JPS5933430B2 - Color matching painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color matching coating method that enables color matching to be performed by separately painting metal parts and organic material parts that are finally assembled into one.

In recent years, in order to reduce the weight of automobiles, there has been a tendency to use organic materials for parts such as sunroofs, fenders, nose panels, and bumpers.

Since these organic material-based parts are ultimately assembled into a car body made of iron or other metal materials, they must be painted in a color that matches the paint of the car body. By the way, when painting the metal parts that make up the car body,
A high-temperature curing paint made by adding, for example, a melamine resin-based curing agent to a mixture of film-forming resin and pigment is used, and after application, the metal parts are heated to a high temperature (for example, 140°C) to form a paint film. A coating method that involves curing is generally employed.

However, since such a coating method includes a high-temperature baking treatment, it is impossible to apply it to the coating of the above-mentioned organic material-based parts from the viewpoint of heat resistance. Therefore, conventionally,
For the above-mentioned organic material-based parts, a low-temperature curing paint made by adding, for example, an isocyanate resin-based curing agent to the mixture of the above-mentioned film-forming resin and pigment is used, and after application, the organic material-based parts are coated. A coating method is used in which the paint film is cured by heating at a relatively low temperature (for example, 80° C.).

However, on the other hand, the coating film formed by this coating method has extremely poor weather resistance due to the low baking temperature.
After a long period of time, there is a problem that a large difference in gloss arises between the paint film and the paint film of the metal parts, and color matching becomes impossible. In order to improve the weather resistance of the coating film formed on the organic material-based parts, when the baking temperature is raised to near the heat-resistant temperature of the organic material-based parts, the isocyanate resin-based curing agent in the paint is There is a problem in that the color changes and a significant color difference occurs between the paint and the coating on the metal parts.

The present invention was developed as a result of repeated experimental research in an attempt to solve this problem, and it uses a conventional isocyanate resin-based curing agent as a curing agent for a low-temperature curing type paint used for coating the above-mentioned organic material-based parts. In addition to the curing agent, using a suitable amount of melamine resin-based curing agent, which is a curing agent for high-temperature curing paints used for painting metal parts, may cause discoloration due to the isocyanate resin-based curing agent. The baking temperature of the coating film on the organic material-based parts is raised to the limit of the heat-resistant temperature of the organic material-based parts, while the curing reaction is carried out well without causing any damage. The purpose of the present invention is to provide a color matching coating strength method that improves the weather resistance of metal parts and enables good color matching of paint films between metal parts and organic material parts even after a long period of time. It is something.

That is, the present invention is a coating force method that enables color matching to be performed by separately painting metal parts and organic material parts that are finally assembled together, and in which a coating film-forming resin and a pigment are used. A first curing type paint is formed by mixing a melamine resin curing agent with the paint component, and the first curing type paint is applied to the metal parts and then heated and cured to form a coating film. An isocyanate resin-based curing agent and a melamine resin-based curing agent are added to the film components to form a second curing type paint, and the second curing type paint is applied to the organic material-based parts and then heated and cured to form a coating film. It is characterized by forming.

Hereinafter, the present invention will be explained in detail based on the drawings.

Figure 1 shows the case where the color matching coating strength method of the present invention is applied to an automobile painting process. After passing through electrodeposition process 2 and being sent to sealer and intermediate coating process 3, top coating process 4 and baking process 5
is transferred to the assembly process 6. Organic material parts such as automobile sunroofs and fenders go through a molding process 7, a pretreatment process 8, and a primer and sealer application process 9.
After that, it is transferred to the assembly process 6 through a topcoating process 10 and a baking process 11, where it is finally assembled into the metal parts. In addition, a first multi-component automatic measuring machine 12 that automatically measures and mixes various coating components is installed in the top coating process 4 for the metal parts, and each of the first multi-component automatic measuring machines 12 Paint tanks 13 to 15 each store paint pastes of three colors, for example, white, red, and blue, which are made by mixing a paint film-forming resin and a pigment, and each paste is polymerized and cured at high temperature. a first curing agent tank 16 that stores a melamine resin-based curing agent;
It is connected to a thinner tank 17 that stores thinner for thinning paint.

- A second multi-liquid automatic measuring machine 18 similar to the first multi-liquid automatic measuring machine 12 is installed in the overcoating process 10 for organic material parts, and the second multi-liquid automatic measuring machine 18 is It is connected to the paint tanks 13 to 15, the first curing agent tank 16, and the cinnatanta 17, and stores an isocyanate resin curing agent that polymerizes and hardens the coating paste in the paint tanks 13 to 15 at low temperature. Second
It is connected to a curing agent tank 19. In such a painting process, when topcoating metal parts and organic material parts while matching colors, the first multi-liquid automatic metering machine 12 fills the paint tank 13 to
15 to the paint paste from one of the first hardener tanks 16
A predetermined amount of a melamine resin curing agent is mixed to form a first curing type paint that reacts and cures at high temperature, and this first curing type paint is applied to a metal part passing through the top coating step 4, and then this metal part In the baking step 5, the first curing type paint is polymerized and cured by heating it to a temperature of, for example, 140°C to form a coating film.

In the case of organic material-based parts, the second multi-liquid automatic measuring machine 18 uses the same coating paste as the first curing paint used for coating the metal parts in the second curing agent tank 19. An appropriate amount of the isocyanate resin curing agent from the above and the melamine resin curing agent from the first curing agent tank 16 are added to a high temperature within the heat resistance range of the organic material parts (for example, 12°C). ), a second curing type paint is formed which is reactively cured, this second curing type paint is applied to the organic material-based parts passing through the topcoating step 10, and then the organic material-based parts are heated at, for example, 120° C. in the baking step 11. Above by heating to temperature? A coating film is formed by polymerizing and curing the 2-curing paint. Color matching painting is performed as described above. Therefore, when metal parts and organic material parts are color matched coated in this manner, the melamine resin curing agent, which is the most powerful curing agent in the second curing type paint applied to the organic material parts, is removed. is a high-temperature curing agent, so it does not change color at all at baking temperatures of about 120°C, and isocyanate resin-based curing agents, which are other-purpose curing agents,
Although it changes color at a baking temperature of .degree. C., its content is as small as the amount of the melamine resin curing agent added, so its influence on the overall color change is extremely small. This eliminates the color difference between the coating film formed on the metal component and the coating film formed on the organic material component, and it is possible to achieve good color matching between the two. In addition, since the baking temperature of the coating film on organic material parts is as high as 120°C, the weather resistance is greatly improved and becomes equivalent to the weather resistance of the coating film on metal parts. The gloss etc. of the paint film and the paint film of the organic material component are kept the same, and color matching can be maintained stably for a long period of time.

The color matching coating strength method of the present invention can be applied to various painting processes other than the automobile painting process as described in the above embodiments.

Alternatively, an appropriate amount of the melamine resin curing agent may be added to the paint paste in advance, and then the isocyanate resin curing agent may be added using the second multi-liquid automatic metering device 18.

Next, a specific example will be explained.

First, a first curing type paint for application to metal parts is formed in three colors: white, red, and blue, and these first curing type paints are applied to a steel fender part of an automobile, and then baked and painted. A film was formed.

Table 1 shows the paint component ratio and baking conditions in that case. In addition, the second curing type paint to be applied to organic material parts was made using the same paint paste as the first curing type paint, and by varying the blending ratio of the two types of curing agents to produce white, red, and blue. These second curing type paints were applied to fender parts manufactured by RRIM and then baked to form a coating film.

The paint component ratio and baking conditions in that case are as shown in Table 2. Then, the color of the coating film formed on the R-RIM fender part was compared with the color of the coating film formed on the steel fender part to determine the color difference between the two, and the results are shown in FIG.

Considering this Figure 2, in order to keep the color difference between the coating film of organic material parts and the coating film of metal parts within the permissible range,
Isocyanate resin curing agent (HM) of melamine resin curing agent (butylated melamine resin) in the second curing type paint
The equivalent ratio α to DI prepolymer 1) was set to 40/60 (=
4/6) or higher, and if the amount of melamine resin thread hardener added is zero (conventional coating strength method), the baking temperature for baking treatment to harden the coating film will be 80℃. In this case, the above color difference is well within the permissible range, but if the baking temperature is set to a high temperature of 120°C, the color difference exceeds the permissible range and becomes defective.

Furthermore, the low-temperature flexibility of the coating film was tested when it was coated under the same coating conditions as for the R-RIM fender parts described above, and the test results are shown in FIG.

As is clear from FIG. 3, in order to keep the low-temperature flexibility level within the permissible range (100,711!L or less in terms of mandrel diameter), the equivalent ratio α of the melamine resin curing agent to the isocyanate resin curing agent is required. 95/5 (=1
9) It turns out that it is necessary to do the following. Then,
In order to keep both color difference and low-temperature flexibility within acceptable ranges, it is necessary to set the above equivalent ratio α within the range of 4/6 × α × 95/5, that is, the blending ratio of the melamine resin curing agent m parts by weight, and if the blending ratio of the isocyanate resin curing agent is e parts by weight, then the coating film forming resin (alkyd resin)
The proper blending range of the curing agent added to the hardening agent is the range shown by 6 m × 1.-, and when the allowable range of these mixing ratios is expressed graphically, it is the area surrounded by the dashed line in Fig. 4.

In addition, the part surrounded by the solid line in FIG. 4 is most preferable. Finally, accelerated weather resistance tests were conducted on the coating films formed on these metal parts and the coating films formed on organic material parts.

In that case, the equivalent ratio of the melamine resin curing agent and the isocyanate resin curing agent in the second curing paint applied to the organic material parts is 75/25 and 25/75.
The latter is a reference example (outside the color difference tolerance range), and as a comparative example, a paint made using a conventional hardening method in which a paint consisting only of an isocyanate resin-based hardener is applied and then baked at a temperature of 80°C. After applying the paint film and urethane resin paint 8
The same accelerated weathering test as above was also conducted on a coating film formed by baking at a temperature of 0°C. The results of these tests are shown in FIGS. 5 to 7. As is clear from FIGS. 5 to 7, the coating film of the organic material-based parts formed by the coating method of the present invention is composed of the coating film formed by the conventional coating force method and the urethane resin-based paint. It can be seen that it has extremely superior weather resistance compared to other coatings, and has weather resistance equivalent to that of coatings on metal parts.

Therefore, even after a long period of time, the coating film on the metal parts and the coating film on the organic material parts exhibit almost the same gloss, and color matching can be maintained stably for a long period of time. As explained above, according to the color matching coating strength method of the present invention, an isocyanate resin curing agent that reacts and cures the coating components at a low temperature is added to the second curing type coating applied to the organic material component. By including the melamine resin curing agent, which is the curing agent in the first curing type paint applied to metal parts and which reacts and hardens the paint components at high temperatures, it cures without causing discoloration of the paint film. Since the baking temperature of the second curing type paint can be raised while allowing the reaction to proceed well, it is possible to improve the weather resistance of the organic material-based component C-coating film to the same level as that of the parent coating film of the metal part. Therefore, even after a long period of time, there is no difference in the gloss or color difference between the metal parts and organic parts, and the color matching between the two can be maintained stably over a long period of time. is what makes it possible

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and Fig. 1 is an overall system diagram of an automobile painting process. Fig. 2 shows a coating film formed with the second curing type paint and a coating film formed with the first curing type paint. Fig. 3 is a graph showing the low-temperature flexibility of a coating film formed with the second curing agent paint, and Fig. 4 is a graph showing the allowable blending range of both curing agents in the second curing type paint. , and FIGS. 5 to 7 are graphs showing the weather resistance of three-color paint films of white, red, and blue, respectively. 4...Top coating process, 5...Baking process,
6... Assembly process, 10... Top coating process, 11... Baking process, 13-15...
Paint tank, 16...First curing agent tank, 18
...Second multi-liquid automatic measuring machine, 19...Second curing agent tank.

Claims (1)

[Claims] 1 A coating method that enables color matching by separately painting metal parts and organic material parts that are finally assembled into one, and in which melamine resin is used as a paint component containing film-forming resin and pigment. A first curing type paint is formed by mixing a curing agent, and the first curing type paint is applied to the metal parts and cured by heating to form a coating film, while an isocyanate resin curing agent is added to the above paint component. A color matching characterized in that a second curing type paint is formed by adding a melamine resin type curing agent, and the second curing type paint is applied to the organic material component and then heated and cured to form a coating film. Painting method.