Continuous production of polyamides

Claim 1

A CONTINUOUS PROCESS FOR THE PRODUCTION OF POLYAMIDES IN A VERTICAL REACTION TUBE WHICH COMPRISES FEEDING AN ALKYLENE DIAMINE AND AN ALIPHATIC DICARBOXYLIC ACID IN AQUEOUS SOLUTION INTO AN UPPER ZONE IN SAID VERTICAL REACTION TUBE WHICH IS MAINTAINED AT SUBSTANTIALLY ATMOSPHERIC PRESSURE, INITIATING CONDENSATION OF SAID DICARBOXYLIC ACID AND SAID DIAMINE BY PASSING THEM DOWNWARDLY FROM SAID UPPER ZONE INTO AND THROUGH AN INTERMEDIATE ZONE IN SAID VERTICAL TUBE, SAID INTERMEDIATE ZONE BEING A LIQUID BODY OF AN INERT, ORGANIC SOLVENT FOR THE CONDENSATE OF SAID DICARBOXYLIC ACID AND SAID DIAMINE FORMED IN SAID INTERMEDIATE ZONE, SAID SOLVENT HAVING AN ATMOSPHERIC BOILING POINT AT LEAST 25*C. ABOVE THE BOILING POINT OF WATER WITH THE FURTHER PROVISO THAT THE BOILING POINT OF SAID SOLVENT AT ABOUT ATMOSPHERIC PRESSURE IS ABOVE THE MELTING POINT OF THE DIAMINE-DICARBOXYLIC ACID CONDENSATE IN SAID INTERMEDIATE ZONE AND BELOW THE MAXIMUM POLYCONDENSATION TEMPERATURE IN SAID TUBE, SAID SOLVENT FURTHER CHARACTERIZED BY THE FACT THAT IT FORMS AZEOTROPIC BOILING MIXTURES WITH WATER IN AMOUNTS OF SAID SOLVENT NOT HIGHER THAN 50% OF SAID AZEOTROPIC MIXTURE, MAINTAINING THE TEMPERATURE IN SAID UPPER ZONE AT THE BOILING POINT OF THE LIQUID PHASE IN SAID UPPER ZONE AND DISTILLING OFF FROM SAID UPPER ZONE THE WATER INTRODUCED INTO SAID UPPER ZONE BY THE AQUEOUS SOLUTION OF SAID DICARBOXYLIC ACID AND SAID DIMINE, MAINTAINING THE TEMPERATURE IN SAID INTERMEDIATE ZONE ABOVE SAID TEMPERATURE IN SAID UPPER ZONE BUT BELOW THE BOILING POINT OF SAID SOLVENT IN SAID INTERMEDIATE ZONE AT SAID SUBSTANTIALLY ATMOSPHERIC PRESSURE, WHEREBY SAID SOLVENT IN SAID INTERMEDIATE ZONE IS IN THE LIQUID STATE AND THE LIQUID SOLVENT IN SAID INTERMEDIATE ZONE AND THE LIQUID AQUEOUS PHASE IN SAID UPPER ZONE ARE STATIFIED IN SAID VERTICAL REACTION TUBE TO FORM SAID UPPER AND INTERMEDIATE ZONES, COMPLETING THE POLYCONDENSATION OF SAID DICARBOXYLIC ACID AND SAID DIAMINE BY PASSING THE CONDENSATE FORMED IN SAID INTERMEDIATE ZONE FROM SAID INTERMEDIATE ZONE INTO A BOTTOM ZONE IN SAID VERTICAL REACTION TUBE, SAID BOTTOM ZONE BEING MAINTAINED AT A POLYCONDENSING TEMPERATURE WHICH IS BETWEEN 200*C. AND 300* C. AND ABOVE THE BOILING POINT OF SAID SOLVENT AT SAID SUBSTANTIALLY ATMOSPHERIC PRESSURE, THEREBY DISTILLING OFF FROM THE POLYAMIDE IN SAID BOTTOM ZONE AND INTO THE LIQUID SOLVENT BODY IN SAID INTERMEDIATE ZONE SUBSTANTIALLY ALL OF SAID ORGANIC SOLVENT, CONDENSING THE DISTILLED VAPORS OF SAID SOLVENT IN THE COOLER UPPER PARTS OF SAID TUBE, WHEREBY SAID DISTILLATION CAUSES STRATIFICATION IN SAID VERTICAL REACTION TUBE OF THE LIQUID SOLVENT OF SAID INTERMEDIATE ZONE AND THE POLYAMIDE MELT OF SAID BOTTOM ZONE, WHICH MELT REMAINS UPON DISTILLATION OF SAID SOLVENT FROM THE POLYAMIDE OF SAID BOTTOM ZONE, AND WITHDRAWING FROM SAID BOTTOM ZONE THE CONDENSED POLYAMIDE AS A MELT CONTAINING A SMALL PROPORTION OF SAID SOLVENT.