GB670951A - Improvements in or relating to method of and apparatus for producing and conditioning filaments - Google Patents

Abstract

<PICT:0670951/IV (a)/1> A filament of plastic material such as a polyvinyl resin is p delivered while in a deformable condition to a first point at a substantially constant rate of volume though subject to variations in linear rate of delivery, and is driven at a second point at a controlled linear rate sufficient to stretch the filament to a desired extent; the movement of the filament between the first and second points is restrained by a force of constant value, this force being maintained constant throughout any variations in the linear rate at which the filament is delivered to the first point in response to changes in stiffness of the material of the filament moving between the first and second points. A filament is thereby produced with a uniformly-oriented crystalline structure and a cross-sectional area of constant value. The stretching is preferably carried out continuously with the formation of the filament by extrusion. The apparatus used may comprise an extruder, a roller adapted to receive the filament, means for driving this roller at constant speed, another roller between the extruder and the constant speed roller also adapted to receive the filament, and drag means connected with this roller adapted to impart a constant tension on the filament between the two rollers, this tension remaining constant throughout any variations in the linear rate of delivery of the filament to the drag roller consequential to changes in stiffness of the filament between the two rollers. The drag means may be an electric generator driven by the drag roller. Adjustments of the drag may be effected by an electric control system (see Group XXXV). A wind-up reel for the stretched filament may be provided and this reel may be driven by a constant horsepower motor. The filament may be made from a polymer of vinylidene chloride or 2,3-dichloro-1,3-butadiene, or a copolymer of these two or of either of them with vinyl chloride, bromide, acetate, butyrate, or stearate; vinyl ethyl ketone, vinyl isobutyl ether, styrene, indene, coumarone, or acrylonitrile. As shown in Fig. 1, an extruder 10 has a forcing screw 11 driven by motor 12. The motor also drives generator 15. Filaments 17 issuing in hot plastic state from device 10 are passed through cooling liquid in tank 21. They are passed several times round rolls 25, 28, and then stretched by the pull of roll 29 which is driven at constant speed by the direct current motor 30. Roll 25 is driven by the filaments under the pull of roll 29, and roll 25 drives the direct current generator 26 which exerts a drag on roll 25 so as to maintain the filaments under constant tension. The armature of motor 30 and that of generator 26 are connected in parallel with that of generator 15. Roll 29 may have a peripheral speed of 350 per cent of that of roll 25. The filaments pass several times round rolls 29, 32, and are then wound up on reels 33 under constant tension, the reels being driven by constant horsepower motor 34. An electrical control system may be provided for motor 34 so that the filament tension is held at a constant pre-determined value despite the increasing diameter of the wound package of filaments (see Group XXXV). An electric control system is also provided for generator 26 to sense speed changes in roller 25 due to changes in the elongation of the filament at the prescribed tension and to make the required adjustments. The apparatus may also be provided with means for automatically compensating for the increased friction when it is operated at increased speed; an electric control system for this purpose is described (see Group XXXV).