Process to produce polyesters from the polyalkylene terephthalate family from terephthalic acid (PTA) or dimethyl terephthalate (DMT) and diols using the UIF proprietary two-reactor (2R) process consisting of the tower reactor ESPREE and the DISCAGE finisher, for textile applications, engineering applications or precursor.
A slurry composed of a dicarboxylic acid and a diol is prepared at a low mole ratio. The slurry is fed to the tower reactor’s bottom where the main esterification occurs under pressure or under vacuum at temperatures ranging between 170°C to 270°C. This reaction may be catalyzed or autocatalyzed.
Monomer is transferred via a pressurized pipe to the reactor top where reaction side products are flashed out. Higher conversion rates (97%–99%) are achieved by a cascade of four to six reaction cups at decreasing pressures and increasing temperatures.
Stirring and intermix are done by reaction vapors while passing through the cups. A precondensate with i.V.s of 0.28 to 0.35 is obtained after surface-active film evaporation—done as a twin assembly, under vacuum and higher temperature. The prepolymer may be finished in the melt phase with UIF’s DISCAGE reactor.
A process column separates side reaction low boilers from the diol, which is then recycled back to the reaction. Spray condensers and vacuum units recover unreacted feedstock and recycle the diol, thus improving the economics of this process.
Economics: This new process reduces conversion cost by more than 25% as compared to conventional/historical processes by its compact design, low energy input, short-term reaction and agitator-less design. A product yield of more than 99.5% is attainable.
Energy cost can be reduced by more than 20%. Additionally, the end product’s quality is improved due to eliminating intermediate product lines; it offers narrow residence time distribution as well as intensive surface renewal and fast reaction.
Licensor: Uhde Inventa-Fischer