JP5089518B2 - Repair painting method - Google Patents

Description

  The present invention relates to a method for forming a glittering composite coating film including a repairing process for an intermediate coating film in the coating of an article to be coated, for example, an automobile body skin. In particular, the present invention relates to an electrodeposition coating film provided on an object to be coated, a white intermediate coating film adjusted to have an L value of 70 to 95, a base coat film containing a pearl pigment, and a clear coat. The present invention relates to a method for repairing an intermediate coating film in a multilayer coating film comprising a coating film.

  The formation of a glittering composite coating film in an automobile production line generally involves forming an electrodeposition coating film and an intermediate coating film, and after baking and drying, the glittering base coating film and the top clear coating film are applied in a wet-on-wet system. It is done by doing. The wet-on-wet method is a coating film forming method in which a coating film used in the next step is applied onto an unheated and dried coating film to form an unheated and dried composite coating film. In this automobile production line, if it is necessary to remove dust adhering to the intermediate coating film, or if coating defects such as sagging, pinholes, dents, etc. occur, it is necessary to repair the coating film in that part. .

  Specifically, for example, a sanding process is performed on the intermediate coating film to form a sharpened portion, and after repairing by applying a repair coating to the sharpened portion, the base coating film and the clear coating film are formed. To form.

  The repair is usually carried out by spray painting such as hand-blown air spray, but the repaired coating film repaired in this way may naturally have the same appearance as the non-repaired coating film. Required.

  In the above repair part, it becomes a three-layer coating film of the repair coating film, the base coating film and the clear coating film, a mixed layer of three layers occurs, the coating surface becomes uneven, and the coating surface smoothness is poor. Thus, there is a problem that the finished appearance is poor. In particular, when the base coat film is aqueous, this problem tends to be remarkable.

  Also, in the base paint film containing glitter pigment, the orientation of the glitter pigment in the paint film differs between the non-repaired part painted by electrostatic coating and the repaired part painted by hand-blown air spray etc. For this reason, in the coating film of the repaired portion, the same appearance as that of the coating film of the non-repaired portion cannot be obtained, and there is a problem that a different appearance is exhibited due to a shift in hue.

  Regarding the repair coating method of glittering composite coating film including the repair process of the intermediate coating film, all or all of the pigments are removed from the glittering base paint as a way to solve the difference in appearance due to the difference in orientation state. A coating film for repairing is formed without baking and drying; a coating film for forming a glittering base coating film on the coating film for repairing and the intermediate coating film on the non-repaired part. A repair method has been proposed (Patent Document 1).

  However, the above method is not suitable when the glittering base paint is water-based, and when the glittering base paint is water-based, the repair coating film, the base coating film, and the clear coating film are not suitable. The problem of poor finished appearance due to the mixed layer coating cannot be solved.

JP 2002-239454 A

  An object of the present invention is to provide an electrodeposition coating film formed on an object to be coated, a white intermediate coating film adjusted to have an L value of 70 to 95, an aqueous base coat coating film and a clear coat containing a pearl pigment. The base coat film in the repaired part and the non-repaired part does not cause a problem of the finished appearance due to the mixed layer in the wet-on-wet coating in the repair process for the intermediate coating film in the multilayer coating film composed of the coating film. It is an object of the present invention to provide a repair coating method capable of repairing so as to exhibit the same appearance without causing a difference in appearance due to a difference in the orientation state of the glittering pigment.

  As a result of intensive studies, the present inventors have found that this time, an electrodeposition coating film, a white intermediate coating film adjusted to have an L value of 70 to 95, and an aqueous solution containing a pearl pigment. It is readily soluble in silicon-containing inorganic thickeners and water when repairing defects that occur in the intermediate coating film in the intermediate coating film forming process in the coating line that forms a multilayer coating film consisting of a base coat film and a clear coat film. A solvent-type repair paint having a whiteness equivalent to that of the intermediate coating film, containing a specific amount of a high boiling point solvent, is applied to the repaired part, and then an aqueous base coat paint containing a pearl pigment is applied, and further the aqueous base coat paint film It is found that the above object can be achieved by coating a solvent-type clear coat paint on the top and simultaneously curing the three-layer coating film to form a multilayer coating film, thereby completing the present invention. Led was.

Thus, the present invention
An electrodeposition coating film (A) using an intermediate coating material capable of forming a coating film having a whiteness L value in the range of 70 to 95 based on the CIE color matching function when coated with a film thickness equal to or greater than the concealment film thickness The intermediate coating film (B) having an L value of 70 to 95 formed on the top,
Repair coating is performed with a solvent-type repair paint (C) that can form a coating film having a whiteness L value in the range of 70 to 95 based on the CIE color matching function when coated with a film thickness equal to or greater than the concealment film thickness.
Next, an aqueous base coat paint (D) containing a pearl pigment is applied at a film thickness of 5 to 15 μm,
Furthermore, a solvent-based clear coat paint (E) is applied on the aqueous base coat paint (D) coating film,
A method of forming a multilayer coating film by simultaneously heating and curing the coating films of paints (C), (D) and (E),
Repair paint (C) is a solvent having a boiling point of 200 ° C. or higher that is 0.5 to 3 mass% of silicon-containing inorganic thickener and easily soluble in water, based on the total amount of resin solids in repair paint (C). Is contained in an amount of 5 to 60% by mass.

  According to the repair coating method of the present invention, it becomes possible to perform the baking drying of the intermediate coating repair part simultaneously with the baking drying of the non-repaired part overcoat film (aqueous base coat film and solvent-type clear coat film). The baking process in the repair coating process can be reduced.

  The solvent-type repair paint used in the repair coating method of the present invention contains a silicon-containing inorganic thickener, so that the swelling of the repair paint is suppressed. As a result, the repair paint film and the base paint film In addition, since the mixed layer of the three-layer coating film of the clear coating film can be suppressed, the finished appearance is not deteriorated due to the mixed layer of the three-layer coating film of the repaired portion, and a good finished appearance is obtained even in the repaired portion. be able to.

In addition, the solvent-type repair paint used in the repair coating method of the present invention contains a high-boiling solvent that is easily soluble in water, thereby improving the affinity between the aqueous base paint film and the repair paint paint film. Since the difference in the orientation state of the pearl pigment between the non-repaired portion and the non-repaired portion can be reduced, there is an effect that the repaired portion and the non-repaired portion exhibit the same appearance without a sense of incongruity.

  Hereinafter, the repair coating method of the present invention (hereinafter sometimes referred to as “the present method”) will be described in more detail.

BEST MODE FOR CARRYING OUT THE INVENTION

Object to be coated:
The article to be repaired by this method is not particularly limited, but is preferably the body of various vehicles such as automobiles, motorcycles, and containers. In addition, for example, cold rolled steel sheets, galvanized steel sheets, zinc alloy plated steel sheets, stainless steel sheets, tin plated steel sheets, etc., metal base materials such as aluminum plates and aluminum alloy plates; various plastic materials It may be. In addition, the object to be coated may be one in which a surface treatment such as a phosphate treatment, a chromate treatment, or a complex oxide treatment is performed on the metal surface of the vehicle body or the metal substrate.

Electrodeposition coating (A):
In this method, the electrodeposition coating applied to the article to be coated is not particularly limited, and may be an electrodeposition coating formed from any known electrodeposition coating.

Electrodeposition paints that can be used may be cationic resin-based or anionic resin-based, and may be water-soluble or dispersed. In automobile painting, a cationic resin type is generally used from the viewpoint of anticorrosion and the like, and a cationic type can also be suitably used in this method.
Specific examples of the cationic resin-based electrodeposition paint include a cationic electrodeposition paint containing a base resin having a hydroxyl group and a cationic group and a block polyisocyanate compound.

In the base resin, the hydroxyl group is involved in the crosslinking reaction with the block polyisocyanate compound, and the cationic group is for forming a stable aqueous dispersion. Examples of the base resin include the following: be able to.
(I): Reaction product of polyepoxy resin and cationizing agent.
(Ii): A polycondensate of polycarboxylic acid and polyamine (see US Pat. No. 2,450,940) protonated with an acid.
(Iii): Polyisocyanate compound and polyaddition product of polyol and mono- or polyamine protonated with acid.
(Iv): A hydroxyl group- and amino group-containing acrylic or vinyl monomer copolymer protonated with an acid (see Japanese Patent Publication Nos. 45-12395 and 45-12396).
(V): A product obtained by protonating an adduct of a polycarboxylic acid resin and an alkyleneimine with an acid (see US Pat. No. 3,403,088).

  Specific examples and production methods of these cationic resins are described in, for example, Japanese Patent Publication No. 45-12395, Japanese Patent Publication No. 45-12396, Japanese Patent Publication No. 49-23087, US Pat. No. 2,450,940, US Patent No. 3,403,088, U.S. Pat. No. 3,891,529, U.S. Pat. No. 3,963,663, and the like.

  Moreover, as a block polyisocyanate compound used as said crosslinking agent, the normal well-known block polyisocyanate compound by which the isocyanate group was blocked by the blocking agent can be used without being restrict | limited in particular.

  In the cationic resin-based electrodeposition coating, the constituent ratio of the base resin and the block polyisocyanate compound is not particularly limited, but the base resin is generally 40 to 90% based on the total solid weight of the two components. In particular, the range of 50 to 80%, and the block polyisocyanate compound is generally preferably 60 to 10%, particularly preferably 50 to 20%.

  Cationic resin-based electrodeposition coating is manufactured by neutralizing the cationic groups in the base resin with acidic compounds such as acetic acid, formic acid, lactic acid, and phosphoric acid, and dispersing and mixing them in water together with the block polyisocyanate compound. The aqueous dispersion preferably has a pH usually in the range of 3-9, in particular 5-7, and the resin solids concentration is usually in the range of 5-30% by weight, in particular 10-25% by weight. The inside is suitable.

  When the electrodeposition paint is a cationic resin-based paint, the electrodeposition coating can be carried out by a known method in which the object to be coated is a cathode and a separate anode is provided for electrodeposition. In the case of resin-based paints, the electrode can be opposite to the case of cationic resin-based paints, and the object to be coated can be an anode, and a separate cathode can be provided for electrodeposition. More specifically, for example, in the case of a cationic resin-based paint, the object to be coated is a cathode, the carbon plate is an anode, the bath temperature is 20 to 35 ° C., the voltage is 100 to 400 V, and the current density is 0.01 to 5 A. The energization time can be 1 to 10 minutes. Electrodeposition coating can be performed such that the coating film thickness after heat curing is usually in the range of 10 to 40 μm, preferably 15 to 30 μm. Heat curing can usually be performed by heating at a temperature of about 140 ° C. to about 2 ° C. for about 10 to 40 minutes.

  In this method, the intermediate coating film (B) is formed on the electrodeposition coating film (A) thus formed. The intermediate coating can be applied on the uncured electrodeposition coating (A), but it is usually preferable to apply the coating after the electrodeposition coating (A) is cured.

Intermediate coating film (B):
The intermediate coating material applied on the electrodeposition coating film (A) is applied to improve the smoothness, sharpness, gloss, etc. of the multilayer coating film formed by this method. , A white system in which the L value of whiteness based on the CIE color matching function is in the range of 70 to 95, preferably 80 to 93, more preferably 85 to 92 when coated with a film thickness equal to or greater than the hidden film thickness. What was adjusted so that a coating film may be formed is used. The intermediate coating composition is not particularly limited as long as it can form a coating film having the L value in the above range, and an intermediate coating composition known per se can be used.

  Examples of the intermediate coating that satisfies the above conditions include, for example, a resin component, a solvent, and a titanium white pigment, and, if necessary, a heat formed by blending other color pigments, extender pigments, and other paint additives. A curable paint can be suitably used.

  As the resin component, a thermosetting resin composition is preferable. Specifically, for example, an acrylic resin having a crosslinkable functional group such as a hydroxyl group, a polyester resin, an alkyd resin, a urethane resin, a melamine resin, Examples include a combination of a crosslinking agent such as a urea resin and a polyisocyanate compound (including a block body). The intermediate coating composition can be prepared by dissolving or dispersing these components in a solvent (organic solvent and / or water).

  The titanium white pigment is a white pigment mainly composed of titanium dioxide, and generally has a particle size in the range of 0.2 to 0.35 μm, particularly 0.25 to 0.30 μm.

  The intermediate coating film (B) is a film thickness based on a cured coating film having a thickness equal to or greater than the concealment film thickness on the cured or uncured electrodeposition coating film (A). Can be formed by coating and heat curing.

  In this specification, the “concealment film thickness” means the film thickness after pasting a black and white checkered pattern concealment rate test paper defined in 4.1.2 of JIS K5600-4-1 to a mild steel plate. After the paint is applied in a slant so that it continuously changes, it is dried or cured, and the paint surface is visually observed under diffuse daylight. It is the value which measured the film thickness with the electromagnetic film thickness meter.

  The intermediate coating material used in this method preferably has a concealing film thickness of generally 45 μm or less, particularly 20 to 35 μm, more particularly 25 to 30 μm.

  The concealing film thickness of the intermediate coating can be adjusted, for example, by selecting the pigment concentration and the type of pigment used. In order to prepare an intermediate coating material that forms a coating film having a whiteness L value based on the CIE color matching function in the range of 70 to 95 when coated with a film thickness equal to or greater than the concealment film thickness, for example, titanium white When using a pigment, it is used in a proportion such that it is usually in the range of 50 to 200 parts by weight, particularly 80 to 150 parts by weight, more particularly 80 to 120 parts by weight, per 100 parts by weight of the solid content of the resin component of the intermediate coating. It is preferable.

  The thickness of the intermediate coating film is generally within the range of 10 to 60 μm, particularly 20 to 40 μm, based on the cured coating film, and the intermediate coating film is usually 20 to 40 at a temperature of about 100 to about 170 ° C. It can be cured by crosslinking for about a minute.

  The method for applying the intermediate coating is not particularly limited, and can be performed by an ordinary method. Examples thereof include air spray coating, airless spray coating, rotary atomization coating, and curtain coat coating. In these coating methods, electrostatic application may be performed as necessary. Among these, rotation atomization coating by electrostatic application is particularly preferable. The coating can be performed once or several times so as to obtain a desired film thickness.

  As described above, an intermediate coating film (B) having an L value adjusted to whiteness in the range of 70 to 95 is formed, and the pearl pigment is then contained on the coating surface of the intermediate coating film (B). The water-based base coat paint (D) is applied, whereby a multi-layer coating film having excellent white pearl-like pearl luster and the like can be formed.

  If the L value of the intermediate coating film (B) deviates from the range of 70 to 95, the color stability and high whiteness pearly luster of the formed multilayer coating film are deteriorated, which is not preferable.

  The repair coating method according to the present invention is based on dust, blisters, etc. generated in the intermediate coating film (B) formed on the electrodeposition coating film (A) and having an L value in the range of 70 to 95 after heat curing. Solvent-type repair paint that removes coating defects before polishing with water-based base coat paint (D) containing pearl pigment, and forms a paint film with the same whiteness as the intermediate paint film on that part ( C) is painted and repaired.

To remove coating defects due to dust, blisters, etc. in the intermediate coating film (B), grind the coating film manually using abrasive paper or abrasive cloth, or by attaching these to a tool (sander). Can be done by. Specifically, for example, first, the coating defect portion is ground and removed by using abrasive paper or abrasive cloth containing abrasive material of relatively coarse particles of about # 400 to 600, and then fine of about # 1000 to 1500. In order to improve the finished appearance of the multilayer coating film, it is preferable to use a polishing paper or polishing cloth containing an abrasive having a particle size to smooth the ground surface. And in order to remove the powder of the coating film etc. which arise by grinding, it is preferable to wipe the coating surface with organic solvents, such as gasoline, and to degrease simultaneously by it. This grinding can be performed in a so-called spot range, which is performed only in the above-described coating defect portion and its peripheral portion of the intermediate coating film (B), or the entire intermediate coating film can be polished.

  The grinding depth can be appropriately selected depending on the size and degree of dust and blisters, but is usually within 50 μm, particularly preferably about 10 to 30 μm. This grinding may extend not only to the intermediate coating film (B) but also to the lower electrodeposition coating film (A).

  In this method, after removing and curing the coating defect portion of the intermediate coating film (B), the solvent type repair paint (C) is applied to the coating defect portion.

Solvent type repair paint (C):
The solvent-type repair paint (C) in the present invention is a paint that is applied to the ground portion of the intermediate coating film (B) that has been ground to remove paint defects such as dust and blisters. The paint is adjusted so as to form a coating film having a whiteness L value in the range of 70 to 95 based on the CIE color matching function when coated with a film thickness.

  The solvent-type repair paint (C) contains 0.5 to 3% by mass of a silicon-containing inorganic thickener based on the total resin solid content in the repair paint (C) at the time of painting, and is in water. It is necessary to contain 5-60 mass% of easily soluble solvents having a boiling point of 200 ° C. or higher.

  As the solvent-type repair paint satisfying the above conditions, for example, it contains a resin component, a titanium white pigment, a silicon-containing inorganic thickener, and a solvent having a boiling point of 200 ° C. or higher that is easily soluble in water. A thermosetting paint obtained by blending other color pigments, extender pigments, other paint additives and the like can be suitably used.

  The resin component is preferably a thermosetting resin composition. Specifically, for example, a base resin such as a polyester resin having a crosslinkable functional group such as a hydroxyl group, an alkyd resin, an acrylic resin, or a urethane resin, particularly a polyester resin or an acrylic resin. A combination of a resin and a crosslinking agent such as a melamine resin, a urea resin, or a polyisocyanate compound (including a block body) can be used. These base resins and crosslinking agents can be used alone or in combination of two or more.

  As said polyester resin, what is normally manufactured by making esterification reaction of a polybasic acid and a polyhydric alcohol can be used. A polybasic acid is a compound having two or more carboxyl groups in one molecule, such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexahydro Examples thereof include phthalic acid, hetic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid, and anhydrides thereof. A polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule. For example, ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, hydrogenated bisphenol A , Triethylene glycol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol and the like.

In addition, as the polyester resin, (semi) drying oil such as linseed oil fatty acid, palm oil fatty acid, safflower oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, eno oil fatty acid, hemp oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, etc. A fatty acid-modified polyester resin modified with a fatty acid or the like can also be used. It is generally suitable that the modified amount of these fatty acids is 30% by weight or less in terms of oil length. Further, a product obtained by partially reacting a monobasic acid such as benzoic acid may be used.

  Polyester resins generally have a number average molecular weight in the range of 1000 to 50000, in particular 2000 to 20000, generally a hydroxyl value in the range of 20 to 200 mg KOH / g, in particular 50 to 150 mg KOH / g, and generally 0 to 100 mg KOH / g, in particular 0. Those having an acid value in the range of -70 mgKOH / g are preferred.

  The hydroxyl group and carboxyl group can be directly or indirectly bonded to the polyester resin skeleton. For example, a polybasic acid and a polyhydric alcohol having 3 or more carboxyl groups and hydroxyl groups in one molecule are used in combination. Can be introduced into the resin.

  The said acrylic resin can use what is manufactured by (co) polymerizing a polymerizable monomer by a conventional method. Specifically, for example, it is produced by copolymerizing a polymerizable monomer component containing a hydroxyl group-containing polymerizable monomer, a carboxyl group-containing polymerizable monomer, and an acrylic monomer under normal conditions. Can do. Acrylic resins generally have a number average molecular weight in the range of 1000 to 100,000, in particular 5000 to 80000, generally 20 to 200 mg KOH / g, in particular 50 to 150 mg KOH / g, and generally 0 to 100 mg KOH / g, in particular What has an acid value within the range of 0-70 mgKOH / g is preferable.

  The hydroxyl group-containing polymerizable monomer is a compound having at least one hydroxyl group and a polymerizable unsaturated bond in one molecule. For example, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meta And monoesterified product of glycol having 2 to 20 carbon atoms such as acrylate and (meth) acrylic acid.

  The carboxyl group-containing polymerizable monomer is a compound having at least one carboxyl group and polymerizable unsaturated bond in one molecule, for example, acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, mesacone. Examples thereof include acids and anhydrides and half esterification thereof.

  Acrylic monomers include monoesters of (meth) acrylic acid and monohydric alcohols having 1 to 22 carbon atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, and ethyl methacrylate. Propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, octyl methacrylate, lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and the like.

  In the present specification, “(meth) acrylate” means acrylate or methacrylate, and “(meth) acrylic acid” means acrylic acid or methacrylic acid.

  In producing the acrylic resin, in addition to the above-mentioned hydroxyl group-containing polymerizable monomer, carboxyl group-containing polymerizable monomer and acrylic monomer, other polymerizable monomers can be used in combination.

Examples of other polymerizable monomers include (meth) acrylic acid such as methoxybutyl acrylate, methoxybutyl methacrylate, methoxyethyl acrylate, and methoxyethyl methacrylate, and alkoxy esters having 2 to 18 carbon atoms; N, N-dimethylamino Ethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl acrylate, N, N-diethylaminoethyl methacrylate, Nt-butylaminoethyl acrylate, Nt-butylaminoethyl methacrylate, N, N- Aminoacrylic monomers such as dimethylaminopropyl acrylate and N, N-dimethylaminopropyl methacrylate; acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacryl Acrylamide monomers such as amide, N-ethylacrylamide, N-ethylmethacrylamide, N-butylacrylamide, N-butylmethacrylamide, N-dimethylacrylamide, N-dimethylmethacrylamide; glycidyl acrylate, glycidyl methacrylate Examples thereof include glycidyl group-containing monomers such as a rate; styrene, α-methylstyrene, vinyltoluene, acrylonitrile, vinyl acetate, vinyl chloride and the like.

  Specific examples of the melamine resin include di-, tree, tetra-, penta- or hexa-methylol melamine, and alkyl ethers thereof (alkyl includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, -Ethyl hexyl alcohol, etc.) and condensates thereof. Specific examples thereof include, for example, the Cymel series such as Cymel 254 manufactured by Mitsui Cytec Industries, Inc., and Uban 20SB manufactured by Mitsui Chemicals. The Yuban series can be listed.

  When melamine resin is used as a crosslinking agent, sulfonic acids such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and salts of these sulfonic acids with amines should be used as catalysts. Can do.

The blocked polyisocyanate compound includes a blocked polyisocyanate compound obtained by blocking an isocyanate group of a polyisocyanate compound having at least two free isocyanate groups in one molecule with a blocking agent. Examples of the polyisocyanate compound include: Aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, lysine diisocyanate, burette type adducts and isocyanurate cycloadducts of these polyisocyanates; isophorone diisocyanate, 4,4′-methylenebis (Cyclohexyl isocyanate), methylcyclohexane-2,4- (or-2,6-) diisocyanate, 1,3- (or 1 , 4-) di (isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate, and the like, burettes of these polyisocyanates Type adducts and isocyanurate cycloadducts; xylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 4 , 4′-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate, (m- or p-) phenylene diisocyanate, 4,4′-biphenylene diisocyanate, Aromatic diisocyanate compounds such as 3,3′-dimethyl-4,4′-biphenylene diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate), and burette type addition of these polyisocyanates And isocyanurate cycloadducts; hydrogenated MDI and derivatives of hydrogenated MDI; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6 -Polyisocyanates having at least three isocyanate groups in one molecule such as triisocyanatotoluene, 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate, and these polyisocyanates Burette-type adducts and isocyanurate cycloadducts of A polyisocyanate compound is reacted with a hydroxyl group of a polyol such as lene glycol, propylene glycol, 1,4-butylene glycol, dimethylolpropionic acid, polyalkylene glycol, trimethylolpropane, hexanetriol and the like in an excess amount of isocyanate groups. Urethanized adducts, burette type adducts of these polyisocyanates, and socyanurate ring adducts.

  Examples of the blocking agent for blocking the isocyanate group of these polyisocyanate compounds include phenol, ε-caprolactam, propyl alcohol, methyl ethyl ketoxime, diethyl malonate, and 3,5-dimethylpyrazole.

  The constituent ratio of the base resin and the crosslinking agent in the resin component of the solvent-type repair coating is not particularly limited, but the base resin is usually 40 to 90%, particularly 50 to 80, based on the total solid weight of both components. %, And the crosslinking agent is preferably in the range of usually 60 to 10%, particularly 50 to 20%.

  The titanium white pigment blended in the solvent-type repair paint is a white pigment mainly composed of titanium dioxide, and its particle size is generally within a range of 0.2 to 0.35 μm, particularly 0.25 to 0.30 μm. Some are preferred.

  The solvent-type repair paint used in this method has an L value of whiteness based on the CIE color matching function of 70 to 95, preferably 80 to 93, more preferably 85, when coated with a film thickness equal to or greater than the hidden film thickness. It is necessary to be adjusted to form a coating film in the range of ~ 92.

  The solvent-type repair coating used in this method preferably has a concealing film thickness of 45 μm or less, particularly 20 to 35 μm, more particularly 25 to 30 μm.

  The concealing film thickness of the solvent-type repair paint can be adjusted by, for example, the pigment concentration and the type of pigment used.

  In order to prepare a solvent-type repair paint having a whiteness L value based on the CIE color matching function in the range of 70 to 95 when coated with a film thickness equal to or greater than the hidden film thickness, when using a titanium white pigment, Titanium white pigment is used in such a ratio that it is usually in the range of 40 to 200 parts by weight, particularly 80 to 150 parts by weight, more particularly 80 to 120 parts by weight, per 100 parts by weight of the solid content of the solvent-type repair paint resin component. It is preferable to do.

  The solvent-type repair coating material may contain a coloring pigment and an extender pigment other than the titanium white pigment as required, as long as the whiteness in the L value range is not deviated.

  Coloring pigments other than titanium white pigment include, for example, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium Inorganic or organic coloring pigments such as pigments and perylene pigments can be mentioned. Examples of extender pigments include talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, and alumina white. Can be mentioned.

  If necessary, blending of color pigments and extender pigments can be performed by making a paste using a part of the base resin component described above and adding this together with other components to the remaining resin component. . In preparing the paste, conventional additives such as an antifoaming agent, a dispersing agent and a surface conditioner can be used as necessary.

  Examples of the silicon-containing inorganic thickener blended in the solvent-type repair coating include metal silicate, montmorillonite, organic montmorillonite, and silica fine particles. Among the above, the metal silicate can be easily obtained by, for example, purifying clay minerals such as hectorite and bentonite or synthesizing them by a known method. Examples of metals include sodium, magnesium, and lithium. Can be mentioned.

  By adding a silicon-containing inorganic thickener to the solvent-based repair coating, it is possible to impart thixotropic properties to the solvent-based repair coating, which is sufficient when high shear stress is applied, such as during spray coating. It is possible to easily perform spray coating work on the other hand, while increasing the apparent viscosity when low shear stress is applied after applying to the repaired surface. It becomes possible. In particular, when heat is applied during baking, the viscosity can be maintained. As a result, when the base coating film and the clear coating film are later formed into a three-layer coating film of the repair coating film, the base coating film and the clear coating film, the repair coating film swells. It is possible to suppress the mixing of the three-layer coating film of the repair coating film, the base coating film, and the clear coating film, resulting in a deterioration of the finished appearance due to the three-layer coating layer of the repairing part. In addition, a good finished appearance can be obtained even in the repair portion.

  As the silicon-containing inorganic thickener, for example, bentonite, montmorillonite, organic montmorillonite, silica fine particles, and derivatives thereof can be preferably used. Specifically, as bentonite, for example, “Bentone 27”, “Bentone 34”, “Bentone 38”, “Bentone SD-1”, “Bentone SD-2”, “Bentone SD-3”, “Bentone 52”, "Bentone 57" (all of which are manufactured by Rheox, trade names), "Tixogel VP", "Tixogel TE", "Tixogel UN", "Tixogel EZ100", "Tixogel MP100", "Tixogel MP250" Chemical name, product name) and the like.

  Examples of the montmorillonite include “Claytone 40”, “Claytone 34”, “Claytone HT”, “Claytone APA”, “Claytone AF”, “Claytone HY” (all of which are manufactured by Southern Clay Products, Inc.). And so on.

Silica fine particles are silica (SiO ₂ ) fine particles, and those having silanol groups on the particle surface are generally used. If necessary, the particle surface is hydrophobized with octylsilane or dimethyl silicone oil. Can also be used. The silica fine particles preferably have a primary particle having a small average particle size (usually 20 nm or less). Specifically, for example, “Aerosil RX200”, “Aerosil R812”, “Aerosil R805”, “AerosilRY200”, “Aerosil R202”. (All of these are trade names manufactured by Nippon Aerosil Co., Ltd.).

  These are mainly in powder form, and there are fine ones that can be added to the solvent-type repair coating as they are, but usually it is preferable to mix them while mechanically dispersing.

  The content of the silicon-containing inorganic thickener varies depending on the type and the like, but is 0.5 to 3% by mass, preferably 1 to 3% by mass, particularly based on the total solid content of the solvent-type repair coating resin component. Preferably it can be in the range of 2-3 mass%.

If necessary, the solvent-based repair paint may be used in combination with a thickener other than the above-mentioned silicon-containing inorganic thickener, for example, a thickener known per se such as polyethylene wax or amide.

  In this method, the solvent-type repair paint further contains a solvent having a boiling point of 200 ° C. or higher, preferably 200 to 260 ° C., more preferably 210 to 250 ° C. It can be contained within a range of 5 to 60% by mass, preferably 20 to 60% by mass, and more preferably 30 to 50% by mass, based on the total amount. Here, “easily soluble in water” means mixing at an arbitrary ratio with distilled water at room temperature (20 ° C.) without causing phase separation to form a transparent solution.

  By adding a high-boiling solvent that is readily soluble in water to the solvent-type repair coating, the affinity between the aqueous base coating film and the repair coating film in the repair area is improved, and the non-repaired portion of the orientation state of the pearl pigment is improved. As a result, it is possible to perform repair finishing so that the repaired part and the non-repaired part have the same appearance without a sense of incongruity.

  Examples of solvents that are readily soluble in water and have a boiling point of 200 ° C. or higher include, for example, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, polyethylene glycol monomethyl ether (for example, High-mol PM (manufactured by Toho Chemical Industry Co., Ltd., trade name)), glycol ethers such as tripropylene glycol monomethyl ether; triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether (for example, Hisolv MPM (Toho Chemical Industry Co., Ltd.) Product name)), glycol diethers such as tetraethylene glycol dimethyl ether , And the like 1,3-butylene glycol; diethylene glycol monoethyl ether acetate.

  Among the above, glycol ether can be preferably used. These solvents can be used alone or in combination of two or more.

  If the boiling point of the water-soluble solvent used is less than 200 ° C., the effect of reducing the difference from the non-repaired portion of the orientation state of the pearl pigment may be reduced. In addition, if the content of the solvent having a boiling point of 200 ° C. or higher that is readily soluble in water is less than 5% by mass, the effect of reducing the difference from the non-repaired portion of the orientation state of the pearl pigment may be insufficient, If it exceeds 60% by mass, the sagging property of the coating film may be lowered.

  The solvent-type repair paint (C) can contain other solvents as necessary.

  Solvent type repair paint (C) is usually used in the paint field such as curing catalyst, UV absorber, light stabilizer, other surface conditioner, anti-degradation agent, anti-settling agent and antifoaming agent as needed. Can be contained appropriately.

  The solvent-type repair paint (C) can be prepared by blending the components described above and mixing them uniformly.

  The non-volatile content concentration during the application of the solvent-type repair paint (C) can be usually 20 to 50% by mass. From the viewpoint of air pollution prevention and resource saving, a high solid type with a small amount of organic solvent is preferable.

The solvent-type repair paint (C) has a paint viscosity of 20% at Ford Cup No. 4 is usually adjusted within a range of 10 to 20 seconds, preferably 12 to 16 seconds, and is ground by air spray, airless spray, electrostatic coating, etc., to remove coating defects such as dust and blisters. It is preferable to perform spot coating around the ground portion of the intermediate coating surface. It is preferable that the coating film thickness is a grade which fills the intermediate coating film part removed by grinding.

  In the repair coating method of the present invention, the solvent-type repair paint (C) is applied spot-wise or in some cases as a whole centering on the ground portion of the intermediate coating surface, and then the solvent-type repair paint (C) is applied. Leave the film at room temperature for 1 to 20 minutes as necessary without heating and curing the film, and then apply the pearl pigment on the uncured coating surface and the intermediate coating surface on which the solvent-based repair coating (C) is not applied. The aqueous base coat paint (D) it contains is painted.

Water-based base coat paint (D):
The aqueous base coat paint (D) is an aqueous paint comprising a resin component, a pearl pigment, and a solvent, and further containing a color pigment, an extender pigment, and other paint additives as necessary. The solvent-type repair paint (C) coating part (repair part) and the solvent-type repair paint (C) are applied to the uncoated part (non-repair part).

  The resin component is preferably a thermosetting resin composition. Specifically, for example, a base resin such as an acrylic resin having a crosslinkable functional group such as a hydroxyl group, a polyester resin, an alkyd resin urethane resin, a melamine resin, a urea resin, Examples include those used in combination with a crosslinking agent such as a polyisocyanate compound (including a block product), and these can be used by dissolving or dispersing in an organic solvent and / or water.

  The pearl pigment is a scaly pigment that imparts a pearly luster to the coating film, and examples include mica, titanium oxide-coated mica, iron oxide-coated mica, and mica-like iron oxide. Titanium-coated mica can be preferably used. Titanium oxide-coated mica is generally called white mica or silver mica and is distinguished from interference mica.

  The titanium oxide-coated mica is obtained by coating the surface of scaly mica powder with titanium oxide.

  These pearl pigments preferably have a longitudinal direction of 1 to 30 μm and a thickness of about 0.05 to 1 μm. The content of the pearl pigment is usually in the range of 5 to 30% by mass based on the total amount of the solid content of the resin component.

  In the case of titanium oxide-coated mica, those having a maximum diameter of generally 5 to 60 μm, particularly 5 to 25 μm, and a thickness generally in the range of 0.25 to 1.5 μm, particularly 0.5 to 1 μm are preferred. .

  In particular, in order to finish the multi-layer coating film in white pearl tone or silver pearl tone, the thickness of the titanium oxide layer covering the surface of the titanium oxide-coated mica is generally 90 to 160 nm, particularly 100, based on the optical thickness. It is preferably in the range of ~ 150 nm and generally 40-70 nm, in particular 45-65 nm, based on geometric thickness.

  When titanium oxide-coated mica is used, the blending amount is not strictly limited, but is usually 5 to 30% by mass, particularly about 7 to 20% by mass, based on the total amount of solids of the resin component. It is preferable.

  The water-based base coat paint (D) can contain glitter pigments, color pigments and the like other than the pearl pigment, if necessary, to the extent that the white pearl luster is not impaired.

Examples of bright pigments other than the pearl pigment include, for example, scaly metal pigments such as aluminum, copper, nickel alloys, and stainless steel, scaly metal pigments whose surfaces are coated with metal oxides, and color pigments that are chemically adsorbed on the surface. Scale-like metal pigments, scale-like aluminum pigments with an aluminum oxide layer formed by causing an oxidation-reduction reaction on the surface, aluminum solid-plated iron oxide pigments, glass flake pigments, glass flakes coated with metal oxides on the surface Examples thereof include a pigment, a glass flake pigment in which a colored pigment is chemically adsorbed on the surface, a graphite pigment whose surface is coated with titanium dioxide, and a silica flake and an alumina flake pigment whose surface is coated with titanium dioxide.

  Examples of the color pigment include titanium dioxide, zinc oxide, basic lead sulfate, calcium leadate, zinc phosphate, aluminum phosphate, zinc molybdate, calcium molybdate, bitumen, ultramarine blue, cobalt blue, copper phthalocyanine blue, indium Dunslon Blue, Yellow Lead, Synthetic Yellow Iron Oxide, Transparent Brown (Yellow), Bismuth Vanadate, Titanium Yellow, Zinc Yellow (Zinc Yellow), Strontium Chromate, Lead Cyanamide, Monoazo Yellow, Disazo Yellow, Isoindolinone Yellow, Metal Complex salt azo yellow, quinophthalone yellow, isoindoline yellow, benzimidazolone yellow, red bean, transparent red bean (red), red lead, monoazo red, unsubstituted quinacridone red, azo lake (Mn salt), quinacridone magenta, anthrone Di, dianthraquinonyl red, perylene maroon, quinacridone magenta, perylene red, diketopyrrolopyrrole chromium vermilion, basic lead chromate, chromium oxide, chlorinated phthalocyanine green, brominated phthalocyanine green, pyrazolone orange, benzimidazolone Examples thereof include orange, dioxazine violet, and perylene violet.

  The non-volatile content concentration at the time of application of the aqueous base coat paint (D) can be usually about 15 to 35% by mass.

  The water-based base coat paint (D) has a paint viscosity of 20 ° C. 4 is adjusted to a viscosity of usually 20 to 70 seconds, preferably 30 to 60 seconds, and the uncured solvent-type repair paint coating surface (repair part) and the solvent-type repair paint (C) are not applied. It is painted on the intermediate coating surface (non-repaired part).

  The coating method is not particularly limited, and can be performed by a conventional method. Examples thereof include air spray coating, airless spray coating, rotary atomization coating, and curtain coat coating. In these coating methods, electrostatic application may be performed as necessary. Among these, rotation atomization coating by electrostatic application is particularly preferable. The coating can be performed once or several times so as to obtain a desired film thickness.

  The coating thickness of the aqueous base coat paint (D) is generally within the range of 5 to 20 μm, particularly 5 to 15 μm, more particularly 7 to 12 μm, based on the cured coating film.

  The coating film itself of the aqueous base coat paint (D) can be crosslinked and cured by heating at a temperature of about 100 to about 170 ° C. for about 20 to 40 minutes, but in the repair coating method of the present invention, it is crosslinked and cured. The solvent-type clear coat paint (E) is applied on the coated surface without any problem.

Solvent type clear coat paint (E):
The solvent-type clear coat paint (E) contains a resin component and a solvent, and if necessary, blends color pigments and other paint additives as long as they do not impair the transparency of the paint film. A liquid paint can be used.

The resin component that can be used in the clear coat paint (E) is preferably a thermosetting resin composition. Specifically, for example, an acrylic resin, a polyester resin, an alkyd resin, a urethane resin having a crosslinkable functional group such as a hydroxyl group. And a base resin such as melamine resin, urea resin, and polyisocyanate compound (including block body) in combination.

  The clear coat paint (E) can be applied to the surface of the uncured aqueous base coat paint (D) by, for example, air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, In these coating methods, electrostatic application may be performed as necessary. Among these, air spray coating by electrostatic application is particularly preferable. The coating can be performed once or several times so as to obtain a desired film thickness.

  The coating thickness is generally 20 to 80 μm, particularly 25 to 65 μm, more preferably 30 to 50 μm, based on the cured coating film. The clearcoat paint (E) coating can be crosslinked and cured by heating at a temperature of about 100 to about 170 ° C. for about 20 to 40 minutes.

  In the repair coating method of the present invention, after all of the solvent-based repair paint (C), the water-based base coat paint (D) and the solvent-type clear coat paint (E) are applied, the paints (C), (D) and (E ), The defective coating is repaired.

  Heat curing can usually be performed by heating at a temperature of about 100 to about 160 ° C. for about 20 to 40 minutes.

  Moreover, in order to accelerate | stimulate volatilization of a solvent after application | coating of the said coating materials (C), (D), and (E), preliminary drying can also be performed as needed. Pre-drying is usually preferably performed at a temperature of about 50 to about 100 ° C. for about 3 to 10 minutes.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to a following example. In the following, “part” and “%” are both based on mass, and the film thickness of the coating film is based on the cured coating film.

(Production Examples 1 to 15) Production of solvent-type repair paint (C) Pigment dispersion paste (34.7 parts of acrylic resin solution (non-volatile content: 50%), 130 parts of titanium oxide and 23 parts of xylene were mixed to form a ball mill. 187.7 parts of pigment dispersion paste obtained by dispersing) 105.3 parts of acrylic resin solution (Note 1) having a non-volatile content of 50% and Super Becamine L-127-75b (Dainippon Ink Co., Ltd.) , Trade name, melamine resin, solid content 75%) 40 parts and thickener and solvent of the amount shown in Table 1 were added and mixed. Further, Swazol 1000 (trade name, hydrocarbon solvent manufactured by Cosmo Oil Co., Ltd.) Ford cup no. 4 was adjusted to 14 seconds to obtain each of the solvent-type repair paints (C-1) to (C-15).
(Note 1) Acrylic resin solution 37.5 parts of methyl methacrylate, 17 parts of ethyl acrylate, 17 parts of n-butyl acrylate, 7 parts of 2-hydroxyethyl methacrylate, Plaxel FM-3 (manufactured by Daicel Chemical Industries, trade name 2 -Compound obtained by ring-opening polymerization of 3 mol of ε-caprolactone in 1 mol of hydroxyethyl methacrylate) A copolymer of 20 parts and 1.5 parts of acrylic acid, weight average molecular weight 55000, nonvolatile content 50%).

In addition, the amount of the thickener and the solvent in Table 1 represents mass% (solid content for the thickener) based on the total resin solid content in the repair coating (C). Each has the following meaning.
(Note 2) Aerosil 200: Nippon Aerosil Co., Ltd., trade name, silicon-containing inorganic thickener.
(Note 3) Bentone 27: Rheox, trade name, silicon-containing inorganic thickener. (Note 4) Disparon 6900-20X: Enomoto Kasei Co., Ltd., trade name, amide thickener. (Note 5) Varita 100: manufactured by Sakai Chemical Industry Co., Ltd., trade name, barium sulfate.
(Note 6) Diethylene glycol monobutyl ether: Solvent, boiling point 230 ° C., readily soluble in water. (Note 7) Tripropylene glycol monomethyl ether: Solvent, boiling point 242 ° C., easily soluble in water.
(Note 8) Ethylene glycol monobutyl ether: solvent, boiling point 171 ° C.
(Note 9) Dipropylene glycol n-propyl ether: Solvent, boiling point 212 ° C., not readily soluble in water.

  In addition, all the solvent-type repair paints had a masking film thickness of 27 μm, and the L value of whiteness based on the CIE color matching function was 91 when applied with a film thickness equal to or greater than the masking film thickness.

Other paints (1) Electrodeposition paint (A): “Electron 9400HB”, manufactured by Kansai Paint Co., Ltd., trade name, epoxy resin polyamine cationic resin blended with a block polyisocyanate compound as a curing agent.

(2) Intermediate coating (B): “Lugabake intermediate coating white”, concealment film thickness: 27 μm, L value of whiteness based on CIE color matching function when coated with film thickness greater than or equal to concealment film thickness: 91, Kansai paint Product name, polyester resin / melamine resin, organic solvent type.

(3) Water-based base coat paint containing pearl pigment (D): Water-based resin composition comprising 65 parts of hydroxyl group-containing acrylic resin (Note 10), 15 parts of urethane resin (Note 11) and 20 parts of melamine resin (Note 12) “Iriodin 103R” (trade name, titanium oxide-coated flake mica, maximum diameter 10 to 20 μm, thickness 0.5 to 1 μm, optical thickness of titanium oxide per 100 parts by weight of resin solid content of the emulsion A water-based paint in which 10 parts (about 140 nm, geometric thickness about 60 μm) were added and the solid content was adjusted to 20%.
(Note 10) Hydroxyl group-containing acrylic resin: Neutralized with dimethylethanolamine, an acrylic emulsion having an average particle size of 0.1 μm and a hydroxyl value of 35.
(Note 11) Urethane resin: Water-elongated emulsion. Neutralized with triethylamine.
(Note 12) Melamine resin: U-Ban 28SE (trade name, hydrophobic melamine resin, manufactured by Mitsui Toatsu Chemical Co., Ltd.).

(4) Clear coat paint (E): Lugabake clear, manufactured by Kansai Paint Co., Ltd., trade name, acrylic resin / amino resin paint, organic solvent type.

Examples 1-7 and Comparative Examples 1-8
Cationic electrodeposition paint (A) was electrodeposited to a film thickness of 20 μm by a conventional method on a steel plate (JISG 3141, size 400 × 300 × 0.8 mm) subjected to degreasing and zinc phosphate treatment, and 170 ° C. After heating for 20 minutes and crosslinking and curing, an intermediate coating (B) was applied to the electrodeposition coated surface to a film thickness of 35 μm and heated at 140 ° C. for 30 minutes for crosslinking and curing.

  A part of this intermediate coating surface was polished with a water-resistant abrasive paper having a roughness of # 600. The polishing range was a circle having a diameter of about 40 mm, and the polishing was performed with an inclination so that the central portion of the circular polishing portion was the deepest and the circumferential portion was the shallowest. The maximum depth of the polished part is about 30 μm.

  Next, each solvent type repair paint C-1 to 15 was applied to the polished portion of the intermediate coating surface. This coating is performed so that the portion where the intermediate coating film has been removed by polishing is filled, and after the coating, the cured coating surface coated with the repair coating and the unpainted intermediate coating surface are smooth without unevenness. It is desirable to paint like this.

  The repair coating film is left to stand at room temperature for 5 minutes without being cured by heating, and then the aqueous base coat paint (D) containing the pearl pigment is used at a booth temperature of 25 ° C. and a booth humidity using a bell-type rotary electrostatic coating machine. The entire surface was coated so that the coating film thickness was 10 μm at 75%.

  After heating at 80 ° C for 5 minutes in a hot air circulating drying oven, apply clear coat (E) to the coating surface using a bell-type rotary electrostatic coater at a booth temperature of 25 ° C and a booth humidity of 75%. The coating was applied so that the coating thickness was 35 μm. After standing in the room for 3 minutes, it is heated in a hot air circulation drying oven at 140 ° C. for 30 minutes, and each of the composites consisting of the solvent-based repair paint (C), the aqueous base coat paint (D) and the clear coat paint (E) is used. The layer coating was simultaneously crosslinked and cured.

Evaluation Results The color consistency and coating cracking of the multilayer coating film obtained from the coating material were evaluated according to the following criteria.

Color consistency:
The color difference (ΔE) between the repaired part and the non-repaired part was evaluated according to the following criteria. The smaller the ΔE value, the better the color matching. ΔE was determined by the following equation.
ΔE = (E value of non-repaired part) − (E value of repaired part)
The E value was measured using CR400 manufactured by Konica Minolta (trade name, tristimulus value direct-reading color meter, D65 light source, 2 ° visual field, diffuse illumination vertical light reception (d / 0)). The E value is a value based on the CIE 1976 L ^* a ^* b ^* color system.
○: ΔE <0.5,
Δ: 0.5 ≦ ΔE <1,
×: 1 ≦ ΔE.

Coating crack:
It was visually evaluated whether cracks occurred in the coating film formed with the aqueous base coat paint (D) containing the pearl pigment.
○: Good without cracks,
X: Crack (crack) is generated and defective.

  The evaluation results are shown in Table 2 below.

Claims (1)

An electrodeposition coating film (A) using an intermediate coating material capable of forming a coating film having a whiteness L value in the range of 70 to 95 based on the CIE color matching function when coated with a film thickness equal to or greater than the concealment film thickness The intermediate coating film (B) having an L value of 70 to 95 formed on the top,
Repair coating is performed with a solvent-type repair paint (C) that can form a coating film having a whiteness L value in the range of 70 to 95 based on the CIE color matching function when coated with a film thickness equal to or greater than the concealment film thickness.
Next, an aqueous base coat paint (D) containing a pearl pigment is applied at a film thickness of 5 to 15 μm,
Furthermore, a solvent-based clear coat paint (E) is applied on the aqueous base coat paint (D) coating film,
A method of forming a multilayer coating film by simultaneously heating and curing the coating films of paints (C), (D) and (E),
Repair paint (C) is a solvent having a boiling point of 200 ° C. or higher that is 0.5 to 3 mass% of silicon-containing inorganic thickener and easily soluble in water, based on the total amount of resin solids in repair paint (C). A repair coating method characterized by containing 5 to 60% by mass.