JPS60137472A - Painting method in 2-coat painting system - Google Patents

Abstract

PURPOSE:To obtain inexpensively a coated film having high ultraviolet resistance and a good appearance by forming an overcoated film contg. an ultraviolet absorbing agent between the undercoated film and the overcoated film. CONSTITUTION:2-3pts. benzophenone compd. used as an ultraviolet absorbing agent of an overcoated film 6 contg. the ultraviolet absorbing agent is incorporated into 100pts. overcoating resin, and the obtained material is coated on the undercoated film 2 in 10-15mu layer thickness to regulate the transmittance of the ultraviolet light to the undercoated film 2 to <=0.05%. In this case, the total thickness of the coated film 6 and the overcoated films 4 and 5 is regulated to about 60mu, and the overcoating paint contg. no ultraviolet absorbing agent is coated on the film 6 on a wet-on-wet basis.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a two-coat painting method for painting the body of an automobile, in which a top coat is immediately applied after applying an undercoat.

(Prior Art) The surface of an automobile body made of steel plate or the like is painted for the purpose of protecting the material, maintaining durability, and adding beauty.

Currently, commonly used coating systems are roughly divided into three-coat coating systems consisting of a base coat, intermediate coat and top coat, and two-coat coating systems consisting only of a base coat and a top coat.

The painted film deteriorates under the influence of sunlight and rain, but when applying a two-coat paint system, especially in light tones among solid colors, and some metallic colors, the undercoat film is damaged by ultraviolet rays. deterioration is likely to occur. When such deterioration occurs, peeling (interlayer delamination) occurs at the interface between the undercoat and topcoat.

Durability decreases. In order to prevent the above-mentioned peeling between the eyebrows, adding an intermediate layer between the base coat and top coat to create a 3-coat system increases the resistance to UV rays, but it costs significantly more than a 2-coat system. Also, in 2-coat paint systems, metallic paint colors are made by adding UV absorbers to the paint to increase its resistance to UV rays, but if too much is added, the quality of the finish of the paint film will deteriorate. Moreover, it increases the painting cost.

(Object of the Invention) The present invention is intended to solve the problems in the above-mentioned prior art, and its purpose is to provide a simple and simple coating that has the same UV resistance and appearance as the conventional 3-coat coating system. To provide an inexpensive two-coat painting method.

(Structure of the Invention) That is, the two-coat coating method of the present invention involves forming an undercoat film on a material, forming an overcoat film containing an ultraviolet absorber on the undercoat film, and forming an overcoat film containing an ultraviolet absorber. The method is characterized in that a top coat is further formed on top of the top coat.

As the ultraviolet absorber, those conventionally used for this type of application can be used. For example, berezophenone compounds such as 0-hydroxybenzophenone and 2-(2-hydroxyphenyl)benzotriazole can be used.

If the amount of the ultraviolet absorber is too large, the object of the coating film will be deteriorated and the cost will be high, and if it is too small, the optical effect cannot be achieved, so it is preferably 2 to 100 parts of resin of the top coat. It is recommended to use one to three parts.

What is the thickness of the layer containing the above ultraviolet absorber?

It is desirable to keep the UV transmittance to the undercoat below 0.0!1, although it varies depending on the amount of UV absorber blended and the thickness and color tone of the topcoat base coat and topcoat clear coat provided on the upper layer. When the total thickness of the top coat is about 60μ, the thickness is usually 10μ to 15μ.

The top coat containing an ultraviolet absorber and the top coat that does not contain an ultraviolet absorber are applied wet-on-wet.

Examples of resins used in the top coat may include acrylic resins, melamine resins, alkyd resins, and mixtures thereof (Examples) The present invention will be explained in more detail in the following examples. Note that the present invention is not limited to the following examples.

Example 1: A top coat consisting of Formulation Example 1 in the table below was applied to a steel plate coated with an undercoat to a thickness of 15 μm, and further wet
On-wet aluminum pigment.

A coloring agent, additives, a top coat base paint consisting of an acrylic-melamine resin, and a top coat clear paint consisting of an acrylic-melamine resin alone were successively applied and baked at 140° C. for 20 minutes to prepare a coated board.

The resulting coating film was coated using conventional 3 coats/1 bake (3C/IB
) It had the same aesthetic appearance as a metallic color, and the ultraviolet transmittance up to the undercoat film was 0.04%. Furthermore, the peeling between the eyebrows at the interface between the top coat and the top coat was equivalent to that of the metallic color of the conventional three-coat coating system (accelerated weather resistance passed 1200 hours).

Example 2: A top coat consisting of the composition 1y112 shown in the table below was applied to a steel plate that had been undercoated in the same manner as in Example 1 to a thickness of lθμ, and then the top coat was applied in the same manner as in Example 1. A painted board was created. The resulting coating film is the conventional 3C/IB
It had the same aesthetic appearance as a metallic color, and the ultraviolet transmittance up to the undercoat film was 0.05%. Further, no peeling between the eyebrows at the base coat-top coat interface occurred at all until 24 months of outdoor exposure.

Table: Comparison of conventional top coat paints containing ultraviolet absorbers and examples of the present invention: Figure 81 shows an outline of the operating procedure of the coating process for the conventional 3C/IB metallic color and the 2C/IB metallic color of the present invention.

As is clear from the figure, the coating method of the present invention involves spraying a top coat containing an ultraviolet absorber to form a coating film instead of the conventional three-coat spraying and baking intermediate coat, and then wet-coating. Since the top coat base paint is sprayed in an on-wet state, one baking step can be omitted.

Figure 2 shows a partially enlarged cross-sectional view of a conventional three-coat coating.
FIG. 3 shows a partially enlarged sectional view of the 2:1-to-based coating film of the present invention in Example 2. In Figures 2 and 3, 1 is the material and 2 is the undercoat film.

3 indicates an intermediate coating film, 4 indicates a top coat base coating film, 5 indicates a top coat clear coating film, and 6 indicates an ultraviolet absorber-containing top coat film. Also, the arrows and numbers at the right end of each figure indicate the percentage of ultraviolet transmittance in each coating layer.

As you can clearly see, the conventional one is quite thick (about 30μ).
Substantially the same ultraviolet shielding effect as the intermediate coating film 3 can be obtained with this ultraviolet absorber-containing top coating film 6 having a thickness of lθμ.

(Effects of the Invention) As described above, the coating method of the present invention combines a top coat layer containing an ultraviolet absorber with enhanced ultraviolet absorbing ability with an undercoat layer.
By providing it between the base coat and the base coat, it prevents peeling between the undercoat and topcoat due to ultraviolet rays, so the 2-coat system has the same durability as the conventional 3-coat system. and appearance are obtained.

Furthermore, the top coat layer containing the ultraviolet absorber described above has a thin thickness, which saves material, and a wet-on-coat layer is applied thereon.
Because the top coat base paint can be applied wet, it is possible to apply the top coat base paint in a wet manner.
Compared to coat painting systems, one baking step can be omitted, improving work efficiency, and running costs can be reduced, which is effective in reducing painting costs.

[Brief explanation of drawings]

Figure 1 shows the conventional 3C/IB metallic color and the 2nd color of the present invention.
C/ 1872922 A schematic diagram of the operating procedure for the two-color coating process. Figure 2 is a partially enlarged sectional view of a conventional three-coat coating film. FIG. 3 is a partially enlarged sectional view of the two-coat coating film of the invention. ■...Material 2...Undercoat film 3...Intermediate coat film 4...Top coat base m film 5...Top coat clear film 6...Top coat film with UV absorber J

Claims (1)

[Claims] It is characterized by forming an undercoat film on the material, forming an overcoat film containing an ultraviolet absorber on the undercoat film, and further forming an overcoat film on the top coat film containing the ultraviolet absorber. A two-coat painting method.