| 摘要 |
<p>1,202,684. Regenerating baths used in spinning acrylic threads. SOC. ITALIANA RESINE S.p.A. 17 Jan., 1969 [27 Jan., 1968], No. 2989/69. Heading B5B. Spinning baths used in making acrylonitrile polymer threads of 0À2 to 1À0 den. by extruding a solution of the polymer in dimethylformamide into a coagulating bath comprising cumene, D.M.F. and linear paraffins having 10 to 16 carbon atoms per molecule, and stretching the threads thereby formed in baths essentially comprising said paraffins, are regenerated by mixing together the solution enriched in impurities and D.M.F., which is discharged from the coagulating bath, with the solution enriched in cumene, D.M.F. and impurities, which is discharged from the stretching bath, subjecting the mixture to liquid/liquid extraction using D.M.F. as the solvent in order to separate a refined phase consisting essentially of paraffins and an extracted phase consisting essentially of cumene and dimethylformamide, recycling a fraction of the refined phase to the stretching bath after removing dimethylformamide therefrom by treatment with small proportions of water, recycling the remaining fraction of the refined phase as such to the coagulating bath, treating the extracted phase with water to separate an organic phase essentially comprising cumene and an aqueous phase containing D.M.F. and impurities, recycling the cumene phase to the coagulating bath, separating from the aqueous phase first water, and next D.M.F. by distillation, recycling the D.M.F. in part to to the extraction stage and in part to the coagulating bath, and utilizing the remaining dimethyl-formamide in preparing the spinning solution. The mixture of the solution discharged from the coagulating bath with the solution discharged from the stretching bath may be fed to an intermediate region between the top and foot of an extraction column, the D.M.F. extraction solvent being fed to the end of the column at which the refined phase is separated, so as to obtain an extracted phase essentially comprising cumene and D.M.F. and a refined phase essentially comprising paraffins. The D.M.F. used as solvent may contain 0À5 to 10% by weight of water. The aqueous phase containing D.M.F. and impurities may be freed from water first by distillation in vacuum and from D.M.F. next by a thin layer technique.</p> |
