| 摘要 |
PROBLEM TO BE SOLVED: To improve oxidation resistance by dispersing ferrite group particles coated with a surface active agent into kerosine-based oil in the presence of monoalkyl ether, or monoaliphatic acid ester of hydroquinone, ammonium salt thereof, or organic amine salt thereof. SOLUTION: Ferrite group particles coated with a surface active agent, to which a hydroquinone derivative is added as an additive, are dispersed into kerosine-based oil or an aqueous medium, thereby preparing a magnetic fluid. As the hydroquinone derivative, monoalkyl ether or monoaliphatic acid ester of hydroquinone is used. Alternatively, the hydroquinone derivative is used, when the remaining hydroxyl group in a free state is caused to form a salt with ammonium or organic amine. In the case where the particles are dispersed into the aqueous medium, a surface active agent is used together with the hydroquinone derivative (salt). |
