Particles from Gas-Saturated Solutions PGSS

In both processes of depressurization crystallization, namely, particles from gas-saturated solutions (PGSS) and rapid expansion from supercritical solutions (RESS), the solid solute and the SCF solvent constitute the binary system. Supersaturation is attained as a result of a drastic reduction of solubility by rapid depressurization, and subsequently the two-phase (S-V) system is formed. The process chosen depends on the solubility of the solid solute and its melting point. 

Kikic I, Lora M, Bertucco A. Thermodynamic analysis of three phase equilibria in binary and ternary systems for applications in rapid expansion of a supercritical solution (RESS) particles from gas-saturated solutions (PGSS) and supercritical antisolvent (SAS). Ind Eng Chem Res 1997 36 5507-5515. 

PARTICLES FROM GAS-SATURATED SOLUTIONS (PGSS) AND RELATED METHODS... 

Mandel FS, Don Wang J, Me Hugh MA. Pharmaceutical material production via supercritical fluids employing the technique of particles from gas saturated solutions (PGSS). Proceedings of the 7th Meeting on Supercritical Fluids, Antibes, France, 2000 1 35-46. 

Formation of Particles from Gas Saturated Solution (PGSS)... 

Different precipitation processes based on supercritical carbon dioxide have been proposed in which CO2 performs different functions as solvent, in the rapid expansion of supercritical solutions (RESS) process, as antisolvent, in the supercritical antisolvent (SAS) process, or as solute, in the particles from gas saturated solutions (PGSS) process. 

One of the interesting apphcations where scC02-processing of polymeric materials is beneficial is the method of PGSS (Particles from Gas Saturated Solution). PGSS is a technique able to form polymer/active compound foams, solid particles, or droplets [160]. The principle of the technique is for CO2 to form a gas-saturated solution/suspension which may then be foamed or passed through a nozzle to produce sohd particles or droplets. The technique is suited to thermally labile components, since the process is undertaken at near ambient temperature. Control of particle size has been achieved by the introduction of N2 back-pressure in the collection chamber, as demonstrated by Hao et al. [161] with poly(DL-lactic acid). The PGSS method has been shown to enhance the dissolution characteristics of nifedipine from PEG 400 [162, 163]. 

Some examples of commercial active component production and production of substances with defined and uniform particle sizes (organic and inorganic materials) realized on pilot plant by using the RESS are given in Table 24.8. Other processes were also tested for synthesis of the particles with uniform size distribution as well as production of particles with specific structure (gas antisolvent recrystallization, GASR precipitation with a compressed antisolvent, PCA solution enhanced dispersion of solids, SEDS particles from gas-saturated solutions, PGSS) as shown in Table 24.9. All these processes are of special interest in pharmaceutical industry and in the production of different polymers. 

Both the nucleation of supercritical anti-solvent bubbles in a polymer+organic solvent-rich phase in the supercritical anti-solvent process (SAS) (or, equivalently, precipitation with a compressed antisolvent PCA) (e.g., [76]) and the nucleation of bubbles of a dissolved supercritical fluid from a saturated and nozzle-expanded solution containing a solute to be precipitated, in the formation of particles from gas-saturated solutions (PGSS) [77] are bubble nucleation problems, to which the above ideas apply. In the latter case, the nucleation of bubbles occurs simultaneously with that of solid particles within the bulk supersaturated solution. 

Kikic, I., Lora, M. and Bertucco, A. (1997) A Thermodynamic Analysis of Three-Phase Equilibria in Binary and Ternary Systems for Applications in Rapid Expansion of a Supercritical Solution (RESS), Particles from Gas-Saturated Solutions (PGSS), and Supercritical Antisolvent (SAS), Ind. Eng. Chem. Res. 36,5507-5515. 

Jun-Ho, Y., Hye-Youn, L., Asaduzzaman, A. K. M., B3nang-Soo, C. (2013). Micronization and characterization of squid lecithin/polyethylene glycol composite using particles from gas saturated solutions (PGSS) process,/. Ind. Eng. Chem., 19,686-691. 

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