JPS59209678A - Application of clear paint - Google Patents

Abstract

PURPOSE:To apply clear paint which does not change its color over a long period with high efficiency, by forming an electric conductive layer containing a nitric ammonium salt on the surface of an insulating workpiece to be coated, electrostatically applying clear paint onto the electric conductive layer while impressing voltage thereon. and then drying the obtd. coating film. CONSTITUTION:A nitric ammonium salt, e.g. ammonium stearoamide propyldimethyl-beta-hydroxyethyl nitrate, is sprayed as its isopropyl alcohol solution onto the surface of an ornamental plastic frame 1 for a ventilation fan to form an electric conductive layer 2. Thereafter, high voltage is impressed on said electric conductive layer 2, and clear paint is electrostatically applied through the electric conductive layer 2 onto the surface of the ornamental frame 1 to form a coating film 3. Said coating film is dried at about 50 deg.C for about 25min to inhibit the yellowing of the electric conductive layer 2. Hence, efficient coating is performed without deteriorating the external appearance of the ornamental frame over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a clear paint coating method for applying a clear paint to an insulating object to be coated by a so-called electrostatic coating method.

[Technical background of the invention and its problems]

Conventionally, for example, there is a system in which a decorative frame of a ventilation fan is coated with a releasable Kuri 17 paint to form a coating film, and this coating film is peeled off together with oil stains etc. that adhere when the ventilation fan is used. For this product, the worker held a spray knife in his hand and sprayed the clear paint onto each decorative frame one by one ("JB"), but this method was not efficient. It has the disadvantage of being bad.

Therefore, it has recently been considered to apply this clear paint automatically using an electrostatic coating method.

In this case, since the decorative frame is made of plastic and has no ordinary properties, it is necessary to form a conductive layer on the surface of the decorative frame. It is conceivable to apply a conductive agent using a spray.

However, as mentioned above, with the conventional conductive material applied and then painted with clear paint, there is a problem that localized yellowing occurs on the surface after about 2 months or more after painting, which significantly impairs the appearance of the decorative frame. Kaatsu 1 child.

As a result of repeated analyzes and experiments, the inventor of the present invention found that the cause of the yellowing was alkyltrimethyl ammonium chloride contained in the conductive agent.

That is, the conventional conductive agent is composed of isobyl alcohol as a melt, a trace amount of alkyl 1-limedyl ammonium chloride and nonylphenoxy polyethanol dissolved therein, and yellowing is caused by clear paint. A phenomenon is observed in which the conductive agent is concentrated in areas where the coating film is incomplete and where the conductive agent adheres to many cans (=I). It was assumed that the azo compound diffused into the clear paint film and reacted with the alkyl 1-rimedyl ammonium chloride in the conductive agent to produce a yellow-colored azo compound. Yellowing occurs intensively in areas where the film is incomplete and thin, or where a large amount of conductive agent has adhered and alkyltrimethylammonium chloride is concentrated. This is not a problem at all when painting with colored paints, but it becomes a serious problem when painting with clear paints in which the conductive layer is visible.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide a method for applying a clear paint that does not cause yellowing over a long period of time and does not cause any damage to the appearance.

[Summary of the invention]

As a result of further repeated analysis and experiments, the present inventor found that yellowing of the conductive layer could be reliably prevented by using a nitric acid-based ammonium salt instead of a chlorine-based ammonium salt, and the present invention The method includes a conductive layer forming step of forming a conductive layer containing a nitrate-based ammonium salt on the surface of the object to be painted, and applying a voltage to the conductive layer to electrostatically apply chestnut hair coating to the object to be painted. A coating film forming step of forming a coating film;
The drying step of drying the coating) is sequentially performed.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, an example of the object to be painted is a plastic decorative frame of a ventilation fan, and an example of the clear paint is a peelable clear paint.

First, an approximately 0.05% isopropyl alcohol solution of ammonium nitrate salt such as stearamidopropyldimethyl-β-hydroxylethyl ammonium nitrate is prepared as a conductive agent. The structural formula of the nitric acid ammonium salt is expressed as follows. That is, OH.

(R is a hydrocarbon chain of stearic acid).

Then, this conductive agent is applied to the surface of the decorative frame 1 to a thickness of approximately 5 to 10 μm (the amount of application is 0.5 (1/
Form an S conductive layer 2 (conductive layer forming step) of C11l' or higher). After that, a high voltage is applied to the conductive layer 2, and a clear paint is sprayed on the conductive layer 2 using an electrostatic coating method, which is applied for about 10 minutes.
A coating film 3 having a thickness of 5 to 20 μm is formed (coating film forming step). Then, supplementary clear A is applied to areas where the coating film 3 is insufficiently formed.
7 After applying the top coat of paint, it is dried for 25 minutes at about 50° C. (drying step).

The following table shows the results of tests on decorative frames painted using the above J: method. In addition, in the table, the comparative example refers to a case coated in the same manner as the present example using a conventional conductive agent containing a chlorinated ammonium salt, and the P1~cycle refers to the case where the decorative frame was painted at -20°C and 60°C. This indicates that each is maintained alternately for 1 hour.

As is clear from the above table, according to this example, yellowing does not occur even when left for a long period of time, and it is possible to reliably prevent the appearance of the decorative frame from being damaged.

This is presumed to be because the nitrate-based ammonium salt in the conductive layer 2, unlike conventional chlorine-based ammonium salts, does not react with nitrogen oxides in the air to produce yellow-colored azo compounds. .

[Effects of the Invention] As described above, the present invention is characterized in that a conductive layer containing a nitric acid-based ammonium salt is formed on the surface of the object to be coated, and a clear paint is electro-coated in one step. As a result, it is possible to prevent yellowing of the conductive layer, which prevents the appearance of the object being painted from being damaged even if it is left unused for a long period of time. This has the effect of improving efficiency.

[Brief explanation of drawings]

The drawing is a cross-sectional view showing a state of coating on a decorative frame according to an embodiment of the present invention. In the figure, 1 is a decorative frame (object to be painted), 2 is a conductive layer, and 3 is a coating film. Applicant Tokyo Shibaura Electric Co., Ltd. Agent Patent Attorney Sato

Claims (1)

[Claims] 1. A conductive layer forming step of forming a conductive layer containing a nitrate-based ammonium salt on the surface of the object to be painted, and applying a voltage to the conductive layer to electrostatically apply a clear paint to the object to be painted. A method for applying a Kuri 17 paint, characterized by sequentially performing a coating film forming step to form a coating film, a drying step to dry the coating film, and the like.