Our innovative spray coating in the fluidized or spouted bed coats small particles.
With this method, a film material is applied evenly which produces optimal coating of the particle surface.
This is how it works: Particles of different sizes and shapes are moved in the fluid bed or spouted bed and are sprayed with a liquid. This liquid can be an aqueous or organic solution, a suspension or a melt. The solution evaporates, the melt solidifies, and the contained solid forms an enclosure, the coating layer. For any particle to be completely enclosed, it must have a size of at least 100 micrometers.
Particles in the nanometer range can be coated by core-shell coating using powder synthesis.
This coating layer has several advantages for your planned products: As a protective layer it increases shelf life or storage stability. It can also improve the functionalization of particles, for example, for odor and taste masking or for the targeted release of active ingredients.
Spray coating at Glatt
What specific requirements does your project place on the coating of particle surfaces? With our innovative coating technologies, we can specifically influence and optimize the desired product properties.
We carry out spray coating in all our fluid bed systems – both in batch and continuous operation. Process parameters, plant design, and formulation are coordinated to avoid agglomeration due to liquid bridges.
Our fluid bed and spouted bed coating processes allow an optimal residence time of the particles in the coating zone and ensure excellent coating qualities. Depending on the direction from which the particle is to be sprayed, we coat in these processes:
- top spray coating
- bottom spray coating, also called Wurster process or Wurster coating
- tangential spray coating, also called rotor or HP coating
Which coating are you interested in? Learn more about it:
Top Spray Coating – for your optimized product handling
In top spray coating, the spray liquid is sprayed onto the fluidizing particles from above. To avoid agglomerate formation, the particles must have a larger diameter. The process is very suitable, for example, for covering the surface of sticky products or for coloring particles. Products coated with the top spray process score with improved product handling and increased storage stability.
Top Spray Coating
in a fluidized bed
Bottom Spray Coating or Wurster Processing for targeted functionalization
First of all, the great advantage of bottom spray coating, also known as Wurster process or Wurster coating: a very uniform coating, coupled with optimum film quality.
Depending on the application, coating in the bottom spray process can be carried out with or without a Wurster tube.
To achieve a controlled release of active substances/active ingredients, the use of a Wurster tube is advantageous. It separates the particles to be coated from the already coated, drying particles.
What happens during bottom spray coating? The spray nozzles are integrated in the bottom plate and spray from the bottom to the top. By combining the inflow bottom and the riser tube, we achieve a targeted and controlled movement of the particles: This results in the precisely desired application of the coating materials to the particle surfaces.
Our bottom spray coating achieves an optimum film quality that specifically functionalizes your products – without any undesirable side effects:
- the uniform residence times of the particles in the spray zone ensure homogeneous film quality
- the high particle velocity in the riser tube prevents the particles from sticking together when wet; this allows us to coat even very small particles without agglomeration
- since the nozzle is located in the middle of the product flow and sprays evenly, the spray droplets hit the surface directly and can spread ideally, since the solvent does not evaporate prematurely
Bottom Spray Coating
in a fluidized bed
Tangential Spray Coating – Our All-in-one Solution for Pellets
Tangential Spray Coating, HP Spray Coating or also known as the Rotor Coating process, is ideally suited for coating pellet products. The reason: this innovative process variant makes it possible to combine a so-called dry powder layering process with a subsequent film coating spray process as a one-pot process; in other words, the entire process takes place “all-in-one” in the same coating system.
A HP nozzle projecting into the product bed distributes the coating material from the side – tangentially, so to speak, to a circular line of the container bottom. This variant of spray coating is ideally suited:
- for a uniform coating of particle surfaces and a very high film quality
- to achieve a controlled release of active ingredients
- to prevent undesired spray drying of the coating material
In the central process parameters, this option is similar to bottom spray coating (Wurster coating). Difference: In tangential spray coating, we generate the uniform material movement either by means of a motor-driven disk, a rotor, or by means of a specially manufactured Conidur inflow base; this creates a defined air flow that swirls the pellets.