Process for preparing high viscosity linear condensation polyesters from partially polymerized glycol terephthalates

Claim 1

IN THE PREPARATION OF LINEAR CONDENSATION POLYESTERS WHEREIN GLYCOL TEREPHTHALATE IS PARTIALLY POLYMERIZED TO FORM AN AMORPHOUS MELT OF POLYESTER, THE MELT IS SOLIDIFIED AND THE POLYMERIZATION IS CONTINUED IN THE SOLID PHASE, THE PROCESS FOR PREPARING POLYESTER OF UNUSUALLY HIGH INTRINSIC VISCOSITY WHICH COMPRISES THE COMBINATION OF STEPS: (A) QUENCHING THE MELT RAPIDLY TO FORM A SUBSTANTIALLY AMORPHOUS SOLID POLYESTER, THE MOLTEN POLYESTER BEING PARTIALLY POLYMERIZED TO AN INTRINSIC VISCOSITY OF 0.20 TO 0.65 WHEN QUENCHED, (B) HEATING THE SOLID POLYESTER AT 150* TO 200*C. TO FORM A PARTIALLY CRYSTALLIZED POLYESTER, (C) GRINDING THE PARTIALLY CRYSTALLIZED POLYESTER INTO PARTICLES PASSING A 20-MESH SCREEN, WITH LESS THAN 10% FINE ENOUGH TO PASS THROUGH A 200-MESH SCREEN, AND (D) POLYMERIZING THE GROUND POLYESTER AT 200* TO 235* C. IN A FLUIDIZED-BED SOLID-PHASE POLYMERIZATION TO AN INTRINSIC VISCOSITY OF AT LEAST 0.8.