GB1025241A - Process for drawing and crimping synthetic meltspun filaments - Google Patents

Abstract

1,025,241. Drawing and crimping melt spun filaments. IMPERIAL CHEMICAL INDUSTRIES Ltd. Jan. 30, 1963 [Nov. 24, 1961], No. 42101/61. Heading B4B. A process for the manufacture of crimped filaments from undrawn melt spun filaments having a natural draw ratio at room temperature making them capable of being drawn to a draw ratio of at least 2: 1 and which in the case of filaments melt spun from polyethylene terephthalate have an intrinsic viscosity between 0À4 and 0À7 and an optical birefringence between 0À001 and 0À015, which process forms an integral part of a drawing process comprises drawing the filaments to a draw ratio of 2À5: 1 and 6: 1 between feed rolls and draw rolls and localizing the draw zone with a non-rotatable snubbing pin interposed between the rolls, heating the filament in a 1st zone maintained close to and before the snubbing pin to a temperature 10-45‹ C. above the 2nd order transition temperature of the polymer from which the filaments are made, 90‹ to 125‹ C. in the case of polyethylene terephthalate, passing the heated filaments without allowing them to cool and under such tension that stretching is limited to less than 20% and without drawings to said snubbing pin capable of being internally heated and maintained at a temperature between the second order transition temperature and 30‹ C. above the melting point of the filaments and at a temperature at least 45‹ C. above the 2nd order transition temperature and 30‹ C. above the melting temperature if a curved convex stationary heating surface is used in the first zone, the snubbing pin having a radius of curvature less than 6 mm. and as small as is consistent with structural strength and providing a surface and an arc of contact capable of localizing the draw zone by a tension gradient such that substantially all the drawing takes place on the snubbing pin and between it and the draw rolls but close to the snubbing pin and without reaching the draw rolls and while the filaments are spread into a ribbon so that they become heated by the snubbing pin, when making an arc of contact of at least 90 degrees and up to four turns around the pin, passing the filaments to the draw rolls rotating at a speed of at least 1000 ft. per minute, forwarding the filaments under a tension less than the drawing tension and subsequently relaxing the filaments at least 70% at room temperature, without any intermediate heating to a temperature above the second order transition temperature to show their full crimp of at least four crimps per inch and a crimp elongation of at least 70%, solely as a result of the specified drawing process. The filaments may be of polyethylene terephthalate or of polyamides. The arc of contact of the filaments with the snubbing pin may be 180 to 360 degrees. The 1st zone may consist of a curved cylindrical surface or a rotating roll, the distance of which from the snubbing pin expressed as a free tangential distance of the filament paths is 2 to 8 cm. The drawing speed may be 2000 to 4000 ft. per minute. The snubbing pin used may have a low heat conductivity and may be made of a ceramic material. The internal temperature of the pin may be from over 80‹ up to 290‹ C., particularly 130‹ to 190‹ C., when measured at the centre of the pin. The pin may have a diameter of 1À5 to 6À5 mm.