Coating for sterilization using UV light

Abstract

To provide a coating composition that allows sterilization of various surfaces using UV-C light while remaining transparent.SOLUTION: Coating compositions include: a polyurethane component; and nanoparticles having an average particle size of from about 30 nm to about 400 nm, where the nanoparticles absorb light having a wavelength of from about 100 nm to about 290 nm. The nanoparticles are present in an amount of less than about 25 wt.% of total solids in the coating composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] 1.Technical Field The present disclosure relates to coatings and methods for disinfecting aircraft lavatories and other surfaces, and in particular to coatings that can be used in combination with ultraviolet (UV) light for disinfection. [Background technology]

[0002] 2. Related technologies Current galley and lavatory cleaning is usually performed frequently by airline cleaning companies, typically during aircraft turnaround times. During these cleaning procedures, chemical disinfectants are used to clean exposed surfaces such as counters, sinks, cart doors, and floors. The interiors of compartments such as ovens, freezers, storage bins, etc. are also cleaned periodically.

[0003] However, this process takes a long time and, as a result, there is a need for improved technology for cleaning and disinfecting aircraft. Summary of the Invention

[0004] Embodiments of the present disclosure provide various coating compositions and methods for sterilization. Advantageously, the coating compositions enable sterilization of various surfaces using UV-C light while maintaining transparency. The coating compositions protect the surface from UV-C light, but allow the UV-C light to kill or inactivate microorganisms on the surface.

[0005] In one embodiment of the present disclosure, a coating composition includes a polyurethane component and nanoparticles having an average particle size of about 30 nm to about 400 nm. The nanoparticles absorb light having a wavelength of about 100 nm to about 290 nm (i.e., UV-C light) and are present in an amount of less than about 25 weight percent of the total solids in the coating composition. In some embodiments, the polyurethane component includes a crosslinked aliphatic polyurethane.

[0006] In some embodiments, the nanoparticles comprise chemically inert, non-combustible particles. Suitable nanoparticles include, but are not limited to, metal oxides (e.g., titanium dioxide, tin oxide, silicon dioxide, or zinc oxide), polytetrafluoroethylene (PTFE), or polyamides.

[0007] In various embodiments, the coating composition further comprises a UV light blocker. Any suitable UV blocker can be used. In embodiments, a phenolic antioxidant is included in the coating composition.

[0008] A method of applying a coating composition to an article includes providing the coating composition described above and applying the coating composition to the exterior surface of the article.

[0009] In a second aspect of the present disclosure, an article includes a substrate having an exterior surface and a coating composition on the exterior surface. The coating composition includes a crosslinked aliphatic polyurethane and nanoparticles having an average particle size of about 30 nm to about 400 nm. The nanoparticles absorb light having a wavelength of about 100 nm to about 290 nm and are present in an amount of less than about 25 weight percent of the total solids in the coating composition.

[0010] In various embodiments, the substrate comprises a metal or a plastic. In several embodiments, the nanoparticles comprise one or more of titanium oxide, zinc oxide, tin oxide, silicon oxide, polytetrafluoroethylene (PTFE), or polyamide.

[0011] In some embodiments, a method of sterilizing a surface comprises exposing the exterior surface of an article to light having a wavelength of about 200 nm to about 240 nm, hi some embodiments, the coating composition is transparent on the exterior surface after exposure to light having a wavelength of about 200 nm to about 240 nm.

[0012] In a further aspect, a method includes providing a coating composition and applying the coating composition to a surface to be sterilized. The coating composition includes a crosslinked aliphatic polyurethane and nanoparticles having an average particle size of about 30 nm to about 400 nm. The nanoparticles absorb light having a wavelength of about 100 nm to about 290 nm and are present in an amount of less than about 25 weight percent of total solids in the clear coating composition.

[0013] In some embodiments, the nanoparticles comprise one or more of titanium oxide, zinc oxide, tin oxide, silicon oxide, polytetrafluoroethylene (PTFE), or polyamide. In other embodiments, the coating composition further comprises a UV light blocker.

[0014] In some embodiments, the method also includes exposing the surface to light having a wavelength of about 200 nm to about 240 nm, hi some embodiments, the surface is exposed to light having a wavelength of about 220 nm in intermittent bursts.

[0015] In various embodiments, applying the coating composition comprises spray application. In some embodiments, the surfaces to be sterilized include one or more of the following: surfaces on and around a toilet inside a lavatory, surfaces in and around a sink inside a lavatory, a lavatory floor, a surface of a door handle, or a surface of a drawer handle or cabinet knob.

[0016] The scope of the present disclosure is defined by the claims, which are incorporated by reference into this section. Those skilled in the art will understand the disclosed methods and formulations for iron-tungsten coatings, and the above and additional advantages thereof, upon consideration of the following detailed description of one or more embodiments of the present disclosure. Reference is made herein to various figures of the accompanying drawings, which are briefly described below. In the figures, like reference numerals are used to identify like elements shown in the figures. [Brief explanation of the drawings]

[0017] [Figure 1] 1 illustrates an aircraft lavatory according to one embodiment of the present disclosure. [Figure 2] 1 illustrates an exemplary process for sterilizing a surface of an article, according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] In aircraft lavatories, toilets, counters, cabinet doors, sinks, and floors are cleaned by cleaning companies during aircraft turnarounds and / or at the end of scheduled flights. Aircraft lavatories provide an environment that passengers often consider unsanitary due to the potential presence of microbial contamination. Furthermore, because they are used by hundreds of people, the risk of infectious diseases is thought to be increased due to lavatory use. Because various pathogens can survive on hard surfaces for several weeks, various viral or bacterial infections can be spread. Additionally, the immune systems of aircraft crew members are constantly adversely affected by circadian rhythm disruption, stress, and a foreign environment, which can increase their vulnerability to various pathogens. Because this pathogen environment is constantly changing daily, it is desirable to address lavatory decontamination.

[0019] UV-C light is germicidal. UV-C light inactivates the DNA of bacteria, viruses, and other pathogens. UV-C light damages the nucleic acids of microorganisms by forming covalent bonds between some adjacent bases in the DNA. Such formation prevents DNA replication. If the microorganism attempts to replicate, it will die.

[0020] However, UV-C light has undesirable effects on plastics, dyes, and coatings. Common coatings deteriorate or darken after repeated exposure to UV-C light, and more robust coatings, such as those used in hospitals, become dull. Countertops and surfaces in lavatories are often made with patterns that resemble granite or marble, but airline passengers do not want these patterns hidden by the dull coating.

[0021] Thus, a clear coating is described in this disclosure that can be sterilized with UV-C light without degrading or discoloring.

[0022] This disclosure describes coating compositions and methods that can be used to sterilize or disinfect surfaces, such as aircraft lavatory surfaces. The coating compositions include a base material and nanoparticles that do not interact with visible light, so that the coating compositions do not appear dull or colored when applied to various substrates, such as metal or plastic. Various substrates containing the coating compositions can be exposed to UV-C light and disinfected without degradation or discoloration. As used herein, UV-C light refers to ultraviolet-C light having a wavelength of about 100 nm to about 290 nm.

[0023] In some embodiments, the base material of the coating composition includes a polyurethane component, such as a crosslinked aliphatic polyurethane. Exterior-grade polyurethane coatings include PPG's Desothane® HS CA8000 polyurethane topcoat, AkzoNobel's Eclipse Semi-Gloss high-solids decorative topcoat, or Sherwin-Williams' Skyscapes® clearcoat topcoat.

[0024] The nanoparticles have an average particle size of about 30 nm to about 400 nm. Therefore, the nanoparticles typically have a particle size smaller than the wavelength of visible light (380-740 nm). Due to this size, the nanoparticles do not interact with visible light, and the coating composition appears clear or transparent, rather than dull or colored.

[0025] Additionally, the nanoparticles can absorb UV-C light and convert it into harmless infrared radiation (e.g., heat), and thus the UV-C light does not interact with (e.g., degrade or destroy) the coating composition or the substrate underlying the applied coating composition.

[0026] The concentration of nanoparticles required to protect the surface of a substrate generally depends on the solids content of the coating. In embodiments, the nanoparticles are present in an amount of less than about 25 weight percent of the total solids in the coating composition. For example, the nanoparticles may be present in an amount of about 5, 10, or 20 weight percent of the total solids in the coating composition, which may be sufficient to protect the surface of the substrate without interfering with the manufacture or application of the coating or adversely affecting the appearance, performance, or lifespan of the resulting coating.

[0027] Suitable nanoparticles include chemically inert, non-combustible inorganic particles. Examples include metal oxides (e.g., titanium dioxide, tin oxide, silicon dioxide, or zinc oxide), polytetrafluoroethylene (PTFE), or polyamides (e.g., nylon). Inorganic particles are less soluble (and therefore less likely to leach) in cleaning agents, can provide some abrasion or scratch resistance to coating compositions, are less likely to produce colored decomposition products compared to organic particles, consume energy without degrading (fragmenting) into smaller species or particles, and are commercially available.

[0028] Coating compositions can be prepared using conventional methods. For example, a solution of the base material is prepared, and then the appropriate amount of inorganic particles is mixed into the solution to form the coating composition. Typically, the base material comprises two parts that are mixed immediately before use. Smaller inorganic particle sizes can affect the viscosity of the coating composition, which can affect how well the coating composition applies or how quickly it dries due to solvent evaporation. This can require slowing the blending of some of the necessary solvents (i.e., a slower-evaporating solvent), which can affect the remaining amount of solvent in the coating composition and, in the case of spray applications, how the spray droplets form, coalesce, and dry. All of these factors can also affect pot life (i.e., the amount of time it takes for the initial mixed viscosity to double). Using the guidance of this disclosure, one of ordinary skill in the art can prepare an appropriate coating composition based on the desired viscosity of the coating composition.

[0029] The coating composition may further comprise a UV-blocking agent. Suitable UV-blocking agents are IRGANOX® products. IRGANOX® is a trade name for BASF's phenolic antioxidants. These are characterized by having a phenol group substituted with tert-butyl groups at two adjacent positions on the ring. An example of an IRGANOX® product is the IRGANOX® 1010 product shown below.

[0030] TIFF0007745997000001.tif152170

[0031] Referring now to the drawings, and in particular to Figure 1, a lavatory 100 is illustrated according to one embodiment. As shown, the lavatory 100 may be located within a vehicle. The vehicle may take the form of an aerospace vehicle, such as an aircraft, a spacecraft, a space shuttle, a space station, or any other type of aerospace vehicle. In other embodiments, the vehicle may take the form of a land vehicle or a water vehicle, such as a bus, a train, a submarine, a boat, or a ship.

[0032] As shown, the lavatory 100 includes multiple surfaces. Such surfaces include any surface within the lavatory 100 that needs to be disinfected due to potential contact with a person, an animal, or any number of pathogen-carrying objects. Such pathogens include airborne pathogens derived from coughs, sputum, or any type of bodily fluid released by a person or animal. The multiple surfaces include, for example, surfaces 101 on and around the toilet within the lavatory 100, surfaces 103 in and around the sink within the lavatory 100, the lavatory floor 101, one or more door handles, one or more drawer handles or cabinet knobs, and any other type of surface that may become infected through direct or indirect contact with a person, an animal, or an object.

[0033] UV-C light from a variety of sources can be used to disinfect surfaces within lavatory 100. While UV-C light source 105 is shown positioned above sink area 103, the light source can be mounted on any surface within lavatory 100. In particular, UV-C light source 105 can be mounted in a location that allows the UV-C light emitted by UV-C light source 105 to reach the greatest number of surfaces within lavatory 100. Advantageously, surfaces 101, 102, and 103 include a coating composition that protects surfaces 101, 102, and 103 from damage caused by the UV-C light emitted by UV-C light source 105. In one embodiment, UV-C light source 105 is selected to emit a wavelength of about 200 nm to about 240 nm. In one embodiment, the UV-C light source emits light having a wavelength of about 220 nm.

[0034] In many cases, the UV-C light source 105 is configured as an automatic light that is activated when the door to the lavatory 100 closes and deactivated when the door opens, so that passengers are not exposed to light when entering or exiting the lavatory 100. In some embodiments, passengers are provided with the option to activate a disinfection process before entering the lavatory 100. When this option is activated, the lavatory door automatically locks, preventing passengers from entering the lavatory until the disinfection process is complete. The disinfection process is typically short-term, e.g., lasting a few seconds, and is performed in intermittent bursts; for example, the UV-C light is activated for 1-2 seconds, deactivated for 5 seconds, and then reactivated for 3-4 seconds. In the event of an intrusion, the disinfection process can be interrupted to protect passengers' eyes from the UV-C light.

[0035] When surfaces 101, 102, and 103 are exposed to UV-C light from UV-C light source 105, the UV-C light begins to disinfect surfaces 101, 102, and 103. Disinfecting surfaces 101, 102, and 103 involves destroying pathogens that may be present on surfaces 101, 102, and 103. When exposed to UV-C light, critical hydrogen bonds that link the pathogen's DNA strands together are disrupted.

[0036] 2 shows an exemplary process for applying a coating composition to an article. In block 202, a coating composition is provided. In block 204, the coating composition is applied to the exterior surface of the article. Any suitable article having an exterior surface to be disinfected can include the coating composition. Examples include toilets, sinks, floors, counters, tabletops, cabinet doors, doorknobs, faucets, and walls.

[0037] The coating composition can be applied by manual application or by spray application, for example, the coating composition can be loaded into a spray gun or other type of spray applicator and then sprayed onto the surface to be coated.

[0038] In block 206, the coating composition is dried or cured (or otherwise solidified). For example, the coating composition can be dried at room temperature or at elevated temperatures (e.g., 30-40° C.). In other examples, infrared (IR) heating with an infrared lamp or the use of UV light to crosslink various reactive species in the coating composition is used.

[0039] In block 208, once the coating composition has dried or cured, the surface can be sterilized with UV-C light having a wavelength of about 200 nm to about 240 nm. Advantageously, the coating composition remains transparent on the exterior surface of the article even after exposure to light having a wavelength of about 200 nm to about 240 nm. The nanoparticles in the coating composition absorb UV-C light rather than reflecting it.

[0040] Additionally, the present disclosure includes embodiments according to the following clauses:

[0041] Clause 1. A coating composition comprising a polyurethane component and nanoparticles having an average particle size of about 30 nm to about 400 nm and absorbing light having a wavelength of about 100 nm to about 290 nm, wherein the nanoparticles are present in an amount of less than about 25 weight percent of total solids in the coating composition. Clause 2. The coating composition of clause 1, wherein the nanoparticles are chemically inert, non-combustible particles. Clause 3. The coating composition of clause 2, wherein the chemically inert, non-combustible particles comprise one or more of a metal oxide, polytetrafluoroethylene (PTFE), or a polyamide. Clause 4. The coating composition of clause 3, wherein the metal oxide comprises one or more of titanium dioxide, tin oxide, silicon dioxide, or zinc oxide. Clause 5. The coating composition of any of clauses 1-4, further comprising an ultraviolet (UV) light blocking agent. Clause 6. The coating composition of clause 5, wherein the UV blocker comprises a phenolic antioxidant. Clause 7. The coating composition of any of clauses 1-6, wherein the polyurethane component comprises a crosslinked aliphatic polyurethane. Clause 8. A method of applying a coating composition to an article, comprising providing the coating composition of any of clauses 1-7 and applying the coating composition to an exterior surface of the article. Clause 9. An article comprising a substrate having an exterior surface and a coating composition on the exterior surface, wherein the coating composition comprises a crosslinked aliphatic polyurethane and nanoparticles having an average particle size of about 30 nm to about 400 nm and absorbing light having a wavelength of about 100 nm to about 290 nm, wherein the nanoparticles are present in an amount of less than about 25 weight percent of total solids in the coating composition. Clause 10. The article of clause 9, wherein the coating composition is transparent on the exterior surface after exposure to light having a wavelength of about 200 nm to about 240 nm. Clause 11. Articles according to clauses 9 or 10, the substrate of which comprises metal or plastic. Clause 12. The article of any of clauses 9-11, wherein the nanoparticles comprise one or more of titanium oxide, zinc oxide, tin oxide, silicon oxide, polytetrafluoroethylene (PTFE), or polyamide. Clause 13. A method of sterilizing a surface, comprising exposing the exterior surface of the article of any of clauses 9-12 to light having a wavelength of about 200 nm to about 240 nm. Clause 14. A method comprising: providing a coating composition comprising a crosslinked aliphatic polyurethane and nanoparticles having an average particle size of about 30 nm to about 400 nm and absorbing light having a wavelength of about 100 nm to about 290 nm, wherein the nanoparticles are present in an amount of less than about 25 weight percent of total solids in the clear coating composition; and applying the coating composition to a surface to be sterilized. Clause 15. The method of clause 14, further comprising exposing the surface to light having a wavelength of about 200 nm to about 240 nm. Clause 16. The method of clause 15, wherein the surface is exposed to light having a wavelength of about 220 nm in intermittent bursts. Clause 17. Any of the methods of clauses 14-16 where application includes spray application. Clause 18. Any of the methods of clauses 14-17, wherein the surface includes one or more of the following: surfaces on and around a toilet inside a lavatory; surfaces in and around a sink inside a lavatory; a lavatory floor; a door handle surface; or a drawer handle or cabinet knob surface. Clause 19. The method of any of clauses 14-18, wherein the nanoparticles comprise one or more of titanium oxide, zinc oxide, tin oxide, silicon oxide, polytetrafluoroethylene (PTFE), or polyamide. Clause 20. The method of any of clauses 14-19, wherein the coating composition further comprises an ultraviolet (UV) light blocking agent.

[0042] When presenting elements of the invention or exemplary aspects or embodiments thereof, the articles "a," "an," "the," and "said" mean that there are one or more of the elements. The terms "comprise," "include," and "have" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Although the invention has been described with reference to specific embodiments, the details of these embodiments should not be construed as limiting. Various aspects, embodiments, and features are defined in detail herein. Each aspect, embodiment, or feature so defined may be combined with any other aspect, embodiment, or feature (preferred, advantageous, or otherwise) unless clearly indicated to be inconsistent. The above-described examples are illustrative of the invention, not limiting of the disclosure. It should also be understood that many modifications and variations are possible in accordance with the principles of the disclosure. Accordingly, the scope of the invention is defined solely by the claims.

Claims

1. a polyurethane component; and Nanoparticles having an average particle size of 30 nm to 400 nm and absorbing light having a wavelength of 100 nm to 290 nm 1. A coating composition comprising:

1. A coating composition for sterilization using UV light, wherein the nanoparticles are present in an amount of less than 25 weight percent of the total solids in the coating composition, and the nanoparticles comprise one or more of polytetrafluoroethylene (PTFE) or polyamide.

2. 10. The coating composition of claim 1, wherein the nanoparticles comprise one or more of titanium dioxide, tin oxide, silicon dioxide, or zinc oxide.

3. The coating composition of claim 1 further comprising an ultraviolet (UV) light blocking agent different from the nanoparticles.

4. The coating composition of claim 3 , wherein the UV blocker comprises a phenolic antioxidant.

5. The coating composition of claim 1 , wherein the polyurethane component comprises a crosslinked aliphatic polyurethane.

6. Providing (202) a coating composition according to claim 1; and Applying the coating composition to the exterior surface of the article (204). A method of applying a coating composition to an article, comprising:

7. a substrate having an outer surface; and Coating composition for sterilization using UV light on external surfaces 1. An article comprising a coating composition comprising: crosslinked aliphatic polyurethane; and Nanoparticles having an average particle size of 30 nm to 400 nm and absorbing light having a wavelength of 100 nm to 290 nm wherein the nanoparticles are present in an amount less than 25 weight percent of the total solids in the coating composition, and the nanoparticles comprise one or more of polytetrafluoroethylene (PTFE), or polyamide.

8. The article of claim 7 , wherein the substrate comprises a metal or a plastic.

9. 10. A method of sterilizing a surface, comprising exposing (208) an exterior surface of the article of claim 7 to light having a wavelength of 200 nm to 240 nm.

10. crosslinked aliphatic polyurethane; and Nanoparticles having an average particle size of 30 nm to 400 nm and absorbing light having a wavelength of 100 nm to 290 nm providing a coating composition comprising (202), wherein the nanoparticles are present in an amount of less than 25 weight percent of total solids in the clear coating composition, and the nanoparticles comprise one or more of polytetrafluoroethylene (PTFE), or polyamide; applying (204) the coating composition to the surface to be sterilized; exposing the surface to light having a wavelength of 200 nm to 240 nm (208); 1. A method of sterilizing a surface comprising:

11. 11. The method of claim 10, wherein the surface is exposed to light having a wavelength of 220 nm in intermittent bursts.

12. The method of claim 10 , wherein applying comprises spray application.

13. 11. The method of claim 10, wherein the surfaces include one or more of the following: surfaces on and around a toilet (101) inside the toilet unit (100), surfaces in and around a sink (103) inside the toilet unit (100), a floor (102) of the toilet unit (100), a surface of a door handle, or a surface of a drawer handle or cabinet knob.

14. The method of claim 10 , wherein the coating composition further comprises an ultraviolet (UV) light blocking agent different from the nanoparticles.

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