JPH06272089A - Coating device - Google Patents

Abstract

PURPOSE:To improve coating quality by preventing a secondary sagging of an electrodeposition liquid in an oven for drying the electrodeposition liquid stuck on an object to be coated in an electrodeposition process. CONSTITUTION:A sagging cutting zone 52 is provided between the electrodeposition process 11 forming an electrodeposition coating film on the object to be coated and the oven for drying and hardening the electrodeposition film formed on the object in the electrodeposition process. The sagging cutting property of the electrodeposition liquid is improved by setting a transportation time of the object at the sagging cutting zone 52 to >=7 minutes or using a cleaning liquid containing a surfactant as the cleaning liquid used in cleaning processes 21a to 21c provided at the sagging cutting zone or keeping the cleaning liquid or the object at >=30 deg.C. In such a manner, coating quality is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus having an electrodeposition process and an oven for drying and curing an electrodeposition coating film.

[0002]

2. Description of the Related Art An automobile body painting process usually includes an undercoating process by electrodeposition coating, and an intermediate coating and a topcoating process mainly by electrostatic coating. The vehicle body is conveyed to the electrodeposition step as the undercoating step after the oils adhering to the vehicle body are removed in advance by the pretreatment step and the chemically stable inorganic film is formed on the steel plate surface. After passing through this electrodeposition coating process, the vehicle body is transported into an oven, that is, a drying oven to dry and harden the electrodeposition coating film, and then is sequentially transported to an intermediate coating process and a top coating process. This means, for example, Automotive Engineering Complete Book No. 1
Volume 9 "Manufacturing method of automobiles" April 20, 1980; Pages 202 to 208, "Painting equipment", published by Sankaido Co., Ltd.
It is introduced in the item.

[0003]

As described above, the automobile body after the undercoating is completed in the electrodeposition coating process is conveyed to the oven where the undercoating film is dried and cured. Since an intermediate coating film and an overcoating film are formed on this undercoating film, if the film thickness of this undercoating film does not reach a predetermined film thickness, the final overcoating film surface The finish is not good.

When the cause of coating defects was investigated when the final finish of the coating film was not good, the coating surface of the electrodeposition coating for forming the undercoat coating film had a good film thickness. It turned out to be because it was not. In other words, in order to speed up the painting work, conventionally, the car body that has finished the electrodeposition coating process is brought into the oven as soon as possible. If the vehicle body is loaded into the oven without the liquid being removed, the vehicle body will be loaded into the oven while the excess electrodeposition liquid is flowing along the vehicle body. There may be a part where the film thickness is increased, and a part where a uniform coating surface is not finally formed may occur. In particular, the car body, which is the object to be coated, has a bag-shaped portion such as the inside of a door, and the electrodeposition liquid drops from this portion and gradually flows along the surface of the car body. It was found that this affected the formation of a good coating surface.

The present invention has been made in view of the above-mentioned problems of the prior art, and is designed to be carried into an oven after the electrodeposition liquid has been sufficiently removed from the automobile body after passing through the electrodeposition process. The purpose is to improve the coating quality.

[0006]

The present invention for achieving the above object comprises an electrodeposition step of forming an electrodeposition coating film on an article to be coated,
During the electrodeposition process, the electrodeposition film formed on the article to be coated is dried and cured between the oven and the excess electrodeposition liquid adhering to the article to be coated in the electrodeposition step is completed. The coating apparatus is characterized in that a sagging cut zone that is removed from the object to be coated is installed before being carried into the oven. In the sagging zone, the transport time of the article to be coated here is set to 7 minutes or more, or a cleaning liquid containing a surfactant is sprayed onto the article to be coated, or sprayed onto the article to be coated. The temperature of the cleaning liquid or the temperature of the article to be coated is set to 30 ° C. or higher.

[0007]

In the present invention having the above-mentioned structure, the sagging cutting zone is provided between the electrodeposition step and the oven. In the sagging cutting zone, the transport time of the material to be coated, the temperature of the cleaning liquid, and the temperature of the material to be coated are reduced. By setting the temperature of the coating material to a predetermined temperature, the sagging resistance was significantly improved, and the coating quality after finishing the intermediate coating and the top coating on the coating object after passing through the oven was improved.

[0008]

1 and 2 are views showing an embodiment of a coating apparatus according to the present invention. In the drawings, electric power is applied to a vehicle body after a pretreatment or a chemical conversion treatment step in a coating step is completed. Of the parts from the step of coating and coating to the oven for drying and curing the surface of the electrodeposition coating film, the first half is shown in FIG. 1 and the second half is shown in FIG.

The coating process shown in the drawing is arranged along a conveyor 10 which conveys an automobile body, which is an object to be coated, in a suspended state. On the upstream side of this, an electrodeposition tank 11 for performing electrodeposition coating as an undercoat coating on the vehicle body is arranged, and this electrodeposition tank 11 forms an electrodeposition process. A sub-tank 12 is arranged on the carry-out side of the electrodeposition tank 11, and the electrodeposition liquid L discharged from the vehicle body carried out from the electrodeposition tank 11 is stored in the sub-tank 12.
In order to return the electrodeposition liquid L in the sub tank 12 to the electrodeposition tank 11, a circulation path 13 is provided between the sub tank 12 and the electrodeposition tank 11.
Is connected, and a pump P and a filter F are provided in this circulation path 13.

On the downstream side of the sub-tank 12, first to third
Water washing steps 21a to 21c are arranged, and recovery tanks 22a to 22c for collecting the cleaning liquid sprayed on the vehicle body are provided below the respective water washing steps 21a to 21c.
Are arranged. Spray nozzles 23a to spray the cleaning liquid in the recovery tanks 21a to 21c onto the vehicle body
The circulation tanks 24a to 24c having 23c are the recovery tank 21.
a to 21c, each circulation path 24a
A pump P and a filter F are provided at 24c.

A dip washing tank 31 is arranged as a fourth washing step on the downstream side of the third washing step 21c, and a sub-tank 32 for accommodating the washing liquid overflowing from the dip washing tank 31 is arranged on the carry-out side. ing.
A circulation path 34 having a spray nozzle 33 for spraying a cleaning liquid onto the vehicle body is connected to the dip washing tank 31.
The circulation path 34 is provided with a pump P and a filter F. Further, the dip washing tank 31 is connected with a circulation path 36 having a spray nozzle 35 for spraying the washing liquid onto the vehicle body before being carried therein.

A final cleaning step 41 is installed on the downstream side of the sub-tank 32. The cleaning solution in the recovery tank 42 for recovering the cleaning solution sprayed on the vehicle body in this cleaning step is a circulation path having a spray nozzle 43. It is supplied to the vehicle body by 44. Further, a cleaning liquid supply path 46 having a spray nozzle 45 is provided on the downstream side of the spray nozzle 43, and the industrial water supplied into the tank 47 is sprayed onto the vehicle body by the supply path 46.

The vehicle body, which is the object to be coated after such a water washing process, is heated by the conveyor 10 in the oven, that is, the drying oven 5.
It is carried in 1. From the aforementioned electrodeposition tank 11 to the oven 51
The area up to is a sagging zone 52. By prolonging the time during which the sagging cut zone 52 is conveyed, the sagging of the electrodeposition liquid L can be reduced.

FIG. 3 shows a side sill of an automobile in the case where the conveying speed of the conveyor 10 in the sag cutting zone 52 is the same as the conventional one (Experimental example 1) and the case where the conveying speed is low (Experimental example 2). The result of measuring the number of sags of the electrodeposition liquid L falling from the portion is shown. The vertical axis in FIG. 3 represents the number of secondary sags. The transport speed of the conveyor 10 in Experimental Example 2 is about 6.3 times higher than that in Experimental Example 1.
% Has been reduced. As described above, it was found that the secondary sagging of the electrodeposition liquid L in the oven 51 is reduced by prolonging the residence time of the coating object in the sagging cut zone 52. In particular, the amount of secondary sag for rank A was significantly reduced.

FIG. 4 is a graph showing the results of measuring the time for which the object to be coated stays in the sag cutting zone 52 and the number of secondary sags. From the results of this experiment, the residence time that does not pose a practical problem is 7 minutes or more. It turned out to be.

FIG. 5 shows the first to third washing steps 21a-2.
For the cleaning liquid A containing 0.02% of a surfactant as the cleaning liquid sprayed on the article to be coated in 1c and the industrial water B containing no surfactant, the temperature is from 25 ° C to 5 ° C.
It is a graph which shows the result of having measured secondary sagging property to 40 degreeC at every other place. In this experiment, "x" indicates that the secondary sagging property is not good, "△" is normal, "○" is good, and "⊚" is quite good.

As is clear from the results of this experiment, the cleaning solution A containing the surfactant has a better secondary sag property than the cleaning solution containing no surfactant, and the sagging zone In the cleaning step provided at 52, the secondary sag was improved by spraying a cleaning liquid containing a surfactant as a cleaning liquid onto the article to be coated.

As is clear from the results of this experimental example, it was found that the higher the temperature of the cleaning liquid, the better the secondary sagging property, and even when industrial water was used, the cleaning liquid It was found that the secondary sagging property with practically no problem can be obtained by setting the temperature of 30 ° C. or higher.

FIG. 6 is a graph showing the relationship between the temperature and the viscosity of the electrodeposition liquid L. The viscosity of the electrodeposition liquid L is 50 ° C.
It has been experimentally determined that the viscosity significantly decreases when the value exceeds. From this experimental result and the experimental result shown in FIG. 5, it can be understood that it is more preferable to set the temperature of the cleaning liquid to 50 ° C. or higher.

In the experimental example shown in FIG. 5, the residence time in the sag cutting zone 52 is 1 minute, and if this time is made longer, a sufficient sag cutting property for improving the final coating quality can be obtained. It has been found.

As described above, it has been found that when the temperature of the cleaning liquid is set to 30 ° C. or higher, the sagging resistance is improved, but the object to be coated may be heated without heating the cleaning liquid. . FIG. 7 shows two values for each residence time in the sagging cut zone 52 for the case C in which the object to be coated is preheated and set to 80 ° C. and the case D in which the object to be coated is kept at room temperature without being preheated. The following is the experimental result of measuring the sagging resistance. The temperature of the cleaning liquid at this time is set to 30 ° C. As can be seen from this experiment, by preheating the coated object, a considerably good secondary sagging resistance was obtained.

As described above, in the present invention, the sag cutting zone 52 is provided between the electrodeposition step 11 and the oven 51 for removing the electrodeposition liquid adhering to the object to be coated in the electrodeposition step. There is. In the sag cutting zone 52, the conveying time of the article to be coated is set to 7 minutes or more, or a cleaning liquid containing a surfactant is sprayed onto the article to be coated in the washing process provided in the sagging zone 52. Alternatively, by setting the temperature of the cleaning liquid or the temperature of the coated object to 30 ° C or higher,
The sagging in the sagging zone 52 can be sufficiently performed, and the improvement of the coating quality after the intermediate coating and the top coating after passing through the oven 51 is achieved. When heating the cleaning liquid or the object to be coated,
One of the object to be coated and the cleaning liquid may be set to the temperature of 30 ° C. or higher, or both of them may be set to the temperature or higher.

[0023]

As described above, according to the present invention, the sagging zone is provided between the electrodeposition step and the oven. Therefore, the electrodeposition liquid adhered to the article to be coated in the electrodeposition step Was reliably removed in the sagging zone, and the coating quality was improved. In this sagging zone, the transport time of the article to be coated is set to 7 minutes or more, a surfactant is sprayed onto the article in the sagging zone, or the temperature of the article to be cleaned or the cleaning liquid is set to 30 ° C. With the above settings, it is possible to ensure sufficient sagging resistance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a first half portion of a coating apparatus according to an embodiment of the present invention,

FIG. 2 is a schematic cross-sectional view showing the latter half of the coating apparatus according to the embodiment of the present invention,

FIG. 3 is a graph showing an experiment result of sag breakage when the transport time of a coated object in the sagging cut zone is delayed,

FIG. 4 is a graph showing the relationship between the transport time of an object to be coated in a sagging zone and sagging ability;

FIG. 5 is a graph showing the results of measuring sagging resistance under various temperature conditions for a cleaning liquid containing a surfactant and a cleaning liquid not containing a surfactant as a cleaning liquid used in the cleaning step provided in the sag breaking zone.

FIG. 6 is a graph showing the relationship between the viscosity of the electrodeposition liquid and the temperature,

FIG. 7 is a graph showing the experimental results of measuring the relationship between the transport time of the coated object in the sagging cut zone and the sagging cutability, with and without preheating of the coated object. .

[Explanation of symbols]

10 ... Conveyor, 11 ... Electroplating tank, 21a-21c ... Washing process, 51 ... Oven, 52 ... Sagging zone.

Claims (4)

[Claims] 1. An electrodeposition step between forming an electrodeposition coating film on an article to be coated and an oven for drying and curing the electrodeposition film formed on the article to be coated in the electrodeposition step. A coating device, characterized in that a sagging zone is provided to remove excess electrodeposition liquid adhering to the article to be coated from the article to be coated in the oven after the electrodeposition step is completed. 2. A coating apparatus, wherein a transport time of the article to be coated in the sagging cut zone is set to 7 minutes or more. 3. A coating apparatus, wherein a cleaning liquid containing a surfactant is sprayed onto an object to be coated in the sagging zone. 4. A coating apparatus, wherein the temperature of the cleaning liquid sprayed on the article to be coated or the temperature of the article to be coated is set to 30 ° C. or higher in the sagging zone.