Spinel-type spherical, black iron oxide particles and process for the producing the same

• US 5,336,421 A
• Filed: 08/10/1993
• Issued: 08/09/1994
• Est. Priority Date: 11/22/1990
• Status: Expired due to Fees

• Current Assignee: TODA Kogyo Corporation
• Original Assignee: TODA Kogyo Corporation
• Inventors: Kurokawa, Haruki, Kurita, Eiichi, Fujioka, Kazuo
• Primary Examiner(s): Cooper, Jack
• Application Number:
  US08/104,401
• Time in Patent Office: 364 Days
• Field of Search: 252/62.62, 423/594
• US Class Current: 252/62.62
• CPC Class Codes: C01G 49/0063 containing zinc
• CPC Class Codes: C01P 2002/32 spinel-type (AB2O4)
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/32 Spheres
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/42 Magnetic properties
• CPC Class Codes: C01P 2006/60 Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: G03G 9/0833 Oxides
• CPC Class Codes: G03G 9/0835 Magnetic parameters of the magnetic components
• CPC Class Codes: G03G 9/0836 Other physical parameters of the magnetic components
• CPC Class Codes: G03G 9/0837 Structural characteristics of the magnetic components, e.g. shape, crystallographic structure
• CPC Class Codes: G03G 9/1075 Structural characteristics of the carrier particles, e.g. shape or crystallographic structure
• CPC Class Codes: G03G 9/108 Ferrite carrier, e.g. magnetite
• CPC Class Codes: G11B 5/70642 iron oxides

Abstract

Disclosed herein are spinel-type spherical black iron oxide particles containing 1.5 to 17.0 wt % of Zn, and having a specific surface area of 5 to 15 m² /g, a magnetization of not less than 70 emu/g in an external magnetic field of 1 kOe and a coercive force (Hc) of not more than the value obtained from the following expression:

Hc(Oe)=15+3×(specific surface area of the particles).

and a process for producing the same.

Claims

1. Spinel-type spherical black iron oxide particles having the formula:

space="preserve" listing-type="equation">Zn.sub.x Fe.sub.1-x O.Fe.sub.2 O.sub.3

2. wherein x is a number in the range of 0.05 to 0.62, said particles containing 1.5 to 17.0 wt % of Zn, and having a specific surface area of 5 to 15 m² /g, a magnetization of not less than 70 emu/g in an external magnetic field of 1 kOe and a coercive force (Hc) of not more than the value obtained from the following expression:

space="preserve" listing-type="equation">Hc(Oe)=15+3×

(specific surface area of the particles).

3. Spinel-type spherical black iron oxide particles having the formula:

space="preserve" listing-type="equation">Zn.sub.x Fe.sub.1-x O.Fe.sub.2 O.sub.3

4. wherein x is a number in the range of 0.05 to 0.62, said particles containing 1.5 to 17.0 wt % of Zn, and having a specific surface area of 5 to 15 m² /g, a magnetization of not less than 70 emu/g in an external magnetic field of 1 kOe and a coercive force (Hc) of not more than the value obtained from the following expression:

space="preserve" listing-type="equation">Hc(Oe)=15+3×

(specific surface area of the particles)

said particles produced by preparing a mixed suspension which contains ferrous hydroxide and zinc hydroxide and which has a pH of 6 to 9 in a non-oxidizing atmosphere by using an aqueous ferrous salt solution, a zinc compound and an aqueous alkaline solution; and

blowing an oxygen-containing gas into the mixed suspension so as to oxidize ferrous hydroxide until the pH reaches a value in the range of 4 and 6 and the oxidation degree is such that Fe³⁺ in the mixed suspensions is 60 to 70 mol % based on the total amount of iron and zinc in the oxidization step.

5. A process for producing spinel-type spherical black iron oxide particles having the formula:

space="preserve" listing-type="equation">Zn.sub.x Fe.sub.1-x O.Fe.sub.2 O.sub.3

6. wherein x is a number in the range of 0.05 to 0.62, said particles containing 1.5 to 17.0 wt % of Zn, and having a specific surface area of 5 to 15 m² /g, a magnetization of not less than 70 emu/g in an external magnetic field of 1 kOe and a coercive force (Hc) of not more than the value obtained from the following expression:

space="preserve" listing-type="equation">Hc(Oe)=15+3×

(specific surface area of the particles),

said process comprising the steps of;

(a) preparing a mixed suspension which contains ferrous hydroxide and sufficient zinc hydroxide to produce black iron oxide particles containing 1.5 to 17.0 wt % zinc by weight based upon the product and which has a pH of 6 to 9 in a non-oxidizing atmosphere by using an aqueous ferrous salt solution, a zinc compound and an aqueous alkaline solution; and

(b) oxidizing the ferrous hydroxide by blowing an oxygen-containing gas into the mixed suspension so as to oxidize ferrous hydroxide until the pH reaches a value in the range of 4 to 6 and the oxidation degree is such that Fe³⁺ in the mixed suspension is 60 to 70 mol % based on the total amount of iron and zinc in the oxidation step.