Manufacture of diesters of dicarboxylic acids with substantial waste water purification

Claim 1

IN A CONTINUOUS PROCESS FOR THE MANUFACTURE OF THE DIESTER OF A DICARBOXYLIC ACID BY ESTERIFICATION OF A DICARBOXYLIC ACID COMPONENT SELECTED FROM THE GROUP CONSISTING OF PHTHALIC ANHYDRICE, MALEIC ANHYDRIDE AND ACIDS OF THE FORMULA HOOC-(CH2)N-COOH IN WHICH N IS A WHOLE NUMBE OF 1 TO 8 WITH AN ALCOHOL SELECTED FROM THE GROUP CONSISTING OF NUTANOL, N-OCTANOL-1, N-OCTANOL-2, 2-ETHYLHEXANOL-1, N-NONYL ALCOHOL, DECANOL AND ISODECANOL, ESTERIFICATION BEING CARRIED OUT WITH RECYCLING OF THE ALCOHOL USED IN EXCESS AND IN THE ABSENCE OF AN ESTERIFICATION CATALYST AT A TEMPERATURE OF FROM 150* TO 150* C AND THE REACTION MIXTURE BEING SEPARATED FROM THE WATER OF REACTION, STEAMED OUT AND THEN MIXED WITH AN AQUEOUS ALKALI FOR SEPARATION OF THE MONOESTER, THE RESULTING AQUEOUS MONOESTER SALT SOLUTION BEING ACIDIFIED FOR THE RECOVERY OF THE MONOESTER, THE IMPROVEMENT WHICH COMPRISES: TREATING THE AQUEOUS MONOESTER SALT SOLUTION AFTER ACIDIFICATION WITH FROM0.5 TO 1 TIMES ITS WEIGHT OF THE SAME ALCOHOL AS USED IN THE ESTER SUNTHESIS; SEPARATING THE RESULTING MIXTURE INTO ALCOHOLIC ANC AQUEOUS PHASES AND THEN EXTRACTING THE SEPARATED AQUEOUS PHASE WITH FROM 1 TO 2 TIMES ITS WEIGHT OF THE SAME ALCOHOL; RECYCLING THE ALCOHOLIC PHASE FROM SAID SEPARATION AND SAID EXTRACTION TO THE ESTERIFICATION REACTION; COMBINING SAID WATER OF REACTON SEPARATED FROM THE ESTERIFICATION REACTION MIXTURE AS A WASTE WATER WITH SAID AQUEOUS PHASE RESULTING FROM THE EXTRACTION STEP; AND REMOVING THE ALCOHOL TRACES WHICH REMAIN IN THE RESULTING COMBINED WASTE WATER AND AQUEOUS PHASE BY BLOWING STEAM THERETHROUGH.