KR19980703484A - Multi-Layer Coating Method - Google Patents

Abstract

According to the present invention, a cationic electrodeposition coating is applied to a metal object, heat cured, and a first color base coat having a background hiding property is coated on the electrodeposition drawing, and the agent has transparency on the coating film without substantially curing. After coating the 2 color base coat, it heats and hardens both coating films of a 1st color base coat and a 2nd color base coat, Next, a clear paint is apply | coated and heat-cured, The method of forming a multilayer film is provided. According to the above method, a multilayer coating film excellent in finish appearance, design, cosmetic properties, corrosion resistance, weather resistance, chipping resistance, physical performance, and the like of the coating film can be formed.

Description

Multi-Layer Coating Method

Background Art Conventionally, exterior plates of automobiles, motorcycles, electrical appliances, etc., in which a cosmetic appearance is important, are finished and coated with an organic solvent dilution type thermosetting paint that forms a coating film excellent in smoothness, linerability, weather resistance, and the like. The coating process is usually coated with a cationic electrodeposition paint for imparting anticorrosion, followed by an intermediate paint for securing weather resistance and chipping resistance, and after heat-curing the coatings of both, As a finishing coating for imparting, a thermosetting paint (hereinafter referred to as a color base coat) containing a coloring pigment and / or a metallic pigment is applied, and after the air drying, the thermosetting clear paint is repeatedly applied, and then the two coating films are applied. In many cases, the two-coat 1 bake system, which is heat-cured at the same time, is formed.

However, in recent years, the appearance of the coating process which skipped the intermediate coating process is calculated | required from a viewpoint of resource saving, process reduction, pollution prevention, and the cost of coating being low.

The present invention provides a multi-layer coating having low coating film cost and excellent coating properties, designability, cosmetic properties, corrosion resistance, weather resistance, resistance to chipping, physical performance, and the like on metallic coatings, especially automobile bodies. It relates to a method of forming.

The inventors of the present invention have a low coating cost and are excellent in finish appearance, design, plastering, anticorrosion, weathering resistance, chipping resistance, etc. of the coating film, and are also polite for the purpose of developing an advantageous coating method for pollution prevention by saving resources. The study was conducted.

As a result, by using a cationic electrodeposition paint, two kinds of color base coats with different functions, and a clear paint, it was found that the above object can be achieved without using an intermediate lacquer paint, and the present invention has been completed.

Therefore, according to the present invention, after coating and heating the cationic electrodeposition paint (A) to the metal coating, the electrodeposited drawing is coated with a first color base coat (B) having a concealment property and not substantially cured. After coating the second color base coat (C) having transparency on the coating film, it is heated to cure both coating films of the first color base coat (B) and the second color base coat (C), followed by a clear paint ( A coating coating film forming method is provided by coating D) by heat curing.

A feature of the present invention is the conventional general cationic electrodeposition paint, without coating the conventional general intermediate paint, and the two-coat 1 bake method to coat both the color base coats (B) and (C) as a finishing paint It is in point that we can paint.

In the method of the present invention, since the first color base coat (B) has a ground concealability even when the intermediate coating process is omitted and the direct coating is directly applied to the bake cured coating film surface of the cationic electrodeposition coating. It has been found that the weather resistance peeling (the phenomenon that the electrodeposited coating film causes photodeterioration due to the light transmitted through the finished coating film and the peeling occurs between the electrodeposited coating film and the finished coating film during outdoor exposure) does not occur at all. In addition, according to the method of the present invention, since the intermediate coating process can be omitted, it is possible to obtain an advantage that the coating cost can be reduced.

Moreover, in the method of this invention, since the said 2nd color base coat (C) has color transparency, it is excellent in the appearance of finishing, such as a touch, smoothness, clarity, a sense of depth, high gloss, a high metallic feeling, and a color deviation | reduced_variance. It can be completed as a feature.

Therefore, by combining the first color base coat (B) and the second color base coat (C) in accordance with the present invention, it is possible to form a multilayer coating film having novel designability and aesthetic properties that are not available in the prior art.

Moreover, in the method of this invention, since a clear paint is apply | coated on the coating film of the heat-hardened color base coat, the advantage that arbitrary types of clear paints, such as a solvent type, aqueous or powder, can be used can also be acquired.

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

Metallic Subjects:

The object to be coated according to the method of the present invention is not particularly limited as long as it is a metal product capable of cationic electrodeposition coating, for example, iron, copper, aluminum, tin, zinc and the like, and alloys containing these metals, and these Metal plating or vapor deposition products; and the like. Specifically, automobile bodies such as passenger cars, trucks, motorcycles, and buses formed by using these metal members are mentioned. These metal coatings are preferably chemically treated with phosphate, chromate or the like in advance.

Cationic Electrodeposition Paint (A)

The cationic electrodeposition coating (A) used in the method of the present invention is a coating material for directly coating the metal coating material, and the kind thereof is not strictly limited, and various known cationic electrodeposition coatings can be used. Specifically, the main component contains a water-soluble or water-dispersible resin which is neutralized with a neutralizing agent of a resin having a basic value in the range of about 30 to about 200, such as an epoxy resin, an acrylic resin, or a polybutadiene resin modified with an amino group-containing compound. And a crosslinking agent (for example, a block polyisocyanate, an alicyclic epoxy resin, etc.), a coloring paint, an antirust pigment, an extender pigment, a hydrophilic organic solvent, and the like, as necessary. Here, as a neutralizing agent, For example, organic acids, such as acetic acid, hydroxyl acetic acid, propionic acid, butyric acid, lactic acid, glycine; Inorganic acids, such as sulfuric acid, hydrochloric acid, and phosphoric acid, etc. can be used. The amount of the neutralizer used is suitably within the range of about 0.1 to about 0.4 with a neutralization equivalent relative to the base value of the resin.

The paint is diluted with deionized water or the like so that the solid content concentration is in the range of about 5 to about 40% by weight, preferably about 10 to about 30% by weight, and the pH is maintained in the range of 5.5 to 8, preferably 5.5 to 7 Electrodeposition can be done according to the commercial law. The coating film can be cured by heating to a temperature of about 140 to about 210 ° C., preferably about 160 to about 190 ° C., and the coating film thickness is about 10 to about 60 μm, in particular about 15 to about 40, based on the cured coating film. The range of micrometer is preferable.

First Collar Base Coat (B):

The 1st color base coat (B) which concerns on this invention is a coating material which has a base hiding property as a coating material for apply | coating the said cationic electrodeposition drawing heat-hardened. The type is not strictly limited, and for example, a thermosetting paint of its own known aqueous type or organic solvent type containing a base resin, a curing agent, a pigment, water and / or an organic solvent can be used. have.

The gas resin forms the main component of the coating film formed by the first color base coat (B), and is preferably a resin for paint, which has good weather resistance and transparency, and which can be dissolved or dispersed in water or an organic solvent. And acrylic resins, polyester resins, epoxy resins, urethane resins and the like.

As said acrylic resin, the monomer copolymerizable with another (meth) acrylic acid ester which has functional groups, such as (alpha), (beta)-ethylenically unsaturated carboxylic acid, hydroxyl acid, an amide group, a methylol group, for example, the said functional group Acid value obtained by copolymerizing (meth) acrylic acid ester which does not have a substituted, unsubstituted styrene, olefin, etc., is about 0 to about 100, Preferably it is about 5 to about 30, and a hydroxyl group is about 20 to about 200, Preferably About 40 to about 120 resins can be mentioned.

As a polyester resin, what is obtained by condensation reaction of polybasic acid, a polyhydric alcohol, and a modified oil by a conventional method can be used. Moreover, as an epoxy resin, an epoxy ester is synthesize | combined by reaction of an epoxy group and an unsaturated fatty acid, The epoxy ester resin etc. which are obtained by the method of adding, (beta)-unsaturated acid, the esterification of the hydroxyl group of an epoxy ester, and polybasic acid, such as phthalic acid and trimellitic acid, etc. are mentioned.

Examples of the urethane resin include those obtained by reacting the diisocyanate compound with the acrylic resin, polyester resin or epoxy resin to obtain high molecular weight, which is mainly used as a water dispersible resin.

In the case of using an aqueous type paint as the first color base coat (B), as these basic resins, a sufficient amount of hydrophilic groups such as carboxyl groups, hydroxyl groups, methylol groups, amino groups, and sulfonic acid groups are sufficient for water solubilization or water oxidation of the resin. The resin can be water-soluble or water-oxidized by most commonly using a carboxyl group such as a polyoxyethylene bond or the like, and neutralizing the hydrophilic group to an alkali salt. In this case, the amount of the hydrophilic group, for example, the carboxyl group is not particularly limited, and may be arbitrarily selected depending on the degree of water solubilization or water oxidation, but is generally about 10 or more, preferably 10 to 100, more preferably based on the acid value. Preferably, it can be in the range of 15-50, and as an alkaline substance used for neutralization, sodium hydroxide, various amines, etc. are mentioned, for example.

In addition, the water oxidation of the said resin is also achieved by emulsion-polymerizing the said monomer component in presence of surfactant and water-soluble resin. It is also possible to obtain the resin by dispersing it in water in the presence of, for example, an emulsifier. In the above-mentioned water oxidation, the base resin does not need to contain all the said hydrophilic groups, or can contain less than the said water-soluble resin.

On the other hand, in the case of using an organic solvent-based paint as the first color base coat (B), the paint includes the gas resin (the hydrophilic group does not need to be contained particularly, but may be contained) and other paint components in the organic solvent. It can be prepared by dissolving or dispersing. As an organic solvent used at this time, what is normally used for paint can be applied, For example, Hydrocarbon type, such as toluene, xylene, hexane, heptane; Esters such as ethyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl acetate; Ethers such as ethylene glycol monomethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether and diethylene glycol dibutyl ether; Alcohols such as butanol, propanol, octanol, cyclohexanol, diethylene glycol; And ketones such as methyl ether ketone, methyl isobutyl ketone, cyclohexanone, and isophorone.

Examples of the organic solvent paint include a solution type, a high solid type, a non-aqueous dispersion type, and the like.

The curing agent that can be blended into the first color base coat (B) is for crosslinking and curing the gas resin three-dimensionally by heating, and specifically, melamine, benzoguanamine, urea and the like are condensed or formed with formaldehyde. The amino resin obtained by condensation and etherification with a lower monohydric alcohol, if necessary, can be preferably used. Moreover, a polyisocyanate compound or a block polyisocyanate compound can also be used preferably.

The pigment which can be mix | blended with a 1st color base coat (B) gives a background hiding property to the coating film formed by a 1st color base coat (B), Specifically, for example, aluminum powder and bronze powder Metallic pigments such as copper powder, tin powder, lead powder, zinc powder, iron phosphate, pearl-shaped metal coating mica powder and mica-type iron oxide; Anti-rust pigments such as dink chromate, strontium chromate, calcium chromate, lead cyanamide, calcium lead acid and zinc phosphate; Titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, carbazole violet, anthrapyridine, azo orange, yellow, prabansron yellow, isoindrin yellow, azo yellow, indersron blue, dibrom undersrone red, perylene Pigmented pigments such as red, azored, unsarkinone red, kinaclidon red and bio red; Extender pigments such as barita powder, precipitated barium sulfate, barium carbonate, gypsum, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, grossbone white, satin white, mica powder, and the like. These pigments can be used independently, respectively and may use two or more types together.

It is preferable that a 1st color base coat (B) contains metallic pigment and / or coloring pigment as a pigment component among said pigments.

A pigment can also be mix | blended with a 1st color base coat (B) as needed. As the dye, it is preferable to use a dye having excellent light resistance and solubility with water or an organic solvent, and specifically, a monoazo dye, a polyazo dye, a metal complex azo dye, a pyrazolone azo dye, a stilbenazo dye and a thia Azo dyes, such as a sol azo dye; Anthraquinone dyes such as anthraquinone derivatives and anthrone derivatives; Indigo dyes such as indigo derivatives and thioindigo derivatives; Phthalocyanine dyes; Carbonium dyes such as diphenylmethane dye, triphenylmethane dye, chixanthene dye and acridine dye; Quinone imine dyes such as adine dyes, oxadine dyes, and tajine dyes; Methine dyes such as polymethine (or cyanine) dyes and adimethine dyes; Kinorin Fuel; Nitro dyes; Nitron dyes; Benzokinone and naphthoquinone dyes; Naphthalimide dyes; Perinone dye etc. can be mentioned, 1 type, or 2 or more types selected from these can be used.

The proportion of each component in the first color base coat (B) is not strictly limited, and may be arbitrarily selected according to the purpose and the like. The gaseous resin and the curing agent are generally based on the total weight of the two components. It is preferable to make it into the range of 60-90 weight%, especially 70-85 weight%, the latter 40-10 weight%, especially 30-15 weight%.

The pigments can be blended suitably in accordance with the background concealability, desired color, and the like, and the blending amount is in the range of 400 to 700 nm in the thickness of the cured coating film having a thickness of 30 μm formed using the first color base coat. Suitable amounts are such that the light transmittance is generally 5% or less, preferably 3% or less. Although the specific amount can not be uniformly prescribed | regulated according to the kind of pigment, Usually, it is 1-250 weight part per 100 weight part of resin solid content (total amount of gaseous resin and a hardening | curing agent), Preferably it shall be in the range of 5-150 weight part. Can be.

In addition, the light transmittance of the coating film in this specification is made by coating a glass plate so that the thickness of the coating film after hardening may be set to predetermined | prescribed film thickness, and hardening | curing, after immersing in hot water of 60-70 degreeC, and peeling and drying the said coating film, It is an average spectral transmittance when the coating film obtained is measured with the wavelength of 400-700 nm using a spectrophotometer (Hitachi Corporation, EPS-3T type) as a sample.

Coating of the first color base coat (B) can be carried out according to a conventional method. For example, additives such as deionized water and / or an organic solvent, a thickener, and an antifoaming agent may be added to the paint to obtain a solid content. 10 to 70% by weight, preferably about 15 to 55% by weight, and a viscosity of 10 to 60 seconds, in particular 12 to 30 seconds (pod cup # 4/20 ° C) in the case of solvent-based paints, and water-soluble or moisture In the case of acidic paint, after adjusting to 200-5000 cps / 6 rpm, especially 300-3000 cps / 6 rpm (B-type viscometer), it is possible to, for example, adhere to the electrodeposition hardened film surface by the above cationic electrodeposition paint (A). It can be coated by spray coating or the like so as to have a cured film thickness of about 5 to 60 µm, preferably about 8 to 25 µm. In the method of this invention, after apply | coating a 1st collar base coat (B), it does not harden a coating film substantially, and it air-drys at room temperature with air blow etc. as it is, and then coats the following 2nd collar base coat (C) It is preferable.

2nd collar base coat (C)

The color base coat (C) which concerns on this invention is a paint which has transparency as a coating material for apply | coating to the figure of said 1st color base coat (B). The type is not strictly limited, and a thermosetting coating of its own known aqueous type or organic solvent, which contains a gas resin, a curing agent, a pigment, water and / or an organic solvent, can be used.

All of these coating components can be used, selecting from the thing demonstrated about said 1st color base coat (B).

A dye can also be mix | blended with a 2nd color base coat (C) as needed, As said dye, 1 type, or 2 or more types can be selected and used out of what was demonstrated by the said 1st color base coat (B).

The proportion of each component in the second color base coat (C) is not strictly limited and can be arbitrarily selected according to the purpose. The gaseous resin and the curing agent generally have an electron ratio of from 60 to 60 based on the total weight of the above two components. It is preferable to make it into the range of 90 weight%, especially 70 to 85 weight%, the latter 40 to 10 weight%, especially 30 to 15 weight%.

It is preferable that a 2nd color base coat (C) contains metallic pigment and / or a coloring pigment as a pigment component, The total content of pigments has the transparency that the formation film of the said 2nd color base coat (C) has transparency, It is preferable that it is comparatively small quantity of the grade which can recognize the color of a 1st color base coat through normally, and it is preferable that it is usually smaller than the total content of the pigment in a 1st color base coat (B).

Specifically, the light transmittance of the film thickness formed by the second color base coat (C) in the range of 400 to 700 nm in the cured coating film having a thickness of 30 μm is 6 to 95%, particularly 10 to 90%, more particularly It is preferable to mix | blend a pigment in the quantity which exists in the range of 20 to 80%, and the quantity is not uniformly prescribed | regulated depending on the kind of pigment, but normally, a pigment per 100 weight part of resin solid content (total amount of gaseous resin and a hardening | curing agent) It is preferable to mix | blend in the range of 0.01-100 weight part in total, especially 0.1-80 weight part, and to make it smaller than those content of a 1st color base coat (B).

Coating of the second color base coat (C) can be carried out according to a conventional method, for example, by adding additives such as deionized water and / or an organic solvent and, optionally, a thickener and an antifoaming agent to the paint. 10 to 70% by weight of the solid content, preferably about 20 to 60% by weight and the viscosity, in the case of solvent-based paint 10 to 60 seconds, preferably 13 to 40 seconds (pod cup # 4/20 ℃) And in the case of water-soluble or water-dispersible paint, after adjusting to 200-5000 cps / 6 rpm, Preferably 300-3000 cps / 6 rpm (B-type viscometer), for example, 10-70 micrometers, Especially 15- Coating may be performed by spray coating or the like so as to have a cured film thickness of about 50 μm. As described above, in the method of the present invention, after coating the first color base coat (B), the film is dried at room temperature with an air blow or the like without substantially curing the coating film, and then the second color base coat (C). It is preferable to paint. After coating, the first color base coat (B) is heated by heating at a temperature of about 80 to about 170 ° C, preferably at about 120 to about 160 ° C for about 3 to about 40 minutes, preferably about 10 to about 30 minutes. The second collar base coat (C) can be cured at the same time. As a heating method, the method generally used, for example, hot air heating, infrared heating, high frequency heating, etc. can be used.

Clear Paint (D):

According to the present invention, in order to further improve the plastering, finished appearance, weather resistance, chemical resistance, water resistance, moisture resistance, and the like of the multilayer coating formed, a clear paint (D) is applied to the drawing of the second color base coat (C). You can paint. The clear paint (D) forms a colorless or colored transparent coating film. As a remedy, the gaseous resin and the curing agent are mainly used, and if necessary, the coloring paint, the metallic pigment, and the dye are formed. Conventionally blended to the extent not inhibited, a thermosetting water-soluble or water-dispersible paint, an organic solvent type paint or a powder paint known per se can be used.

Among the above-mentioned paints, the gaseous resin which can be used for water-soluble or water-dispersible and organic solvent type paint, and the organic solvent which can be used for hardening | curing agent and organic solvent type paint can use what was selected from what was demonstrated by the said 1st color base coat (B). Can be. Moreover, the ratio of a gaseous resin and a hardening | curing agent is also preferable in the range demonstrated by the said 1st color base coat.

Water-soluble or water-dispersible clear paints and organic solvent-type clear paints may be added with deionized water and / or organic solvents and, if necessary, additives such as thickeners and antifoaming agents, and the solid content may be 10 to 95% by weight, Preferably about 30-80 weight% and viscosity are 10 to 70 second in the case of a solvent type paint, Preferably it is 15 to 40 second (pod cup # 4/20 degreeC), and in the case of water-soluble or water dispersible paint, After adjusting to 200-5000 cps / 6 rpm, preferably 300-3000 cps / 6 rpm (B-type viscometer), for example, it sprays so that it may become a cured film thickness of 10-70 micrometers, especially about 15-50 micrometers. It can coat with a painting etc. The coating film after coating can be cured by heating for about 20 to about 40 minutes at a temperature of about 80 to about 170 ° C, preferably about 120 to about 160 ° C. As a heating method, the method generally used, for example, hot air heating, infrared heating, high frequency heating, etc. can be used.

In addition, the powder coating which can be used as the clear coating (D) mainly consists of a gas resin and a curing agent, and as the base resin, for example, one or more crosslinkable functional groups selected from hydroxyl group, carboxyl group, glycidyl group, etc. Acrylic resins, polyester resins, fluororesins, urethane resins and modified substances thereof (for example, graft polymers), and the like, may be mentioned, but these are merely examples and are not limited thereto. It is preferable that the gas resin has a glass transition temperature of generally 40 ° C. or higher, particularly 50 to 120 ° C., more particularly 60 to 100 ° C., and the composition and molecular weight are not particularly limited and may be arbitrarily selected according to the purpose. Can be.

The curing agent is a component for crosslinking and curing the gas resin three-dimensionally by heating. For example, an alkoxymethyrolmelamine, a block polyisocyanate compound, an epoxy compound, an isocyanurate compound and an aliphatic dibasic acid may be used. have.

As for the ratio of a gaseous resin and a hardening | curing agent, it is most preferable that the molar ratio of the said functional group in a gaseous resin and a functional group in a hardening | curing agent becomes substantially equimolar.

The powder coating may be further blended with a paint additive such as a flow regulator, an ultraviolet absorber and a light stabilizer as necessary.

Powder coating can be obtained by melt-kneading each said component, and after cooling, grinding | pulverizing to a suitable particle diameter.

The coating method of the powder coating is not particularly limited, and any powder coating method such as electrostatic spray coating and flow immersion method can be used.

The coating film thickness of the powder coating is also not particularly limited, but generally within the range of 20 to 200 µm, and in particular, in order to improve the smoothness, linerability, glossiness and texture of the finished coating film, the thickness is 20 to 120 µm. It is preferable to coat by thickness. The curing temperature of the coating film of the powder coating may be a curing temperature of the powder coating, for example, in a range of about 120 to about 180 ° C, preferably about 130 to about 170 ° C.

Hereinafter, the present invention will be described in more detail with reference to Examples. In addition, below "part" and "%" represent a "weight part" and "weight%."

Ⅰ. Preparation of sample

1) Cationic electrodeposition paint (A)

(A-1): "Ereklon # 9200" (Kansai Paint Co., Ltd. make, brand name, a polyamine modified epoxy resin, a block polyisocyanate type) is diluted with deionized water etc. so that solid content concentration may be about 16 weight%, and it is pH Is kept within the range of 5.5 to 8.0 and electrodeposited by the conventional method. The coating film thickness was about 20 micrometers based on the cured coating film, and it heated at about 175 degreeC, and hardened the coating film.

2) 1st color base coat (B)

50% acrylic resin solution (S-1) : 30 parts of methyl methacrylate, 59 parts of ethyl acrylate, 10 parts of hydroxyethyl acrylate and 1 part of acrylic acid were used by using the polymerization initiator α, α'-azobisisobutyronitrile. In the mixed solvent of xylene / n-butanol = 70/30 by a conventional method to obtain an acrylic resin solution (S-1) having a weight average molecular weight of 25,000 and a resin solid content of 50%.

20% acrylic resin aqueous dispersion (W-1) : 140 parts of deionized water, 30% `` Newcol 707SF '' (surfactant, 2.5 parts by Nihon New Kazai Co., Ltd.) in the reaction vessel and the following monomer mixture (1) 1 part was added, stirred and mixed in a stream of nitrogen gas, and 3 parts of an aqueous 3% ammonium persulfate solution was added at 60 ° C. After raising the temperature to 80 ° C., a monomer emulsion consisting of 79 parts of the following monomer mixture (1), 2.5 parts of 30% “Newcol 707SF”, 4 parts of 3% aqueous ammonium persulfate solution and 42 parts of deionized water was quantified for 4 hours. The pump was used to add to the reaction vessel. After completion of the addition, aging was carried out for 1 hour. Further, 20.5 parts of the following monomer mixture (2) and 4 parts of 3% aqueous ammonium persulfate solution at 80 ° C. were simultaneously added in parallel to the reaction vessel for 1.5 hours. After completion of the addition, the mixture was aged for 1 hour, diluted with 30 parts of deionized water, and filtered through a nylon mesh of 200 mesh at 30 ° C. To this was further added deionized water to pH 7.5 with dimethylaminoethanol to obtain an aqueous acrylic resin dispersion (W-1) having an average particle diameter of 0.1 µm and a nonvolatile content of 20%.

Monomer mixtures (1)

Methyl methacrylate 55 parts

Styrene part 10

N-butyl acrylate 9 parts

2-hydroxyethyl acrylate 5 parts

1 part methacrylic acid

Monomer mixtures (2)

Methyl methacrylate part 5

N-butyl acrylate 7part

2-hydroxyethyl acrylate 5 parts

Methacrylic acid part 3

30% `` Newcol 707SF '' 0.5 part

27% melamine resin aqueous dispersion (M-1) : 126 parts of melamine, 80% of paraformaldehyde (manufactured by Mitsui Totsuga Chemical Co., Ltd.) 225 parts in a two-liter four-hole flask equipped with a thermometer, agitator and reflux cooler, After 592 parts of n-butanol were adjusted and adjusted to pH 9.5-10.0 with 10% caustic soda aqueous solution, it was made to react at 80 degreeC for 1 hour. Then, 888 parts of n-butanol were added, it adjusted to pH 5.5-6.0 with 5% sulfuric acid solution, and made it react at 80 degreeC for 3 hours. After completion of the reaction, the mixture was neutralized with a 20% aqueous solution of caustic soda to pH 7.0 to 7.5, concentrated under reduced pressure at 60 to 70 ° C, and filtered to obtain a hydrophobic melamine resin. Non-volatile content of 80%, solvent dilution rate of water / methanol mixed solvent (weight ratio 35/65) 3.6%, weight average molecular weight 800.

The melamine resin was placed in a stirring vessel so that the solid content was 25 parts, and an aqueous solution of acryl resin (n-butyl acrylate, methyl methacrylate, styrene, 2-hydroxyethyl methacrylic acid, 50% resin solution consisting of acrylic acid) was added to 20 80 parts of deionized water was gradually added while stirring with a disper of 1000 to 1500 revolutions of rotation speed, followed by another 30 minutes, followed by stirring for 30 minutes to obtain a water-soluble melamine resin dispersion having a solid content of 27% and an average particle size of 0.11 µm (M-1 )

(B-1):

50% acrylic resin solution (S-1) 150 parts

88% Cymel 370 (Note 1) Part 28

Pigment Ingredients-1 (Note 2) 30 parts

0.3 parts of dibutyl phosphate

The mixture was adjusted to a viscosity of 20 seconds (pod cup # 4/20 ° C.) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of vertical solvent part acetate, and 20 parts of butyl vertical solvent part, thereby adjusting the solvent type first color base. The coat (B-1) was obtained. The pigment content of the coat (B-1) is 26.5 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener), and the total content of the metallic pigment and / or the pigmented pigment is 6.5 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener). It was negative and the light transmittance of the formed coating film was 0.1% or less at 30 micrometers of cured film thickness.

(Note 1) 88% Cymel 370: 55% of 1 nucleolus of methyl methol melamine which consists of a trade name, a methoxy group, and a methylol group made by Mitsui Cyanamide Co., Ltd. are 55% based on solid content.

(Note 2) Pigment component-1: Pigment component consisting of 10 parts of "Alpaste N-1700NL" (manufactured by Toyo Aluminum Co., Ltd., product name, aluminum content 65%) and 20 parts of barium sulfate.

(B-2)

20% acrylic resin water dispersion (W-1) 325 parts

27% melamine resin water dispersion (M-1) 131 parts

Pigment Ingredients-2 (Note 3) 10 parts

Deionized Water 171 Part

Three awasol ASE-60 (note 4) three

Dimethylaminoethanol0.3part

The mixture was adjusted to a viscosity of 30 seconds (pod cup # 4/20 ° C) with deionized water to obtain an aqueous first color base coat (B-2). The pigment content of the coat (B-2) is 6.5 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener), and the total content of the metallic pigment and / or the pigmented pigment is 6.5 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener). It was negative and the light transmittance of the formed coating film was 0.1% or less at 30 micrometers of cured film thickness.

(Note 3) Pigment component-2: Brand name "Alpaste N-1700NL", product made from Toyo Aluminum, 65% of aluminum content.

(Note 4) Akwasol ASE-60: The brand name, thickener of the Rohm and Haas company.

(B-3);

50% acrylic resin solution (S-1) 150 parts

88% Cymel 370 (Note 1) Part 28

Pigment Ingredients-3 (Note 5) 23 parts

0.3 parts of dibutyl phosphate

The mixture was adjusted to a viscosity of 20 seconds (pod cup # 4/20 ° C.) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of cerosebuacetate, and 20 parts of butylcerosol, thereby adjusting the solvent type color base coat B-3) was obtained. The pigment content of the coat (B-3) is 23 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener), and the total content of the metallic pigment and / or the pigmented pigment is 3 parts by weight of 100 parts by weight of the resin solid (gas resin and hardener). The light transmittance of the formed coating film was 0.1% or less at a cured film thickness of 30 µm.

(5) Pigment component-3: Pigment component consisting of 3 parts of carbon black and 20 parts of barium sulfate.

(E-1) (for comparison):

50% acrylic resin solution (S-1) 150 parts

88% Cymel 370 (Note 1) Part 28

Pigment Ingredients-4 (Note 6) 28 parts

0.3 parts of dibutyl phosphate

The mixture was adjusted to a viscosity of 20 seconds (pod cup # 4/20 ° C.) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of vertical solvent part acetate, and 20 parts of butyl vertical solvent part, and was prepared for comparison. Base coat (E-1) was obtained. The pigment content of the coat (E-1) is 28 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener), and the total content of the metallic pigment and / or the pigmented pigment is 8 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener). It was negative and the light transmittance of the formed coating film was 0.1% or less at 30 micrometers of cured film thickness.

(Note 6) Pigment component-4: Pigment component consisting of 3 parts of carbon black, 5 parts of "Infinite Color YBG-06-SK3" (pearl pigment, the Shiseido company make, brand name), and 20 parts of barium sulfate.

3) second collar base coat (C)

(C-1):

150 parts of the 50% acrylic resin solution (S-1)

Above 88% Cymel 370 (Note 1) 28 parts

Pigment Ingredients-5 (Note 7) 3 parts

0.3 parts of dibutyl phosphate

The mixture was adjusted to a viscosity of 20 seconds (pod cup # 4/20 ° C.) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of vertical solvent part acetate, and 20 parts of butyl vertical sole part, thereby adjusting the solvent type second color base. The coat (C-1) was obtained. The pigment content of the coat (C-1) is 2.2 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener), and the total content of the metallic pigment and / or the pigment is 2.2 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener). The light transmittance of the formed coating film was 10% or less at a cured film thickness of 30 µm.

(Note 7) Pigment component-5: Brand name "Alphapth 891K", the product made from Toyo Aluminum, 72% of aluminum content.

(C-2):

20% acrylic resin aqueous dispersion (W-1) 325 parts

131 parts of the 27% melamine resin aqueous dispersion (M-1)

The pigment component-5 (Note 7) 3 parts

Deionized Water 171 Part

Three awasol ASE-60 (note 4) mentioned above

Dimethylaminoethanol0.3part

The mixture was adjusted to a viscosity of 30 seconds (pod cup # 4/20 ° C) with deionized water to obtain an aqueous second color base coat (C-2). The pigment content of the coat (C-2) is 2.2 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener), and the total content of the metallic pigment and / or the pigmented pigment is 2.2 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener). It was negative and the light transmittance of the formed coating film was 70% or less in cured film thickness of 30 micrometers.

(C-3);

150 parts of the 50% acrylic resin solution (S-1)

Above 88% Cymel 370 (Note 1) 28 parts

Pigment Ingredients-6 (Note 8) 1.5 parts

0.3 parts of dibutyl phosphate

The mixture was adjusted to a viscosity of 20 seconds (pod cup # 4/20 ° C.) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of vertical solvent part acetate, and 20 parts of butyl vertical sole part, thereby adjusting the solvent type second color base. The coat (C-3) was obtained. The pigment content of the coat (C-3) is 1.5 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener), and the total content of the metallic pigment and / or the pigment is 1.5 parts by weight per 100 parts by weight of the resin solid (gas resin and hardener). The light transmittance of the formed coating film was 10% or less at a cured film thickness of 30 µm.

(Note 8) Pigment component-5: "Infinite Color YBG-06-SK3" (pearl pigment, the Shiseido company make, brand name).

4) Clear Paint (D)

(D-1):

25 parts of methyl methacrylate, 25 parts of ethyl acrylate, 36.5 parts of n-butyl acrylate, 12 parts of 2-hydroxyethyl acrylate and 1.5 parts of acrylic acid and a polymerization initiator (α, α'-azobisisobutyronitrile) It polymerized in xylene using 2.5 parts and obtained the acrylic resin solution of 60% of resin solid content. The hydroxyl value of the said resin was 58 and the acid value was 12. This resin and the `` oil-based 20SE '' (hydrophobic melamine resin, manufactured by Mitsui Totsuga Chemical Co., Ltd., 60% nonvolatile matter, weight average molecular weight 3000 to 4000) were mixed so as to be 75:25 at a solid content weight ratio, and an organic solvent was added to give a viscosity of 25 It adjusted by the second (pod cup # 40/20 degreeC), and obtained the solvent type clearcoat (D-1).

(D-2);

20% acrylic resin aqueous dispersion (W-1) 325 parts

131 parts of the 27% melamine resin aqueous dispersion (M-1)

Deionized Water 171 Part

Three awasol ASE-60 (note 4) mentioned above

Dimethylaminoethanol0.3part

The mixture was adjusted to a viscosity of 30 seconds (pod cup # 4/20 ° C) with deionized water to obtain an aqueous clearcoat (D-2).

(D-3):

40 parts of methyl methacrylate, 30 parts of n-butylmethacrylate, 30 parts of glycidyl methacrylate, 10 parts of styrene and 1 part of t-butylperoxide (polymerization initiator), kalinooleate (surfactant) 2 parts were added and heat-polymerized by suspension polymerization method, and the obtained copolymer (glass transition temperature about 60 degreeC) was dried. 100 parts of the obtained copolymer, 25 parts of decamethylene carboxylic acid, and 1 part of drawing control agent were melt-mixed and kneaded at 120 degreeC for 10 minutes using a heating kneader. Subsequently, the mixed dough was cooled and pulverized using a grinder to obtain a powder clearcoat (D-3) having a particle size of about 20 to 150 µm.

II. Examples and Comparative Examples

Examples 1-5

The steel plate surface-treated with "Bonderite # 3030" (made by Nippon Parkarizing Co., Ltd., zinc phosphate treatment agent) was immersed in the bath of the cationic electrodeposition paint (A-1), and electrodeposition-coated by the conventional method. The coating film thickness was about 20 micrometers based on the cured coating film, and after pulling up in the bath and washing with water, it heated to about 175 degreeC and hardened the coating film. Next, on the said electrodeposition hardened film surface, the solvent-type 1st color base coat (B-1) or (B-3) or viscosity 30 second (pod cup) adjusted to viscosity 20 second (pod cup # 4/20 degreeC) The aqueous first color base coat (B-2) adjusted to # 4/20 ° C.) was coated with an air spray so as to have a thickness of about 20 μm based on the cured coating film, and left at room temperature for about 10 minutes.

Then, the solvent-free second color base coat (C-1) or (C-3) or viscosity 30 seconds (adjusted to an uncured drawing of the first color base coat at a viscosity of 20 seconds (pod cup # 4/20 ° C)) The aqueous second color base coat (C-2), adjusted by pod cup # 4/20 ° C.), was coated with an air spray so as to have a thickness of about 30 μm based on the cured coating film, and left at room temperature for about 10 minutes, and then at 140 ° C. By heating for 30 minutes, the coating film of the 1st color base coat and the 2nd color base coat was simultaneously crosslinked.

Next, solvent-type clear coat (D-1) or viscosity 25 second (pod cup # 4/20 degreeC) adjusted to the viscosity 25 second (pod cup # 4/20 degreeC) on the cured coating film surface of a 2nd color base coat. The aqueous clearcoat (D-2) adjusted by the paint is coated with an air spray to have a thickness of about 40 µm based on the cured coating film, or the powder clearcoat (D-3) is coated so that the cured coating film has a thickness of 50 µm by electrostatic powder coating. After standing at room temperature for about 10 minutes, it was crosslinked and cured by heating under baking conditions shown in Table 1 later.

Comparative Example 1

Solvent-type intermediate coating paint "TP-37" (trade name, manufactured by Kansai Paint Co., Ltd.), adjusted to a viscosity of 20 seconds (Pod Cup # 4/20 ° C) on the electrodeposition-cured coating film surface, to about 30 µm based on the cured coating film. It sprayed, sprayed and left at room temperature for about 10 minutes, and heated at 140 degreeC for 30 minutes.

Next, on the cured coating surface of the intermediate coating material, the solvent-type first color base coat (B-1) adjusted to a viscosity of 20 seconds (pod cup # 4/20 ° C) was about 15 μm based on the cured coating film. It was coated with an air spray and left for about 10 minutes at room temperature.

Thereafter, on the uncured drawing of the first color base coat, a solvent-type clear coat (D-1) adjusted to a viscosity of 25 seconds (pod cup # 4/20 ° C.) was heated to about 40 μm based on the cured coating film. After coating, the mixture was left at room temperature for about 10 minutes and then heated at 140 ° C. for 30 minutes to simultaneously crosslink and cure the coating films of the first color base coat and the second color base coat.

Comparative Example 2

On the electrodeposition cured coating surface, a solvent-type first color base coat (C-1) adjusted to a viscosity of 20 seconds (pod cup # 4/20 ° C) was coated with an air spray so as to have a thickness of about 18 μm based on the cured coating film. It was left at room temperature for about 10 minutes. Then, about 40 micrometers of the solvent-type clear coats (D-1) which adjusted to the uncured drawing of the 2nd color base coat (C-1) with the viscosity of 25 second (pod cup # 4/20 degreeC) based on a cured coating film The mixture was coated with an air spray so that it was left to stand at room temperature for about 10 minutes, and then heated at 140 ° C. for 30 minutes to crosslink and cure.

Comparative Example 3

In the said Example 1, it carried out similarly to Example 1 except having used the 1st collar base coat (C-1) as the 2nd collar base coat, respectively.

Comparative Example 4

Except having used the 1st color base coat (E-1) in the said comparative example 1, it carried out similarly to the comparative example 1.

III. Performance test result

The performance test of the multilayer coating film obtained by the said Example and the comparative example was done. The test results are shown in Table 1.

Test Methods

Horizontal part finishing property: It measured using the linearity measuring instrument (PGD-IV type) system (sales agency Japan Color Research Institute). Larger value means better selectivity.

Exposure durability: The test was conducted by 25 cycles of this test, after which the test plate was immersed in hot water for 24 hours in 40 ℃ hot water after 200 hours of accelerated exposure with Sunshine Weather Omder (light quantity 1100K Joule / ㎡ · hr). -5400 According to the check-mark tape method of 8.5.2, 100 pieces of 2 mm x 2 mm were created, and the peeling degree of the pieces when the tape was brought into close contact with the surface was peeled off to evaluate the following criteria. .

(Circle): Peeling between coating layers is not seen.

X: The partial or whole peeling is seen between an electrodeposition coating film and a basecoat coating film.

Chipping resistance : Impact was applied to the coating by spraying 500 g of No. 7 crushed stone with air pressure of 0.3 MPa at -20 ° C at an angle of 45 ° with reference to the drawing using a glove (made by Q Parnell) as a test piece. Gives. Next, an adhesive tape was attached to the above drawings, and the peeled state of the coating film around the damage caused by the impact after peeling it rapidly was examined.

(Circle): No or almost no peeling of a film is seen in the periphery of damage.

(Triangle | delta): The peeling of a coating film is clearly seen in the periphery of a damage.

X: Peeling of a film can be seen remarkably in a damaged periphery.

Glossiness : The plate was visually evaluated based on the following criteria.

◎: Glossiness is very good

○: glossiness is good

×: Glossiness is poor

Interference Color Intensity : C * at 45 ° incidence and 15 ° light reception was determined using MA68 from X-Rite. The larger the value, the better the designability and the plasticity. Flip-flop property: The orientation of an alumina was evaluated using the "alcope" (the product made from a pipe paint, a device name, a metallic feel measuring device). Larger value means better orientation.

Example Comparative example One 2 3 4 5 One 2 3 4 Painting process Electrodeposition coating Paint name A-1 A-1 A-1 A-1 A-1 A-1 A-1 A-1 A-1 Baking condition ① ① ① ① ① ① ① ① ① Film thickness (μ) 20 20 20 20 20 20 20 20 20 Middle Paint Paint name - - - - - TP-37 - - TP-37 Baking condition - - - - - ② - - ② Film thickness (μ) - - - - - 30 - - 30 Finish First collar base coat (B) Paint name B-1 B-2 B-3 B-1 B-1 B-1 - C-1 E-1 Baking condition none none none none none none - none none Film thickness (μ) 15 15 15 15 15 15 - 15 15 2nd collar base coat (C) Paint name C-1 C-2 C-3 C-1 C-1 - C-1 B-1 - Baking condition ② ② ② ② ② - none ② - Film thickness (μ) 30 30 30 30 30 - 30 30 - Clear Paint (D) Paint name D-1 D-1 D-1 D-2 D-3 D-1 D-1 D-1 D-1 Baking condition ② ② ② ② ③ ② ② ② ② Film thickness (μ) 40 40 40 40 50 40 40 40 40 evaluation Horizontal finish 1.0≤ 1.0≤ 1.0≤ 1.0≤ 1.0≤ 0.8 0.6 0.7 0.8 Exposure ○ ○ ○ ○ ○ ○ × ○ ○ Chipping resistance ○ ○ ○ ○ ○ △ × △ △ Gloss ◎ ◎ ◎ ◎ ◎ ○ △ ○ △ Interference Color Intensity - - 70 - - - - - 50 Flip flop 1.7 1.8 - 1.8 1.8 1.5 1.3 1.5 - (Note) Baking conditions: ①175 ℃ × 20 minutes, ②140 ℃ × 30 minutes, ③160 ℃ × 30 minutes

The method of the present invention has a low coating cost, is excellent in finish appearance, design, cosmetic properties, corrosion resistance, weather resistance, chipping resistance, etc. of the coating film, and is an advantageous coating method for saving resources and pollution countermeasures. It can be widely used for painting two-wheeled vehicles and electric products.

Claims (14)

After coating and heat-curing the cationic electrodeposition paint on the metal coating, the second color base coat having transparency on the coating film is applied to the electrodeposition drawing without applying the first color base coat having concealment and substantially hardening it. After coating, it heats and hardens both coating films of a 1st color base coat and a 2nd color base coat, Next, a clear paint is apply | coated and heat-cured, The multilayer coating film formation method characterized by the above-mentioned. The method of claim 1 wherein the first color base coat contains metallic pigments and / or pigmented pigments. The method of claim 1, wherein the first color base coat has a light transmittance of 5% or less at a cured film thickness of 30 μm. The method of claim 1, wherein the first color base coat has a light transmittance of 3% or less at a cured film thickness of 30 μm. The method according to claim 1, wherein the first color base coat contains a pigment in the range of 1 to 250 parts by weight per 100 parts by weight of the resin solid content. The method of claim 1, wherein the first color base coat is coated so as to have a cured film thickness of 5 to 60 µm. The method of claim 1 wherein the second color base coat contains metallic pigments and / or colored pigments. The method according to claim 1, wherein the second color base coat has a light transmittance in the range of 6 to 95% at a cured film thickness of 30 µm. The method according to claim 1, wherein the second color base coat has a light transmittance in the range of 10 to 90% at a cured film thickness of 30 µm. The method according to claim 1, wherein the second color base coat contains a pigment in the range of 0.01 to 100 parts by weight per 100 parts by weight of the resin solid content. The method according to claim 1, wherein the second color base coat is coated so as to have a cured film thickness within a range of 10 to 70 µm. The method according to claim 1, wherein both coating films of the first color base coat and the second color base coat are heated and cured at a temperature of 80 to 170 ° C. The method according to claim 1, wherein the clear coat is water-soluble, water dispersible, organic solvent type, or powder coating. An article painted by the method of claim 1.