JPH0221495B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paint suitable for coating the heat collecting surface of a solar collector, and in particular, by applying it to the heat collecting substrate surface, it imparts excellent selective absorption to the heat collecting surface. Regarding the paint to be applied.

In order to improve the heat collection efficiency, the heat collection surface for a solar heat collector must have a high absorption rate for sunlight and a low heat emissivity at the operating temperature of the collector. Such a heat collecting surface is called a selective absorption surface, and various types have been proposed in the past. One example is a selective absorption surface formed by coating a substrate with paint. This selective absorption surface is obtained by applying a coating for the heat collecting surface of the solar collector, which is made of pigment, binder, solvent (diluent), etc., to the substrate surface and solidifying it. That is, this film has a structure in which pigment particles are dispersed in a binder, and pigments such as ternary oxides of iron, copper, and manganese absorb sunlight well and absorb infrared rays (3 to 30 Micronmeter)
In addition, if you use a binder that transmits infrared rays well as described above, the solar absorption rate of the heat collecting surface will be high, and its thermal emissivity is determined by that of the substrate surface, so if you use a metal plate such as stainless steel, Thermal emissivity becomes small.

Conventionally, the above-mentioned selective absorption surface has been prepared by applying ternary oxides of iron, copper, and manganese as pigments, silicone resin as a binder, etc. on the surface of a substrate such as stainless steel.
A paint consisting of at least one of polyester, fluororesin, silicone-modified polymethyl methacrylate, etc., and xylene as a solvent is sprayed and dried to form a film several micrometers thick. Obtained by baking at approximately 200℃. However, since a binder with relatively poor infrared transmittance as described above was used, conventional paints could not provide a heat collecting surface with low thermal emissivity, and the selective absorbing surface coated with it was not able to obtain a heat collecting surface with low thermal emissivity. The absorption properties were not fully satisfactory. In particular, as the film becomes thicker, the selective absorption properties drop sharply, so the thickness of the film needs to be 1 micron or more and 5 micrometers or less. That is, when the film thickness is 5 microns, the solar absorption rate is 0.90 and the thermal emissivity is 0.55, and when the film thickness is 10 microns, the solar absorption rate is
0.92, thermal emissivity is 0.80, and there is no selective absorption for coatings with a thickness of 10 micrometers or more.

This invention was made in order to eliminate the drawbacks of the conventional products as mentioned above.
Copper-manganese ternary oxide lead oxide, vanadium oxide,
One of tantalum oxide and niobium oxide and their composite oxide, titanium carbide, silicon carbide, tantalum carbide, niobium carbide, tungsten carbide, hafnium carbide and lanthanum carbide, and their composite carbide, nickel sulfide, sulfide Chromium, cobalt sulfide, one kind of lead sulfide and mercury sulfide, one kind of yttrium boride and samarium boride, hafnium nitride, niobium silicide, nickel phosphide, at least one pigment among these, and this pigment. By using polystyrene, which is a binder, and at least one solvent selected from triene, xylene, and isophorone, which disperses the pigment and dissolves the polystyrene, the absorption rate is as good as that of the conventional method. The object of the present invention is to provide a coating material for the heat collecting surface of a solar heat collector that has a low emissivity.

The polystyrene used in this invention has a large light transmittance in the infrared region (3 to 30 micrometers), which is related to thermal emissivity.

The pigment used in this invention preferably has a high solar absorption rate of 0.8 or more, and a high infrared transmittance or infrared reflectance (in the range of 3 to 30 micrometers) of 0.5 or more. No effect will be obtained below each value. Pigments that meet these requirements include triiron tetroxide, iron-copper-manganese ternary oxide, lead oxide, vanadium oxide, tantalum oxide, and niobium oxide, as well as their composite oxides, titanium carbide, silicon carbide, and tantalum carbide. , niobium carbide,
Tungsten carbide, hafnium carbide, lanthanum carbide, and composite carbides thereof, nickel sulfide, chromium sulfide, cobalt sulfide, lead sulfide and mercury sulfide, yttrium boride and samarium boride, nitride Hafnium, niobium silicide, nickel phosphide, and at least one of these.

Further, the solvent used in one embodiment of the present invention is at least one of xylene, toluene, and isophorone, which dissolves polystyrene and disperses pigment powder well.

EXAMPLES The present invention will be explained in detail with reference to Examples below, but the present invention is not limited thereto.

Example 1 50 g of triiron tetroxide powder with an average particle size of 0.5 micrometers was added to a solution prepared by dissolving 100 g of polystyrene in 1000 g of toluene, and after performing ball mill mixing in a porcelain container for about 2 hours, this mixture was mixed. Pass the liquid through a 325 mesh stainless wire mesh,
This liquid was used as a paint.

This paint was applied to the surface of a cleaned stainless steel substrate using a conventional spray method. In this case, heating the stainless steel substrate was advantageous because the paint adhering to the substrate did not drip off. After spraying, heat treatment was performed at 150° C. for about 1 hour in a dryer to form a selective absorption surface.

The solar absorption rate and thermal emissivity of this selected absorption surface are determined by measuring the hemispherical spectral reflectance in the wavelength range of 0.3 to 25 microns, and converting the measured values into solar spectral radiant intensity and blackbody spectral radiant intensity (60℃). Calculated using the usual method of weighting. When the coating thickness of the paint was 5 micrometers, the solar absorption rate was 0.90 and the thermal emissivity (60°C) was 0.25, and when the coating thickness was 10 micrometers, the solar absorption rate was 0.92 and the thermal emissivity was 0.60.

Example 2 A paint was prepared using the following materials in the same manner as in Example 1, and a selective absorption surface was formed on a stainless steel substrate.

Binder: Polystyrene 100g Solvent: Xylene 1000g Pigment: Iron with an average particle size of 0.5 microns,
Copper and manganese ternary oxide powder 50g This selective absorption surface has a solar absorption rate of 0.90 and a thermal emissivity of 0.25 when the paint film thickness is 5 microns, and when the paint film is 10 microns thick, it absorbs sunlight The thermal emissivity was 0.92 and the thermal emissivity was 0.50.

Example 3 A paint was prepared using the following materials in the same manner as in Example 1, and a selective absorption surface was formed on a stainless steel substrate.

Binder: 100 g of polystyrene Solvent: 1000 g of xylene Pigment: 50 g of titanium carbide with an average particle size of 1 μm This selected absorption surface has a solar absorption rate of 0.90 and a thermal emissivity of 0.40 when the paint film thickness is 5 μm.
It was hot.

Example 4 A paint was prepared using the following materials in the same manner as in Example 1, and a selective absorption surface was formed on a stainless steel substrate.

Binder: 100 g of polystyrene Solvent: 1000 g of toluene Pigment: 40 g of copper sulfide with an average particle size of 2 microns This selected absorption surface has a solar absorption rate of 0.92 and a thermal emissivity when the film thickness of the coating composition is 5 microns.
It was 0.25.

Example 5 A paint was prepared using the following materials in the same manner as in Example 1, and a selective absorption surface was formed on the aluminum substrate surface.

Binder: 100g of polystyrene Solvent: 1000g of toluene Pigment: 30g of zirconium diboride with an average particle size of 2 microns This selected absorption surface has a solar absorption rate of 0.90 and a thermal emissivity when the paint film thickness is 10 microns. 0.55
It was hot.

Example 6 A paint was prepared using the following materials in the same manner as in Example 1, and a selective absorption surface was formed on the copper substrate surface.

Binder: 100 g of polystyrene Solvent: 1000 g of toluene Pigment: 30 g of silicon powder with an average particle size of 1 micron meter This selected absorption surface has a solar absorption rate of 0.89 and a thermal emissivity of 0.40 when the paint film thickness is 10 μm.
It was hot.

Example 7 A paint was prepared using the following materials in the same manner as in Example 1, and a selective absorption surface was formed on a galvanized iron plate surface.

Binder: 100 g of polystyrene Solvent: A mixture of 900 g of toluene and 100 g of isophorone Pigment: 20 g of carbon black with an average particle size of 0.02 microns This selective absorption surface has a solar absorption rate of 0.92 and a heat absorption rate of 0.92 when the paint film thickness is 10 microns. The emissivity was 0.55.

As is clear from the above examples, the selective absorption surface formed on a metal substrate using the paint of one example of the present invention has a good solar absorption rate and a small amount of heat even if the film becomes thick. It has emissivity. That is, a 10 micron thick film formed on a stainless steel substrate using a conventional paint consisting of ternary oxide powders of iron, copper, and manganese as pigments and modified methyl methacrylate as a binder has a solar absorption rate of 0.92, While the thermal emissivity was 0.80, a 10 micrometer thick film formed on a stainless steel substrate using the paint of this invention made of the same pigment and polystyrene had a solar absorption rate of 0.80.
0.92 and thermal emissivity of 0.50, and the film formed using the paint of one embodiment of the present invention has extremely excellent selective absorption even in thick films.

As explained above, this invention utilizes triiron tetroxide,
One of iron-copper-manganese ternary oxides, lead oxide, vanadium oxide, tantalum oxide, and niobium oxide, and their composite oxides, titanium carbide, silicon carbide, tantalum carbide, niobium carbide, tungsten carbide, hafnium carbide, and carbide. A type of lanthanum and a composite carbide thereof, nickel sulfide, chromium sulfide, cobalt sulfide, lead sulfide and mercury sulfide, yttrium boride and samarium boride, hafnium nitride, niobium silicide, phosphide Nickel, comprising at least one of these pigments, polystyrene as a binder for the pigment, and at least one of triene, xylene and isophorone for dispersing the pigment and dissolving the polystyrene. By using this method, it was possible to obtain a coating for the heat collecting surface of a solar heat collector, which had absorption coefficients as good as conventional ones and a small emissivity.

Therefore, by using the paint of this invention, it is possible to obtain excellent selective absorption properties that are less affected by the thickness of the applied film.For example, the application work becomes extremely easy, and the manufacturing cost of the heat collecting surface can be reduced. This is a significant reduction in

Claims (1)

[Claims] 1 Triiron tetroxide, iron-copper-manganese ternary oxide lead oxide, vanadium oxide, tantalum oxide and niobium oxide, and composite oxides thereof,
Titanium carbide, silicon carbide, tantalum carbide, niobium carbide, tungsten carbide, hafnium carbide and lanthanum carbide, and composite carbides thereof, nickel sulfide, chromium sulfide, cobalt sulfide, lead sulfide and mercury sulfide, borium One of yttrium oxide and samarium boride, hafnium nitride, niobium silicide, nickel phosphide, at least one pigment among these, polystyrene as a binder for this pigment, and the above pigment are dispersed, and the above polystyrene is dissolved. A paint for a heat collecting surface of a solar collector, comprising at least one of triene, xylene and isophorone dissolved therein.