Claims
- 1. Method of preparing rutile microcrystalline titanium dioxide having crystals with an average crystal size in the range of 24 nm to 30 nm from solid titanium dioxide hydrate comprising the steps of:
- (a) forming an aqueous alkaline pH slurry comprising said titanium dioxide hydrate and a base;
- (b) separating solids from said alkaline pH slurry;
- (c) forming an acidic slurry comprising said solids and hydrochloric acid, said acidic slurry having an hydrochloric acid content of between about 8-12 g/l which precipitates rutile titanium dioxide particles;
- (d) adjusting said acidic slurry formed in step (c) to a pH value of 4-6 to form a neutralized slurry containing said rutile titanium dioxide particles;
- (e) separating said rutile titanium dioxide particles from said neutralized slurry
- (f) washing the rutile titanium dioxide particles to obtain washed rutile titanium dioxide particles; and
- (g) calcining said washed rutile titanium dioxide particles at a temperature of 400.degree.-550.degree. C. to form said rutile microcrystalline titanium dioxide.
- 2. A method as recited in claim 1 wherein said alkaline pH slurry formed in step (a) comprises a solid content, expressed as titanium dioxide, of at least 70 g/liter.
- 3. A method as recited in claim 1 wherein in said step (a) said base is provided in a concentration of about 300-350 g NaOH/liter of H.sub.2 O.
- 4. A method as recited in claim 1 wherein in said step (a) said base comprises NaOH and said step (a) comprises heating said alkaline pH slurry.
- 5. A method as recited in claim 4 wherein said step (a) comprises forming said slurry at a temperature of about 60.degree. C., then raising said temperature for about 2 hours to about 95.degree. C., followed by washing said slurry with warm water.
- 6. A method as recited in claim 1 wherein said step (c) comprises raising the temperature of said slurry to about 60.degree. C.
- 7. Method as recited in claim 6 wherein in said step (c) said slurry comprises a solid content of about 95-180 g/l, expressed as titanium dioxide.
- 8. Method as recited in claim 6 wherein in said step (c) said slurry has a pH of about 1.5-2.0.
- 9. Method as recited in claim 8 wherein in said step (c) said slurry has a pH of about 1.8.
- 10. Method as recited in claim 6 wherein in said step (c), said hydrochloric acid is provided as 37% HCl.
- 11. Method as recited in claim 1 wherein said step (c) comprises raising the temperature of said slurry to at least 90.degree. C. over a period of about 120 minutes.
- 12. Method as recited in claim 1 wherein said step (d) comprises contacting said acidic slurry with a member selected from the group consisting of sodium carbonate and sodium hydroxide, and wherein step (e) comprises filtering said neutralized slurry.
- 13. Method as recited in claim 1 further comprising, subsequent to said step (g) grinding said rutile microcrystalline titanium dioxide.
Priority Claims (1)
Number |
Date |
Country |
Kind |
901053 |
Mar 1990 |
FIX |
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Parent Case Info
This is a continuation of application Ser. No. 663,492, filed Mar. 1, 1991, now abandoned.
US Referenced Citations (7)
Foreign Referenced Citations (4)
Number |
Date |
Country |
962142 |
Feb 1975 |
CAX |
57124 |
Jun 1980 |
FIX |
381790A1 |
Dec 1988 |
DEX |
2205088 |
Nov 1988 |
GBX |
Non-Patent Literature Citations (3)
Entry |
Official Action for Kemura Oy, Finland dated 16 Jun. 1992. |
Finnish Office Action w/English translation (901053) (no date). |
EP Search Report (913011839) (no date). |
Continuations (1)
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Number |
Date |
Country |
Parent |
663492 |
Mar 1991 |
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