Abstract: A process for making ultra-fine particles of a high performance polymer in a yield greater than 90%, which includes dissolving the high performance polymer in an organic solvent capable of dissolving the polymer to form a solution; emulsifying the solution by combining the solution with water and a surfactant to form an emulsion; transferring the emulsion into a receiving water containing a surfactant to remove the organic solvent and form a slurry; and recovering particles of less than 75 microns in diameter in a yield greater than 90%.

Abstract: A process for making ultra-fine particles of a high performance polymer in a yield greater than 90%, which includes dissolving the high performance polymer in an organic solvent capable of dissolving the polymer to form a solution; emulsifying the solution by combining the solution with water and a surfactant to form an emulsion; transferring the emulsion into a receiving water containing a surfactant to remove the organic solvent and form a slurry; and recovering particles of less than 75 microns in diameter in a yield greater than 90%.

Abstract: A method for purifying oxybisphthalic anhydrides is provided. A first mixture comprising at least one oxybisphthalic anhydride, at least one solvent, and at least one inorganic salt is diluted with a solvent such that the concentration of oxybisphthalic anhydride is less than 25 weight percent. This second mixture is then heated to dissolve the oxybisphthalic anhydride thereby providing a third mixture. The third mixture is then filtered at a temperature above the crystallization temperature of the oxybisphthalic anhydride. The oxybisphthalic anhydride present in the filtrate is then crystallized to provide a purified oxybisphthalic anhydride as a slurry. Also included within the scope of the present invention are a method for preparing oxybisphthalic anhydrides and a method for preparing polyetherimides comprising structural units derived from the oxybisphthalic anhydride purified by the method of the present invention.

Abstract: A process for preparing polyimide resins comprises stirring a diamine and a dianhydride in a solvent to form a slurry; heating the slurry to a temperature sufficient for the diamine and dianhydride to react wherein the temperature is below the melting point of the dianhydride, below the melting point of the diamine, or below the melting points of the dianhydride and diamine; and reacting the diamine and dianhydride to form a polyimide having sufficient molecular weight to precipitate from the solvent.

Abstract: A method for preparing a polyimide includes introducing a mixture of an oligomer and a solvent to an extruder, removing solvent via at least one extruder vent, and melt kneading the oligomer to form a polyimide. The polyimide has a low residual solvent content. The method is faster than solution polymerization of polyimides, and it avoids the stoichiometric inaccuracies associated with reactive extrusion processes that use monomers as starting materials.

Abstract: Methods of reducing the amount of undesirable by-products in the production of polymers are disclosed. The resulting polyetherimides have lower polydispersivity and enhanced thermomechanical properties. In some embodiments, cyclic and low molecular weight linear oligomers are also obtained.