Silica microsphere and preparation method thereof

Abstract

The invention provides a silicon dioxide microsphere and a preparation method thereof. The preparation method of the silicon dioxide microspheres comprises the following steps: carrying out first reaction on a first silane coupling agent and a second silane coupling agent to obtain a silane coupling agent containing a bridge group; mixing the silane coupling agent containing the bridge group with a first solution, adding an acid agent, and carrying out hydrolysis reaction; adding an alkaline agent into the solution after the hydrolysis reaction, and carrying out condensation reaction to obtain silicon dioxide microspheres; wherein a group contained in the first silane coupling agent comprises at least one of a carbon-carbon double bond, a carbon-carbon triple bond and an isocyanate group; the group contained in the second silane coupling agent comprises at least one of sulfydryl, amino, hydroxyl and epoxy group.

Description

Technical Field

[0001] This application relates to the field of silica materials technology, specifically to a silica microsphere and its preparation method. Background Technology

[0002] Organic-inorganic hybrid silica microspheres are a class of composite materials that combine the rigidity and thermal stability of inorganic materials with the modifiability and functionality of organic materials. They are widely used in drug carriers, catalyst carriers, heavy metal adsorption, and biolabeling. Traditional silica microspheres are mainly prepared from silicon sources such as tetraethyl orthosilicate (TEOS) via the sol-gel method. Although they possess good thermal stability and chemical inertness, their surface functional groups are limited, making it difficult to achieve specific functionalization modifications, thus restricting their application in the field of high-performance materials.

[0003] To expand the functionality of silica microspheres, researchers have attempted to introduce silane coupling agents containing functional groups such as amino, thiol, and vinyl groups during the preparation process to achieve surface functionalization. Existing methods mostly involve directly blending silanes with different functional groups, lacking effective bridging structures between these functional groups, making it difficult to achieve synergistic enhancement effects and limiting the functional integration and structural stability of the microspheres.

[0004] Therefore, there is an urgent need to develop a new preparation method that can achieve stable bridging of organic functional groups and structural enhancement while maintaining the original performance advantages of silica microspheres, thereby obtaining organic-inorganic hybrid silica microspheres with uniform particle size and stable structure. Summary of the Invention This application aims to at least partially address one of the technical problems existing in the prior art. To this end, one objective of this application is to provide a silica microsphere and a method for its preparation, which enables organic components to be covalently embedded into the silica framework via CSC bridging groups, urea groups, thiourea groups, or urethane bridging groups, thereby improving structural stability and ensuring uniform distribution of organic functional groups within the microsphere.

[0005] Therefore, in a first aspect of this application, a method for preparing silica microspheres is proposed. According to an embodiment of this application, the method includes: reacting a first silane coupling agent with a second silane coupling agent to obtain a silane coupling agent containing a bridging group; mixing the bridging group-containing silane coupling agent with a first solution, adding an acidic agent, and performing a hydrolysis reaction; adding an alkaline agent to the solution after the hydrolysis reaction, and performing a condensation reaction to obtain silica microspheres; wherein the first silane coupling agent contains at least one of carbon-carbon double bonds, carbon-carbon triple bonds, and isocyanate groups; and the second silane coupling agent contains at least one of mercapto, amino, hydroxyl, and epoxy groups.

[0006] First, this application employs a specific reaction between a first silane coupling agent containing carbon-carbon double bonds, carbon-carbon triple bonds, or isocyanate groups and a second silane coupling agent containing mercapto, amino, hydroxyl, or epoxy groups to generate a silane coupling agent containing a specific bridging group. This bridging group is a chemically inert, high-bond-energy rigid / flexible connecting unit. Using this bridging-group silane coupling agent as a precursor, silica microspheres are prepared, ultimately forming an organic-inorganic hybrid structure of "inorganic framework support + organic functional group functionalization": the microspheres use silica as the inorganic core, retaining the inherent advantages of inorganic materials such as high hardness, high temperature resistance, and solvent resistance; simultaneously, the organic functional groups introduced into the bridging group, as functionalized phases, effectively improve the brittleness of traditional silica microspheres and significantly enhance their interfacial compatibility with organic matrices. Furthermore, the preparation method of this application also has advantages such as mild reaction conditions and simple operation procedures, making it suitable for large-scale industrial production.

[0007] According to embodiments of this application, the first silane coupling agent contains carbon-carbon double bonds or carbon-carbon triple bonds.

[0008] According to an embodiment of this application, the second silane coupling agent contains a thiol group.

[0009] According to an embodiment of this application, the first silane coupling agent contains an isocyanate group.

[0010] According to embodiments of this application, the second silane coupling agent contains at least one of thiol, amino, hydroxyl, and epoxy groups.

[0011] According to embodiments of this application, the first silane coupling agent is selected from at least one of vinyltrimethoxysilane (VTMS), vinyltriethoxysilane, propargyltrimethoxysilane, propargyltriethoxysilane, isocyanate-propyltrimethoxysilane (IPTMS), and isocyanate-propyltriethoxysilane.

[0012] According to embodiments of this application, the second silane coupling agent is selected from at least one of mercaptotrimethoxysilane (MPTMS), aminopropyltriethoxysilane (APTES), aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, diethylaminomethyltriethoxysilane, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0013] According to an embodiment of this application, the molar ratio of the first silane coupling agent to the second silane coupling agent is 1:(0.98-1.02).

[0014] According to an embodiment of this application, the first reaction is carried out under the action of an initiator.

[0015] According to embodiments of this application, the initiator includes at least one of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), etc.

[0016] According to an embodiment of this application, the amount of initiator is 0.1-1.0% of the sum of the masses of the first silane coupling agent and the second silane coupling agent.

[0017] According to an embodiment of this application, the temperature of the first reaction is 20-80°C.

[0018] According to an embodiment of this application, the time for the first reaction is 2-12 hours.

[0019] According to embodiments of this application, the first solution is an aqueous solution or an alcohol-water solution.

[0020] According to an embodiment of this application, the volume ratio of alcohol to water in the alcohol-water solution is 0:10-8:2.

[0021] According to an embodiment of this application, the volume ratio of the silane coupling agent containing the bridging group to the first solution is 1:(20-100).

[0022] According to embodiments of this application, the acid includes at least one of formic acid, acetic acid, hydrochloric acid, and nitric acid.

[0023] According to the embodiments of this application, after adding an acid, the pH value of the solution is 2.0-7.0.

[0024] According to an embodiment of this application, the temperature of the hydrolysis reaction is 30-80°C.

[0025] According to an embodiment of this application, the hydrolysis reaction takes 1-60 minutes.

[0026] According to embodiments of this application, the alkaline agent includes at least one of ammonia, sodium carbonate, sodium hydroxide, and potassium hydroxide.

[0027] According to an embodiment of this application, after adding an alkali agent to the solution following the hydrolysis reaction, the pH value of the solution is 9.0-11.0.

[0028] According to an embodiment of this application, the temperature of the condensation reaction is 30-80°C.

[0029] According to an embodiment of this application, the condensation reaction takes 1-12 hours.

[0030] According to an embodiment of this application, the method further includes: centrifuging, washing and drying the product after the condensation reaction to obtain the silica microspheres.

[0031] In a second aspect of this application, a silica microsphere is proposed. According to an embodiment of this application, the silica microsphere is prepared by the method described in the first aspect. Therefore, the silica microsphere prepared by the above method has the following advantages due to its specific bridging structure: Firstly, the bridging itself has high bond energy and strong chemical inertness, which can improve the structural stability of the silica microsphere, making it less prone to bond breakage and hydrolysis failure in high-temperature, strong acid and alkali environments or during long-term use; secondly, the introduction of organic bridging groups reduces the surface polarity of the silica microsphere, enhances its interfacial interaction with organic matrices such as resins and rubbers, ensuring that the microsphere can be uniformly dispersed in the organic matrix and is less prone to interfacial delamination; finally, the urea groups, CSC segments, and other organic functional groups contained in the bridging groups can not only serve as inherent functional sites, but also directly endow the microsphere with specific properties such as adsorption and oleophilicity, expanding the application scenarios of the product.

[0032] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0033] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a flowchart of a method for preparing silica microspheres according to an embodiment of this application; Figure 2 This is the infrared spectrum of MPTMS-VTMS according to Embodiment 1 of this application; Figure 3 This is the 1H NMR spectrum of MPTMS-VTMS according to Embodiment 1 of this application; Figure 4 This is a SEM image of silica microspheres according to Embodiment 1 of this application; Figure 5 This is the infrared spectrum of IPTMS-APTES according to Embodiment 2 of this application; Figure 6 This is the IPTMS-APTES 1H NMR spectrum according to Embodiment 2 of this application; Figure 7 This is a SEM image of silica microspheres according to Embodiment 2 of this application. Detailed Implementation

[0034] The embodiments of the silica microspheres and their preparation methods described herein are disclosed in detail below with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0035] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is also expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0037] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0038] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0039] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "First feature" and "second feature" may include one or more of the indicated feature.

[0040] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0041] In one aspect of this application, a method for preparing silica microspheres is provided. According to an embodiment of this application, the method for preparing hollow silica microspheres includes: S100: The first silane coupling agent and the second silane coupling agent are reacted in a first reaction to obtain a silane coupling agent containing a bridging group.

[0042] According to some embodiments of this application, the first silane coupling agent and the second silane coupling agent are monosubstituted coupling agents. According to some embodiments of this application, the first silane coupling agent contains at least one of a carbon-carbon double bond, a carbon-carbon triple bond, and an isocyanate group; the second silane coupling agent contains at least one of a mercapto group, an amino group, a hydroxyl group, and an epoxy group. Thus, the carbon-carbon double bond or carbon-carbon triple bond in the first silane coupling agent can undergo a thiol-ene or alkyne click reaction with the mercapto group in the second silane coupling agent, and the isocyanate group in the first silane coupling agent can undergo a ureation reaction with the mercapto, amino, hydroxyl, or epoxy group in the second silane coupling agent. This allows for the efficient and precise formation of bridging structures containing CSC or thiourea, urea, or carbamate groups, avoiding product disorder caused by non-specific reactions and ensuring the uniformity of the bridging structure (high bond energy, strong chemical inertness), laying the foundation for the excellent structural stability of the microspheres.

[0043] According to some embodiments of this application, the first silane coupling agent contains a carbon-carbon double bond or a carbon-carbon triple bond, and the second silane coupling agent contains a mercapto group. Thus, the carbon-carbon double or triple bond in the first silane coupling agent and the mercapto group in the second silane coupling agent can undergo a thiol-alkene or alkyne click reaction, thereby efficiently and precisely forming a bridging structure containing CSCs.

[0044] According to some embodiments of this application, the first silane coupling agent contains an isocyanate group, and the second silane coupling agent contains at least one of a mercapto, amino, hydroxyl, or epoxy group. Thus, the isocyanate group in the first silane coupling agent can undergo a ureation reaction with the mercapto, amino, hydroxyl, or epoxy group in the second silane coupling agent, thereby efficiently and precisely forming a bridging structure containing a thiourea, urea, or carbamate group.

[0045] According to some embodiments of this application, the first silane coupling agent is selected from, but not limited to, at least one of vinyltrimethoxysilane (VTMS), vinyltriethoxysilane, propargyltrimethoxysilane, propargyltriethoxysilane, isocyanate-propyltrimethoxysilane (IPTMS), and isocyanate-propyltriethoxysilane.

[0046] According to some embodiments of this application, the second silane coupling agent is selected from, but not limited to, at least one of mercaptotrimethoxysilane (MPTMS), aminopropyltrimethoxysilane, aminopropyltriethoxysilane (APTES), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, diethylaminomethyltriethoxysilane, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0047] According to some embodiments of this application, the molar ratio of the first silane coupling agent to the second silane coupling agent is 1:(0.98-1.02). For example, it can be 1:0.98, 1:0.99, 1:1, 1:1.01, 1:1.02, or any range of the above values. Therefore, by controlling the molar ratio of the first silane coupling agent to the second silane coupling agent within the above range, the functional groups of the two types of coupling agents can be approximately equimolarly, ensuring sufficient reaction and maximizing conversion rate; simultaneously, it reduces side reactions caused by excess of a certain reactant, reduces impurity formation, and ensures the uniformity and purity of the bridging coupling agent structure.

[0048] According to some embodiments of this application, the first silane coupling agent contains a carbon-carbon double bond or a carbon-carbon triple bond, the second silane coupling agent contains a thiol group, and the first reaction is carried out under the action of an initiator. Thus, the initiator can generate free radicals through decomposition, initiating the addition reaction of thiols with unsaturated bonds; simultaneously, the addition of the initiator can lower the activation energy of the reaction, allowing the addition reaction to be initiated and carried out efficiently under mild conditions, thereby constructing a CSC covalent bridge structure. The isocyanate group can directly undergo nucleophilic addition reactions with thiol, amino, hydroxyl, or epoxy groups.

[0049] According to some embodiments of this application, the initiator includes at least one of azobisisobutyronitrile (AIBN) and benzoyl peroxide. Thus, by using an initiator selected from the above categories, free radicals can be effectively generated through decomposition, efficiently initiating the addition reaction of thiols with unsaturated bonds, thereby constructing a CSC covalent bridge structure.

[0050] According to some embodiments of this application, the amount of initiator is 0.1-1.0% of the sum of the masses of the first silane coupling agent and the second silane coupling agent. For example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc., or a range of any of the above values. Therefore, by controlling the amount of initiator within the above range, sufficient free radicals can be generated, allowing the directional addition reaction of thiols with carbon-carbon double or triple bonds to dominate, reducing side reactions and the formation of impurities.

[0051] According to some embodiments of this application, the temperature of the first reaction is 20-80°C, for example, it can be 20°C, 22°C, 25°C, 28°C, 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, 80°C, etc., or any range of the above values. Thus, by keeping the temperature within the above range, the isocyanate group reacts well with the mercapto, amino, hydroxyl, or epoxy groups. Temperatures such as 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, and 80°C can promote the decomposition of the initiator, generating an appropriate amount of free radicals, thereby promoting the addition reaction of thiols with carbon-carbon double or triple bonds, and thus ensuring the structural integrity of the silane coupling agent containing the bridging group.

[0052] According to some embodiments of this application, the reaction time of the first reaction is 2-12 hours. For example, it can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, or any range of the above values. Therefore, by controlling the reaction time within the above range, the reaction between the first silane coupling agent and the second silane coupling agent can be made more complete, thereby ensuring that the silane coupling agent containing the bridging group has a uniform structure and high purity.

[0053] S200: The silane coupling agent containing the bridging group is mixed with the first solution, an acid is added, and a hydrolysis reaction is carried out.

[0054] According to some embodiments of this application, the first solution is an aqueous solution or an alcohol-water solution.

[0055] According to some embodiments of this application, the volume ratio of alcohol to water in the alcohol-water solution is 0:10-8:2. For example, it can be 0:10, 1:9, 1.5:8.5, 2:8, 2.5:7.5, 3:7, 3.5:6.5, 4:6, 4.5:5.5, 5:5, 5.5:4.5, 6:4, 6.5:3.5, 7:3, 7.5:2.5, 8:2, etc., or a range of any of the above values.

[0056] It should be noted that the "alcohol-water solution" mentioned in this application refers to a binary mixture system composed of an alcohol compound and water. This application does not specifically limit the types of alcohol compounds mentioned, and those skilled in the art can choose them reasonably according to actual experimental needs. For example, the alcohol compound can be selected from commonly used low molecular weight alcohols such as methanol, ethanol, propanol, and isopropanol.

[0057] According to some embodiments of this application, the volume ratio of the bridging silane coupling agent to the first solution is 1:(20-100). For example, it can be 1:20, 1:25, 1:30, 1:36, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:88, 1:90, 1:95, 1:100, etc., or any range of the above values. Therefore, by controlling the volume ratio of the bridging silane coupling agent to the first solution within the above specific range, the rapid and disordered cross-linking of intermediates to form irregular aggregates can be avoided, ensuring the morphological regularity and size controllability of the oligomer microspheres.

[0058] According to some embodiments of this application, the acid agent includes at least one of formic acid, acetic acid, hydrochloric acid, and nitric acid. This makes the pH of the solution acidic, promoting the hydrolysis reaction towards the formation of silanols (-Si-OH), reducing the hydrophobicity of silane molecules, and improving their dispersion stability in the aqueous phase.

[0059] According to some embodiments of this application, the acid agent includes dilute nitric acid with a mass concentration of 4-5%.

[0060] According to some embodiments of this application, after adding the acid, the pH value of the solution is 2.0-7.0. For example, it can be 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, etc., or any range of the above values. The silane coupling agent containing the bridging group is a hydrophobic organosilicon compound, which has poor compatibility with pure water and easily forms oil droplet-like aggregates, causing the hydrolysis reaction to occur only at the phase interface, resulting in the problem of "sufficient local hydrolysis but uneven overall hydrolysis". By controlling the pH value within the above range, protons (H... + It can protonate the oxygen atom (-Si-OR) in silane molecules, promoting the hydrolysis reaction to proceed in the direction of generating silanol (-Si-OH), reducing the hydrophobicity of silane molecules, improving their dispersion stability in the aqueous phase, and at the same time, the generated silanol is conducive to the occurrence of subsequent condensation reactions.

[0061] According to some embodiments of this application, the temperature of the hydrolysis reaction is 30-80°C. For example, it can be 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, 80°C, etc., or any range of the above values. Therefore, by keeping the temperature within the above range, the molecular diffusion rate can be increased, the contact probability between silane and water molecules can be enhanced, and the hydrolysis reaction can be accelerated.

[0062] According to some embodiments of this application, the hydrolysis reaction time is 1-60 min. For example, it can be 1 min, 5 min, 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 38 min, 40 min, 42 min, 45 min, 48 min, 50 min, 52 min, 55 min, 58 min, 60 min, etc., or any range of the above values. This allows the silane coupling agent containing the bridging group to undergo sufficient hydrolysis, generating a silanol intermediate (-Si-OH).

[0063] S300: An alkaline agent is added to the solution after the hydrolysis reaction to carry out a condensation reaction and obtain silica microspheres.

[0064] According to some embodiments of this application, the alkaline agent includes at least one of ammonia, sodium carbonate, sodium hydroxide, and potassium hydroxide. Thus, by using an alkali selected from the above types, an alkaline environment can be created in the solution, solidifying the oligomer precursor formed by the previous hydrolysis into a structurally regular and mechanically stable microsphere core.

[0065] According to some embodiments of this application, after adding an alkali agent to the solution following the hydrolysis reaction, the pH value of the solution is 9.0-11.0. For example, it can be 9.0, 9.2, 9.4, 9.6, 9.8, 10.0, 10.2, 10.4, 10.6, 10.8, 11.0, or any range of the above values. Thus, under alkaline conditions, the silanol or oligomer precursor formed in the previous hydrolysis can be solidified into a structurally regular and mechanically stable microsphere core.

[0066] According to some embodiments of this application, the temperature of the condensation reaction is 30-80°C. For example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc., or it can be any range of the above values.

[0067] According to some embodiments of this application, the condensation reaction time is 1-12 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, etc., or it can be any range of the above values. Therefore, by controlling the condensation reaction time within the above specific range, it can be ensured that most of the silanol groups (-SiOH) in the system are fully cross-linked, forming silica microspheres with a dense structure and excellent mechanical strength.

[0068] According to some embodiments of this application, the method further includes: centrifuging, washing, and drying the product after the condensation reaction to obtain the silica microspheres. Thus, high-purity, highly dispersible, and structurally stable silica microspheres can be obtained.

[0069] It should be noted that when centrifuging the product after the condensation reaction, the centrifugation speed and time do not need to be strictly limited, as long as the silica microspheres (solid phase) and the dispersion (liquid phase) can be effectively separated, and the separated solid product has no obvious agglomeration and its structure is intact. For example, the centrifugation speed can be selected from 2000-4000 r / min, and the centrifugation time can be selected from 5-20 min. Those skilled in the art can make adaptive adjustments to the speed and time according to the actual product volume, microsphere particle size and concentration after the condensation reaction, provided that the above separation effect is met, all of which are within the scope of protection of this application.

[0070] According to some embodiments of this application, the washing is performed using water or ethanol. This removes surface-adsorbed catalysts (acids / alkalis), reducing the risk of secondary hydrolysis and structural degradation of the microspheres during storage or application due to residual acids or alkalis.

[0071] In a second aspect of this application, a silica microsphere is proposed. According to an embodiment of this application, the silica microsphere is prepared by the method described in the first aspect. Therefore, the silica microsphere prepared by the above method has the following advantages due to its specific bridging structure: Firstly, the bridging itself has high bond energy and strong chemical inertness, which can improve the structural stability of the silica microsphere, making it less prone to bond breakage and hydrolysis failure in high-temperature, strong acid and alkali environments or during long-term use; secondly, the introduction of organic bridging groups reduces the surface polarity of the silica microsphere, enhances its interfacial interaction with organic matrices such as resins and rubbers, ensuring that the microsphere can be uniformly dispersed in the organic matrix and is less prone to interfacial delamination; finally, the urea groups, CSC segments, and other organic functional groups contained in the bridging groups can not only serve as inherent functional sites, but also directly endow the microsphere with specific properties such as adsorption and oleophilicity, expanding the application scenarios of the product.

[0072] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0073] Example 1 Add 0.2 mol MPTMS and 0.2 mol VTMS to a 250 ml three-necked flask, heat to 60 °C and stir rapidly. Add 0.15% (by mass) AIBN of the monomers (MPTMS and VTMS), and react for 5 h to obtain MPTMS-VTMS, which is a transparent liquid with a certain viscosity. The specific reaction formula is as follows: ; Mix 40 ml of water and 10 ml of ethanol, stir, heat to 60 °C, add 1 ml of MPTMS-VTMS, adjust the pH to 2.0 with 4.2% dilute nitric acid, react for 30 min, then add 1 ml of ammonia water, adjust the pH to 10.5, and react for 5 h. After multiple centrifugations, wash twice with water and twice with ethanol, and dry to obtain CSC-group organic-inorganic hybrid silica microspheres.

[0074] Example 2 Add 0.2 mol APTES to a 250 ml three-necked flask, heat to 60 °C and stir rapidly, then slowly add 0.2 mol IPTMS dropwise to obtain IPTMS-APTES, which is a pale yellow viscous liquid. The specific reaction formula is as follows:

[0075] Heat 50 ml of water to 60 °C, add 2 ml of IPTMS-APTES, adjust the pH to 2.0 with 4.2% dilute nitric acid, react for 30 min, then add 1 ml of ammonia water, adjust the pH to 10.5, and react for 5 h. After multiple centrifugations, wash twice with water and twice with ethanol, and dry, to obtain urea-based organic-inorganic hybrid silica microspheres.

[0076] Test case The MPTMS-VTMS prepared according to the method of Example 1 and the IPTMS-APTES prepared according to the method of Example 2 were subjected to infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The infrared spectrum of the MPTMS-VTMS is shown below. Figure 2 As shown in the figure, the vinyl groups disappear, and all CSC bonds are formed. The MPTMS-VTMS 1H NMR spectrum is shown below. Figure 3 As shown in the figure, the product structure is correct. The infrared spectrum of IPTMS-APTES is as follows. Figure 5 As shown in the figure, the isocyanate group reacts completely to form a urea group. The 1H NMR spectrum of IPTMS-APTES is shown below. Figure 6 As shown in the figure, the product structure is correct.

[0077] The silica microspheres prepared according to the method in Example 1 and the silica microspheres prepared according to the method in Example 2 were observed using a scanning electron microscope (SEM). The experimental results are as follows: Figure 4 and Figure 7 As shown, it has a good spherical morphology.

[0078] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0079] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing silica microspheres, characterized in that, include: The first silane coupling agent and the second silane coupling agent are subjected to a first reaction to obtain a silane coupling agent containing a bridging group; The silane coupling agent containing the bridging group is mixed with the first solution, and an acid is added to carry out a hydrolysis reaction; An alkaline agent is added to the solution after the hydrolysis reaction to carry out a condensation reaction, thereby obtaining silica microspheres; The first silane coupling agent contains at least one of the following groups: carbon-carbon double bond, carbon-carbon triple bond, and isocyanate group; The second silane coupling agent contains at least one of the following groups: mercapto, amino, hydroxyl, and epoxy.

2. The method according to claim 1, characterized in that, The first silane coupling agent and the second silane coupling agent are monosubstituted coupling agents; And / or, the first silane coupling agent contains carbon-carbon double bonds or carbon-carbon triple bonds; And / or, the second silane coupling agent contains a thiol group.

3. The method according to claim 1, characterized in that, The first silane coupling agent contains an isocyanate group; And / or, the second silane coupling agent contains at least one of thiol, amino, hydroxyl, and epoxy groups.

4. The method according to any one of claims 1-3, characterized in that, The first silane coupling agent is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, propargyltrimethoxysilane, propargyltriethoxysilane, isocyanate-propyltrimethoxysilane, and isocyanate-propyltriethoxysilane; And / or, the second silane coupling agent is selected from at least one of mercaptotrimethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, diethylaminomethyltriethoxysilane, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane; And / or, the molar ratio of the first silane coupling agent to the second silane coupling agent is 1:(0.98-1.02); And / or, the first reaction is carried out under the action of an initiator.

5. The method according to claim 4, characterized in that, The initiator includes at least one of azobisisobutyronitrile and benzoyl peroxide; And / or, the amount of the initiator is 0.1-1.0% of the sum of the masses of the first silane coupling agent and the second silane coupling agent.

6. The method according to claim 1, characterized in that, The temperature of the first reaction is 20-80℃; And / or, the time for the first reaction is 2-12 h.

7. The method according to claim 1, characterized in that, The first solution is an aqueous solution or an alcohol-water solution; optionally, the alcohol-water volume ratio in the alcohol-water solution is 0:10-8:

2. And / or, the volume ratio of the silane coupling agent containing the bridging group to the first solution is 1:(20-100); And / or, the acid includes at least one of formic acid, acetic acid, hydrochloric acid, and nitric acid; And / or, after adding an acid, the pH of the solution is 2.0-7.0; And / or, the hydrolysis reaction is carried out at a temperature of 30-80°C; And / or, the hydrolysis reaction takes 1-60 min.

8. The method according to claim 1, characterized in that, The alkaline agent includes at least one of ammonia, sodium carbonate, sodium hydroxide, and potassium hydroxide; And / or, after adding an alkaline agent to the solution following the hydrolysis reaction, the pH value of the solution is 9.0-11.0; And / or, the temperature of the condensation reaction is 30-80°C; And / or, the condensation reaction takes 1-12 hours.

9. The method according to claim 1, characterized in that, Further includes: The product after the condensation reaction was centrifuged, washed, and dried to obtain the silica microspheres.

10. A silica microsphere, characterized in that, The silica microspheres are prepared by the method described in any one of claims 1 to 9.

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