JPH0450071B2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention is achieved by repeating the process of spraying a solvent-based paint on both sides of a sheet-like thin plate and the process of curing the paint film using a far-infrared radiator multiple times. The present invention relates to a method for producing high-quality double-sided precoated thin sheets for use in home appliances, which could not be obtained by coating using conventional roll coaters or curtain flow coaters and using a circulating hot air furnace.

BACKGROUND TECHNOLOGY In the painting of home appliances, pre-coated thin sheets are being introduced in place of conventional post-coating from the viewpoints of energy saving, space saving, pollution control, and cost reduction.

Conventional methods for producing pre-coated thin plates include coating with a roll coater or flow coater, and baking and hardening the coated film using a hot air circulation furnace. [“Current status of paints for home appliances” (Rust Prevention Management 11 (’821), “Future Painting for Home Appliances” (Practical Surface Technology 10 (’801), etc.) Problems that the invention seeks to solve However, the problems that the invention attempts to solve When producing a pre-coated thin plate using a roll coater method, if it is a coiled thin plate, a reverse roll coater method can be used to produce a pre-coated thin plate with a beautiful surface condition, but when it comes to sheet-shaped thin plates (so-called cut plates), , only a natural roll coater can be applied, and roll marks remain on the surface of the coating film, resulting in poor appearance quality.Moreover, if you try to paint both sides, the paint will bleed to the back side, and if both sides are painted in different colors, the appearance will be unsightly. .

On the other hand, in the case of a curtain flow coater, a pre-coated thin plate with a beautiful appearance can be obtained even when the plate is cut, but if the plate is warped, the paint tends to sag and defects such as underarms are likely to occur. The edges are particularly prone to wrinkles, so it is necessary to cut off the four corners after painting with a cutting board.

In either method, if you try to manufacture a double-sided pre-coated sheet, there is a problem that the back side is easily scratched by the conveyor, and in addition, the surface coated first becomes overbaked under hot air atmosphere conditions, reducing workability. At the same time, there was a problem that the color also changed. For this reason, although double-sided precoated thin plates were available in the industry, the back side was usually provided as a service coat without guaranteeing scratches, color, or processing quality.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has provided a thin sheet-like plate that is arranged horizontally, a solvent-based paint is sprayed onto the thin plate, and then the paint film is cured using a far-infrared radiant heating element. The present invention provides a method for producing a double-sided precoated thin plate by repeating the step of forming a double-sided precoated thin plate multiple times on both sides of the sheet-like thin plate.

Effect The present inventor has discovered an effective method for producing a double-sided precoated thin plate for application to home appliances such as single-layered microwave oven containers. This method has extremely important practical significance in terms of the industrial manufacturing method of pre-coated thin sheets.

Examples of thin sheets to be used here include iron sheets such as untreated bare steel sheets, galvanized steel sheets, and zinc phosphate-treated steel sheets, and thin aluminum sheets.

As pre-coat paints, epoxy paints, polyester paints, acrylic paints, vinyl paints, etc. have been conventionally used, and any of them can be applied. By spraying paint dissolved in a solvent onto horizontally arranged thin sheets, a painted surface with an extremely beautiful appearance can be obtained. Since the coating is cured by heating using a far-infrared radiant heating element rather than a hot air drying furnace, a temperature difference occurs between the front side and the back side of the coating film due to the directionality of the light. This temperature difference is important when painting the back side after one side has already been painted. In particular, when compared to a hot air circulation furnace, in addition to overbaking the previously painted surface, the coating film softens and
Although it is easily damaged, since a far-infrared radiant heating element is used, a temperature difference is generated between the front and back surfaces, which prevents overbaking, which is advantageous in dealing with the problem of scratches.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

FIG. 1 is a conceptual diagram of the present invention. In FIG. 1, 1 is a spray paint machine that sprays a solvent-based paint downward. 2 is a far-infrared radiant heating body. This far-infrared radiant heating element heats the sheet-like thin plate 3 onto which paint is sprayed from above. Both air and airless spray paint machines are applicable. When moving the sheet-like thin plate horizontally, a plurality of spray paint machines may be arranged side by side, or the spray paint machines themselves may be moved in the form of a rem locator. After allowing a setting time of 1 to 5 minutes with a wet coating film formed,
The coating film is completely cured using a far-infrared radiant heating element. As the far-infrared radiation heating body, it is preferable to use a heat-resistant metal base material such as stainless steel or a ceramic base material such as alumina coated with far-infrared paint. As the heating energy source, electricity, gas, and oil can all be used.

An electrogalvanized steel plate with dimensions of 100 mm x 100 mm x 0.5 mm was used for testing. The paints used were V-nit #180 primer and #6100 top coat paint manufactured by Dainippon Toyo Co., Ltd.

200mm x 200mm x 0.8mm as a far infrared heating element
A far-infrared radiant paint containing zirconium oxide, aluminum oxide, and titania was applied to a stainless steel plate with a film thickness of approximately 20 μm using polybororeloxane resin as a binder, and then heated at 600℃ for 30 minutes.
The separately fired product was used as a heat radiating plate, a sheathed heater was attached to the back side to form a planar radiator, a thermocouple was attached to the surface to control the temperature, and this was placed on the ceiling with a size of 20cm x 20cm x 20cm. A furnace was constructed.

For safety, air was taken in and exhausted from the furnace at an air flow rate of 2/min.

Attach thermocouples to the front and back sides of the test piece so that the surface temperature of the electrogalvanized steel sheet can be measured on both sides, and apply V-nit #180 primer to 7 μm and #6100 top coat to 12 μm wet-on-wet. , the surface temperature of the far-infrared radiator is 500℃, and the distance between the test piece and the far-infrared radiator is 12
When heated as cm, the coating surface became 245 mm in about 90 seconds.
It became ℃. At this time, the temperature on the back side was 183°C. The paint film is completely cured. Next, when the same process was carried out on the back side, the temperature of the coated side reached 243°C in about 80 seconds, and the temperature of the side coated before the back side was 178°C.

Next, when the temperature of the far-infrared heating element was set to 700°C and a similar test was conducted, both the front and back sides were completely cured in about 35 to 40 seconds. In this case as well, the temperature difference between the heated surface and the back surface was approximately 60°C.

Effects of the Invention As described above, the present invention uses a far-infrared radiant heating element to spray a solvent-based paint onto a horizontally arranged sheet-like thin plate, and then heat and harden it. Not only can a thin plate be obtained, but it can be cured in an extremely short time. Therefore, it is possible to manufacture the precoated thin plate in a small space and also to save energy.

The color change is simple because it is a spray method, and it can be applied to boards of various sizes, and it is extremely effective in practical terms, as it is excellent in adapting to the production of various types.

[Brief explanation of drawings]

The figure is a sectional view of a method for manufacturing a double-sided precoated thin plate according to an embodiment of the present invention. 1... Spray paint machine, 2... Far-infrared radiant heating element, 3... Sheet-like thin plate.

Claims (1)

[Claims] 1. A method for producing a double-sided precoated thin plate in which the process of arranging a sheet-like thin plate horizontally, spraying a solvent-based paint thereon, and then curing the coating film with a far-infrared radiant heating element is repeated multiple times on both sides of the sheet-like steel plate. .