Fluid Bed Coating – Changing Properties of Solids as Desired

Related Vendors

Glatt Ingenieurtechnik GmbH

DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

Italvacuum, Srl

Different Approaches – Different Results

It became apparent that with all process variants optically very uniform and dense coating could be produced. Also the particle size distributions do not vary significantly from each other.

The small differences are certainly caused by the fact that the originating particles (cellets) are relatively coarse (d5O=1250 µm) and the two coating layers with application amounts of seven percent with the model active agent and five percent with the SR Coating are very small.

Examining Methods of Fluid Bed Coating

In contrast to the optical appearance release measurements showed differences between the individual profiles as shown in Fig. 3. Here, the film coating of the rotor apparatus released the active agent the quickest, which can be explained by a comparatively low strength or density of the film coating. The Wurster process, among all variants, provided the most dense coating so that the release took place very slowly. In comparison, a very irregular release was caused by the Top Spray coating. As very broad wall thickness distribution of the SR film applied was suspected to be the reason, caused by the irregular particle movement through the spray zone. The release profile of the Bottom Spray method without inner partition ranges between the Top Spray and Wurster method.

Effective Influence on Solids and Granulates

In summary it can be noted that the application properties of solids can be influenced very effectively and specifically through the coating process. The process variants available – in addition to the substance-related parameters (the recipe parameters) – provide additional options for optimization.

When establishing coating processes in practice, the technology to be used needs to be analyzed systematically during the development phase to be able to achieve optimal product quality. Differences between the process variants can be significant, which, for example, can make the transfer of products between different production systems more difficult.

Another aspect in the process development is the general decision whether the process shall run in batches or continuously. Important decision criteria are, amongst others, the required product volume, the work organization of the company as well as the requirements on the coating quality or uniformity. Rectangular fluid bed units are usually used for continuous coating processes (Fig. 4).

In all practical cases the development phase requires experimental studies, which can be performed at the Technology Center of Glatt Ingenieurtechnik in Weimar on a laboratory and pilot scale. Coating equipment working both in batch mode and continuous can be tested there.

* Dr. M. Jacob is the director of the plant and engineering division at Glatt Ingenieurtechnik GmbH, Weimar and K. Meyer is a student at the Otto-von-Guericke-Universität Magdeburg.

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