GB674954A - Improvements in the manufacture of synthetic linear polyamides and apparatus therefor - Google Patents

Abstract

<PICT:0674954/IV (a)/1> Linear polyamides are prepared by passing an aqueous solution of a diamine dibasic carboxylic acid salt at the requisite temperature and pressure through a first reaction zone in which the major portion of the salt is polymerized with removal of steam, then passing the resulting reaction mass through a second reaction zone in which polymerization is substantially completed, this zone comprising a tube which increases in diameter in the direction of flow and in which water is progressively vaporized and the pressure progressively reduced to substantially atmospheric by fluid friction in the tube, sufficient heat being supplied to the tube to prevent cooling below the melting point of the reaction mass, and finally passing the polyamide composition through a third zone at substantially atmopheric pressure where polymerization is completed and separation of the polymer and steam occurs. As described, the first zone is an autoclave 2, operating at 230 DEG C. and 250 lb. pressure from which the partially reacted mass passes to the second zone 4 comprising a tube heated by "Dowtherm" introduced at 8 DEG to 290 DEG C., the tube comprising three sections the lengths of which are in the ratio 2 : 1 : 1 and the diameters in the ratio 1 : 2 : 3. The third zone or finisher 5 is heated to a 275 DEG C., steam being released at 10 and molten polymer being drawn off at 7 at about 8 lb. per hour, the residence time in the finisher being about 1 hour. The process may be a batch one or continuous. Specifications 461,236 and 461,237, and U.S.A. Specification 2,361,717 are referred to.ALSO:<PICT:0674954/III/1> Linear polyamides are prepared by heating an aqueous solution of diamine dibasic carboxylic acid salt at the requisite temperature and pressure (e.g. 230 DEG C, 250 p.s.i.) in an autoclave 2 in which the major part of the salt is polymerized with removal of steam, passing the resulting reaction mass through a tube 4, heated by a "Dowtherm" jacket, in which polymerization is substantially completed, the tube increasing in diameter in the direction of flow and water being progressively vaporized as the pressure is reduced to substantially atmospheric by fluid friction in the tube, and finally passing the polyamide composition through a heated third zone 5, at substantially atmospheric pressure, where polymerization is completed and separation of the polyamide and steam (drawn off at 10) occurs. Polyamide is drawn off at 7. As shown the tube comprises three sections the length of which are in the ratio 2:1:1 and the diameters in the ratio 1:2:3. The process may be continuous or batch. U.S.A. Specification 2,361,717 is referred to. Specifications 461,236 and 461,237, [both in Group IV], also are referred to.