Patent ID: 6054214
Filing Date: 2000-04-25
Classification: D01F,Y10T

Abstract:
A carbon fiber prepared according to a process comprising the steps of:(a) obtaining an extruded fiber comprising a substantially metal-free, substantially vinyl-sulfonic acid monomer-free polyacrylonitrile in an amount of about 95% to about 98% based on weight, a vinyl carboxylic acid monomer in an amount sufficient to retain in the copolymer ammonium ion or amine catalyst in an amount of about 1% to about 4% based on molar ratio, and optionally vinyl carboxylic acid ester monomer in an amount up to about 2% based on weight;(b) adding to the fiber an oxidation catalyst which is a member selected from the group consisting of ammonia and low molecular weight amines;(c) washing, drying and stretching the fiber to form a precursor;(d) removing the precursor to an oxidation zone;(e) heating the precursor at a temperature below the fusion temperature of said precursor for a time sufficient to initiate crosslinking reactions between the ammonium ion or amine catalyst and pendant cyano groups of the copolymer;(f) increasing the heating in subsequent stages, as the fusion temperature of the precursor increases, to a temperature of about 400.degree. C. for a time sufficient to increase the fiber density to about 1.40 g/cc;(g) withdrawing an oxidized precursor from the oxidation zone;(h) passing the oxidized precursor to a carbonization zone;(i) carbonizing the oxidized precursor at a temperature of about