JPS641914B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carbon-based coiled resistance heating element.
The term carbonaceous here includes carbonaceous (amorphous) and graphite (crystalline). Therefore, the carbon-based coiled resistance heating element consists of a carbonaceous coiled resistance heating element that is substantially made of carbon and has properties specific to carbon, and a graphite coiled resistance heating element that is substantially made of graphite and has properties specific to graphite. It includes both.

Carbon-based materials exhibit excellent heat resistance and corrosion resistance without melting or deforming in a non-oxidizing atmosphere. It also exhibits electrical conductivity close to that of metals. This property is useful as a heating element for high-temperature electric furnaces, and in the past it was used in laboratories such as Tammann furnaces and Kryptor furnaces, but in recent years, with the development of the semiconductor industry, it has been used as a heating element for production equipment in that field. It is being used extensively. There are other high-temperature furnaces such as combustion furnaces, electric arc furnaces, plasma furnaces, and electron beam furnaces, but electric resistance furnaces are characterized by uniformity of temperature, precision of temperature control, ease of controlling the atmosphere inside the furnace, and low noise. It has an advantage over other furnaces in terms of preventing pollution such as exhaust gas.

Carbon-based materials as resistive heating elements have the following useful characteristics. In other words, under normal pressure, it does not melt and its sublimation temperature is as high as approximately 3650°C. Steam pressure is 2200℃
is extremely low, on the order of 10 ^-6 atm. High corrosion resistance against corrosive gases. The radioactivity is large, approximately 0.8. Unlike metal materials, it does not soften even at high temperatures, and its strength increases in proportion to temperature up to 2500℃.
Graphite has a suitable electrical resistance, and the resistance increases in proportion to temperature above about 500°C. It has a small coefficient of thermal expansion, so it has extremely good thermal shock resistance. It is easy to obtain high purity products and generates little gas even under high vacuum. Cheaper than other competing materials such as platinum, rhodium, tungsten, molybdenum, tantalum or silicon carbide.

However, carbon-based materials have poor malleability and, like metals and plastics, are extremely difficult to precisely machine into desired shapes. Therefore, in the past, it was necessary to perform complex and difficult work such as cutting out a large molded carbon material block and cutting it with an NC lathe. In particular, in the case of tubular or plate-shaped heating elements, various methods have been considered to increase the resistance, such as making cuts in a circular or longitudinal direction, but these are not only difficult to process, but also weigh heavily. The mechanical strength of the notched area becomes weak, so the structure of the heating element and terminal connections must be designed so that they are not subjected to various bending and tensile stresses, including expansion and contraction, and must be handled carefully. It also has the disadvantage of requiring special attention.

On the other hand, recently, cloths, strings, etc. made from carbon fibers have been considered as flexible heating elements. Due to its flexibility, it can be wrapped around the furnace body, and can compensate for the drawbacks of conventional carbon-based heating elements to some extent, but in the form of cloth or string, it itself lacks elasticity. In order to maintain close contact with the furnace body, special holders must be devised, and if it is tied too tightly to maintain close contact,
There is also the problem of stress durability caused by expansion, contraction, etc. Furthermore, since carbon fiber itself is expensive, cloth and string made from it are also necessarily expensive.

Considering the adhesion with the furnace body, the relaxation of stress generated inside the heating element, the method of attachment to the furnace body, the ease of handling, etc., the coiled heating element, which has traditionally been made of metal wire, is suitable. Although it is preferable because it has good elasticity and flexibility, if a coil-shaped heating element is provided by forming a carbonaceous material into a coil shape, it is the most ideal resistance heating element. However, it is considered extremely difficult to manufacture a coiled carbon-based coil-shaped heating element with high strength using the conventional method of cutting it from a carbon block, and it has not yet been commercialized.

An object of the present invention is to provide a carbon-based coiled resistance heating element, the production of which has heretofore been virtually impossible.

The inventors of the present application took advantage of the carbon material's excellent heat resistance, corrosion resistance, radiation, high strength, appropriate electrical conductivity, and thermal shock resistance to create a carbonaceous or graphite coiled heating element in any size and shape with precision. As a result of intensive research to avoid expensive and easy production, organic linear bodies or
After forming an organic linear body compositely reinforced with carbon fiber, graphite whiskers, crystalline graphite powder, and amorphous carbon powder into any desired coil shape, carbon precursor treatment is performed as necessary. The inventors have come up with the idea of obtaining a carbonaceous or graphite coiled heating element by applying heat treatment in an inert atmosphere, thereby achieving the object of the present invention.

The carbon-based coiled resistance heating element of the present invention has extremely high processing accuracy, does not require post-processing, and has excellent heat resistance, corrosion resistance, radiation, high strength, appropriate electrical conductivity, and thermal shock resistance. It has a reliable and highly accurate elastic modulus, is lightweight, has appropriate flexibility, and has extremely good adhesion to the electric furnace body, and the coil elasticity does not expand or contract. It has the advantage of being able to absorb internal stress caused by such factors, and does not require any special ingenuity in the method of attachment to the furnace body or the design of the terminals.

The organic linear body used in the carbon-based coiled resistance heating element of the present invention is made of a linear body formed from a mixture of one or more of organic polymer substances, asphalt pitches, carbonized pitches, etc. Composite reinforced organic linear bodies are carbon fibers, graphite whiskers, crystalline graphite powders, amorphous carbon powders, etc., for organic polymer substances and one or more mixtures of asphalt pitches, carbonized pitches, etc. It is made by uniformly dispersing one or more types of bodies, etc., and forming them into a linear body in a highly oriented manner.

In general, a linear body has a diameter of 0.1 m/m to several m/m.
Generally speaking, a fiber with a diameter of several μm or less is considered a fibrous body, and a diameter of several m/m or more is considered a rod-like body, but the present invention does not strictly distinguish the diameters.

Further, organic polymer substances used in the present invention include polyvinyl chloride, polyacrylonitrile, polyvinyl alcohol, polyvinyl chloride-vinyl acetate copolymer, polyamide, thermoplastic resin such as polyimide, phenolic resin, furan resin, epoxy resin, Thermosetting resins such as unsaturated polyester resins,
Natural polymeric substances having a condensed polycyclic aromatic group in the basic structure of the molecule, such as lignin, cellulose, gum tragacanth, gum arabic, sugars, etc., and formalin condensates of naphthalene sulfonic acid, indanthrene series, which are not contained in the above. There are synthetic polymeric substances, such as vat dyes and their intermediates, which have fused polycyclic aromatics in their basic molecular structure.

As pitches, carbonized distillates of hydrocarbon compounds such as petroleum asphalt, coal tar pitch, naphtha cracked pitch, petroleum asphalt coal tar pitch, and synthetic resins at temperatures below 400°C are used.

Also, among these substances, there are those that have poor shaping properties and those that are difficult to progress to ideal carbonization, but those that have poor shaping properties are, for example, the thermoplastic resins mentioned above. It is possible to use one or more of them in combination as a molding binder by blending them, and those that are difficult to ideally carbonize are Lewis acids such as iron, nickel, and cobalt oxides and aluminum chloride. It is possible to easily form a carbon precursor and co-carbonize it by mixing it with a carbonization promoting catalyst such as exemplified by and other compounds, heating it, and subjecting it to dehydrogenation treatment.

The carbon fibers, graphite whiskers, crystalline graphite powder, and amorphous carbon powder used as composite reinforcing agents in the present invention will be explained below.

The content of these composite reinforcing agents in the composite reinforced organic linear body varies depending on the type of matrix material used and the diameter of the intended organic linear body, but it is 20 to 80% by weight in the organic linear body composition. %, preferably 40 to 70% by weight.

The composite reinforcing agent used in the present invention is characterized by the wire diameter, mechanical strength,
Carbon fiber, graphite whisker, crystalline graphite powder, carbon fiber, graphite whisker, crystalline graphite powder, One or more types of amorphous carbon powder are appropriately selected and added.

The organic linear body of the present invention is an organic polymer substance, a thermoplastic resin curable resin, a natural polymer substance,
Disperse well by directly melting one or more of the synthetic polymer substances and pituits, or by adding a solvent, plasticizer, carbonization accelerating catalyst, crosslinking agent, polymerization initiator, etc. as necessary. After that, it is pelletized and extruded into a desired diameter using an extruder or the like.

In order to obtain a composite reinforced organic linear body, one or more of carbon fibers, graphite whiskers, crystalline graphite powder, and amorphous carbon powder may be added to the above compound depending on the purpose. Just add it.

When mixing two or more types of blended compositions, the blended compositions are dispersed using a high-speed blender, and then blended using a kneader that can apply a high shear force, such as a pressure kneader, two-roll kneader, or co-kneader. It is better to use a method of uniformly dispersing and kneading the composition.

During extrusion molding, it is preferable to perform an appropriate stretching operation for the purpose of improving the physical properties of the linear body.

When forming into a coil shape as the second step, the obtained organic linear body and composite reinforced organic linear body are heated at 1000°C with a smooth surface of desired cross section and dimensions.
A circular or polygonal rod or pipe made of a heat-resistant material that can withstand the above-mentioned high temperatures is used as a supporting base material, and is wound around the support base material in a coil shape, and both ends of the rod or pipe are fixed.

Next, in order to carbonize and graphitize while maintaining these shapes, a method of adding a carbonization accelerating catalyst, a crosslinking agent, a polymerization initiator, etc., a method of acid treatment, a method of applying chlorine, ozone, heated air, etc. 50 in the atmosphere
Insoluble or infusible treatment is performed by any of the following methods, such as a method of crosslinking by heating to ~300° C., a method of crosslinking and curing by irradiation with ultraviolet rays, electron beams, radiation, etc., and carbon precursor treatment.

Next, the coil-shaped excipient that has been treated with the carbon precursor is wrapped around a support base material such as a heat-resistant rod or pipe for the purpose of preventing deformation and adding tension. In the case of a carbonaceous coiled resistance heating element, it is gradually heated to a maximum temperature of 500 to 1500°C, preferably 1000 to 1500°C. Further, in order to obtain a graphite coiled resistance heating element, heating is performed to a maximum temperature of 2000 to 3000°C, preferably 2500 to 3000°C.

Next, the present invention will be specifically explained using examples.

Example 1 Straight vinyl chloride resin 100 with an average degree of polymerization of 700
Homogeneously disperse 30 parts by weight of DOP in a Henschel mixer. Next, the material is thoroughly kneaded under heating using a pressure kneader while maintaining the material temperature at 150°C.

Next, the material is made into pellets using a pelletizer.
A polyvinyl chloride linear body with a diameter of 0.8 mmφ was obtained using a screw extrusion molding machine. This was wound around a carbonaceous bobbin with a diameter of 10.0 mm and a smooth surface. Next, this was heated at 100℃ for 10 hours in the presence of air.
After being kept at 180℃ for 24 hours and treated to become an insoluble and infusible carbon precursor, it was heated at a heating rate of 10℃/hr in a nitrogen gas phase.
Raise the temperature to 500℃, and then increase the temperature at a rate of 50℃/hr.
The temperature was raised to 1000°C, maintained at that temperature for 3 hours, and then allowed to cool naturally to room temperature.

The excipient is released from the carbonaceous bobbin, and the wire diameter is 0.4mm.
A carbonaceous coiled resistance heating element with a φ coil inner diameter of 10.0 mm and a φ coil length of 500 mm was obtained.

Example 2 100 parts by weight of furan resin (furfuryl alcohol initial condensate) and 100 parts by weight of straight vinyl chloride resin with an average degree of polymerization of 700, 50 parts by weight of crystalline graphite powder with an average particle size of 2.0 μm, and 10 parts by weight of DOP as a plasticizer. was added and uniformly dispersed using a Henschel mixer, and then kneaded for 30 minutes in a pressure kneader while maintaining the material temperature at 140°C to obtain a homogeneous composition.

Next, the preformed composition, which had been sufficiently degassed in the vacuum preformer, was extruded into a diameter of 1.0 mm using a plunger type hydraulic extruder to obtain a linear body.

This linear body was then wrapped around a carbon round rod with a diameter of 15.0 mm and both ends were fixed.

This coiled excipient is kept in an oven heated to 180°C in the presence of air for 24 hours, and the furan resin is sufficiently hardened by the hydrogen chloride generated when the vinyl chloride resin decomposes, turning it into an insoluble and infusible carbon precursor. After treatment, heat up to 300°C at 10°C/hr in a nitrogen gas phase and then 20°C.
The temperature was raised to 500°C at a rate of 50°C/hr, then raised to 1000°C at a rate of 50°C/hr, held at 1000°C for 3 hours, and then allowed to cool naturally to room temperature.

The excipient is released from the carbonaceous bobbin, and the wire diameter is 0.75mm.
A carbonaceous coiled resistance heating element with a coil inner diameter of 15.0 mm and a coil length of 500 mm was obtained.

Example 3 The carbonaceous coiled excipient obtained in Example 1 was heated at 300°C/hr up to 1000°C and at 2800°C above 1000°C in an argon gas phase without removing it from the carbonaceous support.
The temperature was raised at a rate of 400°C/hr to 2800°C, and after being held at 2800°C for 60 minutes, it was naturally cooled and graphitized to obtain the intended graphite coiled resistance heating element.

Claims (1)

[Claims] 1. A method for manufacturing a carbon-based coiled resistance heating element that is substantially made of carbon and has properties unique to carbon, which comprises shaping an organic linear body into a coil shape and then carbonizing it.