Patent GB-737258-A (GB)
Title: Improvements in the manufacture of fibres from acrylonitrile polymers by dry-spinning methods
IPC: D01F6/18
Filed: 1953-06-08
Abstract: Filaments are obtained by extruding a solution of an acrylonitrile polymer into an evaporative medium through a spinning jet, the face of which is coated with graphite or with graphite in admixture with a wax.  The wax is preferably one of low melting point, i.e. of melting point below 60 DEG  C.  A mixture of graphite and wax containing 20 per cent or more of graphite e.g. a mixture containing 40 per cent of graphite and 60 per cent of a wax of melting point 48 DEG  C., may be used.  The coating of graphite on the jet face overcomes the tendency of the individual filaments to coalesce and to form a mass which adheres to the jet face.  The polymer may be polyacrylonitrile itself or a copolymer of acrylonitrile with another unsaturated compound such as vinyl acetate, propionate, butyrate or chloride, or acrylic or methacrylic acid, methyl methacrylate, acrylamide, dimethyl maleate, dimethyl fumarate, styrene, isobutylene or butadiene. The solvent may be N,N-dimethyl formamide or acetamide, gamma-butyrolactone, N-formyl-pyrrolidone, dimethyl sulphone, sulpholane, fumaronitrile or cyclic ethylene carbonate.  The solution is preferably extruded at 80-120 DEG  C. through a heated jet into a heated evaporative atmosphere such as air.  The heated p  spinning solution is preferably filtered and homogenized just before it reaches the spinning jet by passing it through a bed of finely-divided granular material such as a sand pack.  Air may be admitted to the spinning cell at two or more points, one being in the region of the jet and another at or about half way down the cell.  In an example, polyacrylonitrile is stirred with a cooled solution of dimethyl formamide and the slurry is heated on a water-bath until a viscous solution is obtained.  The solution is heated to 130 DEG  C. and then filtered.  After de-aeration, the solution is forced through a sand pack, consisting of three layers of increasing fineness of grain, which is supported just above a spinning jet.  The jet, which is heated to about 123 DEG  C., has its outer face coated with a thin layer of a graphite and wax composition.  The solution is extruded to form filaments which pass down the spinning cell.  The cell is heated by the circulation of oil at 250 DEG  C. in a surrounding jacket, and air at 124 DEG  C. is blown into the cell at the top and at a point about half way down, the temperature of the air rising to about 220 DEG  C. near the bottom of the cell.  The filaments, still containing a substantial proportion of solvent, are led out of the cell and passed over a roll which applies to them an aqueous solution containing triethanolamine, a partial ester of n-decyl alcohol and phosphoric acid, and a polyethylene glycol monoester of oleic acid. The yarn passes over take-up rolls and is wound on a perforated bobbin while being twisted.  Water at 85 DEG  C. is subsequently forced through the bobbin to remove the remainder of the solvent from the yarn.  The yarn may then be treated with an anti-static agent and stretched while travelling through an atmosphere of steam at 176 DEG C.  After the stretching operation, the yarn may be subjected to a relaxation treatment to increase its extension at break.