Supercritical impregnation

In order to overcome the main limitations of the impregnation processes, connected to the limited solubility of the compounds in the supercritical fluids, Perman [68] proposed an alternative method. A supercritical impregnation process was coupled with a liquid solvent (preferentially water) to enhance the drug solubilization. The system composed of a liquid drug solution and the polymeric support was pressurized with the supercritical fluid. Consequently, the swelled polymer allows rapid diffusional transport of the solute into the polymeric substrate. In different examples, bovine serum albumin microspheres were impregnated with insulin, trypsin and gentamicin (see Table 9.9-5). 

Muth O, Hirth T, Vogel H. Pol5uner modification by supercritical impregnation. J Supercrit Fluids 2000 17 65-72. 

Kikic, 1. Vecchione, F. (2003) Supercritical Impregnation of Polymers. Curr. Opin. Solid State Mater. Sci. Vol.7, No.4-5, pp.399-405... 

Kikic, I. and F. Vecchione, Supercritical impregnation of polymers. Current Opinion in Solid State Materials Science, 2003. 7(4,5) p. 399 05. 

Yoda S, Otake K, Takabayashi Y, Sugeta T, Sato T (2001) Effects of supercritical impregnation conditions on the properties of silica-titania aerogels. J Non-Cryst Solids 285 8-12... 

Muth, 0., Hirth, T, and Vogel, H. (2000) Polymer modification by supercritical impregnation. 7. Supercrit. Fluid, 17, 65-72. 

Ibuprofen is a nonsteroidal anti-inflammatoiy drug (NSAID) used for pain relief due to the anti-inflammatory effects [56], however this drug has low solubility in aqueous solutions [57, 58], which implies involvement in negative absorption by the body. Then researchers are using supercritical fluid technology to overcome these drawbacks. Antonov et al., [59] studied the solubility of ibuprofen in supercritical CO2 by fourier transform infrared spectroscopy, moreover ibuprofen was also studied in supercritical impregnation processes polymers [60, 61], in theoretical RESS process [62, 63] and experimentally for micronization of particles with reductions from 45 pm to 2.85 pm [64], and formation of even smaller nanoparticles by RESOLV [65]. Furthermore, Molnar et al., [66] studied the enantioseparation of racemic ibuprofen in SFE and realized that the system pressure of the extraction is directly related to resolution efficiency. 

Salima Varona, Soraya Rodriguez-Rojo, Angel Martin, Maria Jose Cocero, Catarina M.M. Duarte, Supercritical impregnation of lavandin (Lavandula hybrida) essential oil in modified starch, The Journal of Supercritical Fluids 58 (2011), p. 313-319. 

Y. Masmoudi, L. Ben Azzouk, 0. Forzano, J.-M. Andre, E. Badens, Supercritical impregnation of intraocular lenses, The Journal of Supercritical Fluids 60 (2011), p. 98-105. 

Impregnation, 17 509 of nonwovens, 17 513 supercritical, 24 19-20 Impregnation coating, 10 12 Impression dental plasters, 3 290 compressive strength, 8 289t Impression dental wax, 8 298-299 specification, 8 300t Impressions in blood, 12 102... 

Polymer miscibility, enhancing, 14 476 Polymer modification, supercritical fluid impregnation in, 24 20 Polymer networks, interpenetrating, 79 834 20 327... 

Surface engineering of polymers by infusion. Supercritical-fluid contact can reversibly swell some polymer surfaces and films thus helping to enhance impregnation by monomers with subsequent polymerization to form nanocomposite anchored layers. - ... 

Dyeing with supercritical fluids Cell structure treatment with supercritical fluids (e.g., C02) 80 - 300 dyeing of fabrics tobacco impregnation... 

In contrast to the decaffeination of coffee, which is primarily executed with green coffee, black tea has to be extracted from the fermented aromatic material. Vitzthum and Hubert have described a procedure for the production of caffeine-free tea in the German patent application, 2127642 [11]. The decaffeination runs in multi-stages. First, the tea will be clarified of aroma by dried supercritical carbon dioxide at 250 bar and 50°C. After decaffeination with wet CO2 the moist leaf-material will be dried in vacuum at 50°C and finally re-aromatized with the aroma extract, removed in the first step. Therefore, the aroma-loaded supercritical CO2 of 300 bar and 40°C will be expanded into the extractor filled with decaffeinated tea. The procedure also suits the production of caffeine-free instant tea, in which the freeze-dried watery extract of decaffeinated tea will be impregnated with the aromas extracted before. 

In another process, patented by Berens [67], the additive must again be solubilized in the supercritical solvent, as in Sand s process but, in this case, the patent is mainly concerned with reactive monomers that successively polymerize, modifying the host polymer. Nevertheless, in some examples (with a film of polyurethane), the problem of solid-drug impregnation is also considered. 

In this chapter, we will discuss current applications and research on the use of C02 as a solvent for coatings. The first section deals with spray coating from supercritical C02. Subsequent sections deal with the use of liquid coatings, such as spin and free meniscus coatings, and impregnation coatings. 

The coating methods presented earlier are all used to create films of materials upon surfaces. There is another class of coatings from C02 that has not yet been discussed. Using both liquid and supercritical C02, it is possible to coat or impregnate porous and woven materials with a desired polymer or chemical agent. Three specific applications will be discussed in turn. 

Howdle, S. M. Ramsay, J. M. Cooper, A. I. (1994). Spectroscopic Analysis and in situ Monitoring of Impregnation and Extraction of Polymer Films and Powders Using Supercritical Fluids. J. Polym. Sci., Part B Polym Phys. 1994, 32. 

Levien, K. L. Morrell, J. J. Sahle-Demessie, E. Impregnating Porous Solids Using Supercritical C02. CHEMTECH March, 1998, 12-18. 

Ma, X. Tomasko, D. L. Coating and Impregnation of a Nonwoven Fibrous Polyethylene Material with a Nonionic Surfactant Using Supercritical Carbon Dioxide. Ind. Eng. Chem. Res. 1997, 736, 1586-1597. 

Grunwaldt et al. (2003b) reported XAFS measurements recorded during palladium-catalyzed alcohol oxidation in supercritical CO2. A commercial shell-impregnated catalyst consisting of 0.5 wt% Pd on alumina was used for benzyl alcohol oxidation (to benzaldehyde) in supercritical CO2 with pure O2 as oxidant. The conditions were 353 K and 150 bar. The results are summarized in Table 8. The authors reported only Pd XANES data, not EXAFS data, and thus the analysis is limited to information about the average oxidation state of the palladium. 

Supercritical fluids (scf) are highly compressed liquids or gases. The latter already have an established role in "clean extraction (substitution of chlorinated/organic solvents) on an industrial scale (e. g. decaffeination of coffee and tea, extraction of hops, spices, etc.). The specific physical and chemical properties of scf make them particularly suitable for a variety of other applications, e. g. reactions, powder technology and impregnation. 

Other reagents and solvents were obtained from commercial sources. The samples were prepared by mixing various chiral bases with racemic acids in 0.5 1 molar ratio. A porous supporting material (Perfilt), impregnated with these mixtures, was put into the extractor vessel and extracted with supercritical carbon dioxide. 

Impregnation of Porous Supports with Active Substances by Means of Supercritical Fluids... 

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