Patent US3843773A successfully refreshed from Google Patents.
US3843773A
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Process for producing fine acicular gamma ferric oxide crystals
Assignee: Eastman Kodak Co
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Filing: 1972-01-31
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Granted: 1974-10-22
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Expires: 1992-01-31
Abstract
Abstract Fine goethite crystals (alpha-FeO.OH, ferric oxide hydrate) are prepared by mixing together a ferrous salt such as the sulfate or chloride and an alkali hydroxide to form a hydroxide precipitate as a dispersion, blowing oxygen through the dispersion at 20*60*C. to convert ferrous hydroxide particles to goethite crystals, discontinuing blowing, boiling the dispersion to perfect crystallization of goethite crystals, and recovering the goethite crystals by filtering, washing and drying. The goethite crystals so produced are only about 0.3 microns long, and can be transformed into magnetic ferric oxide crystals which have exceptionally good properties for magnetic recording tapes, particularly for improving the background noise dynamic so that there is less noise during intermittent no-signal periods that may occur during sound recording.
Inventors
- 👤 B Pingaud
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:17
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; C; C01; C01G; C01G49/00; C01G49/02; C01G49/06; G11B5/70647; C01P; C01P2004/00; C01P2004/10; C01P2004/51; C01P2004/52; C01P2004/60; C01P2004/62
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
147 words
A PROCESS FOR PREPARING FINE ACICULAR CRYSTALS OF GAMMA FERRIC OXIDE FOR MAGNETIC RECORDING COMPRISING REACHING UNDER NON-OXIDIZING CONDITIONS, AT A TEMPERATURE BELOW 60*C, AN AQUEOUS SOLUTION OF A FERROUS SALT WITH AN AQUEOUS SOLUTION OF A STOICHIOMETRIC EXCESS OF AN ALKALINE HYDROXIDE TO FORM AN AQUEOUS DISPERSION OF FERROUS HYDROXIDE PARTICLES; INTRODUCING OXYGEN INTO SAID DISPERSION AT A TEMPERATURE OF 20*-60*C, FOR A PERIOD OF TIME SUFFICIENT TO CONVERT SAID FERROUS HYDROXIDE PARTICLES TO CRYSTALS OF ALPHA FEO.OH, THE CONCENTRATION OF FERROUS SALT IN SAID AQUEOUS SOLUTION BEING SUCH THAT THE CONCENTRATION OF SAID ALPHA FEO.OH FORMED IN SAID DISPERSION IS LESS THAN 15 GRAMS PER LITER; DISCONTINUING INTRODUCTION OF SAID OXYGEN; BOILING SAID DISPERSING TO OBTAIN FURTHER CRYSTALIZATION OF SAID ALPHA FEO.OH CRYSTALS; RECOVERING SAID ALPHA FEO.OH CRYSTALS FROM SAID DISPERSING; AND SUBJECTING SAID CRYSTALS TO DEHYDRATION REDUCTION AND OXIDATION FROM GAMMA FERRIC OXIDE CRYSTALS.
Claim 2
Dependent Claim
147 words
A PROCESS FOR PREPARING FINE ACICULAR CRYSTALS OF GAMMA FERRIC OXIDE FOR MAGNETIC RECORDING COMPRISING REACHING UNDER NON-OXIDIZING CONDITIONS, AT A TEMPERATURE BELOW 60*C, AN AQUEOUS SOLUTION OF A FERROUS SALT WITH AN AQUEOUS SOLUTION OF A STOICHIOMETRIC EXCESS OF AN ALKALINE HYDROXIDE TO FORM AN AQUEOUS DISPERSION OF FERROUS HYDROXIDE PARTICLES; INTRODUCING OXYGEN INTO SAID DISPERSION AT A TEMPERATURE OF 20*-60*C, FOR A PERIOD OF TIME SUFFICIENT TO CONVERT SAID FERROUS HYDROXIDE PARTICLES TO CRYSTALS OF ALPHA FEO.OH, THE CONCENTRATION OF FERROUS SALT IN SAID AQUEOUS SOLUTION BEING SUCH THAT THE CONCENTRATION OF SAID ALPHA FEO.OH FORMED IN SAID DISPERSION IS LESS THAN 15 GRAMS PER LITER; DISCONTINUING INTRODUCTION OF SAID OXYGEN; BOILING SAID DISPERSING TO OBTAIN FURTHER CRYSTALIZATION OF SAID ALPHA FEO.OH CRYSTALS; RECOVERING SAID ALPHA FEO.OH CRYSTALS FROM SAID DISPERSING; AND SUBJECTING SAID CRYSTALS TO DEHYDRATION REDUCTION AND OXIDATION FROM GAMMA FERRIC OXIDE CRYSTALS.
Claim 3
Dependent Claim
17 words
A process in accordance with claim 1 in which said alkaline hydroxide is an alkali metal hydroxide.
Claim 4
Dependent Claim
33 words
A process in accordance with claim 2 wherein the introduction of oxygen into said dispersion is for at least 24 hours, and the boiling of said dispersion is for at least 6 hours.
Claim 5
Dependent Claim
23 words
A process in accordance with claim 2, wherein said ferrous salt is FeSO4 . 7H2O, and said alkali metal hydroxide is sodium hydroxide.
Claim 6
Dependent Claim
19 words
A process in accordance with claim 2 wherein said reacting step is conducted at a temperature below about 40*C.
Claim 7
Dependent Claim
27 words
A process in accordance with claim 2 wherein the concentration of alkali metal hydroxide in said alkali metal hydroxide solution is less than 60 grams per liter.
Claim 8
Dependent Claim
31 words
A process in accordance with claim 2 wherein said oxygen is introduced as air at a rate of about 5-30 liters/hr per liter of dispersion for a period of 1-5 days.
Claim 9
Dependent Claim
26 words
A process in accordance with claim 6 wherein said aqueous solution of a ferrous salt is added to said aqueous solution of an alkali metal hydroxide.
Claim 10
Dependent Claim
46 words
A process in accordance with claim 6 wherein an aqueous solution of said alkali metal hydroxide is introduced into a vessel, and then said ferrous salt solution and an additional quantity of an aqueous solution of said alkali metal hydroxide are introduced simultaneously into said vessel.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-21 | 1978-04-22 | 1978-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-21 | 1982-04-22 | 1982-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-21 | 1986-04-22 | 1986-10-22 | $7700.00 | Window Closed / Lapsed |