Method of producing precipitated magnetites
AssigneeBayer Aktiengesellschaft
InventorUlrich Meisen
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Abstract
The present invention relates to a method of producing magnetite particles useful for the production of toners by (a) placing an alkaline component in the form of an aqueous solution in a vessel under a protective gas, (b) adding 1.0 to 3.0 mol %, relative to Fe of the magnetite, of a silicate component to form a reaction mixture, (c) heating the reaction mixture to a precipitation temperature of 60 to 80° C., (d) adding an iron(II) component at a rate of 0.5 to 1.5 mol of Fe/hour per mol of the alkaline component until the pH of the suspension is 7.0 to 8.5, and (e) oxidizing the suspension with an oxidizing agent at a rate of 20 to 5 mol % of Fe(II)/hour to an Fe(III) content of 65 to 75 mol % of Fe(III).
Claims10
A method of producing a magnetite having a specific surface of 9 to 15 m2/g, a coercivity of 45 Oe to 75 Oe, and a settled apparent density of 1.1 to 1.3 g/cm3 comprising
- (a) placing an alkaline component in the form of an aqueous solution in a vessel under a protective gas,
- (b) adding 1.0 to 3.0 mol %, relative to Fe of the magnetite, of a silicate component to form a reaction mixture,
- (c) heating the reaction mixture to a precipitation temperature of 60 to 80° C.,
- (d) adding an iron(II) component at a rate of 0.5 to 1.5 mol of Fe/hour per equivalent of the alkaline component until the pH of the suspension is 7.0 to 8.5, and
- (e) oxidizing the suspension with an oxidizing agent at a rate of 20 to 5 mol % of Fe(II)/hour to an Fe(III) content of 65 to 75 mol % of Fe(III).
Dependencies are inferred from the claim text.