Spray-dried particles materials

The dispersed droplet size, referred to as emulsion or particle size, can be reduced in the spray drier infeed matrix by more vigorous mixing or homogenization. There is also a new technique for creating small emulsions termed microfluidization which will be discussed later. This research was designed to determine whether the size of emulsion in the infeed solution will affect the characteristics of the final spray dried powder. Materials and Methods... 

Microcrystalline cellulose is one of the most commonly used filler-binders in direct compression formulations because it provides good binding properties as a dry binder, excellent compactibility, and a high dilution potential. It also contributes good disintegration and lubrication characteristics to direct compression formulas. When compressed, microcrystalline cellulose undergoes plastic deformation. The acid hydrolysis portion of the production process introduces slip planes and dislocations into the material. Slip planes, dislocations, and the small size of the individual crystals aid in the plastic flow that takes place. The spray-dried particle itself, which has a higher porosity compared with the absolute porosity of cellulose, also deforms... 

Fig. 3. SEM images of various dry powders for inhalation, (a) Spray-dried particles (see Subheading 3.1.)- Reproduced from ref. 5. (b) Particles prepared by emulsification techniques (see Subheading 3.2.1.), Reproduced from ref. 10. (c) Particles prepared by supercritical C02 swelling (see Subheading 3.2.2.), The particles in panel b were the starting material for these particles. Reproduced from ref. 10. (d) TI particles (see Subheading 3.4.2.),...

Physical and Mechanical Properties Depending on the manufacturing technology used for the manufacture of the amorphous solid dispersion, the material will have different physical properties clearly impacting flow and compression behavior of the material. Comparing spray-dried powders, for instance, with milled extrudates will reveal the difference of both materials. The smaller spray-dried particles have a higher tendency towards cohesion and thus impacting powder flow. On the other... 

Figure 11 Potential spray-dried particle morphologies in relation to process conditions and material characteristics. (From Ref 17.)...

Fig. 6.11 SEM picture of (a) outside and (b) inside structure of spray-dried particles. The active core material (o-limonene emulsion) is in the form of small droplets embedded in the...

The reconstitution behavior of porous particles (their so-called instant properties ) can be explained by the fact that the solvent has to penetrate first into the pores of the particles in order to loosen contact forces by, for example, dissolving contact bridges formed by crystals or amorphous material between primary particles (Pfalzer et al., 1973 Schubert, 1975) or by reducing inter-particulate van der Waals forces. The penetration time of the liquid into a porous spray-dried particle with diameter d (wetting time) is given by the well-known Washburn equation (Washburn, 1921 Schubert, 1990) ... 

Spray Dryers A spray diyer consists of a large cyhndrical and usu ly vertical chamber into which material to be dried is sprayed in the form of small droplets and into which is fed a large volume of hot gas sufficient to supply the heat necessary to complete evaporation of the liquid. Heat transfer and mass transfer are accomphshed by direct contact of the hot gas with the dispersed droplets. After completion of diying, the cooled gas and solids are separated. This may be accomplished partially at the bottom of the diying chamber by classification and separation of the coarse dried particles. Fine particles are separated from the gas in external cyclones or bag collectors. When only the coarse-particle fraction is desired for fini ed product, fines may be recovered in wet scrubbers the scrubber liquid is concentrated and returned as feed to the diyer. Horizontal spray chambers are manufactured with a longitudinal screw conveyor in the bottom of the diying chamber for continuous removal of settled coarse particles. 

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