Process for the preparation of linear thermoplastic mixed polyesters having softening temperatures above 100 u deg. c

Claim 1

IN A PROCESS FOR THE PREPARATION OF LINEAR THERMOPLASTIC MIXED POLYSTERS HAVING SOFTENING TEMPERATURES OF ABOVE 100*C. WHICH COMPRISES HEATING A MIXTURE COMPRISING 0 TO 100 PERCENT OF A DIARYL TEREPHTHALATE, 100 TO 0 MOLE PERCENT OF A DIARYL ISOPHTHALATE, 0 TO 10 MOLE PERCENT OF A DIARYL ESTER SELECTED FROM THE GROUP CONSISTING OF DIARYL CARBONATES AND DIARYL OXALATS, THE TOTAL AMOUNT OF SAID DIARYL TEREPHTHALATE AND DIARYL ISOPHTHALATE IN SAID MIXTURE BEING FROM 90 TO 100 MOLE PERCENT AND THE TOTAL MOLE ERCENT OF SAID DIARYL TEREPHTHALATE, SAID DIARYL ISOPHTHALTATE AND SAID DIARYL ESTER BEING EQUAL TO 100 MOLE PERCENT, AND ABOUT 100 MOLE PERCENT OF A DIHYDRIC PHENOL TO ABOUT 320*C. TO EFFECT A TRANSESTERIFICATION AND POLYCONDENSATION TO PRODUCE A MIXED POLYSTER, THE IMPROVEMENT WHICH COMPRISES ADDING TO SAID MIXTURE AT TEMPERATURES OF UP TO ABOUT 280*C. AS SOON AS THE MELTING VISCOSITY OF SAID MISTURE REACHES A VALUE OF FROM ABOUT 2000 TO 4000 POISE AT SAID TEMPERATURE ABOUT 15 TO 120, BY WEIGHT, BASED ON THE THEORETICAL WEIGHT OF POLYSTER PRODUCED BY SAID TRANSESTERIFICATION AND POLYCONDENSATION, OF A LINEAR THERMOPLASTIC POLYESTER CONSISTING OF UNITS OF RESIDUES OF A DIPRIMARY DIALCOHOL AND RESIDUES OF AN ACID SELECTED FROM THE GROUP CONSISTING OF TEREPHTHALIC ACID, ISOPHTHALIC ACID AND MIXTURES THEREOF, AND SUBSEQUENTLY CONTINUING THE POLYCONDENSATION REACTION UNTIL A LINEAR THERMOPLASTIC MIXED POLYESTER PRODUCT HAVING DESIRED MECHANICAL PROPERTIES IF OBTAINED.