The device (1) comprises a first roller (3) rotatable about a first rotation axis (3A) and a second roller (5) rotatable about a second rotation axis (5A), parallel to the first rotation axis (3A). The two are in mutual contact and define between them a yarn passage (7) and at least of them is motorized. The device further comprises 5 guide members (9) defining a feed path of at least a yarn (F; F1, F2, F3, F4), associated with the yarn passage (7) between the first roller (3) and the second roller (5). The guide members (9; 13) are movable with respect to the rollers (3, 5) in a direction substantially parallel to the first rotation axis (3A) and to the second rotation axis (5A), so as to take the yarn path temporarily outside the mutual contact 10 area between the rollers.

The device (1) comprises a first roller (3) rotatable about a first rotation axis (3A) and a second roller (5) rotatable about a second rotation axis (5A), parallel to the first rotation axis (3A). The two are in mutual contact and define between them a yarn passage (7) and at least of them is motorized. The device further comprises 5 guide members (9) defining a feed path of at least a yarn (F; F1, F2, F3, F4), associated with the yarn passage (7) between the first roller (3) and the second roller (5). The guide members (9; 13) are movable with respect to the rollers (3, 5) in a direction substantially parallel to the first rotation axis (3A) and to the second rotation axis (5A), so as to take the yarn path temporarily outside the mutual contact 10 area between the rollers.

Friction disc for a false-twist device, comprising an annular hub, on which it is possible to fix a circular race formed by a polyurethane (PU) layer and has a minimum wall thickness required for a secure interlocking fit, the hub having a circumferential support ring and a central hole, by which the friction disc is fixed on one of the shafts of the false-twist device. To ensure better dimensional and form stability over a long service life of the friction disc, the formed race fixed on the hub is ground according to a predefinable profile such that the flanks of the race have a predefinable width dimension following the grinding process, and/or in that the hub has, at a spacing from the support ring, a circumferential shoulder for abutment for the fixable PU layer, a cross-sectional width of the shoulder being smaller than a cross-sectional width of the support ring.

The present invention provides a production process characterized in that a false twisting process is added between a spinning process and a winding process so that yarn slivers undergo excessive pre-torsion in an axial direction and twists which are same in quantity but different in twisting direction are generated on the yarn slivers. Absorption of glucose-containing sulfur dyestuff is performed in a dyeing process. An ammonia removal process is performed in a high-temperature and high-pressure tank so that residual ammonia in a fabric is evaporated. The evaporated ammonia is collected and then fed back to a mercerizing process for continuous use. The present invention also provides a production line including a spinning unit having a false twisting device, a dyeing unit configured to realize the dyeing process, and a liquid ammonia finishing unit consisting of a fabric mercerizing device, an ammonia removal device, an ammonia recycling device and a controller.