(532c) Novel Method to Isolate Polymeric Slurry Based Systems in a Continuous Process

During polymerization reactions, if the final polymer is not soluble in the solvent, a slurry or precipitate is formed as the molecular weight builds up. Typically, after the reaction is completed, a series of unit operation such as centrifugation followed by drying is used to isolate dry polymer. Slurry processes have inherent challenges with maintaining stable flow control for continuous operation; powder carryover with vapor; powder handling and other risks associated with potentially explosive dusts.

To describe the new process, we have used the example of a polymer that forms a slurry in the solvent most suitable to carry out its reaction. It was identified that above a certain temperature higher than the boiling point of the solvent, the polymer was soluble in the solvent. In order to form a solution, the reaction mixture would need to be maintained at an elevated temperature and corresponding vapor pressure. By having a polymer solution instead of a slurry, it was possible to use standard thermomechanical separators such as an agitated thin film evaporator (ATFE) or devolatization extruders to isolate the polymer in the continuous process. It was observed that the polymer would crash out of the solution if the temperature or pressure dropped below a certain limit. With this in mind, an overview of the risk mitigation activities undertaken to test the feasibility of reaction and isolation of the polymer in an ATFE operating under pressure is provided. A similar approach could be taken for isolation of other polymers, which are not soluble in a solvent below its boiling point, but are soluble above the boiling point and can be achieved under elevated pressure conditions.