Fluid Bed Coating – Changing Properties of Solids as Desired

Related Vendors

Glatt Ingenieurtechnik GmbH

DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

Italvacuum, Srl

The choice of the respective process depends on the product quality to be produced, the properties of the raw materials used as well as the solids to be coated. Important factors are:

• size distribution of the solid to be coated

• viscosity of the spray liquid, the solvent portion (e.g. water) in the spray liquid

• thickness of the coating layer (film thickness) to be applied

• type of spray liquid (solution, suspension, dispersion or melt) or

• requirement regarding uniformity.

In addition to the variables already mentioned, fluidization parameters can also be changed to influence the coating process. For example, products with non-uniform structures, e.g. extrudates, may be coated very effectively in the rotor process.

Coating with Rotor Fluid Beds

In rotor fluid beds – in addition to fluidization by air – mechanical forces are applied to the moving bulk material by using a rotating disk instead of the typical air distribution plate. This rotor disk moves the particles toward the outside where they are moved upwards by an airflow which enters the process chamber through a circular gap. This creates an intensive helical shaped flow of the particles allowing for the very effective tangential spraying (Fig. 1).

Defining Product Properties of Coating Processes

The different coating processes can be applied to achieve different product properties. To demonstrate such effects by way of experiment starter particles (cellets) first received a model active agent layer (NaCl). Using the different coating methods a function layer (Eudragit) was subsequently applied to retard the release of the model active agent (SR: sustained release). The different thermal process conditions were not varied to ensure comparable film formation conditions.

Fig. 2 shows the images of particles from the different process phases. The two coating layers were colored differently for better illustration.

On page 4, we take a closer look at the exact results of each given method...

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