Melt Pelletization and Size Reduction
Pelletization is a downstream operation for a melt extrusion process where materials are taken from a device such as an extruder or melt pump, pumped through a die, cooled, and cut into a "pellet." Many products enter their first solid or densified state in a "pellet" form. This chapter provides a simple description of commercially available pelletizers and chill rolls with pin breakers that are used to make small/compounded particles in preparation for subsequent downstream process operations. Micropellets are small, free-flowing, spherical or semispherical units, made up of fine powders or granules of bulk drugs and excipients. They can be coated and are very often used in controlled-release dosage forms. For an air quench pelletizer, the die swell calculation is much more critical because a drawdown of the product is not possible. Therefore, die swell must be recognized as a critical parameter during the design phase of the die hole geometry to make the correct pellet geometry.