JPS5815913B2 - Seizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrothermal heat-generating coating (hereinafter simply referred to as a "heat-generating coating") on a surface.

), and relates to a manufacturing process for an infrared radiator having excellent thermal stability and electrical properties.

In the present invention, the term "infrared radiator" means an electrothermal heating element, and hereinafter, the infrared radiator is simply referred to as "one heating element".

"Thermal stability" refers to the property of being able to withstand use at high temperatures (approximately 450°C), that is, the property of not causing distortion or cracks at high temperatures; in other words, the property of maintaining good mechanical strength at high temperatures. Also, "electrical properties" refers to the stability and appropriateness of conductivity, that is, the property of keeping the resistance value constant.

Conventionally, as a manufacturing method for a heating element having a heat-generating film on the surface, such as a panel heater, an electrothermal film material such as a tin chloride mixed solution is adhered to the surface of heat-resistant glass, and then this is heated at a high temperature. A so-called spray coating method is known in which a tin oxide film is formed as a heat-generating film on the surface.

However, since this method employs spray coating technology, the process is complicated and requires high temperatures.

Furthermore, this method cannot produce a heating element with excellent electrical properties.

Furthermore, as a heating element, a heating coating made of a grafted carbon resin sheet is also known and widely known.

However, this material does not have heat resistance, and its heat resistance temperature is at most 150° C. or lower.

Furthermore, it has poor electrical properties.

An object of the present invention is to provide a method for producing a heating element that eliminates the various drawbacks mentioned above, that is, a heating element that has a heat-generating coating on its surface and has excellent thermal stability and electrical properties.

According to the first aspect of the present invention, the object is to apply a mixture formed by mixing a combination of silicone resin and graphite powder with an organic solvent onto the surface of a heat-resistant non-conductive substrate to generate heat on the surface. Form a film and then apply it to 250 to 45
Having an exothermic coating on the surface fired at a temperature of 0°C,
This is achieved by providing a method for producing a heating element with excellent thermal stability and electrical properties.

Furthermore, according to the second aspect of the present invention, the above object is achieved by adding one or more types of insulating powder to a mixture formed by mixing a combination of silicone resin and graphite powder with an organic solvent, and making this mixture heat resistant. It is applied onto the surface of a non-conductive substrate to form an exothermic coating on the surface, which is then coated at 250° C.
This is achieved by providing a method for manufacturing a heating element having excellent thermal stability and electrical properties and having a heating coating on its surface, which is fired at a temperature of ~450°C.

The present invention will be explained in detail below.

A combination is made by mixing 100 parts by weight of silicone resin (resin only) and 80 to 250 parts by weight of graphite powder, and then mixed with an appropriate amount of an organic solvent to form a fluid mixture.

As the silicone resin, 30% silicone resin Fewanis is usually used.

An example of such a varnish is "5R-116j" manufactured by Toshiba Silicone Corporation.

Its main component is polyalkyl or polyallylsiloxane.

The organic solvent has solubility in the silicone resin, such as evabenzene, toluene, xylene, petroleum solvents (Stottard solvent, solvent kerosene, etc.) and ketones (methyl ethyl ketone (MEK), methyl isobutyl ketone (Ml, BK), etc.). ).

Next, the mixture is applied to a desired thickness onto the surface of a heat-resistant non-conductive substrate of a desired shape such as a plate or pipe made of heat-resistant glass, ceramics, asbestos slate, heat-resistant reinforced plastic (FRP), etc. A heat generating film is formed on the surface by coating, and after drying, the film is heated and baked at a temperature of 250° C. to 450° C. for 60 to 300 minutes to produce a heat generating element.

Furthermore, in order to freely adjust the conductivity or electrical resistance value of the heat-generating coating to a desired value, an appropriate amount of one or more types of insulating powder is further added to the mixture, and this mixture is used to conduct the above-mentioned process. A heating element is manufactured in the same manner.

Examples of such insulating powder include silicon oxide powder, mica powder, and magnesium oxide powder.

The heating element manufactured in this manner is a product in which the heating coating and the base are firmly adhered to each other, and has excellent thermal stability and electrical properties.

In this way, the present invention imparts excellent thermal stability and electrical properties to the exothermic coating, and further strengthens the adhesion between the exothermic coating and the substrate. The purpose is to manufacture heating elements with excellent electrical properties.

The present invention may further include adding a desired amount of a suitable fluidity modifier to the mixture, if necessary, in order to change the rheological properties of the mixture.

As such a regulator, for example, US National
[Benton] manufactured by Read Chemical
J (main component: chemically treated bentonite).

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

Example 1 Silicone resin varnish (trade name "5R-116J" manufactured by Toshiba Silicone Co., Ltd.: Resin content approximately 30% Stodard solvent,
Graphite powder, silicon oxide powder, mica powder, and flow modifier "Benton J (U.S. National
(manufactured by Read Chemical) were blended in the ratios shown in Table 1A to prepare fluid mixture samples 1 to 5.

Each sample plate 1 to 5 as shown in Table IA was prepared with a thickness of 3
It was coated on one surface of ~5 mm asbestos slate to a thickness of 0.2 mm over an area of 550 mm x 380 mm, and then, after air drying, each of the slates was heated in a heating furnace at a temperature of 350 °C. It was baked for 180 minutes.

In this way, each Table-I
As shown in B, thickness 0.2mm, area 550mm x 380mm
Heat generating elements of scraps 1 to 5 having heat generating coatings of mm were manufactured.

The loading direction and charging power rate Watt (Vol tXAmpar
e).

The temperature of each of these was raised to the temperature shown in Table IB due to the resistance heat of the heat generating coating.

All of the heating elements ml to 5 do not generate distortion or cracks when heated, so they can be said to have excellent thermal stability, and the surface temperature hardly changes, so they have excellent electrical properties. It can be said that

In addition, none of the heating elements No. 1 to 5 could separate the heat-generating coating and the asbestos slate, and therefore it can be said that the heat-generating coating and the asbestos slate were firmly adhered to each other.

In this way, the heating elements No. 1 to 5 all have excellent thermal stability and electrical properties.

Furthermore, as is clear from Tables IA and IB, the surface temperatures of heating elements Nos. 2 to 5 change depending on the changes in the silicon oxide powder and mica powder contents in mixture samples Nos. 2 to 5.

Therefore, by including two or more of the above insulating powders in any desired amount in the mixture, the electrical resistance value of the heating element can be freely adjusted to a desired value.

The heating elements No. 1 to 5 each radiated heat rays (infrared rays) of energy corresponding to their surface temperatures from their heating coatings.

Infrared rays at temperatures between 180°C and 220°C are rich in wavelengths between 4 and 9μ (No.

1, No. 2 and No. 5), has excellent temperature sensitivity to the human body, and infrared rays at temperatures of 220 to 360°C
It contains abundant wavelengths of 6μ and can be used in industrial equipment for drying purposes.

Example 2 The fluid mixture of sample No. 1 shown in Table-IA was applied onto the surfaces of eight asbestos slates and dried in the same manner as in Example 1.

The slate coated in this way was heated in a firing furnace at 100°C, 200°C, 250°C, 300°C, and 350°C, respectively.
, 400°C, 450°C and 500°C for 180 minutes to produce heating element samples A-H.

The electrical resistance value of each of these heating element samples was measured, and the occurrence of damage (cracks, etc.) was observed, and the results are shown in Table 2.

If we compare and study the resistance values between each sample shown in Table 2,
It is clear that:

In other words, the change in resistance between samples A and B (both fired at temperatures below 250°C) was very large, and therefore these samples were all found to have unstable conductivity and poor electrical properties. Furthermore, the resistance values of these samples are too thick and are not appropriate values for use as a heating element, and on the other hand, the resistance value change between samples C and H (fired at a temperature of 250℃ or higher) is extremely large. It can be said that these samples have stable conductivity and excellent electrical properties, and their resistance values are
This is an appropriate value for a heating element.

Furthermore, the following is also clear from this Table-2.

That is, samples A-G fired at temperatures up to 450°C
In both cases, damage such as cracks does not occur, but on the other hand,
Sample H, which was fired at a temperature of 450° C. or higher, developed cracks in the substrate due to the high temperature.

Therefore, from Example 2, it can be said that the most suitable calcination temperature used in the present invention is a temperature within the range of 250-450<0>C.

As described above, the present invention enables the production of a heating element with excellent thermal stability and electrical properties.

Claims (1)

[Claims] 1. A mixture obtained by mixing a combination of silicone resin and graphite powder with an organic solvent is applied onto the surface of a heat-resistant non-conductive substrate to form an electrothermal heating film on the surface. and then firing this at a temperature of 250°C to 450°C. 2. Add one or more types of insulating powder to a mixture of a combination of silicone resin and graphite powder mixed with an organic solvent, and apply this mixture on the surface of a heat-resistant non-conductive substrate. . A method for producing an infrared radiator having an electrothermal heating coating on a substrate surface, the method comprising forming an electrothermal heating element on the surface and then firing the same at a temperature of 250 to 450°C.