Patent GB-1136689-A (GB)
Title: Spinneret
Inventor: KERN HELMUT
IPC: D01D5/24
Filed: 1967-10-30
Abstract: 1,136,689. Spinneret for hollow filaments. CHEMIEFASERWERK SCHWARZA "WILHELM PIECK" VEB. 30 Oct., 1967, No. 49196/67. Heading B5B. A spinneret plate with annular exit bores of cross-sectional shapes adapted for spinning hollow filaments of circular or non-circular cross-section from melts of synthetic linear high polymers, is characterized in that the exit bores of the spinneret plate have conical or hyperbolic fore-bores, inserts flattened at their upper ends being inserted into said fore-bores and fixed to the spinneret plate, said inserts being shaped, at their lower ends as a cylinder or as a truncated cone and being provided at their lower ends with one or more narrow bridges, which also join the spinneret plate to the insert, at least one bridge traversing each exit bore. Preferably, the cylindrical or cone-shaped parts of the insert terminate at the same level as the upper ends of the exit bores of the spinneret plate in which they are centred exactly, the angle of aperture of the fore-bores is 40 to 120 degrees, and the bridges have a width equal to or less than 0.1 mm. Thus in Fig. 1, a spinneret plate 1 has a conical bore 2, into which a truncated cone-shaped insert 3 is inserted and welded to the plate 1. The lower side of the spinneret plate and the surface of the truncated cone lie in the same plane and the cone of the insert 3 and the spinneret 4 both have an angle of 60 degrees. Fig. 2 shows a top view of an orifice according to Fig. 1, showing the flattening of the insert 3 at its upper end. Thus there are formed two conveying channels 4 for the spinning components. For spinning conventional filaments, melts of the same kind are supplied through both conveying channels 4 but for spinning bi-component filaments, two different spinning components are supplied which coalesce at the bridges after having left the annular slit formed by the spinneret exit bore and the insert. Fig. 3 shows the annular slit 6 of the spinneret plate 1 of Fig. 1. By means of the bridge 5, installed in the truncated coneshaped insert 3 and projecting beyond it on both sides, there are formed two narrow points of connection between spinneret plate 1 and insert 3 by means of which air can penetrate into the interior of the filament. Due to the bridge, there results the shape of a double C as extrusion area for the spinning melt. Coalescence of the two streams of molten extruded material formed takes place below the orifice. Fig. 4 shows a spinneret plate 7, the bore of which consists of a conical fore-bore and a cylindrical exit bore. A conical insert 8, flattened on both sides, has a cylindrically-terminating part, into which is inserted a bridge 10. As shown in Fig. 5, this bridge only projects beyond the insert 8 on one side and gives only one narrow point of connection between the insert 8 and the spinneret plate 7, so that the spinning melts coalesce at this spot. Fig. 6 shows a spinneret bore for spinning non-circular hollow filaments. The spinneret plate 11 has an exit bore 12 of trilobal cross-section, the insert 3 having the same shape as in Fig. 1. By means of slight alterations of the shape of the inserts, e.g. by the use of an additional central bore or the like, filaments with more than one hollow space in each capillary can be spun. The spinneret is useful in spinning hollow filaments of circular or non-circular cross-section from melts of synthetic linear high polymers, as for example polyamides and polyesters.