(Meth)acrylic acid copolymer, coating composition, coated article, and method for forming multilayer coating film

Abstract

The present invention provides a coating composition that can effectively perform a repair operation on a coating film after coating, a (meth)acrylic copolymer suitable for obtaining the coating composition, and a coating article and a method for forming a multilayer coating film using the coating composition. A (meth)acrylic copolymer is a (meth)acrylic copolymer comprising a structural unit derived from a macromonomer (a) and a structural unit derived from a vinyl monomer (b), wherein the hydroxyl value of the (meth)acrylic copolymer is 120 mgKOH / g or more and 260 mgKOH / g or less, and the content of the structural unit having a primary hydroxyl group in the (meth)acrylic copolymer is 30 parts by mass or less relative to 100 parts by mass of the structural unit derived from the macromonomer (a) and the structural unit derived from the vinyl monomer (b).

Description

Technical Field

[0001] The present invention relates to a (meth)acrylic copolymer, a coating composition, a coated article, and a method for forming a multilayer coating film.

[0002] This application claims priority based on Japanese Patent Application No. 2016-224089, filed in Japan on November 17, 2016, the contents of which are incorporated herein by reference. Background Art

[0003] In the painting of automobiles, the following operations are performed: after painting with a base paint mixed with a colorant, a clear paint containing a film-forming resin and a curing agent is applied and heated to cure. Examples of the film-forming resin include copolymers of a (meth)acrylic monomer having a hydroxyl group and other vinyl monomers.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-40390 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, in the case of acrylic paint using the above-mentioned acrylic resin as the film-forming resin, it is difficult to efficiently perform repair work by polishing with sandpaper or the like after coating.

[0009] In order to improve the efficiency of the repair work after painting, it is considered to reduce the amount of curing agent to reduce the hardness of the coating. If the hardness of the coating is reduced, grinding becomes easier and the work efficiency is improved. However, when the hardness of the coating is low, it becomes easy to be scratched by sand, car washing machine brushes, etc.

[0010] The present invention is made in view of the above situation, and its purpose is to provide a coating composition that can effectively perform a repair operation on the coating film after painting, a (meth)acrylic copolymer suitable for obtaining the coating composition, and a coated object and a method for forming a multi-layer coating film using the coating composition.

[0011] Means used to solve problems

[0012] The present invention has the following aspects.

[0013] [1] A (meth)acrylic copolymer comprising a structural unit derived from a macromonomer (a) and a structural unit derived from a vinyl monomer (b), wherein the (meth)acrylic copolymer has a hydroxyl value of 120 mgKOH / g or more and 260 mgKOH / g or less, and the content of the structural unit having a primary hydroxyl group in the (meth)acrylic copolymer is 30 parts by mass or less relative to 100 parts by mass of the structural unit derived from the macromonomer (a) and the structural unit derived from the vinyl monomer (b).

[0014] [2] The (meth)acrylic copolymer according to [1], wherein the content of the structural unit having at least one of a secondary hydroxyl group and a tertiary hydroxyl group is 15 parts by mass or more and 60 parts by mass or less based on 100 parts by mass of the structural unit of the (meth)acrylic copolymer.

[0015] [3] A (meth)acrylic acid-based copolymer comprising a structural unit derived from a macromonomer (a) and a structural unit derived from a vinyl monomer (b), wherein at least one of the structural unit derived from the macromonomer (a) and the structural unit derived from the vinyl monomer (b) has a hydroxyl group, and the gel fraction after one day of coating is 70% or less and the gel fraction after eight days of coating is 80% or more.

[0016] [4] A (meth)acrylic copolymer comprising a structural unit derived from a macromonomer (a) and a structural unit derived from a vinyl monomer (b), wherein at least one of the structural unit derived from the macromonomer (a) and the structural unit derived from the vinyl monomer (b) has a hydroxyl group, and the relationship between the gel fraction after 1 day of coating and the gel fraction after 8 days of coating is represented by the following formula (I).

[0017] 100 ≥ (gel fraction 8 days after coating) - (gel fraction 1 day after coating) ≥ 40… (I)

[0018] [5] The (meth)acrylic copolymer according to any one of [1] to [4], wherein the number average molecular weight of the macromonomer (a) is 500 or more and 100,000 or less.

[0019] [6] The (meth)acrylic copolymer according to any one of [1] to [5], wherein the macromonomer (a) has a radical polymerizable group and has two or more structural units represented by the following formula (a′).

[0020] [Chemistry 1]

[0021]

[0022] [7] A coating composition comprising the (meth)acrylic copolymer according to any one of [1] to [6].

[0023] [8] The coating composition according to [7], wherein the content of the (meth)acrylic copolymer is 30% by mass or more relative to the resin solid content of the coating composition.

[0024] [9] The coating composition according to [7] or [8], further comprising a curing agent.

[0025]

[10] The coating composition according to any one of [7] to [9], wherein the Martens hardness of the coating film one day after coating is 10 or less, and the Martens hardness of the coating film eight days after coating is 100 or more.

[0026]

[11] A coated article coated with the coating composition according to any one of [7] to

[10] above.

[0027]

[12] A method for forming a multilayer coating film, comprising applying a first colored base coating on a cured coating film of an electrodeposition coating to form a first colored base coating film, applying a second colored base coating on the first colored base coating to form a second colored base coating film, then preheating the first colored base coating film and the second colored base coating film, applying a clear coating on the second colored base coating film to form a clear coating film, and simultaneously heating and curing the three layers of coating films to form a multilayer coating film.

[0028] As the clear coating material, the coating composition described in any one of [7] to

[10] is used.

[0029] Effects of the Invention

[0030] The present invention can provide a coating composition capable of efficiently repairing a coating film after coating, a (meth)acrylic copolymer suitable for obtaining the coating composition, and a coated article and a method for forming a multilayer coating film using the coating composition. DETAILED DESCRIPTION

[0031] The following definitions of terms apply throughout the specification and claims.

[0032] The "(meth)acrylic copolymer" refers to a copolymer in which at least a part of the structural units are structural units derived from a (meth)acrylic monomer. The (meth)acrylic copolymer may further have structural units derived from a monomer other than the (meth)acrylic monomer (for example, a vinyl monomer such as styrene).

[0033] The "structural unit" is a structural unit derived from a monomer formed by polymerizing the monomer.

[0034] The "monomer" refers to a polymerizable compound (polymerizable monomer).

[0035] The "vinyl monomer" refers to a monomer having an ethylenically unsaturated bond (polymerizable carbon-carbon double bond).

[0036] The "(meth)acrylic monomer" refers to a monomer having a (meth)acryloyl group.

[0037] “(Meth)acryloyl” is a general term for acryloyl and methacryloyl. “(Meth)acrylate” is a general term for acrylate and methacrylate. “(Meth)acrylic acid” is a general term for acrylic acid and methacrylic acid. “(Meth)acrylonitrile” is a general term for acrylonitrile and methacrylonitrile. “(Meth)acrylamide” is a general term for acrylamide and methacrylamide.

[0038] [(Meth)acrylic acid copolymer]

[0039] The (meth)acrylic copolymer of the present invention (hereinafter also referred to as “copolymer (A)”) contains a structural unit derived from a macromonomer (a) and a structural unit derived from a vinyl monomer (b).

[0040] The copolymer (A) has a graft copolymer or block copolymer structure in which a polymer chain derived from the macromonomer (a) and a polymer chain composed of a structural unit derived from the vinyl monomer (b) are bonded.

[0041] <Structural Unit Derived from Macromonomer (a)>

[0042] The macromonomer (a) is a compound having two or more structural units derived from a radical polymerizable group and a monomer having the radical polymerizable group (hereinafter also referred to as "monomer (a1)"). The two or more structural units of the macromonomer (a) may be the same or different.

[0043] As the radical polymerizable group possessed by the macromonomer (a), a group having an ethylenically unsaturated bond is preferred. Examples of the group having an ethylenically unsaturated bond include CH2=C(COOR)-CH2-, (meth)acryloyl, 2-(hydroxymethyl)acryloyl, and vinyl.

[0044] Here, R represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alicyclic group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group.

[0045] As the unsubstituted alkyl group in R, for example, a branched or straight chain alkyl group having 1 to 20 carbon atoms is mentioned. Specific examples of the branched or straight chain alkyl group having 1 to 20 carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, isobutyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, isooctyl, nonyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl. In addition, an alkyl group having 20 or more carbon atoms can also be used.

[0046] The unsubstituted alicyclic group in R may be a monocyclic group or a polycyclic group, and examples thereof include alicyclic groups having 3 to 20 carbon atoms. The alicyclic group is preferably a saturated alicyclic group, and specific examples thereof include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, bicyclo[2.2.1]heptyl, cyclooctyl, and adamantyl.

[0047] Examples of the unsubstituted aryl group in R include aryl groups having 6 to 18 carbon atoms. Specific examples of the aryl group having 6 to 18 carbon atoms include phenyl and naphthyl.

[0048] Examples of the unsubstituted heterocyclic group in R include heterocyclic groups having 5 to 18 carbon atoms. Specific examples of the heterocyclic group having 5 to 18 carbon atoms include oxygen-containing heterocyclic groups such as γ-butyrolactone and ε-caprolactone, nitrogen-containing heterocyclic groups such as pyridyl, carbazolyl, pyrrolidinyl, and pyrrolidonyl, and morpholino.

[0049] Examples of the substituent in R (the substituent in each of the alkyl group having a substituent, the alicyclic group having a substituent, the aryl group having a substituent, and the heterocyclic group having a substituent) include alkyl groups (excluding the case where R is an alkyl group having a substituent), aryl groups, -COOR 11 , cyano, -OR 12 、-NR 13 R 14 、-CONR 15 R 16 , a halogen atom, an allyl group, an epoxy group, a siloxy group and a hydrophilic or ionic group.

[0050] Here, R 11 ~R 16 Each independently represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, or an unsubstituted or substituted aryl group. These groups are the same as those mentioned above.

[0051] Examples of the alkyl group and the aryl group in the substituent include the same groups as the unsubstituted alkyl group and the unsubstituted aryl group mentioned above, respectively.

[0052] As -COOR in the above substituent 11 R 11 , preferably a hydrogen atom or an unsubstituted alkyl group. 11 A carboxyl group or an alkoxycarbonyl group is preferred. Examples of the alkoxycarbonyl group include a methoxycarbonyl group.

[0053] As -OR in the above substituent 12 R 12 , preferably a hydrogen atom or an unsubstituted alkyl group. That is, -OR 12 A hydroxyl group or an alkoxy group is preferred. Examples of the alkoxy group include alkoxy groups having 1 to 12 carbon atoms, and a specific example thereof includes a methoxy group.

[0054] As -NR in the above substituent 13 R 14 , for example, amino, monomethylamino, dimethylamino, etc. are mentioned.

[0055] As -CONR in the above substituent 15 R 16 For example, there are carbamoyl (-CONH2), N-methylcarbamoyl (-CONHCH3), N,N-dimethylcarbamoyl (dimethylamide: -CON(CH3)2), and the like.

[0056] Examples of the halogen atom in the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0057] Examples of the hydrophilic or ionic substituents include alkali salts of carboxyl groups or alkali salts of sulfonyl groups, poly(alkylene oxide) groups such as polyethylene oxide groups and polypropylene oxide groups, and cationic substituents such as quaternary ammonium bases.

[0058] R is preferably an unsubstituted or substituted alkyl group or an unsubstituted or substituted alicyclic group, and more preferably an unsubstituted alkyl group or an unsubstituted or substituted alicyclic group.

[0059] Among the above, based on the ease of availability, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, hexyl, 2-ethylhexyl, heptyl and octyl are preferred, and methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclopropyl, cyclobutyl, isobornyl and adamantyl are preferred.

[0060] As the radical polymerizable group possessed by the monomer (a1), a group having an ethylenically unsaturated bond is preferred, similarly to the radical polymerizable group possessed by the macromonomer (a).

[0061] As the monomer (a1), various monomers can be used, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, hexadecyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, tert-butyl (meth)acrylate, butyl (meth)acrylate, iso ... (meth)acrylates containing hydrocarbon groups such as cyclohexyl (meth)acrylate, tetrahydrofuran (meth)acrylate, isobornyl (meth)acrylate, 3,5,5-trimethylcyclohexyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, terpene acrylate and its derivatives, hydrogenated rosin acrylate and its derivatives, and docosyl (meth)acrylate; (meth)acrylates containing hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and glycerol (meth)acrylate;

[0062] Carboxyl group-containing vinyl monomers such as (meth)acrylic acid, 2-(meth)acryloxyethylhexahydrophthalic acid, 2-(meth)acryloxypropylhexahydrophthalic acid, 2-(meth)acryloxyethylphthalic acid, 2-(meth)acryloxypropylphthalic acid, 2-(meth)acryloxyethylmaleic acid, 2-(meth)acryloxypropylmaleic acid, 2-(meth)acryloxyethylsuccinic acid, 2-(meth)acryloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, monomethyl maleate, monoethyl maleate, monooctyl maleate, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, monooctyl itaconate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monooctyl fumarate, and monoethyl citraconate;

[0063] Vinyl monomers containing anhydride groups, such as maleic anhydride and itaconic anhydride;

[0064] Unsaturated dicarboxylic acid diester monomers such as dimethyl maleate, dibutyl maleate, dimethyl fumarate, dibutyl fumarate, dibutyl itaconate, and diperfluorocyclohexyl fumarate;

[0065] Epoxy-group-containing vinyl monomers such as glycidyl (meth)acrylate, α-glycidyl (meth)acrylate, and 3,4-epoxybutyl (meth)acrylate;

[0066] (meth)acrylate-based vinyl monomers containing an amino group such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate;

[0067] (Meth) acrylamide, N-tert-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-isopropyl acrylamide, hydroxyethyl acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide, maleic acid amide, maleimide and other vinyl monomers containing an amide group;

[0068] Vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, (meth)acrylonitrile, vinyl chloride, vinyl acetate, vinyl propionate, etc.;

[0069] Multifunctional vinyl monomers such as divinylbenzene, ethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, triallyl cyanurate, diallyl maleate, polypropylene glycol diallyl ether, and N,N'-methylenebis(meth)acrylamide;

[0070] Acryloylmorpholine, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, n-butoxyethyl (meth)acrylate, isobutoxyethyl (meth)acrylate, tert-butoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, nonylphenoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, acetoxyethyl (meth)acrylate, "Placcell FM" (a caprolactone-added monomer, trade name, manufactured by Daicel Chemical Co., Ltd.), "Brenma PME-100" (a methoxypolyethylene glycol methacrylate (a substance having two ethylene glycol chains, trade name, manufactured by NOF Corporation), "Brenma PME-200" (a methoxypolyethylene glycol methacrylate, manufactured by NOF Corporation), acrylate (a substance with 4 ethylene glycol chains), trade name), "Brenma PME-400" (a substance with 9 ethylene glycol chains, manufactured by NOF Corporation), "Brenma 50POEP-800B" (a substance with 8 ethylene glycol chains and 6 propylene glycol chains, manufactured by NOF Corporation), trade name) and "Brenma 20ANEP-600" (trade name of nonylphenoxy (ethylene glycol-polypropylene glycol) monoacrylate manufactured by NOF Corporation), "Brenma AME-100" (trade name of NOF Corporation), "Brenma AME-200" (trade name of NOF Corporation), and "Brenma 50AOEP-800B" (trade name of NOF Corporation) Silaplane FM-0711 (trade name of JNC Corporation), Silaplane FM-0721 (trade name of JNC Corporation), Silaplane FM-0725 (trade name of JNC Corporation), Silaplane TM-0701 (trade name of JNC Corporation), Silaplane Silane coupling agent-containing monomers such as TM-0701T (manufactured by JNC Corporation, trade name), X-22-174DX (manufactured by Shin-Etsu Chemical Co., Ltd., trade name), X-22-2426 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name), X-22-2475 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name), 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane;

[0071] Trimethylsilyl(meth)acrylate, triethylsilyl(meth)acrylate, tri-n-propylsilyl(meth)acrylate, tri-n-butylsilyl(meth)acrylate, tri-n-pentylsilyl(meth)acrylate, tri-n-hexylsilyl(meth)acrylate, tri-n-octylsilyl(meth)acrylate, tri-n-dodecylsilyl(meth)acrylate, triphenylsilyl(meth)acrylate, tri-p-methylphenylsilyl(meth)acrylate, tribenzylsilyl(meth)acrylate, triisopropylsilyl(meth)acrylate, triisobutylsilyl(meth)acrylate, tri-sec-butylsilyl(meth)acrylate, tri-2-methylisopropylsilyl(meth)acrylate, tri-tert-butylsilyl(meth)acrylate, ethyldimethylsilyl(meth)acrylate, n-butyldimethylsilyl(meth)acrylate ) acrylate, diisopropyl n-butylsilyl (meth) acrylate, n-octyl di-n-butylsilyl (meth) acrylate, diisopropyl stearyl silyl (meth) acrylate, dicyclohexylphenyl silyl (meth) acrylate, tert-butyl diphenyl silyl (meth) acrylate, lauryl diphenyl silyl (meth) acrylate, triisopropyl silyl methyl maleate, triisopropyl silyl amyl maleate ... Organosilyl-containing monomers other than silane coupling agent-containing monomers such as n-butylsilyl-n-butylmaleate, tert-butyldiphenylsilylmethylmaleate, tert-butyldiphenylsilyl-n-butylmaleate, triisopropylsilylmethylfumarate, triisopropylsilylpentylfumarate, tri-n-butylsilyltri-n-butylfumarate, tert-butyldiphenylsilylmethylfumarate, and tert-butyldiphenylsilyl-n-butylfumarate;

[0072] Halogenated olefins such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, and chlorotrifluoroethylene, (meth)acrylate-2-isocyanatoethyl-2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluorophenyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 3-(perfluorobutyl)-2-hydroxypropyl (meth)acrylate, 2-(perfluorohexyl)ethyl (meth)acrylate, 3-perfluorohexyl-2-hydroxypropyl (meth)acrylate, 3-(perfluoro-3-methylbutyl)-2-hydroxypropyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,5 Fluorine-containing monomers such as H-octafluoropentyl (methyl) methacrylate, 1H,1H,2H,2H-tridecafluorooctyl (meth) acrylate, 1H-1-(trifluoromethyl)trifluoroethyl (meth) acrylate, 1H,1H,3H-hexafluorobutyl (meth) acrylate, and 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl (meth) acrylate (excluding halogenated olefins), monomers having an acetal structure such as 1-butoxyethyl (meth) acrylate, 1-(2-ethylhexyloxy)ethyl (meth) acrylate, 1-(cyclohexyloxy)ethyl methacrylate, and 2-tetrahydropyranyl (meth) acrylate, 4-methacryloyloxybenzophenone, and 2-isocyanatoethyl (meth) acrylate. These monomers may be used alone or in combination of two or more.

[0073] It is preferred that at least a part of the monomer (a1) is a (meth)acrylic acid-based monomer.

[0074] When the structural unit derived from the vinyl monomer (b) does not include a structural unit having a hydroxyl group, the structural unit derived from the macromonomer (a) includes a structural unit having a hydroxyl group. That is, the monomer (a1) includes a monomer having a hydroxyl group.

[0075] Examples of the monomer having a hydroxyl group include the same monomers as exemplified above.

[0076] When the structural unit derived from the vinyl monomer (b) includes a structural unit having a hydroxyl group, the monomer (a1) may or may not include a monomer having a hydroxyl group.

[0077] As the structural unit derived from the monomer (a1), a structural unit represented by the following formula (a') (hereinafter also referred to as "structural unit (a')") is preferred.

[0078] [Chemistry 2]

[0079]

[0080] In the formula, R1 represents a hydrogen atom, a methyl group or CH2OH, R 2 Represents OR 3 , halogen atoms, COR 4 、COOR 5 、CN、CONR 6 R 7 or R 8 , R 3 ~R 7 Each independently represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, an unsubstituted or substituted aryl group, an unsubstituted or substituted heteroaryl group, an unsubstituted or substituted non-aromatic heterocyclic group, an unsubstituted or substituted aralkyl group, an unsubstituted or substituted alkaryl group, or an unsubstituted or substituted organosilyl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group (COOH), a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group (SO3H) and a halogen atom, and R 8 represents an unsubstituted or substituted aryl group, or an unsubstituted or substituted heteroaryl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group, a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group, an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted olefin group and a halogen atom.

[0081] R 3 ~R 7 Examples of the unsubstituted alkyl group, unsubstituted alicyclic group and unsubstituted aryl group in are the same as the unsubstituted alkyl group, unsubstituted alicyclic group and unsubstituted aryl group in R described above.

[0082] Examples of the unsubstituted heteroaryl group include a pyridyl group and a carbazolyl group.

[0083] Examples of the unsubstituted non-aromatic heterocyclic group include a pyrrolidinyl group and a pyrrolidonyl group.

[0084] Examples of the unsubstituted aralkyl group include a benzyl group and a phenylethyl group.

[0085] Examples of the unsubstituted organosilyl group include -SiR 17 R 18 R 19 (Here R 17 ~R 19Each independently represents an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, or an unsubstituted or substituted aryl group).

[0086] As R 17 ~R 19 Examples of the unsubstituted or substituted alkyl group in include the same ones as those mentioned above, such as methyl, ethyl, propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-dodecyl, stearyl, lauryl, isopropyl, isobutyl, sec-butyl, 2-methylisopropyl, benzyl, etc. Examples of the unsubstituted or substituted alicyclic group include the same ones as those mentioned above, such as cyclohexyl, etc. Examples of the unsubstituted or substituted aryl group include the same ones as those mentioned above, such as phenyl, p-methylphenyl, etc. R 17 ~R 19 They may be the same or different.

[0087] R 3 ~R 7 In the substituents (the substituents in each of the alkyl group having a substituent, the alicyclic group having a substituent, the aryl group having a substituent, the heteroaryl group having a substituent, the non-aromatic heterocyclic group having a substituent, the aralkyl group having a substituent, the alkaryl group having a substituent, and the organosilyl group having a substituent), as the carboxylate group, for example, the above-mentioned -COOR 11 R 11 A group which is an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, or an unsubstituted or substituted aryl group.

[0088] As the alkoxy group, the above-mentioned -OR 12 R 12 A group which is an unsubstituted alkyl group.

[0089] As the secondary amino group, the above-mentioned -NR 13 R 14 R 13 is a hydrogen atom, R 14 A group which is an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, or an unsubstituted or substituted aryl group.

[0090] As the tertiary amino group, the above-mentioned -NR 13 R 14 R 13 and R 14 Each of them is an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, or an unsubstituted or substituted aryl group.

[0091] Examples of the unsubstituted or substituted alkyl group, the unsubstituted or substituted aryl group and the halogen atom include the same groups as mentioned above.

[0092] R 8 The unsubstituted aryl group and the unsubstituted heteroaryl group in are the same as those mentioned above.

[0093] R 8 Among the substituents (the substituents in each of the aryl group having a substituent and the heteroaryl group having a substituent), the carboxylate group, alkoxy group, primary amino group, secondary amino group, tertiary amino group, unsubstituted or substituted alkyl group, unsubstituted or substituted aryl group and halogen atom are the same as those mentioned above.

[0094] Examples of the unsubstituted olefin group include an allyl group and the like.

[0095] As the substituent in the olefin group having a substituent, there are exemplified the following: 8 The substituents in the same group.

[0096] The structural unit (a') is derived from CH2=CR 1 R 2 As a structural unit of CH2=CR 1 R 2 As specific examples, the following substances are given.

[0097] Substituted or unsubstituted alkyl (meth)acrylates [e.g., methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, 1-methyl-2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 3-methyl-3-methoxybutyl (meth)acrylate], substituted or unsubstituted aralkyl (meth)acrylates [e.g., (meth)acrylate (meth)acrylate monomers containing a hydrophobic group such as benzyl (meth)acrylate, m-methoxyphenylethyl (meth)acrylate, p-methoxyphenylethyl (meth)acrylate], substituted or unsubstituted aryl (meth)acrylates [e.g., phenyl (meth)acrylate, m-methoxyphenyl (meth)acrylate, p-methoxyphenyl (meth)acrylate, o-methoxyphenylethyl (meth)acrylate], alicyclic (meth)acrylates [e.g., isobornyl (meth)acrylate, cyclohexyl (meth)acrylate], halogen atom-containing (meth)acrylates [e.g., trifluoroethyl (meth)acrylate, perfluorooctyl (meth)acrylate, perfluorocyclohexyl (meth)acrylate];

[0098] (Meth)acrylate monomers containing an oxyethylene group, such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, and 2-(2-ethylhexyloxy)ethyl (meth)acrylate;

[0099] Hydroxyl-containing (meth)acrylate monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and glycerol (meth)acrylate;

[0100] Terminal alkoxy allylated polyether monomers such as methoxy polyethylene glycol allyl ether, methoxy polypropylene glycol allyl ether, butoxy polyethylene glycol allyl ether, butoxy polypropylene glycol allyl ether, methoxy polyethylene glycol-polypropylene glycol allyl ether, butoxy polyethylene glycol-polypropylene glycol allyl ether, etc.;

[0101] Epoxy-group-containing vinyl monomers such as glycidyl (meth)acrylate, α-glycidyl (meth)acrylate, and 3,4-epoxybutyl (meth)acrylate;

[0102] Vinyl monomers containing primary or secondary amino groups, such as butylaminoethyl (meth)acrylate and (meth)acrylamide;

[0103] A tertiary amino group-containing vinyl monomer such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, dimethylaminobutyl (meth)acrylate, dibutylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylamide, and dimethylaminopropyl (meth)acrylamide;

[0104] Heterocyclic basic monomers such as vinyl pyrrolidone, vinyl pyridine, vinyl carbazole, etc.

[0105] Trimethylsilyl(meth)acrylate, triethylsilyl(meth)acrylate, tri-n-propylsilyl(meth)acrylate, tri-n-butylsilyl(meth)acrylate, tri-n-pentylsilyl(meth)acrylate, tri-n-hexylsilyl(meth)acrylate, tri-n-octylsilyl(meth)acrylate, tri-n-dodecylsilyl(meth)acrylate, triphenylsilyl(meth)acrylate, tri-p-methylphenylsilyl(meth)acrylate, tribenzylsilyl(meth)acrylate, triisopropylsilyl(meth)acrylate, triisobutylsilyl(meth)acrylate, tri-n-hexylsilyl(meth)acrylate, tri-n-octylsilyl(meth)acrylate, tri-n-dodecylsilyl(meth)acrylate, triphenylsilyl(meth)acrylate, tri-p-methylphenylsilyl(meth)acrylate, tribenzylsilyl(meth)acrylate, triisopropylsilyl(meth)acrylate, triisobutylsilyl(meth)acrylate, tri-n-hexylsilyl(meth)acrylate, tri-n-octylsilyl(meth)acrylate, tri-n-dodecylsilyl(meth)acrylate Vinyl monomers containing an organosilyl group such as sec-butylsilyl (meth)acrylate, tri-2-methylisopropylsilyl (meth)acrylate, tri-tert-butylsilyl (meth)acrylate, ethyldimethylsilyl (meth)acrylate, n-butyldimethylsilyl (meth)acrylate, diisopropyl-n-butylsilyl (meth)acrylate, n-octyldi-n-butylsilyl (meth)acrylate, diisopropylstearylsilyl (meth)acrylate, dicyclohexylphenylsilyl (meth)acrylate, tert-butyldiphenylsilyl (meth)acrylate, and lauryldiphenylsilyl (meth)acrylate;

[0106] Carboxyl group-containing ethylenically unsaturated monomers such as methacrylic acid, acrylic acid, vinyl benzoic acid, tetrahydrophthalic acid monohydroxyethyl (meth)acrylate, tetrahydrophthalic acid monohydroxypropyl (meth)acrylate, tetrahydrophthalic acid monohydroxybutyl (meth)acrylate, phthalic acid monohydroxyethyl (meth)acrylate, phthalic acid monohydroxypropyl (meth)acrylate, succinic acid monohydroxyethyl (meth)acrylate, succinic acid monohydroxypropyl (meth)acrylate, maleic acid monohydroxyethyl (meth)acrylate, and maleic acid monohydroxypropyl (meth)acrylate;

[0107] Vinyl monomers containing cyano groups, such as acrylonitrile and methacrylonitrile;

[0108] Vinyl ether monomers such as alkyl vinyl ethers [e.g., ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, 2-ethylhexyl vinyl ether, etc.] and cycloalkyl vinyl ethers [e.g., cyclohexyl vinyl ether, etc.];

[0109] Vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, etc.;

[0110] Aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene, etc.

[0111] Halogenated olefins such as vinyl chloride and vinyl fluoride.

[0112] The macromonomer (a) may further have other structural units other than the structural unit (a'). Examples of other structural units include those derived from the monomer (a1) not belonging to CH2=CR 1 R 2 The structural unit of the monomer.

[0113] Preferred specific examples of other structural units include structural units derived from the following monomers.

[0114] Vinyl monomers containing an organosilyl group such as triisopropylsilyl methyl maleate, triisopropylsilyl amyl maleate, tri-n-butylsilyl n-butyl maleate, tert-butyldiphenylsilyl methyl maleate, tert-butyldiphenylsilyl n-butyl maleate, triisopropylsilyl methyl fumarate, triisopropylsilyl amyl fumarate, tri-n-butylsilyl n-butyl fumarate, tert-butyldiphenylsilyl methyl fumarate, and tert-butyldiphenylsilyl n-butyl fumarate;

[0115] Vinyl monomers containing anhydride groups, such as maleic anhydride and itaconic anhydride;

[0116] Carboxyl-containing ethylenically unsaturated monomers such as butenoic acid, fumaric acid, itaconic acid, maleic acid, citraconic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, monooctyl itaconate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monooctyl fumarate, and monoethyl citraconic acid;

[0117] Unsaturated dicarboxylic acid diester monomers such as dimethyl maleate, dibutyl maleate, dimethyl fumarate, dibutyl fumarate, dibutyl itaconate, and diperfluorocyclohexyl fumarate;

[0118] Halogenated olefins such as vinylidene chloride, vinylidene fluoride, chlorotrifluoroethylene, etc.

[0119] Polyfunctional monomers such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl methacrylate, triallyl cyanurate, diallyl maleate, polypropylene glycol diallyl ether, etc. Monomers obtained by esterification reaction between epoxy group-containing unsaturated monomers and carboxyl group-containing monomers, etc.

[0120] The macromonomer (a) is preferably a macromonomer having a radical polymerizable group introduced at the terminal of a main chain containing two or more structural units (a′), and more preferably a macromonomer represented by the following formula (1).

[0121] [Chemistry 3]

[0122]

[0123] (In the formula, R represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted cycloalkyl group, an unsubstituted or substituted aryl group, or an unsubstituted or substituted heterocyclic group, Q represents a main chain portion containing two or more structural units (a'), and Z represents a terminal group.)

[0124] In the formula (1), R is the same as R in the aforementioned CH2=C(COOR)-CH2-, and the preferred embodiments are also the same.

[0125] The two or more structural units (a') contained in Q may be the same as or different from each other.

[0126] Q may be composed of the structural unit (a') alone, or may further contain other structural units other than the structural unit (a').

[0127] The number of structural units constituting Q can be appropriately set within the range in which the number average molecular weight of the macromonomer (a) is within the above range.

[0128] Examples of Z include a hydrogen atom, a group derived from a radical polymerization initiator, and a radical polymerizable group, similar to the terminal group of a polymer obtained by known radical polymerization.

[0129] As the macromonomer (a), a macromonomer represented by the following formula (2) is particularly preferred.

[0130] [Chemistry 4]

[0131]

[0132] (wherein, R represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted cycloalkyl group, an unsubstituted or substituted aryl group, or an unsubstituted or substituted heterocyclic group, R 21 represents a hydrogen atom or a methyl group, R 22represents an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, an unsubstituted or substituted aryl group, an unsubstituted or substituted heteroaryl group, an unsubstituted or substituted aralkyl group, an unsubstituted or substituted alkaryl group, or an unsubstituted or substituted organosilyl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group, a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group, and a halogen atom, and n represents a natural number greater than 2, and Z represents a terminal group.)

[0133] In formula (2), R and Z are the same as those described above.

[0134] R 22 The groups in COOR 5 R 5 The same as mentioned in .

[0135] n is a natural number of 2 or more. It is preferred that n be within the range of 500 or more and 100,000 or less of the number average molecular weight (Mn) of the macromonomer (a). 21 , R 22 They may be the same or different.

[0136] The number average molecular weight (Mn) of the macromonomer (a) is preferably 500 or more and 100,000 or less, more preferably 800 or more and 30,000 or less, further preferably 900 or more and 10,000 or less, and particularly preferably 1,000 or more and 5,500 or less. When the number average molecular weight of the macromonomer (a) is at least the lower limit of the range, the hardness and water resistance of the coating film are more excellent. When the number average molecular weight of the macromonomer (a) is at most the upper limit of the range, the storage stability of the solution of the copolymer (A) or the coating composition containing the solution is more excellent.

[0137] The number average molecular weight of the macromonomer (a) is measured by gel filtration chromatography (GPC) using polystyrene as a reference resin.

[0138] The glass transition temperature (hereinafter also referred to as "Tga") of the macromonomer (a) is preferably 0°C or higher and 150°C or lower, more preferably 10°C or higher and 120°C or lower, and further preferably 30°C or higher and 100°C or lower. When Tga is at least the lower limit of the above range, the hardness and water resistance of the coating film are more excellent. When Tga is at the upper limit of the above range, the storage stability of the solution of the copolymer (A) or the coating composition containing the solution is more excellent, and it is easy to make these solutions or coating compositions have a high solid content but a low viscosity.

[0139] Tga can be measured using differential scanning calorimetry (DSC).

[0140] Tga can be adjusted by the composition of monomers forming the macromonomer (a) and the like.

[0141] As the macromonomer (a), those produced by a known method may be used, or those commercially available may be used.

[0142] Examples of the method for producing the macromonomer (a) include a method using a cobalt chain transfer agent, a method using an α-substituted unsaturated compound such as α-methylstyrene dimer as a chain transfer agent, a method chemically bonding a radical polymerizable group to a polymer, and a method utilizing thermal decomposition.

[0143] Among these, as a method for producing the macromonomer (a), a method using a cobalt chain transfer agent is preferred in terms of having a small number of production steps and using a catalyst with a high chain transfer constant. In addition, when the macromonomer (a) is produced using a cobalt chain transfer agent, it has a structure represented by the above formula (1).

[0144] Examples of methods for producing the macromonomer (a) using a cobalt chain transfer agent include bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and other aqueous dispersion polymerization methods. Aqueous dispersion polymerization is preferred from the viewpoint of simplicity of the recovery step.

[0145] Examples of methods for chemically bonding a radical polymerizable group to a polymer include a method of replacing the halogen group of a polymer having a halogen group with a compound having a radical polymerizable carbon-carbon double bond, a method of reacting a vinyl monomer having an acid group with a vinyl polymer having an epoxy group, a method of reacting a vinyl polymer having an epoxy group with a vinyl monomer having an acid group, a method of reacting a vinyl polymer having a hydroxyl group with a diisocyanate compound to obtain a vinyl polymer having an isocyanate group, and reacting the vinyl polymer with a vinyl monomer having a hydroxyl group, and the like. The polymer can be produced by any method.

[0146] The number average molecular weight of the macromonomer (a) can be adjusted by using a polymerization initiator, a chain transfer agent, and the like.

[0147] <Structural Unit Derived from Vinyl Monomer (b)>

[0148] The vinyl monomer (b) is a monomer having an ethylenically unsaturated bond and not belonging to a macromonomer. The vinyl monomer (b) is not particularly limited, and the same monomer as the monomer for obtaining the macromonomer (a) mentioned above can be used. Any one of these vinyl monomers can be used, or two or more can be used in combination.

[0149] The vinyl monomer (b) preferably contains at least one monomer selected from the group consisting of 2-ethylhexyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, styrene and isobornyl (meth)acrylate (hereinafter referred to as "monomer (b1)"). When the copolymer (A) contains a structural unit derived from the monomer (b1), the weather resistance, water resistance, gloss, etc. of the coating film are more excellent.

[0150] When the structural unit derived from the macromonomer (a) does not include a structural unit having a hydroxyl group, the structural unit derived from the vinyl monomer (b) includes a structural unit having a hydroxyl group, that is, the vinyl monomer (b) includes a vinyl monomer having a hydroxyl group (hereinafter also referred to as "monomer (b2)").

[0151] Examples of the monomer (b2) include the same monomers as those exemplified above as the monomers having a hydroxyl group, and preferred embodiments are also the same.

[0152] When the structural unit derived from the macromonomer (a) includes a structural unit having a hydroxyl group, the vinyl monomer (b) may or may not contain the monomer (b2).

[0153] The vinyl monomer (b) may further contain other vinyl monomers other than the monomers (b1) to (b2). As other vinyl monomers, the same monomers as those exemplified above for obtaining the macromonomer (a) can be used.

[0154] <Structural Unit Having Hydroxyl Group>

[0155] In copolymer (A), relative to the gross mass of all structural units, the content of the structural unit with hydroxyl is preferably more than 0.5 mass parts and less than 80 mass parts, more preferably more than 5 mass parts and less than 60 mass parts, further preferably more than 10 mass parts and less than 50 mass parts. If the content of the structural unit with hydroxyl is above the lower limit of the scope, when copolymer (A) is solidified by a curing agent, the crosslinking density fully becomes high, and the hardness of the coating film is further improved. If the content of the structural unit with hydroxyl is below the upper limit of the scope, water resistance is more excellent.

[0156] The content of the structural units containing hydroxyl groups in the copolymer (A) is the total amount of the content of the structural units containing hydroxyl groups in the structural units derived from the macromonomer (a) and the content of the structural units containing hydroxyl groups in the structural units derived from the vinyl monomer (b) (structural units derived from monomer (b2)) (including the case where the content of the structural units containing hydroxyl groups in the structural units derived from the macromonomer (a) or the structural units derived from the vinyl monomer (b) is 0% by mass).

[0157] The structural unit having a hydroxyl group preferably includes a structural unit having any one or both of a secondary hydroxyl group and a tertiary hydroxyl group (hereinafter also referred to as a "secondary / tertiary OH-containing unit"). By including the unit containing a secondary / tertiary OH, repair work can be effectively performed by delayed curing. The unit containing a secondary / tertiary OH may further have a primary hydroxyl group.

[0158] Examples of the secondary / tertiary OH-containing unit include a structural unit derived from a monomer having either or both of a secondary hydroxyl group and a tertiary hydroxyl group (hereinafter also referred to as a "secondary / tertiary OH-containing monomer").

[0159] As the monomer containing secondary / tertiary OH, a vinyl monomer having any one or both of a secondary hydroxyl group and a tertiary hydroxyl group is preferred. The monomer containing secondary / tertiary OH may be a monohydric alcohol monomer having one hydroxyl group, or a polyhydric alcohol monomer having two or more hydroxyl groups. The monohydric alcohol monomer may be a secondary alcohol monomer in which the hydroxyl group is a secondary hydroxyl group, or a tertiary alcohol monomer in which the hydroxyl group is a tertiary hydroxyl group.

[0160] Examples of the secondary alcohol monomer include monohydroxyalkyl (meth)acrylates having a secondary hydroxyl group such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-hydroxybutyl (meth)acrylate; and polyalkylene glycol mono(meth)acrylates having a secondary hydroxyl group such as polypropylene glycol (meth)acrylate.

[0161] Examples of the tertiary alcohol monomer include 3-hydroxy-1,3-diethylbutane (meth)acrylate, 3-hydroxy-1-adamantyl (meth)acrylate, 2-hydroxy-2-methylpropyl (meth)acrylate, and 2-hydroxy-1,2-dimethylpropyl (meth)acrylate.

[0162] Examples of the polyol monomer include polyhydric hydroxyalkyl (meth)acrylates having a secondary hydroxy group such as glycerol mono(meth)acrylate.

[0163] These monomers may be used alone or in combination of two or more.

[0164] As the secondary / tertiary OH-containing monomer, from the viewpoint of availability, monohydroxyalkyl (meth)acrylates in which the hydroxyl group is a secondary hydroxyl group are preferred, and 2-hydroxypropyl (meth)acrylate is particularly preferred.

[0165] Among the structural units having hydroxyl groups, the content of the structural units having primary hydroxyl groups (hereinafter also referred to as "primary OH-containing units") is preferably 30 parts by mass or less relative to 100 parts by mass of the structural units derived from the macromonomer (a) and the structural units derived from the vinyl monomer (b). The primary OH-containing units can adjust the ratio between the secondary and tertiary hydroxyl groups and the primary hydroxyl groups, and adjust the gel fraction after one day of coating.

[0166] Examples of the primary OH-containing unit include a structural unit derived from a monomer having a primary hydroxyl group but not having a secondary hydroxyl group or a tertiary hydroxyl group (hereinafter also referred to as a “primary OH-containing monomer”).

[0167] As the primary OH-containing monomer, a vinyl monomer having a primary hydroxyl group but not having a secondary hydroxyl group or a tertiary hydroxyl group is preferred, for example, monohydroxyalkyl (meth)acrylates having a primary hydroxyl group such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; polyalkylene glycol mono (meth)acrylates having a primary hydroxyl group such as polyethylene glycol (meth)acrylate, etc. These monomers may be used alone or in combination of two or more.

[0168] As the primary OH-containing monomer, monohydroxyalkyl (meth)acrylate having a primary hydroxyl group is preferred, and 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate are particularly preferred.

[0169] Regarding the primary hydroxyl-containing unit, the content of the structural unit having a primary hydroxyl group in the (meth)acrylic copolymer is 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less, relative to 100 parts by mass of the structural unit derived from the macromonomer (a) and the structural unit derived from the vinyl monomer (b). If it is 30 parts by mass or less, it is easy to perform repair work on the formed coating film.

[0170] In the structural unit having a hydroxyl group, the content of the unit containing secondary / tertiary OH is preferably 20% by mass or more and 100% by mass or less, more preferably 30% by mass or more and 100% by mass or less, and further preferably 50% by mass or more and 95% by mass or less, relative to the total mass of the structural unit having a hydroxyl group. If the content of the unit containing secondary / tertiary OH is above the lower limit of the range, it is easy to perform repair work on the formed coating film.

[0171] <Content of Each Structural Unit>

[0172] In the copolymer (A), the content of the structural unit derived from the macromonomer (a) is preferably 7% by mass or more and 60% by mass or less, more preferably 8% by mass or more and 50% by mass or less, and further preferably 10% by mass or more and 40% by mass or less, relative to the total mass (100% by mass) of all structural units. If the content of the structural unit derived from the macromonomer (a) is above the lower limit of the range, the hardness is more excellent. If the content of the structural unit derived from the macromonomer (a) is below the upper limit of the range, the coating property of the solution of the copolymer (A) or the coating composition containing the solution is more excellent.

[0173] In copolymer (A), the content of the structural unit from vinyl monomer (b) is preferably 40% by mass or more and 93% by mass or less, more preferably 50% by mass or more and 92% by mass or less, and further preferably 60% by mass or more and 90% by mass or less relative to the total mass (100% by mass) of all structural units. If the content of the structural unit from vinyl monomer (b) is above the lower limit of the range, the coating property of the solution of copolymer (A) or the coating composition containing the solution is more excellent. If the content of the structural unit from vinyl monomer (b) is below the upper limit of the range, the coating film hardness is more excellent.

[0174] In the copolymer (A), the composition of the monomers constituting the macromonomer (a) and the composition of the monomers constituting the vinyl monomer (b) are preferably different. The composition refers to the types and content ratios of the monomers.

[0175] The weight average molecular weight (Mw) of the copolymer (A) is preferably 2000 or more and 100000 or less, more preferably 2500 or more and 40000 or less, and further preferably 3000 or more and 20000 or less. If the weight average molecular weight of the copolymer (A) is below the upper limit of the range, the viscosity of the solution formed by dissolving the copolymer (A) in the solvent becomes lower, and it is easy to obtain a material with high solid content and low viscosity as a coating composition. If the weight average molecular weight is above the lower limit of the range, the hardness, durability, etc. of the formed coating film are more excellent.

[0176] The hydroxyl value of the copolymer (A) is 120 mgKOH / g or more and 260 mgKOH / g or less, more preferably 150 mgKOH / g or more and 230 mgKOH / g or less, and particularly preferably 150 mgKOH / g or more and 200 mgKOH / g or less. If the hydroxyl value of the copolymer (A) is above the lower limit of the range, the crosslinking density is sufficiently increased when a curing agent is added to the copolymer (A) to cure it, and the strength of the coating film is further improved. If the hydroxyl value of the copolymer (A) is below the upper limit of the range, the water resistance is more excellent.

[0177] The hydroxyl value of the copolymer (A) is measured by method A of JIS K 1557-1.

[0178] The acid value of the copolymer (A) is preferably 0 mgKOH / g to 80 mgKOH / g, more preferably 0 mgKOH / g to 50 mgKOH / g, and further preferably 0 mgKOH / g to 30 mgKOH / g. When the acid value of the copolymer (A) is below the upper limit of the above range, water resistance is further excellent.

[0179] The acid value of the copolymer (A) is measured by the following measurement method.

[0180] Accurately weigh (A (g)) about 0.5g of sample in a beaker, add 50mL of toluene / ethanol solution. Add a few drops of phenolphthalein, titrate with 0.5N KOH solution and measure (titration = B (mL), titer of KOH solution = f). Measure the blank in the same way (titration = C (mL)), and calculate the acid value according to the following formula.

[0181] Acid value (mgKOH / g) = {(BC) × 0.2 × 56.11 × f} / A / solid content

[0182] The glass transition temperature (Tg) of the copolymer (A) is preferably 0°C or more and 100°C or less, more preferably 10°C or more and 50°C or less. It is particularly preferably 20°C or more and 40°C or less. If the Tg of the copolymer (A) is above the lower limit of the range, the hardness of the coating film is more excellent. If the Tg of the copolymer (A) is below the upper limit of the range, the crack resistance is more excellent.

[0183] The Tg of the copolymer (A) is a value calculated by the Fox calculation formula from the glass transition temperature of the homopolymer of each monomer constituting the copolymer (A) and the mass fraction of each monomer (the ratio of the mass of each monomer to the total mass when the total mass of all monomers is 1). The monomers constituting the copolymer (A) include the monomers constituting the macromonomer (a) and the vinyl monomer (b).

[0184] The calculation formula of Fox is a calculated value obtained by the following formula, and can be obtained using the value described in Polymer Handbook [Polymer HandBook, J. Brandrup, Interscience, 1989].

[0185] 1 / (273+Tg)=Σ(Wi / (273+Tgi))

[0186] (Wherein, Wi represents the mass fraction of monomer i, and Tgi represents the Tg (°C) of the homopolymer of monomer i.)

[0187] In the copolymer (A), the glass transition temperature (Tga) (°C) of the macromonomer (a) and the glass transition temperature (TgB) (°C) of the polymer (B) obtained by polymerizing only the vinyl monomer (b) preferably have the relationship of the following formula (3) from the viewpoint that the properties of the structural units derived from the macromonomer (a) and the structural units derived from the vinyl monomer (b) can be fully reflected. That is, Tga-TgB>0°C is preferred.

[0188] Tga>TgB…(3)

[0189] More preferably, Tga-TgB>60°C, and most preferably, Tga-TgB>80°C.

[0190] TgB was calculated by Fox's calculation formula in the same manner as Tg of the copolymer (A).

[0191] The copolymer (A) has a hydroxyl group, and thus the copolymer (A) can be cured by reacting with a curing agent.

[0192] At least a part of the hydroxyl groups in the copolymer (A) are preferably either or both of secondary hydroxyl groups and tertiary hydroxyl groups. This allows the gel fraction to be 70% or less one day after coating. The gel fraction one day after coating will be described in detail below.

[0193] The copolymer (A) may contain primary hydroxyl groups in addition to secondary hydroxyl groups and tertiary hydroxyl groups. The gel fraction after one day of coating can be adjusted by the ratio between secondary hydroxyl groups and tertiary hydroxyl groups and primary hydroxyl groups. The higher the ratio of secondary hydroxyl groups and tertiary hydroxyl groups, the easier the repair work becomes.

[0194] The total proportion of the structural units having at least one of the secondary hydroxyl group and the tertiary hydroxyl group is preferably 15 parts by mass or more and 60 parts by mass or less, more preferably 25 parts by mass or more and 50 parts by mass or less, and further preferably 30 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the structural units of the copolymer (A). If the total proportion of the secondary hydroxyl group and the tertiary hydroxyl group is greater than the lower limit of the range, the gel fraction after one day of coating will be sufficiently reduced.

[0195] The hydroxyl group may be contained in the structural unit constituting the copolymer (A), may be contained in the main chain terminal of the copolymer (A), or may be contained in both. From the viewpoint of increasing the crosslinking density of the coating film, it is preferably contained in at least the structural unit.

[0196] The copolymer (A) preferably has a gel fraction of 70% or less one day after application.

[0197] The gel fraction after one day of coating is the gel fraction measured by the following measuring method on the coating film 24 hours after the formation of the coating film of the copolymer (A) by the following coating method.

[0198] "Painting method"

[0199] A coating composition is obtained by dissolving a (meth)acrylic copolymer (copolymer (A)) and an isocyanurate of hexamethylene diisocyanate in an organic solvent at a molar ratio of NCO / OH of 1 / 1. The coating composition is applied to a polypropylene plate using a 6 mil applicator and dried at 70°C for 30 minutes to form a coating film, which is then stored at a temperature of 23.5°C and a relative humidity of 50%.

[0200] "Method for measuring gel fraction"

[0201] About 0.2 g of the coating film was measured and wrapped with a stainless steel mesh (SUS316, twill metal mesh, φ0.04×300 mesh), and the end was clamped with a clip to prepare a sample. The sample was placed in 500 g of a mixed solvent of methanol:acetone = 1:1 (mass ratio), and refluxed and stirred at 65°C for 4 hours. Then, the sample was taken out from the mixed solvent, washed with 10 g of acetone, and dried at 105°C for 2 hours using a hot air dryer. After that, the mass of the coating film remaining in the sample was measured as the mass after drying, and the gel fraction was calculated from the mass after drying and the mass of the measured coating film according to the following formula.

[0202] Gel fraction (%) = mass after drying (g) / mass of measured coating film (g) × 100

[0203] The gel fraction is an index showing the degree of curing of the coating composition. The lower the gel fraction one day after coating, the more difficult it is for the coating composition to be cured (crosslinked).

[0204] When the gel fraction is 70% or less one day after coating, the hardness of the coating film does not become too high during the period from coating of the coating composition containing the copolymer (A) and the curing agent to the completion of the repair work, so that repair work such as grinding is easy to perform. In addition, since curing is difficult to proceed, the coating composition has a long service life, excellent handling properties, high fluidity immediately after coating, and excellent appearance of the coating film (surface smoothness, thickness uniformity, etc.).

[0205] Based on the above viewpoints, the gel fraction one day after coating is preferably 70% or less, more preferably 65% ​​or less, and even more preferably 55% or less.

[0206] The gel fraction after one day of coating can be controlled by, for example, the reactivity of the hydroxyl groups of the copolymer (A). In the copolymer (A), the reactivity of the secondary hydroxyl group or the tertiary hydroxyl group is lower than that of the primary hydroxyl group. The higher the ratio of the secondary hydroxyl group and the tertiary hydroxyl group in the hydroxyl group of the copolymer (A), the more delayed the curing is, and the lower the gel fraction after one day of coating tends to be.

[0207] The copolymer (A) preferably has a gel fraction of 80% or more 8 days after coating.

[0208] The gel fraction after 8 days of coating is the gel fraction of the copolymer (A) measured by the above-mentioned measuring method 192 hours after forming a coating film formed by the above-mentioned coating method.

[0209] If the coated object is moved before the coating film hardens to a certain extent, the coating film will be deformed and the appearance will deteriorate. Therefore, the next process cannot be carried out until the coating film hardens to a certain extent. If the gel fraction is 80% or more after 8 days of coating, the time until the next process can be fully shortened after coating, and the productivity is excellent. In addition, when the coating film is completely cured, the hardness of the coating film is fully improved, and it is difficult to be scratched by sand, etc., or by the rotating brush when washing with a car washing machine.

[0210] Based on the above viewpoints, the gel fraction 8 days after coating is preferably 80% or more, more preferably 85% or more. The upper limit of the gel fraction 8 days after coating is not particularly limited, and may be 100%.

[0211] From the viewpoint of repairability and abrasion resistance of the coating film, the gel fraction after one day and eight days mentioned above is preferably 100 ≥ (gel fraction after eight days of coating) - (gel fraction after one day of coating) ≥ 40. More preferably, it is 100 ≥ (gel fraction after eight days of coating) - (gel fraction after one day of coating) ≥ 45, and most preferably, it is 100 ≥ (gel fraction after eight days of coating) - (gel fraction after one day of coating) ≥ 70.

[0212] The Martens hardness (HM) of the copolymer (A) one day after coating is preferably 10 or less, more preferably 9 or less, particularly preferably 8 or less. The Martens hardness (HM) 8 days after coating is preferably 100 or more, further preferably 120 or more, particularly preferably 140 or more, and most preferably 160 or more. If the Martens hardness (HM) of the copolymer (A) one day after coating is 10 or less, repair work can be performed more effectively. If the Martens hardness (HM) of the copolymer (A) 8 days after coating is 100 or more, scratch resistance is more excellent.

[0213] (Hardness of coating film (HM))

[0214] The Martens hardness (HM) of the coating can be measured by an ultra-micro hardness tester (Fischer Instrument Co., Ltd., product name: HM2000). The measurement conditions are set as F (test force) = 50mN / 10 seconds, C (maximum load creep time) = 10 seconds. The Martens hardness is measured at 5 different locations of the same coating, and the average value is used as the hardness of the coating.

[0215] (Solubility Parameter (SP))

[0216] In the copolymer (A), from the viewpoint of fully expressing the characteristics of the structural units derived from the macromonomer (a) and the structural units derived from the vinyl monomer (b), the solubility parameter SP (SPa) of the macromonomer (a) and the SP (SPB) of the polymer (B) obtained by polymerizing only the vinyl monomer (b) are preferably SPB-SPa>3. More preferably, SPB-SPa>3.5, and most preferably, SPB-SPa>4.

[0217] Each SP is determined by a known method described in RF Fedors, "Polym. Eng. Sci." (1974), 14(2), p. 147, p. 472. Specifically, the SP is a value calculated by the following formula.

[0218] δ=Σ(miδi)

[0219] In the above formula, mi represents the molar fraction of monomer i constituting the polymer, and δi represents the SP of monomer i constituting the polymer.

[0220] <Method for producing copolymer (A)>

[0221] The copolymer (A) can be produced by copolymerizing a macromonomer (a) and a vinyl monomer (b).

[0222] At least one of the macromonomer (a) and the vinyl monomer (b) preferably contains a monomer having a hydroxyl group. The monomer having a hydroxyl group preferably contains a monomer containing a secondary / tertiary OH group, and may further contain a monomer containing a primary OH group.

[0223] As a method for producing the copolymer (A), a method of polymerizing a monomer mixture containing a macromonomer (a) and a vinyl monomer (b) is preferred (hereinafter also referred to as "production method (α)"). That is, the copolymer (A) is preferably a polymer of a monomer mixture containing a macromonomer (a) and a vinyl monomer (b). In the case of such a polymer, the structural units derived from the macromonomer (a) and the structural units derived from the vinyl monomer (b) are arranged randomly. That is, polymer chains derived from a plurality of macromonomers (a) are bonded to the entire main chain of the copolymer (A). Such a polymer, for example, tends to have a coating film having a better hardness and elastic modulus than a case where only a structural unit derived from a macromonomer (a) is bonded to the end of a polymer chain composed of structural units derived from a vinyl monomer (b).

[0224] The types of monomers constituting the monomer mixture and the content (mass %) of each monomer relative to the total mass of all monomers are the same as the types of structural units derived from monomers constituting the copolymer (A) and the content (mass %) of each structural unit relative to the total mass of all structural units.

[0225] For example, when the content of the structural units derived from the macromonomer (a) in the copolymer (A) is 7% by mass or more and 60% by mass or less relative to the total mass (100% by mass) of all the structural units, the content of the macromonomer (a) relative to the total mass of all the monomers constituting the monomer mixture is set to 7% by mass or more and 60% by mass or less.

[0226] As a method for polymerizing the monomer mixture, for example, known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization can be applied. Solution polymerization is preferred in terms of productivity and coating film performance.

[0227] The polymerization may be carried out by a known method using a known polymerization initiator. For example, a method is exemplified by reacting the above-mentioned monomer mixture at a reaction temperature of 60 to 190° C. for 2 to 14 hours in the presence of a free radical initiator. During the polymerization, a chain transfer agent may be used as necessary.

[0228] As the radical initiator, a known substance can be used, for example, 2,2-azobisisobutyronitrile, 2,2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(2-methylbutyronitrile), benzoyl peroxide, cumene hydroperoxide, lauroyl peroxide, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanoate, etc.

[0229] As the chain transfer agent, known ones can be used, and examples thereof include mercaptans such as n-dodecyl mercaptan, thioglycolates such as octyl thioglycolate, α-methylstyrene dimer, terpinene, and the like.

[0230] As the solvent used in the solution polymerization, for example, a general organic solvent such as toluene, xylene, propylene glycol monomethyl ether acetate, methyl isobutyl ketone, n-butyl acetate, ethyl-3-ethoxypropionate, etc. can be used.

[0231] The copolymer (A) can be obtained as described above.

[0232] However, the method for producing the copolymer (A) is not limited to the production method (α), and the copolymer (A) may be produced by a production method other than the production method (α).

[0233] Examples of production methods other than the production method (α) include a production method in which a macromonomer (a) is added to a polymer composed of a vinyl monomer (b).

[0234] <Effects>

[0235] In the case of copolymer (A), since it contains structural units derived from macromonomer (a) and structural units derived from vinyl monomer (b), it has hydroxyl groups, and the content of structural units having primary hydroxyl groups is 30 parts by mass or less relative to 100 parts by mass of structural units derived from macromonomer (a) and structural units derived from vinyl monomer (b), after the coating composition containing copolymer (A) is applied to the coated object, the formed coating film can be effectively repaired. In addition, a coating composition with a long service life is obtained. In addition, the fluidity is high just after the coating composition is applied, and a coating film with excellent appearance is obtained.

[0236] In the case of a random copolymer having the same composition as the copolymer (A), that is, a random copolymer in which the monomer constituting the macromonomer (a) and the vinyl monomer (b) are copolymerized at the same ratio without using the macromonomer (a) (hereinafter referred to as "random copolymer (X)"), the gel fraction after one day of coating exceeds 70%, and the difference between the gel fraction after one day of coating and the gel fraction after eight days of coating tends to be small. Similarly, in the case of a copolymer having only primary hydroxyl groups as hydroxyl groups (hereinafter referred to as "copolymer (Y)"), even if it contains structural units derived from the macromonomer (a) and structural units derived from the vinyl monomer (b), the gel fraction after one day of coating exceeds 70%, and the difference between the gel fraction after one day of coating and the gel fraction after eight days of coating tends to be small.

[0237] Therefore, as a copolymer (A) that satisfies both the gel fraction of 70% or less one day after coating and the gel fraction of 80% or more eight days after coating, it is preferred to contain a structural unit derived from the macromonomer (a) and a structural unit derived from the vinyl monomer (b) and have either or both of a secondary hydroxyl group and a tertiary hydroxyl group.

[0238] In the copolymer (A), as described above, the reactivity of secondary hydroxyl groups or tertiary hydroxyl groups is lower than that of primary hydroxyl groups. By having secondary hydroxyl groups and tertiary hydroxyl groups, curing is delayed, and the gel fraction after one day of coating becomes low. On the other hand, even if curing is delayed, as long as hydroxyl groups are sufficiently present, curing is sufficiently advanced after 8 days of coating, so the gel fraction can be increased.

[0239] The copolymer (A) of the present invention can be used in coating compositions, decorative films, inks, dispersants, viscosity adjusters, compatibilizers, adhesives, tackifiers, and the like, and is particularly useful as a film-forming resin for coating compositions.

[0240] [Coating composition]

[0241] The coating composition of the present invention contains the above-mentioned copolymer (A) as a film-forming resin.

[0242] The copolymer (A) contained in the coating composition may be one kind or two kinds.

[0243] <Content of each ingredient>

[0244] The content of the copolymer (A) in the coating composition is preferably 30% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, relative to 100% by mass of the resin solid content of the coating composition, and may be 100% by mass. If the content of the copolymer (A) is above the lower limit, the hardness of the coating film and the rate of increase of the hardness after the coating film is formed are further improved.

[0245] The resin solid content is the total mass calculated as the solid content of the resin component contained in the coating composition.

[0246] <Curing Agent>

[0247] The coating composition of the present invention may further contain a curing agent.

[0248] When the coating composition contains a curing agent, a coating film with a high crosslinking density is formed during curing, and the coating film tends to have better hardness, film-forming properties, etc. In addition, when the copolymer (A) has self-crosslinking properties, for example, when it has both a hydroxyl group and an isocyanate group, sufficient hardness, film-forming properties, etc. can be obtained even without a curing agent.

[0249] As the curing agent, any compound that can react with the hydroxyl group of the copolymer (A) to cure the coating composition can be selected appropriately from known curing agents, for example, compounds having reactive functional groups such as two or more isocyanate groups, blocked isocyanate groups, amino groups, epoxy groups, carboxyl groups, carbodiimide groups, and metal chelate curing agents.

[0250] Examples of the compound having two or more reactive functional groups include isocyanate curing agents such as polyisocyanate compounds and blocked polyisocyanate compounds, and amino resins, among which isocyanate curing agents are preferred.

[0251] The polyisocyanate compound is a compound having at least two isocyanate groups in the molecule, and examples thereof include aliphatic diisocyanate compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate;

[0252] Alicyclic diisocyanate compounds such as hydrogenated xylylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate;

[0253] Aromatic diisocyanate compounds such as toluene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, and naphthalene diisocyanate;

[0254] Trivalent or higher organic polyisocyanate compounds such as 2-isocyanatoethyl-2,6-diisocyanatohexanoate, 3-isocyanatomethyl-1,6-hexamethylene diisocyanate, and 4-isocyanatomethyl-1,8-octamethylene diisocyanate (commonly known as triaminononane triisocyanate);

[0255] Dimers or trimers of these polyisocyanate compounds;

[0256] Prepolymers obtained by subjecting these polyisocyanate compounds to a urethanization reaction with a polyol, a low molecular weight polyester resin or water under conditions in which the isocyanate groups are excessive.

[0257] The blocked polyisocyanate compound is a compound in which the isocyanate groups of the polyisocyanate compound are blocked with a blocking agent.

[0258] Examples of the blocking agent include phenol-based blocking agents such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxybiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate;

[0259] Lactam blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam, etc.;

[0260] Aliphatic alcohol blocking agents such as methanol, ethanol, propanol, butanol, amyl alcohol, and lauryl alcohol;

[0261] Ether blocking agents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol;

[0262] Alcohol-based blocking agents such as benzyl alcohol, glycolic acid, glycolic acid methyl ester, glycolic acid ethyl ester, glycolic acid butyl ester, lactic acid, methyl lactate, ethyl lactate, butyl lactate, hydroxymethyl urea, hydroxymethyl melamine, diacetone alcohol, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate;

[0263] Oxime blocking agents such as aminoformoxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexanone oxime, etc.;

[0264] Active methylene blocking agents such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone, etc.

[0265] Mercaptan blocking agents such as butyl mercaptan, tert-butyl mercaptan, hexyl mercaptan, tert-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol, etc.;

[0266] Amide-based blocking agents such as acetanilide, methoxyacetanilide, acetyltoluidine, acrylamide, methacrylamide, acetamide, stearamide, benzamide, etc.;

[0267] Imine blocking agents such as succinimide, phthalimide, maleimide, etc.

[0268] Amine blocking agents such as diphenylamine, phenylnaphthylamine, dimethylaniline, N-phenyldimethylaniline, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine, etc.;

[0269] Urea-based blocking agents such as urea, thiourea, ethylene urea, ethylene thiourea, and diphenyl urea;

[0270] Carbamate blocking agents such as N-phenylcarbamate; imine blocking agents such as ethyleneimine and propyleneimine;

[0271] Sulfite-based blocking agents such as sodium bisulfite and potassium bisulfite;

[0272] Pyrazole or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole, imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole, and pyrrole-based blocking agents such as imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0273] As the amino resin, a partially methylolated amino resin or a completely methylolated amino resin obtained by a reaction between an amino component and an aldehyde component can be used. Examples of the amino component include melamine, urea, guanamine, acetoguanamine, stereoguanamine, spiroguanamine, and dicyandiamide. Examples of the aldehyde component include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde.

[0274] As the amino resin, a resin obtained by partially or completely etherifying the methylol groups of the above-mentioned methylolated amino resin with an alcohol may be used. Examples of the alcohol used for etherification include methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, 2-ethylbutanone, and 2-ethylhexanol.

[0275] As the amino resin, a cyanamide resin is preferred, and a methyl-etherified cyanamide resin in which the methylol groups of a partially or completely hydroxymethylated cyanamide resin are partially or completely etherified with methanol, a butyl-etherified cyanamide resin in which the methylol groups of a partially or completely hydroxymethylated cyanamide resin are partially or completely etherified with butanol, or a methyl-butyl mixed etherified cyanamide resin in which the methylol groups of a partially or completely hydroxymethylated cyanamide resin are partially or completely etherified with methanol and butanol, is more preferred. A methyl-butyl mixed etherified cyanamide resin is more preferred.

[0276] The weight average molecular weight of the melamine resin is preferably about 400 to 6,000, more preferably about 800 to 5,000, further preferably about 1,000 to 4,000, and most preferably about 1,200 to 3,000.

[0277] <Organic Solvents>

[0278] The coating composition of the present invention preferably contains an organic solvent. When the coating composition contains an organic solvent, coating suitability, water resistance of the formed coating film, film-forming properties, etc. are more excellent.

[0279] The organic solvent is not particularly limited as long as it can dissolve the copolymer (A), and examples thereof include hydrocarbon solvents such as heptane, cyclohexane, toluene, xylene, octane, and rosin water;

[0280] Ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, and diethylene glycol monobutyl ether acetate;

[0281] Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexane, etc.; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, sec-butanol, isobutanol, etc.;

[0282] Ether solvents such as dioxane, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monopropyl ether;

[0283] Aromatic petroleum-based solvents such as Swazer 310, Swazer 1000, and Swazer 1500 manufactured by Cosmo Oil Co., etc. These organic solvents may be used alone or in combination of two or more.

[0284] <Other ingredients>

[0285] The coating composition of the present invention may further contain other components in addition to the copolymer (A), the curing agent and the organic solvent as needed within a range that does not impair the effects of the present invention.

[0286] Examples of other components include resins other than the copolymer (A), such as polyester resins, phenol resins, polyether resins, epoxy resins, curing catalysts, anti-sag agents, resins, pigments (coloring pigments, bright pigments, extender pigments, etc.), antifouling agents, defoaming agents, pigment dispersants, leveling agents, anti-sagging agents, matting agents, ultraviolet absorbers, antioxidants, heat resistance improvers, slip agents, preservatives, plasticizers, viscosity control agents, and the like.

[0287] Examples of the curing catalyst include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, triethylamine, diethanolamine, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, neutralized salts of the above sulfonic acids and amines, and neutralized salts of phosphoric acid ester compounds and amines.

[0288] A preferred coating composition of the present invention is a clear coating composition. The coating composition of this embodiment contains a copolymer (A) and an organic solvent but does not contain a coloring pigment. The coating composition of this embodiment may further contain a curing agent. The coating composition of this embodiment may further contain other ingredients other than the copolymer (A), the curing agent and the coloring pigment.

[0289] From the viewpoint of the efficiency of the repair work, the coating composition of the present invention preferably has a gel fraction of 70% or less, more preferably 65% ​​or less one day after coating.

[0290] The gel fraction of the coating composition one day after application is measured in the same manner as the gel fraction of the copolymer (A) one day after application, except that the coating composition of the present invention is used as the coating composition for forming the coating film. That is, the coating composition of the present invention is applied on a polypropylene plate with a 6 mil applicator, dried at 70° C. for 30 minutes to form a coating film, and stored (cured) at a temperature of 23.5° C. and a relative humidity of 50%. After 24 hours from the start of storage, the gel fraction of the coating film is determined by the above-mentioned gel fraction measurement method.

[0291] The gel fraction of the coating composition one day after coating can be controlled, for example, by the type of copolymer (A), the type or amount of the curing catalyst, etc. For example, the gel fraction one day after coating tends to be lower as the content of the curing catalyst is lower.

[0292] The coating composition of the present invention preferably has a gel fraction of 80% to 100%, more preferably 85% to 100%, 8 days after coating, from the viewpoints of productivity, scratch resistance, and the like.

[0293] The gel fraction of the coating composition 8 days after coating is measured in the same manner as the gel fraction of the copolymer (A) 8 days after coating, except that the coating composition of the present invention is used as the coating composition for forming the coating film.

[0294] <Content of each ingredient>

[0295] The content of the copolymer (A) in the coating composition is preferably 30% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, relative to the resin solid content (100% by mass) of the coating composition. If the content of the copolymer (A) is above the lower limit, the hardness of the coating film and the rate of increase of the hardness during storage are further improved.

[0296] The resin solid content is the total mass calculated as the solid content of the resin component contained in the coating composition.

[0297] When the coating composition contains a curing agent, the content of the curing agent in the coating composition can be appropriately set according to the type of the curing agent.

[0298] For example, when the curing agent is a polyisocyanate compound or a blocked polyisocyanate compound, the molar ratio (NCO / OH) of the isocyanate groups of the polyisocyanate compound or the blocked isocyanate groups of the blocked polyisocyanate compound to the hydroxyl groups of the copolymer (A) is preferably within a range of 0.5 to 2.

[0299] When the coating composition contains an organic solvent, the content of the organic solvent in the coating composition can be appropriately set in consideration of the solid content, viscosity, and the like of the coating composition.

[0300] The solid content of the coating composition is preferably 30% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 78% by mass or less, and further preferably 45% by mass or more and 75% by mass or less. If the solid content is below the upper limit of the range, the viscosity of the coating composition can be sufficiently reduced.

[0301] The solid content is measured by the measurement method described in Examples below.

[0302] The coating composition of the present invention can be produced, for example, by producing the above-mentioned copolymer (A) and, if necessary, mixing a curing agent, an organic solvent, other components and the like into the obtained copolymer (A).

[0303] <Effects>

[0304] In the case of the coating composition of the present invention, since the copolymer (A) is contained, after the coating composition is applied to the object to be coated as described above, the repair work of the formed coating film can be effectively performed. In addition, a coating composition with a long service life is obtained. In addition, the fluidity just after the coating composition is applied is high, and a coating film with excellent appearance is obtained.

[0305] 〔Painted materials〕

[0306] The coated article of the present invention is a coated article coated with the coating composition of the present invention described above.

[0307] The coated article of the present invention can be manufactured by applying the coating composition of the present invention to the coated article to form a coating film. Specifically, the coating composition of the present invention is applied to the surface of the coated article to form an uncured coating film, and the uncured coating film is cured to form a cured coating film. Thus, the coated article is obtained.

[0308] The so-called cured coating film is a coating film in a cured and dried state as specified in JIS K 5600-1-1 (2004), that is, when the center of the coating surface is pinched firmly between the thumb and index finger, there will be no depression on the coating surface caused by fingerprints, and the movement of the coating film cannot be felt. In addition, when the center of the coating surface is quickly scratched with the fingertips, no scratch marks will be left on the coating surface.

[0309] The uncured coating film refers to a state in which the coating film has not yet reached the above-mentioned cured dry state, and includes a dry-to-touch state and a semi-cured dry state as defined in JIS K5600-1-1.

[0310] The objects to be coated are not particularly limited, and examples thereof include outer panels of automobile bodies such as passenger cars, trucks, motorcycles, and buses; automobile parts such as bumpers, steering wheels, central control panels, instrument panels, and wheels; underwater structures such as ships or various fishing nets, port facilities, oil booms, bridges, and seabed bases; home appliances such as mobile phones and audio equipment; outer panels of industrial machines such as agricultural machinery and construction machinery, etc. Among these, outer panels of automobile bodies and automobile parts are preferred.

[0311] The material of the object to be coated is not particularly limited, and examples thereof include metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, lead-plated steel, lead-plated alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.) steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, and various film materials; plastic materials such as various fiber reinforced plastics (FRP); inorganic materials such as glass, cement, and concrete; wood; fiber materials such as paper and cloth, etc. Among these, metal materials and plastic materials are preferred.

[0312] When the material of the object to be coated is a metal material, the surface of the object to be coated may be subjected to a surface treatment such as a phosphate treatment, a chromate treatment, or a complex oxide treatment.

[0313] A film may be formed in advance on the surface of the object to be coated. When the material of the object to be coated is a metal material, the film may be formed on the surface subjected to the surface treatment.

[0314] Examples of the coated object having a film formed on the surface include an object in which a surface treatment is performed as necessary to form a primer coating film thereon, and an object in which a mid-coat coating film is formed on the primer coating film.

[0315] Examples of the primer coating include electrodeposition coatings such as cationic electrodeposition coatings.

[0316] The coating method of the coating composition is not particularly limited, and for example, known coating methods such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc. can be used. During coating, static electricity may be applied as needed.

[0317] The film thickness of the formed coating film can be appropriately set and is not particularly limited. For example, the film thickness of the cured coating film can be about 500 nm to 500 μm.

[0318] The uncured coating film can be cured by heating (heat curing). The heating of the uncured coating film can be carried out by known heating means. As the heating means, for example, a drying furnace such as a hot air furnace, an electric furnace, an infrared induction heating furnace, etc. can be used. The heating temperature is not particularly limited, but preferably 50 to 180°C. The heating time is not particularly limited, but preferably 1 to 60 minutes.

[0319] After coating the coating composition, before heat curing, in order to prevent the occurrence of coating film defects, preliminary heating or air blowing may be performed under heating conditions that do not substantially cure the coating film.

[0320] The preheating temperature is preferably about 30 to 100° C. The preheating time is preferably about 30 seconds to 15 minutes.

[0321] Air blowing is usually performed by spraying air heated to a temperature of about 30 to 100° C. onto the coating surface for about 30 seconds to 15 minutes.

[0322] After the coating film is heat-cured, it may be cured (stored) to increase the hardness of the coating film.

[0323] The curing conditions may be, for example, 0 to 60° C. for about 1 to 10 days.

[0324] During curing, the coating film can be repaired as needed.

[0325] Examples of the repair work include grinding with sandpaper, buffing, and other grinding means.

[0326] When performing repair work, it is preferably done within 3 days after starting curing.

[0327] [Method for forming a multi-layer coating]

[0328] The coating composition of the present invention can be used for forming a multi-layer coating film.

[0329] Examples of the multilayer coating film include (1) a multilayer coating film composed of a colored base coating film and a clear coating film, and (2) a multilayer coating film composed of a first colored base coating film, a second colored base coating film, and a clear coating film.

[0330] The coating composition of the present invention is particularly useful as a clear coating material for forming a clear coating film in each of these multilayer coating films.

[0331] As an example of a method for forming a multilayer coating film using the coating composition of the present invention, a method is provided in which the coating composition of the present invention is used as the clear coating in the method for forming a multilayer coating film. The method for forming a multilayer coating film is as follows: a first colored base coating is applied on a cured coating film of an electrodeposition coating to form a first colored base coating film, and then the first colored base coating film is not preheated or is preheated or heat-cured, and then a second colored base coating is applied on the first colored base coating film to form a second colored base coating film, and then the first colored base coating film and the second colored base coating film are preheated, and then a clear coating is applied on the second colored base coating film to form a clear coating film, and the three layers of coating films formed are simultaneously heat-cured to form a multilayer coating film.

[0332] In the method for forming the multilayer coating film, the multilayer coating film of (2) is formed on the cured coating film of the electrodeposition paint.

[0333] The method for forming the multilayer coating film can be carried out by a known method except that the coating composition of the present invention is used as a clear coating.

[0334] The cured coating film of the electrodeposition coating material can be formed by, for example, subjecting the surface of a metal coating object such as a steel plate to surface treatment as necessary, applying the electrodeposition coating material thereon, and heating and curing the surface.

[0335] The first colored base coating and the second colored base coating can use known coatings respectively. For example, a thermosetting coating composition comprising a film-forming resin with a crosslinking functional group, a curing agent and a coloring pigment is cited. The thermosetting coating composition can contain a bright pigment, a dye, a body pigment, an ultraviolet absorber, a light stabilizer, a defoamer, a thickener, a rust inhibitor, a surface adjuster, etc. as needed. The thermosetting coating composition can be any kind of an organic solvent-based coating composition, an aqueous coating composition, or a powder coating composition. As the crosslinking functional group possessed by the film-forming resin, for example, a hydroxyl group, a carboxyl group, an epoxy group, etc. are cited. As the type of the film-forming resin, for example, an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, etc. are cited. As a curing agent, a curing agent identical to the above is cited.

[0336] The application of the first colored base coating material and the second colored base coating material, and the preheating and heat curing of the formed coating films can be carried out in the same manner as the application of the coating composition of the present invention, and the preheating and heat curing of the coating films.

[0337] When the three layers of coating are cured by heat at the same time, the heating temperature is preferably about 80 to 180° C., more preferably about 100 to 170° C., and still more preferably about 120 to 160° C. The heating time is preferably about 10 to 60 minutes, and more preferably about 20 to 40 minutes.

[0338] After the three layers of coating film are cured by simultaneous heating, they can be cured. The same conditions as described above are given as the curing conditions.

[0339] The film thickness of the first colored base coating film is usually preferably about 5 to 50 μm, more preferably about 10 to 30 μm, and further preferably about 15 to 25 μm as a cured film thickness.

[0340] The film thickness of the second colored base coating film is preferably about 3 to 30 μm, more preferably about 5 to 25 μm, further preferably about 8 to 20 μm, and particularly preferably about 9 to 16 μm, as a cured film thickness.

[0341] The film thickness of the clear coating film is usually preferably about 10 to 80 μm, more preferably about 15 to 60 μm, and further preferably about 20 to 45 μm in terms of cured film thickness.

[0342] The above-mentioned method for forming a multilayer coating film can be used, for example, for painting automobiles.

[0343] In the painting of automobiles, electrodeposition paint is usually applied to the surface of the vehicle body, etc., and then a mid-coat paint is applied to form a mid-coat coating film, and then a top-coat paint is applied to form a top-coat coating film. After the electrodeposition paint is applied, when a composite coating film is formed thereon by the above-mentioned multi-layer coating film forming method, the first colored base coating film of the multi-layer coating film corresponds to the mid-coat coating film, and the second colored base coating film and the clear coating film correspond to the top-coat coating film.

[0344] [Example]

[0345] The present invention will be described in more detail below, but the following examples are not intended to limit the scope of the present invention. In each of the following examples, "part" means "part by mass".

[0346] The measurement method used in each example is shown below.

[0347] <Measurement method>

[0348] (Solid content (NV))

[0349] 0.50 g of the test sample (copolymer solution or coating composition) is measured in an aluminum dish, 3 mL of toluene is added with a syringe, and the sample is spread uniformly on the bottom of the dish for preliminary drying. Preliminary drying is a process in which the test sample is spread over the entire dish to make the solvent easily volatilize through main drying. In preliminary drying, the test sample and toluene are heated and dissolved in a water bath at 70 to 80°C and evaporated to dryness. After preliminary drying, main drying is performed in a hot air dryer at 105°C for 2 hours. From the mass of the test sample before preliminary drying (mass before drying) and the mass after main drying (mass after drying), the solid content (heating residue) is calculated using the following formula.

[0350] Solid content (mass %) = mass after drying / mass before drying × 100

[0351] (Hydroxy value (OHV) of copolymer)

[0352] The hydroxyl value (mgKOH / g) of the copolymer was measured by method A of JIS K 1557-1.

[0353] (Number average molecular weight (Mn) and weight average molecular weight (Mw) of copolymer)

[0354] The number average molecular weight (Mn) and weight average molecular weight (Mw) of the copolymer were measured using a gel permeation chromatography (GPC) apparatus (manufactured by Tosoh Corporation, HLC-8220). TSK gel α-M (manufactured by Tosoh Corporation, 7.8 mm×30 cm) and TSK guard column α (manufactured by Tosoh Corporation, 6.0 mm×4 cm) were used as chromatographic columns. The calibration curve was prepared using F288 / F1 / 28 / F80 / F40 / F20 / F2 / A1000 (manufactured by Tosoh Corporation, standard polystyrene) and styrene monomer.

[0355] (Glass transition temperature of copolymer (calculated Tg))

[0356] The glass transition temperature of the copolymer is calculated from the glass transition temperature of the homopolymer of each monomer constituting the copolymer and the mass fraction of each monomer by the calculation formula of Fox.

[0357] (SP)

[0358] For the copolymer using the macromonomer, the SP (solubility parameter: δ (J / cm 3 ) 1 / 2). For copolymers without macromonomers, the SP of the entire copolymer was determined. Each SP was determined by a known method described in RF Fedors, "Polym. Eng. Sci.", (1974), 14(2), p.147, p.472. Specifically, the value was calculated using the following formula.

[0359] δ=Σ(miδi)

[0360] In the above formula, mi represents the molar fraction of monomer i constituting the polymer, and δi represents the SP of monomer i constituting the polymer.

[0361] (Gel fraction of coating film)

[0362] Measure about 0.2g of the coating and use a stainless steel mesh (SUS316, twill metal mesh, The sample was wrapped with a mesh (1:1 mesh) and clamped with a clip at the end to serve as a sample. The sample was added to a 2L flask together with 500g of a mixed solvent of methanol:acetone = 1:1 (mass ratio), and refluxed and stirred at 62°C for 4 hours. Then, the sample was taken out from the mixed solvent, washed with 10g of acetone, and dried at 105°C for 2 hours using a hot air dryer. After that, the mass of the coating film remaining in the sample was measured as the mass after drying, and the gel fraction was calculated from the mass after drying and the mass of the measured coating film by the following formula.

[0363] Gel fraction (%) = mass after drying (g) / mass of the measured coating film (g) × 100

[0364] Furthermore, the difference between the gel fraction 8 days after coating and the gel fraction 1 day after coating was determined.

[0365] (Hardness of coating film (HM))

[0366] The Martens hardness (HM) of the coating was measured by an ultra-micro hardness tester (Fischer Instrument Co., Ltd., product name: HM2000). The measurement conditions were set as F (test force) = 50 mN / 10 seconds, C (maximum load creep time) = 10 seconds. The Martens hardness was measured at 5 different locations on the same coating, and the average value was taken as the hardness of the coating.

[0367] <Synthesis example 1>

[0368] (Manufacturing of Dispersant 1)

[0369] 900 parts of deionized water, 60 parts of 2-sulfoethyl sodium methacrylate, 10 parts of potassium methacrylate and 12 parts of methyl methacrylate (MMA) were added to a polymerization device equipped with a stirrer, a cooling tube, a thermometer and a nitrogen inlet tube, and stirred. The polymerization device was substituted with nitrogen while the temperature was raised to 50°C. Among them, 0.08 parts of 2,2'-azobis(2-methylpropionamidine) dihydrochloride were added as a polymerization initiator, and the temperature was further raised to 60°C. The temperature was raised to, and MMA was continuously dripped at a rate of 0.24 parts / minute for 75 minutes using a drip pump. After the reaction solution was kept at 60°C for 6 hours, it was cooled to room temperature to obtain a dispersant 1 having a solid content of 10% by mass as a transparent aqueous solution.

[0370] (Manufacture of chain transfer agent)

[0371] In a synthesis apparatus equipped with a stirring device, 1.00 g of cobalt acetate (II) tetrahydrate, 1.93 g of diphenylglyoxime, and 80 ml of diethyl ether previously deoxygenated by nitrogen bubbling were added under a nitrogen atmosphere, and stirred at room temperature for 30 minutes. Then, 10 ml of boron trifluoride diethyl ether complex was added, and stirred for further 6 hours. The mixture was filtered, and the solid was washed with diethyl ether and vacuum dried for 15 hours to obtain 2.12 g of chain transfer agent 1 as a reddish brown solid.

[0372] (Production of Macromonomer 1)

[0373] In a polymerization apparatus equipped with a stirrer, a cooling tube, a thermometer, and a nitrogen inlet tube, 145 parts of deionized water, 0.1 parts of sodium sulfate, and 0.25 parts of a dispersant 1 (solid content 10% by mass) were added and stirred to prepare a uniform aqueous solution. Then, 100 parts of MMA, 0.008 parts of a chain transfer agent 1, and 0.8 parts of Paoketa (registered trademark) O (1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate, manufactured by NOF Corporation) as a polymerization initiator were added to prepare an aqueous suspension.

[0374] Next, the polymerization apparatus was purged with nitrogen, the temperature was raised to 80°C, and the reaction was carried out for 1 hour. Furthermore, the temperature was raised to 90°C to increase the polymerization rate and maintained for 1 hour. Thereafter, the reaction solution was cooled to 40°C to obtain an aqueous suspension containing a macromonomer. The aqueous suspension was filtered with a filter, the residue remaining on the filter was washed with deionized water, dehydrated, and dried at 40°C for 16 hours to obtain a macromonomer 1. The number average molecular weight of the macromonomer 1 was 1700, and the glass transition temperature measured by DSC was 63°C. Table 1 shows the materials used for the manufacture of the macromonomer 1 and the Mn of the macromonomer 1.

[0375] (Production of Macromonomer 2)

[0376] A macromonomer was obtained in the same manner except that 100 parts of MMA in Synthesis Example 1 was changed to 50 parts of MMA, 50 parts of IBXMA, and 0.8 parts of Perokta (registered trademark) O (1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate, manufactured by NOF Corporation) was changed to 1.1 parts. The number average molecular weight was 1700. Table 1 shows the materials used in the preparation of the macromonomer 2 and the Mn of the macromonomer 2.

[0377] [Table 1]

[0378]

[0379] <Example 1>

[0380] (Manufacturing of copolymer solution)

[0381] In a reaction vessel equipped with a thermometer, a temperature controller, a stirrer, a reflux cooler, a nitrogen inlet pipe, and a dripping device, 50 parts of butyl acetate and 30 parts of a macromonomer (MM-MMA) were added, the inside of the polymerization device was replaced with nitrogen, and the temperature was raised to 120°C. A monomer mixture containing 20 parts of styrene, 13.9 parts of isobornyl acrylate, 36 parts of 2-hydroxypropyl acrylate, 0.1 part of acrylic acid, 10 parts of butyl acetate, 3.0 parts of Parbutil O (tert-butyl peroxy 2-ethylhexanoate, manufactured by NOF Corporation) and 3.0 parts of 2,2'-azobis(2-methylbutyronitrile) was dripped therein over 4 hours. After the dripping was completed, 5 parts of butyl acetate was rapidly dripped, and then aging was performed for 30 minutes. Then, a mixture of 20 parts of butyl acetate and 0.2 parts of Pabuthyl O was dripped over 30 minutes, and after the dripping was completed, it was aged for 1.5 hours. Then, 15 parts of butyl acetate was further added to obtain a copolymer solution with a solid content of 51.8% by mass. The copolymer contained in the obtained copolymer solution had a hydroxyl value (OHV) of 155 mgKOH / g, a number average molecular weight (Mn) of 4000, a weight average molecular weight (Mw) of 8800, a calculated Tg of 38.4°C, and a main chain SP of 23.6 (J / cm 3 ) 1 / 2 , the SP of the side chain is 20.3 (J / cm 3 ) 1 / 2 .

[0382] (evaluate)

[0383] The copolymer solution and isocyanurate of hexamethylene diisocyanate (Duranet (registered trademark) TPA100, manufactured by Asahi Kasei Corporation, nonvolatile matter 100%, NCO group content 23.1%) were mixed at a molar ratio of NCO / OH of 1 / 1 to prepare a coating composition.

[0384] The coating composition was applied on a polypropylene plate using a 6 mil applicator, dried at 70° C. for 30 minutes to form a coating film, and then cured (stored) at a temperature of 23.5° C. and a relative humidity of 50%.

[0385] The gel fraction and hardness of the coating film were measured 24 hours after the start of curing (storage) (one day after coating) and 192 hours after the start of curing (storage) (eight days after coating).

[0386] <Examples 2 to 6, Comparative Examples 1 to 3>

[0387] A copolymer solution was obtained in the same manner as in Example 1 except that the composition of the material added before heating in the reaction vessel (initial charge) and the monomer-containing mixture first added dropwise after heating were respectively as shown in Table 2. Table 2 shows the hydroxyl value (OHV), number average molecular weight (Mn), weight average molecular weight (Mw), calculated Tg and SP of the copolymer contained in each copolymer solution.

[0388] The obtained copolymer solution was evaluated in the same manner as in Example 1. Table 2 shows the results.

[0389] [Table 2]

[0390]

[0391] In the table, the abbreviations of the monomer mixtures have the following meanings.

[0392] Macromonomer 1: The macromonomer with a number average molecular weight of 1700 obtained in Synthesis Example 1.

[0393] Macromonomer 2: the macromonomer obtained in Synthesis Example 2 having a number average molecular weight of 1,700.

[0394] MMA: methyl methacrylate.

[0395] St: Styrene.

[0396] IBXA: Isobornyl acrylate.

[0397] EHA: 2-ethylhexyl acrylate.

[0398] HPMA: 2-hydroxypropyl methacrylate.

[0399] HPA: 2-hydroxypropyl acrylate.

[0400] HEA: 2-hydroxyethyl acrylate.

[0401] AA: Acrylic acid.

[0402] AMBN: 2,2'-azobis(2-methylbutyronitrile).

[0403] The copolymer of Comparative Example 1 had a gel fraction of more than 70% one day after coating, because the structural unit having a primary hydroxyl group exceeded 30 parts by mass, even though the macromonomer 1 was used. The copolymer of Comparative Example 2 had a hydroxyl value of less than 120 mgKOH / g, so the gel fraction was 80% or less eight days after coating, and HM was also less than 100. The copolymer of Comparative Example 3, which was a random copolymer without using a macromonomer, had a gel fraction of more than 70% one day after coating.

[0404] These results show that when the macromonomer-derived structural unit and the vinyl monomer-derived structural unit are contained and the primary hydroxyl group is 30 parts by mass or less, the gel fraction and hardness 8 days after coating can be sufficiently improved while suppressing the initial hardness.

[0405] Industrial Applicability

[0406] The present invention can provide a coating composition that can effectively perform repair work on a coating film after coating, a (meth)acrylic copolymer suitable for obtaining the coating composition, and a coated article and a method for forming a multilayer coating film using the coating composition.

Claims

1. A composition comprising a (meth)acrylic copolymer and a polyisocyanate compound or a blocked polyisocyanate compound, wherein the molar ratio NCO / OH of the isocyanate group of the polyisocyanate compound or the blocked isocyanate group of the blocked polyisocyanate compound relative to the hydroxyl group of the (meth)acrylic copolymer is 0.5 to 1, The (meth)acrylic copolymer is a (meth)acrylic copolymer comprising a structural unit derived from a macromonomer (a) and a structural unit derived from a vinyl monomer (b). The (meth)acrylic acid-based copolymer has a hydroxyl value of 120 mgKOH / g or more and 260 mgKOH / g or less, The content of the structural unit having a primary hydroxyl group of the (meth)acrylic copolymer is 30 parts by mass or less relative to 100 parts by mass of the structural unit derived from the macromonomer (a) and the structural unit derived from the vinyl monomer (b); the content of the structural unit having at least one of a secondary hydroxyl group and a tertiary hydroxyl group is 15 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the structural unit of the (meth)acrylic copolymer; in, The monomer (a) is represented by the following formula (1): In the formula, R represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted cycloalkyl group, an unsubstituted or substituted aryl group, or an unsubstituted or substituted heterocyclic group, Q represents a main chain portion containing two or more structural units (a'), and Z represents a terminal group. Wherein, the structural unit (a') is shown in the following formula (a'): In the formula, R 1 represents a hydrogen atom, a methyl group or CH2OH, R 2 Represents OR 3 , halogen atoms, COR 4 、COOR 5 、CN、CONR 6 R 7 or R 8 , R 3 ~R 7 Each independently represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, an unsubstituted or substituted aryl group, an unsubstituted or substituted heteroaryl group, an unsubstituted or substituted non-aromatic heterocyclic group, an unsubstituted or substituted aralkyl group, an unsubstituted or substituted alkaryl group, or an unsubstituted or substituted organosilyl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group (COOH), a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group (SO3H) and a halogen atom, and R 8 represents an unsubstituted or substituted aryl group, or an unsubstituted or substituted heteroaryl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group, a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group, an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted olefin group and a halogen atom.

2. A composition comprising a (meth)acrylic copolymer and a polyisocyanate compound or a blocked polyisocyanate compound, wherein the molar ratio NCO / OH of the isocyanate group of the polyisocyanate compound or the blocked isocyanate group of the blocked polyisocyanate compound relative to the hydroxyl group of the (meth)acrylic copolymer is 0.5 to 1, The (meth)acrylic copolymer is a (meth)acrylic copolymer comprising a structural unit derived from a macromonomer (a) and a structural unit derived from a vinyl monomer (b). At least one of the structural unit derived from the macromonomer (a) and the structural unit derived from the vinyl monomer (b) has a hydroxyl group, and the hydroxyl value of the (meth)acrylic copolymer is 120 mgKOH / g or more and 260 mgKOH / g or less, The gel fraction is less than 70% one day after coating and more than 80% eight days after coating. in, The monomer (a) is represented by the following formula (1): In the formula, R represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted cycloalkyl group, an unsubstituted or substituted aryl group, or an unsubstituted or substituted heterocyclic group, Q represents a main chain portion containing two or more structural units (a'), and Z represents a terminal group. Wherein, the structural unit (a') is shown in the following formula (a'): In the formula, R 1 represents a hydrogen atom, a methyl group or CH2OH, R 2 Represents OR 3 , halogen atoms, COR 4 、COOR 5 、CN、CONR 6 R 7 or R 8 , R 3 ~R 7 Each independently represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, an unsubstituted or substituted aryl group, an unsubstituted or substituted heteroaryl group, an unsubstituted or substituted non-aromatic heterocyclic group, an unsubstituted or substituted aralkyl group, an unsubstituted or substituted alkaryl group, or an unsubstituted or substituted organosilyl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group (COOH), a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group (SO3H) and a halogen atom, and R 8 represents an unsubstituted or substituted aryl group or an unsubstituted or substituted heteroaryl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group, a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group, an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted olefin group and a halogen atom, "Painting method" A coating composition is obtained by dissolving a (meth)acrylic acid copolymer and an isocyanurate of hexamethylene diisocyanate in an organic solvent at a molar ratio of NCO / OH of 1 / 1, applying the coating composition on a polypropylene plate with a 6 mil applicator, drying at 70° C. for 30 minutes to form a coating film, and storing the coating film at a temperature of 23.5° C. and a relative humidity of 50%; "Method for determination of gel fraction" Measure about 0.2g of the coating and use SUS316, twill metal mesh, The sample was wrapped with a stainless steel mesh with a mesh, and the end was clamped with a clip to serve as a sample; the sample was placed in 500 g of a mixed solvent of methanol:acetone=1:1 by mass ratio, and refluxed and stirred at 65°C for 4 hours, then the sample was taken out from the mixed solvent, washed with 10 g of acetone, and dried with a hot air dryer at 105°C for 2 hours; then, the mass of the coating film remaining in the sample was measured and taken as the mass after drying, and the gel fraction was calculated from the mass after drying and the mass of the measured coating film according to the following formula; Gel fraction % = mass after drying / mass of the measured coating × 100, The mass after drying and the mass of the measured coating film are both in g.

3. A composition comprising a (meth)acrylic copolymer and a polyisocyanate compound or a blocked polyisocyanate compound, wherein the molar ratio NCO / OH of the isocyanate group of the polyisocyanate compound or the blocked isocyanate group of the blocked polyisocyanate compound relative to the hydroxyl group of the (meth)acrylic copolymer is 0.5 to 1, The (meth)acrylic copolymer is a (meth)acrylic copolymer comprising a structural unit derived from a macromonomer (a) and a structural unit derived from a vinyl monomer (b). At least one of the structural unit derived from the macromonomer (a) and the structural unit derived from the vinyl monomer (b) has a hydroxyl group, and the hydroxyl value of the (meth)acrylic copolymer is 120 mgKOH / g or more and 260 mgKOH / g or less, The relationship between the gel fraction after 1 day of coating and the gel fraction after 8 days of coating is expressed by the following formula (I): 100 ≥ (gel fraction 8 days after coating) - (gel fraction 1 day after coating) ≥ 40… (I); in, The monomer (a) is represented by the following formula (1): In the formula, R represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted cycloalkyl group, an unsubstituted or substituted aryl group, or an unsubstituted or substituted heterocyclic group, Q represents a main chain portion containing two or more structural units (a'), and Z represents a terminal group. Wherein, the structural unit (a') is shown in the following formula (a'): In the formula, R 1 represents a hydrogen atom, a methyl group or CH2OH, R 2 Represents OR 3 , halogen atoms, COR 4 、COOR 5 、CN、CONR 6 R 7 or R 8 , R 3 ~R 7 Each independently represents a hydrogen atom, an unsubstituted or substituted alkyl group, an unsubstituted or substituted alicyclic group, an unsubstituted or substituted aryl group, an unsubstituted or substituted heteroaryl group, an unsubstituted or substituted non-aromatic heterocyclic group, an unsubstituted or substituted aralkyl group, an unsubstituted or substituted alkaryl group, or an unsubstituted or substituted organosilyl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group (COOH), a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group (SO3H) and a halogen atom, and R 8 represents an unsubstituted or substituted aryl group or an unsubstituted or substituted heteroaryl group, wherein the substituent in each of these groups is at least one selected from the group consisting of a carboxylic acid group, a carboxylate group, an epoxy group, a hydroxyl group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanate group, a sulfonic acid group, an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted olefin group and a halogen atom, "Painting method" A coating composition is obtained by dissolving a (meth)acrylic acid copolymer and an isocyanurate of hexamethylene diisocyanate in an organic solvent at a molar ratio of NCO / OH of 1 / 1, applying the coating composition on a polypropylene plate with a 6 mil applicator, drying at 70° C. for 30 minutes to form a coating film, and storing the coating film at a temperature of 23.5° C. and a relative humidity of 50%; "Method for determination of gel fraction" Measure about 0.2g of the coating and use SUS316, twill metal mesh, The sample was wrapped with a stainless steel mesh with a mesh, and the end was clamped with a clip to serve as a sample; the sample was placed in 500 g of a mixed solvent of methanol:acetone=1:1 by mass ratio, and refluxed and stirred at 65°C for 4 hours, then the sample was taken out from the mixed solvent, washed with 10 g of acetone, and dried with a hot air dryer at 105°C for 2 hours; then, the mass of the coating film remaining in the sample was measured and taken as the mass after drying, and the gel fraction was calculated from the mass after drying and the mass of the measured coating film according to the following formula; Gel fraction % = mass after drying / mass of the measured coating × 100, The mass after drying and the mass of the measured coating film are both in g.

4. The composition according to any one of claims 1 to 3, wherein The number average molecular weight of the macromonomer (a) is 500 or more and 100,000 or less.

5. A coating composition comprising the composition according to any one of claims 1 to 4.

6. The coating composition according to claim 5, wherein The content of the (meth)acrylic copolymer is 30% by mass or more relative to the resin solid content of the coating composition.

7. The coating composition according to claim 5 or 6, wherein The composition also contains a curing agent.

8. The coating composition according to claim 5 or 6, wherein The Martens hardness of the coating film 1 day after coating was 10 or less, and the Martens hardness of the coating film 8 days after coating was 100 or more.

9. A coated article coated with the coating composition according to claim 5 or 6.

10. A method for forming a multilayer coating film, comprising applying a first colored base coating on a cured coating film of an electrodeposition coating to form a first colored base coating film, applying a second colored base coating on the first colored base coating to form a second colored base coating film, then preheating the first colored base coating film and the second colored base coating film, applying a clear coating on the second colored base coating film to form a clear coating film, and simultaneously heating and curing the three layers of coating films to form a multilayer coating film, As the clear coating material, the coating composition according to claim 5 or 6 is used.

Images