JPS6048171A - Partial painting method of automotive body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a method for partially painting an automobile body.

In recent years, due to design requirements, a method of partially applying black paint to door window frames, the top of the center pillar, etc. has been adopted for car body painting, and the partial painting method is as follows. . An undercoat film is formed on the surface of the automobile body by electrodeposition coating, etc., and after baking and hardening, an intermediate coating film is formed on the entire outer panel of the automobile body,
Without drying this intermediate coating film, parts to be painted black, such as the window frame of a door, the upper part of a center pillar, etc., are coated with black paint, and the blank coating film is baked and cured at the same time as the intermediate coating film. After that, the black painted parts necessary for the design are masked using masking materials such as paper, aluminum foil, tape, etc., and then a top coat is applied to the entire outer panel of the car body to form a top coat.
After baking and hardening, the masking material is removed to partially form a blank coating film.

However, according to this partial painting method, in order to prevent paint defects such as scratches and color unevenness due to design requirements, in addition to the necessary painting parts to form a blank paint film,
Therefore, the overspray area has an uneven coating surface with a mixture of the intermediate coating film and the black coating film over a wide area, and also lacks smoothness. This results in a poor finish of the topcoat film, which requires a lot of man-hours to be wet-sanded with vapor to make it smooth. Also, as the top coat has become brighter and darker in color recently, its hiding power has deteriorated.
The blank painted area in the overspray area may appear to be missing. For this reason, when applying a top coat with poor hiding power, stop painting the black after the intermediate coat, and mask the entire car body except for the parts necessary to form the blank paint film after the top coat. The problem is that it requires a lot of man-hours and masking material to form a black coating film.

The present invention has been made to solve the above-mentioned problems.The purpose of the present invention is to minimize the wide overspray area when applying partially coated paint, reduce the number of steps required for wet sanding, and apply a top coat with poor concealment properties. An object of the present invention is to provide a method for partially painting an automobile body, which makes it possible to paint parts of an automobile body.

The above-mentioned object of the present invention is to form an undercoat film on the surface of an automobile body, to bake and harden it, and then to form an intermediate coat film on the surface of the undercoat film, and to bake and harden the intermediate paint film. In addition, the area around the intermediate coating film except for the partially painted area is covered with a plastic masking cover having a volume resistivity of 1゜Ω・1 or more to prevent it from coming into contact with the intermediate coating film on the outer panel of the vehicle body. and form a coating film on the partial coating area using an electrostatic air spray gun at a spray air pressure of 1 to 3 kg/-, and then baking and curing the intermediate coating film and the partial coating coating simultaneously, This is achieved by a method for partially painting an automobile body, which further comprises masking the painted area of the partially painted film and forming a top coat on the surface of another intermediate coat.

Hereinafter, the partial coating method of the present invention will be explained with reference to the drawings.

FIG. 1 shows a side view of the partial painting method according to the present invention, and FIG. 2 is a perspective view showing an example of a masking cover used in the partial painting method of the present invention.

In Figs. 1 and 2, ■ is the body of a passenger car, and an undercoat film (not shown) is formed on the surface of this car body l by the usual electrodeposition coating method, and is then heated in a drying oven. Bake hardened. Next, a normal intermediate coating film 2 is formed on the outer panel surface of the vehicle body l on which this primer coating film has been formed. Then, without baking and hardening this intermediate coating film 2, a part 9 of the center pillar of the vehicle body 1 is left and a masking cover 3.4 is set around it. This masking cover 3.4 is made of a plastic material such as polyethylene resin, polypropylene resin, or fluorocarbon resin having a volume resistivity of 1012 Ω·1 or more, and is formed to cover the surrounding area except for a part 9 of the center pillar. has been done. For example, in the case of a masking cover 3 set around a door 5, the masking cover 3 is formed into a substantially U-shape as shown in FIG. At the same time, a groove 7 is formed in the center portion to be inserted so as to sandwich the center pillar part 9. When this masking cover 3 is placed around the door 5, it is fixed to the inner steel plate of the car body 1 by the magnet 6 of the inner plate 3a, and the outer plate 3b of the masking cover 3 is formed on the outer plate surface of the car body l. From the undried intermediate coating film 2, 1 to
They are held apart within a range of 3 ml. Furthermore, when the masking cover 4 is set around the ceiling 8, it is fixed to the inner steel plate of the vehicle body 1 by a magnet (not shown) provided on the inner plate 4a like the masking cover 3, and the outer plate 4b of the masking cover 4 is 1 to 3 IIm from the undried intermediate coating film 2 formed on the surface of the ceiling 8 of the vehicle body 1.
are kept within a range of

Next, with the masking cover 3.4 set, use a commonly used electrostatic air spray gun (not shown) to increase the spray air pressure to 1 to 3 kg/cIA.
Partial coating paint is applied to the center pillar part 9 within the range of , and a coating film is formed. At this time, masking cover 3.4
Since the outer plates 3a and 4a are located in the electrostatic field area between the vehicle body 1 and the electrostatic air spray gun, they are charged to the same polarity as the paint particles atomized from the electrostatic air spray gun, and the paint particles are repelled. The coating area of the partial coating paint, that is, the center pillar part 9, is concentrated on the coating area, and the coating is only slightly wider than the required painting area of the center pillar part 9, and the masking cover 3.4 is There is also less staining due to partially painted paint.

The car body 1 coated with the partially painted paint is transported to a drying oven, where the intermediate coat 2 and the partially painted film are simultaneously baked and hardened, and the painted areas of the partially painted film are masked with paper or the like. A normal topcoat film (not shown) is formed on the area. Thereafter, the vehicle body 1 is transported to a drying oven, where the top coat is cured by baking, and the partial painting of the vehicle body 1 is completed.

The masking covers 3 and 4 used in the present invention must have a volume resistivity of 101 tΩ·1 or more, and if it is less than this, the repulsive force of the paint particles will be weak when painting with an electrostatic air spray gun. This is undesirable because the paint particles get inside the masking cover 3.4 and overspray onto the intermediate coat 2 over a wide area. Also, the spray air pressure of the electrostatic air spray gun is 1 to 3 kg/
The range of d is desirable, and the spray air pressure is 1kg/CIA.
If the spray air pressure is 3 kg/ad or more, the atomization pressure of the partially applied paint will be insufficient and the paint will not be sufficiently atomized, causing paint defects such as spots. This is undesirable because it spreads and the partially painted paint adheres to other areas. Furthermore, according to the invention, the outer plate 3b of the masking cover 3.4.

4b is desirably separated from the uncured intermediate coating film 2 formed on the surface of the outer panel of the car body 1 within a range of 1 to 3 lengths, and if it is less than 1 crane, when placing it on the car body 1,
It is undesirable because it contacts the uncured intermediate coating film 2 and causes damage, and it is undesirable if it exceeds 3f1 because the paint particles of the partially coated paint will go around.

Next, the partial coating method of the present invention will be specifically explained using examples.

Example A zinc phosphate film was formed on the body of a passenger car according to the pretreatment process of degreasing, water washing, chemical conversion treatment, and water washing (precipitated film 3).
g/cd), apply cationic electrodeposition paint (
A film with a thickness of 15 to 25 μm was formed using Nireclone 9000 (manufactured by Kansai Paint Co., Ltd.), and the furnace temperature was 180 μm.
It was baked and cured for 30 minutes in a drying oven set at .degree. C. to obtain an undercoat film.

Next, an epoxy ester intermediate paint (manufactured by Kansai Paint Co., Ltd., gray color) is applied to the surface of the outer panel of the car body on which the undercoat film has been formed, and a film thickness of 25 to 25 cm is applied using the usual spray painting method.
An intermediate coating film was formed in a range of 30 μm. Then, without baking and hardening this intermediate coating film, a masking cover was placed to cover the area around the center pillar of the car body, leaving part of it intact. This masking cover is made of polypropylene resin with a thickness of 3■■, and the volume resistivity is t o
It was +2Ω・0. Further, the outer plate of the masking cover was set at a distance of 3 mm from the surface of the uncured intermediate coat.

With the masking cover in place, use a REA electrostatic hand air spray gun (manufactured by Landsburg), spray air pressure 1.6 kg/c+d, applied voltage -60 KV.
A black coating film with a film thickness of 20 to 25 μm was formed on a part of the center pillar using an alkyd blank paint (manufactured by Nippon Paint Co., Ltd.). After that, the masking cover was removed and the car body was placed in a drying oven with an internal temperature of 140°C for 30 minutes.
The intermediate coating film and blank coating film were baked and cured at the same time.

Next, after sandpapering the entire surface of the intermediate coating film with 400 mesh sandpaper, the painted areas of the blank coating film were masked with paper, and the surface of the other intermediate coating film was coated with melamine Alkit-based topcoat paint (Japanese). (manufactured by Paint Co., Ltd., red) to a film thickness of 30 mm using the usual spray painting method.
A top coat film was formed in the range of ~35 μm, and this was baked and cured for 30 minutes in a drying oven with an internal temperature of 140° C. to obtain a top coat film. After that, the masking of the black paint film was removed, and a black paint film was formed on part of the center pillar of the car body.
A passenger car body was obtained in which a red paint film was formed on other parts.

The hiding film thickness of the top coat used in this example was 60
μ (based on JISK5400 white/black concealment paper),
This paint has poor hiding properties.

Due to the partial painting method of this example, the overspray of the black paint film that occurred on the top and bottom of a part of the center pillar remained within the range of 1 to 5, and the wet sanding time for that part was completed in about 0.2 minutes. did. Furthermore, no abnormalities were observed in the finish of the oversprayed portion of the coating after the topcoat was formed, either in terms of gloss or smoothness. Furthermore, there was almost no difference in paint color from that of general painted parts, and there was no problem with the paint quality of passenger car bodies. For comparison, when a conventional partial painting method was carried out using the same paint as in this example, the overspray in one part of the blank paint film was over 10 cm, and the number of wet sanding steps was also reduced to the upper and lower part of the center pillar. It took about 2 minutes. In addition, the color of the top coat on the wide overspray area after the top coat was formed appeared darker than other general top coat parts, and the quality of the paint was not suitable for passenger car bodies.

As explained above, in the partial coating method of the present invention, after forming an intermediate coating film on the surface of an undercoat film, the area where the intermediate coating film is to be partially coated is removed without being baked and hardened. (After placing a plastic masking cover with a volume resistivity of 1012Ω・0 or more around it so that it does not come into contact with the intermediate coating film, spray air pressure using an electrostatic air spray gun. 1~3kg/c
Since the partial paint film is formed within the fA range, the masking cover is located in the electrostatic field area between the vehicle body and the electrostatic air spray gun when forming the partial paint film, and the electrostatic air spray The paint particles are charged to the same polarity as the paint particles atomized from the gun, and the paint particles are repelled and concentrated in the painting area of the partial painting area, so the partial painting paint reduces overspray over a wide range to a minimum area. It can be stopped. Therefore, since the amount of overspray is small, the number of steps required for wet sanding can be significantly reduced, and it is also possible to apply a top coat with poor hiding properties. In addition, in the present invention, since masking with paper, aluminum foil, etc. only needs to be performed on the areas where the partial paint film has been formed, the use of masking materials such as paper, aluminum foil, etc. can be significantly reduced. be.

[Brief explanation of drawings]

FIG. 1 is a side view for explaining the partial painting method according to the present invention, and FIG. 2 is a perspective view showing an example of a masking cover used in the partial painting method of the present invention. 1----One car body 2---One coat coating 3.4---Masking cover 3a, 4a---Inner plate 3b, 4b---One outer plate 5- -Door-6--Magnet 7--Groove 8--Ceiling 9--Part of the center pillar and Figure 1D Figure 2

Claims (1)

[Claims] After forming an undercoat film on the surface of an automobile body and baking and hardening it, an intermediate coat film is formed on the surface of the undercoat film, and the intermediate coat film is cured without baking and curing the intermediate coat film. The volume resistivity of the area excluding the partially painted area is 101.
Cover with a plastic masking cover made of 2Ω・0 or more to prevent it from coming into contact with the intermediate coating film on the outer panel of the car body, and spray with an electrostatic air spray gun at a spray air pressure in the range of 1 to 3 kg/cA. A coating film is formed on the partial coating area, and then the intermediate coating coating film and the partial coating coating film are baked and cured at the same time, and the coating area of the partial coating coating film is masked, and the coating film is coated on the surface of the other intermediate coating coating film. A method for partially painting an automobile body, characterized by forming a top coat film.