GB1152647A - A Process for the Preparation of Self-Crimping Fibres - Google Patents

Abstract

1,152,647. Self-crimping polyester fibres. KURASHIKI RAYON, K.K. 28 Nov., 1967 [2 Dec., 1966], No. 54166/67. Heading B5B. A process for the preparation of self-crimping fibres comprises melt-spinning a linear polyester, characterized in that the polyester is extruded through a spinneret having orifices of 0À55 to 5À5 mm. in diameter, and the filaments are contacted with a high velocity gaseous current at a region between 3 and 50 cms. below the spinneret, the average velocity of the component of velocity of the current transverse to the filaments' forwarding direction being at least 3À3 m. per sec., and the filaments coming into no direct contact with the high velocity current within the region less than 3 cms. below the spinneret. The preferred polyester is polyethylene terephthalate and its copolymers. The copolymers may contain a minor proportion of a dibasic acid component other than terephthalic acid, e.g. isophthalic or adipic acid; and also may contain a minor proportion of another glycol component as e.g. propylene, butylene, neopentyl, diethylene or polyethylene glycol. The copolymers may contain another ester-forming compound or compounds such as a monobasic carboxylic acid, a monoalcohol, a tri-funcfcional polyalcohol such as glycerine, a tetra-functional polyalcohol such as pentaerythritol, a tribasic acid such as trimesic acid, a carboxylic acid having a hydroxyl group such as para-hydroxybenzoic acid or #-hydroxy-p-ethoxy benzoic acid, and phenols. Preferably the diameter of the orifices is 1 to 2 mm., the rate of polymer discharge from each orifice is from 0À2 to 25 grams per minute, especially from 0À5 to 4À5 grams per minute, the high velocity gaseous current is applied to the spun filaments within a region of 5 to 15 cms. below the spinneret, the peak value of the component of velocity of the current transverse to the filaments' forwarding direction is at least 4 m. per sec., said high velocity gaseous current having a vertical width of at least 3 cms., and the take-up speed of the spun filaments is suitably from 300 to 1200 m. per min; the take-up speed referring to the supply rate of the spun filaments to the drawing zone, in the case where a filament drawing is performed immediately after the spinning and the filaments are wound up after being drawn. The orifices need not be circular; and where non-circular orifices are used the hydraulic radius of the non-circular orifice (defined in the Specification as equal to the cross-sectional area of the polymer stream divided by the wetted perimeter) is substantially the same as that of the circular orifice which is 0À55 to 5À5 mm. in diameter. In the case of a hollow fibre the crosssection of which contains voids, the voids are included in calculating the cross-sectional area of the polymer stream. The filaments obtained, which may be drawn either immediately after spinning, or separately after the winding, have their latent crimp developed when the filaments are further heat treated or swollen in a relaxed or tension-free condition; heating is preferred. In Example 1 a polyethylene terephthalate is spun to yield filaments which are subjected to a 2-stage drawing to a draw ratio of 1À8, the first stage drawing using a hot water bath at 75‹ C., and the second stage drawing a hot water bath at 98‹ C. The filaments are then heat treated for 10 minutes by a hot air current at 145‹ C. in a relaxed state. Highly crimped fibres were obtained having 8 crimps per inch, a degree of crimp of 15% and a crimp recovery of 93%. In Examples 2-7, similar methods are employed. In Example 8 a polyethylene terephthalate containing 5 mole per cent of isophthalic acid as a copolymeric component is spun by the technique of Example 1. In Example 9 a polyethylene terephthalate is spun through a spinneret having 60 Y-shaped orifices. Each branch of the Y-shape was 0À3 mm. wide and 0À9 mm. long. After winding the filaments were drawn to a draw ratio of 2À05 with hot water baths, and heat treated by a hot air stream at 140‹ C. for ten minutes. The resulting self-crimping fibres had a crimp frequency of 12 per inch, a degree of crimp of 15% and a crimp recovery of 92%.