Fiber production method and carbon fiber production method

Abstract

A method of producing a fiber, the method including discharge, from a spinneret 1 , a spinning dope solution containing a fiber-forming polymer dissolved in a solvent, once allowing the solution to run in air, and then guiding, the solution into the liquid of a coagulation bath 4 to allow coagulation, wherein a gas-phase portion thrilled in a vertically downward direction from a discharge surface of the spinneret 1 to the liquid surface of the coagulation bath 4 has an air flow rate per unit time (Af) which satisfies, in relation to the amount of the solvent in the spinning dope solution per unit time (As) in the gas-phase-portion volume (Vh), the relational expression 0.0008 m 3 ≤Af(As/Vh)≤0.0015 m 3 , and the hourly average of the absolute humidity at each of four points in an outer periphery of the spinneret in the gas-phase portion is not more than 20 g/m 3 . A method of producing a fiber, which, in dry-jet wet spinning, suppresses occurrence of dew condensation in the spinneret, and reduces deterioration of the appearance caused by winding on rollers in the subsequent process or by fuzzing or yarn break in the stretching process, to enable significant improvement of the productivity and the appearance as a whole, is provided.

1 . A method of producing a fiber, the method comprising discharge, from a spinneret, a spinning dope solution containing a fiber-forming polymer dissolved in a solvent, once allowing the solution to run in air, and then guiding the solution into a coagulation bath liquid to allow coagulation, wherein a gas-phase portion formed in a vertically downward direction from a discharge surface of the spinneret to a coagulation bath liquid surface has an air flow rate per unit time (Af) which satisfies, in relation to the amount of the solvent in the spinning dope solution per unit time (As) in the gas-phase-portion volume (Vh), the relational expression 0.0008 m 3 ≤Af/(As/Vh)≤0.0015 m 3 , and the hourly average of the absolute humidity at each of four points in an outer periphery of the spinneret in the gas-phase portion is not more than 20 g/m 3 . 
     
     
         2 . The method of producing a fiber according to  claim 1 , wherein the relative standard deviation of the wind velocities at four points in an outer periphery of the spinneret in the gas-phase portion is not more than 40%. 
     
     
         3 . The method of producing a fiber according to  claim 1 , wherein the number of holes in the spinneret is not less than 2,000 and not more than 50,000. 
     
     
         4 . The method of producing a fiber according to  claim 1 , wherein the fiber-forming polymer is an acrylonitrile copolymer. 
     
     
         5 . A method of producing a carbon fiber, comprising producing a fiber by the method of producing a fiber according to  claim 4 , performing oxidation treatment in an oxidizing gas at 200 to 300° C., and then heating the fiber in an inert gas at not less than 1,000° C.