Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2002-08-05
2004-08-17
Pianalto, Bernard (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S385500, C427S407100, C427S409000
Reexamination Certificate
active
06777032
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and a system for painting a vehicle body.
2. Description of Related Art
Painting a vehicle body, in particular an exterior body panel of a vehicle body that has a demand for attractive exterior appearance and durability properties, typically comprises an undercoat, an intermediate coat and an overcoat. The undercoat is often applied by electrodepositing a coating composition so as thereby to form an undercoat layer and finished by baking and drying the undercoat layer. The intermediate coat is applied by spraying a coating composition over the undercoat layer that has been baked and dried so as to form an intermediate layer, and then finished by baking and drying the intermediate coat layer. Finally, the overcoat is applied by spraying a coating composition over the intermediate coat layer that has been baked and dried so as to form an overcoat layer, and then finished by baking and drying the overcoat layer.
Application of coat for the overcoat of the vehicle body is not confined to only once and the number of times of the application of coat for the overcoat depends upon the type of coating composition and the grade of finish. For example, when using one selected from a group of solid coating compositions, the application of coat for the overcoat is often made only once. However, in the case where the overcoat is completed by applying a coat of a coating composition selected from the group of metallic coating compositions two times, a base coat of a color coating composition containing a metallic powder is applied first and then a clear coat is applied over the color base coat layer. Otherwise, a solid type coating composition is sometimes employed for the color base coat in place of the metallic powder contained coating composition. One of examples in which the overcoat is completed by applying a coat three times is the case of an overcoat comprising a bright coat. Specifically, after a coating composition for the color base coat that contains a metallic powder is applied first, a bright base coat is applied, and a clear coat is subsequently applied to finish the overcoat. In these multiple coating processes, the overcoat is performed by what is called a wet-on-wet application. That is, a succeeding coat is applied over the last coat layer which has not yet been dried, in other words, which remains still wet. The overcoat layers formed in the wet-on-wet application are finally baked and dried all together in an oven.
In the multiple coating processes including an application of a brightener material contained coating composition such as a coating composition containing mica, while a color base coat layer without containing a brightener material remains wet, a brightener material contained coating composition is sprayed so as to form a bright coat layer over the color base coat layer and then a coating material is applied so as to form a clear coat layer over the bright base coat layer that remains wet. These three coat layers are baked and dried all together in an oven. Such a process, that is called three coats-simultaneous baking process, is disclosed, for example, in Japanese Unexamined Patent Publication No. 10-277478.
As disclosed, for example, in Japanese Unexamined Patent Publication No. 10-296178, when using the three coats-simultaneous baking process for forming an overcoat by spraying a coating composition containing a brightener material to exterior body portion, the overcoat is completed in specific steps of spraying coating compositions in relation to a coat applied to an interior door portion (interior portions near a door). That is, an application of a color base coat to the interior door portion and thereafter to the exterior body portion, an application of a mica base coat to the exterior body portion and an application of a clear coat to the interior door portion and thereafter to the exterior body portion are sequentially performed in the wet-on-wet application in this order. All the coat layers formed on the exterior body portion and the interior door portion are simultaneously baked and dried together. The three-coats simultaneous baking process always has the necessity of both an application of an intermediate coat prior to an application of the overcoat and baking and drying the intermediate coat layer in advance of the application of the overcoat like the conventional painting processes.
It is also known, for example, from Japanese Unexamined Patent Publication No. 10-216617, that a color base coat is applied to form a color base coat layer over an intermediate coat layer that remains wet and then a clear coat is applied to form a clear coat layer over the color base coat layer that remains wet, and all the three coat layers are finally baked and dried together.
Meanwhile, as for the vehicle body painting, although the overcoat of the exterior body portion is of the most importance in view of attractive exterior appearance and durability properties, it is also necessary to paint an interior door portion, an engine compartment, a cargo compartment, etc. The interior door portion also has a demand for attractive interior appearance and also a demand for finished color and quality similar to those of the exterior body portion as the interior door portion is eye catching for occupants of the vehicle and conspicuous when the doors are open. Therefore, the overcoats applied to the interior door portion and the exterior body portion are generally identical in color and quality with each other.
Since the engine and cargo compartments are kept out of sight, there is less demand for attractive exterior appearance and durability properties, it is suffice for the coat of the engine and/or cargo compartments to be identical in color with or similar in color to the exterior body portion.
In designing vehicle body painting, it is necessary to consider an overspray problem in addition to respective coating requirements of the exterior body portion, the interior door portion and the engine and/or cargo compartments. That is, when applying a coat the exterior body portion, a coating composition is sprayed more than a little on the interior door portion and the engine and cargo compartments. A similar overspray problem occurs when applying a coat to the interior door portion or the engine and/or cargo compartments.
One aspect of the overspray problem is color mixing. That is, when a coat layer is partly sprayed with a coating composition, the part of the coat layer is mingled in color with the coating composition and is stained differently from the remaining part. Another aspect of the overspray problem is a defect of paintwork (a deterioration in the flatness and smoothness of coat layer). The defect of paintwork becomes marked when a coating composition is sprayed on a coat layer having been backed and dried once. However, the defect of paintwork is practically insignificant when a coating composition is sprayed on a coat layer remaining wet. This is because the coating composition is fused together with the coat layer before long.
In order to avoid the color mixing, a color intermediate coat is often applied by spraying a coating composition having a color identical with or similar to the overcoat. Specifically, while it is desirable to employ a gray coating composition for the intermediate coat from the viewpoint of cost, it is general in turn to apply a color intermediate coat to both the exterior body portion and the engine and/or cargo compartments for the purpose of preventing an occurrence of color mixing due to an overspray or to the engine and/or cargo compartments only. Further, it is expensive but effective to apply not intermediate coat but a color base coat that forms a part of an overcoat to the engine and/or cargo compartments.
If the step of baking and drying an intermediate coat layer that is essential in the conventional painting processes can be dispensable, the painting process offers a lot of advantages in terms of costs for installation of printing
Kamesako Yusuke
Kanda Teruo
Ogasahara Toshifumi
Sakoda Toshiyuki
Mazda Motor Corporation
Nixon & Peabody LLP
Pianalto Bernard
Studebaker Donald R.
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