A method for preparing a microspherical silica

Abstract

The application discloses a preparation method of micron-sized spherical silica, which comprises the following steps: taking ethanol as a solvent, adding tetraethyl orthosilicate into the ethanol, the adding amount of the tetraethyl orthosilicate being 100g / L-630g / L, stirring and uniformly mixing to prepare solution A, and reserving; in a reaction kettle, using isopropyl alcohol and ethanol as cosolvents, the mass ratio of the two being 1:3-1:4, adding a weak alkaline catalyst, water and an electrolyte into the cosolvents, the adding amount of the weak alkaline catalyst being 5g / L-40g / L, the adding amount of the water being 60g / L-300g / L, the adding amount of the electrolyte being 0.2g-1g / L, stirring and mixing, then adding a eutectic solvent to prepare solution B, and reserving; adding the solution A and the solution B into a reactor to react, then centrifuging and drying to obtain dry powder.

Description

Technical Field

[0001] This invention relates to the technical field of micron-sized material preparation, and particularly to a method for preparing micron-sized spherical silica. Background Technology

[0002] Monodisperse SiO2 micron-sized particles have different applications than nanoparticles, generally used in high-performance ceramic / ceramic manufacturing, heterogeneous catalysis, and chromatographic packed columns. Simultaneously, silica is also used as a filler in printed circuit boards (PCBs). With the advent of the 5G era and the increase in data transmission, PCBs require higher data transmission rates and lower data transmission latency, which necessitates that the dielectric loss tangent (Df) of the materials constituting the PCB be as low as possible. The Df value of silica itself is affected by its purity and the polarity of its molecules, requiring the highest possible purity and the lowest possible number of polar molecules. Therefore, SiO2 synthesized using liquid-phase methods has become the filler choice for high-end PCBs.

[0003] The most traditional liquid-phase method is the sol-gel method, which generally involves hydrolysis and condensation in alcohol or water solvents using ammonia as a weakly basic catalyst to prepare monodisperse SiO2 particles. However, the particle size is generally no larger than the submicron level (0.5 μm). Submicron fillers lead to increased viscosity, making it impossible to achieve high filling density. Therefore, developing a liquid-phase method for preparing high-purity micron-sized SiO2 is urgently needed.

[0004] CN 115504479A, "A method for preparing SiO2 microspheres and precursors", discloses a method of adding different silicon sources in three steps to obtain SiO2 microspheres with a raspberry-like surface morphology, but the particles are uneven and the surface smoothness is poor.

[0005] JP 1998287415A, "Method for Manufacturing High-Purity Spherical Silica," discloses a method for preparing spherical silica by hydrolyzing and condensing methyl silicate in a mixed medium of water and organic solvent. Methanol is used as the organic solvent, and ammonia is used as a weakly basic catalyst. Methanol-diluted methyl silicate is added dropwise to a medium at 0 to 20°C under stirring to induce hydrolysis and condensation reactions. The prepared spherical silica particles have an average particle size of 0.5 to 5 µm, exhibiting a wide particle size range.

[0006] CN116947057A, "A Method for Synthesizing Monodisperse Micron-sized Silica," discloses a method for synthesizing monodisperse micron-sized silica, which requires the addition of nano-sized SiO2 solid as seed crystals and ultrasonic uniform dispersion to obtain a seed solution, resulting in high costs.

[0007] CN112624131B, "A Method for Preparing Monodisperse Large-Aspect Ratio Silica Microspheres," discloses a method of slowly adding an ionic liquid solvent to a mixed solvent, which can improve the activity and size controllability of silica microspheres while avoiding secondary nucleation and ensuring the formation of monodisperse silica microspheres. However, Scheme 1 produces products with an uneven surface, and the solution is added to the system in stages, which is not conducive to continuous production. Scheme 4 requires the introduction of an ionic liquid, which is environmentally unfriendly and expensive, making it difficult for the products to be used as CCL fillers. Furthermore, the above methods employ a two-step reaction of seed particle generation and silica particle growth. Therefore, the manufacturing process is complex and inevitably leads to high costs. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for preparing micron-sized spherical silica that is reasonably designed, has a narrow particle size distribution, a smooth surface, and good dispersibility, in order to overcome the shortcomings of the prior art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing micron-sized spherical silica, characterized by comprising the following steps: (1) Prepare solution A Using ethanol as a solvent, tetraethyl orthosilicate is added to ethanol at a concentration of 100 g / L to 630 g / L. After stirring and mixing thoroughly, solution A is prepared and set aside. (2) Prepare solution B In a reaction vessel, isopropanol and ethanol are used as co-solvents in a mass ratio of 1:3 to 1:4. A weakly basic catalyst, water, and electrolyte are added to the co-solvent. The amount of weakly basic catalyst added is 5 g / L to 40 g / L, the amount of water added is 60 g / L to 300 g / L, and the amount of electrolyte added is 0.2 g / L to 1 g / L. The mixture is stirred and mixed thoroughly. Then, 20 g to 55 g of a eutectic solvent, which is a mixture of choline chloride and urea in a molar ratio of 1:1.5 to 2, is added to each liter of co-solvent. The mixture is stirred and mixed again to obtain solution B, which is then set aside. (3) Preparation of micron-sized silica Solution A and solution B are added to the reactor and reacted at 70℃-90℃ for 2-4 hours. After the reaction is completed, the mixture is centrifuged and dried to obtain dry powder, which is micron-sized silica.

[0010] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the weak alkaline catalyst is one or two of amino acids, ammonium carbonate, ammonium bicarbonate, urea, and ammonia water.

[0011] The technical problem to be solved by the present invention can also be achieved by the following technical solution, wherein the electrolyte is potassium chloride or ammonium chloride.

[0012] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in the reaction process described in step (3), a gradient temperature is adopted, the first gradient is 20℃-40℃, the reaction time is 1.5h-2.5h, the second gradient is 70℃-90℃, the reaction time is 0.5h-1.5h.

[0013] The technical problem to be solved by the present invention can also be achieved through the following technical solution: In step (3), the post-processing of the powder includes heat treatment and grinding. The heat treatment conditions are 800℃-1000℃ and the time is 3h-6h. The grinding process is a ball mill, and the grinding medium is silica balls. The final true density is >2.1 g / cm³. 3 Electronic filler-grade powder.

[0014] The technical problem to be solved by the present invention can also be achieved through the following technical solution: the ethanol is selected from industrial ethanol with a concentration of 99% or higher, and the isopropanol is selected from industrial isopropanol with a concentration of 99% or higher.

[0015] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the reactor is a supergravity reactor, the gas phase is an inert gas (such as nitrogen or helium), solution B is first added to the supergravity reactor, and then solution A is introduced into the rotor cavity through the liquid inlet pipe of the supergravity reactor.

[0016] The principle of the preparation method of micron-sized spherical silica described in this invention is: the hydrolysis and condensation reaction of tetraethyl orthosilicate, the overall reaction formula of which is:

[0017] Compared with the prior art, the present invention has the following technical effects: First, this invention can directly promote the hydrolysis of tetraethyl orthosilicate to produce micron-sized spherical silica with a diameter of less than 0.85 nm and a sphericity of more than 95% by simply adding isopropanol, electrolyte, and eutectic solvent. This process is simpler and does not cause particles to stick together, resulting in good dispersibility. Second, by adding isopropanol and ethanol as co-solvents, the surface potential between silica particles decreases when isopropanol is used as a solvent, further accelerating the aggregation of particles; by adding electrolytes, the electrolytes ionize in the solution to generate anions and cations, attracting the surrounding charged silica particles, acting as a bridge, causing the silica particles to aggregate with each other, accelerating the aggregation of particles, and promoting particle growth. Third, by adding a eutectic solvent, the conductivity is further enhanced, which is beneficial to the agglomeration of silica particles; Fourth, by employing a supergravity reactor, the unique flow behavior of a multiphase flow system under supergravity conditions is utilized to enhance the relative velocity and contact between phases, and to promote efficient mass and heat transfer processes, thereby further promoting particle agglomeration and achieving automatic particle classification and sieving. Attached Figure Description

[0018] Figure 1 This is a particle size distribution diagram of the product obtained in Example 3; Figure 2 This is an SEM image of the product obtained in Example 3. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Example 1: A method for preparing micron-sized spherical silica, comprising the following steps: (1) Prepare solution A Ethanol was added as a solvent to tetraethyl orthosilicate. The ethanol used was 99% industrial grade ethanol, and the amount of tetraethyl orthosilicate added was 100 g / L. After stirring and mixing evenly, solution A was prepared and set aside. (2) Prepare solution B In the reaction vessel, isopropanol and ethanol are used as co-solvents. The ethanol used is 99.5% industrial grade ethanol, and the isopropanol used is 99% industrial grade isopropanol, with a mass ratio of isopropanol to ethanol of 1:3. A weakly basic catalyst (amino acid) and an electrolyte (potassium chloride) are added to the co-solvents at a concentration of 5 g / L, water at 60 g / L, and the electrolyte at 0.2 g / L. The mixture is stirred and mixed thoroughly. Then, a eutectic solvent (20 g / L) is added, and the mixture is stirred again to obtain solution B, which is then set aside. (3) Preparation of micron-sized silica Solution B is first added to the hypergravity reactor. An inert gas is selected for the gas phase. Solution A is introduced into the rotor cavity through the liquid inlet pipe of the hypergravity reactor to carry out the entire reaction process. The reaction temperature is increased in a gradient manner. The first gradient is 20℃ and the reaction time is 1.5h. The second gradient is 70℃ and the reaction time is 0.5h. After the reaction is completed, solid-liquid separation is carried out by distillation, centrifugation and drying to obtain dry powder, which is micron-sized silica.

[0021] Example 2: A method for preparing micron-sized spherical silica, the method comprising the following steps, (1) Prepare solution A Ethanol was added as a solvent to tetraethyl orthosilicate. The ethanol used was industrial grade ethanol with a concentration of 99.5%. The amount of tetraethyl orthosilicate added was 630 g / L. After stirring and mixing evenly, solution A was prepared and set aside. (2) Prepare solution B In the reaction vessel, isopropanol and ethanol are used as co-solvents. The ethanol used is 99.5% industrial grade ethanol, and the isopropanol used is 99.5% industrial grade isopropanol, with a mass ratio of isopropanol to ethanol of 1:4. A weakly basic catalyst, urea, and an electrolyte, ammonium chloride, are added to the co-solvent at a concentration of 40 g / L. The mixture is stirred and mixed thoroughly. Then, a eutectic solvent is added at a concentration of 40 g / L, and the mixture is stirred again to obtain solution B, which is then set aside. (3) Preparation of micron-sized silica Solution B is first added to the hypergravity reactor. An inert gas is selected for the gas phase. Solution A is introduced into the rotor cavity through the liquid inlet pipe of the hypergravity reactor to carry out the entire reaction process. The reaction temperature is increased in a gradient manner. The first gradient is 40℃ and the reaction time is 2.5h. The second gradient is 90℃ and the reaction time is 1.5h. After the reaction is completed, solid-liquid separation is carried out by distillation, centrifugation and drying to obtain dry powder, which is micron-sized silica.

[0022] Example 3: A method for preparing micron-sized spherical silica, comprising the following steps: (1) Prepare solution A Ethanol was added as a solvent to tetraethyl orthosilicate. The ethanol used was industrial grade ethanol with a concentration of 99.9%. The amount of tetraethyl orthosilicate added was 200 g / L. After stirring and mixing evenly, solution A was prepared and set aside. (2) Prepare solution B In the reaction vessel, isopropanol and ethanol are used as co-solvents. The ethanol used is 99.9% industrial grade ethanol, and the isopropanol used is 99.9% industrial grade isopropanol, with a mass ratio of isopropanol to ethanol of 1:3.5. A weakly basic catalyst and electrolyte are added to the co-solvent. The weakly basic catalyst is ammonia water, and the electrolyte is potassium chloride. The amount of ammonia water added is 17 g / L, the amount of water added is 180 g / L, and the amount of electrolyte added is 0.5 g / L. After stirring and mixing evenly, a eutectic solvent is added. The eutectic solvent is choline chloride and urea, with a molar ratio of 1:2, and the amount of eutectic solvent added is 50 g / L. The mixture is stirred and mixed again to obtain solution B, which is then set aside. (3) Preparation of micron-sized silica Solution B is first added to the hypergravity reactor. An inert gas is selected for the gas phase. Solution A is introduced into the rotor cavity through the liquid inlet pipe of the hypergravity reactor to carry out the entire reaction process. The reaction temperature is increased in a gradient manner. The first gradient is 30℃ and the reaction lasts for 2 hours. The second gradient is 80℃ and the reaction lasts for 1 hour. After the reaction is completed, solid-liquid separation is carried out by distillation, centrifugation and drying to obtain dry powder, which is micron-sized silica.

[0023] Example 4: A method for preparing micron-sized spherical silica, comprising the following steps: (1) Prepare solution A Ethanol was added as a solvent to tetraethyl orthosilicate. The ethanol used was industrial grade ethanol with a concentration of 99.3%. The amount of tetraethyl orthosilicate added was 350 g / L. After stirring and mixing evenly, solution A was prepared and set aside. (2) Prepare solution B In the reaction vessel, isopropanol and ethanol are used as co-solvents. The ethanol used is 99.3% industrial grade ethanol, and the isopropanol used is 99.3% industrial grade isopropanol, with a mass ratio of isopropanol to ethanol of 1:3. A weakly basic catalyst and an electrolyte are added to the co-solvent. The weakly basic catalyst is ammonium carbonate, and the electrolyte is ammonium chloride. The amount of weakly basic catalyst added is 20 g / L, the amount of water added is 200 g / L, and the amount of electrolyte added is 0.4 g / L. After stirring and mixing evenly, a eutectic solvent is added. The eutectic solvent is choline chloride and urea, with a molar ratio of 1:1.5, and the amount of eutectic solvent added is 45 g / L. The mixture is stirred again to obtain solution B, which is then set aside. (3) Preparation of micron-sized silica Solution B is first added to the hypergravity reactor. An inert gas is selected for the gas phase. Solution A is introduced into the rotor cavity through the liquid inlet pipe of the hypergravity reactor to carry out the entire reaction process. The reaction temperature is increased in a gradient manner. The first gradient is 35℃ and the reaction time is 2.5h. The second gradient is 75℃ and the reaction time is 0.5h. After the reaction is completed, solid-liquid separation is carried out by distillation, centrifugation and drying to obtain dry powder, which is micron-sized silica.

[0024] Example 5: A method for preparing micron-sized spherical silica, comprising the following steps: (1) Prepare solution A Ethanol was added as a solvent to tetraethyl orthosilicate. The ethanol used was industrial grade ethanol with a concentration of 99.7%. The amount of tetraethyl orthosilicate added was 400 g / L. After stirring and mixing evenly, solution A was prepared and set aside. (2) Prepare solution B In the reaction vessel, isopropanol and ethanol are used as co-solvents. The ethanol used is 99.7% industrial grade ethanol, and the isopropanol used is 99.7% industrial grade isopropanol, with a mass ratio of isopropanol to ethanol of 1:4. A weakly basic catalyst and an electrolyte are added to the co-solvent. The weakly basic catalyst is ammonium bicarbonate, and the electrolyte is potassium chloride. The amount of ammonia added is 10 g / L, the amount of water added is 250 g / L, and the amount of electrolyte added is 0.6 g / L. After stirring and mixing evenly, a eutectic solvent is added. The eutectic solvent is choline chloride and urea, with a molar ratio of 1:1.8, and the amount of eutectic solvent added is 40 g / L. The mixture is stirred again to obtain solution B, which is then set aside. (3) Preparation of micron-sized silica Solution B is first added to the hypergravity reactor. An inert gas is selected for the gas phase. Solution A is introduced into the rotor cavity through the liquid inlet pipe of the hypergravity reactor to carry out the entire reaction process. The reaction temperature is increased in a gradient manner. The first gradient is 25℃ and the reaction time is 2 hours. The second gradient is 85℃ and the reaction time is 1 hour. After the reaction is completed, solid-liquid separation is carried out by distillation, centrifugation and drying to obtain dry powder, which is micron-sized silica.

[0025] Comparative Example 1: Micron-sized spherical silica was prepared using the existing sol-gel method.

[0026] Comparative Example 2: Isopropanol was added, and the rest was the same as Comparative Example 1.

[0027] Comparative Example 3 introduced a eutectic solvent, and the rest was the same as Comparative Example 1.

[0028] Comparative Example 4 uses a hypergravity reactor, and is otherwise the same as Comparative Example 1.

[0029] Comparative Example 5: When preparing solution B, isopropanol was not added, and only ethanol was used as the solvent. The rest was the same as in Example 3.

[0030] Comparative Example 6 did not use a supergravity reactor, but only a regular mixer, and was otherwise the same as Example 3.

[0031] Comparative Example 7 was the same as Example 3, except that no eutectic solvent was introduced.

[0032] The particle size, density, sphericity, and pitch of the spherical silica prepared in Examples 1-3 and Comparative Examples 1-7 were tested, and the following data results were obtained:

[0033]

[0034] In summary, from Figure 1As shown in the experimental data above, the particle size of the spherical oxide particles prepared in Example 3 can be controlled within the range of D100: 4μm-6.5μm and D50: 2μm-4μm, exhibiting more concentrated and superior particle size distribution. (Refer to...) Figure 2 It can be seen that the spherical oxide particles prepared in Example 3 are smooth spheres with good sphericity.

[0035] The experimental results above show that without isopropanol, the diameter increases; without electrolyte, the particles do not grow large and the D50 is very small; without introducing a eutectic solvent but adding an electrolyte, the particle D50 is <1 μm and the particles do not grow large; without using a hypergravity reactor, the diameter increases and the D50 is <2 μm.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing micron-sized spherical silica, characterized in that, The method includes the following steps: (1) Prepare solution A Using ethanol as a solvent, tetraethyl orthosilicate is added to ethanol at a concentration of 100 g / L to 630 g / L. After stirring and mixing evenly, solution A is prepared and set aside. (2) Prepare solution B In a reaction vessel, isopropanol and ethanol are used as co-solvents in a mass ratio of 1:3 to 1:

4. A weakly basic catalyst, water, and an electrolyte are added to the co-solvent. The weakly basic catalyst is one or two of amino acids, ammonium carbonate, ammonium bicarbonate, urea, and ammonia water. The electrolyte is potassium chloride or ammonium chloride. The amount of weakly basic catalyst added is 5 g / L to 40 g / L, the amount of water added is 60 g / L to 300 g / L, and the amount of electrolyte added is 0.2 g / L to 1 g / L. The mixture is stirred and mixed thoroughly. Then, 20 g to 55 g of a eutectic solvent, a mixture of choline chloride and urea in a molar ratio of 1:1.5 to 2, is added to each liter of co-solvent. The mixture is stirred and mixed again to obtain solution B, which is then set aside. (3) Preparation of micron-sized silica Solution A and solution B are added to the reactor and the temperature is raised to 70℃-90℃ for 2h-4h. After the reaction is completed, the mixture is centrifuged and dried to obtain dry powder, which is micron-sized silicon dioxide. In the reaction process described in step (3), a gradient temperature is used. The first gradient is 20℃-40℃ for 1.5h-2.5h, and the second gradient is 70℃-90℃ for 0.5h-1.5h. The reactor is a hypergravity reactor and the gas phase is an inert gas. Solution B is added to the hypergravity reactor first, and then solution A is introduced into the rotor cavity through the liquid inlet pipe of the hypergravity reactor.

2. The method for preparing micron-sized spherical silica according to claim 1, characterized in that, In step (3), the post-processing of the powder includes heat treatment and grinding. The heat treatment conditions are 800℃-1000℃ and the time is 3h-6h. The grinding process employed a ball mill, with silica balls as the grinding media, ultimately yielding a true density >2.1 g / cm³. 3 Electronic filler-grade powder.

3. The method for preparing micron-sized spherical silica according to claim 1, characterized in that, The ethanol used is industrial ethanol with a concentration of 99% or higher, and the isopropanol used is industrial isopropanol with a concentration of 99% or higher.

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