GB859521A - Process for the production of a thermoplastic filament - Google Patents

Abstract

<PICT:0859521/IV(a)/1> Filaments of organic thermoplastic high polymers are made by drawing a continuous narrow strip of the polymer through a slot which is narrower than the width of the strip so as both to fold the strip longitudinally in an irregular manner and to flatten the strip, and thereafter stretching the resultant folded, flattened strip lengthwise at an elevated temperature to produce the filament. The term "strip" is defined as including a tube, in which case the width of the strip is the diameter of the tube. The strips may be formed by continuously cutting in the longitudinal direction a travelling continuous length of film into a number of narrow strips. As shown, a travelling web of film 15 of a polymer such as polyethylene made by a low-pressure process, or polyvinyl chloride is longitudinally slit by knives 14 into parallel strips 16 of a uniform breadth, e.g. 1/10 to 1/2 inch, which are drawn by a pair of rollers 1 in the direction of the arrow P and then by a pair of rollers 3 through nozzle-shaped slots 17 in the rail 7. These slots have a rectangular cross-section of such a size that the individual strips 16 are folded over somewhat irregularly in the slots, the breadth of each strip after being folded being, for example, one-third to one-half of its original breadth. The folded strips 19 are drawn over a guide roller 9, under two guide rollers 10, 11 half immersed in a bath of water at 80-100 DEG C., over a guide roller 12 and through the nip of a pair of rollers 5. the peripheral speed of which is about three to four times that of the rollers 3. Each of the folded and stretched strips, now in the form of a filament, is taken up on a conical bobbin 13. The lower portion of the rail 7 dips in a bath of glycerine maintained at about 70-80 DEG C. The stretching may be carried out while the strips are passing through a hot air duct instead of a water bath. Each strip may be drawn through a series of slots of consecutively decreasing width prior to the stretching stage. The slots may widen towards their inlet ends (which may be rounded) and towards the tops of the rails in which they are located. Fabrics woven from polyethylene filaments produced according to the invention have a tensile strength and resistance to abrasion greater than that of linen or cotton fabric of the same weight. The fabric may be rendered practically water tight while remaining permeable to air by maintaining it at 100-120 DEG C. for about 15-100 seconds while preventing it from shrinking fully.