JPH06170335A - Coating method - Google Patents

Abstract

PURPOSE:To relax the limit of selection of a mica-base coating material and a clear coating material to increase the freedom of design and still improve the finishing. CONSTITUTION:In the coating method, a color base coating material and a mica-base coating material composed of a resin different from that of the color base coating material as main component are applied by the wet-on-wet method, stoved and dried, and then a clear coating material is applied, stoved and dried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method used for finishing the decorative coating of automobiles.

[0002]

2. Description of the Related Art In recent years, high-definition coatings containing mica-based pigments have been increasingly used for coating outer panels of passenger cars. Unlike conventional metallic coatings containing aluminum flakes, this coating gives a unique depth feeling by providing a pearlescent luster peculiar to mica pigments and interference colors such as rainbow colors due to light interference.

By the way, a mica-based paint containing a mica-based pigment has a problem that it is inferior in hiding power. Therefore, if a mica-based paint is applied with a normal film thickness, the underlying material can be seen through, and the color tone of the underlying material is exposed, so high-quality coating cannot be achieved. Therefore, conventionally, a color base paint of the same color as the base is first applied, and then a mica base paint is applied thereon. In addition, clear paint is further applied to protect the mica-based paint film.

The conventional high-design coating process for automobiles will be described in order. First, a chemical conversion-treated automobile steel sheet is first subjected to electrodeposition coating with an electrodeposition paint and then baked and dried to form an electrodeposition coating film. It Next, an intermediate coating material such as an alkyd-melamine system is applied, baked and dried to form an intermediate coating film. After the intermediate coating film is subjected to water polishing, a color base coating material such as an alkyd-melamine-based or acrylic-melamine-based coating is applied and baked to dry to form a color base coating. Then, a mica-based paint such as an acrylic-melamine-based paint and a clear paint of the same type as the mica-based paint are applied wet-on-wet, respectively, and integrally baked and dried.

[0005]

By the way, while the mica-based paint only has to have a function of retaining the mica-based pigment, the clear paint has various excellent coating properties such as scratch resistance, gloss and weather resistance. Membrane performance is required. However, in the conventional coating process, since the mica base paint and the clear paint are applied wet-on-wet, there is a problem in the gloss of the coating film obtained when the compatibility between the mica base paint and the clear paint is poor. May occur. Therefore, the first condition was that the mica base paint and the clear paint had good compatibility. For this reason, there are cases where the selection of materials is largely restricted and the degree of freedom in design is low, the mica-based paint has an excessive quality, and the improvement of the quality of the clear paint is restricted.

Further, since the mica base paint is applied to a dried color base coating film, when it is applied to a thick film, dripping occurs. Therefore, it cannot be applied to a certain thickness or more, and the improvement in the orientation of the mica-based pigment due to the volume shrinkage is small, so that further improvement in the flip-flop property cannot be expected. On the other hand, since the clear paint is applied to a mica-based wet coating film, there is a problem that the surface of the clear coating film becomes wavy and the leveling property is not so good.

The present invention has been made in view of the above circumstances, and relaxes restrictions on selection of materials for mica-based paints and clear paints, increases design flexibility, and further improves finish. With the goal.

[0008]

The coating method of the present invention for solving the above-mentioned problems comprises a first coating step of applying a baking type color base coating to form a wet color coating film, and a luster material on the surface of the wet color coating film. A wet base coating film is formed by applying a baking type base coating material containing a resin different from the resin component of the color base coating material as a main component.
A coating process, a first drying process in which a wet color coating film and a wet base coating film are simultaneously baked and dried to form a base coating film, and a clear coating film is applied to the base coating film surface to form a wet clear coating film. 3 coating process, and a second drying process for drying the wet clear coating film to form a clear coating film,
It is characterized by consisting of.

The glittering material is a mica pigment or an aluminum flake pigment, and the base coating material containing this glittering material generally has a low hiding property. The greatest feature of the present invention is that the color base paint and the base paint are applied wet-on-wet, baked and cured, and then the clear paint is applied. As a result, as will be described later, it is possible to independently design the base paint and the clear paint, which greatly increases the degree of freedom in design.

[0010]

In the coating method of the present invention, the color base coating material and the base coating material are coated wet-on-wet and integrally baked and cured. The color base paint is merely for coloring, and the base paint is for holding the luster color material. Therefore, neither of them requires the performance of clear paint, and compatibility with clear paint is not a problem. Even if the compatibility between the color base paint and the base paint is poor and the gloss of the resulting base coating film is poor, since a clear coating film is formed on the surface, no problem occurs. Therefore, the selection of the color base paint and the material of the base paint is not limited as in the case of the conventional base paint and the clear paint, and there is a relatively high degree of design freedom. Further, with regard to clear paints, restrictions such as compatibility with mica base paints are lifted, so that the degree of freedom in design becomes extremely large.

Further, the resin component of the base paint is a resin different from the resin component of the color base paint. Therefore, when the base coating material is applied wet-on-wet to the surface of the wet color coating film, it is prevented from mixing with the wet color coating film and color is prevented from being mixed into the wet base coating film. As a result, the color component and the luster color material component have independent effects, respectively, and the sharpness of the obtained base coating film is not impaired.

Further, the mica base paint is applied to the wet color coating film surface in a wet state. At this time, if the coating particles of the mica-based paint adhere to the surface of the wet color coating film, the solvent usually transfers from the coating particles of the mica-based coating film to the wet color coating film due to the difference in the concentration of the solvent contained therein. Therefore, the viscosity of the mica-based paint particles increases instantaneously, and the viscosity of the wet base coating film thus applied is higher than in the past, and it is possible to apply it in a thicker film than before. . When the wet base coating film becomes thick as described above, the volumetric shrinkage rate at the time of baking becomes large, and the orientation of the glittering material contained therein is improved. The mica-based coating film thus obtained has an increased luster and flip-flop property, and can have a higher design.

Since the clear coating material is applied to the surface of the hardened base coating film, the original leveling property of the clear coating material is exhibited without the adverse effect of the base coating film, and the surface of the clear coating film becomes extremely smooth.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. (Example) First, a test plate coated with an intermediate coating film and water-polished was prepared. In addition, color base paints, mica base paints and clear paints shown in the table were prepared.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3] Using "μμ Bell electrostatic coating machine" (manufactured by Randsburg),
The above-mentioned color base paint was applied to the surface of the test plate so that the dry film thickness was 3
It was applied so as to have a thickness of 0 to 35 μm.

Then, after taking 5 minutes as a flash time, the above mica base paint was applied to the surface of the wet base paint using a "REA electrostatic coater" (manufactured by Lansberg) so that the dry film thickness was 15 to 20 .mu.m. Was applied to. After that, a setting time was set for 10 minutes, and baking and drying were performed at 140 ° C. for 30 minutes in a drying oven for overcoating to integrally form a color base coating film and a mica base coating film.

After the test plate was cooled to room temperature, the above-mentioned clear paint was applied on the surface of the mica base coating film to a dry film thickness of 30 to 35 μm using a “μμbell electrostatic coating machine” (manufactured by Landsberg). did. And setting time is 10
It was taken for a minute and baked and dried at 140 ° C. for 30 minutes in a drying oven for top coating to form a clear coating film. (Conventional example) The above-mentioned three kinds of paints were used and coated as follows. First, a color base coating material was applied in the same manner as in the above-mentioned example, and after setting time was set for 10 minutes, it was baked and dried at 140 ° C. for 30 minutes in a top coat drying oven to form a color base coating film.

Next, after cooling the test plate to room temperature, the mica base paint was applied to the surface of the color base coating film in the same manner as in the example, and after taking 5 minutes as a flash time, the clear paint was wet-based in the same manner as in the example. It was applied to the surface of the coating film. Then, the setting time was taken for 10 minutes, and baking and drying were carried out at 140 ° C. for 30 minutes in a drying furnace for overcoating to integrally form a mica base coating film and a clear coating film. (Evaluation) With respect to the coated plates obtained in the examples and the conventional example, the finished appearance and the flip-flop feeling were visually determined, and the results are shown in Table 4.

From Table 4, it can be seen that the coated plates obtained in the examples have excellent smoothness and luster, and also have a strong flip-flop feeling and exhibit high designability. It is clear that this is due to the fact that the color base paint and the mica base paint were applied wet-on-wet, baked, and then the clear paint was applied. Although ordinary coating film physical property tests such as water resistance, pencil hardness, adhesion, and weather resistance were also performed, no difference in these coating film physical properties was observed between the coated plates of the examples and conventional examples.

[0022]

[Table 4]

[0023]

That is, according to the coating method of the present invention, the designability can be improved with the same man-hours as the conventional one. In addition, the degree of freedom in designing the composition of each paint is increased, and it is possible to obtain the optimum composition without the need for excessive quality as in the past. This makes it possible to reduce costs.

Further, as in the conventional case, curing and drying can be carried out by using the drying furnace for top coating twice. Therefore, the number of steps is not increased, and there is no problem that dust or the like adheres to the coated surface during drying.

Claims (1)

[Claims] 1. A first coating step of applying a baking type color base coating to form a wet color coating, and a resin different from the resin component of the color base coating containing a glittering material on the surface of the wet color coating. A second coating step of forming a wet base coating film by applying a baking base coating composition as a component, and a first drying step of simultaneously baking and drying the wet color coating film and the wet base coating film to form a base coating film. A step of applying a clear paint to the surface of the base paint film to form a wet clear paint film, and a second step of drying the wet clear paint film to form a clear paint film
A coating method comprising a drying step.