Petoca, Ltd.

Tanaka Kikinzoku Kogyo K.k.

Tetsuo Yamada

Susumu Shimizu

Haruki Yamasaki

Tomiji Hosotsubo

Toshifumi Kawamura

Yasuyuki Takai

Hiroshi Eziri

Hidekazu Saito

A process for preparing mesophase pitch based carbon fibers is disclosed, wherein mesophase pitch fibers are gas-phase nitrated in an atmosphere of an oxygen-containing gas such as air or an inert gas such as nitrogen containing 0.1 to 50% by volume of NO.sub.2 at a low temperature of not higher than 100.degree. C. for a long period of time. The carbon fibers thus obtained are excellent in both mechanical strength and elastic modulus and have well-balanced physical properties.

Process for producing carbon fibers

Disclosed herein is a spinning nozzle having one or more discharge openings and one or more introduction openings located upstream the discharge openings for producing pitch-based carbon fibers characterized by the presence of one or more spiral members in each introduction openings. According to the nozzle of the present invention, part of the pitch which is introduced to the introduction opening flows down along the spiral member while the flow of the pitch is affected by the spiral member. The remaining pitch flows into the discharge opening without being in contact with the spiral member, and then both are spun after being mixed through the discharge opening to prepare carbon fibers having a random structure. Especially, the carbon fibers of higher performances can be prepared when a spiral having uneven outer diameters is employed.

Nozzle for spinning pitch-based carbon fibers

Carbon fibers are provided essentially consisting of liquid crystal pitch based continuous monofilaments having an average filament diameter of 30 .mu.m or greater. The carbon fibers can have modulus of elasticity of 80,000 Kgf/mm.sup.2 or greater and tensile strength of 200 Kgf/mm.sup.2 or greater. The carbon fibers can be used as a multifilament fiber consisting of plural monofilaments as in the case of conventional carbon fibers but it is particularly preferable that a number of constituting monofilaments is one.

Process of making pitch-based carbon fibers

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Ibaraki-ken, Japan

Tetsuo Yamada