JPH06146117A - Production of carbon fiber by vapor-phase method - Google Patents

Abstract

PURPOSE:To obtain carbon fiber having excellent adhesivity to a matrix in making into a composite material by producing fibers having high growth rate and necessary length in a short time. CONSTITUTION:A hydrocarbon is used as a carbon supply source and a catalyst is introduced to a carbon fiber precipitating zone where the hydrocarbon exists by a pulse method to produce carbon fibers by a vapor-phase method.

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 vapor grown carbon fiber.

[0002]

2. Description of the Related Art Carbon fibers have excellent properties such as high strength and high elasticity as compared with glass fibers and the like, and therefore, organic materials such as plastics, inorganic materials such as ceramics and cement, or metal materials are used as a matrix. As a composite material combined as above, it has been attracting attention and used in a wide range of fields such as electronics, electric machinery, space, aviation, vehicles, construction, and leisure goods.

Conventionally, in the production of carbon fibers, a method of carbonizing organic fibers such as synthetic fibers and petroleum pitch fibers,
A production method by a gas phase method in which a hydrocarbon such as benzene or methane is used as a carbon supply source and is thermally decomposed under a catalyst to produce carbon fiber is well known. Regarding the production method of carbon fiber by the vapor phase method, in addition to the former description in Japanese Patent Publication No. 41-12091, many reports have been made so far. However, the conventional methods have a drawback that the growth rate of carbon fiber is slow and a long reaction time is required, and in particular, contact with catalyst particles causes simultaneous generation of carbon fiber growth seed particles and fiber growth. It was very difficult to obtain the optimum seed particles in order to proceed. The obtained carbon fibers also have a smooth surface and are dendritic or uneven (Japanese Patent Application Laid-Open Nos. 48-41038 and 57-117623) and dense microvilli (special characteristics). However, when used as a composite material, there is a drawback that the adhesion to the matrix is insufficient and the reinforcing effect cannot be obtained sufficiently.

[0004]

DISCLOSURE OF THE INVENTION As a result of various studies on a method of introducing a catalyst, the present invention shows that the growth rate of carbon fiber is high,
The present invention provides a method for producing a carbon fiber in a short time, and further provides a carbon fiber having excellent adhesion to a matrix.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, in a method for producing a vapor grown carbon fiber using a hydrocarbon as a carbon source, a catalyst component is introduced in a pulse form into a carbon fiber deposition zone where hydrocarbon is present. Is a method for producing a vapor grown carbon fiber.

The most characteristic feature of the present invention resides in that the catalyst component is introduced into the high temperature reaction zone as a pulse rather than being quantitatively flowed together with the carbon source. As a result, it becomes possible to obtain a high-density catalyst fine particle region, the heat transfer to the catalyst fine particles becomes very good, and the contact between the generated catalyst fine particles and the carbon supply source becomes instantaneous and the carbon seed fine particles become Since the generation of carbon occurs first and then the carbon fiber grows due to the contact between the supplied carbon source and the seed particles, it is possible to distinguish the seed particle generation process from the fiber growth process. It is possible to freely control the amount of fine particles and carbon supply source, the time until they come into contact with each other, the time for seed fine particles to come into contact with the carbon supply source, and the time for fiber growth. It is possible to easily generate seed fine particles having a size, and it is possible to obtain carbon fibers at a growth rate several tens to several hundreds of times that of conventional methods.

Further, according to the present invention, since the catalyst fine particles are generated at a high density, the catalyst fine particles and the seed fine particles which have not been able to grow the fibers adhere closely to the surface of the grown fiber. Thus, it is possible to obtain a carbon fiber in which carbon is hemispherically deposited on the surface of the fiber, and further, carbon is deposited in the gaps by thermal CVD so that fine carbon particles are densely packed on the surface. This fine granular material exhibits a strong drawing effect when forming a composite with the matrix, and can exhibit excellent properties with high adhesion between the fiber and the matrix.

As the carbon source used in the present invention, hydrocarbons are usually used, for example, aliphatic hydrocarbons such as methane, ethane, propane, acetylene, ethylene, propylene, benzene, toluene, naphthalene,
Aromatic hydrocarbons such as anthracene are used.

As the catalyst, a metal catalyst is used, and as the metal, iron, nickel, cobalt, titanium, zircon, vanadium, niobium manganese, rhodium, tungsten, palladium, platinum, silicon, etc. are directly used. The metal can be evaporated or used as an organometallic compound.

As the carry gas, a reducing gas such as hydrogen gas or carbon monoxide gas is used alone, or is mixed with nitrogen gas, carbon dioxide gas or the like.

The method of the present invention will be described in detail below with reference to schematic drawings. FIG. 1 shows an example of a fiber production procedure in a reactor part. Hydrogen is constantly used as a carrier gas in the reactor 1, and benzene vapor is constantly supplied as a carbon supply source from a raw material inlet 2 in the middle part of the reactor. A solution of ferrocene, which is an organic compound of iron as a catalyst, dissolved in benzene is poured into the flow () and then to this state by a liquid pulse from the quantitative pulse pump 3 to collide with the reactor wall 4.
The reactor wall 4 is heated to a predetermined temperature, and the liquid pulse impinging on the reactor wall instantly generates heated catalyst fine particles and diffuses them throughout the carbon fiber deposition zone 5 (). The generated catalyst fine particles contact with benzene vapor and become seed fine particles, and the vapor grown carbon fibers (VGCF) continue to grow in a short time and are trapped in the inner pipe 6 installed downstream of the reactor. Fiber continues to grow (). Further, even if this inner tube is not provided, the grown fiber is carried downstream of the reaction tube. At that time, some fibers adhere to the reaction tube and grow. After a lapse of a certain reaction time, the carrier gas is switched to nitrogen gas to stop the reaction, and VGCF is recovered ().

In addition to the method shown in the schematic diagram, the catalyst may be introduced by spraying a pulse with ultrafine particles from an ultrafine tube to the center of the reactor.
Further, it is also possible to flow benzene vapor together with the carrier gas from the beginning, or to pre-heat the reactor. The fibers may be trapped by their own weight, or may be discharged to the outside of the reactor or vertically dropped.

The introduction of the liquid pulse is preferably carried out at a pulse interval within the range of 0.2 to 4.0 seconds, preferably 0.3 to 0.6 seconds.
Usually, the reaction temperature in the precipitation zone is 800 to 1300 ° C., the reaction time is 10 seconds to 10 minutes in the batch system, and the growth zone residence time is 10 seconds to 2 minutes in the continuous system. Supply amount of carbon source is 0.01 ~ 0.1ml
/ Min, the flow rate of the carrier gas is 10 to 60 ml / min. By appropriately adjusting the pulse interval, reaction temperature, reaction time, type and supply amount of carbon source, type of solvent, etc., the growth rate of carbon fiber, the thickness, length, surface condition of the obtained carbon fiber, etc. Can be controlled. The growth of carbon fiber can be controlled at a speed of 100-1500 μm / sec,
A fiber having a fiber diameter of 1.0 to 6.0 μm and a length of 3 to 50 mm can be obtained. The size of the fine carbon particles densely packed on the carbon fiber surface is 0.10 to 15.0 μm. Examples will be shown below.

[0014]

【Example】

(Example 1) A reactor having a preheating part and a reaction part (carbon fiber deposition zone) with a raw material inlet was installed in an electric furnace, and nitrogen gas was allowed to flow for 30 minutes, and then hydrogen gas was supplied. 60 ml /
Heat the reaction tube by letting it flow at a flow rate of min. When the temperature of the preheating part reached 800 ° C and the temperature of the reaction part reached 1050 ° C, benzene was flowed from the raw material inlet at a flow rate of 0.1 ml / min, and when it was stable, 10% benzene solution of ferrocene was added to 0.025 m.
Impulses were made from the raw material introduction port to the opposite wall for 1 second with a pulse at intervals of 0.5 seconds in l units, and when the reaction had elapsed for 0.5 minutes after the initiation of the injection, the supply of benzene and hydrogen gas was stopped, and the reaction was stopped by switching to nitrogen gas. The obtained carbon fiber has a surface of 0.18
~ 1.0μm dense carbon granules, diameter 10 ~ 20μm, length 3
It was 5 to 45 mm.

Example 2 In Example 1, the temperature of the reaction section was 1100 ° C., the benzene flow rate was 0.07 ml / min, and the liquid pulse was 0.3.
The reaction was carried out in the same manner as in Example 1 except that the interval was 1 second and the reaction elapsed time was 0.25 minutes. The obtained carbon fiber has a diameter of 2.5, in which 1.0 to 4.5 μm of carbon particles are densely packed on the surface.
It was about 6.0 μm and a length of 40 to 50 mm.

[0016]

EFFECTS OF THE INVENTION According to the present invention, the growth rate of carbon fiber is high, and the fiber having the required length can be obtained in a short time.
Moreover, it is possible to obtain a carbon fiber having excellent adhesion to the matrix when it is made into a composite material.

[Brief description of drawings]

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

[Explanation of symbols]

 1: Reactor 2: Raw material inlet 3: Constant pulse pump 4: Reactor wall 5: Carbon fiber deposition zone 6: Inner tube

Claims (1)

[Claims] 1. A method for producing a vapor grown carbon fiber using a hydrocarbon as a carbon source, wherein the catalyst is introduced in a pulse form into a carbon fiber deposition zone where the hydrocarbon is present. Manufacturing method.