AbstractThe lower critical solution temperature (LCST) locus for ethylene‐propylene copolymers has been determined as a function of pressure in a variety of single and multicomponent solvents. The lower critical end‐point temperature (LCEP), which is the intersection of the LCST locus with the vapor‐pressure curve, was found to be predictable from the solvent density as previously established for single‐component solvents by Charlet and Delmas.1Dissolving a low‐molecular hydrocarbon gas such as propylene in an alkane has a dramatic effect on lowering the LCEP, and can reduce phase‐separation temperatures to levels at which this technique becomes attractive as a practical method for polymer recovery from diluents such as those used in solution polymerizations. Temperatures considerably above the LCEP are needed to minimize the residual polymer concentration in the solvent in the two‐liquid‐phase region. The solvent critical temperature must be approached for essentially complete elimination of the polymer from the solvent phase. The LCST locus was found to be a linear function of pressure for all of the systems investigated, and the slope of the line,d(LCST)/dP, could be well correlated as a function of solvent density and critical temperature. From the relationship between the LCEP and solvent density and the correlation for d(LCST)/dP, the location of the LCST locus can be readily predicted from a knowledge of sol
展开▼
