Method and apparatus for producing oriented synthetic filamentary structures

摘要

Filaments of synthetic high polymers are oriented by hot stretching them over draw or snubbing pins which are hollow, closed at one end and heated internally by supplying hot vapours continuously thereto in such a manner that condensate forming in the pins flows back to the vapour source. As shown in Figs. 1 and 2, an elongated cylindrical boiler 1 is provided with openings 3 at intervals in its upper portion, which openings communicate with tapered interior channels 5 in hollow cylindrical blocks 4. A hollow cylindrical draw or snubbing pin 6 is mounted near the free end of and at right angles to each block 4, the pin pointing downwards at an angle of at least about 3 degrees to the horizontal. The hollow tapered interior 7 of each pin 6 communicates with the tapered interior channel 5 in the block 4 through a drilling 8 in the side of the block. The hollow interior 7 of the pin 6 is tapered sufficiently to overcome the reverse tilt of the pin 6 and provide a downward slope from the end of the pin towards the drilling 8 of at least about 1 degree from the horizontal. Accordingly, vapour from a heating liquid 10 in the boiler which condenses in the pin will drain from the pin along the bottom 33 thereof, through the drilling 8 into the channel 5 in the block 4 and down the slope 34 of the block back into the boiler. At the same time, the continuous flow of vapour to the pin displaces any non-condensible gases present in the pin upwards along the upper surfaces 35, 36 and into the upper section of the boiler 1 for removal through vents 14 normally closed by valves. The boiler is provided near the bottom with two horizontal tubes 11 running its entire length and containing rod-shaped electric heating elements 12. One element is designed to operate continuously and provide about 60-85 per cent of the heat required, and the other is controlled to supply heat as required by means of a thermostat element located in the well 13 at one end of the boiler. In an example, the boiler is provided with six snubbing pins 6 of copper covered with bonded titanium dioxide sleeves and is charged with trichlorotrifluoroethane which is thermostatically maintained at 99 DEG /sB 0.5 DEG C. Under conditions such that considerable amounts of non-condensable gases tend to accumulate in the apparatus, the modified form shown in Figs. 3 and 4 is preferred. The cylindrical block 15 sealed to the upper part of the flat side of an elongated boiler 16 of semi-circular cross-section is provided with two tapered interior channels 17, 18 such that the lower surface 37 of lower channel 17 slopes downwards to the boiler, the upper surface 38 of upper channel 18 slopes upward towards the top of the boiler, and the partition 39 between the channels 17, 18 joins a curved baffle 25 running the entire length of the boiler and having openings 28 below the level of the heating liquid 27 to allow the liquid in each side of the baffle to attain a common level. A hollow cylindrical snubbing pin 21 mounted on the side of and near the free end of the block 15 has a hollow tapered interior 22 which communicates with the channels 17, 18 in the block 15 by an opening 23 in the side of the block. A baffle 24 fixed to the block between the channels 17, 18 is aligned with the partition 39 and divides opening 23 into upper and lower channels 231, 232, and extends into the hollow interior 22 of the pin for a considerable distance (Fig. 4). The boiler 16 is provided with vents 29, tubes 30 for heating elements 31, and a well 32 for the thermostat element. Non-condensable gases are forced into the upper section of the boiler, where they are trapped. Since the upper section of the boiler receives heat from the lower section only indirectly, vapour condenses in the upper section, causing a continuous gentle flow of vapour from the lower section of the boiler through channels 17, 232 into the hollow pin 21, and through channels 231, 18 into the upper section of the boiler. The upper part of the boiler may be left uninsulated in order to increase condensation of vapour in that part and hence the rate of flow of vapour through the hollow pins. In another modification the hollow pins are attached directly to a boiler of any desired shape and a small portion of the pin next to the boiler is thermally insulated. The invention enables the tenperature of the pins to be maintained constant within about 1 DEG C. and the dyeability of the filaments drawn over the pins to be thereby rendered more uniform. U.S.A. Specifications 2,071,251, 2,289,232 and 2,474,912 are referred to.