A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification

Abstract

The present application relates to the technical field of medical nano-silica, and specifically discloses a method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, comprising the following steps: (1) mixing sodium silicate with sulfuric acid for reaction, centrifugation and washing, and drying to obtain silicic acid powder; (2) subjecting the silicic acid powder obtained in step (1) to laser irradiation to obtain water vapor containing nano-silica; (3) subjecting the water vapor containing nano-silica obtained in step (2) to negative pressure vacuum dehydration, spraying a modified mixed solution, and curing the solution with ultraviolet light to obtain a finished product; the modified mixed solution is composed of the following raw materials in parts by weight: 5-10 parts of PDMS; 0.1-0.5 parts of a photosensitizer; 0.1-0.5 parts of a platinum catalyst; and 89-94.8 parts of a solvent. The present application can prepare hydrophobically modified nano-silica with high dispersibility and uniform particle size, and has low cost and low energy consumption, and has strong applicability in practical applications as a whole.

Description

Technical Field

[0001] The present application relates to the technical field of medical nano-silica, and more specifically, to a method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification. Background Art

[0002] Nanosilica is a material with unique properties and broad application prospects. Ranging in size from 1 to 100 nanometers, it is non-toxic, odorless, and non-polluting. It appears as an amorphous white powder with a spherical microstructure and exhibits flocculent and reticular quasi-granular structures. Silica has a variety of uses in the pharmaceutical field, primarily as a drug carrier, lubricant, glidant, excipient, anti-adhesive agent, adsorbent, and drug delivery vehicle.

[0003] The surface of silica usually has hydroxyl groups, which easily absorbs water and is hydrophilic. However, the hydrophilic surface of silica has high surface energy and is in a thermodynamically unstable state. Because the nanoparticles have strong van der Waals forces, they are very easy to aggregate into clumps, and subsequent dispersion requires additional treatment and is difficult to completely disperse. At the same time, the bonding between it and the organic matrix is ​​also poor, and it is easy to produce interfacial defects. Therefore, the above situation affects the application effect and stability of silica in medical materials.

[0004] To mitigate these negative effects, silica is typically dehydrated and treated to render its surface hydrophobic. This can improve or enhance the dispersibility of silica nanoparticles and their compatibility and binding with other substances. Hydrophobicity of nanosilica is often achieved through chemical methods, including sol-gel, hydrothermal, vapor phase, and precipitation methods.

[0005] Regarding the aforementioned technologies, the sol-gel method is time-consuming and prone to residual organic matter; the hydrothermal and vapor phase methods require high temperatures and pressures, are demanding on equipment, and consume a lot of energy; and the precipitation method often produces a large number of extremely fine and coarse particles, making it difficult to achieve a uniform particle size distribution. Therefore, a solution to these technical problems is urgently needed. Summary of the Invention

[0006] In order to prepare highly dispersible and uniformly sized hydrophobically modified nano-silica, the present application provides a method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification.

[0007] This application provides a method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which adopts the following technical solution:

[0008] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification comprises the following steps:

[0009] (1) Sodium silicate and sulfuric acid are mixed and reacted, and then centrifuged, washed, and dried to obtain silicic acid powder;

[0010] (2) irradiating the silicic acid powder obtained in step (1) with laser to obtain water vapor containing nano-silicon dioxide;

[0011] (3) After dehydrating the water vapor containing nano-silicon dioxide obtained in step (2) under negative pressure, spraying the modified mixed liquid, and curing it with ultraviolet light to obtain a finished product;

[0012] The modified mixed solution is composed of the following raw materials in parts by weight:

[0013] PDMS 5-10 parts;

[0014] Photosensitizer 0.1-0.5 parts;

[0015] 0.1-0.5 parts of platinum catalyst;

[0016] 89-94.8 parts of solvent.

[0017] By adopting the above technical solution, an excess amount of sulfuric acid is used in step (1) to ensure that the sodium silicate is fully reacted, and then the excess residual sulfuric acid is removed by washing to obtain silicic acid powder; then, in the laser irradiation treatment in step (2), the silicic acid is instantaneously dehydrated to generate nano-silicon dioxide; finally, in step (3), negative pressure vacuum dehydration is first performed to avoid secondary agglomeration of the particles, and then the modified mixed liquid is sprayed, and after ultraviolet light curing, hydrophobically modified nano-silicon dioxide with uniform particle size and stable shape is obtained. The main components of the modified mixture are PDMS, a photosensitizer, and a platinum catalyst. PDMS reacts chemically with the hydroxyl groups on the silica surface to form a covering layer of organic molecules. This covering layer can significantly change the surface properties of the silica, giving the modified silica excellent dispersibility, hydrophobicity, and stability. The photosensitizer, through its optical properties, can promote the grafting of hydrophobic groups during the UV curing process and enhance the chemical bond strength between PDMS and the silica surface. The platinum catalyst can accelerate the condensation reaction between PDMS and the hydroxyl groups on the silica surface to form a stable siloxane bond, thereby fixing the hydrophobic groups and achieving efficient grafting of the hydrophobic groups. Therefore, the modified mixture with PDMS, a photosensitizer, and a platinum catalyst as the main components can ensure the excellent modification effect during application. Based on the mutual coordination between the various steps, it can prepare highly dispersible and uniformly sized hydrophobically modified nano-silica. At the same time, the raw material cost used in the above preparation method is low, the energy consumption in the process is also low, and the overall applicability is strong in practical application.

[0018] Preferably, the modified mixed solution is composed of the following raw materials in parts by weight:

[0019] PDMS 8 parts;

[0020] 0.3 parts of photosensitizer;

[0021] 0.3 parts of platinum catalyst;

[0022] 91.4 parts of solvent.

[0023] By adopting the above technical solution, when the above raw materials in parts by weight are mixed and used as a modified mixed liquid, the corresponding effects exerted by mutual cooperation are relatively excellent, which can ensure that high-quality laser-dehydrated and in-situ hydrophobically modified nano-silica is finally obtained.

[0024] Preferably, in step (2), the energy density of laser irradiation is 10-15 J / cm 2 .

[0025] By adopting the above technical solution, when the energy density of laser irradiation is low, it may lead to uneven heat distribution, causing microstress in local areas due to thermal expansion differences, and unable to effectively remove surface defects, resulting in high surface roughness. When the energy density of laser irradiation is high, it may induce thermal stress, leading to cracks or uneven nanostructures. All of the above will ultimately cause the modified silica to perform poorly in terms of dispersibility and particle size uniformity. Laser irradiation within the above energy density range can ensure the stability of nano-silica during the production process, and can ultimately obtain highly dispersible and uniformly sized hydrophobically modified nano-silica.

[0026] Preferably, in step (3), the wavelength of the ultraviolet light source is 320-400 nm, and the energy density is 5-25 mW / cm 2 , time is 10-15 minutes.

[0027] By adopting the above technical solution, the wavelength of the ultraviolet light source in the above range can ensure efficient initiation of free radical polymerization reaction and promote the grafting of the hydrophobic modifier on the surface of silica. Too low energy density will lead to a low reaction rate of silica surface modification, showing poor uniformity of the coating layer; too high energy density will easily lead to agglomeration of silica particles and produce structural unevenness due to local overheating; therefore, the selection of the above energy density range can enable a uniform reaction between the modified mixed liquid and silica particles, and the binding is excellent and stable. The selection of the above time can achieve a relatively balanced reaction efficiency and structural stability. In the ultraviolet curing treatment of step (3), the selection and combination of the above operating parameters can ultimately obtain highly dispersed and uniformly sized hydrophobically modified nano-silica.

[0028] Preferably, in step (3), the weight ratio of the modified mixed solution to the nano-silica is 1:(1.8-2.2).

[0029] By adopting the above technical solution and selecting and coordinating the amounts of the above raw materials, a uniform and stable hydrophobic structure can be formed on the surface of the nano-silica, and ultimately the nano-silica obtained by laser dehydration and in-situ hydrophobic modification has better performance in high dispersibility and uniform particle size.

[0030] Preferably, the operation of step (2) is carried out in container one, and the operation of step (3) is carried out in container two; the container one is in the shape of an inverted triangle, with a laser generator provided on the top, and the container two is provided with a vacuum negative pressure device, an ultraviolet light device and a spray device, and both container one and container two are also provided with a stirring device and are connected by an airtight valve.

[0031] By adopting the above technical solution, silicic acid is prepared by precipitation method using sodium silicate and sulfuric acid with lower cost as main raw materials, and the excess sulfuric acid and sodium salt are washed off, and the silicic acid powder is obtained by drying and placed in container one; the inverted triangle shape of container one is to allow the powder to naturally accumulate downwards, and the laser generator on the top allows the silicic acid to be rapidly dehydrated to generate nano-silicon dioxide and float up with the steam, and then the airtight valve is opened, and the vacuum negative pressure device in container two is used for synchronous suction, at which time the steam and nano-silicon dioxide mixed floating matter enters container two, which can avoid secondary agglomeration of particles; after the silicic acid powder in container one is completely decomposed, the airtight valve is closed, and the water in it is completely removed by the vacuum negative pressure device in container two, and then the modified mixed liquid is sprayed by the spray device, and the ultraviolet light device is turned on to allow the modified mixed liquid to react completely with the nano-silicon dioxide, and finally highly dispersed and uniform particle size hydrophobically modified nano-silicon dioxide is obtained. Through the coordination between container one and container two, the method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification can achieve continuous preparation in practical applications, making the overall application more convenient and efficient.

[0032] Preferably, the temperature in the container is 80-100° C., and the stirring speed is 500-1000 rpm.

[0033] Preferably, the temperature in the second container is 50-70° C., and the stirring speed is 3000-5000 rpm.

[0034] By adopting the above technical solution, in container one and container two, the selection and combination of the above temperature and stirring speed enable the various material components in the containers to fully play their role in the entire preparation process, ensuring that the highly dispersed, uniform particle size hydrophobically modified nano-silica is obtained with stable and excellent quality.

[0035] Preferably, 1-3 parts by weight of a modification aid is further added to the modified mixed solution, wherein the modification aid consists of cage-type polysilsesquioxane and hexamethyldisilazane, and the weight ratio of cage-type polysilsesquioxane to hexamethyldisilazane is 1:(1.2-1.8).

[0036] By adopting the above technical solution, the cage-type polysilsesquioxane has a nano-cage structure and is an organic-inorganic hybrid material. It can be embedded in the silica matrix through its own structure, and cooperate with the covering layer on the surface of the nano-silica to form a micron-nanoscale rough structure, which not only improves the hydrophobicity, but also improves the high dispersibility and particle size uniformity to a certain extent; hexamethyldisilazane can react with the hydroxyl groups on the surface of silica, significantly reducing the number of hydrophilic groups on the surface of nano-silica, reducing the polarity of the silica surface, reducing particle agglomeration, and enhancing the corresponding effect brought by the modified mixed solution; and when the cage-type polysilsesquioxane and hexamethyldisilazane are used as a modification auxiliary agent, the two can exert an excellent composite synergistic effect on each other, can form an intertwined molecular chain structure on the surface of nano-silica, and then bring structural optimization to the covering layer formed by the modified mixed solution, so that the dispersibility and particle size uniformity of the nano-silica dehydrated and in-situ hydrophobically modified nano-silica are significantly improved.

[0037] Preferably, the weight ratio of the cage-type polysilsesquioxane to hexamethyldisilazane is 1:1.5.

[0038] By adopting the above technical solution, when the cage-type polysilsesquioxane and hexamethyldisilazane in the above weight ratio are used in combination, the corresponding effects exerted by each other are relatively excellent, and the enhancement effect brought about by the application of the modified mixed liquid is more significant, thereby obtaining better quality laser dehydrated and in-situ hydrophobically modified nano-silica.

[0039] In summary, this application has the following beneficial effects:

[0040] 1. This application uses relatively low-cost sodium silicate and sulfuric acid as main raw materials, prepares silicic acid by precipitation method, washes off excess sulfuric acid and sodium salt, and dries to obtain silicic acid powder; then the silicic acid powder is treated with laser irradiation to achieve instantaneous dehydration of the silicic acid to produce nano-silica; finally, it is subjected to negative pressure vacuum dehydration, spraying of a modified mixture containing PDMS, a photosensitizer, and a platinum catalyst as main components, and ultraviolet light curing to finally obtain highly dispersible, uniformly sized hydrophobically modified nano-silica. The entire preparation process has low raw material costs, low energy consumption during the preparation process, and outstanding practical applicability;

[0041] 2. In the present application, a modification aid consisting of cage-type polysilsesquioxane and hexamethyldisilazane is added to the modified mixed liquid. By compounding cage-type polysilsesquioxane and hexamethyldisilazane, the covering layer on the surface of the nano-silica has a lower surface energy structure and a more uniform and stable structure, thereby obtaining better quality laser-dehydrated and in-situ hydrophobically modified nano-silica. DETAILED DESCRIPTION

[0042] The present application is further described in detail below with reference to the following examples and comparative examples.

[0043] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0044] PDMS was purchased from Dow Corning DC184;

[0045] The photosensitizer is 9,10-diethoxyanthracene;

[0046] Platinum catalyst was purchased from Shandong Huachen New Materials Co., Ltd.;

[0047] The solvent is toluene;

[0048] Cage polysilsesquioxane was purchased from Shanghai Huiyan New Materials Co., Ltd. HY-P302;

[0049] Hexamethyldisilazane was purchased from Kobler Y03.

[0050] Example

[0051] Example 1

[0052] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification comprises the following steps:

[0053] (1) Sodium silicate and sulfuric acid are mixed and reacted, and then centrifuged, washed, and dried to obtain silicic acid powder;

[0054] (2) irradiating the silicic acid powder obtained in step (1) with laser to obtain water vapor containing nano-silicon dioxide;

[0055] (3) After the water vapor containing nano-silicon dioxide obtained in step (2) is vacuum-dehydrated under negative pressure, the modified mixed liquid is sprayed on the mixed liquid, and the mixed liquid is cured by ultraviolet light to obtain a finished product.

[0056] Note: The raw materials and their corresponding weight parts of the modified mixed solution used in the above steps are shown in Table 1. In step (2), the energy density of laser irradiation is 12.5 J / cm 2 , wavelength 1064 nm. In step (3), the vacuum degree of negative pressure vacuum dehydration is 0.08 MPa; the wavelength of the ultraviolet light source is 360 nm, and the energy density is 15 mW / cm 2 , time is 12.5min; the weight ratio of the modified mixed liquid to nano-silica is 1:2.

[0057] The operation of step (2) is carried out in container one, and the operation of step (3) is carried out in container two; container one is in the shape of an inverted triangle, with a laser generator provided on the top, and container two is provided with a vacuum negative pressure device, an ultraviolet light device and a spray device, and both container one and container two are also provided with a stirring device and are connected by an airtight valve.

[0058] During the application process: the silicic acid powder obtained in step one is placed in container one; the laser generator on the top of container one allows the silicic acid to quickly dehydrate to generate nano-silicon dioxide and float up with the steam, then the airtight valve is opened, and the vacuum negative pressure device in container two is synchronously operated to achieve suction, at which time the steam and nano-silicon dioxide mixed floating matter enters container two; after the silicic acid powder in container one is completely decomposed, the airtight valve is closed, and the water in it is completely removed using the vacuum negative pressure device in container two, and then the modified mixed liquid is sprayed through the spray device, and the ultraviolet light device is turned on to allow the modified mixed liquid to react completely with the nano-silicon dioxide.

[0059] The temperature in container 1 was 90°C and the stirring speed was 750 rpm.

[0060] The temperature in the second container was 60° C., and the stirring speed was 4000 rpm.

[0061] Examples 2-4

[0062] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification is different from Example 1 in that the raw materials of the modified mixed solution and their corresponding weight parts are shown in Table 1.

[0063] Table 1 Raw materials of modified mixed solutions of Examples 1-4 and their corresponding weight parts (parts / kg)

[0064]

[0065] Example 5

[0066] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which is different from Example 1 in that in step (2), the energy density of laser irradiation is 10 J / cm 2 .

[0067] Example 6

[0068] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which is different from Example 1 in that in step (2), the energy density of laser irradiation is 15 J / cm 2 .

[0069] Example 7

[0070] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which is different from Example 1 in that, in step (3), the wavelength of the ultraviolet light source is 320 nm and the energy density is 5 mW / cm 2 , time is 15 minutes.

[0071] Example 8

[0072] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which is different from Example 1 in that, in step (3), the wavelength of the ultraviolet light source is 400 nm and the energy density is 25 mW / cm 2 , time is 10 minutes.

[0073] Example 9

[0074] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification is different from Example 1 in that, in step (3), the weight ratio of the modified mixed solution to the nano-silica is 1:1.8.

[0075] Example 10

[0076] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification is different from Example 1 in that, in step (3), the weight ratio of the modified mixed solution to the nano-silica is 1:2.2.

[0077] Example 11

[0078] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification is different from Example 1 in that the temperature in container 1 is 80° C. and the stirring speed is 1000 rpm.

[0079] Example 12

[0080] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification is different from Example 1 in that the temperature in container 1 is 100° C. and the stirring speed is 500 rpm.

[0081] Example 13

[0082] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification is different from Example 1 in that the temperature in the second container is 50° C. and the stirring speed is 5000 rpm.

[0083] Example 14

[0084] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification is different from Example 1 in that the temperature in the second container is 70° C. and the stirring speed is 3000 rpm.

[0085] Example 15

[0086] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which differs from Example 1 in that 1-3 parts by weight of a modification aid is further added to the modified mixed liquid, and the modification aid is composed of cage-type polysilsesquioxane and hexamethyldisilazane in a weight ratio of 1:1.5.

[0087] Example 16

[0088] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which differs from Example 15 in that the weight portion of the modified auxiliary agent added is 1-3 parts.

[0089] Example 17

[0090] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which differs from Example 15 in that the weight portion of the modified auxiliary agent added is 1-3 parts.

[0091] Example 18

[0092] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which differs from Example 15 in that the modification aid consists of cage-type polysilsesquioxane and hexamethyldisilazane in a weight ratio of 1:1.2.

[0093] Example 19

[0094] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which differs from Example 15 in that the modification aid consists of cage-type polysilsesquioxane and hexamethyldisilazane in a weight ratio of 1:1.8.

[0095] Example 20

[0096] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which differs from Example 15 in that cage-type polysilsesquioxane is not used in the modified mixed solution.

[0097] Example 21

[0098] A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, which differs from Example 15 in that hexamethyldisilazane is not used in the modified mixed solution.

[0099] Performance testing

[0100] Test sample: The laser dehydration and in-situ hydrophobic modified nano-silica preparation method of Example 1-21 was applied to obtain hydrophobic modified nano-silica, which is Test Sample 1-21.

[0101] Test method: (1) D50 value test: the particle size distribution of silica particles is measured by a laser particle size distribution analyzer to determine the D50 value, accurate to 0.5; the D50 value can be used to understand the degree of particle size dispersion in the hydrophobically modified nano-silica particle population.

[0102] (2) Contact angle test: The water drop method is used to test the contact angle value using the HE-CA200 water drop contact angle meter. The smaller the contact angle, the greater the adhesion of the liquid on the solid surface, and the more hydrophilic the surface; conversely, the larger the contact angle, the smaller the adhesion of the liquid on the solid surface, and the more hydrophobic the surface.

[0103] (3) PDI test: The PDI value of silica refers to the polydispersity index of its particle size distribution, which is used to characterize the uniformity of particle distribution. The PDI value range is between 0 and 1, where PDI = 0 indicates complete monodispersity, that is, the size of all particles is exactly the same; PDI < 0.1 indicates that the particle size is relatively uniform; PDI > 0.5 indicates that the particle size distribution is wide and there is a large polydispersity.

[0104] After performing the above tests on test samples 1-21, the test results are recorded in Table 2.

[0105] Table 2 Test results of test samples 1-21

[0106]

[0107] From Example 1 and Example 2-4 and Table 2, it can be seen that the present application uses relatively low-cost sodium silicate and sulfuric acid as the main raw materials, prepares silicic acid by precipitation method, washes off the excess sulfuric acid and sodium salt, and dries to obtain silicic acid powder; then the silicic acid powder is treated with laser irradiation to achieve instantaneous dehydration of silicic acid to generate nano-silica; finally, it is subjected to negative pressure vacuum dehydration, spraying of a modified mixture with PDMS, photosensitizer and platinum catalyst as the main components, and ultraviolet light curing to finally obtain hydrophobically modified nano-silica. After the above tests, the laser dehydrated and in-situ hydrophobically modified nano-silica prepared in the present application has a smaller D50 value, a larger contact angle value, and a smaller PDI value, indicating that its particle size is smaller and it performs outstandingly well in terms of hydrophobicity, dispersibility and particle size uniformity. Among them,

[0108] Combining Example 1 with Examples 5-6 and Table 2, it can be seen that the energy density of laser irradiation is 10-15 J / cm 2 , which can ensure the stability of nano-silica during the generation process and ultimately obtain highly dispersible and uniformly sized hydrophobically modified nano-silica.

[0109] Combining Example 1 with Examples 7-8 and Table 2, it can be seen that the wavelength of the ultraviolet light source is 320-400 nm, and the energy density is 5-25 mW / cm 2, the time is 10-15 minutes, which can make the modified mixed liquid and the silica particles react evenly and obtain a relatively balanced reaction efficiency and structural stability, so that the obtained laser dehydrated and in-situ hydrophobically modified nano-silica has relatively stable D50 value, contact angle value and PDI value after the above test.

[0110] Combining Example 1 and Examples 9-10 with Table 2, it can be seen that when the weight ratio of the modified mixed liquid to the nano-silica is 1:(1.8-2.2) for use, laser-dehydrated and in-situ hydrophobically modified nano-silica with excellent quality and stability can be obtained.

[0111] Combining Example 1 and Examples 11-14 with Table 2, it can be seen that the temperature in container 1 is 80-100°C, the stirring speed is 500-1000 rpm, and the temperature in container 2 is 50-70°C, and the stirring speed is 3000-5000 rpm, which enables the various material components in the containers to fully play their role in the entire preparation process, thereby obtaining corresponding high-quality and stable laser-dehydrated and in-situ hydrophobically modified nano-silica.

[0112] In combination with Example 1 and Examples 15-19 and Table 2, it can be seen that the addition of a modification aid consisting of a cage polysilsesquioxane and hexamethyldisilazane to the modified mixture can further reduce the D50 value, indicating that the particle size becomes smaller; the contact angle increases, indicating that the hydrophobicity and dispersibility are improved; the PDI becomes smaller, indicating that the particle size uniformity is better; and in combination with Examples 20-21 and Table 2, it can be seen that if any one of the cage polysilsesquioxane and hexamethyldisilazane is used alone, although it can bring about an improvement in the corresponding effect, the improvement effect is extremely limited, and the sum of the improvement effects brought by the addition of each of the two is far less than the excellent combination of the two. It can be seen that the combination of cage polysilsesquioxane and hexamethyldisilazane can bring a significant improvement effect of 1+1>2, thereby obtaining better quality laser dehydration and in-situ hydrophobic modified nanosilica.

[0113] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification, characterized in that: The following steps are involved: (1) Sodium silicate and sulfuric acid are mixed and reacted, and then centrifuged, washed, and dried to obtain silicic acid powder; (2) irradiating the silicic acid powder obtained in step (1) with laser to obtain water vapor containing nano-silicon dioxide; (3) After dehydrating the water vapor containing nano-silicon dioxide obtained in step (2) under negative pressure, spraying the modified mixed liquid, and curing it with ultraviolet light to obtain a finished product; The modified mixed solution is composed of the following raw materials in parts by weight: PDMS 5-10 parts; Photosensitizer 0.1-0.5 parts; 0.1-0.5 parts of platinum catalyst; 89-94.8 parts of solvent.

2. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 1, characterized in that: The modified mixed solution is composed of the following raw materials in parts by weight: PDMS 8 parts; 0.3 parts of photosensitizer; 0.3 parts of platinum catalyst; 91.4 parts of solvent.

3. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 1, characterized in that: In step (2), the energy density of laser irradiation is 10-15 J / cm 2 .

4. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 1, characterized in that: In step (3), the wavelength of the ultraviolet light source is 320-400 nm, and the energy density is 5-25 mW / cm 2 , time is 10-15 minutes.

5. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 1, characterized in that: In step (3), the weight ratio of the modified mixed solution to the nano-silica is 1:(1.8-2.2).

6. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 1, characterized in that: The operation of step (2) is carried out in container one, and the operation of step (3) is carried out in container two; the container one is in the shape of an inverted triangle, and a laser generator is provided on the top; the container two is provided with a vacuum negative pressure device, an ultraviolet light device and a spray device, and both container one and container two are also provided with a stirring device and are connected by an airtight valve.

7. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 6, characterized in that: The temperature in the container is 80-100° C., and the stirring speed is 500-1000 rpm.

8. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 6, characterized in that: The temperature in the second container is 50-70° C., and the stirring speed is 3000-5000 rpm.

9. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 1, characterized in that: The modified mixed liquid is further added with 1-3 parts by weight of a modification aid, wherein the modification aid is composed of cage-type polysilsesquioxane and hexamethyldisilazane, and the weight ratio of cage-type polysilsesquioxane to hexamethyldisilazane is 1:(1.2-1.8).

10. The method for preparing nano-silica by laser dehydration and in-situ hydrophobic modification according to claim 9, characterized in that: The weight ratio of the cage-type polysilsesquioxane to hexamethyldisilazane is 1:1.5.

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