Preparation method of nano silicon dioxide composite organic silicon coating with core-shell structure

Abstract

The invention relates to the technical field of organic silicon coatings, in particular to a preparation method of a core-shell structure nano silicon dioxide composite organic silicon coating. The preparation method of the nano silicon dioxide composite organic silicon coating with the core-shell structure comprises the following steps: carrying out first emulsion polymerization on silicon dioxide nano particles and acryloyloxy alkyl alkoxy silane in a redox system, and then carrying out second emulsion polymerization with fluorine-containing acrylate to obtain a modified nano particle emulsion; and then mixing with organic silicon resin, and carrying out cross-linking curing to obtain the organic silicon coating. Acryloyloxy alkyl alkoxy silane and fluorine-containing acrylate are grafted on the surface of silicon dioxide through core-shell emulsion polymerization, and alkoxy silane in a redox system is hydrolyzed and cross-linked to connect polymerized chain segments into a network, so that fluorine-silicon modification of silicon dioxide is realized, and the dispersity of silicon dioxide is improved; the modified silicon dioxide is introduced into an organic silicon coating, so that the amphiphobic property of the organic silicon coating can be improved, and the mechanical property is improved while the surface energy of the coating is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of organosilicon coatings, and in particular to a method for preparing a core-shell structured nano-silicon dioxide composite organosilicon coating. Background Art

[0002] Low surface energy antifouling coatings are also called non-toxic antifouling coatings, which mainly refer to low surface energy antifouling coatings based on fluorocarbon resins and organosilicon compounds. Their common characteristics are that they do not contain toxic substances and have very low surface energy. From the perspective of environmental protection, non-toxic antifouling coatings are undoubtedly the most attractive choice for antifouling coatings. The reason why they are called antifouling coatings is that due to their unique surface properties, the adhesion interface of the fouling on them is very weak, and they can be easily removed by using their own weight, the impact of water flow during navigation, or the cleaning of auxiliary equipment.

[0003] Current research focuses on low surface energy antifouling coatings based on silicone and organic fluorine. Among them, the research on silicone antifouling coatings focuses on small molecule silicone oil modification and modified coating matrix. The performance of pure silicone materials is slightly insufficient when used in antifouling coatings. The mechanical properties of silicone materials are poor and it is difficult to be used in marine environments. In actual applications, the integrity of the paint film is easily destroyed, and the damaged areas are easily colonized and attached by fouling organisms and are difficult to repair. The research on organic fluorine antifouling coatings focuses on fluorinated acrylates and perfluoropolyethers, but fluorinated polymers are expensive and costly.

[0004] The application of nano-silica to reinforce resin-based polymer materials has a long history, and the existing technology obtains nanoparticles with lower surface energy by grafting fluorine-containing functional groups on the surface to construct micro-nano multi-scale amphiphilic coatings. However, nano-silica has hydrophilic groups that are easy to agglomerate. The method of introducing nanoparticles to construct a micro-nano structure on the coating surface to obtain a low surface energy surface affects the coating performance due to the uneven dispersion of nanoparticles in the matrix. The reinforcement effect of nano-silica on silicone materials is difficult to meet the needs of anti-fouling coating applications.

[0005] In March 2022, Guan Jiawei prepared three types of functionalized silica in the article "Preparation and Performance Study of Functionalized Silica Modified Silicone Coatings" and applied them to modified reinforced silicone coatings. Among them, atom transfer radical polymerization was used to introduce natural antifouling active molecules eugenol and fluorinated hydrophobic monomer octafluoropentyl methacrylate on the silica surface to prepare grafted natural antifouling active molecules nano-silica and made into silicone coatings. After the polymerization of fluorinated monomers was initiated on the surface of nano-silica, fluorinated polymer chains would precipitate on the surface of the coating. When the addition amount of functionalized silica was 5%, the water contact angle of the coating was 120.05°, and the coating's inhibition rates on boat algae and triangular brown finger algae were 94.09% and 90.73%, respectively.

[0006] However, the above antifouling coating cannot simultaneously achieve the low surface energy and high mechanical properties of the silicone coating. Summary of the invention

[0007] The invention provides a method for preparing a core-shell structured nano-silicon dioxide composite organosilicon coating, which solves the problem that the surface energy and mechanical properties of the existing organosilicon coating cannot be improved simultaneously.

[0008] In order to solve the above technical problems, the technical solution of the preparation method of the core-shell structure nano-silicon dioxide composite organic silicon coating of the present invention is as follows:

[0009] A method for preparing a core-shell structured nano-silicon dioxide composite organic silicon coating comprises the following steps:

[0010] 1) subjecting silica nanoparticles, acryloxyalkylalkoxysilane and an emulsifier to a first emulsion polymerization in an organosiloxane containing a Si-N bond / persulfate redox system, and then adding a fluorinated acrylate to the organosiloxane containing a Si-N bond / persulfate redox system for at least one second emulsion polymerization to obtain a fluorinated silicon-modified silica nanoparticle emulsion having a core-shell structure;

[0011] 2) Mixing the fluorine-silicon modified silica nanoparticle emulsion with a core-shell structure obtained in step 1), a silicone resin, a coupling agent, a crosslinking agent and a catalyst to obtain a silicone coating, which is applied to a substrate and crosslinked and cured to obtain a core-shell structure nano-silica composite silicone coating.

[0012] The present invention is an improvement on the prior art, and provides a method for preparing a core-shell structured nano-silica composite organosilicon coating. The method comprises the following steps: core-shell emulsion polymerization is carried out in an organosiloxane / persulfate redox system containing Si-N bonds, acryloxyalkylalkoxysilane is grafted onto the surface of a silicon dioxide nanoparticle via an alkoxy group in a first emulsion polymerization, and a fluorinated acrylate is grafted onto the nanoparticle via an acryloxyalkylalkoxysilane in a second emulsion polymerization, so as to obtain fluorinated silicon-modified silicon dioxide nanoparticles having a core-shell structure; at the same time, a plurality of Si-O in the organosiloxane containing Si-N bonds is hydrolyzed and crosslinked each time the emulsion polymerization is carried out. The acrylic acid-containing chain segments after polymerization are connected into a network, and the Si-O groups and the hydroxyl groups on the surface of the silica are cross-linked, thereby initiating polymerization on the surface of the silica to achieve functional modification of the nanoparticles; the functionalized nano-silica is introduced into the organosilicon coating, and the chemical bonds formed by the hydrolysis and condensation of the siloxane of the organosilicon matrix and the hydroxyl groups on the surface of the silica combine the silica with the organosilicon matrix. The functional groups introduced by the functionalization can improve the hydrophobicity and oleophobicity of the coating (the amphiphobicity of the coating), and the water contact angle reaches more than 121°, and the diiodomethane contact angle reaches more than 101°, and has a low surface energy, as low as 8.1mJ m-2 Below, the tensile strength of the coating reaches above 0.6MPa, while reducing the surface energy of the silicone coating, the mechanical properties of the coating are improved.

[0013] The present invention performs emulsion polymerization in an organosiloxane / persulfate redox system containing Si-N bonds, and uses an organosilicon compound containing silicon-nitrogen bonds and ammonium persulfate as redox initiators, so that the polymerization reaction can be carried out in an aqueous phase without the need to react in an organic solvent. The reaction can be carried out at room temperature and is easy to control. The product of the emulsion polymerization is not easy to agglomerate and the reaction time is short.

[0014] In order to further improve the properties of the copolymer grafted on the surface of the silica nanoparticles and improve the surface energy and mechanical properties of the coating, preferably, the acryloxyalkylalkoxysilane is γ-methacryloxypropyltrimethoxysilane, and the fluorine-containing acrylate is dodecafluoroheptyl methacrylate.

[0015] In order to further increase the density of grafted functional groups of silica nanoparticles, preferably, the molar ratio of the acryloxyalkylalkoxysilane used in the first emulsion polymerization and the total fluorinated acrylate used in the second emulsion polymerization is (2.5-3):(4.5-5); the mass ratio of silica nanoparticles and acryloxyalkylalkoxysilane is (0.9-1):(7-8).

[0016] In order to further improve the mechanical properties of the organic silicon coating while reducing the surface energy of the coating, preferably, the mass ratio of the organic silicon resin to the silicon dioxide nanoparticles is (90-100): (0.9-1).

[0017] In order to further reduce the start-up energy of emulsion polymerization, preferably, the organosiloxane containing Si-N bonds has a structure shown in Formula I:

[0018]

[0019] In Formula I, R1, R2, R3, R 10 , R 11 and R 12 Each is independently selected from C1-C5 alkyl; R4 and R5 are each independently selected from C1-C6 alkylene; R6, R7, R8 and R9 are each independently selected from methyl, ethyl or propyl;

[0020] The persulfate is selected from one or more of ammonium persulfate, potassium persulfate and sodium persulfate.

[0021] In order to further reduce the start-up energy of emulsion polymerization, preferably, the mass ratio of organosiloxane containing Si-N bonds and persulfate in each emulsion polymerization is (1.5-2):(0.1-0.5), and the added amount of organosiloxane containing Si-N bonds is 20-25% of the mass of acryloxyalkylalkoxysilane.

[0022] In order to further increase the initiation rate during the emulsion polymerization, preferably, an alkali metal salt as a promoter is introduced each time the emulsion polymerization is carried out, wherein the alkali metal salt is selected from one or more of calcium chloride, sodium chloride and lithium chloride, and the amount of the alkali metal salt added is 0.8-1% of the mass of the acryloxyalkylalkoxysilane.

[0023] In order to further reinforce the organosilicon coating, preferably, fumed silica with a particle size of 8 to 16 nm is added during mixing in step 2), and the mass ratio of the organosilicon resin to the fumed silica is (90 to 100): (4 to 4.5).

[0024] In order to further improve the curing efficiency of the silicone coating, preferably, in step 2), the mass ratio of the silicone resin, coupling agent, crosslinking agent and catalyst is (90-100): (1.8-3): (9-10): (0.2-0.4).

[0025] In order to further improve the curing efficiency of the silicone coating, preferably, the coupling agent in step 2) is 3-aminopropyltriethoxysilane and aminosilane polymer; the cross-linking agent is vinyltrimethoxysilane; the catalyst is dibutyltin dilaurate; and the mass ratio of 3-aminopropyltriethoxysilane to aminosilane polymer is (0.9-1.5):(0.9-1.5). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a reaction principle diagram of SiO2-Si@F in Example 1 of the present invention;

[0027] Figure 2 This is a photo of the SiO2-Si@F emulsion of Example 1 of the present invention;

[0028] Figure 3 This is a photo of a coating formed by applying the organosilicon coating of Example 1 of the present invention on a cement board;

[0029] Figure 4 FT-IR spectrum of SiO2-Si@F of Example 1 of the present invention;

[0030] Figure 5 TEM image and EDS image of SiO2-Si@F of Example 1 of the present invention;

[0031] Figure 6 This is a photo of the contact angle test of the silicone coating;

[0032] Figure 7 This is a stress-strain curve diagram of the silicone coating of Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The technical concept of the preparation method of the core-shell structure nano-silicon dioxide composite organic silicon coating of the present invention is as follows:

[0034] The existing technology is to graft silane coupling agent KH550 and bromoisobutyryl bromide (BIBB) on the surface of silica, introduce eugenol methacrylate (EMA) monomer to undergo polymerization reaction, and then introduce octafluoropentyl methacrylate (FMA) monomer to polymerize to obtain functionalized nanoparticles SiO2-KH550-BIBB-EMA-FMA. During the curing process of the silicone material, the fluorine-containing chain segments migrate to the surface of the coating to stabilize it. At the same time, the EMA segments with antifouling activity are also precipitated on the surface, which is beneficial to inhibit small biological fouling and further improve the antifouling performance of the material.

[0035] The present invention grafts acryloxyalkylalkoxysilane and fluorine-containing acrylate on the surface of silica through core-shell emulsion polymerization, utilizes the hydrolysis cross-linking of multiple Si-O of organic siloxane containing Si-N bonds, connects the acrylic acid-containing chain segments after polymerization into a network, and cross-links with the hydroxyl groups on the surface of silica, thereby initiating polymerization on the surface of silica, improving the dispersibility of silica nanoparticles in the organic silicon coating, and after the introduction of the organic silicon coating, the functionalized nano-silica combines silica with the organic silicon matrix through the chemical bonds formed by silane condensation, and utilizes the functionalized silica to improve the hydrophobicity and oleophobicity of the coating, reduce the surface energy of the coating, slow down the adhesion of contaminants on the coating, and improve the mechanical properties of the coating, so that it is not easy to be damaged in practical applications, thereby increasing the life of the coating.

[0036] The preparation method of the core-shell structured nano-silica composite organosilicon coating of the present invention specifically comprises the following steps: 1) mixing an aqueous dispersion of silicon dioxide nano-particles, an emulsifier aqueous solution and an acryloxyalkylalkoxysilane, respectively adding thereto an organosiloxane containing a Si-N bond, an aqueous persulfate solution and an alkali metal salt solution under stirring conditions to carry out a first emulsion polymerization, and then adding fluorinated acrylate and an organosiloxane containing a Si-N bond, a persulfate solution and an alkali metal salt solution to carry out at least one second emulsion polymerization to obtain a fluorine-silicon modified silicon dioxide nano-particle emulsion with a core-shell structure; and 2) mixing the fluorine-silicon modified silicon dioxide nano-particle emulsion with a core-shell structure obtained in step 1), an organosilicon resin, fumed silica, a coupling agent, a crosslinking agent and a catalyst to obtain an organosilicon coating, which is applied to a substrate and crosslinked and cured to obtain a nano-silica composite organosilicon coating.

[0037] In a specific embodiment, after the first emulsion polymerization in step 1) is completed, the second emulsion polymerization is carried out twice, specifically, after the first emulsion polymerization is completed, fluorinated acrylate and organosiloxane containing Si-N bonds, persulfate aqueous solution and alkali metal salt aqueous solution are added to carry out a second emulsion polymerization, and then fluorinated acrylate and organosiloxane containing Si-N bonds, persulfate aqueous solution and alkali metal salt aqueous solution are added to carry out a second second emulsion polymerization. It is understandable that after the first emulsion polymerization in step 1) is completed, a second emulsion polymerization can also be carried out once, specifically, after the first emulsion polymerization is completed, fluorinated acrylate and organosiloxane containing Si-N bonds, persulfate aqueous solution and alkali metal salt aqueous solution are added to carry out a second emulsion polymerization.

[0038] In a specific embodiment, the reaction time of the first emulsion polymerization is 20 to 40 minutes; the reaction time of each second emulsion polymerization is 15 to 20 minutes.

[0039] In a specific embodiment, the emulsifier is OP-20, and the mass ratio of acryloxyalkylalkoxysilane to the emulsifier is (7-8):(0.9-1).

[0040] In a specific embodiment, the concentration of the silica nanoparticle aqueous dispersion is 2.5-3%; the concentration of the emulsifier aqueous solution is 9-10%.

[0041] In a specific embodiment, in step 2), fumed silica with particle sizes of 8 nm and 16 nm is added during mixing, and the mass ratio of fumed silica with particle sizes of 8 nm and 16 nm is (2-2.25):(2-2.25).

[0042] The organosiloxane containing Si-N bonds is prepared according to the method described in patent CN115490805A.

[0043] In a specific embodiment, the organosiloxane containing Si-N bonds is TBPDD, and the chemical formula of TBPDD is as follows:

[0044]

[0045] In a specific implementation manner, the organic silicon resin used is methyl-terminated 107 silicone rubber with a viscosity of 1000 to 15000 Pa·s.

[0046] The embodiments of the present invention are further described below in conjunction with specific examples. The chemical reagents involved in the following examples are all commercially available conventional products unless otherwise specified.

[0047] 1. Specific embodiments of the method for preparing the core-shell structure nano-silicon dioxide composite organosilicon coating of the present invention

[0048] Example 1

[0049] The preparation method of the core-shell structure nano-silicon dioxide composite organic silicon coating of this embodiment is as follows:

[0050] 1) 0.9 g SiO2 and 0.94 g emulsifier were dissolved in 35 g and 10 g water to form SiO2 aqueous dispersion and OP-20 aqueous solution, respectively. The SiO2 aqueous dispersion, OP-20 aqueous solution and 7.45 g γ-methacryloxypropyltrimethoxysilane (γ-MPS) were mixed, emulsified by an emulsifier and added to a three-necked flask. 2 g aqueous solution containing 0.1 g ammonium persulfate and 0.06 g calcium chloride and 1.5 g TBPDD were added dropwise at a certain stirring speed to carry out the first emulsion polymerization. After the reaction for 20 min, 9 g dodecafluoroheptyl methacrylate (DMFA, the addition was completed within 10 min) was added dropwise, and 2 g aqueous solution containing 0.1 g ammonium persulfate and 0.06 g calcium chloride and 1.5 g TBPDD were added again. After the addition of TBPDD, a second emulsion polymerization was carried out. After the reaction for 15 minutes, 9 g of dodecafluoroheptyl methacrylate was added again (the addition was completed within 10 minutes), and 2 g of an aqueous solution containing 0.1 g of ammonium persulfate and 0.06 g of calcium chloride and 1.5 g of TBPDD were added. After the addition was completed, a second emulsion polymerization was carried out. The reaction was carried out for 20 minutes. The reaction principle is as follows: Figure 1 As shown, a fluorine-silicon modified silica nanoparticle emulsion with a core-shell structure is obtained, which is denoted as SiO2-Si@F emulsion. Figure 2 As shown;

[0051] 2) After 2.25 g 8 nm, 2.25 g 16 nm fumed silica, 2.7 g SiO2-Si@F emulsion obtained in step 1) and 90 g methyl-terminated 107 silicone rubber (viscosity of 1500 Pa·s) were mixed uniformly, 0.9 g 3-aminopropyltriethoxysilane and 0.9 g aminosilane polymer (Zhejiang Boiling Point Chemical Co., Ltd., R-8104), 9.9 g vinyltrimethoxysilane and 0.25 g dibutyltin dilaurate were added, and it was ensured that the stirred product was mixed uniformly after each addition, and finally an organosilicon coating was prepared, which was applied to a cement board and cross-linked and cured in the air at room temperature to obtain a nano-silica composite organosilicon coating. The coating photo is shown in FIG. Figure 3 shown.

[0052] 2. Comparison

[0053] Comparative Example 1

[0054] The preparation method of the organic silicon coating of this comparative example is basically the same as that of Example 1, except that SiO2-Si@F is not introduced. Specifically, 2.25g 8nm, 2.25g 16nm fumed silica, and 90g methyl-terminated 107 silicone rubber (viscosity of 1500pa·s) are mixed evenly, and then 0.9g 3-aminopropyltriethoxysilane and 0.9g aminosilane polymer (Zhejiang Boiling Point Chemical Co., Ltd., R-8104), 9.9g vinyltrimethoxysilane and 0.25g dibutyltin dilaurate are added, and it is ensured that the stirred product is mixed evenly after each addition, and finally the organic silicon coating is prepared, which is applied on the cement board and cross-linked and cured in the air at room temperature to obtain the organic silicon coating.

[0055] Comparative Example 2

[0056] The preparation method of the nano-silicon dioxide composite organic silicon coating of this comparative example is as follows:

[0057] 1) 0.9 g SiO2 and 0.94 g emulsifier OP-20 were dissolved in 35 g and 10 g water to form SiO2 aqueous dispersion and OP-20 aqueous solution, respectively; the SiO2 aqueous dispersion, OP-20 aqueous solution, 7.45 g γ-methacryloxypropyltrimethoxysilane and 18 g dodecafluoroheptyl methacrylate were mixed, emulsified by an emulsifier and added to a three-necked flask; 2 g aqueous solution containing 0.1 g ammonium persulfate (APS) and 0.06 g calcium chloride and 1.5 g TBPDD were added dropwise at a certain stirring speed, respectively, and the mixture was reacted for 1 h to obtain a fluorine-silicon-modified silica nanoparticle emulsion, which was recorded as SiO2-SiF emulsion;

[0058] 2) After 2.25 g 8 nm, 2.25 g 16 nm fumed silica, 2.7 g SiO2-SiF emulsion obtained in step 1) and 90 g methyl-terminated 107 silicone rubber (viscosity of 1500 Pa·s) were mixed uniformly, 0.9 g 3-aminopropyltriethoxysilane and 0.9 g aminosilane polymer (Zhejiang Boiling Point Chemical Co., Ltd., R-8104), 9.9 g vinyltrimethoxysilane and 0.25 g dibutyltin dilaurate were added, and it was ensured that the stirred product was mixed uniformly after each addition, and finally an organosilicon coating was prepared, which was applied to a cement board and cross-linked and cured in air at room temperature to obtain a nano-silica composite organosilicon coating.

[0059] 3. Experimental Examples

[0060] Experimental Example 1

[0061] This experimental example characterizes the SiO2-Si@F obtained in Example 1. Figure 4 is the FT-IR spectrum of SiO2-Si@F. Figure 4It can be seen that 1716cm -1 、1640cm -1 、1093cm -1 、692cm -1 The characteristic peaks at belong to C=O, NH, Si-O-Si and CF, respectively, indicating that acryloxyalkylalkoxysilane and fluorinated acrylate were successfully introduced onto the SiO2 surface.

[0062] Figure 5 TEM and EDS images of SiO2-Si@F. Figure 5 It can be seen that after emulsion polymerization, the particles present an obvious core-shell structure, and the outermost layer is lighter in color. The EDS graph shows that C, F, O, Si, and N elements are distributed on the surface of the silica particles, proving the successful grafting of γ-methacryloxypropyltrimethoxysilane and dodecafluoroheptyl methacrylate, and the F element on the surface of the silica particles is evenly distributed and has a high content, indicating that dodecafluoroheptyl methacrylate is polymerized in the outer layer of the particles, significantly increasing the F content in the outer layer of the particles.

[0063] Experimental Example 2

[0064] This experimental example characterizes and tests the performance of the organosilicon coatings of the embodiments and comparative examples.

[0065] The hydrophobicity and oleophobicity of the coating were evaluated by contact angle test, and the surface energy of the coating was tested. The test results of water contact angle, diiodomethane contact angle and surface energy are shown in Table 1, and the contact angle test photos are shown in Figure 6 As shown, Figure 6 a, c, and e are photos of the water contact angles of the silicone coatings of Comparative Example 1, Comparative Example 2, and Example 1, respectively. Figure 6 b, d, and f are the diiodomethane contact angle photographs of the organosilicon coatings of Comparative Example 1, Comparative Example 2, and Example 1, respectively.

[0066] From Table 1 and Figure 6 It can be seen that compared with the organosilicon coating without the introduction of modifying ions (Comparative Example 1), the water contact angle and diiodomethane contact angle of the organosilicon coating of the present invention are increased, and the surface energy of the coating is reduced, indicating that the introduction of SiO2-Si@F into the coating can improve the amphiphobicity of the organosilicon coating and reduce the surface energy of the coating, thereby slowing down the adhesion of contaminants on the coating, making the contaminants easier to remove.

[0067] In addition, compared with the SiO2-SiF modified by direct copolymerization (Comparative Example 2), the water contact angle and diiodomethane contact angle of the silicone coating of the present invention are also increased, and the surface energy of the coating is reduced, indicating that the modified particles SiO2-Si@F with a core-shell structure introduced into the coating of the present invention can improve the amphiphobicity of the coating and reduce the surface energy compared with the SiO2-SiF modified by direct copolymerization.

[0068] Table 1 Contact angle and surface energy test results of coatings

[0069]

[0070]

[0071] The mechanical properties of the coating were characterized by tensile tests. A national standard sample of silicone material with a thickness of 2±0.2 mm was prepared according to GB / T1024.2-2006. The tensile speed was set to 50 mm / mm. The measured stress-strain curve was as follows: Figure 7 As shown, from Figure 7 It can be seen that, compared with the organosilicon coating without the introduction of modified particles, the breaking strength of the organosilicon coating of the present invention is greatly improved from 0.37 MPa to 0.61 MPa, and the breaking elongation is increased from 186% to 269%.

[0072] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a core-shell structured nano-silicon dioxide composite organic silicon coating, characterized in that: The following steps are involved: 1) subjecting silica nanoparticles, acryloxyalkylalkoxysilane and an emulsifier to a first emulsion polymerization in an organosiloxane containing a Si-N bond / persulfate redox system, and then adding a fluorinated acrylate to the organosiloxane containing a Si-N bond / persulfate redox system for at least one second emulsion polymerization to obtain a fluorinated silicon-modified silica nanoparticle emulsion having a core-shell structure; 2) Mixing the fluorine-silicon modified silica nanoparticle emulsion with a core-shell structure obtained in step 1), a silicone resin, a coupling agent, a crosslinking agent and a catalyst to obtain a silicone coating, which is applied to a substrate and crosslinked and cured to obtain a core-shell structure nano-silica composite silicone coating.

2. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 1, characterized in that: The acryloxyalkylalkoxysilane is γ-methacryloxypropyltrimethoxysilane, and the fluorine-containing acrylate is dodecafluoroheptyl methacrylate.

3. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 1 or 2, characterized in that: The molar ratio of the acryloxyalkylalkoxysilane used in the first emulsion polymerization and the total fluorinated acrylate used in the second emulsion polymerization is (2.5-3):(4.5-5); the mass ratio of the silica nanoparticles and the acryloxyalkylalkoxysilane is (0.9-1):(7-8).

4. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 1, characterized in that: The mass ratio of the silicone resin to the silicon dioxide nanoparticles is (90-100): (0.9-1).

5. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 1, characterized in that: The Si-N bond-containing organosiloxane has a structure shown in Formula I: In Formula I, R1, R2, R3, R 10 , R 11 and R 12 Each is independently selected from C1-C5 alkyl; R4 and R5 are each independently selected from C1-C6 alkylene; R6, R7, R8 and R9 are each independently selected from methyl, ethyl or propyl; The persulfate is selected from one or more of ammonium persulfate, potassium persulfate and sodium persulfate.

6. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 1 or 5, characterized in that: The mass ratio of the organosiloxane containing Si-N bonds to the persulfate in each emulsion polymerization is (1.5-2):(0.1-0.5), and the added amount of the organosiloxane containing Si-N bonds is 20-25% of the mass of the acryloxyalkylalkoxysilane.

7. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 6, characterized in that: An alkali metal salt is introduced as a promoter each time the emulsion polymerization is carried out. The alkali metal salt is selected from one or more of calcium chloride, sodium chloride and lithium chloride. The amount of the alkali metal salt added is 0.8-1% of the mass of the acryloxyalkylalkoxysilane.

8. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 1, characterized in that: In step 2), fumed silica with a particle size of 8 to 16 nm is added during mixing, and the mass ratio of the silicone resin to the fumed silica is (90 to 100): (4 to 4.5).

9. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 1, characterized in that: In step 2), the mass ratio of the silicone resin, coupling agent, crosslinking agent and catalyst is (90-100): (1.8-3): (9-10): (0.2-0.4).

10. The method for preparing the core-shell structured nano-silicon dioxide composite organic silicon coating according to claim 1 or 9, characterized in that: The coupling agent in step 2) is 3-aminopropyltriethoxysilane and aminosilane polymer; the crosslinking agent is vinyltrimethoxysilane; the catalyst is dibutyltin dilaurate; the mass ratio of 3-aminopropyltriethoxysilane to aminosilane polymer is (0.9-1.5):(0.9-1.5).

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