Hydrophobized spherical polyalkylsilsesquioxane fine particles, external additive for toner, dry toner for electrophotography, and method for producing hydrophobized spherical polyalkylsilsesquioxane fine particles

摘要

Polyalkylsilsesquioxane fine particles having hydrophobicity and small particle size, external additives for toner using the same, dry toner for electrophotography, and a method for producing hydrophobized spherical polyalkylsilsesquioxane fine particles provide. Hydrophobized spherical polyalkylsilsesquioxane fine particles having a median diameter based on mass by centrifugal sedimentation method within a range of 0.05 to 0.3 m. The fine particles are obtained, for example, by mixing a raw material solution prepared using an alkyltrialkoxysilane and an alkaline aqueous medium to obtain a polycondensation reaction solution, further mixing this polycondensation reaction solution with an aqueous solution to obtain fine particle dispersion To obtain a liquid, and then adding a hydrophobizing agent to the fine particle dispersion.