Supercritical solutions rapid expansion

Besides the supercritical fluid extraction (SFE) for preparation of medicines and materials processing, supercritical fluid technology involves processes such as supercritical anti-solvent (SAS), rapid expansion supercritical solutions (RESS), rapid expansion of a supercritical solution into a liquid solvent (RESOLV), supercritical assisted atomization (SAA), impregnation and solution enhanced dispersion by supercritical CO2 (SEDS) that involves the supercritical fluid in drug processing to drug delivery systems. 

Guney-Altay, 0., Levit, N., Pestov, D., Tepper, G. (2006). Precipitation of nanocomposite particles from a multi-component, rapidly expanding supercritical solution,/. Supercrit Fluids, 27,229-241. Chernyak, Y, Henon, F., Harris, R. B., Gould, R. D., Franklin, R K., Edwards J. R, De Simone, J. M., Carbonell, R G. (2001). Formation of perfluoropolyether coatings by the rapid expansion of supercritical solutions (RESS) process. Part 1. Experimental results, Ind. Eng. Chem. Res., 40,6118-6126. 

Rapid expansion from supercritical solutions (RESS)... 

Supercriticalfluid solvents are those formed by operating a system above the critical conditions of the solvent. SolubiHties of many solutes ia such fluids often is much greater than those found for the same solutes but with the fluid at sub atmospheric conditions. Recently, there has been considerable iaterest ia usiag supercritical fluids as solvents ia the production of certain crystalline materials because of the special properties of the product crystals. Rapid expansion of a supercritical system rapidly reduces the solubiHty of a solute throughout the entire mixture. The resulting high supersaturation produces fine crystals of relatively uniform size. Moreover, the solvent poses no purification problems because it simply becomes a gas as the system conditions are reduced below critical. 

Crystallization Solutes may be crystallized from supercritical fluids by temperature and/or pressure changes, and by the PCA process described above. In the rapid expansion from supercritical solution (BESS) process, a SCR containing a dissolved solute is expanded through a nozzle or orifice in less than 1 ms to form small particles or fibers. A variety of inorganic crystals have been formed naturally and synthetically in SCR water. 

Depolymerization, e.g., polyethylene terephthalate and cellulose hydrolysis Hydrothermal oxidation of organic wastes in water Crystallization, particle formation, and coatings Antisolvent crystallization, rapid expansion from supercritical fluid solution (RESS)... 

Tsutsumi, A., Nakmoto, S., Mineo,T., and Yoshida, K., A Novel Fluidized-Bed Coating of Fine Particles by Rapid Expansion of Supercritical Fluid Solutions, Proc. 1st Int. Particle Technol. Forum, pp. 452-455, Denver, CO (1994)... 

RESS [Rapid Expansion of Supercritical Solutions] A process for depositing a film of solid material on a surface. The substance is dissolved in supercritical carbon dioxide. When the pressure is suddenly reduced, the fluid reverts to the gaseous state and the solute is deposited on the walls of the vessel. Used for size-reduction, coating, and microencapsulation. First described in 1879. Developed in 1983 by R. D. Smith at the Battelle Pacific Northwest Laboratory. 

A number of techniques are based on supercritical fluid technology. Three are of particular pharmaceutical interest, namely the supercritical antisolvent (SAS) system, the rapid expansion of supercritical solution (RESS) method, and the gas antisolvent (GAS) technique [126]. 

Rapid expansion of supercritical solutions containing dissolved dmg, and... 

Journal of Applied Polymer Science 11, No.7, 15th Aug.2000, p. 1478-87 MORPHOLOGIES OF BLENDS OF ISOTACTIC POLYPROPYLENE AND ETHYLENE COPOLYMER BY RAPID EXPANSION OF SUPERCRITICAL SOLUTION AND ISOBARIC CRYSTALLIZATION FROM SUPERCRITICAL SOLUTION... 

By rapid expansion of supercritical propane solution (RESS), and isobaric crystallisation (ICSS), isotactic polypropylene and ethylene-butylene copolymers were precipitated from the supercritical solution. The RESS process produced microfibres with a trace of microparticles, while the ICSS process produced microcellular products. Improvement in thermal stability was achieved by first synthesising a thermoplastic vulcanisate from polypropylene and ethylene-propylene-diene terpolymer from a supercritical propane solution, followed by RESS. 28 refs. 

The Chinese scientists [123] have reported the preparation of nanoscale RDX (-50 nm) and nanoscale HMX (=70 nm) by an impinging method [124]. Researchers from China have also reported preparation and characterization of n-NTO and their data indicate that it decomposes at a lower temperature and at the same time, it is less sensitive to impact compared with m-NTO. This property of n-NTO is likely to be of tremendous significance for insensitive munitions [125]. The preparation of n-RDX particles with a mean size (=110-120 rim) but narrow distribution has also been reported by a novel method known as rapid expansion of supercritical solution (RESS) [126]. 

Micronization with supercritical fluids - Crystallization - Rapid expansion - Gas anti-solvent Recrystallization - Precipitation with compressed anti-solvent - Solution-enhanced dispersion - Particles from gas-saturated solutions 80 - 300 fine particles and powders from various products and of designed properties... 

By utilizing the rapid expansion of supercritical solutions, small-size particles can be produced from materials which are soluble in supercritical solvents. In this process, a solid is dissolved in a pressurized supercritical fluid and the solution is rapidly expanded to some lower pressure level which causes the solid to precipitate. This concept has been demonstrated for a wide variety of materials including polymers, dyes, pharmaceuticals and inorganic substances. 

In the latest literature, the production by supercritical techniques of pharmaceuticals-loaded bio-polymer micro-particles is widely considered [34], All of these applications take advantage of the solvent or anti-solvent power of CO2. Various techniques have been proposed so far, such as the rapid expansion from supercritical solution (RESS) [35], the gas... 

Yalkowsky, S. H. 1999Solubility and solubilization in aqueous media. New York Oxford University Press. Young, T. J., S. Mawson, K. P. Johnston, I. B. Henriksen, G. W. Pace, and A. K. Mishra. 2000. Rapid expansion from supercritical to aqueous solution to produce submicron suspensions of water-insoluble drugs. Biotechnol. Prog.16 402-407. 

Turk, M., B. Helfgen, P. Hils, R. Lietzow, and K. Schaber. 2002. Micronization of pharmaceutical substances by rapid expansion of supercritical solutions (RESS) Experiments and miRtetio ... 

Vemavarapu, C., M. J. Mollan, andT. E. Needham. 2002. Crystal doping aided by rapid expansion of supercritical solutions APS Pharm Sci TedBi1-15. 

Deryagin, B. M. Levi, S. M. Film Coating Theory, The Focal Press New York, 1964. Domingo, C. Berends, E. Van Rosmalen, G. M. Precipitation of Ultrafine Organic Crystals from the Rapid Expansion of Supercritical Solutions over a Capillary and a Frit Nozzle. J. Supercrit. Fluids, 1997, 10, 35-55. 

Kim, J.-H. Paxton, T. E. Tomasko, D. L. Microencapsulation of Naxopren Using Rapid Expansion of Supercritical Solutions. Biotechnol. Prog. 1996, 12, 650-661. 

Kwauk, X. Debenedetti, P. G. Mathematical Modeling of Aerosol Formation by Rapid Expansion of Supercritical Solutions in a Converging Nozzle. J. Aerosol Sci. 1993, 24, 445-469. 

Matson, D. W. Petersen, R. C. Smith, R. D. Formation of Silica Powders from the Rapid Expansion of Supercritical Solutions. Adv. Ceram. Mater. 1986a, 1, 242-246. 

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