WERKWIJZE VOOR HET TERUGWINNEN VAN OPLOSMIDDELEN BIJ HET VERVAARDIGEN VAN SYNTHETISCHE VEZELS.

摘要

1536394 Recovering dimethyl acylamide spinning solvent BAYER AG 21 March 1977 [27 March 1976] 11832/77 Heading B5B [Also in Division C2] Dimethyl acyl amides, e.g. dimethyl formamide and dimethyl acetamide, are recovered from the aqueous solutions generated during spinning of acrylonitrile and urethane polymers by (a) concentrating the aqueous solution to dimethylacyl amide content not exceeding 60% in a series of distillation columns wherein the head product of one column is used to heat the next column and (b) subsequently distilling the concentrate in a further column and collecting the dimethyl acyl amide as vapour. In concentration step (a) the still residue from each distillation unit is passed on to the next for further concentration. The concentration steps may be carried out at progressively decreasing superatmospheric pressures.