GB645275A - Improvements in or relating to filaments of thermoplastic material and manufacture thereof - Google Patents

Abstract

A normally crystalline vinylidene chloride polymer or co-polymer is extruded in molten condition into a chamber 30-50 feet high, the temperature at least in the upper portion being about 200 DEG F., and the filaments obtained are elongated in the chamber by the tension exerted by their own weight. If desired, the filaments may be maintained in a hot plastic condition for only a short part of their vertical travel and may then be cooled so as to become solidified in amorphous form during the remainder of their vertical travel. Copolymers of vinylidene chloride with vinyl chloride or acetate may be used. Plasticizers, pigments, and other ingredients may be included in the composition. As shown in the Figure, the vinylidene chloride polymer is supplied through hopper 10 to an extrusion device 17, provided with extrusion screw 15 and heating devices to bring the material to the desired state of plasticity or viscosity for extrusion. The material may be heated gradually to about 320 DEG F. It is extruded through spinneret 21 into chamber 24. Relatively large orifices may be used. Heated air may be passed through the long chamber 24 to maintain a temperature of 200 DEG F. and keep the extruded filaments in a plastic state during their entire travel through the chamber. The weight of the filaments causes them to elongate to a high degree. The filaments 23 are passed into bath 27 containing a quenching liquid, e.g. water or oil, at 40-50 DEG F. The filaments then pass into a second bath 32 which may contain talc, aluminium stearate, or other powdered lubricant. The filaments are then wound on reel 34. The filaments when in the amorphous unoriented state are stored at temperatures below 50 DEG F. If desired, the filaments 23 may pass from bath 27 to a system of stretching rolls which subject them to elongation accompanied by molecular orientation with increase in tensile strength. If desired some of the weight of the suspended length of the filaments may be prevented from acting on the hot plastic portion. For this purpose the lower end of chamber 24 may be closed and hot water or other liquid may be passed through the chamber to support partially the filaments. The chamber 24 may be divided into two compartments, the upper and shorter one being heated to about 200 DEG F., and the lower one being heated only to about 50 DEG F., so as to prevent crystallization of the resin in an unoriented manner while in the chamber. The polymer may be a copolymer of 5-15 per cent <PICT:0645275/IV (a)/1> vinyl chloride with 85-95 per cent of vinylidene chloride. The Specification as open to inspection under Sect. 91 comprises also the production of filaments from other thermoplastic materials. This subject-matter does not appear in the Specification as accepted.