JPS61291071A - Electrodeposition painting method - Google Patents

Abstract

PURPOSE:To reduce the color difference of electrodeposition painting, in applying the coating of predetermined hue, by applying the electrodeposition painting of an approximate color and washing, heating and drying the coating film before applying powder electrostatic painting by remaining heat. CONSTITUTION:When electrodeposition painting of hue of which the color phase is a Y-system and the brightness is 6 or more is applied to the box body or frame of a power-board or a control board, cationic electrodeposition painting of the approximate color thereof is applied and the electrodeposition paint adhered to the surface of an article to be painted is subsequently washed with fluxed washing water. Then, said paint is heated and dried without performing finishing washing and the electrostatic painting of a polyurethane resin powder is applied by the remaining heat of heating and drying and adjusted to indicated hue.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an electrodeposition coating method.

[Technical background of the invention and its problems]

Conventionally, when electrocoating the boxes and frames of switchboards and control panels, anionic electrocoating was applied as an undercoat, followed by a solvent-based topcoat.

In recent years, cationic electrodeposition coating has been adopted, and due to its excellent corrosion resistance, consideration has been given to omitting the top coat and using only electrodeposition coating.

However, as shown in Figure 2, the degree of yellowing is affected by the heating temperature and heating time during electrodeposition coating drying, the ventilation conditions in the electric furnace, etc., and the color difference △E is 6 to 8 on a normal electrodeposition coating line. If the air in the electric furnace is not sufficiently ventilated, the temperature can reach as high as 10 to 20, and if switchboards and control panels with large color differences are placed side by side, the aesthetic appearance will be spoiled.

For example, when applying electrodeposition coating to the Munsell symbol 5 Y 7/1 color tones applied to the boxes and panels of switchboards and control boards, the process is: preliminary degreasing → degreasing → first washing → second washing. → Surface conditioning → Film formation → Third washing → Fourth washing → Pure water washing → Draining and drying → Electrodeposition coating (20 to 30 μm) → First washing → Second washing → Third washing → Pure water washing → Drying → Top coat (Solvent-based coating 30-40μm
)→Dry.

[Purpose of the invention]

An object of the present invention is to obtain an electrodeposition coating method with less color difference.

[Summary of the invention]

To apply a coating in a predetermined color tone, after applying a cationic electrodeposition coating of a color similar to the color, the electrodeposition paint on the surface of the object to be coated is washed with fluxed washing water, and then heated without finishing washing with water. After drying, electrostatic powder coating in the above color tone is applied to a thickness that allows adjustment of the specified color.

[Embodiments of the invention]

It was painted with an epoxy resin-based cationic electrodeposition coating with a Munsell value of 5 Y 7/1, washed with flux, omitted the final water wash, and dried by heating at 180 to 210°0. In order to correct the yellowing of No. 1, electrostatic coating of polyurethane resin powder of No. 5 Y 7/1 is applied after heating and drying.

The treatment process is: Pre-degreasing → Degreasing → First washing → Second washing → Surface conditioning → Film formation → Third washing → Fourth washing → Pure water washing → Draining and drying → Electrodeposition coating (20 to 30 μm) → First flux washing → Second flux washing → Drying → Powder electrostatic coating (5 to 10 μm).

[Effect of the embodiment]

When adjusting the discoloration caused by heating and drying the electrodeposition coating by electrostatic powder coating, preheating for heating and drying the electrodeposition coating is used, so heating and drying after the electrostatic powder coating can be omitted.

In addition, even if you omit the final washing with water after electrodeposition coating, unlike applying powder electrostatic coating after the electrodeposition coating film has cooled, the polyurethane resin fine powder is fused using the residual heat of heating and drying the electrodeposition coating. , the interlayer adhesion between the electrodeposition coating film and the powder coating film is improved.

[Effects of Examples]

When painting the box panel of the switchboard with 5Y7/1 color, apply cationic electrodeposition coating using epoxy resin in the approximate color above, and immediately after washing 7-Lux with water, apply cationic electrodeposition coating to 180 to 200 degrees.
After heating and drying at 0 for 20 minutes, a polyurethane resin powder electrostatic coating of 5Y771 color was applied, and an electrodeposition coating was applied to adjust the specified color tone by fusing with the residual heat from the heating and drying of the electrodeposition coating.

As a result, by applying polyurethane resin powder coating with a film thickness of about 5 to 10 μm as shown in Fig. 1, the color difference of about 20% can be reduced by applying a polyurethane resin powder coating with a film thickness of about 5 to 10 μm, as shown in Fig. 1. (ΔE) can be adjusted to 2 to 3 color tones or less.

In addition, in order to investigate the interlayer adhesion between the epoxy resin electrodeposited film and the polyurethane resin powder coating film, a cross-cut cellophane tape test with a width of 1 mm was performed, and as a result, no peeling was observed at 100/100, indicating good adhesion. showed that.

Furthermore, according to the method of the present invention, the final washing after electrodeposition coating can be omitted, the discharge of washing water containing electrodeposition paint is eliminated, and a wastewater treatment device for the washing water after electrodeposition coating is provided. Since the powder electrostatic coating can be heated and dried using residual heat during heating and drying, a heating device after the powder electrostatic coating can be omitted.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the effect of the electrodeposition coating method of the present invention, and Fig. 2 shows the color difference (△E) of the specified color 5 Y 7/1 of the coating film under heating drying conditions of the conventional electrodeposition coating method. FIG.

Claims (2)

[Claims] (1) For electrocoating with a Y-based hue and a lightness of 6 or more, apply an electrocoat of the similar color, wash with water, heat dry, and then use the residual heat to apply electrostatic powder coating to adjust the color tone. An electrodeposition coating method characterized by: (2) The electrodeposition coating method according to claim 1, characterized in that the rinsing step involves only rinsing the flux, and no rinsing water is discharged after the electrodeposition coating.