Coating: Protection of sensitive particles by coating

Precursors for Coating

A coarse powder, granulate or bulk material to be treated is loaded into the plant and fluidised by the inlet air stream. For coating, a liquid (aqueous solution, suspension or emulsion, or a melt, melt emulsion or melt suspension of the coating material) is sprayed into the fluidised bulk material.

Process Technologies for Coating

Coating comprises applying a surface layer to, or the encapsulation of sensitive particles. By coating the surface morphology of the precursor is changed to achieve a particular effect. Macroscopic particles from 150 µm – 200 µm (even up to 5 mm) can be individually and gently coated with the aid of fluidised-bed technology, using either a water-soluble or a hydrophobic system based on

  • aqueous solutions, suspensions or emulsions
  • melts

This achieves the efficient protection of sensitive raw materials from external (e.g. moisture, atmospheric oxidation) or internal influences (e.g. other components of the formulation), or protects the environment from aggressive components by coating them.

Particles may also be coated with the objective that their intended effect occurs to the fullest possible extent at a particular “location” and a defined “time”.

The desired release of a coated active substance can be achieved by a variety of mechanisms which render the coating material intentionally permeable by means of an appropriate reaction, or even cause it to dissolve (“controlled-release” mechanism), e.g. through pH or temperature changes or by adding a specific trigger reagent (e.g. an enzyme).

A “slow-release” mechanism is when a coated substance is continuously released. This occurs by semi-permeable diffusion through coating systems that are insoluble in water.

Both mechanisms can be adjusted and controlled by careful selection of the coating materials.

Results and Advantages of the Coating Process

  • Homogeneous distribution of the coating material on the individual particles
  • Protects particles from external influences
  • Protects particles from internal incompatibilities
  • Protects the environment from particles
  • Specific “controlled-release” mechanisms
  • Controlled semi-permeable diffusion (“slow release”)
  • Improved storage stability
  • Particles suitable for tablet pressing (direct compression)
  • Influence the properties of your product (such as hygroscopicity, smell, flowability, surface morphology, visual appearance, solubility)