Determination of polybutylene terephthalate polycondensation equilibrium constant using a batch reactor

Abstract

The PBT polycondensation equilibrium constant at 255°C was determined using a batch reactor. Starting from a Polybutylene terephthalate (PBT) prepolymer having a degree of polymerisation of 12.7, equilibrium experiments were performed in the range of 1 to 50 mbar. The equilibrium degree of polymerisation (i) was determined indirectly using dilute solution viscometry of a solution of 1 weight % PBT in m ‐ cresol. The degree of polymerisation of PBT obtained at equilibrium in the range of 1 to 50 mbar at 255°C as a function of the BDO partial pressure (mbar) could be expressed by: i = 111.47 − 86.18 exp(−1.14 $P^{-1.44}_{bdo}$ ). The equilibrium solubility of 1,4 butanediol (BDO) in the PBT melt was derived form the BDO partial pressure using the Flory ‐ Huggins theory. The PBT polycondensation reaction equilibrium constant was related to the degree of polymerisation by the equation: $K_e = {0.187 \over 1 -19243 e^{-0.3932}} $ in the range i = 26 − 100. The PBT polycondensation equilibrium constant at high degrees of polymerisation is in line with literature data and thermodynamics.

The synthesis of poly(butylene terephthalate) from terephthalic acid, part I: The influence of terephthalic acid on the tetrahydrofuran formation

“…Different kinetic studies were already published by Pilati et al14 and Hsu and Choi,16, 24 with the aim of obtaining information on the reaction orders and the mechanism of the Ti(OBu) 4 ‐catalyzed model reactions for the synthesis of PBT. Darda et al25 determined the PBT polycondensation equilibrium constant starting from a PBT prepolymer (degree of polymerization (DP) = 12.7), heated in a batch reactor to 255°C. The same group recently studied the reaction kinetics of the forward polycondensation reaction of PBT by thermogravimetric analysis.…”

PISOX Copolyesters─Bio- and CO2-Based Marine-Degradable High-Performance Polyesters

“…All other esters still seem far away from equilibrium, even after 6 h reaction at 190 °C. The equilibrium state found for DGO is considerably higher compared to the reaction equilibrium values mentioned (0.1 to 1.0) for typical nonphenolic alcohols used in polyester synthesis, such as ethylene glycol or 1,4-butanediol with terephthalic acid to produce PET or PBT . In similar carbonate polymerization chemistry, advantages in reactivity were also observed for ortho-substituted phenyl groups: in the work of Kamps et al, bis(methylsalicyl) carbonate showed reactivity benefits over diphenyl carbonate. , The reactivity benefits of DGO can be used to make the polymerization catalyst-free and/or milder and shorter, resulting in better color and fewer side reactions.…”

A segment probability method for calculating the molecular weight distributions of linear polycondensates in a continuous reactor

“…Table 2 shows the kinetic scheme along with the corresponding kinetic parameters. The initial values of these kinetic parameters are retrieved from references, 30–33,36,38–40 are then tuned to best fit the MWD of PBT1. The relative mean error of the number‐average molecular weight, defined by Equation (), is 4.7%.…”