Xerox Corporation

Allan C Berg

Lewis O Jones

John W Fitzpatrick

A process for preparing humidity-insensitive electrostatographic ferrite carrier materials comprising dry-blending ferrite-forming metal oxides, calcining the blended oxides to provide them with a saturation magnetic moment of about 6 to 30 electromagnetic units per gram, milling the calcined oxides in a slurry to reduce their particle size to about 0.8 to 1.6 microns while adding manganese oxide, copper oxide, and a sodium-free deflocculant to the slurry, pumping the milled slurry to holding/feeding tanks and adding a binder material to the slurry, spray-drying the slurry to form substantially spherical beads, screening the spray-dried beads, firing the screened beads in an ambient atmosphere at a temperature of up to about 2500.degree. F. for up to about 8 hours, deagglomerating the fired beads, and screening the beads to obtain ferrite carrier particles having controlled surface species and physical properties.

Production of ferrite electrostatographic carrier materials having

Humidity-insensitive electrostatographic ferrite carrier materials having an average particle diameter from between about 30 to about 1,000 microns prepared by blending an essentially stoichiometric mixture of ferrite forming metal oxides, calcining the blended oxides to provide the blended oxides with a saturation magnetic moment of between about 6 to about 30 electromagnetic units per gram, milling the calcined oxides in a slurry to reduce their particle size, adding manganese oxide, copper oxide, sodium-free deflocculant, and water to the slurry to provide a slurry having about 80.0 percent by weight of solids, pumping the slurry to hold/feed tanks with continuous mixing while adding a binder material, spray-drying the slurry, screening the particles, firing the particles to provide them with a saturation magnetic moment of about 48 electromagnetic units per gram, deagglomerating the particles, and screening the particles to obtain ferrite particles characterized as having surface sodium in an amount of less than about 20 parts per million, surface zinc in an amount of less than about 5,000 parts per million, and a BET surface area of between about 170 cm.sup.2 /gram and about 500 cm.sup.2 /gram.

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Rochester, NY, United States of America

Allan C Berg