JP5366491B2 - MULTILAYER COATING FORMATION METHOD AND COATED ARTICLE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a multilayer coating film having an excellent appearance where a flip flop property is high and metallic unevenness is suppressed with a three-coat/one bake process. <P>SOLUTION: The method for forming a multilayer coating film, wherein an intermediate coating material X containing a filming resin A, a base coating Y containing a filming resin B and an organic solvent C, and a clear coating material Z are sequentially coated on an object to be coated, and they are also baked/cured, the absolute value of the difference (SP<SB>A</SB>-SP<SB>B</SB>) between SP<SB>A</SB>of the SP value of the filming resin A and SP<SB>B</SB>of the SP value of the filming resin B is 0.2 or larger, the absolute value of the difference (SP<SB>A</SB>-SS<SB>C</SB>) between SP<SB>A</SB>of the SP value of the filming resin A and that SP<SB>C</SB>of The SP value of the organic solvent C is 1.0 or less, and the content of the organic solvent C in the base coating Y stays within 20-800 pts.wt. based on 100 pts.wt. of the solid content of the filming resin B, and an article coated by the method are provided. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  In the present invention, an organic solvent-type intermediate coating, an organic solvent-type base coating, and an organic solvent-type clear coating are sequentially applied on an object to be coated. The present invention relates to a method for forming a multilayer coating film having an excellent appearance by a one-bake method, and a coated article formed by the method.

  As a method of forming a coating film on an automobile body, an electrodeposition coating film is formed on an object to be coated, followed by “Coating of an intermediate coating → Bake curing> Base coating → Clear coating → Bake curing” A method of forming a multi-layer coating film by the bake (3C2B) method has been widely adopted. However, in recent years, from the viewpoint of energy saving, the baking and curing step after painting of the intermediate coating is omitted, and electrodeposition is performed on the object to be coated. After the coating film is formed, a three-coat one-bake (3C1B) system has been attempted, which is “intermediate paint application → base paint application → clear paint application → baking and curing”.

  However, since the coating by the 3C1B method tends to cause a mixed layer of the intermediate coating film and the base coating film, the smoothness and sharpness of the resulting coating film are likely to be lower than the 3C2B system, and the base film When a paint containing a luster pigment is used as the paint, there is a problem that flip-flop properties and metallic unevenness are liable to occur, and it is difficult to obtain a sufficient luster feeling.

  For example, Patent Document 1 discloses a process of sequentially applying an intermediate coating composition, a base coating composition, and a clear coating composition on a substrate on which an electrodeposition coating film is formed, and three coated layers. A method of forming a laminated coating film comprising a step of baking and curing the coating composition, wherein the intermediate coating composition comprises a specific urethane-modified polyester resin (a), a melamine resin (b), a specific blocked isocyanate compound (c), and a core shell. A non-aqueous dispersion resin (d) having a structure and a flat pigment (e), and the base coating composition comprises a specific acrylic resin, melamine resin (I), polymerized fine particles (U) and glitter pigment ( D) a solvent-based base coating composition containing a carboxyl group-containing acrylic resin (A) and a carboxyl group-containing polyester resin (B). And when it contains an epoxy group-containing acrylic resin (C), it is disclosed that the resulting coatings with excellent appearance. However, even in the coating film forming method, the flip-flop property may be inferior or metallic unevenness may occur.

JP 2007-75791 A

  An object of the present invention is to provide a multi-layer coating film forming method by a three-coat one-bake method in which an organic solvent-type intermediate coating, an organic solvent-based base coating, and an organic solvent-type clear coating are sequentially applied. It is to provide a method capable of forming a coating film having an excellent appearance in which is suppressed, and a coated article formed by the method.

As a result of intensive studies to achieve the above-mentioned object, the present inventors have made a three-coat one-bake method using an organic solvent-type intermediate coating material, an organic solvent-type base coating material, and an organic solvent-type clear coating material. In the step of forming a multilayer coating film, a paint containing a specific film-forming resin is used as the organic solvent-type intermediate coating, and a specific film-forming resin and an organic solvent are used as the organic solvent-type base paint. The present inventors have found that a multilayer coating film having an excellent appearance with a high flip-flop property and little metallic unevenness can be formed when using a coating material containing.

Thus, according to the present invention, the organic solvent-type intermediate coating (X) containing the film-forming resin (A), the film-forming resin (B), and the organic solvent (C) are contained on the article to be coated. The organic solvent type base coating (Y) and the organic solvent type clear coating (Z) are sequentially applied, and the intermediate coating film, the base coating film, and the clear coating film to be formed are simultaneously baked and cured to form a coating film. the absolute value of the difference between the solubility parameter value SP _B of rESIN (a) of the solubility parameter value SP _a and the film-forming resin _{(B) (SP a -SP B} ) is 0.2 or more, and the coating the absolute value of the difference between the solubility parameter value SP _C of the solubility parameter value SP _a and organic solvent forming resin _{(a) (C) (SP} a -SP C) is 1 or less, and an organic solvent-based Content of organic solvent (C) in paint (Y) Method for forming a multilayer coating film, characterized in that in the range of 20-800 parts by weight based on 100 parts by weight of the solid content of the film-forming resin (B) is provided.

  According to the present invention, an article coated by the multilayer coating film forming method is also provided.

  According to the method for forming a multilayer coating film of the present invention, a multilayer coating film having an excellent appearance with high flip-flop properties and little metallic unevenness can be formed in a three-coat one-bake method.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, the multilayer coating film forming method of the present invention will be described in more detail.

Application of Organic Solvent Type Intermediate Coating Material (X) According to the method for forming a multilayer coating film of the present invention, first, an organic solvent type intermediate coating material (X) is applied on an object to be coated.

The material of the object to which the method of the present invention can be applied is not particularly limited. For example, iron, aluminum, brass, copper, stainless steel, tinplate, galvanized steel, alloyed zinc ( Zn-Al, Zn-Ni, Zn-Fe, etc.) Metal materials such as plated steel; polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane Resins such as resins and epoxy resins and various plastic materials such as FRP; inorganic materials such as glass, cement and concrete; wood; fiber materials (paper, cloth, etc.), among others, metal materials and plastics Material is preferred.

  In addition, the object to which the method of the present invention can be applied is not particularly limited. For example, the outer plate of an automobile body such as a passenger car, a truck, a motorcycle, or a bus; an automobile part; a home such as a mobile phone or an audio device. An outer plate portion of an electric product can be exemplified, and among them, an outer plate portion of an automobile body and an automobile part are preferable.

  The object to be coated may be a metal surface such as a phosphate treatment, a chromate treatment, or a complex oxide treatment applied to the metal surface of the metal material or a vehicle body formed from the metal material. Further, the object to be coated may be one in which an undercoat film such as various electrodeposition paints is formed on the metal material or the vehicle body, and in particular, the undercoat film is formed by a cationic electrodeposition paint. A vehicle body is particularly suitable.

Organic solvent type intermediate coating (X)
The organic solvent-type intermediate coating (X) to be coated on the object to be coated contains a film-forming resin (A) and an organic solvent, and if necessary, a coloring pigment, an extender pigment, a bright pigment, A liquid paint comprising a curing catalyst, a thickener, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a surface conditioner, an anti-settling agent and the like can be used. In the present specification, the organic solvent type paint refers to a paint whose main component is an organic solvent.

Film-forming resin (A)
In the present invention, the film-forming resin (A) used for the organic solvent-type intermediate coating (X) is a polyester resin, acrylic resin, vinyl resin or alkyd resin having a crosslinkable functional group such as a hydroxyl group or a carboxyl group. And a resin composition for coatings comprising a base resin such as a urethane resin and a crosslinking agent such as a melamine resin, a polyisocyanate compound, or a blocked polyisocyanate compound. Among these, it is preferable to use a hydroxyl group-containing acrylic resin and / or a hydroxyl group-containing polyester resin as the base resin, and an amino resin as the crosslinking agent.

  The hydroxyl group-containing acrylic resin is, for example, (co) polymerized under normal conditions at least one unsaturated monomer component including a hydroxyl group-containing unsaturated monomer and optionally another unsaturated monomer copolymerizable with the monomer. It can be manufactured by caulking.

  The hydroxyl group-containing unsaturated monomer is a compound having at least one hydroxyl group and polymerizable unsaturated bond in one molecule, such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, Monoesterified product of (meth) acrylic acid such as 3-hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate and a dihydric alcohol having 2 to 8 carbon atoms; (meth) acrylic acid and 2 to 2 carbon atoms Ε-caprolactone modified product of monoesterified product of 8 dihydric alcohol; allyl alcohol; (meth) acrylate having a polyoxyethylene chain whose molecular terminal is a hydroxyl group.

  In this specification, (meth) acrylate is a general term for acrylate and methacrylate, (meth) acrylic acid is a general term for acrylic acid and methacrylic acid, and (meth) acrylamide is a general term for acrylamide and methacrylamide. And (meth) acryloyl is a general term for acryloyl and methacryloyl.

Examples of other unsaturated monomer copolymerizable with the hydroxyl group-containing unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and i-propyl (meth) acrylate. , N-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) ) Acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) A) Alkyl or cycloalkyl (meth) acrylates such as relay, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate; unsaturated monomers having an isobornyl group such as isobornyl (meth) acrylate; adamantyl Unsaturated monomer having an adamantyl group such as (meth) acrylate; aromatic ring-containing unsaturated monomer such as styrene, α-methylstyrene, vinyltoluene, phenyl (meth) acrylate; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris ( Unsaturated monomers having an alkoxysilyl group such as 2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane; Perfluoroalkyl (meth) acrylates such as orobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; unsaturated monomers having a fluorinated alkyl group such as fluoroolefin; and photopolymerizable functional groups such as maleimide groups Unsaturated monomers having: N-vinyl pyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate and other vinyl compounds; (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate, etc. Saturated monomer: (meth) acrylonitrile, (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, adduct of glycidyl (meth) acrylate and amines Any nitrogen-containing unsaturated monomer; glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4- Epoxy group-containing unsaturated monomers such as epoxycyclohexylpropyl (meth) acrylate and allyl glycidyl ether; (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-acrylamido-2-methylpropanesulfonic acid, allyl Unsaturated monomer having sulfonic acid group such as sulfonic acid, sodium styrene sulfonate, sulfoethyl methacrylate and sodium salt or ammonium salt thereof; 2-acryloyloxyethyl acid phosphate Unsaturated monomers having a phosphate group such as 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate; 2-hydroxy-4- (3-methacryloyloxy-2-hydroxy Propoxy) benzophenone, 2-hydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′- Ultraviolet rays such as dihydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H-benzotriazole Unsaturated monomer having an absorbing group; 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethyl Piperidine, 1- (meth) acryloyl-4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethyl Unsaturated monomers having UV-stabilizing performance such as lupiperidine; acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrol, vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone) , Vinyl ethyl ketone, vinyl butyl ketone) and the like, and these can be used alone or in combination of two or more.

  The hydroxyl group-containing acrylic resin is generally 1 to 200 mg KOH / g, preferably 5 to 150 mg KOH / g, more preferably 10 to 100 mg KOH / g, from the viewpoint of storage stability and water resistance of the resulting coating film. And acid values generally in the range of 1 to 200 mg KOH / g, preferably 2 to 150 mg KOH / g, more preferably 3 to 100 mg KOH / g. Further, the hydroxyl group-containing acrylic resin can generally have a weight average molecular weight in the range of 1,000 to 500,000, preferably 2,000 to 300,000, and more preferably 3,000 to 100,000.

  The amount of the hydroxyl group-containing acrylic resin is usually 2 to 90 parts by mass, preferably 5 to 60 parts by mass, based on 100 parts by mass of the solid content of the film-forming resin (A) in the organic solvent-type intermediate coating (X). Part, more preferably within the range of 10 to 40 parts by weight.

  The hydroxyl group-containing polyester resin can be produced, for example, by an esterification reaction or a transesterification reaction between a polybasic acid component and a polyhydric alcohol component. It can be produced by setting the equivalent ratio of the hydroxyl group in the polyhydric alcohol component (COOH / OH) to less than 1 and carrying out the esterification reaction with more hydroxyl groups than carboxyl groups.

  The polybasic acid component includes a compound having at least two carboxyl groups in one molecule, such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, Polybasic acids such as tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid and pyromellitic acid; anhydrides of these polybasic acids; lower alkyl esterified products of these polybasic acids These may be used alone or in combination of two or more.

  The polyhydric alcohol component includes a compound having at least two hydroxyl groups in one molecule. For example, ethylene glycol, 1,2-propylene glycol, 1,2-butylene glycol , 2,3-butylene glycol, 1,2-hexanediol, 1,2-dihydroxycyclohexane, 3-ethoxypropane-1,2-diol, 3-phenoxypropane-1,2-diol, etc. Glycol; neopentyl glycol, 2-methyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexane Diol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3- Lopandiol, 2-phenoxypropane-1,3-diol, 2-methyl-2-phenylpropane-1,3-diol, 1,3-propylene glycol, 1,3-butylene glycol, 2-ethyl-1,3- Octanediol, 1,3-dihydroxycyclohexane, 1,4-butanediol, 1,4-dihydroxycyclohexane, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, 3-methyl-1 , 5-pentanediol, 1,4-dimethylolcyclohexane, tricyclodecane dimethanol, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate (this is hydroxypivalic acid) And bisphenol A) , Bisphenol F, bis (4-hydroxyhexyl) -2,2-propane, bis (4-hydroxyhexyl) methane, 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8 , 10-tetraoxaspiro [5,5] undecane, diethylene glycol, triethylene glycol, glycerin, diglycerin, triglycerin, pentaerythritol, dipentaerythritol, sorbitol, mannitol, trimethylolethane, trimethylolpropane, ditrimethylolpropane , Tris (2-hydroxyethyl) isocyanurate and the like, and these can be used alone or in combination of two or more.

  The esterification or transesterification reaction of the polybasic acid component and the polyhydric alcohol component can be carried out by a method known per se. For example, the polybasic acid component and the polyhydric alcohol component are heated at about 180 to about 250 ° C. It can be carried out by polycondensation at a temperature.

Further, the hydroxyl group-containing polyester resin can be modified with a fatty acid, a monoepoxy compound, or the like, if necessary, during the preparation of the polyester resin or after the esterification reaction. Examples of the fatty acid include coconut oil fatty acid, cottonseed oil fatty acid, hemp seed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydrated castor Examples of the monoepoxy compound include “Cardura E10P” (trade name, manufactured by HEXION Specialty Chemicals, Inc., a glycidyl ester of a synthetic highly branched saturated fatty acid).

  The hydroxyl group-containing polyester resin is generally 10 to 300 mgKOH / g, preferably 25 to 250 mgKOH / g, more preferably 50 to 200 mgKOH / g from the viewpoint of storage stability and water resistance of the resulting coating film. And generally have an acid value in the range of 1 to 200 mg KOH / g, preferably 2 to 100 mg KOH / g, more preferably 3 to 60 mg KOH / g. The hydroxyl group-containing polyester resin can generally have a weight average molecular weight in the range of 500 to 50,000, preferably 1,000 to 40,000, more preferably 1,500 to 30,000.

  The amount of the hydroxyl group-containing polyester resin is usually 2 to 90 parts by mass, preferably 10 to 60 parts by mass, based on 100 parts by mass of the solid content of the film-forming resin (A) in the organic solvent-type intermediate coating (X). Parts, more preferably in the range of 15-50 parts by weight.

  In the present specification, the number average molecular weight and the weight average molecular weight are converted values using polystyrene having a known molecular weight as a standard substance, measured using a gel permeation chromatograph and tetrahydrofuran as a solvent.

  The hydroxyl group-containing acrylic resin and the hydroxyl group-containing polyester resin are used in combination with a so-called urethane-modified acrylic resin or urethane-modified polyester resin obtained by extending a polyisocyanate compound to a part of the hydroxyl group in the resin by a urethanization reaction to increase the molecular weight. Also good.

  Examples of the amino resin include partial or completely methylolated amino resins obtained by reacting amino components such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, and dicyandiamide with aldehyde. Examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. In addition, a partially or completely etherified part of this partially or fully methylolated amino resin with alcohol can be used. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, and n-propyl. Examples include alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethylbutanol, and 2-ethylhexanol.

  As the amino resin, a melamine resin is preferable, and in particular, methyl ether obtained by partially or completely etherifying a methylol group of a partially or completely methylolated melamine resin with methyl alcohol from the viewpoint of water resistance of the obtained coating film. Alkyl etherified melamines such as methylated melamine resins, butyl etherified melamine resins partially or fully etherified with butyl alcohol, methyl-butyl mixed etherified melamine resins partially or fully etherified with butyl alcohol Resins are preferred.

  The melamine resin usually has a weight average molecular weight in the range of 500 to 5,000, particularly 600 to 4,000, more particularly 700 to 3,000, from the viewpoint of water resistance of the resulting coating film. Is preferred.

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

  The polyisocyanate compound is a compound having at least two isocyanate groups in one molecule, and examples thereof include aliphatic diisocyanates such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate. Alicyclic diisocyanates such as methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), 1,3- (isocyanatomethyl) cyclohexane; Aromatic diisocyanates such as isocyanate, xylylene diisocyanate, diphenylmethane diisocyanate; lysine triisocyanate, etc. Organic polyisocyanates such as polyisocyanates having three or more valences themselves; adducts of these organic polyisocyanates with polyhydric alcohols, low molecular weight polyester resins or water; cyclized polymers of these organic polyisocyanates ( For example, isocyanurate), biuret type adduct, and the like. These polyisocyanate compounds can be used individually by 1 type or in mixture of 2 or more types.

  In addition, as the blocked polyisocyanate compound, those obtained by blocking the isocyanate group of the polyisocyanate compound with a blocking agent such as oxime, phenol, alcohol, lactam, mercaptan can be used.

  The blending ratio of the base resin and the cross-linking agent is based on the total solid mass of both, the former is generally 40 to 90%, particularly 50 to 80%, and the latter is generally 60 to 10%, particularly 50 to 20%. The inside is suitable.

The film-forming resin (A) has a solubility parameter value SP _A of 8.5 to 11.0, preferably 9.0 to 10.5, from the viewpoint of improving the flip-flop property of the obtained coating film and suppressing metallic unevenness. More preferably, it is in the range of 9.5 to 10.0.

The solubility parameter value is also called an SP value, and indicates a measure of solubility. In the present invention, the solubility parameter value of the film-forming resin is a value measured by a cloud point titration method. W. SUH, J. et al. M.M. CORBETT equation (Journalof
Applied Polymer Science, VOL. 12, 2359-2370 (1968)).

Solubility parameter value = {(V _ml ) ^1/2 × δ _H + (V _mh ) ^1/2 × δ _D }
/ {(V _ml ) ^1/2 + (V _mh ) ^1/2 }

Here, V _ml , V _mh , δ _H and δ _D are 0.5 g of sample at a measurement temperature of 20 ° C.
(Solid content) was dissolved in 10 mL of acetone, and at a measurement temperature of 20 ° C., 0.5 g (solid content) of the sample was added to 10 mL of acetone at a turbid point when n-hexane was added. It is a value calculated by applying the titration amount D (mL) at the cloud point when deionized water is added to the following equation to the following formula.
V _ml = 74.4 × 130.3 / {(1−V _H ) × 130.3 + V _H × 74.4}
V _mh = 74.4 × 18 / {(1−V _D ) × 18 + V _D × 74.4}
V _H = H / (10 + H)
V _D = D / (10 + D)
δ _H = 9.75 × 10 / (10 + H) + 7.24 × H / (10 + H)
δ _D = 9.75 × 10 / (10 + D) + 23.43 × D / (10 + D)

  The molecular volume (mL / mol) of each solvent is acetone: 74.4, n-hexane: 130.3, deionized water: 18, and the SP value of each solvent is acetone: 9.75, n -Hexane: 7.24, deionized water: 23.43.

  When the film-forming resin (A) is composed of two or more components such as a base resin and a crosslinking agent, the solubility parameter value of the film-forming resin is obtained by multiplying the solubility parameter value of each component by the mass fraction. This is the sum of the values.

  In the organic solvent-type intermediate coating (X), examples of the color pigment blended as necessary include titanium oxide; zinc white; carbon black; molybdenum red; Prussian blue; cobalt blue; permanent red and disazo yellow. Azo pigments such as phthalocyanine blue and phthalocyanine green; quinacridone pigments such as quinacridone red and quinacridone violet; isoindolinone pigments such as isoindolinone yellow and isoindolinone orange; anthrapyrimidine yellow and di Slen pigments such as anthraquinonyl red and indanthrone blue; perylene pigments such as perylene red and perylene maroon; dioxazine pigments such as carbazole violet; It is like diketopyrrolopyrrole pigments such as de, which may be used either alone or in combination of two or more. Among these, titanium oxide and carbon black can be preferably used.

  When the organic solvent-type intermediate coating (X) contains the above-mentioned color pigment, the blending amount of the color pigment is 100 parts by mass of the solid content of the film-forming resin (A) in the organic solvent-type intermediate coating (X). Is usually in the range of 1 to 150 parts by mass, preferably 10 to 120 parts by mass, and more preferably 15 to 90 parts by mass.

  Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white. Among them, it is preferable to use barium sulfate and / or talc.

  When the organic solvent type intermediate coating (X) contains the above extender, the amount of the extender is 100 parts by mass of the solid content of the film-forming resin (A) in the organic solvent intermediate coating (X). Is usually in the range of 1 to 100 parts by mass, preferably 5 to 60 parts by mass, and more preferably 8 to 40 parts by mass.

  Examples of the bright pigment include non-leafing type or leafing type aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, Examples thereof include mica coated with titanium oxide or iron oxide, and glass flakes. Among these, aluminum, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide are preferably used, and aluminum is particularly preferably used. The above luster pigments can be used alone or in combination of two or more.

  The glitter pigment is preferably flake shaped. Further, as the bright pigment, those having a longitudinal dimension of 1 to 100 μm, particularly 5 to 40 μm, and a thickness of 0.001 to 5 μm, particularly 0.01 to 2 μm are suitable.

When the organic solvent-type intermediate coating (X) contains the above-mentioned glittering pigment, the blending amount of the glittering pigment is the solid content 100 of the film-forming resin (A) in the organic solvent-type intermediate coating (X). It can be in the range of usually 1 to 50 parts by weight, preferably 2 to 30 parts by weight, more preferably 3 to 20 parts by weight, based on parts by weight.

  The organic solvent-type intermediate coating (X) has a solid content concentration of 30 to 65 parts by mass, preferably 35 to 60 parts by mass, from the viewpoint of flip-flop properties and smoothness of the resulting coating film. Preferably it is in the range of 40 to 55 parts by mass.

  The organic solvent-type intermediate coating (X) can be applied on the substrate by a method known per se, for example, air spray, airless spray, rotary atomizer, etc. May be performed. The coating film thickness is usually 10 to 100 μm, preferably 10 to 50 μm, and more preferably 15 to 35 μm as a cured film thickness.

Application of organic solvent type base paint (Y) Next, an organic solvent type base paint (Y) is applied onto the intermediate coating film formed as described above.

  From the viewpoint of improving the flip-flop property of the obtained coating film and suppressing metallic unevenness, the intermediate coating film has a solid content of 70 before applying the organic solvent base coating (Y). It is preferable to adjust so that it may become in the range of -100 mass%, especially 75-99 mass%, and especially 80-98 mass%.

Here, the solid content of the intermediate coating film can be measured by the following method:
First, the organic solvent-type intermediate coating (X) is applied onto the article to be coated, and at the same time, the organic solvent-type intermediate coating (X) is applied onto the aluminum foil whose mass (W ₁ ) has been measured in advance. ). Subsequently, immediately after the coating, the aluminum foil that has been left standing (setting) in the same manner as the coating of the organic solvent-type intermediate coating (X) is immediately before the organic solvent-based base coating (Y) is applied. And its mass (W ₂ ) is measured. Next, the recovered aluminum foil is dried at 110 ° C. for 60 minutes, and allowed to cool to room temperature in a desiccator. Then, the mass (W ₃ ) of the aluminum foil is measured, and the solid content is determined according to the following formula.
Solid content of intermediate coating film (mass%) = {(W ₃ −W ₁ ) / (W ₂ −W ₁ )} × 100

  The solid content of the intermediate coating film is adjusted by adjusting the boiling point of the organic solvent in the organic solvent type intermediate coating (X) or after applying the organic solvent type intermediate coating (X). It can be adjusted by changing the leaving (setting) time until the mold base paint (Y) is applied.

Organic solvent base paint (Y)
The organic solvent type base paint (Y) to be coated on the intermediate coating film contains a film-forming resin (B) and an organic solvent (C), and if necessary, other than the organic solvent (C) Liquid paints containing organic solvents, colored pigments, extender pigments, glitter pigments, curing catalysts, thickeners, UV absorbers, light stabilizers, antifoaming agents, surface conditioners, anti-settling agents, etc. Can be used.

Film-forming resin (B)
The film-forming resin (B) is a polyester resin, acrylic resin, vinyl resin, alkyd resin, or urethane resin having a crosslinkable functional group such as a hydroxyl group or a carboxyl group, as in the case of the film-forming resin (A). The resin composition for coatings which consists of base resins, such as these, and crosslinking agents, such as a melamine resin, a polyisocyanate compound, and a blocked polyisocyanate compound, is designated. Among these, it is preferable to use a hydroxyl group-containing acrylic resin and / or a hydroxyl group-containing polyester resin as the base resin, and an amino resin as the crosslinking agent.

In the present invention, the solubility parameter value SP _B of the film-forming resin (B) has a value different from the solubility parameter value SP _A of the film-forming resin (A) by 0.2 or more. That is, the absolute value of the difference between the solubility parameter value SP _B solubility parameter value SP _A and the film-forming resin of the film-forming resin _{(A) (B) (SP} A -SP B) is 0.2 or more is there. Among _them, it is preferable that the absolute value of _(SP A -SP _B) is in the range of 0.2 to 3.0, more preferably in the range of 0.25 to 2.0. Further, the solubility parameter value SP _B of the film-forming resin (B) is preferably higher than the solubility parameter value SP _A film-forming resin (A).

Adjustment of the absolute value of the difference between the solubility parameter value SP _B solubility parameter value SP _A and the film-forming resin of the film-forming resin _{(A) (B) (SP} A -SP B) is film-forming resin It can be carried out by changing the type of the base resin and the curing agent used as (A) and the film-forming resin (B), or changing the monomer composition of the base resin. Specifically, for example, the acrylic resin having a relatively high solubility parameter value is adjusted by blending more in the organic solvent type base coating (Y) than in the organic solvent type intermediate coating (X). Is preferred.

Organic solvent (C)
The organic solvent (C) is an organic solvent having a difference from the solubility parameter value SP _A of the film-forming resin (A) of 1 or less. That is, the absolute value of the difference between the solubility parameter value SP _C of the solubility parameter value SP _A and an organic solvent of the film-forming resin _{(A) (C) (SP} A -SP C) is 1 or less. Among these, the absolute value of (SP _A -SP _C ) is preferably in the range of 0.05 to 0.95, and more preferably in the range of 0.1 to 0.9. Further, the solubility parameter value SP _{C of} the organic solvent (C) is preferably lower than the solubility parameter value SP _{A of} the film-forming resin (A).

  In the present invention, the solubility parameter values of the organic solvent are those described in Journal of Paint Technology, Vol. 42 no. 541, 76-118 (February 1970).

  In the present invention, the organic solvent-type base paint (Y) is an organic solvent (C) in an amount of 20 to 800 parts by weight, preferably 40 to 40 parts by weight, based on 100 parts by weight of the solid content of the film-forming resin (B). 500 mass parts, More preferably, it contains 50-400 mass parts.

In the multilayer coating film forming method of the present invention, the use of a specific film-forming resin and an organic solvent results in the formation of a coating film having an excellent appearance with high flip-flop properties and suppressed metallic unevenness. The solubility parameter value SP _A of the film-forming resin (A) in the organic solvent-type intermediate coating (X) is the solubility of the film-forming resin (B) in the organic solvent-based base coating (Y). Since it is separated from the parameter value SP _B by a certain value or more, mixing at the interface between the intermediate coating film and the base coating film hardly occurs, and the orientation of the glitter pigment is hardly disturbed, so that the flip-flop property of the formed coating film is improved. It is inferred. Further, the solubility parameter value SP _C of the organic solvent in the organic solvent-based coating material (Y) (C) is a solubility parameter value SP of the film-forming resin in an organic solvent-based intermediate coating composition (X) (A) _Since it is close to _A , after the organic solvent type base paint (Y) is coated on the intermediate coating film, the organic solvent (C) in the base coating film moves into the intermediate coating film, and the viscosity of the base coating film is Since it rises, it is guessed that the glitter pigment in a base coating film becomes difficult to move, and a metallic nonuniformity is suppressed.

In addition, from the viewpoint of the flip-flop property of the coating film obtained, the boiling point of the organic solvent (C) is generally 160 to 230 ° C, preferably 170 to 220 ° C, more preferably 180 to 210 ° C. Is preferred. Specific examples of such organic solvents include “Swazole 1000” and “Swazole 1500” (both trade names, manufactured by Cosmo Oil Co., Ltd.,
Petroleum-based aromatic hydrocarbon solvents) and the like can be preferably used.

Further, from the viewpoint of the flip-flop property of the obtained coating film, the viscosity (V _Y1 ) of the organic solvent-based base coating composition (Y) is generally measured under conditions of a shear rate of 230 sec ⁻¹ and a temperature of 20 ° C. 0.5 to 100, preferably 1 to 50, more preferably 10 to 20 mPa · sec, and the viscosity (V _Y2 ) after 1 minute of application of the organic solvent-based base coating composition (Y) , Measured under conditions of a shear rate of 1.15 sec ⁻¹ and a temperature of 20 ° C., generally 10,000 to 50,000, preferably 15,000 to 45,000, more preferably 20,000 to 40,000 mPa · s. It is preferable to be within the range of sec.

The viscosity of the organic solvent-based coating composition _{(Y) (V Y1),} using a viscoelasticity measuring apparatus at a temperature 20 ° C., when the shear rate is changed from 10,000Sec ^-1 to 0.0001Sec ^-1 a viscosity measured at a 230Sec ^-1, as a viscoelasticity measuring apparatus, for example, can be used to "HAAKE RheoStress RS150" (trade name, manufactured by HAAKE Co.).

The viscosity (V _Y2 ) after 1 minute of application of the organic solvent-based base coating composition (Y) is 45 cm long × 30 cm wide × 0.8 mm thick. A tin plate is coated so that the cured film thickness is 15 μm, and the organic solvent-based base coating composition (Y) is applied to the tin plate, and a part of the coating film is scraped with a spatula after 1 minute has passed. the viscosity of the taken were taken, using the viscoelasticity measuring apparatus at a temperature 20 ° C., as measured by 1.15Sec ^-1 when the shear rate is changed from 10,000Sec ^-1 to 0.0001Sec ^-1 It is.

The viscosity (V _Y1 ) of the organic solvent-type base coating composition (Y) and the viscosity (V _Y2 ) after 1 minute of application are, for example, blending of the thickener in the organic solvent-type base coating composition (Y) It can be adjusted by adjusting the amount.

  In the organic solvent base paint (Y), the color pigment further blended as necessary includes, for example, titanium oxide, zinc white, carbon black, molybdenum red, Prussian blue, cobalt blue, permanent red, disazo yellow and the like. Azo pigments; phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; quinacridone pigments such as quinacridone red and quinacridone violet; isoindolinone pigments such as isoindolinone yellow and isoindolinone orange; anthrapyrimidine yellow and dianthra Slen pigments such as quinonyl red and indanthrone blue; perylene pigments such as perylene red and perylene maroon; dioxazine pigments such as carbazole violet; It is like diketopyrrolopyrrole pigments such as de, which may be used either alone or in combination of two or more.

  When the organic solvent-type base paint (Y) contains the above-mentioned color pigment, the blending amount of the color pigment is based on 100 parts by mass of the solid content of the film-forming resin (B) in the organic solvent-type base paint (Y). In general, it can be in the range of 1 to 150 parts by mass, preferably 3 to 120 parts by mass, and more preferably 5 to 90 parts by mass.

  Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white. Among them, it is preferable to use barium sulfate and / or talc.

When the organic solvent type base paint (Y) contains the above extender, the blending amount of the extender pigment is based on 100 parts by mass of the solid content of the film-forming resin (B) in the organic solvent type base paint (Y). As, it is 1-100 mass parts normally, Preferably it is 5-60 mass parts, More preferably, it can exist in the range of 8-40 mass parts.

  Examples of the bright pigment include non-leafing type or leafing type aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, Examples thereof include mica coated with titanium oxide or iron oxide, and glass flakes. Among these, aluminum, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide are preferably used, and aluminum is particularly preferably used. The above luster pigments can be used alone or in combination of two or more.

  The glitter pigment is preferably flake shaped. Further, as the bright pigment, those having a longitudinal dimension of 1 to 100 μm, particularly 5 to 40 μm, and a thickness of 0.001 to 5 μm, particularly 0.01 to 2 μm are suitable.

  When the organic solvent-type base paint (Y) contains the above-mentioned glitter pigment, the blending amount of the glitter pigment is 100 parts by mass of the solid content of the film-forming resin (B) in the organic solvent-type base paint (Y). Is usually in the range of 1 to 50 parts by weight, preferably 3 to 30 parts by weight, more preferably 5 to 25 parts by weight.

  In addition, the organic solvent type base paint (Y) has a solid content concentration of 10 to 30 parts by weight, preferably 12 to 28 parts by weight, from the viewpoint of improving the flip-flop property of the obtained coating film and suppressing metallic unevenness. More preferably, it is in the range of 15 to 25 parts by mass.

  The organic solvent-based base paint (Y) can be applied onto a substrate by a method known per se, for example, air spray, airless spray, rotary atomizing coating machine, etc. You may go. The coating film thickness is usually in the range of 1 to 30 μm, preferably 2 to 20 μm, more preferably 3 to 15 μm as a cured film thickness.

Application of Organic Solvent Type Clear Paint (Z) An organic solvent type clear paint (Z) is further applied onto the uncured coating film of the organic solvent type base paint (Y) formed as described above.

  As the organic solvent-type clear coating (Z), for example, those known per se that are usually used in the coating of automobile bodies can be used. Specifically, for example, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, an epoxy resin, or a fluororesin having a crosslinkable functional group such as a hydroxyl group, a carboxyl group, an epoxy group, or a silanol group, and melamine It is possible to use a resin, urea resin, polyisocyanate compound which may be blocked, carboxyl group-containing compound or resin, epoxy group-containing compound or organic solvent-based thermosetting paint containing a crosslinking agent such as resin as a resin component it can. Among these, a thermosetting paint comprising a hydroxyl group-containing acrylic resin and a melamine resin, a thermosetting paint comprising a hydroxyl group-containing acrylic resin and an optionally blocked polyisocyanate compound, or a carboxyl group-containing resin and an epoxy group A thermosetting paint comprising a resin is particularly preferred.

  Further, as the organic solvent-type clear paint (Z), a one-component paint or a two-component paint such as a two-component urethane resin paint may be used.

The organic solvent-type clear paint (Z) can contain the above-mentioned color pigment, glitter pigment, dye, and the like as long as it does not hinder transparency. An ultraviolet absorber, a light stabilizer, an antifoaming agent, a thickener, a surface conditioner, and the like can be appropriately contained.

  The organic solvent-type clear paint (Z) can be applied to the coating surface of the organic solvent-type base paint (Y) by a method known per se, for example, airless spray, air spray, rotary atomizing coating machine, etc. Electrostatic application may be performed during coating. Usually, it can coat so that it may become in the range of 10-60 micrometers by dry film thickness, Preferably it is 25-50 micrometers.

  After application of the organic solvent-type clear paint (Z), if necessary, leave it for 1 to 60 minutes at room temperature, preferably 3 to 20 minutes, or set it at about 40 to 80 ° C. for 1 to 60 minutes. Preheat for minutes.

Baking A multi-layered film consisting of three layers of an intermediate coating film, a base coating film, and a clear coating film formed as described above is subjected to, for example, hot air heating by a normal coating film baking means. It can be simultaneously cured by heating at a temperature of about 80 to about 170 ° C., preferably about 120 to about 160 ° C. for about 20 to about 40 minutes, by infrared heating, high-frequency heating or the like.

  EXAMPLES Hereinafter, although an Example is raised and this invention is demonstrated further more concretely, this invention is not limited only to these Examples. “Parts” and “%” indicate “parts by mass” and “% by mass”.

Production of film-forming resin Production Example 1
A reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube and dropping device was charged with 50 parts of xylene and 20 parts of butyl acetate, heated to 115 ° C., and then 5 parts of styrene and 50 parts of methyl methacrylate. , 15.5 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl acrylate, “Placcel FM3X” (trade name, manufactured by Daicel Chemical Industries, Ltd., xylene-diluted product of 2-hydroxyethyl methacrylate ε-caprolactone 3 mol adduct, solid A mixture of 20 parts, 1.5 parts of dimethylaminoethyl methacrylate, 1 part of acrylic acid, 15 parts of xylene and 1.0 part of 2,2′-azobisisobutyronitrile over 3 hours, After completion of dropping, the mixture was aged for 1 hour. Thereafter, a mixture of 5 parts of xylene and 1 part of 2,2′-azobis (2,4-dimethylvaleronitrile) was added dropwise over 1 hour, followed by aging for 1 hour after completion of the addition. Further, 10 parts of xylene was added to obtain a hydroxyl group-containing acrylic resin solution having a solid content of 50%. The obtained hydroxyl group-containing acrylic resin had a solubility parameter value of 10.86, an acid value of 7.8 mgKOH / g, a hydroxyl value of 69.5 mgKOH / g, and a weight average molecular weight of 40,000.

Production Example 2
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 107.8 parts 1,2-cyclohexanedicarboxylic anhydride, 85.8 parts 1,6-hexanediol and Tris (2 -Hydroxyethyl) isocyanurate 71.3 parts in the presence of 0.063 parts of the esterification catalyst dibutyltin oxide is heated to 230 ° C. and held for 1 hour, then xylene is added and the temperature is maintained for about 6 hours. The mixture was refluxed while distilling off water to obtain a hydroxyl group-containing polyester resin solution (PE). The obtained hydroxyl group-containing polyester resin had a solubility parameter value of 9.5, a hydroxyl value of 194 mgKOH / g, an acid value of 2 mgKOH / g, and a weight average molecular weight of 8,000.

Production of organic solvent type intermediate coating (X) Production example 3
80 parts of the hydroxyl group-containing acrylic resin solution (AC) obtained in Production Example 1, “JR-806” (trade name, manufactured by Teica, rutile titanium dioxide), 40 parts, “Carbon MA-100” (trade name, Mitsubishi Chemical) Carbon black) 1.7 parts, "Variace B-35" (trade name, manufactured by Sakai Chemical Industry Co., Ltd., barium sulfate powder) 15 parts, "MICRO ACE S-3" (trade name, manufactured by Nippon Talc, Glass beads were added to a mixture consisting of 3 parts of talc and 15 parts of xylene and dispersed with a paint shaker for 30 minutes, and then the glass beads were removed to obtain a pigment dispersion paste.
Next, 154.7 parts of the pigment dispersion paste, 43 parts of the hydroxyl group-containing polyester resin solution (PE) obtained in Production Example 2, melamine resin (MF-1) (methyl-butyl mixed etherified melamine resin, solid content 70 %, Solubility parameter value 9.06, weight average molecular weight 2,800) 43 parts, xylene 20 parts and propylene glycol monomethyl ether acetate 64 parts are mixed into a paint, and an organic solvent having a solid content of 49% A mold intermediate coating (X-1) was obtained. The solubility parameter value SP _A of the film-forming resin (A) in the obtained organic solvent-type intermediate coating (X-1) was 9.91.

Production Example 4
In Production Example 3, 64 parts of propylene glycol monomethyl ether acetate was changed to a mixed solvent consisting of 32 parts of propylene glycol monomethyl ether acetate and 32 parts of 3-methoxybutyl acetate. 49% of an organic solvent-type intermediate coating (X-2) was obtained. The solubility parameter value SP _A of the film-forming resin (A) in the obtained organic solvent-type intermediate coating (X-2) was 9.91.

Production Example 5
In Production Example 3, except that 64 parts of propylene glycol monomethyl ether acetate was changed to 64 parts of 3-methoxybutyl acetate, an organic solvent-type intermediate coating (X- 3) was obtained. The solubility parameter value SP _A of the film-forming resin (A) in the obtained organic solvent-type intermediate coating (X-3) was 9.91.

Production of organic solvent type base paint (Y) Production Example 6
100 parts of the hydroxyl group-containing acrylic resin solution (AC) obtained in Production Example 1, 29 parts of the hydroxyl group-containing polyester resin solution (PE) obtained in Production Example 2, melamine resin (MF-2) (butyl etherified melamine resin, solid content contained Rate 60%, solubility parameter value 9.75, weight average molecular weight 2,000), “Swazole 1500” (trade name, manufactured by Cosmo Oil Co., Ltd., petroleum aromatic hydrocarbon solvent, solubility parameter value 9. 02, boiling point 183 to 207 ° C) 30 parts, butyl acetate (solubility parameter value 8.69, boiling point 127 ° C) 320 parts, xylene (solubility parameter value 8.89, boiling point 138 to 144 ° C) 70 parts, "GX -180A "(Asahi Kasei Metals Co., Ltd., metal content 74%) 16.2 parts and" Dispalon 6900 "(trade name, manufactured by Enomoto Kasei Co., Ltd., thickener, solid content included Perform paint rates 10%) 3 parts were mixed and stirred to obtain a solids content of 18% organic solvent-based coating material (Y-1). The obtained organic solvent type base coating material (Y-1) had a shear rate of 230 sec ⁻¹ and a viscosity (V _Y1 ) at a temperature of 20 ° C. of 18 mPa · sec. Further, the solubility parameter value SP _B of the resulting organic solvent-based coating material (Y-1) film-forming resin in (B) was 10.26.

Production Examples 7 to 16
In Production Example 6, organic solvent base paints (Y-2) to (Y-11) were obtained in the same manner as in Production Example 6 except that the composition was changed as shown in Table 1 below. Solid content of the obtained organic solvent-type base paint, shear rate 230 sec ⁻¹ , viscosity at a temperature of 20 ° C. (V _Y1 ), and solubility of the film-forming resin (B) in the obtained organic solvent-type base paint The parameter value SP _B is shown in Table 1 below together with the organic solvent base paint (Y-1) obtained in Production Example 6.

Coating Film Formation Method Organic Solvent Type Intermediate Coating Paints (X-1) to (X-3) Obtained in Production Examples 3 to 5 and Organic Solvent Type Base Paint (Y-1) Obtained in Production Examples 6 to 16 Using (Y-11), test coated plates were respectively prepared as described below and subjected to evaluation tests.

(Preparation of test article)
"Electron GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., cationic electrodeposition paint) is electrodeposited onto a cold-rolled steel sheet that has been subjected to zinc phosphate chemical conversion treatment so that the cured film thickness is 20 μm. It was cured by heating for 30 minutes to obtain a test article.

Example 1
The organic solvent-type intermediate coating (X-1) obtained in Production Example 3 is rotationally atomized on the test object and the aluminum foil for measuring the solid content of the coated film described above. Using an electrostatic coating machine of the type, electrostatic coating was performed so that the cured film thickness was 20 μm to form an intermediate coating film. After leaving for 1 minute (setting), the solid content of the intermediate coating film was measured. The measurement results are shown in Table 2.

Next, the viscosity (V _Y2 ) of the organic solvent type base coating material (Y-1) obtained in Production Example 6 after application of the intermediate coating film and the organic solvent type base coating composition (Y) described above is 1 minute. On the tin plate for measurement, using a rotary atomizing type electrostatic coating machine, electrostatic coating was performed so that the cured film thickness was 12 μm, thereby forming a base coating film. After leaving for 1 minute (setting), the viscosity (V _Y2 ) after 1 minute of application of the organic solvent base coating composition (Y) was measured.

Further, “Magicron KINO-1210” (trade name, manufactured by Kansai Paint Co., Ltd., acrylic resin-based solvent-borne clear coating, hereinafter referred to as “clear coating (Z-1)”) may be cured on the base coating film. After electrostatic coating so that the film thickness becomes 30 μm and left for 7 minutes,
By heating at 140 ° C. for 30 minutes, the intermediate coating film, the base coating film and the clear coating film were simultaneously cured to prepare a test coating plate.

Examples 2-11, Comparative Examples 1-2
In Example 1, the organic solvent type intermediate coating material (X-1) obtained in Production Example 3 was changed to any one of the organic solvent type intermediate coating materials (X-1) to (X-3) shown in Table 2. Example 1 except that the organic solvent type base paint (Y-1) obtained in Production Example 6 is changed to any one of the organic solvent type base paints (Y-2) to (Y-11) shown in Table 2. A test coated plate was prepared in the same manner as described above.

The solubility parameter value SP _A of the film-forming resin (A) in the organic solvent-type intermediate coatings (X-1) to (X-3) obtained in Production Examples 3 to 5 is 9.91. Yes, since the solubility parameter value of “Swazole 1500” and “Swazole 1000” is 9.02, “Swazole 1500” and “Swazole 1000” correspond to the organic solvent (C).

Evaluation Test Each test coated plate obtained in Examples 1 to 11 and Comparative Examples 1 and 2 was evaluated by the following test method. The evaluation results are shown in Table 2.

(Test method)
Flip-flop property: About each test coating plate, FI value was measured using the multi-angle spectrocolorimeter "MA68II" by X-Rite. The FI value is an abbreviation for Flop Index, and the larger the value, the higher the flip-flop property and the better the appearance of the coating film.
Metallic unevenness: Each test coated plate was visually observed, and metallic unevenness was evaluated according to the following criteria.
A: Metallic unevenness is not recognized,
○: Metallic unevenness is hardly recognized,
Δ: Some metallic unevenness is observed,
X: Many metallic unevenness is recognized.

Claims (3)

Organic solvent type intermediate coating (X) containing film-forming resin (A), organic solvent-based base coating (Y) containing film-forming resin (B) and organic solvent (C) And the organic solvent-type clear coating (Z) is sequentially applied, and the formed intermediate coating, base coating and clear coating are simultaneously baked and cured, and the solubility of the film-forming resin (A) The absolute value of the difference (SP _A -SP _B ) between the parameter value SP _A and the solubility parameter value SP _B of the film-forming resin (B) is 0.2 or more and the dissolution of the film-forming resin (A) The absolute value of the difference (SP _A -SP _C ) between the solubility parameter value SP _A and the solubility parameter value SP _C of the organic solvent (C) is 1 or less, and the organic solvent in the organic solvent base paint (Y) Content of (C) is solid content 100 of film-forming resin (B) Method for forming a multilayer coating film, characterized in that a certain quantity portion in the range of 20-800 parts by weight based.   The method for forming a multilayer coating film according to claim 1, wherein the boiling point of the organic solvent (C) is in the range of 160 to 230 ° C. The viscosity (V _Y1 ) of the organic solvent-type base paint (Y) is in the range of 0.5 to 100 mPa · sec as measured under conditions of a shear rate of 230 sec ⁻¹ and a temperature of 20 ° C. The viscosity (V _Y2 ) after 1 minute application of the solvent-based base coating (Y) is measured under the conditions of a shear rate of 1.15 sec ⁻¹ and a temperature of 20 ° C., and is 10,000 to 50,000 mPa · sec. The method for forming a multilayer coating film according to claim 1 or 2, which is within the range.