Process for the production of the glycol ester of terephthalic acid suitable for polymerization

Claim 1

A PROCESS FOR THE PRODUCTION OF TEREPHTHALIC ACID GLYCOL ESTER WHICH COMPRISES REACTING TEREPHTHALIC ACID WITH GLYCOL AT A TEMPERATURE OF ABOUT 220* C. TO ABOUT 240* C., THE ADDITION OF THE GLYCOL TAKING PLACE IN TWO STEPS, WHEREIN ONE PORTION OF THE GLYCOL IS ADDED FOR AN INITIAL REACTION WITH THE TEREPHTHALIC ACID DURING WHICH REACTION WATER IS FORMED, COOLING THE REACTION PRODUCTS OF THE INITIAL REACTION TO A TEMPERATURE UNDER THE BOIL ING POINT OF THE GLYCOL, REMOVING SAID WATER IN THE FORM OF STEAM, ADDING THE SECOND PORTION OF THE GLYCOL, REHEATING THE MIXTURE, COOLING TO A TEMPERAWTURE OF ABOUT 125* C., DISTILLING OFF EXCESS GLYCOL, POURING THE LIQUID RESIDUE INTO A WATER-SOLUBLE SALT SOLUTION MAINTAINED AT A TEMPERATURE BETWEEN ABOUT 80* C. AND 100* C., WHEREBY INSOLUBLE CONDENSATION PRODUCTS PRECIPITATE OUT COOLING TO ABOUT 50* C., SELECTIVELY REMOVING THE INSOLUBLE CONDENSATION PRODUCTS, HEATING THE RESIDUE TOGETHER WITH ABOUT 5 TO 7 TIMES THE AMOUNT OF GLYCOL THEORETICALLY NECESSARY TO FORM BIS-GLYCOL-TEREPHTHALATE AND COOLING SAID RESIDUE TO ABOUT 10* C., AT WHICH TIME THE MONOMERIC TEREPHATHALIC ACID GLYCOL ESTER CRYSTALLIZES OUT.