1,161,689. Dry spinning artificial filaments. CELANESE CORP. 8 Nov., 1966 [12 Nov., 1965], No. 49987/66. Heading B5B. In the production of cellulose acetate filaments by dry spinning the gaseous evaporative medium is supplied to the spinning cell at a point situated between the face of the spinneret and the outlet from the cell through which the formed filaments are withdrawn (the point being preferably somewhat nearer to the latter) and the solvent carrying evaporative medium is exhausted from the cell at two points, one in the neighbourhood of the point where the formed filaments are withdrawn and the other in the neighbourhood of the spinneret. The evaporative medium is supplied at a flow rate and temperature such that its temperature at the spinneret face is between 25‹ and 50‹ C. when spinning cellulose triacetate dope and between 50‹ and 80‹ C. when spinning secondary cellulose acetate dope. The dope may be preheated before passing through the spinneret to a temperature of 40‹ to 110‹ C. and preferably 50‹ to 95‹ C. The evaporative medium in practice is air, but any other inert gas, e.g. nitrogen, may be used. The medium may be supplied at a temperature of 30‹ to 100‹ C., preferably 40‹ to 90‹ C., and its flow rate may be 1 to 100, preferably 5 to 35 cubic feet per minute. For a spinning cell 25 feet high the inlet for the air is preferably 15 feet below the spinneret face and 10 feet above the filament outlet. The lower part of the cell may be provided with heating means to supplement the heat provided by the evaporative medium.
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