Modeling of a finishing polymerization reactor for the synthesis of poly(ethylene terephthalate)

Semibatch and continuous melt condensation in rotating disk reactors have been studied for the synthesis of poly(ethylene terephthalate). Batch rotating disk reactor experiments were carried out to measure the thickness of thin polymer layers and the melt holdup on a rotating disk for different polymer molecular weights. For high molecular weight prepolymers, the polymer film layer profiles on a disk vary significantly in both radial and angular directions. The experimentally measured film thickness data were used to develop an empirical correlation for the calculation of film thickness and total polymer melt holdup on a rotating disk. An experimental study of flow pattern and axial mixing phenomena in a continuous rotating disk reactor has also been carried out. The residence time distribution characteristics were investigated in a model reactor with aqueous carboxymethyl cellulose solution as a test fluid. The observed RTD curves were fitted with a mixing cell model which consists of a well mixed bulk phase and a film phase represented by plug flow. In a semibatch rotating disk reactor, a two parameter model was proposed to describe the behaviours of the film phase on the disks and the bulk phase in the trough. The effects of temperature, pressure, disk number, and disk rotation speed on the reactor performance were investigated. It has been observed that the polymer holdup on the disk and the mass transfer parameter vary considerably with the progress of reaction. In particular, it was found that about 90% of ethylene glycol was removed from the film phase. The two parameter model was extended to the development of a continuous rotating disk polycondensation reactor. The polymer melt holdup on the disk as well as molecular weight increase as the polymer melt travels through the reactor. The effects of temperature, residence time, and interfacial surface area on the polycondensation have been studied through model simulation. A two phase model was also developed to examine the dynamic behaviour of continuous polymerization reactor. It was observed that feed prepolymer properties have significant effect on the final polymer properties.