US4136158A
Expired / Lapsed
US
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Production of acicular magnetic iron oxides
Assignee: Toda Kogyo Corp
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Filing: 1977-11-01
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Granted: 1979-01-23
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Expires: 1997-11-01
Abstract
Abstract In the production of acicular ferromagnetic iron oxide of highly uniform particle size by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, reducing and optionally further reoxidizing this into ferromagnetic iron oxide, the improvement which comprises providing the iron (II) hydroxide suspension with a water-soluble silicate in an amount of less than 1.7% by atom based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si to Fe (II) while prior to the oxidation of the suspension with the oxygen-containing gas.
Inventors
- 👤 Yosiro Okuda
- 👤 Nanao Horiishi
- 👤 Hiroshi Sumita
- 👤 Tosiharu Harada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 14:44
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70663; C; C01; C01G; C01G49/00; C01G49/02; C01G49/06; C01P; C01P2004/00; C01P2004/54; C01P2004/60; C01P2004/62; C01P2006/00; C01P2006/42
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
104 words
In the production of acicular ferromagnetic iron oxide of highly uniform particle size by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, and reducing said acicular iron (III) oxide hydroxide into ferromagnetic iron oxide, the improvement which comprises: prior to the oxidation of said suspension with said oxygen-containing gas, providing said iron (II) hydroxide suspension with a water-soluble silicate in an amount of 0.1-1.7 atomic % based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si to Fe (II).
Claim 2
Dependent Claim
104 words
In the production of acicular ferromagnetic iron oxide of highly uniform particle size by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, and reducing said acicular iron (III) oxide hydroxide into ferromagnetic iron oxide, the improvement which comprises: prior to the oxidation of said suspension with said oxygen-containing gas, providing said iron (II) hydroxide suspension with a water-soluble silicate in an amount of 0.1-1.7 atomic % based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si to Fe (II).
Claim 3
Dependent Claim
26 words
The process of claim 1, wherein said ferromagnetic iron oxide produced by reducing said iron (III) oxide hydroxide is further oxidized into ferromagnetic iron (III) oxide.
Claim 4
Dependent Claim
50 words
The process of claim 1, in which the amount of water-soluble silicate contained in the iron (II) hydroxide suspension is in the range of 0.1 to 1.7 atomic % based on the amount of iron (II) hydroxide in the suspension and calculated as the ratio of Si to Fe (II).
Claim 5
Dependent Claim
31 words
The process of claim 3, in which the reduction of the acicular iron (III) oxide hydroxide is carried out in a reducing gas at a temperature between 300° and 600° C.
Claim 6
Dependent Claim
26 words
The process of claim 4, in which the reduction temperature of the acicular iron (III) oxide hydroxide is in the range of 400° to 550° C.
Claim 7
Dependent Claim
70 words
The process of claim 1, in which the iron (II) hydroxide suspension is prepared by precipitating iron (II) hydroxide from an aqueous iron (II) salt solution by addition of an aqueous alkaline solution containing water-soluble silicate in an amount between 0.1 and 1.7 atomic % based on the amount of the iron (II) hydroxide in the suspension to be formed and calculated as the ratio of Si to Fe (II).
Claim 8
Dependent Claim
31 words
The process of claim 6, in which the reduction of the acicular iron (III) oxide hydroxide is carried out in a reducing gas at a temperature between 300° and 600° C.
Claim 9
Dependent Claim
26 words
The process of claim 7, in which the reduction temperature of the acicular iron (III) oxide hydroxide is in the range of 400° to 550° C.
Claim 10
Dependent Claim
134 words
In the production of acicular ferromagnetic iron oxide of highly uniform particle size and large length-to-width ratio by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, and reducing said acicular iron (III) oxide hydroxide into ferromagnetic iron oxide, the improvement which comprises: prior to the oxidation of said suspension with said oxygen-containing gas, providing said iron (II) hydroxide suspension with a water-soluble silicate and zinc compound in amounts between 0.1-1.7 atomic % and 0.1-2.3 atomic % based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si or Zn to Fe (II) respectively, the ratio of Si plus Zn to Fe (II) being in the range of 0.3-2.5 atomic %.
Claim 11
Dependent Claim
134 words
In the production of acicular ferromagnetic iron oxide of highly uniform particle size and large length-to-width ratio by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, and reducing said acicular iron (III) oxide hydroxide into ferromagnetic iron oxide, the improvement which comprises: prior to the oxidation of said suspension with said oxygen-containing gas, providing said iron (II) hydroxide suspension with a water-soluble silicate and zinc compound in amounts between 0.1-1.7 atomic % and 0.1-2.3 atomic % based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si or Zn to Fe (II) respectively, the ratio of Si plus Zn to Fe (II) being in the range of 0.3-2.5 atomic %.
Claim 12
Dependent Claim
49 words
The process of claim 9, in which the ratios of Si to Fe (II) and Zn to Fe (II) are in the ranges of 0.3-0.7 atomic % and 1.0-2.0 atomic % respectively, the ratio of Si plus Zn to Fe (II) is in the range of 1.0-2.5 atomic %.
Claim 13
Dependent Claim
26 words
The process of claim 9, wherein said ferromagnetic iron oxide produced by reducing said iron (III) oxide hydroxide is further oxidized into ferromagnetic iron (III) oxide.
Claim 14
Dependent Claim
31 words
The process of claim 9, in which the reduction of the acicular iron (III) oxide hydroxide is carried out in a reducing gas at a temperature between 300° and 600° C.
Claim 15
Dependent Claim
26 words
The process of claim 12, in which the reduction temperature of the acicular iron (III) oxide hydroxide is in the range of 400° to 550° C.
Claim 16
Dependent Claim
70 words
The process of claim 9, in which the iron (II) hydroxide suspension is prepared by precipitating iron (II) hydroxide from an aqueous iron (II) salt solution by addition of an aqueous alkaline solution containing water-soluble silicate in an amount between 0.1 and 1.7 atomic % based on the amount of the iron (II) hydroxide in the suspension to be formed and calculated as the ratio of Si to Fe (II).
Claim 17
Dependent Claim
50 words
The process of claim 14, in which the ratios of Si to Fe (II) and Zn to Fe (II) are in the ranges of 0.3-0.7 atomic % and 1.0-2.0 atomic % respectively, while the ratio of Si plus Zn to Fe (II) is in the range of 1.0-2.5 atomic %.
Claim 18
Dependent Claim
31 words
The process of claim 15, in which the reduction of the acicular iron (III) oxide hydroxide is carried out in a reducing gas at a temperature between 300° and 600° C.
Claim 19
Dependent Claim
26 words
The process of claim 16, in which the reduction temperature of the acicular iron (III) oxide hydroxide is in the range of 400° to 550° C.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-01-22 | 1982-07-24 | 1983-01-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-01-22 | 1986-07-24 | 1987-01-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-01-22 | 1990-07-24 | 1991-01-23 | $7700.00 | Window Closed / Lapsed |