Carbon fiber bundle and method of producing carbon fibers
Provided are carbon fibers which have a thicker single fiber fineness of the polyacrylonitrile-based precursor fiber bundles and lower production costs, and which have excellent mechanical properties. Also provided are: carbon fiber bundles having a single fiber fineness of 0.8-2.1 dtex, a strand strength of 4.9 GPa or greater, and a strand elastic modulus of 200 GPa or greater; carbon fiber bundles having a single fiber fineness of 0.8-2.5 dtex, a strand strength of 3.0 GPa or greater, and a strand elastic modulus of 240 GPa or greater; and an optimal method for producing said carbon fiber bundles. carbon fiber bundles having a single fiber fineness of 0.8-2.5 dtex, a strand strength of 3.0 GPa or greater, and a strand elastic modulus of 240 GPa or greater; and an optimal method for producing said carbon fiber bundles.
1. A carbon fiber bundle,
wherein
a single fiber fineness of the carbon fiber bundle is at least 0.8 dtex to no more than 2.1 dtex;
a strand strength of at least 4.9 GPa and a strand modulus of elasticity of at least 200 GP is determined by a method of ASTM D4018; and
a degree of variability between fibers in a single fiber modulus of elasticity in a single fiber tension test is no more than 20%, wherein the degree of variability is calculated by the formula below:
Degree of variability (%)=(standard deviation/average value)×100.
2. The carbon fiber bundle according to claim 1 , wherein the single fiber fineness is at least 1.1 dtex.
3. The carbon fiber bundle according to claim 1 , wherein a total fineness is at least 4800 dtex to no more than 56000 dtex.
4. The carbon fiber bundle according to claim 1 , wherein a number of the single fibers is at least 6,000 to no more than 50,000.
5. The carbon fiber bundle according to claim 4 , wherein the number of the single fibers is no more than 36,000.
6. A resin-based composite material comprising the carbon fiber bundle according to claim 1 .
7. A method of producing carbon fiber bundles for obtaining the carbon fiber bundle according to claim 1 , comprising a heat treatment step of heat treating, for at least 80 minutes to no more than 240 minutes under an oxidizing atmosphere rising in temperature within the temperature range of 220 to 300° C., a polyacrylonitrile-based precursor fiber bundle having a single fiber fineness of at least 1.7 dtex to no more than 4.2 dtex consisting of a polyacrylonitrile-based copolymer containing 96 to 99% by mole of acrylonitrile units and 1 to 4% by mole of hydroxyaklyl methacrylate units, and/or a polyacrylonitrile-based precursor fiber bundle having a single fiber fineness of at least 1.7 dtex to no more than 4.2 dtex having a constant velocity temperature rising exothermic curve of 30° C. to 450° C. measured in an air flow of 100 ml/min that is a flowrate based on 30° C. at 0.10 MPa and at a heating rate of 10° C./min using a heat flux-type differential scanning calorimeter that satisfies conditions (A) and (B) below:
(A) heat amount Ja obtained by integrating the heat generation rate of at least 230° C. to no higher than 260° C. of a constant velocity temperature rising exothermic curve is at least 140 kJ/kg to no more than 200 kJ/kg; and
(B) heat amount Jb obtained by integrating the heat generation rate of at least 260° C. to no higher than 290° C. is at least 600 kJ/kg to no more than 1,000 kJ/kg.
8. The method of producing carbon fiber bundles according to claim 7 , wherein a heat treatment time T1 (minutes) in the heat treatment step satisfies condition (C) below:
(C) 140×single fiber fineness (dtex) of polyacrylonitrile-based precursor fiber bundle−100≧heat treatment time T1 (minutes)≧140×single fiber fineness (dtex) of polyacrylonitrile-based precursor fiber bundle−270.
9. The method of producing carbon fiber bundles according to claim 7 , wherein a carbonization treatment is conducted to heat treat the fiber bundle obtained from the heat treatment step at a highest temperature of 1,000° C. to 1,700° C. under an inert gas atmosphere, so as to make a carbon fiber bundle having a strand strength obtained by the method of ASTM D4018 of at least 4.9 GPa.
10. The method of producing carbon fiber bundles according to claim 7 , wherein a number of single fibers in the polyacrylonitrile-based precursor fiber bundle is at least 6,000 to no more than 50,000.
11. The method of producing carbon fiber bundles according to claim 7 , wherein an elongation rate of polyacrylonitrile-based precursor fiber bundles in the heat treatment step is at least −5% to no more than 5%.
12. A carbon fiber bundle, wherein a single fiber fineness of the carbon fiber bundle is at least 0.8 dtex to no more than 2.5 dtex, a strand strength obtained by the method of ASTM D4018 is at least 3.0 GPa, and a strand modulus of elasticity obtained by the method is at least 240 GPa, and
wherein a degree of variability between fibers in a single fiber modulus of elasticity in a single fiber tension test is no more than 20%, wherein the degree of variability is calculated by the formula below:
Degree of variability (%)=(standard deviation/average value)×100.
13. The carbon fiber bundle according to claim 12 , wherein the strand modulus of elasticity obtained by the method of ASTM D4018 is at least 265 GPa.
14. The carbon fiber bundle according to claim 12 , wherein the single fiber fineness is at least 1.1 dtex.
15. The carbon fiber bundle according to claim 12 , wherein the total fineness is at least 4800 dtex to no more than 56000 dtex.
16. The carbon fiber bundle according to claim 12 , wherein the number of single fibers is at least 6,000 to no more than 50,000.
17. The carbon fiber bundle according to claim 16 , wherein the number of single fibers is no more than 36,000.
18. A resin-based composite material comprising the carbon fiber bundle according to claim 12 .
19. A method of producing carbon fiber bundles for obtaining the carbon fiber bundle according to claim 12 , comprising:
a heat treatment step of heat treating, for at least 80 minutes to no more than 240 minutes under an oxidizing atmosphere rising in temperature within the temperature range of 220 to 300° C., a polyacrylonitrile-based precursor fiber bundle having a single fiber fineness of at least 1.7 dtex to no more than 4.6 dtex consisting of a polyacrylonitrile-based copolymer containing 96 to 99% by mole of acrylonitrile units and 1 to 4% by mole of hydroxyaklyl methacrylate units, and/or a polyacrylonitrile-based precursor fiber bundle having a single fiber fineness of at least 1.7 dtex to no more than 4.6 dtex having a constant velocity temperature rising exothermic curve of 30° C. to 450° C. measured in an air flow of 100 ml/min that is a flowrate based on 30° C. at 0.10 MPa and at a heating rate of 10° C./min using a heat flux-type differential scanning calorimeter that satisfies conditions (A) and (B) below:
(A) heat amount Ja obtained by integrating the heat generation rate of at least 230° C. to no higher than 260° C. of a constant velocity temperature rising exothermic curve is at least 140 kJ/kg to no more than 200 kJ/kg;
(B) heat amount Jb obtained by integrating the heat generation rate of at least 260° C. to no higher than 290° C. is at least 600 kJ/kg to no more than 1,000 kJ/kg; and
a step of conducting carbonization treatment to heat treat the fiber bundle obtained from the heat treatment step at a highest temperature of at least 1,500° C. under an inert gas atmosphere, so as to make a carbon fiber bundle having a strand modulus of elasticity obtained by the method of ASTM D4018 of at least 240 GPa.
20. The method of producing carbon fiber bundles according to claim 19 , wherein the highest temperature is at least 1,800° C.
21. The method of producing carbon fiber bundles according to claim 19 , wherein a number of single fibers in the polyacrylonitrile-based precursor fiber bundle is at least 6,000 to no more than 50,000.
22. The method of producing carbon fiber bundles according to claim 19 , wherein an elongation rate of polyacrylonitrile-based precursor fiber bundles in the heat treatment step is at least −5% to no more than 5%.