JP2016112522A - Method for forming multi-layered coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a multi-layered coating film capable of forming a multi-layered coating film excellent in finishing property, chipping resistance and weatherproofness.SOLUTION: In a method for forming a multi-layered coating film, a process of applying aqueous intermediate coating material (X) on an object to be coated subjected to electrodeposition to form an intermediate coating film, a process of applying aqueous base coating material (Y) onto the formed intermediate coating film to form a base coated film, a process of applying clear coating material (Z) onto the formed base coating film to form a clear coated film and a process of heating and curing the coating films at one time are performed in the order. Therein, the aqueous intermediate coating material (X) contains a hydroxide group-containing resin (A1), an active methylene block polyisocyanate compound (B1) having a hydrophilic group and pigment(C1), and the aqueous base coating material (Y) contains a hydroxide group-containing resin (A2), an active methylene block polyisocyanate compound (B2) having a hydrophilic group and pigment (C2).SELECTED DRAWING: None

Description

  The present invention relates to a method for forming a multilayer coating film capable of forming a multilayer coating film having excellent finish, chipping resistance, and weather resistance.

  Conventionally, as a method of forming a coating film on an automobile body, an electrodeposition coating is applied to an object to be coated, followed by heat curing, followed by intermediate coating coating → heat curing → base coating coating → preheating (preheating) → clear coating. There are a wide variety of methods for forming multi-layer coatings using the 3-coat 2-bake method in which coating is sequentially applied and heat-cured, and the 2-coat 2-bake method in which intermediate coating is applied, heat-curing, top-coating is applied, and heat-curing is sequentially performed. Has been done.

  In general, the 3-coat 2-bake method is performed when a so-called metallic-colored coating film is formed using a base coat paint containing a luster pigment, and the 2-coat 2-bake method contains a color pigment. This is carried out when a so-called solid color film such as white or black is formed using a top coating.

  In recent years, from the viewpoint of energy saving, the heat curing process after painting of the intermediate coating is omitted, and the coating of the intermediate coating is applied → preheating (preheating) → base coating is applied → preheating (preheating) → clear coating is applied → heating A 3-coat 1-bake system in which curing is performed sequentially and a 2-coat 1-bake system in which intermediate coating is applied, preheated (preliminary heating), top coating is applied, and heat-cured are sequentially studied.

  Among these, from the viewpoint of suppressing environmental pollution due to volatilization of organic solvents, the above-mentioned 3-coat 1-bake method using a water-based paint as the intermediate coat paint and the base coat paint is particularly required.

  However, in the 3-coat 1-bake method using the water-based intermediate coating material and the water-based base coating material, the water resistance of the formed coating film decreases due to the use of a water-soluble or water-dispersible resin. The smoothness and sharpness of the formed coating film may be deteriorated due to a mixed layer between the aqueous base coat paint or between the aqueous intermediate coat and the aqueous top coat, which has been a problem.

  On the other hand, for example, Patent Document 1 uses a thermosetting aqueous intermediate coating (A), a thermosetting aqueous base coat (B) and a thermosetting clear coat coating (C), and the aqueous intermediate coating (A). And the aqueous base coat (B) by a wet-on-wet method, wherein the neutralizing value of the base resin of the aqueous intermediate coating (A) is 10 to 40 mg KOH / g, and the base of the aqueous base coat (B) It is described that when the neutralization value of the resin is made 10 to 20 larger than that of the water-based paint (A), the finished appearance such as gloss and sharpness does not deteriorate. However, the multilayer coating film obtained by the coating method sometimes has insufficient chipping resistance.

  In Patent Document 2, a coating composition containing an aqueous film-forming resin (A), a specific block polyisocyanate compound (B), and acrylic urethane resin composite particles (C) is used as an aqueous first colored paint (X). A first colored coating film is formed by coating, and an aqueous second colored coating (Y) is applied on the uncured first colored coating film to form a second colored coating film. A clear paint (Z) is applied onto the second colored paint film to form a clear paint film, and these paint films are simultaneously heated and cured to provide excellent smoothness, sharpness, adhesion and chipping resistance. Forming a coated film is described. However, further improvement in chipping resistance is required.

  In Patent Document 3, in a so-called intermediate coating-less coating in which a multilayer coating film composed of an aqueous base coating film and a clear coating film is formed on an electrodeposition coating film, interlayer adhesion and chipping resistance of the resulting coating film, etc. In order to improve the coating performance of the coating composition, an aqueous base coating composition comprising an acrylic resin emulsion (A); a polyether polyol (A); an active methylene type block polyisocyanate (U); a talc pigment (E); Is described. However, the method described in Patent Document 3 is inferior in smoothness, sharpness, and weather resistance of the resulting coating film, and has insufficient chipping resistance.

JP-A-8-290102 Japanese Patent Application Laid-Open No. 2014-080569 JP 2010-253386 A

  An object of the present invention is to provide a multilayer coating film forming method capable of solving the above-mentioned problems and forming a multilayer coating film having excellent finish, chipping resistance, and weather resistance.

  As a result of intensive studies to achieve the above object, the present inventors have used a specific water-based intermediate coating (X), water-based base coating (Y) and clear coating (Z). The inventors have found that a multilayer coating film excellent in chipping property and weather resistance can be formed, and have completed the present invention.

That is, the present invention provides an electrodeposition-coated article with the following steps (1) to (4),
Step (1): A step of coating the water-based intermediate coating (X) to form an intermediate coating film,
Step (2): A step of coating the water-based base coating (Y) on the intermediate coating film formed in the step (1) to form a base coating film,
Step (3): A step of applying a clear paint (Z) on the base coating film formed in the step (2) to form a clear coating film, and a step (4): the steps (1) to ( A step of heat-curing the intermediate coating film, base coating film and clear coating film formed in 3) at a time,
A multilayer coating film forming method for sequentially performing,
The aqueous intermediate coating (X) contains a hydroxyl group-containing resin (A1), an active methylene block polyisocyanate compound (B1) having a hydrophilic group, and a pigment (C1),
The aqueous base paint (Y) contains a hydroxyl group-containing resin (A2), an active methylene block polyisocyanate compound (B2) and a pigment (C2) having a hydrophilic group, and the clear paint (Z) contains a hydroxyl group-containing acrylic resin (D And a polyisocyanate compound (E).

  According to the method for forming a multilayer coating film of the present invention, it is excellent in finish, chipping resistance, and weather resistance by using a specific aqueous intermediate coating (X), aqueous base coating (Y), and clear coating (Z). A multilayer coating film can be formed.

  The coated object to which the water-based intermediate coating (X) can be applied according to the present invention is, for example, electrodeposition-coated on a metal material such as an outer plate of an automobile body such as a passenger car, a truck, a motorcycle, or a bus, or an automobile part. It is.

  The metal material is not particularly limited. For example, iron, aluminum, brass, copper, tinplate, stainless steel, galvanized steel, alloyed zinc (Zn-Al, Zn-Ni, Zn-Fe, etc.) plating is used. Steel etc. can be mentioned.

  The metal surface of the metal material or the vehicle body formed from the metal material may be subjected to surface treatment such as phosphate treatment, chromate treatment, or complex oxide treatment.

  The electrodeposition coating is performed using a known electrodeposition paint. Furthermore, a cured electrodeposition coating film is formed by heat curing. As the electrodeposition paint, a cationic electrodeposition paint can be preferably used. Although it does not specifically limit as this cationic electrodeposition coating material, Generally, it is preferable to use the electrodeposition coating material containing the epoxy resin (cationic epoxy resin) modified with amine and block polyisocyanate. By using the electrodeposition paint, a multilayer coating film having excellent rust prevention properties can be formed. The thickness of the cured electrodeposition coating film is usually 5 to 40 μm, particularly 7 to 30 μm, more preferably 10 to 25 μm.

Process (1)
In this step, the intermediate coating film is formed by applying the water-based intermediate coating (X) onto the electrodeposited object.

Waterborne intermediate coating (X)
The aqueous intermediate coating (X) contains the hydroxyl group-containing resin (A1) and the active methylene block polyisocyanate compound (B1) having a hydrophilic group as essential thermosetting resin components, and further contains a pigment (C1). If necessary, other resin components, organic solvents, thickeners, anti-settling agents, curing catalysts, ultraviolet absorbers, light stabilizers, surface conditioners, antifoaming agents, plasticizers, etc. are blended. A water-based liquid paint can be used. In this specification, the water-based paint is a paint in which the main component of the solvent is water.

  As said hydroxyl-containing resin (A1), the acrylic resin, polyester resin, urethane resin, vinyl resin, etc. which have a hydroxyl group can be used.

  Especially, it is suitable to use a hydroxyl-containing acrylic resin (I-1) and / or a hydroxyl-containing polyester resin (I-2) as a hydroxyl-containing resin (A1).

  The hydroxyl group-containing acrylic resin (I-1) is known per se for at least one unsaturated monomer component including, for example, a hydroxyl group-containing unsaturated monomer and optionally another unsaturated monomer copolymerizable with the monomer. It can be produced by (co) polymerization by a method such as a solution polymerization method in an organic solvent or an emulsion polymerization method in water.

  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.

  Other unsaturated monomers copolymerizable with the hydroxyl group-containing unsaturated monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, 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 , Lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate , Alkyl or cycloalkyl (meth) acrylates such as t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate; unsaturated monomers having an isobornyl group such as isobornyl (meth) acrylate; adamantyl (meta ) Unsaturated monomer having an adamantyl group such as acrylate; aromatic ring-containing unsaturated monomer such as styrene, α-methylstyrene, vinyltoluene, phenyl (meth) acrylate; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2- Unsaturated monomers having an alkoxysilyl group such as methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane; Perfluoroalkyl (meth) acrylates such as tilethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; Unsaturated monomers having fluorinated alkyl groups such as fluoroolefins; Nonpolymers having photopolymerizable functional groups such as maleimide groups Saturated monomers; vinyl compounds such as N-vinyl pyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate and vinyl acetate; carboxyl group-containing unsaturated monomers such as (meth) acrylic acid, maleic acid, crotonic acid and β-carboxyethyl acrylate ; (Meth) acrylonitrile, (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, adducts of glycidyl (meth) acrylate and amines, etc. Nitrogen unsaturated monomer: glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexyl Epoxy group-containing unsaturated monomers such as propyl (meth) acrylate and allyl glycidyl ether; (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid , Unsaturated monomers having a sulfonic acid group such as sodium styrenesulfonate, sulfoethyl methacrylate, and sodium salts and ammonium salts thereof; 2-acryloyloxyethyl acid phosphate; Unsaturated monomers having a phosphate group such as methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate; 2-hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone 2-hydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4 UV rays such as-(3-acryloyloxy-2-hydroxypropoxy) benzophenone and 2- (2'-hydroxy-5'-methacryloyloxyethylphenyl) -2H-benzotriazole Unsaturated monomer having an astringent 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.

  In the present specification, “(meth) acrylate” means “acrylate or methacrylate”. “(Meth) acrylic acid” means “acrylic acid or methacrylic acid”. “(Meth) acryloyl” means “acryloyl or methacryloyl”. “(Meth) acrylamide” means “acrylamide or methacrylamide”.

  The hydroxyl group-containing acrylic resin (I-1) is generally 1 to 200 mgKOH / g, preferably 2 to 100 mgKOH / g, more preferably 3 to 80 mgKOH / g, from the viewpoints of storage stability and water resistance of the resulting coating film. And an acid value in the range of 1 to 200 mg KOH / g, preferably 2 to 150 mg KOH / g, more preferably 5 to 100 mg KOH / g. The hydroxyl group-containing acrylic resin (I-1) is generally in the range of 1,000 to 5,000,000, preferably 2,000 to 3,000,000, more preferably 3,000 to 1,000,000. Can have a weight average molecular weight of

  In this specification, the number average molecular weight and the weight average molecular weight are the retention time (retention capacity) measured using a gel permeation chromatograph (GPC), the retention time of standard polystyrene with a known molecular weight measured under the same conditions ( It is a value obtained by converting to the molecular weight of polystyrene by (retention capacity). Specifically, “HLC8120GPC” (trade name, manufactured by Tosoh Corporation) is used as a gel permeation chromatograph, and “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL” are used as columns. ”And“ TSKgel G-2000HXL ”(trade names, all manufactured by Tosoh Corporation), a differential refractometer is used as a detector, mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: It can be measured under the condition of 1 mL / min.

  The compounding amount of the hydroxyl group-containing acrylic resin (I-1) is usually 0 to 90% by mass, preferably 5 to 60% by mass, more preferably 10 based on the total amount of resin solids in the aqueous intermediate coating (X). It can be in the range of ˜50 mass%.

  The hydroxyl group-containing polyester resin (I-2) 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 manufactured by setting the equivalent ratio (COOH / OH) of the carboxyl group in the component and the hydroxyl group in the polyhydric alcohol component to less than 1 and carrying out the esterification reaction in a state where there are more hydroxyl groups than carboxyl groups.

  The polybasic acid component is a compound having at least two carboxyl groups in one molecule. For example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, tetrahydro Polybasic acids such as phthalic 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, etc. These may be used alone or in combination of two or more.

  The polyhydric alcohol component is a compound having at least two hydroxyl groups in one molecule, such as ethylene glycol, 1,2-propylene glycol, 1,2-butylene glycol. Α-glycol such as 2,3-butylene glycol, 1,2-hexanediol, 1,2-dihydroxycyclohexane, 3-ethoxypropane-1,2-diol, 3-phenoxypropane-1,2-diol -Neolyl glycol, 2-methyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propyl Pandiol, 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 hydroxypivalin) Acid and neopentyl glycol esterified product), 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, glycerol, diglycerol, triglycerol, pentaerythritol, dipentaerythritol, sorbitol, mannitol, trimethylolethane, trimethylolpropane, ditrimethylolpropane, Examples thereof include tris (2-hydroxyethyl) isocyanurate, 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 (I-2) may be modified with a fatty acid, a monoepoxy compound, or the like as 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 (I-2) is generally 10 to 300 mgKOH / g, preferably 25 to 250 mgKOH / g, more preferably 50 to 200 mgKOH / g, and generally 1 to 200 mgKOH / g, preferably Can have an acid value in the range of 5-100 mg KOH / g, more preferably 10-60 mg KOH / g. The hydroxyl group-containing polyester resin (I-2) generally has a weight average molecular weight in the range of 500 to 50,000, preferably 1,000 to 40,000, and more preferably 1,500 to 30,000. Can do.

  The compounding amount of the hydroxyl group-containing polyester resin (I-2) is usually 0 to 90% by mass, preferably 10 to 60% by mass, more preferably, based on the total amount of resin component solids in the aqueous intermediate coating (X). It can be in the range of 15-50 mass%.

  Further, the hydroxyl group-containing acrylic resin (I-1) and the hydroxyl group-containing polyester resin (I-2) are part or all of the carboxyl groups that may be contained in them in order to facilitate water-solubilization or water-dispersion. Is preferably neutralized with a basic compound. Examples of basic compounds include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide; ammonia; ethylamine, propylamine, butylamine, Primary monoamines such as benzylamine, monoethanolamine, neopentanolamine, 2-aminopropanol, 2-amino-2-methyl-1-propanol, 3-aminopropanol; diethylamine, diethanolamine, di-n-propanolamine , Secondary monoamines such as di-iso-propanolamine, N-methylethanolamine, N-ethylethanolamine; dimethylethanolamine, trimethylamine, triethylamine, triisopropylamine, methyldiethanol Triethanolamine, 2- (dimethylamino) tertiary monoamines such as ethanol; diethylenetriamine, hydroxyethylaminoethylamine, ethylamino ethylamine, may be mentioned polyamines such as methylamino propylamine. The amount of the basic compound used is usually 0.1 to 1.5 equivalents, preferably 0.2 to 1.2 equivalents relative to the acid groups of the hydroxyl group-containing resin (A1).

  As the urethane resin, in addition to a normal urethane resin, a polyisocyanate compound is extended to a part of the hydroxyl group in the hydroxyl group-containing acrylic resin (I-1) and the hydroxyl group-containing polyester resin (I-2) by a urethanization reaction. Examples thereof include a urethane resin having a high molecular weight.

  Examples of the active methylene block polyisocyanate compound (B1) having a hydrophilic group include a blocked polyisocyanate compound obtained by reacting an active methylene compound with an isocyanate group in a polyisocyanate compound into which a hydrophilic group has been introduced. Particularly in the present invention, as the active methylene block polyisocyanate compound (B1) having a hydrophilic group, a hydrophilic group is introduced by reacting a part of the isocyanate group in the polyisocyanate compound (b1) with an active hydrogen-containing compound having a hydrophilic group. Furthermore, the block polyisocyanate compound (b3) obtained by reacting the active methylene compound (b2) with the isocyanate group in the polyisocyanate compound (b1) can be preferably used. Those obtained by reacting a secondary alcohol (b4) having 6 or more carbon atoms can be suitably used.

  The polyisocyanate compound (b1) is a compound having at least two isocyanate groups in one molecule, and examples thereof include aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, And polyisocyanate derivatives.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3. -Aliphatic diisocyanates such as butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate (common name: lysine diisocyanate); 2 , 6-Diisocyanatohexanoic acid 2-isocyanatoethyl, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,6 1-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyl Examples thereof include aliphatic triisocyanates such as octane.

  Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name) : Isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), 2-methyl-1,3-cyclohexylene diisocyanate, 1,3- or 1,4-bis (isocyanato) Methyl) cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture thereof, methylenebis (4,1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), alicyclic diisocyanate such as norbornane diisocyanate 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2 .1) Heptane, 2- (3-isocyanatopropyl) -2,6-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 3- (3-isocyanatopropyl) -2,5- Di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) ) Heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanate) Toethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) -heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3 An alicyclic triisocyanate such as -isocyanatopropyl) -bicyclo (2.2.1) heptane can be used.

  Examples of the araliphatic polyisocyanate include methylene bis (4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω′-diisocyanato- Aromatic aliphatic diisocyanates such as 1,4-diethylbenzene, 1,3- or 1,4-bis (1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or mixtures thereof; 1,3 And araliphatic triisocyanates such as 5-triisocyanatomethylbenzene.

  Examples of the aromatic polyisocyanate include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4-tolylene diisocyanate (common name: 2,4- TDI), 2,6-tolylene diisocyanate (common name: 2,6-TDI) or mixtures thereof, aromatic diisocyanates such as 4,4′-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate; triphenylmethane-4 , 4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene and the like; 4,4′-diphenylmethane-2,2 ′ , 5,5'-tetraisocyanate and other aromatics Mention may be made of the tiger isocyanate.

  Examples of the polyisocyanate derivatives include, for example, the above-mentioned polyisocyanate dimers, trimers, biurets, allophanates, uretdiones, uretimines, isocyanurates, oxadiazine triones, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI). And Crude TDI.

  The above polyisocyanates and derivatives thereof may be used alone or in combination of two or more. Of these polyisocyanates, the polyisocyanate compound (b1) is less likely to be yellowed during heating of the resulting block polyisocyanate compound (B1), so that aliphatic diisocyanates, alicyclic diisocyanates, and these The derivatives of are preferred. Of these, aliphatic diisocyanates and derivatives thereof are more preferable from the viewpoint of improving the flexibility of the formed coating film.

  Examples of the active hydrogen-containing compound having a hydrophilic group include an active hydrogen-containing compound having a nonionic hydrophilic group, an active hydrogen-containing compound having an anionic hydrophilic group, and an active hydrogen-containing compound having a cationic hydrophilic group. These can be used alone or in combination of two or more. Especially, since the reaction which blocks the isocyanate group in the said polyisocyanate compound (b1) by the said active methylene compound (b2) is hard to be inhibited, it is preferable to use the active hydrogen containing compound which has a nonionic hydrophilic group. .

  As the active hydrogen-containing compound having a nonionic hydrophilic group, for example, an active hydrogen-containing compound having a polyoxyalkylene group can be suitably used. As said polyoxyalkylene group, a polyoxyethylene group, a polyoxypropylene group, etc. are mentioned, for example, These can be used individually or in combination of 2 or more types. Especially, the active hydrogen containing compound which has a polyoxyethylene group is preferable from a viewpoint of the storage stability of this coating material.

  The active hydrogen-containing compound having a polyoxyethylene group is 3 or more, preferably 5 to 100, more preferably 8 from the viewpoints of storage stability of the paint and adhesion of the formed multilayer coating film. It is preferred to have ~ 45 consecutive oxyethylene groups.

  Moreover, the active hydrogen containing compound which has the said polyoxyethylene group may contain oxyalkylene groups other than an oxyethylene group other than the continuous oxyethylene group. Examples of the oxyalkylene group other than the oxyethylene group include an oxypropylene group, an oxybutylene group, and an oxystyrene group. In the active hydrogen-containing compound having the polyoxyethylene group, the molar ratio of the oxyethylene group in the oxyalkylene group is preferably in the range of 20 to 100 mol% from the viewpoint of the storage stability of the paint, It is preferably within the range of 50 to 100 mol%. When the molar ratio of the oxyethylene group in the oxyalkylene group is less than 20 mol%, imparting hydrophilicity may not be sufficient, and the storage stability of the paint may be reduced.

  In addition, the active hydrogen-containing compound having a nonionic hydrophilic group has a number average molecular weight in the range of 200 to 2,000 from the viewpoint of storage stability of the paint and water resistance of the formed multilayer coating film. Preferably there is. As a minimum of a number average molecular weight, 300 is more preferable from a viewpoint of the storage stability of this coating material, and 400 is still more preferable. As an upper limit, 1,500 is more preferable from the viewpoint of water resistance of the multilayer coating film to be formed, and 1,200 is more preferable.

  Examples of the active hydrogen-containing compound having a nonionic hydrophilic group include polyethylene glycol monoalkyl ethers (also known as ω-alkoxypolyoxyethylene) such as polyethylene glycol monomethyl ether and polyethylene glycol monoethyl ether, polypropylene glycol monomethyl ether, and Polypropylene glycol monoalkyl ethers such as polypropylene glycol monoethyl ether (also known as ω-alkoxypolyoxypropylene), ω-alkoxypolyoxyethylene (oxypropylene), ω-alkoxypolyoxyethylene (oxypropylene), etc. Oxyethylene (oxypropylene), polyethylene glycol (propylene glycol) monomethyl ether, polyethylene glycol Poly (ethylene glycol) (propylene glycol) monoalkyl ether such as ru (propylene glycol) monoethyl ether, polyethylene glycol, polypropylene glycol, polyethylene glycol (propylene glycol), α- (aminoalkyl) -ω-alkoxypolyoxyethylene, α- ( Aminoalkyl) -ω-alkoxypolyoxypropylene, α- (aminoalkyl) -ω-alkoxypolyoxyethylene (oxypropylene) and the like can be mentioned, and these can be used alone or in combination of two or more. Of these, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether and polyethylene glycol are preferable, and polyethylene glycol monomethyl ether is more preferable.

  Moreover, as a commercial item of the said polyethyleneglycol monomethyl ether, for example, "UNIOX M-400", "UNIOX M-550", "UNIOX M-1000", "UNIOX M-" made by NOF CORPORATION 2000 "and the like. Examples of the commercially available polyethylene glycol include “PEG # 200”, “PEG # 300”, “PEG # 400”, “PEG # 600”, “PEG # 1000”, “ PEG # 1500 "," PEG # 1540 "," PEG # 2000 "and the like.

  The reaction between a part of the isocyanate groups in the polyisocyanate compound (b1) and the active hydrogen-containing compound having the hydrophilic group can be performed at 0 to 150 ° C., and a solvent may be used. In this case, the solvent is preferably an aprotic solvent, and particularly preferably an ester, ether, N-alkylamide, ketone or the like. Moreover, the active hydrogen containing compound which did not react with the isocyanate group in a polyisocyanate compound (b1) can be removed after completion | finish of reaction. The reaction ratio between the polyisocyanate compound (b1) and the active hydrogen-containing compound having a hydrophilic group is determined in view of the storage stability and curability of the paint, and the smoothness, sharpness and adhesion of the multilayer coating film to be formed. To 1 mol of the isocyanate group in the polyisocyanate compound (b1), the number of moles of active hydrogen in the active hydrogen-containing compound is in the range of 0.03 to 0.6 mol, and further 0.04 to 0.00. It is preferably within the range of 4 moles.

  Examples of the active methylene compound (b2) include dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, di-sec-butyl malonate, and malonic acid. Di-t-butyl, di-n-pentyl malonate, di-n-hexyl malonate, di (2-ethylhexyl) malonate, methyl isopropyl malonate, ethyl isopropyl malonate, methyl n-butyl malonate, ethyl n-malonate Malonic acid diesters such as butyl, methyl isobutyl malonate, ethyl isobutyl malonate, methyl sec-butyl malonate, ethyl sec-butyl malonate, diphenyl malonate and dibenzyl malonate, methyl acetoacetate, ethyl acetoacetate, n-acetoacetate -Propyl, isopropyl acetate , N-butyl acetoacetate, isobutyl acetoacetate, sec-butyl acetoacetate, t-butyl acetoacetate, n-pentyl acetoacetate, n-hexyl acetoacetate, 2-ethylhexyl acetoacetate, phenyl acetoacetate and benzyl acetoacetate Acetoacetic acid ester, methyl isobutyryl acetate, ethyl isobutyryl acetate, n-propyl isobutyryl acetate, isopropyl isobutyryl acetate, n-butyl isobutyryl acetate, isobutyl acyl acetate, sec-butyl isobutyryl acetate, t-butyl isobutyryl acetate, n-pentyl isobutyryl acetate, Examples include isobutyryl acetate such as n-hexyl isobutyryl acetate, 2-ethylhexyl isobutyryl acetate, phenyl isobutyryl acetate and benzyl isobutyryl acetate. It may be used in combination of two or more.

  Among these, from the viewpoint of smoothness and sharpness of the formed multilayer coating film, the active methylene compound (b2) is dimethyl malonate, diethyl malonate, diisopropyl malonate, methyl acetoacetate, ethyl acetoacetate, isobutyryl. It is preferably at least one compound selected from the group consisting of methyl acetate and ethyl isobutyryl acetate, and more preferably at least one compound selected from the group consisting of diisopropyl malonate, methyl isobutyryl acetate and ethyl isobutyryl acetate. preferable. Among these, diisopropyl malonate is more preferable from the viewpoint of the smoothness and sharpness of the formed multilayer coating film, the reactivity of the resulting block polyisocyanate compound (B1), and the storage stability of the paint. .

  In the blocking reaction of the isocyanate group with the active methylene compound (b2), a reaction catalyst can be used as necessary. Examples of the reaction catalyst include metal hydroxide, metal alkoxide, metal carboxylate, metal acetyl acetylate, hydroxide of onium salt, onium carboxylate, metal salt of active methylene compound, onium salt of active methylene compound, aminosilanes Basic compounds such as amines and phosphines are preferred. As the onium salt, ammonium salts, phosphonium salts, and sulfonium salts are suitable. The amount of the reaction catalyst used is usually preferably in the range of 10 to 10,000 ppm, based on the total solid mass of the polyisocyanate compound (b1) and the active methylene compound (b2). More preferably, it is in the range of 000 ppm.

  The blocking reaction of the isocyanate group with the active methylene compound (b2) can be performed at 0 to 150 ° C., and a solvent may be used. In this case, the solvent is preferably an aprotic solvent, and particularly preferably an ester, ether, N-alkylamide, ketone or the like. If the reaction proceeds as intended, an acid component may be added to neutralize the basic compound as a catalyst and stop the reaction.

  In the blocking reaction of the isocyanate group with the active methylene compound (b2), the amount of the active methylene compound (b2) used is not particularly limited, but is 0.1% with respect to 1 mol of the isocyanate group in the polyisocyanate compound (b1). It is suitable to use -3 mol, preferably 0.2-2 mol. Further, the active methylene compound that has not reacted with the isocyanate group in the polyisocyanate compound (b1) can be removed after the blocking reaction is completed.

  In addition to the active methylene compound (b2), for example, blocking agents such as alcohols, phenols, oximes, amines, acid amides, imidazoles, pyridines, and mercaptans may be used in combination.

  As described above, the activated methylene compound (b2) is reacted with the isocyanate group in the polyisocyanate compound (b1) to obtain the block polyisocyanate compound (b3). The block polyisocyanate compound (b3) can be further reacted with a secondary alcohol (b4) having 6 or more carbon atoms.

  Examples of the secondary alcohol (b4) having 6 or more carbon atoms include 4-methyl-2-pentanol, 5-methyl-2-hexanol, 6-methyl-2-heptanol, and 7-methyl-2-octanol. These may be used alone or in combination of two or more.

  The reaction of the block polyisocyanate compound (b3) and the secondary alcohol (b4) can be carried out by removing a part or all of the alcohol derived from the active methylene in the block polyisocyanate compound (b3) by, for example, heating or reducing pressure. A method obtained by distilling off and promoting the reaction is preferred.

  As the above production method, specifically, the pressure is reduced as necessary at a temperature of 20 to 150 ° C., preferably 75 to 95 ° C., and 5 minutes to 20 hours, preferably 10 minutes to 10 hours. It is appropriate to remove some or all of the alcohol.

  The blending ratio of the block polyisocyanate compound (b3) and the secondary alcohol (b4) is such that the secondary alcohol (b4) is in the range of 5 to 500 parts by mass based on 100 parts by mass of the solid content of the block polyisocyanate compound (b3). It is preferably within the range, and more preferably within the range of 10 to 200 parts by mass.

  Further, in the reaction of the block polyisocyanate compound (b3) and the secondary alcohol (b4), in order to adjust the molecular weight of the block polyisocyanate compound (B1), the block polyisocyanate compound (b3) and the secondary alcohol ( The removal operation may be performed after adding a polyfunctional hydroxyl group-containing compound to b4).

  The number average molecular weight of the block polyisocyanate compound (B1) obtained as described above is compatible with other paint components, smoothness of the formed multilayer coating film, sharpness, water resistance and chipping resistance, etc. From the viewpoint, it is preferably in the range of 600 to 30,000, more preferably in the range of 900 to 10,000.

  The blending ratio of the hydroxyl group-containing resin (A1) and the active methylene block polyisocyanate compound (B1) having a hydrophilic group is generally 40 to 90% by mass, particularly 50 to 80% by mass, based on the total solid content of both. The latter is generally suitable within the range of 60 to 10% by mass, particularly 50 to 20% by mass.

The aqueous intermediate coating material (X) can further contain a crosslinking agent other than the block polyisocyanate compound (B1) as necessary. As the crosslinking agent, from the viewpoint of water resistance of the resulting coating film, a melamine resin that can react with a hydroxyl group, a block polyisocyanate compound other than the block polyisocyanate compound (B1), and a carbodiimide group-containing compound that can react with a carboxyl group are preferable. Melamine resin is particularly preferred.
The aqueous intermediate coating material (X) further contains a pigment (C1). Examples of the pigment (C1) include coloring pigments, extender pigments, and luster pigments, which can be used alone or in combination of two or more.

  Examples of the color pigment include titanium oxide, zinc oxide, carbon black, lead sulfate, calcium lead acid, zinc phosphate, aluminum phosphate, zinc molybdate, calcium molybdate, bitumen, ultramarine blue, cobalt blue, copper phthalocyanine blue, Indanthrone blue, yellow lead, yellow iron oxide, transparent brown (yellow), bismuth vanadate, titanium yellow, zinc yellow (zinc yellow), monoazo yellow, isoindolinone yellow, metal complex azo yellow, quinophthalone yellow, benzimidazolone Yellow, red rose, red lead, monoazo red, quinacridone red, azo lake (Mn salt), quinacridone magenta, ansanthrone orange, dianthraquinonyl red, perylene maroon, quinacridone magenta, perylene red, diketopyrrolo Examples include roll chrome vermilion, chlorinated phthalocyanine green, brominated phthalocyanine green, pyrazolone orange, benzimidazolone orange, dioxazine violet, and perylene violet. Among them, titanium oxide, carbon black, etc. can be preferably used. it can. Examples of extender pigments include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white. Among these, barium sulfate and / or talc are preferably used.

  In particular, the aqueous intermediate coating material (X) preferably contains chlorine-based titanium oxide and yellow iron oxide as the pigment (C1) from the viewpoint of the concealability obtained and the weather resistance of the multilayer coating film.

  The chlorinated titanium oxide is an industrially produced titanium oxide pigment, which is produced in the following steps. As a raw material, natural titanium or synthetic titanium is used. Coke is added to the raw material and reacted with chlorine gas at a high temperature to produce crude TiCl4. The produced crude TiCl 4 is rectified at a temperature of 136 ° C. or higher after removing solid impurities. The purified high purity TiCl 4 is heated to about 1000 ° C. and reacted with oxygen to produce titanium oxide particles. The obtained titanium oxide particles are pulverized, sized, surface-treated, washed, dried, and finish-pulverized to produce a titanium oxide pigment that can be used as a coating material. The chlorine-based titanium oxide used in the present invention may be surface-treated with an oxide or hydroxide such as silica, alumina, zirconia, or the like, or an organic typified by polydimethylsiloxane from the viewpoint of improving the weather resistance. It may be surface-treated with a silicon compound or a higher fatty acid typified by stearic acid or an organic titanium compound typified by isopropyl triisostearoyl titanate.

  As said chlorine method titanium oxide, it is preferable to use the thing within the range of the average particle diameter of 200 nm-700 nm from the point of the coloring power and finish of the coating film obtained by coating, More preferably, average particle diameter of 300 nm- The thing in the range of 500 nm can be used. Here, the average particle diameter of the titanium oxide pigment is an average particle diameter measured by observation with an electron microscope. Since the titanium oxide pigment is substantially spherical, the diameter is measured. Specifically, 100 particles are selected from the transmission electron microscope image, and the average particle diameter is obtained using NIH Image 1.63 free software manufactured by NIH (National Institute of Health).

  The content of the chlorine-based titanium oxide pigment is within the range of 40 to 150% by mass based on the total amount of solid resin components in the water-based intermediate coating (X) from the viewpoint of hiding power and finish for the object to be coated. Further, the range of 50 to 120% by mass is preferable.

  The yellow iron oxide pigment is a yellow pigment made of iron oxyhydroxide represented by α-FeO (OH) or α-Fe 2 O 2 · H 2 O, and a natural one and a synthetic one are marketed.

  Natural yellow iron oxide has been used as a colorant since prehistoric times, and is classified as ocher, amber, siena, etc., and naturally produced in various parts of the world such as India, France, Italy, South Africa, the United States and China It is.

  The yellow iron oxide by synthesis can be obtained, for example, as follows. A precipitate of ferrous hydroxide obtained by adding alkali to ferrous sulfate aqueous solution is oxidized with air to form α-Fe 2 O 2 .H 2 O crystal nuclei. Further, when iron scrap is added to an aqueous ferrous sulfate solution and air is blown in for heating to cause hydrolysis, α-Fe 2 O 2 .H 2 O crystal nuclei grow and bright yellow iron oxide can be obtained.

  Yellow iron oxide belongs to the goethite crystal system (orthorhombic) and has a needle shape. In the water-based intermediate coating (X), needle-like pigments having a length / width of about 6/1 to 10/1 are used from the viewpoint of the color tone of the coating film obtained by painting. Moreover, the dimension of a length direction can use a 0.6-1.2 micrometer thing. Here, the numerical value indicating the shape of the yellow iron oxide pigment is a numerical value measured by observation with an electron microscope.

  The content of the yellow iron oxide pigment is 0.01 to 1 on the basis of the total solid content of the resin component in the water-based intermediate coating (X) from the viewpoint of controlling the color tone and ultraviolet transmission of the coating film obtained by coating. It is preferably in the range of mass%, more preferably in the range of 0.05 to 0.5 parts by mass.

  The aqueous intermediate coating material (X) can contain carbon black having a primary average particle size of 15 to 80 nm as a pigment (C1) for the purpose of controlling the brightness and hue of the coating film.

  In this specification, the primary average particle diameter of carbon black is an average particle diameter measured by observation with an electron microscope. Since carbon black forms a structure, the primary particle diameter of carbon black means a numerical value obtained by measuring the diameter of a spherical portion in the structure. Specifically, the primary average particle diameter of carbon black is selected from 100 spherical portions in the structure from the transmission electron microscope image, and free software: NIH Image 1.63 manufactured by NIH (National Institute of Health) is used. And calculating the average particle size.

  When the carbon black is used, the content thereof is in the range of 0.01 to 10% by mass, and further 0.01 to 8% by mass, based on the total solid content of the resin component in the aqueous intermediate coating (X). Within the range of is preferable.

  The aqueous intermediate coating material (X) preferably contains a scaly aluminum pigment, particularly a non-leafing scaly aluminum pigment, from the point of concealing the object to be coated as the pigment (C1).

  The scale-like aluminum pigment preferably has an average particle size in the range of 5 to 30 μm from the viewpoint of the finish of the coated film and the lightness of the hiding power, more preferably the particle size. The diameter is in the range of 5 to 20 μm, particularly preferably in the range of 6 to 12 μm. It is preferable to use a thickness in the range of 0.05 to 0.5 μm. The particle size and thickness referred to here are numerical values obtained by observing the scaly aluminum pigment with an optical microscope or an electron microscope.

  Moreover, when using a scale-like aluminum pigment, the content is 0.1 on the basis of the total amount of resin component solids in the water-based intermediate coating (X) in terms of the finish of the coating film obtained by coating. It is preferably within the range of ˜25% by mass, more preferably within the range of 0.3 to 20% by mass.

  The water-based intermediate coating (X) is such that the average value of the light transmittance at a wavelength of 420 nm to 480 nm of the coating film obtained by coating so as to be 25 μm as a cured coating film is 0.1 to 1.0%. In addition, it is desirable to adjust the amount and composition of the pigment.

  The water-based intermediate coating (X) can be applied onto the above-mentioned article by a method known per se, for example, air spray, airless spray, rotary atomizing coater or the like. Of these, methods such as air spray coating and rotary atomization coating are preferred. Electrostatic application may be performed during coating. The coating film thickness is usually 10 to 70 μm, preferably 10 to 50 μm, and more preferably 15 to 35 μm as a cured film thickness.

  Before applying the aqueous base paint (Y), the intermediate coating film formed by the aqueous intermediate paint (X) in the step (1) has a solid content of 70 to 100% by mass, particularly 75 to 75%. It is preferably adjusted to 99 mass%, more particularly 80 to 98 mass%.

  The solid content can be adjusted by means such as preheating (preheating) or air blowing. The preheating temperature can be room temperature to about 100 ° C., preferably about 40 to about 90 ° C., more preferably about 60 to about 80 ° C., and the preheating time is 30 seconds to 15 minutes, preferably 1 to 10 Minutes, more preferably about 3 to 5 minutes.

Step (2)
Next, the aqueous base coating material (Y) is applied onto the intermediate coating film formed by the aqueous intermediate coating material (X) in the step (1).

Water-based paint (Y)
The aqueous base paint (Y) contains a hydroxyl group-containing resin (A2) and an active methylene block polyisocyanate compound (B2) having a hydrophilic group as essential thermosetting resin components, and further contains a pigment (C2). If necessary, other resin components, organic solvents, thickeners, anti-settling agents, curing catalysts, ultraviolet absorbers, light stabilizers, surface conditioners, antifoaming agents, plasticizers, etc. Liquid paint can be used.

  As said hydroxyl-containing resin (A2), the acrylic resin, polyester resin, urethane resin, vinyl resin, alkyd resin, etc. which have a hydroxyl group can be used. Especially, it is suitable to use what was demonstrated by the said hydroxyl-containing acrylic resin (I-1) and / or hydroxyl-containing polyester resin (I-2) as a hydroxyl-containing resin (A2).

  As the active methylene block polyisocyanate compound (B2) having a hydrophilic group, it is preferable to use those described for the active methylene block polyisocyanate compound (B1) having a hydrophilic group.

  The ratio of the hydroxyl group-containing resin (A2) and the active methylene block polyisocyanate compound (B2) having a hydrophilic group is generally 40 to 90% by mass, particularly 50 to 80% by mass based on the total solid content of both. The latter is generally suitable in the range of 60 to 10% by weight, particularly 50 to 20% by weight.

  As the pigment (C2), the color pigments and extender pigments exemplified in the description of the water-based intermediate coating (X) can be used, and further, by using a bright pigment as at least one pigment component. Further, a metallic or pearly coating film having a dense feeling can be formed.

  Examples of the bright pigment include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide and iron oxide, and titanium oxide and iron oxide. Mica, glass flakes, hologram pigments and the like. Among them, it is preferable to use aluminum, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, or mica coated with titanium oxide or iron oxide. The above luster pigments can be used alone or in combination of two or more.

  The glitter pigment is preferably scaly. Further, as the glitter pigment, those having a longitudinal dimension of 1 to 100 μm, particularly 5 to 40 μm, and a thickness of 0.0001 to 5 μm, particularly 0.001 to 2 μm are suitable.

  When the water-based base paint (Y) contains the above-mentioned glittering pigment, the blending amount of the glittering pigment is 1 to 30% by mass, especially 3 based on the total amount of resin component solids in the aqueous base paint (Y). It is preferable to be within a range of ˜20% by mass.

  The aqueous base paint (Y) preferably contains barium sulfate from the viewpoint of the finish of the resulting multilayer coating film. The barium sulfate usually has an average primary particle diameter in the range of 0.001 to 0.8 μm, particularly 0.01 to 0.08 μm.

  When the aqueous base paint (Y) contains barium sulfate, the blending amount of the barium sulfate is 2 to 30% by mass, particularly 5 to 20% by mass, based on the total amount of resin component solids in the aqueous base paint (Y). % Is preferable.

  The aqueous base paint (Y) can be applied onto the above-mentioned article by a method known per se, for example, air spray, airless spray, rotary atomizing coater or the like. Of these, methods such as air spray coating and rotary atomization coating are preferred. Electrostatic application may be performed during coating. The coating film thickness is usually 10 to 70 μm, preferably 10 to 50 μm, and more preferably 15 to 35 μm as a cured film thickness.

  Before applying the clear paint (Z), the base coating film formed with the aqueous base paint (Y) in the step (2) has a solid content of 70 to 100% by mass, particularly 75 to 99% by mass. In particular, it is preferably adjusted to be in the range of 80 to 98% by mass.

  The solid content can be adjusted by means such as preheating (preheating) or air blowing. The preheating temperature can be room temperature to about 100 ° C., preferably about 40 to about 90 ° C., more preferably about 60 to about 80 ° C., and the preheating time is 30 seconds to 15 minutes, preferably 1 to 10 Minutes, more preferably about 3 to 5 minutes.

Process (3)
Next, the clear paint (Z) is applied onto the base coating film formed by the aqueous base paint (Y) in the step (2). The clear paint (Z) contains a hydroxyl group-containing acrylic resin (D) and a polyisocyanate compound (E).

  The hydroxyl group-containing acrylic resin (D) can be produced by copolymerizing a hydroxyl group-containing unsaturated monomer and another unsaturated monomer copolymerizable with the monomer by a conventional method. The hydroxyl group-containing unsaturated monomer and other unsaturated monomers copolymerizable with the monomer are the hydroxyl group-containing unsaturated monomers listed in the description of the hydroxyl group-containing acrylic resin (I-1) and other monomers copolymerizable with the monomer. These unsaturated monomers can be appropriately selected and used.

  The synthesis of the hydroxyl group-containing acrylic resin (D) can be carried out by using a general unsaturated monomer polymerization method, but in consideration of versatility and cost, it is carried out by a solution type radical polymerization method in an organic solvent. Is most suitable. For example, aromatic solvents such as xylene and toluene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate and 3-methoxybutyl acetate; n-butanol and isopropyl alcohol It can be easily obtained by carrying out a copolymerization reaction at a temperature of about 60 to about 150 ° C. in the presence of a polymerization initiator such as an azo catalyst or a peroxide catalyst in a solvent such as an alcohol solvent. it can.

  The hydroxyl group-containing acrylic resin (D) has a hydroxyl value of 80 to 200 mgKOH / g, particularly 90 to 170 mgKOH / g, more particularly 100 from the viewpoint of finished appearance such as smoothness and sharpness and coating performance such as weather resistance. The acid value is preferably in the range of ~ 140 mgKOH / g, and the acid value is preferably in the range of 1 to 40 mgKOH / g, particularly 3 to 30 mgKOH / g, more particularly 5 to 20 mgKOH / g. In addition, the hydroxyl group-containing acrylic resin (D) has a weight average molecular weight of 4,000 to 20,000, particularly 6,000 to 16,000, more particularly 8,000 to 12,000, from the viewpoint of finished appearance such as smoothness and sharpness and coating performance such as weather resistance. It is preferable to be within the range.

  The polyisocyanate compound (E) is a compound having at least two isocyanate groups in one molecule, for example, an aliphatic polyisocyanate, an alicyclic polyisocyanate, an araliphatic polyisocyanate, an aromatic polyisocyanate, Polyisocyanate derivatives and the like can be mentioned, and can be used by appropriately selecting from the polyisocyanate compounds listed in the description of the polyisocyanate compound (b1) described above. You may use together. Of the polyisocyanate compounds, aliphatic diisocyanates and aliphatic diisocyanate derivatives can be suitably used from the viewpoints of smoothness and sharpness of the coating film obtained, weather resistance, and the like.

  The equivalent ratio (NCO / OH) of the hydroxyl group of the hydroxyl group-containing acrylic resin (D) and the isocyanate group of the polyisocyanate compound (E) is preferably 0.5 to 2.0, more preferably 0.8 to 1.5. Is within the range.

  In addition, the clear paint (Z) can contain, if necessary, a color pigment, a bright pigment, a dye, etc. to such an extent that the transparency is not hindered. An agent, a light stabilizer, an antifoaming agent, a thickener, a rust inhibitor, a surface conditioner, and the like can be appropriately contained.

The clear paint (Z) can be applied to the coating surface of the water-based base paint (Y) by a method known per se, for example, airless spray, air spray, rotary atomizer, etc. At this time, electrostatic application may be performed. A coating film thickness can be normally applied as a cured film thickness in the range of 10 to 60 μm, preferably 25 to 50 μm.
Process (4)
A multi-layer coating film composed of three layers of an intermediate coating film, a base coating film, and a clear coating film formed as described above, for example, by hot air heating, By infrared heating, high-frequency heating, etc., it can be cured by heating at a temperature of about 80 to about 160 ° C., preferably about 100 to about 140 ° C. for about 20 to about 40 minutes.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to only these examples. “Part” and “%” are based on mass.

Production and Production Example 1 of Hydroxyl-Containing Acrylic Resin (I-1)
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device, 70.7 parts of deionized water and “Aqualon KH-10” (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., emulsifier, active ingredient) 97%) 0.52 part was charged, stirred and mixed in a nitrogen stream, and heated to 80 ° C. Next, 1% of the total amount of the following monomer emulsion and 5 parts of an aqueous solution of ammonium persulfate having a concentration of 6% were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Thereafter, the remaining monomer emulsion was dropped into a reaction vessel maintained at the same temperature over 3 hours, and after aging was completed for 1 hour, 40 parts of 2- (dimethylamino) ethanol aqueous solution having a concentration of 5% was reacted. The mixture was cooled to 30 ° C. while gradually being added to the container, and discharged while filtering through a 100 mesh nylon cloth to obtain a hydroxyl group-containing acrylic resin emulsion (I-1-1) having a solid content concentration of 45%. The resulting hydroxyl group-containing acrylic resin had an acid value of 12 mgKOH / g and a hydroxyl value of 43 mgKOH / g.

  Monomer emulsion: 50 parts of deionized water, 10 parts of styrene, 40 parts of methyl methacrylate, 35 parts of ethyl acrylate, 3.5 parts of n-butyl methacrylate, 10 parts of 2-hydroxyethyl methacrylate, 1.5 parts of acrylic acid, Aqualon KH -10 1.0 part of ammonium persulfate and 0.03 part of ammonium persulfate were mixed and stirred to obtain a monomer emulsion.

Production Example 2
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device was charged with 130 parts of deionized water and 0.52 part of “AQUALON KH-10” and stirred and mixed in a nitrogen stream at 80 ° C. The temperature was raised to. Next, 1% of the total amount of the following monomer emulsion (1) and 5.3 parts of an aqueous solution of ammonium persulfate having a concentration of 6% were introduced into the reaction vessel and kept at 80 ° C. for 15 minutes. Then, the remaining monomer emulsion (1) was dripped in the reaction container hold | maintained at the same temperature over 3 hours, and ageing | curing | ripening was performed after completion | finish of dripping. Thereafter, the following monomer emulsion (2) was added dropwise over 1 hour and aged for 1 hour, and then cooled to 30 ° C while gradually adding 40 parts of a 5% aqueous dimethylethanolamine solution to the reaction vessel, and 100 mesh The sample was discharged while filtering through a nylon cloth, and the average particle size was 100 nm (submicron particle size distribution measuring device “COULTER N4 type” (trade name, manufactured by Beckman Coulter), diluted with deionized water and measured at 20 ° C. And a hydroxyl group-containing acrylic resin emulsion (I-1-2) having a solid content concentration of 30% was obtained. The obtained hydroxyl group-containing acrylic resin had an acid value of 33 mgKOH / g and a hydroxyl value of 25 mgKOH / g.

  Monomer emulsion (1): 42 parts of deionized water, 0.72 part of “AQUALON KH-10”, 2.1 parts of methylenebisacrylamide, 2.8 parts of styrene, 16.1 parts of methyl methacrylate, 28 parts of ethyl acrylate and 21 parts of n-butyl acrylate was mixed and stirred to obtain a monomer emulsion (1).

  Monomer emulsion (2): 18 parts of deionized water, 0.31 part of “AQUALON KH-10”, 0.03 part of ammonium persulfate, 5.1 part of methacrylic acid, 5.1 part of 2-hydroxyethyl acrylate, styrene 3 Part, 6 parts of methyl methacrylate, 1.8 parts of ethyl acrylate and 9 parts of n-butyl acrylate were mixed and stirred to obtain a monomer emulsion (2).

Production Example 3
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device was charged with 35 parts of propylene glycol monopropyl ether, heated to 85 ° C., then 30 parts of methyl methacrylate, 2-ethylhexyl acrylate 20 Parts, n-butyl acrylate 29 parts, 2-hydroxyethyl acrylate 15 parts, acrylic acid 6 parts, propylene glycol monopropyl ether 15 parts and 2,2'-azobis (2,4-dimethylvaleronitrile) 2.3 parts. The mixture was added dropwise over 4 hours and aged for 1 hour after completion of the addition. Thereafter, a mixture of 10 parts of propylene glycol monopropyl ether 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, 7.4 parts of diethanolamine was added to obtain a hydroxyl group-containing acrylic resin solution (I-1-3) having a solid content of 55%. The obtained hydroxyl group-containing acrylic resin had an acid value of 47 mgKOH / g and a hydroxyl value of 72 mgKOH / g.

Production Example 4 of Hydroxyl-Containing Polyester Resin (I-2)
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 174 parts trimethylolpropane, 327 parts neopentyl glycol, 352 parts adipic acid, 109 parts isophthalic acid and 1,2-cyclohexanedicarboxylic acid After charging 101 parts of acid anhydride and heating from 160 ° C. to 230 ° C. over 3 hours, the condensed water produced was kept at 230 ° C. while distilling off with a water separator, and the acid value was 3 mgKOH / g or less The reaction was continued until To this reaction product, 59 parts of trimellitic anhydride was added, and after 30 minutes of addition reaction at 170 ° C., the reaction product was cooled to 50 ° C. or less, and 2- (dimethylamino) ethanol was added in an equivalent amount to the acid group. After neutralization, deionized water was gradually added to obtain a hydroxyl group-containing polyester resin solution (I-2-1) having a solid content concentration of 45% and a pH of 7.2. The obtained hydroxyl group-containing polyester resin had an acid value of 35 mgKOH / g, a hydroxyl value of 128 mgKOH / g, and a weight average molecular weight of 13,000.

Production Example 5
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator was charged with 109 parts of trimethylolpropane, 141 parts of 1,6-hexanediol, 126 parts of hexahydrophthalic anhydride and 120 parts of adipic acid. The mixture was heated and heated from 160 ° C. to 230 ° C. over 3 hours, and then subjected to a condensation reaction at 230 ° C. for 4 hours. Subsequently, in order to add a carboxyl group to the obtained condensation reaction product, 38.3 parts of trimellitic anhydride was further added and reacted at 170 ° C. for 30 minutes, followed by 1-octanol (alcohol having a boiling point of 195 ° C.). Then, a hydroxyl group-containing polyester resin solution (I-2-2) having a solid content concentration of 70% was obtained. The obtained hydroxyl group-containing polyester resin had an acid value of 46 mgKOH / g, a hydroxyl value of 150 mgKOH / g, and a weight average molecular weight of 6,400.

Production Production Example 6 of Active Methylene Block Polyisocyanate Compound (B)
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, dropping device and removal solvent simple trap, “Sumidule N-3300” (trade name, manufactured by Sumika Bayer Urethane Co., Ltd. Isocyanurate structure-containing polyisocyanate derived from methylene diisocyanate, solid content: about 100%, isocyanate group content: 21.8%) 360 parts, “Uniox M-550” (manufactured by NOF Corporation, polyethylene glycol monomethyl ether, average molecular weight: about 550) 60 parts and 0.26 parts of 2,6-di-tert-butyl-4-methylphenol were charged, mixed well, and heated at 130 ° C. for 3 hours under a nitrogen stream. Next, 110 parts of ethyl acetate and 252 parts of diisopropyl malonate were charged, and 3 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, followed by stirring at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.12 mol / Kg. To this, 683 parts of 4-methyl-2-pentanol was added, and the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 80 to 85 ° C. to obtain a block polyisocyanate compound solution (B-1). 1010 parts were obtained. The removal solvent simple trap contained 95 parts of isopropanol. The resulting block polyisocyanate compound solution (B-1) had a solid content concentration of about 60%.

Production Example 7
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, dropping device and removal solvent simple trap, 360 parts of “Sumidule N-3300”, “UNIOX M-400” (NOF) 50 parts of polyethylene glycol monomethyl ether, average molecular weight of about 400), 5 parts of “PEG # 600” (manufactured by NOF Corporation, polyethylene glycol, average molecular weight of about 600), and 2,6-di-tert-butyl-4- 0.2 parts of methylphenol was charged, mixed well, and heated at 130 ° C. for 3 hours under a nitrogen stream. Next, 110 parts of ethyl acetate and 247 parts of diisopropyl malonate were added, and 3 parts of a 28% methanol solution of sodium methoxide was added while stirring under a nitrogen stream, followed by stirring at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.11 mol / Kg. To this, 670 parts of 4-methyl-2-pentanol was added, and the solvent was distilled off for 3 hours under reduced pressure while maintaining the temperature of the system at 80 to 85 ° C. to obtain a block polyisocyanate compound solution (B-2). 1010 parts were obtained. The removal solvent simple trap contained 92 parts of isopropanol. The resulting block polyisocyanate compound solution (B-2) had a solid concentration of about 60%.
Production Example 8
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, dropping device and removal solvent simple trap, 480 parts of “Sumidule N-3300”, 150 parts of ethyl acetate and 365 parts of diisopropyl malonate Then, 4 parts of a 28% methanol solution of sodium methoxide was added with stirring under a nitrogen stream and stirred at 65 ° C. for 8 hours. The amount of isocyanate in the obtained resin solution was 0.07 mol / Kg. To this was added 870 parts of 4-methyl-2-pentanol, the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 90 to 95 ° C., and 4-methyl-2-pentanol was further removed. 120 parts were added to obtain 1400 parts of a blocked polyisocyanate compound solution (B-3). The removal solvent simple trap contained 183 parts of isopropanol. The solid content concentration of the obtained block polyisocyanate compound solution (B-3) was about 60%.

Production production example 9 of water-based intermediate coating (X)
36 parts of the hydroxyl group-containing acrylic resin solution (I-1-3) obtained in Production Example 3 (20 parts of resin solid content), “TITANIX JR-806” (trade name, rutile sulfuric acid method titanium oxide, manufactured by Teika) 90 Part, “Carbon MA-100” (trade name, carbon black, average primary particle size 20 nm, manufactured by Mitsubishi Chemical Corporation) 0.1 part and 5 parts deionized water were mixed, and pH 8. After adjusting to 0, the mixture was dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste.

  Next, 131 parts of the obtained pigment dispersion paste, 67 parts of the hydroxyl group-containing acrylic resin emulsion (I-1-1) obtained in Production Example 1 (30 parts of resin solid content), and the hydroxyl group-containing polyester resin obtained in Production Example 4 44 parts of solution (I-2-1) (resin solid content 20 parts), 33 parts of block polyisocyanate compound solution (B-1) obtained in Production Example 6 (solid content 60%) (resin solid content 20 parts), “Cymel 327” (trade name, manufactured by Nippon Cytec Industries, Inc., melamine resin, solid content 90%) 11 parts (resin solid content 10 parts) was uniformly mixed.

  Next, “UH-752” (trade name, manufactured by ADEKA, thickener), 2- (dimethylamino) ethanol and deionized water were added to the obtained mixture, pH 8.0, paint solid content 48% Ford Cup No. 20 at 20 ° C. An aqueous intermediate coating material (X-1) having a viscosity of 4 according to 30 seconds was obtained.

Production Example 10
In Production Example 9, the same procedure as in Production Example 9 was used except that the blocked polyisocyanate compound solution (B-2) obtained in Production Example 7 was used instead of the blocked polyisocyanate compound solution (B-1) obtained in Production Example 6. Thus, an aqueous intermediate coating material (X-2) was obtained.

Production Example 11
In Production Example 9, the same procedure as in Production Example 9 was used except that the blocked polyisocyanate compound solution (B-3) obtained in Production Example 8 was used instead of the blocked polyisocyanate compound solution (B-1) obtained in Production Example 6. Thus, an aqueous intermediate coating material (X-3) was obtained.

Production Example 12
36 parts of hydroxyl group-containing acrylic resin solution (I-1-3) obtained in Production Example 3 (20 parts of resin solid content), 90 parts of “TIPAQUE UT-771” (trade name, chlorine-based titanium oxide manufactured by Ishihara Sangyo Co., Ltd.) , “TAROX LL-50” (trade name, yellow iron oxide pigment, manufactured by Titanium Industry Co., Ltd.) 0.2 part, “Carbon MA-100” (trade name, carbon black, average primary particle size 20 nm, manufactured by Mitsubishi Chemical Corporation) 0.1 part and 5 parts of deionized water were mixed, adjusted to pH 8.0 with 2- (dimethylamino) ethanol, and then dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste.

  Next, 131 parts of the obtained pigment dispersion paste, 67 parts of the hydroxyl group-containing acrylic resin emulsion (I-1-1) obtained in Production Example 1 (30 parts of resin solid content), and the hydroxyl group-containing polyester resin obtained in Production Example 4 44 parts of solution (I-2-1) (resin solid content 20 parts), 33 parts of block polyisocyanate compound solution (B-1) obtained in Production Example 6 (solid content 60%) (resin solid content 20 parts), 11 parts of “Cymel 327” (10 parts of resin solids) were mixed uniformly.

  Next, “UH-752”, 2- (dimethylamino) ethanol and deionized water were added to the resulting mixture, pH 8.0, paint solids 48%, Ford Cup No. 20 at 20 ° C. An aqueous intermediate coating material (X-4) having a viscosity of 4 according to 30 seconds was obtained.

Production Example 13
In a stirring and mixing vessel, aluminum pigment paste “CR-9800” (trade name, manufactured by Asahi Kasei Chemicals Corporation, scaly aluminum pigment, metal content 32%, average primary particle size 7 μm) 20 parts, 1-octanol 30 parts, phosphorus 8 parts of an acid group-containing resin solution (* 1) and 0.2 part of 2- (dimethylamino) ethanol were uniformly mixed to obtain a bright pigment concentrate (P-1).

  36 parts of hydroxyl group-containing acrylic resin solution (I-1-3) obtained in Production Example 3 (20 parts of resin solid content), 90 parts of “TIPAQUE UT-771”, 0.2 part of “TAROX LL-50”, “carbon” 0.1 part of MA-100 and 5 parts of deionized water were mixed, adjusted to pH 8.0 with 2- (dimethylamino) ethanol, and then dispersed with a paint shaker for 30 minutes to obtain a pigment dispersion paste.

  Next, 131 parts of the obtained pigment dispersion paste, 67 parts of the hydroxyl group-containing acrylic resin emulsion (I-1-1) obtained in Production Example 1 (30 parts of resin solid content), and the hydroxyl group-containing polyester resin obtained in Production Example 4 44 parts of solution (I-2-1) (resin solid content 20 parts), 33 parts of block polyisocyanate compound solution (B-1) obtained in Production Example 6 (solid content 60%) (resin solid content 20 parts), 11 parts of “Cymel 327” (10 parts of resin solid content) and 10 parts of bright pigment concentrate (P-1) were uniformly mixed.

  Next, “UH-752”, 2- (dimethylamino) ethanol and deionized water were added to the resulting mixture, pH 8.0, paint solids 48%, Ford Cup No. 20 at 20 ° C. An aqueous intermediate coating material (X-5) having a viscosity of 4 according to 30 seconds was obtained.

  (* 1) Phosphate group-containing resin solution: A mixed solvent of 27.5 parts of methoxypropanol and 27.5 parts of isobutanol is placed in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device. , Heated to 110 ° C., 25 parts of styrene, 27.5 parts of n-butyl methacrylate, 20 parts of “isostearyl acrylate” (trade name, Osaka Organic Chemical Industries, Ltd., branched higher alkyl acrylate), 4-hydroxybutyl acrylate 7 .5 parts, phosphoric acid group-containing polymerizable monomer solution (* 2) 15 parts, 2-methacryloyloxyethyl acid phosphate 12.5 parts, isobutanol 10 parts and t-butyl peroxyoctanoate 4 parts 121 0.5 part is added to the above mixed solvent over 4 hours, and t-butyl peroxyoctanoate A mixture consisting of 5 parts and 20 parts of isopropanol was added dropwise for 1 hour. Thereafter, the mixture was aged and stirred for 1 hour to obtain a phosphate group-containing resin solution having a solid concentration of 50%. The acid value due to the phosphoric acid group of this resin was 83 mgKOH / g, the hydroxyl value was 29 mgKOH / g, and the weight average molecular weight was 10,000.

  (* 2) Phosphoric acid group-containing polymerizable monomer: In a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, and a dropping device, 57.5 parts of monobutyl phosphoric acid and 41 parts of isobutanol are placed and heated to 90 ° C After raising the temperature, 42.5 parts of glycidyl methacrylate was added dropwise over 2 hours, followed by stirring and aging for another hour. Thereafter, 59 parts of isopropanol was added to obtain a phosphate group-containing polymerizable monomer solution having a solid content concentration of 50%. The acid value due to the phosphate group of the obtained monomer was 285 mgKOH / g.

Production and production example 14 of pigment dispersion for water-based paint
In a stirring and mixing container, 10 parts of interference mica pigment “Xirallic T60-10WNT crystal silver” (trade name, manufactured by Merck, titanium oxide-coated mica, solid content: 100%), 35 parts of 1-octanol, phosphate group-containing resin solution (* 1) 8 parts and 0.2 part of 2- (dimethylamino) ethanol were mixed uniformly to obtain a bright pigment concentrate (P-2).

Production Example 15
180 parts of the hydroxyl group-containing acrylic resin solution (I-1-3) obtained in Production Example 3, 360 parts of deionized water, “Surfinol 104A” (trade name, defoamer manufactured by Air Products, solid content: 50%) 6 parts and 250 parts of “Varifine BF-1” (trade name, manufactured by Sakai Chemical Industry Co., Ltd., barium sulfate powder, average primary particle size: 0.05 μm) were added with glass bead medium in a paint conditioner, and at room temperature. Mixing and dispersing for 1 hour gave a barium sulfate dispersion (P-3).

Production and production example 16 of water-based paint (Y)
153 parts of hydroxyl group-containing acrylic resin emulsion (I-1-2) obtained in Production Example 2 (46 parts of resin solid content), 29 parts of hydroxyl group-containing polyester resin solution (I-2-2) obtained in Production Example 5 (resin) 20 parts of solid content), 53 parts of the bright pigment concentrate (P-2) obtained in Production Example 14, 32 parts of the barium sulfate dispersion (P-3) obtained in Production Example 15, and obtained in Production Example 6. Block polyisocyanate compound solution (B-1) (solid content 60%) 50 parts (resin solid content 30 parts) were mixed uniformly, and further “Primal ASE-60” (trade name, manufactured by Rohm and Haas, Inc.) Viscosity agent), 2- (dimethylamino) ethanol and deionized water were added, pH 8.0, paint solid content 25%, Ford Cup No. 20 at 20 ° C. An aqueous base paint (Y-1) having a viscosity according to 4 of 40 seconds was obtained.

Production Example 17
In Production Example 16, the same procedure as in Production Example 16 was used except that the blocked polyisocyanate compound solution (B-2) obtained in Production Example 7 was used instead of the blocked polyisocyanate compound solution (B-1) obtained in Production Example 6. Thus, an aqueous base paint (Y-2) was obtained.

Production Example 18
In Production Example 16, the same procedure as in Production Example 16 was used except that the blocked polyisocyanate compound solution (B-3) obtained in Production Example 8 was used instead of the blocked polyisocyanate compound solution (B-1) obtained in Production Example 6. Thus, an aqueous base paint (Y-3) was obtained.

Production Example 19
In Production Example 16, a water-based base coating material (Y-4) was obtained in the same manner as in Production Example 16, except that the entire amount of the blocked polyisocyanate compound solution (B-1) obtained in Production Example 6 was replaced with 37 parts of “Cymel 327”. It was.

Production and production example 20 of hydroxyl group-containing acrylic resin (D)
31 parts of ethoxyethyl propionate was charged into a four-necked flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet, and the temperature was raised to 155 ° C. under nitrogen gas flow. After reaching 155 ° C., nitrogen gas flow was stopped, 30 parts of styrene, 37.5 parts of n-butyl acrylate, 30 parts of 2-hydroxypropyl acrylate, 2.5 parts of acrylic acid and ditertiary mil peroxide (polymerization started) Agent) A monomer mixture composed of 4 parts was added dropwise over 4 hours. After 30 minutes, a polymerization initiator solution in which 0.5 part of 2,2′-azobis (2,4-dimethylvaleronitrile) (polymerization initiator) was dissolved in 3 parts of Swazol 1000 (hydrocarbon solvent) was added for 1 hour. It was dripped over. Next, after aging for 2 hours while ventilating nitrogen gas at 155 ° C., the solution was cooled to 100 ° C. and diluted with 29 parts of butyl acetate to obtain a hydroxyl group-containing acrylic resin (D-1) solution having a solid content of 60%. Obtained. The obtained hydroxyl group-containing acrylic resin (D-1) had a hydroxyl value of 129 mgKOH / g, an acid value of 19 mgKOH / g, and a weight average molecular weight of about 12,000.

Production Example 21
In Production Example 20, a composition blended of 30 parts of styrene, 37.5 parts of n-butyl acrylate, 30 parts of 2-hydroxypropyl acrylate, 2.5 parts of acrylic acid and 4 parts of ditertiary mil peroxide (polymerization initiator). A monomer blended with a composition comprising 30 parts of styrene, 40.5 parts of n-butyl acrylate, 27 parts of 2-hydroxyethyl acrylate, 2.5 parts of acrylic acid and 4 parts of ditertiary mil peroxide (polymerization initiator). A hydroxyl group-containing acrylic resin (D-2) solution having a solid content of 60% was obtained by producing in the same manner as in Production Example 20 except that the mixture was changed to a mixture. The obtained hydroxyl group-containing acrylic resin (D-2) had a hydroxyl value of 129 mgKOH / g, an acid value of 19 mgKOH / g, and a weight average molecular weight of about 12,000.

Production and production example 22 of clear paint (Z)
Hydroxyl-containing acrylic resin (D-1) solution 100 parts obtained in Production Example 20 (solid content 60 parts), “Duranate TLA-100” (trade name, manufactured by Asahi Kasei Chemicals Co., Ltd., polyisocyanate compound), “BYK- 300 ”(trade name, manufactured by BYK Chemie, surface conditioner, active ingredient 52%), 0.2 part,“ TINUVIN 900 ”(trade name, manufactured by BASF, benzotriazole ultraviolet absorber, effective 100 parts of component 100%) and 1.0 part of “TINUVIN292” (trade name, manufactured by BASF, hindered amine light stabilizer, active ingredient 100%) were mixed uniformly, “Swazol 1000” (trade name, manufactured by Cosmo Oil Co., Ltd., hydrocarbon solvent) was added, and Ford Cup No. A clear paint (Z-1) having a viscosity according to 4 of 25 seconds was obtained.

Production Example 23
In Production Example 22, the same procedure as in Production Example 22 was used except that the hydroxyl group-containing acrylic resin (D-2) solution obtained in Production Example 21 was used instead of the hydroxyl group-containing acrylic resin (D-1) solution obtained in Production Example 20. Thus, a clear paint (Z-2) was obtained.

Production of test article : "Electron GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., cationic electrodeposition paint) is applied to a cold-rolled steel sheet that has been subjected to zinc phosphate chemical conversion treatment. Electrodeposition coating was performed, and the coating was tested by heating at 170 ° C. for 30 minutes and curing. Ra of the surface roughness of the test object 1 was 0.21.

Preparation Example 1 of Test Coating Plate
Electrostatically apply the water-based intermediate coating (X-1) obtained in Production Example 9 to the above-described test object so as to have a dry film thickness of 25 μm using a rotary atomization type electrostatic coating machine. After coating and allowing to stand for 2 minutes, preheating was performed at 80 ° C. for 3 minutes.

  Next, the water-based base paint (Y-1) obtained in Production Example 16 is applied to the uncured intermediate coating film so as to have a dry film thickness of 15 μm using a rotary atomizing electrostatic coater. The coating was electrostatically coated and allowed to stand for 2 minutes, followed by preheating at 80 ° C. for 3 minutes.

  Further, the clear coating (Z-1) obtained in Production Example 22 was electrostatically coated on the base coating film so as to have a dry film thickness of 35 μm, and left for 7 minutes. Subsequently, it heated at 140 degreeC for 20 minutes (keep time), and the test coating board was produced by heat-hardening an intermediate coating film, a base coating film, and a clear coating film.

Examples 2 to 10 and Comparative Examples 1 to 3
In Example 1, a test coated plate was produced in the same manner as in Example 1 except that the water-based intermediate coating, water-based base coating, and clear coating were combined as shown in Table 1 below.

Evaluation test The test plates obtained in Examples 1 to 10 and Comparative Examples 1 to 3 were evaluated by the following test methods. The evaluation results are also shown in Table 1 below.

(Test method)
Smoothness: Evaluated using the Wc value measured by Wave Scan DOI (trade name, manufactured by BYK Gardner). The Wc value is an index of the amplitude of the surface roughness having a wavelength of about 1 to 3 mm, and the smaller the measured value, the higher the smoothness of the coated surface.

  Vividness: Evaluated using Wa values measured by Wave Scan DOI. The Wa value is an index of the amplitude of the surface roughness having a wavelength of about 0.1 to 0.3 mm, and the smaller the measured value, the higher the clearness of the coated surface.

  Accelerated weather resistance: Irradiation and rain conditions under the test conditions described in JIS K5600-7-7 (Method 1) using a Superxenon weather meter (trade name, Accelerated Weather Resistance Tester, manufactured by Suga Test Instruments Co., Ltd.) A combined cycle test was conducted. After a total cycle test time of 3000 hours, the film was further immersed in warm water at 40 ° C. for 2 days to evaluate the adhesion of the coating film. For adhesion, after making 100 square grids of 2 mm x 2 mm on the coating film according to JIS K 5600-5-6 (1990) on each test plate, affixing adhesive tape to the surface and peeling it off rapidly The number of cross-cut coating films remaining on the coating surface was evaluated. The 98 or more remaining cross-cut coating films are acceptable levels.

  Chipping resistance: A test plate was placed on a specimen holder of a stepping stone testing machine JA-400 (chipping test device) manufactured by Suga Test Instruments Co., Ltd., and at −20 ° C., a distance of 30 cm from 0.392 MPa (4 kgf / cm 2). ) 50 g of granite crushed stone of size 7 was made to collide with the test plate at an angle of 45 degrees. Thereafter, the obtained test plate is washed with water, dried, and a cloth adhesive tape (manufactured by Nichiban Co., Ltd.) is applied to the coated surface. After peeling it off, the degree of scratches on the coating film is visually observed. And evaluated according to the following criteria.

◎: Scratch size is very small, electrodeposition surface and base steel plate are not exposed ○: Scratch size is small, electrodeposition surface and base steel plate are not exposed △: Scratch size is Although it is small, the electrodeposited surface and the base steel plate are exposed. ×: The size of the scratch is quite large, and the base steel plate is also exposed greatly.

Claims (4)

The following steps (1) to (4) are applied to the electrodeposited object.
Step (1): A step of coating the water-based intermediate coating (X) to form an intermediate coating film,
Step (2): A step of coating the water-based base coating (Y) on the intermediate coating film formed in the step (1) to form a base coating film,
Step (3): A step of applying a clear paint (Z) on the base coating film formed in the step (2) to form a clear coating film, and a step (4): the steps (1) to ( A step of heat-curing the intermediate coating film, base coating film and clear coating film formed in 3) at a time,
A multilayer coating film forming method for sequentially performing,
The aqueous intermediate coating (X) contains a hydroxyl group-containing resin (A1), an active methylene block polyisocyanate compound (B1) having a hydrophilic group, and a pigment (C1),
The aqueous base paint (Y) contains a hydroxyl group-containing resin (A2), an active methylene block polyisocyanate compound (B2) and a pigment (C2) having a hydrophilic group, and the clear paint (Z) contains a hydroxyl group-containing acrylic resin (D And a polyisocyanate compound (E). The method for forming a multilayer coating film according to claim 1, wherein the aqueous intermediate coating (X) contains chlorine-based titanium oxide and yellow iron oxide as the pigment (C1). The method for forming a multilayer coating film according to claim 1, wherein the aqueous base paint (Y) contains barium sulfate as the pigment (C2). The coated article obtained by the multilayer coating-film formation method of any one of Claim 1 thru | or 3.