JP5686476B2 - Repair base layer and repair coating method - Google Patents

Description

  The present invention relates to a repair base layer and a repair coating method that are useful for repair coating of metal products such as automobile outer plates, railway vehicles, and industrial equipment, and are obtained in consideration of the environment.

  For the purpose of improving the adhesion of the coating system to the metal base during the coating of various metal materials, or temporarily providing rust prevention power from the preparation of the metal material to full-scale coating. As a primer for surface treatment of a metal material used, there is a wash primer (a paint defined in JIS K 5633, which may be called an etching primer).

  As such a wash primer, a liquid paint containing a phosphoric acid compound that reacts with a base metal and a polyvinyl butyral resin and a zinc chromate rust preventive pigment as a vehicle is generally well known.

  However, the zinc chromate rust preventive pigment contained in the wash primer is mainly composed of zinc and chromium, and from the recent environmental considerations, the chromate rust preventive pigment is used without using the chromate rust preventive pigment. There is a demand for the development of a primer having an equivalent or better coating performance.

  By the way, repair painting of automobiles aims to restore as much as possible the quality of the existing old paint film that has not damaged the damaged part.

  An automobile body is provided with a multi-layer coating including an undercoat including an electrodeposition layer, an intermediate coat, and a top coat including a clear layer. When reaching the surface, usually after applying a primer such as wash primer or epoxy primer as described above to the damaged part, it is filled with putty to restore the body shape, and the resulting putty layer surface is primer Repair coating is performed in the order of surface coating, base coating and clear coating.

  As a chromium-free primer applicable to such repair coating, a primer composition comprising a main agent containing a polyvinyl butyral resin, a phosphite compound, aluminum orthophosphate and a silane coupling agent, and an additive containing phosphoric acid, A two-component coating composition comprising a main agent containing a polyvinyl butyral resin, an epoxy resin, a non-chromate rust preventive pigment and an extender pigment, and an additive containing a silane coupling agent has been proposed (Patent Documents 1 and 2). .

  The primer compositions described in Patent Documents 1 and 2 are non-chromium, quick-drying, and excellent in adhesion to metal materials. When applied, the adhesion between the primer and putty layers is not sufficient, and if a strong impact is applied to the putty layer after the next repair coating such as primer surfacer coating or top coating, coating film peeling may occur. It was.

  On the other hand, it is known that a coating film excellent in adhesion can be formed by utilizing a crosslinking system with a tertiary amino group, an epoxy group and an alkoxysilyl group. (Non-patent document 1) However, even if the composition described in the document is applied as a primer composition not containing a chromium-based pigment, sufficient performance has not yet been obtained.

JP-A-8-302272 JP 2010-168524 A

Color material, 63 [6], p344-352, 1990

  An object of the present invention is to propose a repair base layer and a repair coating method that are useful for repair coating of metal products such as automobile outer plates, railway vehicles, and industrial equipment, and that are obtained in consideration of the environment.

As a result of intensive studies on the above-described problems, the present inventors have developed a coating film made of a primer composition containing an acrylic resin having a tertiary amino group, a rust preventive pigment, and an epoxy group and a hydrolyzable silyl group-containing compound. It was found that the adhesiveness between the polyester resin-based putty composition and the putty layer was excellent, and the present invention was achieved.
That is, the present invention
1. In the damaged part of the metal material coated article having the damaged part,
(1) A step of coating a primer composition comprising a tertiary amino group-containing acrylic resin , a rust preventive pigment, and an epoxy group and a hydrolyzable silyl group-containing compound to form a primer coating film,
(2) A repair base layer formed by a step of filling a damaged portion treated in the above step (1) with a polyester resin-based putty composition,
2. The repair underlayer according to claim 1, wherein the damaged part reaches the metal surface of the coated article.
3. Item 1 or 2 wherein the epoxy group and the epoxy group contained in the hydrolyzable silyl group-containing compound are within a range of 0.5 to 5 moles per mole of the tertiary amino group contained in the tertiary amino group-containing acrylic resin. Repair base layer according to paragraph,
4). Item 1. The primer composition is a two-component composition comprising a component containing a tertiary amino group-containing acrylic resin and a rust preventive pigment as a main component and a component containing an epoxy group and a hydrolyzable silyl group-containing compound as a curing agent. Or the repair underlayer according to any one of items 3 to 3,
5. The repair underlayer according to any one of items 1 to 4, wherein the primer composition does not substantially contain a chromium-based pigment and a PRTR-regulated substance,
6). The repair underlayer according to any one of claims 1 to 5, wherein the polyester resin-based putty composition is substantially free of styrene and PRTR-regulated substances,
7). A method for forming a repair base layer according to any one of items 1 to 6,
8). A repair coating method in which a primer surfacer is applied on the repair base layer described in any one of items 1 to 6, and then a top coat is applied on the obtained coating film.
9. The repair coating method according to item 8, wherein both the primer surfacer and the top coat are substantially free of PRTR-regulated substances.
About.

  According to the present invention, using a reaction of a tertiary amino group, an epoxy group, and a hydrolyzable silyl group, a coating film by a primer composition containing a rust preventive pigment is attached to a putty layer and a metal material by a polyester resin-based putty. Since these are excellent in both properties, applying these to damaged parts that require repair coating may interfere with the appearance and water resistance of the repair coating layer in the next process, such as primer surfacer and top coat for repair. Therefore, an excellent repair base layer can be formed. In addition, according to this repair coating method, there is an advantage that it is a low pollution type and is environmentally friendly.

≪Applicable substrate≫
Examples of the coated article made of a metal material to which the repair base layer of the present invention is applied include vehicles such as automobiles, motorcycles, bicycles, and railroads, industrial equipment, and the like. A stratum is formed. In particular, since the primer coating film by the primer composition described later is excellent in adhesion to the metal surface, the effect of the present invention is exhibited more significantly when the damaged part of the coated article reaches the metal surface. Can do.

In forming the repair underlayer of the present invention, the damaged portion is subjected to a kelen treatment, and after further degreasing and washing with water, the primer composition is applied. Hereinafter, the primer composition used in the present invention will be described.
≪Process (1) Primer coating film formation process≫
The primer composition used for the lower layer of the repair underlayer of the present invention contains a tertiary amino group-containing copolymer, a rust preventive pigment, and an epoxy group and a hydrolyzable silyl group-containing compound.

  The tertiary amino group-containing copolymer in the present invention is a copolymer having a tertiary amino group in the molecule, and the tertiary amino group introduction method, resin type, and production method are not particularly limited, It is also possible to use commercially available products.

  Examples of the copolymer include a copolymer containing a tertiary amino group-containing polymerizable unsaturated monomer as a copolymerization component.

  Specific examples of the tertiary amino group-containing polymerizable unsaturated monomer include, for example, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl ( N, N-dialkylaminoalkyl (meth) acrylates such as (meth) acrylate, N, N-di-t-butylaminoethyl (meth) acrylate, N, N-dimethylaminobutyl (meth) acrylate; N, N-dimethylamino N, N-dialkylaminoalkyl (meth) acrylamides such as ethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, etc. are mentioned. , N-dimethylaminoethyl (meth) acryl Over preparative and N, the N- diethylaminoethyl (meth) acrylate are preferred.

  The tertiary amino group-containing copolymer may be a copolymer obtained by copolymerizing other polymerizable unsaturated monomer other than the tertiary amino group-containing polymerizable unsaturated monomer, if necessary. Specific examples of such other polymerizable unsaturated monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth). Acrylic acid or methacrylic acid such as acrylate, stearyl (meth) acrylate “isostearyl acrylate” (produced by Osaka Organic Chemical Co., Ltd.), methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate Monoesterified product with monohydric alcohol having 1 to 20 carbon atoms; aromatic vinyl monomer such as styrene, α-methylstyrene and vinyltoluene; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meta Monoesterified products of (meth) acrylic acid such as acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and dihydric alcohols having 2 to 8 carbon atoms, (meth) acrylic acid and carbon Ε-caprolactone modified products of monoesterified products with dihydric alcohols of several 2 to 8, N-hydroxymethyl (meth) acrylamide, allyl alcohol, (meth) acrylate having a polyoxyethylene chain whose molecular terminal is a hydroxyl group, etc. Hydroxyl group-containing polymerizable unsaturated monomers; carboxyl group-containing polymerizable unsaturated monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid; acrylamide, methacrylamide, dimethylacrylamide, N-butoxymethylacrylamide, diacetone Polymerization of acrylamide etc. Polymerizable unsaturated group-containing nitrile compounds such as acrylonitrile and methacrylonitrile; Diene compounds such as butadiene and isoprene; Vinyl compounds such as vinyl acetate, vinyl propionate and vinyl chloride; Glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, allyl methacrylate, allyl acrylate, divinylbenzene, trimethylolpropane triacrylate, methylene bis (meth) acrylamide And polyvinyl compounds such as ethylenebis (meth) acrylamide; and the like, and can be used alone or in combination of two or more.

  As the copolymerization amount of the above-mentioned tertiary amino group-containing polymerizable unsaturated monomer, it is obtained by this repair coating method that the copolymer is in the range of 1 to 50% by mass, preferably 5 to 20% by mass. The resulting anti-corrosive coating film has good anticorrosive properties, and is suitable from the viewpoint of adhesion between the two when a polyester putty is applied after the primer composition is applied.

  Further, the weight average molecular weight of the tertiary amino group-containing copolymer is generally 5000 or more, particularly in the range of 10,000 to 60,000, and is applied to the repair underlayer obtained in the present invention and this. This is suitable from the viewpoint of the water resistance and solvent resistance of the repair coating film.

  Here, the weight average molecular weight is a value obtained by converting the weight average molecular weight measured with a gel permeation chromatograph (“HLC8120GPC” manufactured by Tosoh Corporation) based on the weight average molecular weight of polystyrene. The columns are “TSKgel G-4000H × L”, “TSKgel G-3000H × L”, “TSKgel G-2500H × L”, “TSKgel G-2000H × L” (both manufactured by Tosoh Corporation, trade name). These were carried out under the conditions of mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 ml / min, detector: RI.

  In the present invention, the primer composition contains a rust preventive pigment. As such rust preventive pigments, those conventionally known and not chromium-based rust preventive pigments are suitable. For example, zinc phosphate, phosphorus zinc silicate, aluminum zinc phosphate, calcium zinc phosphate, calcium phosphate, aluminum pyrophosphate, pyro Known per se such as calcium phosphate, aluminum dihydrogen triphosphate, aluminum metaphosphate, calcium metaphosphate, zinc oxide, zinc phosphomolybdate, aluminum phosphomolybdate can be used alone or in combination of two or more. In the present invention, the anticorrosive pigment may be a surface-treated pigment or a pigment modified with a metal oxide or metal salt.

  In the present invention, the amount of the anticorrosive pigment is such that the solid content of the anticorrosive pigment is 1 to 50 parts by mass and further 5 to 30 parts by mass with respect to 100 parts by mass of the solid content of the tertiary amino group-containing copolymer. It is preferable that it is within the range from the viewpoint of adhesion to a metal material and corrosion resistance.

  The primer composition may contain extender pigments in addition to the antirust pigments. Such extender pigments are not particularly limited. For example, calcium carbonate, barium sulfate, hydrous magnesium silicate (talc), magnesium carbonate, calcium sulfate (gypsum), diatomaceous earth, mica (mica powder), clay (kaolin) Silica or the like can be used. The extender pigment may be subjected to a surface treatment for the purpose of increasing the affinity with the tertiary amino group-containing copolymer. Surface treatment includes fatty acids and their salts, resin acids, other carboxylic acids and their salts and surfactants alone or in combination, treatments with titanate or silane coupling agents, inorganic acids, alkalis, silica And surface treatment with alumina, zinc compound and the like.

  In the present invention, from the viewpoint of the storage stability of the primer composition and the water resistance of the primer coating obtained by coating, one or more of calcium carbonate, barium sulfate, and hydrous magnesium silicate (talc) are selected. It is preferable to use, and it is particularly preferable to use a combination of calcium carbonate and barium sulfate.

  Although the content of the extender pigment is not particularly limited, it is 5 to 170 with respect to 100 parts by mass of the total solid content of the tertiary amino group-containing copolymer from the viewpoint of the storage property of the primer composition and the smoothness of the coating film. It is preferably in the range of parts by mass, and more preferably in the range of 40 to 130 parts by mass.

  In the present invention, the blending ratio of the rust preventive pigment and the extender pigment is within the range of 5/95 to 95/5 as the ratio of the former / the latter from the viewpoint of storability, coating workability and water resistance of the primer coating film. It is preferable that it is in the range of 10/90 to 50/50, particularly preferably.

  The primer composition may further contain a color pigment. As the colored pigment, conventionally known pigments for ink and paint can be used alone or in combination of two or more. Specific examples of color pigments include metal oxide pigments such as titanium oxide and iron oxide, composite metal oxide pigments such as titanium yellow, carbon black, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, and perylene pigments. Perinone pigments, benzimidazolone pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, indigo pigments, etc. These can be used alone or in combination of two or more.

  When the said primer composition contains a color pigment, the compounding quantity is in the range of 0.5-100 mass parts with respect to 100 mass parts of said tertiary amino group containing copolymer solid content from the point of coloring power. It is preferable that it is within the range of 1 to 50 parts by mass.

  The total amount of the pigment of the primer composition is 15 to 320 with respect to 100 parts by mass of the resin solid content in the paint from the viewpoint of adhesion to a metal material, storage property of the primer composition and smoothness of the primer coating film. It is preferably within the range of parts by mass, and more preferably within the range of 40 to 200 parts by mass.

  In the present invention, the primer composition contains an epoxy group and a hydrolyzable silyl group-containing compound. The compound improves the curability of the primer coating film and helps to improve the water resistance and adhesion of the repair coating film obtained in the next step.

  The compound is not particularly limited as long as it has an epoxy group and a hydrolyzable silyl group in the molecule, and a compound having an epoxy group and an alkoxysilyl group is particularly preferable.

  Examples of such compounds include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, etc .; these polycondensates, or polycondensates of these compounds with alkoxysilane compounds, etc. can be mentioned, and these can be used alone or in combination of two or more. Can be used.

  In the above primer composition, the epoxy coating of the epoxy group and the hydrolyzable silyl group-containing compound is 0.5 to 5 mol, particularly 1 to 3 mol of the primer coating film with respect to 1 mol of the tertiary amino group. Suitable from the point of curability and water resistance.

  The primer composition may be a one-component type, but the main component is a component containing a tertiary amino group-containing copolymer and a rust preventive pigment, and the epoxy group and hydrolyzable silyl group-containing compound. It is suitable to be provided as a two-component composition containing a component containing a curing agent, such as a solvent such as water or an organic solvent, a pigment dispersant, an antisettling agent, a curing catalyst, an antifoaming agent, and an antioxidant. Various additives such as ultraviolet absorbers can be appropriately contained in either the main agent or the curing agent as necessary.

  Among these, examples of the organic solvent include hydrocarbon solvents such as n-butane, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane and cyclobutane; gasoline, coal tar naphtha (including solvent naphtha), petroleum Ether, petroleum naphtha, petroleum benzine, turpentine oil, mineral spirit (including mineral thinner, petroleum spirit, white spirit and mineral terpene), etc .; ketone solvents such as methyl isobutyl ketone; n-butyl ether, dioxane, ethylene glycol monomethyl ether Ether solvents such as ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol; ethyl acetate, n-butyl acetate Ester solvents such as isobutyl acetate, ethylene glycol monomethyl ether acetate and butyl carbitol acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and diisobutyl ketone; ethanol, isopropanol, n-butanol, sec-butanol, isobutanol and the like A conventionally well-known solvent, such as alcohol solvent, can be mentioned.

  Curing catalysts include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diethylhexanolate, dibutyltin dioctate, dibutyltin dimethylmalate, dibutyltin diethylmalate, dibutyltin dibutylmalate, dibutyltin diisooctylmer. Tetravalent, such as dirate, dibutyltin ditridecylmalate, dibutyltin dibenzylmalate, dibutyltin maleate, dioctyltin diacetate, dioctyltin distearate, dioctyltin dilaurate, dioctyltin diethylmalate, dioctyltin diisooctylmalate Divalent tin compounds such as tin octylate, tin naphthenate and tin stearate; monobutyltin compounds such as monobutyltin trisoctoate and monobutyltin triisopropoxide and monooctyl Monoalkyl tins such as compounds; titanates such as tetrabutyl titanate and tetrapropyl titanate; organoaluminum compounds such as aluminum trisacetylacetonate, aluminum trisethylacetoacetate, diisopropoxyaluminum ethylacetoacetate; zirconium tetra Chelate compounds such as acetylacetonate and titanium tetraacetylacetonate; butylamine, octylamine, laurylamine, dibutylamine, monoethanolamine, diethanolamine, triethanolamine, diethylenetriamine, triethylenetetramine, oleylamine, cyclohexylamine, benzylamine, Diethylaminopropylamine, xylylenediamine, triethylenediamine, guanidine Diphenylguanidine, 2,4,6-tris (dimethylaminomethyl) phenol, morpholine, N-methylmorpholine, 2-ethyl-4-methylimidazole, 1,8-diazabicyclo (5,4,0) undecene-7 (DBU) ) And other amine compounds, or salts of these amine compounds with carboxylic acids, etc .; reactants and mixtures of amine compounds and organotin compounds such as laurylamine and tin octylate reactants or mixtures; Low molecular weight polyamide resin obtained from polyamine and polybasic acid; reaction product of excess polyamine and epoxy compound; amino such as γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) aminopropylmethyldimethoxysilane Silanol curing catalyst such as silane coupling agent having a group; Kill.

  The main agent is prepared by mixing and dispersing the aforementioned components. Further, from the viewpoint of the efficiency of dispersion mixing and storage stability, the solid content of the main agent is preferably in the range of 30 to 70% by mass, and preferably in the range of 40 to 60% by mass.

  On the other hand, the curing agent may contain a volatile component such as an organic solvent. In that case, the content of the epoxy group and alkoxysilyl group-containing compound in the curing agent is generally 0.1 to 5% from the viewpoint of mixing stability with the main agent. It is in the range of 100% by mass, preferably 5 to 90% by mass.

  In the present invention, when the primer composition is a two-component composition, the main agent and the curing agent can be mixed and adjusted to a viscosity suitable for coating with an organic solvent or the like as necessary.

  When the primer composition is a two-component composition, it is suitable that the ratio of the main agent and the curing agent is such that the ratio of the tertiary amino group to the epoxy group is within the above range.

  The primer composition used in the present invention is a low pollution type considering the environment and does not substantially contain chromium-based pigments and PRTR-regulated substances (particularly toluene and xylene). In this specification, the term “substantially free” means that the content is less than 1.0% by mass.

  A conventionally known coating method can be used as the primer composition coating method, but spray coating is preferably performed from the viewpoint of the finish of the primer coating film. Drying after coating is not particularly limited, but for example, it is preferably left at room temperature, and then dried at a temperature of, for example, 20 to 100 ° C., preferably 40 to 100 ° C. for 5 to 60 minutes. The film thickness can be adjusted as appropriate according to the state of the substrate, but in general, the dry film thickness is 5 to 50 μm, and particularly within the range of 10 to 30 μm, the anticorrosion and water resistance of the repair coating film It is preferable from the point.

≪Process (2) Putty composition filling process≫
The repair underlayer of the present invention is obtained by filling the damaged portion treated in the above step (1) with a polyester resin-based putty composition.

  As the polyester resin-based putty composition used in the step (2), conventionally known ones can be used without limitation, and generally contains an unsaturated polyester resin, an extender pigment, a component containing a polymerizable unsaturated monomer as a main component, The composition which uses the component containing an organic peroxide as a hardening | curing agent can be mentioned.

  A composition substantially free of styrene and PRTR-regulated substances can also be suitably applied as the polyester resin-based putty composition.

  The filling operation of the putty composition into the damaged part to which the primer composition has been applied is not particularly limited, but can be performed using various irons and spatulas. After the putty layer is formed, it may be polished as necessary. Examples of the polishing method include a manual method using sandpaper, a method using a power tool such as a disk sander, and the like.

  The polishing operation can usually be performed after the putty composition is cured and dried. The putty layer can be dried in the same manner as the primer coating step.

  In the present invention, there is provided a repair coating method in which a primer surfacer is coated on a repair base layer obtained as described above, and then a top coating is coated on the obtained coating film.

  Since the above-mentioned repair base layer is excellent in adhesion and water resistance, even if repair coating is applied on it, it is close to the appearance of a repair coating film with an excellent finished appearance, that is, an existing old coating film that is not damaged A repair coating film can be formed, and its appearance can be maintained over a long period of time.

  The repair underlayer obtained in the present invention has good polishing properties, can smooth the coating surface, and has excellent water resistance, adhesion to damaged parts and repair paints for the next process, etc. Conventionally known water-based and organic solvent-based ones can be used without limitation.

  As the primer surfacer and the top coating used in the repair coating method of the present invention, conventionally known ones can be used, but in particular, a composition substantially free from PRTR-regulated substances can be preferably used. It is possible to form an excellent repair coating film while considering the above.

  A conventionally known coating method can be used as the primer surfacer coating method, but spray coating is preferably performed from the viewpoint of the finish of the coating film. Drying after coating is not particularly limited, but for example, it is preferably left at room temperature and then dried at a temperature of 20 to 100 ° C., preferably 40 to 100 ° C. for 5 to 60 minutes. The film thickness can be appropriately adjusted according to the state of the repaired undercoat layer and the surrounding old paint film. Generally, the dry film thickness is adjusted within the range of 5 to 100 μm, particularly 10 to 60 μm. It is preferable from the viewpoint that the surface roughness of the formation can be adjusted and the adhesion of the primer surfacer coating film is secured. After drying, from the viewpoint of the finish of the coating film, the surface can be smoothed by polishing and then a top coat described later can be applied. Examples of the polishing method include a manual method using sandpaper and a method using a power tool such as a disk sander. In the case of polishing, it is possible to apply a top coat described later after removing dust and solids during polishing by washing with water or solvent degreasing. Further, if there is no problem in surface smoothness after the primer surfacer is applied, the top coat may be applied without any particular treatment.

  For the top coating, there are conventionally known coatings such as a one-coat finish using only a base paint composed of a metallic pigment and / or a colored pigment, or a two-coat finish using the base paint and a clear paint. Can be determined as appropriate according to the desired color and texture.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to only these examples. In the following examples, “part” and “%” mean “part by mass” and “% by mass”, respectively.

<Manufacture of primer composition>
Production Examples 1-15
A base composition and a curing agent were produced with the composition shown in Table 1 below, and both were mixed immediately before use to obtain a primer composition. In addition, the resin compounding quantity of Table 1 is a solid content display.

(Note 1) Tertiary amino group-containing acrylic resin: methyl methacrylate / n-butyl methacrylate / n-butyl acrylate / dimethylaminoethyl methacrylate = 30/30/30/10 copolymer, weight average molecular weight 52,000,
(Note 2) Tertiary amino group-containing acrylic resin: methyl methacrylate / n-butyl methacrylate / n-butyl acrylate / dimethylaminoethyl methacrylate = 20/30/30/20 copolymer, weight average molecular weight 52,000,
(Note 3) Glycidyl group-containing acrylic resin: methyl methacrylate / n-butyl methacrylate / n-butyl acrylate / glycidyl methacrylate = 30/30/30/10 copolymer, weight average molecular weight 52,000,
(Note 4) Hydroxyl group-containing acrylic resin: methyl methacrylate / n-butyl methacrylate / n-butyl acrylate / 2-hydroxyethyl acrylate = 30/30/30/10 copolymer, weight average molecular weight 52,000,
(Note 5) Polyvinyl butyral resin: “ESREC B BM-1” (trade name, polyvinyl butyral resin, weight average molecular weight 40,000, manufactured by Sekisui Chemical Co., Ltd.)
(Note 6) Epoxy resin: “jER-1001” (trade name, bisphenol A type epoxy resin, manufactured by Japan Epoxy Resin Co., Ltd.)
(Note 7) Zinc phosphate-based rust preventive pigment: “ZAP-2” (trade name, manufactured by Wilber Ellis Co., Ltd., a pigment obtained by treating aluminum trihydrogen phosphate with zinc oxide).

<Paint>
Examples 1-10 and Comparative Examples 1-5
Cold-rolled steel sheet (SPCC-SB) is water-polished with # 120 water-resistant sandpaper, and after drying at room temperature, the substrate is degreased and washed using KAR silicon off (trade name, degreasing agent, manufactured by Kansai Paint Co., Ltd.) Each primer composition obtained in the production example was diluted with “Letane PG Eco thinner” (trade name, manufactured by Kansai Paint Co., Ltd., total content of thinner, toluene and xylene being less than 1.0% by mass) ( The primer composition was diluted with 20 parts of thinner with 100 parts of the main agent in the primer composition) and was allowed to stand at room temperature for 5 minutes, and then heated at 60 ° C. for 10 minutes using a hot air circulating drying oven. Heated for a minute to obtain a coating film having a dry film thickness of 12 μm. After that, based on “Letane PG Eco Putty” (trade name, two-component polyester repair putty, total content of styrene, toluene and xylene less than 1.0 mass%, manufactured by Kansai Paint Co., Ltd.), the mass ratio of the curing agent is 100 : The composition mixed so as to be 2 was coated with a spatula so as to be 200 μm as a cured coating film, allowed to stand at room temperature for 30 minutes, and then the surface of the coating film was sharpened with # 400 water-resistant sandpaper After degreasing and washing, “Letane PG Hybrid Eco Filler” (trade name, two-component primer surfacer, total content of toluene and xylene of less than 1.0% by mass, manufactured by Kansai Paint Co., Ltd.) and “Letane PG Eco Thinner 20 Is mixed with a base, a curing agent, and a thinner mass ratio of 100: 20: 20 so that the dry film thickness is 50 μm. Painted with spray. After leaving at room temperature for 10 minutes, it was heated at 60 ° C. for 30 minutes using a hot-air circulating drying oven. The surface of the dried coating film was polished with a # 600 water resistant sandpaper, dried at room temperature, and degreased and cleaned using “KAR Silicon Off”. Next, “Letane PG Hybrid Eco # 202 Sun Metallic Base” (trade name, one-pack type automotive top coat, manufactured by Kansai Paint Co., Ltd., total content of toluene and xylene less than 1.0% by mass) 20 ”was mixed with an air spray so that the dry film thickness was 15 μm. “Letane PG Eco HX (Q) Clear” (trade name, top clear coating for automotive repair, toluene and xylene total content 1 mass on the uncured coating film left at room temperature for 10 minutes after painting %, Kansai Paint Co., Ltd.) and “Letane PG Eco thinner” base, curing agent, composition mixed to have a thinner mass ratio of 100: 50: 20, air spray to a dry film thickness of 40 μm After coating for 10 minutes at room temperature, it was heated at 60 ° C. for 20 minutes using a hot air circulating drying oven to obtain a test plate. In addition, as for each composition used for primer coating, primer surfacer coating, metallic base coating, and clear coating, the total content of toluene and xylene is less than 1% by mass even after thinner dilution.

<Evaluation test>
Each test coated plate obtained above was subjected to the following test. The results are shown in Table 2.

(* 1) Adhesion after immersion in water The above-mentioned test coated plate was subjected to an adhesion test immediately after immersion in water at 40 ° C. for 10 days. A cross-cut test conforming to JIS K 5600 5-6 (1999) was used for the adhesion test. Specifically, 100 cuts that reach the material in a grid pattern at intervals of 2 mm vertically and horizontally are placed on the coating film, and an adhesive tape having a width of 25 mm is applied. And this adhesive tape was peeled off, the peeling state of the coating film was investigated, and the following reference | standard evaluated.
4: No abnormality,
3: Slight peeling between primer / putty
2: There is a large separation between the primer and putty,
1: Almost missing.

(* 2) Corrosion resistance Each test coating plate was subjected to a salt spray test in accordance with JIS K 5600 7-9 (2006). After the 240 hour test, the state of the general part and the penetration (maximum value) of rust from the cut part were evaluated according to the following criteria.
4: There is no rust from the cut part, and there is no rust in the general part.
3: Less than 1 mm intrusion of rust from the cut part, no rust in the general part,
2: Intrusion of rust from the cut part is 1 mm or more and less than 5 mm, rust is generated in the general part,
1: Intrusion of rust from the cut part is 5 mm or more and rust is generated on the entire general part.

Claims (9)

In the damaged part of the metal material coated article having the damaged part,
(1) A step of coating a primer composition comprising a tertiary amino group-containing acrylic resin , a rust preventive pigment, and an epoxy group and a hydrolyzable silyl group-containing compound to form a primer coating film,
(2) A repair underlayer formed by a step of filling a damaged portion treated in the step (1) with a polyester resin-based putty composition. The repair base layer according to claim 1, wherein the damaged portion reaches the metal surface of the coated article. The epoxy group contained in the epoxy group and the hydrolyzable silyl group-containing compound is in the range of 0.5 to 5 moles relative to 1 mole of the tertiary amino group contained in the tertiary amino group-containing acrylic resin. 2. The repair ground layer according to 2. The primer composition is a two-component composition comprising a component containing a tertiary amino group-containing acrylic resin and a rust preventive pigment as a main component and a component containing an epoxy group and a hydrolyzable silyl group-containing compound as a curing agent. The repair underlayer according to any one of 1 to 3. The repair underlayer according to any one of claims 1 to 4, wherein the primer composition does not substantially contain a chromium-based pigment and a PRTR-regulated substance. The repair base layer according to any one of claims 1 to 5, wherein the polyester resin-based putty composition is substantially free of styrene and PRTR-regulated substances. A method for forming a repair base layer according to any one of claims 1 to 6. A repair coating method in which a primer surfacer is coated on the repair base layer according to any one of claims 1 to 6, and then a top coating is coated on the obtained coating film. The repair coating method according to claim 8, wherein both the primer surfacer and the top coat are substantially free of PRTR-regulated substances.