ABSTRACT

A new ‘assisted’ dry granulation method has been devised for the twin-screw granulator. The method may be beneficial to drug preparation as it limits heat exposure to only one barrel zone, much shorter than melt granulation. Its mechanism was investigated using four placebo formulations, each containing a polymer binder with a glass transition temperature lower than 130°C. Variables of study included screw configuration, screw speed, barrel zone temperature and moisture content. Granulated samples were characterized for size and porosity while feed powders were examined for their thermal transitions, inter-particle friction, cohesion, and sintering rate. Results indicated that granule coalescence relied upon melting of polymer binder in the kneading blocks by a combination of heat conducted from barrel and generated from screw speed friction. Successful granulation was possible with minimal addition of water, though varying the moisture content showed the relevance of the polymer’s glass transition temperature and sintering progress.

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