GB1248089A - Process and apparatus for producing crimped yarns - Google Patents

Abstract

1,248,089. Crimping yarn. UNITIKA Ltd. 28 Feb.; 1969 [29 Feb., 1968; 8 May, 1968; 28 May, 1968; 12 Sept., 1968; 5 Dec., 1968 (2)], No. 10915/69. Heading D1F. A process for producing a crimped yarn comprises heating a travelling thermoplastic synthetic yarn at or above the softening temperature of the yarn, cooling the yarn below the secondary transition temperature of the yarn and false twisting the yarn by contacting the yarn with a forcibly cooled moving friction surface. Apparatus for carrying out the process comprises means 4 for heating the yarn, means 5 for cooling the heated yarn, at least one rotary tube 6 mounted for rotation around its centre axis, and constructed to false-twist yarn by contact with a friction surface at each end of the tube, and means 7 for directing compressed gas upon each friction surface to cool the surface. The heater 4 preferably comprises two spaced rotary rollers with a heated plate between, the yarn making several passes over the plate. The cooling means 5 may comprise a conduit with restricted inlet and outlet for guiding the yarn, and a lateral inlet and outlet for supplying cooling liquid to the conduit to bathe the yarn. The liquid is preferably water and may contain a scouring agent such as ethylene glycol. In a further embodiment, the cooling means 5 comprises a wetted rotatable roller and a conduit for cooling medium having a yarn groove at its outer surface, the conduit and groove preferably being curved. In another embodiment, the cooling means comprises a conduit with restricted inlet and outlet for the yarn and an inlet for sprayed coolant near the upstream end of the conduit, and an outlet near the downstream and to discharge the coolant. In a further embodiment, the cooling means comprises a conduit for the yarn having a narrow outlet therefor, a lateral inlet for the supply of coolant near the upstream end of the conduit, a narrow gap in the intermediate region of the conduit, the outside of the upstream portion and the inside of the downstream portion of the conduit being tapered, a chamber surrounding the gap and means supplying compressed gas to the chamber whereby the coolant is converted to spray, an outlet for the coolant being disposed near the downstream end of the conduit. In a preferred embodiment the frictionswisting device comprises two rotary tubes arranged to rotate in opposite directions, the surface of each end of each tube forming a conic section curve at a plane containing the central axis of the tube, the curve being convex to the said axis. Grooved rollers 8 are provided for defining the path of the yarn through the rotary tubes. Compressed gas is directed by jetting nozzles 7 on to the surfaces of the tubes, the gas being at a pressure of 0.5-4 kg./sq. cm. The apparatus preferably includes means 10 for advancing the untwisted yarn in a relaxed state. The means 10 may comprise a conduit for the yarn terminating in a downstream direction within an elongate chamber arranged -for passage of compressed gas, the chamber terminating in a downstream direction in a conduit for the travel of. yarn and gas. A further embodiment of yarn relaxing and advancing means 10 comprises a conduit for the yarn, a narrow gap in an intermediate region of the conduit, the outside of the upstream portion and the inside of the downstream portion being tapered, a chamber surrounding the gap, and means for supplying compressed gas to the chamber whereby gas and yarn pass together along the downstream portion of the conduit. The yarn treated may be mono- or multifilament yarn and is preferably formed of a polyamide, a polyester, polyacrylonitrile, polyolefin or a copolymer thereof. The yarn may be continuously drawn from undrawn yarn prior to the heating step.