Manufacture of high linear polyesters from refractory aromatic dicarboxylic acids and cyclic glycol carbonates

Claim 1

A PROCESS WHICH COMPRISES CONTINUOUSLY ADDING A FREE REFRACTORY AROMATIC DICARBOXYLIC ACID AND A CYCLIC GLYCOL CARBONATE TO AT LEAST HALF THEIR COMBINED WEIGHT OF A MELT OF A PERFORMED LOW LINEAR POLYESTER OF SAID ACID AND SAID CARBONATE OF INTRINSIC VISCOSITY BETWEEN 0.1 AND 0.4, SAID AROMATILC DICARBOXYLIC ACID BEING SELECTED FROM THE GROUP CONSISTING OF TEREPHTHALIC ACID, PARA-PHENYLENE DIACETIC ACID, DIPHENYL-4.4''-DICARBOXYLIC ACID, A,W-DIPHENYLALKANE-4.4''-DICARBOXYLIC ACIDS, A,W-DIPHENOXYALKANE 4,4''DICARBOXYLIC ACIDS, 1.5-NAPHTHALENE-DICARBOXYLIC ACID, 2.6-NAPHTHALENE-DICARBOXYLIC ACID AND 2.7 NAPHTHALENEDICARBOXYLIC ACID, HEATING AND REACTING SAID ACID AND SAID CARBONATE IN THE RESULTING MIXTURE TO FORM ADDITIONAL LOW LINEAR POLYESTER OF INTRINSIC VISCOSITY BETWEEN 0.1 AND 0.4, CONTINUOUSLY WITHDRAWING FROM SAID MIXTURE A QUANTITY OF MOLTEN LILNEAR POLYESTER OF INTRINSIC VISCOSITY BETWEEN 0.1 AND 0.4 EQUIVALENT TO THE AMOUNT OF ACID AND CARBONATE ADDED THERETO, MIXING WITH SAID WITHDRAWN LINEAR POLYESTER A CATALYTIC AMOUNT OF A POLYESTERIFICATION CATALYST SELECTED FROM THE GROUP CONSISTILNG OF ORGANIC CARBOXYLIC ACID SALTS OF MANGANESE AND ANTIMONY, ALKALI METAL ANTIMONATES, ALKALI AND ALKLINE EARTH METAL ALUMINATES AND ALKALI METAL ZINCATES, AND FURTHER HEATING THE MIXTURE OF CATALYST AND WITHDRAWN LINEAR POLYESTER TO INCREASE THE INTRINSIC VISCOSITY AND PRODUCE A FIBRE-FORMING LINEAR POLYESTER.