Claims
- 1. A method for preparing carbon fibers from a pitch, wherein the pitch is spun into pitch fibers, the pitch fibers are treated with an oxidizing gas and the treated fibers are carbonized into the carbon fibers, said method comprising:
- introducing the loaded pitch fibers on a net-belt conveyor into a infusibilizing furnace having at least two exposing chambers arranged in series of increasing temperature said exposing chambers having a temperature gradient of 5.degree. to 100.degree. C. per chamber in the direction of from the inlet to the outlet of said infusibilizing furnace;
- exposing the introduced pitch fibers to a gaseous mixture of air and a gaseous oxidizing agent by passing said gaseous mixture between said introduced fibers at a temperature lower than the softening point of said pitch fibers by 5.degree. to 50.degree. C., said gaseous mixture is circulated at a velocity represented by the equation (1): ##EQU3## wherein U.sub.G represents said velocity of said gaseous mixture in circulation in said infusibilizing furnace and is in a range of not less than 0.1 and not larger than 1.5 Nm/sec, .rho..sub.B represents the packing density of said pitch fibers loaded on said net-belt conveyer and is in a range of not less than 30 and not larger than 300 kg/m.sup.3, H represents the packing height of said pitch fibers loaded on said net-belt conveyer and is in a range of not less than 0.02 and not larger than 0.5 m and .theta. represents the time period of infusibilization in said infusibilizing furnace and is in a range of not less than 1 and not larger than 4 hours, within said infusibilizing furnace forcibly.
- 2. A method according to claim 1, wherein the highest temperature at which said infusibilization is 300.degree. C. and not higher than 300.degree. C.
- 3. A method according to claim 1, wherein said gaseous oxidant is selected from the group consisting of oxygen, ozone, sulfur dioxide and nitrogen dioxide.
- 4. A method according to claim 1 or claim 3, wherein said gaseous oxidant is nitrogen dioxide.
- 5. A method according to claim 1, wherein the amount of nitrogen dioxide is 0.1 to 10% by volume to the amount of air.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of our copending application Ser. No. 105,130, filed Dec. 19, 1979, now U.S. Pat. No. 4,314,981.
US Referenced Citations (3)
Foreign Referenced Citations (3)
Number |
Date |
Country |
911660 |
Oct 1972 |
CAX |
1416614 |
Dec 1975 |
GBX |
1479218 |
Jul 1977 |
GBX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
105130 |
Dec 1979 |
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