Patent GB-1150587-A (GB)
Title: Process for production of Crimped Filaments and Crimped Elastic Filaments
IPC: D01F6/04
Filed: 1966-09-13
Abstract: 1,150,587. Polypropylene filaments. ASAHI KASEI KOGYO K.K. 13 Sept., 1966 [15 Sept., 1965 (2); 15 June, 1966 (2); 16 June, 1966], No. 40835/66. Heading B5B. Crimped filaments are made by melt-spinning a composition comprising at least 80% by weight of crystalline polypropylene having a depolymerization degree of at most 2À0 and a reduced viscosity (determined in tetralin solution of 0À1% concentration at 135‹ C.) of 0À8 to 3À0 and containing not more than 10% by weight of additives, through a spinneret heated at a temperature in the range 240‹ to 280‹ C., using a spinning speed of not less than 550 metres per minute, drawing the thus obtained undrawn filaments at a temperature in the range 10‹ to 110‹ C., and relaxing the same. Where the composition contains at most 2% by weight of additives it may be melt-spun through a spinneret heated at 245‹ to 280‹ C., using a spinning speed of more than 600 m./min., and the filaments drawn at a drawing temperature in the range 10‹ to 100‹ C. In this latter process the filament may be heat-treated, prior to drawing, at 70‹ to 160‹ C. and the heat-treated filaments then drawn at a draw ratio of at least 2À5. Alternatively, in such latter process crimped elastic filaments may be obtained by heat-treating filaments, prior to drawing, in the temperature range 70‹ to 160‹ C. and then drawing the heat-treated filaments at a draw ratio in the range 1À1 to 2À5. Where the composition contains at least 2% by weight of additives it may be melt-spun through a spinneret heated at a temperature not exceeding 265‹ C. In this type of process the filaments may be heat-treated, prior to drawing at 70‹ to 150‹ C. and the heat-treated filaments then drawn at a draw ratio of at least 2À5. Crimped elastic filaments may be made in this type of process by heat-treating the filaments, prior to drawing, at 70‹ to 150‹ C. and then drawing the heat-treated filament at a draw ratio at the range 1À1 to 2À5. In general, spinning speeds used increase in proportion to the denier of the spun filaments; thus speeds of 800 to 1000 metres per minute are preferred for 2 to 3 denier filaments; a 1000 to 1200 m./min. for 6 deniers; a 1000 to 1300 m./min. for 9 deniers; and 1100 to 1400 m./min. for 15 deniers, the denier being that of a drawn single filament. In the production of crimped filaments, potential crimp is first given to the undrawn filaments in the spinning step and the crimps develop in the subsequent drawing and other steps. Microscopic examination of undrawn filaments of the invention shows sheath-core structures which may be partly defected. Conventional drawing apparatus may be used. Crimps are produced in the drawn filaments by release of tension, heatsetting being unnecessary, although desirable to improve crimp stability. Such heat-treatment is suitably effected using air, steam or water at 50‹ to 130‹ C. for 5 mins. to one hour. Both batch and continuous heat-treatment methods may be used. Heat-treatment and drawing may be effected using the apparatus shown. Undrawn filaments 5 supplied from a bobbin (not shown) are heated at the electrically heated roller 1, cooled at the roller 2, and heat drawn between roller 2 and roller 3 while contacting the heating plate 4, and the thus drawn filaments 7 are wound up on another bobbin (not shown). Such a continuous system may be used as only an extremely short contacting time of about 0À1 seconds is required for the heat-treatment, using a temperature of about 140‹ C. Examples are given.