Dr. Dale Wurster at the University of Wisconsin pioneered the Wurster process in the 1950s. In recent years, this process has gained traction within the Indian pharmaceutical industry due to the burgeoning opportunities in the generic market.
Almost all leading companies are now exploring particle coating using the Wurster method. Furthermore, this process can be executed with equal efficiency for both aqueous and non-aqueous applications.
The Wurster process has been utilized for many years to apply coatings to particles, spheres, granules, and tablets.
Systems have been developed to accommodate a range of coating formulations, including aqueous solutions, organic solvents, hot saturated solutions, and hot melts.
The fundamental principle of Wurster coating, which is also referred to as air suspension coating, involves the separation of particles within an air (gas) stream. During this process, a coating formulation is sprayed onto the particles while they remain suspended.
The fluid bed particulate coating process operates on the principle of suspending particles in a fluid-like state through the introduction of gas at the base of the bed. Depending on the location of the spraying nozzle, the coating solution is applied directly onto or into the particles. The gas, serving as a momentum carrier, enhances the drying of the coating. Consequently, the coating layer on the particles is formed during the processes of wetting and drying, in conjunction with the motion of the particles.
The Wurster equipment comprises a cylindrical insert situated within an outer quasi-conical chamber, with a gap existing between the insert and the bottom distributor plate. The open area of the distributor plate in these two sections dictates the relative volume of air that flows into both the insert and the annulus.