Vapor Grown Carbon Fiber, and Production Method and Use Thereof

Abstract

A producing method of a carbon fiber by spraying a raw material solution containing a carbon source and a transition metallic compound into a reaction zone and subjecting the raw material solution to thermal decomposition, which is characterized in (1) spraying the raw material solution at a spray angle of 3° to 30° and (2) feeding a carrier gas through at least one site other than an inlet through which the raw material solution is sprayed. A composite material comprising a vapor grown carbon fiber, each fiber filament of the carbon fiber having a branching degree of at least 0.15 occurrences/μm and a bulk density of 0.025 g/cm 3 or less.

1 . A method for producing a vapor grown carbon fiber comprising spraying a raw material solution containing a carbon source and a transition metallic compound into a reaction zone and subjecting the raw material solution to thermal decomposition, characterized in that the raw material solution is sprayed at a spray angle of 3° to 30°. 
     
     
         2 . The method for producing a vapor grown carbon fiber according to  claim 1 , wherein droplets of the raw material solution have an average diameter of at least 5 μm. 
     
     
         3 . The method for producing a vapor grown carbon fiber according to  claim 1 , wherein the raw material solution and a carrier gas are fed through a concentric multi-tube nozzle into a reaction tube. 
     
     
         4 . The method for producing a vapor grown carbon fiber according to  claim 3 , wherein the raw material solution is fed through one of the tubes of the multi-tube nozzle, and another tube serves as a passage for the carrier gas only. 
     
     
         5 . The method for producing a vapor grown carbon fiber according to  claim 4 , wherein the raw material solution and the carrier gas are fed through the inner tube of concentrically disposed two tubes, and the carrier gas is fed through the outer tube of the tubes. 
     
     
         6 . The method for producing a vapor grown carbon fiber according to  claim 4 , wherein the carrier gas is fed through the innermost tube and the outermost tube of concentrically disposed three tubes, and the middle tube of the tubes serves as a passage for the raw material solution only. 
     
     
         7 . The method for producing a vapor grown carbon fiber according to  claim 1 , wherein the raw material solution containing a carbon source and a transition metallic compound further contains a surfactant and/or thickening agent. 
     
     
         8 . The method for producing a vapor grown carbon fiber according to  claim 1 , which comprises heating and firing recovered carbon fiber in a non-oxidative atmosphere at 800° C. to 1,500° C. and subsequently heating the thus-fired carbon fiber in a non-oxidative atmosphere at 2,000 to 3,000° C., to thereby graphitize the carbon fiber. 
     
     
         9 . The method for producing a vapor grown carbon fiber according to  claim 8 , wherein, before being graphitized through heating, the recovered carbon fiber is doped with at least one boron compound, serving as a crystallization facilitating compound, selected from the group consisting of boron, boron oxide, boron carbide, a boric ester, boric acid or a salt thereof, and an organic boron compound in an amount of 0.1 to 5 mass % as reduced to boron. 
     
     
         10 . A method for producing a vapor grown carbon fiber comprising spraying a raw material solution containing a carbon source and a transition metallic compound into a reaction zone and subjecting the raw material solution to thermal decomposition, characterized in that a carrier gas is fed through at least one site other than an inlet through which the raw material solution is sprayed. 
     
     
         11 . The method for producing a vapor grown carbon fiber according to  claim 10 , wherein the raw material solution is sprayed at a spray angle of 3° to 30°. 
     
     
         12 . The method for producing a vapor grown carbon fiber according to  claim 10 , wherein the raw material solution containing a carbon source and a transition metallic compound further contains a surfactant and/or thickening agent. 
     
     
         13 . The method for producing a vapor grown carbon fiber according to  claim 10 , which comprises heating and firing recovered carbon fiber in a non-oxidative atmosphere at 800° C. to 1,500° C. and subsequently heating the thus-fired carbon fiber in a non-oxidative atmosphere at 2,000 to 3,000° C., to thereby graphitize the carbon fiber. 
     
     
         14 . The method for producing a vapor grown carbon fiber according to  claim 13 , wherein, before being graphitized through heating, the recovered carbon fiber is doped with at least one boron compound, serving as a crystallization facilitating compound, selected from the group consisting of boron, boron oxide, boron carbide, a boric ester, boric acid or a salt thereof, and an organic boron compound in an amount of 0.1 to 5 mass % as reduced to boron. 
     
     
         15 . A composite material comprising a vapor grown carbon fiber produced through a method according to  claim 1 . 
     
     
         16 . A resin composition comprising a vapor grown carbon fiber produced through a method according to  claim 1 . 
     
     
         17 . A composite material comprising a vapor grown carbon fiber produced through a method according to  claim 10 . 
     
     
         18 . A resin composition comprising a vapor grown carbon fiber produced through a method according to  claim 10 . 
     
     
         19 . A composite material comprising a vapor grown carbon fiber, each fiber filament of the carbon fiber having a branching degree of at least 0.15 occurrences/μm, and wherein the vapor grown carbon fiber has a bulk density of 0.025 g/cm 3  or less. 
     
     
         20 . A composite material comprising a vapor grown carbon fiber characterized by comprising carbon fiber filaments, each having a branching degree of at least 0.15 occurrences/μm, in an amount of at least 10 mass %, and wherein the vapor grown carbon fiber has a bulk density of 0.025 g/cm 3  or less.