| 摘要 |
A composition for making artificial filaments comprises 80-98 per cent of polystyrene and 20-2 per cent of a copolymer consisting of (1) a binary copolymer of styrene and at least 20 per cent of acrylonitrile or (2) a ternary copolymer of styrene and at least 20 per cent each of acrylonitrile and alpha-methyl styrene. The ternary copolymer may consist of about 35 per cent styrene, about 30 per cent acrylonitrile and about 35 per cent alpha-methyl styrene, and may comprise about 8 per cent of the composition, the balance being polystyrene. The composition may be melt-spun to form a monofilament, which is cooled to below its melting-point either in a gaseous medium or in a liquid non-solvent bath, stretched to effect orientation, and then twisted or flexed to effect longitudinal rupture or splitting of the monofilament into a multiplicity of long continuous filaments, with little or no transverse rupture of the monofilament or of the finer filaments into which it splits. After the monofilament has been twisted and split longitudinally, the resulting bundle of filaments may be held so that the twist is maintained, and may be heated at about 80 DEG C. while thus held in order to set the twist. In a series of examples mixtures of 80-98 per cent of polystyrene with 20-2 per cent of the above ternary copolymer are extruded at about 460 DEG F. through an orifice 0.1 inch in diameter, the hot extruded monofilament formed being withdrawn from the orifice by a pair of rubber draw-rolls operated at a speed to reduce the diameter of the filament to 0.075 inch and positioned a distance from the orifice sufficient to permit partial cooling of the monofilament to about 230 DEG F. before stretching occurs. The partially stretched filament, after passing around snubbing rolls, is stretched further at a ratio of 5.8 to 9.2 by a second set of draw-rolls to reduce its diameter to about 0.02 to 0.03 inch. The resulting oriented filament is twisted about its longitudinal axis or flexed several times to split it into a multifilamentary strand, which is heated for about an hour at 80 DEG C. to set the twist permanently.
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