PEP Review 97-1
PET Bottle Resin by Pyromellitic Dianhydride Process
Published: September 1998
This PEP review examines a technology developed by Sinco SpA of Italy, which uses pyromellitic dianhydride (PMDA) as an agent to reduce the time necessary for solid-phase polymerization (SSP) of PET. SSP is a necessary step in upgrading PET resin from melt-phase polymerization (intrinsic viscosity < 0.6 dl/g) to PET resin suitable for bottling applications (> 0.8 dl/g for one-piece bottles).
Other innovations in the process are the use of a whirling-bed crystallizer stage and of catalytic oxidation to remove glycols from the inert gas stream used in SSP. Compared to processes previously reviewed, the Sinco process enables savings on capital costs, but these are offset in the production cost by the added price of the PMDA additive. Detailed information on how the addition of PMDA affects the properties of the resulting PET resin was not available.
This review will be of interest to PET producers and to licensors of PET technology.