JP2556838B2 - Undercoat treatment method for automobile body painting, etc. - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for undercoating in automobile body painting or the like.

[Conventional technology]

In general, painting of automobile bodies is usually performed by baking, and the standard process is to finish with three coats of undercoat, intermediate coat and top coat.

Conventionally, this undercoating process has been mainly performed by the cationic electrodeposition coating method described in JP-B-59-32558 (see FIGS. 2 and 3 of the attached drawings).

This cationic electrodeposition coating method will be described in detail. First, as a degreasing process 50, an object 3 to be suspended that is suspended on a transport rail 1 by a hanker 2 passes through a booth entrance 4, and then in a preliminary degreasing step A. Liquid temperature from tank 5 65 ℃
The degreasing treatment is performed by spraying the alkaline aqueous solution of No. 3 from the degreasing agent spraying device 6 for 60 seconds. Next, in the degreasing step B, the degreasing process is performed by immersing the alkaline solution in the degreasing tank 7 at a liquid temperature of 65 ° C. for 120 seconds to perform a degreasing process 51.
In the washing step C, the industrial water supplied from the water tank 9 is sprayed from the water spraying device 8 at room temperature for 30 seconds to wash, and further in the second washing step D into the industrial water in the water tank 9 at room temperature.
Immerse for 30 seconds for cleaning.

Further, in the surface conditioning step F as a process 52 such as chemical conversion treatment, the surface conditioning agent in the tank 10 is sprayed from the surface conditioning agent spraying device 11 for 30 seconds to perform the surface conditioning. Then, in the chemical conversion treatment step G, the chemical conversion treatment solution such as an aqueous solution of zinc phosphate in the chemical conversion treatment tank 12 is immersed at 50 ° C. for 150 seconds to form a chemical conversion film on the surface of the article to be coated. Next, as the water washing process 53, in the third water washing step H, the industrial water supplied from the water tank 14 is sprayed from the water spraying device 13 at room temperature for 30 seconds to be washed, and then supplied from the water tank 15 in the fourth water washing step I. It is washed by immersing it in a water tank 14 storing water for 30 seconds at room temperature. Furthermore, in the circulating pure water washing step J,
In the next step K, the water sprayer 16 circulates and sprays the water from the water tank 15 storing the wash water at room temperature, and then, in the fresh pure water washing step K, a pure or ion-exchanged water is supplied from the water supply pipe 17 to the water sprayer. Clean from 18 by spraying at room temperature.

The article 3 that has been washed with water is then subjected to a direct-drain hot-air circulation-type draining dry process in which hot air is supplied from the air supply port 19 and exhausted from the exhaust port 20 in the water-drying drying process L in the water-drying drying process 54. Drying and drying for 10 minutes at an ambient temperature of 100 ° C. in the device 21 After performing draining and drying for 10 minutes at an ambient temperature of 100 ° C. in the device 21, in the forced air cooling step M, cold air is supplied from the air supply port 22 and an exhaust port In the forced air cooling device 24 exhausted from 23, cold air is blown for 5 minutes from a blowing port (not shown) to forcibly cool the object to be coated to 40 ° C. or less.

Next, in the electrodeposition coating process 55, in the cation electrodeposition step N, the cooled coating object 3 is immersed in the cation electrodeposition coating bath solution in the electrodeposition tank 25 at a bath temperature of 27 ° C. and energized for 3 minutes to generate cations. After performing electrodeposition coating, the paint is cut on the overflow tank 26. Next, in the rinsing process 56, in the fifth rinsing step O, the sixth rinsing water at room temperature from the sixth water tank 29 is sprayed by the water spray device 28 for cleaning, and then in the sixth rinsing step P, the water tank 31 The normal-temperature furnace water washing water is sprayed from the water spray device 30 for cleaning, and in the furnace-water washing step Q, the room-temperature ultrafiltrate supplied from the ultrafiltration device 33 is sprayed from the water spray device 32. And wash. In FIG. 3, 34 is a filter, 35 is a heat exchanger, 36 is a tank, and P is a pump.

The article to be coated 3 thus coated with the cationic electrodeposition paint
Next, in the baking process 57, in the baking step R, an atmosphere temperature of 185 ° C. is set in a baking oven 39 of a direct-fire hot-air circulation type in which hot air is supplied from the air supply port 37 and exhausted from the exhaust port 38. Bake dry for minutes.

Further, in this undercoating step, as shown in FIG. 2, polishing is carried out by a polishing process 58 in order to improve the adhesion with the coating film applied thereon.

This polishing process 58 is a so-called surfacer water polishing, in which the coated surface is polished with sandpaper, rotary sander, vibration sander, etc. to remove dust and various deposits and smooth the coated surface, and at the same time finely coat the coated surface. Finishing is done by scratching to increase the surface area and improving the adhesion of the coating applied on it, completing the undercoating process. Then, the coating work proceeds in the order of the next intermediate coating process and the top coating process.

[Problems to be solved by the invention]

In the conventional undercoating process as described above, the polishing process 58 is performed after the baking process 57 of the electrodeposition coating film. For this reason, the resin that forms the electro-deposited coating is thermoset, and the hardness of the electro-deposited coating is higher than that of ordinary coatings.Therefore, rough sand paper is required for polishing. However, there was a problem that it becomes a factor of garbage and lumps. Also, since rough sandpaper is applied to the surface of the hard electrodeposition coating film, the scratches created by the large grinding powder on the surface of the electrodeposition coating film may be larger than necessary and sharpened. , The paint on top of this doesn't paint on average,
Further, there is a problem in that the smoothness of the coated surface is poor.

In view of the above points, the present invention improves the smoothness of the electrodeposition coating film, improves the adhesion of the coating film to be coated thereon by forming appropriate fine irregularities on the coating surface, and further sharpens the sandpaper. It is an object of the present invention to newly provide an undercoating treatment method capable of removing dust and dust caused by powder.

[Means for solving problems]

The undercoat treatment method in the automobile body coating and the like of the present invention is a baking coating method for an automobile body including at least an overcoating step and an undercoating step, in which an electrodeposition coating is formed by an electrodeposition coating process (55) in the undercoating step of baking coating, Next, in the preheat process (60), heat treatment is applied to the electrodeposition coating film so that it has an appropriate soft viscosity in the initial stage of curing, and then smoothing and polishing are performed while the electrodeposition coating film has the above-mentioned soft viscosity. The surface of the electrodeposition coating is smoothed by applying a treatment to form fine irregularities on the undercoating material to improve the adhesion with the coating material, and then the baking process (57).
The above-mentioned electrodeposition coating film is baked to finish.

[Work]

According to such an undercoat treatment method, since the electro-deposition coating film is given a soft viscosity by the heat treatment by the preheating process, the polishing work is performed in a state where the electro-deposition coating film has an appropriate soft viscosity. Therefore, the coated surface can be easily and appropriately smoothed, and since the coating film is soft, it is possible to use sandpaper or silicon paper having fine eyes, and further, it is possible to remove the cause of dust and lumps, and further, the coating film Has an appropriate soft viscosity, so it can prevent sharpening of fine irregularities on the coating surface formed by polishing powder, etc., improve adhesion with the coating film applied on it, and smooth the coating surface. It has the effect of improving the property.

〔Example〕

An embodiment of an undercoating method for coating automobile bodies of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIGS. 2 and 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

The undercoating treatment method of this example is a treatment method in the undercoating step in the coating of an automobile body. That is, as shown in FIG. 1, a car body degreasing process 50 is executed, and then a water washing process 51, a process 52 such as chemical conversion treatment, a water washing process 53, a water draining drying process 54, an electrodeposition coating process 55,
A treatment process similar to the conventional process such as the water washing process 56 is executed. Then, after this, the process goes to the preheat process 60, and in this example, about 10
Heat treatment is performed at a temperature of 0 ° C. for about 5 minutes. This heat treatment melts and softens the resin in the electrodeposition coating, lowers its viscosity, and the fluidity of the resin is good. Become.

Next, in a smoothing process 61, the moderately viscous electrodeposited coating surface in a good malleability state is rubbed with a sponge containing water to smooth the surface. Further, in the polishing process 62, fine irregularities are rubbed with sand paper or silicon paper to form fine irregularities on the coated surface.
Since these fine irregularities are formed by fine polishing powder in a state where the electrodeposition coating film is appropriately softened and viscous, the corners of the irregularities can be smoothly rounded and sharpened. No more scratches than necessary.

Therefore, by appropriately increasing the surface area, it is possible to improve the adhesion of the intermediate coating composition applied on the electrodeposition coating film.

In addition, the smoothing process 61 and the polishing process 62 described above.
Does not have to be executed as two processes, but can be replaced by one of a treatment with a water-containing sponge and a treatment with finely sandpaper or the like.

Then, the one treated as described above is treated by the same conventional baking process 57 to complete the undercoating step.

Then, after this, the coating is completed through the steps of intermediate coating and top coating.

〔The invention's effect〕

As described in detail above, according to the undercoat treatment method for coating automobile bodies of the present invention, a heat treatment for moderately softening the electrodeposition coating film is performed before the baking treatment, and then appropriately softened and spread. In this case, the smoothing and polishing treatments are carried out in good condition, and then the baking treatment is carried out, and the polishing treatment after the baking treatment is abolished.

Therefore, heat treatment of the electrodeposition coating film to moderately soften the viscosity,
Since smoothing and polishing are performed in a state of good malleability, the smoothness of the coated surface can be improved. Moreover, it is possible to form an appropriate unevenness that is not sharpened on the coated surface.

Further, there is an effect that after the electrodeposition coating film thus treated is baked, the coating film for finishing to be applied on the coated surface is smooth and can be applied with good adhesion.

Further, it is possible to eliminate the difficult work of polishing the cured electrodeposition coating film after the baking treatment, and at that time, by using sandpaper with a rough texture, dust such as polishing powder may be attached,
It is possible to prevent the occurrence of spots, and it is possible to achieve good paint finish.

[Brief description of drawings]

FIG. 1 is an explanatory view of a treatment process showing an embodiment of an undercoating method for automobile body painting of the present invention, and FIG. 2 is an explanatory view showing an example of a conventional undercoating treatment by cationic electrodeposition coating. The figure is a schematic diagram of processing for executing the processing process. 55 …… Electrodeposition coating process, 57 …… Baking process, 60 ……
Preheat process, 61 …… Smoothing process, 62 ……
Polishing process.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location B05D 7/14 B05D 7/14 L

Claims (1)

(57) [Claims] 1. A method for baking a car body comprising at least an overcoating step and an undercoating step, wherein an electrodeposition coating is formed by an electrodeposition coating process (55) in the undercoating step of baking coating, and then a preheat process (60). The electrodeposition coating is heat-treated so that it has an appropriate soft viscosity in the initial stage of curing, and then the electrodeposition coating is smoothed and polished while the electrodeposition coating has the above-mentioned soft viscosity. Characterized by forming fine irregularities that smooth the film surface and improve the adhesion with the paint applied on the undercoat paint, and then finish the baking by the baking process (57). An undercoating method for car body painting, etc.