US3911095A
Expired / Lapsed
US
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Preparation of ferromagnetic chromium dioxide having granulometric and magnetic characteristics varying within wide limits as well as a new chromium dioxide of particular granulometric characteristics
Assignee: Montedison SpA
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Filing: 1973-06-28
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Granted: 1975-10-07
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Expires: 1993-06-28
Abstract
Abstract A process is disclosed for obtaining a ferromagnetic chromium dioxide having granulometric and magnetic characteristics varying within a very wide range, starting from hydrated chromium (III) chromate or from mixtures of metal chromium and chromium oxide having a valency greater than 4, by heating up to between 300* and 500*C under an oxygen pressure of 30-1000 atm., characterized in that the variations of the granulometry and of the magnetic characteristics are obtained by regulating the heating, by means external to the reaction mass or by adding to the starting materials from 0.05 to 30% by weight (with respect to the chromium present) of compounds that decompose exothermically between 100* and 270*C under reaction conditions that lead to CrO2 by favoring the reduction to CrO2 in such a way that the reaction mass will cross the temperature interval of from 200* to 300*C in pre-established times, depending on the granulometry and coercive force desired in the product. Suitable exothermically decomposing compounds include ammonia, oxalic acid, lactic acid, citric acid, and tartaric acid. A novel ferromagnetic chromium dioxide is also disclosed.
Inventors
- 👤 Ugo Montiglio
- 👤 Giampiero Basile
- 👤 Pierfrancesco Aspes
- 👤 Luigi Foco
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 22:56
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70636; C; C01; C01G; C01G37/00; C01G37/02; C01P; C01P2002/00; C01P2002/70; C01P2002/72; C01P2002/74; C01P2004/00; C01P2004/54; C01P2004/60; C01P2004/61; C01P2004/62; C01P2006/00; C01P2006/42; C01P2006/60
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
135 words
IN A PROCESS FOR THE PREPARATION OF FERROMAGNETIC CHROMIUM DIOXIDE BY HEATING AT 300* - 500*C UNDER AN OXYGEN PRESSURE OF 30 - 100ATM. A STARTING MATERIAL SELECTED FROM THE GROUP COMPRISING OF: A. A CHROMIUM (222) CHROMATE CR2(CRO4)3. NH2O WHEREIN THE CR6+CR3+ MOLAR RATIO IS BETWEEN 1.2 AND 1.9 AND N IS BETWEEN 1 AND 8, AND B. A MIXTURE OF CHROMIUM METAL AS SUCH OR PASSIVATED, WITH A CHROMIUM OXIDE WITH A VALENCY ABOVE 4: THE IMPROVEMENT CONSISTING IN REGULATING THE HEATING OF SAID STARTING MATERIAL IN SUCH A WAY THAT THE RESIDENCE TIME OF SAID STARTING MATERIAL WITHIN THE 200% - 300*C TEMPERATURE RANGE BETWEEN 20 AND 35 MINUTES WHEN USING STARTING MATERIAL (A) AND IS LONGER THAN 10 MINUTES BUT NO LONGER THAN 35 MINUTES WHEN USING THE STARTING MATERIAL (B).
Claim 2
Dependent Claim
135 words
IN A PROCESS FOR THE PREPARATION OF FERROMAGNETIC CHROMIUM DIOXIDE BY HEATING AT 300* - 500*C UNDER AN OXYGEN PRESSURE OF 30 - 100ATM. A STARTING MATERIAL SELECTED FROM THE GROUP COMPRISING OF: A. A CHROMIUM (222) CHROMATE CR2(CRO4)3. NH2O WHEREIN THE CR6+CR3+ MOLAR RATIO IS BETWEEN 1.2 AND 1.9 AND N IS BETWEEN 1 AND 8, AND B. A MIXTURE OF CHROMIUM METAL AS SUCH OR PASSIVATED, WITH A CHROMIUM OXIDE WITH A VALENCY ABOVE 4: THE IMPROVEMENT CONSISTING IN REGULATING THE HEATING OF SAID STARTING MATERIAL IN SUCH A WAY THAT THE RESIDENCE TIME OF SAID STARTING MATERIAL WITHIN THE 200% - 300*C TEMPERATURE RANGE BETWEEN 20 AND 35 MINUTES WHEN USING STARTING MATERIAL (A) AND IS LONGER THAN 10 MINUTES BUT NO LONGER THAN 35 MINUTES WHEN USING THE STARTING MATERIAL (B).
Claim 3
Dependent Claim
20 words
The process of claim 1 wherein the chromium (III) chromate has a Cr6 /Cr3 molar ratio between 1.2 and 1.8.
Claim 4
Dependent Claim
18 words
The process of claim 1 wherein the chromium (III) chromate has a Cr6 /Cr3 molar ratio of 1.5.
Claim 5
Dependent Claim
26 words
The process of claim 1 wherein the passivated chromium metal is obtained by heating chromium metal at 200* - 500*C in an air or nitrogen atomsphere.
Claim 6
Dependent Claim
16 words
The process of claim 1 wherein the chromium oxide with a valency above 4 is CrO3.
Claim 7
Dependent Claim
27 words
The process of claim 1 wherein the residence time of the starting material (a) within the 200* - 300*C temperature range is between 20 and 30 minutes.
Claim 8
Dependent Claim
150 words
IN A PROCESS FOR THE PREPARATION OF FERROMAGNETIC CHROMIUM DIOXIDE BY HEATING AT 300* -500*C UNDER AN OXYGEN PRESSURE OF 30 - 100 ATM. A STARTING MATERIAL SELECTED FROM THE GROUP CONSISTING OF: A. A CHROMIUM (111) CHROMATE CR2(CRO4)3.NH2O WHEREIN THE CR6+CR3+ MOLAR RATIO IS BETWEEN 1.2 AND R.9 AND N IS BETWEEN 1 AND 8, AND B. A MIXTURE OF CHROMIUM METAL AS SUCH OR PASSIVATED, WITH A CHROMIUM OXIDE WITH A VALENCY ABOVE 4: THE IMPROVEMENT CONSISTING IN ADMIXING WITH SAID STARTING MATERIAL FROM 0.05 TO 30% B.W. WITH RESPECT TO THE CHROMIUM PRESENT IN THE STARTING MATERIAL OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF AMMONIA, OXALIC ACID, LACTIC ACID, TARTARIC ACID AND CRITIC ACID, SAID GROUP MEMBER BEING OXIDISED UNDER THE EXISTING REACTION CONDITIONS, THEREBY FAVORING THE REDUCTION OF THE STARTING MATERIAL TO CRO2 THROUGH AN EXOTHERMIC REACTION THAT IS PRIMED BETWEEN 100* AND 270*C.
Claim 9
Dependent Claim
150 words
IN A PROCESS FOR THE PREPARATION OF FERROMAGNETIC CHROMIUM DIOXIDE BY HEATING AT 300* -500*C UNDER AN OXYGEN PRESSURE OF 30 - 100 ATM. A STARTING MATERIAL SELECTED FROM THE GROUP CONSISTING OF: A. A CHROMIUM (111) CHROMATE CR2(CRO4)3.NH2O WHEREIN THE CR6+CR3+ MOLAR RATIO IS BETWEEN 1.2 AND R.9 AND N IS BETWEEN 1 AND 8, AND B. A MIXTURE OF CHROMIUM METAL AS SUCH OR PASSIVATED, WITH A CHROMIUM OXIDE WITH A VALENCY ABOVE 4: THE IMPROVEMENT CONSISTING IN ADMIXING WITH SAID STARTING MATERIAL FROM 0.05 TO 30% B.W. WITH RESPECT TO THE CHROMIUM PRESENT IN THE STARTING MATERIAL OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF AMMONIA, OXALIC ACID, LACTIC ACID, TARTARIC ACID AND CRITIC ACID, SAID GROUP MEMBER BEING OXIDISED UNDER THE EXISTING REACTION CONDITIONS, THEREBY FAVORING THE REDUCTION OF THE STARTING MATERIAL TO CRO2 THROUGH AN EXOTHERMIC REACTION THAT IS PRIMED BETWEEN 100* AND 270*C.
Claim 10
Dependent Claim
12 words
The process of claim 7 wherein the said group member is ammonia.
Claim 11
Dependent Claim
13 words
The process of claim 7 wherein the said group member is oxalic acid.
Claim 12
Dependent Claim
13 words
The process of claim 7 wherein the said group member is lactic acid.
Claim 13
Dependent Claim
32 words
The process of claim 8 wherein the starting material is chromium chromate Cr2(CrO4)3.nH2O and the quantity of NH3 is between 0.87 and 1.73% b.w. calculated with respect to anhydrous chromium (III) chromate.
Claim 14
Dependent Claim
33 words
The process of claim 9 wherein the starting material is chromium chromate Cr2(CrO4)3.nH2O and the quantity of oxalic acid is between 5.55 and 22.2% b.w. calculated with respect to anhydrous chromium (III) chromate.
Claim 15
Dependent Claim
21 words
The process of claim 7 wherein the chromium (III) chromate has a Cr6 /Cr3 molar ratio comprised between 1.2 and 1.8.
Claim 16
Dependent Claim
18 words
The process of claim 13 wherein the chromium (III) chromate has a Cr6 /Cr3 molar ratio of 1.5.
Claim 17
Dependent Claim
26 words
The process of claim 7 wherein the passivated chromium metal is obtained by heating chromium metal at 200* - 500*C in an air or oxygen atmosphere.
Claim 18
Dependent Claim
16 words
The process of claim 7 wherein the chromium oxide with a valency above 4 is CrO3.
Claim 19
Dependent Claim
93 words
A process according to claim 7, characterized in that, in order to obtain a chromium dioxide with a particle length between 0.01 and 0.1 micron, a length/width ratio between 1:1 and 5:1 and a coercive force of up to 300 Oersted, the starting chromium (III) chromate with molar ratio Cr6 /Cr3 1.5 is additioned with from 3 to 5% by weight of ammonia (with respect to the anhydrous chromium (III) chromate); or with from 10 to 35% by weight of oxalic acid; or with from 8 to 15% by weight of lactic acid.
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) | 1978-10-06 | 1979-04-07 | 1979-10-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-06 | 1983-04-07 | 1983-10-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-06 | 1987-04-07 | 1987-10-07 | $7700.00 | Window Closed / Lapsed |