Verfahren zum Herstellen zusammengesetzter Acrylfasern

摘要

1,265,874. Polyacrylonitrile conjugate filaments. TOHO BESLON CO. Ltd. 15 Aug., 1969 [16 Aug., 1968], No. 40872/69. Heading B5B. In the wet spinning of acrylonitrile polymer conjugate filaments, a concentrated aqueous zinc chloride solution containing 0À005 to 0À2% by weight (calculated as zinc oxide) of a basic inorganic compound is used as the solvent and the solution is divided into two portions, one portion being extruded through a spinneret adapted to spin conjugate filaments without having been previously heated and the other portion having been heated to a temperature and for a time prior to extrusion through the spinneret such that the difference in T DMF of homo filaments spun from the solutions separately is more than 5‹ C. T DMF is defined as the temperature of maximum contraction of the fibre, measured when heated in aqueous dimethyl formamide solution under specified conditions. The polymers used consist mainly of acrylonitrile and include copolymers of acrylonitrile with methyl acrylate, methyl methacrylate, vinyl acetate, acrylamide, methacrylamide, allylsulphonic acid, methallylsulphonic acid and salts thereof. The acrylonitrile polymer solution may be prepared by continuous solution polymerization comprising the steps of filling a polymerization apparatus with a reaction mixture and applying a pressure of 1-5 kg/cm.2 gauge to the reaction system, and the heat-treated polymer solution is prepared by continuously heating a portion of the solution thus produced while applying a pressure of 1-10 kg/cm.2 gauge to the polymer solution in at least one heating vessel to prevent foaming and gel formation. The heat treatment may be effected at 80-130‹ C. The polymer may be dissolved in an aqueous solution of zinc chloride containing 55-65% by weight of the salt. The solution may also contain sodium chloride. The basic compound present in the spinning solution may be zinc oxide, zinc carbonate, sodium hydroxide or sodium carbonate. The two types of polymer solution are preferably extruded at 10-30‹ C. into an aqueous coagulating bath containing 10 to 40% of the same salts as are present in the spinning solution. The geltow of conjugate filaments thereby obtained is washed with water, stretched at an elevated temperature (e.g. in steam) while wet or dry, and relaxed in hot air, saturated steam or superheated steam, e.g. steam at 220‹ C. A second stretching step may be effected. The conjugate filaments obtained may be immersed in boiling water for 10 minutes whereby they acquire a spiral crimp.