Patent GB-708810-A (GB)
Title: Improvements in and relating to the melting of superpolyamides and other synthetic linear polymers
IPC: D01D1/04
Filed: 1950-10-27
Abstract: <PICT:0708810/IV (a)/1> <PICT:0708810/IV (a)/2> Synthetic linear polymers capable of being melt-spun, such as superpolyamides, are melted by feeding the polymer 17, Fig. 1, in the form of chips by gravity through the pipe 18 on to the central area of the continuous conical or domed upper surface of the heating member 10, which is circular in plan and may be a solid block having cast within it a continuous helical tube 12 through which is passed a liquid or vaporous heating medium which enters the block at 13 and leaves at 14.  An electrical resistance heater may be used instead of the helical tube 12.  The heating member 10 is maintained at a temperature sufficiently high to convert the polymer into a viscous melt, which flows down the upper surface of the heating member as a smooth layer to the edge of the upper surface and through the annular gap 11 between the periphery of the heating member and the wall of the cylindrical melting chamber 9, the upper end of which is closed. The gap 11 is of such width that it is continuously and completely filled with the melt but at the same time allows the latter to flow through it without the level of the melt rising above the gap and at a rate sufficient for the spinning speed required.  After leaving the gap 11 the melt flows down the wall of the lower compartment of the chamber 9 and to the outlet 21.  The upper surface of the heating member 10 may be provided with numerous conical or similarly shaped protuberances 19 arranged in concentric rows staggered in relation to each other, in order to prevent the heat-softened chips of polymer from slipping down the upper surface of the heating member and obstructing the gap 11.  Around the edge of the heating member 10 there may be provided, in addition, an annular sieve trough in which the smaller pieces of polymer are retained.  Before the beginning of the melting operation, the chamber 9 is filled with an inert gas which enters at 15 and is led off at 16.  When the melting operation is in progress the melt filling and flowing down through the gap 11 forms a liquid seal which prevents the melt in the lower compartment of the chamber 9 from absorbing more gas from the upper compartment. The heating member may have a smooth upper surface and the chips of polymer may be prevented from slipping into the gap 11 by a belt-like ring 22 (Fig. 4), between the bottom of which and the upper circumferential edge of the heating member 10 there is a horizontal gap 23 through which the molten material can flow out.  The ring 22 may be carried by ribs 24 cast integrally with the ring 22 and the heating member 10. The underside of the latter may be recessed conically to form an annular beading 25 which prevents the melt from spreading over the underside of the heating member and dripping from it.  In order to maintain the polymer in the molten condition while flowing through the gap 11 and down the wall of the lower compartment of the chamber 9, the latter is surrounded by a heating jacket (not shown).  The process minimizes the solution and occlusion of the inert gas by the melt and the consequent frothing of the latter which necessitates degassing of the melt.