Investigation of phase equilibria in mixtures composed of ethene, 1‐butene, 4‐methyl‐1‐pentene and a polyethylene wax

Abstract

Abstract Some measurements of the vapour‐liquid and/or the demixing equilibrium at moderate pressures were carried out in systems containing the monomers ethene, 1‐butene, 4‐methyl‐1‐pentene and a polyethylene wax. A group‐contribution‐modified chain‐of‐rotators (COR) equation of state was used to calculate the phase diagrams in all binary and ternary subsystems and in the whole quarternary mixture. The calculations lead to a satisfying description of the vapour‐liquid equilibrium and its intersection by a liquid‐liquid region at higher pressures and temperatures. The miscibility gaps in both mixtures of the polyethylene wax with 1‐butene and 4‐methyl‐1‐pentene, respectively, were observed again after adding ethene to these binary mixtures. The calculations indicate a small three phase triangle in all corresponding ternary mixtures. A liquid‐liquid demixing region intersecting the vapour‐liquid surface could also be found in the whole quaternary system by calculation with the modified COR model. This surprisingly complicated phase behaviour has properly to be taken into account during the separation of the monomers after the co‐ or terpolymerization process.