Self-healing coating and microcapsules to make same

Abstract

A self-healing coating, incorporating medium-sized microcapsules filled with a liquid formulation, repairs itself upon physical compromise. In one embodiment, a commercial primer is mixed with these microcapsules and applied. After the coating has cured, any physical compromise of the cured coating results in the microcapsules bursting to release the liquid, in turn filling and sealing the compromised volume of the coating. In applications where a product is used to provide corrosion protection, the liquid contains anti-corrosion material as well as suitable diluents and film-forming compounds. In a preferred embodiment, the microcapsules are provided separately to be mixed with commercial products during preparation for application of the coating. For example, if a paint formulation is known a priori, tailored microcapsules packaged separately from the paint and designed for use with the paint formulation, are wet mixed into the paint during preparation for application.

1 . A self-healing coating that repairs itself upon physical compromise of an application of said self-healing coating that was cured at ambient temperature, comprising:
 at least one liquid COTS coating containing at least some solids; and   medium-sized microcapsules, having a shell defining a volume of a sphere with an average outer diameter between 80 and approximately 150 microns, said volume containing at least one repair substance, said medium-sized microcapsules wet mixed into said liquid COTS coating just prior to application of 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 COTS coating, said microcapsules are resistant to short term degradation by said liquid COTS coating; and 
       wherein said microcapsules in the area of a physical compromise of said applied and cured self-healing coating burst, 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 said at least one liquid COTS coating 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 3  in which said paint is a topcoat 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 liquid COTS coating and said microcapsules comprises a corrosion inhibiting coating. 
     
     
         8 . The self-healing coating of  claim 1  in which the combination of said liquid COTS coating and said microcapsules comprises a decorative coating. 
     
     
         9 . The self-healing coating of  claim 1  in which the average outer diameter of said microcapsule is approximately 100 to 150 microns. 
     
     
         10 . The self-healing coating of  claim 1  in which the average outer diameter of said microcapsule is approximately 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:
 film-forming compounds;   diluents; and   corrosion inhibiting compounds.   
     
     
         14 . The self-healing coating of  claim 13  in which said film-forming compounds are selected from the group consisting of polybutene, phenolics, phenolic varnishes, and combinations thereof. 
     
     
         15 . The self-healing coating of  claim 13  in which said diluents are selected from the group consisting of: long chain polyester diluents, carrier diluents, and combinations thereof. 
     
     
         16 . The self-healing coating of  claim 13  in which said corrosion inhibiting compounds are selected from the group consisting of: camphor, alkylammonium salt in xylene, polyamine fatty acid in salt in ethanol, and combinations thereof. 
     
     
         17 . The self-healing coating of  claim 1  in which said microcapsules are added as a pre-specified percentage of the dry weight of said solids to said liquid COTS coating 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 the range of about immediately prior to application to about fourteen (14) days prior to application of said self-healing coating. 
     
     
         19 . The self-healing coating of  claim 18  in which said pre-specified percentage is approximately 25% and said pre-specified time is approximately concurrent with preparing said self-healing coating for application. 
     
     
         20 . A microcapsule wet mixed into a liquid COTS coating to produce a self-healing coating cured at ambient temperature, said microcapsule comprising:
 a repair substance; and   a shell enclosing a volume containing said repair substance, in which said shell is a sphere with an average outer diameter of approximately 80 to 150 microns,   whereupon application of said 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 shells near said physical compromise and deployment of said repair substance to fill and seal the compromised volume within said self-healing coating.   
     
     
         22 . The microcapsule of  claim 20  in which said shell has an average outer diameter greater than 80 microns and less than 200 microns. 
     
     
         23 . The microcapsule of  claim 20  in which said shell has an average outer diameter of approximately 150 microns. 
     
     
         24 . The microcapsule of  claim 20  in which said shell comprises urea formaldehyde (UF). 
     
     
         25 . The microcapsule of  claim 20  in which said shell comprises gelatin. 
     
     
         26 . The microcapsule of  claim 20  in which said repair substance comprises:
 film-forming compounds;   diluents; and   corrosion inhibiting compounds.   
     
     
         27 . The microcapsule of  claim 26  in which said film-forming compounds are selected from the group consisting of: polybutene, phenolics, phenolic varnishes, and combinations thereof. 
     
     
         28 . The microcapsule of  claim 26  in which said diluents are selected from the group consisting of: long chain polyester diluents, carrier diluents, and combinations thereof. 
     
     
         29 . The microcapsule of  claim 26  in which said corrosion inhibiting compounds are selected from the group consisting of camphor, alkylammonium salt in xylene, polyamine fatty acid in salt in ethanol, and combinations thereof. 
     
     
         30 . A method for providing a liquid self-healing coating that repairs itself after application and curing, comprising:
 providing a liquid non-self healing coating;   providing medium-sized microcapsules of an average diameter between approximately 80 and 150 microns filled with a repair substance compatible with said non-self healing coating; and   in preparation for 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.   
     
     
         31 . A method for producing a self-healing coating upon a substrate, comprising:
 providing a liquid non-self healing coating;   providing medium-sized microcapsules of an average diameter between approximately 80 and 150 microns filled with a repair substance compatible with said non-self healing coating;   in preparation for 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 thus producing a liquid 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, spraying, and combinations thereof; and   permitting said applied liquid self-healing coating to cure prior to use of said substrate.