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Research paper : Establishment of compact processes (A. Suzuki et al.)−159−Synthesiology - English edition Vol.3 No.2 (2010) that could be used was limited due to the problem of line clogging. In contrast, the carbon dioxide painting process that we developed uses the high-pressure micromixer based on the turbulence mixing theory, and enables extremely fast mixing and allows stable painting regardless of the type of paint. The conceptual flow diagram of the carbon dioxide painting technology is shown in Fig. 15. The paint and carbon dioxide are mixed instantly in the mixer, and the carbon dioxide dissolves completely in the paint. As a result, the viscosity decreases and spraying is enabled. The mixer was a version of the central collision micromixer modified for painting, and it was originally developed to realize the rapid heat exchange in the supercritical water reaction. As a result of evaluation by a third party of the painted sample using this method (mixer condition: 40 ºC, 10 MPa), it was confirmed that the paint film quality was of practical level[20]. Therefore, the VOC from the thinner solvent can be basically reduced, and seen from the amount of thinner solvent used currently (several hundred-thousand tons per year), the effect of reduction is thought to be significant.5 Summary and future developmentThe organic and inorganic synthesis reactions using high-temperature and high-pressure water have the potential of greatly changing the conventional process of the large-scale production at concentrated sites. In this reaction field, an efficient and ideal substance synthesis is possible through rapid and precise temperature, pressure, and spatiotemporal control. As a result, fine chemical synthesis and creation of high value-added substance by natural product conversion in addition to bulk chemical synthesis is strongly expected.For example, the -caprolactam that was described as the prologue in the organic synthesis using supercritical water is produced at about 100,000-ton scale per year per factory. It consumes the same amount of sulfuric acid and about half of ammonia, and discards about 1.5 times the amount of ammonium nitrate as waste product. If this is done as low-volume distributed production using the supercritical water organic synthesis of 10,000-ton scale per year, production is possible without using sulfuric acid or ammonia. Though further advancement in high-pressure microengineering is necessary to increase the processing amount at a basic unit (structure), to achieve this, a compact process of 10,000-ton scale per year can be realized.On the other hand, the quick diffusion of carbon dioxide painting is demanded as the key technology for reducing VOC. The objective of this technology is not simply to reduce VOC, but also to save energy by reducing the energy for the drying process etc, and can be considered as the key technology in reducing carbon dioxide. The atomization using carbon dioxide can also be applied to wide ranging areas such as the technologies for painting, printing, adhesion, and application (film coating) of functional films, as well as particle technologies for drugs, polymers, and functional substances.The establishment of high-pressure microengineering to realize the integration of the microreactor technology and the supercritical fluid technology will help to realize the low-volume distributed production (compact process) and contribute greatly to a sustainable society.Fig. 15 Schematic diagram of carbon dioxide painting technologyCentral collision type micromixer developed for painting was employed as the mixer. Object to bepaintedSpray gunMixerPaint tankHeaterHigh-pressurepaint pumpCoolerCarbon dioxidegas cylinderHeaterHigh-pressureCO2 pumpK. Mae: Advanced chemical processing using microspace, Chem. Eng. Sci., 62, 4842-4851 (2007).H. Weingärtner and E. U. Franck: Supercritical water a solvent, Angew. Chem. Int. Ed., 44, 2672-2692 (2005).W. L. Marshall and E. U. Franck: Ion product of water substance, 0–1000 ºC, 1–10,000 bars new international formulation and its background, J. Phys. Chem. Ref. Data, 10, 295-304 (1981).P. G. Jessop, W. Leitner eds.: Chemical Synthesis Using Supercritical Fluids, WILEY-VCH, Weinheim (1999).O. Sato, Y. Ikushima and T. Yokoyama: Noncatalytic Beckmann rearrangement of cyclohexanone-oxime in supercritical water, J. Org. Chem., 63, 9100-9102 (1998).Y. Ikushima, H. Hatakeda, O. Sato, T. Yokoyama and M. Arai: Acceleration of synthetic organic reactions using supercritical water, Noncatalytic Beckmann and pinacol rearrangements, J. Am. Chem. Soc., 122, 1908-1918 (2000).Y. Ikushima, K. Hatakeda, O. Sato, T. Yokoyama and M. Arai: Structure and base catalysis of supercritical water in the noncatalytic benzaldehyde disproportionation using water at high temperatures and pressures, Angew. Chem. Int. Ed., 40, 210-213 (2001).Y. Ikushima, K. Hatakeda, M. Sato, O. Sato and M. Arai: Innovation in a chemical reaction process using a supercritical water microreaction system: environmentally friendly production of -caprolactam, Chem. Commun., 2208-2209 (2002).S. –I. Kawasaki, Y. Wakashima, A. Suzuki, Y. Hakuta and K. Arai: Continuous hydrothermal synthesis of nano particles using T-shape micromixer, Proc. 11th Euro. Meet. Supercrit. Fluids, (Barcelona) P_PR_36 (2008).Y. Wakashima, A. Suzuki, S. –I. Kawasaki, K. Matsui and Y. Hakuta: Development of a new swirling micromixer for [1][2][3][4][5][6][7][8][9][10]References

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