JPS6138278B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for cleaning an electrodeposition coating jig.

Conventionally, a strong alkali such as caustic soda has been used to clean the jig for anion electrodeposition, but when this is used to clean the jig for cation electrodeposition, the small amount of alkali remaining on the jig has a significant negative effect on cation electrodeposition. Therefore, it is necessary to thoroughly wash and remove residual alkali. However, this sufficient cleaning takes a long time, and it is not preferable to incorporate this process into an automated electrodeposition coating line.

On the other hand, in order to eliminate the above-mentioned drawbacks, the use of a stripping agent containing an organic acid and an organic solvent has been tested for cleaning the cationic electrodeposition jig. However, with the above-mentioned organic stripping agent, a localized unreleased paint film remains on the jig, and this peels off in the electrodeposition bath and causes paint film contamination, or causes the remaining paint film to grow during repeated operations, which can cause the jig and the paint to be coated. This causes poor conductivity between coatings.

The cause of partial residual coating when using a stripping agent containing an organic acid and an organic solvent has not been clarified so far, and a solution to this problem has been sought solely by improving stripping agents. However, no satisfactory means have yet been found.

As a result of repeated research to fundamentally elucidate the cause of the paint film remaining, the inventors of the present invention found that the above cause was due to the stripping agent present in the paint film being washed away by the spray of cleaning water.
It was discovered that the paint that had swollen in the peeling bath re-hardened, returning to a point where it could no longer be removed even with normal cleaning water. The present invention improves conventional cleaning systems employed in electrodeposition coating lines and provides a cleaning system that does not leave a coating film behind even when a stripper is used.

That is, the present invention attaches a release agent to an electrodeposition jig,
The present invention relates to a method for cleaning an electrodeposition jig, which comprises jetting cleaning water alternately from an upward nozzle and a downward nozzle.

As mentioned above, the present invention prevents the cleaning water sprayed from the nozzle from getting wet as much as possible except for the parts directly cleaning the jig, and the wet parts are coated with the next nozzle before the stripper is washed away. It is characterized by washing off the entire film and leaving no unremoved paint film. Therefore, high water pressure is applied to the area where the cleaning water is sprayed by the nozzle to give a strong blow, and the paint film is not peeled off, but only the release agent on it is washed away first. Nozzles and nozzle arrangements suitable for the above requirements are shown in FIGS. 1 to 3.

FIG. 1 shows a nozzle pattern of a nozzle used in the present invention. 1 is a nozzle, 2 is a spray part on the object to be coated, and γ is a spray angle. In conventional cleaning of electrodeposition coating jigs, spray angles γ are extremely narrow, such as 1 degree or less, or wide, such as 30 to 60 degrees, but in either case, it is difficult to achieve the purpose of the present invention. not enough. In the present invention, 2 to 15 degrees, especially 3 to 15 degrees
Preferably, a nozzle with a spray angle γ of 5 degrees is used.

Two nozzles are used, one facing upward and one facing downward, and the hanger is sprayed from above and below. The angle of elevation or depression of the nozzle is between 30 and 60 degrees, particularly preferably between 40 and 50
degree.

A riser tube with an upward nozzle and a riser tube with a downward nozzle are shown in FIGS. 2 and 3. In the figure, 3 indicates a riser pipe, and 4 indicates a hanger.

The water pressure ejected from the nozzle is 1.5-3.5Kg/cm ² ,
Preferably it is 2 to 3 Kg/cm ² . The flow rate of cleaning water is 5-15/min per nozzle, preferably 10-15/min.
11/min.

The stripping agent used in the present invention contains an acid and an organic solvent that dissolves or swells the coating film as essential components, but in particular solid carboxylic acid, solid alcohol, and/or their esters are added to the above components as a softening agent. A release agent containing is preferred.

Paraffin, which has traditionally been commonly added as a solvent evaporation inhibitor, is effective as a release agent component, but release agents that only contain paraffin as a softening agent tend to be washed away by water. However, stripping agents containing solid carboxylic acids, solid alcohols, etc. penetrate into the interior of the paint film, and the water tends to leave a residual paint film on the areas that were hit by the water spray. Therefore, there is less tendency for only the release agent to be washed away. Therefore, in combination with the effects of the method of the present invention, very excellent results are achieved in paint removal.

As a component of the stripping agent, appropriate acids such as phosphoric acid, formic acid, and oxalic acid can be used, but from the viewpoint of solubility with solvents, stripping properties, etc., organic acids are preferred, typically formic acid. When using formic acid, the amount used is 5 to 20% by weight, preferably 10 to 15% by weight of the total amount of the stripping agent.
Weight%.

Solid carboxylic acids are saturated fatty acids with 12 or more carbon atoms,
For example, lauric acid, myristic acid, palmitic acid, stearic acid, etc.; solid alcohols include alcohols that are solid at room temperature such as lauryl alcohol, cetyle alcohol, and stearyl alcohol; esters of the above carboxylic acids or alcohols include solid monoglycerides, diglycerides, Examples include triglycerides. These components account for 1 to 10% by weight, preferably 1.5 to 5% by weight of the total release agent.

The solvent has the property of swelling or dissolving the coating film,
For example, methylene chloride, trichlene, trichloropropane, dichloropropane, etc. may be used as appropriate, but methylene chloride is typically used. These solvents usually contain 60 to 90% by weight, preferably 65 to 85% by weight of the total amount of the stripping agent.

The stripping agent may further contain other solubilizing agents, thickeners, and the like.

After the hanger on which the coating film has been formed by the electrodeposition and curing process is unloaded, it is immersed in a release agent solution and kept at room temperature for 2 to 10 minutes, preferably 2 to 5 minutes.
After the coating has been swollen, it is transported to a first water washing step (all of which are automated and move continuously) and processed under the conditions described above. Processing time is 0.5~2
minutes is enough. The hanger is treated with second and third water washing steps if desired. The treatment conditions in this water washing step do not necessarily have to be based on the method of the present invention. The peeled hangers are loaded, degreased, washed with water, and then transported to the electrodeposition bath.

The present invention will be explained below with reference to Examples.

Example: After cationic electrodeposition coating (paint: Power Top U-30 manufactured by Nippon Paint Co., Ltd.), the hanger (length 1800 mm, arm length 500 mm) from which the object to be coated was removed was moved on an overhead conveyor while the following formulation was removed. Immerse for 4 minutes in a stripping bath containing the agent.

Stripping agent formulation: Parts by weight Methylene chloride 68 Formic acid 15 Methanol 15 Lauryl alcohol 2 After leaving the stripping tank, the hanger moves in the atmosphere for 2 minutes and enters the first washing process. The nozzle spray angle γ of the first water washing process is 5 degrees, and the shortest distance between the nozzle and the hanger is 350 degrees.
mm, 36 nozzles per riser pipe (nozzle pitch 100 mm), cleaning water flow rate 10 to 11/min (nozzle 1
(per book), the water pressure of the cleaning water is 2.5Kg/ ^cm2 , and the riser pipe with an upward nozzle (elevation angle 45 degrees) and the riser tube with a downward nozzle (elevation angle 45 degrees) are 200mm.
Arrange 8 pieces alternately at intervals. The nozzle sprays cleaning water diagonally toward the hanger.

The hanger passes through the first water washing step in 1 minute.

The hanger is then passed through a second washing process. The second water washing step is a step to completely remove the release coating film and release solution caught on the hanger, and a spray nozzle with a spray angle of 60 degrees is used at a water pressure of 1 Kg/cm ² .

The above cleaning process can be carried out at a speed sufficient to be incorporated into a normal electrocoating line, and moreover, the coating film on the hanger is almost completely removed.

[Brief explanation of the drawing]

Figure 1 shows the nozzle pattern used in the present invention, and Figure 2 shows the nozzle pattern used in the present invention.
The figure shows a riser tube with upwardly directed nozzles, and FIG. 3 shows a riser tube with downwardly directed nozzles. In the figure, 1 is the nozzle, 2 is the injection part on the object to be coated,
γ indicates the injection angle, 3 indicates the riser pipe, and 4 indicates the hanger.

Claims (1)

[Scope of Claims] 1. A method for cleaning an electrodeposition coating jig, which comprises applying a stripping agent to the electrodeposition jig and spraying cleaning water onto the jig alternately from an upward nozzle and a downward nozzle. 2. The method according to item 1, wherein the spray angle of the nozzle is 2 to 15 degrees. 3. The method according to item 1, wherein the injection is performed at a water pressure of 1.5 to 3.5 Kg/cm ² . 4. The method according to item 1, wherein the amount of cleaning water sprayed from one nozzle is 5 to 15/min. 5. The method according to item 1, wherein the upward nozzle and the downward nozzle each have an elevation angle and a depression angle of 30 to 60 degrees. 6. The method according to item 1, wherein the stripping agent contains as main components a solvent that swells or dissolves the coating film, formic acid, solid alcohol, solid carboxylic acid, and/or esters thereof.