A new process for continuous melt polymerization of aromatic dianhydrides and diamines has been developed. The process consists of several integrated stages: feeding, melting, devolatilization, mixing, and advanced polymerization. The transport phenomena and coupled reaction rates have been studied in a corotating, intermeshing twin-screw reactor/extruder. Each stage in this process has been analyzed. The results show the importance of viscous heat for melting monomers, free surface generation in mass transfer, total shear strain in distributive mixing, and back mixing for extended residence time and advanced polymerization. High molecular weight polyetherimide (Mw 50 × 103) was obtained with this process for a variety of conditions. The reactions were run with 3 mole % of monofunctional anhydride to cap the polymer ends at a specific molecular weight for the most desirable balance of mechanical and physical properties.
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Schmidt et al. (1989) studied this question.
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