JPH02119979A - Method for solid coating of automobile - Google Patents

Abstract

PURPOSE:To enhance the clearness of solid coating by forming a colored finishing coat on a base coat and coating the finishing coat with fluororesin paint similar in color to the finishing coat by a dry-on-wet process to form a clear coat. CONSTITUTION:An electrodeposited coat 2, a second coat 3 and a colored finishing coat 4 are successively formed on a steel panel 1. The finishing coat 4 is coated with fluororesin paint similar in color to the coat 4 by a dry-on-wet process and the paint is baked and dried at about 130-150 deg.C for about 15-20min to form a clear coat 5 of about 15-30mum thickness. The fluororesin is preferably a copolymer consisting of two kinds of repeating units represented by formulae I, II (where X is F, Cl or trifluoromethyl and R is H, hydroxyalkyl, carboxyalkyl or alkyl).

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a solid coating method for automobiles.

[Conventional technology/issues to be solved by the invention] Conventionally, in solid painting of automobile bodies, etc., an electrodeposited film is formed on a steel plate, an intermediate coat is formed if necessary, a top coat is applied on top of that, and then coloring is performed. It is known that a clear coating film is formed by applying a fluororesin-based clear coating that does not contain pigments wet-on-wet (Japanese Unexamined Patent Application Publication No. 6-113)
1-197074).

The above-mentioned solid coating has the advantage that waxing is not necessary due to the use of a fluororesin clear coating film, but there is a problem that the depth and vividness of the color are not necessarily sufficient.

In recent years, with the diversification of user needs in automobile painting, there has been a growing demand for highly decorative coatings, but the solid coatings described above cannot adequately meet this demand.

In view of the above points, it is an object of the present invention to provide a solid coating that does not require waxing and exhibits a color tone with a level of high saturation that cannot be achieved with the solid coatings described above.

[Means for Solving the Problems] The present invention involves forming a colored topcoat film on a base coat film, and applying a fluororesin paint of the same color to the topcoat film by dry fist-on-wet. This invention relates to a solid coating method for automobiles, which is characterized by forming a clear coating film.

[Example] Next, the method of the present invention will be explained based on the drawings.

FIG. 1 is a schematic sectional view of painting showing an embodiment of the method of the present invention.

In Fig. 1, (1) is a steel plate panel, and the steel plate panel (1) is covered with an electrodeposited coating film (21), an intermediate coating film (3), a colored top coat film (4), and the top coat film (4). ) and a fluororesin clear coating film (5) of the same color are successively formed.

As described above, the present invention is characterized in that a fluororesin clear coat of the same color as the conventional top coat is provided on top of the conventional top coat.

This configuration provides the following effects.

Since the top coat is a fluororesin coating, its high weather resistance, high water repellency, and high stain resistance make it possible to maintain gloss and water repellency without waxing, making it a so-called wax maintenance-free coating. .

Moreover, since the fluororesin clear coating has the same color tone as the colored topcoat, a solid coating color with a high degree of depth and brightness can be obtained. That is, by color clearing, a color tone is created between the surface of the top coat film and the surface of the clear film, and a sense of depth can be created. In addition, by making the color clear, the top coat becomes a type of color intermediate coat, making it possible to achieve a more vivid color than conventional colors.

In addition, since the fluororesin clear coating is applied on top of the hardened top coat of conventional solid coating, the clear coating has good adhesion and durability, and the conventional solid coating method can be continued. Therefore, if high chroma painting is not required, the conventional method is used, and if high chroma and highly durable painting is required, the method of the present invention is used. This is advantageous in terms of productivity.

As the fluororesin paint used for forming the fluororesin clear coating film (5), a paint made of a solvent-soluble fluororesin, especially a baking type paint, is preferably used from the viewpoint of paintability.

The fluororesin has general formulas (1) and (I): (Il ( 1) (wherein, X is a fluorine atom, a chlorine atom, or a trifluoromethyl group, and P is a hydrogen atom, a hydroxyalkyl group, a carboxyalkyl group, or an alkyl group) consisting of two types of repeating units. Polymer resins (average molecular weight of about 2 x 103 to I x 105) are preferably used.

Particularly preferred is a crosslinked type copolymerized fluororesin in which R in the repeating unit ([1] is a hydrogen atom, a hydroxyalkyl group, or a carboxyalkyl group).

As the crosslinking agent for the crosslinking type fluororesin, polyisocyanate, block polyisocyanate, melamine resin, etc. are used. The crosslinking agent is 3 to 151 r per 100 parts by weight of fluororesin! Approximately one part is used.

In addition to the above-mentioned non-crosslinked fluororesins,
Vinylidene fluoride resin, vinyl fluoride resin, etc. can be used.

It is preferable to use a non-crosslinked type fluororesin in combination with a curable resin. As the curable resin, for example, melamine resin, isocyanate resin, etc. can be used. When used together, the amount of curable resin is 1 per 100 parts by weight of fluororesin.
About 0 to 15 parts by weight is used.

The fluororesin clear coating film (5) of the present invention contains a pigment at a low concentration. The pigment concentration in the fluororesin clear coating film is preferably about 5 to IO% (weight%, hereinafter the same). When the pigment concentration is outside the above range, it is difficult to obtain a highly saturated painted color. Pigments are selected so that the paint color is the same as that of the top coat film (4).

Pigments used include common pigments used in the top coat (4), such as red iron oxide, titanium oxide, carbon black, and permanent red 4R.

Underneath the Naori rear coating film (5), a top coating film (4) is provided that has excellent hiding properties and protection for the base coating film, so the clear coating film (5) focuses on the appearance finish. It allows the use of weather-resistant, high-chroma pigments. Examples of the weather-resistant pigments used include fast scarlet, quinacridone red, and green gold. Examples of the highly colored pigments used include quinacridone red, phthalocyanine green, and Fast Skyple N Hansa Yellow 3G. These pigments may be used alone or in mixtures.

In addition to the above-mentioned components, additives such as a dispersant (anti-settling agent), a curing agent, a curing accelerator, an anti-sagging agent, and an ultraviolet absorber may be added for the purpose of improving painting workability and preventing deterioration of the coating film.

The fluororesin, pigment, crosslinking agent if necessary, and other additives are dissolved in a solvent to a solid content concentration of about 50 to BO%,
A paint having a viscosity of about 20 to 25 seconds (Ford Cup Pc Zero 4) is prepared.

As the solvent, xylene, n-butanol, methyl isobutyl ketone, etc. are appropriately mixed and used.

In the present invention, the fluororesin paint is applied dry-on-wet on the top coat of conventional solid paint, and then baked at a temperature of about 130 to 150°C for about 15 to 20 minutes to dry and reduce the thickness. A fluororesin clear coating film (5) of about 15 to 30 um is formed. If the thickness of the fluororesin clear coating film is less than 15J, a highly saturated color can be obtained, but if it is greater than 30", no further improvement in performance can be expected.

In the present invention, the formation of the underlayer coating film on which the fluororesin clear coating film is provided may be carried out in the same manner as in conventional solid coating.

For example, a steel plate panel is painted with an electrodeposition paint and then baked to form an electrodeposition film, and if necessary, an intermediate coating is applied and baked to form an intermediate coating, and then a top coat is applied on top of that after drying. It is coated so that it has a thickness of 20 to 30 m+, and is baked and dried to form a top coat film (4).

Examples of top coats include melamine alkyd resin,
Melamine acrylic resin type, polyester resin type, etc. are used, and the above-mentioned usual coloring pigments are blended. The coloring pigment is used in a proportion of about 5 to 30% based on the solid content of the paint.

The method of the present invention is suitably used for solid coating of automobile bodies and automobile exterior parts.

Next, the present invention will be explained with reference to Examples.

Example 1 A 25 mm thick intermediate coating film was applied using a melamine alkyd resin intermediate coating paint on a steel plate test piece on which an electrodeposited coating film was 20 mm thick.

A melamine alkyd resin solvent-based top coat containing 13% of quinacridone red and red red iron based on the solid content was spray-coated onto the intermediate coating film to a thickness of 80 coats after drying, and then coated at 140°C for 18 minutes. Burnt.

The following fluororesin paint was applied on the top coat to a thickness of 2 after drying.
Spray to a concentration of 8uM, then heat at 140℃
Baked in 18 minutes.

Type of fluororesin: X in repeating unit (1) is a fluorine atom, repeating unit (I [ratio to solid content of copolymerized fluororesin in which R in l is a hydroxyalkyl group = 70%) Type of crosslinking agent Niblock polyisocyanate solid Pigment type: Quinacridone Red, red iron ratio to solid content: 8% Solid content concentration: 55% Solvent composition: xylene/methyl isobutyl ketone - 1/3
Capacity specific viscosity: 22 seconds (FeI2) Comparative Example The same procedure as Example 1 was carried out except that a fluororesin clear paint without pigment was used and a clear paint film was formed on the top coat film by wet-on-wet method. A painted test piece was obtained.

Examples 2 to 3 Example 1 except that the fluororesin paint was changed to the following.
Painted test pieces were obtained in the same manner as above.

Type of fluororesin: Polyvinylidene fluoride (Example 2) or polyvinyl fluoride (Example 3) Proportion to solid content is near 0% Type of curable resin; Proportion to melamine resin solid content: 5% Pigment type: Quinacridone red, red iron Ratio to solid content = 8% Solid content concentration: 55% Solvent composition: xylene/n-butanol-173 volumetric specific viscosity = 22 seconds (FeI4) Regarding the painted test pieces obtained in Examples 1 to 3 and Comparative Example I did a test.

Regarding the painted test pieces obtained in Examples 1 to 3 and Comparative Examples, glossiness, texture, depth, and brightness, and 2.
Coating film durability after annual exposure test [gloss retention rate, water repellency]
Contact angle d-1 constant) and stain resistance (water-based, oil-based marker)] were investigated.

The glossiness, meatiness, depth, and salmon bulk were determined by visual observation according to the following criteria.

0...I feel each feeling of the measurement item very strongly.

Δ...I strongly feel each feeling of the measurement item.

X: Poor feeling in each measurement item.

The stain resistance was judged according to the following FA standard.

0: Can be easily removed.

Δ: Not easy to remove.

X: Cannot be completely removed.

The results are shown in Table 1.

[Margins below] [Effects of the invention] Waxing is unnecessary by providing a dry-on-wet clear coat of fluororesin in the same color as the top coat on top of the conventional solid paint. , and can produce solid paint colors with a level of vividness that cannot be achieved with conventional methods.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a coating showing an embodiment of the solid coating method of the present invention. (Main symbols in the drawings) (1): Steel plate panel (4): Top coat (5): Fluororesin clear coating 1st Figure 1: Steel plate panel 4: Top coat 5: Fluororesin clear coating

Claims (1)

[Claims] 1. A colored top coat is formed on the base coat, and a fluororesin paint of the same color as this is applied dry-on-wet to the top coat to form a clear coat. Automotive solid painting method.