Preparation of anatase titanium dioxide

Patent 5630995 Issued on May 20, 1997. Estimated Expiration Date:

January 17, 2016. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Abstract Claims Description Full Text

Patent References

1795467

1851487

2516548

2721787

3359070

3615204

3625650

3632527

Anatase pigment from ilmenite Patent #: 4183768
Issued on: 01/15/1980
Inventor: Knapp , et al.

Inventors

Assignee

Tioxide Group Services Limited

Application

No. 587614 filed on 01/17/1996

US Classes:

423/616, And utilizing acid423/610, Titanium dioxide423/615Utilizing titanium sulfate as reactant

Examiners

Primary: Bos, Steven

Foreign Patent References

02239119 JP. 09/12/1990
5-163022 JP 06/12/1993
0831736 SU. 05/12/1981
0916521 SU. 03/12/1982
0975577 SU. 11/12/1982
1085935 SU. 04/12/1984
1323535 SU. 07/12/1987
1560476 SU. 04/12/1990
1604820 SU. 11/12/1990
0 934 626 GB. 08/12/1963
1 016 777 GB. 01/12/1966
1 223 639 GB. 03/12/1971
2247009 GB. 02/12/1992
2 247 009 GB. 02/12/1992

International Class

C01G 023/047

Foreign Application Priority Data

1995-01-20 GB

Abstract

A process for preparing anatase titanium dioxide by precipitating hydrous titanium oxide in the absence of added nuclei from a solution of titanium sulphate containing the equivalent of 200 to 300 grams TiO2 per liter and having an acid to titanium ratio in the range 1.6:1 to 2.2:1, the precipitation being induced by the addition of 5 to 35 parts water per 100 parts titanium sulphate solution. The hydrous titanium oxide is calcined in the presence of an amount of potassium compound equivalent to between 0.20 and 0.60 weight percent calculated as K2 O based on TiO2 and between 0.15 and 0.55 weight percent phosphorus calculated as P2 O5 based on TiO2. The hydrous titanium oxide is subjected to calcination in a process having a specified thermal profile. The product of the process is anatase titanium dioxide having an average crystal size larger than conventionally prepared anatase. Said product is easily milled to form a product with a high single crystal fraction.