JPS60213743A - Infrared ray radiator - Google Patents

Abstract

PURPOSE:To obtain an infrared ray radiator whose infrared ray emissivity has been improved by preventing full reflection of the surface, by applying a surface coat of a thin film to an infrared ray radiation surface containing more than 50pts.wt. titanium dioxide. CONSTITUTION:A coat consisting of one or more oxides selected out of either silicon dioxide or aluminum oxide and a cured material of polyborosiloxane resin is provided on an infrared ray radiation surface containing more than 50pts.wt. titanium dioxide. As scattered light works effectively due to a matter that the inside of this film 4 contains gaps produced through a matter that the polyborosiloxane resin has been decomposed thermally, radiation is improved. In other words, when the radiation surface is one containing more than the 50pts.wt. tiatnium dioxide, although positive reflection of the surface becomes even 20-25%, emissivity within a far infrared ray sphere becomes 75-80%, as the positive reflection of the surface is made to deteriorate by the surface film 4, the emissivity of the sphere is improved by 15-20%.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applied to the field of infrared heating in which radiant heating is performed for heating, cooking, etc. In order to form a highly efficient infrared radiator, in particular, 50 parts by weight or more of titanium dioxide is used. Conventional infrared radiators include alumina, zirconia,
It is known that oxides or compounds such as titania are directly coated on a base material by thermal spraying, or that they are dispersed in a binder such as glass frit to form a hollow coating.

Regarding infrared radiation performance, in the case of a radiator whose main component is titanium dioxide, there is a problem that total reflection at the surface becomes large because titanium dioxide has a high refractive index. The basic properties of an infrared radiating material include refractive index and overall absorption coefficient. This is because the light scattering phenomenon of the constituent materials is fundamentally related to the radiation characteristics of an infrared radiator, and the refractive index is more important than the inherent absorption coefficient. Comparing the refractive indexes of three typical materials used as conventional infrared radiators: alumina, zirconia, and titania, alumina has an approximate refractive index of 1.6. Zirconia is 2.2. Titania is 2.8, and titania-based materials are advantageous.

Regarding the internal properties of the radiator, titania-based materials are advantageous, but total reflection on the surface due to their high refractive index poses a problem.

Total surface reflection causes a decrease in infrared emissivity. In particular, the infrared emissivity decreases in the far infrared region of 5 μm or more, reaching an emissivity of about 0.75 at most. As a method for preventing total reflection on a surface, there is a method of forming irregularities on the surface. When forming a porous radiator, total reflection on the surface is prevented, but the radiator itself is brittle, which poses a problem. On the other hand,
If the radiator is dense, total reflection on the surface becomes a problem and high radiation cannot be obtained.

Purpose of the Invention The present invention aims to eliminate the drawbacks of the conventional art, and includes applying a thin film surface coating to an infrared radiation surface containing 50 parts by weight or more of titanium dioxide, thereby preventing total reflection on the surface and increasing the infrared radiation rate. It provides an enhanced infrared radiator. More specifically, the first purpose is to have a wide range of application to radiators, such as enamel surfaces, ceramic surfaces, plasma sprayed surfaces,
It can be applied to various base materials such as painted surfaces, and the second
The purpose is to have high heat resistance, red-hot state, approximately 1000
The third purpose is that it can be easily processed and has excellent productivity.

Structure of the Invention In order to achieve this object, the present invention provides a coating made of a cured product of one or more oxides selected from silicon dioxide or aluminum oxide and a polyborosiloxane resin, which contains 50 parts by weight or more of titanium dioxide. It is formed on an infrared radiation surface.

Polyborosiloxane resins are, for example, The main component is a polymer with the following structure.

This polymer has properties similar to those of a semi-inorganic polymer, and at room temperature exhibits the properties of an organic polymer based on phenyl groups, etc., and is excellent in terms of operation when making into a paint.

When heated, the organic components decompose to form SL, C, and B.

Ceramicize using 0 as a skeleton. Complete ceramification takes place at 600°C.

A coating is obtained by applying and baking a paint obtained by dispersing a polyborosiloxane resin as a binder and a solvent together with one or more oxides selected from silicon dioxide or aluminum oxide.

Since this coating has a low refractive index of around 1.5, it effectively prevents total reflection on the surface. Furthermore, since titanium oxide itself has relatively good radiation properties, it does not impair the high radiation properties of titanium oxide.

Description of Examples The surface coating of the present invention will be explained using conceptual diagrams. 1st
The figure shows a conventional radiator without surface treatment, and FIG. 2 shows a radiator that has been subjected to the surface treatment of the present invention. Figures 1 and 2
In the figure, 1 is a base material made of metal, ceramic, etc. 2 is an infrared radiator containing 50 parts by weight or more of titanium dioxide, 3 is air, and 4 is the surface treatment film of the present invention, selected from a binder whose main component is polyborosiloxane resin 5, and silicon dioxide or aluminum oxide. I did 1
It consists of more than one species of oxide 6.

The case is shown in which the base material side (B side) is heated and the air side (C side) is subjected to radiant heating.

The radiation properties of this type of coating are approximately 10 μm near the surface layer of the coating.
It depends mostly on the properties up to a depth of m.

In the case of the conventional example shown in FIG. 1, the refractive index of the layer of titanium dioxide compound 2 is as high as 2.5 to 2.9, and at the interface between it and air (with a refractive index of 1), the layer has a refractive index of 1.5 to 2.9. Since there is a difference of about 1.9, it is totally reflected on the surface and is not emitted as radiation to the air side, whereas in the case of the present invention shown in FIG.
Since the difference between the refractive index of layer 4 and air (about 1.5) is small at 1 to 1.4, and the difference in the refractive index between layer 4 and air is also small at about 0.5, total reflection is prevented. Ru.

In addition, this film contains voids generated by thermal decomposition of the polyborosiloxane resin, so light scattering works effectively and radiation is increased by forming the film. The emissivity of the base material does not decrease.The plasma absorption wavelength of titanium dioxide is around 5 μm, and the complex refractive index has an imaginary part and an absorption coefficient above 5 μm. Therefore, in the far infrared region of 5 μm or more, the radiation characteristics of titanium dioxide compounds are dominated only by specular reflection characteristics.

In the case of a radiating surface containing 50 parts by weight or more of titanium dioxide, the specular reflection (total reflection) of the surface is as high as 20 to 25%, and is 5 μm.
The emissivity in the above far-infrared region is 75 to 80% at most. The surface coating of the present invention is intended to reduce specular reflection on the surface, and improves the emissivity in the far infrared region of 5 μm or more by 15 to 20%.

The particle size of silicon dioxide and aluminum oxide is 0.1 to 1
A range of μm is preferable. This is mainly based on convenience in handling as a powder.

The best blending ratio of one or more oxides selected from silicon dioxide or aluminum oxide to the cured polyborosiloxane resin is in the range of 173 to 2/1 in terms of weight ratio. If it is less than 1/3, the light scattering effect will be insufficient, and if it is more than 271, the paint will exhibit chicken properties.
This is because it is difficult to handle as a paint because it forms a thin film.

Regarding the thickness of the surface coating, a thickness of about 0.1 .mu.m is sufficient for the effect, but it is impossible from the viewpoint of coating with paint, and the best is around 1 .mu.m, and preferably 2 .mu.m or less. This is because if the film thickness is 2 μm or more, it will affect the radiation characteristics in the near-infrared region of 5 μm or less.

Examples will be described below.

As an organosilicon polymer whose main component is polyborosiloxane resin, the inorganic polymer [sMP-
324 was used. This binder becomes ceramic and stabilized at 600° C., but due to thermal decomposition during that time, 20% of the initial weight is lost and the residue becomes 1/3. The following coating material was prepared using 100 parts by weight of the binder.

■ Contains 25 parts by weight of 5i02 (0.1 μm particle size) @
At'203 (0.3μm 〃 ) 40 〃@5i
02 (above = 10 parts by weight), Aj? 203 (above: 10
(parts by weight) The solvent used was 100 parts by weight of toluene/N-methylpyrrolidone-171 (weight ratio).
The test was carried out over a period of 10 hours* using

A polyborosiloxane resin coating containing 75 parts by weight of titanium dioxide was applied onto a stainless steel (SUS430) base material to a thickness of about 20 am, and heated at 150°C for 30 minutes, at 250°C for 30 minutes, and at 650°C.

The spectral radiation characteristics of the coating obtained by sequential firing for 5 minutes are shown in Figure 3a.

The spectral radiation characteristics shown in Figure 3 are based on the surface temperature of the radiator sample at 50°C.
The temperature was set at 0° C., and the ratio to the black body furnace was evaluated, and a spectroscopic radiator manufactured by JASCO ■ was used.

The paint is applied onto a coating containing titanium dioxide for about 15 minutes.
Coating with a film thickness of μm and baking (300°C).

The results of the evaluation of the coating obtained at 650° C. for 30 minutes and 5 minutes at 650° C. are shown in FIG. b was the best in the case of the paint (2), but both (2) and (2) were only about 5% lower than b, and contributed well to the increase in far-infrared radiation. Here, a borosiloxane resin was used as the base. Although an example of application to a titanium dioxide base material has been described, since it is only applied by spraying, in the case of ceramics, it can be applied to many base material systems such as plasma spraying and enamel.

Effects of the Invention As described above, the infrared radiator of the present invention has the following effects.

(1) When applied to a system containing 50% or more of titanium oxide, the far-infrared emissivity of 5 μm or more is improved by 15 to 20%.

It can be applied by spraying and can be applied to many secret substrates.

(3) Because it is a thin film, it is extremely resistant to heat shock and is highly reliable.

(b) The appearance is also matte, giving a sense of luxury.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the main part of the titanium dioxide-based radiating surface of i-voice, Fig. 2 is a cross-sectional view of the main part of the infrared width envelope according to an embodiment of the present invention, and Fig. 3 is a diagram of the spectral radiation characteristics of the radiator. It is. 1... Base material, 2... Titanium dioxide 5
Infrared radiator containing 0 parts by weight or more, 4...Surface coating of the present invention, 5...Binder whose main component is polyborosiloxane resin, 6...Silicon dioxide or , one or more oxides selected from aluminum oxide. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3

Claims (2)

[Claims] (1) An infrared radiator comprising a coating made of one or more oxides selected from silicon dioxide or aluminum oxide and a cured polyborosiloxane resin on an infrared radiating surface containing 50 parts by weight or more of titanium dioxide. . (2) The infrared radiator according to claim 1, wherein the blending ratio of the oxide polyborosiloxane resin to the cured product is 1/3 to 2/1 by weight, and the film thickness is 2 μm or less. .