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, as well as a method for preparing the hydrophobic coating composition. The method includes step (a) of providing a mixture of multilayer graphene, a fluorinated silane polymer, and an aqueous medium, and step (b) of subjecting the mixture to stirring.

Description

Technical Field

[0001] The present invention relates to a hydrophobic coating composition, a method for manufacturing a hydrophobic coating composition, and a process for applying a hydrophobic coating composition to the surface of an article.

Background Art

[0002] Inclement weather with rain and strong winds promotes the saturation of moisture in building materials and construction materials, and when cold follows after rain, freezing of moisture occurs on the surface layer of such materials, leading to cracking, erosion, and freezing of walls. Also, the World Health Organization (WHO) and the Institute of Medicine have reported that they have determined that the moisture level inside buildings is a negative factor affecting the health of those inside. Corrosion due to moisture also affects the strength of buildings, which may result in increased maintenance and repair costs.

[0003] Hydrophobic coatings and hydrophobic surfaces hold the potential for self-cleaning, anti-fouling, and anti-freezing effects. Various techniques have been developed to prepare hydrophobic surfaces, but many of the known techniques are complex and require pre-coating processes, impregnation of hydrophobic materials into building materials, and the formation of integral hydrophobic compounds within building materials, and / or may be time-consuming. Examples of such hydrophobic materials include those disclosed in Chinese Patent Application No. 112933983, Chinese Patent Application No. 106609006, and Chinese Patent Application No. 105968527. A known drawback of these materials is that they require difficult application processes such as reduced pressure, very high temperatures for drying, or additional dispersion methods such as ultrasonic dispersion during application to the surface.

[0004] Therefore, it is advantageous to provide a hydrophobic or superhydrophobic coating composition that is easily applicable by the user and does not require significant surface treatment or forced drying before or after application.

[0005] Despite the various products in the market for water-repellent coatings, there remains an interest in the development of hydrophobic or superhydrophobic coatings that are inexpensive, easy to manufacture, have low wettability, and provide long-term durability. Therefore, it is advantageous to provide a hydrophobic or superhydrophobic coating composition with a small number of components and a simple manufacturing step. It is also advantageous to provide a hydrophobic or superhydrophobic coating solution. Since this solution is transparent, it maintains the visual effect of the material to be coated and is not exposed to one or more problems of the prior art.

[0006] Moreover, it is advantageous to provide a hydrophobic or superhydrophobic coating composition that does not contain solvents that may have an adverse impact on the environment. That is, since these have a low risk of damaging the environment or the health of users, they can be easily sprayed onto outdoor materials.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The object of the embodiments of the present invention is to overcome one or more problems of the prior art, whether or not explicitly described herein.

Means for Solving the Problems

[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] The "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 a general structure of (RO)3-Si-R’-X. Here, R represents an alkyl group, an alkenyl group, or hydrogen, R’ represents a C1-C5 hydrocarbon bond, and X represents an organic fluorine functional group.

[0011] In some embodiments, R is alkyl or alkenyl and may contain from 1 to 4 carbon atoms. In some embodiments, R is alkyl or alkenyl 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 alternative embodiment, the RO group may be a hydroxyl group such that R is hydrogen.

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

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

[0014] In some embodiments, the organic fluorine 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 14, 13, 12, or 11 or fewer carbon atoms. In some embodiments, the fluorocarbon may contain 4 to 14, 5 to 13, or 6 to 12 carbon atoms. In some embodiments, the fluorocarbon may contain 6 to 12 carbon atoms. In some embodiments, the fluorocarbon has the formula CF3-(CF2)n It may have. Here, n is 5 to 13, 4 to 13 or 6 to 12. In a preferred embodiment, the fluorocarbon may contain 6, 7 or 8 carbon atoms. In some embodiments, the fluorocarbon is of the formula C8F 17 It may be one of. The fluorocarbon chain is advantageous because the long radical chain of the high-energy carbon-fluorine bond gives a hydrophobic effect to 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, the graphene is multilayer graphene. In some embodiments, the multilayer graphene may include 2 to 10 layers of graphene. In some embodiments, the multilayer graphene may include 2, 3, 4, 5, 6, 7, 8, 9 or 10 layers of graphene. In some embodiments, the multilayer graphene may include 4, 5 or 6 layers of graphene. In some embodiments, the multilayer graphene may have an average lateral size of about 110 nm. The multilayer graphene may have grain boundaries and surface defects. The use of multilayer graphene is advantageous in that it has a large surface area, high hydrophobicity and good self-assembly properties. Also, the multilayer graphene is advantageous because it selectively and physically interacts with the alkoxy groups of the fluorinated silane, improving the hydrophobicity of the resulting composition. The multilayer graphene-silane composition provides a strong affinity for the surface on which it is used, thereby improving the durability of the hydrophobic coating.

[0017] In some embodiments, the hydrophobic coating composition comprises at least 0.1 wt%, at least 0.2 wt%, at least 0.3 wt%, at least 0.4 wt% or at least 0.5 wt% of a fluorinated silane. In some embodiments, the hydrophobic coating composition comprises 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less or 3 wt% or less of a fluorinated silane. In some embodiments, the hydrophobic coating composition comprises 0.1 wt% to 5 wt%, 0.2 wt% to 3 wt% or 0.5 wt% to 3 wt% of a fluorinated silane. In some preferred embodiments, the hydrophobic coating composition comprises 0.5 wt% to 1.5 wt% of a fluorinated silane.

[0018] In some embodiments, the hydrophobic coating composition comprises at least 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt% or 1 wt% of graphene. In some embodiments, the hydrophobic coating composition comprises 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5.5 wt% or less, 5 wt% or less, 4.5 wt% or less or 4 wt% or less of graphene. In some embodiments, the hydrophobic coating composition comprises 0.1 wt% to 9 wt%, 0.1 wt% to 8 wt%, 0.1 wt% to 7 wt%, 0.1 wt% to 6 wt%, 0.1 wt% to 5 wt%, 0.2 wt% to 4.5 wt%, 0.3 wt% to 4 wt%, 0.4 wt% to 3.5 wt%, 0.5 wt% to 3 wt%, 4 wt% to 8 wt%, 4 wt% to 7 wt%, 4 wt% to 6 wt% or 3 wt% to 5 wt% of graphene.

[0019] In some embodiments, the hydrophobic coating composition comprises at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% aqueous medium. In some embodiments, the aqueous medium is water. In some embodiments, the hydrophobic coating composition preferably consists of water and does not contain other solvents.

[0020] In some embodiments, the hydrophobic coating composition comprises an 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 can be an alcohol 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%, at least 80%, at least 85%, at least 90%, at least 85%, at least 96%, at least 97%, at least 98% or at least 99% mixture of water and co-solvent. In some embodiments, the ratio of water to co-solvent is from 1:5 to 5:1. In some embodiments, the ratio of water to co-solvent is from 1:4 to 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 from 1.1:1 to 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 contains a mixture of water and isopropanol, the ratio of water to isopropanol is about 3:1.

[0021] In some embodiments, the hydrophobic coating composition comprises a surfactant. In some embodiments, the surfactant is an anionic surfactant. In some embodiments, the surfactant is a salt of a fatty acid. In some embodiments, the surfactant is a salt of a bile acid. In a preferred embodiment, the surfactant is a cholate such as sodium cholate. In some embodiments, the concentration of the surfactant is at least 0.05 wt%, at least 0.1 wt%, at least 0.2 wt%, at least 0.3 wt%, at least 0.4 wt% or at least 0.5 wt% in the final composition. In some embodiments, the concentration of the surfactant is 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less or 3 wt% or less in the final composition. In some embodiments, the concentration of the surfactant is from 0.05 wt% to 5 wt%, from 0.1 wt% to 4.5 wt%, from 0.2 wt% to 4 wt% or from 0.5 wt% to 3 wt% in the final composition. In some embodiments, the concentration of the surfactant is from 0.1 wt% to 1 wt% in the final composition. In some embodiments, the hydrophobic composition comprises a surfactant and the aqueous medium is a mixture comprising water and a co-solvent. In some embodiments, the hydrophobic composition comprises a surfactant and the aqueous medium is water. In some embodiments, the hydrophobic coating composition comprises a surfactant and comprises 0.5 wt% to 4 wt% of graphene. In some embodiments, the hydrophobic coating composition comprises a surfactant and comprises 0.5 wt% to 3.5 wt%, 1 wt% to 3 wt%, 1.5 wt% to 3 wt%, 2 wt% to 2.75 wt% or 2 wt% to 2.5 wt% of graphene. In some embodiments, the hydrophobic coating composition comprises a surfactant and comprises 3.5 wt% or less, 3 wt% or less, 2.9 wt% or less, 2.8 wt% or less, 2.7 wt% or less, 2.6 wt% or less or 2.5 wt% or less of graphene. The presence of the surfactant in the composition is advantageous because the multilayer graphene is stabilized so as not to re-aggregate. Also, the presence of the surfactant stabilizes the suspension, which is also advantageous in that the suspension can be manufactured before use and stored for a certain period of time.

[0022] In some embodiments, the hydrophobic coating composition does not contain a surfactant. In some embodiments, the hydrophobic composition does not contain a surfactant and the aqueous medium is water. In some embodiments, the hydrophobic composition does not contain a surfactant and the aqueous medium is a mixture of water and a co-solvent. In some embodiments, the hydrophobic composition does not contain a surfactant and the aqueous medium is a mixture of water and isopropanol. In some embodiments, the hydrophobic coating composition does not contain a surfactant and contains at least 2.5 wt%, at least 2.6 wt%, at least 2.7 wt%, at least 2.8 wt%, at least 2.9 wt%, at least 3 wt% or at least 3.5 wt% of graphene. In some embodiments, the hydrophobic coating composition does not contain a surfactant and contains at least 4 wt%, at least 4.5 wt%, at least 5 wt%, at least 5.5 wt% or at least 6 wt% of graphene. In some embodiments, the hydrophobic coating composition does not contain a surfactant and contains 10 wt% or less, 9 wt% or less, 8 wt% or less or 7 wt% or less of graphene. In some embodiments, the hydrophobic coating composition does not contain a surfactant and contains 3.5 wt% to 8 wt%, 4 wt% to 7 wt% or 4 wt% to 6 wt% of graphene. Compositions containing at least 3.5 wt% of graphene and not containing a surfactant can be advantageous because the composition improves the hydrophobicity of the surface of the article and the surfactant-free composition is inexpensive. Also, surfactant-free compositions can be advantageous because they can be easier to manufacture on a large scale since surfactants are often high-viscosity or solid-state components that can be difficult to handle. The presence of isopropanol in the surfactant-free hydrophobic coating composition is advantageous because it only requires additional mixing by shaking well to disperse the suspension before the hydrophobic coating composition is applied to the desired surface.

[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. This includes step (a) of providing a mixture of multilayer graphene, fluorinated silane, and an aqueous medium, and step (b) of subjecting the mixture to stirring to achieve a uniform dispersion.

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

[0025] The multilayer graphene may be produced in a step prior to step (a). This step may include, for example, a step of producing multilayer graphene from graphite by a liquid-phase exfoliation method or the like, which may be carried out on 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 an alcohol. 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 in this case, it may not include a surfactant. By the liquid-phase exfoliation method, sheets of multilayer graphene may be formed.

[0026] In some embodiments, the concentration of the surfactant is 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less, or 3 wt% or less in the final composition. In some embodiments, the concentration of the surfactant is 0.05 wt% to 5 wt%, 0.1 wt% to 4.5 wt%, 0.2 wt% to 4 wt%, or 0.5 wt% to 3 wt% in the final composition. In some embodiments, the concentration of the surfactant is 0.1 wt% to 1 wt% in the final composition. In some embodiments, the surfactant is an anionic surfactant. In some embodiments, the surfactant is sodium cholate. In some embodiments, the surfactant is a cholate such as sodium cholate. Sodium cholate is an anionic surfactant containing three hydroxy groups located on the steroid ring and one carboxyl group located at the end of the molecular structure, and there is no distinct lipophilic or hydrophilic region within the molecule. Cholate can be easily removed by dialysis. The surfactant can stabilize the sheets of multilayer graphene and prevent the re-aggregation of multilayer graphene. The production of multilayer graphene from graphite may further include a centrifugation step after the exfoliation step. The centrifugation step may separate the multilayer graphene from the heavier unexfoliated graphite. The heavier unexfoliated graphite does not maintain a dispersed state in the suspension as effectively as the lighter multilayer graphene and leads to separation or the formation of sediment in the hydrophobic coating suspension, so the centrifugation step is considered advantageous.

[0027] In some embodiments, the liquid-phase exfoliation step may not include a surfactant. In some embodiments, the liquid-phase exfoliation step does not include a surfactant and may include water and isopropanol as the aqueous medium. Producing surfactant-free multilayer graphene from graphite in a water / isopropanol medium is considered advantageous in that the graphene production method is cheaper and faster (including only one step) and there is no contamination. The presence of the corresponding organic matter in the aqueous medium can stabilize the sheets of multilayer graphene and prevent the re-aggregation of multilayer graphene.

[0028] In some embodiments, the liquid-phase exfoliation step may include high-speed mixing for at least 10 minutes, at least 20 minutes, at least 30 minutes, at least 40 minutes, at least 50 minutes, at least 60 minutes, at least 70 minutes, at least 80 minutes, at least 90 minutes, at least 100 minutes, at least 110 minutes, at least 120 minutes or at least 130 minutes. In some embodiments, the liquid-phase exfoliation step may include high-speed mixing at a stirring speed of at least 3000 rpm, at least 3250 rpm, at least 3500 rpm, at least 3750 rpm or at least 4000 rpm. In some embodiments, the liquid-phase exfoliation step may include high-speed mixing at a stirring speed of 9000 rpm or less, 8500 rpm or less, 8000 rpm or less, 7500 rpm or less or 7000 rpm or less. In some embodiments, the liquid-phase exfoliation step may include high-speed mixing at a stirring speed of 4000 rpm to 9000 rpm, 3500 rpm to 8000 rpm or 3000 rpm to 7000 rpm.

[0029] In some embodiments, the production of multilayer graphene from graphite may further include a sedimentation step after the liquid-phase exfoliation step. By this sedimentation step, the multilayer graphene in the suspension can be separated from the heavier unexfoliated graphite. Since the heavier unexfoliated graphite does not disperse in the suspension and precipitates, only the supernatant containing the lighter graphene sheets is used for the hydrophobic coating suspension.

[0030] In some embodiments, the concentration of the fluorinated silane is at least 0.01 wt%, at least 0.05 wt%, at least 0.1 wt%, at least 0.2 wt%, at least 0.3 wt%, at least 0.4 wt% or at least 0.5 wt%. In some embodiments, the concentration of the fluorinated silane is 7 wt% or less, 6 wt% or less, 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less or 3 wt% or less. In some embodiments, the concentration of the fluorinated silane is from 0.1 wt% to 5 wt%, from 0.2 wt% to 4.5 wt%, from 0.3 wt% to 4 wt%, from 0.4 wt% to 3.5 wt% or from 0.5 wt% to 3 wt%. In a preferred embodiment, the concentration of the fluorinated silane is from 0.5 wt% to 1.5 wt%.

[0031] In some embodiments, the concentration of the multilayer graphene is at least 0.05 wt%, at least 0.1 wt%, at least 0.2 wt%, at least 0.3 wt%, at least 0.4 wt%, at least 0.5 wt%, at least 0.6 wt%, at least 0.7 wt%, at least 0.8 wt%, at least 0.9 wt% or at least 1 wt%. In some embodiments, the concentration of the multilayer graphene is 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less, 3 wt% or less, 2.5 wt% or less or 2 wt% or less. In some embodiments, the concentration of the multilayer graphene is from 0.1 wt% to 5 wt%, from 0.2 wt% to 5 wt%, from 0.3 wt% to 5 wt%, from 0.5 wt% to 5 wt% or from 1 wt% to 5 wt%. In some embodiments, the concentration of the multilayer graphene is from 3 wt% to 8 wt%, from 4 wt% to 8 wt% or from 4.5 wt% to 7 wt%. In some embodiments, the concentration of the multilayer graphene is from 1.5 wt% to 3 wt%, such as from 1.5 wt% to 2.5 wt%. Such concentrations are particularly useful for providing superhydrophobic properties to the composition when applied to the surface of an article.

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

[0033] Step (b) may be carried out by any suitable mixing process. In a preferred embodiment, the stirring step comprises sonication by ultrasound.

[0034] In some embodiments, step (b) may comprise subjecting the mixture to sonication by ultrasound after completion of step (a). In some embodiments, the sonication by ultrasound may be carried out for 150 minutes or less, 120 minutes or less, 110 minutes or less, 100 minutes or less, 90 minutes or less, 80 minutes or less, 70 minutes or less or 60 minutes or less. In some embodiments, the sonication by ultrasound may be carried out for at least 5 minutes, at least 6 minutes, at least 7 minutes, at least 8 minutes, at least 9 minutes or at least 10 minutes. In some embodiments, the sonication by ultrasound may be carried out for 5 minutes to 120 minutes, 6 minutes to 110 minutes, 7 minutes to 100 minutes, 8 minutes to 90 minutes, 9 minutes to 80 minutes or 10 minutes to 70 minutes. In some embodiments, the sonication by ultrasound may be carried out for 10 minutes to 30 minutes.

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

[0036] According to a third aspect of the present invention, a process for coating an article is provided. The process includes: step (a) of depositing a hydrophobic coating composition according to the first aspect of the present invention on the surface of the article; and step (b) of drying the coating composition to form a coating on the surface.

[0037] In some embodiments, the article may be a building material. In some embodiments, the building material may be any porous building material. In some embodiments, the building material may include a wall component or may be a wall. In some embodiments, the building material may be a brick or a block. In some embodiments, the brick may be formed from clay, sand and lime or fly ash. In some embodiments, the building material may be concrete, or a concrete block or brick. In some embodiments, the article may be a roof such as a concrete roof, a terracotta roof or a painted roof. In some embodiments, the article may be a pretreated building surface such as wood or a cladding. In some embodiments, the article may be a flexible material. The flexible material may be one or more materials selected from the group consisting of leather, synthetic fabric, smart fabric (i.e., fabric material containing electronic components), wool, cotton and any combination thereof. In some embodiments, the article may be an open electrode or any open electronic circuit. Here, open means not encapsulated or without a jacket or protective package. In some embodiments, the article may be an electronic device such as a phone or a computer.

[0038] Step (a) includes a method of depositing a hydrophobic coating composition on the surface of an article. In some embodiments, the application method may be drop casting. In other embodiments, the application method is spraying. In other embodiments, the application method is mechanical application by 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, at least 7°C, at least 9°C, at least 11°C, at least 13°C or at least 15°C. In some embodiments, the hydrophobic coating composition may be sprayed onto the surface of the article at a temperature of 70°C or lower, 65°C or lower, 60°C or lower, 55°C or lower or 50°C or lower. In some embodiments, the hydrophobic coating composition may be sprayed onto the surface of the article at a temperature of 5°C to 70°C, 7°C to 65°C, 9°C to 60°C, 11°C to 55°C or 13°C to 50°C.

[0040] In a preferred embodiment, the hydrophobic coating composition may be sprayed onto the surface of the article at a temperature of 10°C to 40°C. In some embodiments, the hydrophobic coating composition may be sprayed at room temperature or ambient temperature. In some embodiments, the volume of the hydrophobic coating composition to be sprayed is at least 100 mL, at least 150 mL, at least 200 mL, at least 250 mL, at least 300 mL or at least 350 mL per 1000 cm 2 It may be. In some embodiments, the volume of the hydrophobic coating composition to be sprayed is 3000 mL or less, 2750 mL or less, 2500 mL or less, 2250 mL or less or 2000 mL per 1 cm 2 It may be. In some embodiments, the volume of the hydrophobic coating composition to be sprayed is 100 mL to 2000 mL per 1000 cm 2 Or 250 mL to 2500 mL per 1 cm 2 Or 1 cm 2It may be 100 mL to 3000 mL per hit.

[0041] Step (b) may include drying the hydrophobic coating composition on the surface at a temperature of at least 5°C, at least 7°C, at least 9°C, at least 11°C, at least 13°C or at least 15°C. In some embodiments, the hydrophobic coating composition may be dried on the surface of the article at a temperature of 70°C or less, 65°C or less, 60°C or less, 55°C or less or 50°C or less. In some embodiments, the hydrophobic coating composition may be dried on the surface of the article at a temperature of 5°C to 70°C, 7°C to 65°C, 9°C to 60°C, 11°C to 55°C or 13°C to 50°C. In a preferred embodiment, the hydrophobic coating composition may be dried on the surface of the article at a temperature of 10°C to 40°C. This drying step may be completed at ambient temperature so as not to require forced drying.

[0042] In some embodiments, the drying step may be carried out for at least 1 minute, at least 5 minutes, at least 10 minutes or at least 15 minutes. In some embodiments, the drying step may be carried out for 60 minutes or less, 55 minutes or less, 50 minutes or less, 45 minutes or less or 40 minutes or less. In some embodiments, the drying step may be carried out for 1 minute to 60 minutes, 5 minutes to 55 minutes, 10 minutes to 50 minutes or 15 minutes to 45 minutes. In some embodiments, the drying step may be carried out for 15 minutes to 35 minutes.

[0043] The process of depositing the hydrophobic solution on the surface may not require an additional surface treatment step either before step (a), during step (a), before step (b), during step (b), or after step (b). This application process, which includes steps (a) and (b) and does not include an additional surface treatment step, is advantageous because applying the coating to the surface is easy for the user compared to other surface coatings that require, for example, forced drying at high temperatures. This eliminates the need to force-dry the coating and allows for easy application over a large surface area, thus expanding the use of surface coatings.

[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 according to the fourth aspect of the present invention may be produced by the process according to the third aspect of the present invention. The article according to the fourth aspect of the present invention may be produced by the method according to the second aspect of the present invention.

[0045] An article having a hydrophobic coating can exhibit excellent hydrophobic performance. The hydrophobic performance can be measured by measuring the contact angle of water. The "contact angle of water" or "water contact angle" is defined as the angle between the edge of a stationary water droplet and the flat horizontal surface of the solid on which the water droplet is placed. The higher the contact angle, the higher the hydrophobic reaction between the liquid and the surface. When the liquid completely covers the surface to form a film, the contact angle is 0 degrees (0°). If the contact angle is greater than 90°, the surface is called a "hydrophobic" surface. If the contact angle is at least 150° or more, the coating is called a "superhydrophobic" coating. The application process according to the third aspect of the present invention using the hydrophobic coating solution according to the first aspect of the present invention is advantageous because it may result in superhydrophobic performance. In some embodiments, the hydrophobic coating maintains superhydrophobic performance for at least 1 month, at least 2 months, at least 3 months, at least 4 months, at least 5 months, or at least 6 months. In some embodiments, the hydrophobic coating maintains superhydrophobic performance for at least 9 months, at least 10 months, at least 11 months, or at least 12 months.

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

[0047] The non-fluorinated silane does not contain fluorine or is essentially free of fluorine. The hydrophobic coating composition may follow any embodiment of the first aspect of the present invention, except that the hydrophobic coating composition according to the fifth aspect of the present invention contains a non-fluorinated silane instead of a fluorinated silane.

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

[0049] In some embodiments, the silane may be a compound having a general structure of (RO)3-Si-R’-Y. Here, R represents an alkyl group, an alkenyl group or hydrogen, R’ represents a C1-C5 hydrocarbon bond, and Y represents a fluorine-free functional group. R may be according to any embodiment of the first aspect of the present invention. R’ may be according to any embodiment of the first aspect of the present invention. Y may be selected from the group consisting of non-fluorine halogens, non-fluorinated organic halogens, hydrocarbons, alkyls, aryls, alkenyls, alkynyls, alkylaryls, alkoxys, aryloxys, amines, a 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 a fifth aspect of the present invention. This includes step (a) of providing a mixture of multilayer graphene, silane and an aqueous medium, and step (b) of subjecting the mixture to stirring to achieve a uniform dispersion.

[0051] The method according to the sixth aspect of the present invention may be according to any embodiment according to the second aspect of the present invention, in which the hydrophobic coating according to the first aspect of the present invention is replaced with the hydrophobic coating composition according to 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. The process includes step (a) of depositing the hydrophobic coating composition according to the fifth aspect of the present invention on the surface of the article, and step (b) of 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 the hydrophobic coating composition according to the fifth aspect of the present invention. The article according to the eighth aspect of the present invention may be produced by the process according to the seventh aspect of the present invention. The article according to the eighth aspect of the present invention may be produced by the method according to the sixth aspect of the present invention.

Brief Description of the Drawings

[0054] Hereinafter, in order to understand the present invention more clearly, embodiments thereof will be illustratively described with reference to the accompanying drawings.

Figure 1

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Figure 7

[0055] FIG. 1 shows an embodiment of the coated article of the present invention having the form of a coated concrete brick (2). This coated brick includes a brick body (4). On it, an embodiment of the coating composition according to the first aspect of the present invention is coated in the form of a coating (6). The coating contains multi-layer graphene, 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 as Formulations A - U applied to the brick (2) are exemplified in Table 1 and Table 2 below.

[0056] [Example 1] [Preparation of the Surfactant-Based Hydrophobic Coating Composition of the Present Invention] An embodiment of the second aspect of the present invention relates to a method for preparing a hydrophobic coating according to the first aspect of the present invention, as described below. The first embodiment of the second aspect of the present invention includes the following steps. First, multilayer graphene was prepared using the liquid-phase exfoliation method. This liquid-phase exfoliation step includes combining 15 mg / ml of graphite flakes and 5 mg / ml of sodium cholate surfactant with an appropriate amount (800 ml) of deionized water. This mixture was stirred at 4500 rpm for 60 minutes using a high-shear laboratory mixer, for example, an L5M mixer (Silverson Machines, UK) having a rotor head with a diameter of 32 mm. By liquid-phase exfoliation, the van der Waals forces between the graphite layers in the graphite flakes were disrupted, and thin sheets of multilayer graphene were obtained. The sodium cholate surfactant stabilizes the thin sheets of multilayer graphene so that they do not re-aggregate. After liquid-phase exfoliation, centrifugation was performed at 1000 rpm for 100 minutes to remove residual graphite flakes from the mixture of multilayer graphene. The prepared multilayer graphene contained 2 to 10 layers.

[0057] Next, the multilayer graphene was added to a fluorinated silane, which is 1H,1H,2H,2H-perfluorodecyltriethoxysilane in this example. 1 wt% of 1H,1H,2H,2H-perfluorodecyltriethoxysilane was added to a portion of the multilayer graphene according to Formulations B to P shown in Table 1 so that the amount of multilayer graphene in the final product was 1 wt% to 5 wt%. Formulation A is included in Table 1 as a control solution (0%) without multilayer graphene.

[0058] Next, the hydrophobic coating compositions (Formulations B to P) and the control formulation (A) of the present invention were mixed by ultrasonic treatment for 20 minutes so that the resulting product was a suspension.

[0059]

Table 1

[0060] [Example 2] [Preparation of a Surfactant-Free Hydrophobic Coating Composition of the Invention] A second embodiment of the second aspect of the invention, wherein the hydrophobic composition is a composition free of surfactant, comprises the following steps. First, multilayer graphene was produced using a surfactant-free liquid-phase exfoliation method. This liquid-phase exfoliation step includes combining 6 mg / ml of graphite flakes with an appropriate amount of deionized water / isopropanol solution, for example, a 600 ml deionized water / isopropanol solution (the ratio of deionized water:isopropanol is 3:1). This mixture was stirred at 7000 rpm for 120 minutes using a high-shear laboratory mixer, for example, an L5M mixer (Silverson Machines, UK) with a 32 mm diameter rotor head. By liquid-phase exfoliation in the presence of organic components, the van der Waals forces between the graphite layers in the graphite flakes were disrupted, and a high-concentration multilayer graphene dispersion was obtained. The organic molecules in the solution stabilize the multilayer graphene sheets in a short period compared to surfactant-based procedures. After liquid-phase exfoliation, a sedimentation step was performed at room temperature to separate the heavier residual graphite flakes from the multilayer graphene solution. To avoid additional centrifugation, after standing in air for several hours, the upper layer of the final dispersion was decanted. Since residual graphite flakes remained in the precipitate, these were removed. The produced multilayer graphene contained 2 to 10 layers.

[0061] Next, the multilayer graphene was added to a fluorinated silane, which in this example is 1H,1H,2H,2H-perfluorodecyltriethoxysilane. 1 wt% of 1H,1H,2H,2H-perfluorodecyltriethoxysilane was added to a portion of the multilayer graphene such that the amount of multilayer graphene in the final product was 4 wt% to 6 wt%. The formulations of the invention containing 4 wt% to 6 wt% of multilayer graphene are shown as formulations Q to U in Table 2.

[0062] Next, the hydrophobic coating composition of the invention was mixed by sonication for 20 minutes such that the resulting product was a suspension.

[0063]

Table 2

[0064] [Example 3] [Method for Applying the Hydrophobic Coating Composition of Examples 1 and 2 to Articles] Next, embodiments of the hydrophobic coating compositions of Formulations B - U according to the first aspect of the present invention, and the control Formulation A, were each sprayed onto the surface of a concrete cylinder (2) at room temperature to form a hydrophobic coating (6) as shown in FIG. 1. Next, the coating (6) was dried at room temperature for 20 to 30 minutes. The concrete cylinder (2) was prepared using Blue Circle General Purpose Cement and tap water at a concentration ratio of 2:1 by weight. Then, the prepared concrete cylinder (2) was dried overnight.

[0065] Formulations A - U were sprayed onto the concrete cylinder (2) at ambient temperature and dried at ambient temperature for 30 minutes.

[0066] Next, the water contact angle of the hydrophobically coated concrete cylinder (2) was analyzed using Inkscape (copyright) software. Such analyses of Formulations C - M in Table 1 and Formulations Q - U in Table 2 are shown in FIGS. 2 and 3, respectively. Here, the angle between the horizontal concrete surface coated with Formulations C - U and the edge of the water droplet was measured, thereby obtaining the water contact angle.

[0067] The water contact angles of surfactant-free formulations B, H, N, O, and M containing 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt% of multilayer graphene and 1 wt% of silane were measured 1 hour after coating application. A concrete lintel (2) having a hydrophobic coating (6) containing formulations B, H, N, O, and P was stored under ambient conditions for 1 month, and the water contact angle 1 month after application was measured. Figure 4 graphically shows the results of the water contact angles of concrete lintels (2) individually coated with each of formulations B - D. Here, the water contact angle was measured 1 hour after application of the formulation and again 1 month after application of the formulation.

[0068] The water contact angles of concrete lintels (2) coated with a hydrophobic coating (6) containing formulations C - M, containing 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, and 2.5 wt% of multilayer graphene and 1 wt% of silane, were measured 1 hour after application. Next, the concrete lintels (2) were stored for 1 month, and the water contact angle 1 month after application was measured. These experimental results are graphically shown in Figure 5.

[0069] A concrete lintel (2) having a hydrophobic coating (6) containing formulations H - M, containing 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, and 2.5 wt% of multilayer graphene and 1 wt% of silane, was stored for 1 year, and the water contact angle 1 year after application was measured. These experimental results are graphically shown in Figure 6.

[0070] A concrete lintel (2) having a hydrophobic coating (6) containing formulations Q - U, containing 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt%, and 6.0 wt% of multilayer graphene and 1 wt% of silane, was stored for 1 month, and the water contact angles 1 day and 1 month after application were measured. These experimental results are graphically shown in Figure 7.

[0071] All hydrophobic coating compositions (6) were transparent when applied to the concrete lintel (2).

[0072] [Results] The above test results indicate that the concentration of multilayer graphene in the hydrophobic coating composition affects the hydrophobic performance of the coating after spraying and over time. A high water contact angle correlates with good water repellency. Formulation A without multilayer graphene showed a water contact angle of approximately 35° in the test after 1 hour of coating. Therefore, the control formulation A was neither hydrophobic nor superhydrophobic. Formulations B - N of the present invention containing 1 wt% - 3 wt% of multilayer graphene in the surfactant based on the hydrophobic composition, and formulations Q - U containing 4 wt% - 6 wt% of multilayer graphene in the composition without surfactant all showed hydrophobic performance and superhydrophobic performance. This suggests that the presence of multilayer graphene at a concentration of 1 wt% - 6 wt% is important for excellent hydrophobic performance compared to formulations without multilayer graphene.

[0073] Formulations H, I, and J containing 2.0 wt%, 2.1 wt%, and 2.2 wt% of multilayer graphene showed significantly improved hydrophobic performance compared to the formulation without multilayer graphene (control formulation A), and the water contact angles measured 1 month after application were 154°, 155°, and 153° respectively. Therefore, formulations containing 2 wt% - 2.2 wt% of multilayer graphene are superhydrophobic. Formulations S, T, and U containing 5.0 wt%, 5.5 wt%, and 6.0 wt% of multilayer graphene also showed superhydrophobic performance, and the contact angles measured 1 day after coating and 1 month after coating were 161°, 155°, and 152° respectively.

[0074] Formulations (formulations B - G) containing 1 wt% - 1.9 wt% of multilayer graphene showed good hydrophobic performance and good durability, and the water contact angles measured 1 month after coating were 110° - 140°.

[0075] Formulations H, I, J, K, L, and M containing 2 wt% to 2.5 wt% of graphene exhibited excellent hydrophobic performance even when tested one year after coating, with water contact angles ranging from 132° to 155°. Formulations H, I, and J containing 2.0 wt%, 2.1 wt%, and 2.2 wt% of multilayer graphene showed superhydrophobic performance when tested as coatings on concrete one year after coating, with water contact angles of 152°, 155°, and 150° respectively, and demonstrated high durability over at least one year in these hydrophobic coatings. Formulations containing 4 wt% to 6 wt% of graphene (prepared using surfactant-free exfoliation) and a mixture of water and isopropanol, such as Formulations Q and U shown in Table 2, exhibited excellent hydrophobic performance, with water contact angles ranging from 146° to 161°. In particular, formulations containing 5.0 wt%, 5.5 wt%, and 6.0 wt% of multilayer graphene maintained superhydrophobic performance even one year after coating, with water contact angles of 161°, 155°, and 152° respectively. In this application, the hydrophobic performance and good durability exhibited by formulations containing 1 wt% to 6 wt% of multilayer graphene provide good surface protection of materials from water, dust, ice, moss, mold, and fungi, contributing to the maintenance of the good appearance of wall stone structures.

[0076] The above-described embodiments are described for illustrative purposes only. Many modifications are possible without departing from the scope of the invention defined by 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 aforementioned fluorinated silane is (RO) ３ The hydrophobic coating composition according to claim 1, wherein the compound has the general formula -Si-R'-X, where R represents an alkyl group, an alkenyl group, or hydrogen, R' represents a C1-C5 hydrocarbon bond, and X represents an organofluorine functional group, preferably a 1H,1H,2H,2H- perfluorodecyltriethoxysilane.

3. The hydrophobic coating composition according to claim 1 or 2, wherein the graphene is multilayer graphene comprising 2 to 10 layers of graphene.

4. The hydrophobic coating composition according to claim 1, wherein the amount of the fluorinated silane is at least 0.1% by weight.

5. The hydrophobic coating composition according to claim 1, wherein the amount of graphene is 1% by weight to 6% by weight.

6. The hydrophobic coating composition according to claim 1, wherein the aqueous medium is water.

7. The hydrophobic coating composition according to claim 1, wherein the amount of the aqueous medium is 65% to 99%.

8. The hydrophobic coating composition according to claim 1, comprising a cosolvent that is preferably a polar solvent, and more preferably isopropanol.

9. The hydrophobic coating composition according to claim 8, wherein the amount of isopropanol is 0% to 40% by weight.

10. The hydrophobic coating composition according to claim 1, comprising less than 4% by weight of graphene and further comprising a surfactant.

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

12. The hydrophobic coating composition according to claim 10 or 11, wherein the amount of the surfactant is 2% by weight or less.

13. A method for preparing the hydrophobic coating composition according to claim 1, comprising the steps of (a) providing a mixture of multilayer graphene, fluorinated silane, and an aqueous medium, and (b) subjecting the mixture to stirring.

14. The method according to claim 13, further comprising the step of producing multilayer graphene from graphite before step (a).

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

16. The method according to claim 14 or 15, wherein the graphite is mixed with a surfactant.

17. The method according to claim 16, wherein the surfactant is sodium cholate.

18. The method according to claim 14, wherein the graphite is mixed with water and at least one other solvent.

19. The method according to claim 13, wherein step (a) comprises mixing the multilayer graphene and the fluorinated silane in an aqueous medium.

20. The method according to claim 13, wherein step (b) includes mixing the mixture obtained in step (a) using ultrasonic sonication to form a homogeneous dispersion.

21. A process for coating an article, comprising the steps of: (a) depositing the hydrophobic coating composition according to claim 1 onto the surface of the article; and (b) drying the hydrophobic coating composition to form a coating on the surface.

22. The process according to claim 21, wherein the temperature in step (a) is 20°C to 40°C.

23. Step (a) includes spraying the hydrophobic coating composition onto the surface of the article, wherein the volume of the hydrophobic coating composition sprayed is such that it covers 1 cm² of the surface of the article. ２ The process according to claim 21 or 22, wherein the amount is 0.25 mL to 3 mL per unit.

24. The process according to claim 21, wherein the temperature in step (b) is an ambient temperature such as 15°C to 40°C.

25. The process according to claim 21, wherein step (b) comprises drying the hydrophobic coating composition for 20 to 30 minutes.

26. The process according to claim 21, wherein the article is selected from the group consisting of buildings or building materials, textiles, electronic components and electronic textiles.

27. An article having at least one surface coated with the hydrophobic coating composition described in claim 1.

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