Carbon fiber bundle and production method for same

Abstract

To provide a carbon fiber bundle capable of suppressing winding due to ring-shaped fuzzes, which occurs when the carbon fiber bundle is rolled out for advanced processing, and a production method for producing the same. Disclosed is a carbon fiber bundle wherein an average single-fiber diameter B is 6.9 to 11.0 μm, a tensile modulus E of resin-impregnated strands is 230 to 310 GPa, the number of fuzzes inherent in the carbon fiber bundle is 40 fuzzes/m or less, and a proportion of fuzzes with a structure having a difference between skin and core is 1 to 25% of fuzzes inherent in the carbon fiber bundle. Such a carbon fiber bundle is preferably obtained by a method including, in a process of heat-treating a polyacrylonitrile-based precursor fiber bundle with a single-fiber fineness of 0.9 to 2.2 dtex in an oxidizing atmosphere at 200 to 300° C., heat-treating the polyacrylonitrile-based precursor fiber bundle so that a heat generation rate Q, which is the left side of the formula (3), is 150 to 500 J/m 2 /s until the density is 1.22 to 1.24 g/cm 3 , when q (J/g/s) is the heat generation rate of the single fiber, N is the number of filaments, d (dtex) is a single-fiber fineness of the stabilized fiber bundle and W (mm) is a yarn width, heat-treating the fiber bundle while applying a tension of 1.6 to 4.0 mN/dtex until the density is 1.38 to 1.50 g/cm 3 to obtain a stabilized fiber bundle, and heat-treating the stabilized fiber bundle in an inert atmosphere at 1,200 to 1,600° C. Q=q×N×d/W /10  (3)

1 . A carbon fiber bundle wherein an average single-fiber diameter B is 6.9 to 11.0 μm, a tensile modulus E of resin-impregnated strands is 230 to 310 GPa, the number of fuzzes inherent in the carbon fiber bundle is 40 fuzzes/m or less, and a proportion of fuzzes with a structure having a difference between skin and core is 1 to 25% of fuzzes inherent in the carbon fiber bundle. 
     
     
         2 . The carbon fiber bundle according to  claim 1 , wherein a proportion of fuzzes with an area ratio of 50% or less of the cross section perpendicular to the fiber axis is 0 to 3% of fuzzes inherent in the carbon fiber bundle. 
     
     
         3 . The carbon fiber bundle according to  claim 1 , wherein the tensile modulus E of resin-impregnated strands and a crystallite size Lc (nm) satisfy the relationship of the formula (1).
   50× Lc+ 130≤ E≤ 50× Lc+ 180  (1)
   
     
     
         4 . The carbon fiber bundle according to  claim 1 , wherein the crystallite size Lc (nm) is 1.5 to 2.5 nm. 
     
     
         5 . The carbon fiber bundle according to  claim 1 , wherein a yarn width W is 5 to 8 mm. 
     
     
         6 . The carbon fiber bundle according to  claim 1 , wherein the number of filaments N is 10,000 to 50,000. 
     
     
         7 . The carbon fiber bundle according to  claim 1 , wherein a knot strength A (MPa) and the average single-fiber diameter B (μm) satisfy the relationship of the formula (2).
   −88 B+ 1,360≤ A   (2)
 
 
     
     
         8 . The carbon fiber bundle according to  claim 1 , wherein the tensile strength of resin-impregnated strands is 5.5 to 7.0 GPa. 
     
     
         9 . The carbon fiber bundle according to  claim 1 , wherein the area ratio of an outer layer to the entire cross section perpendicular to the fiber axis of the single fiber is 85 to 95 area %. 
     
     
         10 . A method for producing a carbon fiber bundle, which comprises, in a process of heat-treating a polyacrylonitrile-based precursor fiber bundle with a single-fiber fineness of 0.9 to 2.2 dtex in an oxidizing atmosphere at 200 to 300° C., heat-treating the polyacrylonitrile-based precursor fiber bundle so that a heat generation rate Q obtained by the formula (3) is 150 to 500 J/m 2 /s until the density is 1.22 to 1.24 g/cm 3 , when q (J/g/s) is the heat generation rate of the single fiber, N is the number of filaments, d (dtex) is a single-fiber fineness of the stabilized fiber bundle and W (mm) is a yarn width, heat-treating the fiber bundle under tension of 1.6 to 4.0 mN/dtex until the density is 1.38 to 1.50 g/cm 3  to obtain a stabilized fiber bundle, and heat-treating the stabilized fiber bundle in an inert atmosphere at 1,200 to 1,600° C. to obtain a carbon fiber bundle.
     Q=q×N×d/W/ 10  (3)
 
 
     
     
         11 . The method for producing a carbon fiber bundle according to  claim 10 , wherein, in a process of heat-treating in an oxidizing atmosphere, a heat treatment is performed so that the heat generation rate Q obtained by the formula (3) is 150 to 500 J/m 2 /s until the density is 1.22 to 1.24 g/cm 3 , and a heat treatment is performed so that the heat generation rate Q obtained by the formula (3) is 300 to 1,200 J/m 2 /s until the density is 1.32 to 1.35 g/cm 3 , and then a heat treatment is performed so that the heat generation rate Q obtained by the formula (3) is 900 to 1,500 J/m 2 /s until the density is 1.38 to 1.50 g/cm 3 .