Method for producing mesophase pitch

Claim 1

A method for producing a 100% mesophase pitch composed only of Q.I and Q.S. components useful as a raw material for carbon fibers, which comprises the steps of (i) subjecting a petroleum-origin pitch to heat treatment with stirring under a stream of a carrier gas selected from the group consisting of a hydrocarbon of small carbon numbers, a lower boiling point naphtha fraction and a dry gas by-product of the heat treatment of the raw material petroleum-origin pitch and at an atmospheric or super atmospheric pressure and at a temperature of 360° C. to 450° C. to thereby bring the mesophase content in the resulting pitch within the range of 10% to 50%, (ii) holding the heat-treated pitch in a quiescent aging-coalescing state at a temperature of higher than 280° C. and lower than 350° C., to thereby divide the heat-treated pitch into non-mesophase and mesophase, and (iii) separating the non-mesophase of the upper layer and the mesophase of the lower layer by the difference of physical properties therebetween at the same temperature as the aging-coalescing temperature, thereby providing the 100% mesophase composed only of Q.I. and Q.S. components.

Claim 2

A method for producing a 100% mesophase pitch composed only of Q.I and Q.S. components useful as a raw material for carbon fibers, which comprises the steps of (i) subjecting a petroleum-origin pitch to heat treatment with stirring under a stream of a carrier gas selected from the group consisting of a hydrocarbon of small carbon numbers, a lower boiling point naphtha fraction and a dry gas by-product of the heat treatment of the raw material petroleum-origin pitch and at an atmospheric or super atmospheric pressure and at a temperature of 360° C. to 450° C. to thereby bring the mesophase content in the resulting pitch within the range of 10% to 50%, (ii) holding the heat-treated pitch in a quiescent aging-coalescing state at a temperature of higher than 280° C. and lower than 350° C., to thereby divide the heat-treated pitch into non-mesophase and mesophase, and (iii) separating the non-mesophase of the upper layer and the mesophase of the lower layer by the difference of physical properties therebetween at the same temperature as the aging-coalescing temperature, thereby providing the 100% mesophase composed only of Q.I. and Q.S. components.