JPH08299898A - Production of painted metal panel excellent in processability and close adhesiveness - Google Patents

Abstract

PURPOSE: To enhance corrosion resistance and boiling water resistance by performing undercoating and topcoating and setting the difference between the glass transition temps. of topcoat and undercoat films to specific temp. or higher. CONSTITUTION: A metal panel such as a steel panel or an aluminum panel is used in the production of a painted metal panel excellent in the light fastness of the coating film surface thereof used in household electric appliances or a building material and Ni is bonded to a steel panel washed, pickled and polished with an alkali resin in an amt. of 3-100mg/m<2> by electroplating or chemical plating and painting pretreatment such as chromate treatment or zinc phosphate treatment is subsequently applied thereto. Next, a polyester or an epoxy undercoat paint is applied to the metal panel and cured and dried to form an undercoat film layer. If necessary, several coating films are formed and topcoating is subsequently applied. In the case of topcoating, a polyester or an epoxy paint is used but, at this time, 'Tg (glass transition temp.) of undercoating film'-'Tg of topcoating film' is set to 20 deg.C) or higher to enhance corrosion resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a coated metal sheet having excellent light resistance on the surface of a coating film, which is used for home appliances, building materials, automobiles and the like by irradiation with light rays such as ultraviolet rays.

[0002]

2. Description of the Related Art Conventionally, painted products that have been painted after processing are precoated metal sheets (hereinafter referred to as painted metal) to meet the needs of improving the working environment, preventing pollution problems, and omitting processes with low production efficiency. The use of coated metal plates has been increasing as the conversion to plates has progressed. Since a coated metal plate must be formed and processed, it must have a high degree of workability, while it must also satisfy the performance that has been conventionally required, and its coating film design is difficult. there were. In order to satisfy these performances, as a result, the number of kinds of paints is increased, and there is a problem that the performances other than those to be improved are affected. Further, in recent years, the required level for various performances such as workability and light resistance has become extremely high, and it is the current situation that the conventional technology cannot meet this requirement.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a coated metal plate which can meet such high requirements and has improved adhesion, corrosion resistance and workability, and which has good boiling water after processing. To aim.

[0004]

In order to achieve the above-mentioned object, the method for producing a coated metal sheet of the present invention comprises the steps of "Tg of undercoat coating (glass transition temperature)"-"Tg of topcoat". By setting the difference to 20 ° C. or more, corrosion resistance and boiling water resistance are improved, and Ni is 3 to 100 mg / m ² as a pretreatment for coating.
The adhesion improves the adhesion.

[0005]

The metal plate includes, for example, a steel plate, an aluminum plate, a stainless plate, a titanium plate and a copper plate. this house,
Examples of the steel sheet, cold rolled steel sheet, hot rolled steel sheet, hot dip galvanized steel sheet, galvannealed steel sheet, galvanized steel sheet, zinc-iron alloy plating, zinc-aluminum alloy plated steel sheet, aluminized steel sheet, chrome plated steel sheet, Examples of the nickel-plated steel sheet, zinc-nickel alloy-plated steel sheet, tin-plated steel sheet and the like. Further, the metal plate can be subjected to a pretreatment if necessary. As pretreatment, washing with water, washing with hot water,
A steel plate that has been pickled, alkali degreased, ground, and polished is electroplated or chemically plated to deposit 3 to 100 mg / m ² Ni, and then pretreatment such as chromate treatment, zinc phosphate treatment, and complex oxide film treatment is performed. The conditions of the pretreatment may be appropriately selected. If the Ni plating adhesion amount is 3 mg / m ² or less, the adhesiveness is not effective, and if the Ni plating adhesion amount is 100 mg / m ² or more, the adhesion is stagnant. Is 3-100 mg /
It was set to m ² .

Then, an undercoat paint is applied on the metal plate and cured and dried to form an undercoat film layer. Although there is no particular designation as the undercoat paint, there are polyester-based, epoxy-based, urethane-based, etc.,
This is coated with a roll coater, curtain flow coater, roller curtain flow coater, electrostatic coating machine, brush, blade coater, die coater, etc. to the required film thickness, and then hot air stove, induction heating furnace, near infrared furnace An undercoat coating film layer is obtained by curing and drying with the above. In addition, the undercoat may be added with a curing catalyst and, depending on the application, a moisture resistant pigment, a rust preventive pigment, a coloring pigment, an aggregate, an antifoaming agent, a leveling agent, a coupling agent, etc., if necessary. Although the film thickness is arbitrary, it is generally about 1 to 30 μm, particularly 3 to 12 μm in the coated metal plate. When the thickness is 1 μm or less, it is difficult to secure the corrosion resistance, and when the thickness is 30 μm or more, the cost becomes high and defects such as cracks easily occur during drying. The drying conditions may be appropriately selected according to the content of the coating material and the required performance, but the maximum attainable plate temperature of 150 to 23 in a hot air stove, an induction heating stove, etc.
The conditions are generally 0 ° C. and an arrival time of 10 to 200 seconds. In the present invention, the number of coating layers formed is not limited in any way. Top coating is performed after forming several coating layers as necessary. There is no particular specification for resin type and coating method for top coating, and polyester type, epoxy type,
Urethane-based paint may be used. However, in addition to titanium oxide in the top coating, color pigments such as red iron oxide, barium sulfate, silica, cyanine blue, and moisture resistant pigments, resin beads, aluminum flakes, additives such as mica, etc. A foaming agent, a leveling agent, and the like can be added as required. The drying conditions may be appropriately selected according to the coating material, but in a hot-air heating furnace, an induction heating furnace, a near-infrared furnace, etc., the maximum attainable plate temperature is 150 to 250 ° C, and the arrival time is 10 to 10.
A condition of about 200 seconds is general. Although the film thickness is arbitrary, it is about 1 to 50 μm, especially 5 to 3 on the coated metal plate.
A dry film thickness of 0 μm is common.

[0007]

[Example] 0.6 mm hot-dip galvanized steel sheet (60 g /
After degreasing m ² ), a nickel treatment solution (PL4015 manufactured by Nippon Parkerizing Co., Ltd.) stock solution was immersed in a solution diluted to 100 g / L at 50 ° C. to deposit a predetermined amount of nickel. Then, a coating type chromate treatment (ZM1300, manufactured by Nippon Parkerizing Co., Ltd.) was applied to a steel sheet having a chromate film of 50 g / m ² and a polyester having Tg of 60 to 80 ° C.
After applying a melamine-based undercoat paint with a roll coater, a baking undercoat film was formed using an induction heating furnace at a maximum reached plate temperature of 220 ° C. and an arrival time of 45 seconds.

As the top coating, a polyester-melamine coating having a pigment (TiO ₂ ) content of 44% in PWC and a Tg of 25 ° C. is used. After coating with a roll coater, a maximum temperature of 230 ° C. is reached using an induction heating furnace. After baking for 60 seconds, a top coat film was formed.

The evaluation method was as follows. After immersing in boiling water for 3 hours, 100 cross-cuts were made with a cutter of 1 mm square and extruded by 7.5 mm.
The tape was peeled off in the direction of 45 ° C. The degree of peeling at that time was observed. Further, after the corrosion resistance after processing was bent at 20 ° C. and 0 T, salt water at 45 ° C. and 5% was sprayed for 240 hours, and rust and swelling of the processed portion were observed.

Table 1 shows the evaluation results of the above test.

As a result, no effect on the adhesiveness was observed up to a Ni deposition amount of 3 mg / m ² , but the adhesiveness was improved at 3 g / m ² or more, and coating film peeling was eliminated.

The corrosion resistance was improved by increasing the Tg of the undercoat. When Tg was 40 ° C, no effect on corrosion resistance was observed, but the corrosion resistance was improved by increasing Tg so that "Tg of undercoat film"-"Tg of topcoat film" was 20 ° C or higher.

[0013]

[Table 1]

[0014]

According to the present invention, the Tg of the undercoating film is increased so that the difference from the Tg of the topcoating film is 20 ° C. or more.
And, by applying 3 to 100 mg / m ² of Ni as a pretreatment for coating, a coated metal plate having good adhesion, corrosion resistance after processing, and boiling water can be obtained.

Claims (2)

[Claims] 1. A coated metal excellent in processability and adhesion, characterized in that two coats of undercoat and topcoat are carried out, and "Tg of topcoat coating film"-"Tg of undercoat coating film" is 20 [deg.] C. or more. Method of manufacturing a plate. 2. Ni-plating for 3 to 10 as a pretreatment for coating
The method for producing a coated metal sheet having excellent workability and adhesion according to claim 1, wherein the coated metal sheet is applied at 0 mg / m ² .