Carbon fiber, method for producing the same and apparatus therefor

Abstract

An object of the present invention is to provide a method and apparatus for heat-treating carbon fiber, in which impairment of a furnace caused by solidification of a transition metal impurity serving as a catalyst raw material is prevented, and the amount of the metal, such as Fe, Co, or Ni, contained in the carbon fiber is reduced. In the present invention, a vaporized metal impurity is contained in an inert gas that is passed through a furnace, and the gas is discharged from a high-temperature section of the furnace. The impurity contained in the gas discharged from the furnace is cooled to solidify, and then recovered. The resultant gas is recycled as an inert gas in the furnace.

Description

[0001] This application is an application filed under 35 U.S.C. .sctn.111(a) claiming benefit pursuant to 35 U.S.C. .sctn.119(e)(1) of the filing date of Provisional Application 60 / 245,715 filed Nov. 6, 2000 pursuant to 35 U.S.C. .sctn.111(b).

[0002] The present invention relates to a carbon fiber which has been produced through a thermal decomposition reaction from a raw material predominantly containing a carbon source and a transition metal serving as a catalyst. The present invention also relates to a method for producing the carbon fiber; to a high-temperature heat treatment method for the carbon fiber; and to a heat treatment apparatus for the method.

[0003] A variety of processes for producing fine carbon fiber are known. A process in which an organic compound, such as benzene, serving as a raw material, and an organic transition metal compound, such as ferrocene, serving as a metallic catalyst, are introduced into a high-temperature reaction furnace together with a carrier gas...

Examples

example 1

[0064] Vapor grown carbon fiber (about 1000 kg) having a mean diameter of 0.2 .mu.m and containing an element of iron(Fe) (i.e., impurity) in an amount of 2 mass % was subjected to continuous high-temperature heat treatment at 2,800.degree. C. in a hollow cylindrical furnace body having an inner diameter of about 15 cm, while argon gas was passed through the apparatus.

[0065] During heat treatment, the inert gas containing the impurity was temporarily discharged from a furnace body, the impurity was removed from the gas by use of an impurity solidification-recovery container filled with carbon micropowder, and the resultant gas was returned to the furnace.

[0066] After heat treatment of the carbon fiber (about 1000 kg) was completed, the furnace was subjected to inspection. Deposition of iron-containing carbide (about 0.1 kg) in a hollow cylindrical furnace body was observed, but no hole was found in the furnace body. Iron-containing carbide (about 20 kg) was recovered in the solidifi...

example 2

[0068] Vapor grown carbon fiber (about 500 kg) having a mean diameter of 0.02 .mu.m and containing an element of iron in an amount of 3 mass % was subjected to continuous high-temperature heat treatment in a manner similar to Example 1.

[0069] After heat treatment of the carbon fiber (about 500 kg) was completed, the furnace was subjected to inspection. Deposition of iron carbide (about 0.1 kg) in a hollow cylindrical furnace body was observed, but no hole was found in the furnace body. Iron carbide (about 19 kg) was recovered in an impurity solidification-recovery container.

[0070] The amount of Fe detected in the heat-treated carbon fiber was 30 mass ppm.

[0001] This application is an application filed under 35 U.S.C. .sctn.111(a) claiming benefit pursuant to 35 U.S.C. .sctn.119(e)(1) of the filing date of Provisional Application 60 / 245,715 filed Nov. 6, 2000 pursuant to 35 U.S.C. .sctn.111(b).

[0002] The present invention relates to a carbon fiber which has been produced through a thermal decomposition reaction from a raw material predominantly containing a carbon source and a transition metal serving as a catalyst. The present invention also relates to a method for producing the carbon fiber; to a high-temperature heat treatment method for the carbon fiber; and to a heat treatment apparatus for the method.

[0003] A variety of processes for producing fine carbon fiber are known. A process in which an organic compound, such as benzene, serving as a raw material, and an organic transition metal compound, such as ferrocene, serving as a metallic catalyst, are introduced into a high-temperature reaction furnace together with a carrier gas...

Examples

example 1

[0064] Vapor grown carbon fiber (about 1000 kg) having a mean diameter of 0.2 .mu.m and containing an element of iron(Fe) (i.e., impurity) in an amount of 2 mass % was subjected to continuous high-temperature heat treatment at 2,800.degree. C. in a hollow cylindrical furnace body having an inner diameter of about 15 cm, while argon gas was passed through the apparatus.

[0065] During heat treatment, the inert gas containing the impurity was temporarily discharged from a furnace body, the impurity was removed from the gas by use of an impurity solidification-recovery container filled with carbon micropowder, and the resultant gas was returned to the furnace.

[0066] After heat treatment of the carbon fiber (about 1000 kg) was completed, the furnace was subjected to inspection. Deposition of iron-containing carbide (about 0.1 kg) in a hollow cylindrical furnace body was observed, but no hole was found in the furnace body. Iron-containing carbide (about 20 kg) was recovered in the solidifi...

example 2

[0068] Vapor grown carbon fiber (about 500 kg) having a mean diameter of 0.02 .mu.m and containing an element of iron in an amount of 3 mass % was subjected to continuous high-temperature heat treatment in a manner similar to Example 1.

[0069] After heat treatment of the carbon fiber (about 500 kg) was completed, the furnace was subjected to inspection. Deposition of iron carbide (about 0.1 kg) in a hollow cylindrical furnace body was observed, but no hole was found in the furnace body. Iron carbide (about 19 kg) was recovered in an impurity solidification-recovery container.

[0070] The amount of Fe detected in the heat-treated carbon fiber was 30 mass ppm.

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