Tablet coating spray rate

Application/spray rate The optimal application/spray rate should be determined. Spraying too fast will cause the tablets to become overwet, resulting in clumping of tablets and possible dissolution of the tablet surface. Spraying too slowly will cause the coating materials to dry... 

The second approach to coating scale-up involves an understanding of thermodynamic and mass transfer processes. A robust process can be demonstrated by establishing a coating procedure that identifies critical process parameters and their effect on the equilibrium between mass flow (the coating solids applied) and heat transfer (the solvent removed). This approach allows one to evaluate air temperature, air flow, and spray rate as applied to a known mass of tablets, and then scale these conditions into a larger coater. A thermodynamic model for aqueous film coating as described by Ebey is shown in Eq. (9). 

A tablet-coating investigation was conducted to evaluate the effect of spray rate, inlet air temperature, and atomization air pressure on the six-hour dissolution and residual solvent levels of coated tablets. The goal was to find conditions which maximized the dissolution and minimized the residual solvents of the coated tablets. 

Figure 10 (A) Tablet coating study—contour plot for dissolution spray rate and air temperature. Atomization air pressure, 2.3 Bar. (B) Tablet coating study—contour plot for dissolution spray rate and air temperature. Atomization air pressure, 2.9 Bar. (C) Tablet coating study—contour plot for dissolution spray rate and air temperature. Atomization air pressure 3.5 Bar.

Picking Areas of tablet surface are not covered by film coat. Overwet tablets stick together and pull film off surface as they move apart. Decrease spraying rate. Increase drying temperature. 

For hydroxypropyl methylcellulose acetate succinate, a novel enteric dry coating method has been developed [31]. The unique feature of this method is that the enteric polymer is added in powder form (e.g., mixed with talcum directly to tablets or pellets) whereas a plasticizer diluted with paraffin is sprayed separately. The tablet core temperature is around 40°C, and the film is cured for a short time. To achieve a homogenous film, the rates of powder feeding and plasticizer spray have to be adjusted such that the two processes start and end simultaneously. 

The term moisture, usually defined as wetness conferred by an unidentified liquid, is assumed here to be due to water. Thus, the scope of this article is the characterization of and consequences due to relatively small amounts of water associated with solids of pharmaceutical interest. Chemical stability, crystal structure, powder flow, compaction, lubricity, dissolution rate, and polymer film permeability are some properties of pharmaceutical interest that have been demonstrated to be influenced by the presence of moisture. Wet granulation, extrusion, spheronization, tray drying, freeze drying, spray drying, fluid-bed drying, tableting, and aqueous film coating are some unit operations that obviously depend on the amount and state of water present. 

Polyethylene glycol (PEG) 4000, when spray-dried with lactose, has been shown to accelerate the rate and extent of crystallization of lactose. It has also been shown that spray-dried lactose composite particles containing an ion complex of chitosan are suitable for the dry-coating of tablets. Spray-dried lactose and crystallized spray-dried lactose have been evaluated for dry powder inhalation.Amorphous spray-dried lactose has also been studied in composites with PVP. ... 

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