JPH04349113A - Production of carbon material - Google Patents

Abstract

PURPOSE:To efficiently produce a self-sintering granular carbon material and a carbon fiber. CONSTITUTION:A nozzle to be used has a passage 14 for the nonoxidizing gas and pitch and the passages 15a and 15b for the nonoxidizing gas arranged around the passage 14. When a granular carbon material is produced, the heat- treating pitch is heated 100-150 deg.C higher than its softening point, and the nonoxidizing gas is supplied at the flow rate of 3.0-3.5Nm<3> per kg pitch. When a fibrous carbon material is produced, the heat-treating pitch is heated 20-90 deg.C higher than its softening point, and the nonoxidizing gas is supplied from the rear end of the nozzle at the flow rate of 3.0-5.5Nm<3> per kg pitch. The nonoxidizing gas and pitch passed through the passage 14 and the nonoxidizing gas passed through the passages 15a and 15b are joined at the nozzle tip and mixed to form granular or fibrous pitch. The pitches are oxidized.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention relates to a fibrous carbon material useful as various reinforcing materials and a self-sintering particulate material which is a raw material for high-density isotropic carbon material. The present invention relates to a method for manufacturing carbon materials using the same equipment. [0002] High-density isotropic carbon materials are used as electrode materials for electrical discharge machining, crucible materials for aluminum deposition, wall materials for nuclear fusion reactors, and the like. This high-density isotropic carbon material is
Generally, it is manufactured by finely pulverizing petroleum-based coke or coal-based coke into aggregate, adding a binder to the aggregate, and molding the aggregate. Cold isostatic pressing (CIP) is usually used for molding in order to homogenize the properties. The obtained molded body was heated and carbonized at a very slow temperature increase rate of 1 to 10°C/hour, and then heated to a temperature of 2000 to 300°C/hour.
Graphitized at 0°C. [0003] In contrast to the above-mentioned binary raw materials using aggregate and binder pitch, self-sintering raw materials have recently been developed that have both filler and binder functions.
This makes it possible to produce a more homogeneous high-density isotropic carbon material. Bulk mesophase is known as such a self-sintering carbon material. This bulk mesophase contains 350% petroleum-based or coal-based pitch.
It is obtained by heat treatment in the range of .degree. C. to 500.degree. C., and an optically anisotropic structure (liquid crystal) is developed throughout. Finely pulverized material is used as a raw material for high-density isotropic carbon material. This bulk mesophase maintains self-sintering properties and fuses itself together during molding, so there is no need to add a binding agent such as a binder. [0004] Mesocarbon microbeads (MCB) are also known as self-sintering carbon raw materials (see, for example, Japanese Patent Laid-Open No. 49-2379). MCBs are optically anisotropic microspheres with a diameter of about 10 μm that are produced in the process of heat treating various pitches. When the pitch is heat treated, MCB is precipitated into an optically isotropic pitch matrix. If this MCB continues to be heated, it will coalesce into a bulk mesophase, so the heat treatment is stopped at the stage where minute MCBs have precipitated.
Add a large amount of solvent to this and take out the MCB. In addition, in order to further improve the self-sintering property of this MCB, when taking out the MCB from the matrix pitch with a solvent, a part mainly consisting of the β component consisting of the quinoline-soluble part of the matrix pitch is attached to the surface of the MCB. has also been proposed (see Japanese Patent Laid-Open No. 62-41707). In any case, MCB can be used as a raw material for high-density isotropic carbon material without being pulverized. On the other hand, carbon fiber has higher specific strength and specific modulus than other fibers, and has good heat resistance, electrical conductivity, chemical resistance,
It has excellent lubrication and sliding properties, and is widely used in the aerospace field, vehicle field, sports field, and general industrial field. Carbon fiber is mostly used as a structural material, and is also used as a reinforcing material, a functional material, a heat insulating material, and a carbon material. The manufacturing method of carbon fiber is polyacrylonitrile (PAN
), methods that use organic fibers such as rayon, cellulose, phenol formaldehyde, and lignin as raw materials, and methods that use petroleum-based or coal-based heavy oil or pitch as raw materials. [0006] In methods using organic fibers, PAN fibers obtained by wet spinning or melt spinning are used exclusively. This PAN fiber is first infusible at 200 to 300°C. Carbon fibers are obtained by carbonizing and firing the infusible PAN fibers at a temperature of up to about 1000°C and, if necessary, further graphitizing them at a temperature of up to 3000°C. In the method using heavy oil or pitch as a raw material, the raw material is first heat-treated to obtain pitch having a predetermined softening point, and this pitch is spun into pitch fibers. The obtained pitch fibers are oxidized to make them infusible, and then heated to about 1000°C.
Carbon fibers are obtained by firing at a temperature of up to 3,000° C. and graphitizing at a temperature of up to 3,000° C. The pitch-based carbon fiber obtained in this way generally has a higher elastic modulus than that of the PAN-based carbon fiber. Since pitch-based carbon fibers are inexpensive raw materials, they are sometimes produced as short fibers in addition to long fibers that exhibit high performance and high elastic modulus. Short fibers have inferior performance compared to long fibers, but because they can be manufactured at low cost, they are used in general-purpose fields such as architecture and civil engineering. [0008] The production of pitch-based short carbon fibers can be roughly divided into two methods in terms of the spinning method. One method is centrifugal spinning, in which heat-treated pitch is fed onto rotating disks or rolls to produce fibers up to about 30 cm long. Another method is a melt-blowing method in which pitch is blown out from a nozzle and, at the same time, the blown pitch is brought into contact with a gas to apply shear to form fibers. Melt blowing has also been adopted commercially as an economical method. Regarding this method, for example, JP-A-58-
Publication No. 57374 is related to the production of glass fibers, but involves blowing high-temperature gas from surrounding gas nozzles onto molten glass flowing down from an orifice, causing the flow of glass to rotate around its central axis to form a swirling flow. It is disclosed that the fiber diameter can be stretched thinly by stretching the fibers. Application of this method to the spinning of short carbon fibers is disclosed in JP-A-62-263359. Furthermore, in JP-A-63-210042, in order to obtain straighter carbon short fibers, pitch is flowed out from an outlet nozzle with an opening diameter of 0.1 to 1.0 mm, and 300 to 40
It is disclosed that high-temperature gas at 0° C. is sprayed from a nozzle with an opening diameter of 0.2 to 1 mm. The gas blowing angle is 10 to 20 degrees with respect to the central axis of the outflow nozzle, and the flow rate is 480 to 520 m/sec. [0009] As mentioned above, it has been proposed to use MCB as a raw material for high-density isotropic carbon materials, but MCB is The heat treatment must be stopped before coalescing into bulk mesophase. Therefore, a yield of only 40% can be achieved at most, and it cannot be said to be an efficient method for producing a self-sintering raw material. It is also necessary to dilute the obtained MCB-containing pitch with a large amount of solvent to separate the MCB from the matrix pitch. Producing self-sintering raw materials by such complex and low-yield methods is expensive to produce. [0010] Therefore, if the melt-blowing method, which has been commercialized as an economical method for producing carbon fibers, can be applied to the production of microsphere pitch equivalent to MCB, microsphere pitch can be produced efficiently. You can expect it. However, it has been found that the conventional melt-blowing method for producing short carbon fibers is unable to apply sufficient shearing force to the pitch to obtain fine particles. [0011] Accordingly, an object of the present invention is to provide a method for efficiently producing a self-sintering particulate carbon material and carbon fibers, which are raw materials for a high-density isotropic carbon material, from pitch. Means and Effects for Solving the Problems The present inventors efficiently produce a self-sintering particulate carbon material that is a raw material for a high-density isotropic carbon material, and also produce a fibrous particulate carbon material. We have intensively researched methods for producing carbon materials. As a result, certain 2
By using a fluid nozzle to supply heat-treated pitch and non-oxidizing gas, and setting the supply temperature of the heat-treated pitch and the supply ratio of non-oxidizing gas to the heat-treated pitch within predetermined ranges, particle-like It has been found that pitch and fibrous pitch can be obtained. A self-sintering particulate carbon material and a fibrous carbon material are obtained by subjecting the obtained particulate pitch and fibrous pitch to oxidation treatment. That is, according to the present invention, there is provided a first channel through which non-oxidizing gas and pitch flow, and a plurality of channels arranged around the first channel through which non-oxidizing gas flows. 2
When manufacturing a self-sintering particulate carbon material using a nozzle having a flow path, the heat-treated pitch is heated to a temperature of 100° C. to 150° C. higher than its softening point in the first flow path. and non-oxidizing gas at a rate of 6.5 kg per 1 kg of the pitch.
When producing a fibrous carbon material, the first stream is supplied at a flow rate of 0 to 12.0 Nm3 from the rear end of the nozzle at a temperature of 20 to 90 degrees Celsius higher than its softening point. A non-oxidizing gas is supplied from the rear end of the nozzle at a flow rate of 0.5 to 5.0 Nm3 per 1 kg of the pitch, and the supplied non-oxidizing gas is fed into the second flow path. The non-oxidizing gas and pitch that have passed through the first flow path and the non-oxidizing gas that has passed through the gas flow path are merged at the tip of the nozzle. - A method for producing a carbon material is provided, which comprises mixing and oxidizing particulate or fibrous carbon pitch taken out from the tip of the nozzle. The present invention will be explained in more detail below. The raw material pitch used in the present invention may be made from either coal-based residual oil or petroleum-based residual oil. The Mettler softening point of raw material pitch is usually 40°C or higher, 250°C.
℃ or less, more preferably 80℃ to 150℃
It is ℃. If the softening point is below the above range, the yield of heat-treated pitch will decrease when heat-treated later. Furthermore, if the softening point exceeds the above range, the pitch will require a considerably high temperature for melting, and therefore will tend to be difficult to handle in a reaction tank or the like. Although the raw material pitch is heat-treated to adjust its softening point, it may be subjected to hydrogenation treatment before the heat treatment. As is known per se, pitch hydrogenation is carried out under pressure of hydrogen gas at a temperature of 350 to 450°C.
This can be done by processing the pitch for up to 3 hours. As a catalyst, a Ni, Co or Mo based catalyst, red mud, sulfur or the like can be used. Alternatively, hydrogenation can also be carried out by mixing a hydrogen-donating solvent and pitch and treating at a temperature of 350 to 450°C for up to 3 hours. This latter hydrogenation can be carried out either under atmospheric pressure or under increased pressure, each with its own effects. Regardless of the hydrogenation method, if a temperature lower than the above temperature range is used, sufficient hydrogenation cannot be achieved, and if a temperature higher than the above temperature range is used, the added hydrogen may be separated again. As a result, the desired hydrogenation cannot be achieved. [0016] The raw material pitch, both hydrogenated and non-hydrogenated, is heat-treated so that its softening point is 250°C or higher and 400°C or lower. In particular, when obtaining fine particles in the present invention, this heat treatment is preferably performed so that the softening point of the pitch is 270 to 350°C. By having such a softening point, the residual carbon yield during carbonization firing is further improved, and the obtained granular pitch further retains appropriate binder properties. The heat-treated pitch is supplied to the nozzle of the present invention to form fine particles or short fibers. An example of the nozzle used here is shown in FIGS. 1 and 2. FIG. 1 is a longitudinal sectional view of the nozzle, and FIG. 2 is a sectional view along line II-II in FIG. The illustrated nozzle 10 has a cylindrical casing 12 defining an interior area, and a cylindrical body 1 inside the casing 12.
3 are closely spaced. Penetrating the central part of the cylindrical body 13 in the axial direction,
A first pipe with a circular cross section through which non-oxidizing gas and heat-treated pitch flow.
A flow path 14 is provided, and around it are two second flow paths 15a and 15b through which non-oxidizing gas and heat treated pitch flow. The first channel 14 can have an opening diameter of 0.5 to 6 mm, and in this example has an opening diameter of 1.0 mm. Moreover, the second flow paths 15a and 15b
The total opening area of is 1 to 10 of the opening area of the first flow path.
It can be double. In this example, the channels 15a and 15b are
Each has an opening diameter of 2 mm. In addition, the shortest distance between the first flow path and one of the second flow paths (partition walls 13a, 13
b) is, for example, 1.5 mm or less. And bulkhead 1
3a and 13b extend from the cylindrical body 13 to the vicinity of the tip wall of the casing 12. In the middle of the flow path 14, the flow path 14
A pitch supply path 16 for supplying heat-treated pitch is provided in communication with the pitch. A chamber 18 is defined between the rear end of the casing 12 and the cylindrical body 13, into which a non-oxidizing gas flows, which is supplied from a gas introduction port 17 provided at the rear end of the casing 12. From the gas inlet chamber 18, the gas is distributed into the first and second flow paths. The distance between the rear end of the casing 12 and the cylindrical body 13 is, for example, 1
It is 0 mm to 20 mm, and in the case of this example, it is 15 mm. Furthermore, the tip of the casing 12 and the cylindrical body 13
A chamber 19 is defined between them, where the non-oxidizing gas and pitch that have passed through the first flow path 14 and the non-oxidizing gas that has passed through the second flow paths 15a and 15b meet and mix. There is. The distance between the tip of the casing 12 and the cylindrical body 13 is
For example, it is 0.5 mm to 20 mm, and in this example, 1
It is 2mm. The heat-treated pitch mixed in the merging/mixing chamber becomes particulate or fibrous according to the conditions described in detail below, and is ejected from the outlet 20 provided at the tip of the casing 12. The diameter of the outlet 20 is, for example, 1
mm to 10 mm, and in this example, it is 6 mm. Now, in order to produce a carbon material according to the present invention, the heat-treated pitch is transferred from the pitch supply path 16 to the flow path 14,
A non-oxidizing gas is supplied from the gas introduction port 17 to the gas inflow chamber 18 . At this time, when producing particulate carbon material, the heat-treated pitch should be lowered by 1 point below its softening point.
The temperature is 00°C to 150°C higher, and the non-oxidizing gas is supplied at a flow rate of 6.0 to 12.0 Nm3 per 1 kg of heat-treated pitch. In addition, when manufacturing fibrous carbon materials, the heat-treated pitch should be heated to 20°C to 90°C above its softening point.
Heat treatment pitch of 1k by supplying non-oxidizing gas at high temperature
Supplied at a flow rate of 0.5 to 5.0 Nm3/g. In either case, the supplied non-oxidizing gas is distributed into the first flow path 14 and the second flow paths 15a, 15b due to the orifice effect. Then, the non-oxidizing gas and pitch that have passed through the first channel 14 and the non-oxidizing gas that has passed through the gas channels 15a and 15b are combined in the merging/mixing chamber 19, and the two are mixed. , according to the above supply conditions, sufficient shearing force is applied to obtain particles, or sufficient spinning force is applied to obtain fibers,
As a result, particulate or fibrous pitch is ejected from the outlet 20. FIG. 3 shows another example of the nozzle used in the present invention. This nozzle has a flow path 14 and a flow path 15.
The partition walls 13a and 13b between the partition walls 13a and 15b extend into the opening 20 with a gap from the opening 20, and their tips are in the same plane as the outer wall of the casing defining the opening 20, as shown in FIGS. It has the same configuration as the nozzle described in connection with No. 2. When this nozzle is used, the non-oxidizing gas and pitch that passed through the first channel 14 and the non-oxidizing gas that passed through the gas channels 15a and 15b merge at the nozzle tip (near the outlet). and a mixture of the two takes place;
Particulate or fibrous pitch is obtained according to the respective production conditions described above. The non-oxidizing gas may be an inert gas such as nitrogen, a combustion exhaust gas such as carbon dioxide, or heated steam. The temperature of the non-oxidizing gas to be supplied is preferably from room temperature to 800°C. This is because when the temperature exceeds 800°C, normal piping materials cannot be used. A preferable supply temperature of the non-oxidizing gas is 400 to 650°C. [0026] It is convenient to oxidize the fine particulate pitch and fibrous pitch thus obtained at the same time in the same oxidation treatment apparatus in an oxidizing atmosphere. As such an apparatus, a tunnel dryer that can process both fine particle pitch and fibrous pitch, which are powders, can be used. The oxidizing atmosphere within the device can consist of air or oxygen. Oxidation treatment temperature is 180-350
°C is preferred. In the case of fine particle pitch, below this temperature range, sufficient oxidation cannot be achieved; on the other hand, above this temperature range, oxidation tends to proceed too much and sufficient adhesion performance of the particles cannot be ensured. In addition, in the case of pitch fibers, if the temperature is below this range, the surface will not be sufficiently oxidized and will melt during the subsequent carbonization process.On the other hand, if this temperature range is exceeded, the surface oxidation will progress too much and the subsequent carbonization process will not work. Fiber strength tends to decrease. Note that the carbonization and graphitization treatments can be performed by conventional methods. According to the above-described method for producing a carbon material of the present invention, by appropriately changing the supply temperature of heat-treated pitch and the supply ratio of non-oxidizing gas to the heat-treated pitch, particulate carbon material and fibrous carbon can be produced. Materials can be efficiently manufactured at any time. According to the present invention, an average particle size of 10
It is possible to produce a fine particle carbon material of about μm size and a fibrous carbon material with an average diameter of about 10 μm and an average length of about 5 cm. In addition, for any carbon material, since almost the entire amount of the supplied pitch is obtained as each carbon material except for the volatile content of the pitch, the yield is also extremely good. [0028] Example 1 [0029] Pitch having a softening point of 120°C by the Mettler method was heat treated to adjust the softening point to 335°C. This heat-treated pitch was supplied to a nozzle having the structure shown in FIGS. 1 and 2 at a rate of 2 kg per hour at 380°C. Further, as a non-oxidizing gas, nitrogen gas was heated to 600° C. and supplied to the nozzle at a flow rate of 3.6 Nm 3 per hour. thus,
The desired fibrous pitch was obtained. This fibrous pitch is 320
After oxidation treatment at 1000°C, carbonization treatment was performed at 1000°C to obtain carbon fibers. When the tensile strength and tensile modulus of the obtained carbon fibers were measured, the results shown in Table 1 below were obtained. In addition, the same table also shows measured values for commercially available short carbon fibers as Comparative Example 1. table
1 Comparison of properties of short carbon fibers
Evaluation number Fiber diameter Tensile strength Tensile modulus
(Average) (Average) (Average) Example 1
28 pieces 15.2μm 87.3k
g/mm2 8.1 T/mm2
Comparative example 1 27 pieces 15.8 μm
60.7 kg/mm2 2.4 T/mm
2 Example 2 Pitch having a softening point of 120°C determined by the Mettler method was heat treated to adjust its softening point to 303°C. This heat-treated pitch was supplied to a nozzle having the structure shown in FIGS. 1 and 2 at a rate of 2 kg per hour at 420°C. Further, as a non-oxidizing gas, nitrogen gas was heated to 600° C. and supplied to the nozzle at a flow rate of 9.1 Nm 3 per hour. In this way, desired finely divided pitch was obtained (average particle size 10 μm). This fine particle pitch was oxidized at 250° C., then filled into a rubber mold and subjected to CIP molding. Furthermore, carbonization treatment and black smoke treatment were performed by conventional methods to produce a high-density isotropic carbon material. When the bulk density and bending strength of the obtained carbon material were measured, the results shown in Table 2 below were obtained. Table 2 Physical properties of high-density isotropic carbon material
The bulk density
Bending strength Example 2
1.95 g/cm3 950 kg
[Effect of the Invention] As described above, according to the present invention, particulate carbon material and fibrous carbon material can be produced efficiently and efficiently by using the same nozzle and changing manufacturing conditions. Obtained in high yield.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a nozzle used in the present invention.

FIG. 2 is a cross-sectional view along line II-II in FIG. 1;

FIG. 3 is a sectional view showing another example of the nozzle used in the present invention.

[Explanation of symbols]

14...Heat-treated pitch and non-oxidizing gas channel, 15b
, 15b... Non-oxidizing gas flow path, 16... Heat treatment pitch supply path, 17... Non-oxidizing gas supply port, 19... Merging/mixing chamber.

Claims (1)

[Claims] 1. A first flow path through which non-oxidizing gas and pitch flow, and a plurality of second flow paths arranged around the first flow path through which non-oxidizing gas flows. In producing a self-sintering particulate carbon material using a nozzle having a heat-treated pitch, the heat-treated pitch is supplied to the first channel at a temperature of 100 to 150 °C higher than its softening point, and the non-sintering pitch is When producing a fibrous carbon material by supplying oxidizing gas from the rear end of the nozzle at a flow rate of 6.0 to 12.0 Nm3 per 1 kg of the pitch, the heat-treated pitch is heated to a temperature 2 below its softening point.
A non-oxidizing gas is supplied to the first flow path at a temperature higher than 0°C to 90°C, and 0.5 to 5.0 Nm3 per kg of the pitch.
The non-oxidizing gas is supplied from the rear end of the nozzle at a flow rate of The non-oxidizing gas and pitch that passed through the flow path of No. 1 and the non-oxidizing gas that passed through the gas flow path are combined and mixed, and the particulate or fibrous carbon pitch taken out from the tip of the nozzle is oxidized. A method for producing a carbon material, characterized by: