Measurement and prediction of phase equilibria of ethylene + vinyl acetate + methanol + poly(ethylene-co-vinyl acetate) systems

This work investigated the solubilities of ethylene in the 10 wt% poly (ethylene-co-vinyl acetate) (EVA) solutions including vinyl acetate (VA) and methanol which are related to production of EVA. The bubble point pressure (BP) for vapor-liquid equilibrium (VLE) and the cloud point pressure (CP) for liquid-liquid equilibrium (LLE) of ethylene + VA + EVA ternary and ethylene + VA + EVA + methanol quaternary systems were measured at temperatures of 313 K, 343 K, 373 K and at pressures up to 20 MPa with a synthetic method. The experimental results revealed that the BP and CP increased with increasing temperature and ethylene weight fraction, especially the influence of ethylene weight fraction on CP was found to be drastic. The Sanchez-Lacombe equation of state (SL EOS) could correlate the BP data of ethylene + VA + EVA ternary and ethylene + VA + EVA + methanol quaternary systems within 3.6% an average relative deviation. The phase equilibria of the EVA + VA + ethylene ternary system could be predicted over wide polymer concentration ranges by the SL EOS with the determined parameters in the correlations. With increasing pressure, phase behavior changed from VLE at low pressure to vapor-liquid-liquid equilibrium (VLLE) and LLE at high pressures.