| 摘要 |
Filaments, threads, artificial horse hair, tows, films, foils, and similar articles of polymers or copolymers of acrylonitrile are obtained by dry spinning solutions of these polymers in solvents or solvent mixtures having highboiling points, the temperature of extrusion being at least 120 DEG C., the walls of the evaporative chamber being maintained at a temperature of less than 100 DEG C., and the concentration of the solution to be spun, expressed in parts by weight of polymer or copolymer per hundred parts by weight of solution, being greater than the empirical value <FORM:0730902/IV (a)/1> where N is the specific viscosity of the polymer, i.e. the ratio of the difference between the viscosity of a solution of the polymer in the solvent selected for the spinning solution, determined at a concentration of 0.2 per cent and at a temperature of 20 DEG C., and the viscosity of the solvent at 20 DEG C., to the viscosity of the solvent at 20 DEG C. Under these conditions, filaments are obtained which have an indented contour in transverse section and a cellular or porous structure. A current of air may be passed through the spinning chamber. In an example, a solution comprising 34.5 per cent of an acrylonitrile polymer of specific viscosity 0.29 and 65.5 per cent of dimethylformamide is extruded at 128 DEG C. into an evaporative chamber of which the walls are at 75 DEG C. and which is swept through by an air current at the same temperature produced by aspiration applied at the base of the chamber. The filaments obtained are stretched. These filaments are of indented contour with numerous alveoles in the interior and they have a density of 1.125. Specification 605,612 is referred to. |
