| 摘要 |
PURPOSE:To obtain a high-quality magnetic fluid at a high efficiency by incorporating the step of forming agglomerates of ferrite particles of a high precipitation speed with a polar solvent and the step of washing these agglomerates with a mixture of a polar solvent with water to remove water-soluble impurities in a conventional process for producing a magnetic fluid. CONSTITUTION:This process comprises the steps of (1) forming fine ferromagnetic ferrite particles by coprecipitation, (2) modifying the surfaces of the particles with a surfactant, (3) dispersing these particles in a nonpolar or weakly polar solvent, (4) forming agglomerates of a high precipitation speed with a polar solvent, (5) washing the agglomerates with a mixture of a polar solvent with water, (6) redispersing the washed product from the step (5) in a nonpolar or weakly polar solvent, and (7) optionally adding a base oil to the formed dispersion to replace the solvent. |
