| 摘要 |
PURPOSE:To produce the titled fiber causing little fibrillation and cracking, etc., by applying a shear stress of higher than a specific level to a molten pitch material in a capillary part before final nozzle hole and temporarily maintaining the pitch material in a state free from shear stress. CONSTITUTION:A molten pitch material is passed through a circular, modified or slit capillary part placed before the final nozzle hole. A shearing stress of >=1/2 of the stress imparted in the final nozzle hole is applied to the pitch by this process. The pitch material is temporarily maintained in a state essentially free from shear stress and, thereafter, passed through the final nozzle hole to obtain a carbon fiber having stable higher-order cross-sectional structure. At least a part of the fiber cross-section has an onion-like form.
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