JPS581634B2 - Kouko Kabun Hisuibun Sangata Metallic Trio You No To So Houhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high solid content non-aqueous dispersion type metallic paint coating method.
This is an improved coating method for D (non-aqueous dispersion) metallic paint.

In recent years, diffusion of organic solvents discharged from painting booths and drying ovens has become a problem, and research and development of various painting methods is being carried out in this regard.

Among these painting methods, painting with high solids content paint, which has a higher nonvolatile content (solid content) concentration than conventional spray painting, is
It has been viewed as extremely promising in recent years because it can use most of the conventional equipment.

Material methods to increase the solid content concentration during spray painting include: ■ replacing solution-based paints with non-aqueous dispersion (NAD) paints, or reducing the molecular weight of the resin in solution-based paints. However, NAD paints (■) are often used as metallic paints for automobile exterior panels.

This is because in metallic coatings, it is necessary to spray paint with good atomization to create a metallic feel and prevent metal unevenness, and therefore it is necessary to spray paint with low viscosity, and as a result, in order to achieve high solidity with low viscosity. Considering coating film performance, it is more desirable to make the material non-aqueous dispersible than to lower the molecular weight.

The solid content concentration during spray painting of conventional automotive metallic paints varies depending on the paint color, etc., but for 101B*1, it is 2
5-30% by weight, 2C1B*2 Beocoat 20-2
5% by weight is commonly used.

When this is non-aqueous dispersed, in recent years it has become possible to coat approximately 35% by weight of 1C1B and 40% by weight of 2C1B.

FIG. 1 shows the relationship between solid content concentration and viscosity for three types of NAD paints with different degrees of dispersion.

As is clear from this figure, the higher the degree of dispersion, the higher the solid content concentration during spray coating.

Furthermore, products with a high degree of dispersion have a large viscosity change in response to changes in solid content concentration, so even a small amount of solvent evaporates during spraying, the viscosity increases rapidly, and in general, it is difficult to sag and metal unevenness occurs. It is said to have good paintability.

However, the present inventors conducted intensive research on NAD metallic and found that it cannot be said that the paintability is generally good.

NAD paint is generally made by dispersing resin, etc. in an aliphatic hydrocarbon solvent, but if the dispersed paint is applied as is, it is difficult to obtain a smooth surface during application, as shown in the model diagram in Figure 2.

The reason for this is that the dispersed particles stick together and are not easily compatible with each other.

Another possibility is that the viscosity of the paint increases significantly when the solvent evaporates compared to a solution-type paint, making it difficult to flow.

Not only is it difficult to obtain a smooth surface with paint that is simply dispersed in this way, but the viscosity of the applied paint varies greatly due to slight changes in the amount of solvent evaporated, so slight changes in coating conditions can cause changes in the finished surface. This easily results in a narrow paint management width.

It also has other defects such as easy spraying unevenness due to similar reasons.

In order to avoid these defects, non-aqueous dispersion paints generally contain what is called a film coalescing agent.

Plasticizers are usually used as membrane fusing agents, but in NAD paints for automobile metallic coatings, solvents with polar groups, such as esters such as carbitol acetate, cellosolve acetate, butyl cellosolve, etc. are used as membrane fusing agents.
Ethers such as butylcarbitol are used.

By using this film fusing agent, it is possible to obtain a smooth surface by dissolving the coated dispersed particles, and the larger the amount, the wider the control range of the coating.

However, the reason why the film coalescing agent exerts the above effect is because it dissolves the dispersed particles.In other words, the inclusion of particles in the paint impairs the non-aqueous dispersibility and therefore reduces the solid content concentration during spray painting. It turns out.

The reason why I stated above that the larger the amount of film fusing agent is, the wider the coating control range is is that in such cases, NAD paints are closer to solution-type paints, that is, the viscosity changes with respect to solid content concentration are small. As a result, this means that it is possible to expand the scope of painting management.

In Figures 3-a, b, and c, the degree of decentralization is 90%, 50%,
The dilution rate viscosity curves of various solvents are shown for the paint in the case of 0% (=solution).

Even in the case of paints with a high degree of dispersion, solvents that do not reduce the viscosity or increase the viscosity are better as film fusing agents.For this reason, the use of a film fusing agent in paints with a high degree of dispersion is essential for spray painting. This means that the solid content concentration is lowered.

With NAD paints having such a high degree of dispersion, the higher the concentration of nonvolatile matter during spraying, the narrower the control width of the coating and the harder it is to obtain a smooth surface.

This tendency differs depending on the paint color, but in 1C1B metallic paint, the solid content concentration is 35 to 40% by weight or more, and 2C1B
In metallic coatings, it becomes noticeable when the content exceeds 40 to 42% by weight.

However, if a membrane fusing agent is added to avoid this, a dilemma arises in that it ends up lowering the solid content concentration, contrary to the desired increase in solid content concentration.

As a result of intensive research into coating with NAD paints, particularly with NAD paints having a high solids content (40% by weight or more), the inventors of the present invention have discovered a coating method according to the present invention, which solves the above-mentioned contradictions and obtains an excellent painted surface. succeeded in.

The coating method according to the present invention is as follows: 1) When applying a high solid content NAD paint, the solution type paint is applied to the object to be coated in advance or sprayed at the same time, so that the solution type paint is applied on the coated surface or at the time of spraying. 2) Preferably, a polar base solvent (ether, ester) having a film fusion effect of the NAD paint is used in the solvent composition of the solution type paint.

3) Preferably, the solution-type paint is characterized in that it does not contain metal powder.

By doing so, the coating method of the present invention 1) enables coating with a higher solid content than conventional ones, and 2) eliminates the shortcomings of high solid content NAD metallic paints, such as narrow control range and rough skin. Also solved problems such as uneven spraying.

This is because: 1) the above defects can be prevented without incorporating a film fusing agent into the NAD metallic paint, or at least by contacting the solution type paint with the film fusing effect of the solvent in the composition; Metallic paints do not contain a film fusing agent during coating, so it is possible to increase the solids content to a level higher than that of conventional paints.

2) By increasing the amount of film-fusing agent in the solution-type paint, the film-fusing effect can be further enhanced, and the range of control becomes wider accordingly. 3) As is clear from Figure 3C, film-fusing agents are The effect of reducing the viscosity of solution-based paints is greater than that of other solvents, so using this solvent can increase the solid content concentration of solution-based paints. 4) It is better not to include metal powder in solution-based paints. To enable coating with high viscosity, that is, high solid content, without causing defects such as metal unevenness.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 NAD metallic paint A having the properties and composition shown in Table 1
Table 3 shows the properties of the coated surfaces after coating and drying the solution-type clear paint B under the coating conditions shown in Table 2.

It should be noted that the results of each example and reference example were visually observed except for the film thickness, and an evaluation of ■ or higher was considered to pass the test.

Example 2 Paints A and B used in Example 1 were mixed as shown in Table 4 by connecting one end of paint hose 2 to paint A and one end of paint hose 3 to paint B of the double-headed gun shown in Figure 4. Paint under paint conditions and dry.

The double-headed gun is capable of spraying two different paints at the same time to approximately the same location.

That is, paint hoses 2 connected to different paints A and B,
3 connects each other end to the double-headed gun 1, and uses air sent from an air hose 4 to separately spray different paints onto the same spot using nozzles 5 and 6.

Table 5 shows the properties of the obtained painted surface.

Example 3 NAD metallic paint C shown in Table 6, solution type paint D shown in Example 10 Solution type paint B shown in Table 1 were applied under the coating conditions shown in Table 7, and the properties of the dried painted surface are shown in Table 8. show.

Example 4 NAD metallic paint C shown in Table 6 of Example 3 and heated solution type paints E and F shown in Table 9 below were applied under the coating conditions shown in Table 10, and the properties of the dried painted surface are shown below. 11.

Examples 1 and 2 are based on conventional 1C1B metallic coating, and Examples 3 and 4 are based on 2C1B metallic coating.

Comparative paint A of Example 1 and Reference Example 2A contains less polar group solvents (ethers, esters), which are membrane fusion solvents, than conventional paints, and is highly solidified.

Paint B is a solution-type clear paint containing an appropriate amount of polar base solvent and has a high viscosity so that it can be sprayed.

In Example 1, the paint B was applied to the object before applying the paint A according to the coating method of the present invention, and in Reference Example 2A, the paint A was applied as it was using the conventional paint method. Compare the results.

As is clear from the results, the coating method using conventional paints tends to cause rough skin, gun unevenness, metal unevenness, etc., and the control range is narrow, but in the coating method according to the present invention, paint A is different from paint B.
, especially polar group solvents, it becomes possible to paint with a wide control range and with less rough skin, gun unevenness, and metal unevenness.

Discussion of Example 2 In Example 2, by using a double-headed gun, it is possible to spray the same area at the same time, so paints A and B can be sprayed more easily than in Example 1.
The mixing (contact) effect is enhanced, and coating with a good finish can be achieved with a wider control range than in Example 1.

Discussion of Example 3 Paint C is a base coat metallic paint for conventional 2C1B coating, paint B is a solution type paint that has a film fusion effect as in Examples 1 and 2, and paint D teeth,
A clear coat paint that improves gloss.

In this example, paints C and B were applied using a double-headed gun.

Although it is possible to spray paint C after applying paint B as in Example 1, the results are slightly inferior to those obtained when a double-headed gun is used.

Note that the solvent in paint D does not necessarily need to contain a polar base solvent.

Example 4 In this example, a solution-type paint was hot-sprayed in order to coat with a higher solids content.

By doing so, it is possible to further reduce the amount of organic material used during spraying.

Reference example 1 An example of conventional NAD metallic coating for 1C1B and 2C1B. Even though the temporary solid content concentration of the NAD metallic coating is lower than that of coating A in Examples 1 and 2, the coating control width is also implemented. It can be seen that it is narrower than Examples 1 and 2.

Reference Example 2 This example is an example in which paints A and C used in Examples 1 and 3 were applied using a conventional method, and the finished product was hardly finished.

As explained above, the coating method of the present invention allows NAD metallic paint to be applied with a higher solids content than conventional methods, enables coating with a wider range of coating control, and provides an excellent finished surface.

If applied primarily to automotive exterior metallic coatings, the amount of organic solvents emitted from booth drying ovens can be significantly reduced, and the excellent finish will result in superior products.

The words in this text have the following meanings:

*1 1C1B: A method of applying one type of paint and finishing by baking and drying once. *2 2C1B: A method of applying two types of paint and finishing by baking and drying once. This is a method used in automobile painting. Usually called clear coating *3 Metal unevenness: A defect caused by the flow of metal powder in the paint when the viscosity of the applied paint is low *4 Gun unevenness: A paint defect that shows traces of the gun being scanned on the painted surface dries quickly. *5S... Number of recoatings: single means 1 time.

*6W・・・・・・Double the number of times of repainting 2
*7 Stage means how many intervals (flash-offs) to paint. 4 Stage means to paint in 4 times with 3 intervals.

*8 3C1B: A method in which three types of paint are applied and finished by baking and drying them once.

*9 Mist: If the temporary spray solvent evaporates too quickly and is sprayed, the painted surface may appear dusty, a defect that is likely to occur with NAD paints.

*1020 seconds/FC#4/at20℃...Means that the spray viscosity is 20 seconds when measured at 20℃ with food cup #4.

[Brief explanation of the drawing]

Figure 1 shows the degree of decentralization: 90% (a), 50%
(b), 3 types of NAD with parameters of 0% (c solution)
This is a graph showing the relationship percentage between solid content concentration and viscosity of paint.
The figure shows a cross-sectional model diagram of a painted surface painted by the conventional NAD paint coating method according to the present invention, and 3-a, b, c
The figures show various solvent dilution ratio viscosity curves for paints with a dispersion degree of 90%, 50%, and 0% (solution), respectively. Various solvents are forces. Rubitol acetate (l), cellosolve acetate (m), butyl carbitol (n), Sorbetsuso 150 (o), VM and P naphtha (n), aliphatic (q), and Figure 4 is a schematic diagram of the double-headed gun. represents a diagram. The numbers in the diagram are 1...double-headed gun, 2...
・Paint hose, 3...Paint hose, 4...
...Air hose, 5...Nozzle, 6...
・Represents a nozzle.

Claims (1)

[Claims] 1. When applying a high solid content non-aqueous dispersion type metallic paint with a non-volatile content concentration of 40% by weight or more, the metallic paint is applied after or at the same time as the solution-based paint is applied to the object to be coated. A method for applying a high solid content non-aqueous dispersion type metallic paint.