GB982701A - Improvements in or relating to the treatment of filamentary textile material - Google Patents

Abstract

982,701. Regenerated cellulose filaments. COTTON SILK & MAN-MADE FIBRES RESEARCH ASSOCIATION. Feb. 27, 1961 [Dec. 11, 1959], No. 42117/59. Heading B5B. The instability of structure of a regenerated cellulose yarn is reduced, while the yarn is being travelled continuously, by wetting it with water at each of a plurality of stations, and drying it by the application of heat after each wetting station, and so controlling the wetting operation that the content of absorbed moisture in the yarn attains substantially the critical value. The critical value is defined as equal to the absorbed moisture content value that would be reached if the yarn were exposed to air at room temperature and at a relative humidity of 100% for a sufficient length of time for equilibrium conditions to be established. The tow may be viscose rayon, and the process may be carried out continuously on a yarn as it is produced by extrusion. Drying may be effected by passing the tow in contact with the heated surface of a roller, preferably heated to at least 100‹ C., and the number of wetting stations may be from two to ten. The tow may be progressed in a series of laps about a pair of yarn advancing rollers, one at least of which is heated. Both rollers may be heated, the tow being wetted at the requisite number of stations. The wetting stations may be adjacent to a roller surface, or displaced therefrom. One roller may be of considerably larger diameter than the other and may be heated, the other roller guiding the yarn to the wetting stations. In Fig. 1, A and B are heated thread advancing rollers, long enough to contain twenty laps of yarn. The yarn passes on each lap from roller A to the immersion roller C, where it takes up water which is absorbed during passage of the tow from C to roller D. The distance CD is adjusted so that by the time the yarn contacts the heated roller B, its absorbed moisture content is substantially the critical value. The roller D runs in contact with roller B and may be used to squeeze out excess water from the yarn and thus facilitate drying. The length of contact of the yarn with rollers A and B must be sufficient to ensure drying of the yarn before re-wetting for the next cycle. In Fig. 2, A and B are heated thread advancing rollers, and the rollers E, F thus supply water to the yarn when it is at a higher temperature than in the previous method. Penetration of water into the yarn is thus more rapid, but the two rollers E, F are necessary to ensure that the absorbed moisture content of the yarn reaches the critical value, in view of the higher rate of evaporation of moisture from the yarn. In Fig. 3, A and B are thread advancing rollers, A, which is heated, being of much larger diameter than B, e.g. A may be 24 inches diameter, and B 1¢ inches. B is immersed at any required depth in the water tank R, which is slidably mounted in guides G, and the length BD may be adjusted.