METHOD OF PREPARING MAGNETIC FLUID Russian patent published in 2003 - IPC

FIELD: magnetic materials. SUBSTANCE: invention relates to manufacturing magnetic fluid seals, inclination and acceleration transducers, magnetic lubricants. FeCl₃•6H₂O (256 g) and FeSO₄•7H₂O (133 g) are dissolved separately in 2 l distilled water. Solutions are combined and 6% aqueous ammonia solution is poured to pH 11. Resulting precipitate of colloidal magnetite is washed and separated. Magnetite is stabilized in aqueous acetic acid solution at 90 C and stirring with surfactant preheated to 90 C. The latter is fatty acid anhydrides in fatty acid solution at ratio 0.5-2.5, respectively. Fatty acids with acid radical length C11-C25 and C7-C18-fatty acids can be used. Stabilized magnetite is treated at 50-70 C first with nonpolar solvent and then with polar solvent, while controlling fullness of iron and surfactant removal. Thus treated magnetite is peptized in nonpolar dispersion medium, for example liquid linear-structure polymethylsiloxane of general formula M₂D_n, where n=1-8, M is (C₂H₅)₃SiO_0,5, and D is (C₂H₅)₂SiO, or synthetic hydrocarbon oils based on C5-C20-olefin polymer. EFFECT: increased aggregative stability, reduced viscosity, and enhanced magnetization saturation. 6 cl, 3 tbl, 3 ex