Vorrichtung zum Heissverstrecken und zum Reduzieren des Schrumpfvermögens eines Polyäthylenterephthalatfadens

摘要

An apparatus for hot-stretching and heat-setting polyethylene terephthalate filaments comprises a block of a metal or alloy, the thermal conductivity of which, at 20 DEG C. exceeds 0,5 cals. deg. C. -1 cm. -2 cm. sec.,-1 which block is provided with a single source of heat and to one side of which are fixedly attached two metal snubbing pins, the metal of one of which has a thermal conductivity at 20 DEG C. in excess of 0,5 cals. deg. C.-1 cm. -2 cm. sec.-1 and the metal of the other of which has a lower thermal conductivity, the ratio of the cross-sectional areas of the pins at their junctions with the metal block being such that, when the metal block is heated, the temperature of the surface over which the filaments pass of the pin of higher-conductivity is higher than that of the corresponding surface of the other pin, the device being so disposed with respect to the feed and draw rolls of the stretching apparatus that the filaments from the feed rolls pass first over and in contact with the pin at the lower temperature and then over and in contact with the pin at the higher temperature before passing to the draw rolls. As shown, the unstretched thread travels from a spinning bobbin 1 over a feed roll 2 to a snubbing pin 5 of iron (conductivity 0,14) attached to a copper block 4 (conductivity 0,94) by means of a neck having a cross-sectional area of 53,5 mm.2 The thread then passes over a snubbing pin 6 consisting of copper having a cross-sectional area throughout its length of 80,5 mm.2 to draw rolls 7. The copper block 4 is heated by the passage through the copper tube 3 welded to the block of a mixture of diphenyl and diphenyl oxide vapours at 165 DEG C. The temperature of the pin 5 at the surface thereof over which the thread passes is 104 DEG C. and the temperature of the corresponding surface of the pin 6 is 156 DEG C. The thread is stretched to a draw ratio of 370% during its passage through the apparatus. Both pins are provided with thin steel sleeves, the external surfaces of which have been matt-chromed. The heating tube 3 may be common to over 70 stretching devices, the pins of all of which can be maintained within a narrow temperature range. Specification 638,671 is referred to.