JP2001096223A - Heat resistant coated metallic plate excellent in heat ray reflection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat resistant coated metallic plate having >=50% heat ray reflection in 0.5-20 μm wave length with respect to the coated metallic plate, on which a heat resistant coating film containing polyether sulfone resin and fluororesin on the surface of a metallic plate. SOLUTION: The heat resistant coating film controlled to contain 50-240 pts.wt. fluororesin per 100 pts.wt. polyether sulfone resin is formed directly on the metallic plate as a clear coating film and the coating film thickness is controlled to 0.3-3.0 μm. The surface roughness Ra of the metallic plate is desirably controlled to <=1.0 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
And a heat-resistant coated metal plate having a heat ray reflectance of 50% or more.

[0002]

2. Description of the Related Art In the case of a heating appliance such as a stove, a gas stove or an oven whose operating environment temperature is exploded to 200 ° C. or higher, a coated metal plate having a heat resistant temperature of 200 ° C. or higher has been conventionally used for manufacturing interior members. By using it and manufacturing only by machining, manufacturing cost is reduced and productivity is improved. As one type of this heat-resistant coated metal plate, there is one in which a coating film containing a polyethersulfone resin and a fluororesin is formed on the surface of the metal plate. This heat-resistant coated metal plate is made of polyethersulfone resin to increase the heat resistance of the coating film and to make the coating film non-adhesive with a fluororesin so that even if the object to be heated scatters or evaporates on the surface, it does not adhere. It was made.

On this coated metal plate, a stainless steel plate is directly coated with a polyethersulfone resin containing an inorganic pigment and a fluororesin, and is formed to a thickness of 10 to 20 μm (Japanese Patent Laid-Open No. 63-5717). A rust-preventive pigment-containing undercoat layer containing polyethersulfone resin as a main component is formed on the surface of a hot-dip Al-based alloy-coated steel sheet at 3 to 20 μm, and a color pigment containing a polyethersulfone resin and a fluororesin thereon An additive overcoat layer having a thickness of 5 to 40 μm (JP-A-5-8347, JP-A-7-213994), and a polyethersulfone resin in which a rust-proof pigment or a coloring pigment is added to the surface of a hot-dip Al-based alloy-plated steel sheet And a clear overcoat layer containing a polyethersulfone resin and a fluororesin at a thickness of 3 to 20 .mu.m. Those 20μm formed (JP-A-6-91805, JP same 10-71672 JP) and the like.

However, these coated metal plates are heated by a heating source such as a microwave oven or an oven star with a heat ray (heat energy) having a wavelength of 0.5 to 20 .mu.m radiated from an electric heating heater. When used for the inner wall of a cooking appliance,
Heat rays are absorbed by the surface of the inner wall and are not reflected by the object to be heated, so that it takes time to cook.In addition, the heat of the inner wall rises due to the absorption of the heat ray, so that heat is released to the outside through the inner wall and heat loss is large. There was a problem.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heat-resistant coated metal plate which reflects a heat ray, shortens cooking time, and prevents heat loss.

[0006]

Means for Solving the Problems The heat-resistant coated metal plate of the present invention is a coated metal plate having a heat-resistant coating film containing a polyethersulfone resin and a fluororesin formed on the surface of the metal plate. The amount of the resin is 50 to 240 parts by weight based on 100 parts by weight of the polyethersulfone resin, the heat-resistant coating is a clear coating directly formed on a metal plate, and the coating thickness is 0%. 0.3 to 3.0 μm. The surface roughness Ra of the metal plate is 1.0 μm
It is preferable to set the following.

[0007]

The present inventors have repeatedly studied to make a coated metal plate having a heat-resistant coating film containing a polyethersulfone resin and a fluorine resin formed on the surface reflect heat rays on the surface. They devised a method of forming a heat-resistant coating film as a clear coating film and forming it directly on the surface of a metal plate. That is, since the clear coating film absorbs and passes the heat rays without attenuating, if the coating film is formed directly on the surface of the metal plate,
This is because the incident heat rays reach the surface of the metal plate, are reflected there, and reach the object to be heated after passing through the coating film. In conventional coated metal sheets, pigment is added to both the undercoat layer and the overcoat layer, and even if the overcoat layer is a clear coating, the pigment is added to the undercoat layer, so that heat rays are absorbed and attenuated by the pigment. It was. Since the undercoat layer is a resin, heat rays are not reflected from the undercoat layer even if the overcoat layer is a clear coating film.

However, when the heat ray has a wavelength of 0.5 to 20 μm, it has been found that if the coating film is thick as in the prior art, absorption and attenuation of the heat ray are large, and sufficient heat ray reflectivity cannot be obtained.
The coating thickness had to be between 0.3 and 3.0 μm. Here, the reason why the thickness of the coating film is set to 0.3 to 3.0 μm is that 0.3 μm
If it is thinner, it is difficult to form a uniform coating,
If it is thicker, the reflectance of a heat ray having a wavelength of 0.5 to 20 μm becomes 5
It becomes 0% or less, and shortening of the cooking time is insufficient.

A heat-resistant coating film containing a polyethersulfone resin and a fluororesin has a heat resistance and a non-adhesive property even at a high ambient temperature of about 300 ° C. The amount of the fluorine resin is 50 to 240 parts by weight based on 100 parts by weight of the polyethersulfone resin.
If the amount is less than 50 parts by weight, the fluororesin distribution is not uniform when the coating thickness is less than 1.0 μm,
Even when the amount is more than the weight part, the non-stickiness of the coating film is saturated, and
This is because it is not different from the case of 0 parts by weight. When the heat-resistant coating film is a clear coating film, when the wet coating film is dried,
The fluororesin floats when the pigment is added,
Since the polyethersulfone resin is easy to settle, the polyethersulfone resin is concentrated on the lower side (the metal plate side) of the coating film, and the adhesion of the coating film is improved.

In the present invention, since heat rays are reflected on the surface of the metal plate, the smoother the surface of the metal plate, the higher the reflectance. For this reason, the metal plate has a surface roughness Ra of 1.0 μm.
The following smoothness is preferred. As the type of the metal plate, a stainless steel plate, a molten Al-based alloy plated steel plate (for example, a molten Al- (5 to 11%) Si
Alloy-plated steel sheet, 55% Al-Zn alloy-plated steel sheet, etc.). Heat rays are reflected regardless of whether a chemical conversion coating such as chromate treatment, phosphate treatment, or phosphate chromate treatment is formed on the metal plate surface, or a metal plating such as Cr, Ni, or Cu is applied. .

The fluororesin to be added to the polyethersulfone resin may be a known one. For example, polytetrafluoroethylene, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-perfluoroalkylvinylether copolymer, tetrafluoroethylene-perfluoroalkylvinylether copolymer, and the like. .

[0012]

EXAMPLE A 0.5 mm thick stainless steel sheet, a hot-dip Al-9% Si alloy-plated steel sheet, and a hot-dip 55% Al-Zn alloy-plated steel sheet having different surface roughnesses Ra were subjected to a coating-type chromate treatment to obtain chromium. After forming a chromate film having an adhesion amount of 30 mg / m ² , a clear paint having various ratios of a polyethersulfone resin and a fluororesin was roll-coated.
And baked and cured at a maximum temperature of 410 ° C. for 90 seconds. Then, after the temperature of the coated steel sheet reaches room temperature,
The following tests were performed. Table 1 shows the coated steel sheets, and Table 2 shows the test results.

(1) Non-adhesiveness test of coating film surface 5 ml of food such as soy sauce, sauce, lemon juice and coffee was dropped on the coating film surface, and it was placed in an oven at 260 ° C for 1 hour. After heating, cool to room temperature, first wipe off the deposit with a cloth,
Next, it was rinsed with running water. Then, the surface of the coating film was visually observed, and the degree of contamination and discoloration were evaluated according to the following criteria. Symbol Standard ◎ Easy to wipe off, no contamination or discoloration is observed after washing ○ Easy to wipe off, but no obvious contamination or discoloration is observed after washing △ Somewhat difficult to wipe off With slight staining and discoloration after washing with water × Difficult to wipe off, with clear evidence of staining and discoloration after washing with water

(2) Heat ray reflectance test ASTM C capable of measuring a wavelength in the range of 0.1 to 30 μm
The emissivity (ε) of the steel sheet was measured using an emissivity meter (manufactured by AERD S & D) based on 1371, and based on Kirchhoff's law, heat ray reflectance = 1−emissivity (ε)
-The heat ray reflectance was determined by the transmittance (T).

(3) Heat resistance test A coated steel sheet was placed in an electric oven at an ambient temperature of 300 ° C.
After being left for 00 hours, it was taken out of the electric oven and cooled to room temperature. Then, cuts at 1 mm intervals reaching the steel plate base from the coating surface of the cooled coated steel plate with a cutter are formed in a grid pattern to form 100 grids, and a tape is attached to the grid portion. A peeling taping test was performed, and the peeling state of the coating film was evaluated according to the following criteria. Symbol Criteria ○ No peeling of coating film observed at all △ Less than 5 coating films were observed in 100 crosses × 5 or more coating films were observed in 100 or more grids

[0016]

[Table 1] (Note 1) In the type of steel sheet, symbol A is stainless steel sheet, B is hot-dip Al-9% Si alloy plated steel sheet, C is hot-dip 55% Al
-Zn alloy plated steel sheet. (Note 2) PTFE is a polytetrafluoroethylene resin, PFA is a polytetrafluoroethylene-perfluoroalkylvinylether copolymer, and the ratio is 100 parts by weight of the polyethersulfone resin. It is the ratio (parts by weight) to the above.

[0017]

[Table 2]

[0018]

As described above, the surface of the metal plate is made of polyether.
In a coated metal plate on which a heat-resistant coating film containing a tersulfone resin and a fluororesin has been formed, the heat-resistant coating film is a clear coating film directly formed on the metal plate, and the coating thickness is set to 0.1. When the thickness is 3 to 3.0 μm, the heat rays reach the surface of the metal plate without being absorbed or attenuated, are reflected there, and are radiated without being absorbed or attenuated. % Or more. When the amount of the fluorine resin is 50 to 240 parts by weight based on 100 parts by weight of the polyethersulfone resin, the heat resistance and the non-adhesiveness of the coating film can be harmonized. Further, the surface roughness Ra of the metal plate is set to 1.0.
When the thickness is less than μm, the heat ray reflectance increases.

Continued on the front page F-term (reference) 4D075 AC23 BB26Z BB74X BB75X CA18 DA06 DB04 DB05 DC38 EA43 EB16 EB37 4F100 AA22 AB01A AB04 AB10 AB11 AB18 AK17B AK18 AK18J AK54 AK54J AK57B AL01 BA02 DD07AJEJB03

Claims (2)

[Claims] 1. A coated metal plate having a heat-resistant coating film containing a polyethersulfone resin and a fluororesin formed on the surface of a metal plate, wherein the amount of the fluororesin is based on 100 parts by weight of the polyethersulfone resin. 50 to 240 parts by weight, the heat-resistant coating is a clear coating directly formed on a metal plate, and the coating thickness is 0.3 to 3.0 μm.
A heat-resistant coated metal sheet with excellent heat ray reflectivity, characterized in that: 2. The heat-resistant coated metal sheet having excellent heat ray reflectivity according to claim 1, wherein the surface roughness Ra of the metal sheet is 1.0 μm or less.