Coating process
Tablet coating is the application of a coating composition to a moving bed of tablets with the concurrent use of heated air to facilitate evaporation of the solvent. The distribution of the coating is accomplished by the tablets either perpendicular (coating pan) or vertical (air suspension).
Equipment
Most coating processes use one of three general type of equipment: * Standard Coating Pan * Perforated Coating Pan * The fluidized bed (air suspension)
Standard Coating Pan
The Standard coating pan consists of a circular metal pan mounted on a stand. The pan is 8 to 60 inch in diameter and rotated on its horizontal axis by a motor. Heated air is directed in to the pan and on to the tablet bed surface and is exhausted by means of ducts positioned in front of the pan.
A.) The immersion sword system
Drying air is introduced through a perforated metal sword device that is immersed in the tablet bed. The drying air flows upward from the sword through the tablet bed. Since the air is more intimately mixed with the wetted tablets, a more efficient drying environment is provided.
B.) Immersion tube system A tube is immersed in the tablet bed. The tube delivers the heated air and a spray nozzle is built in the tip of the tube. During this operation the coating solution is applied simultaneously with the heated air from the immersed tube. The drying air flows upward through the tablet bed and is exhausted by conventional duct. C.) The Pellegrini Pan System The significant improvement in the drying efficiency of the standard coating pan is achieved by the pellegrini pan, the immersion sword and the immersion tube systems. The pellegrini system has a baffled pan and a diffuser that distributes the drying air uniformly over the tablet bed. Perforated Pans All equipment of this type consists of a perforated or partially perforated or partially perforated drum that is rotated on its