Multi-layer coatings with an inorganic oxide network containing layer and methods for their application

• US 20050266235A1
• Filed: 05/18/2005
• Published: 12/01/2005
• Est. Priority Date: 05/28/2004
• Status: Active Grant

• Current Assignee: PPG Industries Ohio Incorporated (Nouryon BV)
• Original Assignee: PPG Industries Ohio Incorporated (Nouryon BV)
• Inventors: Cheng, Shan, Lin, Chia-Cheng, Colton, James P., Nakajima, Masayuki
• Granted Patent: US 7,354,650 B2
• Time in Patent Office: Days
• US Class Current: 428/336
• CPC Class Codes: C08J 2369/00 Characterised by the use of polycarbonates; Derivatives of polycarbonates
• CPC Class Codes: C08J 2483/02 Polysilicates
• CPC Class Codes: C08J 7/0423 with at least one layer of inorganic material and at least one layer of a composition containing a polymer binder
• CPC Class Codes: C08J 7/046 Forming abrasion-resistant coatings; Forming surface-hardening coatings
• CPC Class Codes: C08J 7/054 Forming anti-misting or drip-proofing coatings
• CPC Class Codes: C08J 7/056 Forming hydrophilic coatings
• CPC Class Codes: C09D 183/02 Polysilicates
• CPC Class Codes: C09D 5/1618 inorganic
• CPC Class Codes: C09D 7/61 inorganic
• CPC Class Codes: C09D 7/67 Particle size smaller than 100 nm
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/265 1 mil or less
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

Multi-layer coatings are disclosed that include (1) a first layer comprising an inorganic oxide network, and (2) a second layer applied over at least a portion of the first layer, wherein the second layer is deposited from at least one liquid composition that is hydrophilic and includes an essentially completely hydrolyzed organosilicate. Also disclosed are substrates coated with such multi-layer coatings, methods of applying such multi-layer coatings to a substrate and methods for improving the anti-fouling, self-cleaning, easy-to-clean, and/or anti-fogging properties of an article.

Claims

1. A multi-layer coating comprising:

(1) a,first layer comprising an inorganic oxide network, and

(2) a second layer applied over at least a portion of the first layer, wherein the second layer is deposited from at least one liquid composition that is hydrophilic and comprises an essentially completely hydrolyzed organosilicate.

2. The multi-layer coating of claim 1, wherein the first layer is deposited from a composition comprising a sol containing a network-forming metal alkoxide.

3. The multi-layer coating of claim 2, wherein the network-forming metal alkoxide comprises an alkoxysilane of the general formula R_xSi(OR′

)_4-x wherein R is an organic radical, R′

is an alkyl radical selected from the group consisting of methyl, ethyl, propyl, and butyl radicals, and x is an integer and less than 4.

4. The multi-layer coating of claim 1, wherein the first layer is transparent.

5. The multi-layer coating of claim 1, wherein the liquid composition from which the second layer is deposited further comprises a photocatalytic material.

6. The multi-layer coating of claim 5, wherein the average crystalline diameter is 3 to 35 nanometers.

7. The multi-layer coating of claim 5, wherein the photocatalytic material is selected from the group consisting of the brookite form of titanium dioxide, titanium dioxide chemically modified by flame pyrolysis, nitrogen doped titanium dioxide, plasma treated titanium dioxide, and mixtures thereof.

8. The multi-layer coating of claim 5, wherein the photocatalytic material is present in the liquid composition in an amount ranging from 0.1 to 0.75 percent by weight based on the total weight of the composition.

9. The multi-layer coating of claim 1, wherein the organosilicate of the liquid composition from which the, second layer is deposited is selected from the group consisting of organoxysilanes, organoxysiloxanes, and mixtures thereof, wherein the organoxysilanes are selected from the groups consisting of tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-t-butoxysilane, tetraphenoxysilane, dimethoxydiethoxysilane, and mixtures thereof.

10. The multi-layer coating of claim 1, wherein the organosilicate is present in the liquid composition from which the second layer is deposited in an amount ranging from 0.1 to 2 percent by weight calculated as SiO₂, based on the total weight of the composition.

11. The multi-layer coating of claim 1, wherein the pH of the liquid composition from which the second layer is deposited is no more than 3.5.

12. The multi-layer coating of claim 1, wherein the pH of the liquid composition from which the second layer is deposited is from 7.0 to 8.5.

13. A substrate coated with the multi-layer coating of claim 1.

14. The substrate of claim 13, wherein the substrate comprises a polymeric substrate.

15. The substrate of claim 14, wherein the polymeric substrate comprises a solid transparent or optically clear solid material.

16. The substrate of claim 15, wherein the polymeric substrate comprises a photochromic material.

17. The multi-layer coating of claim 1, wherein the second layer is applied at a dry film thickness of 20 to 60 nanometers.

18. The multi-layer coating of claim 1, wherein the binder is prepared by a process selected from:

(a) a multi-stage process comprising a first stage wherein a partial-hydrolys is polycondensation reaction product is formed by reacting an organosilicate water in the presence of an acid hydrolysis catalyst, wherein the water is present in an amount that is less than the stoichiometric amount capable of hydrolyzing the organoxy groups of the organosilicate, and a second stage wherein the partial hydrolysis polycondensation reaction product is contacted with a large amount of water to form an essentially completely hydrolyzed organosilicate, and

(b) reacting a tetraalkoxysilane oligomer with water in the presence of an organic acid hydrolysis catalyst and/or an organic solvent, wherein the water is present in an amount that is considerably greater than the stoichiometric amount capable of hydrolyzing organoxy groups of the alkoxysilane to form an essentially completely hydrolyzed organosilicate.

19. The multi-layer coating of claim 18, wherein the binder is prepared by the multi-stage process.

20. The multi-layer coating of claim 19, wherein the water is present during the first stage in a stoichiometric amount capable of hydrolyzing 50 percent of the organoxy groups of the organosilicate.

21. The multi-layer coating of claim 19, wherein the first stage is conducted at conditions that limit the degree of condensation of Si—

OH groups formed as a result of the hydrolysis reaction.

22. The multi-layer coating of claim 21, wherein the conditions that limit the degree of condensation of Si—

OH groups formed as a result of the hydrolysis reaction are selected from controlling the reaction exotherm by external cooling, controlling the rate of addition of the acid catalyst, and/or conducting the first stage hydrolysis in the substantial absence of any organic cosolvent.

23. A method for improving the anti-fouling, self-cleaning, easy-to-clean, and/or anti-fogging properties of an article, wherein the article comprises a surface having, a coating layer comprising an inorganic oxide network deposited thereon, the method comprising the steps of:

(1) applying to at least a portion of the surface a liquid composition comprising an essentially completely hydrolyzed organosilicate; and

(2) curing the composition applied in step (1).

24. The method of claim 23, wherein step (2) is accomplished by air drying.

25. The method of claim 23, wherein the coating layer comprising an inorganic oxide network comprises a network forming metal alkoxide.

26. The method of claim 25, wherein the network forming metal alkoxide comprises an alkoxysilane of the general formula R_xSi(OR)_4-x wherein R is an organic radical, R′

is an alkyl radical selected from the group consisting of methyl, ethyl, propyl, and butyl, radicals, and x is an integer and less than 4.

27. The method of claim 23, wherein the liquid composition applied in step (1) further comprises a photocatalytic material.

28. The method of claim 27, wherein the photocatalytic material comprises a metal oxide selected from the group consisting of zinc oxide, tin oxide, ferric oxide, dibismuth trioxide, tungsten trioxide, strontium titanate, titanium dioxide, and mixtures thereof.

29. The method of claim 27, wherein at least a portion of the photocatalytic material is present in the form of particles having an average crystalline diameter of 3 to 35 nanometers.

30. The method of claim 27, wherein the photocatalytic material is selected from the group, consisting of the brookite form of titanium dioxide, titanium dioxide chemically modified by flame pyrolysis, nitrogen doped titanium dioxide, plasma treated titanium dioxide, and mixtures thereof.

31. The method of claim 27, wherein the photocatalytic material is present in the liquid composition applied in step (1) in an amount ranging from 0.1 to 0.75 percent by weight based on the total weight of the composition.

32. The method of claim 23, wherein the organosilicate of the liquid composition applied in step (1) is selected from the group consisting of organoxysilanes, organoxysiloxanes, and mixtures thereof.

33. The method of claim 23, wherein the organosilicate is present in the liquid composition applied in step (1) in an amount ranging from 0.1 to 2 percent by weight calculated as SiO₂, based on the total weight of the composition.

34. The method of claim 23, wherein the pH of the liquid composition applied in step (1) is no more than 3.5.

35. The method of claim 23, wherein the surface comprises a solid transparent or optically clear solid material.

36. The method of claim 23, wherein the surface comprises a photochromic material.

37. The method-of claim 23, wherein the liquid composition applied in step (1) is applied at a dry film thickness of 20 to 60 nanometers.