Fluid bed granulator: Although there are many advantages, the influencing factors also need to be paid attention to
Fluid bed granulator is also called one-step granulator. It is a machine which can complete the mixing, granulation and drying of conventional wet granulation in a closed container at one time. The Fluid bed granulator can keep the drug powder in suspension fluidization state under the action of bottom-up air flow. The adhesive liquid will be sprayed into the fluidization chamber from the upper or lower part, and the powder will agglomerate into particles.
Fluid bed granulator has many advantages, for example, the dry mixing, wet mixing, stirring, particle forming and drying of materials are completed in the same Fluid bed equipment, which reduces a lot of operation links and saves production practice. The Fluid bed granulator can also make the production carried out in a sealed environment, which can not only prevent the external pollution of drugs, but also reduce the opportunity for operators to contact with irritant or toxic drugs and excipients.
In addition, the particles prepared by Fluid bed granulation technology have uniform particle size, good fluidity and compression formability. It can also make the drug with very low content in the components more evenly distributed in the prepared particles. It is worth mentioning that the Fluid bed can also produce multi-layer and multi-phase functional particles.
Although Fluid bed granulation technology has many advantages, it is a more complex process and is also affected by many factors. For example, equipment factors, in the Fluid bed granulator, the movement of particles in the air distributor and container has an impact. The material and shape of the container have more influence on the particle motion.
If the operator is using the top jet bed, the location of the nozzle will affect the uniformity of spray and the wetting degree of the material. In order to make the particle size distribution as narrow as possible, the spray area should be adjusted to the same extent as the wet bed surface area. Because if the location is too high, the liquid droplet reaches a longer distance from the nozzle to the material, which increases the volatilization of the liquid medium and causes the material to not be wetted completely, which presents the phenomenon of spray drying.
When the position of the nozzle is too low, the adhesive can not fully contact with the material after atomization, resulting in uneven particle size, and the nozzle front edge is prone to spray obstacles. Some experts remind that the structure of the mixer will also have a great impact on granulation when the rotating shear jet Fluid bed is used for granulation.
Another example is prescription factors, including the nature of materials, the choice of adhesives. The author understands that particle size and particle size distribution are important physical properties of materials in Fluid bed granulation. The smaller the particle size of the material powder, the larger the surface area of the material, and the greater the amount of binder required.
When granulating with hydrophilic materials, the powder and adhesive are mutually soluble and easy to agglomerate, so it is suitable to use Fluid bed granulation. However, the hydrophobic materials need to rely on the bridging effect of the adhesive to bond together. After the solvent evaporates, the particles are formed.
When the material is a water absorbent material, such as starch, the powder surface can not be completely wetted due to the water absorption of the material, so the flow rate of the adhesive should be increased. Because even for the same material, due to different water content, the flow rate of the adhesive should not be the same, and under the condition of the same flow rate of the adhesive, the greater the moisture content of the material, the larger the particle size.
Attention should also be paid to the selection of binders. Fluid bed granulation experts say that the role of binders is to form a solid bridge between powders. The type, concentration and addition method of binders have a great impact on granulation. "The selection of binder is the key to the whole Fluid bed granulation process. The ideal binder should have a good affinity with the surface of the material powder, so as to facilitate wetting and mutual bonding into granules." The expert said.
In general, the Fluid bed granulator has the advantages of uniform particle strength, good fluidity and compression formability, more uniform distribution of drugs with low content in the particles, and saving production time. However, although the advantages of Fluid bed granulator are more, there are also many influencing factors, and relevant personnel should be considerate when using technology or equipment.