Mitsubishi Rayon Company, Limited

Toshiyuki Yasunaga

Yoshifumi Furutani

Teruhiko Sugimori

Yoshihiro Nishihara

Yoshinobu Shiraishi

Masaaki Toramaru

A process for producing an acrylic fiber comprising the steps of: (a) dissolving a polymer having a weight-average molecular weight of at least 5.times.10.sup.5 and containing at least 80 wt. % acrylonitrile in a solvent comprising dimethylformamide or dimethylacetamide at a polymer concentration of 5-15 wt. % to provide a spinning solution having a viscosity of 500-1,500 poises at 45.degree. C.; (b) extruding the solution into a gaseous medium to form filaments; (c) introducing the filaments into a coagulation bath comprising water and at least one of dimethylformamide and dimethylacetamide at 0.degree. C. or below; and (d) stretching the coagulated filaments to a draw ratio of at least 3 to provide an acrylic fiber having at least 90% X-ray orientation and an X-ray crystallinity parameter of up to 1 degree. The resulting acrylic fiber has high strength and high modulus.

Process for producing an acrylic fiber having high fiber characteristics

A spinning solution for acrylonitrile polymers is disclosed, which has a viscosity of 30 to 520 poises (at 50.degree. C.) and which comprises an acrylonitrile polymer having a reduced viscosity of not less than 4.0, a solvent, and water, wherein the water concentration and the polymer concentration fall within the range in the drawing surrounded by straight lines connecting point A (1 wt % and 30 wt % respectively), point B (1 wt % and 10 wt % respectively), and point C (10 wt % and 10 wt % respectively). The spinning solution exhibits satisfactory spinnability in spite of its high polymer concentration and provides void-free acrylonitrile fibers having a highly circular cross-section and excellent mechanical strength.

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Otake, Japan

Toshiyuki Yasunaga