A method for preparing monodisperse hydrophobic silica microspheres

Abstract

This invention discloses a method for preparing monodisperse hydrophobic silica microspheres. A silicon source, solvent, and catalyst are mixed and reacted thoroughly to form solution A. The silicon source is a silicate ester or sodium silicate, the solvent is a lower alcohol, and the catalyst is a protic acid or protic base. Solution B containing an organosilicon compound is then poured into solution A and reacted thoroughly. The organosilicon compound is one or more of R'nSi(OR')4-n and R"'nSi(OH)4-n, where R' is one or more of methyl, ethyl, and vinyl groups, R" is a carbon chain compound comprising C1-C16, and R"' is a carbon chain compound comprising C12-C200. After washing the solution after the reaction, it is dried to obtain monodisperse hydrophobic silica microsphere powder. This invention features a simple process, low cost, no special requirements for equipment, mild reaction conditions, high safety, and can achieve large-scale continuous production.

Description

Technical Field

[0001] This invention relates to the field of silica microsphere preparation technology, and specifically to a method for preparing monodisperse hydrophobic silica microspheres. Background Technology

[0002] Silica is a rigid inorganic material with excellent stability and a low coefficient of thermal expansion. Based on surface treatment, silica is classified into hydrophilic and hydrophobic types. Unmodified silica contains a large number of hydroxyl and polar groups on its surface, making particles prone to collision and aggregation, forming secondary aggregates. This affects the uniform dispersion of silica in organic polymers and fails to meet the specific needs of certain industries, particularly the currently constrained field of electronic packaging. Electronic packaging places higher demands on silica materials. Epoxy resin is commonly used as the main carrier for adhesives in electronic packaging applications. However, the high coefficient of thermal expansion (CTE), inherent brittleness, and cracking of epoxy adhesives are particularly prominent in electronic packaging applications, affecting the structural stability and service reliability of packaged devices. Silica microspheres serve as an important filler material in epoxy adhesives. Adding monodisperse hydrophobic silica microspheres to adhesives can improve their brittleness and thermal expansion properties, and significantly enhance their moisture-proof performance, playing a crucial role in preventing external air, water mist, and other impurities from entering electronic devices and contaminating the liquid crystal.

[0003] There are many methods for modifying silica microspheres. Based on different principles, they are divided into physical modification and chemical modification. Existing methods for synthesizing hydrophobic silica are cumbersome, involve many processing steps and consume a lot of energy. The synthesis of silica microspheres involves a large amount of organic reagents, which is costly and not environmentally friendly. The synthesized silica microspheres are in a dispersed state with many different sizes of spheres.

[0004] Invention patent CN105400239B discloses an ultrafine hydrophobic silica and its preparation method. This method is complex, requiring complex modification treatment after mixing and dispersing the hydrophilic silica powder substrate. The presence of a large number of hydroxyl groups in the hydrophilic silica microspheres makes dispersion difficult. Furthermore, this method also requires atomization treatment of the hydrophilic silica microsphere mixture and the modifier, which increases equipment costs and places higher demands on the synthesis conditions.

[0005] Patent application CN111620345A discloses an ultrafine hydrophobic silica and its preparation method. The method involves reacting sodium silicate solution and sulfuric acid solution at 70-80°C to obtain silica material. After washing and drying, the silica is simultaneously ultrafinely pulverized and modified in an air jet mill to obtain ultrafine hydrophobic silica. This method first synthesizes hydrophilic silica, then washes and dries it, and then uses an air jet mill for modification. While simpler than traditional methods, it still requires multiple steps.

[0006] Invention patent application CN115029018A discloses a highly stable hydrophobic modified nano silica and its preparation method. It uses silicon source and organosilicon as raw materials. The process is simple and pollution-free and does not require any organic solvent as a reaction medium. It has the technical characteristics of low cost and green environmental protection. However, it is difficult to synthesize monodisperse hydrophobic silica microspheres with controllable particle size. The synthesized silica microspheres have agglomeration and adhesion.

[0007] To address the existing problems, this invention proposes a one-step method for synthesizing monodisperse hydrophobic silica microspheres. This method can synthesize monodisperse hydrophobic silica microspheres with controllable particle size in one step, without the need for atomization treatment, with a simple preparation method, environmentally friendly and non-toxic raw materials, mild synthesis conditions, and easy large-scale production, thus meeting the needs of electronic packaging materials. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for preparing monodisperse hydrophobic silica microspheres, which can synthesize monodisperse hydrophobic silica microspheres in one step. The process is simple, low-cost, and environmentally friendly, and can achieve large-scale production of monodisperse hydrophobic silica microspheres that meet the needs of electronic packaging materials.

[0009] A method for preparing monodisperse hydrophobic silica microspheres includes the following steps: Step 1: Mix the silicon source, solvent, and catalyst thoroughly to form solution A. The mass fractions of silicon source, solvent, and catalyst are 10-65%, 0-85%, and 5-40%, respectively. The silicon source is a silicate ester or sodium silicate, the solvent is a lower alcohol, and the catalyst is a protic acid or protic base. Step 2: Pour solution B containing organosilicon compounds into solution A and allow it to react fully. The mass fractions of solvent and organosilicon compounds in solution B in the whole system (the mixed solution composed of solution A and solution B) are 0-85% and 5-40%, respectively. The organosilicon compounds are one or more of R'nSi(OR'')4-n and R'''nSi(OH)4-n, where R' is one or more of methyl, ethyl and vinyl, R'' is a carbon chain compound including C1-C16, and R''' is a carbon chain compound including C12-C200. Step 3: Wash the solution after the reaction is complete, and then dry it to obtain monodisperse hydrophobic silica microsphere powder.

[0010] Furthermore, lower alcohols include one or more of methanol, ethanol, butanol, and isobutanol; protic acids include sulfuric acid or hydrochloric acid; and protic bases include sodium hydroxide, potassium hydroxide, or ammonia.

[0011] Furthermore, the reaction conditions for steps 1 and 2 are 25℃~60℃ in a water bath; the reaction time for step 1 is 3~6 hours, and the reaction time for step 2 is 6~12 hours. The actual reaction time is related to the catalyst concentration and the reaction temperature.

[0012] This invention enables the synthesis of monodisperse 0.1-10 micrometer silica microspheres by controlling the content of silicon source and solvent in solution A. Simultaneously, by adding solution B to solution A and controlling the content of organosilicon compounds and the steric hindrance of different organosilicon compounds, a one-step synthesis of monodisperse hydrophobic silica microspheres is achieved. Furthermore, the synthesized silica microspheres are not only monodisperse but also exhibit no aggregation or adhesion, are hydrophobically stable, and can be fully dispersed in organic matter. This invention features a simple and low-cost process, requires no special equipment, and operates under mild reaction conditions with high safety, enabling large-scale continuous production. Attached Figure Description

[0013] Figure 1 This is an electron microscope image of the silica microspheres prepared in Example 1; Figure 2 The image shows the laser particle size distribution of the silica microspheres prepared in Example 1. Figure 3 This is a schematic diagram showing the contact angle of the silica microspheres prepared in Example 1; Figure 4 This is an electron microscope image of the silica microspheres prepared in Example 2; Figure 5 The image shows the laser particle size distribution of the silica microspheres prepared in Example 2. Figure 6 This is a schematic diagram showing the contact angle of the silica microspheres prepared in Example 2; Figure 7 This is an electron microscope image of the silica microspheres prepared in Example 3; Figure 8 The image shows the laser particle size distribution of the silica microspheres prepared in Example 3. Figure 9 This is a schematic diagram of the contact angle of the silica microspheres prepared in Example 3. Detailed Implementation

[0014] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments and corresponding drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. The technical solutions of the present invention will be described more clearly and completely below with reference to specific embodiments and comparative examples. Example

[0016] A method for preparing monodisperse hydrophobic silica microspheres 1. Preparation of solution A: Add 9g of sulfuric acid (catalyst) and 14g of sodium silicate (silicon source) to the flask and stir. React in a water bath at 60℃ for 4.5h. 2. Preparation of solution B: Mix 150g of methanol (solvent) and 11g of diethoxyvinylsilane (organosilicon); 3. Add solution B to solution A and continue the reaction in a water bath at 60°C for 10 hours; 4. Centrifuge the reaction solution, and ultrasonically disperse and wash it 2-3 times with ethanol. Finally, dry it in a 60℃ oven for 6 hours to obtain monodisperse hydrophobic silica microspheres. The electron micrograph of the sample is shown below. Figure 1 As shown, the laser particle size distribution diagram is as follows: Figure 2 As shown, the contact angle is as follows Figure 3 As shown. Example

[0017] A method for preparing monodisperse hydrophobic silica microspheres 1. Preparation of solution A: Take 130g of ethanol (solvent), 12g of sodium hydroxide (catalyst), and 21g of tetraethyl silicate (silicon source) and add them to the flask in sequence and stir. React in a water bath at 45℃ for 6 hours. 2. Preparation of solution B: Mix 23g of methoxytrimethoxysilane (organosilicon compound) and 25g of diethylethoxysilane (organosilicon compound); 3. Add solution B to solution A and continue the reaction in a water bath at 45°C for 11 hours; 4. Centrifuge the reaction solution, and ultrasonically disperse and wash it 2-3 times with ethanol. Finally, dry it in a 60℃ oven for 6 hours to obtain monodisperse hydrophobic silica microspheres. The electron micrograph of the sample is shown below. Figure 4 As shown, the laser particle size distribution diagram is as follows: Figure 5 As shown, the contact angle is as follows Figure 6 As shown. Example

[0018] A method for preparing monodisperse hydrophobic silica microspheres 1. Prepare solution A: Add 80g of isobutanol (solvent), 7g of ammonia (catalyst), and 28g of tetrabutyl silicate (silicon source) to a flask and stir. React in a water bath at 25°C for 5 hours. 2. Preparation of solution B: Mix 15g of γ-aminopropyltriethoxysilane (organosilicon) and 35g of dimethoxydimethylsilane (organosilicon); 3. Add solution B to solution A and continue the reaction in a water bath at 25°C for 8 hours; 4. Centrifuge the reaction solution, and ultrasonically disperse and wash it 2-3 times with ethanol. Finally, dry it in a 60℃ oven for 6 hours to obtain monodisperse hydrophobic silica microspheres. The electron micrograph of the sample is shown below. Figure 7 As shown, the laser particle size distribution diagram is as follows: Figure 8 As shown, the contact angle is as follows Figure 9 As shown.

[0019] This invention enables the synthesis of monodisperse 0.1-10 micrometer silica microspheres by controlling the content of silicon source and solvent in solution A. Simultaneously, by adding solution B to solution A and controlling the content of organosilicon compounds and the steric hindrance of different organosilicon compounds, a one-step synthesis of monodisperse hydrophobic silica microspheres can be achieved. Furthermore, the synthesized silica microspheres are not only monodisperse but also free from aggregation and adhesion, exhibiting stable hydrophobicity and being fully dispersed in organic matter.

[0020] As can be seen from Examples 1-3, the silica microspheres prepared by the present invention have high particle size uniformity, a contact angle of about 140°, and good hydrophobicity.

[0021] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0022] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing monodisperse hydrophobic silica microspheres, characterized in that, Includes the following steps: Step 1: Mix the silicon source, solvent and catalyst, and react them in a water bath at 25℃~60℃ for 3~6 hours to form solution A. The mass fractions of silicon source, solvent and catalyst are 10-65%, 0-85% and 5-40% respectively. The silicon source is silicate ester or sodium silicate, the solvent is a lower alcohol and the catalyst is a protic acid or protic base. Step 2: Pour solution B containing organosilicon compounds into solution A, and continue to react fully at 25℃~60℃ for 6~12h. The mass fractions of solvent and organosilicon compounds in solution B are 0-85% and 5-40% of the total system, respectively. The organosilicon compounds are one or more of R'nSi(OR'')4-n and R'''nSi(OH)4-n, R' is one or more of methyl, ethyl and vinyl, R'' is a carbon chain compound including C1-C16, and R''' is a carbon chain compound including C12-C200. Step 3: Wash the solution after the reaction is complete, and then dry it to obtain monodisperse hydrophobic silica microsphere powder.

2. The method for preparing monodisperse hydrophobic silica microspheres according to claim 1, characterized in that, Lower alcohols include one or more of methanol, ethanol, butanol, and isobutanol.

3. The method for preparing monodisperse hydrophobic silica microspheres according to claim 1, characterized in that, Protic acids include sulfuric acid or hydrochloric acid, while protic bases include sodium hydroxide, potassium hydroxide, or ammonia.

4. The method for preparing monodisperse hydrophobic silica microspheres according to claim 1, characterized in that, The reaction conditions for steps 1 and 2 are 25℃~60℃ in a water bath.

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