Hydrophobic coating composition

Abstract

The present invention provides a hydrophobic coating composition comprising a suspension of at least one fluorinated silane polymer and graphene in an aqueous medium, and a method of making a hydrophobic coating composition comprising the steps of: a) providing a mixture of multilayer graphene, a fluorinated silane polymer and an aqueous medium; and b) stirring the mixture.

Description

Technical Field

[0001] The present invention relates to a hydrophobic coating composition, a method for making a hydrophobic coating composition, and a process for applying the hydrophobic coating composition to a surface of an object. Background Art

[0002] Wet and windy weather contributes to moisture saturation on building and construction materials, and wet weather followed by cold weather freezes moisture in the surface layers of such materials, causing cracking, erosion, or icing of the wall. In addition, the World Health Organization and the Institute of Medicine have reported that moisture levels in buildings have been identified as a negative factor affecting the health of occupants. Corrosion caused by moisture also affects the strength of buildings and may therefore lead to increased maintenance or repair costs.

[0003] Hydrophobic coatings and surfaces have the potential for self-cleaning, anti-sticking and antifreeze. A variety of technologies have been developed to prepare hydrophobic surfaces; however, many known technologies are complex, require pre-coating steps, impregnation of hydrophobic materials into building materials, formation of overall hydrophobic compounds within building materials and / or are time-consuming. Examples of such hydrophobic materials include those disclosed in CN112933983, CN106609006 and CN105968527. The known disadvantage of these materials is that they require difficult application processes, such as decompression, very high temperatures for drying or additional dispersion methods (such as ultrasonic dispersion during surface application).

[0004] It would therefore be advantageous to provide a hydrophobic or superhydrophobic coating composition that can be easily applied by the user and does not require significant surface pre- or post-treatment or forced drying.

[0005] Despite the various water-repellent coating products on the market, there is still interest in developing hydrophobic or super-hydrophobic coatings that have low wettability response and long-term durability, while being inexpensive and easy to manufacture. Therefore, it would be advantageous to provide a hydrophobic or super-hydrophobic coating composition with a reduced number of ingredients and simple manufacturing steps. It would also be advantageous to provide a hydrophobic or super-hydrophobic coating solution that is transparent so as to maintain the visual effect of the coated material and that does not suffer from one or more of the problems in the prior art.

[0006] Furthermore, it would be advantageous to provide a hydrophobic or superhydrophobic coating composition that does not include solvents that can negatively impact the environment, i.e., they can be easily sprayed onto outdoor materials with low risk of damaging the environment or the health of the user.

[0007] Embodiments of the present invention are directed to overcoming one or more problems in the prior art, whether or not explicitly disclosed herein. Summary of the invention

[0008] According to a first aspect of the present invention, there is provided a hydrophobic coating composition comprising a suspension of at least one fluorinated silane and graphene in an aqueous medium.

[0009] A "suspension" may be defined as a system in which solid particles are unevenly distributed or dispersed in a liquid.

[0010] In some embodiments, the fluorinated silane may be a compound having the general structure (RO)3-Si-R'-X, wherein R is an alkyl, alkenyl, or hydrogen, R' is a C1 to C5 hydrocarbon linkage, and X is an organic fluorine functional group.

[0011] In some embodiments, R is an alkyl or alkenyl group and may contain between 1 and 4 carbon atoms. In some embodiments, R is an alkyl or alkenyl group and may contain 2, 3 or 4 carbon atoms. In some embodiments, R may be selected from ethyl, propyl or butyl. In a preferred embodiment, R is ethyl. In an optional embodiment, the RO group may be a hydroxyl group, so R is hydrogen.

[0012] The oxygen in the RO group can be covalently bonded to the silicon in the fluorinated silane. In some embodiments, all three RO groups in the fluorinated silane are identical. In alternative embodiments, each RO group can be different, or alternatively two can be the same and one can be different. RO groups are advantageous because they create a polar head structure in the fluorinated silane that physically interacts with the graphene in the hydrophobic coating composition during use.

[0013] In some embodiments, the C1 to C5 hydrocarbon chain is a C1 to C5 alkyl chain. In some embodiments, the alkyl chain may contain 2 or 3 carbon atoms. In a preferred embodiment, the alkyl chain may contain 2 carbon atoms (i.e., may contain an ethyl chain). The C1 to C5 hydrocarbon chain may be covalently bonded to the silicon and organic functional groups in the fluorinated silane.

[0014] In some embodiments, the organofluorine functional group may be a fluorocarbon. In some embodiments, the fluorocarbon may be saturated. In some embodiments, the fluorocarbon may contain at least 4, 5, 6, 7, or 8 carbon atoms. In some embodiments, the fluorocarbon may contain no more than 14, 13, 12, or 11 carbon atoms. In some embodiments, the fluorocarbon may contain between 4 and 14, 5 to 13, or 6 to 12 carbon atoms. In some embodiments, the fluorocarbon may contain between 6 and 12 carbon atoms. In some embodiments, the fluorocarbon may have the formula CF3-(CF2)n, wherein n is between 5 and 13, 4 to 13, or 6 to 12. In preferred embodiments, the fluorocarbon may contain 6, 7, or 8 carbon atoms. In some embodiments, the fluorocarbon may be of the formula C8F 17 Fluorocarbon chains are advantageous because the long radical chain of high energy carbon-fluorine bonds provides a hydrophobic effect on the surface to which the coating is applied.

[0015] In some embodiments, the fluorinated silane is 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDTS).

[0016] In some embodiments, graphene is multilayer graphene. In some embodiments, multilayer graphene may include graphene between 2 and 10 layers. In some embodiments, multilayer graphene may include 2, 3, 4, 5, 6, 7, 8, 9 or 10 layers of graphene. In some embodiments, multilayer graphene may include 4, 5 or 6 layers of graphene. In some embodiments, multilayer graphene may have an average lateral size of about 110nm. Multilayer graphene may have grain boundaries and surface defects. The use of multilayer graphene is advantageous because it has a large surface area, good hydrophobicity and good self-assembly properties. Multilayer graphene may also be advantageous because it selectively physically interacts with the alkoxy groups of fluorinated silanes to improve the hydrophobic properties of the resulting composition. The multilayer graphene-silane composition has a strong affinity for the surface it uses, thereby improving the durability of the hydrophobic coating.

[0017] In some embodiments, the hydrophobic coating composition comprises at least 0.1%, 0.2%, 0.3%, 0.4% or 0.5% by weight of fluorinated silane. In some embodiments, the hydrophobic coating composition comprises no more than 7%, 6%, 5%, 4% or 3% by weight of fluorinated silane. In some embodiments, the hydrophobic coating composition comprises between 0.1% and 5%, 0.2% and 3%, or 0.5% and 3% by weight of fluorinated silane. In some preferred embodiments, the hydrophobic coating composition comprises between 0.5% and 1.5% by weight of fluorinated silane.

[0018] In some embodiments, the hydrophobic coating composition comprises at least 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1% graphene by weight. In some embodiments, the hydrophobic coating composition comprises no more than 10%, 9%, 8%, 7%, 6%, 5.5%, 5%, 4.5% or 4% graphene by weight. In some embodiments, the hydrophobic coating composition comprises 0.1% to 9%, 0.1% to 8%, 0.1% to 7%, 0.1% to 6%, 0.1% to 5%, 0.2% to 4.5%, 0.3% to 4%, 0.4% to 3.5%, 0.5% to 3%, 4% to 8%, 4% to 7%, 4% to 6% or 3% to 5% graphene by weight.

[0019] In some embodiments, the hydrophobic coating composition comprises at least 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or at least 99% of an aqueous medium. In some embodiments, the aqueous medium is water. In some embodiments, the hydrophobic coating composition preferably consists of water and is free of other solvents.

[0020] In some embodiments, the hydrophobic coating composition comprises an aqueous medium, the aqueous medium comprising water and at least one additional co-solvent. In some embodiments, the co-solvent is a polar solvent. In some embodiments, the polar solvent is an alcohol, which can be selected from methanol, ethanol, propanol, isopropanol or butanol or any combination thereof. In some embodiments, the co-solvent is isopropanol. In some embodiments, the hydrophobic coating composition comprises at least 75%, 80%, 85%, 90%, 85%, 96%, 97%, 98% or at least 99% of a mixture of water and co-solvents. In some embodiments, the ratio of water to co-solvent is between 1:5 and 5:1. In some embodiments, the ratio of water to co-solvent is between 1:4 and 5:1, 1:3 to 5:1, 1:2 to 5:1 or 1:1 to 5:1. In some embodiments, the ratio of water to co-solvent is between 1.1:1 and 4.5:1, 1.5:1 to 4:1 or 2:1 to 3.5:1. In a preferred embodiment, when the hydrophobic coating composition comprises a mixture of water and isopropyl alcohol, the ratio of water to isopropyl alcohol is about 3:1.

[0021] In some embodiments, the hydrophobic coating composition includes a surfactant. In some embodiments, the surfactant is an anionic surfactant. In some embodiments, the surfactant is a fatty acid salt. In some embodiments, the surfactant is a bile acid salt. In a preferred embodiment, the surfactant is a bile acid salt, such as sodium cholate. In some embodiments, the concentration of the surfactant in the final composition is at least 0.05%, 0.1%, 0.2%, 0.3%, 0.4% or 0.5% by weight. In some embodiments, the concentration of the surfactant in the final composition is no more than 5%, 4.5%, 4%, 3.5% or 3% by weight. In some embodiments, the concentration of the surfactant in the final composition is between 0.05% and 5%, 0.1% and 4.5%, 0.2% and 4% or 0.5% and 3% by weight. In some embodiments, the concentration of the surfactant in the final composition is between 0.1% and 1% by weight. In some embodiments, the hydrophobic composition includes a surfactant, and the aqueous medium is a mixture including water and a cosolvent. In some embodiments, the hydrophobic composition includes a surfactant and the aqueous medium is water. In some embodiments, the hydrophobic coating composition includes a surfactant and includes graphene between 0.5% and 4% by weight. In some embodiments, the hydrophobic coating composition includes a surfactant and includes graphene between 0.5% and 3.5%, 1% and 3%, 1.5% and 3%, 2% and 2.75%, or 2% and 2.5% by weight. In some embodiments, the hydrophobic coating composition includes a surfactant and includes no more than 3.5%, 3%, 2.9%, 2.8%, 2.7%, 2.6%, or no more than 2.5% by weight of graphene. The presence of a surfactant in the composition is advantageous because the surfactant ensures that the multilayer graphene is stable and does not aggregate again. The presence of a surfactant is also advantageous because it stabilizes the suspension so that the suspension can be prepared and stored for a period of time before use.

[0022] In some embodiments, the hydrophobic coating composition is surfactant-free. In some embodiments, the hydrophobic composition is surfactant-free and the aqueous medium is water. In some embodiments, the hydrophobic composition is surfactant-free and the aqueous medium is a mixture of water and a cosolvent. In some embodiments, the hydrophobic composition is surfactant-free and the aqueous medium is a mixture of water and isopropanol. In some embodiments, the hydrophobic coating composition is surfactant-free and comprises at least 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3% or at least 3.5% of graphene by weight. In some embodiments, the hydrophobic coating composition is surfactant-free and comprises at least 4%, 4.5%, 5%, 5.5% or at least 6% of graphene by weight. In some embodiments, the hydrophobic coating composition is surfactant-free and comprises no more than 10%, 9%, 8% or 7% of graphene by weight. In some embodiments, the hydrophobic coating composition is surfactant-free and comprises 3.5% to 8%, 4% to 7% or 4% to 6% of graphene by weight. A surfactant-free composition comprising at least 3.5% graphene by weight may be advantageous because the composition increases the hydrophobicity of the surface of an article, and the surfactant-free composition may be cheaper. A surfactant-free composition may also be advantageous because it is easier to manufacture on a large scale, since surfactants may be difficult to handle due to the fact that surfactants are typically high viscosity or solid components. The presence of isopropyl alcohol in the surfactant-free hydrophobic coating composition is advantageous because it results in a hydrophobic coating composition that only requires additional mixing by sufficient shaking to disperse the suspension before applying it to the surface of interest.

[0023] According to a second aspect of the present invention, there is provided a method for preparing a hydrophobic coating suspension according to the first aspect of the present invention, comprising the following steps: a) providing a mixture of multilayer graphene, fluorinated silane and an aqueous medium; and b) agitating the mixture to form a uniform dispersion.

[0024] In some embodiments, step a) comprises providing multilayer graphene, fluorinated silane, and an aqueous medium, and mixing these components to form a mixture. In some embodiments, step a) comprises adding the multilayer graphene to the mixture of fluorinated silane and aqueous medium.

[0025] Multilayer graphene can be prepared in a step before step a), which may include preparing multilayer graphene from graphite, for example by liquid phase exfoliation of graphite. In some embodiments, the liquid phase exfoliation method may include high-speed mixing of graphite (preferably graphite flakes), a surfactant, and an aqueous medium. In some embodiments, the aqueous medium is water. In some embodiments, the aqueous medium is a mixture of water and a co-solvent. In some embodiments, the aqueous medium is a mixture of water and alcohols. In some embodiments, the aqueous medium is a mixture of water and isopropanol. In some embodiments, the liquid phase exfoliation method may include high-speed mixing of graphite (preferably graphite flakes) and a mixture of water and isopropanol, and may also be surfactant-free. The liquid phase exfoliation method may result in the formation of multilayer graphene sheets.

[0026] In some embodiments, the concentration of the surfactant in the final composition is no more than 5%, 4.5%, 4%, 3.5% or 3% by weight. In some embodiments, the concentration of the surfactant in the final composition is between 0.05% and 5%, 0.1% and 4.5%, 0.2% and 4% or 0.5% and 3% by weight. In some embodiments, the concentration of the surfactant in the final composition is between 0.1% and 1% by weight. In some embodiments, the surfactant is an anionic surfactant. In some embodiments, the surfactant is a bile acid salt. In some embodiments, the surfactant is a cholate, such as sodium cholate. Sodium cholate is an anionic surfactant that includes three hydroxyl groups located on a steroid ring and a carboxyl group located at the end of the molecular structure, and there is no clear lipophilic or hydrophilic region in the molecule. Cholate can be easily removed by dialysis. The surfactant can stabilize the multilayer graphene sheets and prevent the multilayer graphene from reaggregating. The production of multilayer graphene from graphite can further include a centrifugation step after the exfoliation step. The centrifugation step can separate the multilayer graphene from the heavier, unexfoliated graphite. The centrifugation step may be advantageous because heavier, unexfoliated graphite does not remain dispersed as effectively in the suspension as the lighter multilayer graphene and may therefore result in separation or sedimentation formation in the hydrophobic coating suspension.

[0027] In some embodiments, the liquid phase exfoliation step may not include a surfactant. In some embodiments, the liquid phase exfoliation step may not include a surfactant and may include water and isopropanol as the aqueous medium. Surfactant-free production of multilayer graphene from graphite in a water / isopropanol medium may be advantageous because the method of graphene production is cheaper, faster (comprising only one step) and pollution-free. The presence of an organic counterpart in the aqueous medium may stabilize the multilayer graphene sheets, which also prevents the multilayer graphene from reaggregating.

[0028] In some embodiments, the liquid phase stripping step may include high-speed mixing of at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 or 130 minutes. In some embodiments, the liquid phase stripping step may include high-speed mixing with a stirring rate of at least 3000, 3250, 3500, 3750 or 4000 rpm. In some embodiments, the liquid phase stripping step may include high-speed mixing with a stirring rate of no more than 9000, 8500, 8000, 7500 or 7000 rpm. In some embodiments, the liquid phase stripping step may include high-speed mixing with a stirring rate between 4000 and 9000, 3500 and 8000 or 3000 and 7000 rpm.

[0029] In some embodiments, the production of multi-layer graphene from graphite may further include a sedimentation step after the liquid phase exfoliation step. The sedimentation step may separate the multi-layer graphene from the heavier, unexfoliated graphite in the suspension. The heavier, unexfoliated graphite does not remain dispersed in the suspension and will precipitate, so only the supernatant containing the lighter graphene sheets will be used for the hydrophobic coating suspension.

[0030] In some embodiments, the concentration of the fluorinated silane is at least 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, or 0.5% by weight. In some embodiments, the concentration of the fluorinated silane is no more than 7%, 6%, 5%, 4.5%, 4%, 3.5%, or 3% by weight. In some embodiments, the concentration of the fluorinated silane is between 0.1% and 5%, 0.2% and 4.5%, 0.3% and 4%, 0.4% and 3.5%, or 0.5% and 3% by weight. In a preferred embodiment, the concentration of the fluorinated silane is between 0.5% and 1.5% by weight.

[0031] In some embodiments, the concentration of multilayer graphene is at least 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1% by weight. In some embodiments, the concentration of multilayer graphene is no more than 10%, 9%, 8%, 7%, 6%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5% or no more than 2% by weight. In some embodiments, the concentration of multilayer graphene is between 0.1% and 5%, 0.2% and 5%, 0.3% and 5%, 0.5% and 5%, or 1% and 5% by weight. In some embodiments, the concentration of multilayer graphene is between 3% and 8%, 4% and 8%, or 4.5% and 7% by weight. In some embodiments, the concentration of multilayer graphene is between 1.5% and 3% by weight, such as between 1.5% and 2.5% by weight, and such concentration is particularly useful for providing superhydrophobic properties to the composition when the composition is applied to a surface of an article.

[0032] In some embodiments, the hydrophobic coating composition comprises at least 75%, 80%, 85%, 90%, 85%, 96%, 97%, 98% or at least 99% of an aqueous medium. In some embodiments, the aqueous medium may be water. In alternative embodiments, the hydrophobic coating composition may include water and one or more other co-solvents, such as alcohols, which may be selected from methanol, ethanol, propanol and isopropanol, preferably isopropanol.

[0033] Step b) may be performed using any suitable mixing process. In a preferred embodiment, the agitation step comprises ultrasonic treatment.

[0034] In some embodiments, step b) may include ultrasonicating the mixture after step a) is completed. In some embodiments, ultrasonication may be performed for no more than 150, 120, 110, 100, 90, 80, 70 or 60 minutes. In some embodiments, ultrasonication may be performed for at least 5, 6, 7, 8, 9 or 10 minutes. In some embodiments, ultrasonication may be performed for 5 to 120 minutes, 6 to 110 minutes, 7 to 100 minutes, 8 to 90 minutes, 9 to 80 minutes or between 10 and 70 minutes. In some embodiments, ultrasonication may be performed for between 10 and 30 minutes.

[0035] In some embodiments, after step b), if the hydrophobic composition separates upon standing, an additional mixing step may be required to re-homogenize the hydrophobic composition. This additional mixing step may be a mechanical mixing step. In some embodiments, this additional mixing step may include shaking the hydrophobic composition thoroughly.

[0036] According to a third aspect of the present invention, there is provided a process for coating an article, comprising the steps of: a) depositing the hydrophobic coating composition of the first aspect of the present invention onto the surface of the article; and b) drying the coating composition to form a coating on the surface.

[0037] In some embodiments, the article may be a construction material. In some embodiments, the construction material may be any porous construction material. In some embodiments, the construction material may include components of a wall or be a wall. In some embodiments, the construction material may be a brick or block. In some embodiments, the brick may be a clay brick, a sand-lime brick or a fly ash brick. In some embodiments, the construction material may be concrete, and may be a concrete block or a concrete brick. In some embodiments, the article may be a roof, such as a concrete roof, a clay roof or a painted roof. In some embodiments, the article may be a building surface of initial coating, such as wood or a cladding material. In some embodiments, the article may be a flexible material. The flexible material may be one or more materials selected from the group including leather, synthetic textiles, smart textiles (i.e., textile materials containing electronic components), wool, cotton and any combination thereof. In some embodiments, the article may be an open electrode or any open electronic circuit, wherein open means unencapsulated or without a sheath or protective packaging. In some embodiments, the article may be an electronic device, such as a mobile phone or a computer.

[0038] Step a) comprises a method of depositing the hydrophobic coating composition onto the surface of the article. In some embodiments, the application method can be drip coating. In other embodiments, the application method is spraying. In other embodiments, the application method is mechanical application using a roller.

[0039] In some embodiments, the hydrophobic coating composition is applied to the surface of the article at a temperature of at least 5° C., 7° C., 9° C., 11° C., 13° C., or 15° C. In some embodiments, the hydrophobic coating composition may be sprayed on the surface of the article at a temperature not exceeding 70° C., 65° C., 60° C., 55° C., or 50° C. In some embodiments, the hydrophobic coating composition may be sprayed on the surface of the article at a temperature between 5° C. and 70° C., 7° C. and 65° C., 9° C. and 60° C., 11° C. and 55° C., or 13° C. and 50° C.

[0040] In a preferred embodiment, the hydrophobic coating composition can be sprayed on the surface of the article at a temperature between 10°C and 40°C. In some embodiments, the hydrophobic coating composition can be sprayed at room temperature or ambient temperature. In some embodiments, the volume of the sprayed hydrophobic coating composition can be 1000 cm3 / s. 2 At least 100, 150, 200, 250, 300 or 350 mL. In some embodiments, the volume of the sprayed hydrophobic coating composition may be per cm 2No more than 3000, 2750, 2500, 2250 or 2000 mL. In some embodiments, the volume of the sprayed hydrophobic coating composition may be per 1000 cm 2 Between 100 and 2000 mL, or per cm 2 Between 250 and 2500 mL, or per cm 2 Between 100 and 3000mL.

[0041] Step b) may include drying the hydrophobic coating composition on the surface at a temperature of at least 5°C, 7°C, 9°C, 11°C, 13°C or 15°C. In some embodiments, the hydrophobic coating composition may be dried on the surface of the article at a temperature not exceeding 70°C, 65°C, 60°C, 55°C or 50°C. In some embodiments, the hydrophobic coating composition may be dried on the surface of the article at a temperature between 5°C and 70°C, 7°C and 65°C, 9°C and 60°C, 11°C and 55°C or 13°C and 50°C. In a preferred embodiment, the hydrophobic coating composition may be dried on the surface of the article at a temperature between 10°C and 40°C. The drying step may be completed at ambient temperature, so no forced drying is required.

[0042] In some embodiments, the drying step may be carried out for at least 1, 5, 10 or 15 minutes. In some embodiments, the drying step may be carried out for no more than 60, 55, 50, 45 or 40 minutes. In some embodiments, the drying step may be carried out for 1 to 60 minutes, 5 to 55 minutes, 10 to 50 minutes or between 15 and 45 minutes. In some embodiments, the drying step may be carried out for between 15 and 35 minutes.

[0043] The process of depositing the hydrophobic solution on the surface may not require an additional surface treatment step before step a), during step a), before step b), during step b), or after step b). Such an application process comprising steps a), step b) and no additional surface treatment step is advantageous because it is easier for the user to apply the coating to the surface than other surface coatings that require forced drying (e.g., at high temperatures). This expands the application of the surface coating because it can be easily applied to large surface areas without the need for forced drying of the coating.

[0044] According to a fourth aspect of the present invention, there is provided an article comprising a hydrophobic coating composition according to the first aspect of the present invention. The article of the fourth aspect of the present invention may be prepared by a process according to the third aspect of the present invention. The article of the fourth aspect of the present invention may be prepared by a method according to the second aspect of the present invention.

[0045] Articles with hydrophobic coatings can show superior hydrophobic properties. Hydrophobic properties can be measured by measuring the water contact angle. "Water contact angle" or "water contact angle" is defined as the angle between the edge of a static water droplet and the flat horizontal surface of a solid on which the water droplet is placed. The larger the contact angle, the greater the hydrophobic reaction between the liquid and the surface. If the liquid completely covers the surface and forms a film, the contact angle is zero degrees (0 °). If the contact angle is greater than 90 °, the surface is called "hydrophobic". If the contact angle is at least up to or greater than 150 °, this coating is called a "super-hydrophobic" coating. According to the application process of the third aspect of the present invention, it is advantageous to use the hydrophobic coating solution of the first aspect of the present invention because it can lead to super-hydrophobic properties. In some embodiments, the hydrophobic coating maintains super-hydrophobic properties for at least 1, 2, 3, 4, 5 or 6 months. In some embodiments, the hydrophobic coating maintains super-hydrophobic properties for at least 9, 10, 11 or 12 months.

[0046] According to a fifth aspect of the present invention, there is provided a hydrophobic coating composition comprising a suspension of at least one non-fluorinated silane and graphene in an aqueous medium.

[0047] The non-fluorinated silane may be fluorine-free or substantially fluorine-free.The hydrophobic coating composition may be any embodiment according to the first aspect of the invention, except that the hydrophobic coating composition of the fifth aspect of the invention comprises a non-fluorinated silane instead of a fluorinated silane.

[0048] The hydrophobic coating composition may include any of the ingredients of the first aspect of the invention (except that the fluorinated silane of the first aspect is replaced by a non-fluorinated silane of the fifth aspect).

[0049] In some embodiments, the silane may be a compound having a general structure (RO)3-Si-R'-Y, wherein R is an alkyl, alkenyl or hydrogen, R' is a C1 to C5 hydrocarbon chain, and Y is a functional group that does not include fluorine. R may be any embodiment according to the first aspect of the present invention. R' may be any embodiment according to the first aspect of the present invention. Y may be selected from the group consisting of non-fluorine halogen, non-fluorine organic halogen, hydrocarbon, alkyl, aryl, alkenyl, alkynyl, alkylaryl, alkoxy, aryloxy, amine, second silane and hydrogen or any combination thereof.

[0050] According to a sixth aspect of the present invention, there is provided a method for preparing a hydrophobic coating suspension according to the fifth aspect of the present invention, comprising the following steps: a) providing a mixture of multilayer graphene, silane and an aqueous medium; and b) agitating the mixture to form a uniform dispersion.

[0051] The method of the sixth aspect of the present invention may be any embodiment of the second aspect of the present invention, wherein the hydrophobic coating of the first aspect of the present invention is replaced by the hydrophobic coating composition of the fifth aspect of the present invention.

[0052] According to a seventh aspect of the present invention, there is provided a process for coating an article, comprising the steps of: a) depositing the hydrophobic coating composition of the fifth aspect of the present invention onto the surface of the article; and b) drying the coating composition to form a coating on the surface.

[0053] According to an eighth aspect of the present invention, there is provided an article comprising a hydrophobic coating composition according to the fifth aspect of the present invention. The article of the eighth aspect of the present invention may be prepared by a process according to the seventh aspect of the present invention. The article of the eighth aspect of the present invention may be prepared by a process according to the sixth aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order that the present invention may be more clearly understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0055] Figure 1 A cross-sectional view of an embodiment of an article of the invention in the form of a tile coated with a hydrophobic coating of the invention (the hydrophobic coating of the invention is applied to the top and side surfaces) is shown.

[0056] Figure 2 Shown are measurements of water contact angles of tap water drops on concrete cubes after 1 month, wherein each concrete cube was coated with a surfactant-based hydrophobic coating composition of the present invention, comprising 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4% or 2.5% by weight of multilayer graphene and 1% by weight of silane according to formulations C to M in Table 1.

[0057] Figure 3 Shown are measurements of water contact angles of tap water drops on concrete cubes after 1 day and after 1 month, wherein each concrete cube was coated with a surfactant-free hydrophobic coating composition of the present invention, the hydrophobic coating composition comprising 4.0%, 4.5%, 5.0%, 5.5% or 6.0% by weight of multilayer graphene and 1% by weight of silane according to formulations Q to U in Table 2.

[0058] Figure 4 The water contact angle of concrete cubes coated with the surfactant-based hydrophobic coating composition of the present invention is shown, wherein each concrete cube is coated with the hydrophobic coating of the present invention, and the hydrophobic coating comprises 1%, 2%, 3%, 4% or 5% by weight of multilayer graphene and 1% by weight of silane according to the formulations B, H, N, O and P in Table 1, wherein the water contact angle is measured after 1 hour of application and again after 1 month of application.

[0059] Figure 5The water contact angle of concrete cubes coated with the surfactant-based hydrophobic coating composition of the present invention, according to the formulations C to M in Table 1, the hydrophobic coating composition comprising 1.5% to 2.5% by weight of multilayer graphene and 1% by weight of silane, is shown, wherein the water contact angle is measured after 1 hour of application and again after 1 month of application.

[0060] Figure 6 The water contact angle of concrete cubes coated with the surfactant-based hydrophobic coating composition of the present invention is shown, wherein the hydrophobic coating composition comprises 2.0% to 2.5% by weight of multilayer graphene and 1% by weight of silane according to formulations H to M in Table 1, wherein the water contact angle is measured after 1 year of application.

[0061] Figure 7 The water contact angle of concrete cubes coated with the surfactant-free hydrophobic coating composition of the present invention, according to the formulations Q to U in Table 2, the hydrophobic coating composition comprising 4.0% to 6.0% by weight of multilayer graphene and 1% by weight of silane, wherein the water contact angle is measured after 1 month of application. DETAILED DESCRIPTION

[0062] Figure 1 An embodiment of a coated article of the present invention in the form of a coated concrete brick (2) is shown. The coated brick comprises a brick body (4) on which a coating composition according to an embodiment of the first aspect of the present invention is applied in the form of a coating (6). The coating comprises multilayer graphene, a fluorinated silane and an aqueous medium. The fluorinated silane is 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane, and the aqueous medium is water. The formulations of the hydrophobic coating composition applied to the brick (2) are exemplified in Tables 1 and 2 below as formulations A to U.

[0063] Example 1

[0064] Production of the surfactant-based hydrophobic coating composition of the present invention

[0065] The embodiment of the second aspect of the present invention describes a method for preparing the hydrophobic coating of the first aspect of the present invention, as described below. The first embodiment of the second aspect of the present invention comprises the following steps. First, multilayer graphene is produced using a liquid phase exfoliation method. The liquid phase exfoliation step comprises combining 15 mg / ml of graphite flakes and 5 mg / ml of sodium cholate surfactant with an appropriate amount (800 ml) of deionized water. The mixture is stirred with a high shear laboratory mixer, for example, using a mixer L5M of SilversonMachines Ltd. in the UK, equipped with a rotor head of 32 mm diameter. The mixture is stirred at 4500 rpm for 60 minutes. Liquid phase exfoliation causes the van der Waals forces between the graphite layers in the graphite flakes to be destroyed, thereby obtaining thin multilayer graphene sheets. The sodium cholate surfactant stabilizes the thin multilayer graphene sheets so that they no longer aggregate. Liquid phase exfoliation is then centrifuged at 1000 rpm for 100 minutes to remove the residual graphite flakes from the multilayer graphene mixture. The multilayer graphene produced includes 2-10 layers.

[0066] The multilayer graphene is then added to the fluorinated silane, which in this embodiment is 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane. 1% by weight of 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane is added to a portion of the multilayer graphene so that the amount of multilayer graphene in the final product is between 1% and 5% by weight according to the formulas B to P shown in Table 1. Formula A is included in Table 1 as a control liquid, which does not include multilayer graphene (0%).

[0067] The hydrophobic coating compositions of the present invention (Formulations B to P) and the control formulation (A) were then mixed by ultrasonic treatment for 20 minutes to make the resulting products into suspensions.

[0068] Table 1

[0069]

[0070] Example 2

[0071] Production of the surfactant-free hydrophobic coating composition of the present invention

[0072] The second embodiment of the second aspect of the present invention (wherein the hydrophobic composition is a surfactant-free composition) comprises the following steps. First, multilayer graphene is produced using a surfactant-free liquid phase exfoliation method. The liquid phase exfoliation step includes combining 6 mg / ml of graphite flakes with an appropriate amount of deionized water / isopropanol solution (e.g., 600 ml of a solution of deionized water and isopropanol, with a ratio of deionized water: isopropanol of 3:1). The mixture is stirred with a high shear laboratory mixer, for example, using a mixer L5M from Silverson Machines Ltd., UK, equipped with a rotor head of 32 mm diameter. The mixture is stirred at 7000 rpm for 120 minutes. Liquid phase exfoliation in the presence of an organic component causes the van der Waals forces between the graphite layers in the graphite flakes to be destroyed, thereby obtaining a high concentration of multilayer graphene dispersion. Relative to surfactant-based methods, the organic molecules in the solution stabilize the multilayer graphene sheets for a shorter time. Liquid phase exfoliation is then subjected to a sedimentation step at room temperature, wherein the heavier residual graphite flakes are separated from the multilayer graphene solution. Decantation of the final dispersion after several hours of standing in air avoids additional centrifugation. Residual graphite flakes remain in the precipitate and are removed. The multilayer graphene produced consists of 2-10 layers.

[0073] The multilayer graphene is then added to the fluorinated silane, which in this embodiment is 1H,1H,2H,2H-perfluorodecyltriethoxysilane. 1% by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane is added to a portion of the multilayer graphene so that the amount of multilayer graphene in the final product is 4% to 6% by weight. Inventive formulations including 4% to 6% by weight of multilayer graphene are shown as formulations Q to U in Table 2.

[0074] The hydrophobic coating composition of the present invention was then mixed by ultrasonic treatment for 20 minutes to make the resulting product a suspension.

[0075] Table 2

[0076]

[0077] Example 3

[0078] Method of applying the hydrophobic coating composition of Examples 1 and 2 to an article

[0079] The embodiments of the hydrophobic coating composition of formulations B to U according to the first aspect of the present invention and the control formulation A were then each sprayed onto the surface of the concrete tile (2) at room temperature to form a hydrophobic coating (6), such as Figure 1The coating (6) was then dried at room temperature for 20 to 30 minutes. The concrete brick (2) was prepared using Blue Circle General Purpose Cement and tap water at a concentration ratio of 2:1 by weight. The prepared concrete brick (2) was then dried overnight.

[0080] Formulations A to U were each sprayed onto concrete tiles (2) at ambient temperature and dried at ambient temperature for 30 minutes.

[0081] The water contact angle of the hydrophobic coated concrete tile (2) was then calculated using The analysis was performed using the software. This analysis was performed on formulations C to M in Table 1 and formulations Q to U in Table 2, respectively. Figure 2 and Figure 3 , where the angle between the edge of a water drop and a horizontal concrete surface coated with Formulations C to U was measured to give the water contact angle.

[0082] The water contact angles of surfactant-free formulations B, H, N, O and M containing 1%, 2%, 3%, 4% and 5% by weight of multilayer graphene and 1% by weight of silane were measured 1 hour after application. Concrete tiles (2) with hydrophobic coatings (6) containing formulations B, H, N, O and P were stored under ambient conditions for one month and the water contact angles were measured one month after application. Figure 4 The graph shows the water contact angle results of concrete tiles (2) coated with each of Formulations B to D, respectively, where the water contact angles were measured 1 hour after application of the formulation and again 1 month after application of the formulation.

[0083] The water contact angles on concrete tiles (2) coated with hydrophobic coatings (6) of formulations C to M containing 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4% and 2.5% by weight of multilayer graphene and 1% by weight of silane were measured one hour after application. The concrete tiles (2) were then stored for one month and the water contact angles were measured one month after application. The results of these experiments are shown in Figure 5 Medium picture.

[0084] Concrete tiles (2) with hydrophobic coatings (6) comprising formulations H to M containing 2.0%, 2.1%, 2.2%, 2.3%, 2.4% and 2.5% by weight of multilayer graphene and 1% by weight of silane were stored for one year and the water contact angle was measured after one year of application. The results of these experiments are given in Figure 6 Medium picture.

[0085] Concrete tiles (2) with hydrophobic coatings (6) comprising formulations Q to U containing 4.0%, 4.5%, 5.0%, 5.5% and 6.0% by weight of multilayer graphene and 1% by weight of silane were stored for one month and the water contact angles were measured one day after application and one month after application. The results of these experiments are given in Figure 7 Medium picture.

[0086] When applied to the concrete tile (2), all of the hydrophobic coating composition (6) is transparent.

[0087] result

[0088] The above test results show that the concentration of multilayer graphene in the hydrophobic coating composition affects the hydrophobic properties of the coating after spraying and over time. A large water contact angle is associated with good water repellency. When tested after 1 hour of coating, the water contact angle produced by formula A without multilayer graphene is about 35°. Therefore, the control formula A is not hydrophobic or super-hydrophobic. Formulas B to N of the present invention comprising multilayer graphene between 1% by weight and 3% by weight in a surfactant-based hydrophobic composition and formulas Q to U comprising multilayer graphene between 4% by weight and 6% by weight in a surfactant-free composition all show hydrophobic or super-hydrophobic properties, indicating that the presence of multilayer graphene between 1% by weight and 6% by weight is the key to superior hydrophobic properties compared to formulas that do not include multilayer graphene.

[0089] Formulas H, I and J containing 2.0%, 2.1% and 2.2% multilayer graphene by weight show significantly improved hydrophobic properties than the formula without multilayer graphene (control formula A), and the water contact angles measured after 1 month of application are 154°, 155° and 153°, respectively. Therefore, the formula containing 2% to 2.2% multilayer graphene by weight is super hydrophobic. Formulas S, T and U containing 5.0%, 5.5% and 6.0% multilayer graphene by weight also show super hydrophobic properties, and the contact angles measured after 1 day of coating and 1 month of coating are 161°, 155° and 152°, respectively.

[0090] Formulations containing 1% to 1.9% by weight of multilayer graphene (Formulations B to G) showed good hydrophobic properties and good durability, with water contact angles between 110° and 140° measured 1 month after coating.

[0091] Formulations H, I, J, K, L and M containing 2% to 2.5% by weight of multilayer graphene produced superior hydrophobic properties, with water contact angle results between 132° and 155° even when tested 1 year after application. Formulations H, I and J containing 2.0%, 2.1% and 2.2% by weight of multilayer graphene exhibited superhydrophobic properties, with water contact angle results of 152°, 155° and 150°, respectively, when tested as a concrete coating 1 year after application, showing a high level of durability of the hydrophobic coating compositions of these formulations over a period of at least 1 year. Formulations containing 4% to 6% by weight of graphene (prepared using a surfactant-free stripping method) and a mixture of water and isopropyl alcohol (as exemplified in Formulations Q and U in Table 2) showed superior hydrophobic properties, with water contact angles between 146° and 161°. In particular, the formulations with 5.0%, 5.5% and 6.0% by weight of multilayer graphene maintained superhydrophobic properties one year after application, with water contact angles of 161°, 155° and 152°, respectively. In application, the hydrophobic properties and good durability shown by the formulations containing 1% to 6% by weight of multilayer graphene translate into good surface protection of the material from water, dust, ice, moss, mold and fungus, and help maintain the good appearance of the wall stone structure.

[0092] The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A hydrophobic coating composition comprising a suspension of at least one fluorinated silane and graphene in an aqueous medium.

2. The hydrophobic coating composition according to claim 1, wherein the fluorinated silane is a compound having the general formula (RO)3-Si-R'-X, wherein R is an alkyl, alkenyl or hydrogen, R' is a C1 to C5 hydrocarbon chain, and X is an organic fluorine functional group, and is preferably 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

3. The hydrophobic coating composition according to any preceding claim, wherein the graphene is a multilayer graphene comprising between 2 and 10 layers of graphene.

4. A hydrophobic coating composition according to any preceding claim, wherein: The amount of the fluorinated silane is at least 0.1% by weight.

5. A hydrophobic coating composition according to any preceding claim, wherein: The amount of graphene is between 1% and 6% by weight.

6. A hydrophobic coating composition according to any preceding claim, wherein the aqueous medium is water.

7. A hydrophobic coating composition according to any preceding claim, wherein the amount of the aqueous medium is between 65% and 99%.

8. A hydrophobic coating composition according to any preceding claim, comprising a co-solvent, preferably a polar solvent, and more preferably isopropanol.

9. The hydrophobic coating composition according to any one of claim 8, wherein the amount of isopropyl alcohol is between 0% and 40% by weight.

10. A hydrophobic coating composition according to any preceding claim, comprising graphene in an amount of less than 4% by weight, and further comprising a surfactant.

11. The hydrophobic coating composition according to claim 10, wherein the surfactant is a fatty acid salt, preferably a bile acid salt.

12. The hydrophobic coating composition according to any one of claims 10 or 11, wherein the amount of the surfactant is not more than 2% by weight.

13. A method for preparing a hydrophobic coating composition according to any one of claims 1 to 12, comprising the following steps: a) providing a mixture of multilayer graphene, fluorinated silane and an aqueous medium; as well as b) agitating the mixture.

14. The method for preparing a hydrophobic coating composition according to claim 13, wherein there is a step of preparing multilayer graphene from graphite before step a).

15. The method for preparing a hydrophobic coating composition according to claim 14, wherein the multilayer graphene is prepared on graphite using a liquid phase exfoliation method.

16. The method for preparing a hydrophobic coating composition according to claim 14 or 15, wherein the graphite is mixed with a surfactant.

17. The method for preparing a hydrophobic coating composition according to claim 16, wherein the surfactant is sodium cholate.

18. A method for preparing a hydrophobic coating composition according to any one of claims 13 to 17, wherein the graphite is mixed with water and at least one other solvent.

19. The method for preparing a hydrophobic coating composition according to any one of claims 13 to 18, wherein step a) comprises mixing multilayer graphene with the fluorinated silane in an aqueous medium.

20. The method for preparing a hydrophobic coating composition according to any one of claims 13 to 19, wherein step b) comprises mixing the mixture obtained from step a) using ultrasonic treatment to form a uniform dispersion.

21. A process for coating an article comprising the steps of: a) depositing the hydrophobic coating composition according to any one of claims 1 to 12 on the surface of the object; as well as b) drying the hydrophobic coating composition to form a coating on the surface.

22. A process for coating an article according to claim 21, wherein the temperature of step a) is between 20°C and 40°C.

23. A process for coating an article according to claim 21 or 22, wherein step a) comprises spraying the hydrophobic coating composition onto the surface of the article, and wherein the spray volume of the hydrophobic composition is 100% per cm 2 Between 0.25mL and 3mL on the surface of the item.

24. A process for coating an article according to any one of claims 21 to 23, wherein the temperature of step b) is ambient temperature, such as between 15°C and 40°C.

25. A process for coating an article according to any one of claims 21 to 24, wherein step b) comprises drying the hydrophobic coating composition for between 20 and 30 minutes.

26. A process for coating an article according to any one of claims 21 to 25, wherein the article is selected from the group consisting of building or construction materials, textiles, electronics and e-textiles.

27. An article comprising a hydrophobic coating according to the composition of any one of claims 1 to 12 applied on at least one surface thereof.

Images