GB750008A - Improvements in the manufacture of organic substances of very high molecular weight - Google Patents

Abstract

Organic substances of high molecular weight, e.g. cellulose esters and ethers such as cellulose acetate, propionate, butyrate, acetate-propionate, acetate butyrate, acetate-stearate and methyl and ethyl cellulose, and polyvinyl resins such as polyvinyl alcohol, chloride and acetate and vinylidene chloride-acrylonitrile copolymers, are precipitated from their solutions in a fibrous form by causing an unsupported continuous stream or streams of the solution and an unsupported continuous stream or streams of precipitant to impinge simultaneously on the <PICT:0750008/IV(a)/1> same area or on immediately adjacent areas of a solid impact surface. The solution and/or the precipitant may be heated. The streams are preferably separately extruded from a common nozzle 16 through adjacent slits or orifices and caused to impinge on the base of a vessel 11 across which a further stream of precipitant may be supplied from a pipe 12, the precipitate and liquid being discharged at 15 for separation. Nozzles with three parallel adjacent rectangular slits or three annular orifices are described, the solution in each case preferably being extruded through the medial slit or orifice and the precipitant through the others. In another nozzle, the solution is extruded through an inner tubular orifice and the precipitant through a surrounding annular orifice, or vice-versa. Preferably the linear speed of the solution leaving the various nozzles is less than that of the precipitant. As applied to an acetic acid solution of cellulose acetate, the precipitant is water or dilute acetic acid.ALSO:<PICT:0750008/III/1> Organic substances of high molecular weight, e.g. cellulose esters and ethers and polyvinyl resins, are precipitated from their solutions in a fibrous form by causing an unsupported continuous stream or streams of the solution and an unsupported continuous stream or streams of precipitant to impinge simultaneously on the same area or on immediately adjacent areas of a solid impact surface. The solution and/or the precipitant may be heated. The streams are preferably separately extruded from a common nozzle 16 through adjacent slits or orifices and caused to impinge on the base of a vessel 11 across which a further stream of precipitant may be supplied from a pipe 12, the precipitate and liquid being discharged at 15 for separation. Nozzles with three parallel adjacent rectangular slits or three annular orifices are described, the solution in each case preferably being extruded through the medial slit or orifice and the precipitant through the others. In another nozzle, the solution is extruded through an inner tubular orifice and the precipitant through a surrounding annular orifice or vice-versa. Preferably the linear speed of the solution leaving the various nozzles is less than that of the precipitant.