Supsakulchai A, Ma G H, Nagai M, Omi S
Graduate School of Bio-Applications and Systems Engineering (BASE), Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei, Tokyo, 184-8588, Japan.
J Microencapsul. 2002 Jul-Aug;19(4):425-49. doi: 10.1080/02652040210142542.
Anatase-type titanium dioxide (TiO(2)) was encapsulated using an Shirasu porous glass (SPG) membrane emulsification technique and followed by solvent evaporation. The oil phase, consisting of fine#10; powder of anatase TiO(2), Disperbyk-180, the hydrophobic oil phase additive, and polymer wall solution, was pushed through the membrane pores into the aqueous phase of poly(vinyl alcohol) and sodium dodecyl sulfate to form the solid-in-oil-in water, (S/O)/W, emulsion droplets. Three types of styrene-based copolymer poly(styrene-co-acrylic acid) (PS-AA), poly(styrene-co-2-ethyl hexyl acrylate) (PS-2EHA) and poly(styrene-co-dimethyl aminoethylmethacrylate) (PS-DMAEMA) were used as an encapsulating shell. Uniform droplets were successfully obtained by modifying the oil phase using methyl laurate or hexadecanol as the oil phase additive, together with carefully monitoring the emulsification flow rate during the emulsification. The (S/O)/W emulsion was gently stirred in a sealed reactor, and evacuation of solvent started under moderate heating with increasing a vacuum intensity. Those uniform-sized TiO(2) microcapsules revealed fine porous morphologies on their surfaces as a result of a mild phase separation induced from the addition of the oil phase additive. The encapsulation efficiency was influenced by the stability of TiO(2) in the oil phase, the polymer wall employed, and the operational control of the glass membrane emulsification process. The membrane emulsification process could prepare the TiO(2) microcapsules with about approximately 6-8.5 wt% of encapsulation loadings. PS-AA and PS-2EHA copolymers provided better encapsulation efficiency compared to PS-DMAEMA. SPG membranes with 1.42, 2.8, 5.25, 7.0, or 9.5 microm were employed and 2-20 microm microcapsules were subsequently obtained.
采用白土多孔玻璃（SPG）膜乳化技术对锐钛矿型二氧化钛（TiO₂）进行包封，随后进行溶剂蒸发。将由锐钛矿TiO₂细粉、疏水油相添加剂Disperbyk - 180和聚合物壁溶液组成的油相通过膜孔挤入聚乙烯醇和十二烷基硫酸钠的水相中，形成水包油包固体（S/O）/W乳液滴。使用三种苯乙烯基共聚物聚（苯乙烯 - 丙烯酸）（PS - AA）、聚（苯乙烯 - 2 - 乙基己基丙烯酸酯）（PS - 2EHA）和聚（苯乙烯 - 二甲基氨基乙基甲基丙烯酸酯）（PS - DMAEMA）作为包封壳。通过使用月桂酸甲酯或十六醇作为油相添加剂对油相进行改性，并在乳化过程中仔细监测乳化流速，成功获得了均匀的液滴。将（S/O）/W乳液在密封反应器中轻轻搅拌，并在适度加热下随着真空强度的增加开始抽提溶剂。由于添加油相添加剂引起的温和相分离，那些尺寸均匀的TiO₂微胶囊在其表面呈现出精细的多孔形态。包封效率受TiO₂在油相中的稳定性、所采用的聚合物壁以及玻璃膜乳化过程的操作控制影响。膜乳化过程可以制备包封量约为6 - 8.5 wt%的TiO₂微胶囊。与PS - DMAEMA相比，PS - AA和PS - 2EHA共聚物具有更好的包封效率。使用孔径为1.42、2.8、5.25、7.0或9.5微米的SPG膜，随后获得了2 - 20微米的微胶囊。
