JPH0784342B2 - High efficiency far infrared heater manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a high-efficiency far-infrared heater, and in particular, a high-efficiency far-infrared heater made of a ceramic mainly containing ferric oxide. Regarding the method.

[Prior Art] Conventionally, focusing on the fact that water and organic substances have large absorption characteristics in the far-infrared wavelength region, it is possible to dry materials using far infrared rays, evaporate volatile organic substances, or bake resins and paints. Has been done.

The applicants of the present application have already proposed a highly efficient ceramic infrared heater used for such a purpose in Japanese Patent Application No. 61-129855.

The ceramic infrared heater proposed by the applicants of the present invention is the second oxide of titanium oxide and / or tin oxide in a predetermined amount.
Since it uses iron, it has conductivity and has an excellent energy emissivity in the far-exposure wavelength range.

[Problems to be Solved by the Invention] Since the ceramic infrared heater has conductivity, it is necessary to cover the surface with an electric insulating film so as to prevent leakage during use depending on the application.

However, the infrared heater does not deteriorate the infrared radiation efficiency of the ceramic infrared heater, does not deteriorate even at a high temperature of about 600 ° C., which has the best infrared heating efficiency, and does not peel due to the difference in thermal expansion coefficient. It was not easy to coat.

[Means for Solving Problems] The present invention has the following structure for the purpose of solving the above problems.

That is, the gist of the present invention is that a self-glazing component is mixed in an amount of 0.2 to 5.0% by weight with respect to a raw material powder composed of ferric oxide containing 1 to 20 mol% of titanium oxide and / or tin oxide. It is a method of manufacturing a high-efficiency far-infrared heater, which is characterized by molding and sintering.

The raw material powder is a mixture of titanium oxide and / or tin oxide powder in a predetermined amount, ferric oxide powder in which a predetermined amount of titanium oxide and / or tin oxide is solid-solved, or titanium oxide and / or tin oxide by sintering. Oxidized with a predetermined amount of solid solution
Any material that becomes iron may be used.

The self-glazing component is a component that moves to the surface of the sintered body and reacts during sintering to form an amorphous electrical insulating layer in many cases. Since this self-glazing component needs to move to the surface during firing, it is preferable that the self-glazing component easily evaporates and diffuses on the surface. As such self-glazing component, manganese,
Vanadium, boron, nickel, or their compounds such as oxides, chlorides, sulfates, bromates, chlorides of iron,
Compounds such as sulfates and bromates, various phosphates and petalite can be used alone or in combination.

If the content of this self-glazing component is less than 0.2% by weight, it is not possible to form a sufficient electric insulation layer on the surface of the obtained high-efficiency salt infrared heater, and if it is more than 5.0% by weight, the electric insulation layer formed. Becomes thicker and becomes easier to peel off, and the self-glazing component remains inside the heater to reduce the conductivity of the high-efficiency far-infrared heater.

The above raw materials can be mixed in a predetermined amount in a wet or dry manner by a usual means such as a ball mill or a vibro mill. The mixed raw materials are molded into a desired shape by a usual molding method such as die molding or extrusion molding.

The molded body is 1200 to 1350 ° C, preferably 1300 to 1350
At ℃, in the air or in a neutral or weak reducing atmosphere such as a muffle furnace, it becomes a high efficiency far infrared heater.

[Operation] When a compact made of the above raw material is sintered, the ferric oxide to which titanium oxide and / or tin oxide is added has conductivity and becomes a sintered compact having high energy radiation efficiency in the far infrared region. At the same time, the self-glazing component contained in this raw material moves to the surface of the sintered body and is fired to form an electric insulating layer. This electrical insulating layer does not lower the infrared radiation efficiency, does not deteriorate even at a high temperature of about 600 ° C, which has the highest infrared heating efficiency, and does not peel off due to the difference in thermal expansion coefficient. It is possible to easily manufacture the high-efficiency far-infrared heater having the above.

[Examples] Examples of the present invention will be described.

First Example 5 mol% of tin oxide was added to commercially available ferric oxide and mixed well, and then treated at 1300 ° C. for 2 hours to form a solid solution of tin oxide in ferric oxide.

Then, 1.0 wt% of manganese dioxide, which is a self-glazing component, was added to this ferric oxide solid solution, and the mixture was pulverized and mixed in a ball mill for 24 hours.

Then, the obtained powder is molded with a molding pressure of 750 kg / cm.
^{In 2} , a disk having a diameter of 6 cm and a thickness of about 5 mm was formed.

Then, the temperature of this molded body was raised at 100 ° C / hr to reach the maximum temperature of 13
It was held at 00 ° C. for 1 hour for sintering, and then naturally cooled. As a result, a sintered body having a black surface was obtained.

This sintered body was cut out into a test piece with a width of 5 mm and a length of 37 mm.

The surface resistance and internal resistance of this test piece were measured using JIS C using a milli-meter made by Yokogawa Hewlett Packard and a digital multimeter made by Advantest.
It was measured according to 2141-1974. The surface layer portion was measured by bringing an electrode into contact with the surface of the test piece, and the inside was measured after scraping off the surface of the test piece by a predetermined amount.

As a result, about 0.3 mm of the surface mounting part of this test piece has a large electrical resistance at room temperature of about 100 to 500 × 10 ³ Ωcm, but the internal resistivity at room temperature is about 0.2 to
It showed conductivity of 4 Ω · cm.

A comparative sample (high-efficiency far-infrared heater described in Japanese Patent Application No. 61-129855) obtained by the same method as above except that manganese dioxide was not added was similarly measured for specific resistance at room temperature. , About 0.1 to 3 Ω · cm over the entire sample.

Further, FIG. 1 shows the results of measuring the infrared emissivity characteristics of the first example and the comparative sample with an infrared emission spectrum measuring apparatus. This infrared radiation spectrum measuring device is composed of a sample heating furnace, a black body furnace, and an infrared spectrophotometer (measurement wavelength range 2 to 30.3 μm), and has a diameter of about 4 cm and a thickness of about 3 mm set in the sample heating furnace. The infrared emissivity characteristic of the flat plate sample is measured as a suggested infrared emission spectrum when the emissivity of the black body furnace is 1.

From the above, the surface of the sample manufactured according to this example is covered with an electrical insulating layer, and the sample of this example has a slightly lower infrared emissivity characteristic than the conventional high-efficiency far-infrared heater. It has been confirmed that it has sufficient emissivity characteristics over the entire outer wavelength range and has no practical problem.

-Second Example A sintered body was prepared in the same manner as in the first example except that 5 mol% of anatase-type titanium oxide was used instead of the tin oxide of the first example, and a test piece was prepared. .

When the characteristics of this test piece were measured by the same method as in the first embodiment, the specific resistance of the surface layer portion at room temperature was about 100 to 600 × 10 ³ Ω · cm at room temperature, which was electrically insulating, and the internal room temperature. It was confirmed that the specific resistance was about 0.8 to 6 Ω · cm and was conductive.

It was also confirmed to have the same infrared emissivity characteristic as that of the first embodiment.

Third Example Commercially available ferric oxide was mixed with titanium oxide 5 mol%, conductive tin oxide sol (Sb ₂ O ₅ about 5%, balance SnO ₂ and solid content 23.4 wt%) in terms of solid content of 0.5 wt%. (SnO ₂ is about 0.5 mol%),
And 1.0% by weight of manganese dioxide was added as a self-glazing component, and a powder was obtained in the same manner as in Example 1. This powder was molded and sintered in the same manner as in Example 1 to prepare a test piece.

The infrared emission characteristics of the test piece of this example were measured in the same manner as in the first example, and an infrared emissivity close to 0.9 was obtained over the entire measurement wavelength range.

The relationship between the temperature and the specific resistance of the surface layer and the inside of the test piece was measured according to JIS C 2141-1974. Results are shown in FIG.

From FIG. 2, it was confirmed that in the range of 25 to 800 ° C., the surface layer portion was an insulator having a sufficient specific resistance and the inside was a low resistance conductor.

Fourth Example A powder was obtained in the same manner as in the first example using 5 mol% titanium oxide and 2% by weight manganese phosphate, which is a self-glazing component, with respect to the second iron oxide. 0.1% by weight of PVA (polyvinyl alcohol) was added to this powder, and extrusion molding was performed and sintering was performed to obtain a round bar having a diameter of about 6 mm.

When the specific resistance of the surface of this round bar at room temperature was measured by the above method, it was about 100 × 10 ³ Ω · cm.

Next, this round bar was cut into a length of 120 mm, a predetermined voltage (AC 60 Hz) was applied with both ends as electrodes, and the surface temperature of the sample was measured using a surface thermometer (HLB-50R manufactured by Anritsu). The results are shown in FIGS. 3 and 4.

From FIG. 3, it was found that the voltage and surface temperature of the sintered body obtained in this example were proportional to each other.

Further, from FIG. 4, the sintered body obtained in this example is
It was found that the temperature rises well after energization and reaches a constant temperature in a short time.

Fifth Example 5 mol% of titanium oxide was added to ferric oxide, and petalite (Li ₂ O.Al ₂ O ₃ .8Si), which is a self-glazing component, was added.
O ₂ ) and NiO were added in an amount of 0.5% by weight and adjusted in the same manner as in Example 4 to obtain a rod-shaped sintered body.

The surface of the obtained sintered body shines black as in the case of manganese dioxide, and the specific resistance of the surface at room temperature is 180 × 10 ³ Ω.
・ While it was cm, the inside showed 870 Ω · cm.

An AC voltage of 60 Hz was applied to this sintered body by the same method as in the fourth embodiment, and the surface temperature of the sintered body was measured. In the case of a round bar having a heating portion length of 100 mm and a thickness of 6 mm, At a voltage of 20 V, a temperature rising characteristic of 523 ° C. in 2 minutes, 558 ° C. in 5 minutes, and 568 ° C. in 100 minutes after application was shown.

In addition, when this sintered body was processed into a flat plate and the infrared emissivity was measured by the same method as described above, it was found to be in the range of 2.0 to 25 μm.
An excellent value of 0.8 or more was shown.

Furthermore, when the above-mentioned sintered body was subjected to an acid resistance test at room temperature by a method according to JIS R1503, the weight loss rate was 3.2.
%showed that.

-Sixth Example Similar to the first example, titanium oxide was added to the commercially available ferric oxide in a range of 1 to 20 mol% and manganese dioxide (1.0% by weight) was added as a self-glazing component. Thus, various powders having different titanium oxide contents were obtained. These powders were molded and sintered in the same manner as in Example 1 to prepare test pieces.

Infrared radiation characteristics of each test piece were measured in the same manner as in the first embodiment, and the test pieces containing 1 to 20 mol% of titanium oxide all had an emissivity close to 0.9 over the entire measured infrared wavelength range. Indicated.

Further, regarding the surface layer portion and the inside of each test piece, the specific resistance at room temperature was examined in the same manner as in the first embodiment. As a result, it was confirmed that in the range of 1 to 20 mol% of titanium oxide, the surface layer portion of any of the test pieces was an insulator having a sufficient specific resistance, and the inside was a low resistance conductor. .

Seventh Example To a commercially available ferric oxide, 5 mol% of titanium oxide was added, and 0.2 to 5.0% by weight of manganese dioxide, which is a self-glazing component, was added, and self-glazing was performed in the same manner as in the first example. Various powders having different component contents were obtained. These powders were molded and sintered in the same manner as in Example 1 to prepare test pieces.

Infrared radiation characteristics of each test piece were measured in the same manner as in the first example, and it was found that the test pieces containing 0.2 to 5.0% of manganese dioxide, which is a self-glazing component, had a value of 0.9 over the entire infrared wavelength range measured. It showed a close emissivity.

Further, regarding the surface layer portion and the inside of each test piece, the specific resistance at room temperature was examined in the same manner as in the first embodiment. As a result, it was confirmed that in the range of 1 to 20 mol% of titanium oxide, the surface layer portion of any of the test pieces was an insulator having a sufficient specific resistance, and the inside was a low resistance conductor. .

[Effect of the Invention] The high-efficiency far-infrared heater manufactured according to the present invention has an emissivity of 0.9 or more even in a linear infrared region having a wavelength of 5.6 μm or more and has a surface electrically insulated by directly energizing the heater. It is very convenient to handle because it is covered by layers.

[Brief description of drawings]

FIG. 1 is a diagram for comparing infrared emissivity of a high school rate far infrared heater according to the first embodiment of the present invention and a comparative example, and FIG. 2 is a relationship between temperature and specific resistance of the third embodiment of the present invention. FIG. 3 and FIG. 3 are diagrams showing the relationship between voltage and temperature in the fourth embodiment of the present invention, and FIG. 4 is a diagram showing the relationship between time and temperature at the constant voltage.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Shiro Kitagawa 2-24-15 Chiyoda, Naka-ku, Nagoya, Aichi Kitagawa Industry Co., Ltd. Takeshi

Claims (1)

[Claims] 1. A self-glazing component is mixed in an amount of 0.2 to 5.0% by weight with respect to a raw material powder composed of ferric oxide containing 1 to 20 mol% of titanium oxide and / or tin oxide, and the mixture is sintered. A method for manufacturing a high-efficiency far-infrared heater, which is characterized by the above.