شبیه سازی درخشش واکنشگر از فرآیند ذوب مستمر استریفیکاسیون شده پلی کربنات

A model of the continuous melt transesterification process of bisphenol-A and diphenyl carbonate in a continuous stirred tank reactor to produce polycarbonate is presented. The model is developed by using the molecular species model of polycarbonate melt polycondensation and the modeling method of reactive flash. Liquid phase is treated as perfect mixed flow and the vapor phase is assumed following the ideal gas law. With this model, the continuous melt transesterification process of bisphenol-A and diphenyl carbonate is examined with respect to different process parameters.

Bisphenol A polycarbonate is a very important engineering thermoplastic, which has excellent mechanical properties such as impact resistance, excellent heat resistance, transparency and other properties. It has conventionally been manufactured by the interfacial phosgenation of bisphenol-A (BPA) with phosgene and the method of an ester interchange or transesterification process with BPA and diphenyl carbonate (DPC) in melt. Although the product qualities can be controlled easily, the interfacial phosgenation method using high toxic phosgene and a great deal of organic solvents brings many environmental problems. The melt transesterification method is environment benign and it takes advantages of lower cost over the interfacial phosgenation method. Melt transesterification is a reversible reaction and the reaction byproduct (phenol) must be removed by vacuum to obtain high molecular weight polymer. Typical melt transesterification process includes several stages under different conditions, respectively for transesterification and condensation polymerization. By comparison, the continuous melt transesterification process[ 1-31 to produce polycarbonate is a better choice than the batch melt transesterification. Although the melt transesterification of BPA and DPC has been studied widely[4-7], open literature on the continuous melt transesterification process to produce polycarbonate is scarce and the modeling of continuous melt transesterification process of polycarbonate has not been reported. Present publications are focused on the continuous polycondensation process[ 8,9]. This paper describes the simulation of the continuous melt transesterification of BPA and DPC in a continuous stirred tank reactor (CSTR) by reactive flash modeling.

A molecular species model of continuous melt transesterification of bisphenol A and diphenyl carbonate is developed in terms of reactive flash. The model takes into account effects of all species on the reaction process. Solution of the model gives molecular weight, polydispersity index, contents of BPA,DPC, phenol and different type oligomers in the reaction mixture, composition of vapor phase and lost DPC fraction, almost all aspects relevant to the reaction process. The effects of process parameters on the product and the process are studied with the model. Time, vacuum, reaction temperature and catalyst concentration play a positive role in improving the reaction extent. Two CSTR in series gives a higher reaction extent and a lower polydispersity than a single CSTR at the same mean residence time and other process parameters. Future work will be concentrated on the experiments to validate the model.