JPS6112751B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrostatic powder coating method, and particularly to an electrostatic powder coating method in which the object to be coated is preheated when the temperature of the object to be coated is low during spraying of the powder coating. Conventionally, in general, in the electrostatic powder coating method, the temperature of the object to be coated when powder coating is sprayed in the spray booth was left to the natural ambient air temperature, so it was particularly sensitive to seasonal fluctuations in outside air temperature. When the temperature of the object to be coated drops in winter, the electrical resistance of the object increases and the grounding effect of the object deteriorates, making it necessary to significantly increase the voltage applied to the sprayer. By increasing the applied voltage in this way, there is a risk that repelling phenomena (appearing as minute crater-like depressions on the surface to be coated) or rough skin phenomena may occur due to electrostatic repulsion. Therefore, the present inventors conducted actual research to find out at what temperature the object to be painted would be able to prevent the occurrence of the above-mentioned problems when spraying powder coating onto the object. I found that 45℃ is sufficient. The present invention involves spraying and adhering a charged powder coating onto an object to be coated with a high potential difference between it and the coating machine, and then heating the object at a baking hardening temperature to melt the powder coating. In the electrostatic powder coating method for curing, when spraying the powder coating onto the object to be coated, if the temperature of the object to be coated is low, the object to be coated is preheated to 30 to 45 ° C. It is an object of the present invention to provide an electrostatic powder coating method that can prevent the occurrence of repelling phenomena, rough skin phenomena, etc. on the surface of an object to be coated. First, to explain the coating apparatus for carrying out the method of the present invention, as shown in FIG. 1 and FIG. is hung, and the bumper 3 is conveyed by the conveyor 1. The bumper 3 passing through near the spray booth 4 between the hanging position and the spray booth 4
The heating device 5 is attached to the bumper 3 at a slight distance to the side of the bumper 3.
installed so as to face the In this embodiment, the heating device 5 is a plurality of infrared lamps evenly arranged. A baking hardening furnace 6 is provided adjacent to the rear of the spray booth 4. Next, specific examples of the electrostatic powder coating method of the present invention will be described. In the hanging process, the bumper 3 is hung on the hanging fitting 2, and the bumper 3 is transferred to the heating device 5. While passing through the side of the heating device 5, the bumper 3 is heated to about 45°C, and further Move and enter the spraying booth 4. After the bumper 3 was heated, the temperature decreased slightly to about 30℃ while reaching the spray booth 4, and 40KV was applied to the bumper 3, which was grounded via the conveyor 1, in this preheated state. Powder coating is sprayed from a powder coating gun to adhere to the painted surface of the bumper 3, and then heated and melted and hardened at a baking hardening temperature of 220°C to 230°C in a baking hardening furnace 6. , the painting of the bumper 3 is completed. Table 1 shows the implementation conditions of the above examples and the results obtained therefor in comparison with the conventional case in which no preheating treatment is performed. As is clear from Table 1, heating the object to be coated does not cause deterioration of the grounding effect, so the voltage applied between the object to be coated and the painting gun is lower than that of the comparative example.
The power consumption of the present invention is 40KV compared to 60KV, and the power consumption is greatly reduced. In addition, the amount of powder paint discharged from the painting gun was compared to that of the comparative example.
Compared to 90g/min, in the present invention it is 85g/min, which is slightly reduced. The condition of the painted surface obtained under these implementation conditions was that in the comparative example, the incidence of electrostatic repellent phenomenon was 50% and skin roughness always occurred, whereas in the present invention, the electrostatic repellent phenomenon There was no occurrence of any rough skin.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic side view showing the main parts of a coating apparatus for carrying out the method of the present invention, and FIG.
FIG. 1... Conveyor, 2... Hanging tool, 3... Bumper, 4... Spraying booth, 5... Heating device, 6
...Baking hardening furnace.

Claims (1)

[Claims] 1. After spraying and adhering the charged powder coating to the object to be coated with a high potential difference between it and the coating machine, the object to be coated is heated at a baking hardening temperature to melt and harden the powder coating. In the electric powder coating method,
When spraying the powder coating onto the object to be painted,
An electrostatic powder coating method characterized in that when the temperature of the object to be coated is low, the object to be coated is preheated to 30 to 45°C.