Preparation method and application of hollow spherical silica

Abstract

The application provides a preparation method of hollow spherical silica, which comprises the following steps: 1) uniformly mixing ethanol, an alkaline catalyst and pure water to obtain an alkaline solution; then mixing the solution with ethanol, tetraethyl orthosilicate and a silane coupling agent, and performing a hydrolysis condensation reaction to obtain a silica microsphere emulsion; 2) performing solid-liquid separation, alcohol washing and drying on the silica microsphere emulsion, and the hollow spherical silica is obtained. The size of the hollow spherical silica microspheres and the hydrophobicity of the microspheres can be controlled by controlling the concentration of the silane coupling agent. The preparation method provided by the application is simple in process and easy to control, does not need to use a template, realizes one-step synchronous construction of the hollow structure and the hydrophobic property, and has high hydrophobicity. The hollow spherical silica prepared by the application has high application value in a hydrophobic coating and wide market prospect.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a method for preparing hollow spherical silica and its application. Background Technology

[0002] Hollow silica microspheres are a special new type of inorganic material with a hollow internal structure. Due to their non-toxicity, good thermal stability, high specific surface area, ordered pore structure, ease of surface functionalization, and good biocompatibility, they have many applications in drug sustained release, refractory materials, capsule encapsulation, nanocatalysts, adsorbent materials, optoelectronic materials, anti-reflective coating materials, and energy storage materials.

[0003] Therefore, the preparation and application of hollow silica microspheres have attracted widespread attention from researchers. Currently, the template method is commonly used for the preparation of hollow silica. This method involves depositing the target material on the surface of a template and then removing the template to obtain materials with specific shapes and structures. Removing the template often requires harsh methods such as strong acids, strong alkalis, or high-temperature calcination. These methods may damage the structure of the hollow silica microspheres or create defects on the surface, affecting their performance. Chinese patent CN113213489A uses PS microspheres as a hard template, TEOS as a silicon source, and ammonia as a catalyst. Hydrolysis and condensation occur on the surface of modified PS microspheres to form a silica shell coating the surface of the modified PS microspheres. Finally, the template is removed through subsequent heat treatment to obtain silica microspheres with a hollow structure. Chinese patent CN111620342A uses a droplet soft template method, with tetraalkoxysilane as the silicon source, to prepare hollow silica microspheres through in-situ hydrolysis and cross-linking reactions under acidic or alkaline conditions. However, these existing methods often suffer from complex preparation processes and problems such as energy consumption, pollution, or residues during template removal.

[0004] Based on this, this application was developed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing hollow spherical silica. This method employs a template-free self-assembly phase separation approach, using an alkaline solution as the reaction medium. TEOS and fluorinated silanes are added to the system, and through selective hydrolysis and differential phase separation, hollow silica microspheres with hydrophobic properties are obtained after a certain reaction time. This method enables the simultaneous one-step construction of hollow structure and hydrophobic properties, offers easily controllable reaction conditions, has a simple preparation process, and is suitable for large-scale production of hydrophobic hollow spherical nano-silica.

[0006] The present invention also provides the application of the above-mentioned hollow spherical silica in hydrophobic coatings.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing small-sized hollow silica microspheres includes the following steps: 1) Ethanol, alkaline catalyst and pure water are mixed evenly to obtain an alkaline solution. Then, the alkaline solution is mixed with ethanol, tetraethyl orthosilicate and silane coupling agent and reacted to obtain a mesoporous hollow silica microsphere emulsion. 2) The mesoporous hollow silica microsphere emulsion is obtained by solid-liquid separation (such as centrifugation, vacuum filtration, etc.), alcohol washing and drying.

[0008] Specifically, in step 1), the ethanol can be industrial alcohol (concentration of 95%), and the mass ratio of ethanol to pure water can be (1-4):1.

[0009] Specifically, in step 1), the alkaline catalyst can be one or more of ammonia, triethanolamine, diethanolamine, etc., and the pH value of the alkaline solution is 8-11. The pH value of the alkaline solution is adjusted by controlling the amount of alkaline catalyst used.

[0010] Specifically, in step 1), the silane coupling agent can be one or more of perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, perfluorooctyltrimethoxysilane, and perfluorooctyltriethoxysilane. The mass ratio of the silane coupling agent to ethanol is 1:15-220.

[0011] Specifically, in step 1), the molar ratio of the silane coupling agent to tetraethyl orthosilicate (TEOS) is 1:1-100.

[0012] Specifically, in step 1), the reaction temperature is 45-80℃, and the reaction time is 2-6 hours. During mixing, stirring can be used to ensure uniform mixing; the stirring speed can be 400-800 rpm.

[0013] Specifically, in step 2), the drying is direct drying, the drying temperature is 100-120℃, and the drying time is controlled between 1-5 hours.

[0014] This invention provides hollow spherical silica prepared by the above method, with a diameter of 100-400 nm and a specific surface area of ​​9-30 m². 2 / g, pore volume: 0.01-0.05cm³ 3 / g, pore size: 5-30nm.

[0015] The present invention also provides the application of the above-mentioned hollow spherical silica in hydrophobic coatings.

[0016] This invention proposes a method for preparing hollow spherical silica. From a process perspective, this method is simple to operate, avoiding the complex template preparation and removal processes of traditional hard template methods, as well as the difficulty in precisely controlling the shape and size of microspheres in soft template methods. This invention employs a self-assembly phase separation method without external templates. Raw materials are mixed in a specific ratio and reacted under relatively mild reaction conditions to complete the preparation process, greatly reducing the difficulty and improving the efficiency. Regarding reaction condition control, this invention offers high controllability. By precisely setting the reaction parameters for each step, such as the mass ratio of raw materials, reaction temperature, stirring speed, and reaction time, the stability and repeatability of the reaction process can be ensured, significantly improving the stability of product quality. In terms of product performance, the hollow silica nanospheres prepared by this invention exhibit excellent properties. Their particle size can be precisely controlled between 100-400 nm, with high sphericity. Furthermore, by changing the reaction temperature, time, and the amount of silane containing hydrophobic groups, the particle size and hydrophobicity can be flexibly adjusted to meet the diverse performance requirements of different application scenarios, further broadening the application range of the product. In summary, the preparation method of the present invention has significant advantages in terms of preparation process, reaction condition control, and product performance, bringing a new breakthrough to the preparation and application of hollow mesoporous nano-silica microspheres, and has important economic and social significance.

[0017] The hollow spherical silica nanospheres prepared by the method of this invention have a particle size between 100-400 nm and a uniform particle size distribution. The particle size and hydrophobicity can be controlled by changing the reaction temperature, reaction time, and the amount of silane containing hydrophobic groups. This invention achieves one-step simultaneous construction of hollow structure and hydrophobic properties, with easily controllable reaction conditions and a simple preparation process, making it suitable for industrial production. Using the obtained hollow spherical silica as a filler in coatings, spraying it onto the substrate surface, can yield a coating with high hydrophobicity. Compared with existing technologies, this invention has the following advantages and beneficial effects: 1) The hollow spherical silica prepared in this invention is used as a filler to prepare a hydrophobic coating, which has excellent hydrophobic effect and a contact angle of up to 152°.

[0018] 2) The preparation method provided by the present invention is simple to operate and highly efficient, and can realize hydrophobic modification of large-area and complex-shaped substrates, with strong industrial applicability.

[0019] 3) This invention enables the control of the size and hydrophobicity of hollow spherical silica microspheres by adjusting the concentration of the silane coupling agent. The preparation method provided by this invention is simple, easy to control, and requires no template, achieving simultaneous one-step construction of the hollow structure and hydrophobic properties. The hollow spherical silica obtained by this invention exhibits high hydrophobicity, demonstrating significant application value and broad market prospects in hydrophobic coatings. Attached Figure Description

[0020] Figure 1 TEM image of the hollow spherical silica prepared in Example 1; Figure 2 The particle size diagram of the hollow spherical silica prepared in Example 1 is shown, with a particle size of 144 nm. Figure 3 TEM image of the hollow spherical silica prepared in Example 2; Figure 4 The particle size diagram of the hollow spherical silica prepared in Example 2 is shown, with a particle size of 418 nm. Figure 5 Water contact angle of coatings with different amounts of F-HSiO2 added. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0022] In the following examples, all raw materials used are common commercially available products that can be purchased directly, or can be prepared using conventional techniques in the art. The ethanol used can be industrial ethanol (industrial alcohol, concentration 95%). Example 1

[0023] A method for preparing hollow spherical silica includes the following steps: 1) Weigh 250g of industrial ethanol, 35g of ammonia (25% by mass), and 151.82g of pure water. Stir for about 30 minutes to obtain an alkaline solution with a pH of about 10. Pour the solution into a 1000ml three-necked flask while stirring (at a speed of 400rpm). Heat the solution to 45℃. Then, mix 70g of industrial ethanol, 50g of TEOS, and 2.02g of perfluorodecyltrimethoxysilane and pour the mixture into the flask at a constant speed. React at 45℃ for 2 hours to obtain a hollow silica microsphere emulsion. 2) After the reaction is complete, the resulting liquid is filtered and washed with anhydrous ethanol until the byproducts are removed (the washing liquid is clear and transparent). It is then dried at 120°C for 3 hours to obtain hollow silica nanospheres.

[0024] Figure 1 TEM images of the hollow spherical silica prepared in Example 1 are provided. As can be seen from the images, the generated hollow silica microspheres are spherical and have a hollow internal structure.

[0025] Figure 2 The particle size distribution of the hollow spherical silica prepared in Example 1 is shown in the figure. It can be seen from the figure that the median particle size of the hollow silica microspheres is 144 nm. Example 2

[0026] A method for preparing hollow spherical silica includes the following steps: 1) Weigh 375g of industrial ethanol, 35g of ammonia (25% by mass) and 151.82g of pure water, and stir for about 30 minutes to obtain an alkaline solution with a pH of about 8. Pour the solution into a 1000ml three-necked flask while stirring (at a speed of 400rpm), and heat the solution to 45℃. Then, mix 70g of industrial ethanol, 70g of TEOS and 20.16g of perfluorodecyltrimethoxysilane and pour the mixture into the flask at a constant speed. React at 45℃ for 2 hours to obtain a hollow silica microsphere emulsion. 2) After the reaction is complete, the resulting liquid is filtered and washed with anhydrous ethanol until the byproducts are removed (the washing liquid is clear and transparent). It is then dried at 120°C for 3 hours to obtain hollow silica nanospheres.

[0027] Figure 3 TEM images of the hollow spherical silica prepared in Example 2 are provided. As can be seen from the images, the generated hollow silica microspheres are spherical and have a hollow internal structure.

[0028] Figure 4 The particle size distribution of the hollow spherical silica prepared in Example 2 is shown in the figure. It can be seen from the figure that the median particle size of the hollow silica microspheres is 418 nm.

[0029] Application examples A method for preparing hydrophobic hollow silica / epoxy resin composite coatings includes the following steps:

[0030] 1) The hollow silica microsphere powder prepared in Example 2 was added to a mixture of 828 epoxy resin, methyl hexahydrophthalic anhydride curing agent, and 1-cyano-2-ethyl-4-methylimidazolium accelerator (the mass ratio of resin to curing agent and accelerator was 1:0.9:0.01), and mixed evenly using a three-roll mill (the amount of hollow silica microspheres added was 0%, 10%, 20%, 30%, 40%, 50%, and 60%). 2) Dilute the slurry obtained in step 1) with acetone (the mass ratio of resin to acetone is 1:5), and stir at high speed for 30 minutes to obtain a hollow silica / epoxy resin composite coating. 3) The composite coating obtained in step 2) is sprayed onto a glass slide using a spray gun and cured at 120℃ and 150℃ for 2 hours respectively to obtain a hydrophobic hollow silica / epoxy resin composite coating.

[0031] Figure 5The contact angles of the coatings with different amounts of F-HSiO2 are shown. The figure shows that when hollow silica is added at 50%, the contact angle of the hydrophobic coating is 154.51°, reaching a superhydrophobic state, indicating that the hydrophobic coating prepared in this invention has good hydrophobic properties.

[0032] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes made in deviating from the present invention should be equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A method for preparing hollow spherical silica, characterized in that, Includes the following steps: 1) Ethanol, alkaline catalyst and pure water are mixed evenly to obtain an alkaline solution. Then, the alkaline solution is mixed with ethanol, tetraethyl orthosilicate and silane coupling agent and reacted to obtain a silica microsphere emulsion. 2) The silica microsphere emulsion is obtained by solid-liquid separation, alcohol washing and drying.

2. The method for preparing hollow spherical silica as described in claim 1, characterized in that, In step 1), the ethanol is industrial alcohol, and the mass ratio of ethanol to pure water is (1-4):

1.

3. The method for preparing hollow spherical silica as described in claim 1, characterized in that, In step 1), the alkaline catalyst is one or more of ammonia, triethanolamine, and diethanolamine, and the pH value of the alkaline solution is 8-11.

4. The method for preparing hollow spherical silica as described in claim 1, characterized in that, In step 1), the silane coupling agent is one or more of perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, perfluorooctyltrimethoxysilane, and perfluorooctyltriethoxysilane; the mass ratio of the silane coupling agent to ethanol is 1:15-220.

5. The method for preparing hollow spherical silica as described in claim 1, characterized in that, In step 1), the molar ratio of the silane coupling agent to tetraethyl orthosilicate is 1:1-100.

6. The method for preparing hollow spherical silica as described in claim 1, characterized in that, In step 1), the reaction temperature is 45-80℃ and the reaction time is 2-6h.

7. The method for preparing hollow spherical silica as described in claim 1, characterized in that, In step 2), the drying is direct drying, the drying temperature is 100-120℃, and the drying time is controlled between 1-5 hours.

8. Hollow spherical silica prepared by any one of the methods described in claims 1 to 7.

9. The application of the hollow spherical silica as described in claim 8 in hydrophobic coatings.

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