| abstract |
A process for continuous production of polyamides by continuous transport of a mixture of one or more lactams and from 1 to 15% and preferably from 3 to 8% of water and optionally other polyamide-forming compounds such as the salts of dicarboxylic acids and diamines or aminocarboxylic acids through a number of reaction zones under polyamide-forming conditions, said mixture of starting materials being heated in a first reaction zone to temperatures of from 210° to 330° C and preferably from 220° to 280° C, whereupon the polycondensation mixture is adiabatically vented in a further reaction zone and is then polymerized to completion in yet another reaction state to form high molecular weight polyamides. The process is characterized in that n A. the mixture of starting materials is heated in the first reaction zone at pressures which are above the respective vapor pressures of the starting materials and prevent the formation of a vapor phase, said heating being effected for from 5 minutes to 2 hours and preferably from 10 minutes to 1 hour until a conversion of at least 70% and preferably 80% has been reached; n B. the polycondensation mixture is vented in the second zone to pressures of from 1 to 11 bars and preferably from 1 to 6 bars and is then immediately heated in a third reaction zone, preferably together with the steam formed during adiabatic venting, with the application of heat and evaporation of the major portion of the water at the said pressure obtained by venting or a lower pressure, said heating being carried out for less than 10 minutes and preferably less than 5 minutes at temperatures of from 250° to 350° C and preferably from 260° to 280° C, whereupon n C. the polymerization mixture is separated from the steam in a fourth reaction zone and is polymerized to completion in a further reaction stage to form high molecular weight polyamides. |