JPH0649180B2 - 4 coat painting method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a four-coat coating method, and more particularly to a four-coat coating method for coating outer panels and interiors of automobiles.

(Prior Art) The four-coat coating method is used for coating high-end vehicles in order to obtain a better appearance than ever before. The method comprises four steps of a first coating step (undercoating step), a second coating step (primer step), a third coating step (sealer step) and a fourth coating step (top coating step). Normally, the interior of the vehicle body skin and engine room, luggage room, etc. is painted gray by electrodeposition coating, and in the second coating process, a paint containing a gray pigment consisting of titanium dioxide and carbon black is applied to the vehicle body skin. In the 3 coat process, a paint similar to the paint used in the 2 nd coat process, in which the paint containing the pigment of the paint color is used instead of the gray pigment, is applied to the vehicle body outer plate, and then in the 4 coat process, The coating is performed by applying a coating material containing a coating color pigment and having excellent gloss and durability to the vehicle body outer panel and the interior of the engine room, luggage room and the like. Therefore, in this method, after undercoating in the first coating step, fine adjustment of the unevenness is performed in two steps of the second coating step and the third coating step, and the overcoating is performed after the adhesion between the coating films is increased. It is possible to obtain a coated product that is very excellent in appearance. In the above method, the interior of the engine room or the like is coated in two steps, the first coating step, that is, the undercoating step and the fourth step, that is, the topcoating step.

(Problems to be Solved by the Invention) However, the coating material used in the third coating step and the fourth coating step has a high viscosity because it contains a pigment having a structural viscosity, and therefore, the surface to be coated will not be scratched. There is a problem that so-called "wrinkle skin" (orange peel) is formed in which irregularities such as the surface are formed, and the appearance quality of the finished product is deteriorated. Further, since the pigment is expensive, the coating material containing the pigment is expensive, and when this is used in the third coating step and the fourth coating step, there is a problem that the cost is significantly higher than that of a usual coating method. . further,
In the method, the interior of the engine room or the like is coated in the step of the fourth coating, but the purpose of the coating used in the fourth coating step is to obtain excellent properties in terms of gloss, weather resistance and the like. Therefore, it is expensive and further increases the coating cost. Therefore, it is an object of the present invention to provide a four-coat coating method that prevents deterioration of the appearance quality due to a wrinkled skin and is lower in cost than the conventional four-coat coating method.

(Means for Solving Problems) The four-coat coating method of the present invention for achieving the above-mentioned object is the first coating step in coating the outer panel and the interior of an automobile using the four-coat coating method. After undercoating the outer panel and the interior of the automobile, in the second coating step, the outer panel and the interior are primer-coated, and then baked, and then in the third coating step, a semi-transparent paint or a clear coating is used to apply the outer coating. The plate is coated with a sealer, and in the fourth coating step, the outer plate is top-coated with a colored coating material containing a coating color pigment.

The first coating step (undercoating step) is the same as the conventional method, in which the inside of the vehicle body outer panel and engine room is electrodeposited,
For example, it is formed by cationic electrodeposition coating.

In the second coating step (primer step), the vehicle body outer panel is coated with an appropriate paint containing a gray pigment as in the conventional coating method. As the paint, any paint usually used for this purpose may be used. For example, a paint composed of a vehicle made of polyester varnish and a melamine resin and a paint diluted with thinner may be used. Preferably, in this step, the interior of the engine room or the like is preferably painted with a paint having the same composition as the above paint and containing a pigment of the same color as the topcoat paint color instead of the gray pigment. Of course, if the interior of the room is painted in this step, it is not necessary to paint the interior of the room in the fourth coating step.

In the third coating process (sealer process), a semi-transparent paint or a clear paint is applied to the vehicle body outer panel. The paint used in this step may be any of the paints usually used for this purpose as long as it is translucent or transparent,
For example, a pigment composed of the above vehicle extender pigment can be diluted and used in the same manner as above. Any type of extender pigment may be used, and for example, calcium carbonate, barium sulfate, silica, alumina, magnesium carbonate, kaolinite, halosite, muscovite, talc and the like may be used.

In the fourth coating step (top coating step), a coating material containing a pigment for obtaining a desired coating color and having excellent properties such as gloss and weather resistance is applied. As such a coating material, for example, a vehicle composed of an alkyd resin and a melamine resin and a pigment can be diluted with an appropriate thinner and used. In the above method, the interior of an engine room or the like is coated in two steps, a first coating step, that is, an undercoating step and a second coating step, that is, a primer step.

(Function) As described above, the coated product obtained by applying the 4-coat coating by applying the semi-transparent paint or the transparent paint containing the extender pigment in the third coating step did not cause a defective appearance such as a scratched skin. . This is because, in the conventional method, the highly viscous paint that causes the skin damage is applied in two steps,
The amplitude of the unevenness generated in the third coat was further increased in the fourth coat, resulting in the formation of a wrinkled skin which is a problem in appearance. However, in the present invention, this is only the fourth coat step. It is considered that the amplitude of the resulting unevenness did not reach the level of a problem in appearance. Moreover, in the present invention, after performing the undercoating in the first coating step, the unevenness of the coated surface is finely adjusted in the second coating step and the third coating step, and the overcoating is performed in the fourth coating step. As it is the same as the coat coating, a coating having a very excellent appearance can be obtained as a result.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples.

Example: According to the four-coat coating method of the present invention, an outer panel of a car body and an inner panel of an engine room and a luggage room are coated. The figure shows a coating film 1 formed on a vehicle body outer plate and a vehicle body inner plate according to this embodiment.

Cathode electrodeposition coating was applied to the car body outer panel and the engine room and luggage room inner panel (first coating step). As a result, the undercoat coating film 2 is applied to the outer panel and the inner panel of the vehicle body.
Is formed.

The obtained electrodeposition-coated car body outer panel was composed of a phthalic acid group-containing polyester varnish having a molecular weight of about 5000 and an n-butanol-modified melamine resin varnish having a molecular weight of about 3000 (solid content ratio of polyester / melamine resin = 7/3). 80 parts titanium white, 0.5 carbon black per 100 parts solid vehicle
Parts, and a thinner consisting of 50 parts of xylene, 20 parts of 3-methoxybutyl acetate and 30 parts of Solvesso # 150 (manufactured by Esso Standard Petroleum) so that the viscosity of Ford cup No. 4 is 24 seconds at 20 ° C. The diluted gray paint produced was applied using a rotary atomizing electrostatic coater to obtain a gray paint film 3. Further, 100 parts of the above vehicle, 5 parts of iron oxide pigment (Bengara KNO manufactured by Toda Kogyo Co., Ltd.), 15 parts of organic red pigment (Rubicron Red 451R manufactured by Toyo Soda Co., Ltd.) and 2 parts of titanium white are dispersed, and the thinner is used. The red paint produced by diluting it to the above viscosity is painted in the engine room and the luggage room using an air atomization coating machine, left for 10 minutes, then baked at 140 ° C for 20 minutes, and painted in red. A membrane 4 was obtained. (Second coating step).

Next, disperse 80 parts of barium sulfate extender pigment (precipitating barium sulfate # 100 made by Sakai Chemical Co., Ltd.) in 100 parts of the above-mentioned vehicle solid, and further dilute it with the same thinner as the above gray paint so that it has the same viscosity. The manufactured semi-transparent pigment is automatically applied to the outer skin of the vehicle body by a rotary atomizing electrostatic coating machine, left for 10 minutes, and then baked at 140 ° C for 20 minutes to form a semi-transparent coating film 5 (third coating step). . At this time, a part of the paint enters the engine room and the luggage room through the gap to form a paint film, but since the paint is a semitransparent paint, there is no design problem.

Next, a vehicle (alkyd / melamine solid content ratio = 7/3) consisting of coconut oil fatty acid-modified alkyd resin varnish and n-butanol modified melamine resin varnish was added to the resin solid content of 100%.
5 parts iron oxide pigment, 15 parts organic red pigment, 2 parts titanium white
Parts are dispersed and the red paint produced by diluting it with the thinner used in the 3rd coating process to the same viscosity as above is automatically applied to the outer panel of the vehicle body using a rotary atomizing electrostatic coating machine. Then, after leaving it for 10 minutes, it was baked at 140 ° C. for 20 minutes to form a top coating film 6 on the outer panel of the vehicle body (fourth coating step), and the coating was completed.

Comparative Example: After the electrodeposition coating is performed by the same method as in Example 1 (first coating step), the vehicle body outer panel is coated with the gray coating material shown in Example 1 (second coating step). Then, the second of the first embodiment
The paint applied to the engine room and the luggage room in the coating process was automatically coated with a rotary atomizing electrostatic coating machine, left for 10 minutes, and then baked at 140 ° C for 20 minutes (third coating process). Subsequently, the red paint used in the fourth coating process of Example 1 was applied to the outer skin of the vehicle body using a rotary atomizing electrostatic coating machine, and the red paint was further applied to an engine using an air atomizing coating machine. Paint inside the room and luggage room (4th
The coating process) and painting were completed.

Below is a table that briefly summarizes the methods of the above Examples and Comparative Examples.

When the appearances of the coated products obtained by the above-mentioned Examples and Comparative Examples were compared, the coated products according to the Examples had extremely good finish properties, whereas the coated products according to the Comparative Example formed a part of a yuzu skin. The appearance is inferior.

(Effect of the invention) Since the present invention uses a semi-transparent or transparent paint in the third coating step, a pigment having structural viscosity is used in the fourth coating step.
That is, since it may be added only to the paint used in the top-coating step, it is possible to obtain a coated product which does not cause a scratched skin and has an excellent appearance which is an advantage of the 4-coat coating method. Further, the pigment cost is reduced, and in the conventional method, an expensive paint is required because the inner plate is coated in the fourth coating step, but in the method of the present invention, a relatively inexpensive coating is used in the second coating step. Since the coating is performed, the final coating cost can be significantly reduced.

Further, in the method of the present invention, since the semi-transparent or transparent paint is used in the third coating step of coating the outer panel of the automobile, the semi-transparent coating used in the third coating step is applied to the interior of the automobile coated by the second step. Even if the transparent or transparent paint flows in, it does not deteriorate the designability already formed in the interior of the automobile.

[Brief description of drawings]

The figure is a diagram showing a coating film obtained according to an embodiment of the present invention. 1 ... Coating film, 2 ... Undercoat coating film, 3 ... Gray coating film, 4 ... Red coating film, 5 ... Semi-transparent coating film, 6 ... Topcoat coating film, 7 ... Iron plate

Claims (1)

[Claims] 1. When coating an outer panel and an interior of an automobile using a four-coat coating method, an outer panel and an interior of an automobile are undercoated in a first coating step, and the outer panel and an interior are coated in a second coating step. Is coated with a primer and then baked, then, in a third coating step, the outer panel is sealed with a semi-transparent paint or a clear coating, and in a fourth coating step, the outer panel contains a coating color pigment. A four-coat coating method, characterized in that the above colored paint is top-coated.