Preparation of microcapsules containing fine antimicrobial particles by sol-gel process in reverse suspension

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When silver thiosulfato complex was used as antimicrobial material, dispersing-type microcapsule was not obtained because of the segregation of the complex onto the capsule surface. The complex content inside the microcapsule was somewhat improved by using dispersion stabilizer. However, the complex was released very fast, when the microcapsules were suspended in water. It was found that they were not suitable for the use as antimicrobial materials to be served for a long term.Thus, fine AgCl particles were used instead of silver thiosulfato complex. Polyvinylalcohol (PVA) of a nonionic surfactant was the most effective as a dispersion stabilizer, resulting in microcapsule in which AgCl was uniformly dispersed. The Use of anionic or cationic surfactant did not form stable dispersion. The AgCl content of the microcapsule and the amount of AgCl released to water increased with the increase in the dispersion stabilizer concentration. The release rate decreased with the dispersion stabilizer concentration to about 6% for 48 h.These microcapsules were changed to gray in color during the ordinary handling. This is due to decomposition of AgCl by UV irradiation. By hybridizing the microcapsules with titania from TTIP, they were kept white in color. This is suggested that titania is effective for shielding from UV irradiation and hiding the inside of the microcapsule. The addition of TTIP of 20 - 50 mol/m^3 to the continuous phase resulted in good composites.The antimicrobial effect of the microcapsule was confirmed by cultivating a colon bacillus (Escherichia coli) in suspension of the microcapsules.