The higher the speed, the more energy is imparted to the particle which results in more force during a collision. The optimum speed depends on the characteristics of the product being used and the particle size. In general, smaller particles require higher speed while bigger particles with higher mass which results in more force during a collision require lower speeds. In practice the optimum speed is determined by experimentation. Generally, it is best to start at a high speed and then to lower the speed in the final stage of the process. But again this can be determined by simple practical tests.
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The traditional solution for manufacturing pellets Agglomeration through extrusion and spheronization is one of the oldest techniques for manufacturing pellets.
The process consists of four process steps: Moistening the powder mixture, forming cylinder-shaped agglomerate through extrusion, breaking and rounding the extrudate to round pellets through spheronization, and drying the finished product. The dry, mixed, powdery active substances are kneaded into a dough with a liquid.
This dough then pressed through an extruder. The diameter of the openings in the extrusion plate or extrusion basket determines the strength of the elongated extrusion threads that result. For technical reasons, the resulting pellets are larger than micrometers. The ratio of liquid to solid material together with the size of the extruder holes significantly determines the quality of the extrudates.
The final drying ensures the pellet hardness. Even if the ball-shaped extrudate is imperfect, the evenness of the surface still creates good conditions for subsequent coating. For many pharmaceutical applications, extruded pellets are achieved in suitable quality if a sufficient portion of microcrystalline cellulose is added.
In the pharmaceutical industry, pellets of medium particle sizes from to 2, micrometers are used for most applications. In other industries, the size of the pellets can be several centimeters.
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A Description of the Spheronization Process
The technology chosen is dependent upon multiple active ingredient and formulation criteria, e. It is useful for making dense granules for controlled-release solid oral dosage forms with a minimum amount of excipients, as well as multiparticulates used for immediate, modified, or sustained-release. The process consists of five operations. The wet mass is added into an LCI Multigranulator MG 55 where it is forced through a specific screen to form cylindrical extrudates using either dome, radial or axial extrusion for process optimization. The wet extrudate is added to an LCI Marumerizer QJT spheronizer equipped with a high speed spinning plate which forms uniform spheres from the extrudate "rope". The resultant spheres are dried in a fluid bed dryer and particle size is selected by sieve cuts. The spheres may undergo additional processing steps to apply functional or cosmetic coatings using fluid bed processing with a Wurster insert.
Extrusion / Spheronization