Process for the production of carbon filaments utilizing an acrylic precursor

Claim 1

An improved process for the production of a multifilament carbonaceous fibrous material which is suitable for use as a fibrous reinforcement in a resinous matrix consisting essentially of: (a) contacting a multifilament acrylic fibrous material selected from the group consisting of an acrylonitrile homopolymer and acrylonitrile copolymers containing at least about 85 mol percent acrylonitrile units and up to about 15 mol percent of one or more monovinyl units copolymerized therewith with a liquid medium comprising a dispersion of colloidal silica having a number average particle size of about 5 to 50 millimicrons in a C 1 to C 3 alkanol in a concentration of about 0.002 to 1.0 percent by weight based upon the weight of said alkanol, (b) drying said resulting fibrous material under conditions wherein said C 1 to C 3 alkanol is substantially evolved from said fibrous material and said colloidal silica is deposited upon the surface of said fibrous material in a concentration of about 0.005 to 0.4 percent by weight based upon the weight of said fibrous material, (c) thermally stabilizing said fibrous material bearing said colloidal silica upon its surface by heating in a gaseous atmosphere consisting of air at a temperature of about 230° to 300° C. in the absence of filament coalescence to form a flexible fibrous material which retains its original configuration substantially intact, is non-burning when subjected to an ordinary match flame, and is capable of undergoing carbonization, (d) substantially removing said colloidal silica from said fibrous material, and (e) heating said resulting thermally stabilized fibrous material in a non-oxidizing gaseous atmosphere selected from the group consisting of nitrogen, argon, and helium at a temperature of at least 1000° C. until a carbonized fibrous material containing at least 90 percent carbon by weight is formed.