Bifunctional janus nanosilica and preparation method and application thereof

Abstract

This invention provides a bifunctional Janus nano-silica, its preparation method, and its application, belonging to the field of UV-curable coating technology. This invention uses a silicon source and fluorosilane compounds to design nano-SiO2 into Janus nanoparticles. One side of the prepared bifunctional Janus nano-silica is modified with fluorine-containing organic functional group segments, and the other side is modified with polymerizable unsaturated double bond segments, allowing it to polymerize with monomers and oligomers in UV-curable coatings. By filling the UV-curable coating with these fluorine-containing segments and crosslinkable curable segments, high-performance novel functional coatings can be developed, meeting the material's requirements for special properties such as high wear resistance, corrosion resistance, fingerprint resistance, and radiation resistance.

Description

Technical Field

[0001] This invention relates to the field of ultraviolet curable coating technology, and in particular to a bifunctional Janus nano silica, its preparation method, and its application. Background Technology

[0002] In the coatings industry, ultraviolet (UV) curing coatings are widely used in cosmetics packaging, home appliances, and 3D printing due to their advantages such as short curing time, high production efficiency, and low energy consumption. However, purely organic UV curing coatings suffer from drawbacks such as poor abrasion resistance, low hardness, and weak impact resistance. Furthermore, the surface properties of the material gradually deteriorate with wear during use. Therefore, there is an urgent need to develop a series of long-lasting, high-performance UV-curing coatings to meet the demands of the high-end market.

[0003] To address the aforementioned issues, adding inorganic nanoparticles to coatings can significantly improve the wear resistance of the coating and also substantially enhance the material's heat resistance, oxidation resistance, and other properties. For example, the composite material formed by adding nano-SiO2 to UV-curable coatings can effectively combine the advantages of organic and inorganic systems, improving the hardness and wear resistance of UV-curable coatings. Furthermore, super-lubricating fluorosilicone coatings exhibit excellent hydrophobic, fingerprint-resistant, and biofouling-resistant properties due to their liquid-like and molecularly smooth surface, showing significant application potential. These low surface energy molecules are typically fluorosilicone-based substances, exhibiting minimal adhesion to external liquids, thus producing unique super-lubricating properties. For instance, modifying nano-SiO2 with fluorinated silane coupling agents can yield fluorinated nano-SiO2 particles with dual hydrophobic (hydrophobic and oleophobic) properties. However, in practical chemical applications, such SiO2 nanoparticles with limited surface properties cannot meet the diverse and evolving requirements of chemistry. For example, pure fluorinated SiO2 nanoparticles exhibit poor dispersibility in organic systems and low chemical affinity for monomers and oligomers in UV-curable coatings, resulting in weak adhesion to the substrate. Consequently, the effects of nanoparticles in organic systems are difficult to realize. Furthermore, current UV-curable coatings exhibit poor wear resistance and fingerprint resistance, making it difficult for pure fluorinated SiO2 nanoparticles to meet the application requirements in UV-curable coatings. Summary of the Invention

[0004] The purpose of this invention is to provide a bifunctional Janus nano silica, its preparation method and application, wherein the bifunctional Janus nano silica can form a wear-resistant and fingerprint-resistant photocurable coating.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing bifunctional Janus nano-silica, comprising the following steps:

[0007] A silicon source, polyacrylic acid, a first alkali, and a first organic solvent are mixed and modified to obtain SiO2 nanoparticles modified with unsaturated double bonds; the silicon source includes silica ester and silane coupling agent containing unsaturated double bonds.

[0008] The unsaturated double bond modified SiO2 nanoparticles were mixed with a dispersion medium, and the resulting dispersion was mixed with an oily liquid and emulsified to obtain a Pickering emulsion.

[0009] After drying the Pickering emulsion, the resulting solid product is mixed with acid and etched to obtain the etched product.

[0010] The etching product, the second alkali, the fluorosilane compound, and the second organic solvent are mixed and fluorinated to obtain bifunctional Janus nano silica.

[0011] Preferably, the silicate ester includes one of tetraethyl silicate, tetrabutyl silicate, and tetramethyl silicate; the silane coupling agent containing unsaturated double bonds includes one of allyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, allyltriethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, and γ-methacryloyloxypropyltriethoxysilane; the volume ratio of the silane coupling agent containing unsaturated double bonds to the silicate ester is 1:3 to 9.

[0012] Preferably, the first alkali comprises ammonia; the mass ratio of the first alkali to polyacrylic acid is 500-700:1; and the mass ratio of the silicon source to polyacrylic acid is 250-350:1.

[0013] The oily liquid includes molten paraffin; the emulsification temperature is 65–80°C, and the time is 1–3 hours.

[0014] Preferably, when mixing the obtained dispersion and the oily liquid, a surfactant is also added; the surfactant includes hexadecyltrimethylammonium bromide or sodium dodecyl sulfate; the mass ratio of the surfactant to the unsaturated double bond modified SiO2 nanoparticles is 0:1 to 1:2.

[0015] Preferably, the mass ratio of the unsaturated double-bond modified SiO2 nanoparticles to the emulsifier is 1:10 to 50.

[0016] Preferably, the acid includes hydrofluoric acid, the concentration of the hydrofluoric acid is 1-5 wt%, and the etching time is 1-12 h.

[0017] Preferably, the second alkali comprises ammonia; the fluorosilane compound comprises trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, triethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, or 1H,1H,2H,2H-perfluorodecyltrimethoxysilane; the mass ratio of the fluorosilane compound to the unsaturated double-bond modified SiO2 nanoparticles is 1:6-8; and the fluorination time is 2 hours.

[0018] This invention provides bifunctional Janus nano-silica prepared by the preparation method described in the above technical solution.

[0019] This invention provides the application of the bifunctional Janus nano silica described above in photocurable coatings.

[0020] Preferably, the method of application includes:

[0021] The bifunctional Janus nano silica and UV-curable coating were mixed, and the resulting liquid mixture was coated onto the substrate. Then, the mixture was dried and UV-cured in sequence to obtain a UV-curable coating.

[0022] The mass of the bifunctional Janus nano silica is 1 to 5% of the mass of the UV-curable coating.

[0023] This invention utilizes a silicon source and fluorosilane compounds to design nano-SiO2 into Janus nanoparticles. The prepared bifunctional Janus nano-silica is modified with fluorine-containing organic functional groups on one side and polymerizable unsaturated double-bond segments on the other. This allows it to polymerize with monomers and oligomers in photocurable coatings, forming a uniform, dense, and robust nanoparticle composite coating. This enhances the coating's hardness and wear resistance. The fluorine-containing segments reduce surface tension and possess strong hydrophobicity, thus reducing the adhesion and spread of grease on the surface. This hydrophobic surface structure effectively prevents the adhesion of fingerprints and other grease stains. Therefore, filling photocurable coatings with Janus nano-SiO2 containing these fluorine-containing segments and crosslinkable curable segments enables the development of high-performance novel functional coatings, meeting the material's requirements for high wear resistance, corrosion resistance, fingerprint resistance, and radiation resistance.

[0024] The SiO2 nanoparticles prepared by this invention are spherical in shape and uniform in size, with a diameter between 10 nm and 200 nm, and show no agglomeration.

[0025] This invention can precisely control the area of ​​different functional regions on both sides of the SiO2 particle, the number of functional groups on both sides, and the chemical composition by controlling the ratio of surfactants and the ratio of unsaturated double bond silane coupling agents and fluorosilanes.

[0026] The preparation process of this invention is simple, suitable for large-scale production, and facilitates the development of domestically produced UV-curable coatings, optimizing the wear resistance and fingerprint resistance of the coatings.

[0027] This invention improves the wear resistance of UV coatings by adding bifunctional Janus nano-SiO2 particles to them and using inorganic nanoparticle doping. It also increases the crosslinking density of the coating by polymerizing polymerizable double-bonded segments in bifunctional Janus nano-SiO2 with monofunctional and polyfunctional monomers, thereby improving its hardness. Furthermore, it utilizes fluorine-containing segments in bifunctional Janus nano-SiO2 particles to drive particle enrichment on the surface, improving the surface's structural stability, wear resistance, and fingerprint resistance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the synthesis of Janus nano-SiO2 particles prepared according to Example 1 of the present invention;

[0029] Figure 2 This is a SEM image of the Janus nano-SiO2 particles prepared in Example 1 of this invention;

[0030] Figure 3 The image shows the XRD pattern of Janus nano-SiO2 particles prepared in Example 3 of this invention.

[0031] Figure 4 The IR spectrum of the double-bond modified SiO2 nanoparticles prepared in Example 4 of this invention;

[0032] Figure 5 The image shows the DLS spectrum of Janus nano-SiO2 particles prepared in Example 5 of this invention. Detailed Implementation

[0033] This invention provides a method for preparing bifunctional Janus nano-silica, comprising the following steps:

[0034] A silicon source, polyacrylic acid, a first alkali, and a first organic solvent are mixed and modified to obtain SiO2 nanoparticles modified with unsaturated double bonds; the silicon source includes silica ester and silane coupling agent containing unsaturated double bonds.

[0035] The unsaturated double bond modified SiO2 nanoparticles were mixed with a dispersion medium, and the resulting dispersion was mixed with an oily liquid and emulsified to obtain a Pickering emulsion.

[0036] After drying the Pickering emulsion, the resulting solid product is mixed with acid and etched to obtain the etched product.

[0037] The etching product, the second alkali, the fluorosilane compound, and the second organic solvent are mixed and fluorinated to obtain bifunctional Janus nano silica.

[0038] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.

[0039] This invention involves mixing a silicon source, polyacrylic acid, a first alkali, and a first organic solvent, and then modifying the mixture to obtain SiO2 nanoparticles modified with unsaturated double bonds; the silicon source includes silica esters and silane coupling agents containing unsaturated double bonds.

[0040] In this invention, the molecular weight of the polyacrylic acid is preferably 2000. The main function of the polyacrylic acid in this invention is to facilitate the formation of stable crystal nuclei during the hydrolysis of silane to generate nano-SiO2, thereby producing uniformly sized nano-SiO2 particles.

[0041] In this invention, the first alkali preferably includes ammonia water. The concentration of the ammonia water is not particularly limited in this invention, and commercially available ammonia water known in the art is acceptable. The concentration of the ammonia water in the mixed system formed by polyacrylic acid, the first alkali, and the first organic solvent is preferably 0.5 to 3 wt%, more preferably 1.5 wt%. The mass ratio of the first alkali to polyacrylic acid is preferably 500 to 700:1, more preferably 600:1.

[0042] In this invention, the silicon source comprises silicate and a silane coupling agent containing unsaturated double bonds; the silicate preferably comprises one of tetraethyl silicate, tetrabutyl silicate, and tetramethyl silicate; the silane coupling agent containing unsaturated double bonds preferably comprises one of allyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, allyltriethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, and γ-methacryloyloxypropyltriethoxysilane; the volume ratio of the silane coupling agent containing unsaturated double bonds to the silicate is preferably 1:3 to 9, more preferably 1:5 to 8, and even more preferably 1:6 to 7. This invention controls the content of double bonds on the SiO2 surface by adjusting the ratio of silicate and silane coupling agent.

[0043] In this invention, the mass ratio of the silicon source to polyacrylic acid is preferably 250 to 350:1, and more preferably 300:1.

[0044] In this invention, the first organic solvent is preferably ethanol; the amount of the first organic solvent is not particularly limited and can be adjusted according to actual needs.

[0045] In this invention, polyacrylic acid is preferably dissolved in a portion of a first organic solvent under stirring conditions, then a first alkali is added, and after mixing evenly, a silicon source dissolved in the remaining first solvent is added dropwise; the dropwise addition time is preferably ≤4h.

[0046] In this invention, the modification temperature is preferably 20-80°C, more preferably 25-50°C, and even more preferably 30-40°C, and the modification time is preferably 2 hours.

[0047] After the modification is completed, the present invention preferably performs precipitation separation, washing and drying on the obtained sol in sequence to obtain SiO2 nanoparticles modified with unsaturated double bonds.

[0048] After obtaining SiO2 nanoparticles modified with unsaturated double bonds, the present invention mixes the SiO2 nanoparticles modified with unsaturated double bonds with a dispersion medium, mixes the resulting dispersion with an oily liquid, and emulsifies it to obtain a Pickering emulsion.

[0049] In this invention, the dispersion medium is preferably an aqueous ethanol solution, and the mass concentration of the aqueous ethanol solution is preferably 6.7%; the ratio of the amount of unsaturated double bond modified SiO2 nanoparticles to the dispersion medium is preferably 0.5-1g:50-100mL, more preferably 0.5-1g:80-90mL; the mixing temperature of the unsaturated double bond modified SiO2 nanoparticles and the dispersion medium is preferably 65-80℃, more preferably 75℃.

[0050] In this invention, the oily liquid preferably comprises molten paraffin; the molten paraffin is preferably solid paraffin in a molten state; the mass ratio of the unsaturated double-bond modified SiO2 nanoparticles to the oily liquid is preferably 1:5 to 50, more preferably 1:10 to 30, and even more preferably 1:15 to 20. Preferably, the oily liquid is heated to the temperature at which the SiO2 nanoparticles and the dispersion medium are mixed, and then added to the dispersion under stirring after the oily liquid has melted.

[0051] In this invention, when mixing the obtained dispersion and the oily liquid, it is preferable to further include the addition of a surfactant; the surfactant preferably includes hexadecyltrimethylammonium bromide or sodium dodecyl sulfate; the mass ratio of the surfactant to the unsaturated double bond-modified SiO2 nanoparticles is preferably 0:1 to 1:2, more preferably 0.01 to 0.1:1, and even more preferably 0.02 to 0.03:1. This invention selects whether to add a surfactant based on the strength of surface hydrophilicity (the strength of surface hydrophilicity is determined by the amount of unsaturated double bonds modified on the SiO2 surface) (if there are few unsaturated double bonds modified on the SiO2 surface and the hydrophilicity is weak, then a surfactant is added). This invention utilizes surfactants to control the embedding depth of SiO2 nanoparticles in Pickering emulsions.

[0052] In this invention, the emulsification temperature is preferably 65-80°C, more preferably 70-75°C, and the emulsification time is preferably 1-3 hours.

[0053] After the emulsification is completed, the present invention preferably cools and filters the obtained product in sequence, and then washes it with water and ethanol respectively to obtain Pickering emulsion.

[0054] After obtaining the Pickering emulsion, the present invention dries the Pickering emulsion, mixes the resulting solid product with acid, and etches it to obtain the etched product.

[0055] In this invention, the drying method is preferably vacuum drying; after drying, a solid product is obtained, namely Pickering emulsion droplets, or small wax balls (where unsaturated double bond modified SiO2 nanoparticles are partially embedded on the surface of the small wax balls).

[0056] In this invention, the acid preferably includes hydrofluoric acid, and the concentration of the hydrofluoric acid is preferably 1-5 wt%, more preferably 2-3 wt%. The etching time is preferably 1-12 hours, more preferably 4-5 hours. This invention does not impose any special limitation on the amount of acid used, as long as sufficient acid is used to ensure complete etching.

[0057] This invention obtains an exposed hydroxyl-rich nano-SiO2 surface by etching away the unsaturated double bonds on the surface of SiO2 nanoparticles exposed on the surface of solid Pickering emulsion droplets.

[0058] After the etching is completed, the present invention preferably filters the resulting suspension and rinses off the etched impurities with saturated boric acid aqueous solution and deionized water, respectively.

[0059] After obtaining the etching product, the present invention mixes the etching product, the second alkali, the fluorosilane compound, and the second organic solvent, and fluorinates them to obtain bifunctional Janus nano silica.

[0060] In this invention, the second alkali preferably includes ammonia water. The concentration of the ammonia water is not particularly limited in this invention, and commercially available ammonia water known in the art is acceptable. The concentration of the ammonia water in the mixed system formed by the etching product, the second alkali, and the second organic solvent is preferably 1 to 3 wt%, more preferably 1.25 to 2.0 wt%. The amount of the second organic solvent used in this invention only needs to meet the above-mentioned ammonia water concentration.

[0061] In this invention, the fluorosilane compound preferably includes trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, triethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, or 1H,1H,2H,2H-perfluorodecyltrimethoxysilane; the mass ratio of the fluorosilane compound to the unsaturated double-bond modified SiO2 nanoparticles is preferably 1:6 to 8, more preferably 1:7. This invention controls the content of fluorine-containing groups on the SiO2 surface by adjusting the amount of fluorosilane added.

[0062] In this invention, the second organic solvent is preferably ethanol; the amount of the second organic solvent is not particularly limited and can be adjusted according to actual needs.

[0063] In this invention, the etching product is preferably dispersed in a portion of the second organic solvent, then a second alkali is added, the mixture is stirred evenly, and then a fluorosilane solution dissolved in the remaining second organic solvent is added dropwise.

[0064] In this invention, the fluorination temperature is preferably room temperature, and the time is preferably 2 hours.

[0065] After the fluorination is completed, the present invention preferably performs precipitation separation, washing and vacuum drying in sequence. After dissolving paraffin with a solvent, it is separated, washed and dried in sequence to obtain bifunctional Janus nano silica. The organic solvent used to dissolve the paraffin is preferably chloroform, n-hexane or carbon tetrachloride.

[0066] This invention provides bifunctional Janus nano-silica prepared by the preparation method described in the above technical solution.

[0067] This invention provides the application of the bifunctional Janus nano silica described above in photocurable coatings.

[0068] In this invention, the method of application preferably includes:

[0069] The bifunctional Janus nano silica and UV-curable coating were mixed, and the resulting liquid mixture was coated onto the substrate. The substrate was then dried and UV-cured in sequence to obtain a UV-curable coating.

[0070] In this invention, the mass of the bifunctional Janus nano silica is preferably 1-5% of the mass of the UV-curable coating, more preferably 2-4%, and even more preferably 3%.

[0071] This invention does not specifically limit the ultraviolet curable coating (UV coating), and any UV coating in the art can be made from resins including monofunctional monomers, polyfunctional monomers, solvents, photoinitiators, and pigments.

[0072] The present invention does not impose any special limitation on the substrate, and any related substrate well known in the art is acceptable.

[0073] In this invention, the drying temperature is preferably 50–80°C, more preferably 60–70°C, and the drying time is preferably 2–10 min, more preferably 5–8 min; the present invention achieves solvent evaporation through drying; the energy of the ultraviolet light used for ultraviolet curing is preferably 600–800 mJ / cm². 2 More preferably 600–700 mJ / cm 2 .

[0074] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0075] Example 1

[0076] like Figure 1 As shown:

[0077] 1) Preparation of SiO2 nanoparticles modified with unsaturated double bonds

[0078] Weigh 15 mg of polyacrylic acid (molecular weight 2000) and dissolve it in 164.5 mL of ethanol under stirring. Then add 9 g of ammonia water to make the concentration 1.5 wt%. After complete dissolution, add 4.5 g of silicon source (4.5 mL of tetraethyl silicate and γ-methacryloyloxypropyltriethoxysilane dissolved in 15.5 mL of ethanol, volume ratio 9:1). The addition should be completed within 4 h. Continue the reaction at 35 °C for another 2 h to obtain a sol of unsaturated double bond modified SiO2. After separating, washing and drying the precipitate, unsaturated double bond modified SiO2 nanoparticles are obtained.

[0079] 2) Selective etching and fluorination of unsaturated double bond modified SiO2 nanoparticles

[0080] At 80℃, 1g of the prepared unsaturated double bond modified SiO2 nanoparticles were uniformly dispersed in 50mL of ethanol aqueous solution (6.7%, w / w) to obtain a SiO2 dispersion. Then, 0.02g of hexadecyltrimethylammonium bromide was added. Separately, 10g of solid paraffin was heated to 65℃ and melted. The resulting molten paraffin was added to the above SiO2 dispersion under stirring to obtain a SiO2 nanoparticle-stabilized Pickering emulsion. After stirring for 3h, the mixture was cooled, filtered, washed with water and ethanol respectively, and dried under low temperature vacuum to obtain solid Pickering emulsion microspheres.

[0081] The obtained solid Pickering emulsion microspheres were dispersed in 30 mL of 1 wt% hydrofluoric acid solution and etched for 12 h. The resulting suspension was filtered and rinsed multiple times with saturated boric acid aqueous solution and deionized water. The etched solid product was redispersed in 80 mL of ethanol, and then 4 mL of ammonia water was added to make its concentration 1.25 wt%. After complete dissolution, 10 mL of fluorosilane ethanol solution (0.143 g of fluorosilane) (0.143 mL of 1H,1H,2H,2H-perfluorodecyltriethoxysilane dissolved in 10 mL of anhydrous ethanol) was added dropwise. After the addition was completed, the reaction was continued at room temperature for another 2 h. The precipitate was separated, washed, and dried under low temperature vacuum. The paraffin was then dissolved in chloroform, separated, washed, and dried to obtain bifunctional Janus nano-SiO2 particles with unsaturated double bonds and fluorine-containing functional groups on the surface.

[0082] Example 2

[0083] 1) Preparation of SiO2 nanoparticles modified with unsaturated double bonds

[0084] 10 mg of polyacrylic acid (molecular weight 2000) was weighed and dissolved in 100 mL of ethanol under stirring. Then, 6 g of ammonia was added to make the concentration 1.5 wt%. After complete dissolution, 3 g of silicon source (tetrabutyl silicate and allyltrimethoxysilane dissolved in 3 mL of ethanol in 10 mL of ethanol, volume ratio 7:1) was added dropwise over 4 h. The reaction was continued at 30 °C for another 2 h to obtain a sol of unsaturated double bond modified SiO2. After separating, washing and drying the precipitate, unsaturated double bond modified SiO2 nanoparticles were obtained.

[0085] 2) Selective etching and fluorination of unsaturated double bond modified SiO2 nanoparticles

[0086] At 65℃, 1g of the prepared unsaturated double bond modified SiO2 nanoparticles were uniformly dispersed in 100mL of ethanol aqueous solution (6.7%, w / w) to obtain a SiO2 dispersion. Then, 0.01g of hexadecyltrimethylammonium bromide was added. Separately, 5g of solid paraffin was heated to 80℃ and melted. The resulting molten paraffin was added to the SiO2 dispersion under stirring to obtain a SiO2 nanoparticle-stabilized Pickering emulsion. After stirring for 3h, the mixture was cooled, filtered, washed with water and ethanol respectively, and dried under low temperature vacuum to obtain solid Pickering emulsion microspheres.

[0087] The obtained solid Pickering emulsion microspheres were dispersed in 20 mL of 5 wt% hydrofluoric acid solution and etched for 1 h. The resulting suspension was filtered and rinsed multiple times with saturated boric acid aqueous solution and deionized water. The etched solid product was redispersed in 100 mL of ethanol, and then 5 mL of ammonia water was added to make its concentration 1.25 wt%. After complete dissolution, 10 mL of fluorosilane ethanol solution (0.143 mL of trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane and 10 mL of anhydrous ethanol) was added dropwise. After the addition was completed, the reaction was continued at room temperature for another 2 h. The precipitate was separated, washed, and dried under low temperature vacuum. The paraffin was then dissolved in n-hexane, separated, washed, and dried to obtain bifunctional Janus nano-SiO2 particles with unsaturated double bonds and fluorine-containing functional groups on the surface.

[0088] Example 3

[0089] 1) Preparation of SiO2 nanoparticles modified with unsaturated double bonds

[0090] Weigh 15 mg of polyacrylic acid (molecular weight 2000) and dissolve it in 164.5 mL of ethanol under stirring. Then add 9 g of ammonia water to make the concentration 1.5 wt%. After complete dissolution, add 4.5 g of silicon source (tetramethyl silicate and 3-(acryloyloxy)propyltrimethoxysilane dissolved in 15.5 mL of ethanol in a volume ratio of 3:1). The addition should be completed within 4 h. Then continue the reaction at 40 °C for 2 h to obtain a sol of saturated double bond modified SiO2. After separating, washing and drying the precipitate, unsaturated double bond modified SiO2 nanoparticles are obtained.

[0091] 2) Selective etching and fluorination of unsaturated double bond modified SiO2 nanoparticles

[0092] At 75℃, 0.5g of the prepared unsaturated double bond modified SiO2 nanoparticles were uniformly dispersed in 100mL of ethanol aqueous solution (6.7%, w / w) to obtain a SiO2 dispersion. Then, 0.015g of sodium dodecyl sulfate was added. Separately, 25g of solid paraffin was heated to 75℃ and melted. The resulting molten paraffin was added to the above SiO2 dispersion under stirring to obtain a SiO2 nanoparticle-stabilized Pickering emulsion. After stirring for 3h, the mixture was cooled, filtered, washed with water and ethanol respectively, and dried under low temperature vacuum to obtain solid Pickering emulsion microspheres.

[0093] The obtained solid Pickering emulsion microspheres were dispersed in 30 mL of 3 wt% hydrofluoric acid solution and etched for 4 h. The resulting suspension was filtered and rinsed multiple times with saturated boric acid aqueous solution and deionized water. The etched solid product was redispersed in 80 mL of ethanol, and then 4 mL of ammonia water was added to make its concentration 1.25 wt%. After complete dissolution, 10 mL of fluorosilane ethanol solution (0.072 mL of H,1H,2H,2H-perfluorodecyltrimethoxysilane dissolved in 10 mL of anhydrous ethanol) was added dropwise. After the addition was completed, the reaction was continued at room temperature for another 2 h. The precipitate was separated, washed, and dried under low temperature vacuum. The paraffin was then dissolved with carbon tetrachloride, separated, washed, and dried to obtain bifunctional Janus nano-SiO2 particles with unsaturated double bonds and fluorine-containing functional groups on the surface.

[0094] Example 4

[0095] 1) Preparation of SiO2 nanoparticles modified with unsaturated double bonds

[0096] Weigh 15 mg of polyacrylic acid (molecular weight 2000) and dissolve it in 164.5 mL of ethanol under stirring. Then add 9 g of ammonia water to make the concentration 1.5 wt%. After complete dissolution, add 4.5 g of silicon source (4.5 mL of tetraethyl silicate and γ-methacryloyloxypropyltrimethoxysilane dissolved in 15.5 mL of ethanol, volume ratio 6:1). The addition should be completed within 4 h. Then continue the reaction at 25 °C for another 2 h to obtain a sol of saturated double bond modified SiO2. After separating, washing and drying the obtained precipitate, unsaturated double bond modified SiO2 nanoparticles are obtained.

[0097] 2) Selective etching and fluorination of unsaturated double bond modified SiO2 nanoparticles

[0098] At 80℃, 1g of the prepared unsaturated double bond modified SiO2 nanoparticles were uniformly dispersed in 80mL of ethanol aqueous solution (6.7%, w / w) to obtain a SiO2 dispersion. Separately, 15g of solid paraffin was heated to 80℃ and melted. The resulting molten paraffin was added to the above SiO2 dispersion under stirring to obtain a SiO2 nanoparticle-stabilized Pickering emulsion. After stirring for 3h, the mixture was cooled, filtered, washed with water and ethanol respectively, and dried under low temperature vacuum to obtain solid Pickering emulsion microspheres.

[0099] The obtained solid Pickering emulsion microspheres were dispersed in 30 mL of 2 wt% hydrofluoric acid solution and etched for 5 h. The resulting suspension was filtered and rinsed multiple times with saturated boric acid aqueous solution and deionized water. The etched solid product was redispersed in 80 mL of ethanol, and then 4 mL of ammonia water was added to make its concentration 1.25 wt%. After complete dissolution, 10 mL of fluorosilane ethanol solution (0.143 g of fluorosilane contained in 10 mL of triethoxy(1H,1H,2H,2H-nonafluorohexyl)silane dissolved in 10 mL of anhydrous ethanol) was added dropwise. After the addition was completed, the reaction was continued at room temperature for another 2 h. The resulting precipitate was separated, washed, and dried under low temperature vacuum. The paraffin was then dissolved with carbon tetrachloride, separated, washed, and dried to obtain bifunctional Janus nano-SiO2 particles with unsaturated double bonds and fluorine-containing functional groups on the surface.

[0100] Example 5

[0101] 1) Preparation of SiO2 nanoparticles modified with unsaturated double bonds

[0102] Weigh 20 mg of polyacrylic acid (molecular weight 2000) and dissolve it in 200 mL of ethanol under stirring. Then add 12 g of ammonia water to make the concentration 1.5 wt%. After complete dissolution, add 6 g of silicon source (6 mL of tetraethyl silicate and allyltriethoxysilane dissolved in 20 mL of ethanol, volume ratio 5:1) dropwise. Control the addition to be completed within 4 h. Then continue the reaction at 50 °C for 2 h to obtain a sol of saturated double bond modified SiO2. After separating, washing and drying the precipitate, unsaturated double bond modified SiO2 nanoparticles are obtained.

[0103] 2) Selective etching and fluorination of unsaturated double bond modified SiO2 nanoparticles

[0104] At 75℃, 1g of the prepared unsaturated double bond modified SiO2 nanoparticles were uniformly dispersed in 90mL of ethanol aqueous solution (6.7%, w / w) to obtain a SiO2 dispersion. Separately, 20g of solid paraffin was heated to 80℃ and melted. The resulting molten paraffin was added to the above SiO2 dispersion under stirring to obtain a SiO2 nanoparticle-stabilized Pickering emulsion. After stirring for 3h, the mixture was cooled, filtered, washed with water and ethanol respectively, and dried under low temperature vacuum to obtain solid Pickering emulsion microspheres.

[0105] The obtained solid Pickering emulsion microspheres were dispersed in 30 mL of 1 wt% hydrofluoric acid solution and etched for 12 h. The resulting suspension was filtered and rinsed multiple times with saturated boric acid aqueous solution and deionized water. The etched solid product was redispersed in 80 mL of ethanol, and then 4 mL of ammonia water was added to make its concentration 1.25 wt%. After complete dissolution, 10 mL of fluorosilane ethanol solution (0.143 mL of 1H,1H,2H,2H-perfluorodecyltriethoxysilane dissolved in 10 mL of anhydrous ethanol) was added dropwise. After the addition was completed, the reaction was continued at room temperature for another 2 h. The precipitate was separated, washed, and dried under low temperature vacuum. The paraffin was then dissolved in chloroform, separated, washed, and dried to obtain bifunctional Janus nano-SiO2 particles with unsaturated double bonds and fluorine-containing functional groups on the surface.

[0106] Characterization

[0107] Figure 2 SEM image of Janus nano-SiO2 particles prepared in Example 1; from Figure 2 It can be seen that the particle size of SiO2 nanoparticles is less than 100 nm and the size is uniform.

[0108] Figure 3 The image shows the XRD pattern of the Janus nano-SiO2 particles prepared in Example 3 of this invention; Figure 3 It can be seen that the prepared nano-SiO2 crystals are all amorphous structures.

[0109] Figure 4 The image shows the IR spectrum of the unsaturated double-bond modified SiO2 nanoparticles prepared in Example 4 of this invention; from Figure 4 It is evident that unsaturated double bonds have been successfully modified onto the surface of SiO2 nanoparticles.

[0110] Figure 5 The image shows the DLS spectrum of the Janus nano-SiO2 particles prepared in Example 5 of this invention. Figure 5 It can be seen that the total average particle size of nano-SiO2 is approximately 73.4 nm.

[0111] The components of the UV-curable coating used in the following application examples are: butyl acetate (37wt%), propylene glycol methyl ether acetate (10wt%), thermoplastic acrylic (2wt%, Mitsubishi BR106), DPHA (15wt%), hexafunctional polyurethane (30wt%, Lankel L-6603), inhibitor AG-10 (5wt%), and TPO (1wt%).

[0112] Application Example 1

[0113] Preparation of abrasion-resistant and fingerprint-resistant UV-curable coating

[0114] The bifunctional Janus nano-SiO2 particles prepared in Example 1 were mixed with a UV-curable coating to obtain a homogeneous liquid (the mass of the bifunctional Janus nano-SiO2 particles was 1% of the mass of the UV-curable coating). This homogeneous liquid was coated onto a glass substrate and dried at 50°C for 10 min. The mixture was then subjected to 800 mJ / cm² heat treatment. 2 UV curing yields a bifunctional Janus nano-SiO2 particle-reinforced, abrasion-resistant, fingerprint-resistant UV-cured coating.

[0115] Performance testing

[0116] 1) The water contact angle of the UV-cured coating was tested according to GB / T23764-2009 standard. The test results showed that the water contact angle on the coating surface was 155°, and the roll-off angle was 5°. A larger contact angle indicates better fingerprint resistance.

[0117] 2) The abrasion resistance of the coating was determined using a rubber-alcohol abrasion fastness tester. The rubber-alcohol abrasion resistance test method used a 2×2 rubber abrasion head. Alcohol was dropped onto the coating surface with a load of 1000g. One round trip was counted as one time, and the number of scratches on the surface was recorded.

[0118] Evaluation method: After a certain number of rubbing cycles, observe whether the coating has scratches and record the maximum number of rubbing cycles that can be withstood without scratches.

[0119] The results show that the coating of Application Example 1 has a wear resistance of more than 3300 cycles.

[0120] 3) The hardness of the UV-cured coating was tested according to GB / 6739T standard. The surface hardness of the coating was found to be 9H.

[0121] Application Example 2

[0122] The bifunctional Janus nano-SiO2 particles prepared in Example 2 were mixed with a UV-curable coating to obtain a homogeneous liquid (the mass of the bifunctional Janus nano-SiO2 particles was 5% of the mass of the UV-curable coating). This homogeneous liquid was coated onto a glass substrate, dried at 80°C for 2 min, and then subjected to 600 mJ / cm² heat treatment. 2 UV curing yields a bifunctional Janus nano-SiO2 particle-reinforced, abrasion-resistant, fingerprint-resistant UV-cured coating.

[0123] According to the method in Application Example 1, the water contact angle of the coating surface is 153° and the roll-off angle is 5°. The abrasion resistance of the coating was determined using a rubber-alcohol abrasion fastness tester, and it withstood more than 3000 abrasion cycles; the surface hardness of the coating is 9H.

[0124] Application Example 3

[0125] The bifunctional Janus nano-SiO2 particles prepared in Example 3 were mixed with a UV-curable coating to obtain a homogeneous liquid (the mass of the bifunctional Janus nano-SiO2 particles was 3% of the mass of the UV-curable coating). This homogeneous liquid was coated onto a glass substrate, dried at 70°C for 5 min, and then subjected to 700 mJ / cm² heat treatment. 2 UV curing yields a bifunctional Janus nano-SiO2 particle-reinforced, abrasion-resistant, fingerprint-resistant UV-cured coating.

[0126] According to the method in Application Example 1, the water contact angle of the coating surface is 158°, and the water contact angle hysteresis value is 6.5°. The abrasion resistance of the coating was determined using a rubber-alcohol abrasion fastness tester, and it withstood more than 3500 abrasion cycles; the surface hardness of the coating is 9H.

[0127] Application Example 4

[0128] The bifunctional Janus nano-SiO2 particles prepared in Example 4 were mixed with a UV-curable coating to obtain a homogeneous liquid (the mass of the bifunctional Janus nano-SiO2 particles was 2% of the mass of the UV-curable coating). This homogeneous liquid was coated onto a metal substrate, dried at 60°C for 8 min, and then subjected to 800 mJ / cm² heat treatment. 2 UV curing yields a bifunctional Janus nano-SiO2 particle-reinforced, abrasion-resistant, fingerprint-resistant UV-cured coating.

[0129] According to the method of Application Example 1, the water contact angle of the coating surface is 163° and the water contact angle hysteresis value is 7.2°.

[0130] The coating's abrasion resistance was tested using steel wool. The test method involved using 0000# steel wool with a load of 500g, counting one round trip as one cycle, and recording the number of scratches that appeared on the surface. The evaluation method involved observing whether the coating had scratches after a certain number of rubs and recording the maximum number of rubs it could withstand without scratches. The results showed that the coating could withstand more than 1600 cycles of steel wool abrasion.

[0131] The surface hardness of the coating is 9H.

[0132] Application Example 5

[0133] The bifunctional Janus nano-SiO2 particles prepared in Example 5 were mixed with a UV-curable coating to obtain a homogeneous liquid (the mass of the bifunctional Janus nano-SiO2 particles was 4% of the mass of the UV-curable coating). This homogeneous liquid was coated onto a quartz substrate, dried at 80°C for 2 min, and then subjected to 800 mJ / cm² heat treatment. 2 UV curing yields a bifunctional Janus nano-SiO2 particle-reinforced, abrasion-resistant, fingerprint-resistant UV-cured coating.

[0134] According to the method in Application Example 1, the water contact angle of the coating surface is 155°, and the water contact angle hysteresis value is 6.2°. The abrasion resistance of the coating was determined using a rubber-alcohol abrasion fastness tester, and it withstood more than 3000 abrasion cycles; the surface hardness of the coating is 9H.

[0135] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing bifunctional Janus nano-silica for photocurable coatings, characterized in that, Includes the following steps: A silicon source, polyacrylic acid, a first alkali, and a first organic solvent are mixed and modified to obtain SiO2 nanoparticles modified with unsaturated double bonds; the silicon source includes silica ester and silane coupling agent containing unsaturated double bonds. The unsaturated double bond modified SiO2 nanoparticles were mixed with a dispersion medium, and the resulting dispersion was mixed with an oily liquid and emulsified to obtain a Pickering emulsion. After drying the Pickering emulsion, the resulting solid product is mixed with acid and etched to obtain the etched product. The etching product, the second base, the fluorosilane compound, and the second organic solvent are mixed and fluorinated to obtain bifunctional Janus nano silica. The silicate includes one of tetraethyl silicate, tetrabutyl silicate, and tetramethyl silicate; The silane coupling agent containing unsaturated double bonds includes one of allyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, allyltriethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, and γ-methacryloyloxypropyltriethoxysilane. The fluorosilane compounds include trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, triethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, or 1H,1H,2H,2H-perfluorodecyltrimethoxysilane.

2. The production method according to claim 1, characterized by, The volume ratio of the silane coupling agent containing unsaturated double bonds to the silicone ester is 1:3~9.

3. The production method according to claim 1 or 2, characterized by, The first alkali includes ammonia; the mass ratio of the first alkali to polyacrylic acid is 500~700:1; the mass ratio of the silicon source to polyacrylic acid is 250~350:

1. The oily liquid includes molten paraffin; the emulsification temperature is 65~80℃ and the time is 1~3h.

4. The method of claim 1, wherein, When mixing the resulting dispersion with the oily liquid, a surfactant is also added; the surfactant includes hexadecyltrimethylammonium bromide or sodium dodecyl sulfate; the mass ratio of the surfactant to the unsaturated double bond modified SiO2 nanoparticles is 0:1 to 1:

2.

5. The preparation method according to claim 3, characterized in that, The mass ratio of the unsaturated double bond modified SiO2 nanoparticles to the oily liquid is 1:10~50.

6. The preparation method according to claim 1, characterized in that, The acid includes hydrofluoric acid, the concentration of which is 1-5 wt%, and the etching time is 1-12 h.

7. The preparation method according to claim 1, characterized in that, The second alkali includes ammonia; the mass ratio of the fluorosilane compound to the unsaturated double-bond modified SiO2 nanoparticles is 1:6~8; the fluorination time is 2h.

8. The bifunctional Janus nano silica prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the bifunctional Janus nano silica as described in claim 8 in photocurable coatings.

10. Use according to claim 9, characterized in that, The application method includes: The bifunctional Janus nano silica and UV-curable coating were mixed, and the resulting liquid mixture was coated onto the substrate. Then, the mixture was dried and UV-cured in sequence to obtain a UV-curable coating. The mass of the bifunctional Janus nano silica is 1-5% of the mass of the UV-curable coating.

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