Active energy ray-curable resin composition and coating agent

Abstract

To provide an active energy ray-curable resin composition enabling production of a coated film which has good coating film appearance when the coated film is formed on a base material such as a metal plate, is excellent in adhesibility to the base material, has high surface hardness, and is excellent in bendability, and a coating agent which contains the active energy ray-curable resin composition.SOLUTION: An active energy ray-curable resin composition is provided which includes a (meth)acrylic polymer (A), urethane (meth)acrylate (B) having 1 to 4 (meth)acryloyl groups, a monomer (C) having one or more (meth)acryloyl groups, and a photopolymerization initiator (D), wherein a content of a solvent to the total mass of the active energy ray-curable resin composition is 1 mass% or less, a coating agent is also provided which contains the active energy ray-curable resin composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an active energy ray-curable resin composition and a coating agent. [Background technology]

[0002] BACKGROUND ART Active energy ray-curable resin compositions have been widely used as coating agents such as topcoats and undercoats for various substrates, adhesives, etc., because they can be cured completely by irradiation with active energy rays such as radiation for a very short period of time. In particular, coating agents are required to have good coating film appearance when formed on a substrate, excellent adhesion to the substrate, and high surface hardness. Meanwhile, the pre-coated metal (PCM) method is widely used, in which a coating film is first formed on a plate- or coil-shaped metal substrate, such as a galvanized steel sheet, cold-rolled steel sheet, or aluminum sheet, and then the metal substrate is formed. In addition to the above requirements, the coating film formed by this PCM method must also have flexibility to accommodate the bending of the metal substrate during forming.

[0003] As an active energy ray-curable resin composition used in such a coating agent for pre-coated metals, for example, Patent Document 1 discloses an active energy ray-curable resin composition containing an acrylic copolymer having a specific structure, a urethane (meth)acrylate, a polyfunctional (meth)acrylate, and a photopolymerization initiator. Furthermore, Patent Document 2 discloses an active energy ray-curable resin composition containing a urethane (meth)acrylate compound having a specific structure and a nitrogen-containing (meth)acrylate compound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 06-313127 [Patent Document 2] Japanese Patent Application Publication No. 2019-112627 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the active energy ray-curable resin compositions described in Patent Documents 1 and 2 are used in coating agents for pre-coated metals, the surface hardness of the coating film is insufficient, and the flexibility is also insufficient. Therefore, there is a demand for a coating agent, particularly a coating agent for pre-coated metals, that can provide a coating film with a good balance of both surface hardness and flexibility.

[0006] An object of the present invention is to provide an active energy ray-curable resin composition which, when formed on a substrate such as a metal plate, can give a coating film that has good coating film appearance, excellent adhesion to the substrate, high surface hardness, and excellent flexibility, and to provide a coating agent containing such an active energy ray-curable resin composition. [Means for solving the problem]

[0007] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that by blending a specific (meth)acrylic polymer, a urethane (meth)acrylate, and a monomer into an active energy ray-curable resin composition, a coating film excellent in coating film appearance, substrate adhesion, surface hardness, and flexibility can be obtained, and have completed the present invention.

[0008] That is, the present invention has the following aspects. [1] A composition comprising: a (meth)acrylic polymer (A); a urethane (meth)acrylate having 1 to 4 (meth)acryloyl groups (B); a monomer (C) having one or more (meth)acryloyl groups; and a photopolymerization initiator (D), An active energy ray-curable resin composition, wherein the content of a solvent relative to the total mass of the active energy ray-curable resin composition is 1 mass % or less. [2] The active energy ray-curable resin composition according to [1], wherein, when the total content of the (meth)acrylic polymer (A), the urethane (meth)acrylate (B), and the monomer (C) is 100% by mass, the content of the (meth)acrylic polymer (A) is 1 to 15% by mass, the content of the urethane (meth)acrylate (B) is 20 to 80% by mass, and the content of the monomer (C) is 5 to 50% by mass. [3] The active energy ray-curable resin composition according to [1] or [2] above, wherein the (meth)acrylic polymer (A) has a weight average molecular weight of 5,000 to 100,000. [4] The active energy ray-curable resin composition according to any one of [1] to [3], wherein the (meth)acrylic polymer (A) has a glass transition temperature of 30 to 150°C. [5] The active energy ray-curable resin composition according to any one of [1] to [4] above, wherein the urethane (meth)acrylate (B) has a (meth)acryloyl group equivalent of 100 to 2,500. [6] The active energy ray-curable resin composition according to any one of [1] to [5], wherein the monomer (C) comprises at least one of a monomer having a hydroxyl group and a monomer having a morpholine structure. [7] A coating agent containing the active energy ray-curable resin composition according to any one of [1] to [6] above. [8] The coating agent according to [7] above, which is for pre-coated metal. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an active energy ray-curable resin composition which can give a coating film that, when formed on a substrate such as a metal plate, has a good coating film appearance, excellent adhesion to the substrate, high surface hardness, and excellent flexibility, and a coating agent containing such an active energy ray-curable resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. The following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to these embodiments. The present invention can be implemented in various forms without departing from the spirit of the present invention. In the present invention, "(meth)acrylic" is a general term for "acrylic" and "methacrylic." "(meth)acryloyl group" is a general term for "acryloyl group" and "methacryloyl group." "(meth)acrylate" is a general term for "acrylate" and "methacrylate." "Polymer" is a general term for "homopolymer" and "copolymer." "(meth)acryloyl group equivalent" is the average molecular weight per (meth)acryloyl group in one molecule of urethane (meth)acrylate. In other words, the "(meth)acryloyl group equivalent" is determined by dividing the weight average molecular weight of the urethane (meth)acrylate by the number of (meth)acryloyl groups. In the present invention, the term "coating film" refers to a cured coating film obtained from the coating agent of the present invention. "Workability" refers to the workability when forming a coating film on a substrate such as a metal plate and then molding the substrate.

[0011] [Active energy ray-curable resin composition] The active energy ray-curable resin composition of the present invention (hereinafter also referred to simply as "resin composition") contains a (meth)acrylic polymer (A) (hereinafter also referred to as "component (A)"), a urethane (meth)acrylate (B) (hereinafter also referred to as "component (B)"), a monomer (C) (hereinafter also referred to as "component (C)"), and a photopolymerization initiator (D) (hereinafter also referred to as "component (D)") shown below.

[0012] <Component (A)> The component (A) is a (meth)acrylic polymer (A). Component (A) is a polymer obtained by polymerizing a monomer component containing a (meth)acrylic monomer, that is, component (A) contains structural units derived from a (meth)acrylic monomer. The polymerization method is not particularly limited, but examples thereof include a method in which a monomer component is polymerized in the presence of a conventionally known radical polymerization initiator by a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, or the like. The component (A) may be used alone or in combination of two or more.

[0013] Examples of the (meth)acrylic monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, 2-dicyclopentenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxyethoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methyl ... Examples of the hydroxyl group-containing (meth)acrylate include (meth)acrylates that do not contain a hydroxyl group, such as tetraethoxyethyl (meth)acrylate and tetrahydrofurfuryl (meth)acrylate; hydroxyalkyl (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; and hydroxyl group-containing (meth)acrylates, such as adducts of 2-hydroxyethyl (meth)acrylate and ethylene oxide, adducts of 2-hydroxyethyl (meth)acrylate and propylene oxide, and adducts of 2-hydroxyethyl (meth)acrylate and alkylene oxide or organic lactone. These (meth)acrylic monomers may be used alone or in combination of two or more.

[0014] The monomer component may contain a vinyl monomer other than the (meth)acrylic monomer (hereinafter also referred to as "other monomer"). That is, component (A) may contain a structural unit derived from a (meth)acrylic monomer and a structural unit derived from another monomer. The other monomer is not particularly limited as long as it is copolymerizable with the (meth)acrylic monomer, and examples thereof include styrene or styrene derivatives such as styrene, α-methylstyrene, pt-butylstyrene, and vinyltoluene; acrylamides such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide; unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid; unsaturated nitriles such as (meth)acrylonitrile; unsaturated carboxylic acid esters such as diethyl maleate, dibutyl maleate, dibutyl fumarate, diethyl itaconate, and dibutyl itaconate; and vinyl esters such as vinyl acetate and vinyl propionate. These other monomers may be used alone or in combination of two or more.

[0015] The weight average molecular weight of component (A) is preferably 5000 to 100000, more preferably 8000 to 50000. When the weight average molecular weight of component (A) is at least the lower limit above, the strength of the coating film increases, and when it is at most the upper limit above, the coatability during coating film formation tends to improve. The weight average molecular weight of component (A) is a weight average molecular weight converted into a standard polystyrene molecular weight, and can be measured using a high performance liquid chromatograph.

[0016] The glass transition point of component (A) is preferably 30 to 150° C., more preferably 45 to 110° C. If the glass transition point of component (A) is equal to or higher than the lower limit above, the hardness of the coating film will be increased, and if it is equal to or lower than the upper limit above, the hardness of the coating film will not be too high and processability will tend to be improved. The glass transition point of component (A) can be measured using a differential scanning calorimeter (DSC).

[0017] The content of component (A) is preferably 1 to 15 mass%, more preferably 1 to 10 mass%, based on the total mass of components (A), (B), and (C), where the total content of components (A), (B), and (C) is taken as 100 mass%. If the content of component (A) is equal to or greater than the lower limit, processability improves, and if it is equal to or less than the upper limit, the hardness of the coating film tends to be increased.

[0018] <Ingredient (B)> Component (B) is a urethane (meth)acrylate (B) having 1 to 4 (meth)acryloyl groups. Examples of component (B) include an oligomer (B1) obtained by reacting a polyisocyanate compound (b1), a polyol compound (b2), and a hydroxyl group-containing (meth)acrylate (b3); and an oligomer (B2) obtained by reacting a polyisocyanate compound (b1) and a hydroxyl group-containing (meth)acrylate (b3). In the oligomer (B1), the isocyanate group of the polyisocyanate compound (b1) forms a urethane bond with both the hydroxyl group of the hydroxyl group-containing (meth)acrylate (b3) and the hydroxyl group of the polyol compound (b2). That is, the oligomer (B1) has a urethane bond formed between the isocyanate group of the polyisocyanate compound (b1) and the hydroxyl group of the hydroxyl group-containing (meth)acrylate (b3), and a urethane bond formed between the isocyanate group of the polyisocyanate compound (b1) and the hydroxyl group of the polyol compound (b2). In the oligomer (B2), the isocyanate group of the polyisocyanate compound (b1) forms a urethane bond with the hydroxyl group of the hydroxyl group-containing (meth)acrylate (b3). That is, the oligomer (B2) has a urethane bond formed by the isocyanate group of the polyisocyanate compound (b1) and the hydroxyl group of the hydroxyl group-containing (meth)acrylate (b3). The component (B) may be used alone or in combination of two or more.

[0019] Examples of the polyisocyanate compound (b1) include aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane diisocyanate, modified diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, and lysine diisocyanate; Examples of the isocyanate include acyclic aliphatic diisocyanates such as diisocyanate diisocyanates, hydrogenated diphenylmethane diisocyanate, isophorone diisocyanate, norbornene diisocyanate, alicyclic diisocyanates such as 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane, and polyisocyanate-based compounds obtained by polymerizing the above diisocyanates and having an allophanate structure, a nurate structure, a biuret structure, or the like. These polyisocyanate compounds (b1) may be used alone or in combination of two or more.

[0020] Examples of the polyol compound (b2) include polyhydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, trimethylolpropane, polytrimethylolpropane, pentaerythritol, polypentaerythritol, sorbitol, mannitol, glycerin, and polyglycerin; polyether polyols; polyester polyols synthesized from the above polyhydric alcohols and polybasic acids, polyester polyols such as polycaprolactone polyols, and amide polyols synthesized from lactones and amines. These polyol compounds (b2) may be used alone or in combination of two or more.

[0021] Examples of the hydroxyl group-containing (meth)acrylate (b3) include the hydroxyl group-containing (meth)acrylates exemplified above as the (meth)acrylic monomer in the description of component (A). These hydroxyl group-containing (meth)acrylates (b3) may be used alone or in combination of two or more.

[0022] Component (B) can be produced in accordance with a known method for producing a urethane (meth)acrylate compound. Examples of the method for producing component (B) include a method in which a polyisocyanate compound (b1), a polyol compound (b2), and a hydroxyl group-containing (meth)acrylate (b3) are charged into a reactor all at once or separately and reacted; and a method in which a polyisocyanate compound (b1) and a hydroxyl group-containing (meth)acrylate (b3) are charged into a reactor all at once or separately and reacted.

[0023] In the reaction between the polyisocyanate compound (b1), the polyol compound (b2), and the hydroxyl group-containing (meth)acrylate (b3), and the reaction between the polyisocyanate compound (b1) and the hydroxyl group-containing (meth)acrylate (b3), it is also preferable to use a catalyst to promote the reaction. Examples of such catalysts include organometallic compounds such as dibutyltin dilaurate, dibutyltin diacetate, trimethyltin hydroxide, tetra-n-butyltin, zinc bis(acetylacetonate), zinc bis(tetrafluoroacetylacetonate), zirconium monoacetylacetonate, zirconium ethylacetoacetate, zirconium tris(acetylacetonate)ethylacetoacetate, zirconium tetraacetylacetonate, tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium, and tetrabutoxytitanium; metal salts such as tin octenoate, zinc hexanoate, zinc octenoate, zinc stearate, zirconium 2-ethylhexanoate, cobalt naphthenate, stannous chloride, stannic chloride, and potassium acetate; triethylamine, triethylenediamine, benzyldiethylamine, and 1,2-dimethyl-2,3-dimethyl-2,4 ... amine-based catalysts such as 4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]undecene, N,N,N',N'-tetramethyl-1,3-butanediamine, N-methylmorpholine, and N-ethylmorpholine; bismuth catalysts such as bismuth nitrate, bismuth bromide, bismuth iodide, bismuth sulfide, organic bismuth compounds such as dibutyl bismuth dilaurate and dioctyl bismuth dilaurate, and organic acid bismuth salts such as bismuth 2-ethylhexanoate, bismuth naphthenate, bismuth isodecanoate, bismuth neodecanoate, bismuth laurate, bismuth maleate, bismuth stearate, bismuth oleate, bismuth linoleate, bismuth acetate, bismuth bisneodecanoate, bismuth disalicylate, and bismuth digallate. Among these, dibutyltin dilaurate and 1,8-diazabicyclo[5,4,0]undecene are preferred. These catalysts may be used alone or in combination of two or more.

[0024] An organic solvent may be used in the reaction between the polyisocyanate compound (b1), the polyol compound (b2), and the hydroxyl group-containing (meth)acrylate (b3), and in the reaction between the polyisocyanate compound (b1) and the hydroxyl group-containing (meth)acrylate (b3). The organic solvent is preferably an organic solvent that does not have a functional group that reacts with the isocyanate group of the polyisocyanate compound (b1), and examples thereof include esters such as methyl acetate, ethyl acetate, butyl acetate, 2-ethoxyethyl acetate, and 2-methoxy-1-methylethyl acetate; ketones such as methyl ethyl ketone and methyl isobutyl ketone; and aromatics such as toluene and xylene.

[0025] The number of (meth)acryloyl groups contained in component (B) is 1 to 4, and preferably 2 to 4. If the number of (meth)acryloyl groups is at least the above lower limit, the strength of the coating film increases, and if it is at most the above upper limit, the hardness of the coating film does not become too high, improving processability and substrate adhesion.

[0026] The (meth)acryloyl group equivalent of component (B) is preferably 100 to 2500, more preferably 150 to 2400, and even more preferably 200 to 2200. When the (meth)acryloyl group equivalent of component (B) is at least the above lower limit, the flexibility of the coating film is improved, and when it is no more than the above upper limit, the hardness of the coating film tends to be increased.

[0027] The weight-average molecular weight of component (B) is preferably 300 to 20,000, more preferably 400 to 10,000, and even more preferably 400 to 8,000. When the weight-average molecular weight of component (B) is at least the lower limit, flexibility is further improved, and when it is at most the upper limit, the viscosity of the coating agent does not become too high, and coatability tends to be improved. The weight average molecular weight of component (B) is a weight average molecular weight converted into a standard polystyrene molecular weight, and can be measured using a high performance liquid chromatograph.

[0028] The viscosity of component (B) at 60°C is preferably 50 to 50,000 mPa·s, more preferably 75 to 10,000 mPa·s, and even more preferably 100 to 5,000 mPa·s. When the viscosity of component (B) at 60°C is within the above range, the coatability during coating film formation tends to be improved. The viscosity of component (B) can be measured using an E-type viscometer.

[0029] The content of component (B) is preferably 20 to 80 mass%, more preferably 30 to 70 mass%, based on the total mass of components (A), (B), and (C), where the total content of components (A), (B), and (C) is taken as 100 mass%. If the content of component (B) is at least the lower limit, the processability of the coating film will be good, and if it is at most the upper limit, the viscosity will decrease and coatability will tend to improve.

[0030] <Component (C)> Component (C) is a monomer (C) having one or more (meth)acryloyl groups (excluding urethane (meth)acrylate compounds). Note that the term "urethane (meth)acrylate compounds" used here refers to the above-mentioned component (B) and urethane (meth)acrylates other than component (B). Examples of the component (C) include monofunctional monomers, difunctional monomers, trifunctional or higher functional monomers, and the like. The component (C) may be used alone or in combination of two or more.

[0031] Examples of monofunctional monomers include styrene-based monomers such as styrene, vinyltoluene, chlorostyrene, and α-methylstyrene; methyl (meth)acrylate, ethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-phenoxy-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, glycerin mono(meth)acrylate, glycidyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyl Oxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)-methyl (meth)acrylate, cyclohexanespiro-2-(1,3-dioxolan-4-yl)-methyl (meth)acrylate, cyclic trimethylolpropane formal acrylate, 3-ethyl-3-oxetanylmethyl (meth)acrylate, γ-butyrolactone (meth)acrylate, n-butyl (Meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, n-stearyl (meth)acrylate, benzyl (meth)acrylate, phenol ethylene oxide modified (n=2) (meth)acrylate, nonylphenol propylene oxide modified (n=2.5) (Meth)acrylate monomers such as (meth)acrylate, half (meth)acrylates of phthalic acid derivatives such as 2-(meth)acryloyloxyethyl acid phosphate and 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, furfuryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, carbitol (meth)acrylate, benzyl (meth)acrylate, butoxyethyl (meth)acrylate, allyl (meth)acrylate, and polyoxyethylene secondary alkyl ether acrylate; acryloylmorpholine; and vinyl acetate. These monofunctional monomers may be used alone or in combination of two or more.

[0032] Examples of bifunctional monomers include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, propylene oxide-modified bisphenol A di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, acrylate, ethoxylated cyclohexanedimethanol di(meth)acrylate, dimethylol dicyclopentane di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid-modified neopentyl glycol di(meth)acrylate, and isocyanuric acid ethylene oxide-modified diacrylate. These bifunctional monomers may be used alone or in combination of two or more.

[0033] Examples of trifunctional or higher functional monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly(meth)acrylate, isocyanuric acid ethylene oxide modified triacrylate, caprolactone modified dipentaerythritol penta(meth) ... Examples of the copolymer include lactone-modified dipentaerythritol hexa(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tetra(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, and ethoxylated glycerin triacrylate. These tri- or higher functional monomers may be used alone or in combination of two or more.

[0034] Among the above, it is preferable to contain at least one of a monomer having a hydroxyl group and a monomer having a morpholine structure, from the viewpoint of increasing the elongation of the coating film and improving the processability. Examples of monomers having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-phenoxy-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, glycerin mono(meth)acrylate, 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, and hydroxypivalic acid-modified neopentyl glycol di(meth)acrylate. Examples of the monomer having a morpholine structure include acryloylmorpholine.

[0035] The content of component (C) is preferably 5 to 50 mass% and more preferably 10 to 45 mass% relative to the total mass of components (A), (B), and (C), where the total content of components (A), (B), and (C) is taken as 100 mass%. If the content of component (C) is equal to or greater than the lower limit, the viscosity of the coating agent tends to fall within an appropriate range, and the coatability tends to be good. If the content of component (C) is equal to or less than the upper limit, the hardness of the coating film tends to be higher.

[0036] The total content of components (A), (B), and (C) is preferably 60 to 99.9 mass%, more preferably 70 to 99.5 mass%, and even more preferably 80 to 99 mass%, based on the total mass of the resin composition. When the total content of components (A), (B), and (C) is equal to or greater than the lower limit, good processability is achieved, and when it is equal to or less than the upper limit, good curability can be maintained and coating film formation is facilitated.

[0037] <Ingredient (D)> Component (D) is a photopolymerization initiator (D). Examples of component (D) include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, benzyl dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexane Acetophenones such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer; benzoins such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4 -phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, (4-benzoylbenzyl)trimethylammonium chloride and other benzophenones; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, Thioxanthones such as thionone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one mesochloride; acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide;Examples include oxime esters such as 1,2-octanedione, 1-[4-(phenylthio)phenyl-, 2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime); The component (D) may be used alone or in combination of two or more types.

[0038] In addition, as an auxiliary agent for component (D), for example, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, etc. can also be used in combination. Among these, it is preferable to use benzophenone, benzil dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoin isopropyl ether, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, and 2-hydroxy-2-methyl-1-phenylpropan-1-one.

[0039] The content of component (D) is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the total content of components (A), (B), and (C). When the content of component (D) is at least the lower limit, good curability can be maintained and coating film formation becomes easy, while when the content is at most the upper limit, yellowing of the coating film tends to be suppressed.

[0040] <Solvent> When the resin composition contains a solvent, the solvent may remain in the coating film or the curing components may volatilize during drying. If the solvent remains in the coating film, the solvent may volatilize from the coating film during curing, which may cause cracks or breaks in the coating film, resulting in a poor appearance of the coating film. If the curing components volatilize, this may cause a poor appearance of the coating film or a decrease in hardness. Therefore, the resin composition of the present invention is substantially free of solvent. Here, "substantially no solvent" means that no solvent is actively blended except for unintentional inclusion, and specifically, the solvent content relative to the total mass of the resin composition is 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0.1% by mass or less, relative to the total mass of the resin composition.

[0041] Examples of the solvent include alcohols such as methanol, ethanol, propanol, n-butanol, and i-butanol; ketones such as acetone, methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; cellosolves such as ethyl cellosolve; aromatics such as toluene and xylene; glycol ethers such as propylene glycol monomethyl ether; acetate esters such as methyl acetate, ethyl acetate, and butyl acetate; and diluting solvents such as diacetone alcohol.

[0042] <Optional ingredients> The resin composition of the present invention may further contain components other than component (A), component (B), component (C), component (D) and the solvent (hereinafter also referred to as "optional components") as necessary, as long as the effects of the present invention are not impaired. Examples of optional components include ethylenically unsaturated compounds and ethylenically unsaturated oligomers other than component (C), surface conditioners, leveling agents, polymerization inhibitors, oils, antioxidants, flame retardants, antistatic agents, fillers, stabilizers, reinforcing agents, matting agents, abrasives, organic fine particles, and inorganic particles. The optional components may be used alone or in combination of two or more.

[0043] As the leveling agent, any known leveling agent can be used as long as it has the effect of imparting wettability to the substrate and reducing the surface tension of the coating liquid, and examples thereof include silicone-modified resins, fluorine-modified resins, and alkyl-modified resins. Examples of the polymerization inhibitor include p-benzoquinone, naphthoquinone, toluquinone, 2,5-diphenyl-p-benzoquinone, hydroquinone, 2,5-di-t-butylhydroquinone, methylhydroquinone, hydroquinone monomethyl ether, mono-t-butylhydroquinone, pt-butylcatechol, and 2,6-di-t-butylcresol.

[0044] <Viscosity> The viscosity of the resin composition of the present invention at 25° C. is preferably 50 to 20,000 mPa·s, more preferably 100 to 10,000 mPa·s, and even more preferably 150 to 7,000 mPa·s. When the viscosity of the resin composition at 25° C. is within the above range, the coatability during coating film formation tends to be improved. The viscosity of the resin composition can be measured using an E-type viscometer.

[0045] <Manufacturing method> The resin composition of the present invention can be obtained by mixing component (A), component (B), component (C), and component (D), and, if necessary, optional components. The method for mixing the components is not particularly limited, and the components can be mixed by various methods.

[0046] <Action and effect> The resin composition of the present invention described above contains the above-mentioned components (A), (B), (C), and (D), and has a solvent content of 1 mass% or less. Therefore, when a coating film is formed on a substrate such as a metal plate, the coating film has a good appearance, excellent adhesion to the substrate, high surface hardness, and excellent flexibility.

[0047] <Application> The resin composition of the present invention can be used as a coating agent such as a topcoat agent or an undercoat agent for various substrates, an adhesive, etc. In particular, the resin composition of the present invention is effectively used as a coating agent for forming a coating film. The resin composition of the present invention is applied to a substrate (or, in the case where the resin composition is diluted with an organic solvent, further dried), and then cured by irradiating it with active energy rays. The coating agent containing the resin composition of the present invention will be described below.

[0048] [Coating agent] The coating agent of the present invention contains the above-mentioned resin composition of the present invention. The coating agent of the present invention may consist of only the resin composition, or may further contain, in addition to the resin composition, components other than the resin composition (hereinafter also referred to as "other components"), as necessary. Other components include organic solvents. Examples of the organic solvent include the solvents exemplified above in the description of the resin composition of the present invention. When the coating agent contains an organic solvent, the content of the resin composition is preferably 3 to 90 mass %, more preferably 5 to 60 mass %, relative to the total mass of the coating agent, and the content of the organic solvent is preferably 10 to 97 mass %, more preferably 40 to 95 mass %, relative to the total mass of the coating agent. Furthermore, other components such as monomers, oligomers, polymerization initiators, etc. may be blended into the coating agent as long as the effects of the present invention are not impaired.

[0049] The coating agent of the present invention is applied to various substrates and then cured by irradiating with active energy rays. Examples of substrates to which the coating agent of the present invention can be applied include metal substrates (aluminum, copper, iron, SUS, zinc, magnesium, alloys thereof, metal vapor deposition films, etc.); plastic substrates such as polyolefin resins, polyester resins, polycarbonate resins, acrylic resins, acrylonitrile butadiene styrene copolymers (ABS), polystyrene resins, etc., and molded products thereof (films, sheets, cups, etc.); composite substrates thereof; composite substrates in which glass fibers or inorganic materials are mixed with metal or plastic substrates; and substrates in which a primer layer is provided on a substrate such as glass.

[0050] Examples of methods for applying the coating agent of the present invention include wet coating methods such as spraying, showering, dipping, dispenser, roll, spin, screen printing, inkjet printing, etc. The coating agent is usually applied to a substrate under room temperature conditions.

[0051] When the coating agent contains an organic solvent, it is preferable to dry the coating agent applied to the substrate before curing the coating agent by irradiation with active energy rays. The drying temperature is preferably 40 to 120°C, more preferably 50 to 100°C. The drying time is preferably 1 to 20 minutes, more preferably 2 to 10 minutes.

[0052] Examples of active energy rays used to cure a coating agent applied to a substrate 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, as well as electron beams, proton beams, and neutron beams. Among these, curing by ultraviolet irradiation is advantageous in terms of curing speed, ease of availability of irradiation equipment, cost, etc. Note that when electron beam irradiation is used, curing can occur without using a photopolymerization initiator.

[0053] When curing a coating agent by ultraviolet irradiation, for example, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a chemical lamp, an electrodeless discharge lamp, an LED lamp, or the like that emits light in the wavelength range of 150 to 450 nm is used, and the irradiation intensity is usually 30 to 3,000 mJ / cm. 2 (Preferably 100 to 1500 mJ / cm 2 ) ultraviolet light. After the ultraviolet irradiation, heating may be carried out as necessary to ensure complete curing.

[0054] The coating film thickness (film thickness of the coating film after curing) may be any thickness, and in consideration of light transmission so that the photopolymerization initiator reacts uniformly as an ultraviolet-curable coating film, the thickness is usually 1 to 200 μm, preferably 3 to 100 μm, and particularly preferably 5 to 50 μm.

[0055] The coating agent of the present invention as described above contains the resin composition of the present invention, and therefore when a coating film is formed on a substrate such as a metal plate, it is possible to obtain a coating film that has a good appearance, excellent adhesion to the substrate, high surface hardness, and excellent flexibility. The coating agent of the present invention is particularly useful as a coating agent for pre-coating metals. The coating agent for precoated metal will be described below. The coating agent for precoated metal will also be referred to as "coating agent for precoated metal."

[0056] <Coating agent for pre-coated metal> When producing a precoated metal using the coating agent for precoat metal of the present invention, it is preferable to use the coating agent for precoat metal of the present invention as a top clear layer, for example, and obtain the precoated metal as follows. Specifically, first, a base coating is applied to the surface of a plate-shaped or coil-shaped metal substrate (galvanized steel plate, cold-rolled steel plate, aluminum plate, etc.), and the surface is baked for a short time of 50 to 120 seconds at a maximum plate temperature of approximately 200 to 250°C to form a base layer on the metal substrate. The surface of the metal substrate may be subjected to various surface treatments such as degreasing, chromate-based surface treatment, and phosphate-based surface treatment, as needed, or may be coated with various primers (undercoats) such as epoxy-based primers and polyester-based primers. Examples of the base paint include an aminoplast resin-containing polyester resin paint, a blocked polyisocyanate-containing polyester resin paint, etc. The base paint may contain a luster pigment such as a color pigment, aluminum flake, or pearl pigment, for the purpose of enhancing the design of the resulting pre-coated metal. The base coating material is preferably applied to the surface of the metal substrate using a continuous coating means such as a reverse or natural roll coater or flow coater so that the dry film thickness is approximately 10 to 30 μm, preferably 15 to 25 μm.

[0057] After forming the base layer, the precoat metal coating agent of the present invention is applied by, for example, the above-mentioned coating method, and then irradiated with active energy rays to produce a precoat metal. If the precoat metal coating agent contains an organic solvent, it is preferable to volatilize the organic solvent in the precoat metal coating agent by heating at 50 to 100°C before irradiating with active energy rays.

[0058] By using the coating agent for precoat metal of the present invention, it is possible to form a top clear layer that has a good appearance, excellent adhesion to the substrate, high surface hardness, and excellent flexibility. Depending on the application, the precoat metal coating agent of the present invention may be applied on an undercoat layer formed by applying an undercoat paint, followed by irradiation with active energy rays to form a coating film. Alternatively, the precoat metal coating agent of the present invention may be applied directly to the surface of a surface-treated metal substrate, followed by irradiation with active energy rays to form a coating film. [Example]

[0059] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0060] [Raw materials used] The compounds shown below were used as raw materials. A-1: (meth)acrylic polymer obtained by copolymerizing methyl methacrylate (MMA) and methacrylic acid (MAA) in a mass ratio (MMA:MAA) of 98.5:1.5 (manufactured by Mitsubishi Chemical Corporation, trade name "Dianal BR-87", weight average molecular weight: 25,000, glass transition point: 105°C). A-2: (Meth)acrylic polymer obtained by copolymerizing methyl methacrylate (MMA) and methacrylic acid (MAA) in a mass ratio (MMA:MAA) of 88.7:11.3 (manufactured by Mitsubishi Chemical Corporation, trade name "Dianal MB-7948", weight average molecular weight: 25,000, glass transition point: 126°C). B-1: Urethane (meth)acrylate (manufactured by Daicel-Allnex Corporation, trade name "Ebecryl 4858", weight average molecular weight: 450, number of (meth)acryloyl groups: 2, (meth)acryloyl group equivalent: 225). B-2: Urethane (meth)acrylate (manufactured by Mitsubishi Chemical Corporation, product name "Shikou UV-6630B", weight average molecular weight: 3000, number of (meth)acryloyl groups: 2, (meth)acryloyl group equivalent: 1500). B-3: Urethane (meth)acrylate (manufactured by Mitsubishi Chemical Corporation, product name "Shikou UV-7600B", weight average molecular weight: 1400, number of (meth)acryloyl groups: 6, (meth)acryloyl group equivalent: 233). C-1: 4-Hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd., trade name "4-HBA"). C-2: Acryloylmorpholine (manufactured by KJ Chemicals Co., Ltd., trade name "ACMO"). D-1: 1-Hydroxycyclohexyl phenyl ketone (manufactured by IGM resin, trade name "Omnirad184"). BYK-333: Leveling agent, polyether-modified polydimethylsiloxane (manufactured by BYK Japan Co., Ltd., product name "BYK-333").

[0061] [Example 1] A resin composition was obtained by mixing and dissolving 8 parts by weight of A-1 as component (A), 60 parts by weight of B-1 as component (B), 12 parts by weight of C-1 and 20 parts by weight of C-2 as component (C), 4 parts by weight of D-1 as component (D), and 0.1 part by weight of BYK-333 as an optional component. The viscosity of the resulting resin composition at 25°C was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TVE-20H") and was found to be 3600 mPa s. Test pieces were prepared using the resin compositions obtained by the methods described below, and the coating appearance, adhesion to substrates, surface hardness, and flexibility were evaluated by the methods described below. The results are shown in Table 1.

[0062] <Creating test pieces> The resin composition was applied to a melamine resin-coated steel plate (steel plate thickness: approximately 0.5 mm) as a substrate so that the film thickness was 20 μm. Then, using one 80 W high-pressure mercury lamp, the coating was irradiated with ultraviolet light (cumulative irradiation dose: 500 mJ / cm) for one pass at a conveyor speed of 1.7 m / min from a height of 18 cm. 2 ) was carried out to prepare test pieces each having a coating film formed on a substrate.

[0063] <Evaluation method> (Evaluation of coating appearance) The coating film on the test piece was visually observed, and the appearance of the coating film was evaluated according to the following evaluation criteria. ◯: The surface is smooth and highly glossy. ×: The surface is uneven and not smooth.

[0064] (Evaluation of adhesion to substrate) A cross-cut peel test was carried out on the coating film of the test piece in accordance with JIS K 5400. Specifically, 100 1 mm wide cross-cuts were cut on the coating film with a cutter, adhesive tape was applied to the cross-cuts, and the adhesive tape was quickly peeled off. The number of cross-cuts remaining on the substrate was counted and the adhesion to the substrate was evaluated according to the following criteria. ◯: The number of grids remaining on the substrate is 91 to 100. ×: The number of grids remaining on the substrate is 90 or less.

[0065] (Evaluation of surface hardness) The pencil hardness of the coating film on the test piece was measured in accordance with JIS K 5600-5-4.

[0066] (Evaluation of flexibility) The test piece was bent 180° with the coating side facing outward and several 0.5 mm thick steel plates sandwiched inside the bent portion. The bent portion was visually inspected for cracks or peeling of the coating, and the flexibility was evaluated according to the following criteria. ⊚: When the test piece was bent 180° between two steel plates, no cracking or peeling of the coating was observed. ◯: When the test piece was bent 180° with three steel plates sandwiched between it, no cracking or peeling of the coating was observed. ×: When the test piece is bent 180° with four or more steel plates sandwiched between it, no cracks or peeling of the coating film are observed. In the table, the "Test Results" indicate the number of steel plates when no cracking or peeling of the coating was observed, with "2T" meaning two steel plates, "3T" meaning three steel plates, and ">5T" meaning five or more steel plates.

[0067] [Examples 2 to 5, Comparative Examples 1 to 3] Resin compositions were prepared in the same manner as in Example 1, except that the types and amounts of each component were changed to obtain the blending compositions shown in Table 1. Test pieces were then prepared and various evaluations were carried out. The results are shown in Table 1. A blank space in the table means that the component was not blended (amount blended: 0 parts by mass).

[0068] [Table 1]

[0069] As is clear from the results in Table 1, the coating films formed from the resin compositions obtained in each example had good coating film appearance, excellent adhesion to the substrate, high surface hardness, and excellent flexibility. On the other hand, the coating films formed from the resin compositions of Comparative Examples 1 to 3, which did not contain component (A), were insufficient in one or more of the coating film appearance, adhesion to the substrate, surface hardness and flexibility. [Industrial Applicability]

[0070] The active energy ray-curable resin composition of the present invention has a good coating film appearance when formed on a substrate made of metal or the like, has excellent adhesion to the substrate, has high surface hardness of the coating film, and further has excellent flexibility of the coating film, and is therefore useful as various coating agents, particularly as a coating agent for outermost surfaces, a coating agent for metal steel sheets, and a coating agent for pre-coated metals.

Claims

1. The composition comprises a (meth)acrylic polymer (A) (excluding amide group-containing acrylic polymers derived from acrylamide and polar group-containing (meth)acrylate), a urethane (meth)acrylate (B) having 1 to 4 (meth)acryloyl groups, a monomer (C) having one or more (meth)acryloyl groups, and a photopolymerization initiator (D), the (meth)acrylic polymer (A) has a weight average molecular weight of 5,000 to 100,000; the urethane (meth)acrylate (B) has a (meth)acryloyl group equivalent of 100 to 2500; When the total content of the (meth)acrylic polymer (A), the urethane (meth)acrylate (B), and the monomer (C) is taken as 100% by mass, the content of the (meth)acrylic polymer (A) is 1 to 15% by mass, the content of the urethane (meth)acrylate (B) is 20 to 80% by mass, and the content of the monomer (C) is 5 to 50% by mass, An active energy ray-curable resin composition, wherein the content of a solvent relative to the total mass of the active energy ray-curable resin composition is 1 mass % or less.

2. 2. The active energy ray-curable resin composition according to claim 1, wherein the (meth)acrylic polymer (A) has a glass transition temperature of 30 to 150°C.

3. The active energy ray-curable resin composition according to claim 1 or 2, wherein the monomer (C) comprises at least one of a monomer having a hydroxyl group and a monomer having a morpholine structure.

4. A coating agent comprising the active energy ray-curable resin composition according to any one of claims 1 to 3.

5. The coating agent according to claim 4, which is for pre-coating metal.

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