Process for producing optically anisotropic carbonaceous pitch

Claim 1

A process for producing a homogeneous, optically anisotropic carbonaceous pitch having a softening point in the range from about 230° C. to about 320° C. and an optically anisotropic phase content of about 90% to about 100% comprising: providing a carbonaceous material selected from oils and tars capable of forming a pitch when heated at elevated temperatures, said carbonaceous material having a boiling point in the range of about 250° C. to about 540° C. and being substantially free of chloroform and of n-heptane insoluble matter and containing a n-heptane-soluble material, said n-heptane-soluble material consisting essentially of an aromatic oil and resin, each of which has an aromatic carbon fraction of at least 0.6, a number-average molecular weight of up to 1000 and a maximum molecular weight of up to 2000; heating said carbonaceous material at a temperature in the range of about 380° C. to about 440° C. for a time sufficient to about 20% to about 80% of an optically anisotropic phase; maintaining said heated carbonaceous material at a temperature in the range from about 360° C. to about 380° C. for a time sufficient to form two layers, an upper layer containing a relatively low optically anisotropic phase content and a lower layer containing relatively high optically anisotropic phase content; separating said lower layer from said upper layer; thereafter heating said separated lower layer at a temperature in the range of 380° C. to about 440° C. for a time sufficient to increase the optically anisotropic phase content of said lower layer to at least 90% whereby a homogeneous optically anisotrophic carbonaceous pitch having a softening point in the range of about 230° C. to about 320° C. and an optically anisotropic phase content of about 90% to about 100% is obtained.