Patent GB-1218066-A (GB)
Title: Crimped synthetic filament having a branched cross-section and a method for manufacturing the same
IPC: D01D5/253
Filed: 1968-06-27
Abstract: 1,218,066. Crimped synthetic filaments of branched cross-section. TORAY INDUSTRIES Inc. 27 June, 1968 [30 June, 1967 (3)], No. 30818/68. Heading B5B. A crimped synthetic filament is characterized by a cross-section having at least three extended branches and defined by the following equations: (a) - 0À125 log 10 D + 1À000 # Log 10  N # -0À589 log 10  D + 2À301; (b) 0À606 # log 10  R # 0À111 log 10 D + 0À845; (c) 1 # D # 25. In the above, D equals the fineness of the filament in denier, N equals the number of crimps per 1 inch length of said filament, and R is the measurement of the cross-section of said filament by the method described in the Specification. Cross-sections of such filaments are shown in Figs. 1A to 1G. The crimped synthetic filament may be further characterized by said cross-section being defined by the following equation: (d) 3À0 # x/y # 11À0; (e) 0À15 # X/Y # 0À60. In these equations, x equals the sum of the lengths of the branches of the crosssection of the filament, y equals the average width of the branches of the cross-section of said filament, X equals the cross-sectional area of said filament, and Y is equal to the area of the smallest circumscribed circle of the crosssection of the filament. The filament may be further characterized by the minimum value of the moment of inertia of the area of the crosssection of the filament being more than 1À5 times as large as that of an imaginary circle having the same area and the product of tenacity and breaking elongation of the filament being smaller than 100. The filament may be further characterized by being crimped due to the variation in the thermal shrinkability across its transverse cross-section. Preferably the filament is made of poly #-caproamide, but may be made of other polyamides e.g. polyhexamethylene adipamide, polyesters as for example polyethylene terephthalate, and polyolefins as for example polypropylene or polyethylene. The filaments may be made by melt extrusion of a thermoplastic synthetic polymer through a spinneret having a plurality of orifices each having a cross-section with at least three extending branches whose length is considerably larger than the width thereof, ejecting cooling air strongly on to one side only of an advancing stream of said extruded filaments at a position from 5 to 15 cms. below an outlet of said spinneret and taking up said solidified filaments at a take-up speed higher than 3000 m. per minute. The length of the branches of the spinneret may range between 0À5 and 2À5 mm. and the width of said branches may be smaller than a quarter of said length but larger than 0À07 mm. Fig. 8 illustrates a suitable spinneret orifice. Using the apparatus of Fig. 7, filaments 14 are extruded through the orifices of the spinneret 12 of the melt-spinning apparatus and subjected to cooling air while passing through cooling chamber 13, oil is fed by an oiling roller 15 positioned downstream on the cooling chamber 13 in the same manner as in conventional melt-spinning and the filaments are taken up on to a package 18 at a take-up speed higher than 3000 m. per minute by a drive roller 16 and a take-up roller 17. Cooling air is conducted into cooling chamber 13 through an air conduit 19 and ejected on to one side only of the filaments 14 as shown by the arrows. Ejection of the cooling air must be performed at from 5 to 15 cms. below the outlet of spinneret 12. The ejecting speed of the cooling air should range, in accordance with a number of crimps required for the filament manufactured, from 10 to 100 m. per minute, especially from 15 to 50 m. per minute, and the temperature of the cooling air should range from 15‹ to 22‹ C. In practice, the upper limit of the take-up speed of the filament is 6000 m. per min. By subjecting the multifilament yarn thus manufactured to steam treatment in relaxed condition, numerous curl-shaped crimps can be developed on the multifilament yarn. Examples are given.