Colloidal titanium dioxide sols
View Patent ↗Stable, translucent or transparent titanium dioxide sols comprising amorphous titanium dioxide and an organic peptizing agent are provided that are useful in particulate binding applications. Also provided are methods for preparing the inventive sols. The inventive sols are prepared from titanium dioxide precursors including organotitanium compounds and water-soluble titanium salts that are treated to precipitate amorphous titanium dioxide. The amorphous titanium dioxide is re-dispersed and peptized to form a translucent or transparent mixture. The inventive sols are stable for an extended period of time.
1. A stable colloidal titanium dioxide sol comprising titanium dioxide particles dispersed in an aqueous solution comprising an organic peptizing agent which is a mono-, di- or trialkyl amine base, said titanium dioxide particles being amorphous and having an average particle size of less than about 50 nm, wherein the sol is transparent and stable for at least 1 month at room temperature.
2. The titanium dioxide sol of claim 1 , wherein the titanium dioxide particles have an average particle size of about less than 10 nm.
3. The titanium dioxide sol of claim 1 , wherein the titanium dioxide particles have an average particle size of about less than 5 nm.
4. The titanium dioxide sol of claim 1 , wherein the mono-, di- or trialkylamine comprises a branched alkyl group.
5. The titanium dioxide sol of claim 1 , wherein the amine base is selected from the group consisting of tert-butylamine, triethylamine, isopropylamine, diisopropylethylamine, isobutylamine and isoamylamine.
6. The titanium dioxide sol of claim 1 , wherein the sol comprises between about 5% to about 15% titanium dioxide by weight.
7. The titanium dioxide sol of claim 1 , wherein the sol comprises between about 8% to about 12% titanium dioxide by weight.
8. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 3 months at room temperature.
9. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 6 months at room temperature.
10. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 1 year at room temperature.
11. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 2 years at room temperature.
12. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 1 month at 2-8° C.
13. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 3 months at 2-8° C.
14. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 6 months at 2-8° C.
15. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 1 year at 2-8° C.
16. The titanium dioxide sol of claim 1 , wherein the sol is stable for at least 2 years at 2-8° C.
17. A method for preparing a stable, transparent colloidal titanium dioxide sol comprising amorphous titanium dioxide, comprising:
(i) obtaining a solution of a titanium dioxide precursor compound;
(ii) hydrolyzing the titanium dioxide precursor compound to form titanium dioxide,
wherein the titanium dioxide precipitates from the solution as amorphous titanium dioxide particles having an average particle size of less than 50 nm;
(iii) isolating the amorphous titanium dioxide particles from step (ii);
(iv) forming a dispersion of the amorphous titanium particles of step (iii) in a liquid medium; and
(v) treating the dispersion of step (iv) with an organic peptizing agent to form a stable, transparent or translucent sol comprising amorphous titanium dioxide particles, wherein the peptizing agent is a mono-, di- or trialkylamine.
18. The method of claim 17 , wherein the titanium dioxide precursor is a titanium tetraalkoxide.
19. The method of claim 18 , wherein the titanium tetraalkoxide is selected from the group consisting of titanium tetraisopropoxide, titanium-n-propoxide, titanium tetra-n-butoxide, titanium tetraethoxide, and titanium tetramethoxide.
20. The method of claim 17 , wherein titanium dioxide precursor is a water-soluble titanium salt.
21. The method of claim 20 , further comprising treating a solution of the water-soluble titanium salt with an ion-exchange resin to de-ionize the solution prior to hydrolyzing the titanium dioxide precursor.
22. The method of claim 17 or 21 , wherein the titanium dioxide precursor is treated with a basic chelating agent prior to hydrolyzing.
23. The method of claim 22 , wherein the basic chelating agent is a dialkanolamine or a trialkanolamine.
24. The method of claim 23 , wherein the chelating agent is triethanolamine.
25. The method of claim 17 , wherein the amorphous titanium dioxide is free of crystalline forms of titanium dioxide.
26. The method of claim 17 , wherein the amorphous titanium dioxide particles have an average particle size of about less than 10 nm.
27. The method of claim 17 , wherein the amorphous titanium dioxide particles have an average particle size of about less than 5 nm.
28. The method of claim 17 , wherein the mono-, di- or trialkylamine is selected from the group consisting of tert-butylamine, triethylamine, isopropylamine, diisopropoylethylamine, isobutylamine and isoamylamine.
29. The method of claim 17 , further comprising adjusting the pH of the sol with an acid or base.