Acrylonitrile filament process

A process for making acrylonitrile polymer filaments comprising the steps of:

• (a) extruding a solution of acrylonitrile polymer into a coagulation bath to form filaments thereof;
• wherein said acrylonitrile polymer comprises at least 85 percent by weight acrylonitrile monomer units and up to 15 percent by weight neutral comonomer units;
• wherein said acrylonitrile polymer has from 30 to 250 microequivalents per gram of sulfate groups, sulfonate groups or a combination thereof;
• wherein said solution comprises solvent consisting of N,N-dimethylacetamide, dimethylformamide or a mixture thereof, 20 to 26 percent by weight of said acrylonitrile polymer and 0 to 3 percent by weight water;
• wherein said coagulation bath is at a temperature in the range of 10.degree. C. to 32.degree. C.;
• and wherein said coagulation bath comprises water and said solvent in a mole ratio selected such that Rho, as defined by the formula Rho=2.44 R-1.36, is greater than 0.6, where R=r.sub.1 +r.sub.2 -(r.sub.1 .times.r.sub.2),
• r.sub.1 =e.sup.[(2-W/S)/2],
• W is the moles of water in said coagulation bath,
• S is the moles of solvent in said coagulation bath, and
• r.sub.2 =e.sup.[(microequivalents per sulfate and sulfonate groups-95)/95] ;
• (b) withdrawing said filaments from the bath with a jet stretch of from 0.2 to 1;
• and
• (c) providing said filaments with a wet stretch of 2 to 8.