Process for preparing high molecular linear polyesters from polymethylene glycols and esters of benzene dicarboxylic acids

Claim 1

IN A PROCESS FOR PREPARING A HIGH MOLECULAR WEIGHT LINEAR POLYESTER FROM POLYMETHYLENE GLYCOL CONTAINING FROM 2-6 CARBON ATOMS AND A DIESTER TEREPHTHALIC ACID WITH A MONOHYDRIC ALOC CONTAINING FROM 1-6 CARBON ATOMS, THE STEP WHICH COMPRISES CONDENSING THE COMPONENTS IN THE PRESENCE OF AN INORGANIC CATALYST SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL SILICATES, STANNATES, SELENATES AND TUNGSTATES, ALKALINE EARTH METAL STANNATES, AND MIXTURES THEREOF, SAID CATALYST BEING USED IN A PROPORTION OF FROM 0.005-0.05 MOL PERCENT CALCULATED UPON SAID TEREPHTHALIC ACID DIESTER, HEATING THE REACTION MIXTURE TO A TEMPERATURE ABOVE THE BOILING POINT OF THE MONOHYDRIC ALCOHOL, REMOVING SAID ALCOHOL, FURTHER HEATING SAID MIXTURE UNDER REDUCED PRESSURE AT A TEMPERATURE ABOVE THE MELTING POINT OF THE RESULTING POLYESTER, AND MAINTAINING THE HEATING UNTIL A STAGE IS REACHED AT WHICH FIBERS REMOVED FROM THE RESULTING MASS CAN SUBSEQUENTLY BE STRETCHED.