The Solid State Postcondensation of PET, 2

Abstract

Summary: A process for the solid state polycondensation of PET is proposed. It is shown that by correctly choosing the prepolymerisation conditions it is possible to crystallise the product and to directly polymerise it in a dispersed phase. This process is significantly faster than the “standard” PET processes, and allows one to obtain high molecular weights directly from a prepolymer without the need to use an intermediate solution polymerisation step.Reactor set‐up for precursor preparation and dispersed phase prepolymerisation.magnified imageReactor set‐up for precursor preparation and dispersed phase prepolymerisation.

A Review of Modeling of Diffusion Controlled Polymerization Reactions

“…The solid state polycondensation of PET was recently presented in an excellent and detailed review by the group of McKenna. [181] The main reactions involved in the SSP of PET include the ones shown in Scheme 4. During SSP due to the low reaction temperature, chain mobility is relatively low compared to corresponding melt polymerization process.…”

“…Thus, they assumed that the mobility of the end-groups and consequently the value of the rate coefficient depended on the free volume of the polymer that decreases with reaction time. According to Gantillon et al, [181] if it is considered that PET is a semi-crystalline material, then it is not realistic to consider that the entire macromolecule could diffuse through the matrix on a time scale proportionate with that of the polycondensation. Also not only the local viscosity on the amorphous phase is very high, but a large fraction of macromolecules remain trapped in crystalline occlusions in the polymer matrix.…”

“…The mobility of the macromolecular chains during SSP depend not only on temperature and molecular weight of the polymer but also on the morphology of the crystalline phase of the material since reactive chain ends are concentrated in the amorphous zones of the polymer matrix. [181] In polymerizing systems with a high degree of crystallinity, reactive end-groups could be trapped inside the crystalline occlusions and thus either do not react at all or react very slowly. In contrast, if the amorphous parts of the matrix are distributed in such a way that the reactive end groups are well dispersed, and if the distance they need to diffuse in order to react with neighboring groups is short, then the rate of reaction will be relatively high.…”

Solution viscosity – molar mass relationships for poly(butylene succinate) and discussion on molar mass analysis

“…In the polyester industry, it is common practice to calculate M n -with the help of simple linear empirical relationships between molar mass and reduced viscosity. As an example, very helpful equations have been proposed by Gantillon et al [36] for poly(ethylene terephthalate).…”

The Solid State Postcondensation of PET, 3

“…In Part 2 of this series, [1] it was demonstrated that it is possible to produce high molecular weight PET (a weightaverage molecular weight (M w ) over 50 000) in a dispersed phase, solid state postcondensation (SSP) process. The process proposed consisted of four steps: formulation of the precursor, prepolymerisation, rapid cooling and crystallisation of the prepolymer and SSP.…”