US4675251A
Expired / Lapsed
US
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Spherical particles of titanium dioxide coated with a uniform layer of iron oxides having a narrow size distribution, and process for preparing the same
Assignee: Montedison SpA
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Filing: 1986-02-18
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Granted: 1987-06-23
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Expires: 2006-02-18
Abstract
Abstract Spherical particles having sizes below 1 mu m, or at maximum of 3.04 mu m, a narrow size size distribution consisting, or consisting essentially, of TiO2 coated by a uniform layer having a thickness up to 400 ANGSTROM consisting essentially alpha -, or gamma -Fe2O3, or magnetite, or mixtures thereof, said particles being prepared by a process consisting, or consisting essentially, in the precipitation of the oxide from Fe (III) salt solutions on the surface of solid pre-formed TiO2 particles having a narrow size distribution and a number average diameter below 1 mu m or </=3 mu m, the Fe (III) concentration being </=40% by weight calculated on TiO2, the pH of the suspension ranging from 1.0 to 2.8, extremes excluded, by heating the suspensions to temperatures of from 80 DEG to 100 DEG C., and by aging them under such conditions for at least 30 minutes.
Inventors
- 👤 Egon Matijevic
- 👤 Paola Gherardi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:37
CPC Classifications
B; B82; B82Y; B82Y30/00; C; C09; C09C; C09C1/00; C09C1/36; B01; B01J; B01J21/00; B01J21/06; B01J21/063; C09C1/3607; C09C1/3653; C09C1/3661; C01; C01P; C01P2002/00; C01P2002/50; C01P2002/52; C01P2002/70; C01P2004/00; C01P2004/01; C01P2004/04; C01P2004/30; C01P2004/32; C01P2004/51; C01P2004/60; C01P2004/61; C01P2004/64; C01P2004/80; C01P2004/82; C01P2004/84; C01P2004/86; C01P2006/00; C01P2006/12; C01P2006/42; C01P2006/60; Y; Y10; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991; Y10T428/2993
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
69 words
Sperical non-aggregated particles having a number average diameter higher than 0.05 and up to 3.04 μm, a polydispersion index dw/dn≦2.0, in which dw is the weight average diameter and dn is the number average diameter, and consisting essentially of titanium dioxide coated by a uniform layer having a thickness up to 400 Å and consisting essentially of α- or γ-Fe 2 O 3 , or magnetite, or mixtures thereof.
Claim 2
Dependent Claim
69 words
Sperical non-aggregated particles having a number average diameter higher than 0.05 and up to 3.04 μm, a polydispersion index dw/dn≦2.0, in which dw is the weight average diameter and dn is the number average diameter, and consisting essentially of titanium dioxide coated by a uniform layer having a thickness up to 400 Å and consisting essentially of α- or γ-Fe 2 O 3 , or magnetite, or mixtures thereof.
Claim 3
Dependent Claim
20 words
Spherical particles according to claim 1, in which the uniform layer has a thickness ranging from 10 to 300 Å.
Claim 4
Dependent Claim
18 words
Spherical particles according to claim 1, in which the number average diameter ranges from 0.2 to 0.8 μm.
Claim 5
Dependent Claim
14 words
Spherical particles according to claim 1, in which the polydispersion index dw/dn is ≦1.20.
Claim 6
Dependent Claim
22 words
Spherical particles according to claim 1, in which the layer coating the titanium dioxide consists essentially of α-Fe 2 O 3 .
Claim 7
Dependent Claim
36 words
Spherical particles according to claim 5, in which the coating layer consists essentially of magnetite prepared by subjecting the particles of claim 5 to reduction at a temperature of about 400° C. in a hydrogen stream.
Claim 8
Dependent Claim
35 words
Spherical particles according to claim 6, in which the coating layer consists essentially of γ-Fe 2 O 3 which has been obtained by subjecting the particles of claim 6 to oxidation at about 350° C.
Claim 9
Dependent Claim
121 words
A process for preparing the spherical particles according to claim 1, characterized in that an iron oxide is caused to precipitate from solutions of a Fe (III) salt onto titanium dioxide, consisting essentially of solid, non-aggregated particles having a number average diameter ranging from 0.05 to 3 μm, a polydispersion index dw/dn≦2, in which dw and dn are the same as defined hereinbefore, said particles having a spherical form, by using an amount of FE (III) ≦40% by weight calculated on TiO 2 , the pH value of the solution ranging from 1.0 to 2.8, extremes excluded, by subsequently heating the suspensions to temperatures from 80° to 100° C., and by aging them at these temperatures for at least 30 minutes.
Claim 10
Dependent Claim
29 words
The process according to claim 8, in which the temperature ranges from 90° to 100° C. and the aging time employed is at least 2 hours, at said temperature.
Claim 11
Dependent Claim
20 words
The process according to claim 9, in which the time during which the precipitation occurs is at least 30 hours.
Claim 12
Dependent Claim
18 words
The process according to claim 8, in which the pH of the suspension ranges from 1.6 to 2.0
Claim 13
Dependent Claim
21 words
The process according to claim 8, in which the concentration of FE (III) is ≦30% by weight calculated on titanium dioxide.
Claim 14
Dependent Claim
25 words
The process according to claim 8, in which the salt of Fe (III) is selected from the class consisting of sulphates, nitrates, perchlorates, and chlorides.
Claim 15
Dependent Claim
16 words
The process according to claim 13, in which the selected Fe (III) salt is ferric chloride.
Claim 16
Dependent Claim
22 words
The process according to claim 13, in which the pH of the solution is obtained by adding HCL or HClO 4 .
Claim 17
Dependent Claim
19 words
The process according to claim 13, in which titanium dioxide is treated with solutions of heteropolyacids before being utilized.
Claim 18
Dependent Claim
22 words
The process according to claim 16, in which the heteropolyacid is selected from the class consisting of tungstophosphoric acid and tungstosilicic acid.
Claim 19
Dependent Claim
19 words
The process according to claim 17, in which the heteropolyacid concentration ranges from 10 -4 to 10 -5 moles/liter.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1990-06-22 | 1990-12-22 | 1991-06-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-22 | 1994-12-22 | 1995-06-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-22 | 1998-12-22 | 1999-06-23 | $7700.00 | Window Closed / Lapsed |