| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain powdery magnetite used suitably for magnetic toners for electrophotography and resin dispersion carriers. SOLUTION: This powdery magnetite is coated with 0.1-29wt.% of an aqueous type of resin, preferably an emulsified resin composed of polyvinyl acetate, vinyl acetate-acrylic copolymer, water-soluble colloidal dispersion resin composed essentially of alkyd- or epoxyester-based resin, or water-soluble resin composed essentially of alkyd or acrylic resin, and SiO2 , and has preferably 40sec or shorter bulk density measurement time measured with a powder tester and agitation torque of 0.016kg.cm or less.</p> |
