JP4734919B2 - Coating method and coating apparatus - Google Patents

Description

The present invention relates to a coating method that is preferably applied to an automobile body or the like, and more particularly, to a coating method and a coating apparatus that apply a water-based intermediate coating and a water-based top coating in a wet-on-wet manner and simultaneously cure them.

  Car body paint systems include electrodeposition paints based on epoxy resins, intermediate paints based on polyester resins, acrylic resins or alkyd resins, and polyester paints, acrylic resins or alkyd resins. Using the three types of topcoat paints, the main component of which is electrodeposition coating (undercoating), this is baked, the intermediate coating is applied on the cured electrodeposition coating, and then baked. A so-called three-coat three-bake coating method is employed, which is completed by applying a top coat onto a cured intermediate coat and baking it.

  However, in such a 3-coat 3-bake coating system, a drying furnace is required for each of the electrodeposition coating process, the intermediate coating process, and the top coating process. Therefore, a wide process space for installing the drying furnace is required. There is also a problem that energy consumed in the drying furnace is reflected in the production cost of the automobile.

  Therefore, in order to solve the above problems by reducing the number of drying ovens provided in these three processes to two or less, after applying the intermediate coating and the top coating by wet-on-wet, these are simultaneously applied to one drying oven. Baking and curing is being studied (see Patent Document 1).

  By the way, apart from the problem of shortening the process, changing the organic solvent-based paint to the water-based paint has been studied and put into practical use from the viewpoint of environmental measures. In particular, when an overcoating base paint having a high solvent content (small resin solid content) is switched to a water-based paint, the effect of environmental countermeasures is large. This type of water-based paint has a slower rate of water evaporation from the uncured coating film than organic solvent-based paints, so when the top coat is applied to the surface of an uncured intermediate coat, Moisture contained is transferred into the intermediate coating film, and the boundary between the intermediate coating film and the top coating film is mixed (this phenomenon is also referred to as a mixed layer). As a result, the top coating film typified by sharpness There has been a problem that the smoothness of the material is lowered.

Moreover, in the coating system in which the intermediate coating and the top coating are applied wet-on-wet, and these are baked at the same time, the concealability of the surface unevenness of the electrodeposition coating by the intermediate coating is more than that of the 3-coat 3-bake There was a problem of being low. This is because in the 3 coat 3 bake coating system, the surface smoothness can be expected by the heat flow when baking and curing the intermediate coating film, whereas the coating system in which the intermediate coating and top coating are performed wet on wet. Then, since the top coat film is formed at the time of baking and curing, smoothing due to the heat flow of the intermediate coat film cannot be expected. As a result, there was a problem that the smoothness of the top coat film was lowered.
JP 2002-153805 A

In the present invention, when a water-based intermediate coating and a water-based top coating are applied wet-on-wet and then cured simultaneously, the intermediate coating layer and the top coating layer are prevented from being mixed to prevent the top coating layer from being mixed. It aims at providing the coating method and coating apparatus which can ensure smoothness.
In order to achieve the above object, the coating method of the present invention is formed by applying a water-based intermediate coating to a substrate having a horizontal portion and a vertical portion, and then applying a water-based top coating by wet-on-wet. A coating method for curing the intermediate coating film layer and the top coating film layer to be cured in the same step, wherein the horizontal coating is applied to the horizontal part of the article to be coated, A vertical part intermediate coating process in which an intermediate coating is applied to a vertical part of an object, and in the horizontal part intermediate coating process, using the rotary atomizing bell type coating gun, Set the humidity of the shaping gun's shaping air higher than the general humidity of the painting booth and apply the intermediate coating, and in the vertical intermediate coating process, use the rotary atomizing bell type coating gun Atomized bell-type paint The shaping air humidity is set to the following general humidity of the spray booth, characterized in that coating the intermediate coating.

In addition, the coating apparatus of the present invention coats a water-based intermediate coating on an object having a horizontal portion and a vertical portion, and then coats the water-based top coating with wet-on-wet, thereby forming an intermediate coating film A coating apparatus that cures a layer and a top coat layer in the same process, wherein a horizontal intermediate coating means for applying an intermediate coating on a horizontal portion of the object to be coated, and a middle part on a vertical portion of the object to be coated Vertical portion intermediate coating means for applying a coating, and the horizontal portion intermediate coating means includes a rotary atomizing bell type coating gun, and the humidity of the shaping air of the rotary atomizing bell type coating gun is The vertical portion intermediate coating means includes a rotary atomizing bell-type painting gun, and the humidity of the shaping air of the rotary atomizing bell-type painting gun is set to be higher than the general humidity of the painting booth. Set to below normal humidity And said that you are.

  In the present invention, particularly when the intermediate coating is applied to the horizontal portion of the object to be coated, the humidity atmosphere at the time of coating is carried out in an atmosphere higher than the general humidity of the coating booth. Here, the general humidity of the painting booth means the main part of the painting booth, particularly the humidity around the object to be coated.

  By increasing the humidity atmosphere during application of the intermediate coating, evaporation of the solvent is suppressed during the period from spraying from the coating gun to immediately after application, that is, while the coating particles are flying. The coating viscosity can be kept lower than usual. When the coating viscosity is low, the flowability of the uncured coating film is exhibited, thereby improving the base concealing property. On the other hand, since it is exposed to the general humidity atmosphere of the coating booth after coating, the solvent component is suitably evaporated, which prevents intermixing with the top coating layer, and the clarity of the top coating layer. Will improve.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a process diagram showing a method for painting an automobile body according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a laminated coating film formed by the method for painting an automobile body according to an embodiment of the present invention, and FIG. FIG. 4 is a plan view showing an example of an entire painting process for carrying out a method for painting an automobile body according to an embodiment of the present invention, and FIG. 4 shows an example of an intermediate coating process for carrying out a painting method for an automobile body according to an embodiment of the invention. FIG. 5 is a diagram showing an example of the vertical part intermediate coating unit according to the embodiment of the present invention, and FIG. 6 is a diagram showing an example of the horizontal part intermediate coating unit according to the embodiment of the present invention.

  The method for painting an automobile body according to the present invention comprises applying an intermediate coating and a top coating in a wet-on-wet manner, and applying an uncured intermediate coating layer and a top coating layer formed thereby in the same drying oven. What is necessary is just the coating method which has the process hardened simultaneously. Representative embodiments will be described below. However, the method of painting an automobile body according to the present invention is not limited to these embodiments. Therefore, the elements disclosed in these embodiments are It is intended to include all design changes and equivalents belonging to the technical scope of the invention.

  In this specification, the material applied to the object to be coated is called a paint, and is a layer formed on the surface of the object to be coated by applying this paint, uncured before curing and cured after curing. The coating layer, these uncured coating layer and the cured coating layer are collectively referred to as a coating layer.

  As shown in FIG. 2, the laminated coating film according to the present embodiment includes an electrodeposition coating layer 102 formed on the surface of an automobile body 101 (represented by B in FIG. The intermediate coating layer 103 formed on the surface of the coating layer 102, the base coating layer 104 formed on the surface of the intermediate coating layer 103, and the base coating layer 104 formed on the surface of the base coating layer 104. And a clear coating layer 105.

  As the automobile body 101 to be coated, plastic members can be applied in addition to members made of various metal materials such as a steel plate and an aluminum plate, and an outer plate and an inner plate of the automobile body become a part to be painted. This automobile body is carried into a pretreatment step 1 shown in FIG. 1, where oil components adhering to the automobile body are degreased and washed using an alkaline cleaning solution or the like, and then a zinc phosphate chemical conversion film is formed on the surface of the automobile body. .

  Next, the automobile body on which the chemical conversion film is formed is carried into the electrodeposition coating application process 2 shown in FIG. 1, where the automobile body is placed in the electrodeposition tank filled with the cationic electrodeposition paint or the anion electrodeposition paint. By immersing and applying a predetermined voltage between the automobile body and the electrodeposition paint, an uncured electrodeposition coating layer 102 is formed on the surface of the automobile body 101 by electrophoresis. In the subsequent electrodeposition washing step 3, excess electrodeposition paint adhering to the surface of the automobile body is washed away by spraying or dipping using industrial water or pure water, and the washed electrodeposition paint is recovered and re-applied. Use.

  Next, the electrodeposition coating film cured by bringing the automobile body that has undergone the electrodeposition washing step 3 into the electrodeposition drying furnace that is the electrodeposition curing step 4 and baking it at 160 to 180 ° C. for 15 to 30 minutes, for example. Layer 102 is obtained. The film thickness of the electrodeposition coating layer 102 is, for example, 10 to 40 μm, although it varies depending on the specification and part of the automobile body.

  The intermediate coating layer 103 is composed of a polyester resin, an acrylic resin, a vinyl chloride vinyl acetate copolymer resin, a urethane resin, a cellulose resin, etc. as a main component, and a thermosetting paint obtained by adding a colorant and an additive thereto. Alternatively, it is a room temperature curable paint or a two-component curable paint, which is a water-based paint using water as a solvent. Then, the paint diluted with water is electrolyzed with a coating machine such as a spray coating gun or a rotary atomizing coating gun in the horizontal intermediate coating application step 51 and the vertical intermediate coating application step 52 shown in FIG. Paint on the surface of the coating layer 102.

  In particular, in the horizontal portion intermediate coating step 51 of this example, an intermediate coating is applied mainly to the horizontal portion (hood, roof, trunk lid, etc.) of the automobile body, and in the vertical portion intermediate coating step 52, the vehicle body is mainly vertical. Apply intermediate paint to the part (fender, door, quarter, etc.). Here, the intermediate coating material applied in the horizontal portion intermediate coating step 51 is applied to the horizontal portion in a humidity atmosphere higher than the general humidity of the coating booth, while being applied in the vertical portion intermediate coating step 52. Is applied to the vertical part in a humidity atmosphere below the general humidity of the paint booth. The general humidity of the painting booth means the average humidity around the object that is the main part of the painting booth.

  In other words, in the prepared state before coating, the intermediate coating used in the horizontal portion intermediate coating step 51 and the intermediate coating used in the vertical portion intermediate coating step 52 have the same coating dilution ratio (the same solid content of the coating). However, in the horizontal intermediate coating process 51, the humidity of the atmosphere from spraying from the coating gun to applying to the object is set higher than the humidity of the coating booth, for example, within a range of 20 points or less. . That is, if the general humidity of the coating booth is 70% RH, the humidity atmosphere during the flight of the coating grains in the horizontal portion intermediate coating process 51 is set to 80% RH, for example. Specifically, for the same intermediate coating as the intermediate coating applied in the vertical intermediate coating process, the shaping air humidity of the rotary atomizing bell type coating gun in the horizontal intermediate coating process 51 is applied to the coating booth. Set to be higher than the normal humidity.

  On the other hand, in the vertical portion intermediate coating process 52, if the general humidity of the coating booth is 70% RH, the humidity atmosphere during the flight of the coating grain is 70% RH or less, for example, 50% RH.

  This is due to the following reason. That is, FIG. 8 is a graph comparing the clarity of the conventional 3-coat 2-bake coating system with the clarity of the conventional 3-coat 3-bake coating system. From the results shown in FIG. It is understood that when the top coating material is applied wet-on-wet, the sharpness in the horizontal portion is significantly reduced as compared with the vertical portion of the object to be coated. FIG. 9 is an example of the experimental results confirming the relationship between the intermediate coating viscosity and the sharpness. From the results shown in FIG. 9, the lower the intermediate coating viscosity, the more the coating film at the time of coating. It is understood that the flow concealment is enhanced, so that the base concealing property is enhanced, and as a result, the sharpness is enhanced and the smoothness of the top coat layer is improved. However, there is a concern that sagging may occur when the coating viscosity is low.

  In this example, pay attention to the fact that the horizontal part of the car body has less sagging than the vertical part, and the sharpness deterioration due to wet-on-coating is difficult. In the painting step 51, while the coating viscosity is lowered by adjusting the humidity of the shaping air so that the sharpness exceeds 0.8, for example, the intermediate coating viscosity is 160 to 180 Pa · s, In the vertical portion intermediate coating process 52, the generation of sagging is suppressed by setting the humidity of the shaping air to be equal to or lower than the humidity of the coating booth.

  FIG. 6 shows an example of the horizontal portion intermediate coating means (intermediate coating apparatus). FIG. 5 is a view showing an example of the vertical part intermediate coating means (intermediate coating apparatus), in which the prepared intermediate coating is accommodated in a coating tank 522 and rotated and atomized by a coating pump 523 through a coating pipe. Pumped to bell type paint gun 521. Shaping air is supplied from the shaping air source 524 to the coating gun 521 through an air pipe, and the supply amount is adjusted by a flow rate adjusting valve 525.

  On the other hand, the horizontal portion intermediate coating means shown in FIG. 6 accommodates in the paint tank 512 intermediate paint prepared under the same conditions as the intermediate paint contained in the paint tank 522 shown in FIG. The paint pump 513 supplies pressure to the rotary atomizing bell-type paint gun 511, and the shaping gun 511 is supplied with shaping air from the shaping air source 514 via an air pipe. Adjustment is performed by the control valve 515. And the humidifier 516 is connected in the middle of this air piping, and the humidity of shaping air is controlled. In addition, a humidity sensor 517 is provided in the air piping downstream of the connection portion with the humidifier 516, and a humidity sensor 518 for detecting general humidity is provided in the painting booth, and the output signals of these humidity sensors 517 and 518 are supplied to the humidifier 516. To the controller. Then, the humidity of the shaping air supplied to the painting gun 511 is feedback-controlled by a predetermined value from the general humidity of the painting booth. For example, shaping air having a relative humidity higher than the relative humidity of the painting booth and not more than 20 points is supplied to the painting gun 511.

  FIG. 7A is an enlarged view of the coating gun 511 of the horizontal portion intermediate coating means. The coating particles discharged from the tip of the bell cup 511A are coated with the shaping air blown from the air blowing ring 511B. It is carried in the direction and is applied to the object as shown in FIG. 5B. During the flight period from the bell cup 511A to the object, the coating particles are always in the atmosphere of shaping air. Become. Therefore, it will apply in the humidity atmosphere of shaping air.

  Returning to FIG. 1 and FIG. 2, when the intermediate coating layer 103 is formed in the horizontal portion intermediate coating step 51 and the vertical portion intermediate coating step 52, the solvent contained in the coating layer is evaporated. The automobile body is heated (intermediate coating preheating step 53). In the intermediate coating preheating step 53, the horizontal and vertical portions of the automobile body are heated at a temperature lower than the curing temperature of the intermediate coating using a heat source such as a lamp or a hot air blower.

  Although the heating conditions in the intermediate coating preheating step 53 are not particularly limited, for example, until the coating solid content of the intermediate coating layer 103 reaches a predetermined value (for example, 80% by weight), or the intermediate coating film viscosity is a predetermined value. (For example, around 600 to 800 Pa · s).

  FIG. 4 is a plan view showing the intermediate top coating booth 5A and the intermediate top coating drying furnace 62 according to the present embodiment, and an automobile body B, which is an object to be coated, is carried into the booth 5A from the left side of the figure, and the floor conveyor C Is conveyed at a constant speed in the right direction of the figure. Reference numeral 61 between the intermediate top coating booth 5A and the intermediate top coating drying furnace 62 is a setting chamber after the intermediate coating and top coating are applied.

  A preparation room for wiping the body B is provided at the entrance of the intermediate top coating booth 5A. Next, a reciprocating coating machine 51A for painting mainly the horizontal part of the body B and a mainly vertical part of the body B are provided. An intermediate coater having a pair of left and right reciprocating coaters 52A for painting is provided. At the tip of each reciprocating coating machine, the above-described rotary atomizing type coating gun is mounted, and the intermediate coating is sprayed from here toward the body B. The intermediate coating means shown in FIG. The reciprocating coating machine 52A is provided with the intermediate coating means shown in FIG.

  Then, a lamp or hot air blower 53A for heating the body in the intermediate coating preheating step 53 is provided after the intermediate coating machine. In addition, it can replace with the intermediate coating preheating process 53, and the solvent content contained in the intermediate coating base coating film layer 103 can also be evaporated by putting off flash for about 1-2 minutes.

  Returning to FIG. 1 and FIG. 2, when the intermediate coating preheating process is completed, the top coating base coating is applied to the inner and outer plates of the body in the next top coating base coating process 54. The topcoat base paint is a thermosetting type that is mainly composed of polyester resin, acrylic resin, vinyl chloride vinyl acetate copolymer resin, urethane resin, cellulose resin, etc., and colorants, glittering materials, and various additives added to it. A paint, a room-temperature curable paint, or a two-component curable paint, which is a water-based paint. Then, the paint diluted with water is applied to the surface of the intermediate coating layer 103 using a coating machine such as a spray coating gun or a rotary atomizing coating gun in the top coat base coating step 54 shown in FIG. . Thereby, the top coat base coating layer 104 is formed. Although it differs depending on the specifications and parts of the automobile body 101, the film thickness of the top coat base coating layer 104 is, for example, 10 to 30 μm.

  As shown in FIG. 4, the top coat base coating step 54 comprises a reciprocating coater for painting mainly the horizontal portion of the body B and a pair of left and right reciprocating coaters for painting mainly the vertical portion of the body B. The machine 54A can be configured by arranging two stages. In addition, when the top coat film is a solid-type paint film, the coating machine 54A in the top coat base coating process 54 is forwarded.

  After the top coat base coating is applied, the automobile body is heated to evaporate the solvent contained in the top coat base coating layer 104 in the top coat preheating step 55. In the top coat preheating step 55, the horizontal and vertical parts of the automobile body are heated at a temperature lower than the curing temperature of the top coat base paint using a heat source such as a lamp or a hot air blower. In addition, it can replace with the top coat preheating process 55, and can also evaporate the solvent content contained in the top coat base coating-film layer 104 by putting off flash for about 1-2 minutes.

  In the next clear application step 56, a clear paint is applied to the inner and outer plates of the body. The clear paint is mainly composed of polyester resin, acrylic resin, polyvinyl chloride vinyl chloride copolymer resin, urethane resin, cellulose resin, etc., and various additives are added to this as thermosetting paint or room temperature curable paint or A two-component curable coating material, which is diluted with a solvent, is used as a top coating base coating layer in a clear coating step 56 shown in FIG. 1 by using a coating machine such as a spray coating gun or a rotary atomizing coating gun. 104 is painted on the surface. As a result, a transparent clear coating layer 105 is formed. The thickness of the clear coating layer 105 is, for example, 10 to 40 μm, although it varies depending on the specifications and parts of the automobile body 101. The clear paint according to the present invention can be either water-based paint or organic solvent-based paint.

  As shown in FIG. 4, the clear coating step 56 is a top coater having a reciprocating coater for painting mainly the horizontal part of the body B and a pair of left and right reciprocating coaters for painting mainly the vertical part of the body B. 56A can be configured by arranging two stages.

  After applying the clear paint, after passing through the setting chamber 61 for several minutes, the body is carried into the intermediate top coating curing process 6 (the intermediate / top coating drying furnace 62 shown in FIG. 4) and applied first. The formed intermediate coating layer 103, top coating base coating layer 104, and clear coating layer 105 are simultaneously baked at, for example, 120 to 160 ° C. for 10 to 30 minutes.

  As described above, the cured coatings of the electrodeposition coating layer 102, the intermediate coating layer 103, the top coating layer 104, and the clear coating layer 105 are formed on the surface of the automobile body 101.

  Hereinafter, the present invention will be described more specifically.

Example 1
A dull steel plate test piece having a plate thickness of 0.75 mm and a size of 70 mm × 150 mm is subjected to degreasing and zinc phosphate conversion coating treatment, and after washing with water, a cationic electrodeposition paint (NT-100B manufactured by Kansai Paint Co., Ltd.) Was electrodeposited for 3 minutes at a voltage of 400V. After washing this with water, it was baked under the conditions of holding at 170 ° C. for 30 minutes. The electrodeposition film thickness was 20 μm.

  On this electrodeposition coating, a polyester melamine-based intermediate coating (48% solids solid, Aqua GX sealer manufactured by Nippon Oil & Fats BASF Coatings Co., Ltd.) with the test piece maintained horizontally, a rotary atomizing bell Using a mold coating gun (PPH607 manufactured by Sames), the humidity of the shaping air was adjusted to 80% RH, and coating was performed so that the dry film thickness was 30 μm. The temperature of the coating booth at this time was 24 ° C., and the humidity was 70% RH. The test piece prepared separately at this time was used to measure the solid content of the coating film after 1 minute of coating and the coating film viscosity.

  After 2 minutes of flash-off, an acrylic melamine-based topcoat base paint (paint solid content 20%, Superlac M180 manufactured by Nippon Paint Co., Ltd.) and a solvent-based acid acrylic / epoxy clear paint (paint solids) 51%, Mac Paint O-590 manufactured by Nippon Paint Co., Ltd. was applied wet-on-wet, and the intermediate coating layer, the top coating layer and the clear coating layer were simultaneously baked by holding at 140 ° C. for 30 minutes. The film thickness of the base coating film was 15 μm, and the film thickness of the clear coating film was 40 μm.

  The sharpness of the obtained coated plate was measured using a PGD meter (PGD-TV manufactured by Japan Color Research Institute). The results are shown in Table 1.

Example 2
Example 1 except that the test piece is placed vertically (vertical) when applying the intermediate coating, top coating and clear coating, and the humidity of the shaping air when applying the intermediate coating is 50% RH. Painted under the same conditions. The results are shown in Table 1.

Comparative Example 1
The coating was performed under the same conditions as in Example 1 except that the humidity of the shaping air when applying the intermediate coating was 50% RH. The results are shown in Table 1.

  As is clear from this result, the coating film of Example 1 in which shaping air was humidified from the humidity of the painting booth and applied to the horizontal portion showed an extremely good sharpness of 0.90 compared to Comparative Example 1. It was. Further, no sagging was found in the coating film of Example 2 in which the shaping air was dehumidified from the humidity of the painting booth and applied to the vertical portion, and the sharpness was also good.

It is process drawing which shows the coating method of the motor vehicle body which concerns on embodiment of this invention. It is sectional drawing which shows the laminated coating film formed by the coating method of the motor vehicle body which concerns on embodiment of this invention. It is a top view which shows an example of the whole coating process which enforces the coating method of the motor vehicle body which concerns on embodiment of this invention. It is a top view which shows an example of the intermediate | middle top coat process which enforces the coating method of the motor vehicle body which concerns on embodiment of this invention. It is a figure which shows an example of the vertical part intermediate coating means which concerns on this invention. It is a figure which shows an example of the horizontal part intermediate coating means which concerns on this invention. It is a figure which shows an example of the coating gun which concerns on this invention. It is the graph which compared the sharpness of the conventional 3 coat 2 bake painting system, and the sharpness of the conventional 3 coat 3 bake painting system. It is a graph which shows the relationship between intermediate coating film viscosity and sharpness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pre-processing process 2 ... Electrodeposition coating application process 3 ... Electrode-washing process 4 ... Electrodeposition hardening process 5 ... Middle top coating process 51 ... Horizontal part intermediate coating process 52 ... Vertical part intermediate coating process 53 ... Intermediate coating Preheating process 54 ... Top coating base coating process 55 ... Top coating preheating process 56 ... Clear coating coating process 6 ... Middle top coating curing process 101, B ... Automotive body 102 ... Electrodeposition coating film layer 103 ... Middle coating film layer 104 ... Base coating film layer 105 ... Clear coating layer

Claims (8)

After applying a water-based intermediate coating to the object to be coated having a horizontal part and a vertical part, the water-based top coating is applied wet-on-wet, and the intermediate coating film layer and the top coating film layer formed thereby are the same. A coating method that cures in the process,
A horizontal part intermediate coating process for coating the horizontal part of the object to be coated with an intermediate coating;
A vertical part intermediate coating process for applying an intermediate coating to the vertical part of the article to be coated,
In the horizontal part intermediate coating step, using a rotary atomizing bell type coating gun, the humidity of the shaping air of the rotary atomizing type bell type coating gun is set higher than the general humidity of the coating booth, and the intermediate coating material is applied. As well as painting
In the vertical part intermediate coating step, using a rotary atomizing bell type coating gun, the humidity of the shaping air of the rotary atomizing type bell type coating gun is set to be equal to or lower than the general humidity of the coating booth. A painting method characterized by painting a paint. Characterized in that said shaping air humidity rotary atomization type bell spray gun of the horizontal portion intermediate coating step, the generally greater than the relative humidity of the painting booth, to less humidity plus 20 points to the general relative humidity The coating method according to claim 1.   The relative humidity of the shaping air of the rotary atomizing bell-type paint gun in the horizontal intermediate coating process is controlled in the range of 70 to 90% according to the general relative humidity of the coating booth. The coating method according to claim 1 or 2.   4. The intermediate coating preheating step of evaporating moisture contained in the intermediate coating film layer formed in the horizontal portion intermediate coating step and the vertical portion intermediate coating step. The coating method in any one. After applying a water-based intermediate coating to the object to be coated having a horizontal part and a vertical part, the water-based top coating is applied wet-on-wet, and the intermediate coating film layer and the top coating film layer formed thereby are the same. A coating device for curing in the process,
A horizontal portion intermediate coating means for applying an intermediate coating on the horizontal portion of the article;
A vertical part intermediate coating means for applying an intermediate coating to the vertical part of the article to be coated,
The horizontal portion intermediate coating means includes a rotary atomizing bell type painting gun, and the humidity of the shaping air of the rotary atomizing type bell painting gun is set higher than the general humidity of the painting booth,
The vertical portion intermediate coating means includes a rotary atomizing bell-type painting gun, and the humidity of the shaping air of the rotary atomizing bell-type painting gun is set to be equal to or lower than the general humidity of the painting booth. Coating equipment. The humidity of the shaping air of the rotary atomizing bell-type paint gun of the horizontal portion intermediate coating means exceeds the general relative humidity of the coating booth and is set to be equal to or lower than the humidity obtained by adding 20 points to the general relative humidity . The coating apparatus according to claim 5.   Humidity control means for controlling the relative humidity of the shaping air of the rotary atomizing bell type painting gun of the horizontal portion intermediate coating means within a range of 70 to 90% according to the general relative humidity of the painting booth. The coating apparatus according to claim 5 or 6, wherein   8. The intermediate coating preheating means for evaporating moisture contained in the intermediate coating film layer formed by the horizontal portion intermediate coating means and the vertical portion intermediate coating means. The coating device according to crab.

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