Low Energy Solvent Separation in Solution Polymerization Processes

In solution polymerization processes, after polymerization is carried out in a paraffinic solvent, the solvent is typically removed by evaporation. The evaporation step requires a considerable amount of energy, and additional energy (refrigeration work) is later required to condense the solvent vapors before they can be recirculated into the polymerization reactor.

We have developed a new polymerization process that takes advantage of liquid-liquid separation phenomena in polymer solutions. At the right combination of temperature, pressure, and composition, a fraction of the solvent in a homogenous polymer solution forms a separate liquid phase, free of polymer. The solvent separation occurs rapidly when it proceeds via spinodal decomposition. Solvent is therefore quickly separated from the reactor effluent without providing additional energy, and it can be recirculated without supplying refrigeration work for condensation.