Supercritical carbon dioxide spray

Lewis, J. Argyropoulos, J. N. Nielson, K. A. Supercritical Carbon Dioxide Spray Systems. Metal Finishing 1997, 95 (4), 33-41. 

Unlike previously developed, low-pollution spray systems, the coatings produced by the supercritical carbon dioxide spray are of high quality and thus are highly marketable. Due to the unique decompressive atomization mechanism caused by choked flow, the new spray has a feathered pattern with a narrow droplet-size distribution which produces coatings of more uniform thickness than those of conventional sprays. 

Conventional nitrocellulose lacquer finishing leads to the emission of large quantities of solvents into the atmosphere. An ingeneous approach to reducing VOC emissions is the use of supercritical carbon dioxide as a component of the solvent mixture (172). The critical temperature and pressure of CO2 are 31.3°C and 7.4 MPa (72.9 atm), respectively. Below that temperature and above that pressure, CO2 is a supercritical fluid. It has been found that under these conditions, the solvency properties of CO2 ate similar to aromatic hydrocarbons (see Supercritical fluids). The coating is shipped in a concentrated form, then metered with supercritical CO2 into a proportioning airless spray gun system in such a ratio as to reduce the viscosity to the level needed for proper atomization. VOC emission reductions of 50% or more are projected. 

UNICARB [Union Carbide carbon dioxide] A process for spray painting objects using supercritical carbon dioxide as the solvent. Developed by Union Carbide Company and workers at Johns Hopkins University. 

Supercritical atomization in spray coating, 7 70 Supercritical carbon dioxide, 9 456,24 2, 15 applications of, 24 20 as a medium for chemical reactions, 12 808-809... 

The flavour and modern phytopharmaceutical industries have made big changes to the traditional pharmaceutical extraction processes. Whereas ethanol was really the only significant solvent apart from water used by the traditional pharmaceutical extractors, solvents such as hexane and acetone have been used by flavour companies to make soft-extract oleoresins for natural flavour components. Sub- and supercritical carbon dioxide and also some fluorohydrocarbons are now used to produce some very high-quality extracts. Modern concentration and drying processes such as reverse osmosis, spray-drying and freeze-drying... 

The use of supercritical carbon dioxide (CO2) as a component in a solvent mixture is another ingenious technique to reduce VOC emission by 50 percent or more. This technique takes the advantage of the fact that CO2 is a supercritical fluid below its critical temperature (31.3°C) and critical pressure (7.4 MPa). Sohd coating and supercritical CO2 are metered into a proportioning spray gun in such a ratio so as to reduce the viscosity to the level needed for proper atomization. Airless spray guns are used. 

Baldyga J, Henczka M, Kubicki D, Shekunov BY. Modeling of turbulent mixing with application of supercritical antisolvent. Inz Ap Chem 2002 41 22-23. Wubbolts FE, Bruinsma OSL, Rosmalen GM. Dry-spraying of ascorbic acid or acetaminophen solutions with supercritical carbon dioxide. J Cryst Growth 1999 198/199 767-772. 

Wubbolts FE, Bruinsma OSL, Van Rosmalen GM. Dry-spraying of ascorbic acid or acetaminophen solutions with supercritical carbon dioxide. J Crys Growth 1999 198/199 767-772. 

Corrigan OI, Crean AM. Comparative physicochemical properties of hydro-cortisone-PVP composites prepared using supercritical carbon dioxide by the GAS antisolvent recrystallization process, by coprecipitation and spray drying. Int J Pharm 2002 245 75-82. 

The critical temperature of CO2 is 31 °C. Above this temperature, carbon dioxide can be compressed to a very high pressure and relatively high density supercritical fluid. Like a liquid, the supercritical carbon dioxide will mix with or dissolve the blend of coating and low volatility solvent to form a product that is thin enough to be sprayed easily, in very small droplets. 

Supercritical carbon dioxide is also useful in a variety of applications as a replacement for organic solvents. Union Carbide markets a process for spray-painting in... 

SAA, supercritical assisted atomization This process is based on the solubilization of a fixed amount of supercritical carbon dioxide in the liquid solution then the ternary mixture is sprayed through a nozzle, and as a consequence of atomization, solid particles are formed ]. 

Hao, J., Whitaker, M.J., Wong, B., Serhatkulu, G., Shakesheff, K.M., and Howdle, S.M. Plasticization and spraying of poly (DL-lactic acid) using supercritical carbon dioxide Control of particle size. Journal of Pharmaceutical Sciences 93 (2004) 1083-1090. 

Nicotine is obtained from tobacco plants by extraction or steam distillation. Particularly suitable for this, just as for caffeine, is destraction with supercritical carbon dioxide. [567] Nicotine-rich Mapacho is cultivated for this purpose in the USA but also the waste from tobacco processing is a suitable source. The annual worldwide production for pharmaceutical purposes reaches a total of around 35-40 tonnes, whereof most is attributed to nicotine replacement therapy (nicotine containing patches, nasal spray, chewing gum, lollipops) for smoking cessation. 

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