Patent GB-878217-A (GB)
Title: Vinyl polymer textile yarns and filaments and a process for their production
IPC: D01F6/18
Filed: 1958-01-17
Abstract: A solution of a vinyl polymer or copolymer in a solvent boiling below 100 DEG C. is extruded into a coagulating liquid which is miscible with the solvent but does not dissolve the polymer to form filaments containing not more than 20% by weight of residual solvent, and the temperature of any given point along the yarn is increased either (a) in a stepwise manner by causing the filaments to travel in a path in succession over and in contact with a series of two or more rolls, each succeeding roll being heated to a higher temperature than the preceding roll, or (b) in a continuous non-stepwise manner by causing the filaments to travel in a series of helical loops along mutually inclined thread-advancing rolls, one or more of which are heated in such a manner that a temperature gradient is maintained along the roll or rolls, the temperature increasing axially along the direction of travel of the filaments.  The temperature of the surface of the first roll when using the stepwise procedure or the temperature of the rolls at the points of initial contact of the filaments with the rolls when using the continuous non-stepwise procedure is maintained at at least 60 DEG C. and not exceeding 5 DEG -20 DEG C. below the fusion temperature of the filaments in the condition in which they are on leaving the coagulating liquid, when they still contain a substantial proportion of solvent.  The temperature of the surfaces of the heated rolls is in either case maintained at least 5 DEG C. below the fusion temperature of the filaments throughout the entire temperature gradient, until the temperature of the final roll when using the stepwise procedure, or the temperature at the points of final contact of the filaments with the rolls when using the continuous nonstepwise procedure has reached 135 DEG -190 DEG C., corresponding to a residual solvent content in the filaments of not more than 2% by weight and a fusion temperature of the filaments of at least 150 DEG C.  The latter is defined as the temperature at which the contacting filaments become tacky, fuse together and are difficult or impossible to separate by normal handling.  It is about the temperature at which the filaments will shrink about 50% under no tension.  Preferred polymers contain 40%-75% by weight of acrylonitrile and 25%-60% of another vinyl compound such as vinyl chloride, vinyl acetate or vinylidene chloride, particularly a terpolymer of 68% acrylonitrile, 21% of vinyl chloride, and 11% of vinylidene chloride in acetonitrile solvent.  In an example, 1,724 grams of a terpolymer consisting of 69,6% acrylonitrile, 20,4% vinyl chloride, and 10% vinylidene chloride are dissolved with 26 grams of dioctyl tin maleate in 5,250 grams of acetonitrile and the solution spun at 83 DEG C. into a coagulating liquid consistting of 85 parts of water and 15 parts of acetonitrile.  The freshly coagulated yarn containing 17,3% of residual solvent, and having a fusion temperature of 100 DEG C. is withdrawn from the bath and passed to and continuously along in a series of helical loops a pair of mutually inclined thread-advancing rolls of which one is internally heated with steam in such a manner that the surface temperature of the roll at the point where the yarn first contacts the roll is 90 DEG C. and that of the other end of the roll is 110 DEG C.  At this point the yarn is free from water, contains 5,1% of residual solvent and has a fusion temperature of 185 DEG C.  The yarn is then passed to and along a second pair of rolls of which one is heated to a surface temperature at the yarn discharge end of 187 DEG C.  The yarn is then stretched 522%, annealed at 220 DEG C. for 0,02 second and allowed to shrink 11,2%.  It contains only 0,15% residual solvent. The process of the invention enables continuous filament vinyl polymer yarns to be produced more rapidly than heretofore.