JPH0683814B2 - Painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an improvement in a coating method for forming a coating film of two or more layers on an object to be coated.

[Prior Art] 2 coat 2 that has been conventionally used for coating automobiles, etc.
In a coating method such as baking, two coats and one baking, each coating film is sequentially formed one by one using each coating material.

[Problems to be Solved by the Invention] However, in such a coating method, if adhesion between adjacent coating films is poor, peeling may occur between the coating films.

Therefore, in the past, great efforts have been made to improve paints in order to improve the adhesion between coating films.

It is an object of the present invention to provide a method for forming a coating film to be layered with improved adhesion between coating films, not by improving the coating material itself but by simply improving the coating method.

[Means for Solving the Problems] That is, according to the present invention, the first coating material is used to form a first coating material.
When the second coating film is formed on the first coating film by forming the second coating film on the first coating film, the first coating liquid is sprayed to form the first coating film.
Of the first paint and the second paint are sprayed so that the spray amount of the first paint gradually decreases and the spray amount of the second paint gradually increases correspondingly. The present invention relates to a coating method, which comprises forming a mixed coating film and then spraying a second coating material thereon to form the second coating film.

[Embodiment] Next, the method of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing an example of a coating film formed by the method of the present invention.

It is the article to be coated (1), and is usually previously subjected to electrodeposition coating or the like.

First, the coating material (1) is sprayed with the coating material A to form a coating film (2) consisting only of the coating material A. Next, while gradually decreasing the spray amount of the paint A and simultaneously gradually increasing the spray amount of the paint B, the paint A and the paint B are simultaneously sprayed to produce a mixed coating film of the paint A and the paint B ( 3)
To form. Then, the coating material B is sprayed to form a coating film (4) consisting of the coating material B alone. After that, the coating film is baked to complete the coating.

Thus, in the coating film obtained by the method of the present invention, a mixed coating film of coating material A and coating material B between coating film (2) consisting of coating material A and coating film (4) consisting of coating material B only. (3) is interposed, and in this mixed coating film (3), the proportion of paint A increases as it approaches the coating film (2), while the proportion of paint B increases as it approaches the coating film (4). Has become. With such a coating composition, the coating film (2) and the coating film (4) are almost completely different from those in the conventional method in which the type of the coating material is changed almost completely at the coating film interface between the two coating materials.
The adhesion between and is improved.

The state of the coating film (2) before forming the mixed coating film (3) and the state of the mixed coating film (3) before forming the coating film (4) may be completely cured, but the adhesiveness In order to further improve the above, a completely wet state or a semi-cured state, especially a nearly completely wet state is preferable.

The thickness of the mixed coating film (3) is not particularly limited as long as the adhesion between the coating film (2) and the coating film (4) is improved,
Usually, it is preferably in the range of 5 to 50 g / m ^{2 in} terms of coating amount after drying. If the coating amount after drying is less than 5 g / m ² , improvement in adhesiveness can hardly be expected, while if it is more than 50 g / m ^{2, the} adhesiveness is not further improved and the paint is wasted.

The paint used in the present invention is not particularly limited, solvent-based paint,
Aqueous emulsion paints, non-aqueous emulsion paints, aqueous dispersion paints, non-aqueous dispersion paints, water-soluble paints, powder paints and the like are all used. Paint A, which gives a coating film that touches each other,
It is preferable to use the same type of paint as B, but different paints may be used.

The spray coating of the paint may be performed by a usual air spray method, airless spray method, electrostatic spray method, or the like.

The coating system to which the method of the present invention is applied is not particularly limited as long as it is composed of two or more layers, and examples thereof include the following.

(1) (Substrate) + Intermediate coating + Topcoat (2) (Substrate) + Intermediate coating + Topcoat + Clear coating (3) (Substrate) + Topcoat + Clear coating film (4) (Subject to be coated) + Chipping primer coating film + Top coating film [Example] The present invention will be described below with reference to Examples.

Example A steel sheet which had been subjected to a phosphate chemical conversion treatment and which had been subjected to electrodeposition coating was used as a test piece.

Solvent-based intermediate coating (with epoxy ester resin as the main component) was spray-dried on the test piece at a spray rate of 100 g / min so that the coating rate would be 20 g / m ² , and then the intermediate coating was applied. Spray so that the amount of spray gradually decreases from 100 g / min to zero in 1 minute, and at the same time, spray the solvent-type top coating (containing melamine alkyd resin as the main component) gradually from zero to 100 g / min within the above time. Spray coating to form a mixed coating film so that the coating amount after drying becomes 10 g / m ² , and then the above-mentioned top coating composition is sprayed at 100 g / min and the coating amount after drying becomes 20 g / m ² . So spray painted.

Then, baking was performed at 140 ° C. for 25 minutes to complete the coating.

After subjecting the obtained coating test piece to an outdoor exposure test for 550 days, the adhesion between the top coating film and the intermediate coating film was examined by a cut-off test [JIS K5400 (6.15)]. The results were good.

Comparative Example Coating was performed in the same manner as in Example except that the mixed coating film was not formed, and then the adhesion of the coating film was examined. The result was a failure.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a coating film obtained by the method of the present invention. (Symbols in Drawings) (1): Object to be coated (2): Paint film of paint A (3): Mixed paint film of paint A and paint B (4): Paint film of paint B

Claims (1)

[Claims] 1. When forming a first coating film using a first coating material on an object to be coated and then forming a second coating film using the second coating material, the first coating material is sprayed. Then, the first coating film is formed and then sprayed so that the spray amount of the first paint gradually decreases and correspondingly the spray amount of the second paint gradually increases. A coating method comprising forming a mixed coating film of the second coating material and then spraying a second coating material thereon to form the second coating film.