Patent GB-1173392-A (GB)
Title: Process and Apparatus for the Manufacture of Crimped Filaments of Synthetic Linear Polymers of High Molecular Weight
IPC: D02G1/00
Filed: 1968-01-03
Abstract: 1,173,392. Melt spun filaments having latent crimp. FARBWERKE HOECHST A.G. 3 Jan., 1968 [3 Jan., 1967], No. 446/68. Heading B5B. Crimped filaments are produced by melt spinning synthetic linear polymers, conducting the freshly spun filaments over and in contact with a dry surface of a cooling body without sticking thereto, the length of the path of travel of the filaments in contact with the surface and the temperature of the cooling body being such that the filaments are given a latent three-dimensional crimp, and then drawing the filaments to develop their latent crimp. The temperature at which the cooling body is maintained may be within the range 0‹ C. to 70‹ C., preferably within the range 10‹ C. to 30‹ C. The minimum length of the path of travel of the filaments in contact with the surface may be defined by the formula in which T is the individual filament denier and V is the rate in metres per minute at which the filaments are drawn off from the spinneret. The filaments may be drawn at a temperature within the range of from room temperature to 180‹ C., preferably from room temperature to 80‹ C. After drawing the crimp of the filaments may be further developed by heating without tension, e.g. to a temperature within the range 70 to 230‹ C., preferably 90‹ to 160‹ C. The specific viscosity of the melt from which the filaments are produced may be higher than 0-5, e.g. within the range of from 0-75 to 1-2. The cooling surface may be 10 to 100 cm. from the spinneret, preferably 20 to 30 cm. from the spinneret. A jet of air may be directed on to the filaments immediately before they contact the cooling surface. If the extrusion orifices of the spinneret are disposed in a ring it is advantageous to use cylindrical cooling bodies (Figs. 1 and 3 to 6) of the drawings. If the spinneret orifices are arranged in one or two rows it is preferable to use flat cooling bodies (Figs. 2a to 2e). As shown in Fig. 1, filaments 3 extruded through the annular row of orifices of the spinneret 1 pass over and in contact with the cylindrical surface of the cooling body 2 which is cooled by means of a cooling liquid passed through the body by the pipes 4. The flat cooling body shown in Figs. 2c to 2e is supported by a vertical metal plate the upper edge of which is secured to the spinneret parallel to the two rows of spinneret orifices. The lower edge of the plate is provided with a rail from which the cooling body is suspended in such a manner that it can slide in a direction parallel to the rows of spinneret orifices. This arrangement enables the surface of the cooling body to be cleaned without interrupting the spinning. Figs. 3 to 6 show a cylindrical cooling body 2 supported by a rod 5 secured to the spinneret 1 and on which the cooling body can be moved vertically to a position nearer to or further from the spinneret. A preferred cooling'body 2 provided at its upper end with an annular blowing device 6 having an annular nozzle 7 is shown in Fig. 4. Air (generally at room temperature) is supplied to the device 6 through the pipe 8 and the nozzle 7 is arranged so as to direct the air in substantially the same direction as the travel of the filaments. The cooling body 2 is in Fig. 5 partially and in Fig. 6 completely surrounded by a protective tube 14 of a material impermeable to air, e.g. sheet metal, or permeable to air, e.g. a metal grille. In Fig. 6 the protective tube 14 is provided in a zone 15 with an inner and outer cylindrical metal screen, the inner screen being of finer mesh than the outer. The polymers used may be polyesters, polyamides or polyolefins. In all the examples polyethylene terephthalate is used. The cooling body must be sufficiently far from the spinneret to enable the filaments to cool to a temperature at which they do not stick to the cooling body but not so far that the orientation gradient across each filament is so much reduced that no latent crimp at all is imparted to them.