Composition of light-curing coatings for building materials, curing film, substrate for curing films

Abstract

To provide a photocurable coating composition for building materials that has impact resistance, abrasion resistance, acid resistance, alkali resistance and thinner resistance but can form a high-hardness cured coat.SOLUTION: A photocurable coating composition for building materials contains an active energy ray-curable compound (A), a photopolymerization initiator (B), and cellulose nanofibers (C).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable coating composition for building materials, a cured coating, and a substrate with a cured coating. [Background technology]

[0002] BACKGROUND ART Generally, various substrates such as building materials are provided with a cured coating (paint film, protective layer) for the purpose of protecting the substrate from dirt, scratches, and the like. Furthermore, the cured coating is often required to have not only scratch resistance but also impact resistance, abrasion resistance, acid resistance, alkali resistance and thinner resistance.

[0003] As an example of such a cured coating, Patent Document 1 describes that a cured coating of an ultraviolet-curable paint containing a polyfunctional acrylate monomer or acrylate prepolymer, silica, and a photopolymerization initiator has excellent abrasion resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-274572 Summary of the Invention [Problem to be solved by the invention]

[0005] The higher the hardness (stiffness), the less likely it is to get dents or other scratches when furniture is dragged or when an object is dropped on the floor, so high hardness is particularly required for cured coatings formed on building materials such as wooden floors. However, conventional hardened coatings formed on building materials such as wooden floors tend to become brittle as the hardness increases, and therefore do not simultaneously satisfy high hardness as well as impact resistance, abrasion resistance, acid resistance, alkali resistance, and thinner resistance.

[0006] The present invention has been made in view of the above, and aims to provide a photocurable coating composition for building materials that is capable of forming a cured coating film of high hardness while having impact resistance, abrasion resistance, acid resistance, alkali resistance, and thinner resistance. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have found that the above-mentioned problems can be solved by the following configuration examples, and have completed the present invention. The configuration examples of the present invention are as follows.

[0008] [1] A photocurable coating composition for building materials, comprising an active energy ray-curable compound (A), a photopolymerization initiator (B), and cellulose nanofibers (C).

[0009] [2] The photocurable coating composition for building materials according to [1], wherein the content of the cellulose nanofibers (C) is 0.01 to 15 mass% relative to 100 mass% of the solid content of the photocurable coating composition for building materials.

[0010] [3] The photocurable coating composition for building materials according to [1] or [2], wherein the cellulose nanofibers (C) have an aspect ratio of 50 or more.

[0011] [4] The photocurable coating composition for building materials according to any one of [1] to [3], further comprising an inorganic pigment (D). [5] The photocurable coating composition for building materials according to any one of [1] to [4], wherein the inorganic pigment (D) has an average particle size of 10 to 50 μm.

[0012] [6] The photocurable coating composition for building materials according to any one of [1] to [5], which is used as an intermediate coating.

[0013] [7] A cured coating film formed from the photocurable coating composition for building materials according to any one of [1] to [6]. [8] A substrate with a cured coating, comprising a substrate and the cured coating described in [7]. [Effects of the Invention]

[0014] The photocurable coating composition for building materials according to the present invention can form a cured coating film that has high hardness while also having impact resistance, abrasion resistance, acid resistance, alkali resistance and thinner resistance. Furthermore, the photocurable coating composition for building materials according to the present invention can form a cured coating film that has excellent adhesion to substrates, acid resistance, alkali resistance, and thinner resistance, and is resistant to cracking and loss of adhesion to substrates even after repeated heat and cold tests. The photocurable coating composition for building materials according to the present invention can form a cured coating that exhibits the above-mentioned effects, and is therefore suitable for use when forming a cured coating on building materials, and even on wooden building materials, particularly on wooden floors. DETAILED DESCRIPTION OF THE INVENTION

[0015] ≪Photocurable coating composition for building materials≫ The photocurable coating composition for building materials according to the present invention (hereinafter also referred to as "the composition") contains an active energy ray-curable compound (A) [hereinafter also referred to as "component (A)"; the same applies to other components], a photopolymerization initiator (B), and cellulose nanofibers (C).

[0016] <Active energy ray-curable compound (A)> The component (A) is not particularly limited as long as it is a compound that is cured by active energy rays, but an oligomer or resin having a photocurable group is preferred, an oligomer or resin obtained using a photocurable (meth)acrylate monomer having two or more (meth)acryloyl groups in one molecule is more preferred, and such oligomers are even more preferred. By using component (A), it is possible to form a hard cured coating that has excellent adhesion to the substrate. The component (A) used in the present composition may be one type or two or more types.

[0017] Component (A) is preferably a bifunctional or higher functional compound having two or more photocurable groups in one molecule. However, when the composition is used as an undercoat paint, a bifunctional or trifunctional compound is more preferred, taking into consideration the adhesion between the cured coating film formed from the composition and the topcoat paint film.

[0018] There is no particular distinction between the oligomer and the resin, but the oligomer is preferably an oligomer having a weight average molecular weight measured by GPC of 500 to 10,000, more preferably 600 to 8,000.

[0019] In this specification, "(meth)acrylate" is a concept that encompasses acrylate, methacrylate, or both acrylate and methacrylate, and "(meth)acryloyl" is a concept that encompasses acryloyl, methacryloyl, or both acryloyl and methacryloyl.

[0020] Specific examples of the photocurable (meth)acrylate monomer include urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, epoxy (meth)acrylate, polybutadiene (meth)acrylate, and copolymer (meth)acrylate in which an acryloyl group or methacryloyl group is introduced into the side chain of an acrylic acid ester copolymer.

[0021] Examples of the component (A) include (meth)acrylate oligomers such as urethane (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and polyether (meth)acrylate oligomers, and (meth)acrylate resins such as urethane (meth)acrylate resins, epoxy (meth)acrylate resins, polyester (meth)acrylate resins, and polyether (meth)acrylate resins, and among these, urethane (meth)acrylate oligomers and epoxy (meth)acrylate oligomers are preferred.

[0022] Examples of the urethane (meth)acrylate oligomer or resin include urethane (meth)acrylate oligomers or resins obtained by reacting an isocyanate compound, a hydroxy group-containing (meth)acrylate compound, and optionally a polyol compound. From the viewpoint of being able to easily obtain a cured coating film with excellent yellowing resistance, it is preferable that the compound used as a raw material for the urethane (meth)acrylate oligomer or resin is an aliphatic (including alicyclic) compound.

[0023] Component (A) preferably has any number of (meth)acryloyl groups and any number of urethane bonds as functional groups in the molecule, and it is preferable to use a bifunctional or higher functional urethane (meth)acrylate oligomer or resin having two or more (meth)acryloyl groups as component (A), from the viewpoint of being able to obtain a cured coating film that is superior in impact resistance, abrasion resistance, and hardness.

[0024] The isocyanate compound is not particularly limited as long as it does not impair the effects of the present invention, and for example, linear or branched isocyanate group-containing hydrocarbons, isocyanate group-containing cyclic hydrocarbons, and isocyanate group-containing aromatic hydrocarbons can be used. One or more of such isocyanate compounds may be used.

[0025] Examples of the isocyanate compound include polyisocyanates, and specific examples thereof include isocyanate group-containing linear hydrocarbons such as tetramethylene diisocyanate and hexamethylene diisocyanate [HDI], isocyanate group-containing branched hydrocarbons such as 2,2,4-trimethylhexamethylene diisocyanate [TMHMDI], isocyanate group-containing cyclic hydrocarbons such as isophorone diisocyanate [IPDI], hydrogenated diphenylmethane diisocyanate, hydrogenated xylene diisocyanate and hydrogenated toluene diisocyanate, and p-phenylene diisocyanate. diisocyanate group-containing aromatic hydrocarbons such as 3,3'-dimethyldiphenyl-4,4'-diisocyanate [PPDI], 3,3'-dimethyldiphenyl-4,4'-diisocyanate [TODI], 1,3-xylene diisocyanate [XDI], dianisidine diisocyanate [DADI], tetramethylxylene diisocyanate [TMXDI], 1,5-naphthalene diisocyanate [NDI], tolylene diisocyanate [TDI], and 4,4-diphenylmethane diisocyanate [MDI]; and dimers or trimers of the aforementioned isocyanates (biuret-modified products, isocyanurate-modified products). Among these, hexamethylene diisocyanate [HDI] and isophorone diisocyanate [IPDI] are preferred as the isocyanate compound.

[0026] As the hydroxy group-containing (meth)acrylate compound, a (meth)acrylate having one or more hydroxy groups can be used, and one or more hydroxy group-containing (meth)acrylate compounds may be used.

[0027] Examples of the hydroxy group-containing (meth)acrylate compound include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, hydroxyhexyl (meth)acrylate, and 2-hydroxy-3-chloropropyl (meth)acrylate. hydroxyl group-containing monofunctional (meth)acrylates such as polyethylene glycol mono(meth)acrylate and polypropylene glycol mono(meth)acrylate; and hydroxyl group-containing polyfunctional (meth)acrylates such as trimethylolpropane di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di- or tri(meth)acrylate, diglycerin di- or tri(meth)acrylate, ditrimethylolpropane di- or tri(meth)acrylate, and dipentaerythritol di-, tri-, tetra-, or penta(meth)acrylate. In addition to the above, modified products such as polycaprolactone-modified 2-hydroxyethyl (meth)acrylate may also be used.

[0028] Examples of the polyol compound that can be used include known polyols such as polyether polyols, polyester polyols, and polyolefin polyols. Specific examples include polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, bisphenol A, hydrogenated bisphenol A, an ethylene oxide adduct of bisphenol A, an adduct of hydrogenated bisphenol A and ethylene oxide, a propylene oxide adduct of bisphenol A, polycaprolactone diol, alkylene polyols, neopentyl glycol, 1,6-hexanediol, and trimethylolpropane. One type of such polyol may be used, or two or more types may be used.

[0029] Examples of the epoxy (meth)acrylate oligomer or resin include a (meth)acrylic acid-modified epoxy oligomer or resin obtained by adding (meth)acrylic acid to an epoxy oligomer or resin. Examples of the epoxy oligomer or resin to be modified include an oligomer or resin obtained by reacting bisphenol A, bisphenol F, bisphenol S, or phenol novolak with epichlorohydrin, and an oligomer or resin obtained by reacting cyclopentadiene oxide or cyclohexene oxide with epichlorohydrin. By using the epoxy (meth)acrylate oligomer or resin, it is possible to easily form a cured coating film that is highly hard and has excellent abrasion resistance.

[0030] Examples of the polyester (meth)acrylate oligomer or resin include a polyester (meth)acrylate oligomer or resin obtained by reacting a polyester oligomer or resin synthesized from a polybasic acid or anhydride thereof and a polyhydric alcohol with (meth)acrylic acid.

[0031] Examples of the polybasic acid include phthalic acid, succinic acid, adipic acid, glutaric acid, sebacic acid, isosebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, dimer acid, trimellitic acid, pyromellitic acid, pimelic acid, and azelaic acid.

[0032] Examples of the polyhydric alcohol include 1,6-hexanediol, diethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, neopentyl glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol.

[0033] Examples of the polyether(meth)acrylate oligomer or resin include polyether(meth)acrylate oligomers or resins obtained by transesterification of a polyether with a (meth)acrylic acid ester such as ethyl(meth)acrylate.

[0034] Examples of the polyether include polyethers obtained by ethoxylating or propoxylating trimethylolpropane and pentaerythritol, and polyethers obtained by polyetherifying 1,4-butanediol.

[0035] The content of component (A) is preferably 15 to 95 mass%, more preferably 30 to 80 mass%, and particularly preferably 45 to 65 mass%, relative to 100 mass% of the solid content of the composition, from the viewpoints of being able to easily form a cured coating that has excellent adhesion to the substrate and excellent impact resistance, abrasion resistance, and hardness. In the present invention, the solid content refers to components other than the solvent. The solid content of the present composition also refers to components that constitute the cured coating film obtained by curing the present composition.

[0036] <Photopolymerization initiator (B)> Component (B) is not particularly limited as long as it is a compound that can cure the present composition, but it is preferably a compound that generates radicals or cations upon irradiation with light and can react with component (A), etc. Examples of such component (B) include alkylphenone initiators, acylphosphine oxide initiators, hydrogen abstraction initiators, benzoin initiators, and thioxanthone initiators. The component (B) used in the present composition may be one type or two or more types.

[0037] Examples of alkylphenone initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholino ... Examples include 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, and methylbenzoyl formate.

[0038] Examples of the acylphosphine oxide initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0039] Examples of the hydrogen abstraction initiator include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, methyl benzoylbenzoate, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-ethylanthraquinone, camphorquinone, oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester, and phenylglyoxylic acid methyl ester.

[0040] Examples of the benzoin initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

[0041] Examples of thioxanthone initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone.

[0042] The content of component (B) is preferably 0.1 to 10 mass%, more preferably 0.5 to 5 mass%, and particularly preferably 1 to 3 mass%, relative to 100 mass% of the solids content of the composition, from the viewpoints that the composition can be sufficiently cured and a cured coating film excellent in impact resistance, abrasion resistance, and hardness can be easily formed.

[0043] <Cellulose nanofiber (C)> Component (C) is not particularly limited, and any conventionally known fiber can be used. By using cellulose nanofibers (CNF) instead of other fibers, this composition is able to form a hardened coating that is impact-resistant, abrasion-resistant, acid-resistant, alkali-resistant, and thinner-resistant for the first time. The component (C) used in the present composition may be one type or two or more types.

[0044] Examples of component (C) include cellulose fibers derived from higher plants [for example, natural cellulose fibers (pulp fibers) such as wood fibers (e.g., wood pulp from conifers, broad-leaved trees, etc.), stem fibers (e.g., bamboo fibers), sugarcane fibers, seed hair fibers (e.g., cotton linters, bombax cotton, kapok, etc.), ginseng bark fibers (e.g., flax, ramie, paper mulberry, Mitsumata), leaf vein fibers (e.g., Manila hemp, sisal hemp, New Zealand hemp, pineapple fibers), and fruit fibers (e.g., palm fibers)], cellulose fibers derived from animals (e.g., sea squirt cellulose, valonia cellulose, Cladophora cellulose), and cellulose fibers derived from bacteria.

[0045] The average fiber diameter of component (C) is not particularly limited as long as it is nanometer-sized, but is, for example, 1 to 500 nm, and preferably 2 to 400 nm. The average fiber length of the component (C) is, for example, 0.05 μm or more, preferably 0.05 to 250 μm. The aspect ratio (average fiber length / average fiber diameter) of component (C) is preferably 50 or more, and more preferably 50-500. By using component (C) having an average fiber diameter, average fiber length, and / or aspect ratio within the above ranges, it is possible to easily form a cured coating that has high hardness while also having impact resistance, abrasion resistance, acid resistance, alkali resistance, and thinner resistance.

[0046] The average fiber diameter and average fiber length in this specification are calculated as average values ​​based on the measurement results of randomly selecting 20 fibers from a polarizing microscope photograph of the fiber (group) to be measured and measuring the fiber diameter or fiber length of each of these fibers.

[0047] Component (C) can be obtained by subjecting raw CNF to a defibration treatment or the like. During this defibration treatment, oxidation treatment, chemical modification treatment, or the like may also be performed. Component (C) may also be CNF that has been surface-treated (e.g., hydrophobized), and it is preferable to use hydrophobized CNF because this composition in which component (C) is highly dispersed can be easily obtained. If necessary, the CNF may be pulverized to adjust the aspect ratio of component (C).

[0048] Component (C) used in preparing the present composition may be in the form of a powder or a dispersion in a dispersion medium such as water or methanol, but it is preferable to use a dispersion in an organic solvent such as methanol as the dispersion medium, as this makes it easier to obtain the present composition in which component (C) is highly dispersed. Examples of such component (C) include "Leocrysta CNF-N04" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

[0049] The content of component (C) is preferably 0.01 to 15 mass%, more preferably 0.05 to 12 mass%, and particularly preferably 0.1 to 10 mass%, relative to 100 mass% of the solids content of the composition, from the viewpoint of being able to easily form a cured coating film of higher hardness while maintaining impact resistance, abrasion resistance, acid resistance, alkali resistance, and thinner resistance.

[0050] <Inorganic pigments (D)> The present composition may further contain component (D), and preferably contains component (D) from the viewpoint of further improving the hardness and abrasion resistance of the cured coating. When the present composition contains component (D), the component (D) used in the composition may be one type or two or more types.

[0051] Component (D) is not particularly limited, and any conventionally known inorganic pigment can be used, but it is preferably an antifriction agent, and specific examples include alumina, silica sand, silica, carborundum, alundum, ceramic, and glass. Of these, alumina and silica sand are preferred because they can easily form a hardened coating that has excellent abrasion resistance.

[0052] The average particle size of component (D) is preferably 10 to 50 μm, more preferably 15 to 40 μm, from the viewpoint of being able to easily form a cured coating film with excellent abrasion resistance. The average particle size refers to the average particle size of component (D), which is a raw material used in preparing the present composition.

[0053] The term "average particle size" as used herein refers to the particle size (median size, d50) corresponding to 50% of the volume-based cumulative particle size distribution, measured based on the "Particle size analysis - Laser diffraction and scattering method" specified in JIS Z 8825:2013.

[0054] When the present composition contains component (D), the content of component (D) is preferably 10 to 50 mass%, more preferably 15 to 45 mass%, and particularly preferably 20 to 40 mass%, relative to 100 mass% of the solids content of the present composition, from the viewpoints that the present composition can be sufficiently cured and a cured coating having greater hardness while still having impact resistance, abrasion resistance, acid resistance, alkali resistance, and thinner resistance can be easily formed.

[0055] <Other ingredients> The present composition may contain other components in addition to the above-mentioned components, if necessary. As the other components, conventionally known additives that have been commonly used in the field of the present invention, etc., can be used to the extent that the effects of the present invention are not impaired. Examples of such other components include reactive diluents, leveling agents, antifoaming agents, dispersants, organic solvents, polymerization inhibitors, non-reactive diluents, matting agents, anti-settling agents, heat stabilizers, ultraviolet absorbers, photosensitizers other than component (B), and organic particles such as acrylic resin beads, urethane resin particles, and polyethylene particles. The other components may each be used alone or in combination of two or more.

[0056] [Reactive diluent] The present composition may contain a reactive diluent for the purpose of adjusting the viscosity thereof or the like. The reactive diluent is not particularly limited, but examples thereof include (meth)acrylate monomers, which have an active acryloyl group or methacryloyl group and can react with component (A) upon exposure to light to form a cured coating.

[0057] Examples of (meth)acrylate monomers include (meth)acryloylmorpholine, methoxytriethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, tripropylene glycol di(meth)acrylate (hereinafter, tripropylene glycol diacrylate may be referred to as "TPGDA"), 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, bisphenol A ethoxylate di(meth)acrylate, tetrahydrofuran, Examples of the acrylate include lactone-modified acrylates such as methylfuryl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 2-hydroxyethyl (meth)acrylate, and ε-caprolactone-modified dipentaerythritol (meth)acrylate. Among these, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, bisphenol A ethoxylate di(meth)acrylate, and tripropylene glycol di(meth)acrylate are preferred.

[0058] The reactive diluent may be added to component (A) in advance, or may be added when preparing the composition.

[0059] When the present composition contains a reactive diluent, the content of the reactive diluent is usually 5 to 150 parts by mass, and preferably 15 to 100 parts by mass, per 100 parts by mass of component (A), because this tends to facilitate the formation of a cured coating film that has excellent coating film properties such as hardness and abrasion resistance.

[0060] [UV absorbers, light stabilizers] Examples of the ultraviolet absorber include compounds having a triazine skeleton, compounds having a benzotriazole skeleton, etc. Examples of the light stabilizer include hindered amine light stabilizers.

[0061] Examples of the compound having a triazine skeleton include 2-(2-hydroxy-4-[isooctyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and 2-[4-[(2-hydroxy-3-tridecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine. 2,4-bis(2-hydroxy-4-butyloxyphenyl)-6-(2,4-bis-butyloxyphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-(2'-ethylhexyloxy)propyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine. Examples of commercially available products of these include "TINUVIN 400," "TINUVIN 405," "TINUVIN 460," and "TINUVIN 479" (all manufactured by BASF).

[0062] Examples of the compound having a benzotriazole skeleton include 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, 2-(4-allyloxy-2-hydroxyphenyl)-2H-benzotriazole, and 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol. Examples of commercially available products include "RUVA-93" (manufactured by Otsuka Chemical Co., Ltd.), "DAINSORB T-31" (manufactured by Yamato Chemical Co., Ltd.), "DAINSORB T-84" (manufactured by Yamato Chemical Co., Ltd.), "TINUVIN 928" and "TINUVIN 384-2" (all manufactured by BASF).

[0063] Examples of the hindered amine light stabilizer include bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 2,4-bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine, and decanedioic acid bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidinyl)ester. Examples of commercially available products of these include "TINUVIN 292," "TINUVIN 144," and "TINUVIN 123" (all manufactured by BASF).

[0064] When the present composition contains an ultraviolet absorber and a light stabilizer, the total content of the ultraviolet absorber and light stabilizer is preferably 0.1 to 2 mass %, more preferably 0.2 to 1 mass %, relative to 100 mass % of the solid content of the present composition, in order to ensure that the effects of these agents can be fully exerted without impairing the effects of the present invention.

[0065] [Organic solvents] The present composition may contain an organic solvent in order to adjust the viscosity within a predetermined range. The organic solvent may be any known solvent, such as aromatic hydrocarbons (e.g., xylene, toluene), ketones (e.g., methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone), esters (e.g., ethyl acetate, butyl acetate, isobutyl acetate), alcohols (e.g., methanol, isopropyl alcohol, butanol), and glycol ethers (e.g., propylene glycol monomethyl ether).

[0066] When the present composition contains an organic solvent, the content of the organic solvent is preferably 10 to 90% by mass, and more preferably 15 to 85% by mass, relative to 100% by mass of the present composition.

[0067] <Present composition> The composition can be prepared by mixing the above components by known means. The order in which the components are mixed is not particularly limited, but when component (D) is used, it is preferable to add component (D) to a mixture of other components such as components (A) to (C) immediately before coating.

[0068] The use of the present composition is not particularly limited, but it is preferably used for components (building materials) such as walls, floors, ceilings, doors, stairs, furniture, and window frames for houses, schools, gymnasiums, hospitals, offices, factories, etc., and more preferably for coating wood substrates, and even more preferably for coating flooring materials (wood floors) using wood substrates.

[0069] Although the present composition may be used as a topcoat paint, it is preferably used as an intermediate coat paint in order to more effectively exhibit the effects of the present invention, etc. In particular, when the present composition contains the component (D), it is preferably used as an intermediate coat paint. In the present invention, the intermediate paint refers to a paint that forms a coating film that is formed below the layer (surface layer, top coat paint layer) that is farthest from the substrate among the coating films formed on the substrate. However, in terms of better exerting the effects of the present invention, it is preferable that the intermediate paint forms a coating film that is one layer closer to the substrate than the surface layer (top coat paint layer) (a coating film that is formed below the surface layer and is in contact with the surface layer).

[0070] ≪Cured coating, base material with cured coating≫ The cured coating according to the present invention is a film formed from the present composition, and specifically, can be produced by including a step of curing the present composition by light irradiation (light irradiation step). The cured coating is usually formed on a substrate, i.e., a substrate with a cured coating is formed that includes the substrate and the cured coating. Specifically, a substrate with a cured coating can be produced by including a coating step of coating at least a portion of the substrate with the composition and a light irradiation step of irradiating the coated surface with light to cure the composition.

[0071] The thickness of the cured coating is not particularly limited as long as it is thick enough to exhibit the desired function, but it is usually 5 to 100 μm, preferably 5 to 50 μm, from the viewpoint of easily protecting the substrate from scratches, impacts, abrasion, etc. When forming a cured coating having such a thickness, the cured coating may be formed in one coating application, or in two (or more, if necessary) applications.

[0072] The substrate is not particularly limited, and may be any substrate on which the cured coating is to be formed, and examples thereof include wood (wood substrates), plastics, paper, metals, glass, ceramics, and concrete. Furthermore, the substrate may be a substrate that has been subjected to a conventionally known sealing treatment or coloring treatment, as necessary, or a substrate that has been coated with a conventionally known primer paint, or a substrate that has been treated with a sealing treatment, coloring treatment, or the like and then coated with a primer paint, or the like.

[0073] Examples of plastics include various plastic substrates (e.g., films and molded articles formed from triacetyl cellulose, polyethylene terephthalate (PET), diacetyl cellulose, acetate butyrate cellulose, polyolefin, polyvinyl chloride, polyethersulfone, polyacrylic, polyurethane, polyester, polycarbonate, polysulfone, polyether, polymethylpentene, polyether ketone, (meth)acrylonitrile, etc.).

[0074] The substrate is preferably a wood substrate, as this allows the effects of the present invention to be more effectively exhibited. The wood substrate may be a veneer-covered, paper-covered or sheet-covered substrate, or may be solid wood.

[0075] The coating method in the coating step may be appropriately selected depending on the composition of the present composition used, the type of substrate, etc., and examples thereof include roll coating, spray coating, dip coating, air knife coating, curtain coating, wire bar coating, gravure coating, and extrusion coating.

[0076] The amount of the composition to be applied to the substrate is not particularly limited, but it is preferable to apply the composition so that the thickness of the resulting cured coating falls within the above range, from the viewpoint of easily protecting the substrate from scratches, impacts, abrasion, etc., and specifically, from 7.5 to 200 g / m 2 It is preferable to paint so that

[0077] After the coating step and before the light irradiation step, a drying step or the like may be performed to dry the coated composition. This drying step may be performed under heating at about 5 to 120°C in order to shorten the drying time.

[0078] The light to be irradiated in the light irradiation step is preferably an active energy ray. Examples of the active energy ray include light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, and infrared rays, electromagnetic waves such as X-rays and gamma rays, electron beams, proton beams, and neutron beams. Among these, ultraviolet rays are preferred in terms of curing speed, ease of availability of an irradiation device, price, etc.

[0079] Examples of light sources for irradiating ultraviolet rays include high-pressure mercury lamps, metal halide lamps, xenon lamps, chemical lamps, electrodeless lamps, and LED lamps that emit light in the wavelength range of 200 to 500 nm.

[0080] As for the conditions for ultraviolet irradiation, the irradiation intensity is preferably 50 to 500 mW / cm 2 , more preferably 100 to 350 mW / cm 2The cumulative light intensity is usually 20 to 3,000 mJ / cm 2 , preferably 50 to 500 mJ / cm 2 is. In the light irradiation step, heating may be performed at about 5 to 120° C. after or during light irradiation in order to shorten the curing time.

[0081] In addition to the above steps, known steps may be carried out as necessary when producing a substrate with a cured coating. This step preferably includes a step of applying a conventionally known topcoat paint onto the formed cured coating film and curing it to form a topcoat film.

[0082] The top coat paint may contain components that are typically used in top coat paints for substrates such as wood substrates, and preferably contains an active energy ray-curable compound, a reactive diluent, and a photopolymerization initiator. The topcoat paint may further contain, as necessary, one or more of each of a dispersant, a thixotropic agent, an antifoaming agent, a leveling agent, and a diluent other than the reactive diluent.

[0083] Examples of the active energy ray-curable compound include the same compounds as component (A) described in the section on the present composition. Among these, it is preferable to use a urethane (meth)acrylate oligomer or resin, because it allows for the easy formation of a topcoat film that is excellent in abrasion resistance and yellowing resistance. The active energy ray-curable compounds may be used alone or in combination of two or more.

[0084] Examples of the reactive diluent and photopolymerization initiator include the reactive diluents and compounds similar to component (B) described in the section on the present composition. The reactive diluent and the photopolymerization initiator may each be used alone or in combination of two or more. [Example]

[0085] The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.

[0086] [Example 1] 0.625 parts by weight of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (photopolymerization initiator), 0.1 parts by weight of UV absorber (UVA, TINUVIN 384-2 (BASF)), and 0.05 parts by weight of light stabilizer (HALS, TINUVIN 123 (BASF)) were added to 10 parts by weight of butyl acetate (solvent) and completely dissolved. 25 parts by weight of bisphenol A epoxy acrylate (lipoxy VR-77-80TPA (containing 20% ​​by weight of TPGDA), Showa Denko K.K.) was added to the resulting solution and thoroughly stirred. To the stirred solution was added 100 parts by mass of a CNF methanol dispersion (Leocrysta CNF-N04 (Dai-ichi Kogyo Seiyaku Co., Ltd.), hydrophobically modified CNF content: 2.5 mass%, average CNF fiber diameter: 4 nm, CNF aspect ratio: 100-200), and the CNF was completely dispersed to prepare a photocurable coating composition.

[0087] [Examples 2 to 4 and Comparative Examples 1 to 4] Photocurable coating compositions were prepared in the same manner as in Example 1, except that the raw materials shown in Table 1 were used in the amounts (parts by mass) shown in Table 1. Details of the urethane acrylate, glass fiber, and wollastonite in Table 1 are as follows: Urethane acrylate: UV-55 (Ohtake Meishin Chemical Co., Ltd.), functional group number: 3, contains 25% by mass of TPGDA Glass fiber: Glasslon Milled Fiber MF03JB1-20 (manufactured by Asahi Fiberglass Co., Ltd.), fiber diameter: 10 μm, average fiber length: 30 μm Wollastonite: FPW#400 (Kinseimatec Co., Ltd.), fiber diameter: 8.2 μm, aspect ratio: 3-6

[0088] [Table 1]

[0089] <Preparation of substrate with cured coating> To each of the photocurable coating compositions prepared in Examples 1 to 4, 7.5 parts by mass of fused alumina (Sankei White WA#500, manufactured by Heisei Sankei Co., Ltd., average particle size: 25 μm) was added, and to each of the photocurable coating compositions prepared in Comparative Examples 1 to 4, 30 parts by mass of the fused alumina was added and thoroughly stirred to prepare compositions for forming cured coatings.

[0090] A UV-curable primer (O-LEX No. 822F HSG (manufactured by Chugoku Toryo Co., Ltd.)) was applied to a floor substrate (surface veneer: birch wood) and dried, and then UV-curable primers (O-LEX No. 822S-1 (manufactured by Chugoku Toryo Co., Ltd.) and O-LEX No. 822F-4 (manufactured by Chugoku Toryo Co., Ltd.)) were applied in this order and dried to form a primer coating film. The prepared cured film-forming composition was applied as an intermediate coating film on top of the primer coating film at a rate of 2.7 g / square meter after the solvent had dried. 2 ±0.2g / shaku 2 After applying the coating by spraying, it was cured in a 60°C dryer for 5 minutes, and then irradiated with ultraviolet light (integrated light intensity: 50 mJ / cm 2 A cured coating was formed by this process. A UV-curable topcoat paint (Olex No. 811RS G-20 (manufactured by Chugoku Toryo Co., Ltd.)) was then applied to the cured coating and dried to produce a substrate with a cured coating.

[0091] <Pencil hardness> The pencil hardness of the coating film on the prepared cured coated substrate was measured using a pencil hardness tester manufactured by Yasuda Seiki Seisakusho Co., Ltd., based on the scratch hardness (pencil method) of JIS K 5600-5-4:1999. Specifically, the measurement was performed as follows. The wood was scraped off to create a smooth, flawless cylindrical pencil lead, and the tip of the lead was flattened with sandpaper. The prepared cured-coated substrate was then set so that the pencil movement was perpendicular to the wood grain of the floor substrate, and then the pencil was placed in a pencil hardness tester so that the pencil was angled 45° relative to the cured-coated substrate and a load of 750 g was applied. Immediately after the tip of the pencil touched the coating, the cured-coated substrate was moved so that the pencil movement was perpendicular to the wood grain of the floor substrate, and the hardness of the hardest pencil that did not create a dent in the cured-coated substrate was evaluated. The results are shown in Table 2.

[0092] [Table 2]

[0093] <Adhesion test> Using a cutter and cutter guide, a 2mm wide, 100-hole grid pattern was cut into the coating of the cured substrate at a 45° angle to the wood grain of the floor substrate, reaching down to the primer coating. Cellophane adhesive tape was applied to the grid pattern, and after it had completely adhered, the edge of the tape was grasped and the tape was quickly and firmly pulled off at an angle as close to 45° (forward) as possible. The number of grid patterns of the coating remaining on the cured substrate was counted, with a score of 100 being defined as a condition in which the edges of the cuts were completely smooth (no chipping of the coating along the cuts) and no peeling of any of the grids. The results are shown in Table 3.

[0094] <Cold and heat cycling test> A 150mm x 150mm square test piece was cut from the prepared cured coated substrate. The resulting test piece was placed in an incubator at 80±3°C for 2 hours, then placed in an incubator at -20±3°C for 2 hours. This process was repeated twice, and the number of cycles at which cracks appeared on the surface of the test piece was evaluated. If cracks occurred, the total length of the cracks was measured. After the test, the adhesion after the cold and heat cycle test (secondary adhesion) was evaluated in the same manner as in the adhesion test. The results are shown in Table 3.

[0095] <Acid resistance test, alkali resistance test, thinner resistance test> The cured-coated substrate was placed horizontally, and a 5% aqueous acetic acid solution (acid resistance test), a 1% aqueous sodium carbonate solution (alkali resistance test), or lacquer thinner (thinner resistance test) was dripped onto the coating surface of the cured-coated substrate. A watch glass was placed on the coating surface of the cured-coated substrate with the convex side facing upward, covering the dripped area. After preventing the dripped liquid from drying for 6 hours, the coating surface was immediately rinsed with water and left indoors for 24 hours. The condition of the coating surface after the incubation period was evaluated on a 5-point scale according to the following evaluation criteria. The results are shown in Table 3. Note that the test results are largely dependent on the properties of the cured coating formed from the prepared cured-coating composition, which is the primer paint. Therefore, this test can be said to be a test that indicates the properties of the cured coating formed from the prepared cured-coating composition. (Evaluation criteria) ○: No change in color or gloss ○△: If you look closely, you can see changes in color and gloss. △: A clear change in color and gloss can be seen △×: Cracking, swelling, peeling or softening was observed, but the area was less than 30% of the entire coating surface. ×: Cracking, swelling, peeling or softening was observed, and the area was 30% or more of the entire coating surface.

[0096] <Wear resistance test> A 100mm x 100mm square test piece was cut from the prepared cured coated substrate. The resulting test piece was fixed horizontally on the rotating plate of a Taber abrasion tester manufactured by Yasuda Seiki Seisakusho Co., Ltd. Two rubber disks wrapped with JAS abrasion test abrasive paper were attached, and the test piece was rotated. The total weight applied to the test piece, including the mass of the two rubber disks, was 1000g. The test was stopped when the floor base material was exposed at the point where the test piece and the abrasive paper came into contact (the abrasion point), and the number of rotations at that point was counted. The results are shown in Table 3. When the test was continued beyond 500 revolutions, the abrasive paper was replaced with new one. After that, the abrasive paper was replaced every 500 revolutions.

[0097] <Impact resistance test> The impact resistance of the coated surface of the cured coated substrate was measured using a DuPont impact tester. Specifically, the measurements were carried out as follows. A die with a φ1 / 2 rounded tip and a cradle with a matching recess were set up, and a 300g weight was pinned 50cm above the die. After the cured-coated substrate was sandwiched between the die and the cradle, the pin was removed and the weight was dropped onto the die. The coating cracking and peeling caused by impact deformation were evaluated on a 5-point scale according to the following criteria. The results are shown in Table 3. (Evaluation criteria) ○: No cracks or peeling ○△: If you look closely, you can see that the test area is cracked, but there is no peeling. △: There is a crack in the area where the mold is in contact, but there is no peeling. △×: There is cracking and peeling in the area that comes into contact with the mold. ×: Cracks and peeling are observed not only in the area in contact with the die but also in other areas.

[0098] [Table 3]

Claims

1. A wood floor with a cured coating, comprising, in this order: a wood floor; a cured coating; and a topcoat coating formed from a topcoat paint containing an active energy ray-curable compound, a reactive diluent, and a photopolymerization initiator, the cured coating is a cured coating formed from a photocurable coating composition, The photocurable coating composition contains an active energy ray-curable compound (A), a photopolymerization initiator (B), and cellulose nanofibers (C), The content of the cellulose nanofibers (C) is 3.6 to 15% by mass relative to 100% by mass of the solid content of the photocurable coating composition. Wood floor with hardened coating.

2. The hardened coated wood floor according to claim 1, wherein the aspect ratio of the cellulose nanofibers (C) is 50 or more.

3. A wood floor with a cured coating as described in claim 1 or 2, wherein the photocurable coating composition further contains an inorganic pigment (D).

4. 4. The hardened coated wood floor according to claim 3, wherein the inorganic pigment (D) has an average particle size of 10 to 50 μm.

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