SELF-CLEANING COATINGS AND METHODS FOR MAKING SAME

• US 20130337226A1
• Filed: 06/10/2013
• Published: 12/19/2013
• Est. Priority Date: 06/08/2012
• Status: Active Application

• Current Assignee: University of Houston (University of Houston System)
• Original Assignee: University of Houston (University of Houston System)
• Inventors: Curran, Seamus, Liao, Kang-Shyang, Barton, Killian
• Granted Patent: US 10,266,702 B2
• Time in Patent Office: Days
• US Class Current: 428/141
• CPC Class Codes: B05D 2203/35 Glass
• CPC Class Codes: B05D 3/02 by baking B05D3/04 takes precedence
• CPC Class Codes: B05D 3/12 by mechanical means
• CPC Class Codes: B05D 3/142 Pretreatment
• CPC Class Codes: B05D 5/02 to obtain a matt or rough surface
• CPC Class Codes: B05D 5/083 involving the use of fluoropolymers
• CPC Class Codes: C03C 17/30 with silicon-containing compounds
• CPC Class Codes: C03C 2217/76 Hydrophobic and oleophobic coatings
• CPC Class Codes: C03C 2218/31 Pre-treatment
• CPC Class Codes: C09D 5/00 Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced electrically insulating plastics, resins or waxes H01B3/30; Filling pastes
• CPC Class Codes: C09D 5/1625 organic
• CPC Class Codes: C09D 5/1681 Antifouling coatings characterised by surface structure, e.g. for roughness effect giving superhydrophobic coatings or Lotus effect
• CPC Class Codes: H02S 40/10 Cleaning arrangements
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

A method of forming a self-cleaning coating on a substrate comprises the step of selecting a substrate, cleaning the substrate, and/or roughening the substrate using an abrasive. In an embodiment, roughening of the substrate create microscopic tortuous grooves. Another embodiment of the method comprises coating the roughened surface with at least one hydrophobic chemical agent. In an exemplary embodiment, the hydrophobic chemical agent covalently binds with the substrate creating nanoscopic grooves. Another embodiment of the present disclosure pertains to an apparatus for depositing a self-cleaning coating on a flat substrate. A further embodiment of the present disclosure pertains to a self-cleaning coating on a substrate comprising a hydrophobic chemical agent covalently bonded to at least one roughened surface of the substrate.

Claims

1. A method of forming a self-cleaning coating on a substrate comprising the steps of:

selecting a substrate;

cleaning the substrate;

roughening the substrate to create microscopic tortuous grooves;

washing the substrate with de-ionized water; and

coating the roughened surface with at least one hydrophobic chemical agent, wherein the hydrophobic chemical agent binds to the roughened surface to create nanoscopic grooves, and wherein the coated substrate has a light transmission or reflection similar to or higher than that of the uncoated substrate.

2. The method of claim 1, wherein the substrate is a flat or a non-flat substrate.

3. The method of claim 1, wherein the substrate comprises metals, metal oxides, organic/inorganic composites containing metals/metal oxides and plastic with silicon dioxide or metal oxides layer by sol-gel formation or other methods.

4. The method of claim 1, wherein the step of roughening the substrate to create the microscopic tortuous grooves comprises using a mechanical grinder or a polisher.

5. The method of claim 4, wherein the mechanical grinder is used with a grinding disc or an abrasive paper.

6. The method of claim 4, wherein the polisher is used with a polishing suspension.

7. The method of claim 4, further comprising using at least one abrasive, wherein the hardness of the at least one abrasive is greater than that of the substrate.

8. The method of claim 7, wherein the abrasive is selected from the group consisting of diamond, carbonado, boron, boron nitride, corundum, silicon carbide, tungsten carbide, titanium carbide, chromium, silicon nitride, topaz, zirconia, tungsten, quartz and glass.

9. The method of claim 1, wherein the step of roughening and activating the substrate is by ozone plasma treatment.

10. The method of claim 1, wherein the microscopic tortuous grooves created on the substrate range in depth from about 1 μ

m to about 1 mm.

11. The method of claim 1, wherein the at least one hydrophobic chemical agent comprises a fluoroalkylsilane.

12. The method of claim 11, wherein the fluoroalkylsilane is selected from the group consisting of trichloro(3,3,3-trifluoropropyl)silane, dichloro-methyl(3,3,3-trifluoropropyl)silane, chloro-dimethyl(3,3,3-trifluoropropyl)silane, trichloro(1H,1H,2H,2H-perfluorooctyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorooctyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorooctyl)silane, trichloro(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, dichloro-methyl(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, chloro dimethyl(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, trichloro(1H,1H,2H,2H-perfluorodecyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorodecyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorodecyl)silane, trichloro(1H,1H,2H,2H-perfluorododecyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorododecyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorododecyl)silane and derivatives bearing similar structures.

13. The method of claim 1, wherein the at least one hydrophobic chemical agent comprises chlorosilane, dichlorosilane, trichlorosilane, chlorotrimethylsilane, dichlorodimethylsilane, trichloromethylsilane, chlorophenylsilane, dichlorophenylsilane, trichlorophenylsilane, chloromethylphenylsilane, chlorodimethylphenylsilane, dichloromethylphenylsilane, chlorodimethylphenethylsilane, dichloromethylphenethylsilane, trichlorophenethylsilane, chlorodimethyldodecylsilane, dichloromethyldodecylsilane, trichlorododecylsilane, chlorodecyldimethylsilane, dichlorodecylmethylsilane, trichlorodecylsilane, chlorodimethyloctadecylsilane, dichloromethyloctadecylsilane, trichlorooctadecylsilane, chlorodimethyloctylsilane, dichloromethyloctylsilane, trichlorooctylsilane, chlorodimethylhexylsilane, dichloromethylhexylsilane, trichlorohexylsilane, chlorodimethylthexylsilane, dichloromethylthexylsilane, trichlorothexylsilane, allyldichloromethylsilane, allylchlorodimethylsilane, allyltrichlorosilane, (cyclohexylmethyl)chlorodimethylsilane, (cyclohexylmethyl)dichloromethylsilane, (cyclohexylmethyl)trichlorosilane, and derivatives bearing similar structure.

14. The method of claim 13, further comprising a Fluoroalkylsilane.

15. The method of claim 1, wherein the step of coating the roughened substrate comprises immersing the substrate in a solution of the at least one hydrophobic chemical agent dissolved in an organic solvent.

16. The method of claim 15, wherein the organic solvent is anhydrous toluene.

17. The method of claim 1, wherein the nanoscopic grooves created on the substrate range in depth from about 10 nm to about 1 μ

m.

18. The method of claim 1, wherein the steps of the method are performed in a controlled humidity environment.

19. The step of claim 18, wherein the humidity is controlled to about 20% of related humidity.

20. The method of claim 15, further comprising washing the coated substrate with an organic solvent.

21. The method of claim 20, wherein the organic solvent is anhydrous toluene.

22. The method of claim 20, further comprising drying the substrate in ambient conditions.

23. The method of claim 1, wherein the step of coating the roughened substrate with the hydrophobic chemical agent is by the process of physical vapor deposition.

24. The method of claim 23, wherein the physical vapor phase deposition of the hydrophobic chemical agent is conducted by controlling the evaporation of the hydrophobic chemical agent.

25. The method of claim 24, wherein controlling the evaporation of the hydrophobic chemical agent comprises controlling the pressure of injection and the temperature of heating of the hydrophobic chemical agent.

26. An apparatus for depositing a self-cleaning coating on a substrate comprising:

a station for forming microscopic grooves on the substrate;

a chamber for coating the substrate with at least one hydrophobic chemical agent,

wherein the coating creates nanoscopic grooves on the substrate; and

a drying chamber connected to the coating chamber, wherein the station is operatively connected to transport the substrate to the coating chamber, and wherein the coating chamber is operatively connected to transport the substrate to the drying chamber.

27. The apparatus of claim 26, wherein the station for forming microscopic grooves on the substrate comprises:

at least one flat plate with an abrasive pad;

at least one dispenser for dispensing an abrasive solution;

at least one stage for loading the substrate; and

at least two actuators, wherein one of the at least two actuators is along the Z-axis in reference to the flat plate and upon activation contacts the abrasive pad with the substrate surface, and wherein one of the at least two actuators is along the X-axis in reference to the flat plate and upon activation moves the stage back and forth along the X-axis.

28. The apparatus of claim 27, further comprising at least one actuator along the Y-axis in reference to the flat plate such that upon activation the actuator moves the stage back and forth along the Y-axis.

29. The apparatus of claim 27, wherein the abrasive solution comprises diamond, carbonado, boron, boron nitride, corundum, silicon carbide, tungsten carbide, titanium carbide, chromium, silicon nitride, topaz, zirconia, tungsten, quartz and glass.

30. The apparatus of claim 26, wherein the microscopic grooves range in depth from about 1 μ

m to about 1 mm.

31. The apparatus of claim 26, wherein the chamber for coating the substrate with at least one hydrophobic chemical agent comprises:

a stage for loading the substrate;

at least one dispenser connected to an injector, wherein the dispenser contains the at least one hydrophobic chemical agent;

an applicator for applying the at least one hydrophobic agent on the substrate;

an actuator connected to the applicator,

wherein the applicator is pushed closer to the roughened substrate upon activation of the actuator and upon injection of the hydrophobic chemical agent from the dispenser to spread the hydrophobic chemical agent on to the substrate;

an outlet for reaction by-products; and

a dehumidifier.

32. The apparatus of claim 31, wherein the hydrophobic chemical agent comprises a fluoroalkylsilane.

33. The apparatus of claim 32, wherein the fluoroalkylsilane is selected from the group consisting of trichloro(3,3,3-trifluoropropyl)silane, dichloro-methyl(3,3,3-trifluoropropyl)silane, chloro-dimethyl(3,3,3-trifluoropropyl)silane, trichloro(1H,1H,2H,2H-perfluorooctyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorooctyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorooctyl)silane, trichloro(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, dichloro-methyl(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, chloro dimethyl(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, trichloro(1H,1H,2H,2H-perfluorodecyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorodecyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorodecyl)silane, trichloro(1H,1H,2H,2H-perfluorododecyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorododecyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorododecyl)silane and derivatives bearing similar structures.

34. The apparatus of claim 31, wherein the hydrophobic chemical agent comprises chlorosilane, dichlorosilane, trichlorosilane, chlorotrimethylsilane, dichlorodimethylsilane, trichloromethylsilane, chlorophenylsilane, dichlorophenylsilane, trichlorophenylsilane, chloromethylphenylsilane, chlorodimethylphenylsilane, dichloromethylphenylsilane, chlorodimethylphenethylsilane, dichloromethylphenethylsilane, trichlorophenethylsilane, chlorodimethyldodecylsilane, dichloromethyldodecylsilane, trichlorododecylsilane, chlorodecyldimethylsilane, dichlorodecylmethylsilane, trichlorodecylsilane, chlorodimethyloctadecylsilane, dichloromethyloctadecylsilane, trichlorooctadecylsilane, chlorodimethyloctylsilane, dichloromethyloctylsilane, trichlorooctylsilane, chlorodimethylhexylsilane, dichloromethylhexylsilane, trichlorohexylsilane, chlorodimethylthexylsilane, dichloromethylthexylsilane, trichlorothexylsilane, allyldichloromethylsilane, allylchlorodimethylsilane, allyltrichlorosilane, (cyclohexylmethyl)chlorodimethylsilane, (cyclohexylmethyl)dichloromethylsilane, (cyclohexylmethyl)trichlorosilane, and derivatives bearing similar structure.

35. The apparatus of claim 34, further comprising a Fluoroalkylsilane.

36. The apparatus of claim 26, wherein the nanoscopic grooves created on the substrate range in depth from about 10 nm to about 1 μ

m.

37. The apparatus of claim 31, wherein the hydrophobic chemical agent is dissolved in an organic solvent.

38. The apparatus of claim 37, wherein the organic solvent is anhydrous toluene.

39. The apparatus of claim 31, wherein the dehumidifier keeps the humidity in the coating chamber at about 20% of related humidity.

40. The apparatus of claim 26, wherein the coating chamber comprises a heating element and a vacuum pump.

41. The apparatus of claim 26, wherein the station for creating microscopic grooves on the substrate comprises a controlled humidity chamber comprising:

a rotating trail for suspending the substrate;

a plurality of ultra-violet lamps;

an oxygen supply; and

an outlet for reaction byproducts optionally fitted with chemical filters.

42. The apparatus of claim 26, wherein the coating chamber comprises:

a rotating trail for suspending the substrate;

a liquid pump connected to a dispenser, wherein the liquid pump contains at least one hydrophobic chemical agent;

an inert gas supply, wherein the inert gas supply distributes the at least one hydrophobic chemical agent on to the substrate;

a device for controlling the ratio of the liquid pump spraying pressure to the inert gas pressure;

a dehumidifier; and

an outlet for reaction byproduct and gas optionally fitted with chemical filters.

43. The apparatus of claim 42, wherein the ratio of the liquid pump spraying pressure and the gas pressure is controlled to range from about 1:

10 to about 1;

100,000.

44. A self-cleaning coating on a substrate comprising:

a hydrophobic chemical agent covalently bonded to at least one roughened surface of the substrate, wherein the bonding creates nanoscopic grooves on the roughened surface of the substrate, and wherein the coating renders the substrate self-cleaning when tilted above a critical angle α

.

45. The self-cleaning coating of claim 44, wherein the nanoscopic grooves range in depth from about 10 nm to about 1 μ

m

46. The self-cleaning coating of claim 44, wherein the roughened surface of the substrate is created by polishing the substrate with at least one abrasive.

47. The self-cleaning coating of claim 46, wherein the polishing of the substrate with the at least one abrasive creates microscopic tortuous grooves.

48. The self-cleaning coating of claim 47, wherein the substrate is polished with a second abrasive to create secondary microscopic grooves.

49. The self-cleaning coating of claim 47, wherein the microscopic tortuous grooves range in depth from about 1 μ

m to 1 mm.

50. The self-cleaning coating of claim 44, wherein at least one of the hydrophobic chemical agents comprises a fluoroalkylsilane.

51. The self-cleaning coating of claim 50, wherein the fluoroalkylsilane is selected from the group consisting of trichloro(3,3,3-trifluoropropyl)silane, dichloro-methyl(3,3,3-trifluoropropyl)silane, chloro-dimethyl(3,3,3-trifluoropropyl)silane, trichloro(1H,1H,2H,2H-perfluorooctyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorooctyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorooctyl)silane, trichloro(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, dichloro-methyl(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, chloro dimethyl(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane, trichloro(1H,1H,2H,2H-perfluorodecyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorodecyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorodecyl)silane, trichloro(1H,1H,2H,2H-perfluorododecyl)silane, dichloro-methyl(1H,1H,2H,2H-perfluorododecyl)silane, chloro-dimethyl(1H,1H,2H,2H-perfluorododecyl)silane and derivatives bearing similar structures.

52. The self-cleaning coating of claim 44, wherein the hydrophobic chemical agent comprises chlorosilane, dichlorosilane, trichlorosilane, chlorotrimethylsilane, dichlorodimethylsilane, trichloromethylsilane, chlorophenylsilane, dichlorophenylsilane, trichlorophenylsilane, chloromethylphenylsilane, chlorodimethylphenylsilane, dichloromethylphenylsilane, chlorodimethylphenethylsilane, dichloromethylphenethylsilane, trichlorophenethylsilane, chlorodimethyldodecylsilane, dichloromethyldodecylsilane, trichlorododecylsilane, chlorodecyldimethylsilane, dichlorodecylmethylsilane, trichlorodecylsilane, chlorodimethyloctadecylsilane, dichloromethyloctadecylsilane, trichlorooctadecylsilane, chlorodimethyloctylsilane, dichloromethyloctylsilane, trichlorooctylsilane, chlorodimethylhexylsilane, dichloromethylhexylsilane, trichlorohexylsilane, chlorodimethylthexylsilane, dichloromethylthexylsilane, trichlorothexylsilane, allyldichloromethylsilane, allylchlorodimethylsilane, allyltrichlorosilane, (cyclohexylmethyl)chlorodimethylsilane, (cyclohexylmethyl)dichloromethylsilane, (cyclohexylmethyl)trichlorosilane, and derivatives bearing similar structure.

53. The self-cleaning coating of claim 52, further comprising a Fluoroalkylsilane.

54. The self-cleaning coating of claim 44, wherein the critical angle α

is defined by

tan (y/x), when the substrate surface is tilted on an incline plane and a right triangle is formed by the incline plane (hypotenuse) and the horizontal surface, wherein y=length of the opposite leg of the right triangle and x=length of the adjacent leg of the right triangle.

55. The self-cleaning coating of claim 44, wherein the coating creates a light transmission or reflection similar to or higher than that of the uncoated substrate.