GB1019597A - Improvements in or relating to polyamide yarns - Google Patents

Abstract

1,019,597. Polyamide filaments. ALLIED CHEMICAL CORPORATION, and SNIA VISCOSA SOC. NAZIONALE INDUSTRIA APPLICAZIONI VISCOSA S.p.A. Dec. 3, 1962 [Dec. 12, 1961], No. 45678/62. Heading B5B. Polycaproamide filaments are continuously drawn, continuously heated at temperatures at which they would contract if free from tension, while said contraction is substantially impeded, and cooled at substantially constant length before winding. Molecularly oriented polycaproamide filaments having uniform shrinkage and a high initial modulus of elongation are thereby obtained. Desirably, polycaproamide filaments containing 1-5% #-caprolactam are cold-drawn while in equilibrium with the spinning room atmosphere, advanced at a tension not above 2 g. per denier into a heating zone comprising at least one stationary heated surface maintained at a steady temperature, at least one power-driven roll, and a heat-reflecting body enclosing said heated surface and said power-driven roll; each successive segment of each filament is heated as it advances by continuing contact with said enclosed heated surface and by radiation from said heat-reflecting body and with surface contact with said power driven roll in said heating zone, to temperatures at which the segment would retract if free from tension; and from continued contact with said enclosed surface and roll, each segment being maintained at said temperature and said segment being held at constant length as the filament advances, said successive segments are then advanced on at least one warp over at least one roll, through a cooling zone wherein each advancing segment is maintained at constant length for at least 0À5 sec. and until the restrictive force therein is not above 0À5 g. per denier. In a preferred method, a molecularly oriented yarn of total denier 30-100 is heated and maintained at constant length by contact in at least 5 wraps with said heated surface and with a pair of power-driven rolls in the heating zone, the temperature of the heated surface being 150-200‹ C., and the yarn having a residence time in the heating zone of about 1-5 sees. Cooling may be completed by the use of a jet of gas striking across and among the filaments of the yarn while the yarn is under a tension not above 0À3 g. per denier. Polycaproamide yarn so made may have a total denier of 30-100 and contain about 1-3% by weight of #-caprolactam, and is characterized by shrinkage in boiling water of 6À5 Œ 1% and initial modulus of elongation of 36 Œ 3 g. per denier. In the apparatus of Figs. 1 and 2, in zone A an undrawn nylon-6 yarn 1 is pulled from the bobbin by power-driven holdback roll 3, around cot roll 2 in several turns and through a solenoid type electric yarn clipper 12 actuated by the effect of a yarn break on sensing means 10 and switch 11, via snubbing pin 5 to a pair of power-driven draw rolls 4. The peripheral speeds of rolls 3 and 4 are adjusted to give the desired stretch to the yarn, which passes into heating zone B at a tension not exceeding 2 g. per denier. Zone B comprises power-driven rolls 6 geared for the same peripheral speed as rolls 4, contact heater 7, and cover 8 enclosing the contact heater and the rolls 6. Heater 7 is suitably heated by circulation of a hot fluid. Retraction of the yarn in the heating zone is prevented by contact with the heated rolls 6, the peripheral speed of which is the same as that of the draw rolls. Cover 8 over the contact heater and heating rolls 6 is of heat-reflecting material to assist uniform yarn heating. Yarn cooling is accomplished by a pair of cooling rolls 9, the peripheral speed of which is the same as that of heated rolls 6, and completed by a gas jet 30, e.g. an air jet, as the yarn leaves the cooling rolls under a low tension suitably not exceeding 0À3 g. per denier. In the apparatus of Fig. 6 the rolls used for drawing the yarn are elongated to provide roll surfaces for cooling and setting the yarn. Yarn 41 passes around cot roll 42, holds back roll 43 and snubbing pin 45 and past the heating zone to the draw and cooling rolls 44, then passes through opening 60 in heatreflecting cover 48 to a pair of heating rolls 46, which pass the yarn at constant length in multiple wraps around heater 47. Thereafter the yarn advances under low tension of about 1 g. per denier out of the heating zone via opening 11 in cover 48, around rolls 44, and past air-jet 70 to wind-up.