JPH105683A - Multi-layer coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten the coating efficiency and prevent luster fogging and color phase failure by forming an under layer side coating film by application, raising the concentration of solid matters in the coating by evaporating a solvent in the coating film to the extent within which cross-linking of the under layer side coating film does not occur, and then forming an upper layer side coating film on the under layer side coating film by application. SOLUTION: In the case of coating a vehicular body, a coating material is sprayed to the body out of a coating gun 1 to form an under layer coating film 2 and then hot air is blown to the under layer coating film 2 out of a blowing outlet 3 of a hot air blower to evaporate the solvent in the under layer coating film 2 and raise the concentration of the solid matters in the coating material of the under layer coating film 2. At that time, by evaporating the solvent to the extent within which cross linking does not occur, the fluidity of the under layer coating film 2 is suppressed and inversion and mutual dissolution are prevented in the case that an upper layer coating film 5 is formed on the under layer coating film 2 by spraying a coating material out of a coating gun 4 in the next process and a multi-layer film with excellent quality can be formed by baking in the following process. Consequently, a baking process for the under layer coating film 2 is eliminated and thus the cost can be saved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer coating method used for coating a vehicle body and the like.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
Paint is sprayed from a paint gun 51 to form a lower coating film 52 on a vehicle body or the like.
As shown in the figure, in the multi-layer coating in which another paint is sprayed from the coating gun 54 to form the upper coating film 53, the lower coating film 53 is applied without baking and drying the lower coating film 52. 52 contains 30 to 40% of a solvent.
The fluidity of the paint is high, and inversion and compatibility occur at the interface between the lower coating film 52 and the upper coating film 53 as shown in FIG. That is, inversion is a phenomenon in which the paint of the lower coating film 52 emerges to the upper coating film 53, and compatibility is a phenomenon in which the paints of the lower coating film 52 and the upper coating film 53 are mixed at the boundary surface. It is. Therefore, as shown in FIG.
After baking, there is a problem that gloss reversal or poor hue occurs due to the reversal and compatibility. In order to solve such a problem, if the lower layer coating film 52 is applied and then baked and dried and hardened, the above-described inversion and compatibility can be prevented. However, there is a problem that a step of baking and drying the lower layer coating film 52 is required, and the energy cost is increased.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and does not provide a multi-layer coating method which enhances coating efficiency and does not cause gloss blur and hue defects. The first gist of the present invention is to form a lower-layer coating film and then volatilize the solvent in the coating film to such an extent that the lower-layer coating film does not reach cross-linking. Is raised, and then the upper layer-side coating film is applied and formed on the lower layer-side coating film. The second gist is that hot air is sprayed on the lower-layer-side coating film to volatilize the solvent. The third gist is to elevate the temperature of the lower-layer coating film with far-infrared rays and near-infrared rays to evaporate the solvent of the coating film.

[0004]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a paint is sprayed from a coating gun 1 to a vehicle body to form a lower coating film 2. Thereafter, as shown in FIG. 2, hot air is blown from the outlet 3 of the hot air blower to the lower coating film 2 to volatilize the solvent in the lower coating film 2 and increase the solid concentration of the coating in the lower coating film 2. Let it. Note that the solid content concentration is the weight% of the solid content (pigment, resin) of the paint contained in the lower layer coating film 2, and the solid content concentration is increased to about 80 to 85% by volatilizing the solvent. .

That is, the lower layer coating 2 is heated by hot air blown from the hot air blower outlet 3 to volatilize the solvent in the lower layer coating 2. In this case, the solvent is volatilized to such an extent that crosslinking is not reached. That is,
Crosslinking refers to a phenomenon in which a reaction occurs between the resin of the main component of the paint in the lower layer coating film 2 and the crosslinker to increase the molecular weight, that is, to three-dimensionally cure the lower layer coating film 2. The solvent is volatilized to such an extent that the coating film 2 is not cured by crosslinking. Thereby, the fluidity of the lower coating film 2 is suppressed, and as shown in FIG. 3, even if the upper coating film 5 is formed on the lower coating film 2 by spraying paint from the coating gun 4 as shown in FIG. Reversal,
Compatibility does not occur, and a good multilayer film as shown in FIG. 4 can be obtained by baking thereafter, and since there is no reversal and compatibility as in the prior art, there is no gloss blur or poor color. A good coating film can be secured.
In addition, since the lower layer coating film 2 is not baked and dried,
The baking process of the lower layer coating film 2 is not required, and the existing coating apparatus can be slightly improved to cope with it, and the investment cost can be reduced.

That is, the hot air blower for blowing hot air shown in FIG. 2 can be configured, for example, as shown in FIG. 5. In FIG. 5, the hot air blower 10 is provided on the downstream side of the outside air intake 11. A filter 12 and a roll mat filter 13 are disposed in parallel, a burner 14 is disposed downstream thereof, and a fan 15 and a filter 16 are further disposed downstream thereof.
Further, a motor damper 17 is arranged downstream thereof, and is connected to a painting booth 19 through a duct 18. A painting conveyor 20 for transporting the vehicle body B is arranged in the painting booth 19. The above-described outlets 3, 3, 3 can be arranged on one side, and dust and the like are removed by the filters 12, 13, and the burner 14 is removed.
And heated by a fan 15 and sent into a duct 18 by a fan 15; dust can be removed by a filter 16; and the amount of air supply can be adjusted by a motor damper 17. Hot air is blown onto the lower layer coating 2 from the outlet 3 disposed in the lower layer to volatilize the solvent in the lower layer coating 2 so that the solid content concentration of the coating in the lower layer coating 2 is about 80 to 85%. And the painting booth 1
The temperature of the hot air blown out from the blow-out port 3 can be appropriately adjusted by sending a signal to the burner 14 by a temperature controller 22 via a temperature sensor 21 disposed in the burner 9. 17, for example, the hot air blown out from the outlet 3 is set at a wind speed of 0.5 to 20 M / sec and a temperature of 60 to 80 ° C.
The solid content concentration of the coating material therein can be favorably increased to 80 to 85%.

[0007] Such a hot air blower 1
Numeral 0 can be incorporated in the existing painting booth 19. In this example, hot air is blown from the outlet 3 to the lower coating film 2 to volatilize the solvent of the lower coating film 2, but instead of the hot air blower device 10, for example, a far infrared ray or near infrared ray device is used. Irradiating the lower layer coating 2 with far infrared rays or near infrared rays to raise the temperature of the lower layer coating 2, thereby volatilizing the solvent in the lower layer coating 2 and suppressing the fluidity of the lower layer coating 2. Thereafter, the upper layer coating film 5 can be satisfactorily applied and formed without inversion and compatibility.

[0008]

According to the multilayer coating method of the present invention, after the lower coating film is applied and formed, the solvent in the coating film is volatilized to such an extent that the lower coating film does not reach cross-linking. As the concentration was increased, the upper coating film was then formed on the lower coating film, so that the fluidity of the lower coating film was suppressed, and the upper coating film was formed on the lower coating film. Even if it is formed, there is no inversion and compatibility as in the prior art, and therefore, there is an effect that a good coating film free of gloss blur and poor color tone does not occur. In addition, since the lower coating film is not baked and dried, a baking device can be omitted, energy efficiency can be improved, and existing coating equipment can be slightly improved to reduce investment costs. Can be planned.

In addition, since the solvent is volatilized by blowing hot air on the lower layer coating, the solvent of the lower layer coating is satisfactorily volatilized by the hot air to reduce the solid content concentration of the coating in the lower layer coating. As a result, the fluidity of the lower layer side coating film can be favorably suppressed. Further, since the temperature of the lower coating film is increased by far infrared rays and near infrared rays to evaporate the solvent of the coating film, the solvent of the lower coating film is volatilized favorably using far infrared rays and near infrared rays. In addition, the fluidity of the lower coating film can be suppressed.

[Brief description of the drawings]

FIG. 1 is a work process diagram for applying and forming a lower layer coating film on a vehicle body and the like.

FIG. 2 is a process diagram in which hot air is blown onto a lower layer coating film from an outlet of a hot air blower to volatilize a solvent of the lower layer coating film.

FIG. 3 is a process chart in which an upper layer coating film is formed on the lower layer coating film thereafter.

FIG. 4 is a structural diagram of a coating film after baking.

FIG. 5 is a schematic configuration diagram of a hot air blower device.

FIG. 6 is a process chart for applying and forming a conventional lower layer coating film.

FIG. 7 is a process chart for forming an upper coating film on a conventional lower coating film.

FIG. 8 is a diagram showing a state in which inversion and compatibility have occurred at a boundary surface between a lower layer coating film and an upper layer coating film.

FIG. 9 is a structural view of a conventional coating film after baking.

[Explanation of symbols]

 1,4 Paint gun 2 Lower coating film 3 Hot air blower outlet 5 Upper coating film 10 Hot air blower device 11 Outside air intake 14 Burner 15 Fan 17 Motor damper 19 Painting booth 20 Painting conveyor 22 Temperature controller B Vehicle body

Claims (3)

[Claims] After coating and forming a lower-layer coating film, the solvent in the coating film is volatilized to such an extent that the lower-layer coating film does not reach crosslinking, thereby increasing the solid content concentration of the coating material. A multilayer coating method, wherein an upper layer-side coating film is applied and formed on the lower layer-side coating film. 2. The multi-layer coating method according to claim 1, wherein hot air is blown onto the lower coating film to volatilize the solvent. 3. The multi-layer coating method according to claim 1, wherein the temperature of the lower layer side coating film is raised by far infrared rays and near infrared rays to evaporate a solvent of the coating film.