Micronisation of poly(ethylene oxide) solutions and separation of water by PGSS-Drying

In this article, we describe the drying and the concurrent micronisation of polymer solutions using the PGSS-Drying-process. A solution of poly(ethylene oxide) (PEO) 6000 in water with a mass fraction of 50 wt.% was used as a model substance as much preliminary data is available for pure PEO 6000. It will be shown, that it is possible to separate solvents and to micronise the polymer in only one process step. Powders with different residual solvent contents are obtained. Additionally, the high pressure phase behaviour of poly(ethylene oxide) 6000, water and carbon dioxide is presented at pressures of 100 and 300 bar and temperatures of 353 and 393K. The measurements were performed in an autoclave and carried out according to the static analytical method. With the knowledge of the high pressure phase behaviour, the results of the residual solvent content found in the polymers can be interpreted. In the article we will show, that a condensation of solvent in the spray tower can be avoided, and that the high pressure phase behaviour upstream the decompression step shows significant influence on the remaining amount of solvent in the powder. Concluding, a diagram will be presented, where different possible fields of operation are marked. With the help of the diagram, suitable parameters (pre-expansion temperature, pre-expansion pressure and specific gas amount of carbon dioxide) can be selected in order to obtain powders with low residual solvent contents. (C) 2012 Elsevier B.V. All rights reserved.