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 method of producing a carbon fiber, comprising:
dry-wet-spinning an acrylonitrile-based polymer having a molecular weight distribution 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.
2. The method of claim 1 , wherein the smoothing agent is diluted in an organic solvent or water at a concentration of 0.1 to 1.0 wt % based on the weight of the solvent.
3. The method of claim 1 , wherein applying the smoothing agent to the carbon fiber surface is performed by any one of a spray method, a kissing roll method, a dipping method, and a coating method.
4. The method of claim 1 , further comprising drying a carbon fiber bundle, which comprises the smoothing agent applied to the surface of the carbon fiber, by passage through a hot-air dryer or a heating roller.
5. The method of claim 4 , wherein the drying is performed at a temperature of 130 to 230° C. for 10 seconds to 15 minutes.
6. The method of claim 1 , wherein an amount of smoothing agent attached to the carbon fiber is 0.05 to 0.1 wt % based on the total weight of the carbon fiber.