Oxidized fiber bundles, carbon fiber bundle production method, and oxidation furnace

Abstract

Efficient production of high quality oxidized fiber bundles and carbon fiber bundles is described, comprising a step for heat-treating aligned acryl based fiber bundles in an oxidizing atmosphere while turning them back on guide rollers installed on both ends outside the furnace body of a hot gas heating type oxidation furnace wherein: supply nozzles for supplying hot gas into a heat treatment chamber are installed at an end in the traveling direction of the acryl based fiber bundles; a fiber bundle traveling passage(s) exists above and/or below each nozzle; hot gas is supplied from the supply face(s) located above and/or below the acryl based fiber bundle; and the requirements (1) and (2) are satisfied where Vf and V are defined as described.1.5 m/s≤Vf≤15 m/s   (1)1.5 m/s≤V≤10 m/s   (2)

1 . A production method for an oxidized fiber bundle comprising a step for heat-treating aligned acryl based fiber bundles in an oxidizing gas atmosphere while turning them back on guide rollers installed on both ends outside the furnace body of a hot gas heating type oxidation furnace wherein:
 supply nozzles for supplying hot gas into a heat treatment chamber are installed at an end in the traveling direction of the acryl based fiber bundles;   a fiber bundle traveling passage(s) exists above and/or below each nozzle;   hot gas is supplied from the supply face(s) located above and/or below the acryl based fiber bundle; and   the requirements (1) and (2) are satisfied where Vf is the gas flow speed in a substantially parallel direction to the traveling direction of the acryl based fiber bundle in the fiber bundle traveling passage and V is the gas flow speed in a substantially parallel direction to the traveling direction of the acryl based fiber bundle in the heat treatment chamber,
   1.5 m/s≤ Vf≤ 15 m/s, and   (1)
 
   1.5 m/s≤ V≤ 10 m/s.   (2)
 
   
     
     
         2 . A production method for an oxidized fiber bundle as set forth in  claim 1 , wherein the requirements (3) and (4) are satisfied where Vf is the gas flow speed in a substantially parallel direction to the traveling direction of the acryl based fiber bundle in the fiber bundle traveling passage and V is the gas flow speed in a substantially parallel direction to the traveling direction of the acryl based fiber bundle in the heat treatment chamber,
   1.5 m/s≤ Vf≤ 10 m/s, and   (3)
     1.5 m/s≤ V≤ 6 m/s.   (4)
   
     
     
         3 . A production method for an oxidized fiber bundle as set forth in  claim 1 , wherein the requirement (5) is satisfied where Vn is the gas flow speed at the supply face in the orthogonal direction to the traveling direction of the acryl based fiber bundle,
   0.1 m/s≤ Vn≤ 5 m/s.   (5)
   
     
     
         4 . A production method for an oxidized fiber bundle as set forth in  claim 1 , wherein the hot gas supplied from the supply face has a temperature of 210° C. or more and 295° C. or less. 
     
     
         5 . A production method for an oxidized fiber bundle as set forth in  claim 1 , wherein the acryl based fiber bundle before heat treatment has a single fiber fineness of 0.05 to 0.22 tex. 
     
     
         6 . A production method for a carbon fiber bundle comprising a step for subjecting an oxidized fiber bundle produced by a production method for an oxidized fiber bundle as set forth in  claim 1  to precarbonization treatment at a maximum temperature of 300° C. to 1,000° C. in an inert gas atmosphere to produce a precarbonized fiber bundle and a subsequent step for subjecting the precarbonized fiber bundle to carbonization treatment at a maximum temperature of 1,000° C. to 2,000° C. in an inert gas atmosphere. 
     
     
         7 . An oxidation furnace designed to perform heat treatment of an acryl based fiber bundle comprising:
 (i) a furnace body having slits though which aligned fiber bundles can enter and exit the furnace body,   (ii) a plurality of supply nozzles disposed at intervals along a vertical line located at an end in the traveling direction of the fiber bundles in the heat treatment chamber so that hot gas is supplied into the furnace body,   (iii) a plurality of discharge nozzles disposed at intervals along a vertical line located at the other end in the traveling direction of the fiber bundles in the furnace body so that the hot gas supplied from the supply nozzles is discharged out of the heat treatment chamber,   (iv) at least one gas blowing device designed to circulate hot gas through the supply nozzles and the discharge nozzles,   (v) at least one heating device disposed in a flow path of the circulating hot gas, and   (vi) guide rollers disposed at both ends outside the furnace body to turn back the fiber bundles so that they travel to and from a plurality of times in the heat treatment chamber while passing through the spaces between mutually adjacent supply nozzles and between mutually adjacent discharge nozzles, wherein   (vii) each of the supply nozzles has a supply face(s) at the top and/or bottom so that a first hot gas stream(s) is supplied to the fiber bundle traveling passage(s) running above and/or below the supply nozzle and also has an auxiliary supply face on a side of the supply nozzle facing the interior of the heat treatment chamber so that a second hot gas stream is supplied, and   (viii) adjusting devices to adjust the gas flow speed of the first hot gas stream and the gas flow speed of the second hot gas stream supplied from the supply nozzle.