Preparation method of super-hydrophobic nano-silicon oxide

Abstract

This invention discloses a method for preparing superhydrophobic nano-silica. The method first uses the Stber method to prepare nano-silica. During the preparation process, phenolic resin coating is used to control the particle size of the nano-silica and make its particle size distribution more uniform. Then, the surface is modified by grafting a silane coupling agent to achieve hydrophobicity, ultimately obtaining superhydrophobic nano-silica. The material obtained by this invention has the characteristics of controllable particle size, strong hydrophobic properties, and high mechanical strength.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation technology, specifically relating to a method for preparing superhydrophobic nano-silica. Background Technology

[0002] Superhydrophobic nano-silica (contact angle >140°) has achieved innovative applications in multiple industrial fields due to its unique low surface energy properties. In the coatings industry, adding 1-5 wt% nano-silica can give coatings durable hydrophobicity (water contact angle up to 160°), significantly improving the weather resistance and stain resistance of building exteriors and reducing maintenance costs by more than 30%. Its applications are even more extensive in the self-cleaning field; its photocatalytic properties (85% efficiency in decomposing organic matter under ultraviolet light) are used to develop smart glass coatings, enabling rainwater to automatically wash away pollutants, suitable for high-rise building curtain walls and photovoltaic panels. In the textile industry, nanoparticles are attached to the fiber surface through an impregnation process, giving fabrics water and oil repellency (oil contact angle >140°), which has significant value in outdoor equipment and medical protective clothing. The automotive industry utilizes its superhydrophobic properties to develop anti-fog coatings for rearview mirrors and self-cleaning coatings for car bodies, reducing car wash frequency by 60%.

[0003] St The BER method is a classic method for preparing submicron to micron-sized silica particles. By controlling various conditions during the preparation process, the particle size of silica can be controlled to a certain extent. The patent "A silica nanosphere with controllable particle size and its preparation method" (Patent No.: CN 120081384 A) reports a method using St... The BER method involves first preparing submicron-sized silica seed microspheres, and then using these seed microspheres to prepare silica nanospheres. While this method allows for controllable particle size of the silica nanospheres, its relatively complex process and difficulty in large-scale production are its drawbacks.

[0004] Superhydrophobic surfaces possess two important characteristics: surface roughness at the micron and nanoscale, and complex structures. Numerous studies have demonstrated that superhydrophobic effects can be achieved by coating rough surfaces with low surface energy materials to increase the water contact angle. The patent "An Organically Modified Hydrophobic Hollow Silica Nanosphere and Its Preparation" (Patent No.: CN 103803556 B) reports a method for preparing hydrophobic hollow silica nanospheres by adding a silane coupling agent during the preparation process. This method directly obtains hydrophobic silica nanospheres in a one-step process, but it consumes a large amount of silane coupling agent during preparation. Summary of the Invention

[0005] The purpose of this invention is to address the limitations of current technologies by providing a method for preparing superhydrophobic nano-silica with controllable particle size. This method first employs St... The BER method for preparing nano-silica involves using phenolic resin coating during the preparation process to control the particle size and achieve a more uniform particle size distribution. Furthermore, surface modification with silane coupling agents is used to achieve hydrophobicity, ultimately yielding superhydrophobic nano-silica. The material obtained by this invention features controllable particle size, strong hydrophobicity, and high mechanical strength.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing superhydrophobic nano-silica, comprising the following steps: (1) Mix ammonia water and anhydrous ethanol and stir at 30-40℃ for 10-40 minutes to obtain solution A; The ammonia water has a mass fraction of 20% to 30%, and the volume ratio of ammonia water to anhydrous ethanol is 1:3 to 8. (2) Weigh out tetraethyl orthosilicate, add it to solution A, and stir in a water bath at 30~80℃ for 2~8 hours to obtain solution B; The volume ratio of tetraethyl orthosilicate to ammonia in step (1) is 1:1~4. (3) Weigh out resorcinol, formaldehyde and anhydrous sodium carbonate respectively, add them to solution B, and continue stirring in a water bath at 30~80℃ for 18-24 hours to obtain suspension C; The mass ratio of anhydrous sodium carbonate, resorcinol, and formaldehyde is 1:4~16:2~8, and the mass ratio of resorcinol and tetraethyl orthosilicate added in step (2) is 1:30~200. (4) Filter the suspension C, then wash it with deionized water until pH=7, then wash it with anhydrous ethanol and dry it, and then calcine it in air at 600~900℃ for 3~6h to obtain nano silicon dioxide D. The mass of anhydrous ethanol is 10-20 times that of nano-silica. (5) Add nano-silica D to anhydrous methanol, disperse by ultrasonication, and then add silane coupling agent to obtain suspension E; The silane coupling agents include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, aminopropyltrimethoxysilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, tetradecyltrimethoxysilane, and phenyltrimethoxysilane. The mass ratio of nano-silica, anhydrous methanol and silane coupling agent is 20~120:500~3000:1; (6) Stir the suspension E in an oil bath at 60~100℃ for 4~8 hours, and cool it to room temperature to obtain mixture F; (7) Filter the mixture F, rinse with deionized water, and then replace the residual water with anhydrous ethanol to obtain superhydrophobic nano-silica.

[0007] The essential features of this invention are: This invention is based on St In the BER process for preparing nano-silica, the polymerization reaction of resorcinol and formaldehyde is introduced to coat the growing silica spheres with phenolic resin, thus controlling the size of the final silica spheres. This method is simpler, less costly, and easier to scale up industrially.

[0008] This invention employs a silane coupling agent grafting modification method. Organosilanes are used to cover the hydroxyl groups on the surface of silica spheres, reducing surface hydrophilicity and increasing oleophilicity, thus endowing the silica spheres with superhydrophobic properties. The improved method can first prepare nano-silica with controllable and more uniform particle size. Subsequent hydrophobic modification yields higher quality superhydrophobic nano-silica. Furthermore, because this method completely grafts the silane coupling agent onto the surface of the nano-silica, a very small amount of silane coupling agent is required to obtain nano-silica with a superhydrophobic surface, significantly reducing costs.

[0009] The beneficial effects of this invention are as follows: This invention achieves controllable and uniform particle size of nano-silica through technological innovation of carbon-coated silica spheres and silane coupling agent graft modification. It also obtains a superhydrophobic surface (water contact angle >140°) through modification. Compared with existing technologies, this invention has the advantages of simple method, easy industrialization, and low production cost, and has strong application value. Attached Figure Description

[0010] Figure 1 TEM image of the superhydrophobic nano-silica prepared in Example 1 Figure 2 The particle size distribution of the superhydrophobic nano-silica prepared in Example 1. Detailed Implementation

[0011] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0012] Example 1: Preparation of superhydrophobic nano-silica (material A) Measure 20 mL of ammonia water (mass fraction 25% ~ 30%) and 125 mL of anhydrous ethanol into a three-necked round-bottom flask. Mix for 20 min in a 30℃ water bath with mechanical stirring until the mixture is homogeneous. Add 8 mL of tetraethyl orthosilicate to a constant-pressure dropping funnel, and then add it to the round-bottom flask containing the mixture at a rate of 1 drop / s. Stir in a 40℃ water bath for 3 hours to obtain a liquid after preliminary precipitation. Weigh 0.08 g of resorcinol, 0.04 g of formaldehyde, and 0.01 g of anhydrous sodium carbonate, and add them to the liquid after preliminary precipitation. Continue stirring in a 40℃ water bath for 18 h, then filter, wash with deionized water to pH=7, wash with 120 mL of anhydrous ethanol, dry, and calcine at 800℃ in air for 4 h to obtain nano-silica. Then, weigh 2g of nano-silica, measure 50ml of anhydrous methanol, add them to a three-necked flask, add 0.04g of propyltrimethoxysilane, stir at 80℃ for 6h, then filter and wash to finally obtain superhydrophobic nano-silica.

[0013] Characterization was performed using transmission electron microscopy (TEM) Figure 1 The average particle size of the material can be statistically obtained. Figure 2 Its average particle size is 53 nm; The water contact angle of this material can be measured using a contact angle measuring instrument; the contact angle is 160°.

[0014] Example 2: Preparation of superhydrophobic nano-silica (material B) Measure 20 mL of ammonia water (mass fraction 25% ~ 30%) and 125 mL of anhydrous ethanol into a three-necked round-bottom flask. Mix for 20 min in a 30℃ water bath with mechanical stirring until the mixture is homogeneous. Add 8 mL of tetraethyl orthosilicate to a constant-pressure dropping funnel, and then add it to the round-bottom flask containing the mixture at a rate of 1 drop / s. Stir for 6 hours in a 40℃ water bath to obtain a liquid after preliminary precipitation. Weigh 0.16 g of resorcinol, 0.08 g of formaldehyde, and 0.01 g of anhydrous sodium carbonate, and add them to the liquid after preliminary precipitation. Continue stirring in a 40℃ water bath for 18 h, then filter, wash with deionized water to pH=7, wash with 120 mL of anhydrous ethanol, dry, and calcine at 700℃ in air for 5 h to obtain nano-silica. Then, 2g of nano-silica was weighed, 50ml of anhydrous methanol was measured, and added to a three-necked flask. 0.02g of methyltrimethoxysilane was then added, and the mixture was stirred at 80℃ for 6h. After filtration and washing, superhydrophobic nano-silica was finally obtained with an average particle size of 36nm and a contact angle of 148°. Example 3: Preparation of superhydrophobic nano-silica (material C) Measure 20 mL of ammonia water (mass fraction 25% ~ 30%) and 125 mL of anhydrous ethanol into a three-necked round-bottom flask. Mix for 20 min in a 30℃ water bath with mechanical stirring until the mixture is homogeneous. Add 8 mL of tetraethyl orthosilicate to a constant-pressure dropping funnel, and then add it to the round-bottom flask containing the mixture at a rate of 1 drop / s. Stir in a 60℃ water bath for 3 hours to obtain a liquid after preliminary precipitation. Weigh 0.04 g of resorcinol, 0.02 g of formaldehyde, and 0.01 g of anhydrous sodium carbonate, and add them to the liquid after preliminary precipitation. Continue stirring in a 60℃ water bath for 18 h, then filter, wash with deionized water until pH=7, wash with 120 mL of anhydrous ethanol, dry, and calcine at 900℃ in air for 3 h to obtain nano-silica. Then, 2g of nano-silica was weighed, 50ml of anhydrous methanol was measured, and added to a three-necked flask. 0.06g of ethyltrimethoxysilane was then added, and the mixture was stirred at 80℃ for 6h. After filtration and washing, superhydrophobic nano-silica was finally obtained with an average particle size of 78nm and a contact angle of 156°.

[0015] Example 4: Preparation of superhydrophobic nano-silica (material D) Measure 20 mL of ammonia water (mass fraction 25% ~ 30%) and 125 mL of anhydrous ethanol into a three-necked round-bottom flask. Mix for 20 min in a 30℃ water bath with mechanical stirring until the mixture is homogeneous. Add 8 mL of tetraethyl orthosilicate to a constant-pressure dropping funnel, and then add it to the round-bottom flask containing the mixture at a rate of 1 drop / s. Stir in a 70℃ water bath for 2 hours to obtain a liquid after preliminary precipitation. Weigh 0.08 g of resorcinol, 0.04 g of formaldehyde, and 0.01 g of anhydrous sodium carbonate, and add them to the liquid after preliminary precipitation. Continue stirring in an 80℃ water bath for 18 h, then filter, wash with deionized water until pH=7, wash with 120 mL of anhydrous ethanol, dry, and calcine at 800℃ for 4 h in air atmosphere to obtain nano-silica. Then, 2g of nano-silica was weighed, 50ml of anhydrous methanol was measured, and added to a three-necked flask. 0.08g of aminopropyltrimethoxysilane was then added, and the mixture was stirred at 80℃ for 6h. After filtration and washing, superhydrophobic nano-silica was finally obtained with an average particle size of 103nm and a contact angle of 158°.

[0016] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing superhydrophobic nano-silica, characterized in that the method includes the following steps: (1) Measure ammonia water and anhydrous ethanol, stir at 30-40℃ for 10-40 minutes to obtain solution A; in, The volume ratio of ammonia to anhydrous ethanol is 1:3~8; (2) Add tetraethyl orthosilicate dropwise to solution A and stir in a water bath at 30~80℃ for 2~4 hours to obtain solution B; (3) Weigh out resorcinol, formaldehyde and anhydrous sodium carbonate respectively, add them to solution B, and continue stirring in a water bath at 30~80℃ for 18-24 hours to obtain suspension C; (4) Filter the suspension C, wash and dry it, and then calcine it in air at 600~900℃ for 3~6h to obtain nano-silica D; (5) Add anhydrous methanol to nano-silica D, disperse it by ultrasonication, and then add silane coupling agent to obtain suspension E; (6) Stir the suspension E in an oil bath at 60~100℃ for 4~8 hours, and cool it to room temperature to obtain mixture F; (7) After filtering the mixture F and washing it, superhydrophobic nano-silica is obtained.

2. The method for preparing superhydrophobic nano-silica as described in claim 1, characterized in that: The ammonia mass fraction in step (1) is 20%~30%.

3. The method for preparing superhydrophobic nano-silica as described in claim 1, characterized in that: The volume ratio of tetraethyl orthosilicate in step (2) to ammonia in step (1) is 1:1~4.

4. The method for preparing superhydrophobic nano-silica as described in claim 1, characterized in that: The mass ratio of anhydrous sodium carbonate, resorcinol, and formaldehyde in step (3) is 1:4~16:2~8, and the mass ratio of resorcinol to tetraethyl orthosilicate in step (2) is 1:30~200.

5. The method for preparing superhydrophobic nano-silica as described in claim 1, characterized in that: In step (4), the washing step is to first wash with deionized water until pH=7, and then wash away the residual water with anhydrous ethanol.

6. The method for preparing superhydrophobic nano-silica as described in claim 1, characterized in that: In step (5), the silane coupling agent includes methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, aminopropyltrimethoxysilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, tetradecyltrimethoxysilane, and phenyltrimethoxysilane.

7. The method for preparing superhydrophobic nano-silica as described in claim 1, characterized in that: In step (5), the mass ratio of nano-silica, anhydrous methanol and silane coupling agent is 20~120:500~3000:

1.

8. The method for preparing superhydrophobic nano-silica as described in claim 1, characterized in that: In step (7), the washing process requires rinsing with deionized water first, and then replacing the residual water with anhydrous ethanol.

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