Coated tablets are defined as tablets covered with one or more layers of various substances such as resins, gums, inactive and insoluable fillers, sugars, plasticizers, waxes, authorized coloring materials, and sometimes flavors. Tablet coating processes can be subdivided into different types. Sugar coating, for example provides a combination of insulation, taste masking, smoothing of the tablet core, coloring and modified release. Film coating, on the other hand, is usually a single stage process and easily adaptable for controlled release dosage forms.
Substances used for coating processes are usually applied as a solution or suspension under conditions where the carrier substance evaporates. In the case of sugar coated tablets, either via batch or continuous processing, the tablet must be polished to achieve a final aesthetic quality. Polishing is achieved by applying a mixture of powder waxes, such as carnauba wax, to the tablet in the polishing pan.
Conversely, in the case of film coated tablets, the addition of powdered opaquant extenders, such as talc, achieves a lighter color and greater film coverage.
In both of these coating processes, Coperion K-Tron twin screw feeders are used to provide consistent and metered delivery of these dry powders, directly into the coating equipment.