| 摘要 |
"White" acrylonitrile homopolymers or copolymers containing at least 85% of acrylonitrile and having a "heated colour value" below about 13 may be prepared by polymerizing acrylonitrile, optionally together with ethylenically unsaturated sulphonates and additional comonomers, in aqueous media in the presence of redox catalyst systems comprising water-soluble derivatives, e.g. alkali metal and ammonium salts, of perdisulphuric acid and oxidizable sulphoxy compounds in which the valency of a sulphur atom does not exceed 4, e.g. sodium bisulphite, sodium metabisulphite, sulphur dioxide and sodium hydrosulphite, wherein the weight ratio of sulphoxy to peroxy compound is at least 6 to 1. The media may contain small amounts of iron and the pH may be adjusted, e.g. to 3-4, by adding sulphuric acid. The process may be conducted batchwise or continuously with continuous addition of reactants, and the polymers recovered and washed with water which may contain a sequestering agent, e.g. ethylenediaminetetraacetic acid or oxalic acid. The polymers may be dissolved in de-ionized dimethylformamide and the solutions dry spun into fibres which may be dyed with basic dyes. Many suitable sulphonates and comonomers are listed and examples describe the copolymerization of acrylonitrile with (III and IV) methyl acrylate; (V, VI and XX) methyl acrylate and potassium styrene sulphonate; (VII, VIII, X and XXI) methyl acrylate and sodium styrene sulphonate; (IX) N-tertiary butyl acrylamide and sodium allyl sulphonate; (XI) methyl vinyl ketone and sodium methallyl sulphonate; (XII) vinyl acetate and ammonium vinyl sulphonate; (XIII) styrene and sodium styrene sulphonate; (XIV) acrylamide and sodium styrene sulphonate; (XV) ethyl acrylate, acrylamide and sodium styrene sulphonate; (XVI) methoxyethyl acrylate and sodium styrene sulphonate; (XVII) vinyl formate and sodium styrene sulphonate; (XVIII) methyl methacrylate and potassium styrene sulphonate; (XIX) ethyl acrylate and sodium styrene sulphonate and (XXII) sodium styrene sulphonate. "White" polymers are defined in the Specification as having a "fibre colour value" of less than 6, the fibre colour value being determined from the reflectance ratios from pads of staple fibres in the green and blue filter settings of a differential colorimeter. The "heated colour value," is determined from the increase in optical density on heating a dimethylformamide solution of the polymer at 100 DEG C. for four hours. |
