Patent ID: 6120856
Filing Date: 2000-09-19
Classification: A61K,B03C,G01N,G11B,H01F,Y10T

Abstract:
In a process for making resuspendable, coated magnetic particles by direct application of a coating material to a particulate magnetic substrate, wherein said substrate is prepared from a particulate, magnetic, transition metal oxide starting material selected from the group consisting of chromium (IV) oxide (CrO.sub.2), cobalt ferrite (CoFe.sub.2 O.sub.4), copper ferrite (CuFe.sub.2 O.sub.4), dysprosium ferrogarnet (DyFe.sub.5 O.sub.12), dysprosium orthoferrite (DyFeO.sub.3), erbium orthoferrite (ErFeO.sub.3), gadolinium ferrogarnet (Fe.sub.5 Gd.sub.3 O.sub.12), holmium iron garnet (Fe.sub.5 Ho.sub.3 O.sub.12), iron nickel manganese oxide (FeMnNiO.sub.4), .gamma.-iron oxide (maghemite), iron oxide (magnetite), .alpha.-iron oxide (hematite), lanthanum ferrite (FeLaO.sub.3), magnesium ferrite (MgFe.sub.2 O.sub.4), manganese ferrite (Fe.sub.2 MnO.sub.4), manganese dioxide (MnO.sub.2), neodymium dititanate (Nd.sub.2 O.sub.7 Ti.sub.2), aluminum nickel ferrite (Al.sub.0.2 Fe.sub.1.8 NiO.sub.4), nickel-zinc ferrite (Fe.sub.2 Ni.sub.0.5 O.sub.4 Zn.sub.0.5), nickel zinc ferrite (Fe.sub.2 Ni.sub.0.4 Zn.sub.0.6), nickel zinc ferrite (Fe.sub.2 Ni.sub.0.8 O.sub.4 Zn.sub.0.2), nickel (II) oxide (NiO), nickel ferrite (Fe.sub.2 NiO.sub.4), samarium ferrogarnet (Fe.sub.5 O.sub.12 Sm.sub.3), silver lanthan ferrite (Ag.sub.0.5 Fe.sub.12 La.sub.0.5 O.sub.19), yttrium iron garnet (Fe.sub.5 O.sub.12 Y.sub.3), yttrium orthoferrite (FeO.sub.3 Y), said starting material being subdivided to yield a plurality of aggregable, smaller sized particles, suspended in a liquid medium and contacted with said coating material to form a mixture, before substantial aggregation of said particles occurs, the improvement which comprises heating the mixture to a temperature of at least about 45.degree. C. for a time sufficient for said coating material to adhere to said substrate.