Polyacrylonitrile-based stabilized fiber, carbon fiber, and manufacturing method therefor
View Patent ↗The present invention provides a carbon fiber, which has excellent tensile strength by having fewer internal defects while being a thick fiber having a single-fiber diameter of 6.0 μm or greater, and can provide the effects of reducing costs while increasing production amount to enhance the yieldability of the carbon fiber.
1. A polyacrylonitrile-based stabilized fiber satisfying conditions of the following Equations 1 and 2 while having a single-fiber diameter of 10.0 μm or more:
Log(ρ)≥(αβ)/100 (1)
0.120≤(αβ)/100≤0.135 (2)
where ρ denotes a density (g/cm 3 ) of the stabilized fiber, α denotes an extent of cyclization reaction (EOR (%)) in the stabilized fiber, and β denotes an oxygen content (%) in the stabilized fiber.
2. A carbon fiber which is produced by carbonizing the polyacrylonitrile-based stabilized fiber of claim 1 , wherein a single-fiber diameter of the carbon fiber is 6.0 μm or more, and a resin-impregnated strand of the carbon fiber has a tensile strength of 5.8 to 6.4 GPa.
3. A method for producing a carbon fiber, the method comprising: subjecting a polymer solution to dry-wet spinning in a coagulation bath having a solvent concentration of 30 to 40 wt % and containing water and the same solvent as a solvent used for polymerization, thereby forming a carbon fiber precursor fiber; drawing the obtained carbon fiber precursor fiber through a plurality of water washing baths; applying an oil agent to the drawn yarn, followed by drying and drawing to obtain a carbon fiber precursor fiber having a degree of surface layer densification of 65 to 70% at a wavelength of 380 nm and a degree of surface layer densification of 82 to 95% at a wavelength of 430 nm; and carbonizing the carbon fiber precursor fiber at a temperature of 1,000 to 1,400° C. to have a carbon fiber diameter of 6.0 μm or more.
4. The method according to claim 3 , wherein the polymer has a weight-average molecular weight (Mw) of about 120,000 to 180,000 and a ratio of weight average molecular weight to number average molecular weight (Mw/Mn) of 1.6 to 1.8.
5. The method according to claim 3 , wherein a temperature difference between the polymer solution and the coagulation bath during the spinning is 30° C. or lower.
6. The method according to claim 3 , wherein the method comprises spinning the polymer solution by passage through a nozzle hole having a diameter of 0.12 to 0.18 mm.
7. A high-pressure vessel comprising: a pressure vessel body; and a fiber-reinforced resin layer composed of fiber-reinforced resin formed on a surface of the pressure vessel body; wherein the fiber of the fiber-reinforced resin layer is a carbon fiber produced by carbonizing the polyacrylonitrile-based stabilized fiber of claim 1 , and wherein a single-fiber diameter of the carbon fiber is 6.0 μm or more, a number of filaments in a bundle of the carbon fiber is 24,000 to 36,000, and a resin-impregnated strand of the carbon fiber has a tensile strength is 5.8 to 6.4 GPa and a tensile elongation of 2.2 to 2.6%.