Process for the preparation of an acrylonitrile copolymer and product prepared therefrom

An acrylonitrile copolymer fiber prepared according to a precipitation polymerization process comprising the steps of:

• maintaining in a reaction zone a solvent system consisting essentially of water and a co-solvent which is a member selected from the group consisting of sodium thiocyanate and zinc chloride,
• adding to the reaction zone a vinyl sulfonic acid comonomer-free feedstock comprising a major amount of acrylonitrile monomer and a minor amount of a vinyl carboxylic acid comonomer,
• adding to the reaction zone an initiator mixture comprising a peroxide, a low molecular weight organic mercaptan, and less than 10 ppm of metal ion,
• polymerizing the acrylonitrile monomer and vinyl carboxylic acid monomer under suitable conditions of temperature and pressure to obtain an acrylonitrile copolymer,
• stripping off water and excess monomer and comonomer to obtain a spinnable solution of acrylonitrile copolymer, and
• wet spinning the solution to produce a round fiber.