Patent GB-1171325-A (GB)
Title: Process for producing Crimped Composite Fibers
IPC: D01D5/32
Filed: 1967-08-15
Abstract: 1,171,325. Crimped composite filaments. MITSUBISHI RAYON CO. Ltd. 15 Aug., 1967 [16 Aug., 1966], No. 37514/67. Heading B5B. [Also in Division D1] Crimped composite fibres are made by drawing composite filaments and then heattreating the drawn filaments in a relaxed state, the drawn filaments being heat-treated while being overfed at least 1% more than the sum of the percentage elastic shrinkage of the drawn filaments and the percentage thermal shrinkage of said drawn filaments at the temperature to which the filaments are heat treated in the heat treatment, thereby developing crimps on the drawn filaments and simultaneously fixing the crimps. Drawn composite filaments having a total denier of less than 500 may be heat-treated by passing the filaments through an atmosphere maintained at a temperature above the melting-point of said filaments; thus drawn composite polypropylene filaments may be heattreated so that the temperature of said filaments becomes 90-140‹ C.; drawn composite polyester filaments may be heat-treated to filament temperatures of 140‹ to 220‹ C.; drawn composite polyamide filaments heat-treated to filament temperatures of 140-180‹ C.; and drawn composite acrylic filaments heat-treated to filament temperatures of 160-250‹ C. Both drawn composite filaments having a total denier of more than 500, and drawn composite filaments having a monofilamentary denier of more than 5 and a total denier of less than 500 may be heat-treated by passing the filaments through steam. If desired, the drawn composite filaments may be first subjected to a treatment with a high-speed jet of gas, while being maintained under a tension of below 20 mg. per denier, prior to heat treatment. Preferred drawn composite filaments to be heat-treated in steam are drawn composite polypropylene filaments prepared by drawing undrawn composite polypropylene filaments in which the intrinsic viscosity of the polypropylene component higher in intrinsic viscosity is at least 1À2, the difference in viscosity between the two polypropylene components being 0À05 to 0À5 and the difference in bi-refringence between the two polypropylene components is 5 x 10<SP>-3</SP> to 15 x 10<SP>-3</SP>. Drawn composite filaments may be heattreated to obtain crimped composite filaments having 5 to 50 crimps per 25 mm. and a degree of crimp of 3 to 30%. Crimped composite filaments having this number of crimps and degree of crimp may be subjected to a final heat-treatment in a relaxed state in a heating medium at 100‹ C., whereupon the filaments are shrunk by 3-6% to give a fibre having from 15-80 crimps per 25 mm. and a degree of crimp of 20-60%. This fibre is particularly suitable for interior products such as carpets, and knitted fabrics such as sweaters and socks. Polymer components in the composite filaments to be used in the present invention may be arranged side-by-side or in sheath-core relation. The filaments need not be circular in cross-section but may have irregular cross-sections such as those shown in Figs. 1 and 2. Where filaments of the cross-section of Fig. 2 are used, the projected (unshaded) portion is desirably composed of the lower viscosity component. The filaments may also be hollow filaments having a varied ratio of preferably 5-60%. The composite ratio of the two components in a filament is not critical. Examples are given.