| 摘要 |
964,393. Stretching nylon filaments. MONSANTO CHEMICAL CO. May 29, 1962 [May 31, 1961], No. 20626/62. Drawings to Specification. Heading B5B. Nylon filaments capable of being molecularly oriented are longitudinally fed to a first stretch zone at a predetermined rate, withdrawn from this zone at a predetermined increased rate, the movement of the filaments through this zone being snubbed so that there is a tendency for the point of necking down of the filaments to be localized, heated upon their exit from the first zone to 160-190‹ C. for a time of 0.05 to 0.80 second, the heat being applied while the filaments are maintained at constant length, immediately thereafter further stretched in a second stretch zone while cooling them and without snubbing them, quickly quenched and taken up in an orderly manner, the overall draw ratio employed being 5.0 to 6.1 and the draw ratio employed in the second stretch zone being 1.2 to 1.9. The overall draw ratio may be 5.0 to 6.0 and the temperature of the filaments when snubbed 20‹ to 85‹ C. The temperature to which the filaments are quickly quenched may be at least 60‹ to 90‹ C. below the elevated temperature obtained by the filaments when heated at constant length. The filaments may be stretched in the second stretch zone at an ambient temperature of 20‹ to 85‹ C. The filaments may be quenched by contacting them with a cooled heat conductive surface. In an example, a 140 filament nylon-66 yarn with a spun denier of 4250 is fed to and around a first stage drawing pin having a temperature of 38‹ C., the first stage draw ratio being 3.82. The yarn is then heated by being passed over a heater block at 180‹ C. disposed between a draw roll and an accessory separator roll. Multiple threadline wraps are made around the roll-heater block assembly to raise the yarn temperature to about 170‹ C. while the yarn is maintained at substantially constant length. The yarn is then drawn in a second stage at a draw ratio of 1.5 by means of a larger draw roll and separator roll assembly. No external heat is applied during the second stage drawing and as the larger draw roll is heat conductive and interiorly vaned, heat is dissipated therefrom and the temperature of the roll is prevented from rising above 50‹ C. By means of the process of the invention high tenacity nylon yarn may be produced with only a small number of thread breaks per pound of yarn even when using high overall draw ratios. |
