JPH01167584A - Carbon fiber series heat insulating material - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a heat insulating material surface because of generation gas and to prevent lowering of purity of a substance to be treated due to the dispersion of powdery dust from a heat insulating material, by a method wherein, in a carbon fiber series heat insulating material for a high temperature electric furnace, a carbonaceous sheet is laminated on a surface on the core side. CONSTITUTION:A bulky carbon fiber molded product wherein a felt formed by needle- punching carbon fiber is used as a base material and impregnated with resin having high carbonization factor and cured and carbonized is used as a heat insulating material for a high temperature electric furnace. A carbonaceous sheet is formed by a carbonized sheetform support and a carbonaceous matrix, showing anisotropy under a polarization microscope and fine mosaicform or isotropic optical structure with particle size of 10mum or less and having a carbon content of 95wt.% or more, a gas permeability of 10<-5>-10<-7>cm<2>/S, bulk density of 1.4-1.9g/cm<3>, and a thickness of 0.1-1mm. The carbonaceous sheet is securely laminated on the surface on the core side of the carbon fiber series heat insulating material. This constitution enables the prevention of deterioration of a heat insulating material surface and lowering of purity of a substance to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a carbon fiber-based heat insulating material, and more particularly, to a high-temperature electric furnace carbon fiber-based heat insulating material having a fi layer of carbon thin plates on the surface of the reactor core.

(Problems to be solved by the prior art and the invention) High-temperature electric furnaces such as sintering furnaces, quenching furnaces, brazing furnaces, carbonization furnaces, heat treatment furnaces, vapor deposition furnaces, crystal growth furnaces, HIP furnaces (use conditions are Generally 1
000-3000℃), the reactor core is made of entertainer material,
It is already known that it consists of a heat insulating material surrounding a crucible, a heating element, etc.

The following points should be taken into account as a heat insulating material: (1) It must be a material that completely reflects radiant heat to increase the heating effect inside the furnace, ■ It must have low moisture absorption, ■ It must have a small heat capacity, (4) ) being lightweight and inexpensive (Sugiyama et al. “Metal materials”, Ul[8], p. 81)
(Showa 47)).

By the way, carbon fiber-based insulation materials have recently established themselves as insulation materials for high-temperature furnaces that can satisfy such requirements (Nozaki et al., ``Industrial Heating,'' Sen, [3]). ], 33 (Sho 61)). Incidentally, carbon fiber-based insulation materials include felt made by needle-punching carbon fibers, which is used as a base material, and is impregnated into any shape using resin with a high carbonization rate, and then cured. Later, a bulky carbon m-fiber molded body was produced by carbonizing the molded body. This carbon fiber molded body is compression molded with a graphite binder, so it has a smooth surface and sufficient strength, and it is also self-supporting, so when gas is exhausted or introduced into the furnace, the gas can flow at high speed. There is little scattering of dust or single felt threads even when the material flows out or flows in. Also, since it is self-supporting, it is only necessary to assemble it when loading or replacing the insulation material in the furnace, and there is no need to wrap it around it like felt. It can be said that it is a material suitable for improving workability and working environment (p.
35 and Japanese Patent Publication No. 5O-35930 cited therein). Other molded heat insulating materials have a structure in which graphite sheets are laminated on the surface of the molded body, and carbon fiber felt and graphite sheets are alternately layered in order to better prevent scattering of single felt fibers or to strengthen the surface. Those with (cited above, p.
36 and Utility Model Application Publication No. 54-92471 cited therein), or coated with a special carbon cement, cited above, 9.38).

However, even if such a carbon-41 fiber-based insulation material is used as a high-temperature electric furnace insulation material, it cannot be said that its performance as an insulation material is sufficient.
For example, in ceramic sintering furnaces and silicon single crystal production furnaces, the surface of the insulation material deteriorates due to gases such as vaporized metals and 5iO7, shortening its life, and the purity of the processed material decreases due to dust scattering from the insulation material. . In addition, when a graphite sheet is pasted on the surface of a heat insulating material (Utility Model Application Publication No. 54-92471), the graphite sheet easily peels off, making it impossible to perform high-purity treatment and resulting in poor product purity, so a particularly high level of purity is required. However, carbon fiber-based heat insulating materials are desired to be further improved in these respects.

(Means and effects for solving the problems) The present inventor has proposed that the above-mentioned drawbacks of carbon fiber-based heat insulating materials for high-temperature electric furnaces can be overcome by laminating carbon thin plates on the core side surface of such heat insulating materials. The present invention was completed based on this finding.

Elimination of these drawbacks is due to the fact that the carbonaceous thin plate is dense and has corrosion resistance. According to the present invention, it is also possible to greatly extend the life of the heat insulating material by replacing the carbon thin plate. The laminated carbon thin plates are thin and have a small heat capacity, so there is no problem in cooling or heating the furnace, and they are more self-supporting than graphite sheets, so they can be installed in any shape. .

Here, as the carbonaceous thin plate, for example, JP-A-60-2
Substantially carbonized thin paper-like support used as a base material that can be produced by the method according to No. 39358, and fine mosaic-like or etc. particles with a particle size of 10 μs or less that exhibit anisotropy under a polarizing microscope. A carbonaceous thin plate made of a composite with a carbonaceous matrix exhibiting a tropic optical structure, with a carbon content of 95% by weight or more and a bulk density of 1.4 to 1.
．． Carbon thin plate with physical properties of 9g/cd and JP-A-62-
46909, in which a carbon raw material that is softened by heating and then carbonized and solidified is carbonized while being pressurized by a hot press, and then fired, in which melting occurs between the carbon raw material and the pressing surface of the hot press. One example is a carbonaceous thin plate manufactured by disposing a paper-like material that carbonizes without carbonizing and carbonizing it under pressure.

The carbonaceous thin plate may be laminated over the entire surface of the high-temperature electric furnace carbon 41 fibrous insulation material, or may be laminated locally so as to cover severely corroded areas.

Lamination fixing can be achieved, for example, by using normal port/nut fixing, that is, passing carbon bolts from the core side through holes that penetrate both the carbon thin plate and the insulation layer, and tightening them with nuts on the outside of the insulation layer. I can do it.

The lower limit of the thickness of a carbon thin plate is approximately 0.1 from the viewpoint of manufacturing constraints, strength, secondary workability, etc., and the upper limit of the thickness of a carbon thin plate is approximately 0.1 from the viewpoint of workability, heat capacity, economic efficiency, etc. 1M,
Taking all these aspects into consideration, preferably about 0.5 to about 0.7
It is in the range of IR#l. The W4 layer on the surface of the thin plate heat insulating material may be one thin plate, or several layers may be stacked as necessary.

(Example) 650g1 x 1000rR1 (base area) x 650g1 x 1000rR1 (base area) x 100111#l thick carbon fiber insulation material with bulky structure is used with felt as the base material.
Ceramics were sintered using a square high-temperature electric furnace having a core with a volume of 1000 s (height) and using graphite as a heating element. The raw material was charged into an in-core crucible and heated to 2300°C, and after completion of sintering, it was cooled to room temperature and the product was taken out from the furnace.

After repeating this temperature rise and fall 30 times, the temperature inside the furnace reached 230.
When the temperature was set to 0°C, the temperature on the outside of the insulation material was 300°C or higher, resulting in abnormal insulation properties that made it impossible to maintain satisfactory operating conditions.

This was due to deterioration of the surface of the heat insulating material due to erosion of the surface of the heat insulating material, which was obvious even by visual inspection.

Furthermore, as the experiments progressed, the degree of contamination of the product ceramics due to dust scattering from the surface of the insulation material increased.

On the other hand, the conditions were exactly the same except that carbon thin plates (manufactured according to Example 2 of JP-A-60-239358) with a thickness of 0.61+1#l were laminated on the entire surface of the core side using carbon bolts/nuts. When the above experiment was repeated, 30
Even though the temperature was raised and lowered several times, the operating condition of 300°C or less outside the heat insulating material when the furnace temperature was 2300°C was still satisfied, and no abnormality was observed in the heat insulating properties. Also,
All of the product ceramics were of high purity and free of impurities.

Procedure Ne Fti JE Director General of the Patent Office 1) Moon Takeshi 1, Indication of matter 1 1985 Patent Application No. 32333
No. 1 No. 2, Title of the invention Carbon fiber-based insulation material 3, Supplementary iE
Relationship to this case Patent applicant name (110) Kureha Chemical Industry Co., Ltd. 4, Agent Yamada Building 8, 1-1-14 Shinjuku, Shinjuku-ku, Tokyo Contents of amendment (1) Patent in the specification The scope of claims is amended as shown in Attachment 2.

■ In the third line of page 2 of the same book, ``moisture'' is deleted and ``little'' is corrected to ``small''.

■ Add "gas permeability coefficient of 10-5 to 1 O-7 ci/S" to "at least % by weight" in the second line from the bottom of page 5 of the same book.

C) Replace pages 7 and 8 with Attachment 1.

Separate ellipse 1 The upper limit of hole drilling is approximately 1 m from the viewpoint of workability, heat capacity, economic efficiency, etc., and from these viewpoints, it is preferably 0.5 m.
~0.7m. A single thin plate may be laminated on the surface of the heat insulating material, or several thin plates may be stacked as necessary.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1 Softening point: 285°C, carbonization yield at 900°C firing: 72mm
%, 12 parts by weight of fine powder pitch whose particle size is 10 microns or less is 90 parts by weight or more, 8 parts by weight of grahyde powder with a particle size of 10 microns or less, 0.5 parts by weight of methyl cellulose, 80 parts by weight of water.
The slurry obtained by uniformly mixing the heavy spaces was uniformly applied to carbon paper with a basis weight of 30 g/- manufactured by making pitch-based low elastic modulus carbon 1 fiber, and dried to obtain a basis weight of 230.
A green sheet of 9/- was produced. These four green sheets were stacked and filled into a mold, heated to 370°C at a rate of 300°C/hr, and then pressed at a pressure of 15 kg/cλ for 30 minutes, with a simulated pressure of INg/crl. The temperature was raised to 600°C at a rate of 50°C/hr, and the obtained thin plate was fired at 2000°C in an inert gas atmosphere to a thickness of 0.
．． 611111 carbon thin plate.

A volume of 650a15Ix 11000a+ (base area) x 1000#III+ (height) was formed by surrounding this carbon thin plate with a thickness of 100 using bulky carbon fiber insulation material with felt as the base material. The reactor was laminated and fixed with carbonaceous bolts and nuts on the entire surface of the core side of a rectangular high-temperature electric furnace having a core of 300 mL and a graphite heating element.

Ceramics were sintered using the square high-temperature electric furnace.

The raw materials are charged into a crucible in the core, heated to 2300℃,
After sintering was completed, the product was cooled to a high temperature and taken out from the furnace.

Even after repeating this temperature increase/decrease 30 times, the operating condition of 300° C. or less outside the heat insulating material when the temperature inside the furnace was 2300° C. was satisfied, and no abnormality was observed in the heat insulating properties.

In addition, all of the product ceramics were of high purity and free of impurities.

Comparative Example 1 Ceramics were sintered under the same conditions as in Example 1 except that carbon thin plates were not laminated on the entire surface of the core side. After repeating this temperature rise and fall 30 times, the outside of the insulation material The temperature exceeded 300°C, resulting in abnormal heat insulation properties that made it impossible to maintain satisfactory operating conditions.

When the core side insulation material was observed, erosion and deterioration of the insulation material surface was observed. Additionally, the more the experiment was repeated, the more the product ceramic became contaminated by dust particles flying from the surface of the insulation material.

Comparative Example 2 Ceramics were sintered under the same conditions as in Example 1, except that 0.6 m of Graphoil (graphite sheet manufactured by Union Carbide, USA) was laminated instead of the carbon thin plate. After repeating the temperature rise and fall 15 times, part of the graph oil was missing, the heat insulating effect was lost, and the product ceramic was contaminated, resulting in unsatisfactory results.

■Iokan 2, Claims (1) A carbonized paper-like support and a fine mosaic or isotropic optical structure that shows no anisotropy under a polarizing microscope and has a particle size of 10- or less. The carbon content is 95% by weight or more, and the gas permeability coefficient is 10-5 to 10-7. J/s, bulk density is 1.4-1
．． 9'j/c! A high-temperature electric furnace carbon fiber-based heat insulating material in which carbon thin plates having a thickness of 0.1 to 1#1I11 are laminated on the surface of the reactor core.

Claims (1)

[Claims] A high-temperature electric furnace carbon fiber insulation material with carbon thin plates laminated on the surface of the reactor core.