JPS6099365A - How to paint metal plates - Google Patents

Abstract

PURPOSE:To reduce the heating and the setting time by coating a thermosetting powder paint on a metallic plate, and heating and setting the paint with an infrared gas combustion burner wherein the combustion temp. on the surface of the burner board is regulated to >=600 deg.C. CONSTITUTION:A thermosetting powder paint is coated in about 15-70mu film thickness on a metallic plate having about 1.0-1.5mm. thickness such as an iron plate and a golvanized steel plate with an electrostatic spray or a flow coater method. Then while conveying said metallic plate with a conveyor line, etc., the coated film is set by heating with an infrared gas combustion burner wherein the combustion temp. on the surface of the burner board is regulated to >=about 600 deg.C and <=900 deg.C.

Description

[Detailed Description of the Invention] Recently, in the light electrical industry, building materials industry, etc., machining of pre-painted gold M plates (Zoreccord Metal: PCM) has been used to shorten product manufacturing processes and save labor. and space saving.

Conventionally, solvent-based paints have been used for this type of painting, but solvent-based paints have the risk of fire or poisoning due to organic solvents, are more likely to cause pollution, and require two or more coats. There were drawbacks such as: Therefore, thermosetting powder coatings are attracting attention because they do not have the above-mentioned problems and have excellent PCM film performance and are highly resistant to mechanical processing such as bending, drawing, and press processing. .

However, thermosetting powder coatings generally have a long heat curing time of several minutes to several tens of minutes, which is a fatal drawback for use in PCM, and therefore they have not yet been put into widespread practical use.

The present invention was made without considering the current situation, and an object of the present invention is to provide an excellent coating method that takes advantage of the above-mentioned characteristics of thermosetting powder coatings and can be heated and cured in a few seconds to several tens of seconds. The purpose is to

For this purpose, a thermosetting powder coating is applied to a metal plate that has been subjected to surface treatment as necessary, and then a burner is applied once from a position with a distance of about /θ0% 300 mn from the surface of the metal plate. This is achieved by heating and curing using a gas infrared combustion burner with a surface combustion temperature of about 600° C. or higher.

Incidentally, gas infrared combustion burners have conventionally been widely used in heating stoves, food heaters, dryers for paper, cloth, etc. However, based on the actual situation in the coatings field, the inventors of the present invention unexpectedly found that the long heat curing time, which was considered to be a fatal drawback of thermosetting powder coatings, could be drastically shortened by the above method. This is the heading that led to the present invention.

Note that electric infrared heaters are known as similar to gas infrared combustion burners, but in the former, the combustion surface reaches a predetermined temperature within a few seconds after ignition, and the combustion surface can be touched with the hand within a few seconds after extinguishing. While the temperature drops to
The latter takes several minutes to reach the specified temperature, and even if the source is turned off, it takes several minutes for the temperature to drop to a level that can be touched by hand, so it is inconvenient if a failure occurs in the painting line and the line strands. In addition, the running cost is worse than the former, and the heating and curing time for thermosetting powder coatings with the currently known general electric infrared heaters is long (and is not suitable for PCM). isn't it.

The thermosetting powder coating used in the present invention is produced by adding additives such as crosslinking agents, pigments, anti-sagging agents, surface appearance agents, and ultraviolet absorbers to synthetic resins as required by solution blending, triblending, and melting. It is obtained by mixing by a blending method, etc., and has an average particle size of 15~/jOμ, which has been commonly used in the past.
Thermosetting powder coatings such as those based on acrylic resins, polyester resins, and polyurethane resins can be used as they are.

Examples of the gas infrared combustion burner used in the heat curing means in the present invention include IF burner (trade name manufactured by Osaka Gas and Shohei Seisakusho Co., Ltd.), Marsden Infrared
generator burner (Marsden m
Anufa-Ctur (trade name, manufactured by Ing), etc. are representative examples.

FIG. 1 is a side sectional view of a typical gas infrared combustion burner, and FIG. 2 is an example of the piping flow of a typical gas infrared combustion burner. The main parts of the gas infrared combustion burner A are a burner board 1, a mixed gas chamber 2, a mixed gas dispersion chamber,
The gas infrared combustion burner, which is composed of a cooling pipe 4, a mixed gas inlet 5, and a cooling air inlet 6, can burn natural gas, propane gas,
In this system, a mixed gas made by mixing a fuel gas such as city gas and air using a blast method or the like is sent into a mixed gas chamber 2, ignited by means such as a spark, and burned on the surface of a burner board 1.

Note that the blast method is a method in which the amount of air necessary for combustion is forcibly fed into the fuel gas using a fan to form a mixed gas.

Ceramic perforated plates, metal punched plates, etc. can also be used as the burner head, but ceramic fibers formed by overlapping ceramic fibers are particularly preferred due to their radiation efficiency, light weight, and resistance to mechanical shock and vibration. It is optimal from

The principle of coating film heating using a gas infrared combustion burner is that the fuel gas is burned, and the combustion is completed on the surface of the burner board 1.
The burner makes itself red-hot, and the heat turns into radiant energy. The thermal radiation propagates to the surroundings by wave phenomenon, and turns into heat again within the object to be coated, including the paint film. The heat destroys the paint film. It is heated and cured.

The thermal radiation is mainly infrared rays having a wavelength of about 0.7 to 20μ, and when a ceramic fiber board is used as a burner board, the amount of heat generated per unit area is about 720,000 to 20,000 Kcal/m. 'h, and it becomes possible to heat the board surface temperature to about 950°C.

Next, the metal plate coating method of the present invention will be explained.

First, the thickness of steel plates, galvanized steel plates, aluminum plates, etc. is 0.
．． /～/Jmrn After applying a surface treatment such as pre-treatment Zolimer coating as necessary, the metal plate is conveyed, for example, on a conveyor line, and a thermosetting powder coating is applied by electrostatic spraying or electrostatic electrostatic spraying. A dry film thickness of approximately 7S to 7 can be obtained by using a flow coater, static lightning, fluidized immersion, air spray, scattering, etc.
Paint so that the thickness is approximately 0μ.

Next, the continuously coated metal plate is heated and cured using a gas infrared combustion burner while being conveyed by a conveyor line or the like. At that time, the burner board surface combustion temperature of the gas infrared combustion burner is set to be about 60θ°C or higher. thxF! E.I.
If it is lower than J''-60θ°C, it is not preferable because the coating film cannot be cured in the time targeted by the present invention.The upper limit of humidity is not particularly limited, but for economic reasons, it is preferably 9θO°C or less. The preferred temperature range is 7SO~50℃
Within this range, the coating film can be cured in 5 to 30 seconds, although it varies somewhat depending on the thickness of the metal plate.

Further, the distance between the surface of the metal plate and the surface of the burner of the gas infrared combustion burner is approximately 10θ to 300 mm. If the spacing exceeds SOθ, the paint film cannot be cured in a short time unless the burner board surface combustion temperature is higher than the above range, uneven baking is likely to occur, and the equipment becomes unnecessarily large, so it is not preferable. do not have. On the other hand, if the distance is less than /θOynm, the coating film may be burnt or the reflected heat may interfere with gas infrared combustion burners such as packfires, which is not preferable.

As mentioned above, by the coating method of the present invention, in the prior art,
It has become possible to completely cure a thermosetting powder coating within several tens of seconds, which was unexpected. Therefore, the coating method of the present invention has great practical value, especially in the PCM field, and ii !+I period.

Further, the coating method of the present invention can be applied to wire mesh objects, such as electric wires,
) (It can also be applied to eaves, etc., and the metal plate referred to in the present invention of course includes such linear objects.

Hereinafter, the present invention will be further explained in detail with reference to Examples.

Example/~3 Mounted on a sword mountain, width/θOm, length 3θθ, thickness θ,!
Thermosetting polyester resin powder coating [V-PET#'1000A? Gad Green (trade name, manufactured by Dainippon Toyo Co., Ltd.)] was coated with an electrostatic sprayer to a cured film thickness of 35 μm, and then transferred to a belt conveyor using a gas infrared combustion burner [IF burner (product name, manufactured by Shoei Seisakusho Co., Ltd.)]. 8F+'/ under the conditions shown in the table to heat and cure.

Nao, gas infrared combustion burner board is thickness 300 order x 9AOnm (effective combustion 11i'i/91ytnmXg
! ; 0) ceramic fibers arranged in rows at intervals of Sθmm were used.

The obtained cured films were subjected to various performance tests with M<, and the results are shown in Table 1 below.

Comparative Example/~Example/A coated object was coated in the same manner as in Examples/- and was heated in a hot air oven (Satake type jet oven) instead of a gas infrared combustion burner.
The sample was heated and cured under the conditions shown in Table 1.

The performance test results of the obtained cured coating film are shown in the lower column of Table 1.

Comparative Examples 3-1I A workpiece coated in the same manner as in Example 1 was heated using an electric infrared heater instead of a gas infrared combustion burner [Inclusterine (trade name, manufactured by Nippon Insulator Co., Ltd.); heater effective surface It, 2
80mm x A; 30mm)! T units were lined up at intervals of 0 mm, and were heated and cured by passing them under the pressure conditions shown in Table 1.

The performance test results of the obtained cured coating film are shown in the lower column of Table 1.

Example G~6 Polyester-epoxy resin + I as thermosetting base paint
d Thread body paint [V-PET$5θ0θ Green (trade name, manufactured by Dainippon Toyo Co., Ltd.)] was applied in the same manner as in Example 1, and was applied to a gas infrared combustion burner under the conditions shown in Table 2. It was heated and cured.

The performance test results of the obtained cured coating film are shown in Table 3.

Comparison-1, 5-~B The objects to be coated were coated in the same manner as in Example Tei, and were heat-cured under the conditions shown in Table 2 using a hot air oven instead of a gas infrared burner.

The performance test results of the obtained cured coating film are shown in Table 1, bottom 1.

Comparative Examples 7 to g The coated objects coated in the same manner as in Example D were heated and cured using a vented infrared heater instead of a gas infrared combustion burner under the conditions shown in Table 2.

The performance test results of the obtained cured coating jH are shown in the lower part of Table λ.

Examples 7 to 9' Acrylic i! as a thermosetting powder coating. It was packed in the same manner as in Example 1, except that l-fat powder paint (V-PET$/J70QD7 (&Lee (trade name owned by Dainippon Toyo Co., Ltd.)) was used, and under the conditions shown in Table 3. It was cured by a% using a gas infrared S combustion burner.

The results of the performance test of the obtained cured m-film are shown in the lower column of Table 3.

Comparative Example 7~/θ Temporary smoked product refurbished in the same manner as in Example 7 was heated in a hot air stove instead of a gas infrared combustion burner under the conditions shown in Table 3.
■Heat-cured.

The performance test results of the obtained cured coating film are shown in the 3rd J! Shown below.

Comparative Example /1 ~ /, 2 A @C coating refurbished in the same manner as Example 7 was heated using a gas infrared combustion burner and a mixed heater instead of a gas infrared combustion burner.
It was heat cured under the conditions shown in the table.

The obtained performance test results for the weathered hood are shown in the lower part of Table 3.

As is clear from Tables 1 to 3, excellent coating films were obtained in short bursts (within 30 seconds) by the method of the present invention. On the other hand, Comparative Examples 1-no and S゛- by conventional hot air drying
6.9~/θ, H@ obtained by the method of the present invention
K to obtain something equivalent to j'4 requires several minutes to several tens of minutes of drying time.
It takes a long time to dry, and after drying for 75 seconds, all
It had no function as

Comparative examples 3 to 7 using conventional 4-air infrared heaters
For ~g1//~/, 2, drying for 3 minutes or more is required to obtain a proliferated membrane equivalent to that obtained by the method of the present invention; I didn't have it.

[Brief explanation of the drawing]

FIG. 1 is a IIm sectional view of a typical gas infrared combustion burner used in the present invention, and the Rumoko diagram is an example of the layout a flow of a typical gas infrared combustion burner. AI gas extra combustion burner 1: burner bood 2! Mixed gas chamber 3I Mixed gas distribution chamber 4: Cooling pipe 5N mixed gas insertion port 6: Cooling air insertion lower: Burner single-door non-flammable processing section 8I Burner single-door presser plate ll: Zero governor 12: Adjustment valve 13 = Shilast type mixer

Claims (2)

[Claims] (1) Apply a thermosetting powder coating to a metal plate that has been subjected to surface treatment as necessary, and then apply a coating of about /θ0~ from the surface of the metal plate.
It is characterized by heating and curing using a gas infrared combustion burner with a burner board surface combustion flow rate of approximately goo'c or more from a position where the 30θ tuna spacing is extended.
How to paint metal plates. (2) The above burner board is made of ceramic fiber.
The method for coating a metal plate according to claim 1, characterized in that: