GB893059A - Melt spinning process and apparatus - Google Patents

Abstract

<PICT:0893059/IV (a)/1> <PICT:0893059/IV (a)/2> <PICT:0893059/IV (a)/3> A melt-spinning apparatus comprises a polymer melting zone, a pump, e.g. a gear pump or screw extruder, a spinning pack containing an inlet duct for molten polymer, a filtration medium, e.g. sand, arranged above and separated from an extrusion die or spinneret, and means for imparting a transverse circulatory motion to the incoming polymer stream, located in the region between the polymer melting zone and the top surface of the filtration medium. A transverse circulatory motion is a disturbance of the melt stream such that individual stream lines, normally moving in lines parallel to each other and with the duct walls change their form into a helical shape so that they now move in a sideways motion down the duct. Said means may be located in the duct leading the melt from the gear pump to the filtration medium, and may comprise a rotor driven either by the flow of melt, or mechanically, e.g. from within the gear pump, or from a separate drive shaft. A drive from within the gear pump is preferred, and the rotor may consist of a rotatable duct or paddle driven either by direct coupling with an end of a rotating shaft within the pump or by direct contact with one of the gears of a gear pump. Preferably, (Fig. 2) the rotor is a gear wheel 3 in positive engagement with one of the gears (1, 2) of the gear pump. The rotor gear wheel may have a hollow shaft 4 and holes or slots 9 within the area between its teeth communicating with the hollow shaft, which may contain a vane or vanes 5, extending into the stationary portion of the discharge duct of the gear pump. As shown, the vane may be helical, rotating with the hollow shaft, and the helix of the vane may be in the direction which tends to increase the rotational motion imparted to the melt by the rotation of the hollow shaft. Small notches 6 may be cut asymmetrically along the edges of the vane. In operation, melt entering the gear pump is carried around the outside of the gears 1, 2 to the discharge port occupied by the gear 3, and enters the outlet duct via the rotating ports 9 and hollow shaft 4 of gear 3, the combined effect of gear 3, ports 9 and vane 5 being to impart to the melt a transverse circulatory motion. In a modified apparatus (Fig. 3) the drive shaft 12 of the dirving gear 1 of a gear pump is extended by a vane 13 into the outlet duct from the gear pump. In a further modification (Fig. 4) a gear wheel 14 located in the discharge port of a gear pump is driven by driving gear 1, and the shaft 15 of gear wheel 14 has a hollowed centre 16 connected by ports 17 to layers of fine mesh gauze 18 (or, alternatively, a sintered porous sheath). In operation the melt leaves the discharge port via the rotating gauze 18 and the ports 17 and 16.