Patent US4406694A successfully refreshed from Google Patents.
US4406694A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing acicular ferromagnetic alloy particles and acicular ferromagnetic alloy particles obtained by the said process
Assignee: Toda Kogyo Corp
•
Filing: 1981-07-23
•
Granted: 1983-09-27
•
Expires: 2001-07-23
Abstract
Abstract A process for producing an acicular ferromagnetic alloy particles mainly containing iron and magnesium, which comprises preparing a suspension of iron(II) hydroxide and water-soluble magnesium salt, the suspension having a pH value of at least 11 and containing the magnesium salt in an amount of 0.5 to 20.0 atomic % based on the amount of the iron(II) hydroxide in the suspension and calculated as the ratio of Mg to Fe(II), oxidizing the suspension with an oxygen-containing gas to form an acicular particles of iron(III) oxide hydroxide substituted with magnesium, forming coats of phosphorus compound and subsequent silicon compound on the acicular particles, heating the resultant particle at 500° to 900° C. under a non-reducing atmosphere and then reheating the particle thus treated at 350° to 600° C. under reducing atmosphere.
Inventors
- 👤 Akio Mishima
- 👤 Yosiro Okuda
- 👤 Tosiharu Harada
- 👤 Akira Mukaizaka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:33
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
130 words
A process for producing an acicular ferromagnetic alloy particles mainly containing iron and magnesium, which comprises preparing a suspension of iron(II) hydroxide and water-soluble magnesium salt, the suspension having a pH value of at least 11 and containing the magnesium salt in an amount of 0.5 to 20.0 atomic % based on the amount of the iron(II) hydroxide in the suspension and calculated as the ratio of Mg to Fe(II), oxidizing the suspension with an oxygen-containing gas to form an acicular particles of iron(III) oxide hydroxide substituted with magnesium, forming coats of phosphorus compound and subsequent silicon compound on the acicular particles, heating the resultant particle at 500° to 900° C. under a non-reducing atmosphere and then reheating the particle thus treated at 350° to 600° C. under reducing atmosphere.
Claim 2
Dependent Claim
130 words
A process for producing an acicular ferromagnetic alloy particles mainly containing iron and magnesium, which comprises preparing a suspension of iron(II) hydroxide and water-soluble magnesium salt, the suspension having a pH value of at least 11 and containing the magnesium salt in an amount of 0.5 to 20.0 atomic % based on the amount of the iron(II) hydroxide in the suspension and calculated as the ratio of Mg to Fe(II), oxidizing the suspension with an oxygen-containing gas to form an acicular particles of iron(III) oxide hydroxide substituted with magnesium, forming coats of phosphorus compound and subsequent silicon compound on the acicular particles, heating the resultant particle at 500° to 900° C. under a non-reducing atmosphere and then reheating the particle thus treated at 350° to 600° C. under reducing atmosphere.
Claim 3
Dependent Claim
33 words
The process of claim 1, wherein the acicular iron(III) oxide hydroxide is a particle of the length of long axis of 0.3 to 2.0 μm and the axial ratio of more than 20:1.
Claim 4
Dependent Claim
115 words
The process of claim 1, wherein the step of forming coats comprises the steps of: preparing an aqueous suspension of acicular iron(III) oxide hydroxide while adjusting the pH of the suspension at a value higher than 8; adding a phosphate in an amount of 0.1 to 2 wt% calculated as the amount of PO 3 and based on the amount of the iron(III) oxide hydroxide into the suspension; adding a water-soluble silicate in an amount of 0.1 to 7.0 wt% calculated as the amount of SiO 2 and based on the amount of the iron(III) oxide hydroxide into the suspension; and then adjusting the pH of the suspension in the range of 3 to 7.
Claim 5
Dependent Claim
42 words
The process of claim 1, wherein the amount of water-soluble magnesium salt is preferably in the range of 0.5 to 15.0 atomic % based on the amount of iron(II) hydroxide in the suspension and calculated as the ratio of Mg to Fe(II).
Claim 6
Dependent Claim
126 words
An acicular ferromagnetic alloy particles mainly containing iron and magnesium obtained by preparing a suspension of iron(II) hydroxide and water-soluble magnesium salt, the suspension having a pH value of at least 11 and containing the magnesium salt in an amount of 0.5 to 20.0 atomic % based on the amount of the iron(II) hydroxide in the suspension and calculated as the ratio of Mg to Fe(II), oxidizing the suspension with an oxygen-containing gas to form an acicular particles of iron(III) oxide hydroxide substituted with magnesium, forming coats of phosphorus compound and subsequent silicon compound on the acicular particles, heating the resultant particle at 500° to 900° C. under a non-reducing atmosphere and then reheating the particle thus treated at 350° to 600° C. under reducing atmosphere.
Claim 7
Dependent Claim
126 words
An acicular ferromagnetic alloy particles mainly containing iron and magnesium obtained by preparing a suspension of iron(II) hydroxide and water-soluble magnesium salt, the suspension having a pH value of at least 11 and containing the magnesium salt in an amount of 0.5 to 20.0 atomic % based on the amount of the iron(II) hydroxide in the suspension and calculated as the ratio of Mg to Fe(II), oxidizing the suspension with an oxygen-containing gas to form an acicular particles of iron(III) oxide hydroxide substituted with magnesium, forming coats of phosphorus compound and subsequent silicon compound on the acicular particles, heating the resultant particle at 500° to 900° C. under a non-reducing atmosphere and then reheating the particle thus treated at 350° to 600° C. under reducing atmosphere.
Claim 8
Dependent Claim
36 words
The acicular ferromagnetic alloy particles of claim 5, wherein the acicular iron(III) oxide hydroxide is a particle of the length of long axis of 0.3 to 2.0 μm and the axial ratio of more than 20:1.
Claim 9
Dependent Claim
118 words
The acicular ferromagnetic alloy particles of claim 5, wherein the step of forming coats comprises the steps of: preparing an aqueous suspension of acicular iron(III) oxide hydroxide while adjusting the pH of the suspension at a value higher than 8; adding a phosphate in an amount of 0.1 to 2 wt% calculated as the amount of PO 3 and based on the amount of the iron(III) oxide hydroxide into the suspension; adding a water-soluble silicate in an amount of 0.1 to 7.0 wt% calculated as the amount of SiO 2 and based on the amount of the iron(III) oxide hydroxide into the suspension; and then adjusting the pH of the suspension in the range of 3 to 7.
Claim 10
Dependent Claim
45 words
The acicular ferromagnetic alloy particles of claim 5, wherein the amount of water-soluble magnesium salt is preferably in the range of 0.5 to 15.0 atomic % based on the amount of iron(II) hydroxide in the suspension and calculated as the ratio of Mg to Fe(II).
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) | 1986-09-26 | 1987-03-28 | 1987-09-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-09-26 | 1991-03-28 | 1991-09-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-09-26 | 1995-03-28 | 1995-09-27 | $7700.00 | Window Closed / Lapsed |