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 AND AT A TEMPERATURE OF BETWEEN ABOUT 210* C. AND 250*C., THE GLYCOL BEING ADDED IN AN AMOUNT WHICH IS BETWEEN ABOUT FOUR AND TEN TIMES AS GREAT AS THE THEORETICAL AMOUNT NECESSARY TO FORM BI-GLYCOL TEREPHTHALATE, THE ADDITION WITH THE TEREPHTHALIC ACID DURING TWO STEPS WHEREIN ONE PORTION OF THE GLYCOL TAKING PLACE IN FOR AN INITIAL REACTION WITH THE TEREPHTHALIC ACID DURING WHICH WATER IS FORMED, COOLING THE REACTION PRODUCTS OF THE INITIAL REACTION TO A TEMPERATURE UNDER THE BOILING POINT OF THE GLYCOL, REMOVING SAID WATER IN THE FORM OF STEAM, ADDING THE SECOND PORTION OF GLYCOL, RE-HEATING THE MIXTURE, COOLING TO A PREDETERMINED TEMPERATURE, DISTILLING OFF EXCESS GLYCOL, POURING THE LIQUID RESIDUE INTO A WATER BATH AT ABOUT 80*C., COOLING TO ABOUT 50*C., FILTERING OUT ONE OF THE RESULTING CONDENSATION PRODUCTS, COOLING THE MOTHER LIQUID TO ABOUT 10*C., AT WHICH TIME THE MONOMERIC TEREPHTHALIC ACID GLYCOL ESTER CRYSTALLIZES, AND FINALLY SEPARATING THE CRYSTALS BY FILTRATION.