JP3196794B2 - Painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method applied to automotive coatings, particularly to electrodeposition and intermediate coating.

[0002]

2. Description of the Related Art Coating for automobile bodies is required to provide rust prevention and aesthetics, and high quality is required.

Conventionally, especially in electrodeposition and intermediate coating in automobile coating for passenger cars, (1) electrodeposition coating (primer coating), (2) baking and drying (170 ° C. × 30 minutes) (3) intermediate coating (4) It is common to adopt a baking and drying process (140 ° C. × 30 minutes), and then apply a top coat (for example, “New Automobile Engineering Handbook <Section 9>”).
The Japan Society of Automotive Engineers of Japan May 31, 1983 First edition issued pp. 1-70 to 1-77, “Automotive Technology Handbook <4th Volume> Production, Quality and Maintenance” The Japan Society of Automotive Engineers, September 1991 January 1, 1st edition published pp. 139-146).

[0004]

However, in the above-mentioned conventional coating method for automobiles, there is a problem that energy consumption is apt to increase because of the baking and drying process in each of the electrodeposition and the intermediate coating. Was. In order to prevent such an increase in energy consumption,
If the baking process is performed only once, the appearance of the coated film in the finished state may be inconvenient (e.g., cracking), and the finish (clearness) of the appearance of the coated film may be reduced. There is a problem that even when the baking process is performed only once and the amount of energy consumption is reduced, occurrence of defects in the appearance of the coating film (such as abrasion) is suppressed and the conventional baking process is performed twice. It has been a problem to be able to obtain the same level of appearance finish (clearness) and to reduce energy consumption.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is intended to reduce energy consumption by performing only one baking and drying step in electrodeposition and intermediate coating. In addition, the present invention provides a coating method capable of suppressing the occurrence of defects in the appearance of a coating film (e.g., abrasion) and obtaining the same degree of appearance finish (clearness) as in the case where the conventional baking and drying step is performed twice. It is intended to be.

[0006]

According to the coating method of the present invention, the water content of the electrodeposited film before the intermediate coating is reduced to 5% or less when the coating for automobiles is performed, and the coating is performed without baking and drying. It is characterized in that the composition is such that a polar solvent is added to the coating paint in an amount of 10% or more, the intermediate coating is performed, and then baking and drying is performed. It is a means to solve.

The coating method according to the present invention has the above-described structure. As a result of intensive studies by the present inventors, the water content of the electrodeposition paint, which is a water-based paint, and the electrodeposition coating film before baking and drying. It has been found that the problem can be solved by improving the compatibility between the paint and the intermediate coating.

Specifically, the baking after the intermediate coating is performed by reducing the water content of the electrodeposition coating film before the intermediate coating to 5% or less, and adding a polar solvent to the intermediate coating to at least 10%. Defects in the appearance of the coating film (e.g., wrinkles) due to moisture evaporation during drying, and the appearance of the coating film due to poor adaptation between the electrodeposition coating film and the intermediate coating before baking and drying (brightness ) Can be resolved.

Therefore, in the present invention, the water content of the electrodeposition coating film before the intermediate coating is set to 5% or less. In this case, the water content is adjusted by leaving the electrodeposition coating at room temperature (room temperature) or forced heating. Means can be adopted.

[0010] If the water content of the electrodeposited coating film before the intermediate coating is more than 5%, defects in the appearance of the coating film (such as wrinkles) occur on the surface of the intermediate coating film. In addition, when the amount of the polar solvent added to the intermediate coating is less than 10%, it is not preferable because the finished appearance of the coating film (brightness) is deteriorated.

As such a polar solvent, for example, butanol and iso-butyl ketone can be used, and there is no particular limitation. However, if the amount of the polar solvent added to the intermediate coating is too large, the appearance becomes poor (skin roughness). So 20%
It is preferable to set it to the following level.

Therefore, in the coating method according to the present invention, (1) electrodeposition coating (primer coating;
% Or less. (2) Intermediate coating (10% or more of a polar solvent is added to the intermediate coating). (3) Baking and drying (for example, 140 ° C. × 30 minutes) can be performed, as described in the conventional description. Baking drying after electrodeposition coating (for example, 170 ° C. × 30
) Can be omitted, and the energy consumption can be reduced.

[0013]

The coating method according to the present invention has the above-described structure, and the water content of the electrodeposition coating film before the intermediate coating is set to 5% or less, and the polar solvent is added to the intermediate coating. By performing the intermediate coating by adding 10% or more, the occurrence of poor coating appearance (e.g., abrasion) due to moisture evaporation during baking and drying after the intermediate coating is suppressed, and electrodeposition before baking and drying is performed. This prevents a decrease in the finish (clearness) of the coating film due to poor adaptability between the coating film and the intermediate coating material, thereby omitting the baking and drying process after the electrodeposition coating, thereby increasing energy consumption. It will be further reduced.

[0014]

Hereinafter, examples of the present invention will be described together with comparative examples.

Example 1 A test piece having a size of 70 × 150 mm was subjected to a pre-coating treatment using a pre-treatment agent (trade name: Granozin DP4000, manufactured by Nippon Paint), and then an undercoat paint (trade name: NS336E, Electrodeposition coating (primer coating) was performed by using Nippon Paint Co., Ltd. so as to have a dry film thickness of 20 μm, and left standing for 30 minutes to measure the water content of the electrodeposition coating film.

Subsequently, an intermediate coating (trade name: Hiepiko No. 100, manufactured by NOF Corporation) to which 10% of butanol was added as a polar solvent was used, and the dry film thickness was 35 μm.
m, and baked and dried at 140 ° C. for 30 minutes.

Further, a top coat is applied using a top coat (trade name: Bellcoat No. 5220 black, manufactured by Nippon Oil & Fats Co., Ltd.) to a dry film thickness of 15 μm to form a black color base coat. A wet-on-wet coating was performed using a base resin paint (trade name: Bellcoat No. 6000, manufactured by Nippon Oil & Fat Co., Ltd.) to a dry film thickness of 35 μm, and baking and drying were performed for 140 minutes and 30 minutes.

Example 2 Example 1 was repeated except that the natural standing time after the electrodeposition coating was set to 20 minutes, and the water content of the electrodeposition coating was changed to 5%.
It carried out similarly to.

Example 3 Example 3 was carried out in the same manner as in Example 1 except that the amount of butanol as a polar solvent was changed to 20%.

Example 4 The procedure of Example 1 was repeated, except that iso-butyl ketone was used instead of butanol as the polar solvent.

Comparative Example 1 The procedure of Example 1 was repeated, except that the natural leaving time was 15 minutes and the water content of the electrodeposition coating film was 6%.

Comparative Example 2 The procedure of Example 1 was repeated, except that the amount of butanol as a polar solvent was changed to 9%.

Evaluation Example (1) Appearance of coating film: According to JIS K 5400 6.1, the surface of the intermediate coating film was visually observed and evaluated.
：: good, Δ: normal, ×: bad (occurrence of cracks).

(2) Sharpness: The surface of the overcoated film was measured with a PGD meter and evaluated, and the results are shown in the column of "Sharpness" in Table 1.

(3) Gloss: JIS K 5400
When the evaluation was performed in accordance with No. 7, the results were shown in the column of “gloss” in Table 1.

(4) Cross-cut adhesion (adhesion): JIS
When evaluated according to K 5400 6.15,
The results are shown in the column of "Adhesion in grid" in Table 1.

[0027]

[Table 1]

As is clear from the results shown in Table 1, in Comparative Example 1, since the water content of the electrodeposited coating film was more than 5%, defects in the appearance of the coating film (waki) occurred on the surface of the intermediate coating film. The finish (sharpness) of the coating film appearance was also poor, and in Comparative Example 2, the content of the polar solvent was small, resulting in poor coating film appearance and poor sharpness. Had become something.

On the other hand, in Examples 1 to 4, it was confirmed that the coating film had excellent appearance, sharpness, gloss, and grid adhesion (adhesion).

[0030]

In the coating method according to the present invention, the water content of the electrodeposition coating film before the intermediate coating is reduced to 5% or less, and the coating is applied to the intermediate coating without baking and drying. Since the baking and drying are performed after the intermediate coating is performed by adding a polar solvent of 10% or more, defects in the appearance of the coating film (e.g., abrasion) caused by evaporation of water during baking and drying after the intermediate coating are performed. It is possible to prevent deterioration of the coating film appearance finish (sharpness) due to poor compatibility between the electrodeposition coating film before baking and drying and the intermediate coating material, Even when baking and drying after coating is omitted and baking and drying is performed after intermediate coating, defects in the appearance of the coating (such as abrasion) do not occur, and the finished appearance of the coating (clearness) is good, and energy is consumed. Realized volume reduction Rukoto is brought remarkably excellent effect that it is possible.

Claims (1)

(57) [Claims] 1. When coating an automobile, the water content of the electrodeposition coating film before the intermediate coating is set to 5% or less, and a polar solvent is added to the intermediate coating at 10% or more without baking and drying. A coating method characterized by performing baking and drying after performing intermediate coating.