| 摘要 |
PURPOSE:To obtain a magnetic fluid dispersed in a high-boiling base oil reading, by dripping a dispersion of ultrafine particles of ferrite having adsorbed a surface active agent in a low-boiling base oil into a hot high-boiling base oil and evaporating the low-boiling base oil to carry out replacement of the base oil. CONSTITUTION:(A) A dispersion of ultrafine particles of ferrite having adsorbed a surface active agent in a low-boiling base oil is dipped into (B) high-boiling base oil having compatibility with the low-boiling base oil and heated at >=150 deg.C, and low-boiling base oil is evaporated and replacement of the base oil is carried out to give the aimed magnetic fluid. A hydrocarbon solvent having 30-110 deg.C boiling point is preferable as the low-boiling base oil and a higher alkyl- substituted naphthalene of dicarboxylic acid di-higher-alkyl ester, etc., is preferable as the high-boiling base oil. |
