JPH11239759A - Two-tone finishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve workability of two-tone coating by a method in which the whole surface of an automobile body panel part coated by cationic electrodeposition is coated with a first colored coating, after the coating being cured by heating, only the upper part of the panel part is coated with a second colored coating forming a colored transparent coating film, and after the coating being cured by heating, the whole surface is coated with a clear coating. SOLUTION: In the two-tone coating of an automobile outside panel part, the surface of a metal part, after being subjected in advance to chemical treatment with zinc phosphate, iron phosphate, or the like, is coated by cationic electrodeposition. For example, a cationic electrodeposition coating containing a base resin having hydroxyl groups and cationic groups and a block polyisocyanate compound is used appropriately as the cationic electrodeposition coating. After the electrodeposition coating, the whole surface of the panel part is coated with a colored coating (color 1) and the coating is heat-cured. After that, after a prescribed part (lower part) of the surface coated with the colored coating (color 1) being masked, only the upper part is coated with a colored coating (color 2), and after the coating being heat-cured, the whole surface is coated with a clear coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-tone painting and finishing method for an outer panel of an automobile in which a painting process is simplified.

[0002]

2. Description of the Related Art It is known that a lower part and an upper part of an outer panel portion of an automobile such as a passenger car are separately painted with two kinds of paints having different color tones and finished to two tones. In the two-tone finishing method, usually, for example, cationic electrodeposition coating-heat curing-intermediate coating (entire surface) -heat curing-color 1 paint and clear paint are applied on the lower part by wet-on-wet-heat curing-masking- The upper part is composed of a paint-on-wet paint-on-wet coating and heat-curing process.

However, such a method requires at least five types of paints, six coating steps, and four heat-curing steps. From the viewpoint of resource saving and energy saving, it is possible to use the coating without deteriorating the coating film performance. Number of paint, number of paint transport piping,
Reduction of the number of painting processes is strongly desired.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a coating method for finishing an outer panel of an automobile to two tones, and relates to the number of paints used, the number of paint transport pipes, and the number of coating steps without deteriorating the coating film performance. The purpose of this method is to reduce the number of paints, and use a color paint (color 1) on the entire outer plate, heat and cure it without using an intermediate paint. It was found that the color 2) was to be painted, and as a result, the object was achieved, and the present invention was completed.

That is, according to the present invention, a colored paint (color 1) is applied to the entire surface of an automobile outer plate portion which has been subjected to cationic electrodeposition, and after heating and curing, a colored transparent coating film is formed only on the upper portion of the outer plate portion. The present invention relates to a two-tone finishing method, in which a paint (color 2) is applied and cured by heating, and then a clear paint is applied to the entire outer plate portion and cured by heating.

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

[0007] In the present invention, the automobile outer panel portion to be finished in two tones is a portion facing the outside of the automobile body such as a passenger car, a bus or a truck, and includes a bonnet, a fender, a door, a sill outer, Bumpers, trunk lid panels, roofs, pillars and the like. Then, an arbitrary portion is divided into two parts based on the vertical direction of the door-side part, and the upper part thereof is defined as the upper part of the outer plate part and the lower part thereof is defined as the lower part of the outer plate part based on the substantially horizontal direction. The material of the outer plate portion may be made of only metal including iron or the like, or may be a combination of plastic and metal such as polyolefin or polyurethane.

In carrying out cationic electrodeposition coating on the metal portion of the automobile outer panel, it is preferable that the surface is previously subjected to a chemical conversion treatment with zinc phosphate or iron phosphate. Although the plastic portion is not electrodeposited, it is preferable to perform a degreasing treatment with an acid or an alkali.

Known cationic electrodeposition coatings can be used. For example, a cationic electrodeposition coating containing a base resin having a hydroxyl group and a cationic group and a block polyisocyanate compound can be suitably used. Examples of the base resin include a reaction product of a polyepoxy resin and a cationizing agent, a polycondensate of a polycarboxylic acid and a polyamine protonated with an acid, and a polyisocyanate compound and a polyol or an amine compound. Examples thereof include those obtained by protonating an adduct with an acid, those obtained by protonating a polymer containing a hydroxyl group and an amino group with an acid, and those obtained by protonating an adduct of a polycarboxylic acid resin and an alkyleneimine with an acid. . The block polyisocyanate compound is an aliphatic, alicyclic or aromatic polyisocyanate having two or more isocyanate groups in one molecule.
Is a compound obtained by blocking the isocyanate group of the polymer with a blocking agent.When heated above the dissociation temperature, the free isocyanate group is regenerated and reacts with the hydroxyl group of the base resin to crosslink the electrodeposition coating film. To cure.

[0010] The solid content of the cationic electrodeposition coating material is 5 to 3
A car body (object to be coated) is immersed as a cathode in an electrodeposition bath having a weight of 0% by weight and a pH within the range of 3 to 9.
Electrodeposition coating is performed by applying a current at a voltage of 100 to 400 V for 1 to 10 minutes at a temperature of up to 35 ° C., and the object to be coated is pulled up from the bath, washed with water, and heated at 160 to 200 ° C. for 10 to 40 minutes to form a coating film Crosslink and cure. Its film thickness is 10-4
It is preferably within the range of 0 μm.

[0011] A cationic electrodeposition paint is applied, and a colored paint (color 1) is applied to the entire outer surface of the automobile body obtained by heating and curing the coating.

The color paint (color 1) is a paint that forms a coating film having a different color tone from the color paint (color 2) described below, and is a liquid paint containing a resin component, a color pigment, and a solvent.

The resin component comprises 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 a crosslinking agent such as an ethermelamine resin and a (block) polyisocyanate compound. ing. The hydroxyl value of the base resin having a hydroxyl group is 10 to 1
50, especially 20 to 80, acid value of 50 or less, number average molecular weight of 1000 to 1,000,000, especially 3000 to 5000
It is preferably within the range of 0. The ratio between the base resin and the cross-linking agent is 50% based on the total solid weight of the two.
Suitably, it is in the range of from 90 to 90%, in particular 65 to 85%, the latter being in the range of 50 to 10%, especially 35 to 15%.

As the color pigment, for example, titanium oxide,
Solids such as zinc white, carbon black, cadmium red, molybdenum red, chromium ero, chromium oxide, prussian bull, cobalt bull, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, sulene pigments and perylene pigments Metallic pigments such as color pigments, flaky aluminum, mica, mica surface-coated with a metal oxide, and mica-like iron oxide; but are not limited thereto. Colored paint (color 1)
Can form a solid color coating film or a metallic coating film by incorporating these coloring pigments.

The colored paint (color 1) is preferably colored with these colored pigments so that the undercoating, ie, the electrodeposited surface or the plastic surface, cannot be seen through the single coating film. The thickness is suitably 15 to 30 μm (as a cured coating). As the solvent, an organic solvent and / or water can be used. Examples of the organic solvent include hydrocarbons such as hexane, heptane, xylene, toluene, and cyclohexane; methyl acetate, ethyl acetate,
Ester systems such as ethylene glycol monomethyl ether and diethylene glycol monomethyl ether; ether systems such as isopropyl ether, ethylene glycol monomethyl ether and diethylene glycol monobutyl ether; ethyl alcohol and butyl alcohol And alcohols such as hexyl alcohol; methyl isobutyl ketone, methyl ethyl ketone, isophorone,
Ketones such as acetophenone are preferred.

In order to improve the chipping resistance of the two-tone finished multi-layer coating film of the present invention, the elongation percentage of a single cured coating film of this colored paint (color 1) is 10 to 50%, especially 20.
Preferably, the glass transition temperature is in the range of 30 to 80 ° C, particularly 40 to 60 ° C.

The elongation percentage of the single cured coating film of the colored paint (color 1) was measured at 140 ° C. using a universal tensile tester equipped with a thermostat (manufactured by Shimadzu Corporation, trade name, “Autograph SD”). 3
A single coated film (thickness 30) of the paint cured by heating for 0 minutes
μm) is cut into a length of 20 mm and a width of 10 mm, and + 20 ° C.
Is the elongation when the film is pulled at a speed of 20 mm / min until the coating film breaks. The glass transition temperature is measured by a vibron-type viscoelasticity analyzer, DAINAMIC VISCO.
ELASTOMETER MODEL VIBRON
DDV-II type (TOYO BACDWIN CO ,.
LTD. ) Using a frequency of 110 Hz and a heating rate of 3
Dynamic glass transition temperature (° C) measured in ° C / min.

The elongation and the glass transition temperature of a single cured coating film of the color paint (color 1) can be easily adjusted by the composition of the base resin and the crosslinking agent and the composition ratio thereof.

In the present invention, the outer coating of the automobile is subjected to cationic electrodeposition coating, the coating film is heated and cured, and then the color coating (color 1) is directly applied to the entire outer plate. It is not particularly necessary to apply an intermediate coating prior to color 1).

The color paint (color 1) is applied with a viscosity of 10 to 20 seconds /
Adjust to foad cup # 4/20 ° C, and apply airless spray, air spray, electrostatic method, etc. to the surface of the electrodeposition coating film on the outer panel of the automobile or the entire upper and lower surfaces of the plastic outer panel. Paint. It is suitable that the thickness of the coating is not less than the thickness of the base concealment film (15 to 30 μm) as the cured coating film. Thereafter, if necessary, the film is left at room temperature to 100 ° C. and then heated at 120 to 160 ° C. for 10 to 40 minutes to cure the coating film.

Next, a predetermined portion (lower portion) of the painted surface of the colored paint (color 1) applied to the outer panel of the automobile is masked, and then only the upper portion is painted with the colored paint (color 2).
This masking is performed only on the portion where the application of the colored paint (color 2) is not preferred, and the colored paint (color 2) is applied to the exposed painted surface of the colored paint (color 1) after the masking.

The colored paint (color 2) is a paint that forms a colored transparent coating film, and has such a transparency that the color tone of the colored paint (color 1) coating film can be visually observed through the coating film. It is a paint that forms a colored coating film having a color tone different from that of the colored paint (color 1).
It is a liquid paint containing a color pigment and a solvent.

The resin component comprises 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 a crosslinking agent such as an ethermelamine resin and a (block) polyisocyanate compound. ing. The hydroxyl value of the base resin having a hydroxyl group is 10 to 1
50, especially 20 to 80, acid value of 50 or less, number average molecular weight of 1000 to 1,000,000, especially 3000 to 5000
It is preferably within the range of 0. The ratio between the base resin and the cross-linking agent is 50% based on the total solid weight of the two.
Suitably, it is in the range of from 90 to 90%, in particular 65 to 85%, the latter being in the range of 50 to 10%, especially 35 to 15%.

As the color pigment, for example, titanium oxide,
Solids such as zinc white, carbon black, cadmium red, molybdenum red, chromium ero, chromium oxide, prussian bull, cobalt bull, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, sulene pigments and perylene pigments Metallic pigments such as color pigments, flaky aluminum, mica, mica surface-coated with a metal oxide, and mica-like iron oxide; but are not limited thereto. Colored paint (color 2)
Incorporates these color pigments to form a solid color or metallic transparent coating film.

With respect to a single coating film of the colored paint (color 2), the film has a transparency of a thickness of 15 to 40 μm (as a cured coating film) such that the color tone of the coated surface of the underlying colored paint (color 1) is visible. The underlayer concealment film thickness is suitably 50 to 200 μm. Further, the elongation percentage of the single coated film is 5 to 30%, particularly 10 to 20%, and the glass transition temperature is 50 to 100.
C., particularly preferably in the range of 60 to 80C.

As the solvent, the above-mentioned organic solvents and / or water can be used.

The viscosity of the colored paint (color 2) is 10 to 20 seconds /
The temperature is adjusted to ford cup # 4/20 ° C., and the upper part of the outer panel of the automobile coated with the coloring paint (color 1) is applied by an airless spray, an air spray, an electrostatic method or the like. The coating thickness is 15-30 μm, especially 20-25 μm for the cured coating
Is suitable. Thereafter, if necessary, room temperature to 10
After leaving at 0 ° C., the coating film is cured by heating at 120 to 160 ° C. for 10 to 40 minutes.

According to the method of the present invention, a colored paint (color 1) and a colored paint (color 2) are applied to the outer panel as described above, and after heating and curing, a clear paint is applied to the entire lower and upper portions thereof. This is achieved by curing the coating film by heating.

The clear paint is a paint that is applied to the entire lower and upper portions of the outer plate portion coated with the colored paint (color 1) and the colored paint (color 2), and contains substantially no colored pigment. A colorless and transparent coating film is formed.

The clear paint is a paint that forms a colorless and transparent coating film, and is a liquid paint containing a resin component and a solvent.

The resin component comprises 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 a crosslinking agent such as an ethermelamine resin and a (block) polyisocyanate compound. ing. The hydroxyl value of the base resin having a hydroxyl group is 10 to 1
50, especially 20 to 80, acid value of 50 or less, number average molecular weight of 1000 to 1,000,000, especially 3000 to 5000
It is preferably within the range of 0. The ratio between the base resin and the cross-linking agent is 50% based on the total solid weight of the two.
Suitably, it is in the range of from 90 to 90%, in particular 65 to 85%, the latter being in the range of 50 to 10%, especially 35 to 15%. As the solvent, the above-mentioned organic solvents and / or water can be used.

In the present invention, the elongation percentage of a single cured coating film of the clear paint is 15% or less, particularly 1 to 10%, and the glass transition temperature is 50 to 150 ° C., particularly 60 to 140 ° C. preferable.

The viscosity of the clear paint is set to 10 to 20 seconds / form.
The temperature is adjusted to 4/20 ° C and the lower and upper surfaces of the outer panel coated with colored paint (color 1) and colored paint (color 2) by airless spray, air spray, electrostatic method, etc. Paint. The coating thickness is 15-5 for the cured coating.
0 μm, especially in the range of 20 to 45 μm, is suitable. Then, if necessary, leave at room temperature to 100 ° C.
The two-tone finish of the present invention is achieved by curing the coating by heating at 0-160 ° C for 10-40 minutes.

[0034]

[Effects of the present invention] Cathodic electrodeposition coating-Heat curing-Full coating of colored paint (color 1)-Heat curing-Painting of colored paint (color 2) only on top-Heat curing-Painting of clear paint on entire surface-Heating It consists of curing, the paint used is 4 kinds of paint, the number of coating steps is 4, and the heating step is 4. Compared with the conventional method, the number of paints used, the number of paint pipes,
The number of painting processes can be reduced.

Examples of the present invention and comparative examples will be described below. Parts and percentages are in principle based on weight.

1. Samples 1) Cationic electrodeposition paint a: Amine-modified epoxy resin paint “ELECRON # 96
00 "(manufactured by Kansai Paint Co., Ltd., trade name).

2) Colored paint (color 1) a: 65 parts (solid content) of a hydroxyl group-containing polyester resin (hydroxyl value 90, acid value 10, number average molecular weight 2400), butyl etherified polymer melamine resin (number average molecular weight 1000) ) 25 parts (solid content) and a coloring pigment (3 parts of carbon black) were mixed with an organic solvent to give a viscosity of 15 to 2;
Adjusted to 0 sec / ford cup # 4/20 ° C. 140
The concealed film thickness of a single coating film cured by heating at 30 ° C. for 30 minutes is 2
0 μm, elongation 30%, glass transition temperature 50 ° C.

3) Colored paint (color 2) a: Acrylic resin containing hydroxyl group (having a hydroxyl value of 120 and an acid value of 2)
0, number average molecular weight 70000) 75 parts (solid content), butyl etherified polymer melamine resin (number average molecular weight 1000) 25 parts (solid content), and coloring pigment (cobalt blue-1 part, aluminum flake 0.2 part) ) Was mixed with an organic solvent, and the viscosity was adjusted for 10 to 20 seconds / ford cup # 4 /
The temperature was adjusted to 20 ° C. The opaque film thickness of the single coating film cured by heating at 140 ° C. for 30 minutes is 80 μm, the elongation is 10%, and the glass transition temperature is 70 ° C.

3) Clear paint "Magiclon clear" (manufactured by Kansai Paint Co., Ltd., trade name, acrylic resin / melamine resin-based organic solvent-based clear paint).

2. Example A steel sheet surface-treated with zinc phosphate (size 150 × 8
0 × 0.8 mm) with a solid content of 15% by weight, pH
Cathode is immersed as a cathode in an electrodeposition bath of cationic electrodeposition paint a adjusted to 6.5, and energized at 25 to 30 ° C. at a voltage of 100 V for 5 minutes.
The coating was crosslinked and cured by heating at 0 ° C. for 30 minutes. The thickness of the cured coating was 20 μm.

A colored paint (color 1) a is applied to the entire surface of the electrodeposited steel sheet with an airless spray so as to have a thickness of 20 μm as a cured coating film, left at room temperature for 3 minutes, and then heated at 140 ° C. for 30 minutes. After curing, the lower part is masked, and a colored paint (color 2) a is applied to the upper coated surface with an airless spray so as to have a thickness of 30 μm with a cured coating film, and left at room temperature for 3 minutes. After curing by heating at 30 ° C for 30 minutes, apply a clear paint (“Magiclon Clear”) on the upper and lower parts with an airless spray to a thickness of 40 µm using a cured coating film, and leave at room temperature for 3 minutes. It was cured by heating at 140 ° C. for 30 minutes.

The multilayer coating film thus obtained was tested for chipping resistance, finished appearance, weather resistance, etc., and all were excellent. The test methods are as follows.

Chipping resistance: Using a gravelometer (manufactured by Q Panel Co., Ltd.), apply 400 g of No. 7 crushed stone 4
Spraying at an angle of 5 ° at 20 ° C. with an air pressure of 0.3 MPa and observing the coated surface revealed that little peeling of the coating film was observed.

The finished appearance was the result of visual observation of the smoothness, sharpness, shine and the like of the coated surface, and all were good.

The weather resistance is the result of visually observing the coated surface after a test for 500 hours using a sunshine weatherometer, and no swelling, cracking, decrease in gloss, etc. were observed.

Claims (1)

[Claims] 1. A colored paint (color 2) which forms a colored transparent coating film only on the upper part of the outer plate portion after applying a colored paint (color 1) on the entire surface of the automobile outer plate portion which has been subjected to cationic electrodeposition coating and heating and curing. )
A two-tone finishing method comprising applying a clear paint over the entire outer plate portion after coating and heat-curing, followed by heat-curing.