Process for preparing carbon fibers of high strength

A process for preparing carbon fibers of high strength while preventing agglutination thereof during preparation, comprising forming a polymeric solution by homopolymerizing acrylonitrile or copolymerizing at least 85 percent by weight of acrylonitrile with other vinyl monomers in a solvent of a concentrated zinc chloride aqueous solution to which is added, for decreasing amide groups in the fibers, hydrogen chloride in a concentration, excluding an amount for neutralizing basic salts, if any, in said zinc chloride solution, between 0.01 to 5% by weight, spinning said polymeric solution to form precursor filaments, and carbonizing said precursor filaments to provide carbon fibers.

A process for preparing carbon fibers of high strength by preventing agglutination thereof during preparation, which comprises forming a polymeric solution by homopolymerizing acrylonitrile or copolymerizing at least 85 percent by weight of acrylonitrile with other vinyl monomers in a concentrated zinc chloride aqueous solution which contains impurity levels of basic salts, and for reducing amide groups in said fibers and increasing the strength of carbon fibers formed there being included in said zinc chloride aqueous solution hydrogen chloride in an amount by weight of from 0.01 to 5% in excess of an equivalent amount of the basic salts to form a zinc chloride solution of a pH of at most 2 prior to forming said polymeric solution, spinning said polymeric solution to form precursor filaments, and carbonizing said precursor filaments to provide carbon fibers, said spinning being effected at a temperature of at most 60.degree. C.