Patent GB-1193656-A (GB)
Title: Process and apparatus for Drawing Polyester Filaments
Inventor: FUKUSHIMA TAKAAKI
IPC: D01D5/12
Filed: 1967-08-10
Abstract: 1,193,656. Drawing polyester filaments. TEIJIN Ltd. 10 Aug., 1967, No. 36848/67. Heading B5B. A bundle of undrawn polyester filaments having a filament denier below 150, a birefringence between 0À0005 and 0À015 and containing at least 80 mol per cent of ethylene terephthalate units, is drawn by passing the filaments in a plurality of loops around a positively rotated heated feed roller and a freely rotatable separator roller which co-operates with a freely rotatable pressure roller and from the feed roller to a draw roller provided with a separator roller, the draw roller being positively rotated at a peripheral speed which is higher than the peripheral speed of the feed roller to thereby draw the filaments, the pressure roller having an elastic outer surface and being arranged so that at least the last feed loop on the feed roller is pressed into contact with the outer surface of the feed roller, the point of contact being such that an angle (α) formed by a radius connecting the point where the filaments would depart from the feed roller if the pressure roller were not used with the axis of the feed roller and a radius connecting the said point of contact with the axis of the feed roller does not exceed 20 degrees and is preferably within the range 0 to 3 degrees, the surface temperature (T‹ C.) of the heated feed roller being within the range of the second order transition point of the undrawn filaments (Tg‹ C.) to a temperature 55‹ C. higher than the second order transition point and the contact time of the undrawn filaments with the heated feed roller (t sec.) satisfying the equation A pre-tension may be imparted to the undrawn filaments before they are passed around the feed roller, the pre-tension being within the range of 10 to 90% of the tension at which a neck occurs as shown in a stress-strain curve of the undrawn filaments measured at a temperature of 20‹ C. and a relative humidity of 65%. Means such as a slot heater may be provided for heat treating the filaments during their passage from the feed roller to the draw roller. The means for applying a pre-tension to the undrawn filaments may comprise a nip roller and a delivery roller which in use of the apparatus is adapted to rotate at a peripheral speed in the range of 1/1À001 to 1/1À030 of the peripheral speed of the feed roller. As shown in Figs. 1 and 2 a bundle of undrawn polyester filaments 2 is withdrawn from a supply bobbin 1 through a guide 5 by means of a pair of contrarotating nip rolls 3 and 4 and from thence the filaments pass to an internally heated feed roll 6 positively driven at a peripheral speed slightly higher than that of the nip rolls 3 and 4 whereby a slight tension is imparted to the filaments. The feed roll 6 is provided with a separator roll 8 and is maintained at a predetermined temperature. A freely rotatable pressure roll 7 having a resilient outer surface is urged against the feed roll and is so disposed axially with respect to the feed roll that it presses upon either several wraps of the filaments round the feed roll, including the last wrap before the filaments leave the feed roll, or only upon the last wrap, the position of the necking down zone of the filaments in either case being thereby restricted to the point where the pressure roll 7 presses on the last wrap of the filaments about the feed roll 6. The filaments pass from the feed roll 6 to the positively driven draw roll 10 with its associated separator roll 11. Optionally the filaments may pass through a slot heater 9 in their passage from the feed roll to the draw roll. The position of the pressure roll 7 with respect to the feed roll 6 and the point where the filaments leave the feed roll 6 is shown in Fig. 3, which is a cross-section on an enlarged scale of the feed roll assembly. The angle α between a radius connecting the centre A of the crosssection of the feed roll 6 with the point B where the filaments would leave the feed roll if the pressure roll 7 were not in contact with the feed roll and the radius joining the centre A of the cross-section of the feed roll 6 with the point of contact D between the pressure roll 7 and the feed roll 6 must not exceed 20 degrees. As shown in Fig. 3, point D is upstream of point B with respect to the direction of travel of the filaments round the feed roll 6 and consequently the position of the point B is the same as it would be if the pressure roll 7 were not in contact with the feed roll 6.