The use of liquid-liquid extraction in the EPDM solution polymerization process

The application of liquid-liquid separation as a means of polymer-solvent s eparation was studied. Phase separation experiments were performed with eth ene-propene-diene terpolymer (EPDM) solved in hexane, using propene as an a ntisolvent. The results were interpreted using a thermodynamic model based on the Sako-Wu-Prausnitz (SWP) equation of state. The description of homoge neous polymers is unambiguous, but for heterogeneous polymers further devel opment of the SWP theory is required. It was found that the model shows pro mising results with respect to multicomponent polymer systems. However, the description of the interaction between the components is still unsatisfact ory. Therefore, an empirical model was developed to describe the experiment al results. A flowsheet model was constructed to describe a novel EPDM proc ess containing a liquid-liquid countercurrent extraction column. The effect s of temperature, pressure, antisolvent concentration, and number of theore tical equilibrium stages were studied. With respect to variable costs, liqu id-liquid extraction is a cost-effective option in the purification of rubb er polymer solutions.