Similarities to spray drying

The loss of heat-sensitive material during the spray-drying process has led to a number of alternative methods for dehydration of sprayed microcapsules. Spray-cooling and spray-chilling are similar to spray-drying, where the core material is dispersed in a liquefied coating or wall material and atomized at low temperature. 

There are also other methods such as spray pyrolysis and electrospray pyrolysis besides the above method [26]. To prepare nanoparticles by spray pyrolysis, a starting solution is prepared by dissolving, usually, the metal salt of the product in the solvent. The droplets atomized from a starting solution are introduced to furnace. Drying, evaporation of solvent, diffusion of solute, precipitation, reaction of precursor, and surrounding gas, pyrolysis may occur inside the furnace before the formation of product. It is similar to spray drying except the type of precursor. For this, colloidal particles are typically used as precursors. Some products prepared by spray pyrolysis are listed in Table 34.1. 

Downstream considerations will be similar to spray-dried material. 

Taking into account that nucleophilic substitution reactions of azines 55,56 typically do not occur in untreated DMSO and KF 2H2O under traditional heating, it is safe to assume that microwave irradiation promotes dissociation of KF and desolvation of the fluorine anion, which subsequently takes part in the nucleophilic substitution reaction, similarly to spray-dried KF in anhydrous DMSO (Fig. 2). 

Polyvinyl acetate is described in the literature as a matrix former in theophylline sustained-release tablets obtained by hot-melt extrusion [646]. In a similar way spray-dried PVAc/Povidone can be applied for the production of tablets and pellets using its excellent flowability. In this case the pulverization of polyvinyl acetate by cryogenic grinding can be avoided and the mixture of the active ingredient with the excipients are applied directly to the melt extruder. 

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