Forming optically anisotropic pitches

A process for producing a carbonaceous pitch containing greater than about 90 wt. % of an optically anisotropic phase which is at least 75 wt. % soluble in quinoline when extracted with quinoline at 75.degree. C. comprising:

• treating a carbonaceous isotropic pitch with an organic solvent system having a solubility parameter of between about 8.0 and 9.5, said treating being at a temperature and with an amount of said organic solvent system sufficient to provide a solvent insoluble fraction which is benzene insoluble at a temperature in the range of from about 22.degree. C. to about 30.degree. C. and which undergoes a phase change below about 350.degree. C. when a sample thereof is subjected to differential thermal analysis in the absence of oxygen;
• and, thereafter,
• heating said solvent insoluble fraction to a temperature in the range of from about 230.degree. C. to about 400.degree. C., whereby said solvent insoluble fraction is converted to a pitch containing greater than 90% of an optically anisotropic phase and which is at least 75 wt. % soluble in quinoline when extracted with quinoline at 75.degree. C.

In the process for preparing an optically anisotropic deformable carbonaceous pitch containing greater than 75% of an optically anisotropic phase by heating an isotropic carbonaceous pitch to temperatures in the range of from about 230.degree. C. to about 400.degree. C., the improvement comprising:

• extracting said isotropic carbonaceous pitch with a solvent selected from organic solvents and mixtures thereof, said solvent being at a temperature and in an amount sufficient to provide a solvent insoluble fraction having a carbon/hydrogen ratio of between about 1.6 to 2.0 and capable of undergoing a phase change below about 350.degree. C. as determined by differential thermal analysis of a sample of said insoluble fraction in the absence of oxygen;
• and thereafter heating said solvent insoluble fraction at temperatures in the range of about 230.degree. C. to about 400.degree. C. whereby said solvent insoluble fraction is converted to a deformable pitch containing greater than 75% of an optically anisotropic phase which is greater than 75% by weight soluble in quinoline when extracted by quinoline at 75.degree. C.

A process for preparing a pitch fiber comprising:

• extracting a graphitizable isotropic pitch with an organic solvent system having a solubility parameter of between about 8.0 to about 9.5 at 25.degree. C., said pitch containing less than 5 wt. % of quinoline insolubles as determined by extraction with quinoline at 75.degree. C., said extraction being conducted at a temperature and with an amount of said solvent system sufficient to provide a solvent insoluble fraction which if heated for 10 minutes and less to a temperature about 30.degree. C. above the point where said insoluble fraction becomes fluid, said fraction is converted to a pitch, which being allowed to cool by ambient temperature will have greater than 75% by weight of an optically anisotropic phase and less than 25 wt. % of substances insoluble in quinoline when said pitch is extracted with quinoline at 75.degree. C.;
• heating said solvent insoluble fraction to a temperature of about 300.degree. C. to about 380.degree. C. while extruding said heated insoluble fraction through an extrusion orifice thereby forming a pitch fiber.

A carbonaceous pitch having a suitable viscosity for spinning at temperatures in the range of from about 230.degree. C. to 400.degree. C. and containing greater than 75% by weight of an optically anisotropic phase and which phase is less than about 25 wt. % insoluble in quinoline when extracted with quinoline at 75.degree. C.

A carbonaceous pitch which:

• (1) when heated to temperatures up to about 400.degree. C. at a rate of about 10.degree. C. per minute exhibits a weight loss of less than about 5%;
• (2) when heated at temperatures of above about 230.degree. C. to about 400.degree. C. is converted to a pitch which contains greater than 75% by weight of an optically anisotropic phase which is at least 75% by weight soluble in quinoline when said heated pitch is extracted with quinoline at 75.degree. C.;
• and, (3) when heated to temperatures of from about 230.degree. C. to about 400.degree. C. exhibits a suitable viscosity for spinning.

A carbonaceous pitch fiber which greater than 75% by weight thereof is an optically anisotropic phase and less than 25 wt. % of which phase is insoluble when extracted with quinoline at 75.degree. C.