JPS6145507B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for coating recesses that cannot be coated in electrostatic powder coating. Conventional electrostatic powder coating is a method in which particles are charged and electrostatically applied to the object with airflow, so it is necessary to adjust the paint composition, particle shape, size, etc., or adjust the coating conditions. However, there was a limit to the amount of powder that could be applied to the recesses. When the commonly used high-resistance powder coating of 10 ^{to 10} Ωcm or more is deposited, charge accumulates, and an opposite charge appears in the recess due to the Faraday cage effect, making it impossible for the charged powder that penetrates to be applied. The airtight hole is pressurized and airflow is suppressed, so particles must use their own inertia to penetrate. Therefore, it would be advantageous to have a slightly larger particle size, but it is essentially impossible to completely coat the particle, and in a normal gun, the ratio of hole size to hole depth is , 2:1 is considered to be the limit for coating. The present inventor applied a solution-based paint to recesses that cannot be painted with a normal spray gun, etc., and applied electrostatic powder coating to the recesses to make them sticky in advance, thereby allowing powder paint particles to adhere to the recesses. They have discovered that this is the case, and have completed the present invention. That is, the present invention provides the following features: 1. In a method of electrostatic powder coating an object having recesses, a solution-type paint is applied to the object in advance using a pole gun or the like, and then, after electrostatically applying the powder coating, A painting method characterized by baking. 2. A coating method characterized in that a hydrophilic medium to high boiling point solvent is used in the solution type coating material of 1 above. It is related to. The pole gun used in the present invention may be an air spray type or an airless spray type depending on the size and shape of the recess, and is commercially available as an extension type spray gun from DeVilbis, Inc., for example. The solution-type paint used in the present invention may be any of water-soluble paints, slurry-based paints, and water-insoluble paints for base coating, intermediate coating, and top coating. Furthermore, it is preferable for solution-type paints to have colors similar to those of powder paints in terms of uniformity. Further, a paint obtained by diluting a powder paint with a solvent may be used, but it is preferable that the paint film has some degree of tackiness during electrostatic powder spraying and that the paint film is conductive. Therefore, the specific resistance of the solvent is 10 ⁶ to 10 ⁸
It is preferable to select one with a medium to high boiling point of about Ωcm. For example, butyl cellosolve acetate, cellosolve acetate, butyl cellosolve, cyclohexanone, n-butyl alcohol, octanol, butyl carbitol, water, etc. may be used, and a mixed solvent with a naphtha-based solvent may also be used. The powder coating used in the present invention can be electrostatically coated with any of ordinary acrylic resin paints, epoxy resin paints, and polyester resin paints, and is cured by baking at the standard baking temperature of each powder paint. That's fine. In this way, by applying a solution-type paint using a hydrophilic medium to high boiling point solvent in advance to a workpiece with recesses, and then applying electrostatic powder coating, the penetration into the recesses is improved and at the same time. There is also the additional effect of smoothing by baking, and the finished appearance is similar to that of a flat surface. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 and Comparative Example 1 Evaclad 5230 acrylic orange paint (manufactured by Kansai Paint Co., Ltd.) was applied to objects at angles of ∠30°, ∠45°, and ∠90° using a Lansburg REP-Z gun (manufactured by Landsburg Japan). Table 1 compares the penetrability of the case where electrostatic coating is applied directly (Comparative Example 1) and the case where electrostatic coating is applied after applying a solution type acrylic clear (Example 1).

[Table] ○: Good, ○△: Slightly good, △: Slightly poor.
×: Defective Examples 2, 3, and Comparative Example 2 A metal plate with a diameter of 75 mm and a depth of 10 mm is pasted on a steel plate with round holes of 10, 20, 30, and 60 mm in diameter to prevent air flow from penetrating it. Table 2 shows the results obtained by creating a coating, aiming at the hole, and comparing the results under the same conditions as in Example 1.
It is. Comparative Example 2 was a direct electrostatic coating of Evaclad 5230 acrylic orange paint (manufactured by Kansai Paint Co., Ltd.), Example 2 was an electrostatic coating after applying a solution type acrylic clear, and Example 3 was an electrostatic coating of Evaclad 5230 acrylic paint. An orange enamel made by dissolving orange paint in a ratio of toluene and butyl cellosolve at a ratio of 30:70 was applied using an extension type spray gun JGA502 (MBX4045) manufactured by DeVilbiss, followed by electrostatic painting.

[Table] According to the present invention, when electrostatic powder coating is applied under the same coating conditions as explained above, by adopting the method according to the present invention, the penetration into recesses is clearly improved compared to the conventional method.

Claims (1)

[Scope of Claims] 1. In a method of electrostatic powder coating an object to be painted having recesses, the object to be painted is coated with a solution-type paint in advance using a pole gun, etc., and then powder paint is applied after electrostatic coating. , a painting method characterized by baking. 2. A coating method characterized in that a hydrophilic medium to high boiling point solvent is used in the solution type paint according to claim 1.