US3928709A
Expired / Lapsed
US
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Ferrous ferric oxides, process for preparing same and their use in magnetic recording
Assignee: Eastman Kodak Co
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Filing: 1973-09-07
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Granted: 1975-12-23
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Expires: 1993-09-07
Abstract
Abstract Acicular ferrous ferric oxide crystals such as magnetite are prepared using a process which comprises mixing together aqueous solutions of a ferrous salt such as the sulfate or chloride and an alkali hydroxide such as NaOH or KOH to form a ferrous hydroxide precipitate as a dispersion, passing oxygen through the dispersion at 60*C or lower to convert ferrous hydroxide particles to Alpha ferric oxide hydrate crystals, discontinuing introduction of oxygen, boiling the dispersion to perfect crystallization of the Alpha ferric oxide hydrate, dehydrating the Alpha ferric oxide hydrate crystals to form Alpha ferric oxide and reducing the Alpha ferric oxide to form ferrous ferric oxide crystals. As set forth in the following disclosure, the reaction conditions, reactant concentrations and other parameters of the process are carefully controlled to obtain acicular ferrous ferric oxide crystals that have an acicularity ratio of at least 15 and contain alkali metal ions that impart basicity to the crystals. These crystals can obtain one or more doping metal ions such as alkaline earth metal ions, ions of cobalt, nickel, chromium, zinc or manganese which modify the magnetic recording properties of the crystals. Magnetic recording products such as tapes, discs and the like, containing the ferrous ferric oxide crystals are also disclosed.
Inventors
- 👤 Roger G L Audran
- 👤 Bernard J Pinguad
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 06:39
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; G11B5/70684; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
44 words
ACICULAR FERROUS FERRIC OXIDE CONSISTING ESSENTIALLY OF ACICULAR CRYSTALS THAT HAVE AN ACICULATIRY RATIO OF AT LEAST 15, A COEFFECIENT OF POLYDISPERSION ABOVE 2, AND WHICH COMPRISES ALKYLI METAL IONS WHICH IMPART A BASICITY OF AT LEAST 0.04 MEQ. PER GRAM TO SAID OXIDE.
Claim 2
Dependent Claim
44 words
ACICULAR FERROUS FERRIC OXIDE CONSISTING ESSENTIALLY OF ACICULAR CRYSTALS THAT HAVE AN ACICULATIRY RATIO OF AT LEAST 15, A COEFFECIENT OF POLYDISPERSION ABOVE 2, AND WHICH COMPRISES ALKYLI METAL IONS WHICH IMPART A BASICITY OF AT LEAST 0.04 MEQ. PER GRAM TO SAID OXIDE.
Claim 3
Dependent Claim
36 words
Acicular ferrous ferric oxide according to claim 1 in which said crystals have an acicularity ratio of at least 20 and a basicity in the range of 0.04 to about 0.2 meq. per gram of oxide.
Claim 4
Dependent Claim
32 words
Acicular ferrous ferric oxide according to claim 1 in which said crystals also comprise alkaline earth metal ions in a concentration of about 0.25 to about 1%, by weight, based on oxide.
Claim 5
Dependent Claim
44 words
ACICULAR FERROUS FERRIC OXIDE ACCORDING TO CLAIM 3 IN WHICH SAID ALKALI METAL IONS ARE SODIUM OR POTASSIUM IONS, SAID BASICITY IS IN THE RANGE OF 0.04 TO ABOUT 0.2 MEQ, PER GRAM OF OXIDE AND SAID ALKALINE EARTH METAL IONS ARE CALCIUM IONS.
Claim 6
Dependent Claim
18 words
A product for magnetic recording comprising a support and acicular ferrous ferric oxide as defined in claim 3.
Claim 7
Dependent Claim
49 words
Acicular ferrous ferric oxide according to claim 1 in which said crystals comprise doping metal ions of at least one of cobalt, nickel, chromium, zinc, manganese and cadmium in a concentration of about 1 to about 6%, by weight, based on oxide, in addition to said alkali metal ions.
Claim 8
Dependent Claim
26 words
Acicular ferrous ferric oxide according to claim 6 in which the basicity is in the range of 0.04 to about 0.2 meq. per gram of oxide.
Claim 9
Dependent Claim
25 words
Acicular ferrous ferric oxide according to claim 7 in which said alkali meTal ions are sodium ions and said doping metal ions are cobalt ions.
Claim 10
Dependent Claim
28 words
A product for magnetic recording comprising a support and a layer of non-magnetic binder in which there is dispersed acicular ferrous ferric oxide as defined in claim 7.
Claim 11
Dependent Claim
31 words
A product for magnetic recording according to claim 9 in which said doping metal ions are ions of at least two of the metals cobalt, nickel, chromium, manganese, zinc or cadmium.
Claim 12
Dependent Claim
32 words
A product for magnetic recording according to claim 9 in which said crystals comprise alkaline earth metal ions in a concentration of about 0.25 to about 1%, by weight, based on oxide.
Claim 13
Dependent Claim
19 words
A product for magnetic recording according to claim 11 in which said alkaline earth metal ions are calcium ions.
Claim 14
Dependent Claim
25 words
A product for magnetic recording comprising a support and a ferrous ferric oxide according to claim 6 in which said doping metal ion is cobalt.
Claim 15
Dependent Claim
18 words
A product for magnetic recording comprising a support and acicular ferrous ferric oxide as defined in claim 1.
Claim 16
Dependent Claim
42 words
A product for magnetic recording according to claim 14 comprising at least two superimposed magnetic recording layers on the same surface of said support and said acicular ferrous ferric oxide is in the outermost magnetic recording layer with respect to said support.
Claim 17
Dependent Claim
194 words
A PROCESS FOR PREPARING ACICULAR FERROUS FERRIC OXIDE CRYSTALS FOR MAGNETIC RECORDING WHICH COMPRISES ADDING UNDER NON-OXIDIZING CONDITIONS, AT A TEMPERATURE BELOW ABOUT 60*C, AN AQUEOUS SOLUTION OF FERROUS SALT TO AN AQUEOUS SOLUTION OF A STOICHIOMETRIC EXCESS OF AN ALKALINE HYDROXIDE WHILE SUBSTANTIALLY AVOIDING LOCAL EXCESSES OF SAID FERROUS SALT, TO FORM AN AQUEOUS DISPERSION OF FERROUS HYDROXIDE PARTICLES, SAID ALKALINE HYDROXIDE BEING PRESENT IN SAID AQUEOUS DISPERSION IN A CONCENTRATION OF AT LEAST A 500% STOICHIOMETRIC EXCESS; INTRODUCING OXYGEN INTO SAID DISPERSION AT A TEMPERATURE OF ABOUT 20* TO ABOUT 60*C FOR A PERIOD OF TIME SUFFICIENT TO CONVERT SAID FERROUS HYDROXIDE PARTICLES TO CRYSTALS OF ALPHA FERRIC OXIDE HYDRATE, THE CONCENTRATION OF FERROUS SALT IN SAID AQUEOUS SOLUTION BEING SUCH THAT THE CONCENTRATION OF SAID ALPHA FERRIC OXIDE HYDRATE FORMED IN SAID DISPERSION IS LESS THAN ABOUT 15 GRAMS PER LITER; DISCONTINUING INTRODUCTION OF SAID OXYGEN INTO SAID DISPERSION; BOILING SAID DISPERSION TO OBTAIN FURTHER CRYSTALLIZATION OF SAID ALPHA FERRIC OXIDE HYDRATE CRYSTALS; DEHYDRATING SAID ALPHA FERRIC OXIDE HYDRATE CRYSTALS TO FORM ALPHA FERRIC OXIDE; REDUCING SAID ALPHA FERRIC OXIDE TO FORM FERROUS FERRIC OXIDE AND RECOVERING SAID FERROUS FERRIC OXIDE.
Claim 18
Dependent Claim
194 words
A PROCESS FOR PREPARING ACICULAR FERROUS FERRIC OXIDE CRYSTALS FOR MAGNETIC RECORDING WHICH COMPRISES ADDING UNDER NON-OXIDIZING CONDITIONS, AT A TEMPERATURE BELOW ABOUT 60*C, AN AQUEOUS SOLUTION OF FERROUS SALT TO AN AQUEOUS SOLUTION OF A STOICHIOMETRIC EXCESS OF AN ALKALINE HYDROXIDE WHILE SUBSTANTIALLY AVOIDING LOCAL EXCESSES OF SAID FERROUS SALT, TO FORM AN AQUEOUS DISPERSION OF FERROUS HYDROXIDE PARTICLES, SAID ALKALINE HYDROXIDE BEING PRESENT IN SAID AQUEOUS DISPERSION IN A CONCENTRATION OF AT LEAST A 500% STOICHIOMETRIC EXCESS; INTRODUCING OXYGEN INTO SAID DISPERSION AT A TEMPERATURE OF ABOUT 20* TO ABOUT 60*C FOR A PERIOD OF TIME SUFFICIENT TO CONVERT SAID FERROUS HYDROXIDE PARTICLES TO CRYSTALS OF ALPHA FERRIC OXIDE HYDRATE, THE CONCENTRATION OF FERROUS SALT IN SAID AQUEOUS SOLUTION BEING SUCH THAT THE CONCENTRATION OF SAID ALPHA FERRIC OXIDE HYDRATE FORMED IN SAID DISPERSION IS LESS THAN ABOUT 15 GRAMS PER LITER; DISCONTINUING INTRODUCTION OF SAID OXYGEN INTO SAID DISPERSION; BOILING SAID DISPERSION TO OBTAIN FURTHER CRYSTALLIZATION OF SAID ALPHA FERRIC OXIDE HYDRATE CRYSTALS; DEHYDRATING SAID ALPHA FERRIC OXIDE HYDRATE CRYSTALS TO FORM ALPHA FERRIC OXIDE; REDUCING SAID ALPHA FERRIC OXIDE TO FORM FERROUS FERRIC OXIDE AND RECOVERING SAID FERROUS FERRIC OXIDE.
Claim 19
Dependent Claim
55 words
A process according to claim 16 which comrpises directing said solution of ferrous salt to a suction zone created in the midst of said alkaline hydroxide solution where said ferrous salt solution undergoes a lamellar stretching such that it penetrates into said alkaline hydroxide solution in the form of a sheet of large specific area.
Claim 20
Dependent Claim
28 words
A process according to claim 16 which comprises the additional step of introducing doping metal ions of at least one of Cobalt, nickel, chromium, zinc, manganese and cadmium.
Claim 21
Dependent Claim
19 words
A process according to claim 18 in which said doping metal ions are present in said ferrous salt solution.
Claim 22
Dependent Claim
15 words
A process according to claim 19 in which said doping metal ions are cobalt ions.
Claim 23
Dependent Claim
23 words
A process according to claim 19 which comprises the step of introducing alkaline earth metal ions in addition to said doping metal ions.
Claim 24
Dependent Claim
16 words
A process according to claim 21 in which said alkaline earth metal ions are calcium ions.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-12-22 | 1979-06-23 | 1979-12-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-22 | 1983-06-23 | 1983-12-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-22 | 1987-06-23 | 1987-12-23 | $7700.00 | Window Closed / Lapsed |