| 摘要 |
Polymers of acrylonitrile or copolymers thereof containing at least 85 per cent. of acrylonitrile are dissolved in nitric acid. The polymer is dissolved at room temperature by nitric acid of concentrations of 54 per cent. and higher. The suspension formed by acid of lower concentration is converted by heating into a solution, which gels on cooling. Discoloration of the solution may be avoided by addition of urea. Sulphur dioxide, sulphuric acid, phosphoric acid and boric acid may also be added. The suspension in dilute nitric acid may be degassed and heated to form a solution shortly before entering the spinning nozzle and the threads are freed from nitric acid by hot air or washing. The solution may be used also for forming bands, tubes, blades, films and bristles.
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