Multi-component organic solvent-based primer paint composition and repair painting method

Abstract

To provide a multi-component organic solvent-based primer paint composition that has good finish and adhesion, and excellent substrate opacity and drying properties, and a repair painting method using the same. [Solution] A multi-component organic solvent-based primer paint 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 acrylic polyol (A) contained in the main component (I) comprises an acrylic polyol (A1) with a glass transition temperature of 40 to 70°C and an acrylic polyol (A2) with a glass transition temperature of 0 to 30°C, and the pigment composition (B) contained in the main component (I) contains barium sulfate and clay as part of its components.

Description

Technical Field

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

Background Art

[0002] Generally, repair painting of automobile exterior panels, etc. consists of processes such as peeling the old paint film at the damaged location and sanding, and then sequentially performing putty painting, primer surfacer painting, and topcoat painting at that location.

[0003] Primer surfacer painting generally involves a polishing operation after painting, but when there is no putty painting on the base or when painting on replacement parts where the smoothness of the base is relatively high, the polishing operation process can be omitted. In that case, the smoothness of the painted surface was achieved by means such as painting with a high dilution rate and low viscosity, or using a silicone-based surface conditioner. Patent Document 1 discloses a multi-component organic solvent-based primer coating composition obtained by mixing a main component and a curing agent component, wherein the main 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 main component contains talc as a part of its components, the content of talc is in the range of 50 to 300 parts by mass based on 100 parts by mass of the solid content of the lactone-modified acrylic polyol, and the content of the pigment composition is in the range of 50 to 500 parts by mass based on 100 parts by mass of the solid content of the lactone-modified acrylic polyol.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, when painting with a high dilution ratio to obtain a highly smooth surface, there were challenges such as a decrease in the opacity of the substrate and a longer drying time for the paint film. In addition, when smoothness was achieved using silicone-based surface modifiers, there were issues with the wettability of the topcoat paint (especially water-based paints).

[0006] The problem that the present invention aims to solve is to provide a multi-component organic solvent-based primer paint composition that has good finish and adhesion, as well as excellent substrate concealment and drying properties, and a repair painting method using the same. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors have found that the above problems can be solved by a multi-component organic solvent-based primer paint 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 acrylic polyol (A) contained in the main component (I) contains an acrylic polyol (A1) with a glass transition temperature of 40 to 70°C and an acrylic polyol (A2) with a glass transition temperature of 0 to 30°C, and the pigment composition (B) contained in the main component (I) contains barium sulfate and clay as part of its components, and have completed the present invention.

[0008] In other words, the present invention provides the following multi-component organic solvent-based primer paint composition and repair painting method. It is for the benefit of others. Item 1. A multi-component organic solvent-based primer paint composition obtained by mixing a main component (I) and a hardening agent component (II), The main component (I) comprises an acrylic polyol (A), a pigment composition (B), and an organic solvent (C), and the curing agent component (II) comprises a polyisocyanate compound. The main component (I) contains acrylic polyol (A), which includes acrylic polyol (A1) with a glass transition temperature of 40-70°C and acrylic polyol (A2) with a glass transition temperature of 0-30°C. A primer paint composition in which the pigment composition (B) contained in the main component (I) contains barium sulfate and clay as part of its components. Item 2. The primer paint composition according to Item 1, wherein the solid content ratio of the acrylic polyol (A1) with a glass transition temperature of 40 to 70°C and the acrylic polyol (A2) with a glass transition temperature of 0 to 30°C is 30 / 70 to 99 / 1 by mass ratio. Item 3. The primer paint composition according to item 1 or 2, wherein the content of the pigment composition (B) is in the range of 100 to 300 parts by mass based on 100 parts by mass of the solid content of the acrylic polyol (A). Item 4. The SP value of the acrylic polyol (A) is 8.5 to 9.5 (cal / cm³). 3 ) 1 / 2 A primer paint composition according to any one of items 1 to 3, which falls within the range of items 1 to 3. Item 5. The primer composition according to any one of items 1 to 4, wherein the main component (I) further contains a surface modifier having a nonionic hydrophilic group. Item 6. The primer composition according to any one of items 1 to 5, wherein the main component (I) further contains a silane coupling agent. Item 7. A repair painting method comprising the steps of applying a primer paint composition described in any one of Items 1 to 6 to a part to be repaired, which may have putty applied, to form a primer film of 5 to 50 μm, and then applying a colored paint composition onto the primer film. Item 8. The repair painting method according to Item 7, wherein the colored paint composition is a water-based paint. Item 9. A repair painting method comprising the step of applying a primer paint composition, which is obtained by adding a chlorinated polyolefin to any one of the primer paint compositions described in Items 1 to 6, to a part to be repaired, including a plastic surface. [Effects of the Invention]

[0009] According to the present invention, a multi-component organic solvent-based primer paint composition and a repair painting method using the same can be provided, which have good finish and adhesion, as well as excellent substrate opacity and drying properties. [Modes for carrying out the invention]

[0010] The primer composition of the present invention is a multi-component composition obtained by mixing a main component (I) and a hardening agent component (II). The primer composition of the present invention may also be a multi-component composition obtained by mixing three or more components, including components other than the main component (I) and the hardening agent component (II), as needed. The following describes the components used in this invention.

[0011] <Acrylic polyol (A)> In the present invention, the main component (I) comprises an acrylic polyol (A).

[0012] In the present invention, acrylic polyol (A) is a component that can form a coating film together with the polyisocyanate compound described later. Any conventionally known acrylic polyol can be used without limitation as long as it has dilutability with organic solvents and coating film-forming ability. For example, it can be a copolymer of polymerizable unsaturated monomers that contains a hydroxyl group-containing polymerizable unsaturated monomer as an essential component and also contains at least one (meth)acryloyl monomer.

[0013] 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 forms of the above hydroxyalkyl (meth)acrylates; hydroxyl group-containing (meth)acryloyl monomers such as polyoxyethylene chain-containing (meth)acrylates with hydroxyl groups at the molecular ends; and allyl alcohols. These can be used individually or in combination of two or more.

[0014] Examples of polymerizable unsaturated monomers containing (meth)acryloyl monomers that are copolymerized to the above-mentioned hydroxyl group-containing polymerizable unsaturated monomers 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. Alicyclic alkyl(meth)acrylates such as cyclohexyl(meth)acrylate and isobornyl(meth)acrylate; aralkyl(meth)acrylates such as benzyl(meth)acrylate; alkoxyalkyl(meth)acrylates such as 2-methoxyethyl(meth)acrylate and 2-ethoxyethyl(meth)acrylate; perfluoroalkyl(meth)acrylate; N,N-dialkylaminoalkyl(meth)acrylates such as N,N-diethylaminoethyl(meth)acrylate; (meth)acrylamide; Lyl(meth)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 acrylate, 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 include epoxy group-containing (meth)acryloyl monomers such as 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 oxidative-curable group-containing (meth)acryloyl monomers such as dicyclopentenyloxyethyl (meth)acrylate, dicyclopentenyloxypropyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. These can be used individually or in combination of two or more.

[0015] Other polymerizable polymerizable unsaturated monomers besides (meth)acryloyl monomers include, for example, (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; and (meth)acryloyl Carbonyl group-containing polymerizable unsaturated monomers such as rain, formal styrene, vinyl alkyl ketones having 4 to 7 carbon atoms (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone, etc.), acetoacetoxy allyl ester, etc.; Epoxy group-containing polymerizable unsaturated monomers such as allyl glycidyl ether; Isocyanato group-containing polymerizable unsaturated monomers such as m-isopropenyl-α,α-dimethylbenzyl isocyanate; Alkoxysilyl group-containing polymerizable unsaturated monomers such as vinyl trimethoxysilane, vinyl triethoxysilane; Oxidation-curing group-containing polymerizable unsaturated monomers such as reaction products of epoxy group-containing polymerizable unsaturated monomers or hydroxyl group-containing polymerizable unsaturated monomers and unsaturated fatty acids, etc. These can be used alone or in combination of two or more.

[0016] From the viewpoint of the adhesion of the formed coating film, the above acrylic polyol (A) preferably has a weight average molecular weight in the range of 5,000 to 80,000, more preferably 6,000 to 70,000, and a solid content hydroxyl value preferably in the range of 200 mgKOH / g or less, more preferably 50 to 150 mg / KOH.

[0017] In this specification, the weight average molecular weight is a value obtained by converting the weight average molecular weight measured by gel permeation chromatography (manufactured by Tosoh Corporation, "HLC8120GPC") based on the weight average molecular weight of polystyrene. The columns are "TSKgel G-4000 H×L", "TSKgel G-3000H×L", "TSKgel G-2500H×L", "TSKgel G-2000H×L" (all manufactured by Tosoh Corporation, trade names) 4 This was carried out under the conditions of mobile phase; tetrahydrofuran, measurement temperature; 40 °C, flow rate; 1 ml / min, detector; RI.

[0018] From the viewpoints of organic solvent dilutability and compatibility with the chlorinated polyolefin described below, the above acrylic polyol (A) has a solubility parameter (SP value) of 8.5 to 9.5 (cal / cm 3 ) 1 / 2It is preferable that it be within the range of 8.5 to 9.0 (cal / cm³). 3 ) 1 / 2 It is more preferable to be within the range.

[0019] In this specification, the solubility parameter is defined as follows: The SP value (abbreviation) represents a measure of intermolecular interactions between liquid molecules. The SP values ​​of homopolymers of polymerizable monomers are given in J. Paint Technology, vol. 42. It is described in 176 (1970). The SP value of a copolymer polymer of polymerizable monomer mixtures can be calculated using the following formula. SP value = SP1 × fw1 + SP2 × fw2 + ... + SPn × fwn In the above formula, SP1, SP2, ..., SPn represent the SP values ​​of the homopolymer of each polymerizable monomer, and fw1, fw2, ..., fwn represent the mass fraction of each polymerizable unsaturated monomer relative to the total amount of monomer.

[0020] The above-mentioned acrylic polyol (A) is preferably present in the resin solids content of the main component (I) at a rate of 75% by mass or more, more preferably 85% by mass or more.

[0021] In this specification, solid content or non-volatile content refers to the residue remaining after removing volatile components, and the residue may be solid or liquid at room temperature. For example, it refers to the residue remaining after treating a sample at 105°C for 3 hours to remove volatile components.

[0022] The amount of acrylic polyol (A) in the main component (I) is preferably in the range of 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 10 to 30 parts by mass, in terms of non-volatile content, per 100 parts by mass of the total main component (I).

[0023] In the present invention, the acrylic polyol (A) contains an acrylic polyol (A1) with a glass transition temperature of 40 to 70°C and an acrylic polyol (A2) with a glass transition temperature of 0 to 30°C.

[0024] In this specification, the glass transition temperature (Tg) is a value calculated by the following formula. 1 / Tg(K)=W1 / T1+W2 / T2+...Wn / Tn Tg(°C) = Tg(K) - 273 In the formula, W1, W2, ...Wn are the mass fractions of each monomer, and T1, T2...Tn are the glass transition temperatures Tg(K) of the homopolymers of each monomer. The glass transition temperatures of the homopolymers of each monomer are based on the values ​​in POLYMER HANDBOOK Fourth Edition, edited by J. Brandrup, Eh Immergut, and Ea Grulke (1999). For monomers not listed in this literature, the static glass transition temperature obtained when the homopolymer of that monomer is synthesized to have a weight-average molecular weight of approximately 50,000 is used.

[0025] In this specification, the static glass transition temperature of a resin can be measured, for example, by taking a sample in a measuring cup, completely removing the solvent by vacuum suction, and then measuring the change in heat quantity in the range of -100°C to 150°C at a heating rate of 3°C / min using a differential scanning calorimeter "DSC-50Q" (manufactured by Shimadzu Corporation, trade name), and defining the point of change at the first baseline on the low-temperature side as the static glass transition temperature.

[0026] Acrylic polyols (A1) with a glass transition temperature of 40-70°C are effective in improving the drying properties of coating films, and it is more preferable that the glass transition temperature is in the range of 45-65°C.

[0027] The content of acrylic polyol (A1) with a glass transition temperature of 40 to 70°C is preferably 30 to 95% by mass, and more preferably 50 to 90% by mass, of the resin solids content of acrylic polyol (A) contained in the main component (I).

[0028] The acrylic polyol (A1) with a glass transition temperature of 40-70°C may be a single resin or a combination of two or more resins.

[0029] Acrylic polyols (A2) with a glass transition temperature of 0 to 30°C are effective in improving the finish of coating films, and it is more preferable that the glass transition temperature is in the range of 5 to 25°C.

[0030] The content of acrylic polyol (A2) with a glass transition temperature of 0 to 30°C is preferably 5 to 70% by mass, and more preferably 10 to 50% by mass, of the resin solids content of acrylic polyol (A) contained in the main component (I).

[0031] The acrylic polyol (A2) with a glass transition temperature of 0 to 30°C may be a single resin or a combination of two or more resins.

[0032] The solid content ratio of acrylic polyol (A1) with a glass transition temperature of 40-70°C and acrylic polyol (A2) with a glass transition temperature of 0-30°C is preferably 30 / 70-99 / 1 by mass, more preferably 45 / 55-95 / 5, and particularly preferably 60 / 40-90 / 10.

[0033] Acrylic polyol (A) may also include acrylic polyols other than acrylic polyol (A1) with a glass transition temperature of 40-70°C and acrylic polyol (A2) with a glass transition temperature of 0-30°C.

[0034] <Pigment composition (B)> In the present invention, the main component (I) comprises a pigment composition (B), and as part of its components, barium sulfate and clay are included as extender pigments.

[0035] The inclusion of barium sulfate and clay in the above-mentioned pigment composition (B) improves the drying properties and paintability of the coating film.

[0036] In this invention, barium sulfate and clay can be those known as extender pigments in the paint field, etc., and may be synthetic or natural products, and may have their surfaces treated as needed. There are also no restrictions on their shape or size.

[0037] The blending amounts of barium sulfate and clay acrylic polyol (A), based on 100 parts by mass of solid content, are preferably 5 to 200 parts by mass of barium sulfate, more preferably 10 to 150 parts by mass, and preferably 5 to 100 parts by mass of clay, more preferably 10 to 80 parts by mass.

[0038] Furthermore, the pigment composition (B) may optionally contain known pigments other than barium sulfate and clay, such as extender pigments, coloring pigments, and rust-preventive pigments.

[0039] Other extender pigments among these include, for example, talc, barium carbonate, aluminum silicate, gypsum, calcium carbonate, silica, white carbon, diatomaceous earth, magnesium carbonate, alumina white, gloss white, mica powder, and the like.

[0040] Examples of coloring 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 azored, anthenslon, anthraquinonyl red, and perilemma Examples of pigments include red pigments such as runes, quinacridone-based 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 suren 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 individually or in combination of two or more types.

[0041] When the undercoat paint composition of the present invention contains a coloring pigment, it is preferable from the viewpoint of opacity and the finished appearance of the topcoat that the mass of the coloring pigment is 1 or more and less than 300 parts by mass, preferably 2 to 250 parts by mass, and more preferably 3 to 200 parts by mass, based on a total of 100 parts by mass of barium sulfate and clay.

[0042] In the present invention, the content of the pigment composition (B) is preferably in the range of 100 to 300 parts by mass, more preferably 150 to 250 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solids contained in the main component (I), which is suitable from the viewpoint of adhesion strength of the undercoat film and the finished appearance after topcoat painting.

[0043] <Organic solvent (C)> In the present invention, the organic solvent (C) can be, for example, an organic compound having a molecular weight in the range of 58 to 220, particularly 72 to 200, and can be any known in the field of paints without limitation. It can be used, but it is preferable to include at least one organic solvent selected from, for example, ester-based organic solvents and ketone-based organic solvents.

[0044] 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 individually or in combination of two or more.

[0045] The amount of at least one organic solvent selected from such ester-based organic solvents and ketone-based organic solvents used is preferably 5% by mass or more, and particularly 20% by mass or more, of the total organic solvents contained in the primer coating composition of the present invention.

[0046] In the present invention, other organic solvents besides the ester-based and ketone-based organic solvents mentioned above 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, and 2-methylpentane. Tan, 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- Aliphatic hydrocarbon organic solvents such as branched alkanes including methylheptane, 2-methylnonane, 3-methylnonane, 4-methylnonane, 5-methylnonane, 2-methylundecane, 3-methylundecane, and 2,2,4,6,6-pentamethylheptane; 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; 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 include ether-based organic solvents such as not-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; can.

[0047] The above-mentioned organic solvent (C) can be used as a polymerization solvent or diluent in the production of acrylic polyol (A), or as a diluent in the production of the main component (I).

[0048] <Polyisocyanate compounds> In the present invention, the polyisocyanate compound is a polyisocyanate compound having two or more isocyanate groups in one molecule. Specific examples include polyisocyanate compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, xylylene diisocyanate, meta-tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and lysine diisocyanate, or adducts of these polyisocyanates with polyhydric alcohols, low molecular weight polyester resins, or water, or cyclized polymers of the above-mentioned polyisocyanates, and isocyanate biuret compounds, etc., which may be used individually or in combination of two or more.

[0049] <Main ingredient (I)> In the present invention, the main component (I) comprises an acrylic polyol (A), a pigment composition (B), and an organic solvent (C).

[0050] In the present invention, the non-volatile content concentration of the main component (I) is preferably in the range of 50 to 90% by mass, and particularly suitable in the range of 60 to 80% by mass, from the viewpoint of paintability and the finish of the formed coating film.

[0051] The main component (I) described above can have a low viscosity relative to its solid content concentration, and can exhibit excellent paintability. Specifically, the viscosity in the storage state (sealed can state) can preferably be in the range of 75 to 140 KU, and particularly 80 to 120 KU.

[0052] In this specification, viscosity is defined as the viscosity of a sample adjusted to 25°C and measured using a Stormer-type viscometer.

[0053] <Hardening agent component (II)> In the present invention, the curing agent component (II) includes the polyisocyanate compound (D) described above.

[0054] From the viewpoint of paintability and mixability 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. The non-volatile content concentration of the curing agent component (II) is suitable in the range of 5 to 90% by mass, particularly 20 to 60% by mass, from the viewpoint of paintability and the finish of the formed coating film.

[0055] <Other additives> The primer paint composition of the present invention may further contain paint additives such as viscosity modifiers, curing catalysts, cellulose acetate butyrate and its modified products, modifying resins other than acrylic polyol (A), such as polyester resins, alkyd resins, and polyurethane resins, pigment dispersants, surface modifiers, and resin particles as appropriate. These additives may be contained in either the main component (I) or the curing agent component (II), but from the viewpoint of storage, it is preferable that additives that can directly react with the isocyanate compound be contained in the main component (I).

[0056] The primer composition of the present invention preferably further contains a surface modifier having nonionic hydrophilic groups. Including a surface modifier having nonionic hydrophilic groups improves the finish of the coating film formed by the primer composition and the wettability of the topcoat to the primer composition, thereby improving the finish of the final coating film. The surface modifier having nonionic hydrophilic groups may be included in either the main component (I) or the curing agent component (II) described later, but it is preferable that the main component (I) contains the surface modifier having nonionic hydrophilic groups because storage stability is improved when the main component (I) contains it.

[0057] Examples of nonionic hydrophilic groups include polyoxyethylene groups, polyoxypropylene groups, polyoxyethylene (oxypropylene) groups, and other polyoxyalkylene groups.

[0058] Surface modifiers having nonionic hydrophilic groups can be those known in the field of coatings without restriction, and there are no particular restrictions on synthesis methods, materials used, etc. Commercially available products can also be used.

[0059] The content of the surface modifier having a nonionic hydrophilic group is preferably 0.01 to 10 parts by mass, and more preferably 0.05 to 5 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solids contained in the main component (I).

[0060] From the viewpoint of improving adhesion, it is preferable that the main component (I) contains a silane coupling agent. There are no particular restrictions on the type of silane coupling agent, but examples 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 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 be used in combination. Among these, the use of epoxy group-containing silane coupling agents is preferred.

[0061] The silane coupling agent content is preferably 0.5 to 20 parts by mass, and more preferably 1 to 10 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solids contained in the main component (I).

[0062] If the silane coupling agent does not have a hydroxyl group, the curing agent component (II) described below may contain the silane coupling agent.

[0063] Furthermore, it is preferable that the main component (I) contains a viscosity modifier. Conventional viscosity modifiers can be used, but it is particularly preferable to use an amide-based viscosity modifier.

[0064] By using an amide-based viscosity modifier, the storage stability of the main component (I) and the present invention are improved. This improves the workability of the paint composition and enhances the adhesion strength of the undercoat composition to the topcoat film.

[0065] Such amide-based viscosity modifiers can be any known in the field of paints without restriction, and there are no particular restrictions on the synthesis method or materials used. Commercially available products can also be used.

[0066] Specifically, examples include fatty acid monoamides synthesized by dehydration of fatty acid ammonium salts or ammoniacal decomposition of oils and fats (esters); fatty acid diamides (bisamides) synthesized by condensation reactions of fatty acid amides and formaldehyde, thermal condensation reactions of monocarboxylic acids and diamines, or thermal condensation reactions 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 dimerized unsaturated fatty acids to obtain dimer acids, or ring-opening polymerization of lactams.

[0067] Such amide-based viscosity modifiers may be diluted with a diluent such as an organic solvent.

[0068] In the present invention, the content of the active ingredient (component other than the diluent) of the amide-based viscosity modifier is preferably in the range of 0.1 to 15 parts by mass, more preferably 0.5 to 8 parts by mass, based on 100 parts by mass of the solid content of acrylic polyol (A).

[0069] Furthermore, conventionally known urethane catalysts can be applied without particular limitation as curing catalysts. Examples include metal compounds such as bismuth nitrate, lead oleate, tin octinoate, dibutyltin dilaurate, dibutyltin bis(acetylacetonate), dibutyltin diacetate, dibutyltin octanoate, dioctyltin dilaurate, dioctyltin dineodecanoate, titanium tetrachloride, dibutyltitanium dichloride, tetrabutyl titanate, iron trichloride, and zinc octinoate, as well as tertiary amines.

[0070] The curing catalyst may be included in either the main component (I) or the curing agent component (II). However, when included in the main component (I), the content of the curing catalyst is preferably in the range of 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the solid content of the acrylic polyol (A), which is suitable from the viewpoint of curability of the primer coating composition of the present invention and suppression of viscosity increase after mixing of the main component (I) and the curing agent component (II).

[0071] <Undercoat paint composition> In the primer paint composition of the present invention, the main component (I) and the curing agent component (II) are blended in such a ratio that the isocyanate groups in the curing agent component (II) are preferably 0.8 to 4.0 equivalents, more preferably 1.0 to 3.5 equivalents, per 1 equivalent of hydroxyl groups in the main component (I).

[0072] The primer paint composition of the present invention is a two-component composition in which each component is stored separately. Generally, the components are mixed immediately before application, and the viscosity is adjusted using a diluent thinner as needed before use.

[0073] The present invention further provides a repair painting method using the above-mentioned undercoat paint composition as a base coat.

[0074] The repair coatings applicable to the method of the present invention include, for example, coatings applied to the exterior surfaces of automobiles and household electrical appliances, which are often multi-layer coatings consisting of a primer, an intermediate coating (sometimes omitted), and a topcoat. Furthermore, each of these coatings is solid Either a solid or metallic coating is acceptable. Each of these coatings may be either a three-dimensional cross-linked or non-cross-linked coating.

[0075] In the method of the present invention, first, the damaged portion of the coating is scraped off, and sanding is performed around the damaged area as needed, followed by degreasing as necessary. If the damage is linear or pinpoint, the primer coating composition of the present invention can be applied directly to the degreased area.

[0076] The primer coating composition of the present invention can be applied using conventionally known coating methods, with spray coating being particularly preferred. The coating film thickness of the primer coating composition of the present invention is preferably in the range of 5 to 50 μm, more preferably in the range of 10 to 45 μm, and particularly preferably in the range of 15 to 40 μm, in terms of dry film thickness. Since the primer coating composition of the present invention yields a coating film with good finish, the polishing step for surface adjustment can be omitted.

[0077] The drying conditions can be, for example, 5 to 40°C, preferably 10 to 30°C, for, for, 20 to 120 minutes, preferably 30 to 90 minutes.

[0078] Examples of the topcoat coating include conventionally known coatings such as a one-coat finish using only a colored base paint containing metallic pigments and / or colored pigments, or a two-coat finish using the colored base paint and a clear coat.

[0079] As a base coat for coloring, any topcoat paints commonly used for repairs, such as organic solvent-based or water-based paints, can be used without particular restriction, and can be applied using known painting methods such as spray painting, electrostatic painting, brush painting, and roller painting.

[0080] When applying multiple coats of colored base paint, steps such as flash-off (allowing the paint film to stand at room temperature after application), air blowing, or preheating may be added between each coat as needed.

[0081] The drying time after the application of the colored base coat is not particularly limited, and it may remain uncured if a top clear coat is to be applied. Generally, it is preferable to dry it for 5 to 60 minutes at a temperature of, for example, 20 to 100°C. The film thickness can be adjusted as appropriate depending on the condition of the surface to be coated, but generally, a dry film thickness of preferably 5 to 100 μm, and particularly suitable within the range of 10 to 60 μm, is appropriate.

[0082] As the top clear coating, conventionally known coatings can be used without particular limitations. For example, a curable coating mainly composed of acrylic resin or fluororesin containing crosslinkable functional groups such as hydroxyl groups, and containing a curing agent such as blocked polyisocyanate, polyisocyanate, or melamine resin, or a lacquer coating mainly composed of cellulose acetate butyrate-modified acrylic resin can be suitably used. Furthermore, as needed, coating additives such as pigments, cellulose derivatives, additive resins, ultraviolet absorbers, light stabilizers, surface modifiers, and curing catalysts can be included.

[0083] The top clear coating is preferably dried at a temperature of, for example, 20 to 100°C, more preferably 40 to 100°C, for a period of, for example, 5 to 60 minutes. The film thickness can be adjusted as appropriate depending on the condition of the surface to be coated, but generally, a dry film thickness of, for example, 5 to 100 μm, particularly 10 to 60 μm, is suitable.

[0084] <Painting on plastic surfaces> The primer coating composition of the present invention can have adhesion to plastic surfaces by adding chlorinated polyolefin. The chlorinated polyolefin may be included in the main component (I) or the curing agent component (II) beforehand, and when mixing the main component (I) and the curing agent component (II)... It may be added to it.

[0085] From the viewpoint of compatibility with paint compositions, modified chlorinated polyolefins are preferred, and maleic anhydride-modified chlorinated polyolefins are particularly preferred. Examples of commercially available products include "Supercron 422S", "Supercron 892L", "Supercron 892SL", "Supercron 822", "Supercron 822S", "Supercron 921S", "Supercron 930", "Supercron 930S", "Supercron 842LM", "Supercron 851L", "Supercron 3228S", "Supercron 3221S", "Supercron 2319S" (product names, manufactured by Nippon Paper Industries Co., Ltd., maleic anhydride-modified chlorinated polyolefin), "Ha Commercially available products such as "Drain CY-9122P", "Hardren CY-9124P", "Hardren HM-21P", "Hardren CY-1321P", "Hardren CY-2121P", "Hardren CY-2129P", "Hardren F-225P", "Hardren F-7P", "Hardren M-28P", "Hardren F-2P", "Hardren F-6P", and "Hardren CY-1132" (product names, manufactured by Toyobo Co., Ltd., maleic anhydride-modified chlorinated polyolefin) can also be used, and two or more types can be used in combination.

[0086] From the viewpoint of adhesion strength, the content of chlorinated polyolefin is preferably in the range of 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, based on 100 parts by mass of the acrylic polyol (A) resin solids contained in the main component (I).

[0087] By adding chlorinated polyolefin to improve adhesion to plastic surfaces, the need for primer application, which was originally required for painting plastic surfaces, becomes unnecessary, thus improving work efficiency. [Examples]

[0088] 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.

[0089] Manufacturing Example 1: Synthesis of Acrylic Polyol (A-1) In a reaction vessel, 52 parts of butyl acetate were charged and the temperature was raised to 110°C while stirring. A monomer mixture consisting of 10 parts styrene, 10 parts methyl methacrylate, 5 parts n-butyl methacrylate, 60 parts i-butyl methacrylate, 1 part methacrylic acid, 14 parts 2-hydroxyethyl methacrylate, and 2.3 parts azobisisobutyronitrile, along with a polymerization initiator monomer mixture, was added dropwise at a constant rate over 3 hours using a dropping pump at a temperature below 110°C. After the addition was complete, the temperature was maintained at 110°C for 60 minutes and stirring was continued. Subsequently, as an additional catalyst, 0.5 parts azobisisobutyronitrile dissolved in 7 parts butyl acetate was added dropwise at a constant rate over 60 minutes. After the addition was complete, the temperature was maintained at 110°C for 60 minutes to terminate the reaction. The resulting acrylic polyol solution (A-1) was a homogeneous yellow transparent solution with a non-volatile content of 55%. The weight-average molecular weight of the resin was 18000, the acid value (AV) was 6.5 mgKOH / g, the hydroxyl value (OHV) was 60 mgKOH / g, and the SP value was 8.7 (cal / cm³). 3 ) 1 / 2 The glass transition temperature (Tg) was 61°C.

[0090] Manufacturing Examples 2-7 Acrylic polyol solutions (A-2) to (A-7) were obtained in the same manner as in Production Example 1 above, except that the formulation composition was as shown in Table 1.

[0091] [Table 1]

[0092] Example 1 Preparation of primer paint composition (X-1) To 150 parts of an acrylic polyol solution (A-1) with a solid content of 55% (83 parts resin solids), 26 parts of an acrylic polyol solution (A-5) with a solid content of 65% (17 parts resin solids), 55 parts butyl acetate, 1 part pigment dispersant, 10 parts titanium white, 2 parts carbon, 120 parts barium sulfate, 40 parts clay, 0.5 parts nonionic hydrophilic group-containing surface modifier, 3 parts γ-glycidoxypropyltrimethoxysilane (silane coupling agent), 0.5 parts dibutyltin dilaurate, and 5 parts amide-based thickener (fatty acid amide, amide-based viscosity modifier, 20% active ingredient) were sequentially added, mixed and stirred, and dispersed for 30 minutes to obtain the main component.

[0093] 25 parts of a polyisocyanate compound ("Sumijule N3390EA", trade name, manufactured by Sumika Bayer Urethane Co., Ltd.) and 50 parts of butyl acetate were mixed and stirred to obtain a curing agent component.

[0094] 100 parts of the main component and 20 parts of the hardener component were mixed immediately before use to obtain the primer paint composition (X-1).

[0095] Examples 2-17, Comparative Examples 1-8 Undercoat paint compositions (X-2) to (X-25) were obtained in the same manner as in Example 1, except that the formulations were as shown in Tables 2 to 5.

[0096] [Table 2]

[0097] [Table 3]

[0098] [Table 4]

[0099] [Table 5]

[0100] <Performance Test> If even one of the performance tests listed below results in a "C" rating, the paint composition is considered unacceptable. Quality Test On a 300mm x 100mm x 0.8mm electrodeposited mild steel plate, each undercoat paint composition obtained in the examples and comparative examples was used as a primer surfacer, diluted with thinner to achieve a solid content of 50% during application, and then spray-painted to a dry film thickness of approximately 30μm. Next, it was dried at 20°C for 60 minutes. After drying, Retan PG Hybrid Eco #202 Sun Metallic Base (product name, one-component automotive repair topcoat paint, Kansai Paint Co., Ltd.) was applied to the dried paint film. The paint (manufactured by Kansai Paint Co., Ltd.) was applied using an air spray to a dry film thickness of 15 μm. After leaving the uncured paint film at room temperature for 5 minutes, Retan PG Eco HX (Q) Clear (product name, two-component top clear paint for automotive repair, manufactured by Kansai Paint Co., Ltd.) was applied to a dry film thickness of 40 μm. The panels were painted using an air sprayer to achieve the desired finish. After being left at room temperature for 10 minutes, they were heated in a hot air circulating drying oven at 60°C for 20 minutes to obtain the test panels. The appearance of each test panel was then observed from an oblique direction and evaluated according to the following evaluation criteria. S: Excellent gloss and smooth surface finish. A: Good gloss and smooth surface finish. B: Slightly poor gloss and surface smoothness. C: Poor gloss and surface smoothness.

[0101] Adhesion test On a 300mm x 100mm x 0.8mm mild steel plate, each primer paint composition obtained in the above examples and comparative examples was spray-coated to a dry film thickness of 60μm. After drying at 20°C for 60 minutes, Retan PG Hybrid Eco #202 Sunmetallic Base (product name, one-component automotive repair topcoat paint, manufactured by Kansai Paint Co., Ltd.) was applied to the cured film to a dry film thickness of 1 The paint was applied using an air spray to a thickness of 5 μm. After painting, the uncured paint film was left at room temperature for 5 minutes, and then Retan PG Eco HX (Q) Clear (product name, two-component top clear paint for automotive repair, manufactured by Kansai Paint Co., Ltd.) was applied using an air spray to achieve a dry film thickness of 40 μm. The board was painted with [material name]. After being left at room temperature for 10 minutes, it was heated in a hot air circulating drying oven at 60°C for 20 minutes to obtain a test board. This test painted board was then used to make a Go board in accordance with JIS K5600. A visual test was conducted. Specifically, 100 cuts were made in a grid pattern at 2mm intervals vertically and horizontally on the coating film, reaching the material. Adhesive tape with an adhesion strength of 120gf / 10mm was then applied. The adhesive tape was then instantly peeled off, and the number of coating fragments adhering to the adhesive tape was examined and evaluated according to the following criteria. A: No peeling between the primer film and the metallic base film, or between the mild steel plate and the primer film. B: Less than 10% peeling between the primer film and the metallic base film, or between the mild steel plate and the primer film. C: More than 10% peeling between the primer film and the metallic base film, or between the mild steel plate and the primer film.

[0102] Drying test A 300mm x 100mm x 0.8mm mild steel plate was spray-coated with each of the primer coating compositions obtained in the above examples and comparative examples to a dry film thickness of 30 μm. The coating film was then dried at 20°C for 20 minutes, and the film was evaluated by pressing it with a finger according to the following criteria. S: No stickiness on the fingers at all, no change in the coating at all. A: There is a slight stickiness on the fingers, but there is absolutely no change in the coating. B: A sticky feeling is observed on the fingers, and slight indentations remain on the paint film when pressed with a finger. C: There is a noticeable stickiness on the fingers, and the indentation left by pressing with a finger is clearly visible.

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

[0104] Water-based suitability test A 300mm x 100mm x 0.8mm mild steel plate was spray-coated with each of the primer paint compositions obtained in the above examples and comparative examples to a dry film thickness of 60μm, and then dried at 20°C for 60 minutes. After drying, the paint film was polished with P400 sandpaper, and then Retan WB Eco EV Base #400 Deep Black (product name, one-component water-based topcoat paint for automotive repair, Kansai Pain) was applied. The paint (manufactured by To Co., Ltd.) was applied using an air spray to a dry film thickness of 15 μm. After leaving the uncured paint film at room temperature for 5 minutes, Retan PG Eco HX Clear Q Base (product name, two-component top clear paint for automotive repair, manufactured by Kansai Paint Co., Ltd.) was applied to the dry film thickness. The surface was then coated with an air spray to a thickness of 40 μm. After being left at room temperature for 10 minutes, the surface was heated in a hot air circulating drying oven at 60°C for 20 minutes to obtain test plates. The appearance of each test coated plate was then observed from the translucent direction (oblique direction) and evaluated according to the following evaluation criteria. S: Excellent gloss and smooth surface finish. A: The gloss and surface smoothness are good. B: The gloss and surface smoothness are slightly poor. C: The gloss and surface smoothness are poor.

[0105] Plastic adhesion test 2.5 parts of Supercron 930S (chlorinated polyolefin, manufactured by Nippon Paper Industries Co., Ltd.) and 97.5 parts of N-butyl propionate were mixed to obtain a plastic additive. 5 parts of the above plastic additive were added to 100 parts each of the primer coating compositions (X-2) and (X-4) to (X-7) prepared in Examples 2 and 4-7, and mixed to obtain primer coating compositions (Y-2), (Y-4) to (Y-7) for plastic substrates.

[0106] A 300mm x 100mm x 5mm polypropylene board was spray-coated with the above-mentioned primer paint composition for plastic substrates to a dry film thickness of 60μm, and dried at 20°C for 60 minutes. After drying, the paint film was sanded with P400 sandpaper, and then Retan WB Eco EV Base #400 Deep Black (product name, one-component water-based topcoat paint for automotive repair, Kansai Pain) was applied. The paint (manufactured by To Co., Ltd.) was applied using an air spray to a dry film thickness of 15 μm. After leaving the uncured paint film at room temperature for 5 minutes, Retan PG Eco HX Clear Q Base (product name, two-component top clear paint for automotive repair, manufactured by Kansai Paint Co., Ltd.) was applied to the dry film thickness. The material was then painted using an air spray to a thickness of 40 μm. After being left at room temperature for 10 minutes, the test plates were heated in a hot air circulating drying oven at 60°C for 20 minutes to obtain the test plates. A grid test was conducted on this test coated board in accordance with JIS K5600. Specifically, One hundred cuts were made in a grid pattern on the coating film at 2mm intervals, reaching the material. Adhesive tape with an adhesion strength of 120gf / 10mm was then applied. The adhesive tape was then instantly peeled off, and the number of coating fragments adhering to the tape was measured and evaluated according to the following criteria. A: No peeling between the primer film and the metallic base film, or between the polypropylene board and the primer film. B: Less than 10% peeling between the primer film and the metallic base film, or between the polypropylene board and the primer film. C: Peeling rate of 10% or more between the primer film and the metallic base film, or between the polypropylene board and the primer film.

Claims

1. A multi-component organic solvent-based primer paint composition obtained by mixing a main component (I) and a hardening agent component (II), The main component (I) comprises an acrylic polyol (A), a pigment composition (B), and an organic solvent (C), and the curing agent component (II) comprises a polyisocyanate compound. The main component (I) contains acrylic polyol (A), which includes acrylic polyol (A1) with a glass transition temperature of 40 to 70°C and acrylic polyol (A2) with a glass transition temperature of 0 to 30°C. A primer paint composition in which the pigment composition (B) contained in the main component (I) contains barium sulfate and clay as part of its components.

2. The primer paint composition according to claim 1, wherein the solid content ratio of the acrylic polyol (A1) having a glass transition temperature of 40 to 70°C and the acrylic polyol (A2) having a glass transition temperature of 0 to 30°C is 30 / 70 to 99 / 1 by mass ratio.

3. The primer paint composition according to claim 1, wherein the content of the pigment composition (B) is in the range of 100 to 300 parts by mass based on 100 parts by mass of the solid content of the acrylic polyol (A).

4. The SP value of the aforementioned acrylic polyol (A) is 8.5 to 9.5 (cal / cm³). ３ ) １／２ A primer paint composition according to claim 1, which is within the range.

5. The primer paint composition according to claim 1, wherein the main component (I) further contains a surface modifier having a nonionic hydrophilic group.

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

7. A repair painting method comprising the steps of: applying the primer paint composition according to any one of claims 1 to 6 to a part to be repaired, which may have putty applied to it, to form a primer film of 5 to 50 μm; and applying a colored paint composition on the primer film.

8. The repair painting method according to claim 7, wherein the colored paint composition is a water-based paint.

9. A repair painting method comprising the step of applying a primer paint composition, which is obtained by adding chlorinated polyolefin to the primer paint composition according to any one of claims 1 to 6, to a part to be repaired, including a plastic surface.

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