GB711344A - Improvements in the production of filaments, films and like shaped articles from acrylonitrile polymers - Google Patents

Abstract

A solution of a fibre-forming acrylonitrile polymer is shaped and set by a coagulating medium comprising as the chief or sole constituent a liquid aromatic hydrocarbon or a liquid halogenated aliphatic hydrocarbon to form filaments, films and other shaped articles. The term acrylonitrile polymer includes copolymers in which acrylonitrile is the main constituent (especially exceeding 85 per cent.) with methacrylonitrile, vinyl chloride, vinyl acetate, acrylic acid esters such as methyl and phenyl acrylate, styrene and its derivatives and vinylidene chloride. Aromatic hydrocarbons, especially benzene, toluene, the xylenes and alkyl benzenes such as solvent naphtha are preferred as the coagulating medium. Chlorinated paraffins such as carbon tetrachloride, ethylene dichloride and symmetrical tetrachlorethane may also be used. If desired, a more polar liquid such as ethanol may be added to the coagulating medium in an amount up to 30 per cent. by volume or the limit of miscibility with the aromatic hydrocarbon or halogenated aliphatic hydrocarbon, whichever is the lower. The acrylonitrile polymer may be dissolved in dimethyl formamide, gamma-butyrolactone, gamma- and delta-valerolactones, propiolactone and other beta-lactones, tetramethylene sulphone and solvents comprising nitromethane with or without formic acid. Dimethyl formamide or a mixture of nitromethane and a minor proportion but at least 6 per cent. of water are preferred. Preferably the polymer has a viscosity in 1 per cent. solution in dimethyl formamide at 20 DEG C. of between 2.5 and 4 centistokes. The solution to be extruded or cast may have a concentration between 7.5 and 25 per cent. and the temperature should be high enough to maintain solution. The temperature of the coagulating medium may be preferably between 50 and 100 DEG C. The filaments films and other shaped articles may be stretched or relaxed by known methods. In an example a 20 per cent. solution of polyacrylonitrile (viscosity 2.52 centistokes) in dimethyl formamide at 40 DEG C. is extruded as filaments into benzene or a 5:1 by volume benzene/ethyl alcohol mixture at 60 DEG C. The Provisional p Specification also refers to the following as suitable solvents for the acrylonitrile polymer: nitro ethanol, nitro propanol, and cyclic aliphatic anhydrides such as maleic anhydride, succinic anhydride and glutaric anhydride. Specification 690,553 is referred to.