The invention provides a solution polymerization process comprising: A) polymerizing one or more monomers in the presence of a solvent that comprises a heavy hydrocarbon solvent and a light hydrocarbon solvent, to form a polymer solution; B) transferring the polymer solution to a Liquid-Liquid Separator, without adding heat to the solution, and wherein the pressure of the polymer solution is actively reduced in a controlled manner prior to, or within, the Liquid-Liquid Separator, to induce at least two liquid phases, a polymer-rich phase and a solvent-rich phase, and wherein the concentration of polymer in the polymer-rich phase is higher than that in the polymer solution transferred to the Liquid-Liquid Separator; and C) removing the solvent-rich phase.