| 摘要 |
PROBLEM TO BE SOLVED: To improve chemical stability by covering with surface modifying agent a region which is not covered with surface active agent on the surface of a magnetic particle. SOLUTION: A magnetic fluid consists of magnetic particles at 0.1-40 volume percent, surface active agent at 0.1 to about 33 volume percent, an organic carrier medium at 10- about 99 volume percent and surface modifying agent or addition agent at 0.01 to about 25 volume percent. To cover an exposed surface region of the magnetic particle uncovered with surface active agent, surface-modifying agent or addition agent is added at low molecular weight. The addition agent includes acid-based addition agent and amine-based addition agent, and surface active agent includes silane-based surface active agent and titanium-coupling agent. Acetic acid and benzoic acid are used in the acid-based addition, allantoic acid and tripropylamine are used in the amine-based addition agent. After organic carrier medium are molded at high molecular weight, the magnetic particles are scattered when the carrier medium is vaporized at raised temperature. |
