GB905667A - Improvements in and relating to the production of multifilament yarn - Google Patents

Abstract

Multifilament polyolefine yarns, the denier of each filament not exceeding 25, are produced by melting the polyolefine in a screw extruder which feeds the molten polymer to a gear pump which is maintained at at least 300 DEG C. and which forces the polymer through one or more granular filters and then through one or more multi-hole jets maintained at at least 300 DEG C. to form a number of filaments, cooling them immediately they leave the jet by a transverse current of air directed across the face of each jet and subsequently stretching them over a length of path which is not less than the minimum over which the collected stretched filamentary bundle is substantially free from broken filaments, e.g. for producing 1 to 5 denier filaments, a path of at least 4,5 feet. The length of path is preferably at least 25% greater than the minimum. If the filaments are of high-pressure polythene, they may be stretched at ordinary temperatures, and if of low-pressure polythene, usually at elevated temperatures, e.g. in steam. The stretching may be about fiveto ten-fold. The temperature of the gear pump may be 325 DEG to 380 DEG C., and that of the jet 300 DEG to 320 DEG C. In the example, a mixture of 90 parts of low pressure Phillips polythene, 10 parts of high pressure polythene and 2 parts of low pressure Ziegler polythene is fed by a screw extruder at 300 to 600 p.s.i. and 270 DEG -280 DEG C. to a gear pump at 340 DEG -350 DEG C. which feeds the melt through a sand pack to 45 hole jets. The extruded filaments are cooled by a current of air at ordinary temperature flowing across the jet faces, collected, untwisted, as a cheese, passed from a feed godet through a steam chamber 7 feet long wherein they are stretched 9-fold and thereafter collected as a twisted 175 denier /45 filament yarn. The process facilitates the production of multi-filament polythene and polypropylene yarns of low denier. Specifications 471,590, 472,051, 779,540, 790,195, 790,196, 807,248, 810,023, 818,100 and 905,668 are referred to.