Patent GB-689744-A (GB)
Title: Improvements in or relating to the production of synthetic fibres from polymers and copolymers of acrylonitrile
IPC: D06P3/70
Filed: 1949-12-23
Abstract: Artificial filaments are obtained by extruding a solution of an acrylonitrile polymer or copolymer into an aqueous coagulating liquid maintained at a temperature not exceeding +10 DEG  C., and the filaments are stretched while they are still in the gel condition in presence of moisture at a temperature of 70-110 DEG  C., while they are travelling in a line which is tangential to two rotating circular surfaces and between which there is no other point of frictional contact, one of the circular surfaces having a greater peripheral speed than the other.  The filaments are then dried. Before drying, the filaments may be treated with a liquid composition containing an anti-static agent.  The polymer may have a molecular weight of 35,000-300,000.  The spinning solution may be a solution of the polymer in a concentrated aqueous solution of a chloride, bromide, iodide, thiocyanate, perchlorate, or nitrate of zinc, calcium, lithium, cadmium, sodium, or aluminium, or in a concentrated aqueous solution of guanidine thiocyanate or a mono- or dialkyl <PICT:0689744/IV (a)/1> <PICT:0689744/IV (a)/2> guanidine thiocyanate.  As shown in Fig. 1, the polymer solution is forced through coupling 16 and spinneret 18 into coagulating bath 22.  The solution may be heated just before it reaches the spinning orifices by means of an internal core which is heated electrically or otherwise.  The coagulating liquid may be cooled and circulated through the bath, or ice or a freezing mixture may be added to the liquid in the bath.  The face of the spinneret is preferably arranged so that it just touches the surface of the coagulating liquid.  The filaments are washed in the coagulating liquid, which consists mainly of water, and for this purpose they may be given an extended travel. They are then caused to travel in helical turns over a pair of inclined rollers 42 where they are treated with water from spray 46 to remove any remaining salts. The washing water is preferably at a temperature not greater than +10 DEG  C.  The rollers 42 may be cooled internally.  The filaments are then stretched between rollers 60 and 66 while they travel in a straight line without contact with any thread guide or other solid surface.  The filaments are softened during the stretching by passing them through a trough 64 through which hot water is circulated.  Stretching up to 2000 per cent or more of the original length may be effected.  The filaments are then wound on bobbin 74.  The filaments may be dried while wound on the bobbin, or may first be dyed, and treated with a lubricating and anti-static composition.  Instead of the bobbin 74, a centrifugal spinning pot may be used.  Spinning, stretching, and drying may take place in a continuous operation.  As shown in Fig. 3, the stretched filaments 70 pass in helical turns over inclined rollers 92.  A finishing composition containing an anti-static agent is applied through jet 94 to the first few turns of the filaments. One or both of the rollers 92 may be internally heated or hot air may be directed on to the filaments so as to dry them.  If desired the stretching rollers may be partially immersed in the hot liquid softening bath. Instead of passing the filaments through a bath or trough of softening liquid during the stretching, the liquid may be sprayed on to the filaments which are travelling in a vertical path between the stretching rollers.  Specifications 594,999 and 689,742 are referred to.