JPS581635B2 - Huntai Souhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder coating method as a final finishing process for the body or parts of, for example, an automobile.

Electrostatic powder coating uses electrostatic atomization to atomize the paint,
An air spray gun is generally used as a device for spreading the spray onto the object to be coated.

In other words, the paint is atomized using compressed air and sprayed from the nozzle tip of a spray gun, and the paint is electrostatically atomized and applied by the applied voltage between the gun tip and the object to be coated. A uniform film thickness can be obtained with good coating efficiency.

The pattern shape, pattern width, etc. can be easily adjusted using a spray gun.

The paint is unstable because it is attached to the object only by electrostatic force, and therefore it is necessary to send the paint to a baking drying oven as a post-process to bake the paint onto the object.

Normally, each of these steps is automatically performed on a conveyor line, so that the electrostatic coating step to the baking drying step can be carried out in a fixed short time.

However, there are cases where the electrostatic coating process and the baking drying process are separated by a whole day or more, for example during a holiday, and in such cases, the paint that has already been applied the day before is removed before the baking drying process. Some of them are scattered or are likely to be scattered.

In other words, as the electrostatic force decreases over time, the adhesion force of the powder coating also decreases, and the adhesion force of the powder coating also decreases, resulting in shock during transportation of the object to be coated, or especially when passing through the air curtain seal provided at the entrance of the baking drying oven. At the same time, or alternatively, the paint may be blown away by the blown air in the furnace, resulting in the paint being baked in an incomplete state, for example in a mottled state, resulting in a product that is extremely defective from a quality control standpoint.

According to electrostatic painting, when sent to the baking drying oven after 2 hours as described below, less than 20% of the paint scatters, and it lasts for one day (24 days).
It is assumed that this value will reach 30% or more over time (see Table 1).

The present invention eliminates the above-mentioned drawbacks and provides a powder coating method in which the adhesion of the paint can be restored by only applying electrostatic charge to the object to be coated before the drying process.

The idea of applying electrostatic electricity to restore the adhesion of the paint before the drying process according to the present invention is not limited to electrostatic coating methods, but also applies to all other powder coating methods such as thermal spray powder coating methods. Of course, it can be applied to paints whose adhesion has decreased over a certain period of time, and can be restored to at least the initial adhesion.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Although the following examples are described in terms of electrostatic coating methods, they are not limited thereto as described above.

FIG. 1 diagrammatically shows a powder coating method according to the present invention, in which an object 7 is coated in a powder coating booth 1 using, for example, a spray gun as is known in the art.

Reference numeral 6 indicates a conveyor line for transporting the object 7 to be coated.

If the conveyor is constantly flowing without interruption as described above, the object 7 to be coated will be sent into the baking drying oven 5 and the paint will be completely adhered thereto.

However, as mentioned above, if the conveyor line is interrupted during the transition from the coating process to the baking drying process, the adhesion of the paint decreases depending on the interruption time. Later, it is transferred into the furnace 5.

The electrostatic voltage application chamber 2 has both terminals (pins) connected to the electrostatic voltage application device 8 via cables 9 and 9' as shown in FIG.
3.3', and the object 7 to be coated is applied by passing between the two pins 3, 3'.

The magnitude of the electrostatic voltage and the duration of its application are appropriately determined depending on the duration of the conveyor line interruption.

If the application of electrostatic voltage is unnecessary, the application device 8 may be left inactive.

Instead of carrying out the electrostatic voltage application process using the electrostatic voltage application chamber 2 incorporated into the conveyor line as described above, it is also possible to carry out the process by spraying the paint with a known electrostatic powder coating gun.

The paint whose adhesion has decreased due to the interruption of the conveyor line will not flake off even if it moves on the normal conveyor line 6, and the biggest cause is when it passes through the air curtain 4 installed at the entrance of the baking drying oven 50. It is something that scatters.

The air curtain 4 has air constantly flowing strongly in one direction for the purpose of dustproofing and heatproofing the inside of the furnace 5, and this airflow causes the paint with reduced adhesion to scatter.

In this way, according to the present invention, by adding an electrostatic application step just before sending the coated article to the baking drying oven, even if the coated article is on a stopped conveyor line and has been coated several days ago, Since the adhesion force due to the electrostatic force is restored to its initial state and the baking treatment is then performed, an extremely high quality powder coating method is provided.

If the coating method of the present invention is applied even when the adhesion force has not decreased significantly, the adhesion force will be further increased compared to the initial state, that is, the state immediately after the coating process is completed.

Table 1 below shows the experimental results of the powder coating method according to the present invention.
This figure shows a comparison with a case (conventional method) that does not involve an electrostatic impression process.

The coating method used in this experiment was to apply the coating to the object under the same conditions using a known electrostatic powder coating gun, and then leave it for the various times shown in the table. , the other (prior art) compares the paint scattering rate as a result of direct wind blowing at 8 (m/s).

The applied voltage was -70 (KV). As can be seen from the above table, it will be understood that according to the present invention, the paint adhesion rate is significantly improved compared to the case where the electrostatic voltage application process is not performed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a powder coating process according to the present invention, and FIG. 2 is an illustrative diagram of the electrostatic voltage application chamber of FIG. 1 viewed from the flow direction of the object to be coated. 1...Painting booth, 2...Static voltage application room, 3, 3'
. . . Pin, 4. Air curtain, 5. Baking drying oven, 7. Object to be coated, 8. Electrostatic voltage application device.

Claims (1)

[Claims] 1. A powder that includes a step of applying an electrostatic voltage to the surface of the object to be coated after the coating process of applying the powder coating onto the surface of the object to be coated and immediately before transferring the object to the baking treatment drying oven. Body painting method.