JPS6055191B2 - Powder coating repair method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for partially repairing a powder coating film, and more specifically, a method for partially repairing a top powder coating film that requires uniformity of the coated surface appearance using a powder coating dispersion. This invention relates to a method for repairing a powder coating film by spray painting.

In line with the trends of the times, the paint industry is also transitioning from conventional organic solvent-based paints to non-polluting paints such as powder coatings and water-based paints. Powder coatings are now widely used in steel products such as automobiles, electrical appliances, and fences, but the mainstream coating method is electrostatic spraying, and other methods include fluidized dipping and electrostatic dynamic dipping. However, no matter which coating method is used, there is a problem with the repairability of the powder coating film, and a solution is needed. For example, if the top coat of an automobile exterior panel is electrostatically sprayed powder coated, a method for partially repairing the repaired part of the powder coating film is to electrostatically spray the same powder paint as the top coat powder paint. Spray painting may be considered, but it is difficult to repair small areas with the electrostatic powder coating machines currently in use. Additionally, masking all areas other than partial repairs before electrostatic spray painting poses a problem on the production line. Therefore, if the powder coating film is repaired using powder paint, there is a drawback that the entire film, including areas that do not require repair, must be repainted. Another method would be to spray repair paint using an organic solvent-based paint or water-based paint, which is easy to apply locally, but the fatal drawback of this method is that the color is exactly the same as that of the powder coating. The inability to prepare organic solvent-based paints or water-based coatings. In other words, these coatings differ in the process of forming a coating film from powder coatings, so the colors essentially do not match. Water-based coatings also have the disadvantage that they are difficult to use because their coating workability varies greatly depending on the coating atmosphere conditions. Therefore, it cannot be a satisfactory repair method for top coats that require a uniform finish on the painted surface for cosmetic finishing. In view of the above-mentioned current situation, the present inventors have investigated various methods for partial repair of powder coating films, and have found that, in order to improve the dispersion stability of this powder coating, the same powder coating as the top coat powder coating is used, and Particle size (a). 1 to 100μ), and by spraying the powder by dispersing it in a dispersion medium, it is possible to obtain a coating film with the same color as the top coat powder coating without any trouble even on an industrial line. We obtained the knowledge that it is possible and arrived at the present invention.

That is, in the present invention, when repairing a repaired portion of a top powder coating film, the powder coating used for the powder coating film has a particle size of 0.1.
-100μ in a dispersion medium, the dispersion contains a solid content of 20 to 6% by weight, and the dispersion medium has water as a main component and 5 to 3% solids in the dispersion medium. The present invention relates to a method for repairing a powder coating film, which comprises spraying a dispersion containing a hydrophilic solvent with a saliva content of %.

In the present invention, the powder coating that forms the top powder coating film includes:
Examples of currently used paints include acrylic powder paints, polyester powder paints, and epoxy powder paints.

Acrylic powder coatings and polyester powder coatings are particularly used for coating objects that require weather resistance. These powder coatings are applied to objects to be coated by known methods such as electrostatic spraying, fluidized dipping, and electrostatic dynamic dipping. The repaired areas of the powder coating film obtained after powder coating the object to be coated by a conventional method are then repair coated according to the repair coating method of the present invention.

The paint used for repair painting is the same as the powder paint forming the top powder coating film, and its particle size is 0.1 to 100μ.
It is preferably within the range of 0.1 to 60μ. If the thickness of the coating layer is not uniform and the particle size exceeds 100μ. Potato formation is not desirable. Therefore, in order to achieve a thin and uniform finish on the painted surface of the repaired area, 60μ
It is particularly preferred to use the following: 0.1~100
A powder coating material having a particle size of μ is made into a dispersion liquid using a dispersion medium containing water as a main component.

Preparation of dispersion liquid is powder coating. It is sufficient to simply stir and mix the dispersion medium and the dispersion medium, and its preparation does not require any technical or manufacturing skill, and can be easily prepared on-site in the coating line. The dispersion used in the present invention has a solid content of 20.6% by weight, and the dispersion medium is water as the main component, and a hydrophilic solubilizer is used in the dispersion medium in an amount of 5 to 3%. It is. If the amount of the hydrophilic solvent exceeds 3% by filtration, the ability to dissolve powder particles becomes too large, so when such a dispersion is used, the color of the repaired area will be different. Examples of hydrophilic solvents include slow-volatizing solvents that are completely miscible with water and have a boiling point of 100 to 300 C, such as alcohols, ketones, esters, or ethers, which are used as coating solvents. Examples of the alcohol include butyl alcohol, amyl alcohol, hexyl alcohol, diethylene glycol, propylene glycol, glycerin, isopropyl glycol, hexylene glycol, and the like. Examples of ketones include diacetone alcohol. Examples of the ester include methyl cellosolve acetate, methyl carbitol acetate, carbitol acetate, and ethyl lactate. Examples of ethers include carbitol,
Examples include butyl carbitol, methyl carbitol, butyl cellosolve, methyl cellosolve, cellosolve, methoxybutanol, and the like. One or more types of these solvents can be used. Hydrophilic solvents (for example, methyl alcohol, ethyl alcohol, acetone, etc.) with a boiling point lower than 100'C can also be used, but since these solvents remain volatile, the dispersion can be applied at normal baking temperatures. (approximately 150 to 250 degrees Celsius), it volatilizes before baking, and although it has a positive effect on the dispersibility of the dispersion during stirring, there is no point in using it much. If the dispersion medium is only water, the coating workability will be poor unless the coating conditions (temperature, humidity) are strictly controlled, resulting in sagging, running, or falling of powder particles on the coating surface. When the specific dispersion medium used in the present invention is used, it is particularly effective to prevent sagging and running of the coated surface when a portion of the dispersion medium is used in combination with a high boiling point hydrophilic solvent. It is best to use a dispersion medium for the dispersion liquid of the present invention that does not dissolve even if the surface of the powder particles swells, but up to a certain percentage in the dispersion medium will partially dissolve the powder particles. Even if a solvent is used in combination, the difference in color of the repaired area is within an acceptable range and does not pose a practical problem.

Known nonionic or anionic surfactants can be added to the above-mentioned dispersion.

In the repair coating method of the present invention, the top powder coating is applied to the object to be coated, and after baking, the parts of the painted surface that require repair are wet-sanded, and then the dispersion is sprayed in the usual way. Spray paint with a gun.

This refinish painting process does not cause any process changes to the current automotive refinish painting process. After spray painting, after a setting time if necessary, heat to the specified temperature (150℃~
After baking at a temperature of about 250℃ for a certain period of time, in the case of spot repairs, wax the repaired area, or in the case of part repairs, apply wax to the target object without waxing. sell. By doing so, the repaired area can be painted in a smooth and painted condition that is no different from other normally painted areas. The present invention has made it possible for the first time to repair top powder coatings, which were conventionally considered difficult to repair, by using the above-mentioned dispersion.

This is because the coating film formation process of the dispersion involves the same process as in powder coatings, in which resin particles are melted by baking and then hardened, so no change in color occurs. The dispersion of the present invention can be easily prepared even on an industrial line and can be spray coated, so it is very distinctive in that it is economical and does not require tedious processes. In particular, the ease with which the dispersion can be prepared on-site makes it ideal for use in industrial lines. The method of the present invention is also superior to methods used in conventional refinishing applications. The repair coating method of the present invention can be applied to any object to be coated that can be powder coated, such as automobiles, electrical appliances, steel products such as fences, etc. The present invention will be explained below using examples.

Parts mean parts by weight. Example 1 "Evaclad NO. 54OO" (trade name of acrylic powder paint manufactured by Kansai Paint Co., Ltd., glycidyl acrylic acid-curing type) was applied to a car body that had been electrodeposited in advance.
was powder coated using an electrostatic powder coater (cured film thickness 50 μm) and then baked at 1800 m2 (temperature 20°C).
(The test was carried out under conditions of 60% humidity).

There was some flaking on a part of the painted surface, so I wet-sanded it in a wide area, focusing on the area where flaky flakes had formed, then cleaned the water-sanded area, and after the painted surface had dried, I applied the dispersion listed below at a temperature of 25°C and humidity. Under 80% conditions, a spray paint machine manufactured by Iwata Painting Machinery Co., Ltd. (
The coating was sprayed using a model W-71 (model W-71, coating nozzle φ1.5 mm, gravity type) at an air pressure of 1k9/Clt. After painting, a setting time of 1 minute was allowed, and then baking was performed at 180°C. After that, the unevenness of the spot repair area is
I sanded it with a 100-meter sand vapor and waxed only the repaired areas to make them shiny. The painted surface was so uniform and smooth that even the repaired areas were indistinguishable.
In addition, ΔE was determined by measuring AbL values at 5 arbitrary locations on the body, including the repair painting locations (2 locations adopted), using a color difference meter, and ΔE = 0.2, meaning that most of the differences were not significant. This was recognized. (Preparation of dispersion liquid) A part of Evaclad No. 54OO, which has been sieved to have a particle size of 60μ or less, 9 parts of water, 5 parts of diethylene glycol, and 5 parts of diacetone alcohol are thoroughly stirred with a dispersion machine to form a dispersion liquid. And so.

Claims (1)

[Claims] 1. When repair painting a repaired portion of a top powder coating film, a dispersion liquid in which a powder coating used for the powder coating film with a particle size of 0.1 to 100 μ is dispersed in a dispersion medium, Spray coating a dispersion in which the dispersion contains 20 to 60% by weight of solids, the dispersion medium contains water as a main component, and the dispersion medium contains 5 to 30% by weight of a hydrophilic solvent. A method for repairing a powder coating film characterized by the following.