WO1996033814A1

WO1996033814A1 - Method of multilayer coating

Info

Publication number: WO1996033814A1
Application number: PCT/JP1996/001119
Authority: WO
Inventors: Kyoichi Horibe; Takahisa Kasukawa; Masafumi Kume
Original assignee: Kansai Paint Co., Ltd.
Priority date: 1995-04-27
Filing date: 1996-04-25
Publication date: 1996-10-31
Also published as: EP0823289A1; DE69623949D1; EP0823289B1; CA2219303A1; DE69623949T2; KR100412963B1; KR19980703484A; EP0823289A4

Abstract

A method of multilayer coating, comprising the steps of applying a cationic electrodeposition paint to a metallic object, heating and curing the paint, applying a first color base coat for covering the metallic surface, applying a second color base coat having transparency on the first coat before it is substantially cured, heating and curing both of the first and second color base coats, applying then a clear paint, and heating and curing it. According to this method, it is possible to form a multilayer paint coat that shows improvement in appearance, design, decorativeness, corrosion proofness, weatherability, chipping resistance and other physical properties.

Description

Harm

Multilayer coating method

Technical field

INDUSTRIAL APPLICABILITY The present invention has a low coating cost, and is excellent in finish appearance, design, aesthetics, anticorrosion, weather resistance, chipping resistance, physical properties, etc. of a coating film on a metal object, particularly an automobile body. And a method for forming a reverse coating film.

Background art

Conventionally, outer panels of automobiles, motorcycles, electric appliances, etc., for which aesthetic appearance is important, are organic solvent-diluted thermosetting paints that form coatings with excellent smoothness, clarity, and weather resistance. Finish painted. In the coating process, usually, a cationic electrodeposition paint for imparting anticorrosion properties is applied, and then a middle coat paint for ensuring weather resistance and chipping resistance is applied. After heat-curing, a thermosetting paint (hereinafter referred to as “color base coat”) containing a color pigment and Z or a metallic pigment is applied as a top coat to impart aesthetics. A so-called two-coat one-bake method is often used, in which a thermosetting clear paint is applied repeatedly and then the two coatings are simultaneously heated and cured.

However, in recent years, there has been a long-awaited need for a coating process that eliminates the intermediate coating process from the viewpoint of reducing κ sources and processes, preventing pollution, and reducing the cost of coating.

Disclosure of the invention

The present inventors have found that the coating cost is low, and the finished appearance, design, aesthetics, corrosion protection, weather resistance, chipping resistance, etc. of the coating film are extremely excellent. We worked diligently to develop a coating method. As a result, it was found that the above object can be achieved without using an intermediate coating by using a cationic electrodeposition coating, two types of color base coats having different functions, and a clear coating, and completed the present invention. I got it.

According to the present invention, a cationic electrodeposition coating material (A) is applied to a metal substrate and cured by heating, and then the first color base coat ( B) is coated, and a second color base coat (C) having transparency is applied thereon without substantially curing, and then heated to heat the first color base coat (B) and the second color base coat (B). A method for forming a multi-layer paint flag is provided, which comprises curing (c) 两! FcR, applying a clear paint (D), and then heating and curing.

The feature of the present invention is that the above-mentioned color base coats (B) and (C) are used as top coats without applying a conventional 5 fc paint on the conventional general surface of cationic electrodeposition paint. The point is that it can be painted in two coats and one bake method.

According to the method of the present invention, the intermediate coating step is omitted on the surface of the baking-cured coating film of the cationic electrodeposition coating material, and the first color base coat (B) is applied even if the above coating material is directly applied. Because of the opacity of the base coat, weather-resistant peeling (the light passing through the topcoat film causes the electrodeposition paint flag to undergo photodegradation, and the electrodeposition coat and the overcoat ¾ « It was found that the occurrence of peeling between layers) never occurred. In addition, according to the method of the present invention, the intermediate coating step can be omitted, so that the advantage that the coating cost can be reduced can be obtained.

Further, in the method of the present invention, the second color base coat (C) may be colored. Because of its transparency, it is possible to finish the coating surface with excellent finish appearance such as solid feeling, smoothness, clarity, depth, high gloss, high metallic feeling, and eliminating color stickiness. There is a special mold that can be made.

Therefore, by combining the first color base coat (B) and the second color base coat (C) according to the present invention, it is possible to form a multi-layer coating film having a novel design and aesthetic properties that have never been seen before. .

Further, in the method of the present invention, since the clear paint is applied on the heat-cured color base coat film, there is an advantage that any type of clear paint such as a solvent type, an aqueous type or a powder type can be used. can get.

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

Gold coated object:

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 that can be subjected to cationic electrodeposition coating. For example, iron, copper, aluminum, tin, sub-β, etc. Alloys, and metal plating or vapor-deposited products of these metals. Specifically, there are car bodies such as passenger cars, trucks, motorcycles, and buses formed by using these gold JS members. It is preferable that these gold-coated materials are previously subjected to a chemical conversion treatment with a phosphate, a chromate or the like.

Cationic electrodeposition paint (Α):

The cationic electrodeposition paint (Α) used in the method of the present invention is a paint for directly applying to the above-mentioned gold-made JR coating object, and its type is not strictly limited, and is known per se. Various cationic electrodeposition paints can be used. Specifically, an epoxy resin modified with an amino group-containing compound, A paint containing as a main component a water-soluble or water-dispersible resin obtained by neutralizing a resin having a base ffi within the range of about 30 to about 200, such as krill resin and polybutadiene resin, with a neutralizing agent. In addition, those obtained by blending a crosslinking agent (for example, block polyisocyanate, alicyclic epoxy resin, etc.), a coloring pigment, an anti-pigment pigment, an extender pigment, a hydrophilic organic solvent, and the like as necessary. can give. Here, as the neutralizing agent, for example, organic acids such as acetic acid, hydroxy acetic acid, propionic acid, butyric acid, lactic acid, and glycine; and inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid can be used. The amount of the neutralizing agent used is suitably in the range of about 0.1 to about 0.4 of the neutralization equivalent to the * value of the above tree. The mixture 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 ρ is 5.5. To 8, preferably 5.5 to 5,000, and can be applied by an ordinary method. The coating can be cured by heating to a temperature of from about 140 to about 210, preferably from about 160 to about 190, and the coating thickness can be about 10 to about 10 based on the cured coating. It is preferably in the range of from about 60 m to about 60 m, especially from about 15 to about 40 / zm.

First color base coat (B):

The first color base coat (B) according to the present invention is a paint for applying to the cationically electrodeposited surface after being cured by heating, and has a base concealing property. The type is not strictly limited.For example, a known water-based tie or organic solvent-based thermosetting paint containing a base resin, a curing agent, a pigment, water and Z or an organic solvent is used. Can o

The base resin is made of the colored flag formed by the first color base coat (B). It is a main component, and has good weather resistance and transparency, and is suitable for a coating resin that can be dissolved or dispersed in water or an organic solvent. Examples thereof include acrylic resin, polyester resin, epoxy resin, and urethane resin. Fats and the like.

Upper acrylic resins include, for example, α, 9-ethylenically unsaturated carboxylic acid, a (meth) acrylate having a functional group such as a hydroxyl group, an amide group, or a methylol group, and other copolymers. An acid value of about 0 to about 100, preferably obtained by copolymerizing a possible monomer, for example, a (meth) acrylate ester having no tt functional group, a substituted or unsubstituted styrene, or an olefin. May be about 5 to about 30 and a hydroxyl value of about 20 to about 200, preferably about 40 to about 120.

As the polyester resin, those obtained by subjecting a polybasic acid, a polyhydric alcohol, or a denatured oil to a condensation reaction by an ordinary method can be used. As the epoxy resin, for example, an epoxy group and an unsaturated fatty acid can be used. A method of synthesizing an epoxy ester by this reaction and adding an α, -unsaturated acid to the unsaturated group, a method of adding a hydroxyl group of the epoxy ester to a polybasic acid such as phthalic acid and trimellitic acid, etc. And an esterified ester resin obtained by a method of esterification of the compound.

Examples of the urethane resin include those obtained by reacting a diisocyanate compound with the acryl resin, polyester resin, or epoxy resin to increase the molecular weight, and are mainly used as a water-dispersible resin.

When an aqueous type paint is used as the first color base coat (Β), these base resins include a sufficient amount of a hydrophilic group such as a carboxyl group, a hydroxyl group, Methylol group, Ft generally contains a carboxyl group such as an amino group, a sulfonic acid group, or a polyoxyethylene bond, and the resin is dissolved in water by neutralizing the hydrophilic group to form an alkali salt. Can be made into water or water. The amount of the hydrophilic group, for example, the carboxyl group, is not particularly limited and can be arbitrarily selected according to the degree of water-solubilization or water-saturation, but generally about 1% based on the acid value. 0 or more, preferably 10 to 100, more preferably 15 to 50. Examples of the alkaline substance used for neutralization include sodium hydroxide and various amines. Can be mentioned.

The water dispersion of the resin can also be achieved by subjecting the monomer component to emulsion polymerization in the presence of a surfactant or a water-soluble resin. Furthermore, it can also be obtained by dispersing the above resin in water in the presence of an emulsifier or the like. In this moisture deposition, the base resin may not contain the hydrophilic group at all, 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 base coat (B), the paint does not need to contain the above-mentioned base resin (hydrophilic group in the organic solvent, but may contain it). ) And other paint components can be produced by dissolving or dispersing them. As the organic solvent used at that time, those commonly used in paints can be applied. For example, hydrocarbon-based systems such as toluene, xylene, hexane, and hebutane: ethyl sulphate, butyl sulphate, Ester such as ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl acetate, etc .; Ethers such as methyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, and diethylene glycol dibutyl ether; butanol, propanol, octanol, cyclohexanol, alcohols such as diethylene glycol; methyl ethyl ketone, methyl isobutyl ketone, and cyclohexane Ketones such as xanone and isophorone are exemplified.

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

The curing agent that can be blended with the first color base coat (B) is used to three-dimensionally cross-link and cure the base resin by heating. Specifically, melamine, benzoguanamine, urinary cord and the like are combined with formaldehyde. An amino resin obtained by condensation or co-condensation and, if necessary, further etherification with a lower monohydric alcohol is preferably used. In addition, a polyisocyanate compound or a block polyisocyanate compound can also be suitably used.

The pigment which can be blended in the first color base coat (B) gives the coating film formed by the first color base coat (B) a base-coating property. Specifically, for example, aluminum powder, Metallic pigments such as bronze powder, copper powder, tin powder, lead powder, zinc powder, iron phosphide, pearl-like gold-coated mica powder, and iron oxide ferrite; zinc chromate, strontium chromate, calcium chromate, lead cyanamide , Calcium Lead Acid, Zinc Phosphate, etc .: Titanium Dioxide, Carbon Black, Phthalocyanine Blue, Phthalocyanine Green, Livazole Violet, Anthrapyridine, Azo Orange, Yellow, Flavanthrone Yellow, Isoin Colored pigments such as dry yellow, azo yellow, induthrone blue, dibromanza throne, perylene, red, anthraquinone, quinacridone, biolett, and the like; barita powder, precipitated barium sulfate, barium carbonate, gypsum, clay Examples include fillers such as silica, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, gloss white, satin white, and my powder. These pigments can be used alone or in combination of two or more.

The first color base coat (B) desirably contains, as a pigment component, a metallic pigment & Z or a color pigment among the above pigments.

The first color base coat (B) can further be provided with a dye as required. As the dye, it is desirable to use a dye having excellent light fastness and solubility in water or an organic solvent. Specific examples include a monoazo dye, a polyazo dye, a gold salt azo dye, and a virazolone azo dye. Dazos, azo dyes such as stilbene dyes and thiazole azo dyes: anthraquinone dyes such as anthraquinone conductors and anthrone conductors; indigo dyes such as indigo conductors, thioindigo conductors; phthalocyanine dyes; diphenyl methane dyes; Carbonyl dyes such as enylmethane dyes, xanthen dyes and acridin dyes; quinone imine dyes such as azine dyes, oxazine dyes and thiazine dyes; methine dyes such as polymethine (or cyanine) dyes and azimethine dyes; Dye; Nitro dye; Tron dyes; benzoquinone and naphthoquinone dyes: naphthalimid dyes; perinone dyes and the like, and one or more selected from these can be used. The ratio of each of the above components in the first color base coat (B) is not strictly limited, and can be selected depending on the purpose and the like. However, the base resin and the curing agent are generally Based on the total weight of the two components, the former is preferably in the range of 60 to 90% by weight, the expected 70 to 85% by weight, and the latter in the range of 40 to 10% by weight, particularly 30 to 15% by weight. .

The pigment can be mixed in an appropriate combination depending on the gap concealing property of the base, the desired color, and the like, and the amount of the pigment is 30 m in the film thickness formed using the first color base coat. An appropriate amount is such that the light transmittance of the cured coating film in the wavelength range of 400 to 700 nm is generally 5% or less, preferably 3% or less. The specific amount depends on the type of pigment and cannot be specified unconditionally, but is usually 1 to 250 parts by weight, preferably 5 to 250 parts by weight, per 100 parts by weight of resin solids (total weight of base resin and curing agent). It can be in the range of ~ 150 parts by weight.

In addition, the light transmittance of the coating flag in the present specification is determined by applying the coating on a glass plate so that the thickness of the coating film after curing becomes a predetermined film thickness, curing the coating, and then heating the coating in warm water at 60 to 70. The coating film obtained by immersion, peeling off the coating, and drying was used as a sample, and a range of 400 to 700 nm was measured using a self-recording spectrophotometer (Hitachi, Ltd., £ 3-3 type). This is the average spectral transmittance when measured at a wavelength of.

The coating of the first color base coat (B) can be carried out according to a usual method, and the paint is added with, for example, deionized water and Z or an organic solvent, and if necessary, additives such as a thickener and an antifoaming agent. The solid content is 10 to 70 weight%, preferably about 15 to 55 weight%, and the viscosity is 10 to 60 seconds, especially 12 to 30 seconds (for Ford Cup # 4-20) in the case of solvent type paint, Soshi In the case of water-soluble or water-dispersible paints, after preparing silk to 200-5000 cp sZ6 rpm, especially 300-3000 cp sZ6 rpm (B-type viscometer), the cationic electrodeposition paint (A) Can be applied by spray coating or the like to a cured film thickness of, for example, about 5 to 60 m, preferably about 8 to 25 m. In the method of the present invention, after the first color base coat (B) is applied, the coating film is air-dried at room temperature by air blow or the like without substantially curing the coating film, and then the following second color base coat (C) is applied. Is preferably applied.

Second color base coat (C):

The color base coat (C) according to the present invention is a paint for applying to the coated surface of the first color base coat (B), and is a transparent paint. The type is not strictly limited, and use a known aqueous type or organic solvent-based thermosetting paint containing a base resin, a curing agent, a pigment, water and Z or an organic solvent. be able to.

Any of these coating components can be used by selecting from those described for the first color base coat (B).

A dye may be added to the second color base coat (C), if necessary. As the dye, one or more of the dyes described in the first color base coat (B) may be used. It can be used in treatment.

The ratio of each component in the second color base coat (C) is not strictly limited, and can be arbitrarily selected according to the purpose. However, the base resin and the curing agent generally include the total weight of both components. The former is 60-90% by weight, especially 70-85% by weight, the latter is 40-10% by weight, especially 30 Preferably, it is within the range of ~ 15% by weight.

The second color base coat (C) preferably contains a metallic pigment and / or a coloring pigment as a pigment component. The total content of the pigments is such that the second color base coat (C) has transparency. However, it is desirable that the amount is relatively small such that the color of the first color base coat can be recognized through the coating film, and is usually smaller than the total content of the pigments in the first color base coat (B). Is preferred.

Specifically, the light transmittance of a cured film having a film thickness of 30 i / m formed by the second color base coat (C) in the wavelength range of 400 to 200 nm is 6 to 95%, particularly 10 to 90%. It is desirable to mix the pigment in an amount such that it falls within the range of 20% to 80%, and more particularly, the amount varies depending on the type of pigment and cannot be specified unconditionally. The total amount of pigment per 100 parts by weight of the pigment is 0.01 to 100 parts by weight, especially 0.1 to 80 parts by weight. ) Is preferably lower than their content.

The application of the second color base coat (C) can be carried out according to a usual method, for example, adding deionized water and / or an organic solvent to the paint and, if necessary, further additives such as a thickener and an antifoaming agent. In addition, the solid content is 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 in the case of a solvent type coating (Ford cup # 4 / 20) and, in the case of water-soluble or water-soluble paints, after 200 to 50000086 (111, preferably 300 to 30000 3 6 rpm (B-type viscometer)). 70 m, especially 1 It can be applied by spray coating or the like so as to have a cured film thickness of about 5 to 50 / zm. As described above, in the method of the present invention, after coating the first color base coat (B), the coating film is air-dried at room temperature by air blow or the like without substantially curing the coating film, and then the second color base coat (B) is dried. It is preferable to apply the base coat (C). After painting, by heating at a temperature of about 80 to about 170, preferably about 120 to about 160, for about 3 to about 40 minutes, preferably about 10 to about 30 minutes, The first color base coat (B) and the second color base coat (C) can be cured simultaneously. As a heating method, a commonly used method, for example, hot air heating, infrared heating, high frequency heating, or the like can be used.

Clear paint (D):

According to the present invention, the second color base coat (C) is used in order to further improve the aesthetic makeup, finished appearance, weather resistance, chemical resistance, water resistance, moisture resistance, etc. of the formed multilayer coating film. Clear paint (D) can be applied to the painted surface. The clear paint (D) forms a colorless or colored transparent coating film, specifically, comprises a base resin and a curing agent as main components, and further includes a coloring pigment and a metallic pigment as required. Use a well-cured, water-soluble or water-dispersible paint, organic solvent-based paint or powder paint known per se, which contains a dye, etc., to such an extent that the transparency of the formed coating film is not substantially impaired. be able to.

Among the above paints, the base resin and curing agent that can be used for water-soluble or water-dispersible paints and organic solvent-based paints, and the tangible solvents that can be used for organic solvent-based paints, are described in the first color base coat (B). You can use the one selected from those you did. Also, the ratio of the base resin to the curing agent It is preferably within the range described in the first color base coat.

Water-soluble or water-dispersible clear coatings and organic solvent-based clear coatings are prepared according to the usual methods, using deionized water and / or organic solvents and, if necessary, additives such as thickeners and defoamers. The solid content is 10 to 95% by weight, preferably about 30 to 80% by weight, and the viscosity is 10 to 70 seconds in the case of a solvent type paint, preferably 15 to 40 seconds (Ford cup # 4Z 20V In the case of water-soluble or water-soluble paints, after adjusting to 200 to 5000 cps / 6 rpm, preferably 300 to 3000 cp sZ6 rpm (B-type viscometer), for example, 10 to 70 #m, especially It can be applied by spray coating so as to obtain a cured film thickness of about 15 to 50 jum, etc. The applied coating film is applied at a temperature of about 80 to about 170, preferably about 120 to about 160. It can be cured by heating for about 20 to about 40 minutes. For example, hot air heating, infrared heating, high frequency heating, and the like can be used.

On the other hand, the powder coating which can be used as the clear coating (D) is mainly composed of a base resin and a hardener. The base resin is selected from, for example, a hydroxyl group, a carboxyl group and a glycidyl group. Examples include acrylic resins, polyester resins, fluororesins, polyurethane resins, and modified products thereof (for example, a graft polymer) having at least one kind of crosslinking functional group, but these are merely examples. Yes, but not limited to these. The base resin preferably has a glass transition temperature of generally 4 O! Or more, particularly 50 to 120, and more preferably 60 to 100.The composition and the molecular weight are not particularly limited, and are suitable for the purpose. It can be arbitrarily chosen accordingly. The curing agent is a component for three-dimensionally cross-curing the base resin by heating, for example, an alkoxymethylol melamine, a block poly isocyanate compound, an epoxy compound, an isocyanurate compound, and an aliphatic dibasic acid. Can be used.

Most preferably, the ratio of the base resin to the curing agent is such that the molar ratio of the functional groups in the base resin to the functional groups in the curing agent is substantially equimolar.

The powder coating may further contain paint additives such as flow regulators, ultraviolet absorbers, and light stabilizers as needed.

The powder coating can be usually obtained by melt-kneading the above components, cooling, and pulverizing to an appropriate particle size.

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

The coating thickness of the powder coating is not particularly limited, but is generally in the range of 20 to 200 m.In particular, the smoothness, clarity, In order to improve the gloss, the feeling of holding, and the like, it is preferable to apply the coating to a thickness of 20 to 120. Further, the curing temperature of the coating film of the powder coating is a curing temperature of the powder coating, for example, a temperature in a range of about 120 to about 180, preferably about 130 to about 170. can do.

Example

Hereinafter, the present invention will be described more specifically with reference to examples. Hereinafter, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

I. Sample preparation

1) Cationic electrodeposition paint (A) (A-1): Elecron # 9200 (manufactured by Kansai Paint Co., Ltd., trade name, polyamine-modified epoxy resin, block borosilicate) is removed so that the solid content concentration becomes about 16% by weight. Dilute with ionized water, etc., and keep the pH within the range of 5.5 to 8.0 by electrodeposition coating in the usual way. The coating thickness was about 20 jwm based on the cured coating, and the coating was heated to about 175 to cure the coating.

2) First color base coat (B)

50% acrylyl resin solution (S-1): 30 parts of methyl methacrylate, 59 parts of ethyl acrylate, 10 parts of hydroxyxethyl acrylate and 1 part of acrylic acid Polymerization was carried out using azobisisobutyronitrile in a mixed solvent of xylene Ζη-butanol = 7030 by an ordinary method, and an acrylyl resin solution (S—) with a weight average molecular weight of 25,000 and a resin solid content of 50% (S— 1) was obtained.

20% Acrylic resin aqueous dispersion (W-1): Deionized water 140%, 30% "Newco 1 707 S FJ (surfactant, Nippon Emulsifier Co., Ltd.)" One part of the following monomer mixture (1) was added, and the mixture was stirred and mixed in a stream of nitrogen gas, and 3 parts of a 3% aqueous solution of ammonium persulfate was added at 60. Then, after raising the temperature to 80, the following Monomer mixture of (1) 79%, 30% “Newcol 707SFJ 2.5 parts, 4 parts of 3% ammonium persulfate aqueous solution and 42 parts of deionized water Quantify monomer emulsion over 4 hours The mixture was added to the reaction vessel using a pump, and the mixture was aged for 1 hour after the addition was completed.At 80, 20.5 parts of the lower monomer mixture (2) and 4 parts of a 3% aqueous solution of ammonium persulfate were simultaneously added. 1. Drops were added in parallel to the reaction vessel over 5 hours After the addition was completed, the mixture was aged for 1 hour and deionized water with 30 parts. Diluted and weighed with a 200 mesh nylon cloth at 30 [M. To this, further add deionized water, adjust the pH to 7.5 with dimethylaminoethanol, and separate an acrylonitrile-water solution (W—) with an average particle size of 0.1 Xim and a non-volatile content of 20%. 1) was obtained.

Monomer mixture (1)

Methyl methacrylate 55 parts

Styrene 10 parts

N-butyl acrylate 9 parts

Acrylic acid 2—Hydroxityl 5 parts

Methacrylic acid 1 part

Monomer mixture (2)

Methyl methacrylate 5 parts

N-Butyl acrylate 7 parts

Acrylic acid 2—Hydroxityl 5 parts

Methacrylic acid 3 parts

30% Newcol 707 S FJ 0.5 part 27% melamine resin aqueous dispersion (M-1) Melamine resin in 2-liter four-necked flask equipped with thermometer, stirrer and reflux condenser Add 126 parts, 80% paraformaldehyde (Mitsui Toatsu Chemicals) 225 parts, n-butanol 592, add 10% aqueous sodium hydroxide solution and adjust the pH to 9.5 to 10.0. The reaction was carried out for 1 hour at 80. 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 reaction was carried out at 80 for 3 hours. , Neutralized to pH 7.0-7.5 with 20% aqueous caustic soda, decompressed n-butanol at 60-70 After concentration, the mixture was filtered to obtain a hydrophobic melamine resin. Non-volatile content 80%, solvent dilution ratio of water / methanol mixed solvent (weight ratio 35Z65) 3.6%, weight average molecular weight 800.

This melamine resin is placed in a stirring vessel so as to have a solid content of 25 parts, and an aqueous acrylic resin solution (consisting of n-butyl acrylate, methyl methacrylate, styrene, 2-hydroxyhexyl methacrylate, and acrylic acid) is used. 20% aqueous solution of fatty acid), and gradually add 80 parts of deionized water while stirring with a 1000-1500 rpm disperser, and then stir for another 30 minutes to obtain water-dispersed solids. 2796, an aqueous dispersion of melamin-fat (M-1) having an average particle diameter of 0.11 iim was obtained.

(B-1):

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

88% Cymel 370 (Note 1) 28 copies

Pigment component 1 (Note 2) 30 parts

Dibutyl Acid Phosphate: 0.3 parts L-Lot The above mixture was mixed with 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of sorbose acetate and 20 parts of butylseparate with 20 parts of viscosity (Ford cup # In step S20, the solvent-based first color base 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 resin solids (base resin and curing agent), and the total content of metallic pigment and Z or coloring pigment is resin solids. (Base resin and curing agent) The amount was 6.5 parts by weight per 100 parts by weight, and the light transmittance of the formed coating was 0.1% or less at a cured film thickness of 30.

(Note 1) 88% Cymel 370: Trade name, product of Mitsui Cyanamid Contains 55% of a mononuclear methoxylated methylolmelamine composed of both xyl groups and methylol groups, based on the solid content.

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

(B-2):

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

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

Pigment component 1 (Note 3) 10 parts

Deionized water 171 parts

“Axazole ASE-60” (Note 4) 3 copies

Dimethylaminoethanol 0.3 part The above mixture was adjusted with deionized water to a viscosity of 30 seconds (Ford Cup # 420) 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 resin solids (base resin and curing agent), and the total content of metallic pigment and Z or coloring pigment is resin. Solid content (base resin and curing agent) 6.5 parts by weight per 100 parts by weight. The light transmittance of the formed coating film was 0.1% or less at a cured film thickness of 30 m.

(Note 3) Pigment 1-2: Trade name "Alpaste N-1700NL", manufactured by Toyo Aluminum Co., Ltd., aluminum content 65%.

(Note 4) Axazole AS E-60: Trade name, manufactured by Rohm and Haas Co., Ltd.

(B-3): 150 parts of 50% acryl resin solution (S-1)

88% Cymel 370 (Note 1) 28 copies

Pigment component 1 (Note 5) 23 parts

0.3 parts of dibutyl acid phosphate The above mixture is mixed with 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of sorbose acetate and 20 parts of butylseparate with a viscosity of 20 seconds (Ford cup # 4Ζ20 ^) The solvent-based color base coat (III-3) was obtained. The pigment content of the coat (III-3) is 23 parts by weight per 100 parts by weight of resin solids (base resin and curing agent), and the total content of metallic pigments and / or color pigments is resin solids (base resin and resin). The curing agent was 3 parts by weight per 100 parts by weight, and the light transmittance of the formed coating film was 0.1% or less at a cured film thickness of 30 jt / m.

(Note 5) Pigment component 1: 3 parts of carbon black and barium sulfate 2

A pigment component consisting of 0 parts.

(E-1) (for comparison):

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

88% Cymel 370 (Note 1) 28 copies

Pigment ingredient 1 4 (Note 6) 28 parts

0.3 parts of dibutyl acid phosphate The above mixture is mixed with 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of sorbose acetate and 20 parts of butylseparate with a solvent of 20 seconds (Ford cup # 4/20 The solvent-based color base coat (E-1) for comparison was obtained. The pigment content of the coat (E-1) is 28% per 100 parts by weight of resin solids (base resin and curing agent). Parts, the total content of metallic pigment and z or coloring pigment is 8 parts by weight per 100 parts by weight of resin solids (base resin and curing agent), and the light transmittance of the formed coating film is 30 m at the cured film thickness. It was less than 0.1%.

(Note 6) Pigment component 1: 4: A pigment component consisting of 3 parts of carbon black, 5 parts of "Infinite Color YBG-06-SK3" (Pearl pigment, manufactured by Iseido Co., Ltd.) and 20 parts of barium sulfate.

3) 2nd color base coat (C)

(C-1):

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

88% Cymel 370 (Note 1) 28 parts

Pigment component 1 5 (Note 7) 3 parts

0.3 parts of dibutyl acid phosphate The above mixture is mixed with 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of sorbose acetate and 20 parts of butylseparate with a viscosity of 20 seconds (with a Ford cup # 4Z20). Then, a solvent type second color base coat (C-1) was obtained. The pigment content of the coat (C-11) is 2.2 parts by weight per 100 parts by weight of resin solids (base resin and curing agent), and the total content of metallic pigments and dyes or color pigments is resin solids (substrate (Resin and curing agent) It was 2.2 parts by weight per 100 parts by weight, and the light transmittance of the formed coating was 10% at a cured thickness of 30 m.

(Note 7) Pigment component 1 5: Trade name “Alpaste 891 K”, manufactured by Toyo Aluminum Co., Ltd., aluminum content 72%.

(C-1 2):

325 parts of the above 20% acrylyl spore water-purifying liquid (W-1) 131 parts of the 27% aqueous melamine resin dispersion (M-1)

Pigment component 1 5 (Note 7) 3 parts

Deionized water 171 parts

“Axazole ASE-60J (Note 4) 3 parts

The mixture of 0.3 parts of dimethylaminoethanol was adjusted with deionized water to a viscosity of 30 seconds (Ford cup # 4 Z20 V) to obtain an aqueous second color base coat (C-12). The pigment content of the coat (C-12) is 2.2 parts by weight per 100 parts by weight of resin solids (base resin and curing agent), the total content of metallic pigments and Z or coloring additives. Was 2.2 parts by weight per 100 parts by weight of resin solids (base resin and curing agent), and the light transmittance of the formed coating film was 70% at a cured film thickness of 30 / m. _C (C-3):

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

88% Cymel 370 (Note 1) 28 parts

Pigment component 1 (Note 8) 1.5 parts Dibutyl acid phosphate 0.3 part The above mixture is mixed with 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of sorbose acetate, and 20 parts of butylseparate solvent. The viscosity was adjusted to 20 seconds (with a Ford cup # 4Z20) to obtain a solvent-based second color base coat (C-13). The pigment content of the coat (C-13) is 1.5 parts by weight per 100 parts by weight of resin solids (base resin and curing agent), and the total content of metallic pigment and / or coloring pigment is resin solids (base resin (Fat and curing agent) was 1.5 parts by weight per 100 parts by weight, and the light transmittance of the formed coating film was 10% at a cured thickness of 30 xm. (Note 8) Pigment component-5: infinite Color YBG-06-SK3J (pearl pigment, manufactured by Takaseido Co., Ltd., trade 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-hydroxyshethyl acrylate and 1.5 parts of acrylic acid and a polymerization initiator (α, —azobisisobutyronitrile) 2. Polymerization was performed in xylene using 5 parts 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 “Uban 20S EJ (hydrophobic melamine resin, manufactured by Mitsui Toatsu Chemicals, non-volatile content 60%, weight average molecular weight 3000-4000)” are adjusted so that the solid content weight ratio is 75:25. After mixing, an organic solvent was added and the viscosity was adjusted to 25 seconds (Ford cup # 4 フォード 20 ^) to obtain a solvent-type clear coat (D-1).

(D-2):

Previous Ε20% acrylyl fat and water solution (W-1) 325 parts

Previous27% aqueous dispersion of melamine resin (Μ-1) 131 parts

Ionized water 171 parts

Previous Ε “Axazole ASE—60J (Note 4) 3 copies

Dimethylaminoethanol 0.3 part The above mixture was adjusted with deionized water to a viscosity of 30 seconds (using a Ford cup # 4-20) to obtain an aqueous clear coat (D-2).

(D-3):

40 parts of methyl methacrylate in a flask, η-butyl methacrylate 30 parts of glycidyl methacrylate, 30 parts of styrene, 10 parts of styrene and 1 part of t-butyl peroxide (polymerization initiator), 2 parts of potassium oleate (surfactant) The obtained copolymer (glass transition temperature: about 60) was dried and sooted. 100 parts of the obtained copolymer, 25 parts of decamethylenedicarboxylic acid, and 1 part of the coating surface conditioner were melt-mixed at 120 at 10 minutes using a heating kneader. Then, after cooling the mixed building, it was pulverized using a pulverizer to obtain a powder clear coat (D-3) having a particle size of about 20 to 150 m.

I I. Examples and Comparative Examples

Examples 1 to 5

A steel sheet surface-treated with “Bondelight # 3030” (a zinc phosphate treating agent manufactured by Nippon Parkerizing Co., Ltd.) was dipped in a bath of cationic S-coating paint (A-1) and electrodeposited by a conventional method. The thickness of the coating was about 20 #m based on the cured coating. The coating was pulled out of the bath, washed with water, and heated to about 175 to harden the coating. Next, the solvent-borne first color base coat (B-1) or (B-3) adjusted to a viscosity of 20 seconds (Ford Cub # 4Z20) or a viscosity of 30 seconds (Ford Cup) The water-based first color base coat (B-2) prepared in Step # 420 was applied by air spray to a thickness of about 20 jum based on the cured coating film, and left at room temperature for about 10 minutes.

After that, the uncured coating surface of the first color base coat has a viscosity of 20 seconds (with Ford Cup # 4-20) »A solvent-based second color base coat (C-11) or (C-13) or a viscosity of 30 seconds ( Ford Cup # 4/2 0V) »Fixed aqueous second color base coat (C-1 2) as cured coating Paint at about 30 jt / m by air spray, leave at room temperature for about 10 minutes, and heat at 140 for 30 minutes to simultaneously crosslink the first color base coat and second color base coat. Cured c Then, apply a solvent-type clear coat (D-1) with a viscosity of 25 seconds (Ford Cup # 4/20) or a viscosity of 25 seconds (Ford Cup # 4Z20) on the cured coating surface of the second color base coat. The water-based clear coat (D-2) adjusted to the above is applied by air spray so as to be about 40 m based on the cured coating, or the powder clear coat (D-3) is applied by electrostatic powder coating. The coating was applied to a cured film thickness of 50 by the method, allowed to stand at room temperature for about 10 minutes, and then heated and cured under the baking conditions shown in Table 1 below.

Comparative Example 1

Based on the cured coating film, apply the solvent-based intermediate coating ΓΤΡ-37 ”(manufactured by Kansai Paint Co., Ltd.) with a viscosity of 20 seconds (Ford Cup # 4 20) to the surface of the cured coating film. Coating was performed by air spray to 30 / m, left at room temperature for about 10 minutes, and then heated at 140 for 30 minutes.

Next, a solvent type first color base coat (B-1) adjusted to a viscosity of 20 seconds (Ford Cup # 420) is applied to the cured coating surface of the intermediate coating paint to about 15 m based on the cured coating film. And then left at room temperature for about 10 minutes.

Then, apply a solvent-type clear coat (D-1) with a viscosity of 25 seconds (with Ford cup # 420) to the uncured coating surface of the first color base coat so that it becomes approximately 40 m based on the cured coating film. Paint by air spray, leave it at room temperature for about 10 minutes, then heat it at 140 for 30 minutes. The color base coat and the second color base coat were simultaneously cured by crosslinking.

Comparative Example 2

Apply the solvent-type first color base coat (C-11), which has been adjusted to a viscosity of 20 seconds (Ford cup # 4Ζ20 ^), on the surface of the electrodeposited cured coating film to a thickness of about 18 // m based on the cured coating film. Was painted by air spray and left at room temperature for about 10 minutes. Then, a solvent-type clear coat (D-1) adjusted to a viscosity of 25 seconds (Ford Cup # 4Z20) was applied to the uncured coated surface of the second color base coat (C-1) to about 40 m based on the cured coating film. It was painted by air spray, left at room temperature for about 10 minutes, and then heated at 14 V for 30 minutes to cure it.

Comparative Example 3

Example 1 was carried out in the same manner as in Example 1 except that (C-1) was used as the first color base coat and (B-1) was used as the second color base coat.

Comparative Example 4

Comparative Example 1 was performed in the same manner as Comparative Example 1 except that (E-1) was used as the first color base coat.

I I I, Performance test results

A performance test was performed on the multilayer coating films obtained in the above Examples and Comparative Examples. Table 1 shows the test results.

Test method

Horizontal finish: Measured using a PGD-IV meter (available from Nippon Color Research Laboratory). The higher the value, the better the image quality means.

Violence g Durability: This test was conducted by immersing the coated board in a warm water for 24 hours at 40 after accelerated exposure for 200 hours with a sunshine analyzer (light intensity 1100K J 0 u 1 e / m ² · hr). Perform 25 cycles of the test, and then create 100 mm 2 squares of 2 mm x 2 mm according to the JISK-5400 8.5.2. The degree of peeling of the eyes was evaluated according to the following criteria.

〇: No peeling between lacquer layers was observed.

X: Partial or complete peeling is observed between the electrodeposition coating film and the base coat coating film.

Chipping resistance: Using a grabber mouth meter (manufactured by Q Panel Co., Ltd.) as a tester, spray 500 g of No. 7 crushed stone at an angle of 45 'with respect to the coating surface and at an air pressure of 0.3 MPa at 120. To impact the coating. Then, an adhesive tape was stuck to the coated surface, and after the tape was rapidly peeled off, the peeling state of the coating film around the scratches caused by the impact was flipped.

〇: No or almost no peeling of the coating film around the wound,

Δ: The peeling of the coating film is clearly seen around the wound,

: Remarkable peeling of the coating film around the wound.

Brightness: The coated plate was visually evaluated according to the following criteria.

：: extremely good luster,

〇: Good glitter,

X: Inferior luster.

Length of interference color: X-Rite MA 68, 45. C * at incident and 15 ° light reception was determined. The higher the value, the better the design and aesthetics Means that. Flip-flop property: The orientation of aluminum was evaluated using “Alcorp” (manufactured by Kansai Paint Co., Ltd., equipment name, metallic feel measurement device). The higher the value, the better the orientation of aluminum.

table 1

¾ m Comparison m

1 2 3 4 5 1 2 3 4 Name A-1A-1A-1A-1A-1A-1A-1A-1A-1 Electrodeposition coating conditions (Note) ① ① ① ① ① Φ ① ① ① 囊 Thickness (20 20 20 20 20 20 20 20 20 Coating Paint name 1-1 1-1-TP-37 1 1 TP-37 Middle coat baking conditions (Note) 1 1-1 2-- ② Thickening (μ) ― 1 ― 1 ― 30 1 1 30 1st color Paint name B-1 B-2 B-3 B-1 B-1 B-1 C-1 E-1

I Base coat Baking conditions (Note) None None None None None None None None None

(Β) Thickness t 15 15 1 5 15 15 15 1 15 15 2nd color Paint name C- 1 C- 2 C-3 C-1 C-1 C-1 B-1-Top coat Base coat Baking conditions (Note) ② ② ② ② ② One None ② One

(C) Thickness (/) 30 30 30 30 30 one 30 30 one

Paint name D-1D-1D-1D-2D-3D-1D-1D-1D-1 Clear paint baking conditions (Note) ② ② ② ② ③ ② ② ② ②

(D) 囊 Thickness (//) 40 40 40 40 50 40 40 40 40 Horizontal »Finishability 1.0 ≤ 1.0 ≤ 1.0 ≤ 1.0 ≤ 1.0 ≤ 0.8.0.6.0.6.0.7 0.8 ftff durability 〇〇〇〇〇〇 X 〇チ Anti-chipping property 〇〇〇〇〇 △ X m △ ft Glitter ◎ ◎ ◎ © © 〇 Δ O △ Dry color 70 50 Flip fob 1.1.7.8 1 . 8 1. 8 1. 5 1. 3 1. 5

(Note) 烧 Conditions: ① 175 x 20 minutes, ② 140 x 30 minutes, ③ 160 x 30 minutes <

Industrial applicability

The method of the present invention has a low coating cost, and is extremely excellent in the finished appearance, design, aesthetics, anticorrosion, weather resistance, chipping resistance, etc. of the coating film, and is advantageous in terms of saving resources and pollution control. This method can be widely used in painting automobiles, motorcycles, and electric products.

Claims

The scope of the claims

1. After applying a cationic electrodeposition paint on a metal substrate and curing by heating, a first color base coat having a base concealing property is applied on the electrodeposition coated surface, without substantially curing, After applying a transparent second color base coat on the coating, heating is performed to cure both the first color base coat and the second color base coat, and then a clear paint is applied and heated. A method for forming a multilayer coating film, characterized by the following.

2. The method according to claim 1, wherein the first color base coat contains a metallic pigment and a colorless or colored pigment.

3. The method according to claim 1, wherein the first color base coat has a light transmittance of 5% or less at a cured film thickness of 30 m.

4. The method of claim 1 wherein the first color base coat has a glow factor of 3% or less at a cured flag thickness of 30 / m.

5. The method of claim 1 wherein the first color basecoat contains a pigment in the range of 1-250 weight parts per 100 parts by weight of resin solids.

6. The method according to claim 1, wherein the first color base coat is applied to a cured film thickness of 5 to 60 μπι.

7. The method according to claim 1, wherein the second color base coat contains a metallic pigment and / or a color pigment.

8. The method of claim 1 wherein the second color basecoat has a light transmittance in the range of 6-95% at a cured thickness of 30 m.

9. The method of claim 1 wherein the second color basecoat has a light transmittance in the range of 10 to 90% at a cured belly thickness of 30 #m.

100. The second color base coat has a resin solid content of 100 parts by weight. The method of claim 1 wherein the pigment contains pigment in the range of from 01 to 100 parts by weight.

11. The method of claim 1, wherein the second color basecoat is applied to a cured film thickness in the range of 10-70 jum.

12. Range of purchase where the coating flag of both the first color base coat and the second color base coat is cured by heating to a temperature of 80 to 170.

13. The method according to claim 1, wherein the clear paint is a water-soluble, water-dispersible, organic solvent-type or powder paint.

14. Articles coated by the method of claim 1.