JPH05287616A - Vapor-phase production of carbon fiber - Google Patents

Abstract

PURPOSE:To simply produce gas phase-growing carbon fibers by pyrolysis of hydrocarbons in the presence of selenium. CONSTITUTION:In the presence of selenium or a selenium compound such as hydrogen selenide, carbon diselenide or dimethylselenide, hydrocarbons are pyrolyzed at 700 to 1,200 deg.C to form the objective fibers on the surface of a heat-resistant base plate made of an inorganic substance such as quartz, alumina, graphite or a metal such as copper or platinum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing carbon fiber by vapor phase growth. More specifically, it relates to a method for producing a carbon fiber, which comprises heating a mixed gas of a hydrocarbon compound gas, a selenium compound gas and a carrier gas in the range of 700 to 1200 ° C.

[0002]

2. Description of the Related Art Vapor grown carbon fibers have high strength, high elasticity,
It has excellent properties such as high conductivity, high corrosion resistance, and high biocompatibility. Taking mechanical properties as an example, it is an ideal material because it far surpasses the commercially available PAN-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers.

Conventionally, in the production of vapor-grown carbon fibers, porcelain such as alumina or graphite on the surface of which ultrafine particle catalyst such as nickel is dispersed or graphite is used as a substrate, and benzene is used in a reducing atmosphere of hydrogen carrier gas. Hydrocarbon gas such as 1
There is known a method of thermally decomposing at a temperature of 000 to 1300 ° C. to grow carbon fibers on the substrate. In this method, first, it is necessary to form an ultrafine particle catalyst, which is the carbon growth nucleus, on a substrate. To do this, on the substrate
A method of spraying or applying an alcohol suspension in which ultrafine particles of iron, nickel or their alloys of about 100Å are suspended or dried is used. Also, a method is known in which an iron nitrate aqueous solution is applied to the substrate instead of the suspension and dried, but all of them have poor reproducibility and mass productivity.

Therefore, in the conventional method, complicated substrate pretreatment such as dispersion of ultrafine particles on the substrate is required, and there is a problem that productivity is poor due to poor reproducibility and mass productivity. Therefore, in terms of cost, PAs already commercialized
It can be said that it is impossible to oppose N-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers except for special applications.

[0005]

An object of the present invention is to eliminate the conventional dispersion process of ultrafine particles of iron or the like on a substrate, that is, to produce carbon fibers even if a catalytic ultrafine transition metal does not coexist. It is an object of the present invention to provide a method for producing a vapor-grown carbon fiber capable of increasing productivity.

[0006]

Thus, according to the present invention, in a method for producing a vapor-grown carbon fiber by thermal decomposition of hydrocarbon, the thermal decomposition of hydrocarbon in the presence of selenium or a selenium compound is performed. Provided is a method for producing carbon fiber by vapor phase growth. This method is applied to various inorganic heat-resistant substrates such as quartz, sapphire, alumina, SiC, Si, graphite, and carbonaceous materials, or various metallic heat-resistant substrates such as copper and platinum. When observing the surface of the substrate after the decomposition reaction with a scanning electron microscope,
It was found that the carbon fibers were dense on the substrate surface. Thus, in the conventional method, carbon fibers could not be densely formed on the surface of the heat-resistant substrate without the presence of the ultrafine particulate iron group element, but it was difficult to heat hydrocarbons in the presence of selenium and selenium compounds. The decomposition method has made it possible to densify carbon fibers on various heat-resistant substrates without catalytic action.

There is no limitation on the kind of hydrocarbon as the carbon source used in the production conditions of the present invention, and the raw material gas may be any of aliphatic hydrocarbon, aromatic hydrocarbon, alicyclic hydrocarbon and the like. Of course, these may partially have a substituent (halogen atom, hydroxyl group, sulfone group, nitro group, nitroso group, amino group, carboxyl group, etc.). Specific examples thereof include methane, ethane, propane, butane, pentane, hexane, cyclohexane, naphthalene, anthracene, pyrene, benzene, toluene, pyridine, allylbenzene, hexamethylbenzene, aniline, phenol, ethylene, propylene, 1,2. -Dibromoethylene, 2-butyne, acetylene, biphenyl,
Diphenylacetylene, styrene, acrylonitrile,
Examples thereof include pyrrole, thiophene and substituted derivatives thereof. Generally, since halogen has an effect of suppressing the growth of carbon fiber, it is preferable to use a hydrocarbon containing no halogen.

Selenium and selenium compounds in the present invention include selenium, hydrogen selenide, carbon diselenide, dimethyl selenide, diethyl selenide, dipropyl selenide, diphenyl selenide, selenophene and diphenyl diselenide ((C ₆ H ₅ ). ₂ Se ₂ ), Phenyl selenyl chloride
((C ₆ H ₅ ) SeCl), methyl benz selenazole (C ₈ H ₇ NS
e), selenophenol (C ₆ H ₅ SeH), selenourea (SeC
(NH ₂ ) ₂ ) etc. can be used.

The inert carrier gas of the present invention is helium,
Argon, nitrogen, hydrogen, etc. are mentioned. When the above-mentioned hydrocarbon compound or selenium compound is solid, it is gasified by heating evaporation or sublimation, and is transferred to the reaction tube together with the carrier gas, so that it is in a coexisting state. Further, when they are liquids, by bubbling with the above-mentioned carrier gas, they are transferred to the reaction tube together with the carrier gas, so that they will be in a coexisting state.

The heat-resistant substrate of the present invention is not particularly limited in its type, but is, for example, an inorganic substance such as quartz, sapphire, alumina, SiC, Si, graphite or a carbonaceous material, or copper, platinum, nickel or the like. Metal is used. On the board,
Of course, it is not necessary to carry and add fine metal particles such as iron,
It may be effective to carry and add these fine particles, and at the same time, mix and add selenium or a selenium compound to the raw material hydrocarbon gas. Further, it is a matter of course that these fine particle additives may be added in the form of fine powder or metal carbonyl or an organic metal compound vapor may be mixed and added to the raw material hydrocarbon gas.

The decomposition temperature for thermal decomposition, the amount of the hydrocarbon compound gas supplied, and the amount of the selenium compound gas supplied are different depending on the types of the hydrocarbon compound and the selenium compound used as the starting materials, but are 0.1 to 30 mol%, Preferably, when a hydrocarbon compound having a molecular weight of 150 or less mixed with 2 to 20 mol% of a selenium compound gas is used, the following conditions: Feed rate: 0.05 to 15 mol / hour; Molecular number density: 2 × 10 ²¹ to 2. 6 × 10 ²² molecule / l ・ Flow rate 0.5 to 70 cm / min ・ Pyrolysis temperature 450 to 1300 ° C., preferably 7
By thermally decomposing a hydrocarbon gas at 00 to 1200 ° C, the carbon fiber used in the present invention can be formed.

Under the above conditions, carbon fibers having a diameter of 0.1 to 100 μm and a length of 100 μm to several cm can grow on the surface of the heat resistant substrate. The cross section of the carbon fiber of the present invention is
It consists of concentric carbon layer surfaces parallel to the fiber axis, and the layer spacing is 3.46 to 3.3 from the analysis results of X-ray and electron beam diffraction.
It is 6Å.

[0013]

The mechanism for the catalytic action of carbon fiber formation of selenium gas in the present invention has not been clarified yet. However, in the present invention, it is judged from the fact that carbon fibers are produced by thermally decomposing a mixed gas of a hydrocarbon compound gas and a selenium compound as a carbon source, and a selenium element or a selenium element capable of functioning as a catalyst is determined. It is considered that the fine particles of 2) are generated and form a catalyst atmosphere while flowing in the heating zone, and that the effect is to generate and grow carbon fibers.

Therefore, according to the present invention, since the reaction not only on the substrate surface but also over the entire heating zone as in the conventional case, each fiber is produced under the same condition, and the produced carbon fiber has a uniform aspect ratio. You get something.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for producing vapor grown carbon fiber according to the present invention will be described in detail below with reference to the drawings. First, FIG. 1 shows a schematic view of an apparatus used for producing the vapor grown carbon fiber in the present invention. In FIG. 1, 1 is a graphite raw material container containing an aliphatic hydrocarbon, an aromatic hydrocarbon, an alicyclic hydrocarbon and the like, and 2 is a selenium gas source containing a selenium compound gas material. The material container 3 is a reaction tube, and 7 is a material transfer tube for transferring a material gas to the reaction tube 3. The gas from the graphite raw material container and the gas from the selenium raw material container are mixed in the middle of the transfer pipe 7 and supplied to the reaction pipe 3. A heating furnace 4 heats the reaction tube 3 to thermally decompose the mixed gas of the hydrocarbon and the selenium compound introduced into the reaction tube 3. At this time, the thermally decomposed selenium compound forms a catalytic selenium gas atmosphere. The reaction tube 3 is provided with the substrate holding table 6 on which the deposition generation substrate 5 is placed, so that the pyrolysis gas of hydrocarbons is deposited as carbon fibers on the substrate in the selenium gas atmosphere. The remainder of the steam introduced into the reaction tube 3 is discharged to the outside via the exhaust pipe 8.

Example 1 A process for producing carbon fiber using benzene as a hydrocarbon compound as a graphite raw material and selenium as a selenium raw material will be described with reference to the schematic view of FIG. 1 and FIG. 2 showing the details. Argon gas is supplied from an argon gas control system 19 into a bubble container 11 containing benzene which has been purified by vacuum distillation as a graphite raw material, and benzene is bubbled to a quartz reaction tube 13 via a transfer tube 17. Supply benzene molecules. At this time, the temperature of the liquid benzene in the bubble container 11 is kept constant and the flow rate of the argon gas is set to the first value.
Adjust with the valve 20 to make the benzene molecule quartz reaction tube 13
The amount supplied to the inside was controlled. Selenium gas is mixed from the container 12 containing selenium in the middle of the transfer pipe 17, and a mixed gas of benzene molecules and selenium atoms is supplied to the reaction pipe 13. At this time, the container 12 and the transfer pipe 17 are covered with a heating tape, and the selenium inside the container 12 is evaporated by heating the same to a constant temperature, and the second valve 21 is adjusted so that the selenium vapor is discharged at a constant rate. Reaction tube 13
Transfer to. On the other hand, argon gas is flown from the dilution line 22 to optimize the number density and flow rate of benzene molecules and selenium atoms in the argon gas fed to the quartz reaction tube 13. The reaction tube 13 is inserted into the heating furnace 14 and heated to the reaction temperature. The reaction tube 13 is provided with a holding table 16 on which a deposition generation substrate 15 for growing carbon fibers is placed. The benzene molecules introduced into the reaction tube 13 are heated in the heating furnace 1
4 is pyrolyzed to grow and form a carbon deposit on the substrate. At this time, the selenium atom introduced by mixing with the benzene molecule forms a catalytic atmosphere in the growth process of carbon, and as a result, the obtained carbon deposit becomes fibrous carbon fiber.
The remainder of the steam introduced into the reaction tube 13 is discharged to the outside via the exhaust pipe 18.

In the above process, sapphire is used for the substrate 15 for deposition generation, and the temperature of the heating furnace 14 is set to 1000.
℃, selenium evaporation temperature 400 ℃, benzene and selenium supply rate of 0.50mol / hr, 0.05m
ol / hr with an average diameter of 25 μm and an average of 5000 μ
m, an aspect ratio of about 200, and a uniform carbon fiber of about 5 g /
Obtained at a rate of hr.

In this step, another inert gas such as nitrogen or helium may be used instead of the argon gas. It is also possible to use HCl gas to transport selenium.

Example 2 The selenium used as a raw material for selenium in the manufacturing method of Example 1 above.
Gas instead of benzene.
Obtained by thermal decomposition of selenium compound
The method of forming carbon deposits in a selenium gas atmosphere
Similarly, carbon fiber was obtained. Below, as selenium compounds
Diethyl selenium (Se (C₂H _Five)₂),
According to the manufacturing process of FIG. 3, which shows the schematic diagram of FIG. 1 in more detail.
I will explain. That is, a purification operation by vacuum distillation was performed.
Same as the first bubble container 31 containing benzene.
The second bubble containing the processed diethyl selenium.
An argon gas control system 39 is provided inside each of the containers 32.
Argon gas is supplied from the
Len is bubbled and the quartz reaction tube 33 is transferred through the transfer tube 37.
Feeds mixed gas of benzene molecule and diethyl selenium
To do. At this time, liquid benzene in the first bubble container 31
And the temperature of the liquid diethyl selenium in the second bubble container 32
Is kept constant, and the flow rate of the argon gas is set to the first valve 40.
Adjust the second valve 41 to adjust the benzene molecule and
Independently control the amount of ruthelen molecules supplied into the quartz reaction tube 33.
Control. On the other hand, flow the argon gas through the dilution line 42.
And the benzene contained in the argon gas fed to the quartz reaction tube 33.
Optimized molecular number density and flow rate of zen and diethyl selenium
To do.

In the above process, a nickel base material is used for the deposition generation substrate 35, and the temperature of the heating furnace 14 is set to 110.
Uniform carbon fibers having an average diameter of 15 μm and an aspect ratio of about 130 were obtained at a rate of about 2 g / hr at 0 ° C. and the supply rates of benzene and diethyl selenium were 0.30 mol / hr and 0.015 mol / hr, respectively. The diethyl selenium (Se (C
₂ H ₅ ) ₂ ) instead of liquid or gas at room temperature, hydrogen selenide, hydrogen diselenide, dimethyl selenide, diethyl selenide, dipropyl selenide, diphenyl selenide,
Similar results were obtained using selenophene and the like.

Example 3 In Example 1, propane was used instead of benzene, and the propane feed rate was 2.2 m under the CVD conditions.
ol / hr, the supply rate of selenium is 0.15 mol / h
For r, the average diameter was 10 μm and the average length was 1000 μm in the same manner as in Example 1 except that the thermal decomposition temperature was 1200 ° C.
10g of uniform carbon fiber with m and aspect ratio of about 100
/ Hr.

Example 4 In Example 2, propane was used instead of benzene, and the propane feed rate was 1.2 m under the CVD conditions.
ol / hr, the feed rate of diethyl selenium is 0.05 m
ol / hr, except that the thermal decomposition temperature was 900 ° C., the same as in Example 2 except that the average diameter was 35 μm and the average length was 560.
About 3 carbon fibers with a uniform size of 0 μm and an aspect ratio of about 160
Obtained at a rate of g / hr.

In place of the diethyl selenium (Se (C ₂ H ₅ ) ₂ ) used as the selenium compound in this step, hydrogen selenide, hydrogen diselenide, dimethyl selenide, selenide, which is also liquid or gas at room temperature, is used. Similar results were obtained using diethyl, dipropyl selenide, diphenyl selenide, selenophene and the like.

[0024]

INDUSTRIAL APPLICABILITY By using selenium or a selenium compound, carbon fiber is produced by thermally decomposing a gas of a hydrocarbon compound in a catalytic atmosphere of selenium gas, whereby a conventional method of dispersing a catalytic metal on a substrate is achieved. It made it possible to omit the complicated process of reduction.

As a result, it became possible to continuously produce carbon fibers in the gas phase with high productivity. Further, according to the present invention, since the reaction not only on the substrate surface but also over the entire heating zone as in the conventional case, each fiber is produced under the same condition, and the produced carbon fiber has a uniform aspect ratio. Be done.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a method for producing carbon fiber of the present invention.

FIG. 2 is a schematic view showing an embodiment of the carbon fiber manufacturing apparatus of the present invention.

FIG. 3 is a schematic view showing an embodiment of the carbon fiber manufacturing apparatus of the present invention.

[Explanation of symbols]

 1 Graphite Raw Material Container 2 Insertion Raw Material Container 3 Reaction Tube 4, 14, 34 Heating Furnace 5 Substrate 6, 16, 36 Substrate Holding Platform 7, 17, 37 Raw Material Transfer Pipe 8, 18, 38 Exhaust Pipe 11 Graphite Raw Material Bubble Container 12 Selenium material container 13, 33 Quartz reaction tube 15, 35 Deposition substrate 19, 39 Argon gas control system 20, 40 First valve 21, 41 valve 22, 42 Dilution line 31 First bubble container 32 Second bubble container

Claims (2)

[Claims] 1. A method for producing a vapor-grown carbon fiber by pyrolyzing a hydrocarbon, wherein the hydrocarbon is pyrolyzed in the coexistence of selenium or a selenium compound. .. 2. The method according to claim 1, wherein the selenium compound is hydrogen selenide, carbon diselenide, dimethyl selenide, diethyl selenide, dipropyl selenide, diphenyl selenide or selenophene.