Abstract: An unstretched filament composed of a PET-based aromatic polyester multifilament comprising a polyoxyalkylene-based polyether and an organic ionic compound is subjected to simultaneous stretching and false twisting under specified conditions to produce a polyester false twisted yarn, whereby rapid and stable false twisting can be accomplished without section deformation or fluff generation during false twisting, and the resulting yarn has a highly satisfactory hand quality and a fibrillation resistant fiber structure, while also exhibiting a highly durable antistatic property. Interlacing of the unstretched filament with an unstretched polyester filament comprising a polymethyl methacrylate-based polymer and/or polystyrene-based polymer and stretching/false twisting thereof under specified conditions allows rapid and stable production of conjugated false twisted yarn exhibiting highly satisfactory bulkiness and a spun feel with the absence of fluff, as well as a highly durable antistatic property.

Abstract: A polyester false-twist textured yarn, useful as a yarn for woven or knitted fabrics having excellent water-absorbing and quick drying properties, satisfies all of the requirements (1) to (3) shown below: (1) the cross-sectional profiles of a plurality of individual filaments, from which the false-twist textured multifilament yarn is constituted, each have 3 to 6 concavities, and the average number of the concavities having a ratio (H/W) of a largest depth (H) to a largest width (W) of the individual concavities of 0.3 or more is in the range of from 50 to 80% of the total number of the concavities; (2) the average of the cross-sectional profile flatness factors is in the range of from 1.5 to 3.5; and (3) the standard deviation of the cross-sectional profile flatness factors is in the range of from 0.3 to 1.0.

Abstract: A polyester false-twist textured yarn, useful as a yarn for woven or knitted fabrics having excellent water-absorbing and quick drying properties, satisfies all of the requirements (1) to (3) shown below: (1) the cross-sectional profiles of a plurality of individual filaments, from which the false-twist textured multifilament yarn is constituted, each have 3 to 6 concavities, and the average number of the concavities having a ratio (H/W) of a largest depth (H) to a largest width (W) of the individual concavities of 0.3 or more is in the range of from 50 to 80% of the total number of the concavities; (2) the average of the cross-sectional profile flatness factors is in the range of from 1.5 to 3.5; and (3) the standard deviation of the cross-sectional profile flatness factors is in the range of from 0.3 to 1.0.

Abstract: A method for rethreading a yarn during false twist texturing of the yarn includes setting the temperature of a heater body outside a range having upper and lower limits so that if melted yarn adheres to the heater, the yarn vaporizes quickly if the temperature is above the upper limit or is easily removed by rethreading the yarn if the temperature is below the lower limit. The heater body has a total length between 0.8 and 1.2 m, the heater body and heating member divided into two pieces from upstream side to downstream side of the heat treating apparatus in ratio of length between 1:3 and 1: 1:5. The divided upstream heating member (12) is able to heat the upstream heater body (11) at a temperature higher than 370.degree. C., and the downstream heating member (22) is to heat the downstream heater body (21) at a temperature of between 200.degree. and 320.degree. C. or higher than 370.degree. C.

Abstract: A heater body has a total length between 0.8 and 1.2 m, the heater body and heating member are divided into two pieces from upstream side to downstream side of the heat treating apparatus in ratio of length between 1:3 and 1:1.5, the divided upstream heating member (12) is able to heat the upstream heater body (11) at a temperature higher than 370.degree. C., and the downstream heating member (22) is to heat the downstream heater body (21) at a temperature of between 200.degree. and 320.degree. C. or higher than 370.degree. C., the upstream heater body has yarn guides (15) disposed at a longitudinal pitch of at most 30 mm, and the downstream heater body has yarn guides (24) disposed at a longitudinal pitch between 80 and 120 mm.

Abstract: Disclosed is a level-dyeable mixed false-twisted filament yarn composed of larger denier multifilaments (1) having a denier of 1 to 2.5 and smaller denier multifilaments (2) having a denier of 0.6 or less, which is characterized in that (a) the yarn comprises entangled portions (I) thereof whereat the larger denier filaments and the smaller denier filaments are entangled with one another and opened portions (II) thereof comprising a core composed of the larger denier filaments and a covering composed of the smaller denier filaments, (b) in the coverings of the opened portions, net-like parts thereof are formed by the smaller denier filaments extending obliquely to the longitudinal axis of the yarn and intersecting one another, and scattered therein, (c) the length L.sub.1 of the opened portions is longer than the length L.sub.

Abstract: Disclosed is a worsted yarn-like false-twisted yarn composed of large-denier multifilaments having a thickness of at least 4 de and small-denier multifilaments having a thickness of 0.