METHOD FOR PRODUCING CARBON FIBER AND CARBON FIBER PRODUCED USING SAME
The present invention is a method for producing carbon fiber, characterized by using a carbon-fiber precursor produced from a polymer having a narrow molecular weight distribution and by applying only a small amount of a smoothing agent, composed of a specific component, to the carbon fiber surface immediately before winding of carbon fiber. According to the present invention, it is possible to stably produce carbon fiber, which has excellent dispersibility and do not deteriorate in quality and quality even when a sizing agent is not attached to the carbon fiber surface. In addition, the produced carbon fiber is suitable for use in a composite material which is produced by high-temperature processing using a thermoplastic resin.
1 . A carbon fiber that is obtained by a method, comprising:
dry-wet-spinning an acrylonitrile-based polymer having a molecular weight distribution in a range of 1.6 to 1.9 so as to obtain a polyacrylonitrile-based carbon-fiber precursor fiber;
subjecting the polyacrylonitrile-based carbon-fiber precursor fiber to a thermally stabilizing treatment process, a pre-carbonization process and a carbonization process so as to obtain a carbon fiber, and
applying only a smoothing agent to a surface of the carbon fiber after the carbonization process and immediately before winding of the carbon fiber, without applying a sizing agent composed of a resin component to the surface of the carbon fiber,
wherein the smoothing agent is at least one selected from the group consisting of an alkyl ether compound having 6 to 35 carbon atoms, an aliphatic ester compound having 6 to 35 carbon atoms, an aromatic ester compound having 6 to 35 carbon atoms, and an ether ester compound having 6 to 35 carbon atoms,
wherein the carbon fiber has a hardness of 70 or more and a degree of interlacing in a range of 2.5 to 5.5,
wherein an amount of the smoothing agent attached to the carbon fiber is in a range of 0.05 to 0.1 wt % based on the total weight of the carbon fiber,
wherein the water content of the carbon fiber is 0.1% or less.
2 . The carbon fiber of claim 1 , wherein the carbon fiber is a standard-modulus high-strength type carbon fiber having 5.0 GPa or more, a medium-modulus carbon fiber having 280 GPa or more, or a high-modulus carbon fiber having 320 GPa or more.
3 . The carbon fiber of claim 1 , wherein a bundle of the carbon fiber has a filament count of 3 to 48K.
4 . A thermoplastic composite material comprising the carbon fiber of claim 1 .
5 . A metal-coated carbon fiber that is obtained by coating the carbon fiber of claim 1 with a metal.
6 . A composite material comprising the metal-coated carbon fiber of claim 5 and a thermoplastic resin.