High pressure liquid-liquid equilibria for the system polybutadiene + dimethyl ether

JUAN M. MILANESIO; GUILLERMO MABE; ANDRES CIOLINO; LIDIA MARÍA QUINZANI; MARCELO S. ZABALOY

Natal

Conferencia; II Conferencia Iberoamericana en Fluidos Supercríticos (PROSCIBA 2010); 2010

Universidade Federal do Rio Grande do Norte (Brasil), Universidade Federal de Santa Catarina (Brasil), Universidade Regional Integrada (Brasil), Universidad Nacional del Sur (Argentina), Universidad Nova Lisboa (Portugal), CSIC (España), UAM (España)

Polyethylenes of narrow molecular weight distribution can be obtained through hydrogenation, using, as raw material, Polybutadienes (PBs) with a polydispersity index close to unity. Such PBs come from the anionic polymerization of butadiene. The PB hydrogenation could be conducted in a supercritical solvent, at conditions such that the polymer, the solvent and the hydrogen are kept solubilized within a single fluid phase. This would imply higher mass transfer rates with respect to the conventional hydrogenation process, which takes place in the presence of two fluid phases.For obtaining a homogeneous PB + hydrogen + solvent mixture, we need also the binary subsystem polymer + solvent to be homogeneous. This happens, for a given temperature and for a given system composition, at a pressure greater than the cloud-point pressure. In this work we report new experimental cloud-point pressures for the system PB + Dimethyl ether (DME) in the temperature range from 50 ºC to 150 ºC, at PB concentration values less than 7 PB wt. %. DME has property values that make it become, in principle, an attractive solvent for performing the high pressure hydrogenation of PBs under fluid miscibility conditions. We carried out theexperiments using a high-pressure variable-volume windowed phaseequilibrium cell specially built for this project.