A continuous wet-spinning method for producing a useful filamentary material, such as multi-filaments or a tow, from a spinning solution of an acrylonitrile copolymer in an aqueous saline solvent consisting essentially of zinc chloride. In this method, an aquagel filamentary material obtained by spinning the spinning solution is taken up from an aqueous coagulating bath, continuously stretched in water and continuously dried so as to form a dried filamentary material having a moisture content of less than 5 weight percent and a transparency of at least 70 percent, measured under specific conditions. Subsequently, the dried filamentary material is continuously relaxed under a tension of at least 2 mg. per denier in substantially saturated steam at a temperature, X(.degree.C), such that the following expression is satisfied: 55 log Y + 5M - 417 .ltoreq. X .ltoreq. 100 log Y + 5M - 434 wherein 160.degree.C .ltoreq. x .ltoreq. 100.degree.C, 45 percent .ltoreq. Y .ltoreq. 15 percent and Y is the percent of shrinkage.
Flexing abrasion resistance and anti-fibrillation of acrylic synthetic fibers are improved by wet-spinning a solution of acrylonitrile polymer in an inorganic solvent through spinnerette orifices while maintaining the linear velocity ratio of the free-extrusion above 1 and the jet-stretch ratio above 1.5.
Hygroscopic acrylic fibers having high moisture regain and excellent sweat absorbing property together with the excellent characteristics of the acrylic fibers are disclosed. The fibers contain open capillary voids in a content (X) of 4.0 to 63.2 % and have a free surface area (S) of 1.0 .times. 10.sup.4 to 1.7 .times. 10.sup.6 cm.sup.2 /g and a contact angle of the surface of the fiber with water of at most 45.degree..
A method is disclosed for preparing polyacrylonitrile copolymers by Heterogeneous reaction of polyacrylonitrile aquagel. Generally, the method includes the steps of preparing a solution of polyacrylonitrile by dissolving the polyacrylonitrile in a water-miscible solvent which is capable of dissolving the polyacrylonitrile but incapable of hydrolyzing the nitrile groups of the polyacrylonitrile under the dissolution conditions. Coagulating the polyacrylonitrile solution by replacing the solvent with a coagulating fluid such as water or a water-miscible fluid incapable of dissolving polyacrylonitrile at temperatures below 80.degree. C. and incapable of reacting with the nitrile groups of the polyacrylonitrile, thus obtaining the polymer in the aquagel state. Replacing the coagulating fluid with a fluid reagent capable of reacting with the nitrile groups of the polyacrylonitrile aquagel but incapable of dissolving the polyacrylonitrile aquagel at the selected reaction temperature. Allowing the fluid reagent to chemically react with the nitrile groups of the aquagel while the polyacrylonitrile aquagel is undissolved to form a copolymer product. The copolymer product is then either used in further chemical reactions involving newly formed and/or original side substituents, or isolated and utilized for molding or shaping into various articles. Various plasticizers, which when undiluted are capable of dissolving polyacrylonitrile, may be added to the copolymer product to assist in molding or shaping the material into an article.
