| 摘要 |
A method of extruding polypropylene filaments in which the polypropylene is extruded at a temperature below 375 DEG F., such as in the range 335 DEG F. to 365 DEG F., particularly about 350 DEG F., into a quiescent hot zone having a temperature sufficiently high to retard cooling of the extruded polypropylene filaments. The filaments are then passed through and cooled in a quench zone across which cooling air is blown. The polypropylene has a narrow molecular weight distribution with a swell value less than 2.5, and its melt flow may be greater than 30. The yarn is drawn-down in the hot zone and the filaments may be drawn-down to an undrawn denier of less than 15 with substantial elimination of resonance.
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