JP4517646B2 - How to paint a car body - 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 in which an intermediate coating and a top coating are applied wet-on-wet and cured simultaneously.

  Automobile body coating systems include undercoat coatings that use electrodeposition paints based on epoxy resins, intermediate coatings based on polyester resins, acrylic resins, and alkyd resins, and polyester paints. Three types of topcoats, mainly acrylic resin and alkyd resin, were used for the undercoat and then baked. After the intermediate coat was applied onto the cured undercoat, this was baked and cured. A so-called three-coat three-bake coating method is employed, which is completed by applying a top coat onto an intermediate coat and then baking it.

  However, in such a three-coat three-bake coating system, a drying furnace is required for each of the undercoat coating process, the intermediate coating process, and the topcoat coating process, so that a wide process space is required for installing the drying furnace. There was a problem that the energy consumed in the drying furnace was reflected in the production cost of the automobile.

  Therefore, in order to reduce the number of drying furnaces provided in these three processes to two or less and solve the above problems, after applying the intermediate coating and the top coating by wet-on-wet, these can be performed simultaneously in one drying furnace. Baking and curing is being studied.

  However, in the coating system in which the intermediate coating and top coating are applied wet-on-wet and baked at the same time, they are included in the top coating when the top coating is applied to the surface of the uncured intermediate coating. The solvent moves 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 smoothness of the top coating film typified by sharpness is obtained. There was a problem that the performance decreased.

The present invention provides a method for coating an automobile body that can prevent a mixed layer of an intermediate coating film layer and a top coating film layer when the intermediate coating film and the top coating film are applied wet-on-wet and then cured simultaneously. The purpose is to provide.
In order to achieve the above object, according to the present invention, there is provided a method for coating an automobile body comprising a step of forming at least an intermediate coating layer on an automobile body and a step of forming a top coating layer. the intermediate coating application step and, the surface of the intermediate coating film layer of uncured completing the coating with the intermediate coating application step in applying the intermediate coating, the curing catalyst to accelerate the curing of the intermediate coating layer the coating is applied only the curing catalyst coating step Ru hardening the surface of the intermediate coating layer, a top coat paint on the surface of the intermediate coated film layer in which the curing catalyst is applied in the curing catalyst coating process topcoating There is provided an automobile body coating method comprising: a coating step; and a middle / top coating curing step of simultaneously curing the intermediate coating layer and the top coating layer applied in the top coating step. Be done

In the present invention, before applying the top coating by applying intermediate coating to cure only the surface is coated with a curing catalyst to accelerate the cure of intermediate coating film layer of uncured completing the coating Runode The surface of the intermediate coating layer is cured, and the presence of this surface cured film can prevent the solvent of the top coating from moving into the intermediate coating layer after the top coating is applied. Thereby, a mixed layer does not occur at the boundary portion between the intermediate coating film layer and the top coating film layer, and the smoothness of the top coating film is improved.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The method for coating an automobile body according to the present invention comprises applying an intermediate coating layer and a top coating layer by wet-on-wet, and simultaneously curing the intermediate coating layer and the top coating layer in the same drying furnace. What is necessary is just the coating method which has a process. 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.

  As shown in FIG. 2, the laminated coating film according to this embodiment is formed on the surface of the electrodeposition coating layer 102 formed on the surface of the automobile body 101 that is the object to be coated, and on the surface of the electrodeposition coating layer 102. The intermediate coating layer 103, the base coating layer 104 formed on the surface of the intermediate coating layer 103, and the clear coating layer 105 formed on the surface of the base coating layer 104. ing.

  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. The automobile body 101 is carried into the pretreatment step 1 shown in FIG. 1, where the oil adhering to the automobile body 101 is 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 101. Form.

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

  Next, the automobile body 101 that has completed the electrodeposition washing step 3 is carried into an electrodeposition drying furnace that is the electrodeposition curing step 4, and is cured by baking, for example, at 160 to 180 ° C. for 15 to 30 minutes. A membrane layer 102 is obtained. The film thickness of the electrodeposition coating layer 101 is, for example, 10 to 40 μm, although it varies depending on the specifications and parts of the automobile body 101.

  The intermediate coating layer 103 is mainly composed of a polyester resin, an acrylic resin, a vinyl chloride vinyl acetate copolymer resin, a urethane resin, a cellulose resin, and the like, and a thermosetting paint obtained by adding a colorant or an additive thereto. Or a room-temperature curable coating or a two-component curable coating, which is diluted with a solvent, is applied to the surface of the electrodeposition coating layer 102 using a coating machine such as a spray coating gun or a rotary atomizing coating gun. Paint.

  FIG. 3 is a plan view showing the intermediate top coating booth 50 and the intermediate top coating drying furnace 100 according to the present embodiment, and an automobile body B, which is an object to be coated, is carried into the booth from the left of the figure and is conveyed by the floor conveyor C. It is conveyed at a constant speed in the right direction in the figure. 99 between the intermediate top coat booth 50 and the intermediate top coat drying oven 100 is a setting chamber after the intermediate coat and top coat are applied.

  A preparation room for wiping the body B is provided at the entrance of the intermediate top coating booth 50. Next, a reciprocating coating machine for painting the horizontal part of the body B and the vertical part of the body B are painted. An intermediate coating machine 61 having a pair of left and right reciprocating coating machines is provided. In the example shown in the figure, one stage of this coating machine is provided. At the tip of each reciprocating coater, the above-described rotary atomizing paint gun or spray paint gun is mounted, and the intermediate paint is sprayed from here toward the body B.

  Returning to FIG. 1, when the intermediate coating is applied, the curing catalyst application step 7 is followed by curing that accelerates the curing of the intermediate coating layer 103 on the surface of the uncured intermediate coating layer 103. Apply catalyst. The curing catalyst applied here may include an inorganic acid catalyst or an organic acid catalyst when the intermediate coating is a melamine resin coating, and when the intermediate coating is a urethane resin coating. A curing catalyst such as DBTL (dibutyl / tin / di / laurate) can be used.

  The coating method of the curing catalyst is sufficient as long as the surface of the uncured intermediate coating layer 103 is not mixed with the top coating material to be applied next, and the coating method is not particularly limited. In this embodiment, using the shaping air of the rotary atomizing paint gun, the curing catalyst is sucked into the shaping air and applied in the form of a mist. A painting machine 71 shown in FIG. 3 is a painting machine having a horizontal part reciprocating painting machine and a vertical part reciprocating painting machine equipped with a rotary atomizing painting gun, and FIG. 4 shows one of them. A paint gun 711 is shown.

  The rotary atomizing paint gun 711 includes a bell cup 712 that rotates at a high speed, and paint is supplied to the bell cup 712 from a paint supply device (not shown) when applying a normal intermediate coating or top coating. However, since the coating machine 71 provided in the curing catalyst coating step 7 only needs to mix the curing catalyst with shaping air and apply it, the paint is not supplied to the bell cup 712. Instead, a mixing valve 715 is provided in the middle of an air supply source 713 for supplying the air to a shaping air discharge port provided on the outer periphery of the bell cup 712, and the curing catalyst supplied from the curing catalyst supply source 714 is supplied as air. This is discharged from the discharge port of the shaping air. Thereby, the curing catalyst is applied to the surface of the uncured intermediate coating layer 103, and only the surface is cured.

  Returning to FIG. 1, after the curing catalyst is applied, after a flash-off of about 1 to 2 minutes, the top coat base paint is applied to the inner and outer plates of the body B in the next top coat base paint application process 8. 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. The surface of the intermediate coating layer 103 using a coating machine such as a spray coating gun or a rotary atomizing coating gun, which is a paint, a room temperature curable paint or a two-component curable paint diluted with a solvent. The top coat base coating film layer 104 is formed by painting on. 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. 3, the top coat base coating application process 8 includes 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 coating and painting machine 81 can be configured by arranging two stages. In addition, when the top coat film is a solid-type paint film, the coating machine 81 of this top coat base paint coating process 8 is forwarded.

  After applying the topcoat base paint, after a flash-off of about 1 to 2 minutes, the clear paint is applied to the inner and outer plates of the body B in the next clear paint application process 9. 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, which is diluted with a solvent, is applied on the surface of the top coat base coating layer 104 using a coating machine such as a spray coating gun or a rotary atomizing coating gun. A 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.

  After applying the clear paint, after passing through the setting chamber 99 for a few minutes, the body B is carried into the intermediate top coat drying furnace 100 and applied to form the intermediate coat layer 103 and the top coat base. The coating film layer 104 and the clear coating film layer 105 are simultaneously baked, for example, at 120 ° C. to 160 ° C. for 10 minutes to 30 minutes (intermediate top curing process 10).

  In the present embodiment, since a curing catalyst that accelerates the curing of the surface of the uncoated intermediate coating layer 103 is applied between the intermediate coating application step 6 and the top coating base coating application step 8, the intermediate coating layer is applied. The surface of the layer 103 is cured, and the presence of this surface-cured film can prevent the solvent of the topcoat base paint from migrating into the intermediate coat film layer 103 after the topcoat base paint is applied. Thereby, a mixed layer does not arise in the boundary part of the intermediate coating film layer 103 and the top coat base coating film layer 104, and the smoothness of the laminated coating film is improved.

  Hereinafter, the present invention will be described more specifically.

Example 1
A galvanized steel plate having a plate thickness of 0.75 mm and a size of 70 mm × 150 mm is used as an object to be coated. Electrodeposition coating was performed using a top U-600M) so that the dry film thickness was 20 μm, and an electrodeposition coating layer was formed by baking and curing at 160 ° C. for 30 minutes.

  By spray coating the surface of this electrodeposition coating layer using an intermediate coating (a two-component urethane coating of polyester polyol and non-yellowing isocyanate manufactured by Nippon Bee Chemical Co., Ltd.) to a dry film thickness of 30 μm. An intermediate coating film layer was formed, and then shaping air containing amine as a curing catalyst was applied from the rotary atomizing coating gun to the surface of the uncured intermediate coating film layer.

  Furthermore, a top coat base paint (acrylic melamine paint, silver color, manufactured by Nippon Paint Co., Ltd.) is spray-coated on the surface of the uncured intermediate coat layer so that the dry film thickness is 15 μm, and then clear paint (Japan) Olga 80) manufactured by Paint Co. is spray-coated on the surface of the uncured base coating layer so that the dry film thickness is 30 μm. The intermediate coating layer, the base coating layer and the clear coating layer are formed at 140 ° C. And baked and cured at the same time for 30 minutes.

  The sharpness value (PGD value) of the obtained multilayer coating film was measured using a sharpness value meter (portable sharpness / glossiness meter manufactured by Japan Color Research Institute). The results are shown in Table 1.

Comparative Example 1
After applying the intermediate coating, a laminated coating was formed under the same conditions as in Example 1 except that no amine was applied to the surface of the uncured intermediate coating layer. Table 1 shows the sharpness values of the obtained laminated coating films.

Comparative Example 2
After applying the intermediate coating, a laminated coating film was formed under the same conditions as in Example 1 except that the amine was applied at the same time as the top coating. Table 1 shows the sharpness values of the obtained laminated coating films.

実施例１と比較例３より、中塗り塗料を塗布したのち硬化触媒であるアミンを塗布し、その後上塗りベース塗料を塗布すると（実施例１）、中塗り塗料を塗布して焼き付け硬化させた積層塗膜（比較例３）と同等の鮮映値を示すことが確認された。 Comparative Example 3
After applying the intermediate coating, the intermediate coating layer was baked and cured at 140 ° C. for 30 minutes, and the top coating base coating was applied to the surface of the cured intermediate coating layer under the same conditions as in Example 1. A laminated coating film was formed. Table 1 shows the sharpness values of the obtained laminated coating films.

From Example 1 and Comparative Example 3, after applying an intermediate coating, an amine, which is a curing catalyst, is applied, and then an overcoat base coating is applied (Example 1). It was confirmed that a sharpness value equivalent to that of the coating film (Comparative Example 3) was exhibited.

  In addition, it was confirmed that when the curing catalyst was not applied (Comparative Example 2), the sharpness value was extremely lowered, and even when the curing catalyst was applied simultaneously with the topcoat base paint, the sharpness value was not improved so much.

It is a flowchart 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 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 conceptual diagram which shows an example of the coating device of the curing catalyst application | coating process which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pretreatment process 2 ... Electrode coating application process 3 ... Electrode washing process 4 ... Electrode hardening process 5 ... Middle top coating process 6 ... Intermediate coating application process 7 ... Curing catalyst coating process 8 ... Top coating base coating application process DESCRIPTION OF SYMBOLS 9 ... Clear coating application process 10 ... Middle top coating hardening process 101 ... Automobile body 102 ... Electrodeposition coating layer 103 ... Intermediate coating layer 104 ... Base coating layer 105 ... Clear coating layer

Claims (5)

A method of painting an automobile body comprising a step of forming at least an intermediate coating layer on an automobile body and a step of forming a top coating layer,
An intermediate coating application step of applying an intermediate coating to the automobile body;
On the surface of the uncured intermediate coating film layer of completing the coating with the intermediate coating application step, applying a curing catalyst to accelerate the curing of the intermediate coating layer, only the surface of the intermediate coating layer a curing catalyst coating step Ru cured,
And a top coat coating step for coating the surface of the intermediate coating layer coated with the curing catalyst in the curing catalyst coating step. The method for coating an automobile body according to claim 1, further comprising an intermediate / top coating curing step of simultaneously curing the intermediate coating layer and the top coating layer applied in the top coating step. The method of coating an automobile body according to claim 1 or 2 , wherein in the curing catalyst coating step, the curing catalyst is coated in a mist form. The automobile body according to any one of claims 1 to 3 , further comprising an electrodeposition coating process in which an electrodeposition paint is applied to the surface of the automobile body and cured before the intermediate coating paint application process. How to paint. In the curing catalyst coating process, an automobile body coating method of the claim 1-4 either, which comprises applying by mixing the curing catalyst shaping air rotary atomization coating machine.

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