Polyesterification in two evacuated zones separated by a liquid seal

Claim 1

A CONTINUOUS PROCESS FOR THE FURTHER POLYMERIZATION OF AN INTERMEDIATE MOLECUALR WEIGHT POLYESTER OF (1) A DICARBOXYLIC CONSTITUENT AND (2) AN ALKANEDIOL, WHEREIN SAID MOLECULAR WEIGHT IS BEING INCREASED BY ELIMINATION OF SMALL AMOUNTS OF SAID ALKANEDIOL BY VAPORIZATION AND EVACUATION AT AN ELEVATED TEMPERATURE AND AT A LOW PRESSURE WHILE SAID INTERMEDIATE MOLECULAR WEIGHT POLYESTER AS A LIQUID FLOWS DOWNWARDLY THROUGH AN UPPER POLYMERIZATION ZONE AT ONE PRESSURE INTO AND THROUGH A LOWER POLYMERIZATION ZONE AT A LOWER PRESSURE, SAID ZONES BEING IN SUBSTANTIALLY VERTICAL RELATIONSHIP, SAID INTERMEDIATE MOLECULAR WEIGHT POLYESTER HAVING AN INHERENT VISCOSITY MEASURED IN A SOLUTION OF 40% TETRACHLOROETHANE + 60% PHENOL OF FROM ABOUT 0.05 TO ABOUT 0.4, SAID FURTHER POLYMERIZATION PROCESS COMPRISING: (A) FEEDING SAID INTERMEDIATE MOLECUALR WEIGHT POLYESTER AS A LIQUID INTO A SUBSTANTIALLY HORIZONTAL INTIAL RECEIVING SUB-ZONE IN SAID UPPER POLYMERIZATION ZONE, SAID SUB-ZONE BEING EQUIPPED WITH OVERFLOW MEANS LEADING TO A LOWER SUB-ZONE IN SAID UPPER POLYMERIZATION ZONE WHICH IS SIMILARLY EQUIPPED, (B) OVERFLOWING SAID POLYESTER LIQUID FROM ONE SUCH SUB-ZONE TO THE NEXT, ALL OF SAID SXUB-ZONES IN SAID UPPER POLYMERIZATION ZONE BEING AT A PRESSURE OF LESS THAN 5 CM. OF HG AND BEING GASEOUSLY INTERCONNECTED, (C) FLOWING SAID POLYESTER LIQUID DOWNWARDLY FROM THE LOWERMOST OF SAID SUB-ZONES IN SAID UPPER POLYMERIZATION ZONE THROUGH A LIQUID CONDUCTING MEANS TO SAID LOWER POLYMERIZATION ZONE, THE LIQUID LEVEL OF SAID POLYESTER LIQUID IN SAID LIQUID CONDUCTING MEANS BEING MAINTAINED AT A LEVEL AT LEAST AS HIGH AS IS THE LEVEL OF SAID POLYESTER LIQUID IN AN UPPERMOST RECEIVING SUB-ZONE IN SAID LOWER POLYMERIZATION ZONE INTO WHICH SAID LIQUID CONDUCTING MENAS PROTURDES, (D) OVERFLOWING SAID POLYESTER LIQUID FROM SAID UPPERMOST SUB-ZONE IN SAID LOWER POLYMERIZATION ZONE OVER A SERIES OF EVAPORATIVE SURFACES IN VERTIALLY DESCENDING ORDER IN SAID LOWER POLYMERIZATION ZONE WHREEBY SAID LIQUID POLYESTER FLOWS AS A THIN FILM ACROSS THE MAJOR PORTION OF EACH SURFACE AND DROPS THEREFROM UPON THE NEXT FOLLOWING SURFACE BELOW, ALL OF SAID SURFACES IN SAID LOWER POLYMERIZATION ZONE BEING GASEOUSLY INTERCONNECTED AND MAINTAINED AT A LOWER PRESSURE THAN THE PRESSURE MAINTAINED IN THE UPPER POLYMERIZATION ZONE, (E) FLOWING SAID POLYESTER FROM THE LOWERMOST OF SAID EVAPORATIVE SURFACES TO MEANS FOR REMOVAL FROM SAID LOWER POLYMERIZATION ZONE, WHREBY THE RESULTING FURTHER POLYMERIZED POLYESTER HAS AN INHERENT VISCOSITY AT LEAST 0.2 GREATER THAN THAT OF SAID INTERMEDIATE MOLECULAR WEIGHT POLYESTER BEING FED INTO THE UPPER POLYMERIZATION ZONE, AND (F) MAINTAINING A PRESSURE DIFFERENTIAL OF AT LEAST 0.1 M. OF HG BETWEEN SAID UPPER AND LOWER POLYMERIZATION ZONES.