Processes for producing polyacrylonitrile-base precursor fibers and carbon fibers

Abstract

A process for producing polyacrylonitrile-base precursor fibers for production of carbon fibers, which comprises spinning a spinning dope containing 10 to 25 wt % of a polyacrylonitrile-base polymer having an intrinsic viscosity of 2.0 to 10.0 by extruding the spinning dope from a spinneret by a wet spinning or a dry wet spinning method, drying and heat-treating fibers obtained by the spinning, and then steam drawing the resulting fibers, wherein the linear extrusion rate of the polyacrylonitrile-base polymer from the spinneret is 2 to 15 m/min.

1 . A process for producing polyacrylonitrile-base precursor fibers for production of carbon fibers, which comprises spinning a spinning dope containing 10 to 25 wt % of a polyacrylonitrile-base polymer having an intrinsic viscosity of 2.0 to 10.0 by extruding it from a spinneret by a wet spinning or dry wet spinning method, drying and heat-treating the fibers obtained in the spinning step, and steam-drawing the fibers obtained, wherein the linear extrusion rate of the polyacrylonitrile-base polymer from the spinneret is 2 to 15 m/min. 
     
     
         2 . The process according to  claim 1 , wherein the linear extrusion rate is 2 to 10 m/min. 
     
     
         3 . The process according to  claim 1 , wherein the spinning method is dry wet spinning. 
     
     
         4 . The process according to  claim 1 , wherein the melting point Tm in wet heat of the polyacrylonitrile-base polymer as measured by a differential scanning calorimeter is 186 to 200° C. 
     
     
         5 . The process according to  claim 1 , wherein the polyacrylonitrile-base polymer is a copolymer containing a component copolymerizable with acrylonitrile, and the amount of the copolymerizable component is 0.1 to 0.5 mol %. 
     
     
         6 . The process according to  claim 1 , wherein the single filament fineness of the polyacrylonitrile-base precursor fibers for production of carbon fibers is 0.7 to 1.0 dtex. 
     
     
         7 . A process for producing carbon fibers, comprising stabilizing the polyacrylonitrile-base precursor fibers for production of carbon fibers, produced by the process for producing polyacrylonitrile-base precursor fibers for production of carbon fibers as set forth in  claim 6 , in air having a temperature of 200 to 300° C., while drawing them at a draw ratio of 0.80 to 1.20, preliminarily carbonizing the fibers obtained in an inert atmosphere having a temperature of 300 to 800° C., while drawing them at a draw ratio of 1.00 to 1.30, and carbonizing the fibers obtained in an inert atmosphere having a temperature of 1,000 to 2,000° C., while drawing them at a draw ratio of 0.96 to 1.05. 
     
     
         8 . The process according to  claim 7 , wherein the draw ratio during stabilization is 0.90 to 1.20; the draw ratio during preliminary carbonization is 1.10 to 1.30; and the draw ratio during carbonization is 0.97 to 1.05.