Process for spinning modacrylic fiber having high retraction and reduced inflammability

Process for the manufacture of modacrylic fibers having a retraction of above 35%, reduced inflammability and high glossiness, comprising the steps of:

• (a) preparing a viscous spinning dope constituted by a solution, in an organic spinning solvent miscible with water, of a mixture of copolymers deriving from acrylonitrile, vinylidene chloride, at least a vinyl ester and at least an unsaturated monomer containing at least a sulphonic group, wherein the units deriving from acrylonitrile are present in an amount from 50% to 85% by weight and those derived from the vinyl ester in an amount from 3% to 6% by weight;
• spinning said dope in a coagulating bath constituted by a mixture of water and spinning solvent;
• (b) drawing the coagulated fiber at a draw ratio from 2 to 4 in a liquid selected from the group consisting of water and mixtures of water and spinning solvent at a temperature of from 80.degree. to 100.degree.;
• (c) subsequently drying the fiber by means of hot air at temperatures from 100.degree. and 130.degree. C. while leaving it free concurrently to contract to a degree of about 25% to 30%;
• and
• (d) subsequently subjecting the fiber to a further hot drawing in air at a draw ratio from 1.5 to 3.5 at a temperature from 50.degree. to 100.degree. C.