Patent GB-636476-A (GB)
Title: Improvements in or relating to the production of textile materials having a basis ofpolyacrylonitrile
IPC: D01F6/18
Filed: 1949-02-02
Abstract: Polyacrylonitrile yarns made up of a number of continuous filaments are stretched in a softened condition in contact with an aqueous oil emulsion.  Preferably the yarns comprise filaments made by extruding a solution of polyacrylonitrile in concentrated aqueous zinc chloride into a coagulating bath containing an acid such as hydrochloric, sulphuric or acetic acid.  The emulsion may be applied to the yarn which is then stretched in wet steam at atmospheric or a higher pressure, or the yarn may be stretched in a body of hot aqueous oil emulsion at a temperature above 80 DEG  C. and preferably near 100 DEG  C.  Animal, vegetable or mineral oil may be used, but vegetable oil (for example olive oil) is preferred. The emulsion preferably contains 1-5 per cent of oil.  The tension on the yarn as it passes through the coagulating bath should be as low as possible and before being stretched the yarns may be washed free from acid.  After washing, the yarns may be stored wet, but preferably the yarn is stretched continuously with its production.  Thus the yarn may be drawn from the coagulating bath by a pair of nip rollers, passed through a bath or spray of water or a dilute alkaline solution and fed directly through a forwarding device into the stretching chamber. Preferably the yarns are stretched to more than ten times their original length and usually to the highest possible degree.  The yarns may be stretched in stages with relaxation periods in between. Comparative examples are given in which aqueous emulsions containing olive oil and a cationic emulsifying agent, e.g. "Fixanol" (Registered Trade Mark) are used.  An alkyl pyridinium chloride or a mixture of alkyl pyridinium chlorides may be used instead of "Fixanol," e.g. lauryl pyridinium chloride.  The polyacrylonitrile solution may be made by polymerizing monomeric acrylonitrile dissolved in aqueous zinc chloride solution which may be sufficiently concentrated to dissolve the polyacrylonitrile, i.e. about 60 per cent or above, or may be less than 60 per cent and precipitate, the polyacrylonitrile as it is formed, in which case the precipitate may be redissolved by increasing the zinc chloride concentration.  The polymerization may be performed by heating the solution to above 50 DEG  C., preferably 60-100 DEG  C., with a catalyst, e.g. benzoyl peroxide or ammonium or an alkali metal persulphate.  The solutions so obtained may be left to stand at about 10-30 DEG  C. for one or two weeks, when their viscosity increases.  The solution used in the examples is made by dissolving 365 parts of acrylonitrile in a solution of 2,460 parts of zinc chloride in 820 parts of water, 1.8 parts of ammonium persulphate being added as catalyst.  The solution is heated to 90 DEG  C. under reflux for 6 hours and then allowed to stand for 2 weeks at room temperature.  Copolymers of acrylonitrile with other vinyl compounds may be used, e.g. 40-80 per cent acrylonitrile with 60-20 per cent vinyl chloride or 50-90 per cent acrylonitrile with 50-10 per cent of methacrylonitrile.