ES355813A1 - Process for the preparation of synthetic polymer filaments - Google Patents

Abstract

A process for the production of oriented synthetic polymer filaments comprises extruding a molten polymer through a spinneret 1 to form filaments 2, cooling said filaments (as e.g. by a transversely directed stream of air 3), passing said filaments over a guiding device 4 and around at least one non-driven roll 5, subjecting said filaments to a drag by passing them over at least one snubbing pin 6, the assembly consisting of the guiding device 4, roll or rolls 5 and snubbing pin or pins 6 being at such distance from the spinneret that the filaments when passing over the guiding device and the snubbing pin are cooled to a temperature above their glass transition temperature and at least 50 C. below their melting point, maintaining the guiding device and the snubbing pin at a constant temperature at least 10 C. below the temperature of the filaments and above the dew point of the surrounding air, and orienting the filaments by withdrawing them from the snubbing pin at a tension of less than 1À0 gram per denier. The denier of the filaments is suitably between 1 and 90, and that of the oriented filaments is the same as that of the unoriented, as-spun filaments. Specified materials include polyamides, e.g. polycaprolactam and polyhexamethylene adipamide, copolyamides, especially from hexamethylenediamine adipate and caprolactam, polyesters, especially polyethylene terephthalate, and polyolefines, especially polypropylene. The distance from the spinneret, at which the filaments are in the prescribed temperature range, differs considerably for filaments of different deniers, as thin filaments cool more rapidly than thicker ones. Suitable distances between spinneret and snubbing assembly can be found by observing the respective temperature of the filaments with a pyrometer, but an easier and more exact indirect method is to measure the tension of the filaments between snubbing pins and withdrawal roll. This tension depends on the drag and the temperature of the filaments, and a graph in which the filament tension is plotted against the distance between spinneret and snubbing pin assembly passes through a distinct minimum (see Fig. 2), so that when the assembly is at a distance corresponding to or near this minimum, the filaments are in the prescribed temperature range. In the apparatus of Fig. 1, the guiding device 4 consists of a pin with several U-shaped grooves, one each for a filament or bundle of filaments. The filaments then pass around two non-driven rolls 5 and thence over two snubbing pins 6 mounted on a turntable socket, so that by turning the socket, the arcs of contact between the filaments and the pin and thus the drag on the filaments can easily be varied. Alternatively, one snubbing pin only may be used, or a system of four pins can be employed if increased drag is required. On leaving snubbing pin 6, the filaments pass over a roll 7 which applies a finishing preparation and are finally withdrawn by motordriven rolls 8 and wound-up on bobbin 9. Guiding device 4 and snubbing pins 6 preferably consist of hollow tubes connected to the circulation system in which a liquid is kept at constant temperature by means of a thermostat. The yarns so obtained may be additionally drawn on conventional drawing apparatus comprising feed roll, hot plate, snubbing pin, and draw roll. In an example such filaments are drawn at a ratio of 1À8 to 1. The method enables melt-spun oriented synthetic polymer filaments to be obtained by a one-stage process using conventional withdrawal speeds, and it is possible to obtain oriented single filaments of e.g. 55-85 denier. Withdrawal speeds used in the examples are between 400 and 1000 metres per minute.