CONTINUOUS MANUFACTURE OF POLYAMIDES

摘要

A process for the manufacture of a polyamide by continuously conveying the aqueous solution of a salt of essentially equivalent amounts of a diamine, or of a mixture of several diamines, and of a dicarboxylic acid, or of a mixture of several dicarboxylic acids, through several reaction zones under polyamide-forming conditions, wherein (a) in a first reaction zone the mixture of starting materials is heated to a temperature of at least 220.degree.C, but not higher than 300.degree.C, at a pressure which is above the corresponding saturation vapor pressure of water and prevents the formation of a vapor phase, until the polycondensation conversion is at least 80%, but without completing the condensation in this zone, (b) in a second zone the pressure acting on the polycondensation mixture is released, adiabatically, to levels of not less than 3 atmospheres, and not more then 20 atmospheres, so as to reach temperatures below 215.degree.C, (c) the polycondensation mixture is then heated in a third reaction zone comprising a heat exchanger consisting of heat exchange elements connected in parallel, to from 220 to 330.degree.C, in the course of less than 5 minutes, with evaporation of the bulk of the water, at the pressure level to which the pressure had previously been released or at a lower pressure, (d) in a fourth reaction zone the polycondensation mixture is separated from the water vapor, and (e) finally the condensation is completed under the conditions prevailing at the end of the third reaction zone to form a high molecular weight filamentforming polyamide.