KR100412963B1 - Method for forming a multilayer coating film - Google Patents

Abstract

The present invention relates to a method of coating a metal base material with a cationic electrodeposition coating material and then curing the material by heating and then coating the first color base coat material having a background concealing property on the electrodeposition material, The present invention provides a method for forming a double-layer film, which comprises coating a two-color base coat and then heating it to cure both coating films of the first and second color base coats, then coating a clear paint, According to the above method, it is possible to form a multilayer coating film excellent in finished appearance, designability, finishability, anticorrosion property, weather resistance, chipping resistance, physical performance and the like of a coated film.

Description

Method for forming a multilayer coating film

Conventionally, outer plates such as automobiles, motorcycles, electric appliances and the like where the appearance of the plaster is important are finished with an organic solvent dilution type thermosetting paint forming a coating film excellent in smoothness, linearity and weatherability. The coating process is usually carried out by coating a cationic electrodeposition paint for imparting anticorrosion property, then coating an intermediate coat paint for ensuring weatherability and chipping resistance, heating and curing the positive and negative films respectively, (Hereinafter referred to as " color base coat ") in which a coloring pigment and / or a metallic pigment is blended (hereinafter referred to as " color base coat ") as a finishing paint to be applied, Called two-coat one-bake system in which the coating film is heated and cured at the same time.

However, in recent years, from the viewpoint of saving resources, reducing the number of processes, coping with pollution, and lowering the coating cost, it is demanded that a coating process omitting the intermediate painting process is introduced.

The present invention relates to a method for producing a multilayer coating film which is low in cost of a coating film and excellent in appearance, designability, anticorrosive property, weatherability, resistance to chipping and physical performance of a metallic coating, And a method of forming the same.

The inventors of the present invention have found that the coating cost is low and the finished appearance of the coating film, designability, finishability, anticorrosion property, weather resistance, chipping resistance and the like are excellent. In addition, .

As a result, it has been found that the above objects can be achieved without using an intermediate coat paint by using a cationic electrodeposition paint, two kinds of color base coat and clear paint having different functions, and have accomplished the present invention.

Therefore, according to the present invention, after the cationic electrodeposition coating material (A) is coated on the metal substrate and cured by heating, the first color base coat (B) having the background concealing property is coated on the electrodeposition drawing, A second color base coat C having transparency is coated on the coating film and then heated to cure both coating films of the first and second color base coats B and C, D) is applied and cured by heating.

A characteristic feature of the present invention is that a conventional general cationic electrodeposition coating composition can be produced by coating two color coat basecoats (B) and (C) in a two-coat one-bake system It is in point that it can paint.

In the method of the present invention, since the first color base coat (B) has a background concealing property even if the intermediate coat painting process is omitted and the finish coat paint is applied directly on the baked coat surface of the cationic electrodeposition paint (Peeling occurs between the electrodeposition coating film and the finish coat film during outdoor exposure due to the electrodeposition coating film being photodegraded by the light transmitted through the finish coat film). Further, according to the method of the present invention, since the intermediate painting step can be omitted, the coating cost can be reduced.

In addition, in the method of the present invention, since the second color base coat (C) has a coloring transparency, it is possible to obtain an image having excellent finish appearance such as feel, smoothness, linearity, depth feeling, high gloss, As shown in Fig.

Therefore, by combining the first color base coat (B) and the second color basecoat (C) according to the present invention, it is possible to form a multilayer coating film having a novel design property and a smoothness which are not conventionally available.

Further, in the method of the present invention, a clear paint is applied on the coating film of the color-cured base coat obtained by heat-curing, so that any type of clear paint such as solvent type, water or powder can be used.

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

Metal Coatings:

The substrate 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 being subjected to cationic electrodeposition coating. Examples of the substrate include iron, copper, aluminum, tin, zinc and the like, Metal plating or vapor deposition products, and the like. Specifically, the automobile body such as a passenger car, a truck, a motorcycle, and a bus formed using these metal members can be mentioned. It is preferable that these metal coatings are chemically treated with phosphates, chromates and the like in advance.

Cationic electrodeposition coating (A)

The cationic electrodeposition coating material (A) used in the method of the present invention is a coating material for directly coating the metallic coating material, and the kind thereof is not strictly limited, and various known cationic electrodeposition coating materials can be used. Concretely, a water-soluble or water-dispersible resin neutralized with a neutralizing agent such as an epoxy resin modified with an amino group-containing compound, an acrylic resin, a polybutadiene resin or the like and having a base value within a range of usually about 30 to about 200 is contained as a main component (Block polyisocyanate, alicyclic epoxy resin, etc.), a coloring paint, an anticorrosive pigment, an extender pigment, a hydrophilic organic solvent and the like may be blended as required. Examples of the neutralizing agent include organic acids such as acetic acid, hydroxyl acetic acid, propionic acid, butyric acid, lactic acid and glycine; Sulfuric acid, hydrochloric acid, phosphoric acid and the like can be used. The amount of the neutralizing agent to be used is suitably in the range of about 0.1 to about 0.4 in neutralizing equivalent with respect to the base of the resin.

The paint is diluted with deionized water or the like to maintain the solids concentration in the range of about 5 to about 40 wt%, preferably about 10 to about 30 wt%, and the pH is maintained within the range of 5.5 to 8, preferably 5.5 to 7 Electrodeposition coating can be carried out according to a conventional method. The coating film can be cured by heating to a temperature of about 140 to about 210 캜, preferably about 160 to about 190 캜, and the coating film thickness is about 10 to about 60 탆, particularly about 15 to about 40 탆, Mu m.

First color base coat (B):

The first color base coat (B) according to the present invention is a coating material for coating on the cationically electrodeposited coating which is heat cured and has a hiding power. The type of the thermosetting resin is not strictly limited, and for example, it is possible to use a thermosetting resin of a water-based or organic solvent type known per se comprising a base resin, a curing agent, a pigment, water and / or an organic solvent have.

The gas resin constitutes the main component of the coating film formed by the first color basecoat (B), and is preferably a resin for paint which is excellent in weatherability and transparency and can be dissolved or dispersed in water or an organic solvent. For example, , An acrylic resin, a polyester resin, an epoxy resin, and a urethane resin.

Examples of the acrylic resin include, for example, a copolymerizable monomer other than the (meth) acrylic acid ester having an α, β-ethylenically unsaturated carboxylic acid and a functional group such as a hydroxyl acid, an amide group or a methylol group, Preferably from about 5 to about 30, and a hydroxyl value of from about 20 to about 200, and preferably from about 20 to about 200, obtained by copolymerizing (meth) acrylic acid esters, 40 to about 120 resin.

As the polyester resin, there can be used those obtained by condensation reaction of a polybasic acid, a polyhydric alcohol and a modified oil by a conventional method. As the epoxy resin, for example, an epoxy ester is synthesized by reaction of an epoxy group with an unsaturated fatty acid, , a method of adding a? -unsaturated acid, and an epoxy ester resin obtained by esterifying a hydroxyl group of an epoxy ester and a polybasic acid such as phthalic acid or trimellitic acid.

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

When a water-based paint is used as the first color base coat (B), as the base resin, a hydrophilic group sufficient for water-solubilizing or water-oxidizing the resin, for example, a carboxyl group, hydroxyl group, methylol group, amino group, Or a polyoxyethylene bond, most usually a carboxyl group is used, and the hydrophilic group is neutralized to an alkali salt, whereby the resin can be rendered water-soluble or water-oxidized. The amount of the hydrophilic group at this time, 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, And may be in the range of 15 to 50. Examples of the alkaline substance used for neutralization include sodium hydroxide and various amines.

The water oxidation of the resin is also achieved by emulsion polymerization of the monomer component in the presence of a surfactant or a water-soluble resin. The resin can also be obtained by dispersing the resin in water in the presence of, for example, an emulsifying agent. In the above-mentioned water oxidation, the base resin may not contain all of the hydrophilic groups, or may contain less than the water-soluble resin.

On the other hand, when an organic solvent-based paint is used as the first color basecoat (B), the above-mentioned paint is used as the organic resin in the gas resin (the hydrophilic group is not necessarily contained but may be contained) Or by dissolving or dispersing them. As the organic solvent to be used at this time, those generally used for paints can be used, and examples thereof include hydrocarbon type solvents such as toluene, xylene, hexane and heptane; Esters such as ethyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate and diethylene glycol monobutyl acetate; Ether type solvents 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 and diethylene glycol; Methyl ether ketone, methyl isobutyl ketone, cyclohexanone, and isophorone.

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

The curing agent which can be compounded in the first color basecoat (B) is used for three-dimensionally cross-linking and curing the gas resin by heating. Specifically, melamine, benzoguanamine and urea are condensed with formaldehyde, And an amino resin obtained by etherification with a lower monohydric alcohol, if necessary, can be preferably used. A polyisocyanate compound or a block polyisocyanate compound is also preferably used.

The pigment that can be compounded in the first color basecoat (B) imparts background concealing properties to the coating film formed by the first color basecoat (B). Specifically, for example, aluminum powder, bronze powder , Copper powder, tin powder, lead powder, zinc powder, iron oxide, metallic coated mica powder in the form of pearl-like metal, iron oxide in the form of mica; Rust-preventive pigments such as dichromate, strontium chromate, calcium chromate, lead cyanamide, calcium lead, and zinc phosphate; Titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, carbazole violet, anthrapyridine, azo orange, yellow, pravans riron yellow, isoindoline yellow, azo yellow, indusrone blue, dibromine underiron red, perylene Coloring pigments such as red, azo red, unkyrakon red, quinacridone red and bio red; And extender pigments such as barite powder, precipitated barium sulfate, barium carbonate, gypsum, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, Grossbone white, satin white and mica powder. These pigments may be used alone, or two or more pigments may be used in combination.

The first color base coat (B) preferably contains a metallic pigment and / or a colored pigment as a pigment component.

A pigment may also be blended in the first color base coat (B) if necessary. As the dye, it is preferable to use a dye having excellent light resistance and solubility with water or an organic solvent. Specific examples thereof include monoazo dyes, polyazo dyes, metal complex azo dyes, pyrazolone azo dyes, stilbenazo dyes, Azo dyes such as sol-gel dye; Anthraquinone dyes such as anthraquinone derivatives and anthrone derivatives; Indigoid dyes such as indigo derivatives and thioindigo derivatives; Phthalocyanine dyes; Carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes and acridine dyes; Acyanine dyes, oxazine dyes, and tyine dyes; Methine dyes such as polymethine (or cyanine) dyes, adimethine dyes; Kiesel fuel; Nitro dyes; Nitrone dyes; Benzoquinone and naphthoquinone dyes; Naphthalimide dyes; Perynone dyes, and the like, and one or more selected from these can be used.

The proportions of the respective components in the first color basecoat (B) are not strictly limited, and can be arbitrarily selected depending on the purpose. The gas resin and the curing agent generally have an electron Is in the range of 60 to 90% by weight, especially 70 to 85% by weight, the latter is in the range of 40 to 10% by weight, particularly 30 to 15% by weight.

The pigment can be appropriately combined and blended according to the hiding properties of the base, the desired color, etc. The blending amount of the pigment is preferably in the range of 400 to 700 nm in the cured coating film having a film thickness of 30 mu m formed using the first color basecoat The amount of light transmittance is generally 5% or less, preferably 3% or less. The specific amount varies depending on the type of pigment and can not be uniformly defined. However, it is usually within the range of 1 to 250 parts by weight, preferably 5 to 150 parts by weight, per 100 parts by weight of the resin solid content (total amount of the gas resin and the curing agent) .

In the present specification, the light transmittance of the coating film in this specification is obtained by coating the coating material on the glass plate so that the thickness of the coating film after curing becomes a predetermined film thickness, curing it, immersing it in hot water at 60 to 70 ° C, Is the average spectral transmittance when the obtained coating film is measured with a wavelength in the range of 400 to 700 nm using a magnetic spectrophotometer (Hitachi, EPS-3T type) as a sample.

The 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 and, if necessary, a thickener and defoaming agent are added to the paint, Preferably 10 to 70% by weight, preferably 15 to 55% by weight, and a viscosity of 10 to 60 seconds, in particular 12 to 30 seconds (Ford Cup # 4/20 ° C) (B type viscometer) at 200 to 5000 cps / 6 rpm, particularly 300 to 3000 cps / 6 rpm for the acidic paint, and then the electrodeposition-cured coating film surface of the cationic electrodeposition coating material (A) , And 5 to 60 탆, preferably 8 to 25 탆, by spray coating or the like. In the method of the present invention, after coating the first color base coat (B), the second color base coat (C) is painted after air is blown thereon at room temperature without substantially curing the coating film .

The second color base coat (C)

The color base coat (C) according to the present invention is a paint having transparency as a paint for painting the first color base coat (B). The kind is not strictly limited, and it is possible to use a known water-based or organic solvent-based thermosetting paint containing a gas resin, a curing agent, a pigment, water and / or an organic solvent.

All of these coating components can be selected from those described for the first color base coat (B).

The second color base coat (C) may also contain a dye, if necessary. One or more of the dyes described above for the first color base coat (B) may be selected and used.

The ratio of each component in the second color basecoat (C) is not strictly limited and can be arbitrarily selected according to the purpose. The gas resin and the curing agent generally have an electron quantity of 60 - 90% by weight, particularly 70 to 85% by weight, and the latter is preferably within a range of 40 to 10% by weight, particularly 30 to 15% by weight.

The second color base coat (C) preferably contains a metallic pigment and / or a colored pigment as a pigment component, and the total content of the pigment is such that the coating film of the second color base coat (C) has transparency, It is preferable that the color of the first color basecoat is comparatively small so as to be able to recognize the color of the first color basecoat and is usually smaller than the total content of the pigment in the first color basecoat B. [

Concretely, the light transmittance in the wavelength range of 400 to 700 nm in the cured coating film formed by the second color base coat (C) of 30 m is 6 to 95%, particularly 10 to 90% It is preferable to blend the pigment in an amount within a range of 20 to 80%, and the amount thereof can not be specified uniformly depending on the kind of the pigment. Usually, the amount of the pigment is 100 parts by weight of the resin solid component (total amount of the gas resin and the curing agent) In a total amount of 0.01 to 100 parts by weight, particularly 0.1 to 80 parts by weight, in terms of the total amount of the first color base coat (B).

The second color base coat (C) can be coated by a conventional method. For example, additives such as de-ionized water and / or an organic solvent and, if necessary, a thickener and defoaming agent , The solid content is about 10 to 70% by weight, preferably about 20 to 60% by weight, and the viscosity is 10 to 60 seconds, preferably 13 to 40 seconds (Ford Cup # 4/20 ° C) In the case of water-soluble or water-dispersible paints, it is adjusted to 200 to 5000 cps / 6 rpm, preferably 300 to 3000 cps / 6 rpm (B type viscometer) It can be coated by spray coating or the like so as to have a cured film thickness of about 50 탆. As described above, in the method of the present invention, the first color base coat (B) is applied to the second color base coat (C) after air is blown at room temperature without being cured, . After the coating, the first color basecoats (B) and (B) are heated by heating at a temperature of about 80 to about 170 DEG C, preferably about 120 to about 160 DEG C for about 3 to about 40 minutes, preferably about 10 to about 30 minutes. The second color base coat (C) can be cured at the same time. As the heating method, a commonly used method such as hot air heating, infrared heating, high frequency heating, or the like can be used.

Clear paint (D):

According to the present invention, in order to further improve the fineness, finished appearance, weather resistance, chemical resistance, water resistance, moisture resistance, etc. of the multilayer coating film to be formed, a clear paint (D) is applied to the drawing of the second color base coat It can be painted. The clear paint (D) forms a colorless or colored transparent film. As the remover chuck, a gas resin and a curing agent are used as main components and, if necessary, colored pigments, metallic pigments, dyes and the like are formed. A thermosetting water-soluble or water-dispersible coating material, an organic solvent-based coating material or a powder coating material which has been conventionally known can be used.

Among the above paints, those selected from those described in the first color basecoat (B) can be used as the organic resin usable for the gas resin, curing agent and organic solvent type paint which can be used for water-soluble or water- . The ratio of the gas resin to the curing agent is also preferably within the range described in the first color base coat.

The water-soluble or water-dispersible clear paint and the organic solvent-type clear paint are prepared by adding an additive such as deionized water and / or an organic solvent and, if necessary, a thickener and defoaming agent, in an amount of 10 to 95% Preferably 10 to 70 seconds, preferably 15 to 40 seconds (Ford Cup # 4/20 占 폚) in the case of a solvent-based paint, in the case of a water-soluble or water- After adjusting to 200 to 5000 cps / 6 rpm, preferably 300 to 3000 cps / 6 rpm (B-type viscometer), the coating is sprayed so as to have a cured film thickness of, for example, 10 to 70 μm, It can be painted by painting. The coated film after coating can be cured by heating at a temperature of about 80 to about 170 캜, preferably about 120 to about 160 캜 for about 20 to about 40 minutes. As the heating method, a commonly used method such as hot air heating, infrared heating, high frequency heating, or the like can be used.

The powder coating material which can be used as the clear paint (D) is mainly composed of a gas resin and a curing agent. Examples of the base resin include one or more crosslinkable functional groups selected from a hydroxyl group, a carboxyl group and a glycidyl group, Acrylic resins, polyester resins, fluororesins, urethane resins, and modified products thereof (for example, graft polymers). These are merely illustrative examples, and the present invention is not limited thereto. The gas resin preferably has a glass transition temperature of generally 40 ° C or higher, particularly 50 ° C to 120 ° C, more preferably 60 ° C to 100 ° C. The composition and molecular weight are not particularly limited and may be arbitrarily selected depending on the purpose .

The curing agent is a component for three-dimensionally crosslinking and curing the above-mentioned gas resin by heating, and for example, alkoxymethylol melamine, block polyisocyanate compound, epoxy compound, isocyanurate compound and aliphatic dibasic acid can be used have.

The ratio of the gas resin to the curing agent is most preferably such that the molar ratio of the functional group in the gas resin to the functional group in the curing agent is substantially equal.

The powder coating material may further contain a coating additive such as a flow control agent, an ultraviolet absorber, and a light stabilizer, if necessary.

The powder coating material can be usually obtained by melting, kneading, kneading, cooling the above components, and pulverizing them to a suitable particle size.

The method of applying the powder coating material is not particularly limited, and any powder coating method such as electrostatic spraying and flow-dipping may be used.

The coating film thickness of the powder coating material is also not particularly limited, but it is generally in the range of 20 to 200 占 퐉. In order to improve the smoothness, linearity, gloss and texture of the finished film, By weight. The curing temperature of the coating film of the powder coating material may be a curing temperature of the powder coating material, for example, a temperature within a range of about 120 to about 180 캜, preferably about 130 to about 170 캜.

Hereinafter, the present invention will be described in more detail with reference to examples. In the following, " part (s) " and "% "

I. Preparation of samples

1) Cation electrodeposition coating (A)

(A-1): "Erekron # 9200" (trade name, polyamine-modified epoxy resin block polyisocyanate type) manufactured by Kansai Paint Co., Ltd.) was diluted with deionized water or the like to have a solid content concentration of about 16% Is maintained within the range of 5.5 to 8.0, and electrodeposition is performed by a conventional method. The coating film thickness was about 20 탆 based on the cured coating film, and was heated to about 175 캜 to cure the coating film.

2) The first 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 mixed with the polymerization initiator α, α'-azobisisobutyronitrile And then polymerized by a conventional method in a mixed solvent of xylene / n-butanol = 70/30 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 water dispersion (W-1) : 140 parts of deionized water, 2.5 parts of 30% "Newcol 707SF" (surfactant, manufactured by Nippon Shokubai Co., Ltd.) (1) was added thereto, followed by stirring and mixing in a nitrogen gas stream, and 3% aqueous ammonium persulfate solution was added at 60 ° C. Next, after the temperature was raised to 80 캜, a monomer emulsion composed of 79 parts of the following monomer mixture (1), 2.5 parts of 30% Newcol 707SF, 4 parts of 3% ammonium persulfate aqueous solution and 42 parts of deionized water was metered in for 4 hours Was added to the reaction vessel using a pump. 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 were added dropwise in parallel to the reaction vessel at 80 占 폚 for 1.5 hours at the same time.

After completion of the addition, the mixture was aged for 1 hour, diluted with 30 parts of deionized water, and filtered through a 200-mesh nylon cross at 30 ° C. To this, deionized water was added again to adjust the pH to 7.5 with dimethylaminoethanol to obtain an acrylic resin water dispersion (W-1) having an average particle size of 0.1 mu m and a nonvolatile content of 20%.

The monomer mixture (1)

Methyl methacrylate 55 parts

Styrene 10 parts

N-butyl acrylate 9 parts

2-hydroxyethyl acrylate 5 parts

Methacrylic acid 1 part

The monomer mixture (2)

Methyl methacrylate 5 parts

N-butyl acrylate 7 parts

2-hydroxyethyl acrylate 5 parts

3 parts of methacrylic acid

30% Newcol 707SF 0.5 part

27% melamine resin aqueous dispersion (M-1) : A 2-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser was charged with 126 parts of melamine, 225 parts of paraformaldehyde (manufactured by Mitsui Toatsu Chemical Co., and 592 parts of n-butanol were added. The mixture was adjusted to pH 9.5 to 10.0 with a 10% aqueous sodium hydroxide solution and reacted at 80 ° C for 1 hour. Thereafter, 888 parts of n-butanol was added, the pH was adjusted to 5.5 to 6.0 with a 5% sulfuric acid solution, and the mixture was reacted at 80 DEG C for 3 hours. After completion of the reaction, the solution was neutralized to pH 7.0 to 7.5 with a 20% caustic soda aqueous solution, and n-butanol was concentrated under reduced pressure at 60 to 70 ° C and filtered to obtain a hydrophobic melamine resin. A nonvolatile matter of 80%, a solvent dilution ratio of water / methanol mixed solvent (weight ratio 35/65) of 3.6%, and a weight average molecular weight of 800.

The melamine resin was placed in a stirring container such that the solid content was 25 parts, and an aqueous acryle resin solution (50% aqueous solution of n-butyl acrylate, methyl methacrylate, styrene, 2-hydroxyethyl methacrylate and acrylic acid) And 80 parts of deionized water was gradually added thereto while stirring with a disposer having a rotation number of 1000 to 1500. Thereafter, the mixture was stirred for another 30 minutes to obtain a melamine resin water dispersion (M-1) having a moisture content of 27% and an average particle size of 0.11 mu m ).

(B-1):

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

88% Cymel 370 (note 1) 28

Pigment Component - 1 (Note 2) 30 parts

Dibutyl acid phosphate 0.3 part

The mixture was adjusted to a viscosity of 20 seconds (Ford Cup # 4/20 占 폚) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of cresol tosyl acetate and 20 parts of butyl chrysoceate to obtain a solvent- To obtain a coat (B-1). The content of the pigment of the coat (B-1) was 26.5 parts by weight per 100 parts by weight of resin solids (gaseous resin and curing agent), and the total content of metallic pigment and / or color pigment was 6.5 parts by weight per 100 parts by weight of resin solids And the light transmittance of the formed coating film was 0.1% or less at a cured film thickness of 30 탆.

(Note 1) 88% Cymel 370: 55% based on the solid content of one core of methoxylated methylol melamine, which is a product name of Mitsui Cyanamid Company, a methoxy group and a methylol group.

(Note 2) Pigment component - 1: A pigment component consisting of 10 parts of "Al paste N-1700NL" (trade name, 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 component - 2 (Note 3) 10 parts

Deionized water 171 parts

"Arc and Sol ASE-60" (Note 4) Part 3

Dimethylaminoethanol 0.3 part

The above mixture was adjusted to a viscosity of 30 seconds (deodorized water) (Ford Cup # 4/20 占 폚) to obtain an aqueous first color base coat (B-2). The content of the pigment of the coat (B-2) was 6.5 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent), and the total content of the metallic pigment and / or colored pigment was 6.5 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent) And the light transmittance of the formed coating film was 0.1% or less at a cured film thickness of 30 탆.

(Note 3) Pigment component - 2: "Al paste N-1700NL" manufactured by Toyo Aluminum Co., Ltd., aluminum content 65%.

(Note 4) ARKWOLDS ASE-60: trade name of ROOM AND HAHS, thickener.

(B-3);

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

88% Cymel 370 (note 1) 28

Pigment component - 3 (Note 5) 23 parts

Dibutyl acid phosphate 0.3 part

The mixture was adjusted to a viscosity of 20 seconds (Ford cup # 4/20 占 폚) with a mixed solvent of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of cresol soap acetate and 20 parts of butyl cresol to prepare a solvent type color base coat B - 3) was obtained. The total content of the metallic pigment and / or the color pigment was 23 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent), and 3 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent) And the light transmittance of the formed coating film was 0.1% or less at a cured film thickness of 30 탆.

(Note 5) Pigment Component - 3: A 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) 28

Pigment component - 4 (Note 6) 28 parts

Dibutyl acid phosphate 0.3 part

The mixture was adjusted to a viscosity of 20 seconds (Ford Cup # 4/20 占 폚) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of cresol soap acetate and 20 parts of butyl chrysoleate to obtain a comparative solvent- To obtain a base coat (E-1). The content of the pigment of the coat (E-1) was 28 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent), and the total content of metallic pigment and / or color pigment was 8 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent) And the light transmittance of the formed coating film was 0.1% or less at a cured film thickness of 30 탆.

(Note 6) Pigment Component - 4: A pigment component consisting of 3 parts of carbon black, 5 parts of "Infinite Color YBG-06-SK3" (Pearl pigment, product of Shiseido Co., Ltd.) and 20 parts of barium sulfate.

3) The second color base coat (C)

(C-1):

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

28% of the above 88% Cymel 370 (Note 1)

Pigment component - 5 (Note 7) 3 parts

Dibutyl acid phosphate 0.3 part

The mixture was adjusted to a viscosity of 20 seconds (Ford cup # 4/20 占 폚) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of cresol tosyl acetate and 20 parts of butyl cresol to prepare a solvent- To obtain a coat (C-1). The content of the pigment of the coat (C-1) was 2.2 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent) and the total content of metallic pigment and / or color pigment was 2.2 parts by weight per 100 parts by weight of resin solids And the light transmittance of the formed coating film was 10% or less at a cured film thickness of 30 탆.

(Note 7) Pigment Component - 5: "Al paste 891K" manufactured by Toyo Aluminum Co., Ltd., aluminum content 72%.

(C-2):

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

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

3 parts of the pigment component-5 (Note 7)

Deionized water 171 parts

&Quot; ARKWAZ ASE-60 " (Note 4), 3 parts

Dimethylaminoethanol 0.3 part

The mixture was adjusted to a viscosity of 30 seconds (Ford Cup # 4/20 캜) with deionized water to obtain an aqueous second color base coat (C-2). The pigment content of the coat (C-2) was 2.2 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent), and the total content of metallic pigment and / or color pigment was 2.2 parts by weight per 100 parts by weight of resin solids And the light transmittance of the formed coating film was 70% or less at a cured film thickness of 30 탆.

(C-3);

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

28% of the above 88% Cymel 370 (Note 1)

Pigment Component - 6 (Note 8) 1.5 parts

Dibutyl acid phosphate 0.3 part

The mixture was adjusted to a viscosity of 20 seconds (Ford cup # 4/20 占 폚) with a mixed solvent consisting of 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of cresol soap acetate and 20 parts of butyl cresol to prepare a solvent- To obtain a coat (C-3). The content of the pigment of the coat (C-3) was 1.5 parts by weight per 100 parts by weight of resin solids (gas resin and curing agent), and the total content of metallic pigment and / or color pigment was 1.5 parts by weight And the light transmittance of the formed coating film was 10% or less at a cured film thickness of 30 탆.

(Note 8) Pigment Component - 5: "Infinite Color YBG-06-SK3" (Pearl pigment, trade name, manufactured by Shiseido).

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 (?,? '- azobisisobutyronitrile) Was polymerized in xylene to obtain an acrylic resin solution having a resin solid content of 60%. The resin had a hydroxyl value of 58 and an acid value of 12. This resin and "YUBAN 20 SE" (hydrophobic melamine resin, Mitsui Toatsu Chemical Co., nonvolatile matter 60%, weight average molecular weight 3000 to 4000) were mixed in a solid weight ratio of 75:25, and an organic solvent was added to obtain a viscosity 25 (Ford Cup # 40/20 占 폚) to obtain a solvent type clear coat (D-1).

(D-2);

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

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

Deionized water 171 parts

&Quot; ARKWAZ ASE-60 " (Note 4), 3 parts

Dimethylaminoethanol 0.3 part

The mixture was adjusted to a viscosity of 30 seconds (deodorized water) (Ford Cup # 4/20 占 폚) to obtain an aqueous clearcoat (D-2).

(D-3):

The flask was charged with 40 parts of methyl methacrylate, 30 parts of n-butyl methacrylate, 30 parts of glycidyl methacrylate, 10 parts of styrene and 1 part of t-butyl peroxide (polymerization initiator) 2 parts were placed, and the mixture was heat-polymerized by suspension polymerization, and the resulting copolymer (glass transition temperature: about 60 ° C) was dried. 100 parts of the obtained copolymer, 25 parts of decamethylene carboxylic acid, and 1 part of the drawing control agent were melted and kneaded using a heating kneader at 120 DEG C for 10 minutes. Subsequently, the mixed kneaded product was cooled and pulverized using a pulverizer to obtain a powder clear coat (D-3) having a particle size of about 20 to 150 μm.

Ⅱ. Examples and Comparative Examples

Examples 1-5

The steel sheet surface-treated with "Bondelite # 3030" (zinc phosphate treatment agent manufactured by Japan Pakaraging Co., Ltd.) was immersed in a bath of cationic electrodeposition coating (A-1) and electrodeposited by a conventional method.

The coating film thickness was about 20 탆 based on the cured coating film, and the coating film was heated in a bath and heated to about 175 캜 to cure the coating film. Next, a solvent-type first color base coat (B-1) or (B-3) adjusted to a viscosity of 20 seconds (Ford Cup # 4/20 占 폚) # 4/20 占 폚) was coated with air spray so as to have a thickness of about 20 占 퐉 based on the cured coating film and allowed to stand at room temperature for about 10 minutes.

Thereafter, a solvent type second color basecoat (C-1) or (C-3) adjusted to a viscosity of 20 seconds (Ford Cup # 4/20 ° C) (C-2), which had been adjusted to have a thickness of about 30 탆, was adjusted to about 30 탆 based on the cured coating film, left at room temperature for about 10 minutes, And the mixture was heated for 30 minutes so that the coating film of the first color base coat and the coating film of the second color base coat were simultaneously crosslinked and cured.

Next, a solvent type clear coat (D-1) or a viscosity 25 seconds (Ford Cup # 4/20 ° C) adjusted to a viscosity of 25 seconds (Ford Cup # 4/20 ° C) on the cured coated surface side of the second color base coat, (D-2) adjusted to a thickness of about 40 탆 on the basis of the cured coating film by air spray or by coating the powdery clear coat (D-3) so as to have a cured coating film of 50 탆 by an electrostatic powder coating method, And allowed to stand at room temperature for about 10 minutes, followed by heating at a baking condition shown in the following Table 1 for crosslinking and curing.

Comparative Example 1

TP-37 "(trade name, product of Kansai Paint Co., Ltd.) adjusted to a viscosity of 20 seconds (Ford cup # 4/20 ° C) on the electrodeposited hard coat film surface was coated with air Sprayed, left at room temperature for about 10 minutes, and then heated at 140 占 폚 for 30 minutes.

Next, a solvent type first color base coat (B-1) adjusted to have a viscosity of 20 seconds (Ford Cup # 4/20 占 폚) was applied to the cured coating film surface of the intermediate filler paint to a thickness of about 15 占 퐉 based on the cured coating film Coated with air spray, and allowed to stand at room temperature for about 10 minutes.

Thereafter, a solvent type clear coat (D-1) adjusted to a viscosity of 25 seconds (Ford cup # 4/20 占 폚) was applied to the uncured surface of the first color base coat by air spray And allowed to stand at room temperature for about 10 minutes, followed by heating at 140 DEG C for 30 minutes to simultaneously crosslink and cure the coating films of the first and second color base coats.

Comparative Example 2

A first color base coat (C-1) of a solvent type whose viscosity was adjusted to 20 seconds (Ford Cup # 4/20 占 폚) was applied to the electrodeposited coated film surface by air spray so as to be about 18 占 퐉 based on the cured coating film, And allowed to stand at room temperature for about 10 minutes. Thereafter, a solvent type clear coat (D-1) adjusted to a viscosity of 25 seconds (Ford cup # 4/20 占 폚) was applied to the uncured surface of the second color base coat (C-1) , Left to stand at room temperature for about 10 minutes, and cured by crosslinking at 140 占 폚 for 30 minutes.

Comparative Example 3

The procedure of Example 1 was repeated except that the first color base coat (C-1) and the second color base coat (B-1) were used in Example 1, respectively.

Comparative Example 4

The same procedure as in Comparative Example 1 was carried out except that the first color base coat (E-1) was used in Comparative Example 1.

Ⅲ. Performance test results

Performance tests of the multilayer coating films obtained in the above Examples and Comparative Examples were carried out. The test results are shown in Table 1.

Test Methods

Horizontal Finishing Property: Measured using a line spirituality measuring instrument (PGD-IV type) (Japan Color Research Institute, Inc.). The larger the value, the better the linearity.

Exposure Durability: The test was carried out for 25 cycles by immersing the plate in a sunshine weather oven (light intensity 1100 K Joule / m 2 · hr) for 200 hours and then immersing it in hot water at 40 ° C for 24 hours. -5400 100 pieces of 2 mm x 2 mm were prepared in accordance with the checkered tape method of 8.5.2 and the degree of peeling of the pieces when the tape was adhered to the surface was evaluated based on the following criteria .

○: Peeling between coating layers can not be seen.

X: Partial or whole peeling can be seen between the electrodeposition coating film and the base coat coating film.

Chipping resistance : 500 g of crushed stone No. 7 was sprayed at an angle of 45 ° at -20 캜 with an air pressure of 0.3 MPa using a labeling meter (Q Panel Co., Ltd.) as a test piece, . Next, an adhesive tape was stuck to the above drawing, and the state of peeling of the coating film around the damage due to the impact after abrupt peeling thereof was examined.

○: No or almost no paint film peeling at the damage periphery.

△: Detachment of the coating film on the periphery of the damage can be clearly seen.

X: Peeling of the coating film can be remarkably observed at the periphery of the damage.

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

◎: Very good luster

○: Good glossiness

X: Slightly shiny

Intensity of interfering color : C * at 45 ° incidence and 15 ° light reception was obtained using MA-Rite MA68. The larger the value, the better the design and finish.

Flip-flop property: The alignment property of aluminum was evaluated using "Alkof" (manufactured by Tubei Paint Co., Ltd., instrument name, metal feeler). The larger the value, the better the orientation.

[Table 1]

The method of the present invention is excellent in cost effectiveness and has excellent appearance, finish, finish, anticorrosive property, weatherability, chipping resistance and the like of a coating film, It can be widely used in painting of motorcycle, electric product, and the like.

Claims (14)

A cationic electrodeposition paint is applied to a metal substrate and is heated and cured, and then a first color base coat having a background concealing property is coated and hardened, and a second color base coat having transparency is coated on the coating film And then heating to cure both the first and second color base coats and the second color basecoat, and then applying a clear paint to heat and cure the multilayered film. The method of claim 1, wherein the first color basecoat comprises a metallic pigment and / or a colored pigment. The method of claim 1, wherein the first color basecoat has a light transmittance of 5% or less at a cured film thickness of 30 m. The method of claim 1, wherein the first color basecoat has a light transmittance of 3% or less at a cured film thickness of 30 m. The method of claim 1 wherein the first color basecoat contains a pigment in the range of 1 to 250 parts by weight per 100 parts by weight of resin solids. The method according to claim 1, wherein the first color base coat is coated so as to have a cured film thickness of 5 to 60 탆. The method of claim 1, wherein the second color basecoat comprises a metallic pigment and / or a colored pigment. The method according to claim 1, wherein the second color base coat has a light transmittance in a range of 6 to 95% at a cured film thickness of 30 占 퐉. The method according to claim 1, wherein the second color base coat has a light transmittance in a range of 10 to 90% at a cured film thickness of 30 占 퐉. The method of 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 resin solids. 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 mu m. The method according to claim 1, wherein the positive coating film of the first color base coat and the coating film of the second color base coat are cured by heating at a temperature of 80 to 170 ° C. The method according to claim 1, wherein the clear coating film is water-soluble, water-dispersible, organic solvent-type or powder coating. An article painted by the method of claim 1.