JPH0344821B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a laminated coating film that is applied to automobiles and the like to provide an excellent coating appearance. [Conventional technology] Laminated coating films for automobiles, etc. are made by applying an electrocoating paint as an undercoat to the surface of the steel plate, which is the material to be coated, to ensure anti-corrosion performance, and then reinforcing the anti-corrosion performance and ensuring the finish of the top coat film. It is formed by applying a coating and then layering a top coat. Improving the painted appearance of automobiles made of such paint systems is a major challenge for each automobile manufacturer, but the quality of the painted appearance is often influenced by the pigment composition of the intermediate coating. For example, among conventionally used pigments, calcium carbonate is excellent in terms of painting workability, but has the disadvantage that it has a large amount of water soluble content, has poor moisture resistance and water resistance, and is difficult to produce gloss. On the other hand, scaly pigments such as talc and mica have been proposed to impart chipping resistance (Japanese Patent Publication Nos. 52-43657 and 1983-45813). However, extender pigments with large particle sizes such as talc, mica, or aluminum silicate have the effect of preventing pitting and smoothing out the dullness of the material, and also have no problem with water resistance, but if used in large quantities The suction of the top coat increases, making it difficult to obtain a coating film with excellent gloss. For example, when using an amorphous pigment such as talc, a portion of the intermediate coating surface protrudes, and this portion absorbs the resin component of the top coating, resulting in a phenomenon in which gloss is reduced. [Problems to be Solved by the Invention] Due to the above background, it has been difficult to obtain a laminated coating film that satisfies both smoothness and suction prevention performance using conventional pigment compositions. The present invention improves the defects of the material to be coated due to the intermediate coating film, which could not be solved by conventional techniques,
It also aims to provide a laminated coating film with excellent coating film smoothness and gloss by preventing suction and flow phenomena of the top coat paint. [Means for Solving the Problems] The laminated coating film according to the present invention to achieve the above object consists of applying an undercoat to the surface of the material using an electrodeposition paint and containing 40 to 50% by weight of barium sulfate in the pigment content of the paint. A first intermediate coating containing a colored pigment, a second intermediate coating containing 20 to 40% by weight of barium sulfate in the pigment content of the paint, and a second intermediate coating containing a colored pigment, and a top coat are applied. The compositional feature is that The undercoat of the present invention can be a cationic or anionic electrodeposition paint, and the topcoat can be a solid type using an alkyd/melamine resin or polyester/melamine resin paint, or a commonly used paint such as a metallic type using an acrylic/melamine resin. is used. As the vehicle for the intermediate paint, polyester resins, melamine resins, epoxy resins, etc., which are generally used for automobile painting, are used. The present invention provides a primary intermediate coating that contains 40 to 50% by weight of barium sulfate and a colored pigment in the pigment component, and a primary intermediate coating that contains 20 to 40% by weight of barium sulfate and a colored pigment in the pigment component. The main part of the structure lies in the use of a second intermediate coating, which is coated over and over again. Table 1 shows a comparison of the properties of barium sulfate, which characterizes the pigment component, with titanium white, talc, etc.

[Effect]

The body of an automobile is basically formed of a horizontal part and a vertical part. Particularly in the horizontal areas, the roughness (undulations and roughness) of the iron plate material is easily noticeable, so it is difficult to smooth out the roughness that cannot be covered with an electrodeposition paint (undercoat), and to apply a topcoat with an intermediate coat. The issue in achieving an excellent paint appearance is how much of the suction can be stopped. On the other hand, the finish of the vertical part has a large contribution rate from the top coat;
It is preferable that the intermediate coating be smooth, and it is also an important requirement for the intermediate coating to be difficult to run, in order to obtain a good finish. According to the present invention, by first applying a primary intermediate coating containing 40 to 50% by weight of barium sulfate and a coloring pigment as an intermediate coating, the scratch hiding function of the primary intermediate coating can be applied to the object to be coated and the undercoat. 20~40% of barium sulfate is added to the pigment.
By applying a second intermediate coating containing a colored pigment, preferably titanium white as a main component, a two-sided action to effectively prevent suction of the topcoat is exerted. These effects work together to provide a glossy and excellent coating appearance when formed into a laminated coating. [Example] Five types of paints were prepared as intermediate paints according to the formulation compositions (weight ratios) shown in Tables 2 and 3.

【table】

【table】

[Table] Examples 1 to 4, Comparative Examples 1 to 4 A 10 x 15 cm zinc phosphate-treated SPC-1 steel plate was used as the base material, and electrodeposition paint [manufactured by Nippon Paint Co., Ltd.] was applied to this surface by air spraying. , power top U-30]
Paint to a dry film thickness of 20 to 25 μm (the same applies below),
The undercoat was applied by baking at 180℃ for 20 minutes. On top of this base coat film, combine the intermediate coat paints with the compositions shown in Tables 2 and 3, and use air spray to apply the first intermediate coat paint and the second intermediate coat paint to a film thickness of 30 to 40 μm each. An intermediate coat was applied by applying two coats and two bakes, each coat being painted at 140°C for 30 minutes. The top coat is an acrylic/melamine resin metallic paint (made by Nippon Paint Co., Ltd., Super Lux M-12 Red Metallic) for the base coat and an acrylic/melamine resin paint (made by Nippon Paint Co., Ltd., Super) for the clear coat. Rack O-
70 Clear] and two types of paint (hereinafter referred to as "Paint M").
That's what it means. ) to achieve a film thickness of 20/30μm (applicable to 2C/1b)
There are two methods: one is to paint the paint to a film thickness of 40 μm using a polyester/melamine resin solid topcoat [Nippon Paint Co., Ltd., Orga S-20 White] (hereinafter referred to as "Paint S"). Konatsuta.
The top coat was baked at 140°C for 30 minutes. For the laminated coating film of the test piece obtained in this way, coating film performance such as adhesion, 20° gloss, NPIG value, surface roughness, weather resistance and moisture resistance was measured, and the evaluation results were compared and shown in the table below. 4 (Example) and Table 5 (Comparative Example). Among the coating film performance, adhesion was determined by measuring the laminated coating film at -20℃ using a gravelometer at an angle of 45° and No. 7 crushed stone 100.
The adhesion between the intermediate coat and the top coat was measured at an air pressure of 2 kg/cm ² . 20° gloss is an evaluation of the degree to which the top coat is absorbed into the intermediate coat film, and was measured in accordance with JIS K-5400 6.7. NPIG
The value indicates the degree to which the smoothness and image clarity most approximate the visual appearance, and was measured using an image clarity measuring device (manufactured by Nippon Paint Co., Ltd.). Surface roughness is an index for evaluating the degree of base-hiding ability of the intermediate coating that fills the rough surface of the base and contributes to the finished appearance, and was measured using a surface roughness meter [Surfcom Model SuRF07 B].
In addition, the weather and humidity resistance was measured using a Sunshine type weather meter for 600 hours and humidity resistance (50℃, 98% RH).
The condition was judged after repeating 5 times with 240 hours as one cycle, and it was indicated as ◎, no abnormality, and defective.

【table】

【table】

〔Effect of the invention〕

As described above, according to the present invention, the scratches coming from the object to be coated and the first layer are smoothed by the scratch hiding effect based on the unique intermediate coating, and the appearance of the top coat is improved by preventing suction. It becomes possible to provide a high-performance laminated coating film that could not be achieved using conventional techniques. Therefore, it is useful in satisfying the coating film performance required for automobiles.

Claims (1)

[Scope of Claims] 1. Undercoating with electrodeposition paint on the surface of the material, 40 to 50% by weight of barium sulfate in the pigment content of the paint, a primary intermediate paint containing color pigments, and barium sulfate in the pigment content of the paint. A laminated coating film characterized in that it is formed by applying a second intermediate coating paint containing 20 to 40% by weight of a color pigment and an intermediate coating coating, and a top coating coating. 2. The multilayer coating according to claim 1, wherein the coloring pigment of the second intermediate coating is mainly composed of titanium white, and the blending ratio of titanium white and barium sulfate is 2:1 to 3:1 (weight ratio). film.