Heat- and chemical-resistant acrylic short fibers without spinning

A heat- and chemical-resistant, pulp acrylic short fiber comprising a thickness distribution of 0.1 .mu.m to 50 .mu.m, a length distribution of 1 mm to 20 mm, a glass transition temperature of above 200.degree. C., and insoluble in dimethylformamide at room temperature, produced by a process which comprises:

• heating a mixture of water of 5% to 100% by weight and an acrylonitrile homopolymer or copolymer composed of acrylonitrile of above 70% by weight and a copolymerizable monomer of below 30% by weight and having a viscosity average molecular weight of 10,000 to 500,000 to temperatures above the melting temperature of the same mixture under enclosed conditions to form an amorphous melt;
• cooling the resulting amorphous melt to a temperature between the melting and the solidifying temperatures ranging from 135.degree. C. to 178.degree. C. to obtain a supercooled melt phase;
• extruding the resulting supercooled melt through a slit- or round-shaped extrusion die into an external atmosphere at room temperature and under normal pressure to give extrudates having a sectional structure in which microfibrils formed by solidification of the extrudates while water being automatically removed in the direction of extrusion after the extrusion and extended spaces from which water is drained off, are uniformly arranged in the direction of the extrusion in the enclosed inside of a surface, and a fibrous crystalline structure and a molecular orientation degree above 70% on an X-ray diffraction pattern;
• passing the resulting continuous extrudates under tension through between two rollers, which is maintained at 100.degree. C. to 180.degree. C. and to which compressive force is applied, followed by drying and drawing;
• and
• subjecting the dried and drawn extrudates to heat-stabilization for 1 minute to 4 hours at 180.degree. C. to 300.degree. C., followed by cutting into said length distribution and beating mechanically.