Recovery of adipic acid and hexamethylene diamine from nylon

Claim 1

A PROCESS FOR RECOVERING ADIPIC ACID AND HEXAMETHYLENE DIAMINE FROM POLYHEXAMETHYLENE ADIPAMIDE, SAID PROCESS COMPRISING THE STEPS OF CONTINUOUSLY: HYDROLYZING SAID ADIPAMIDE IN AQUEOUS SULFURIC ACID OF FROM ABOUT 30% TO ABOUT 70% CONCENTRATION, AT A TEMPERATURE OF FROM 75-140*C.; DISCHARGING THE HYDROLYSATE TO A CRYSTALLIZATION ZONE PROVIDED WITH A RECIRCULATION LINE THROUGH WHICH SLURRY IS PUMPED FROM ADJACENT THE BOTTOM TO A POINT BENEATH THE SURFACE LEVEL OF SAID ZONE, SAID HYDROLYZATE BEING DISCHARGED INTO SAID LINE, THE CONTENTS OF SAID ZONE BEING MAINTAINED AT A TEMPERATURE OF ABOUT 25*C.; REMOVING SLURRY FROM SAID ZONE AND FILTERING ADIPIC ACID CRYSTALS THEREFORM, LEAVING A MOTHER LIQUOR; DILUTING THE HYDROLYSATE BEFORE ITS DISCHARGE INTO SAID RECIRCULATION LINE WITH A HEATED PORTION OF THE MOTHER LIQUOR, THEREBY ADJUSTING THE ADIPIC ACID CONCENTRATION TO ABOUT 10% TO ABOUT 20% BY WEIGHT OF THE HYDROLSATE, SAIDD DILUTED HYDROLYSATE BEING MAINTAINED AT AT TEMPERATURE LEVEL OF AT LEAST 90*C.; NEUTRALIZING THE REMAINING MOTHER LIQUOR WITH LESS THAN AN EXCESS OF CALCIUM HYDROXIDE, THUS LIBERATING FROM 98-100% OF THE HEXAMETHYLENE DIAMINE THEREIN; FILTERING CALCIUM SULFATE FROM THE NEUTRALIZED LIQUOR; AND SEPARATING THE FREE DIAMINE THEREFROM.