holding at the above temperature for 2 hours, 0.2 g of ammonium persulfate was added, and the mixture was held at the above temperature for 2 hours to complete the polymerization. Then, aqueous ammonia was added to the flask to make it alkaline, and the temperature was maintained for 3 hours. Thereby, the copolymer was hydrated, swollen, and softened. Then, the flask was cooled to room temperature, and deionized water was added to the flask. Thereby, a coating material imparting mineral oil resistance was obtained as a resin emulsion of the copolymer having a solid content concentration of about 20% by mass.

[0120] Example 3 230 g of ion-exchanged water and 1.5 g of sodium dodecyl sulfate were charged into a separable flask equipped with a stirrer and a reflux condenser, and the inside of the flask was replaced with nitrogen gas. Next, the temperature inside the flask was raised to 75°C. Next, 1.0 g of potassium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 5 hours. The emulsion of the monomer composition contained 45 g of acrylonitrile, 10 g of methyl methacrylate, 40 g of n-butyl acrylate, 5 g of acrylic acid, 0.2 g of sodium dodecyl sulfate, and 56 g of ion-exchanged water.

[0121] Next, after holding at the above temperature for 2 hours, 0.2 g of ammonium persulfate was added, and the mixture was held at the above temperature for 2 hours to complete the polymerization. Then, aqueous ammonia was added to the flask to make it alkaline, and the temperature was maintained for 3 hours. Thereby, the copolymer was hydrated, swollen, and softened. Then, the flask was cooled to room temperature, and deionized water was added to the flask. Thereby, a coating material imparting mineral oil resistance was obtained as a resin emulsion of the copolymer having a solid content concentration of about 20% by mass.

[0122] Example 4 Into a separable flask equipped with a stirrer and a reflux condenser, 230 g of ion-exchanged water and 1.5 g of sodium dodecyl sulfate were charged, and the inside of the flask was replaced with nitrogen gas. Then, the temperature inside the flask was raised to 75 °C. Next, 1.0 g of potassium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 5 hours. The emulsion of the monomer composition contained 24 g of acrylonitrile, 71 g of n-butyl acrylate, 5 g of acrylic acid, 0.2 g of sodium dodecyl sulfate, and 56 g of ion-exchanged water.

[0123] Next, after holding at the above temperature for 2 hours, 0.2 g of ammonium persulfate was added, and the mixture was held at the above temperature for 2 hours to complete the polymerization. Then, aqueous ammonia was added to the flask to make it alkaline, and the temperature was held at that level for 3 hours. Thereby, the copolymer was hydrated, swollen, and softened. Then, the flask was cooled to room temperature, and deionized water was added to the flask. Thereby, an oil-resistant imparting coating material was obtained as a resin emulsion of the copolymer having a solid content concentration of about 20% by mass.

[0124] Comparative Example 1 Into a separable flask equipped with a stirrer and a reflux condenser, 170 g of ion-exchanged water and 1.0 g of sodium dodecyl diphenyl ether disulfonate were charged, and the inside of the flask was replaced with nitrogen gas. Then, the temperature inside the flask was raised to 80 °C. Next, 0.3 g of sodium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 4 hours. The emulsion of the monomer composition contained 44 g of methyl methacrylate, 55 g of ethyl acrylate, 1 g of acrylic acid, 1.0 g of sodium dodecyl diphenyl ether disulfonate, and 40 g of ion-exchanged water.

[0125] Next, the polymerization was completed by holding at the above temperature for 4 hours. Then, ion-exchanged water and an aqueous ammonium solution were added to the flask. Thereby, a resin emulsion of the copolymer having a solid content concentration of about 30% by mass was obtained.

[0126] Comparative Example 2 Into a separable flask equipped with a stirrer and a reflux condenser, 170 g of ion-exchanged water and 1.0 g of sodium dodecyl diphenyl ether disulfonate were charged, and the inside of the flask was replaced with nitrogen gas. Next, the temperature inside the flask was raised to 80°C. Then, 0.3 g of sodium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 4 hours. The emulsion of the monomer composition contained 20 g of acrylonitrile, 24 g of methyl methacrylate, 55 g of ethyl acrylate, 1 g of acrylic acid, 1.0 g of sodium dodecyl diphenyl ether disulfonate, and 40 g of ion-exchanged water.

[0127] Next, the polymerization was completed by holding at the above temperature for 4 hours. Thereafter, ion-exchanged water and an aqueous ammonium solution were added to the flask. As a result, a resin emulsion of a copolymer having a solid content concentration of about 30% by mass was obtained.

[0128] Comparative Example 3 Into a separable flask equipped with a stirrer and a reflux condenser, 57 g of ion-exchanged water and 0.3 g of sodium dodecyl diphenyl ether disulfonate were charged, and the inside of the flask was replaced with nitrogen gas. Next, the temperature inside the flask was raised to 72°C. Then, 0.3 g of potassium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 4 hours. The emulsion of the monomer composition contained 51 g of methyl methacrylate, 44 g of 2-ethylhexyl acrylate, 2 g of methacrylic acid, 2 g of 2-hydroxyethyl methacrylate, 1 g of acrylamide, 0.1 g of t-dodecyl mercaptan, 0.3 g of sodium dodecyl diphenyl ether disulfonate, and 40 g of ion-exchanged water.

[0129] Next, the polymerization was completed by holding at the above temperature for 4 hours. Thereafter, ion-exchanged water and an aqueous ammonium solution were added to the flask. As a result, a resin emulsion of a copolymer having a solid content concentration of about 50% by mass was obtained.

[0130] Comparative Example 4 230 g of ion-exchanged water and 1.5 g of sodium dodecyl sulfate were charged into a separable flask equipped with a stirrer and a reflux condenser, and the inside of the flask was replaced with nitrogen gas. Next, the temperature inside the flask was raised to 75°C. Next, 1.0 g of potassium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 5 hours. The emulsion of the monomer composition contained 15 g of acrylonitrile, 80 g of n-butyl acrylate, 5 g of acrylic acid, 0.2 g of sodium dodecyl sulfate, and 56 g of ion-exchanged water.

[0131] Next, after holding at the above temperature for 2 hours, 0.2 g of ammonium persulfate was added, and the mixture was held at the above temperature for 2 hours to complete the polymerization. Then, aqueous ammonia was added to the flask to make it alkaline, and the temperature was held at that level for 3 hours. Thereby, the copolymer was hydrated, swollen, and softened. Then, the flask was cooled to room temperature, and deionized water was added to the flask. Thereby, a resin emulsion of the copolymer having a solid content concentration of about 20% by mass was obtained.

[0132] Comparative Example 5 230 g of ion-exchanged water and 1.5 g of sodium dodecyl sulfate were charged into a separable flask equipped with a stirrer and a reflux condenser, and the inside of the flask was replaced with nitrogen gas. Next, the temperature inside the flask was raised to 75°C. Next, 1.0 g of potassium persulfate was added to the flask and dissolved. Next, an emulsion of the monomer composition was continuously added to the flask over about 5 hours. The emulsion of the monomer composition contained 22 g of acrylonitrile, 76 g of n-butyl acrylate, 2 g of acrylic acid, 0.2 g of sodium dodecyl sulfate, and 56 g of ion-exchanged water.

[0133] Next, after holding at the above temperature for 2 hours, 0.2 g of ammonium persulfate was added, and the mixture was held at the above temperature for 2 hours to complete the polymerization. Then, aqueous ammonia was added to the flask to make it alkaline, and the temperature was maintained for 3 hours. As a result, the copolymer was hydrated, swollen, and softened. Then, the flask was cooled to room temperature, and deionized water was added to the flask. As a result, a resin emulsion of the copolymer having a solid content concentration of about 20% by mass was obtained.

[0134] Example 5 Into a separable flask equipped with a stirrer and reflux condenser, 80 g of ion-exchanged water and 0.2 g of sodium dodecyl diphenyl ether disulfonate were charged, and the inside of the flask was replaced with nitrogen gas. Next, the temperature inside the flask was raised to 75°C. Then, 0.5 g of ammonium persulfate was added to the flask and dissolved. Next, an emulsion of the primary composition in the monomer composition was continuously added to the flask over about 6 hours. The emulsion of the primary composition in the monomer composition contained 30 g of acrylonitrile, 30 g of n-butyl acrylate, 2 g of methacrylic acid, 3.3 g of 2-hydroxyethyl methacrylate, 1.3 g of N-methylolacrylamide, 0.2 g of sodium dodecyl diphenyl ether disulfonate, and 40 g of ion-exchanged water.

[0135] Next, it was held at the above temperature for 5 hours. Then, the flask was cooled to room temperature. Then, aqueous ammonia was added to the inside of the flask to adjust the pH to 8.0, and further, the non-volatile content was adjusted to about 19% with ion-exchanged water. As a result, a dispersion of the primary polymer was obtained.

[0136] Next, the dispersion of the primary polymer was heated to 75°C. Then, 0.5 part of ammonium persulfate was added to the flask. Next, an aqueous solution of the remainder of the monomer composition was continuously added to the flask over about 2 hours. The aqueous solution of the remainder of the monomer composition contained 6.7 g of methacrylic acid, 3.3 g of 2-hydroxyethyl methacrylate, 23.3 g of methacrylamide, 82 g of distilled water, and 8 g of 25% aqueous ammonia.

[0137] Next, it was held at the above temperature for 2 hours to complete the polymerization. Thereby, core-shell particles of a copolymer containing a core made of a primary polymer and a shell made of a secondary polymer coating the primary polymer were obtained. Further, an oil-resistant mineral oil-imparting coating material was obtained as a resin emulsion of a copolymer having a solid content concentration of about 20% by mass.

[0138] 2. Laminate As a base material containing mineral oil, recycled paper (trade name "OK Prince Premium Eco G100", manufactured by Oji Paper Co., Ltd.) was prepared. An oil-resistant mineral oil-imparting coating material was applied to one surface of the recycled paper so that the dry film thickness was 4 μm, and dried at 90 °C. Thereby, a coating layer (4 μm) of the oil-resistant mineral oil-imparting coating material was formed on the recycled paper. That is, a laminate including the recycled paper and the coating layer of the oil-resistant mineral oil-imparting coating material was manufactured.

[0139] 3. Evaluation <Sample> A sample for evaluating the oil-resistant mineral oil-imparting coating material was prepared. That is, uncoated paper (trade name "Shiratama", manufactured by Oji Paper Co., Ltd.) was prepared. An oil-resistant mineral oil-imparting coating material was applied to one surface of the uncoated paper so that the dry film thickness was 4 μm, and dried at 90 °C. Thereby, a laminate including the uncoated paper and the coating layer of the oil-resistant mineral oil-imparting coating material was manufactured as a sample.

[0140] <Adhesion> An adhesive tape (trade name Cellotape (registered trademark) CT405AP-24, manufactured by Nichiban Co., Ltd.) was attached to the coating layer of the oil-resistant mineral oil-imparting coating material of the above sample, and reciprocated once with a 2 kg roller. Then, the adhesive tape was peeled off and evaluated according to the following criteria.

[0141] ○: No peeling of the coating layer was observed, or material breakage of the coating layer was observed. △: A part of the coating layer peeled off from the base material. ×: The entire coating layer peeled off from the base material.

[0142] <Mineral oil resistance> One drop of mineral oil (hexane or toluene) was dropped onto the coating layer of the mineral oil resistance-imparting coating material for the above sample, and a rubbing test (1 kg load, 50 reciprocations) was performed with a swab. The results were evaluated according to the following criteria.

[0143] ○: No change in the coating layer was confirmed. △: Roughness was confirmed in the coating layer. ×: The coating layer dissolved.

[0144] Note that the higher the evaluation of the rubbing test for the coating layer, the more effectively the exudation of mineral oil onto the surface of the laminate can be suppressed.

[0145] <Flexural resistance, mineral oil resistance of the coating surface after bending> The above sample was bent once in the valley fold direction. Then, the mineral oil resistance of the sample was evaluated by the same method and criteria as above. The results were used as the evaluation of the flexural resistance.

[0146] <Blocking resistance> The blocking resistance of the above sample was evaluated by the following method. That is, two samples (a laminate comprising uncoated paper and a coating layer of a mineral oil resistance-imparting coating material) were laminated, and the surface of the coating layer was brought into contact with the surface of the uncoated paper. Thereby, a sample laminate was obtained. The sample laminate was pressed with a weight of 100 g / cm 2 Then, the sample laminate was allowed to stand for 24 hours in an environment of 40 °C and 75% RH humidity. Thereafter, the sample laminate was peeled off. The blocking resistance was evaluated according to the following criteria.

[0147] ○: The samples were peeled off without resistance. ×: The samples adhered to each other and the uncoated paper (substrate) was damaged.

[0148]

Table 1

[0149] The above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be construed in a limiting manner. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the following claims.

Industrial Applicability

[0150] The mineral oil-resistant coating material and laminate of the present invention are suitably used in packaging materials.

Claims

Claim 1 A copolymer of a monomer composition containing a nitrile group-containing unsaturated ethylenic monomer and a carboxy group-containing unsaturated ethylenic monomer, and an aqueous solvent for dissolving and / or dispersing the copolymer are included, with respect to the total amount of the monomer composition, the content ratio of the nitrile group-containing unsaturated ethylenic monomer is 21% by mass or more and 70% by mass or less, the content ratio of the carboxy group-containing unsaturated ethylenic monomer is 3% by mass or more and 10% by mass or less, a coating material for imparting mineral oil resistance. Claim 2 The glass transition temperature of the copolymer is -30°C or higher and 100°C or lower, The coating material for imparting mineral oil resistance according to Claim 1. Claim 3 Recycled paper, and a coating layer of the coating material for imparting mineral oil resistance according to Claim 1 formed on at least one side of the recycled paper are provided, a laminate.

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