Preparation of improved linear copolyesters employing two stages to polymerize solidparticles

Claim 1

A PROCESS FOR PREPARING AN IMPROVED LINEAR COPOLYESTER OF A DIBASIC ACID COMPONENT AND A GLYCOL COMPONENT, IN WHICH COPOLYESTER AT LEAST THREE COMPONENTS ARE PRESENT, AND WHEREIN FROM 60 TO 100 MOLE PERCENT OF SAID ACID COMPONENT IS AN ORGANIC ACID HAVING TWO CARBOXY RADICALS ATTACHED TO A HEXACARBOCYCLIC NUCLEUS, AND THE REMAINDER OF SAID ACID COMPONENT IS A DIFFERENT DIBASIC ORGANIC ACID HAVING FROM 1 TO 16 CARBON ATOMS, AND WHEREIN FROM 75 TO 100 MOLE PERCENT OF SAID GLYCOL COMPONENT IS A MEMBER SELECTED FROM THE GROUP CONSISTING OF THE CIS AND TRANS ISOMERS OF 1,4-CYCLOHEXANEDIMETHANOL, AND THE REMAINDER OF SAID GLYCOL COMPONENT IS A DIFFERENT GLYCOL HAVING FROM 2 TO 12 CARBON ATOMS, SAID PROCESS COMPRISING TWO STAGES OF OPERATION CONDUCTED UNDER AN INERT ATMOSPHERE AT A PRESSURE NO GREATER THAN ABOUT ATMOSPHERIC PRESSURE AS FOLLOWS: STAGE I-HEATING SOLID PARTICLES OF A PREPOLYMER OF SAID COPOLYESTER HAVING AN INTRINSIC VISCOSITY OF FROM ABOUT 0.1 TO ABOUT 0.45 IN AN ENCLOSED POLYMERIZING ZONE AT A TEMPERATURE OF ABOUT 170* TO 300* WHICH TEMPERATURE IS ALSO ABOUT 35* TO ABOUT 100* BELOW THE MELTING POINT OF SAID IMPROVED COPOLYESTER, SAID TEMPERATURE BEING MAINTAINED FOR AT LEAST 1.5 HOURS UNTIL SAID PREPOLYMER HAS ATTAINED AN INCREASED INHERENT VISCOSITY WHICH HAS INCREASED BY NO MORE THAN 0.1 UNIT HIGHER THAN AT THE BEGINNING OF THIS STAGE I, SAID PARTICLES SUBSTANTIALLY COMPLETELY PASSING A 20 MESH SCREEN WITH LESS THAN 25% PASSING A 200 MESH SCREEN, STAGE II-HEATING SAID PARTICLES OBTAINED BY STAGE I IN AN ENCLOSED POLYMERIZING ZONE AT A TEMPERATURE ABOVE THAT IN STAGE I BUT AT LEAST 20* BELOW THE MELTING POINT OF SAID IMPROVED COPOLYESTER UNTIL AN INHERENT VISCOSITY IS ATTAINED OF AT LEAST 0.6, WHEREBY SAID IMPROVED POLYESTER HAS A MELTING POINT DIFFERENTIAL OF FROM 10* TO 50* ABOVE THE MELTING POINT OF A CORRESPONDING POLYESTER PRODUCED WITHOUT THE EMPLOYMENT OF SAID PRELIMINARY STAGE I PRIOR TO SAID FINAL STAGE II, SAID TEMPERATURES BEING IN DEGREES CENTIGRADE AND SAID INHERENT VISCOSITIES BEING MEASURED IN A MIXTURE OF 60% PHENOL AND 40% TETRACHLOROETHANE.