Large-particle-size silicon dioxide microspheres and preparation method thereof

Abstract

The invention relates to the technical field of microsphere preparation, in particular to a large-particle-size silicon dioxide microsphere and a preparation method thereof.The preparation method comprises the steps that hydroxyl-containing silane and polyisocyanate are mixed, and isocyanate modified silane is obtained after first reaction; mixing the isocyanate modified silane with aminopropyl triethoxy silane, and carrying out a second reaction, so as to obtain high-molecular triethoxy silane; the preparation method comprises the following steps: mixing high-molecular triethoxysilane, alkoxy-containing silane, a catalyst and a solvent, and carrying out hydrolysis reaction to obtain the large-particle-size silicon dioxide microspheres. Silicon dioxide is prepared through co-hydrolysis of high-molecular-weight silane and alkoxy-containing silane, the particle size of prepared silicon dioxide particles can be effectively increased by adding high-molecular-weight triethoxysilane, and silicon dioxide microspheres with uniform particle size and different particle sizes can be prepared by controlling the molecular weight of the high-molecular-weight triethoxysilane. The application requirements of different fields on the silicon dioxide microspheres with different particle sizes are met.

Description

Technical Field

[0001] The present invention relates to the technical field of microsphere preparation, and particularly to a large-sized silica microsphere and a preparation method thereof. Background Art

[0002] Due to their unique physical and chemical properties, silica microspheres have a wide range of applications in various fields; they can be used as reinforcing materials, catalysts, adsorbents, etc., and play an important role in industries such as electronics, chemical engineering, medicine, and energy. For example, in the electronics field, silica microspheres can be used to manufacture high-performance capacitors and semiconductor devices; in the chemical engineering field, they can be used as catalysts or adsorbents to improve reaction efficiency and selectivity; in the medical field, they can be used to prepare targeted drugs and biosensors; these applications demonstrate the versatility and potential commercial value of silica microspheres.

[0003] The existing preparation of silica microspheres usually uses the sol-gel method, mainly because this method can efficiently and uniformly generate silica particles; however, the sol-gel method faces certain challenges in preparing large-sized silica microspheres at the micron level, mainly due to its reaction mechanism and process control. First of all, the sol-gel method usually generates silica gel particles through the hydrolysis and condensation of small molecule silicon source substances such as tetraethoxysilane in aqueous solution. These sol particles are relatively small themselves. As the particles grow, their surface tension and electrostatic repulsion will limit the further aggregation and growth between particles, resulting in difficulty in forming larger-sized microspheres; secondly, while the particles are growing, new particles may form in the solution, further dispersing the growth resources and hindering the continuous expansion of the existing particles. Therefore, although the sol-gel method can effectively prepare silica microspheres from nanometers to microns, to prepare uniform large-sized (micron-level) microspheres, technical difficulties and challenges still need to be overcome.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above deficiencies of the existing technology, the purpose of the present invention is to provide a large-sized silica microsphere and a preparation method thereof, aiming to solve the problem that the existing preparation process cannot prepare large-sized microspheres with uniform size.

[0006] The technical solution of the present invention is as follows:

[0007] A preparation method of a large-sized silica microsphere, comprising the steps of:

[0008] Mix a silane containing hydroxyl groups with a polyisocyanate, and after a first reaction, obtain an isocyanate-modified silane;

[0009] Mix the isocyanate-modified silane with aminopropyltriethoxysilane, and after a second reaction, a high-molecular-weight triethoxysilane is obtained.

[0010] Mix the high-molecular-weight triethoxysilane, the silane containing an alkoxy group, a catalyst, and a solvent, and through a hydrolysis reaction, large-particle-size silica microspheres are obtained.

[0011] The method for preparing the large-particle-size silica microspheres, wherein the hydroxyl group in the silane containing a hydroxyl group is located at one end, both ends, or the middle of the silane molecular chain.

[0012] The method for preparing the large-particle-size silica microspheres, wherein the molecular weight of the silane containing a hydroxyl group is 100 - 3000; the general structural formula of the silane containing a hydroxyl group is:

[0013]

[0014] wherein, R1, R2, and R3 are independently selected from and at least one of R1, R2, and R3 is m is 0 - 10, and n is 1 - 1000.

[0015] The method for preparing the large-particle-size silica microspheres, wherein the polyisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, diphenylmethane diisocyanate trimer, hexamethylene diisocyanate trimer, and isophorone diisocyanate trimer.

[0016] The method for preparing the large-particle-size silica microspheres, wherein the mass ratio of the silane containing a hydroxyl group to the polyisocyanate is 100:(10 - 80); and / or, the temperature of the first reaction is 40°C - 100°C, and the time of the first reaction is 1 h - 10 h.

[0017] The method for preparing the large-particle-size silica microspheres, wherein the mass ratio of the isocyanate-modified silane to the aminopropyltriethoxysilane is 100:(1 - 40); and / or, the temperature of the second reaction is 20°C - 80°C, and the time of the second reaction is 1 h - 4 h.

[0018] The method for preparing the large-particle-size silica microspheres, wherein the silane containing an alkoxy group is selected from one or more of tetraethoxysilane, tetramethoxysilane, diethoxydimethoxysilane, triethoxysilane, and vinyltriethoxysilane; and / or, the catalyst is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, sodium hydroxide, potassium hydroxide, ammonia water, and triethylamine.

[0019] The preparation method of the large-sized silica microspheres, wherein the mass ratio of the polymer triethoxysilane, the silane containing alkoxy groups, and the catalyst is 100:(1-100):(1-25); and / or, the temperature of the hydrolysis reaction is 20°C - 80°C, and the time of the hydrolysis reaction is 1h - 24h.

[0020] A kind of large-sized silica microspheres, which are prepared by using the preparation method of the large-sized silica microspheres.

[0021] The described large-sized silica microspheres, wherein the particle size of the large-sized silica microspheres is 100nm - 20μm.

[0022] Beneficial effects: The present invention provides a kind of large-sized silica microspheres and its preparation method. The preparation method of the large-sized silica microspheres includes the steps: mixing a silane containing hydroxyl groups with a polyisocyanate, and after the first reaction, obtaining an isocyanate-modified silane; mixing the isocyanate-modified silane with aminopropyltriethoxysilane, and after the second reaction, obtaining a polymer triethoxysilane; mixing the polymer triethoxysilane, a silane containing alkoxy groups, a catalyst, and a solvent, and through a hydrolysis reaction, obtaining large-sized silica microspheres. The present invention prepares silica by the co-hydrolysis of a high-molecular-weight silane and a silane containing alkoxy groups. The addition of the polymer triethoxysilane can effectively increase the particle size of the prepared silica particles. By controlling the molecular weight of the polymer triethoxysilane, silica microspheres with different particle sizes can be prepared, so as to meet the application requirements of different particle sizes of silica microspheres in different fields. Moreover, the silica microspheres prepared by using this preparation method have uniform particle size, high purity, and the particle size can reach the micron level, meeting the requirements of large-sized silica microspheres. Description of the Drawings

[0023] Figure 1 It is a process flow schematic diagram of a preparation method of a kind of large-sized silica microspheres of the present invention;

[0024] Figure 2 It is a schematic diagram of the preparation equation of one kind of polymer triethoxysilane. Detailed Embodiments

[0025] The present invention provides a kind of large-sized silica microspheres and its preparation method. To make the purpose, technical solution and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention pertains. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with their meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as herein.

[0027] The sol-gel method generates silanols by controlling the hydrolysis and condensation process of silane precursor substances such as tetraethoxysilane in water, and then further aggregates to form silica sol particles. As the reaction progresses, these sol particles gradually aggregate and coagulate to form silica microspheres with high dispersibility and stability. The advantage of this method is that its preparation conditions are relatively mild, and it is easy to control the reaction parameters to adjust the particle size, morphology, and pore structure of the product; however, the sol-gel method cannot prepare uniform large-sized (micrometer-level) microspheres.

[0028] Based on this, as Figure 1 shown, the present invention provides a method for preparing large-sized silica microspheres, including the steps:

[0029] Step S10: Mix a silane containing hydroxyl groups with a polyisocyanate, and after a first reaction, obtain an isocyanate-modified silane;

[0030] Step S20: Mix the isocyanate-modified silane with aminopropyltriethoxysilane, and after a second reaction, obtain a high-molecular-weight triethoxysilane;

[0031] Step S30: Mix the high-molecular-weight triethoxysilane, a silane containing an alkoxy group, a catalyst, and a solvent, and through a hydrolysis reaction, obtain large-sized silica microspheres.

[0032] In the present embodiment, silica is prepared by the co-hydrolysis of a high-molecular-weight silane and a silane containing an alkoxy group. The addition of the high-molecular-weight triethoxysilane can effectively increase the particle size of the prepared silica particles. By controlling the molecular weight of the high-molecular-weight triethoxysilane, silica microspheres with different particle sizes can be prepared, so as to meet the application requirements of different particle sizes of silica microspheres in different fields. Moreover, the silica microspheres prepared by this preparation method have uniform particle size, high purity, and the particle size can reach the micrometer level, meeting the requirements of large-sized silica microspheres.

[0033] Specifically, the present invention utilizes a polymeric triethoxysilane and a traditional small-molecule silane precursor (i.e., an alkoxy-containing silane) to jointly participate in the hydrolysis reaction. By providing a stable skeletal structure through the polymeric triethoxysilane, the electrostatic and gravitational forces between particles are reduced, and the aggregation rate and degree of particles are slowed down. At the same time, the alkoxy-containing silane provides an additional silicon source, promoting the growth of microspheres. By selecting polymeric triethoxysilanes with different molecular weights and precisely controlling parameters such as the ratio of the two silicon sources, reaction temperature, pH value, and hydrolysis time, fine regulation of the microsphere particle size can be achieved. Through the mixed hydrolysis strategy, the present invention can not only effectively control the growth of microspheres but also contribute to the formation of more uniform and larger silica microspheres, opening up a new way for preparing silica microspheres with specific sizes and properties.

[0034] In some embodiments, the hydroxyl group in the hydroxyl-containing silane is located at one end, both ends, or the middle of the silane molecular chain. After mixing and reacting the hydroxyl-containing silane with a polyisocyanate, an isocyanate-modified silane can be obtained, and the hydroxyl group in the hydroxyl-containing silane can be at one end, both ends, or the middle of the silane molecular chain, and isocyanate modification can be achieved in all cases.

[0035] In some embodiments, the molecular weight of the hydroxyl-containing silane is 100 - 3000; the general structural formula of the hydroxyl-containing silane is:

[0036]

[0037] wherein, R1, R2, and R3 are independently selected from and at least one of R1, R2, and R3 is m is 0 - 10, and n is 1 - 1000.

[0038] Using the hydroxyl-containing silane with this molecular weight as a raw material to prepare an isocyanate-modified silane can effectively regulate the molecular weight of the subsequent prepared polymeric triethoxysilane. By selecting polymeric triethoxysilanes with different molecular weights and precisely controlling parameters such as the ratio of the polymeric triethoxysilane to the alkoxy-containing silane, reaction temperature, pH value, and reaction time, fine regulation of the microsphere particle size can be achieved, aiming to prepare silica microspheres with specific sizes.

[0039] In one embodiment, taking the hydroxyl-containing silane as and the polyisocyanate as as an example, the preparation equation of the polymeric triethoxysilane is as Figure 2 shown.

[0040] In some embodiments, the polyisocyanate is selected from one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate (H12MDI), diphenylmethane diisocyanate trimer, hexamethylene diisocyanate trimer, and isophorone diisocyanate trimer. After mixing the above polyisocyanate with the hydroxyl group-containing silane, the hydroxyl group-containing silane can be modified to obtain an isocyanate-modified silane.

[0041] In some embodiments, the mass ratio of the hydroxyl group-containing silane to the polyisocyanate is 100:(10 - 80); by controlling the mass ratio between the hydroxyl group-containing silane and the polyisocyanate within the above range, the reaction efficiency can be improved, an isocyanate-modified silane with higher purity can be obtained, and waste of raw materials can be avoided.

[0042] In some embodiments, the temperature of the first reaction is 40°C - 100°C, and the time of the first reaction is 1h - 10h; the reaction conditions are mild and the reaction efficiency is relatively high.

[0043] In a preferred embodiment, the temperature of the first reaction is 70°C, and the time of the first reaction is 4h.

[0044] In some embodiments, the mass ratio of the isocyanate-modified silane to the aminopropyltriethoxysilane is 100:(1 - 40); by controlling the mass ratio between the isocyanate-modified silane and the aminopropyltriethoxysilane, the molecular weight of the polymer triethoxysilane can be controlled, and under this mass ratio, the reactants can react completely, avoiding waste of the reactants.

[0045] In some embodiments, the temperature of the second reaction is 20°C - 80°C, and the time of the second reaction is 1h - 4h; the reaction conditions are mild and the reaction efficiency is relatively high.

[0046] In a preferred embodiment, the temperature of the second reaction is 50°C, and the time of the second reaction is 2h.

[0047] In some embodiments, the alkoxy group-containing silane is selected from one or more of tetraethoxysilane, tetramethoxysilane, diethoxydimethoxysilane, triethoxysilane, and vinyltriethoxysilane; by using these small molecule silane precursors to participate in the hydrolysis reaction together with the polymer triethoxysilane, a stable framework structure provided by the polymer triethoxysilane can reduce the electrostatic and gravitational forces between particles, slow down the aggregation rate and degree of particles, and at the same time, an additional silicon source provided by the small molecule silane precursors can promote the growth of microspheres.

[0048] In some embodiments, the catalyst can be an acidic catalyst or a basic catalyst; specifically, the catalyst is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, sodium hydroxide, potassium hydroxide, ammonia water, and triethylamine. Under this catalyst, the high molecular weight triethoxysilane and the silane containing alkoxy groups jointly participate in the hydrolysis reaction to obtain silica microspheres with large particle sizes.

[0049] In some embodiments, the mass ratio of the high molecular weight triethoxysilane, the silane containing alkoxy groups to the catalyst is 100:(1 - 100):(1 - 25); at this mass ratio, the reaction efficiency can be improved, and by controlling the mass ratio between the high molecular weight triethoxysilane and the silane containing alkoxy groups, fine regulation of the particle size of the microspheres can be achieved.

[0050] In some embodiments, the temperature of the hydrolysis reaction is 20°C - 80°C, and the time of the hydrolysis reaction is 1h - 24h; under these hydrolysis reaction conditions, combined with the control of the molecular weight of the high molecular weight triethoxysilane, silica microspheres with different particle sizes can be prepared.

[0051] In a preferred embodiment, the temperature of the hydrolysis reaction is 40°C, and the time of the hydrolysis reaction is 20h.

[0052] In some embodiments, in step S30, the solvent is a mixture of ethanol and water; it can provide a liquid condition for the reaction and can effectively disperse the reactants, improving the reaction efficiency.

[0053] In some embodiments, the mass ratio of the ethanol to the water is (1 - 200):(1 - 50).

[0054] In addition, the present invention also provides a large particle size silica microsphere, which is prepared by using the preparation method of the large particle size silica microsphere.

[0055] In this embodiment, silica is prepared by co-hydrolysis of a high molecular weight silane and a silane containing alkoxy groups. The addition of the high molecular weight triethoxysilane can effectively increase the particle size of the prepared silica particles. By controlling the molecular weight of the high molecular weight triethoxysilane, silica microspheres with different particle sizes can be prepared, so as to meet the application requirements of different fields for silica microspheres with different particle sizes. Moreover, the silica microspheres prepared by this preparation method have uniform particle size, high purity, and the particle size can reach the micron level, meeting the requirements of large particle size silica microspheres.

[0056] In some embodiments, the particle size of the large-particle-size silica microspheres is 100 nm - 20 μm; by co-hydrolyzing high-molecular-weight triethoxysilanes with different molecular weights and ordinary silanes, silica microspheres with different particle sizes can be prepared, and the particle size range is between 100 nm and 20 μm, which can meet the usage requirements of different fields for silica microspheres with different particle sizes. Not only can micron-sized large-particle-size silica microspheres with uniform sizes be prepared, but also nano-sized silica microspheres with uniform sizes can be prepared.

[0057] The following are further examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention fall within the protection scope of the present invention.

[0058] Example 1

[0059] 100 g of a hydroxyl-terminated silane with a molecular weight of 1000 and 52 g of hexamethylene diisocyanate were reacted at 70 °C for 4 h to obtain an isocyanate-modified silane; 100 g of the isocyanate-modified silane and 20 g of aminopropyltriethoxysilane were reacted at 50 °C for 2 h to obtain a high-molecular-weight triethoxysilane; 100 g of the high-molecular-weight triethoxysilane and 50 g of tetraethoxysilane were added to 100 g of ethanol and stirred evenly, then 20 g of water and 10 g of ammonia water catalyst were added and reacted at 30 °C for 12 h, and large-particle-size silica microspheres were obtained by centrifugation and drying.

[0060] Example 2

[0061] 100 g of a hydroxyl-terminated silane with a molecular weight of 1500 and 35 g of isophorone diisocyanate were reacted at 80 °C for 2 h to obtain an isocyanate-modified silane; 100 g of the isocyanate-modified silane and 10 g of aminopropyltriethoxysilane were reacted at 60 °C for 1 h to obtain a high-molecular-weight triethoxysilane; 100 g of the high-molecular-weight triethoxysilane and 60 g of tetramethoxysilane were added to 120 g of ethanol and stirred evenly, then 15 g of water and 10 g of sodium hydroxide catalyst were added and reacted at 35 °C for 15 h, and large-particle-size silica microspheres were obtained by centrifugation and drying.

[0062] Example 3

[0063] 100 g of a silane with a molecular weight of 2000 and having a hydroxyl group in the middle was reacted with 62 g of diphenylmethane diisocyanate at 60 °C for 4 h to obtain an isocyanate-modified silane; 100 g of the isocyanate-modified silane was reacted with 15 g of aminopropyltriethoxysilane at 65 °C for 2 h to obtain a high-molecular triethoxysilane; 100 g of the high-molecular triethoxysilane and 60 g of diethoxydimethoxysilane were added to 160 g of ethanol and stirred evenly, then 20 g of water and 8 g of potassium hydroxide catalyst were added and reacted at 45 °C for 16 h, and large-particle-size silica microspheres were obtained by centrifugal drying.

[0064] Example 4

[0065] 100 g of a silane with a molecular weight of 2500 and having hydroxyl groups at both ends and in the middle was reacted with 80 g of diphenylmethane diisocyanate trimer at 60 °C for 6 h to obtain an isocyanate-modified silane; 100 g of the isocyanate-modified silane was reacted with 56 g of aminopropyltriethoxysilane at 55 °C for 3 h to obtain a high-molecular triethoxysilane; 100 g of the high-molecular triethoxysilane, 40 g of tetraethoxysilane and 40 g of tetramethoxysilane were added to 180 g of ethanol and stirred evenly, then 30 g of water and 20 g of triethylamine catalyst were added and reacted at 40 °C for 20 h, and large-particle-size silica microspheres were obtained by centrifugal drying.

[0066] Comparative Example 1

[0067] 100 g of a silane with a molecular weight of 1000 and having hydroxyl groups at both ends was reacted with 40 g of diphenylmethane diisocyanate at 70 °C for 5 h to obtain an isocyanate-modified silane; 100 g of the isocyanate-modified silane was reacted with 34 g of aminopropyltriethoxysilane at 50 °C for 2 h to obtain a high-molecular tetramethoxysilane; 100 g of the high-molecular triethoxysilane was added to 100 g of ethanol and stirred evenly, then 15 g of water and 10 g of triethylamine catalyst were added and reacted at 35 °C for 20 h, and large-particle-size silica microspheres were obtained by centrifugal drying.

[0068] Comparative Example 2

[0069] 100 g of a silane with a molecular weight of 1500 and having a hydroxyl group in the middle of the molecular chain was reacted with 25 g of toluene diisocyanate at 75 °C for 3 h to obtain an isocyanate-modified silane; 100 g of the isocyanate-modified silane was reacted with 29 g of aminopropyltriethoxysilane at 45 °C for 3 h to obtain a high-molecular tetraethoxysilane; 100 g of the high-molecular triethoxysilane was added to 150 g of ethanol and stirred evenly, then 20 g of water and 12 g of potassium hydroxide catalyst were added and reacted at 30 °C for 16 h, and large-particle-size silica microspheres were obtained by centrifugal drying.

[0070] Comparative Example 3

[0071] 15 g of tetraethoxysilane was added to 80 g of ethanol and stirred evenly. Then, 10 g of water and 8 g of potassium hydroxide catalyst were added, and the reaction was carried out at 35 °C for 16 h. After centrifugation and drying, large-sized silica microspheres were obtained.

[0072] Comparative Example 4

[0073] 20 g of tetramethoxysilane was added to 100 g of ethanol and stirred evenly. Then, 15 g of water and 15 g of ammonia catalyst were added, and the reaction was carried out at 40 °C for 20 h. After centrifugation and drying, large-sized silica microspheres were obtained.

[0074] The particle size and PDI (particle size dispersion index) of the silica microspheres prepared in Examples 1-4 and Comparative Examples 1-4 were measured by dynamic light scattering (DLS). The smaller the PDI value, the more uniform the particle size. The purity of the silica particles was measured by inductively coupled plasma optical emission spectrometer (ICP-OES). The test results are shown in Table 1.

[0075] Table 1

[0076] Serial number Particle size / μm PDI distribution Purity / % Example 1 4.6 0.04 99.6 Example 2 6.3 0.06 99.5 Example 3 8.5 0.12 99.5 Example 4 12.8 0.23 99.5 Comparative example 1 9.8 0.58 99.4 Comparative example 2 15.6 0.69 99.4 Comparative example 3 0.15 0.09 99.5 Comparative example 4 0.12 0.06 96.6

[0077] From the data in Table 1, it can be seen that in Examples 1-4, high-molecular-weight triethoxysilane was prepared by using hydroxy silanes with gradually increasing molecular weights, and then co-hydrolyzed with ordinary silanes to prepare large-sized silica microspheres. It can be seen that as the molecular weight increases, the particle size of the prepared silica microspheres also increases, and the particle size uniformity decreases to a certain extent, but is generally relatively uniform. At the same time, the purity can reach about 99.5%.

[0078] For the silica prepared by the hydrolysis of the high-molecular-weight triethoxysilane prepared in Comparative Examples 1-2 alone, it can be seen that the particle size will further increase. However, since there is no further silicon source provided by small-molecule silanes, and only the hydrolysis and combination of high-molecular-weight silanes, the uniformity of the prepared silica microspheres is very poor. Comparative Examples 3-4 used small-molecule ordinary silanes for hydrolysis to prepare silica. The particle size is small and the dispersion is relatively uniform. However, due to the lack of the skeleton of high-molecular-weight silanes, the particle size of the prepared silica microspheres is all below 1 micron, and it is very difficult to prepare large-sized silica. The purity of the silica prepared in Examples 1-4 and Comparative Examples 1-4 is relatively high, reaching about 99.5%. In summary, the co-hydrolysis of high-molecular-weight triethoxysilane and ordinary silanes can effectively prepare high-purity large-sized silica microspheres. Different particle sizes of silica can be obtained by controlling the molecular weight of high-molecular-weight silanes. This mixed hydrolysis strategy opens up a new way for the preparation of silica microspheres with specific sizes and properties.

[0079] Example 5

[0080] The large-sized silica prepared in Example 2 was added as a reinforcing filler to the existing architectural coating at a mass fraction of 4%, significantly improving the performance of the coating compared to adding nano-sized silica. The adhesion of the coating film increased by 20%, the water resistance increased by 30%, and the abrasion resistance increased by 25%. This not only enhanced the mechanical properties and durability of the coating but also maintained the application performance and leveling property of the coating, enabling the coating to maintain excellent performance in various environments.

[0081] Example 6

[0082] The large-sized silica in Example 3 was added to the epoxy resin binder at a mass fraction of 2%. Compared with adding nano-sized silica, the bonding strength increased by 30% and the curing time was shortened by 20%. In addition, the mechanical properties such as the flexibility of the coating were also improved by 15%. These improvements not only enhanced the bonding effect and sealing performance of the binder but also improved its applicability in harsh environments. In summary, the present invention provides a large-sized silica microsphere and a preparation method thereof. The preparation method of the large-sized silica microsphere includes the steps of: mixing a silane containing hydroxyl groups with a polyisocyanate, and obtaining an isocyanate-modified silane after a first reaction; mixing the isocyanate-modified silane with aminopropyltriethoxysilane, and obtaining a high-molecular-weight triethoxysilane after a second reaction; mixing the high-molecular-weight triethoxysilane, a silane containing alkoxy groups, a catalyst, and a solvent, and obtaining large-sized silica microspheres after a hydrolysis reaction. The present invention prepares silica by co-hydrolyzing a high-molecular-weight silane and a silane containing alkoxy groups. The addition of the high-molecular-weight triethoxysilane can effectively increase the particle size of the prepared silica particles. By controlling the molecular weight of the high-molecular-weight triethoxysilane, silica microspheres with different particle sizes can be prepared, so as to meet the application requirements of different particle sizes of silica microspheres in different fields. Moreover, the silica microspheres prepared by using this preparation method have uniform particle size, high purity, and the particle size can reach the micron level, meeting the requirements of large-sized silica microspheres.

[0083] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or changes can be made according to the above description. All such improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for preparing large-size silica microspheres, characterized in that: Includes steps: The hydroxyl-containing silane is mixed with polyisocyanate to obtain isocyanate-modified silane after a first reaction; The isocyanate-modified silane is mixed with aminopropyltriethoxysilane, and after a second reaction, a high molecular weight triethoxysilane is obtained; The polymer triethoxysilane, silane containing alkoxy groups, a catalyst and a solvent are mixed and subjected to a hydrolysis reaction to obtain large-diameter silica microspheres.

2. The method for preparing large-diameter silica microspheres according to claim 1, characterized in that: The hydroxyl groups in the hydroxyl-containing silane are located at one end of the silane molecular chain, at both ends of the silane molecular chain or in the middle of the silane molecular chain.

3. The method for preparing large-size silica microspheres according to claim 1, characterized in that: The molecular weight of the hydroxyl-containing silane is 100-3000; the general structural formula of the hydroxyl-containing silane is: Wherein, R1, R2, and R3 are independently selected from And at least one of R1, R2, and R3 is m is 0-10, and n is 1-1000.

4. The method for preparing large-diameter silica microspheres according to claim 1, characterized in that: The polyisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, diphenylmethane diisocyanate trimer, hexamethylene diisocyanate trimer, and isophorone diisocyanate trimer.

5. The method for preparing large-diameter silica microspheres according to claim 1, characterized in that: The mass ratio of the hydroxyl-containing silane to the polyisocyanate is 100:(10-80); and / or the temperature of the first reaction is 40° C.-100° C., and the time of the first reaction is 1 h-10 h.

6. The method for preparing large-diameter silica microspheres according to claim 1, characterized in that: The mass ratio of the isocyanate-modified silane to the aminopropyltriethoxysilane is 100:(1-40); and / or, the temperature of the second reaction is 20° C.-80° C., and the time of the second reaction is 1 h-4 h.

7. The method for preparing large-diameter silica microspheres according to claim 1, characterized in that: The alkoxy-containing silane is selected from one or more of tetraethoxysilane, tetramethoxysilane, diethoxydimethoxysilane, triethoxysilane, and vinyltriethoxysilane; and / or the catalyst is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, sodium hydroxide, potassium hydroxide, ammonia water, and triethylamine.

8. The method for preparing large-diameter silica microspheres according to claim 1, characterized in that: The mass ratio of the polymer triethoxysilane, the alkoxy-containing silane and the catalyst is 100:(1-100):(1-25); and / or the temperature of the hydrolysis reaction is 20°C-80°C, and the time of the hydrolysis reaction is 1h-24h.

9. A large-particle silica microsphere, characterized in that: The large-particle-size silica microspheres are prepared by the preparation method according to any one of claims 1 to 8.

10. The large-diameter silica microspheres according to claim 9, characterized in that: The particle size of the large-particle silica microspheres is 100nm-20μm.

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