Process for adjusting the fiber structure of mesophase pitch fibers

Claim 1

A process for producing carbon fiber from a mesophase pitch feed material which comprises passing said pitch feed material into a spinnerette body having an entrance side for the pitch feed material and having an exit side for the carbon fiber; the spinnerette body having a spinnerette channel passing through it from the entrance side to the exit side; the channel comprising a capillary bore leading from within the body and opening out of the exit side thereof and having a capillary length to diameter ratio of from about 2:1 to 8:1; a larger diameter bore leading from the entrance side of the body toward the capillary bore and wherein the ratio of the diameter of the larger diameter bore to the diameter of the capillary bore is in the range between approximately 2:1 to 15:1; and a capillary bore entrance leading from the larger diameter bore into the capillary bore; the entrance being defined by a wall which narrows from the larger diameter bore to the capillary bore; the entrance wall having an entrance angle of from 120 to 170 degrees, which is measured diametrically across the entrance wall in a plane including a diameter of the entrance wall and the apex thereof, which is flat enough for giving the carbon fiber formed through the channel a greater proportion of tangential crossection of fibers.