GB1025393A - Improvements in spinning polyacrylonitrile fibres - Google Patents

Abstract

1,025,393. Polyacrylonitrile filaments. COURTAULDS Ltd. July 17, 1962 [July 18, 1961], No. 25928/61. Heading B5B. Polyacrylonitrile fibres are made by extruding a polyacrylonitrile solution through a jet having a face over an area of which a plurality of spinning orifices are distributed into a chamber containing said jet face and having an aperture opposite the jet face, which aperture is coaxial with and of approximately the same area and shape as said area of the jet face, and is formed in a baffle which in part defines the chamber, introducing a coagulant liquid continuously into the chamber, and withdrawing the fibres and the coagulant through the aperture. Acrylonitrile homopolymers, and copolymers with e.g. styrene, methyl acrylate, itaconic acid, methallyl sulphonic acid and its salts, vinyl acetate and vinyl pyridine, containing at least 80%, preferably 90-95% acrylonitrile units, may be used. The linear speed of the fibres may be from 3À5-8m./min., preferably] 3À5-6 m./min., and the linear flow rate of the coagulant liquid through the aperture may be equal to or slightly less than the linear speed of the fibres through the aperture. Desirably, the aperture and the perforated area of the jet face are both generally circular and the diameter of the aperture is within 15%, preferably 10%, either way of the diameter of that area, the distance of the aperture from the jet face being not more than half the maximum possible path length of the fibres in contact with the coagulant, said distance being preferably ¢ inch-6 inches and especially ¢ inch-1¢ inches. The jet face may be disposed symmetrically in a symmetrical chamber and the means for introducing coaguland liquid may be designed to introduce the liquid symmetrically with respect to the jetface, said means suitably comprising a line of orifices disposed coaxially about the jet face. The baffle may be flat or at least in part frustoconical with the aperture at its narrower end. In apparatus as shown, the jet assembly 1, fed with spinning solution from pipe 2, is axially disposed in a cylindrical vessel 3. The jet is symmetrically surrounded by a frusto-conical baffle 4, which tapers upwardly to a circular aperture of the same diameter as the circular perforated area of the jet face 5. Coagulant liquid is fed continuously via pipes 6 and a perforated baffle 7 into the chamber 8 defined by the baffles 4 and 7, whence it passes with the filaments through the aperture in the baffle 4 into the main body of the vessel 3. From the top of the vessel, the filaments are withdrawn by a godet (not shown) while the coagulant overflows into an annular channel 9, from which it is taken for concentration and re-use.