JPH026617A - Production of carbon fiber - Google Patents

Abstract

PURPOSE:To perform a commercial mass-production of a high-quality carbon fiber grown in vapor phase in high yield at a low production cost by supplying a suspension containing a carbon compound, fine particles of a catalyst and a specific surfactant into a heating zone. CONSTITUTION:A suspension containing (A) a carbon compound (preferably a liquid aliphatic or aromatic hydrocarbon), (B) fine particles of a catalyst (preferably magnetite, etc., having particle diameter of 500Angstrom ) and (C) a surfactant containing an element selected from N-group element, O-group element and halogen element (preferably sulfuric acid ester salt, etc.) is prepared beforehand. The suspension is supplied to a heating zone to effect the contact of the gas of the component A with the suspending component B under heating. Carbon is deposited in the form of fiber by this heat-treatment. Preferably, the ratio of the component B in the suspension is 0.05-5wt.% based on the component A and that of the component C is 0.1-50wt.% based on the component B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing carbon fibers, and particularly to a method for significantly improving the yield when producing carbon fibers by vapor phase growth.

[Prior Art] Carbon fibers have conventionally been commercially produced as PAN-based or pitch-based ones. However, the PAN system is expensive, and the pitch system has fatal drawbacks such as complicated processes and difficult quality control.

In contrast, in recent years, a vapor phase growth method has been proposed in which fibers are directly formed by vapor phase thermal decomposition of hydrocarbons using the catalytic effect of metal particles.

Carbon fibers obtained by the vapor growth method are called vapor growth carbon fibers, and their fine morphology with a high aspect ratio, as well as their excellent crystallinity and orientation, make them suitable for use in various structural materials and functional materials. It is expected that it will be extremely useful as a material.

Conventionally, the manufacturing method for vapor-grown carbon fiber involves placing a substrate made of porcelain such as alumina or graphite in an electric furnace, forming carbon growth nuclei, ultrafine particle catalysts such as iron or nickel on this, and A method (seeding method) is known in which carbon fibers are grown on a substrate by introducing a mixed gas of a hydrocarbon gas such as benzene and a hydrogen carrier gas and decomposing the hydrocarbon at a temperature of 950 to 1300°C. It is being

However, with this method, there are two issues: (1) Subtle temperature unevenness on the substrate surface and non-uniformity in length due to dense rings of surrounding fibers; and (2) scum, which is a source of carbon, is consumed by the reaction. As a result, there is a considerable difference in fiber diameter between the inlet and the outlet of the reaction tube, and (1) the production occurs only on the substrate surface, so the central part of the reaction tube does not participate in the reaction and the yield is poor. , (2) Since there are processes that must be carried out independently, such as dispersion of ultrafine particles onto a substrate, reduction, growth, and extraction of fibers, continuous production is impossible, and therefore there are problems such as poor productivity.

Therefore, a carbon fiber production method (fluidized gas phase method) was proposed in which a mixed gas of a carbon compound gas, an inorganic or organic transition metal compound gas, and a carrier gas is reacted at high temperature (
JP-A-60-54998.60-54999.60-2
24816 etc.).

[Problem to be solved by the invention] However, the above-mentioned Japanese Patent Application Laid-Open No. 60-54998.60-5
Methods such as No. 4999.60-224816 have problems such as a low conversion rate of raw materials into carbon fiber as a product, a low yield, or a low production rate.

For this reason, no mass production process for vapor-grown carbon T&fibers has been developed in the past, which has hindered the production of vapor-grown carbon fibers on an industrial scale.

The purpose of the present invention is to solve the above-mentioned conventional problems and provide a method for manufacturing carbon fibers that can obtain high-quality vapor-grown carbon fibers at a high yield and enable commercial mass production thereof. shall be.

[Means for Solving the Problems] The method for producing carbon fiber of the present invention includes a carbon compound gas,
In a method of depositing carbon in the form of fibers by bringing catalyst particles in a suspended state into contact with each other under heating, a carbon compound, catalyst fine particles, and one type selected from the group consisting of nitrogen group elements, oxygen group elements, and halogen elements. Alternatively, a suspension containing a surfactant containing two or more elements is supplied to the heating zone.

The present invention will be explained in detail below.

In the method of the present invention, carbon compounds serving as raw materials include CCJ24, CHCl13, CH2Cf12, CHs
Particularly useful compounds that are characterized by inorganic compounds such as Cfl, Co, and C32 as well as organic compounds in general are aliphatic hydrocarbons and aromatic hydrocarbons. In addition to these, derivatives containing elements such as nitrogen, oxygen, sulfur, fluorine, iodine, phosphorus, and arsenic can also be used. Some specific examples of individual compounds include methane (natural gas may also be used), alkane compounds such as ethane and propane, alkene compounds such as ethylene and butadiene, alkylene compounds such as acetylene, benzene, toluene, Aryl hydrocarbon compounds such as xylene and styrene; aromatic hydrocarbons with condensed rings such as indene, naphthalene, anthracene, and phenanthrene; cycloparaffin compounds such as cyclopropane and cyclohexane; cyclopentene, cyclohexene, cyclopentadiene, and dicyclopentadiene. alicyclic hydrocarbon compounds having condensed rings such as steroids, derivatives containing oxygen, sulfur, halogen, etc. in these hydrocarbon compounds, such as methylthiol,
Sulfur-containing aliphatic compounds such as methyl ethyl sulfide and dimethylthioketone, sulfur-containing aromatic compounds such as phenylthiol and diphenyl sulfide, sulfur-containing or nitrogen-containing heterocyclic compounds such as pyridine, quinoline, benzothiophene, and thiophene, chloroform, Halogenated hydrocarbons such as carbon tetrachloride, chloroethane, and trichlorethylene, as well as gasoline, kerosene, heavy oil, taleosote oil,
Kerosene, turpentine oil, camphor oil, pine oil, gear oil, cylinder oil, etc. can also be used effectively. It goes without saying that mixtures of these can also be used.

In the present invention, it is preferable to use a liquid carbon compound, especially for the purpose of preparing a suspension.

The catalyst for growing carbon fibers by reacting these raw carbon compound gases may be any catalyst as long as it has a catalytic effect for producing carbon fibers and can be made into fine particles, and there are no particular restrictions. No, but preferably magnetite (Fe304), ferrite (Fe203)
, or alloys containing these, such as M n F
e 203, C0Fe20s, Ba-Fe2Cl5, N
Examples include iFe20s and Ni-Fe2O3Zn-FeaO3. These catalysts may be presulfurized with H2S or the like and used as a sulfide, and in this case, a more excellent yield improvement effect can be obtained.

In the present invention, such a catalyst is preferably used in the form of ultrafine particles with a particle size of 200 OA or less, particularly 100 OA or less, especially about 500 Å.

On the other hand, the surfactants used in the present invention include N, P, As
, Sb, Bi nitrogen group elements, 0, S, Se, Te, Po
Oxygen group elements, F, Cu, Br, 1. It contains 1 fffl or two or more types of At halogen elements.

Specifically, the following can be mentioned.

■ Sulfate ester salt type or sulfonate type anionic surfactant ■ Polyethylene glycol type nonionic surfactant ■ Quaternary ammonium salt type cationic surfactant ■ Sodium polystyrene sulfonate, sodium polyacrylate polymeric surfactant These Among these, anionic surfactants such as sulfuric acid ester salts, sulfonic acid salts, phosphoric acid ester salts, and dithiophosphoric acid ester salts containing S and PXN are particularly suitable. In addition, by using a fatty acid salt type surfactant in combination with these surfactants, dispersibility can be maintained for a longer period of time.

In the present invention, a raw material carbon compound, catalyst fine particles, and a surfactant are mixed to form a suspension.

In preparing the suspension, the mixing ratio of each substance is preferably within the following range, for example.

Catalyst fine particles: 0.05 to 5.0% by weight based on the carbon compound Surfactant: 0.10 to 50% by weight based on the catalyst fine particles In addition, if the carbon compound is a gas or produces a good suspension. If this is not possible, a suitable solvent may be used.

These can be easily made into a suspended state by a method such as forced dispersion using a homomixer, ultrasonic dispersion, ball mill, or the like.

In carrying out the present invention, the suspension containing the raw material carbon compound, catalyst fine particles, and surfactant prepared in this way is introduced into a reaction vessel together with a carrier gas and reacted. Specifically, the carrier gas includes N2 gas, N2 gas, NH3 gas, Ar gas,
Examples include gases mainly consisting of He gas, Kr gas, CO2 gas, Xe gas, or a mixture thereof. this house,
N2 gas is commonly used.

Next, a method of implementing the present invention will be explained in more detail with reference to the drawings.

1 and 2 are configuration explanatory diagrams showing a reaction apparatus suitable for carrying out the present invention, in which FIG. 1 shows a horizontal reaction apparatus, and FIG. 2 shows a vertical reaction apparatus. In the apparatus, reference numeral 10 is a reaction vessel (in this example, a reaction tube) equipped with a heater 11, and one end thereof includes a suspension containing a raw material and a carrier gas supply pipe 12, and a carrier gas supply pipe 12. 13 are connected, and the tip 1 of these pipes 12.13
2a and 13a extend to the vicinity of the installation position of the heater 10. Further, a carbon fiber collector 14 is connected to the other end of the reaction vessel 11, and an exhaust gas extraction pipe 15 is connected to the carbon fiber collector 14.

In such a reactor, the reaction vessel 1 is connected to the pipe 12.
The raw carbon compound and catalyst in the suspension supplied into the tube 1 are heated by the heater 11 in the heating zone T+ near the tip 12a of the pipe 12. At this T+ the catalyst is activated.

If the temperature of this heating zone TI is less than 500° C., tar and soot will increase and the yield will be poor. On the other hand, if the temperature exceeds 1000°C, the carbon compound will be gasified and the yield will drop. Therefore,
The temperature of this heating zone TI is preferably 500 to 1000°C, preferably 600 to 800°C.

The catalyst and the raw material carbon compound activated in the heating zone T1 are further sent through the reaction vessel 10 by a carrier gas, and in the heating zone T2, the reaction proceeds due to the action of the activated catalyst, and carbon fibers are produced. . The temperature of this heating zone T2 is preferably about 800 to 1500°C from the viewpoint of reaction efficiency.

The surfactant in the suspension plays the role of stably maintaining the dispersibility of the raw carbon compound and catalyst so that they are uniformly supplied to the heating zone at a constant rate. At the same time, the nitrogen group elements, oxygen group elements, and halogen elements contained enhance the catalytic action and contribute to improving the yield.

Carbon fibers (not shown) produced in the reaction vessel 10
is introduced into the carbon fiber collector 14 together with the carrier gas. As this collection method, various conventionally known methods such as gravity sedimentation method and electrostatic precipitation method can be employed. Note that the carbon fiber collector 14 also serves to cool the generated carbon fibers. The exhaust gas (carrier gas) extracted from the carbon fiber collector 14 through the extraction pipe 15 may be directly introduced into the exhaust treatment means and released, but it is preferable to circulate it and use it after purification. It's okay.

The device shown in Fig. 2 differs from the device shown in Fig. 1 only in that it is designed vertically, and the configuration and function of each part are the same. The explanation will be omitted.

According to the present invention, carbon fibers having a length of usually about 10 μm to 500 mm and a diameter of about 0.1 to 300 μm can be easily used at a yield more than twice that of the conventional method in which carbon fibers are not used in combination with a surfactant. can be manufactured.

[Operation] By supplying the raw material carbon compound and catalyst fine particles to the reaction system in a uniform suspension state using a surfactant, the ratio of the raw material carbon compound and catalyst is stably maintained at a good ratio. Since the carbon fibers are heated and subjected to the reaction, the reaction activity is improved, the yield is increased, and the quality of the produced carbon fibers is stabilized.

Moreover, since the carbon fibers used in the present invention contain elements such as S, P, and N that act on the catalyst and enhance the catalytic action, that is, have a so-called by-catalyst effect, the yield can be further increased.

[Examples] 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 it exceeds the gist thereof.

Examples 1 to 7 Carbon fibers were produced using an apparatus as shown in FIG. 1 using a quartz glass tube with an inner diameter of 60 mm as a reaction vessel. That is,
After the inside of the reaction vessel was sufficiently replaced with H2, a suspension having the proportion shown in Table 1 was introduced from the supply piping 12 together with the carrier gas (H2), and the carrier gas (H2) was introduced from the piping 13. The feed was carried out for 60-90 minutes.

The substances and reaction conditions used were as shown below.

pressure, normal pressure Introductory temperature T, 600℃ Internal temperature T2: 1150℃ The results (yield) are shown in Table 1.

Comparative Example 1 Carbon fibers were produced in the same manner as in Example 1, except that no surfactant was used.

The results (yield) are shown in Table 1.

As is clear from Table 1, the method of the present invention makes it possible to obtain carbon fibers at a significantly high yield.

[Effects of the Invention] As detailed above, according to the method for producing carbon fiber of the present invention, high-quality carbon fiber can be stably produced with an extremely high yield, and therefore, it is possible to stably produce high-quality carbon fiber in an extremely high yield. mass production is possible. As a result, the cost of raw materials can be reduced by improving the yield, and efficient production is possible.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams illustrating the configuration of an apparatus suitable for carrying out the present invention. 0... Reaction container, 1... Heater, 2... Raw material supply pipe, 3... Carrier gas supply pipe, 4... Carbon fiber collector. Representative Patent Attorney Tsuyoshi Shigeno

Claims (1)

[Claims] (1) In a method in which a carbon compound gas and catalyst particles in a suspended state are brought into contact with each other under heating to precipitate carbon in the form of fibers, a carbon compound, a catalyst fine particle, a nitrogen group element, an oxygen group element, and a halogen A method for producing carbon fibers, comprising supplying a suspension containing a surfactant containing one or more elements selected from the group consisting of elements to a heating zone.