(529b) A New Granulation Method in Supercritical Fluid

Many techniques are known for preparing granules from powdered materials such as wet granulation, solvent granulation and melt granulation. Wet granulation and solvent granulation require the addition of a liquid binder which aggregates the active materials, carriers and other ingredients into granules. After granulation, the liquid generally must be removed by a separate drying step. Melt granulation is similar to wet granulation, but uses a low melting point solid material as a binder. The solid binder in melt granulation is melted and acts as a liquid binder thereby aggregating the powdered active material and other ingredients into granules. Binder thereby, is permanently incorporated into the granules when the granules cool.

Each of these granulation techniques has certain limitations or disadvantages. Wet granulation requires a liquid to be added, and the liquid must subsequently be removed. Therefore, a drying step is needed which further complicates the manufacturing process and risks more contamination. Melt granulation on the other hand avoids the problems associated with adding liquids by incorporating a low melting solid binder. However, the low melting point binder must be heated to at least its softening point and melted during the granulation process, which will strictly limit the number of active materials which can be granulated.

This paper presents a new method for the granulation of fine particles in supercritical CO2 environment, which has the effect of suppressing melting point on organic crystals, as well as the effect of plasticizing certain polymers. Both jet-milled lactose and a crop protection active have been successfully agglomerated into free-flowing granules at temperature as low as 39ºC using a polymer binder: polyethylene glycol (PEG 8000), which has a melting point above 60ºC. Therefore the new granulation method can overcome some limitations that conventional granulation methods have, and being capable of handling especially thermally sensitive active materials used in pharmaceutical and food industries.