New process for directly producing polyesters from all the polyalkylene terephthalate family for bottle-grade resins, based on terephthalic acid (PTA) or dimethyl terephthalate (DMT) and diols using the UIF proprietary two-reactor (2R) process consisting of the tower reactor ESPREE and DISCAGE finisher without a solid-stating postcondensation.
Based on the innovative and patented design modifications to the ESPREE and DISCAGE finisher, which is provided in the medium (MV) or high-viscosity (HV) version. Improved polymer line design, dieface granulation, AA-conditioning, and gentle processing conditions allow to obtain, directly from the melt, highest viscosities of up to 1,500 Pas having a low crystallinity of less than 35% and an AA content below 1 ppm without using a scavenger. The high i. V. polymer melt for bottle-grade PET resins obtained from the DISCAGE finisher is surface cooled and cut by an underwater granulation system in hot water. After separation of pellets and water, the resin is tempered within a few minutes at drying temperatures to avoid stickiness. Later on, the pellets are stored for some hours in a hot air flushed silo to reduce the AA-content to less than 1 ppm.
Economics: The solid state process (SSP) for bottle-grade resins is deleted when applying this new process. The conversion costs are reduced by more than 28% due to lower investment, energy, labor costs and raw material savings. Additionally, the PET resin quality is improved due to low thermal-stress treatment throughout the entire process rendering the lowest polymer degradation, polydispersity, improved color and no core/shell viscosity structure. AA regain during preforming is minimized, as low crystallinity requires significantly less remelting energy.
Licensor: Uhde Inventa-Fischer