Substrate with a photocatalytic coating

• US 20030082367A1
• Filed: 09/05/2002
• Published: 05/01/2003
• Est. Priority Date: 03/05/1998
• Status: Active Grant

• Current Assignee: Saint-Gobain Vitrage
• Original Assignee: Saint-Gobain Vitrage
• Inventors: Chopin, Thierry, Magnin-Feysot, Frederic, Talpaert, Xavier, Lehaut, Corinne, Simonet, Michel
• Granted Patent: US 6,720,066 B2
• Time in Patent Office: Days
• US Class Current: 428/328
• CPC Class Codes: B01J 35/30 characterised by their physical properties
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: C03C 17/007 containing a dispersed phase, e.g. particles, fibres or flakes, in a continuous phase
• CPC Class Codes: C03C 17/256 Coating containing TiO2
• CPC Class Codes: C03C 2217/212 TiO2
• CPC Class Codes: C03C 2217/45 Inorganic continuous phases
• CPC Class Codes: C03C 2217/475 Inorganic materials
• CPC Class Codes: C03C 2217/477 Titanium oxide
• CPC Class Codes: C03C 2217/71 Photocatalytic coatings
• CPC Class Codes: C03C 2218/113 by sol-gel processes
• CPC Class Codes: C04B 20/008 Micro- or nanosized fillers, e.g. micronised fillers with particle size smaller than that of the hydraulic binder colloidal silica C04B14/062 ; silica fume C04B18/146
• CPC Class Codes: C04B 41/4554 the coating or impregnating material being an organic or organo-metallic precursor of an inorganic material
• CPC Class Codes: C04B 41/4582 Porous coatings, e.g. coating containing porous fillers
• CPC Class Codes: C04B 41/463 Organic solvents
• CPC Class Codes: C04B 41/5041 Titanium oxide or titanates
• CPC Class Codes: C09D 1/00 Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
• CPC Class Codes: C23C 30/00 Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process C23C26/00, C23C28/00 take precedence
• CPC Class Codes: H01J 29/88 provided with coatings on the walls thereof; Selection of materials for the coatings H01J29/868 and H01J29/89 take precedence
• CPC Class Codes: Y10T 428/1266 O, S, or organic compound in metal component
• CPC Class Codes: Y10T 428/12667 Oxide of transition metal or Al
• CPC Class Codes: Y10T 428/249953 : Composite having voids in a component [e.g., porous, cellular, etc.]
• CPC Class Codes: Y10T 428/249956 : Void-containing component is inorganic
• CPC Class Codes: Y10T 428/249967 : Inorganic matrix in void-containing component
• CPC Class Codes: Y10T 428/24997 : Of metal-containing material
• CPC Class Codes: Y10T 428/249987 : With nonvoid component of specified composition
• CPC Class Codes: Y10T 428/249988 : Of about the same composition as, and adjacent to, the void-containing component
• CPC Class Codes: Y10T 428/24999 : Inorganic
• CPC Class Codes: Y10T 428/256 : Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/259 : Silicic material

Abstract

The present invention is directed to a process for obtaining a substrate provided with a coating having photocatalytic properties, wherein the coating includes crystallized particles of an oxide of a metal A having photocatalytic properties. The crystallized particles are incorporated into the coating using a mineral binder comprising at least one oxide of a metal B also having photocatalytic properties in the crystallized state. The coating optionally includes at least oxide of a metal M devoid of photocatalytic properties and/or at least one silicon compound of the silicon oxide SiO₂ type. The coating is deposited from liquid-phase dispersions containing the crystallized particles of the oxide of metal A and at least one precursor compound for the oxide of metal B of the binder and optionally a precursor compound for the oxide of metal M and for the Si compound, in a relative proportion A/(B+M+Si) by weight of the metals and Si ranging between 60/40 and 40/60. The present invention is also directed to substrates containing a photocatalytic coating and to liquid-phase dispersions which are used in the preparation of the photocatalytic coatings.

Claims

1. A process for obtaining a substrate comprising

(a) preparing a substrate for deposition with a coating which comprises crystallized particles of an oxide of a metal A having photocatalytic properties, a mineral binder comprising at least one oxide of a metal B having photocatalytic properties, and optionally at least one oxide of a metal M devoid of photocatalytic properties or at least one silicon oxide compound, wherein the coating is deposited from liquid-phase dispersions containing oxides of the metals A and B, and optionally an oxide of metal M and the silicon oxide, in a relative proportion by weight of the metals and Si given by A/(B+M+Si), the relative proportion ranging from 60/40 to 40/60;

(b) applying the coating onto an external or internal layer of the substrate; and

(c) allowing the coating to set.

2. The process according to claim 1, characterized in that the mineral binder is at least partially crystallized.

3. The process according to claim 1, characterized in that the oxides of metals A and B are selected from the group consisting of titanium dioxide, zinc oxide, tin oxide and tungsten oxide.

4. The process according to claim 1, wherein both the oxides of metals A and B are in the form of titanium oxide.

5. The process according to claim 1, wherein the mineral binder consists of the oxide of metal B.

6. The process according to claim 1, wherein the mineral binder comprises an oxide of titanium and a silicon compound.

7. The process according to claim 1, wherein the oxide particles of A have a mean size of about 5 nm to 80 nm and crystalline coherence domains having a mean size of approximately 5 nm to 20 nm.

8. The process according to claim 1, wherein the precursor compound for the oxide of metal B and optionally for the oxide of metal M are chosen from the group consisting of tetraalkoxides of formula X(OR)₄, trialkoxides of formula XR′

(OR)₃, or metal halides, wherein X refers to a metal and R or R′

are carbon-containing radicals.

9. The process according to claim 1, wherein that at least one precursor compound for the oxide of B and optionally for the oxide of M are dispersed in a liquid phase containing at least one chelating or stabilizing agent.

10. The process according to claim 1, wherein the coating is deposited by liquid-phase pyrolysis using a dispersion containing at least one precursor of an orgonometallic-compound type.

11. The process according to claim 1, wherein the coating is deposited using a sol-gel technique.

12. The process of claim 1, wherein the coating is deposited by dipping, cell-coating, laminar-coating, or spray-coating using a dispersion containing at least one organometallic compound.

13. The process according to claim 1, wherein the coating undergoes a heat treatment of at least 400°

C.

14. A substrate comprising a coating wherein the coating comprises crystallized particles of an oxide of a metal A having photocatalytic properties, wherein the particles of the oxide of A are incorporated into the coating using an at least partially crystallized mineral binder comprising an oxide of a metal B also having photocatalytic properties in the crystallized state, and optionally at least one oxide of a metal M devoid of photocatalytic properties or a silicon oxide compound, and wherein the coating has a porosity, calculated from the refractive index, of greater than 45%.

15. The substrate of claim 14 wherein the porosity ranges from between 45% and 65%.

16. The substrate of claim 14, wherein the crystallized particles have a size of about 5 nm to about 80 nm.

17. The substrate of claim 14 further comprising crystalline coherence domains having a size of about 5 nm to about 20 nm.

18. The substrate of claim 14 wherein the mineral binder is at least partially in the form of grains having a size of between 5 nm to 25 nm.

19. The substrate of claim 14 characterized in that the coating comprises a partially crystallized TiO₂-based mineral binder and crystallized TiO₂ particles essentially in anatase form.

20. The substrate of claim 14, wherein that the coating has a refractive index of between about 1.5 and 2.

21. The substrate of claim 14, wherein at least one layer is inserted between the substrate and the coating.

22. The substrate of claim 21, wherein at least one layer functions as a barrier to alkali metals or has an optical, antistatic, or adhesion function.

23. The substrate of claim 21, wherein at least one layer is based on a Si compound or an optionally doped metal oxide such as fluorine-doped tin oxide.

24. The substrate of claim 14, wherein the substrate comprises at least one transparent material of glass, plastic, or composite materials.

25. A liquid-phase dispersion comprising:

particles of crystallized titanium dioxide;

at least one precursor compound for a first metal oxide having photocatalytic properties in the crystallized state;

optionally at least one precursor compound for a second metal oxide or a silicon compound, wherein the ratio of the crystallized titanium oxide particles to the precursors and the silicon compound ranges from 60/40 to 40/60.

26. The dispersion of claim 25, wherein the titanium dioxide particles are predominantly in an anatase crystal form.

27. The dispersion of claim 25, wherein the titanium dioxide particles have a mean size of approximately 5 to 80 nm.

28. The dispersion of claim 25, wherein the titanium dioxide particles have crystalline coherence domains having a mean size of approximately 5 nm to 20 nm.

29. The dispersion of claim 25, wherein the first metal oxide is chosen from at least one of the following:

titanium dioxide, zinc oxide, tin oxide, or tungsten oxide.

30. The dispersion of claim 25, wherein the second metal oxide is aluminum oxide or zirconium oxide.

31. The dispersion of claim 25, wherein the precursor compounds for the first and second metal oxides are organometallic compounds chosen from the group consisting of tetraalkoxides of a formula X(OR)₄, trialkoxides of a formula XR′

(OR)₃, or metal halides, wherein R and R′

represent carbon-containing radicals and X represents metals in the first and second metal oxides.

32. The dispersion of claim 25, wherein the silicon compound is a silicon alkoxide.

33. The dispersion of claim 25, further comprising a chelating or stabilizing agent.

34. The dispersion of claim 25, comprising a solvent chosen from the group consisting of water, ethylene glycol, ethanol, propylene glycol and mixtures thereof.

35. The dispersion of claim 25, wherein the precursor compound for the first metal oxide comprises titanium tetrabutoxide and the silicon compound is a tetraorthosilicate, and the ratio of the crystallized titanium oxide to the precursor for the first metal oxide and silicon compound is approximately 50/50.