Fluorine-doped stannic oxide colloids and method for preparing same
View Patent ↗A method for producing a colloidal alcoholic suspension of fluorine-doped SnO 2 particles. It also pertains to the colloidal suspension thus obtained and to its uses, especially in the manufacture of an antistatic coating for an optical article, such as an ophthalmic lens.
1. A method for producing a colloidal alcoholic suspension of fluorine-doped stannic oxide particles, comprising the following successive steps:
a) preparing a mixture comprising stannous oxalate, a quaternary ammonium fluoride salt, hydrogen peroxide and an acid, in a solvent consisting of deionized water optionally mixed with at least one alcohol,
b) subjecting said mixture to hydrothermal treatment, so as to obtain a suspension,
c) desalting said suspension, and
d) optionally subjecting said desalted suspension to a solvent-exchange step with at least one alcohol.
2. The method according to claim 1 , wherein the solvent consists in a mixture of deionized water with at least one alcohol selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, 1-methoxy-2-propanol and their mixtures.
3. The method according to claim 2 , wherein the volume ratio of alcohol to deionized water in the solvent ranges from 1:12 to 1:4.
4. The method according to claim 1 , wherein the quaternary ammonium fluoride salt is selected from the group consisting of (C 2 H 5 ) 4 NF, (C 3 H 7 ) 4 NF, (C 4 H 9 ) 4 NF and their mixtures.
5. The method according to claim 1 , wherein the molar ratio of hydrogen peroxide to tin ranges from 0:1 to 4:1.
6. The method according to claim 1 , wherein the molar ratio of fluorine to tin ranges from 0.1:1 to 3:1.
7. The method according to claim 1 , wherein the acid used in step (a) is an acid other than hydrochloric acid, such as oxalic acid and/or nitric acid.
8. The method according to claim 1 , wherein the hydrothermal treatment is conducted at a temperature ranging from 120 to 220° C. for a period of time ranging from 6 to 72 hours.
9. The method according to claim 1 , wherein the desalting step is performed by dialysis or ultrafiltration.
10. The method according to claim 1 , wherein the solvent-exchange step is performed by dialysis or diafiltration.
11. The method according to claim 1 , wherein it further includes a step of ultrasonic treatment after formation of the colloidal suspension and/or before the solvent-exchange step and/or a step of pH adjustment by addition of an acid or base.
12. A transparent colloidal alcoholic suspension of fluorine-doped stannic oxide particles, which has a zeta potential of more than 30 mV, in absolute value.
13. The colloidal suspension of claim 12 , wherein the particles have a nanocrystal size ranging from 10 to 15 mV.
14. An antistatic coating for an optical article, such as an ophthalmic lens, comprising the colloidal suspension according to claim 12 .
15. An optical article, such as an ophthalmic lens, comprising a transparent polymer substrate and at least one coating prepared from a composition comprising the colloidal suspension according to claim 12 .
16. The method according to claim 2 , wherein the volume ratio of alcohol to deionized water in the solvent ranges from 1:8 to 1:4.
17. The method according to claim 1 , wherein the molar ratio of hydrogen peroxide to tin ranges from 0.5:1 to 1.5:1.
18. The method according to claim 1 , wherein the molar ratio of hydrogen peroxide to tin is 1:1.
19. The method according to claim 1 , wherein the molar ratio of fluorine to tin ranges from 0.5:1 to 2:1.
20. The method according to claim 1 , wherein the hydrothermal treatment is conducted at a temperature ranging from 160 to 200° C., for a period of time ranging from 20 to 30 hours.