Perfluoroalkyl modified nano silicon dioxide as well as preparation method and application thereof

Abstract

The invention discloses perfluoroalkyl modified nano silicon dioxide, and relates to the technical field of material preparation and coatings, the material is obtained by modifying nano silicon dioxide through perfluoroalkyl chlorosilane, the mass ratio of the perfluoroalkyl chlorosilane to the nano silicon dioxide is 0.001-0.6: 1, the perfluoroalkyl chlorosilane is at least one of CF3 (CF2) n (CH2) mSiCl3, CF3 (CF2) n (CH2) mSiCl3, CF2H (CF2) n (CH2) mSiCl3 and CF2H (CF2) n (CH2) mSiCl2 CH3, n is equal to 0-9, and m is equal to 1-3. The invention also discloses a dispersion liquid prepared from the perfluoroalkyl modified nano silicon dioxide and an application of the dispersion liquid in a coating. The viscosity of the dispersion liquid can be remarkably improved by using a small amount of modified nano silicon dioxide, so that the dispersion liquid has excellent thixotropy and stability.

Description

Technical Field

[0001] This invention relates to the fields of material preparation and coating technology, specifically to a perfluoroalkyl-modified nano-silica, its preparation method, and the application of the dispersion prepared from the perfluoroalkyl-modified nano-silica in coatings. Background Technology

[0002] Coatings are liquid or semi-liquid materials used to coat the surface of objects. Application methods include brushing, rolling, squeegeeing, spraying, and spin coating. For squeegeeing, rolling, or brushing, the viscosity must be sufficiently low during application to facilitate smooth application and even coverage of the substrate. After application, the viscosity must be sufficiently high to prevent defects such as tearing or sagging due to flow. This requires the coating to have high zero-shear viscosity and good thixotropy. The zero-shear viscosity of a coating generally needs to reach at least 100 Pa·s to ensure coating requirements. Thixotropy refers to the phenomenon where, at a certain shear rate, the viscosity of a fluid continuously decreases over time, and when shearing stops, the viscosity gradually recovers over time; examples include paints, slurries, and food products.

[0003] The addition of thixotropic agents can endow a system with thixotropic properties. The mechanism involves thixotropic agent particles forming a reversible three-dimensional network structure within the system through hydrogen bonding, physical stacking, or overlapping. This network, formed by weak interactions, can be disrupted under shear stress and then re-established after resting, thus exhibiting thixotropic behavior. Common thixotropic agents include inorganic particles (such as silica and carbon black), organic compounds (such as hydrogenated castor oil, polyvinyl alcohol, and polyacrylate), and complexes (such as organically modified bentonite). However, existing thixotropic agent systems still suffer from technical bottlenecks such as insufficient viscosity and poor thixotropic response, making it difficult to meet the requirements of coating processes.

[0004] For example, patent document CN114806519A discloses a two-phase thixotropic agent and its preparation method. This invention adds cationic and nonionic surfactants to a solvent and stirs them evenly, then adds modified montmorillonite and stirs again to prepare a thixotropic agent system. This overcomes the shortcomings of existing oil-phase suspension systems and non-oil-phase suspension systems, which have large differences in formulation and cannot be universally applied. However, the viscosity of this system is only 150~300 mPa·s, which cannot be applied to the field of coatable coatings. Silica, as an inorganic thixotropic agent, forms a weakly cross-linked network structure through hydrogen bonding between surface silanol groups, which can induce the solution to form a gel, thereby increasing its viscosity and thixotropic properties. Unmodified hydrophilic silica particles exhibit good dispersibility in polar solvents, but the resulting sol system has low viscosity. In practical coating applications, this low viscosity characteristic easily leads to sagging defects in the coating and makes it difficult to accurately control the film thickness. Typically, a large amount of silica needs to be added for the system to exhibit significant thixotropic behavior. Meanwhile, its rheology is mainly controlled by particle interactions. When silica particles aggregate in clusters to form fractal structures, their effective volume fraction can increase by 3-5 times, thereby significantly improving apparent viscosity.

[0005] Currently, research on silica surface modification focuses on hydrophobic treatment, mainly through the chemical reaction of silanes or fluorosilanes with surface silanol groups to achieve a controllable transformation of its surface properties from hydrophilic to hydrophobic. Although the dispersibility of modified hydrophobic silica in nonpolar solvents is improved, its effect on increasing the viscosity of the system remains limited.

[0006] For example, Zhang Jinlong of Nanjing University of Technology disclosed in his master's thesis "Preparation and Application of Fluorine-Modified Nano-SiO2 Particles" that he used perfluorooctyl sulfonyl fluoride to modify SiO2 particles, and then dispersed the modified particles in dimethyl silicone oil. As the mass fraction of the perfluorinated modifier increased, the viscosity of the system only increased from 2.1 Pa·s to 2.4 Pa·s (the mass ratio of perfluorooctyl sulfonyl fluoride to silicon dioxide was 0.35~0.8:1). Its surface perfluoroalkane content was high, and it could not be dispersed in polar solvents to increase viscosity.

[0007] For example, patent document CN104650625A discloses a method for modifying nano-silica with hydrogenated silicone oil. This method uses a water-soluble metal salt catalyst to catalyze the reaction between hydrogenated silicone oil (Si-H) and nano-silica (Si-OH), grafting hydrophobic groups onto the surface of hydrophilic silica particles. This effectively reduces surface tension and controls the rheological properties of water-based coatings; however, the resulting coating has a low viscosity. Furthermore, during the hydrophobic modification of silica, if the silanol groups on the particle surface are almost completely replaced by hydrophobic units, its dispersion performance in polar solvents will significantly decrease. Only by retaining some hydrophilicity can it be better dispersed in polar solutions. Summary of the Invention

[0008] To improve the compatibility between existing modified silica and polar solutions and enhance the thixotropic properties of silica-containing dispersions, this invention provides a perfluoroalkyl-modified nano-silica. By modifying nano-silica with perfluoroalkyl chlorosilanes, it retains hydrophilicity while also possessing partial hydrophobicity, exhibiting good dispersibility in polar solvents.

[0009] The specific technical solution adopted is as follows: A perfluoroalkyl-modified nano-silica is obtained by modifying nano-silica with a perfluoroalkylchlorosilane, wherein the mass ratio of the perfluoroalkylchlorosilane to the nano-silica is 0.001~0.6:1, and the perfluoroalkylchlorosilane is CF3 (CF2). n (CH2) m SiCl3, CF3(CF2) n (CH2) m SiCl2CH3, CF2H(CF2) n (CH2) m SiCl3 or CF2H(CF2) n (CH2) m One or more of SiCl2CH3, where n = 0~9 and m = 1~3.

[0010] During the modification process, the Si-OH groups on the surface of hydrophilic nano silica react with the Si-Cl bonds of perfluoroalkyl chlorosilanes in a solvent, and perfluoroalkanes are attached to the silica surface to obtain perfluoroalkyl modified silica, and HCl is generated as a byproduct.

[0011] This invention introduces a small number of hydrophobic units on the surface of hydrophilic nano-silica particles, reducing the thickness of the solvation layer on the particle surface. This allows the particles to maintain good dispersibility in polar solvents. Furthermore, the synergistic effect of hydrophobic association between hydrophobic units and hydrogen bonding between silanol groups enables the nano-silica particles to form aggregates or even network structures at low dosages, thereby significantly improving the zero-shear viscosity of the system and exhibiting excellent thixotropic properties.

[0012] Preferably, the mass ratio of the perfluoroalkyl chlorosilane to nano silica is 0.01 to 0.1:1. Within this range, the perfluoroalkyl modified nano silica particles can be completely dispersed in a polar solvent and form a high-viscosity thixotropic dispersion.

[0013] The present invention also provides a method for preparing perfluoroalkyl modified nano silica, comprising the following steps: adding nano silica to an organic solvent and stirring evenly; adding perfluoroalkyl chlorosilane under stirring conditions and reacting it with nano silica in the organic solvent; removing the organic solvent after the reaction is completed; grinding the remaining solid into powder to obtain the perfluoroalkyl modified nano silica.

[0014] Preferably, the organic solvent is one or more of the aprotic organic solvents with a boiling point of less than 150 °C under normal pressure.

[0015] Preferably, the amount of organic solvent used is 5-30 mL per gram of nano-silica.

[0016] The present invention also provides a dispersion obtained by dispersing the perfluoroalkyl-modified nano-silica in a polar solvent.

[0017] This dispersion utilizes the hydrophobic association between perfluoroalkanes on the surface of modified nano-silica particles and the synergistic hydrogen bonding between silanol groups to promote the formation of a nano-silica network structure. The viscosity of the dispersion can be significantly increased even with a low amount of modified nano-silica particles, while also exhibiting good thixotropy and stability.

[0018] The stronger the polarity of the solvent, the stronger the hydrogen bonding between the modified nano silica particles and the polar solvent molecules, and the better its dispersibility in the solvent. This will weaken the hydrophobic association between the modified nano silica particles, resulting in a decrease in the viscosity of the dispersion.

[0019] Preferably, the polar solvent is water or one or more pure substances or aqueous solutions of acrylic acid, propionic acid, acetic acid, formic acid, sulfuric acid, hydrochloric acid, phosphoric acid, ethanol, ethylene glycol, sodium hydroxide, etc.

[0020] The amount of polar solution added must be sufficient to fully disperse or wet the perfluoroalkyl-modified nano-silica particles. Preferably, the mass ratio of the perfluoroalkyl-modified nano-silica to the polar solvent is 0.01~0.2:1. Adding perfluoroalkyl-modified nano-silica particles within this range allows for complete dispersion in the polar solvent, forming a high-viscosity thixotropic dispersion.

[0021] In different application scenarios, to optimize the dispersibility and viscosity of the dispersion in different solvent systems, the perfluoroalkyl modified nano silica dispersion may also contain unmodified hydrophilic nano silica, with the mass ratio of the added unmodified hydrophilic nano silica to perfluoroalkyl modified nano silica being 0.05~20:1.

[0022] The present invention also provides the application of the dispersion in coatings.

[0023] Depending on the type, polarity, and pH of the solvent required for the specific application, coatings can be applied to various specific occasions by adjusting the amount of perfluoroalkyl chlorosilane modified with nano-silica or by adjusting the content and viscosity of the perfluoroalkyl modified nano-silica dispersion.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses perfluoroalkyl chlorosilane to modify nano silica. The resulting perfluoroalkyl modified nano silica retains hydrophilicity while also having some hydrophobicity and has good dispersibility in polar solvents.

[0025] (2) This invention does not add polymeric thickeners, but only uses a small amount of perfluoroalkyl chlorosilane surface-modified nano-silica particles. Through the strong hydrophobic association between the perfluoroalkanes on the particle surface, large-size aggregates are formed, which greatly increases the viscosity of the system and maintains the good thixotropic properties and stability of the nano-silica dispersion. This invention does not add polymers and is suitable for scenarios where coatings still need to polymerize to form coatings (such as hydrogel coatings, elastomer coatings, etc.) after coating application, avoiding phase separation before polymerization that affects the coating performance, polymerization uniformity and mechanical properties of the coating.

[0026] (3) When preparing the dispersion, any polar solvent that can wet the perfluoroalkyl modified nano silica particles can be selected. Therefore, the amount of perfluoroalkyl chlorosilane modification and addition of nano silica can be flexibly adjusted according to the type, polarity, pH value and viscosity requirements of the solvent required for specific applications, so as to prepare a coatable coating for specific applications.

[0027] (4) The raw materials used in this invention are inexpensive and require less quantity, and the preparation process is simple and the cost is low. Attached Figure Description

[0028] Figure 1 The infrared spectra of perfluoroalkyl-modified nano-silica in Examples 1, 3, 5, 6-14 are shown.

[0029] Figure 2 The graph shows a comparison between the theoretical and actual values ​​of the F atom content on the surface of perfluoroalkyl modified nano silica in Examples 1-5.

[0030] Figure 3 The graph shows a comparison between the theoretical and actual values ​​of the F element mass content on the surface of perfluoroalkyl modified nano-silica in Examples 1-5.

[0031] Figure 4 This is a distribution diagram of the fluorine element on the surface of the perfluorinated modified silica particles in Example 5.

[0032] Figure 5The curves show the change in apparent viscosity of the dispersions of Examples 1-5 and Comparative Example 1 as a function of shear rate.

[0033] Figure 6 The curves showing the change in apparent viscosity of the dispersions in Examples 5-9 and Comparative Example 1 as a function of shear rate are shown.

[0034] Figure 7 The curves showing the change in apparent viscosity of the dispersions in Examples 10-12 as a function of shear rate are shown.

[0035] Figure 8 The curves show the change of zero-shear viscosity of the dispersions in Examples 1-5 and Comparative Example 1 over time.

[0036] Figure 9 The zero-shear viscosity of the dispersions in Examples 1-9 and Comparative Example 1 varies with the amount of perfluorinated modification.

[0037] Figure 10 The relationship between zero-shear viscosity and pH value of different dispersions in Examples 5, 10-14 and Comparative Example 1.

[0038] Figure 11 The curves showing the change in the coefficient of friction between the coating and the glass substrate in Application Example 1 and Comparative Example 2 as a function of sliding speed are shown. Detailed Implementation

[0039] The present invention will be further illustrated below with reference to the embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0040] Example 1 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a globular flask and mixed evenly. 65 μL (0.1 g) of 1H, 1H, 2H, 2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The reaction was carried out at room temperature for 4 h. After the reaction was completed, most of the acetone was removed by rotary evaporation. The remaining solid was ground into powder and placed in an oven to remove the remaining acetone, thus obtaining perfluoroalkyl modified silica nanoparticles.

[0041] 2 g of perfluoroalkyl-modified nano-silica was added to 20 g of a 3 mol / L acrylic acid aqueous solution and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 149.01 Pa·s.

[0042] The structural formula of 1H, 1H, 2H, 2H-perfluorohexyltrichlorosilane is:

[0043] Comparative Example 1 2 g of A-400 hydrophilic fumed silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution and dispersed evenly using an ultrasonic cell disruptor to obtain a dispersion of nano-silica in the acrylic acid aqueous solution. The zero-shear viscosity of the resulting dispersion was 0.05 Pa·s.

[0044] Example 2 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 195 μL (0.3 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The reaction was carried out at room temperature for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The remaining solid was ground into powder and placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 822.27 Pa·s.

[0045] Example 3 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 324 μL (0.5 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 2030.74 Pa·s.

[0046] Example 4 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 519 μL (0.8 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 3401.04 Pa·s.

[0047] Example 5 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 13630.0 Pa·s.

[0048] Example 6 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 0.2 g of perfluoroalkyl-modified silica nanoparticles and 1.8 g of hydrophilic fumed silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution. The mixture was dispersed evenly using an ultrasonic cell disruptor to obtain a dispersion with a zero-shear viscosity of 0.264 Pa·s.

[0049] Example 7 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 0.6 g of perfluoroalkyl-modified silica nanoparticles and 1.4 g of hydrophilic fumed silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution. The mixture was dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 232.42 Pa·s.

[0050] Example 8 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 1.0 g of perfluoroalkyl-modified silica nanoparticles and 1.0 g of hydrophilic fumed silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution. The mixture was dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 1237.23 Pa·s.

[0051] Example 9 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 1.6 g of perfluoroalkyl-modified silica nanoparticles and 0.4 g of hydrophilic fumed silica nanoparticles were added to 20 g of a 3 mol / L acrylic acid aqueous solution. The mixture was dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 6443.87 Pa·s.

[0052] Example 10 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of pure water and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 84963.8 Pa·s.

[0053] Example 11 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of sulfuric acid solution (pH = 0; 2; 4; 6) and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion. The zero-shear viscosities of the resulting dispersions were 86204.0 Pa·s, 18663.6 Pa·s, 14873.4 Pa·s, and 31006.5 Pa·s.

[0054] Example 12 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of sodium hydroxide solution (pH = 8; 10) and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion. The zero-shear viscosities of the resulting dispersions were 66910.8 Pa·s and 68247.4 Pa·s, respectively.

[0055] Example 13 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of a 3 mol / L propionic acid aqueous solution and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 11147.8 Pa·s.

[0056] Example 14 Activated type 4A molecular sieves were added to acetone to remove moisture. 10 g of dried A-400 hydrophilic fumed silica nanoparticles and 20 mL of acetone were added to a round-bottom flask and mixed thoroughly. 649 μL (1.0 g) of 1H,1H,2H,2H-perfluorohexyltrichlorosilane was added under mechanical stirring. The mixture was reacted in acetone for 4 h. After the reaction, most of the acetone was removed by rotary evaporation. The mixture was ground into powder and then placed in an oven to remove the remaining acetone, yielding perfluoroalkyl-modified silica nanoparticles. 2 g of perfluoroalkyl-modified silica nanoparticles were added to 20 g of a 3 mol / L aqueous solution of methacrylic acid and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity dispersion with a zero-shear viscosity of 1647.9 Pa·s.

[0057] Application Example 1 The 22 g dispersion prepared in Example 5, 3.35 g of methacryloylethyl sulfobetaine, 0.13 g of photoinitiator 2959, and 0.028 g of crosslinking agent were mixed. N , N An aqueous solution of '-methylenebisacrylamide' was mixed and dispersed evenly using an ultrasonic cell disruptor to obtain a high-viscosity precursor coating. The precursor coating was applied to a tinplate and placed in a UV curing chamber for 6 minutes of strong UV light. After curing, it was immersed in seawater for more than 3 days to obtain an equilibrium marine antifouling coating.

[0058] The adsorption capacity of bovine serum albumin on the surface of the coating prepared in Example 1 was tested using the BCA method, and the adsorption capacity was 125.90 μg / cm³. 2 The coefficient of friction between the coating and the glass substrate was tested using a rotational rheometer as a function of sliding speed, and the resulting curve is shown in the figure. Figure 11 As shown.

[0059] Comparative Example 2 The 22 g dispersion prepared in Comparative Example 1, 3.35 g of methacryloylethyl sulfobetaine, 0.13 g of photoinitiator 2959, and 0.028 g of crosslinking agent were mixed. N , N An aqueous solution of '-methylenebisacrylamide was mixed and dispersed evenly using an ultrasonic cell disruptor to obtain a precursor coating. The precursor coating was applied to a tinplate and placed in a UV curing chamber for 6 minutes of strong UV light. After curing, it was immersed in seawater for more than 3 days to obtain an equilibrium marine antifouling coating.

[0060] The adsorption capacity of bovine serum albumin on the surface of the coating prepared in Comparative Example 2 was tested using the BCA method, and the adsorption capacity was 227.79 μg / cm³. 2 The coefficient of friction between the coating and the glass substrate was tested using a rotational rheometer as a function of sliding speed, and the resulting curve is shown in the figure. Figure 11 As shown.

[0061] Results analysis: I. Detection of fluorine content on the surface of perfluoroalkyl-modified nano-silica Depend on Figure 1 As can be seen from the infrared spectrum, after modification, the silica particles exhibit a certain density at 1223 cm⁻¹. -1 and 880 cm -1 The presence of -CF2- and -CF3- bond stretching vibration peaks at the positions indicates that perfluorohexyltrichlorosilane reacted with Si-OH and attached to FS, successfully preparing the F-FS sample.

[0062] Depend on Figures 2-4 It can be seen that the amount of perfluoroalkane (F / Si ratio) on the surface of the perfluoroalkyl modified nano silica is directly proportional to the amount of perfluorohexyltrichlorosilane added. At the same time, the F element is evenly distributed on the sample surface, indicating that the reaction was successful and the perfluorohexyltrichlorosilane has been uniformly grafted onto the surface of the nano silica, achieving the designed hydrophobic modification effect.

[0063] II. Testing the viscosity and thixotropy of perfluoroalkyl-modified nano-silica dispersions Steady-state shear hysteresis curves of the dispersion were tested using a rotational rheometer. The flat plate fixture had a diameter of 20 mm or 40 mm, the temperature was set to 25 °C, and the shear rate scan range was 10. -3 ·s -1 ~10 3 ·s -1 ~10 -3 ·s -1 The apparent viscosity of the dispersion was measured as a function of shear rate, and the area of ​​the hysteresis loop was used to characterize the thixotropy of the dispersion.

[0064] The thixotropic properties of the dispersion were tested using a rotational rheometer with a 20 mm diameter plate fixture and a set temperature of 25°C. The test was conducted according to a 10-day rotational rheometer. -1 ·s -1 ~10 2 ·s -1 ~10 -1 ·s -1 The shear rate was sequentially scanned for 600 s, and the change curve of the apparent viscosity of the dispersion was tested.

[0065] according to Figure 5 , Figure 8 and Figure 9 It can be seen that, within a certain range, as the amount of perfluoroalkyl modification of silica particles increases, the zero-shear viscosity of the resulting dispersion continuously increases, but the hysteresis loop area increases slightly, indicating that the thixotropy of the dispersion decreases slightly. In Example 5, the amount of perfluorohexyltrichlorosilane added was only 0.83 wt%, but the zero-shear viscosity of the dispersion reached 13630 Pa·s, and it also had good thixotropy, while the zero-shear viscosity of Comparative Example 1 was only 0.05 Pa·s, and its thixotropy was also poor.

[0066] contrast Figure 5 , Figure 6 and Figure 10 It can be seen that if the same amount of perfluoroalkyl modification is maintained, the apparent viscosity and zero-shear viscosity of the two dispersions are basically the same. This indicates that the increase in viscosity of the dispersion system is determined by the perfluoroalkane content on the particle surface, and is unrelated to the amount of silica particles added. Therefore, in practical applications, if a certain amount of particles is required, it is not necessary to prepare silica with different amounts of perfluoroalkyl modification. High-perfluoroalkyl-modified silica can be blended with unmodified silica in different proportions, thereby flexibly adjusting the fluorine content and viscosity of the dispersion, significantly improving its convenience in application and reducing production costs.

[0067] Depend on Figure 7 It is evident that dispersions of perfluoroalkyl-modified silica in solutions with a pH range of 0–10 exhibit similar zero-shear viscosity and steady-state shear hysteresis behavior. For example... Figure 10 As shown, at the same pH, the dispersion prepared by dispersing perfluoroalkyl-modified silica in an acrylic acid solution has a lower viscosity than the dispersion prepared by dispersing it in a dilute sulfuric acid solution. Increasing the concentration of the dilute sulfuric acid solution initially decreases the viscosity of the dispersion, then increases it. This is because H₂SO₄ has a higher degree of ionization in water, and HSO₄… 3- and SO4 2- The hydrogen bonding between ions and Si-OH is relatively weaker than that between -COOH groups. Therefore, the solvation layer formed on the particle surface is thinner, which can form aggregates with larger particle sizes and the dispersion has higher viscosity.

[0068] III. Testing the antifouling and drag-reducing properties of coatings prepared from perfluoroalkyl-modified nano-silica dispersions. The results of the detection of the amount of bovine serum albumin adsorbed on the surface of the coatings prepared in Application Example 1 and Comparative Example 2 show that, compared with the coating in Comparative Example 2, the amount of bovine serum albumin adsorbed on the surface of the coating in Application Example 1 was reduced by 44.73%, which proves that the introduction of perfluoroalkyl modified silica dispersion can significantly improve the antifouling performance of the coating.

[0069] Depend on Figure 11 It is evident that the coating prepared by perfluoroalkyl modified silica dispersion exhibits a faster reduction in the coefficient of friction in the mixed lubrication zone and can be wetted by seawater more quickly during sliding, effectively reducing the coefficient of friction in the mixed lubrication zone and enabling it to enter hydrodynamic lubrication more rapidly. This demonstrates that the introduction of perfluoroalkyl modified silica dispersion can improve the drag reduction performance of the coating.

[0070] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A perfluoroalkyl-modified nano-silica, characterized in that, It is obtained by modifying nano-silica with perfluoroalkylchlorosilane, wherein the mass ratio of the perfluoroalkylchlorosilane to the nano-silica is 0.001~0.6:1, and the perfluoroalkylchlorosilane is CF3 (CF2). n (CH2) m SiCl3, CF3(CF2) n (CH2) m SiCl2CH3, CF2H(CF2) n (CH2) m SiCl3, CF2H(CF2) n (CH2) m One or more of SiCl2CH3, where n = 0~9 and m = 1~3.

2. The perfluoroalkyl-modified nano-silica according to claim 1, characterized in that, The mass ratio of the perfluoroalkyl chlorosilane to nano-silica is 0.01~0.1:

1.

3. A method for preparing perfluoroalkyl-modified nano-silica, characterized in that, Includes the following steps: Nano-silica was added to an organic solvent and stirred until homogeneous. Perfluoroalkyl chlorosilane was then added under stirring conditions and reacted with the nano-silica in the organic solvent. After the reaction was completed, the organic solvent was removed, and the remaining solid was ground into powder to obtain the perfluoroalkyl modified nano-silica.

4. The method for preparing perfluoroalkyl-modified nano-silica according to claim 3, characterized in that, The organic solvent is an aprotic organic solvent with a boiling point of less than 150 °C under normal pressure.

5. The method for preparing perfluoroalkyl-modified nano-silica according to claim 3, characterized in that, The amount of organic solvent used is 5-30 mL per gram of nano-silica.

6. A dispersion, characterized in that, It is obtained by dispersing the perfluoroalkyl-modified nano-silica as described in claim 1 or 2 in a polar solvent.

7. The dispersion according to claim 6, characterized in that, The polar solvent is water or one or more pure substances or aqueous solutions of acrylic acid, propionic acid, acetic acid, formic acid, sulfuric acid, hydrochloric acid, phosphoric acid, ethanol, ethylene glycol, and sodium hydroxide.

8. The dispersion according to claim 6, characterized in that, The mass ratio of the perfluoroalkyl modified nano-silica to the polar solvent is 0.01~0.2:

1.

9. The dispersion according to claim 6, characterized in that, Unmodified nano-silica may also be added to the dispersion, and the mass ratio of the added unmodified nano-silica to the perfluoroalkyl modified silica is 0.05~20:

1.

10. The application of the dispersion according to any one of claims 6-9 in coatings.

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