JP2002339099A - Method for forming coarted film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a layered coarted film having excellent finish characteristics, painting workability, corrosion resistance and chipping resistance in the case of forming the coated film on an automobile body. SOLUTION: This method for forming the coarted film has the following steps: step 1 for applying cation electrodeposition coating (1) having a paint color of chromatic color or white on a member having a bag structure such as an automobile body; step 2 for rinsing the coated member in water and drying; step 3 for applying cation electrodeposition coating (2) on the coated member; step 4 for rinsing the double-coated member in water and drying; step 5 for applying a top coat which consists of three layers of a colored base coat (A), a metallic base coat (B) and a clear coat (C) and a paint color of chromatic color having a color tone of the same type by Munsell hue, as that of the paint color of the coated film (1) or white; and step 6 for baking the coated films obtained in the steps 1 to 5 at a once to cure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a coating film, and applies two kinds of cationic electrodeposition coatings having different functions to an object having a bag, such as an automobile body and an automobile part, by two coats and two bake. After that, in the method of forming a coating film in which a top coating material is applied again, the coating color of the first cationic electrodeposition coating film (outer plate surface) is changed to a three-layer top coating film to be coated thereon, It is assumed that the hue in the display is a similar chromatic color or white. The present invention relates to a coating film forming method for improving the finish of the outer plate surface and improving the anticorrosion property of the inner plate surface (bag portion) by the second cationic electrodeposition coating film.

[0002]

2. Description of the Related Art Conventionally, as a method of coating an object having a bag portion such as an automobile body or an automobile part with a coating film, a coating color of gray or black is applied to a cationic electrodeposition coating, and then an intermediate coating is applied. Painting and overcoating are performed.

[0003] On the other hand, in order to reduce the cost of the body and the types of vehicles produced in the Asian region, in consideration of cost, the intermediate coating paint and the intermediate coating without the intermediate coating process are omitted, and rust-proof steel sheets such as galvanized are used. In many cases, it is manufactured from a cold-rolled steel sheet whose main component is iron without using steel.

[0004] Therefore, the weather resistance of the outer plate surface, the finish,
Functions such as throwing power and anticorrosion properties of the inner plate surface (bag portion) are required for a cationic electrodeposition paint which is an undercoat paint of a vehicle body.

Therefore, in order to fully satisfy the function,
Satisfactory results cannot be obtained by simply applying one type of electrodeposition paint, and an electrodeposition coating method of applying two types of electrodeposition coatings having different functions (hereinafter sometimes abbreviated as "double-coat electrodeposition coating"). ), JP-A-3-223496 and JP-A-6-296.
Japanese Patent Application Laid-Open No. 57-496 and Japanese Unexamined Patent Application Publication No. 12-239576 as a coating method for performing two coats and two baking.

For example, when the intermediate coating is omitted, the top coating is performed directly on the cationic electrodeposition coating film.
There is an increasing demand for "high whiteness glossiness" in the range of N9.5, preferably closer to N10 which is pure white, and "high sharpness" at 60 degrees glossiness. As countermeasures against this, it is conceivable to lower the pigment concentration in order to improve the flowability of the overcoat film, or to increase the finish thickness by increasing the coating film thickness.

For example, a large amount of titanium white having a low hiding power is used as a coloring pigment for the white of the topcoat paint. However, in response to the demand for "high whiteness glossiness", the pigment concentration is reduced for the purpose of improving the heat flow property. There is a limit to the amount of the pigment to be reduced in consideration of hiding.

Further, when the thickness of the coating film is increased, the cost increases and the finish is deteriorated due to sagging of the top coating film on the vertical surface of the object to be coated (for example, under a press line of a door part or around a keyhole). I do.

When the top coating is blue, a small amount of a pigment having a high hiding power, such as carbon black, is added in order to ensure the hiding power of the base. There have been problems such as a decrease in the lightness and chroma of the coating film, and concealment properties can be obtained only in a limited color gamut.

[0010] In addition, in order to obtain a base hiding property and a desired hue, it is conceivable to increase the pigment concentration of the overcoat paint. However, since the coating film becomes hard, the physical properties of the coating film such as chipping resistance are reduced. In addition, there was a decrease in finishability due to suppression of heat flow.

[0011]

Means for Solving the Problems Therefore, the present inventors have
The result of intensive studies to solve the above problems. After the double-coat electrodeposition coating, the first, preferably the second, cation electrodeposition coating color is set to a chromatic or white color, and the top coating color to be applied on the first, preferably the second, cation electrodeposition coating color. Thus, the problem was solved by making the colors similar to the Munsell display hue, and the invention was completed.

That is, the present invention provides: The following steps, Step 1: For an object having a bag structure such as an automobile body,
A step of applying a cationic electrodeposition paint (1) having a chromatic or white coating color to form a coating film, and step 2: washing an object to be coated with water and removing an excessively adhered cationic electrodeposition paint (1). After the removal, a step of curing and drying the obtained coating film; Step 3: a step of applying a cationic electrodeposition paint (2) to the object to be coated obtained in the above step to form a coating film; Step 4 : A step of washing the object to be coated with water to remove excess cationic electrodeposition paint (2), and then curing and drying the obtained coating; Step 5: coating of the cationic electrodeposition coating (1) In the step of applying a chromatic color similar to the paint color and the hue of the Munsell display or a white top coat, the top coat is composed of a colored base coat (A), a metallic base coat (B), and a clear coat (C). A step of applying a top coat comprising a layer, step 6: obtained in steps 1 to 5 A coating film forming method of curing dry baked film at the same time, the features, 2. 2. The method for forming a coating film according to item 1, wherein the step of applying the top coat paint is performed by sequentially applying the colored base coat (A), the metallic base coat (B), and the clear coat (C) without curing. In the step 5, the coloring base coat (A),
After the metallic base coat (B) is applied, the two coats are cured, and the clear coat (C) is applied. In step 5 of Section 4.1, the colored base coat (A) is applied. After curing and drying, metallic base coat (B)
Coating and curing and drying to apply a clear coat (C).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, processes 1 to 1 in the present invention are described.
Step 6 and the top coat will be described. Process 1: As an object to be coated, an object having a bag structure such as a car body, an automobile part, a locker portion, a sill portion, and a pillar portion is effective. Although there is no limitation, a rust-preventive steel plate such as galvanized is preferable from the viewpoint of corrosion resistance.

As the steel sheet, a hot-dip galvanized steel sheet, an electro-galvanized steel sheet, an electro-galvanized iron double-layer coated steel sheet, an organic composite coated steel sheet, and the like, and a base material such as these steel sheets and cold-rolled steel sheets may be used, if necessary. After the surface is cleaned by degreasing or the like, a surface treatment such as a phosphate chemical conversion treatment or a chromate treatment may be performed.

In the method of the present invention, the cationic electrodeposition coating (1) used in the first electrodeposition coating may be any resin such as an epoxy resin, an acrylic resin, a polybutadiene resin, an alkyd resin or a polyester resin. Can be.

The coating color of the cationic electrodeposition paint (1) to be first electrodeposited is that of a top coat applied thereon since a coating film is formed on an outer plate surface of an automobile body or the like. The colors and the hues (R, Y, G, B, P, etc.) of the Munsell display (the color display method based on the three attributes of JIS Z8721) are similar colors.

Preferably, by setting the color difference between the electrodeposition coating film and the overcoating film: ΔE (note) to 10 or less, more preferably 6 or less, the concealing property of the undercoat is increased and the finished appearance is improved. all right.

(Note) Color difference: ΔE is JIS Z 873
The color difference, which is the difference between the two colors, was measured according to the L ^* a ^* b ^* reading value by 0. Further, a metallic or pearl-like electrodeposition paint containing aluminum, mica, or the like may be used.

Examples of the pigment used in the cationic electrodeposition coating composition (1) include white pigments such as titanium oxide, zinc white, lead white, basic lead sulfate, lead sulfate, lithopone, zinc sulfide, and antimony white. Carbon black, acetylene black, lamp black, bone black, graphite,
Black pigments such as iron black and aniline black; graphite, ocher,
Barium chromate, yellow iron oxide, naphthol yellow S,
Hansa Yellow 10G, 5G, 3G, G, GR,
A, RN, R, Pigment Yellow L, Benzidine Yellow, G, GR, Permanent Yellow NCG, Vulcan Fast Yellow 5G, R, Tartrazine Rake, Quinoline Yellow Lake, Anslagen Yellow 6GL
Yellow pigments such as chrome orange, chrome vermillion, Sudan I, permanent orange, lithol fast orange 3GL, permanent orange GTR, Hansa Yellow 3R, Vulcan Fast Orange GG, benzidine orange G, Persian orange, Indazlen brilliant orange GK, RK Brown pigments such as iron oxide and amber; red iron red, permanent red 4R, permanent red 4R, F5R, parared, fire red, parachloroorthonitroaniline red, lithol fast scarlet G, brilliant fast scarlet, brilliant carmine BS , 6B, permanent red F2R, F4R, FRL, FR
LL, F4RH, Fast Scarlet VD, Vulcan Fast Rubin B, Vulcan Fast Pink G, Light Fast Red Toner B, R, Permanent Carmine FB, Lake Red, Ansosine B, Brilliant Scarlet G, Lysole Rubin GK, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2R, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Lite, Bon Maroon Museum, Eosin Lake, Rhodamine Lake B, Y, Alizarin Lake, Thio Indigo Red B, Thio Indigo Maroon, Quinacridone Red Red pigments such as pigments; purple pigments such as cobalt violet, manganese violet, fast violet B, methyl violet lake, ultramarine, navy blue, cobalt blue, celery Nburu, metal-free phthalocyanine blue, phthalocyanine blue, fast sky blue,
Blue pigments such as Indaslen Blue RS, BC, and Indigo; and green pigments such as chrome green, pigment green B, naphthol green B, green gold, and phthalocyanine green.

As extenders, kaolin, barita powder,
Precipitating barium sulfate, barium carbonate, calcium carbonate, gypsum, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, gloss white, satin white, mica powder, etc. Examples include bismuth oxide, organic bismuth, zinc chromate, strontium chromate, calcium chromate, lead cyanamide, calcium leadate, lead silicate, and zinc phosphate.

Other metal powder pigments and metal luster pigments include aluminum powder, bronze powder, copper powder, tin powder, lead powder, zinc powder, iron phosphide, pearl-like metal-coated mica powder, and mica-like iron oxide. And the like. Examples of the catalyst include dibutyltin oxide (DBTO) and dioctyltin oxide (DOTO).

These pigments and catalysts are prepared by adding a tertiary amine-type epoxy resin, a quaternary ammonium salt-type epoxy resin, a tertiary amine-type acrylic resin, etc., as a dispersing resin, and a neutralizing agent and deionized water. Thereafter, the pigment paste is dispersed by a ball mill, a sand mill or the like to obtain a pigment paste.

The amount of the coloring pigment to be added to the cationic electrodeposition paint is 1 to 100 parts by weight of the resin solid content.
The range is preferably from 50 to 50 parts by weight, more preferably from 5 to 40 parts by weight. If the amount of the coloring pigment is less than 1 part by weight, the concealing effect is ineffective, and if it exceeds 50 parts by weight, the stability of the paint is impaired.

As the base resin used for the emulsion for cationic electrodeposition, for example, an epoxy-based cationic electrodeposition paint containing an epoxy resin as a main component, an acrylic cationic electrodeposition paint containing an acrylic resin as a main component, and the like can be given. it can. It is desirable to use a small amount of an epoxy resin as the other electrodeposition resin in the acrylic electrodeposition paint containing an acrylic resin as a main component from the viewpoint of anticorrosion properties.

The cationic electrodeposition paint containing an epoxy resin as a main component includes, as an epoxy resin, an amine-added epoxy resin. The amine-added epoxy resin is a polyamine resin commonly used in electrodeposition paints, for example,
(I) adducts of polyepoxide compounds with primary mono- and polyamines, secondary mono- and polyamines or mixed primary and secondary polyamines (see, for example, US Pat. No. 3,984,299)
(Ii) adducts of polyepoxide compounds with secondary mono- and polyamines having a ketiminated primary amino group (see, for example, US Pat. No. 4,017,438).
(Iii) a reaction product obtained by etherification of a polyepoxide compound with a ketiminated hydroxy compound having a primary amino group (see, for example, JP-A-59-1984).
No. 43013).

The polyepoxide compound used for producing the polyamine resin is a compound having two or more epoxy groups in one molecule, and is generally at least 200, preferably 400 to 4,000, more preferably 800.
Those having a number average molecular weight in the range of 2,000 to 2,000 are suitable, and those obtained by the reaction of a polyphenol compound with epichlorohydrin are particularly preferred. Examples of the polyphenol compound that can be used for forming the polyepoxide compound include bis (4-hydroxyphenyl) -2,2-propane, 4,4'-dihydroxybenzophenone, bis (4-hydroxyphenyl) -1,
1-ethane, bis (4-hydroxyphenyl) -1,1
-Isobutane, bis (4-hydroxy-tert-butyl-
Phenyl) -2,2-propane, bis (2-hydroxynabutyl) methane, 1,5-dihydroxynaphthalene,
Bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone, phenol novolak, cresol novolak and the like can be mentioned.

The polyepoxide compound is a polyol,
It may be partially reacted with a polyether polyol, a polyester polyol, a polyacid amine, a polycarboxylic acid, a polyisocyanate compound, or the like, and may be a product obtained by graft polymerization of ε-caprolactone, an acrylic monomer, or the like. You may.

In the acrylic cationic electrodeposition paint, a conventionally known acrylic resin can be used.
For example, those obtained by copolymerizing an amino group-containing monomer, a hydroxyl group-containing monomer, and another vinyl monomer can be used.

The hydroxyl value of the acrylic resin is not particularly limited, but is usually 30 to 200 mgKOH / g,
Preferably, the range of 50 to 150 mgKOH / g is appropriate. If the hydroxyl value is less than 30, the curability of the resulting coating film tends to be poor, and if it exceeds 200 mgKOH / g, the weather resistance and corrosion resistance tend to be poor. The molecular weight of the cationic electrodepositable acrylic resin is usually about 5,000 to 10
A range of 0000, preferably 10,000 to 50,000 is suitable.

The blocked polyisocyanate compound used as a curing agent in the cationic electrodeposition coating composition (1) is a compound obtained by blocking an aliphatic and / or alicyclic polyisocyanate compound with a blocking agent.

Polyisocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanate methyl)
Aromatic, aliphatic, or alicyclic polyisocyanate compounds such as cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate.

The blocking agent is one that blocks by adding to the isocyanate group of the polyisocyanate compound, and the blocked polyisocyanate compound formed by the addition is stable at room temperature and about 100 to 20.
When heated to 0 ° C, preferably 120 to 150 ° C, it is desirable that the blocking agent be dissociated to regenerate free isocyanate groups.

As such a blocking agent, for example,
Lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenol compounds such as phenol, para-t-butylphenol and cresol; fats such as n-butanol and 2-ethylhexanol Aromatic alcohols such as phenylcarbinol and methylphenylcarbinol; ether alcohol compounds such as ethylene glycol monobutyl ether;

The amount of the blocking agent is preferably 1: 1 to 1: 1.3 with respect to the NCO group of the isocyanate. When the ratio exceeds 1.3, the blocking agent remains to reduce the corrosion resistance of the coating film, and when the ratio is less than 1.0, NCO groups remain to impair the stability of the coating, which is not preferable.

The neutralization of the base resin and dispersion in water are usually carried out by using a curing agent, a surfactant, a surface conditioner (such as an acrylic resin, a fluororesin, or a silicon resin), or a curing catalyst (for example, tin, zinc, lead, bismuth, etc.). After addition of other additives, etc., the base resin is made of an aliphatic carboxylic acid, for example, glycolic acid, glyceric acid, lactic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid, tartaric acid, It is carried out with a water-soluble organic acid such as malic acid, hydroxymalonic acid, dihydroxysuccinic acid, trihydroxysuccinic acid, methylmalonic acid, acetic acid and formic acid.
Use of formic acid as a neutralizing agent is preferable because of excellent throwing power.

The above-mentioned cationic electrodeposition coating material (1) is appropriately
Diluted with deionized water to have a solid concentration of about 5 to 25% by weight,
Adjust so that the pH is in the range of 5.5-8. As a method and an apparatus for performing electrodeposition coating on an object to be coated using the cationic electrodeposition coating (1), known methods and apparatuses conventionally used in electrodeposition coating can be used.

At this time, the conditions for electrodeposition coating are not particularly limited, but generally, the bath temperature is 15 to 35 ° C. (preferably 20 to 30 ° C.), and the voltage: 100 to 400 V (preferably 200 to 300 V), energization time: 30 seconds to 10
Min, pole area ratio (A / C) = 8/1 to 1/8, distance between poles 1
It is desirable to perform electrodeposition under a stirring state of 0 to 200 cm. The thickness of the electrodeposition coating film formed by the cationic electrodeposition paint may be appropriately selected according to the intended performance, but is preferably in the range of 5 to 60 μm, and more preferably 10 to 40 μm.

Step 2 is a step in which the object to be coated is washed with water to remove excess cationic electrodeposition paint (1), and then the resulting coating film is cured and dried. As the washing water, industrial water, pure water, ultrafiltration (UF) filtrate,
Cationic electrodeposition paint on painted surface by RO permeated water
It is preferable to wash sufficiently with water so that (1) does not remain.

The baking temperature of the coating film is generally in the range of 120 to 200 ° C., preferably 140 to 200 ° C. on the surface of the substrate.
180 ° C temperature is suitable and baking time is 5-60
It is preferable that the surface of the object to be coated is held for about 10 minutes, preferably about 10 to 30 minutes.

In step 3, the object to be coated obtained in the above step is
In this step, the cationic electrodeposition paint (2) is applied to form an electrodeposition coating film. The coating film is preferably applied to the portion of “5” on the inner plate surface of the “two-piece” test plate in FIG. 1 and applied to the bag portion, so that an epoxy resin system having good corrosion resistance is preferable.

Step 4 is a step in which the object to be coated is washed with water to remove the excessively adhered cationic electrodeposition coating material (2), and then the coating film is cured and dried. The baking temperature of the coating film is generally in the range of 120 to 200 ° C.
Preferably, the temperature is 140 to 180 ° C, and the baking time is 5 to 60 minutes, preferably about 10 to 30 minutes, and the surface of the object to be coated is preferably held.

In step 5, the colored base coat (A), metallic base coat (B), and clear coat (C)
In the step of applying the top coat composed of layers, the coat color of the top coat is similar to the coat color of the cationic electrodeposition paint (1), which is the base, in the Munsell hue.

Colored base coat of top coat (A)
Is a thermosetting paint containing a resin component, a color pigment, and an organic solvent, and containing a color pigment, an extender pigment, and other paint additives. The color tone is chromatic or white, but aluminum and mica can be blended to obtain a novel finished coating film.

Specific examples of the resin component in the colored base coat (A) include a melamine resin, a urea resin, a blocked isocyanate compound and a base resin such as an acrylic resin, a polyester resin, and an alkyd resin having a crosslinkable functional group such as a hydroxyl group. And the like, which are used in combination with a crosslinking agent such as an organic solvent and / or a solvent such as water. Examples of the color pigment include the color pigment and extender used in the cationic electrodeposition paint (1) or the cationic electrodeposition paint (2).

The coating of the colored base coat (A) can be applied by a method such as air spray, airless spray, electrostatic coating machine, and the like, and the thickness thereof is preferably in the range of 5 to 40 μm based on the dry coating film. .

The metallic base coat (B) is a paint to be applied after the colored base coat (A) is uncured or after the colored base coat (A) is baked and cured, and is made of resin, aluminum oxide flake, pearl mica,
A pearly or metallic thermosetting paint having a brilliant sensation containing an organic solvent and the like, and further containing a coloring pigment, an extender pigment, and other additives as necessary.

As the resin used for the metallic base coat (B), specifically, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin having a crosslinkable functional group such as a hydroxyl group, a melamine resin, a urea resin And a (blocked) polyisocyanate compound or the like.

The metallic base coat (B) can contain aluminum powder, flake-like aluminum oxide, pearl mica, flake-like mica, etc., and has a dense feeling by containing one or more of these. A pearly coating film with a metallic or soft feeling can be obtained. Aluminum powder is conventionally used for a metallic base coat and is mixed in a paste form. The metallic base coat (B) is applied by an air spray, an airless spray, an electrostatic coater or the like, and the dry coating film has a thickness of 15 to 70 μm, preferably 20 to 50 μm.

The clear coat (C) is the uncured coated surface of the metallic base coat (B) or 120 to 170 ° C.
The coating surface of the metallic base coat (B), which is crosslinked and cured by heating for 10 to 60 minutes, can be applied by a method such as an electrostatic coating machine, an air spray, or an airless spray. 10 to 100 μm based on
Is preferably within the range.

The component of the clear coat (C) contains a resin and an organic solvent as main components, and further contains a coloring pigment and other additives for paint, if necessary, to the extent that the transparency of the coating film is not impaired. This is a paint that forms a colorless or colored transparent coating film.

The resin used in the clear coat (C) is preferably a thermosetting resin, specifically, an acrylic resin having a crosslinkable functional group such as a hydroxyl group, a carboxyl group, an epoxy group, a polyester resin, an alkyd resin, a urethane resin. A resin in which a base resin such as a resin is used in combination with a crosslinking agent such as a melamine resin, a urea resin, a (blocked) isocyanate compound, a carboxyl group-containing compound (or resin), and an epoxy group-containing compound (or resin); As the solvent, an organic solvent and / or water can be used.

The coating condition in step 5 is a coating film forming method in which a colored base coat (A), a metallic base coat (B), and a clear coat (C) are sequentially applied while being uncured. A coating film forming method in which a colored base coat (A) and a metallic base coat (B) are applied, and then both the coating films are cured to apply a clear coat (C). In addition, a coating film is formed by applying a colored base coat (A), curing the coating film, then applying a metallic base coat (B), curing the coating film, and then applying a clear coat (C). Method and the like.

Step 6 is a step of simultaneously baking and curing and drying the coating films obtained in steps 1 to 5. The drying temperature is 110 to 200 ° C., preferably 130 to 180 ° C. at the surface of the substrate, and the drying time is 10 to 180 minutes, preferably 20 to 40 minutes.
As the drying equipment, an electric hot air dryer, a gas hot air dryer, or the like can be used.

[0054]

EFFECTS OF THE INVENTION The coating film forming method of the present invention can be used to form a gray or black cationic electrodeposition coating in two coats and two bake of double coat electrodeposition coating capable of forming coatings having different functions. It is characterized in that the paint color is similar to the paint color of the overcoat paint composed of three layers to be applied thereon and the hue of the Munsell display.

From this, it was found that the base electrode concealing property can be obtained even when the thickness of the overcoating film and the pigment concentration are reduced, as compared with the coating color of the cationic electrodeposition coating film which is gray or black. further,
Cost reduction by reducing the film thickness, and improved sagging on vertical painted surfaces such as door fenders. By lowering the pigment concentration, a plasticizing effect is exerted on the coating film, so that an effect of improving chipping resistance was obtained.

As another effect, there is a co-color intermediate paint having a similar color to the top coat color applied to the outer panel surface applied to the trunk, door inner, pillar, etc. of the automobile body. Since the color is similar to that of the film, it is possible to omit the intermediate color paint of the same color, which contributes to resource saving and process saving.

[0057]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by this. Note that “parts” and “%” indicate “parts by weight” and “% by weight”.

Preparation Example of Pigment Paste A for Cationic Electrodeposition A tertiary amine-acid neutralized dispersion resin having a solid content of 55% 9.09
Parts (5 parts solids) and 2.7 parts of 10% acetic acid.
Further, 16.1 parts of deionized water was added and mixed and stirred. Next, 20 parts of titanium white, 2 parts of bismuth oxide, and 1 part of organic tin were mixed therein, and dispersed in a ball mill for 20 hours to obtain 55% of a pigment paste A.

Preparation of Pigment Pastes BD for Cathodic Electrodeposition
Pigment pastes B to D were prepared in the same manner as in the example pigment paste A with the blending contents shown in Table 1.

[0060]

[Table 1]

Amine-added epoxy resin for cationic electrodeposition
Production Example Epicoat 828EL (product name, epoxy resin, manufactured by Yuka Shell Co., Ltd.) 1010 g, bisphenol A 390 g,
0.2 g of dimethylbenzylamino was added and reacted at 130 ° C. until the epoxy equivalent became 800. Next, 260 g of ε-caprolactone and 0.03 g of tetrabutoxy titanium
Was added, and the temperature was raised to 170 ° C. Sampling was performed over time while maintaining this temperature, and the amount of unreacted ε-caprolactone was tracked by infrared absorption spectrum measurement.
When it became 8% or more, the temperature was lowered to 120 ° C. Next, 160 g of diethanolamine and 65 g of methyl isobutyl diketimine compound of diethylenetriamine were added, and
The mixture was reacted at 4 ° C. for 4 hours, and 420 g of butyl cellosolve was added to obtain an amine-added epoxy resin having an amine value of 58 and a solid content of 80% as a base resin.

Curing agent No. for cationic electrodeposition paint 1 Manufacturing
Example 50 parts of isophorone diisocyanate (IPDI) were added dropwise to 40 parts of methyl ketoxime at 40-60 ° C.
The mixture was heated at 0 ° C. for 1 hour, and a (blocked) polyisocyanate compound having a solid content of 90% and a curing agent No. 1 were prepared. 1 was obtained.

Curing agent No. for cationic electrodeposition paint 2 Manufacturing
Example: diphenylmethane-4,4'-diisocyanate (MD
I) Add 250 g and 44 g of methyl isobutyl ketone and add 7
The temperature was raised to 0 ° C.

After slowly adding 146 g of methylacetamide, the temperature was raised to 90 ° C. While maintaining this temperature, sampling was conducted over time, and infrared absorption spectrum measurement confirmed that the absorption of unreacted isocyanate had disappeared, whereby a (blocked) polyisocyanate compound having a solid content of 90% and a curing agent No. 2 was obtained.

Emulsion No. for cationic electrodeposition One
Production Example 87.5 parts (solid content 70 parts) of 80% epoxy resin, curing agent no. 1 (IPDI) 33.3 parts (solid content 30
Parts), 2.5 parts of liquid organotin (1 part of solid content), 8.2 parts of 10% formic acid, and after stirring uniformly, deionized water 18
4.1 parts was dripped over about 15 minutes with vigorous stirring to obtain a cationic electrodeposition emulsion No. 32.0% solids.
1 was obtained.

Emulsion No. for cationic electrodeposition Two
Production Example 87.5 parts of epoxy resin (solid content 70 parts),
Curing agent No. 2 (MDI) 33.3 parts (solid content 30
Parts), 2.5 parts of liquid organotin (1 part of solid content), 8.2 parts of 10% formic acid, and after stirring uniformly, deionized water 18
4.1 parts was dripped over about 15 minutes with vigorous stirring to obtain a cationic electrodeposition emulsion No. 32.0% solids.
2 was obtained.

The cationic electrodeposition paint No. Preparation Example 32 32% cationic electrodeposition emulsion No. 1 1
315.6 parts (101 parts solid content), 70 parts (38.5 parts) of 55% pigment paste A, and 311.9 pure water
Of cationic electrodeposition paint No. 20% solids. 1
(Paint color white) was obtained.

The cationic electrodeposition paint No. 2-No. Made of 5
Cationic electrodeposition paint in combination, such as Zorei Table 2 No. Two
No. 5 was created.

[0069]

[Table 2]

The top paint No. 1 to No. Production Example 6 After stirring with a disper with the composition as shown in Table 3, diluting with Ford cup # 4 with swazol # 1000 to a viscosity of 20 seconds / 20 ° C., coloring base coat (A)
As the top coating paint No. 1 to No. 6, Topcoat paint No. as metallic base coat (B). 7 was created.
As the clear coat (C), Luga Bake Clear (Note 7) was used.

[0071]

[Table 3]

[0072] (Note 1) Hydroxyl group-containing acrylic resin: hydroxyl value 110,
Number average molecular weight 25,000 (Note 2) Melamine resin: Butyl etherified melamine resin (Note 3) Hydroxyl-containing acrylic resin: Hydroxyl value 100,
Number average molecular weight 20,000 (Note 4) Butylated melamine resin: Methyl-butyl mixed etherified melamine resin (Note 5) Aluminum flake: Aluminum oxide flake coated with iron oxide, 10 parts of iron oxide per 100 parts of aluminum oxide flake (Note 6) Pearl mica white: Iron oxide coated mica, manufactured by Mark Co., Ltd., thickness: 0.2 to 0.5 μm (Note 7) Luga bake clear: manufactured by Kansai Paint Co., trade name, acrylic resin / Amino resin type.

EXAMPLES AND COMPARATIVE EXAMPLES Example 1 Step 1: Cold rolled steel sheet (70 × 150 × 0.8 mm) treated with a chemical conversion treatment Palbond # 3020 (trade name, manufactured by Nippon Parker Rising Co., trade name, zinc phosphate chemical conversion treatment agent) ) And a “two-folded” test plate as shown in FIG. 1 (paint white) was applied. Step 2: Next, the object having the electrodeposition coating film obtained above was washed with water, and the cationic electrodeposition paint No. 1
After baking, baking was performed at 170 ° C for 20 minutes at the temperature of the substrate. Step 3: The coated object having the electrodeposition coating film obtained in the above step was further coated with a cationic electrodeposition coating No. 4 (paint color gray)
Was painted. Step 4: The object having the electrodeposition coating film obtained in the above step was washed with water, and the cationic electrodeposition paint No.
After removing 4, baking was performed at 170 ° C. for 20 minutes. Cathode electrodeposition paint No. was applied to the outer plate surface “part 1” and the inner plate surface “part 4”. Reference numeral 1 denotes a painted portion corresponding to a co-color intermediate coating of the automobile body. In addition, cationic electrodeposition paint No. The electrodeposited coating film No. 4 was obtained, which corresponds to the bag of the automobile body. Step 5: A topcoat paint No. was applied to the “part 1” of the outer plate surface of the electrodeposition coating film prepared by the above steps. 1 (colored base coat (A)) was applied by spraying to a dry film thickness of 20 μm. Then, the top coat No. 7 (metallic base coat (B)) was placed at 10 μm, Luger bake clear was placed at 25 μm, and each setting time was placed for 7 minutes. Step 6: Thereafter, setting is performed for 10 minutes to evaporate the solvent from the coating film, and baking is performed at 140 ° C. for 20 minutes.
Top coat paint No. 1, top coating No. 7. An overcoat film consisting of three layers of clear coat (C) was obtained.

Examples 2, 3 and Comparative Examples 1 to 3 Coating compositions and coating steps as shown in Table 4 were prepared and subjected to tests. The results are shown.

[0075]

[Table 4]

(Note 8) Corrosion protection: Inner plate surface of uncoated part (unpainted part and second electrodeposition coating film) prepared through steps 1 to 4 using "two-piece" test plate A portion having a thickness of 5 μm or less was masked and excluded from the test), and a salt spray test was performed for 240 hours using a 35 ° C. salt spray tester. After the test, check for the occurrence of rust and blisters at the boundary. ○: No rust and blistering ×: Rust and blistering.

(Note 9) 60 ° gloss: Using a “two-piece” test plate, the top-coated surface of the coated plate prepared through steps 1 to 6 was subjected to JIS K-5400 7.6 (1990).
According to the 60 ° gloss, the degree of gloss of the coating film, the incident angle and the light-receiving angle were each measured the reflectance when 60 °,
The specular gloss is expressed as a percentage when the gloss of the reference surface is set to 100.

(Note 10) Sharpness: Using a “two-piece shank” test plate, the overcoated surface of the coated plate prepared through steps 1 to 6 was measured with a sharpness measuring device PGD-IV (Sold by Japan) Color Research Laboratory). The measurement was performed with the angle fixed at 55 °. The larger the value (PGD value), the better the sharpness. (Note 11) Chipping resistance: Using a "two-piece" test plate, apply a QGR gravelometer (manufactured by Q Panel Co., Ltd.) to the overcoated surface of the coated plate created through steps 1 to 6.
50g of No. 7 crushed stone using 0.39MPa (4kgf / c
air pressure m ^2), spraying the crushed stones to the test plate at a temperature of 20 ° C., rusting was in accordance with JIS Z-2371 defined method after shocked the coating film to salt spray test for 48 hours Is evaluated comprehensively and displayed according to the following criteria. ：: Excellent (rust generated on a 70 × 150 mm test plate)
以下: good (rust generated on 70 × 150 mm test plate)
3-9 or less) △: Slightly inferior (rust occurs on a 70 × 150 mm test plate)
×: Inferior (rust generated on a 70 × 150 mm test plate)
20 or more) (Note 12) Sagging property: Assuming the keyhole part of the door part as the object to be coated, the keyhole part of the door part is assumed to have a diameter of 10 as shown in FIG.
A steel plate with a punch mm hole was used. Step 1
The coated plate prepared in step 6 was vertically coated with a top coat paint, and the sagging state of the coating film around the punch hole was observed after baking. ○: Good without any problem △: About 1 mm around the keyhole Sagging of coating film observed ×: Sagging of coating film of 2 mm or more around keyhole

[Brief description of the drawings]

FIG. 1 is a model diagram of a “two-panned” test plate having a clearance portion used in a coating test of the present invention, and after baking by electrodeposition coating, a clip is removed and an outer coating is applied to the outer panel surface.

FIG. 2 shows a test plate used in a “sagging” coating test. It is a steel plate with a punch hole of 10 mm in diameter, assuming a keyhole part of a door part.

[Explanation of symbols]

1. This is the outer plate surface of the "two-piece" test plate. 2. This is a clip for closing the painted plate of the "two-piece" test plate. 3. The clearance is 1 mm, and the spacer is sandwiched between both ends. 4. This is the portion of the inner plate surface of the "two-piece" test plate, which was coated by the first electrodeposition coating. (It is assumed that the second electrodeposition paint is not applied, but the part of the trunk of the car body that has been painted with the same color intermediate coat.) This is the portion of the inner plate surface of the "Two Kasane" test plate that has been painted by the second electrodeposition coating. (Assumed bag portion of car body) There is no electrodeposition coating at the spacer. Seal during testing. 7. 7. Hole with a diameter of 10 mm General part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K044 BA21 BB06 BB16 BC02 CA17 CA53 CA62

Claims (4)

[Claims] 1. The following steps: Step 1: An article to be coated having a bag structure, such as an automobile body,
A step of applying a cationic electrodeposition paint (1) having a chromatic or white coating color to form a coating film, and step 2: washing an object to be coated with water and removing an excessively adhered cationic electrodeposition paint (1). After the removal, a step of curing and drying the obtained coating film; Step 3: a step of applying a cationic electrodeposition paint (2) to the object to be coated obtained in the above step to form a coating film; Step 4 : A step of washing the object to be coated with water to remove excess cationic electrodeposition paint (2), and then curing and drying the obtained coating; Step 5: coating of the cationic electrodeposition coating (1) In the step of applying a chromatic color similar to the paint color and the hue of the Munsell display or a white top coat, the top coat is composed of a colored base coat (A), a metallic base coat (B), and a clear coat (C). A step of applying a top coat comprising a layer, step 6: obtained in steps 1 to 5 A coating film forming method of curing dry baked film at the same time, the features. 2. The coating method according to claim 1, wherein the step of applying the top coat paint is carried out sequentially without curing the colored base coat (A), the metallic base coat (B), and the clear coat (C). Film formation method. 3. The process according to claim 1, wherein after the colored base coat (A) and the metallic base coat (B) are applied,
A coating film forming method, comprising curing both coating films and applying a clear coat (C). 4. The process according to claim 1, wherein the colored base coat (A) is applied, cured and dried, the metallic base coat (B) is applied, cured and dried, and the clear coat (C) is applied. Coating film forming method.