GB874652A - Drawing process for polyethylene terephthalate filaments - Google Patents

Abstract

High-tenacity multi-filament tows of polymethylene terephthalates, of at least 1,000 denier, are made by subjecting filamentary material comprising such tows to the following series of operations in a continuous sequence. (a) The filamentary material is led from a melt-spinning machine comprising a pressure feed, a melting zone, a metering pump and spinneret pack, as a flat ribbon on to a series of feed rolls and is heated to 80 DEG -110 DEG C. while travelling at not less than 500 ft./min.; (b) The tow is led on to a second series of rolls having a surface speed at least 4, but less than 6, times that of the feed rolls and is heated to 80 DEG -110 DEG C.; (c) The tow is led through a heating zone and is heated to 150 DEG -180 DEG C.; (d) The tow is led on to a third series of rolls having a surface speed 6,0-6,4 times that of the feed rolls; (e) The tow passes, under tension such that no further elongation takes place, to a collecting means. The tow may be heated in stages (a) and (b) by using rolls which are heated, e.g. by a fluid heat-transfer medium or electrically. Slippage of the tow around the rolls may be prevented by using rolls of highly polished chromium-plated steel, or by having sufficient arc and length of contact of the tow around the rolls so that slippage cannot occur, or by passing the tow several times around a skewed idler roller and an adjacent driven roller, or a loaded cot roller may press against the filaments passing around the first feed roll. These methods may be used singly or in combination. As the heating zone of stage (c) may be used a radiant heater, a heated fluid bath, or a steam-heated plate which may have a matt-finished chromium plated surface. Collecting means may comprise a split drum traverse as in Specification 874,651. As shown, a flat ribbon of spun yarn 1 is led successively around the series of electrically heated rolls (2) and (3), corresponding to stages (a) and (b), over hot plate 4 (stage (c)), around a series of rolls (5) (stage (d)), and then passes to a traverse roll and wind up unit (not shown). Drawing takes place between 2 and 3 and between 3 and 5. Tows so made have a strength greater than 6 gms. per denier, e.g. a tow of 3,140 denier may have a tenacity of 7,0 gms. per denier and an elongation of 10%.