Process for Manufacturing Medium and High Molecular Weight Polyesters

Abstract

Medium and high molecular weight polyester polymers are prepared in syrup form from an ester oligomer. The oligomer is converted to the polymer by polycondensation at elevated pressure and elevated temperature in a nonreactive carrier capable of forming an azeotrope with water. The ester oligomerization or polycondensation reactions desirably are monitored using a non-viscometric technique. The process has a rapid cycle time. The syrup contains the polymer and nonreactive carrier, and may more conveniently be used to make initially non-solid products such as polyester coatings than is the case when employing pelletized solid polyester resins.

What is claimed is: 
     
         1 - 20 . (canceled) 
     
     
         21 . A polyester syrup comprising a nonreactive carrier and a linear polyester derived from an ester oligomer, wherein the hydroxyl:acid or hydroxyl;ester ratio is from about 0.98:1 to about 1.1:1, and wherein the linear polyester has a number average molecular weight of 6,000 to 20,000 amu and a hydroxyl number of 5 to 20, the polymer having a backbone free of or substantially free of ethylene oxide or propylene oxide groups and the syrup being free of or substantially free of alcohols, glycols or esters that react with the polymer at polycondensation temperatures. 
     
     
         22 . A polyester syrup according to  claim 21  wherein the polymer has a number average molecular weight of 8,000 to 15,000 amu, the nonreactive carrier comprises an alkane, aromatic hydrocarbon, petroleum solvent, plant-derived solvent, ketone or mixture thereof, and the nonreactive carrier has a boiling point of about 140 to about 300° C. 
     
     
         23 . A packaged polyester product comprising a container suitable for interstate or export shipment within which is stored a polyester syrup comprising a solution of high molecular weight polyester polymer derived from an ester oligomer wherein the hydroxyl:acid or hydroxyl;ester ratio is from about 0.98:1 to about 1.1:1 in a nonreactive carrier capable of forming an azeotrope with water, the solution being free of or substantially free of alcohols, glycols or esters that react with the polymer at polycondensation temperatures and containing at least about 5% or more of nonreactive carrier. 
     
     
         24 . A packaged polyester product according to  claim 23  wherein the container is a shipping drum, tote, trailer tank car or rail tank car. 
     
     
         25 . A packaged polyester product according to  claim 23  wherein the polymer has a number average molecular weight of 7,001 to 30,000 amu, the nonreactive carrier comprises an alkane, aromatic hydrocarbon, petroleum solvent, plant-derived solvent, ketone or mixture thereof, and the nonreactive carrier has a boiling point of about 140 to about 300° C. 
     
     
         26 . A packaged polyester product according to  claim 23  wherein the polymer has a number average molecular weight of 8,000 to 15,000 amu, the nonreactive carrier comprises an alkane, aromatic hydrocarbon, petroleum solvent, plant-derived solvent, ketone or mixture thereof, and the nonreactive carrier has a boiling point of about 140 to about 300° C. 
     
     
         27 . (canceled)