Patent GB-936729-A (GB)
Title: Improvements in melt spinning synthetic polymers
IPC: D01D4/02
Filed: 1960-05-02
Abstract: <PICT:0936729/IV(a)/1> <PICT:0936729/IV(a)/2> <PICT:0936729/IV(a)/3> <PICT:0936729/IV(a)/4> <PICT:0936729/IV(a)/5> <PICT:0936729/IV(a)/6> <PICT:0936729/IV(a)/7> A synthetic fibre-forming polymer is extruded downwardly through a spinneret having a plurality of orifices, and one or more streams of quenching fluid are directed against each filament within one inch of the spinneret face at an angle between 45 degrees below and 45 degrees above the horizontal, the filaments being under a tension of at least 0,003 gram per denier and being cooled to a temperature more than 15 DEG C., and preferably more than 25 DEG C., below the melting point of the polymer at a distance less than two inches from the spinneret.  The spinneret orifices may be spaced one from the other by 0,125 inch or less between centres, and preferably form a pattern in which their centres are positioned at the corners of contiguous quadrilaterals formed by lines connecting the centres of adjacent orifices, each side of each quadrilateral being between 0,005 and 0,125 inch in length, all inside angles of each quadrilateral being at least 30 degrees, and the polymer is extruded at a rate of at least 4 g./min./cm2., preferably at least 10 g./min./cm2., of effective spinneret face area (i.e. the area within a quadrilateral defined by four straight lines between the centres of four adjacent orifices).  The quenching fluid may be air, or dry or wet steam, especially wet steam containing water droplets substantially all of which have diameters less than half the diameter of the filaments extruded.  The quenching fluid may travel asymmetrically with respect to the filaments, i.e. may quench the individual filaments of the yarn at different rates across the yarn, and potentially crimpable filaments may be made by using an asymmetric quenching stream, especially a stream of sufficient velocity to impart a tension of at least 19 mg./denier to the filaments.  Specified materials include polyamides, especially polyhexamethylene adipamide of relative viscosity at least 12, polyesters, especially of relative viscosity at least 9, and polyolefins, especially polypropylene.  Spinning conditions may be such that the filaments formed, after a subsequent drawing step, have an individual denier between 0,1 and 1,0.  The spinneret orifices may be non-circular, and the cross-sections of filaments so made closely resemble the orifice shape, e.g. orifices of the types shown in Figs. 5 and 6 give rise to filaments of the cross-sections shown in Figs. 8 and 9 respectively, while the orifices of Fig. 7 give rise to filaments of triangular cross-section.  Spinneret orifices may be arranged in a square or in staggered rows, or in concentric circles. Where the latter arrangement is used, the quenching stream is preferably directed radially inward or radially outward, the spacing between adjacent circles of orifices being less than 0,125 inch.  In a preferred apparatus (Figs. 3 and 4) molten polymer is forced through sand pack 12 and channels 13 to orifices 14 of the spinneret 15, the temperature of which, and of the quenching fluid is controlled by band heater 16.  Filaments 17 are immediately quenched by the flow of gas from nozzles 18, directed across the bundle of filaments and parallel to the spinneret face.  After passing through the initial quenching zone, the filaments enter a secondary cooling zone in which they are subjected to a flow of gas from nozzles 19, which further cools the filaments, and counteracts the deflection due to the action of gas from nozzles 18.  Gas supplied to nozzles 18 and 19 passes over flow chopper vanes 20, to ensure even distribution. The nozzles may also be covered by screens 21 to make the flow of gas more homogeneous.  Fig. 4 is a plan view of the spinneret, which is divided into two areas ABGH and CDEF each containing 810 holes arranged in rows with a centre-to-centre spacing of 0,060 inch between rows and between holes, each area having 14 rows of holes perpendicular to the direction of travel of the quenching gas. Specifications 461,236, 578,079 and U.S.A.  Specifications 2,071,250, 2,130,523, 2,130,948, 2,190,770 and 2,273,105 are referred to.