JPS6259749B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a release agent for electrodeposition jigs. In the electrodeposition coating line, the object to be coated is held in a suitable jig and transported to the electrodeposition, washing, and baking steps. At this time, since the jig is also electrodeposited and baked together with the object to be coated, a cured coating film is also formed on the jig. Therefore, when a jig is repeatedly used, not only do the coating films become laminated, making the jig heavy, but they also peel off due to some kind of impact, staining the electrodeposition bath and the coating on the object to be coated. Therefore, the work of removing the coating film on the jig is an important process in electrodeposition coating. However, in automated continuous systems,
The time and processing conditions that can be spent on the coating film removal process are limited, and the coating must be able to be easily removed in a short period of time. Conventional electrodeposition coatings are mainly anionic electrodepositions, and strong alkalis such as caustic potash are used to treat the coating on jigs. However, in recent years, as cationic electrodeposition has been adopted for electrodeposition coating, the use of alkali as a stripping agent, even if the amount remaining in the jig and carried into the electrodeposition bath is small, It tends to be avoided because it has a considerable negative effect on electrodeposition. However, on the other hand, there is no effective paint remover that can replace alkali, and jig cleaning has become a major obstacle in automatic continuous systems for electrodeposition coating lines. A typical composition that has been put to practical use as a jig stripping agent in place of an alkali is one in which an acid such as formic acid is dissolved in a solvent that can swell or dissolve the paint film.
The effect is not sustainable due to solvent evaporation. In order to suppress the evaporation of the solvent, some products have added paraffin to it, but paraffin has a weak ability to penetrate into the coating film and is not very useful in softening the film itself, so it is not effective in preventing evaporation of the solvent. When the paint is washed away with the solvent, the solvent that has entered the paint film evaporates in a short period of time, and the paint film quickly hardens. For example, when cleaning a jig with a release agent applied in several stages using nozzle jet water, the part that was first hit with the water jet can be washed well, but the part that was splashed with the jet water is washed off with the release agent. is removed, and the coating film tends to harden and become more difficult to remove. The present invention provides an acid-solvent type paint stripping agent for electrodeposition coating jigs that does not coagulate due to splashed water in the water washing process. That is, the present invention relates to a stripping agent for electrodeposition coating jigs that contains as main components a solvent that swells or dissolves a coating film, formic acid, solid carboxylic acid, solid alcohol and/or its esters. As the solvent for swelling or dissolving the coating film used in the present invention, solvents conventionally used in paint stripping agents, such as methylene chloride, trichlene, trichloropropane, dichloropropane, etc., may be used as appropriate. Most preferred for the present invention is methylene chloride, but is not limited thereto. The above solvent is usually blended in an amount of 60 to 90% by weight, preferably 65 to 85% by weight of the total amount of the release agent. The acid component used in the present invention is limited to formic acid. Satisfactory results are not obtained using other acids. The amount of formic acid used is 5 to 20% by weight, preferably 10 to 15% by weight of the total amount of the stripping agent. When the amount of formic acid is less than 5% by weight, the peeling effect decreases;
Even if it exceeds % by weight, it does not contribute to the peeling effect at all. The solid carboxylic acid, solid alcohol, and/or their esters used in the present invention are very effective in preventing the stripping agent from coagulating due to adhesion to water and preventing evaporation of the solvent, and effectively sustaining the action of the stripping agent during the cleaning process. and is easily removed by washing with water. Solid carboxylic acids useful in the present invention include saturated fatty acids having 12 or more carbon atoms, such as lauric acid, palmitic acid, and stearic acid, and fatty acids that are liquid or paste-like at room temperature, such as oleic acid and linoleic acid, are not effective. Solid alcohols include saturated aliphatic alcohols with 12 or more carbon atoms, such as lauryl alcohol,
Alcohols that are liquid at room temperature are not effective, such as cetyl alcohol and stearyl alcohol. Of course, synthetic alcohols with side chains are also effective if they are solid at room temperature. The above carboxylic acid or alcohol esters include solid monoglycerides, diglycerides,
Triglycerides, pentaerythritol esters, esters of higher fatty acids and higher alcohols, ie waxes, may also be used. Although it is desirable that these substances themselves are solid, it is also possible to use solid acids or alcohols produced by hydrolysis. The above fatty acids, alcohols, and esters may be used alone or as a mixture. Particularly preferred components are methyl stearate and stearic acid monoglyceride. The blending amount of these components is 1 to 10% by weight, preferably 1.5 to 10% by weight of the total amount of the release agent.
It is 5% by weight. Other components may be added to the stripping agent of the present invention.
For example, a solubilizing agent for dissolving formic acid in the above-mentioned solvent, such as cyclohexanol, t-butanol, ethylene carbonate, surfactant; a thickener for applying a stripping agent thickly onto the coating film and preventing it from running off. , such as ethyl cellulose, carboxymethyl cellulose, colloidal silica, etc.; after washing,
An emulsifying dispersant or the like may be appropriately blended to properly emulsify and disperse the removing components (release agent, swollen coating film pieces, etc.) in the washing water. By using the release agent for electrodeposition jig of the present invention,
The problems with cationic electrodeposition coating that conventionally occurred when using alkaline strippers and the aforementioned problems that occurred with acidic strippers are all solved at once, and satisfactory paint stripping can be achieved in a short period of time. The cleaning line in the automatic continuous system of the coating line can be shortened, and the electrodeposition work can be made more efficient. It goes without saying that the release agent of the present invention can be used as a release agent for anionic electrodeposited coatings. Examples will be described below. Examples 1 to 10 and Comparative Examples 1 to 4 Cation electrodeposition was performed on a stainless steel test panel according to a conventional method (liquid temperature: 27±1° C., voltage: 250 V, electrodeposition time: 3 minutes). The paint used was Elekron 9000 (epoxy-based cationic electrodeposition paint) manufactured by Kansai Paint Co., Ltd., and was baked at a temperature of 210℃ for 20 minutes to obtain a film thickness of 20±3.
A coating film of μm was obtained. The above electrodeposited panel was immersed in a stripping solution (20 to 25℃) with the formulation shown in Table 1 for 5 minutes, and after being pulled up,
Tap water (faucet diameter 7
The hardness of the coating films was compared after washing for 1 minute at a flow rate of 2/min (mm flow 2/min). A hard coating indicates difficulty in subsequent washing with water. 【table】

Claims (1)

[Scope of Claims] 1. A stripping agent for an electrodeposition coating jig, which contains as a main component a solvent that swells or dissolves a coating film, formic acid, solid carboxylic acid, solid alcohol, and/or their esters. 2. The stripping agent according to item 1, wherein the solvent is methylene chloride. 3. The stripping agent according to item 1, wherein the solid carboxylic acid is a saturated fatty acid having 12 or more carbon atoms. 4. The stripping agent according to item 1, wherein the solid alcohol is a saturated alcohol having 12 or more carbon atoms. 5 A first compound containing 89 to 75 parts by weight of a solvent, 10 to 20 parts by weight of formic acid, and 1 to 5 parts by weight of solid carboxylic acids, solid alcohols, and/or esters thereof.
Release agent as described in section.