JPS59190208A - Preparation of ultrafine silicon carbide powder - Google Patents

Abstract

PURPOSE:To prevent the disintegration of granulated raw material during the reaction in the preparation of SiC powder using silica and granulated fine carbon powder as raw materials, and to obtain ultrafine SiC powder, by using carbon powder having high wettability with water as the above raw material. CONSTITUTION:A granulated raw material obtained by compounding silica powder with C powder having a specific surface area of 1-1,000m<2>/g and a C-based binder, is charged in the reactor 6 through the inlet port 1, and spontaneously lowered through the preheating zone 2 to the heating zone 3. The above C powder used as a raw material is the one prepared by using C powder having improved wettability with water, and mixing the powder with water up to the latest prior to the granulation. The raw material in the heating zone 3 is heated horizontally, and the SiC-formation reaction is carried out controlling the reaction temperature at 1,500-2,000 deg.C. The reaction product is lowered to the cooling zone 4, cooled in an non-oxidative atmosphere, and discharged from the bottom of the cooling zone 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a method for producing ultrafine silicon carbide powder which is excellent as a raw material for producing sintered silicon carbide. The present invention relates to a method for producing silicon carbide powder.

The inventors first published the patent application in Japanese Patent Application Publication No. 2003-110003. Itx-33gqq and Japanese Patent Publication No. S5-Hiro 0327, proposed an invention relating to a method for producing silicon carbide mainly composed of β-type crystals, and developed the world's first industrial continuous production method of silicon carbide composed of β-type crystals. Established.

By the way, silicon carbide consisting of β-type crystals has recently been recognized to have extremely excellent properties when used as a raw material for producing pressureless sintered bodies, and according to the application, the finer the silicon carbide, the easier it is to sinter. Particularly fine particles are required because they have excellent cohesiveness and uniform shrinkage; for example,
According to Japanese Patent Publication No. 20θ, a β-type silicon carbide powder with a submicron particle size and a method for producing the same by plasma jet reaction from silicon halides and hydrocarbons, and a method for producing the same, are also disclosed in Japanese Patent Application Laid-Open No.
Publication No. 7599 discloses a method for producing high purity β-type silicon carbide powder of less than 1 μm F obtained by thermally decomposing an organosilicon polymer compound. However, all of the starting materials used in the methods described in the above-mentioned publications are extremely expensive. A manufacturing method is not yet known.

By the way, there is a method for producing fine silicon carbide powder using silica and carbon as starting materials (-), for example, IFh Kosho Rij-/θ Ri No. 73 discloses an invention related to "Process for producing pigment silicon carbide". According to the invention, it is stated that in order to produce fine silicon carbide powder, it is important to use carbon powder as fine as possible.

The present inventors used extremely fine carbon powder for the purpose of producing fine silicon carbide powder using the method previously proposed by the present inventors! I tried to use it for historical purposes. However, in the method previously proposed by the present inventors, if extremely fine carbon powder with a specific surface area of i, 12/y or more is used, the crushing strength of the granular raw material in the reaction zone will significantly deteriorate and collapse, resulting in the reaction. It was discovered that stable continuous operation could not be performed due to deterioration of gas leakage in the area.

That is, the above method is a method in which a granular raw material made of silica and carbon is charged from the upper part of a vertical reaction vessel and the SiC conversion reaction is continuously carried out.The granular raw material disintegrates during handling and reaction. It is necessary that the material has the strength to be able to maintain its shape without breaking.Also, in order to produce fine silicon carbide powder, it is preferable to carry out the reaction at as low a reaction temperature as possible. The method of carrying out the continuous K SiC conversion reaction proposed by the inventors is difficult to use for the reasons mentioned above, and it is difficult to use a carbon powder bed with relatively coarse particle size and poor reactivity. This has the disadvantage that the reaction must be operated at a relatively high reaction temperature considering production efficiency and workability during operation.

Based on this viewpoint, the present inventors developed t! to improve the crushing strength in the reaction zone of granular raw materials using extremely fine carbon powder. ! After much research, I decided to apply for a special patent application in 1987-7! ;
, No. 32'1, when the raw material is granulated using extremely fine carbon powder as a starting material, a carbon-based binder containing an organic solvent-soluble component is used as a binder for one granular raw material, and the starting material is By using an organic solvent during mixing or granulation, it is possible to create a granular raw material that has strong crushing strength even in the reaction zone and can maintain its original shape, making it possible to produce silicon carbide powder consisting of extremely fine β-type crystals at low cost. An invention that can be easily and continuously manufactured, patent application filed in 1973
When granulating raw materials using extremely fine carbon powder as a starting material, the wettability between the carbon powder and a dispersion medium in which a carbon-based binder is dissolved is significantly improved. By using a surfactant that can be used as a granular material, it is possible to easily produce a granular raw material that has strong crushing strength even in the reaction zone and can maintain its original shape. Invention and patent application that allows continuous production at low cost and easily
According to No. 2g99, very fine carbon powder is used as a starting material and the raw material is granulated, and the carbon powder and a carbon-based binder are mixed using a dispersion medium or ( By mixing the carbon powder and the carbon-based binder using a dispersion medium and a surfactant, and then completely adding and mixing the silica and the carbon-based binder, the crushing strength is strong even in the reaction zone, and the initial The present invention proposes an invention that can easily produce a granular raw material that maintains its shape, and can inexpensively and easily continuously produce silicon carbide powder consisting of extremely fine β-type crystals.

By the way, according to the method described in 11J proposed by the present inventors, in order to produce a granular raw material that has sufficient crushing strength even in the reaction zone, a carbon-based binder is mixed in carbon powder and the carbon powder is mixed with each other. Since the carbon-based binder is blended in a relatively large amount, the carbon produced when the binder carbonizes binds the carbon powder to each other and forms coarse particles. This has the disadvantage that the product tends to contain relatively coarse silicon carbide powder due to the coarse particles.

The present inventors have further improved the method previously proposed by the present inventors to further reduce the amount of carbon-based binder used when producing granular raw materials using fine carbon powder,
Moreover, as a result of intensive research to improve the crushing strength in the reaction zone of granular raw materials, we have improved the wettability of the carbon powder to water when granulating the entire raw material using extremely fine carbon powder as a starting raw material. It was newly discovered that by using the above-mentioned granular raw material, a granular raw material with strong crushing strength and able to maintain its original shape even in the reaction zone has a surprising effect that could not be predicted at all. The present inventors have come up with the idea that silicon carbide powder consisting of extremely fine β-type crystals can be produced continuously at low cost and easily by using the method, and have completed the present invention.

That is, according to the present invention, the specific surface area of silica is /~1
A raw material prepared by blending carbon powder within the range of 0θo @2 / y and a carbon-based binder and forming it into granules is charged into the upper part of a reaction vessel having a preheating zone, a heating zone, and a cooling zone. The introduced raw material is brought to the heating zone while falling under its own weight in the pre-heating zone, and is heated horizontally within the heating zone to control the reaction temperature within the range of 1500 to 2000 ° C. to perform the SiO conversion reaction. In the method for producing ultrafine silicon carbide powder, the reaction product is lowered into a cooling zone and cooled in a non-oxidizing atmosphere, and then the reaction product is discharged from the lower part of the cooling zone of the reaction vessel, wherein the carbon powder is By mixing a material with good water-meltability with water at the latest before granulation, it is possible to prevent the granular raw material from collapsing during the reaction and to produce ultrafine silicon carbide powder. can.

Next, the present invention will be explained in detail.

A silicon carbide production reaction using silica and carbon as starting materials is generally represented by the following formula (1).

SiO2+3C-+SiC+YcO・・・・・・・・・
(1) However, in reality, the main generation mechanism is that SiO gas is generated according to the following formula (, 2), and the SiO
It is known that gas and carbon react according to the following formula (3) to produce silicon carbide.

5102 + O→SiO+CQ...4...
(2) SiO+ 2 C, -+ SiO+ Co...
- Output... (3) By the way, according to the present invention, the SiO gas generated by the above equation (, 2) is quickly subjected to the SIC reaction according to the above equation (3), and the partial pressure of the SiO gas in the reaction vessel is reduced. It is desirable not to increase the amount by that much.

This is because, in the present invention, when the SiO gas partial pressure in the reaction vessel increases, the above formula (
,? ) is relatively faster, but in this case, the reaction according to equation (3) is mainly a reaction in which SiC crystals grow and N11 becomes a dog, so under conditions of high SiO gas partial pressure, , it becomes difficult to obtain fine 810 particles, and in even more severe cases, a part of the SiO gas rises to the preheating zone and causes the reaction shown in the following equation (4'), (age, (A)). EIiO2,S occurs in the preheating zone.
i.

SiO, O, etc. are precipitated in a mixed state. Because the precipitates are sticky, the raw materials coagulate with each other, which significantly impedes the smooth movement and descent of the raw materials, which is the most important factor in the continuous production of silicon carbide, and makes stable continuous operation over a long period of time difficult. .

2 SiO→5102+Si・・・・・・・・・・・・
(/I)S10+CO-+SiO2+C...
(5) 3 SiO+ Co→25in2+ 5iC-1
・19. (B) According to the present invention, in order to suppress the increase in the SiO gas partial pressure and obtain extremely fine silicon carbide powder, carbon powder having a specific surface area of /~10oo@2/g is used. It is necessary to use The reason for this is that when the specific surface area is smaller than /@2/f, there are fewer places where the reaction according to the above formula (3) occurs, and the reaction that produces S1C due to crystal growth is the main reaction, which is not suitable for the purpose of the present invention. It is difficult to produce fine silicon carbide powder,
On the other hand, 10θOm2/? Carbon powder with a larger specific surface area is considered to be extremely suitable from the viewpoint of reactivity, but such carbon powder is not only difficult to obtain, but also has an extremely low bulk specific gravity, so it cannot be used in granular materials. Carbon powder has the disadvantage of high porosity and extremely low crushing strength, but carbon powder in the range of 10-soo@2/y is relatively easy to obtain, and it is possible to obtain favorable results. can.

The carbon powder is mainly contact black.

Furnace Black, Thermal Black, Rumph.

It is preferable to use at least seven types of carbon black selected from blanks, but among them, thermal black is the most preferable since it can be made into a granular raw material with a low chain structure or chain structure of carbon black particles, that is, a structure with a high crushing strength. suitable.

According to the present invention, the silica has an average particle size of 20 to 70
It is advantageous to use those in the μm range. The reason is that the average particle size is smaller than 20 μm and the formula (3)
The reaction is extremely fast and it is difficult to maintain the SiO gas partial pressure low. On the other hand, if the thickness is larger than 70/Lm, the part where the silica was present becomes pores in the granules after the reaction, resulting in a decrease in crushing strength. This is because it has the disadvantage that the value becomes extremely low, and more suitable results can be obtained within the range of 30 to AO μm.

According to the present invention, compared to conventional raw materials, both silica and carbon powder (7) are used, which are fine and highly reactive, so silica and carbon powder are granulated to improve the permeability of the raw materials and react. It is effective to improve the outgassing of the CO gas that is sometimes produced to facilitate the reaction and to make the partial pressure of the SiO gas in the reaction vessel uniform.
It is advantageous that the bulk density of the φ9 particles is within the range of o, qo to 0°9θ7/-.

The reason why it is advantageous to set the porosity of the granules to 3s -, S-5tI) is that if the porosity is lower than the porosity, the permeability in the granules is poor and the reaction product gas is difficult to release. , the SiO gas partial pressure increases locally within the granules,
This is because the crystal grains tend to become coarse.On the other hand, it is preferable that the porosity is as high as possible in consideration of the release of the gas produced by the reaction, but if it is higher than the lampshade, the strength of the granules will be extremely low and one reaction will be difficult. This is because the granules are crushed in the container, resulting in a significant deterioration in air permeability.

The bulk density of the granules is 0.110-0.90? /cm
The reason why it is advantageous to set it within the range of 3 O is that a lower bulk density is preferable in terms of air permeability and other aspects;
In order to make the granules lower than 3, it is necessary to significantly increase the porosity of the granules, or to adjust the particle size of the granules to a narrow range.If the porosity is too high, as mentioned above, the porosity of the granules On the other hand, o, qo ? /ari", the permeability of the reaction product gas is poor and the flow of high-temperature gas in the preheating zone becomes uneven9, and not only is the heat exchange between the raw material and the high secondary gas insufficient, but also the This is because the particles are more susceptible to the influence of precipitates, inhibiting the smooth fall of their own weight and making it difficult to maintain long-term stable operation.The bulk density of the granules is θ, SO~θ,
The best results are obtained within the range of g0y/crti.

Also ? i Advantageously, the average particle size of the granules is in the range from 3 to 1 m/g. The reason for this is that if the average particle diameter of the granules is smaller than 3 dragons, there is almost no effect as a granule, while if it is thicker than 7 gm 7 W, the reaction rate within the granules becomes slow, making it uneconomical.

According to the present invention, it is extremely important that the granules maintain their original shape even when exposed to high temperatures in the reaction zone, and the carbon powder has improved wettability to water at the latest by the time it is granulated. It is necessary that it be something that is enforced. The reason for this is that the carbon powder used in the present invention, which has an extremely large specific surface area, usually exists in the form of a particle group in which many fine particles are aggregated, that is, in the form of primary particles, but the carbon powder in these secondary particles is The bond between them is not so strong, and simply granulating with a mixture of silica and a carbon-based binder produces a granule with crushing strength that can maintain its original shape without collapsing even in the reaction zone. It was extremely difficult to make it into grain raw material. However, the above-mentioned carbon powder with improved resistance to water exhibits the surprising effect of making it possible to easily produce a granulated raw material that maintains crushing strength without collapsing even in the reaction zone. be.

It should be noted that, although it is not yet possible to obtain crushing strength that does not collapse even in the reaction zone by using carbon powder with improved wettability against water as described above, In the drying process after wetting, the carbon powder with improved properties is attracted to each other by the surface tension of water, and its bulk density becomes relatively high. This has some effect on improving the crushing strength in the reaction zone. It is presumed that it is giving the following.

According to the present invention, the softness of the carbon powder in water can be improved by uniformly mixing a surfactant with the carbon powder or by heating the carbon powder in an oxidizing atmosphere to oxidize the powder particle surface. It is preferable to improve.

According to the invention, the surfactant is an amine.

It is preferable to use at least 7 types selected from organic compounds having a carboxyl group, organic compounds having a sulfo group, esters, ammonium compounds, organic compounds having an ether bond, 9 alcohols, such as fatty acid salts, alkylbenzenesulfonic acids, etc. salt, linear alkylbenzene sulfonate, α-olefin sulfonate, naphthalene-formalin condensate sulfonate, polyoxyethylene alkylphenyl ether, ia.

There are various other alcohols, and these can be used alone or in combination.

According to the present invention, the amount of the surfactant added is 1/1 of the carbon powder.
Preferably, the amount is at least 0.00 parts by weight to 0.00 parts by weight. The amount of the surfactant added is O, OS
If the amount is less than 1 part by weight, the wettability of the carbon powder with water will be insufficiently improved and the crushing strength of the granular raw material in the reaction zone will be weak and the granular raw material will collapse in the reaction zone, and it is not economical to add too much. However, it is advantageous to keep the content to less than 0.7 parts by weight, and most preferably from 0.7 to 3 parts by weight.

According to the present invention, a method for uniformly mixing a surfactant into carbon powder is to add a surfactant in the form of an aqueous solution when mixing a mixture of silica, carbon powder, and a carbon-based binder. A method of simultaneously blending silica, carbon powder, a carbon-based binder, water, and a surfactant, or a method of adding a surfactant and water to the carbon powder before blending the silica and carbon-based binder. The surfactant can be uniformly mixed with the carbon powder by any of the mixing methods.

According to the present invention, the heating temperature when heating carbon powder in an oxidizing atmosphere to oxidize the powder particle surface is at least 2.
00° C. and advantageously a heating time of 0.5 hours or more. The reason is that the heating temperature is
If the heating time is lower than 200°C, it is difficult to oxidize the particle surface of the carbon powder, and if the heating time is shorter than the O, S time, the yield is likely to be insufficient, and the wettability to water can hardly be improved. It is from. If the heating temperature is too high, the oxidative consumption of the carbon powder will be significant, so it is advantageous to keep the heating temperature below 100°C or to control the amount of oxygen in the atmosphere.

According to the invention, it is advantageous to include water vapor in the oxidizing atmosphere. The reason for this is that - by including water vapor in the atmosphere, oxidation of the surface of carbon powder particles can be promoted, and the wettability of carbon powder to water can be efficiently improved even at relatively low temperatures. It is.

According to the invention, the oxygen content of the carbon powder is preferably at least 00.2% by weight. The reason is,
If the oxygen content of the carbon powder is less than O9.2% by weight, the carbon powder's wettability with water is not so good and it is difficult to form a granular raw material that maintains crushing strength without collapsing even in the reaction zone. This is because carbon powder with an excessively high oxygen content is not only extremely difficult to produce, but also has poor yield as a carbon source. be.

According to the present invention, the blending amount of the carbon-based binder is preferably within the range of 3 to 3 parts by weight in terms of fixed carbon amount based on a total of 700 parts by weight of silica and carbon powder. The reason for this is that if the amount is less than 3 parts by weight, the crushing strength of the granular raw material in the reaction zone will be low and the product will easily collapse in the reaction vessel, while if it is more than 3 parts by weight, the cost required for the binder will increase. This is because the amount of carbon produced by thermal decomposition of the binder increases, making it easier to produce coarse silicon carbide particles. The best results are obtained within the range of -20 parts by weight.

According to the present invention, the carbon-based binder is selected from petroleum pitch, coal cour pitch, wood tar pitch, asphalt, phenol M fat, petroleum tar, coal coeur, wood tar, sugar, lignin sulfonate, and alginate. Preferably, at least one of the following is selected:
Among them, petroleum pitch, coal tar pitch, wood tar pitch, asphalt, phenol m fat, petroleum tar,
Poorly water-soluble carbon-based binders such as coal tar and wood tar do not disperse much into the secondary particles of carbon powder, so the yield is good and suitable results can be obtained with a small amount of use.
On the other hand, easily water-soluble carbon-based binders such as phenolic resins, sugars, lignin sulfonates, and alginic salts are advantageous because they can be cooled in the form of aqueous solutions during granulation.

According to the present invention, in producing fine silicon carbide powder,
It is effective to increase the amount of carbon in the raw material to increase the number of locations where the reaction of formula (3) occurs, and to suppress the increase in the SiO gas partial pressure. /5102 molar ratio 3°, 2-y,
Advantageously, it is in the range 0.

According to the present invention, the blend of silica, carbon powder, and carbon-based binder is mixed thoroughly and homogeneously, and then, for example, a pan-type granulator, a drum-type granulator, a horizontal vibration-type granulator, a briquette, etc. It is granulated by a granulator such as a machine or a fluidized mixing granulator.

According to the present invention, it is preferable to add 7 to 8 parts by weight of water to 700 parts of the blend before or during granulation of the blend. If the amount of water added is less than 7 M parts, the water content in the granular raw material becomes uneven, making it difficult to maintain the crushing strength in the reaction zone, whereas if it is added in an amount greater than 3 parts by weight, This is because it is not only difficult to uniformly granulate the compound, but also the granular raw materials may deform during handling or stick to each other and become lumpy, so it is particularly preferable to use a powder in the range of 70 to J parts by weight. results.

According to the invention (/'C), the granular raw material is charged from the top of a reaction vessel having a pre-heating zone, a heating zone, and a cooling zone, and the charged raw material is passed through the pre-heating zone continuously or intermittently. The reaction product is allowed to fall under its own weight until it reaches a heating zone, and is heated horizontally within the heating zone to carry out the SIC reaction.Then, the reaction product is lowered to a cooling zone, and after being cooled under a non-oxidizing atmosphere, Silicon carbide is produced by continuously or intermittently discharging the reaction product from the lower part of the cooling zone of the reaction vessel.

According to the present invention, in producing extremely fine silicon carbide powder, the reaction temperature in the heating zone is set at 7500 to 2000°C.
It is necessary to control the amount within the range.

The reason for this is that if the AfJ reaction temperature is lower than 7500°C, the reaction rate shown by the above formula (2) is extremely slow and it becomes difficult to efficiently produce silicon carbide, i4 powder. On the other hand, if it is higher than 2000'c, silicon carbide once formed is likely to undergo crystal growth, making it difficult to form extremely fine β-type silicon carbide, which is the object of the present invention.

However, the above reaction temperature is -C lower than the reaction temperature required in the conventional continuous production method of silicon carbide invented and proposed by the present inventors, and requires less energy for operation. It also has the advantage of significantly improving the durability of equipment.

Next, seven examples of mold-making devices directly used for carrying out the method of the present invention will be explained with reference to the drawings.

As shown in the figure, the apparatus directly used for carrying out the method of the present invention has a raw material charging inlet, a preheating zone, a heating zone 3, a cooling zone, and a sealable product outlet S, which are arranged vertically. A reaction vessel B is connected to a reactor vessel B, in which the barrel forming the heating zone is made of graphite, and is equipped with means g and 9 for indirectly heating the charge in the heating zone, and at least the heating zone is It has a heat insulating layer made of carbon or graphite on the outside of the tropics.

The reaction vessel B is installed in the center of the apparatus, and the indirect heating means g and 9 are surrounded by a graphite heating element and a graphite reflector tube provided close to the outside of the heating element. Non-oxidizing gas inlet//for example Ar, He, N2
．． CO, N2. Other non-oxidizing gases are enclosed, 9
Oxidative wear and tear of the graphite heating element due to air intrusion is prevented.

The present invention will now be described with reference to embodiments.

Example 1 Tumul black powder (F) with a specific surface area of 23 m2/2
, C, - weight, 5 weight part) polyogyzoethylene alkylphenyl ether/, 57 [Okipart and water/θθ weight? After thoroughly mixing using a fret mill, the mixture was dried at 0.degree. C. until it became a wet powder. The thermal black powder has an average particle size of
mto Silica m powder (5io2-qq, g weight%
)/AJ'R, ii, ttfj Mitakavia Chil,) End (F, O, == jO,'l Weight%, &/%μm
F-100%)! ; and 3 parts by weight were added and mixed thoroughly. Next, the mixture was put into a pan-type granulator and granulated while spraying a 095% CMG aqueous solution, and then put into a band-type ventilation dryer and dried with hot air at /so° C. for 90 minutes. The water content contained in the granular raw material before drying is about 72% by weight, and the granular raw material obtained by drying has an average particle size of //, Omm + a porosity of the granular material of
Particulate bulk density is 0.7 f/d, O/8402
The molar ratio was y,,o.

Next, this granular raw material is charged from the upper part of a vertical indirect heating furnace as shown in the figure, and the inside of the heating furnace is continuously lowered by its own weight to a heating zone where the reaction temperature is controlled to /qoo°C. The charge in the heating zone was reduced to 0. l-Oyl/
After the SiO conversion reaction was carried out by indirect heating in the horizontal direction while lowering the reactor by its own weight at a descending rate of hr, the reactor was lowered by its own weight into a cooling zone, and the reaction product was continuously discharged from the outlet.

The main uses of the indirect heating furnace used are shown in Table 1.

Table 1 After removing free carbon from the obtained reaction product, it was milled using an iron ball mill with an inner diameter of 2!1 cTLφ at a rotational speed of 11.
wet disintegration for 5 hours at 1 g rpm, then hydrofluoric acid 1
Free silica was removed and purified by immersion in a 0% aqueous solution for 3 hours. = The content of silicon carbide consisting of β-type crystals in the silicon carbide obtained by the purification was measured by X-ray diffraction method and had a coefficient of 9LlI, and its specific surface area was 3Q, g.
It was 7712/9. Furthermore, when the particle shape was observed using a scanning electron microscope, it was found that the particle shape was extremely round and the particle size was relatively uniform.

Example 2. Comparative Example 1 Granular raw materials were prepared in the same manner as in Example 1, but with different amounts of surfactant and water added as shown in Table 2.

The granular raw material was appropriately sampled, placed in a Tamman furnace in an argon gas atmosphere, and maintained at 7700°C for 7 hours to obtain a reaction product.

The physical properties of the obtained reaction product were measured in the same manner as in Example 1 and are shown in Figure 2.

All of the reaction products of Example 2 had sufficient crush strength to maintain their original shapes. On the other hand, the reaction product of Comparative Example 1-1 has a low crushing strength and is unsuitable for continuous operation. If there is too much, it will not be possible to granulate any of them. In addition, Comparative Example 1-4-, in which the porosity was reduced by increasing the transfer time during graining, had good crushing strength, but not only was the reactivity inferior, but also the diameter of the formed silicon carbide was coarse. It was recognized that the

The crushing strength of the product is a value measured by applying a static load to the product.

Example 3 Same as Example 1, but in place of polyoxyethylene alkyl phenyl ether, abata salt, alkylbenzene sulfonate, linear alkylbenzene sulfonate, α
-Olefin sulfonate.

Sulfonic acid salt of naphthalene-formalin condensate.

Granular raw materials were prepared using each of polyoxyethylene alkyl ether and polyoxyethylene nonylphenol ether, and a reaction product was obtained in the same manner as in Example 2.

All of the reaction products id had sufficient crushing strength to maintain their original shapes, and all of the silicon carbide powders obtained by purifying the reaction products were extremely fine.

Example 4 Same as Example 1, but channel black powder (specific surface 41<=/, !g m2/?) was used as the carbon powder.
+F, C, -9g, /weight ratio) was used to prepare a 'CC-shaped raw material, and a reaction product was obtained.

The physical properties of the obtained reaction product were measured in the same manner as in Example 1. What was the content of silicon carbide consisting of β-type crystals?
A, /H, and its specific surface area is 1. +,,2/f
It is recognized that this is the case. Zuta Misao-kun, you spoke in a very sloppy manner.

Example 5 Same as Example 1, but the reaction temperature/q00°C was controlled higher than in Example 1, and the F rate of the charge was reduced to 0. g
The reaction product was obtained at a rate of Om/hr.

The physical properties of the obtained reaction product were measured in the same manner as in Example 1. The results are shown in Table 2, and although the specific surface area of the silicon carbide powder was slightly smaller at 2q, 3@2/y, the dead weight of the charge was falling smoothly and stable continuous operation was possible for a long period of time. The production capacity per unit of equipment was high.

Example 6 Same as Example 1, but using granulated sugar, 51Jli instead of polyoxyethylene alkyl phenyl ether.
Novolac type phenolic resin (F, C, -5/
, 6-fold'l? A granular raw material was prepared using Example 1), and a reaction product was obtained in the same manner as in Example 1.

The crushing strength of the reaction product was 7 kg, which was slightly higher than that of the reaction product obtained in Example 1.

- Furthermore, the silicon carbide powder obtained by purification was extremely fine and fully satisfied the purpose of the present invention, and the operation could be carried out stably for a long time.

In addition, the C/51o2 molar ratio in the granular raw material was adjusted to be 0.0 and 0.0.

Example 7 Cernle Black powder 1 similar to that used in Example 1
0θ weight part and silica powder similar to that used in Example U/
63 parts by weight, 53 parts by weight of the same high pitch powder used in Example 1, 111 parts by weight of ethylene glycol, and 15 parts by weight of water.
0 parts by weight were sufficiently mixed using a fret mill, and then a granulated raw material was prepared in the same manner as in Example 1.

A reaction product was obtained in the same manner as in Example 1 using the granular raw material.

The physical properties of the obtained reaction product were measured in the same manner as in Example 1. The results are shown in Table 2.

The operating conditions of Example 7 were extremely stable, and continuous operation was possible for a long period of time.

Example 8 The same thermal black powder as used in Example 1 was used.
The sample was placed in a furnace maintained at 230°C and heat-treated in an air atmosphere for several hours. The thermal black powder after the heat treatment has a specific surface area x7712/y and an oxygen content fjt of about 0.
．． 37 in terms of weight, and the wettability to water was good.

700 parts by weight of the thermal black powder, 63 parts by weight of the silica powder used in Example 1, and 53 parts by weight of the high pitch powder used in Example 1 were thoroughly mixed using a Nauta mixer, and then mixed in the same manner as in Example 1. The granulated raw material was prepared by the method.

A reaction product was obtained in the same manner as in Example 1 using the granular raw material.

The physical properties of the obtained reaction product V were measured in the same manner as in Example Y, and the content of silicon carbide consisting of β-type crystals was 9A! ;%, and its specific surface area was found to be 35.2 m2/2.

Example 9. Comparative Examples 2 and 3 Granular raw materials were prepared in the same manner as in Example 8 using the same method as in Example 8, but using thermal black powder that had been heat treated by changing the heat treatment conditions as shown in Table 3. A reaction product was obtained in the same manner as in Example 2.

All of the thermal black powders of Example 9 had good wettability with water, and the reaction products had sufficient crushing strength to maintain their original shapes. On the other hand, the thermal black powder of Comparative Example 2 which was not subjected to heat treatment hardly got wet with water, and the reaction product collapsed during the EiiO reaction. Unfortunately, in Comparative Examples 3-1 and 3-2, the heat treatment was insufficient and the water wettability was not improved that much, and the reaction product vlJ collapsed and froze in the same way as in Comparative Example 2. Ta. In addition, in Comparative Example 3-3, there was only one ignition during the heat treatment.

As described above, according to the present invention, ultrafine silicon carbide powder with an average particle size larger than 7 μm and an extremely large specific surface area (T1) suitable for producing a pressureless sintered body of silicon carbide can be easily produced in high yield. It is easy to manufacture, and its contribution to production is extremely large.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view of a vertical continuous manufacturing apparatus used in an example of the present invention. l... Raw material charging port, U... Preheating zone, 3... Heating zone, D... Cooling zone, S-... Product discharge port, 6... Reaction vessel, 7... Processing Cylinder forming the tropics, g... graphite heating element, D... graphite reflective tube, 10... heat insulating layer, /
c. Non-oxidizing gas charging port, /2... Guide electrode, /3
...Flexible conductor, //I...Bus bar, /3...
Temperature measurement pipe, /6... Outer shell, /7... Firebrick,
1g...exhaust duct), /q...raw material hot. Patent applicant: Ibiden Co., Ltd. Representative Patent Attorney Mura [1 Politics]

Claims (1)

[Claims] 11 Noriyoku powder and specific surface area of /~1000rrL2
A raw material prepared by blending carbon powder and a carbon-based binder within the range of is brought to the heating zone while falling under its own weight in the pre-heating zone, and heated horizontally in the heating zone to bring the reaction temperature to 7500~2θ.
The SiC conversion reaction is carried out by opening the side 1 within the range of θO゛C, and then the reaction product is lowered into a cooling zone and cooled in a non-oxidizing atmosphere. In the method for producing ultrafine silicon carbide powder in which the product is discharged, M carbon powder having good wettability with water is used by mixing it with water at the latest before granulation. A method for producing ultrafine silicon carbide powder characterized by preventing disintegration of granular raw materials 1.2,
%J carbon powder is mainly contact black, furnace black, and thermal black. The manufacturing method according to claim 1, wherein at least seven types are selected from lamp blacks. 3. The manufacturing method according to claim 1 or 2, wherein the carbon powder has improved wettability with water by uniformly mixing it with a surfactant. 4. The surfactant mentioned above is an amine, an organic compound having a carboxyl group, an organic compound having a sulfo group, an ester,
The manufacturing method according to claim 3, wherein at least seven types are selected from ammonium compounds, organic compounds having an ether bond, and alcohols. 5. The manufacturing method according to claim 3 or 4, wherein the amount of the surfactant added is at least θ, θS parts by weight per 100 parts by weight of carbon powder. 6. The manufacturing method according to any one of claims 3 to 5, wherein after uniformly mixing the carbon powder, surfactant, and water, silica and a carbon-based binder are blended and mixed. 7. The manufacturing method according to claim 1 or 2, wherein the carbon powder is heated in an oxidizing atmosphere to oxidize the powder particle surface to improve its wettability with water. a The heating temperature in the oxidizing atmosphere is at least 2
The manufacturing method according to claim 7, wherein the temperature is 00°C. 9. The manufacturing method according to claim 7 or 8, wherein the oxygen content of the carbon powder is at least a2 weight ratio. 10. Any one of claims 1 to 9, wherein the blending amount of the carbon-based binder is within the range of 3 to 100 parts by weight in terms of fixed carbon amount, based on a total of 100 parts by weight of silica and carbon powder. The manufacturing method described in Crab. 11. The carbon-based binder is selected from petroleum pitch, coal tar pitch, wood tar pitch, asphalt, phenol resin, furan resin, oil tar, coal tar, wood tar, ill, genine sulfonate, and alginate. The manufacturing method according to any one of claims 1 to 10, wherein at least 7 types of