Self-healing coatings using microcapsules

• US 20060042504A1
• Filed: 08/24/2004
• Published: 03/02/2006
• Est. Priority Date: 08/24/2004
• Status: Active Grant

• Current Assignee: Ashok Kumar, Larry D. Stephenson
• Original Assignee: Ashok Kumar, Larry D. Stephenson
• Inventors: Kumar, Ashok, Stephenson, Larry D.
• Granted Patent: US 7,342,057 B2
• Time in Patent Office: Days
• US Class Current: 106/14.340
• CPC Class Codes: C04B 20/1037 obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: C04B 2103/0075 Anti-dusting agents
• CPC Class Codes: C04B 2111/00482 Coating or impregnation materials
• CPC Class Codes: C04B 22/002 Water
• CPC Class Codes: C04B 22/064 of the alkaline-earth metals
• CPC Class Codes: C04B 24/2611 Polyalkenes
• CPC Class Codes: C04B 26/02 Macromolecular compounds
• CPC Class Codes: C04B 40/0641 Mechanical separation of ingredients, e.g. accelerator in breakable microcapsules
• CPC Class Codes: C04B 40/0675 Mortars activated by rain, percolating or sucked-up water; Self-healing mortars or concrete
• CPC Class Codes: C08K 9/10 Encapsulated ingredients
• CPC Class Codes: C09D 5/002 Priming paints C09D5/08 takes precedence
• CPC Class Codes: C09D 7/40 Additives
• CPC Class Codes: C09D 7/69 Particle size larger than 1000 nm
• CPC Class Codes: Y10T 428/2985 Solid-walled microcapsule from synthetic polymer

Abstract

Self-healing coatings incorporate microcapsules of about 60-150 microns diameter that contain film formers and dust suppression compounds suitable for controlling spalling of lead dust, for example. In one embodiment, a primer paint is mixed with these microcapsules and applied by brushing or rolling. After the coating has cured, any physical compromise of the coating results in microcapsules bursting to release liquid that fills and seals the compromised volume. The microcapsule contents protect the underlying substrate from damage and repair some of the outer coating. In one application, embodiments of these self-healing coatings seal existing lead-based paint for suppression of lead dust. In another embodiment, microcapsules are provided separately to enhance commercially available products. For example, if a paint formulation is known a priori, specifically configured microcapsules, packaged separately from the paint and designed for use with the paint formulation, are added to the paint just prior to application.

Claims

1. A self-healing coating suitable for suppression of dust from an undercoating thereto, comprising:

at least one liquid solvent;

at least one solid dispersed in said solvent; and

microcapsules, having a shell defining a volume, said volume containing at least one repair substance suitable for suppression of dust from an undercoating to said self-healing coating,

wherein said shell is resistant to degradation by said repair substance; and

wherein prior to application of said self-healing coating and after addition of said microcapsules to said liquid solvent/solid mixture, said microcapsules are resistant to short term degradation by each of said at least one liquid solvent, and said at least one solid material; and

wherein said microcapsules burst upon physical compromise of said applied and cured self-healing coating, releasing said at least one repair substance to fill and seal the compromised volume within said self-healing coating.

2. The self-healing coating of claim 1 in which the combination of said at least one liquid solvent and said at least one solid comprises a protective coating.

3. The self-healing coating of claim 2 in which said protective coating is a paint.

4. The self-healing coating of claim 3 in which said paint is a primer selected from the group consisting of:

polyurethanes, oil-based enamels, enamel undercoater, latex acrylics, acrylic formulations and epoxy formulations.

5. The self-healing coating of claim 1 further comprising a topcoat paint selected from the group consisting of:

polyurethanes, oil-based enamels, enamels, latex acrylics, acrylic formulations and epoxy formulations.

6. The self-healing coating of claim 3 in which said paint is a self-priming paint selected from the group consisting of:

polyurethanes, oil-based enamels, enamels, latex acrylics, acrylic formulations and epoxy formulations.

7. The self-healing coating of claim 1 in which the combination of said at least one liquid solvent and said at least one solid comprises a protective coating.

8. The self-healing coating of claim 1 in which the combination of said at least one liquid solvent and said at least one solid comprises a decorative coating.

9. The self-healing coating of claim 1 in which said shell is a sphere with an outer diameter within the approximate range of 50 to 200 microns.

10. The self-healing coating of claim 1 in which said shell is a sphere with an outer diameter within the approximate range of 60 to 150 microns.

11. The self-healing coating of claim 1 in which said shell comprises urea formaldehyde (UF).

12. The self-healing coating of claim 1 in which said shell comprises gelatin.

13. The self-healing coating of claim 1 in which said repair substance comprises materials selected from the group consisting essentially of:

film-forming compounds, dust suppression compounds, diluents, and combinations thereof.

14. The self-healing coating of claim 13 in which said film-forming compounds are selected from the group consisting essentially of polybutene, Ca(OH)₂, and combinations thereof.

15. The self-healing coating of claim 13 in which said diluents are selected from the group consisting essentially of:

long chain polyester diluents, carrier diluents, water, and combinations thereof.

16. The self-healing coating of claim 14 in which said dust suppression compounds are selected from the group consisting essentially of:

Ca(OH)₂, polybutene, and combinations thereof.

17. The self-healing coating of claim 1 in which said microcapsules are added as a pre-specified percentage of the weight of said solids and said liquids comprising a non-self healing coating, said microcapsules added at a pre-specified time prior to application of said self-healing coating.

18. The self-healing coating of claim 17 in which said pre-specified percentage lies in the approximate range of 10 to 40% and said pre-specified time is within about fourteen (14) days prior to application of said self-healing coating.

19. The self-healing coating of claim 17 in which said pre-specified percentage is approximately 20% and said pre-specified time is approximately concurrent with preparing said self-healing coating for application.

20. A microcapsule suitable for adding to a liquid protective coating to be cured at ambient temperature to facilitate self-healing of said resultant coating after curing thereof, said self-healing further suppressing dust dispersion from an existing undercoating to said resultant coating, said microcapsule comprising:

a repair substance suitable for said suppressing of dust dispersion; and

a shell enclosing a volume containing said repair substance,

whereupon application of said resultant self-healing coating to a substrate and curing of said self-healing coating thereon, physical compromise of said self-healing coating results in rupture of said shell and deployment of said repair substance to fill and seal the compromised volume within said coating adjacent said microcapsule.

21. The microcapsule of claim 20 in which said shell is a sphere with an outer diameter within the approximate range of 50 to 200 microns.

22. The microcapsule of claim 20 in which said shell is a sphere with an outer diameter within the approximate range of 60 to 150 microns.

23. The microcapsule of claim 20 in which said shell comprises urea formaldehyde (UF).

24. The microcapsule of claim 20 in which said shell comprises gelatin.

25. The microcapsule of claim 20 in which said repair substance comprises materials selected from the group consisting essentially of:

film-forming compounds, dust suppression compounds, diluents, and combinations thereof.

26. The microcapsule of claim 25 in which said film-forming compounds are selected from the group consisting essentially of:

polybutene, Ca(OH)₂, and combinations thereof.

27. The microcapsule of claim 25 in which said diluents are selected from the group consisting essentially of:

long chain polyester diluents, carrier diluents, water, and combinations thereof.

28. The microcapsule of claim 25 in which said dust suppression compounds are selected from the group consisting essentially of:

Ca(OH)₂, polybutene, and combinations thereof.

29. A method for composing a liquid self-healing coating that repairs itself after application and curing while suppressing at least some dust from an underlying coating upon compromise of said self-healing coating, comprising:

providing a liquid non-self healing coating;

providing microcapsules filled with at least one repair substance compatible with said non-self healing coating and suitable for at least said suppressing of dust from an existing coating to be covered by said self-healing coating; and

at a pre-specified time prior to applying said liquid self-healing coating, mixing said microcapsules into said liquid non-self healing coating such that said microcapsules are fully wetted and interspersed evenly throughout said liquid non-self healing coating.

30. A method for producing a self-healing coating upon a substrate having an existing coating, said self-healing coating suitable for suppressing at least some dust from said existing coating upon compromise of said self-healing coating, comprising:

providing a liquid non-self healing coating;

providing microcapsules filled with a repair substance compatible with said non-self healing coating and suitable for said suppressing of dust;

at a pre-specified time prior to applying said self-healing coating, mixing said microcapsules into said liquid non-self healing coating such that said microcapsules are fully wetted and interspersed evenly throughout said liquid non-self healing coating;

applying said liquid self-healing coating to said substrate by any of a number of means selected from the group consisting of;

brushing, rolling, drawing down, and combinations thereof; and

permitting said applied self-healing coating to cure prior to use of said substrate.