| 摘要 |
1,123,984. Polyacrylonitrile spinning. SNIA VISCOSA SOC. NAZIONALE INDUSTRIA APPLICAZIONI VISCOSA S.p.A. 13 Jan., 1966 [23 Jan., 1965], No. 1626/66. Addition to 1,016,505. Heading B5B. The process of the parent Specification (wherein dimethylformamide is recovered from coagulation baths used in wet-spinning polyacrylonitrile and comprising dimethylformamide and concentrated aqueous solutions of potassium formate or acetate by extracting the dimethylformamide from the bath with monomeric acrylonitrile and the extract is purified by passing it through animal charcoal or an ion exchange resin) is modified in that the extract is treated with two types of ion-exchange resins used either successively or concurrently. The resins comprise cationic resins consisting of a sulphonic group-containing styrene and divinylbenzene copolymers and anionic resins which contain quaternary ammonium in the hydrate form or aliphatic amines. The extract may be passed through a single bed comprising both types of resin. The ion exchange resins used remove from the acrylonitrile-dimethylformamide mixture substantially all the impurities which adversely affect the polymerization of the monoacrylonitrile in the presence of dimethylformamide and the mixture may, therefore, be used (after the addition of an appropriate additional proportion of monoacrylonitrile) for the preparation of further quantities of polyacrylonitrile. |
