A process for thermal separation of a solution comprised of a thermoplastic polymer and a solvent involves heating a solvent under pressure above a critical point of the solvent; decompressing the heated solvent in a first vessel, such that a polymer-rich and a low-polymer phase form; and supplying the polymer-rich phase to a second vessel. In embodiments, on entry into the second vessel, a pressure jump occurs, the pressure jump leading to a thermal flash in the second vessel such that a polymer part of the polymer-rich phase rises to at least 70%, and a resulting polymer-rich solution is provided.