Multicomponent type organic solvent-based primer composition and repair coating method

Abstract

To provide a multicomponent type organic solvent-based primer composition which has good finishing property and adhesion even in thick film coating, and is excellent in polishing workability, and a repair coating method using the same.SOLUTION: A multicomponent type organic solvent-based primer composition is obtained by mixing a main agent component (I), and a curing agent component (II), wherein the main agent component (I) contains acryl polyol (A), a pigment composition (B) and an organic solvent (C), the curing agent component (II) contains a polyisocyanate compound, the pigment composition (B) contained in the main agent component (I) contains barium sulfate and talc and / or clay as a part of the component, a content of the pigment composition (B) is within the range of 250 to 500 pts.mass based on 100 pts.mass of the solid content of the acryl polyol (A), and a content of the barium sulfate contained in the pigment composition (B) is 120 to 400 pts.mass based on 100 pts.mass of the solid content of the acryl polyol (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a multi-component organic solvent-based primer coating composition and a refinish coating method using the multi-component organic solvent-based primer coating composition. [Background technology]

[0002] Generally, repair painting of automobile exterior panels and the like involves removing the old paint film from the damaged area and sanding it, then sequentially painting the affected area with putty, primer surfacer, and topcoat.

[0003] Among these, primer surfacer coatings generally require polishing after application. Thick coatings of 100 μm or more are often required, in which case application is performed at a low dilution rate to achieve high viscosity. Furthermore, improving polishing workability has traditionally been achieved by designing coatings with high pigment concentrations (especially talc). Patent Document 1 discloses a multi-component organic solvent-based primer coating composition obtained by mixing a base component and a curing agent component, wherein the base component contains a lactone-modified acrylic polyol, a pigment composition, and an organic solvent, the curing agent component contains a polyisocyanate compound, the pigment composition contained in the base component contains talc as part of its components, the talc content is 50 to 300 parts by mass based on 100 parts by mass of the lactone-modified acrylic polyol solids content, and the pigment composition content is 50 to 500 parts by mass based on 100 parts by mass of the lactone-modified acrylic polyol solids content. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-96594 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when applied at a low dilution rate to create a thick coating, the coating surface becomes rough, and it takes time to polish it to a smooth surface. Also, coatings with high pigment concentrations have issues with adhesion to the top coat and base coat.

[0006] The problem to be solved by the present invention is to provide a multi-component organic solvent-based primer paint composition that has good finish and adhesion even when used in thick-film coatings and is excellent in sanding workability, and a repair painting method using the same. [Means for solving the problem]

[0007] As a result of intensive research into solving the above-mentioned problems, the inventors have discovered that the above-mentioned problems can be solved by a multi-component organic solvent-based primer coating composition obtained by mixing a main component (I) and a curing agent component (II), wherein the main component (I) comprises an acrylic polyol (A), a pigment composition (B), and an organic solvent (C), the curing agent component (II) comprises a polyisocyanate compound, the pigment composition (B) contained in the main component (I) comprises barium sulfate and talc and / or clay as part of its components, the content of the pigment composition (B) being in the range of 250 to 500 parts by mass based on 100 parts by mass of the solids content of the acrylic polyol (A), and the content of the barium sulfate contained in the pigment composition (B) being in the range of 120 to 400 parts by mass based on 100 parts by mass of the solids content of the acrylic polyol (A), and have completed the present invention. That is, the present invention provides the following multi-component organic solvent-based primer coating composition and repair coating method. Item 1. A multi-component organic solvent-based primer coating composition obtained by mixing a main component (I) and a curing agent component (II), The main agent component (I) contains an acrylic polyol (A), a pigment composition (B), and an organic solvent (C), and the curing agent component (II) contains a polyisocyanate compound; The pigment composition (B) contained in the main component (I) contains barium sulfate and talc and / or clay as part of its components, the content of the pigment composition (B) is within a range of 250 to 500 parts by mass based on 100 parts by mass of the solid content of the acrylic polyol (A); An undercoat paint composition, wherein the content of barium sulfate contained in the pigment composition (B) is within the range of 120 to 400 parts by mass based on 100 parts by mass of the solid content of the acrylic polyol (A). Item 2. The solubility parameter (SP value) of the acrylic polyol (A) is 8.5 to 9.5 (cal / cm 3 ) 1 / 2 Item 1. The undercoat paint composition according to item 1, which is within the range of Item 3. The undercoat coating composition according to Item 1 or 2, wherein the main component (I) and / or the curing agent component (II) further contain a hydroxyl-free acrylic resin (D) having a weight-average molecular weight of 3,000 to 10,000. Item 4. The primer coating composition according to any one of Items 1 to 3, wherein the main component (I) further contains a surface conditioner having a nonionic hydrophilic group. Item 5. The undercoat coating composition according to any one of Items 1 to 4, wherein the main component (I) further contains a silane coupling agent. Item 6. A repair coating method comprising the steps of applying the primer coating composition according to any one of items 1 to 5 to a repair area that may have been applied with putty to form a primer coating film of 30 to 500 μm, and then applying a colored coating composition on the primer coating film. Item 7. The repair painting method according to Item 6, wherein the colored paint composition is a water-based paint. Item 8. A repair coating method comprising a step of applying an undercoat coating composition obtained by adding a chlorinated polyolefin to the undercoat coating composition according to any one of items 1 to 5 to a repair area including a plastic surface. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a multi-component organic solvent-based primer paint composition that has good finish and adhesion even when applied to a thick film and is excellent in sanding workability, and a repair painting method using the same. DETAILED DESCRIPTION OF THE INVENTION

[0009] The primer coating composition of the present invention is a multi-component composition obtained by mixing a main component (I) and a curing agent component (II). If necessary, the primer coating composition of the present invention can also be a multi-component composition obtained by mixing three or more components including components other than the main component (I) and the curing agent component (II). Each component used in the present invention will be described below.

[0010] <Acrylic polyol (A)> In the present invention, the main component (I) contains an acrylic polyol (A).

[0011] The acrylic polyol (A) in the present invention is a component that can serve as a coating film-forming component together with the polyisocyanate compound described below. Any conventionally known acrylic polyol can be used without limitation as long as it has organic solvent dilutability and coating film-forming ability, and can be, for example, a copolymer of polymerizable unsaturated monomers containing a hydroxyl group-containing polymerizable unsaturated monomer as an essential component and at least one (meth)acryloyl group-containing monomer.

[0012] Examples of hydroxyl group-containing polymerizable unsaturated monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate; ε-caprolactone-modified products of the above hydroxyalkyl (meth)acrylates; hydroxyl group-containing (meth)acryloyl monomers such as polyoxyethylene chain-containing (meth)acrylates whose molecular terminals are hydroxyl groups; and allyl alcohol, and these can be used alone or in combination of two or more.

[0013] Examples of the polymerizable unsaturated monomer to be copolymerized with the hydroxyl group-containing polymerizable unsaturated monomer include linear or branched alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; cyclohexyl (meth)acrylate; acrylate, alicyclic alkyl (meth)acrylate such as isobornyl (meth)acrylate; aralkyl (meth)acrylate such as benzyl (meth)acrylate; alkoxyalkyl (meth)acrylate such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate; perfluoroalkyl (meth)acrylate; N,N-dialkylaminoalkyl (meth)acrylate such as N,N-diethylaminoethyl (meth)acrylate; (meth)acrylamide; allyl (meth)acrylate acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tetra(meth)acrylate (Meth)acryloyl monomers having at least two polymerizable unsaturated groups in one molecule, such as glycerol di(meth)acrylate, 1,1,1-trishydroxymethylethane di(meth)acrylate, 1,1,1-trishydroxymethylethane tri(meth)acrylate, and 1,1,1-trishydroxymethylpropane tri(meth)acrylate; (meth)acrylic acid; carbonyl group-containing (meth)acryloyl monomers, such as acetoacetoxyethyl (meth)acrylate and diacetone (meth)acrylamide;Examples of the epoxy group-containing (meth)acryloyl monomers include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, and 3,4-epoxycyclohexylpropyl (meth)acrylate; isocyanato group-containing (meth)acryloyl monomers such as isocyanatoethyl (meth)acrylate; alkoxysilyl group-containing (meth)acryloyl monomers such as γ-methacryloyloxypropyltrimethoxysilane and γ-methacryloyloxypropyltriethoxysilane; and oxidatively curable group-containing (meth)acryloyl monomers such as dicyclopentenyloxyethyl (meth)acrylate, dicyclopentenyloxypropyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. These may be used alone or in combination of two or more.

[0014] Examples of copolymerizable polymerizable unsaturated monomers other than (meth)acryloyl monomers include (meth)acrylonitrile; vinyl ester compounds such as vinyl acetate and vinyl propionate; vinyl aromatic compounds such as styrene and α-methylstyrene; polyvinyl compounds having at least two polymerizable unsaturated groups in one molecule such as triallyl isocyanurate, diallyl terephthalate and divinylbenzene; carboxyl group-containing polymerizable unsaturated monomers such as maleic acid, crotonic acid and β-carboxyethyl acrylate; (meth)acrolein, formyl styrene, vinyl alkyl ketones having 4 to 7 carbon atoms (for example, vinyl methyl ketone and vinyl ethyl ketone), vinyl butyl ketone, etc.), acetoacetoxy allyl ester, and other carbonyl group-containing polymerizable unsaturated monomers; allyl glycidyl ether, and other epoxy group-containing polymerizable unsaturated monomers; m-isopropenyl-α,α-dimethylbenzyl isocyanate, and other isocyanato group-containing polymerizable unsaturated monomers; vinyltrimethoxysilane, vinyltriethoxysilane, and other alkoxysilyl group-containing polymerizable unsaturated monomers; and oxidatively curable group-containing polymerizable unsaturated monomers, such as reaction products of epoxy group-containing polymerizable unsaturated monomers or hydroxyl group-containing polymerizable unsaturated monomers with unsaturated fatty acids. These may be used alone or in combination of two or more.

[0015] From the viewpoint of adhesion of the formed coating film, the acrylic polyol (A) suitably has a weight average molecular weight in the range of 5,000 to 80,000, preferably 6,000 to 70,000, and a solids hydroxyl value of 200 mgKOH / g or less, preferably 50 to 150 mgKOH.

[0016] In this specification, the weight-average molecular weight is a value obtained by converting the weight-average molecular weight measured using a gel permeation chromatograph ("HLC8120GPC" manufactured by Tosoh Corporation) to the weight-average molecular weight of polystyrene as a standard. Four columns, "TSKgel G-4000HxL," "TSKgel G-3000HxL," "TSKgel G-2500HxL," and "TSKgel G-2000HxL" (all manufactured by Tosoh Corporation), were used, and the measurement was performed under the following conditions: mobile phase: tetrahydrofuran, measurement temperature: 40°C, flow rate: 1 ml / min, and detector: RI.

[0017] The acrylic polyol (A) has a solubility parameter (SP value) of 8.5 to 9.5 (cal / cm 3 ) from the viewpoint of dilutability with an organic solvent and compatibility with the chlorinated polyolefin described below. 3 ) 1 / 2 It is preferable that the range is 8.5 to 9.0 (cal / cm 3 ) 1 / 2 It is more preferable that the temperature is in the range of

[0018] In this specification, the solubility parameter (abbreviated as "SP value") represents a measure of the intermolecular interaction of liquid molecules. The SP value of a homopolymer of a polymerizable monomer is described in J. Paint Technology, vol. 42, 176 (1970). The SP value of a copolymer of a polymerizable monomer mixture can be calculated using the following formula. SP value = SP1 x fw1 + SP2 x fw2 + ... + SPn x fwn In the above formula, SP1, SP2, .... SPn represent the SP values ​​of the homopolymers of the respective polymerizable monomers, and fw1, fw2, .... fwn represent the mass fractions of the respective polymerizable unsaturated monomers relative to the total amount of monomers.

[0019] The acrylic polyol (A) is suitably contained in an amount of 75% by mass or more, preferably 85% by mass or more, of the resin solid content contained in the main component (I).

[0020] In this specification, the term "solid content" or "non-volatile content" refers to the residue remaining after removing the volatile components, and the residue may be solid or liquid at room temperature. For example, the term refers to the residue remaining after treating a sample at 105°C for 3 hours to remove the volatile components.

[0021] The content of the acrylic polyol (A) in the main component (I) is typically 1 to 50 parts by mass, preferably 5 to 40 parts by mass, and more preferably 10 to 30 parts by mass, in terms of non-volatile content, per 100 parts by mass of the total mass of the main component (I).

[0022] <Pigment composition (B)> In the present invention, the main component (I) contains a pigment composition (B), and as part of its components, barium sulfate and talc and / or clay are contained as extender pigments.

[0023] In the present invention, barium sulfate, talc, and clay may be any of those known as extender pigments in the field of paints, etc. They may be synthetic or natural products, and may be surface-treated as necessary. There are no limitations on their shape or size.

[0024] The undercoat paint composition of the present invention is characterized in that the content of barium sulfate contained in the pigment composition (B) is within the range of 120 to 400 parts by mass based on 100 parts by mass of the solid content of the acrylic polyol (A) contained in the main component (I).

[0025] In the present invention, the undercoat paint composition contains barium sulfate, and by keeping the barium sulfate content within this range, the finish when a thick film is applied and the adhesion to the topcoat paint film and the base are improved.

[0026] In the present invention, the content of barium sulfate based on 100 parts by mass of the solid content of the acrylic polyol (A) is preferably 120 to 350 parts by mass, more preferably 140 to 270 parts by mass.

[0027] Furthermore, by including talc and / or clay in addition to barium sulfate in the pigment composition (B), the undercoat paint composition can be improved in thickness and sandability. Although either talc or clay may be included, it is particularly preferred that both talc and clay are included.

[0028] When the pigment composition (B) contains talc, it preferably contains 5 to 100 parts by mass, particularly preferably 10 to 90 parts by mass, based on 100 parts by mass of the solid content of the acrylic polyol (A).

[0029] When the pigment composition (B) contains clay, it preferably contains 5 to 100 parts by mass, particularly preferably 10 to 80 parts by mass, based on 100 parts by mass of the solid content of the acrylic polyol (A).

[0030] Furthermore, the pigment composition (B) may contain known pigments such as extender pigments other than barium sulfate, talc, and clay, color pigments, and rust-preventive pigments, as required.

[0031] Among these, examples of other extender pigments include barium carbonate, aluminum silicate, gypsum, calcium carbonate, silica, white carbon, diatomaceous earth, magnesium carbonate, alumina white, gloss white, and mica powder.

[0032] Examples of color pigments include white pigments such as titanium dioxide; black pigments such as carbon black, acetylene black, lamp black, bone black, graphite, iron black, and aniline black; yellow pigments such as yellow iron oxide, titanium yellow, monoazo yellow, condensed azo yellow, azomethine yellow, bismuth vanadate, benzimidazolone, isoindolinone, isoindoline, quinophthalone, benzidine yellow, and permanent yellow; orange pigments such as permanent orange; red iron oxide, naphthol AS-based azo red, anthanthrone, anthraquinonyl red, and perilemma. Examples of pigments that can be used include red pigments such as rune, quinacridone red pigments, diketopyrrolopyrrole, watching red, and permanent red; purple pigments such as cobalt purple, quinacridone violet, and dioxazine violet; blue pigments such as cobalt blue, phthalocyanine blue, and threne blue; green pigments such as phthalocyanine green; metallic pigments such as aluminum powder, bronze powder, copper powder, tin powder, iron phosphide, and zinc powder; and pearlescent pigments such as metal oxide-coated mica powder and mica-like iron oxide. These pigments can be used alone or in combination of two or more.

[0033] When the undercoat paint composition of the present invention contains a color pigment, it is preferable from the viewpoint of hiding power and the finished appearance of the top coat that the mass of the color pigment is 1 or more and less than 100 parts by mass, preferably 2 to 80 parts by mass, and more preferably 3 to 60 parts by mass, based on 100 parts by mass of the total of barium sulfate, talc, and clay.

[0034] In the present invention, the content of the pigment composition (B) is in the range of 250 to 500 parts by mass, preferably 300 to 400 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solids contained in the main component (I), from the viewpoints of workability of the primer coating composition and adhesion strength of the coating film.

[0035] <Organic solvent (C)> In the present invention, the organic solvent (C) may be, for example, an organic compound having a molecular weight in the range of 58 to 220, particularly 72 to 200, and any organic solvent known in the field of coatings may be used without limitation. However, it is desirable that the organic solvent (C) contains at least one organic solvent selected from, for example, ester-based organic solvents and ketone-based organic solvents.

[0036] Examples of such ester-based organic solvents include ethyl acetate, butyl acetate, isobutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, 3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and diethylene glycol monoethyl ether acetate. Examples of ketone-based organic solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl isoamyl ketone, diisobutyl ketone, methylhexyl ketone, and isophorone. These can be used alone or in combination of two or more.

[0037] The amount of at least one organic solvent selected from such ester-based organic solvents and ketone-based organic solvents used is desirably 5% by mass or more, and particularly 20% by mass or more, of the total organic solvents contained in the undercoat paint composition of the present invention.

[0038] In the present invention, examples of organic solvents other than the above-mentioned ester-based organic solvents and ketone-based organic solvents include linear alkanes such as n-butane, n-hexane, n-heptane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane, n-hexadecane, and n-heptadecane; 2-methylbutane, 2,2-dimethylpropane, 2-methylpentane; hexane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 2,4-dimethylpentane, 2,2,3-trimethylpentane, 2,2,4-trimethylpentane, 3,4-diethylhexane, 2,6-dimethyloctane, 3,3-dimethyloctane, 3,5-dimethyloctane, 4,4-dimethyloctane, 3-ethyl-3- branched alkanes such as methylheptane, 2-methylnonane, 3-methylnonane, 4-methylnonane, 5-methylnonane, 2-methylundecane, 3-methylundecane, and 2,2,4,6,6-pentamethylheptane; aliphatic hydrocarbon organic solvents such as cyclic alkanes such as cyclopentane, t-decalin, cyclohexane, methylcyclohexane, ethylcyclohexane, 1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, propylcyclohexane, isopropylcyclohexane, 1,2-methylethylcyclohexane, 1,3-methylethylcyclohexane, 1,4-methylethylcyclohexane, 1,2,3-trimethylcyclohexane, 1,2,4-trimethylcyclohexane, and 1,3,5-trimethylcyclohexane; and aromatic hydrocarbon organic solvents such as toluene and xylene.Dioxane, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol mono Examples of the organic solvent include ether-based organic solvents such as tert-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, and dipropylene glycol monoisopropyl ether; and alcohol-based organic solvents such as methanol, isopropanol, tert-butanol, secondary butanol, isobutanol, n-butanol, 2-ethylhexanol, n-octanol, and benzyl alcohol.

[0039] The organic solvent (C) can be blended as a polymerization solvent or dilution solvent in the production of the acrylic polyol (A), or as a dilution solvent in the production of the main component (I).

[0040] <Polyisocyanate compounds> In the present invention, the polyisocyanate compound refers to a polyisocyanate compound having two or more isocyanate groups per molecule. Specific examples include polyisocyanate compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, xylylene diisocyanate, meta-tetramethylxylylenediisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and lysine diisocyanate, as well as adducts of these polyisocyanates with polyhydric alcohols, low-molecular-weight polyester resins, or water, as well as cyclized polymers of the above-mentioned polyisocyanates, and isocyanate-biuret compounds, which may be used alone or in combination of two or more.

[0041] <Main ingredient (I)> In the present invention, the main component (I) contains an acrylic polyol (A), a pigment composition (B), and an organic solvent (C).

[0042] In the present invention, the non-volatile content of the main component (I) is suitably in the range of 50 to 90 mass %, particularly 60 to 80 mass %, from the viewpoints of coating workability and the finish of the formed coating film.

[0043] The main agent component (I) can have a low viscosity relative to its solid content, and can exhibit excellent coating workability. Specifically, the viscosity in the storage state (sealed can state) can be set to a range of 75 to 140 KU, particularly 80 to 120 KU.

[0044] In this specification, the viscosity is measured using a Stormer viscometer on a sample adjusted to 25°C.

[0045] <Hardening agent component (II)> In the present invention, the curing agent component (II) contains the above polyisocyanate compound.

[0046] From the viewpoints of workability and miscibility with the main component (I), it is preferable that the curing agent component (II) contains an organic solvent. The organic solvent can be appropriately selected from the compounds exemplified in the description of the organic solvent (C) above. From the viewpoints of coating workability and the finish of the formed coating film, the non-volatile content of the curing agent component (II) is suitably in the range of 5 to 90 mass%, particularly 20 to 60 mass%.

[0047] <Other additives> The undercoat coating composition of the present invention may further contain, as appropriate, paint additives such as viscosity modifiers, curing catalysts, modifying resins other than the acrylic polyol (A), such as cellulose acetate butyrate and its modified products, polyester resins, alkyd resins, polyurethane resins, etc., pigment dispersants, surface conditioners, resin particles, etc. These additives may be contained in either the main component (I) or the curing agent component (II), but from the viewpoint of storage stability, it is preferable that additives capable of directly reacting with the isocyanate compound be contained in the main component (I).

[0048] The undercoat coating composition of the present invention preferably contains an acrylic resin (D) that does not contain a hydroxyl group. By containing an acrylic resin (D) that does not contain a hydroxyl group, the polishability of the coating film is improved.

[0049] Specific examples of the acrylic resin (D) having no hydroxyl groups include ARUFON UP1000, ARUFON UP1010, ARUFON UP1020, ARUFON UP1021, ARUFON UP1060, ARUFON UP1061, ARUFON UP1070, and ARUFON UP1080 (all manufactured by Toagosei Co., Ltd.).

[0050] The weight average molecular weight of the acrylic resin (D) having no hydroxyl groups is preferably 3,000 to 10,000, and more preferably 4,000 to 9,000.

[0051] The content of the acrylic resin (D) having no hydroxyl groups is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solid content contained in the main component (I).

[0052] The acrylic resin (D) having no hydroxyl groups may be contained in either the main component (I) or the curing agent component (II), but is preferably contained in the main component (I).

[0053] The primer coating composition of the present invention preferably further contains a surface conditioner having a nonionic hydrophilic group. The inclusion of a surface conditioner having a nonionic hydrophilic group improves the finish of the coating film formed from the primer coating composition and the wettability of the topcoat coating to the primer coating composition, thereby improving the finish of the final coating film. The surface conditioner having a nonionic hydrophilic group may be contained in either the main component (I) or the curing agent component (II), but since the storage stability is improved when the main component (I) contains a surface conditioner having a nonionic hydrophilic group, it is preferably contained in the main component (I).

[0054] Specific examples of the nonionic hydrophilic group include polyoxyalkylene groups such as polyoxyethylene groups, polyoxypropylene groups, and polyoxyethylene (oxypropylene) groups.

[0055] As the surface conditioner having a nonionic hydrophilic group, any surface conditioner known in the field of coatings can be used without limitation, and the synthesis method, materials used, etc. are not particularly limited, and commercially available products can also be used.

[0056] The content of the surface conditioner having a nonionic hydrophilic group is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solid content contained in the main component (I).

[0057] From the viewpoint of improving adhesion, it is preferable that the main component (I) contains a silane coupling agent. The type of silane coupling agent is not particularly limited, but examples thereof include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)methyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)methyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl)methyldimethoxysilane; 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2 Examples of suitable silane coupling agents include amino group-containing silane coupling agents such as (aminoethyl) 3-aminopropyltrimethoxysilane and N-2(aminoethyl) 3-aminopropylmethyldimethoxysilane; mercapto group-containing silane coupling agents such as 3-mercaptopropyltrimethoxysilane; vinyl group-containing silane coupling agents such as vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris(methoxyethoxy)silane; and (meth)acryloyl group-containing silane coupling agents such as 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, and 3-(meth)acryloyloxypropyldimethoxymethylsilane. Two or more of these can also be used in combination. Among these, it is preferable to use an epoxy group-containing silane coupling agent.

[0058] The content of the silane coupling agent is preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solid content contained in the main component (I).

[0059] When the silane coupling agent does not have a hydroxyl group, the curing agent component (II) may contain the silane coupling agent.

[0060] Furthermore, the main component (I) preferably contains a viscosity modifier. As the viscosity modifier, any known viscosity modifier can be used, but it is particularly preferable to use an amide-based viscosity modifier.

[0061] The use of an amide-based viscosity modifier improves the storage stability of the main component (I) and the coating workability of the primer coating composition of the present invention, and also has the effect of improving the adhesion strength of the primer coating composition to the topcoat coating film.

[0062] As such an amide-based viscosity modifier, any of those known in the field of coatings can be used without any limitation, and there are no particular limitations on the synthesis method, materials used, etc., and commercially available products can also be used.

[0063] Specific examples include fatty acid monoamides synthesized by dehydration of fatty acid ammonium salts or ammonolysis of fats and oils (esters); fatty acid diamides (bisamides) synthesized by the condensation reaction of fatty acid amides and formaldehyde, the thermal condensation reaction of monocarboxylic acids and diamines, or the thermal condensation reaction of dibasic acids and monoamines; fatty acid polyamides obtained by polycondensation of dibasic acids and diamines, polycondensation of diamine derivatives and dibasic acids, polycondensation of diamines and dibasic acid derivatives or dimer acids obtained by dimerization of unsaturated fatty acids, or ring-opening polymerization of lactams.

[0064] Such an amide-based viscosity modifier may be diluted with a diluting medium such as an organic solvent. In the present invention, the content of the active ingredients (components other than the diluting medium) of the amide-based viscosity modifier is desirably within a range of 0.1 to 15 parts by mass, preferably 0.5 to 8 parts by mass, based on 100 parts by mass of the solid content of the acrylic polyol (A).

[0065] Furthermore, as the curing catalyst, any conventionally known urethane catalyst can be used without any particular limitation, and examples thereof include metal compounds such as bismuth nitrate, lead oleate, tin octoate, dibutyltin dilaurate, dibutyltin bis(acetylacetonate), dibutyltin diacetate, dibutyltin octanoate, dioctyltin dilaurate, dioctyltin dineodecanoate, titanium tetrachloride, dibutyltitanium dichloride, tetrabutyl titanate, iron trichloride, and zinc octoate, as well as tertiary amines.

[0066] The curing catalyst may be contained in either the main component (I) or the curing agent component (II). When the curing catalyst is contained in the main component (I), the content of the curing catalyst is suitably in the range of 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the solid content of the acrylic polyol (A), from the viewpoints of curability of the composition of the present invention and suppression of viscosity increase after mixing the main component (I) and the curing agent component (II).

[0067] <Undercoat paint composition> In the present invention, it is suitable to mix the main component (I) and the curing component (II) so that the ratio of isocyanate groups in the curing component (II) is 0.8 to 4.0 equivalents, preferably 1.0 to 3.5 equivalents, per equivalent of hydroxyl groups in the main component (I).

[0068] The primer paint composition of the present invention is a two-component composition in which each component is stored separately, and is generally prepared by mixing the components together immediately before application, and adjusting the viscosity using a diluting thinner as necessary.

[0069] The present invention further provides a method for repair coating in which the above composition is used as a base coat.

[0070] The repair coatings applicable to the method of the present invention include coatings applied to the exterior panels of automobiles and household electrical appliances. These coatings are often multi-layer coatings consisting of an undercoat, an intermediate coating (which may be omitted), and a topcoat. The coatings may be either solid or metallic. These coatings may be three-dimensional cross-linked or non-cross-linked.

[0071] In the method of the present invention, first, the damaged portion of the coating film is scraped off, and if necessary, sanding is performed around the damaged portion, followed by degreasing as necessary. If the damage is linear or dotted, the composition of the present invention can be applied directly to the degreased portion. Depending on the damage, various putties can be filled into the scraped portion and then the composition of the present invention can be applied. The putty can be applied by a known method, such as with a spatula. Examples of putties include conventional sheet metal putties and resin putties, such as soluble nitrocellulose, acrylic resin, epoxy acrylate resin, unsaturated polyester resin, and urethane resin. When the putty is applied, it is preferable to dry the putty and then polish the putty surface. However, since the composition of the present invention has good base concealment properties, a rough polished surface is acceptable.

[0072] The composition of the present invention can be applied by a conventionally known application method, with spray application being particularly suitable. The primer coating composition of the present invention allows for thick film application, with the dry film thickness being in the range of 30 to 500 μm, preferably 50 to 200 μm. The primer coating composition of the present invention can provide a coating film with good finish even when it is thick.

[0073] Drying conditions include, for example, a temperature of 5 to 40° C., preferably 10 to 30° C., for 20 to 120 minutes, particularly 30 to 90 minutes.

[0074] The top coat can be a one-coat finish using only a colored base paint containing a metallic pigment and / or a colored pigment, or a two-coat finish using the colored base paint and a top clear paint, both of which are well known in the art.

[0075] As the colored base paint, any topcoat paint such as an organic solvent-based or water-based paint normally used for repairs can be used without any particular restrictions, and it can be applied by known painting methods such as spray painting, electrostatic painting, brush painting, and roller painting.

[0076] When applying multiple coats of colored base paint, steps such as flash-off (leaving the paint film at room temperature after application), air blowing, or pre-heating may be carried out between coats as needed.

[0077] There are no particular restrictions on the drying time after application of the colored base paint, and if a top clear coat is to be applied, the paint may be left uncured. Generally, drying is preferably performed at a temperature of 20 to 100°C for 5 to 60 minutes. The film thickness can be adjusted as appropriate depending on the condition of the surface to be coated, but a dry film thickness of 5 to 100 μm, and particularly 10 to 60 μm, is generally suitable.

[0078] As the top clear coating material, any conventionally known coating material can be used without any particular limitation. For example, curing type coating materials containing an acrylic resin or fluororesin containing a crosslinkable functional group such as a hydroxyl group as the main component and containing a blocked polyisocyanate, polyisocyanate, melamine resin, or the like as a curing agent, or lacquer coating materials containing a cellulose acetate butyrate-modified acrylic resin as the main component can be suitably used, and further coating additives such as pigments, cellulose derivatives, added resins, ultraviolet absorbers, light stabilizers, surface conditioners, and curing catalysts can be contained as necessary.

[0079] The top clear coating is preferably dried for 5 to 60 minutes at a temperature of, for example, 20 to 100° C., preferably 40 to 100° C. The film thickness can be adjusted appropriately depending on the condition of the surface to be coated, but a dry film thickness of 5 to 100 μm, and particularly 10 to 60 μm, is generally suitable.

[0080] <Painting on plastic surfaces> The primer coating composition of the present invention can have adhesion to plastic surfaces by adding a chlorinated polyolefin. The chlorinated polyolefin may be contained in the main component (I) or the curing agent component (II) beforehand, or may be added when the main component (I) and the curing agent component (II) are mixed.

[0081] As the chlorinated polyolefin, it is preferable to use a modified chlorinated polyolefin, and it is particularly preferable to use a maleic anhydride-modified chlorinated polyolefin, from the viewpoint of compatibility with the coating composition. Commercially available products include, for example, "Superclone 422S", "Superclone 892L", "Superclone 892SL", "Superclone 822", "Superclone 822S", "Superclone 921S", "Superclone 930", "Superclone 930S", "Superclone 842LM", "Superclone 851L", "Superclone 3228S", "Superclone 3221S", and "Superclone 2319S" (trade names, manufactured by Nippon Paper Industries Co., Ltd., maleic anhydride-modified chlorinated polyolefin), and "Han Commercially available products such as "DRAIN CY-9122P," "HARDLEN CY-9124P," "HARDLEN HM-21P," "HARDLEN CY-1321P," "HARDLEN CY-2121P," "HARDLEN CY-2129P," "HARDLEN F-225P," "HARDLEN F-7P," "HARDLEN M-28P," "HARDLEN F-2P," "HARDLEN F-6P," and "HARDLEN CY-1132" (trade names, manufactured by Toyobo Co., Ltd., maleic anhydride-modified chlorinated polyolefin) can also be used, and two or more types can also be used in combination.

[0082] The content of the chlorinated polyolefin is preferably within a range of 0.1 to 20 parts by mass, and more preferably 0.5 to 15 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solid content contained in the main component (I) from the viewpoint of adhesive strength.

[0083] Adding chlorinated polyolefins to the coating to impart adhesion to plastic surfaces eliminates the need for primer, which was previously required when painting plastic surfaces, thereby improving work efficiency. [Example]

[0084] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. In the following examples, "parts" and "%" mean "parts by mass" and "% by mass," respectively.

[0085] Production Example 1 Synthesis of Acrylic Polyol (A-1) A reaction vessel was charged with 52 parts of butyl acetate and heated to 110°C with stirring. A monomer mixture consisting of 10 parts of styrene, 10 parts of methyl methacrylate, 5 parts of n-butyl methacrylate, 60 parts of i-butyl methacrylate, 1 part of methacrylic acid, 14 parts of 2-hydroxyethyl methacrylate, and 2.3 parts of azobisisobutyronitrile and a polymerization initiator was added dropwise at a constant rate over 3 hours using a dropping pump at temperatures below 110°C. After the dropwise addition, the temperature was maintained at 110°C for 60 minutes, and stirring was continued. Subsequently, an additional catalyst, a solution of 0.5 parts of azobisisobutyronitrile in 7 parts of butyl acetate, was added dropwise at a constant rate over 60 minutes. After the dropwise addition, the temperature was maintained at 110°C for 60 minutes, and the reaction was terminated. The resulting acrylic polyol solution (A-1) was a uniform, yellow, transparent solution with a non-volatile content of 55%, and the resin had a weight-average molecular weight of 18,000, an acid value (AV) of 6.5 mg KOH / g, a hydroxyl value (OHV) of 60 mg KOH / g, and an SP value of 8.7 (cal / cm 3 ) 1 / 2 The glass transition temperature (Tg) was 61°C.

[0086] Manufacturing Examples 2-3 Acrylic polyol solutions (A-2) to (A-3) were obtained in the same manner as in Production Example 1 above, except that the blending compositions shown in Table 1 were used.

[0087] [Table 1]

[0088] Example 1 Preparation of primer coating composition (X-1) To 180 parts of an acrylic polyol solution (A-1) with a solids content of 55% (100 parts by mass of resin solids), 90 parts of butyl acetate, 1.5 parts of pigment dispersant, 10 parts of titanium white, 2 parts of carbon, 240 parts of barium sulfate, 40 parts of clay, 50 parts of talc, 1 part of acrylic resin ("ARUFON UP-1080", product name, manufactured by Toa Gosei Co., Ltd., hydroxyl-free acrylic resin, molecular weight 6,000), 0.5 parts of a nonionic hydrophilic group-containing surface conditioner, 3 parts of gamma-glycidoxypropyltrimethoxysilane (silane coupling agent), 1 part of dibutyltin dilaurate, and 30 parts of an amide-based thickener (fatty acid amide, amide-based viscosity modifier, active ingredient 20%) were sequentially blended, mixed, stirred, and dispersed for 30 minutes to obtain a main component.

[0089] A curing agent component was obtained by mixing and stirring 40 parts of a polyisocyanate compound (product name "Sumidur N3390EA", manufactured by Sumika Bayer Urethane Co., Ltd.) and 90 parts of butyl acetate.

[0090] 100 parts of the main component and 20 parts of the curing agent component were mixed immediately before use to obtain an undercoat paint composition (X-1).

[0091] Examples 2 to 22, Comparative Examples 1 to 8 Undercoat coating compositions (X-2) to (X-30) were obtained in the same manner as in Example 1 above, except that the formulations shown in Tables 2 to 6 were used.

[0092] [Table 2]

[0093]

Table 3

[0094]

Table 4

[0095]

Table 5

[0096]

Table 6

[0097] (Note 1) ARUFON UP-1080: Product name, manufactured by Toagosei Co., Ltd., acrylic resin without hydroxyl groups, molecular weight 6,000, (Note 2) ARUFON UP-1020: Product name, manufactured by Toagosei Co., Ltd., acrylic resin without hydroxyl groups, molecular weight 2,000, (Note 3) ARUFON UP-1000: Product name, manufactured by Toagosei Co., Ltd., acrylic resin without hydroxyl groups, molecular weight 3,000, (Note 4) Sumidur N3390EA: Trade name, manufactured by Sumika Bayer Urethane Co., Ltd., polyisocyanate compound.

[0098] <Performance test> A coating composition fails if it receives a "C" rating in any one of the following performance tests:

[0099] Finishability test A 300 x 100 x 0.8 mm mild steel plate was spatula-spread with "LUC Poly Putty" (Kansai Paint Co., Ltd., unsaturated polyester putty) to a thickness of approximately 2 mm and dried at 20°C for 60 minutes. The surface was then sanded with P120 dry sandpaper to smooth the surface. Each primer coating composition obtained in the Examples and Comparative Examples was spray-applied to the surface as a primer surfacer, diluted with thinner to a solids content of 50% at the time of application, to a dry film thickness of approximately 50 μm, and then dried at 20°C for 60 minutes. The dried coating was then sanded with P400 sandpaper, and Retan PG Hybrid Eco #202 Sun Metallic Base (trade name, one-component automotive refinish topcoat, Kansai Paint Co., Ltd.) was spray-applied to a dry film thickness of 15 μm. After painting, the uncured coating was left at room temperature for 5 minutes, and then Retan PG Eco HX(Q) Clear (trade name, two-component top clear paint for automotive refinishing, manufactured by Kansai Paint Co., Ltd.) was sprayed onto the coating using an air spray to a dry film thickness of 40 μm. After leaving it at room temperature for 10 minutes, it was heated at 60°C for 20 minutes in a hot air circulation drying oven to obtain a test panel. The appearance of each test panel was then observed from the perspective (diagonal direction) and evaluated according to the following criteria. S: Excellent gloss and surface smoothness. A: Good gloss and smoothness of the coating surface. B: Gloss and surface smoothness are slightly poor. C: Poor gloss and surface smoothness.

[0100] Adhesion Test Each primer coating composition obtained in the above Examples and Comparative Examples was spray-coated onto a 300 x 100 x 0.8 mm mild steel plate to a dry film thickness of 60 μm, followed by drying at 20°C for 60 minutes. The dried coating was sanded with P400 paper, and then Retan PG Hybrid Eco #202 Sun Metallic Base (trade name, one-component automotive refinish topcoat paint, manufactured by Kansai Paint Co., Ltd.) was applied by air spray to a dry film thickness of 15 μm. The uncured coating was left at room temperature for 5 minutes after application, and then Retan PG Eco HX(Q) Clear (trade name, two-component automotive refinish top clear paint, manufactured by Kansai Paint Co., Ltd.) was applied by air spray to a dry film thickness of 40 μm. After leaving the coating at room temperature for 10 minutes, the coating was heated at 60°C for 20 minutes in a hot air circulating oven to obtain a test panel. A cross-cut test was then performed on this test panel in accordance with JIS K5600. Specifically, 100 cuts were made in the coating film at 2mm intervals in a grid pattern, reaching down to the substrate, and adhesive tape with an adhesion strength of 120gf / 10mm was applied. The adhesive tape was then instantly peeled off, and the number of pieces of coating that adhered to the adhesive tape was counted and evaluated according to the following criteria. A: No peeling between the primer and metallic base coat, or between the mild steel plate and the primer. B: Peeling less than 10% between the primer and metallic base coating, or between the mild steel plate and the primer. C: Peeling of 10% or more between the primer coating and metallic base coating, or between the mild steel plate and the primer coating.

[0101] Abrasion test Each primer coating composition obtained in the above Examples and Comparative Examples was spray-coated onto a 300 x 100 x 0.8 mm mild steel plate to a dry film thickness of 60 μm, and then dried at 20° C. for 60 minutes. The dried coating film was sanded with P320 paper at a fixed load a fixed number of times, and the condition of the coated surface was evaluated according to the following criteria. A: The surface irregularities that occurred during painting have been completely smoothed out. B: Some of the surface irregularities that occurred during painting remain. C: Most of the surface irregularities created during painting remain.

[0102] Thickness test Each of the primer coating compositions obtained in the above Examples and Comparative Examples was applied to a mild steel plate measuring 450 x 100 x 0.8 mm, and the thickness of the coating at which sagging occurred was evaluated. A: The film thickness where dripping occurred is 200 μm or more. B: The film thickness at which dripping occurred is 100 μm or more and less than 200 μm. C: Dripping occurred when the film thickness was less than 100 μm.

[0103] Water resistance test The coated panels obtained in the above finish test were immersed in warm water at 40°C for 10 days, and then the coating surface was observed. S: Very good, A: Very slight swelling of the coating film is observed. B: Swelling of the coating film is observed throughout the entire surface. C: The coating film swells and abnormalities such as blisters and whitening are observed.

[0104] Water-based suitability test Each primer coating composition obtained in the above Examples and Comparative Examples was spray-coated onto a 300 x 100 x 0.8 mm mild steel plate to a dry film thickness of 60 μm and then dried at 20°C for 60 minutes. The dried coating was sanded with P400 paper, and then Retan WB Eco EV Base #400 Deep Black (trade name, one-component water-based topcoat for automotive refinishing, manufactured by Kansai Paint Co., Ltd.) was applied by air spray to a dry film thickness of 15 μm. The uncured coating was left at room temperature for 5 minutes after application, and then Retan PG Eco HX Clear Q Base (trade name, two-component top clear coating for automotive refinishing, manufactured by Kansai Paint Co., Ltd.) was applied by air spray to a dry film thickness of 40 μm. After leaving the coating at room temperature for 10 minutes, the coating was heated at 60°C for 20 minutes in a hot air circulating oven to obtain a test panel. The appearance of each test panel was then observed from the oblique direction and evaluated according to the following criteria. S: The gloss and surface smoothness are very good. A: Good gloss and smoothness of the coating surface. B: Gloss and surface smoothness are slightly poor. C: The gloss and smoothness of the coating surface are poor.

[0105] Plastic Adhesion Test A plastic additive was obtained by mixing 2.5 parts of Superchlorine 930S (chlorinated polyolefin, manufactured by Nippon Paper Industries Co., Ltd.) and 97.5 parts of N-butyl propionate. Five parts of the above plastic additive were added to 100 parts of each of the primer coating compositions prepared in Examples 2, 11, and 12, and mixed to obtain primer coating compositions for plastic substrates Y-2, Y-11, and Y-12.

[0106] The above primer coating compositions for plastic substrates were spray-coated onto 300 x 100 x 5 mm polypropylene plates to a dry film thickness of 60 μm and dried at 20°C for 60 minutes. The dried coating film was sanded with P400 paper, and then Retan WB Eco EV Base #400 Deep Black (trade name, one-component water-based topcoat paint for automotive refinishing, manufactured by Kansai Paint Co., Ltd.) was applied by air spray to a dry film thickness of 15 μm. After leaving the uncured coating film at room temperature for 5 minutes, Retan PG Eco HX Clear Q Base (trade name, two-component top clear paint for automotive refinishing, manufactured by Kansai Paint Co., Ltd.) was applied by air spray to a dry film thickness of 40 μm. After leaving the coating at room temperature for 10 minutes, the coating was heated at 60°C for 20 minutes in a hot air circulating drying oven to obtain a test plate. The test plate was subjected to a cross-cut test in accordance with JIS K5600. Specifically, 100 cross-cuts were made in the coating film at 2mm intervals, reaching all the way to the substrate, and adhesive tape with an adhesion strength of 120gf / 10mm was applied. The adhesive tape was then immediately peeled off, and the number of pieces of coating that adhered to the tape was counted and evaluated according to the following criteria. A: There is no peeling between the primer and metallic base coat, or between the polypropylene board and the primer. B: Peeling less than 10% between the primer and metallic base coating, or between the polypropylene board and the primer. C: Peeling of 10% or more between the primer coating and metallic base coating, or between the polypropylene board and the primer coating.

Claims

1. A multi-component organic solvent-based primer coating composition obtained by mixing a main component (I) and a curing agent component (II), The main agent component (I) contains an acrylic polyol (A), a pigment composition (B), and an organic solvent (C), and the curing agent component (II) contains a polyisocyanate compound, The pigment composition (B) contained in the main component (I) contains barium sulfate and talc and / or clay as part of its components, the content of the pigment composition (B) is in the range of 250 to 500 parts by mass based on 100 parts by mass of the solid content of the acrylic polyol (A); A primer coating composition, wherein the content of barium sulfate contained in the pigment composition (B) is in the range of 120 to 400 parts by mass based on 100 parts by mass of the solid content of the acrylic polyol (A).

2. The solubility parameter (SP value) of the acrylic polyol (A) is 8.5 to 9.5 (cal / cm ３ ) １／２ The primer coating composition of claim 1, wherein the viscosity of the primer coating composition is in the range of

3. 2. The undercoat paint composition according to claim 1, wherein the main component (I) and / or the curing agent component (II) further contain a hydroxyl-free acrylic resin (D) having a weight-average molecular weight of 3,000 to 10,000.

4. 2. The primer coating composition according to claim 1, wherein the main component (I) further contains a surface conditioner having a nonionic hydrophilic group.

5. 2. The primer coating composition according to claim 1, wherein the main component (I) further contains a silane coupling agent.

6. A repair coating method comprising the steps of applying the primer coating composition according to any one of claims 1 to 5 to a repair area that may have been applied with putty to form a primer coating film of 30 to 500 μm, and then applying a colored coating composition on the primer coating film.

7. 7. The repair coating method according to claim 6, wherein the colored coating composition is a water-based coating.

8. A repair coating method comprising a step of applying an undercoat coating composition obtained by adding a chlorinated polyolefin to the undercoat coating composition according to any one of claims 1 to 5 to a part to be repaired, including a plastic surface.

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