Patent GB-740903-A (GB)
Title: Improvements in and relating to steam stills
IPC: C08L75/00
Filed: 1952-12-11
Abstract: A slurry containing a polymer, water and a water-immiscible organic solvent is steamdistilled to remove the organic solvent before separating the polymer from the slurry.  Slurries referred to are (1) that obtained in the production of a polyurethane by reacting an aqueous solution of a polyamine with a solution <PICT:0740903/IV(a)/1> <PICT:0740903/IV(a)/2> of a bis-chloroformate in an organic solvent (see Specifications 683,504 and 685,729), and (2) that obtained in the production of a polyamide by reacting an aqueous solution of a diamine with a solution of a chloride of a dicarboxylic acid as described in Specification 737,184.  The polymer slurry enters the still 11 through an inlet pipe 21 and flows in a zigzag path to the outlet pipe 23 through compartments 28 defined by baffles 26 and 27 attached respectively to the side walls 14 and 16 of the still. Live steam is lead into the bottom of the still through a sparge pipe 32 provided with several sets of holes 33, alternate sets being on opposite sides in alternate compartments so that the steam is projected in a direction which is horizontal and counter-current to the side-to-side flow of liquid in each compartment.  The material distilled off is removed via a dome 36 fitted with baffles 38 and 39 to remove entrained liquid.  To break up foam on the surface of the slurry, a blast of air is directed on to it from rotatable pipes 51 and 52 each having several sets of air holes so arranged that above any compartment there is one set of holes directing a blast of air at an angle which is downward and counter-current to the side-to-side flow of the polymer slurry in that compartment.  In examples, a slurry of 4,4-polyurethane obtained by reacting an aqueous solution of tetramethylene diamine containing sodium carbonate and sodium lauryl sulphate with a toluene solution of 1,4-butanediol-bis-chloroformate was steam distilled until 90 per cent of the toluene had distilled over.  The polymer was then filtered, washed with hot water, and dried in air or in vacuum.ALSO:Steam distillation apparatus comprises a distillation vessel extending substantially horizontally and having an inlet and outlet for process liquid, a plurality of baffles defining with the walls of the vessel a plurality of compartments so that the liquid flows from the inlet in a zig-zag path through the compartments to the outlet, means for introducing steam below the level of the liquid in at least one compartment in a direction opposed to the transverse components of flow of the process liquid and means for removing gaseous distillation products from the vessel.  The apparatus is particularly useful for removing the organic solvent from a <PICT:0740903/III/1> <PICT:0740903/III/2> slurry containing a polymer, water and a water-immiscible organic liquid (see Group IV(a)).  Process liquid enters the still 11 through an inlet pipe 21 and flows in a zig-zag path to the outlet pipe 43 through compartments 28 defined by baffles 26 and 27 attached respectively to the side walls 14 and 16 of the still. Live steam is lead into the bottom of the still through a sparge pipe 32 provided with several sets of holes 33, alternate sets being on opposite sides in alternate compartments so that steam is projected in a direction which is horizontal and counter-current to the side-to-side flow of liquid in each compartment.  The material distilled off is removed via a dome 36 fitted with baffles 38 and 39 to remove entrained liquid.  To break up foam on the surface of the process liquid, a blast of air is directed on to it from rotatable pipes 51 and 52 each having several sets of air holes so arranged that above any one compartment there is one set of holes directing a blast of air at an angle which is downward and counter-current to the side-to-side flow of the process liquid in that compartment.