JPH08299903A - Production of coated metallic sheet excellent in decorativeness - Google Patents

Abstract

PURPOSE: To produce a coated metallic sheet excellent in decorativeness with high productivity by conducting powder coating without baking the undercoat. CONSTITUTION: A plating film or an org. coating film is formed on the surface of a metallic sheet such as steel sheet to be used for an electrical product, etc., to impart rust preventing property, electrical insulating property, decorativeness, etc., to the sheet. In this case, the sheet is powder-coated without baking the underoat to produce a coated metallic sheet excellent in decorativeness. For example, non-contact powder coating is applied on a steel sheet, and a necessary layer is formed on an undercoat layer without baking the undercoat and then baked. When >=2 laminated coating film layers are formed, the number of layers can be increased with only one powder coating, and the cost is lowered. Further, the coating appearance is not adversely affected because of the non-contact coating.

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 plate which is used in home appliances, building materials, automobiles and the like and has excellent design.

[0002]

2. Description of the Related Art In metal plates such as steel plates, aluminum plates, and copper plates used for electric products, building materials, automobile parts, etc.,
Conventionally, an organic film has been formed by plating or painting on the surface for the purpose of imparting rust prevention, electrical insulation, designability, etc. Along with this, many properties are required for this metal plate, and designability more than ever before is required. Similarly for resin plates, there is an increasing demand for designability, and in order to meet this demand, various organic films are often formed on metal plates, resin plates and the like.

[0003]

Conventionally, coated products that have been painted after processing are pre-coated metal plates (for the needs of improving the working environment, preventing pollution problems, omitting processes with low production efficiency, etc.). Since then, the use of coated metal sheets has been increasing as the conversion to coated metal sheets has progressed. As a coating device, a roll coater system in which a plurality of rolls are combined is often adopted. As a general roll coater, there is a three roll coater system. Conventionally,
After applying the coating on the metal plate, the coating is applied by hot air baking furnace, induction heating, irradiation with energy rays such as electron beam or near-infrared furnace to achieve the function of the coating, or a combination of these. It is dried and cured. Usually, when two or more coating films are formed on a precoated metal plate, after coating the first coating film, the coating film is dried and cured, and then the next coating film is coated and dried and cured. In this way, it is necessary to repeat coating application and drying and curing multiple times, which reduces productivity and
The production cost was increasing. In particular, in order to bring out the design, it is often necessary to laminate coating films of more than two layers,
Therefore, in a normal 2-coat 2-bake production line, the line is passed twice to improve the design, resulting in a significant cost increase. In addition, problems such as the occurrence of defects due to passing the line several times occur.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a coated metal plate having high productivity and excellent design.

[0005]

In order to achieve the above-mentioned object, in the present invention, by using non-contact powder coating on a steel sheet, it is necessary to apply it on the undercoat layer without passing through the baking process after undercoat coating. When making multiple layers of coating by baking different layers and baking, it is possible to increase the number of layers by passing the plate once for the number of powder coatings. The production cost can be reduced as compared with a production line that requires a post-painting baking process. In addition, since it is non-contact, there is no adverse effect on the coating appearance due to the surface condition of the roll, and since it is not necessary to pass through the plate multiple times in order to achieve designability, defects such as scratches on the coated surface during line passing can occur. It can be suppressed.

[0006]

In the present invention, a coated metal plate having a design property can be efficiently manufactured at a low cost by using one set of dry baking apparatus.

Examples of the metal plate include a steel plate, an aluminum plate, a stainless plate, a titanium plate and a copper plate. Of these, examples of steel sheets include cold-rolled steel sheets, hot-rolled steel sheets, hot-dip galvanized steel sheets, galvannealed steel sheets, electrogalvanized steel sheets, zinc-iron alloy plated steel sheets, zinc-aluminum alloy plated steel sheets, aluminized steel sheets. , Chromium-plated steel sheet, 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 the pretreatment, prepainting treatment such as water washing, hot water washing, pickling, alkaline degreasing, grinding, polishing, chromate treatment, zinc phosphate treatment, and complex oxide film treatment is performed. The conditions of the pretreatment may be appropriately selected.

Next, an undercoat paint is applied on the metal plate.
The undercoat paint is not particularly specified, but for example, there are polyester-based, epoxy-based, urethane-based, etc., which are applied to obtain a film thickness required for powder coating. Further, the undercoating may be added with a curing catalyst and, if necessary, a moisture resistant pigment, a rust preventive pigment, a coloring pigment, an aggregate, an antifoaming agent, a leveling agent, a coupling agent and the like. In addition to titanium oxide, in addition to titanium oxide, coloring pigments such as red iron oxide, barium sulfate, silica, cyanine blue and moisture-resistant pigments, resin beads, aluminum flakes, mica and other additives are included in the undercoat paint to emphasize the design of the undercoat. You may let me. The film thickness is arbitrary. In the present invention, the number of coating layers formed is not limited in any way, and top coating is performed after forming several coating layers as necessary. Regarding the top coating, there is no particular specification for the resin type and coating method, and polyester-based, epoxy-based, or urethane-based coating may be used. However, in addition to titanium oxide in the topcoat paint, coloring pigments such as rouge, barium sulfate, silica, cyanine blue and moisture-resistant pigments, resin beads, aluminum flakes, additives such as mica, and defoaming to improve paintability. If desired, additives such as agents and leveling agents can be included. In addition, a transparent clear layer may be applied in order to provide the design of the undercoat. The drying conditions may be appropriately selected according to the coating material, but in a hot-air heating furnace, induction heating furnace, near-infrared furnace, etc., the maximum reaching plate temperature is 150 to 250 ° C, and the reaching time is generally about 10 to 200 seconds. Target. The film thickness is arbitrary.

[0009]

[Example] 0.6 mm hot-dip galvanized steel sheet (60 g /
m ² ) after degreasing, coating chromate treatment (ZM1300, manufactured by Nippon Parkerizing Co., Ltd.) was applied to a steel plate with a chromate film of 50 g / m ² coated with a polyester-melamine base coat by a roll coater and then top coat. Is a polyester-melamine paint containing 44% of pigment (TiO ₂ ) in PWC. After electrostatic powder coating, a polyester-melamine paint containing 20% of a pearl pigment in order, and a polyester-melamine paint containing no pigment After applying the electrostatic powder coating to each clear layer, bake it using an induction heating furnace at a maximum reaching plate temperature of 230 ° C and an arrival time of 60 seconds,
A coating film was formed.

As a comparative product, a coating film having the same structure as described above is used by using a line having two roll coaters and two baking ovens, and after each coating material is dried and cured, the line is passed twice. The material manufactured in 1. was used.

In comparison of the performances of the comparative product and the product of the present invention, the hardness of the coating film was determined by pencil hardness so that it would not be damaged and would not break. Further, the workability was a 2T bending test at 20 ° C, and the corrosion resistance was a salt spray test in which a crosscut was put in the sample for 120 hours, and then the rust and swelling of the flat surface portion and the crosscut portion were observed.

The productivity index targets the time required to produce a coated steel sheet and is compared with the conventional example as 100.
The appearance was visually observed, the gloss was measured at 60 ° gloss, and the sharpness was measured by a PGD meter. Coating adhesion is 1 with a cutter knife
A square grid of mm mm was put in, extruded by 7.5 mm with Erichsen, and then the tape was peeled off to examine.

The product of the present invention is superior in adhesiveness of the coating film to the comparative product.
The workability, surface hardness and corrosion resistance are comparable, and the gloss is high.
The image clarity was remarkably excellent, and the appearance was beautiful with no surface pattern on the roll. The appearance of the comparison product is a pattern with rolls,
There are scratches in the coating film caused by passing through the line twice, which impairs the appearance. In addition, the productivity was also significantly improved compared to the conventional two-line production line.

[0014]

[Table 1]

[0015]

As described above, according to the present invention, 1
Using a set of drying and curing furnace equipment, one roll coater, and three powder coating equipment, it has a better appearance than the comparative product and is comparable to other workability, corrosion resistance, adhesion, etc. It was possible to produce unpainted metal sheets with high productivity.

Claims (1)

[Claims] 1. A method for producing a coated metal sheet having an excellent design property, which comprises coating using powder coating without baking after the undercoat coating.