GB982754A - Production of spandex filaments by dry spinning - Google Patents

Abstract

982,754. Dry spinning spandex filaments. E. I. DU PONT DE NEMOURS & CO. Nov. 8, 1963, No. 44241/63. Heading B5B. Spandex filaments are produced by extruding a solution of a spandex polymer in a volatile organic solvent downwards into a spinning cell from a spinneret having a number of orifices arranged in at least one circle to form filaments, simultaneously introducing a stream of heated gas into the spinning cell at a level higher than that of the spinneret face in the direction of travel of the filaments at a velocity below 2À5 feet per second, measured in the spinning cell at the level of the spinneret face, confining the stream of gas to a restricted passage of annular cross-section encompassing the filaments, and extending from a level adjacent to that of the spinneret face for a substantial distance along the path of travel of the filaments, and having a cross-sectional area at least 75% of the crosssectional area of the spinning cell at the same level, and continuously withdrawing the filaments and removing gas from the spinning cell at a position or positions along the direction of travel of the filaments remote from the spinneret. A major portion of the passage of annular cross-section adjacent to the spinneret has a constant cross-sectional area, and a minor portion of the passage remote from the spinneret has a cross-sectional area which continuously increases until it equals the crosssectional area of the spinning cell. The annular passage may be bounded on the outside by the wall of the spinning cell and on the inside by the wall of a solid body of circular cross-section coaxial with the spinneret and extending downwards from a level at most 1 inch from the spinneret face. The individual filaments may be caused to coalesce in the spinning cell to form a coalesced multifilament. As shown in Figs. 1 and 2, a dry; heated gas is introduced into spinning cell 12 through inlet 14 and gas manifold 4. The heated gas is uniformly distributed by gas distributer 6 and is directed downwardly into the spinning cell 12 in an even flow pattern by baffle 8 which is so positioned adjacent to spinneret assembly 10 as to prevent flow of gas between the baffle and the assembly without itself protruding below the bottom face of the spinneret. A spinning solution is extruded through orifices 16 arranged in a circle to produce a corresponding number of filaments 1 which first travel through a passage of annular cross-section where the heated gas enters the circle of filaments. This passage is deferred by the wall of spinning cell 12 and the peripheral outer surface of a cylindrical body 21 which is centrally positioned in the spinning cell and secured to the face of the spinneret assembly 10. A counter-current stream of heated gas may be introduced through inlet 18 at the bottom of the cell to minimize condensation of the solvent at the bottom of the cell. The two streams of gas meet and are drawn off evenly around the periphery of the cell wall through an aspirator device 20. The filaments 1 are withdrawn from spinning cell 12 through opening 30 as a twisted coalesced filament bundle 26, twisting being accomplished by the jet twister 22 which imparts a false twist to the filaments. The cylinder 21 may be replaced by the device shown in side view in Fig. 3. In the example, spandex filaments are produced by dry-spinning a solution of a segmented polyurethane in dimethylformamide. Filaments produced according to the invention have improved uniformity of denier. Specifications 796,041, 796,044, 849,154, 849,156, and U.S.A. Specifications 2,929,801, 2,929,802, 2,929,804, 2,962,470, 2,999,839 and 3,009,901 are referred to.