A method for preparing a silicon sol with controllable particle shape

Abstract

The application relates to a preparation method of a silicon sol with controllable particle shape. The silicon sol is prepared by a hydrolysis alkoxysilane method, first, the monomer shape is controlled by using an auxiliary agent, then the monomer condensation is controlled under the action of a catalyst, and then the silicon sol aqueous solution with a mass fraction of 5%-20% and different particle shapes is prepared by using a reduced pressure distillation mode. The method can more effectively control the morphology of the silicon sol particles, and the particles have good dispersity and high repeatability.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation, specifically relating to a method for preparing silica sol with controllable particle shape based on the alkoxide method. Background Technology

[0002] Silica sol, formed by the stable dispersion of nano-sized silica particles in a continuous phase composed of water or other organic solvents, is widely used as a precursor or final product in fields such as papermaking, catalysts, and fillers. In recent years, with the continuous development of semiconductor technology, silica sol has been applied as a polishing slurry in the CMP polishing process of silicon wafers and other semiconductor devices. Targeted control of the silica sol particle morphology to adapt to different polishing applications and meet diverse polishing requirements is of crucial significance.

[0003] Currently, silica sol particles can be prepared using methods such as gas-phase methods, elemental silicon hydrolysis, ion exchange, and alkoxide methods. The gas-phase method uses silicon tetrachloride as the silicon source and reacts at temperatures above 1000℃, often producing chain-like particles that need to be dispersed in a desired solvent to obtain silica sol. The elemental silicon hydrolysis method uses elemental silicon and water as reactants under strong alkali conditions to prepare silica sol, often producing near-spherical particles. The ion exchange method uses water glass as the main raw material, but controlling the particle shape flexibly is difficult. The alkoxide method uses acid or alkali as a catalyst and alkoxysilanes and water as reactants, allowing for simple control of particle shapes. Therefore, research on controlling particle shape using the alkoxide method has significant feasibility and research potential.

[0004] Currently, the most commonly used method for preparing silica sol particles based on the alkoxide method is the traditional method. The method involves directly adding alkoxysilanes to a mixture of catalyst, organic solvent, and water, and reacting for a period of time to obtain silica sol particles. This method is often used to prepare spherical particles. Although particles of different shapes can be obtained by adjusting the reactant ratio, it still has the following drawbacks: the obtained sample has a high proportion of spherical particles, it is difficult to form chain particles with trimerization or higher, and the particle shape control relies on experience with poor precision. Summary of the Invention

[0005] This invention addresses the shortcomings of existing alkoxide methods by innovatively proposing a method for preparing silica sol with controllable particle shape. First, an auxiliary agent is used to control the morphology of hydrolyzed monomers, and then the monomer condensation is controlled under the action of a catalyst, thereby preparing silica sol with different particle shapes.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A method for preparing silica sol with controllable particle shape includes the following steps:

[0008] (1) Preparation of solution A: Mix organic solvent, water and alkaline catalyst in a certain proportion until homogeneous;

[0009] (2) Preparation of solution B: Mix the optional organic solvent, alkoxysilane and water in a certain proportion, then add a certain amount of organic acid, stir, preferably under microwave action, add a certain amount of additive and stir to mix evenly.

[0010] (3) Preparation of initial silica sol: At a certain temperature, liquid B is added to liquid A which is being stirred at a certain flow rate, and the reaction is carried out to obtain initial silica sol;

[0011] (4) Vacuum distillation: The initial silica sol is diluted with water and the organic solvent, additives and alkaline catalyst are removed by displacement under reduced pressure to obtain a concentrated silica sol with a mass fraction of 5-20%.

[0012] Preferably, the organic solvent in steps (1) and (2) is one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, cyclohexane, methyl ethyl ketone, diethyl ether, ethyl propyl ether, etc.; preferably, the organic solvent in liquid B is the same as the organic solvent in liquid A; more preferably, a certain proportion of acetonitrile, a solvent with a high dielectric constant, is added to liquid A.

[0013] Preferably, the alkaline catalyst in step (1) is selected from at least one of alkali metal hydroxides, ammonia, or organic amine compounds; preferably, the alkaline catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, triethanolamine, or tetramethylammonium hydroxide. Preferably, the organic solvent has a mass fraction of 60%-80%, the water has a mass fraction of 15%-35%, and the alkaline catalyst has a mass fraction of 0.5%-5%.

[0014] Preferably, in step (1), the preparation temperature of solution A is between 5-60°C; more preferably 10-40°C.

[0015] Preferably, in step (2), the alkoxysilane is one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, preferably tetramethoxysilane. The organic solvent has a mass fraction of 0%-20%, and the molar ratio of water to alkoxysilane is 20:1-4:1, preferably 15:1-8:1. The organic acid is one or more of acetic acid, malic acid, citric acid, and benzoic acid, and the amount used is 1000-10000 ppm of the total amount of silica generated, preferably 2000-6000 ppm.

[0016] Preferably, the auxiliary agent is selected from one or more of diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, diisopropylamine, and aniline substances, with triethylamine being the most preferred. The auxiliary agent has the following specific effects in regulating monomer morphology. In the preparation of silica sol particles by the alkoxide method, acidic conditions favor hydrolysis. Introducing the auxiliary agent into the hydrolysate can achieve the following three objectives: First, the auxiliary agent can increase the pH of the system, thereby reducing the hydrolysis reaction rate and inhibiting further changes in monomer morphology, creating conditions for controlling the morphology of hydrolyzed monomers; second, the auxiliary agent can also act as a condensation catalyst, promoting the continued condensation of uncondensed hydrolyzed monomers with existing oligomers, resulting in a more uniform morphology of the hydrolyzed monomers; finally, the auxiliary agent contains lone pairs of electrons, which can interact with silanol groups through hydrogen bonds, stabilizing the hydrolyzed monomers and inhibiting further condensation, thus controlling the hydrolyzed monomers to ensure their stable existence in a defined morphology.

[0017] Preferably, in step (2), solution B is prepared at an operating temperature of 5-30°C. The microwave frequency is set to 2.45 GHz, and the microwave power per milliliter of mixture is 1W-4W. The stirring time is 10-120 min, and the molar ratio of alkoxysilane to auxiliary agent is 120:1-20:1. Preferably, a stirring time of 10-30 min and a molar ratio of alkoxysilane to additive of 120:1-90:1, with pH controlled at 5.5-6.5, are conducive to the formation of spherical particles; and / or, a stirring time of 30-70 min and a molar ratio of alkoxysilane to additive of 90:1-60:1, with pH controlled at 4.5-5.5, are conducive to the formation of dimer and trimer particles; and / or, a stirring time of 70-120 min and a molar ratio of alkoxysilane to additive of 60:1-20:1, with pH controlled at 3.5-4.5, are conducive to the formation of tetramer and higher-order chain particles.

[0018] Preferably, the initial silica sol preparation in step (3) is carried out at a reaction temperature between 5-60°C; more preferably between 10-40°C. The dropping time of liquid B is 0.1 min-70 min; the stirring speed is 200 r / min-1000 r / min.

[0019] Preferably, in step (4), the initial silica sol is first diluted with water to a target mass fraction of about 5-20%, and then heated to boiling under vacuum conditions of 5kPa-40kPa to remove organic solvents. The mass fraction of the silica sol is then concentrated to 5-20% as required.

[0020] Compared to existing technologies, this invention innovatively proposes a method for preparing silica sol with controllable particle shape, achieving high precision and strong controllability of particle shape. The silica sol particle morphologies provided by this invention include spherical particles, dimer and trimer particles, and chain-like particles that are tetramers or higher. Attached Figure Description

[0021] Figure 1 (a) is a TEM image of the spherical silica sol particles in Example 1 of the present invention.

[0022] Figure 1 (b) is a TEM image of the dimer and trimer-shaped silica sol particles in Example 3 of the present invention.

[0023] Figure 1 (c) is a TEM image of tetrameric or higher chain-like silica sol in Example 4 of the present invention.

[0024] Figure 1 (d) is a TEM image of the network structure obtained when preparing solution B without adding any additives. Detailed Implementation

[0025] To better understand the technical solution of the present invention, the preparation method of the present invention will be further explained and illustrated below through more specific embodiments, but this does not constitute any limitation.

[0026] A method for preparing silica sol with controllable particle shape includes the following steps:

[0027] (1) Preparation of solution A: Mix organic solvent, water and alkaline catalyst in a certain proportion until homogeneous;

[0028] (2) Preparation of solution B: Mix the optional organic solvent, alkoxysilane and water in a certain proportion, then add a certain amount of organic acid, stir, preferably stir under microwave action for a period of time, add a certain amount of additive and stir to mix evenly.

[0029] (3) Preparation of initial silica sol: At a certain temperature, liquid B is added to liquid A which is being stirred at a certain flow rate, and the reaction is carried out to obtain initial silica sol;

[0030] (4) Vacuum distillation: The initial silica sol is diluted with water and the organic solvent, additives and alkaline catalyst are removed by displacement under reduced pressure to obtain a concentrated silica sol with a mass fraction of 5-20%.

[0031] The organic solvent in step (1) is one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, cyclohexane, methyl ethyl ketone, diethyl ether, ethyl propyl ether, etc.; preferably, methanol and acetonitrile with high dielectric constants are added. The alkaline catalyst is at least one of sodium hydroxide, potassium hydroxide, ammonia, triethanolamine, or tetramethylammonium hydroxide.

[0032] In step (2), the organic solvent has a mass fraction of 0%-20% and is selected from one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, cyclohexane, methyl ethyl ketone, diethyl ether, and ethyl propyl ether. Preferably, the type and ratio of organic solvent in solution B should be the same as those in solution A. The alkoxysilane is one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, preferably tetramethoxysilane. The molar ratio of water to alkoxysilane is 20:1-4:1, preferably 15:1-8:1. The organic acid is one or more of acetic acid, malic acid, citric acid, and benzoic acid, preferably malic acid. The amount of organic acid used is 1000-10000 ppm of the total amount of silica produced, preferably 2000-6000 ppm. The auxiliary agent is selected from one or more of diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, diisopropylamine, and aniline substances, preferably triethylamine.

[0033] In step (2), adjusting the stirring hydrolysis time and the amount of additive yields silica sol particles with different particle shapes. When the stirring time is 10 min-120 min, the molar ratio of the alkoxysilane to the additive is 120:1-20:1. Preferably, a stirring time of 10 min-30 min and a molar ratio of alkoxysilane to additive of 120:1-90:1, with pH controlled at 5.5-6.5, is conducive to the formation of spherical particles; and / or, a stirring time of 30 min-70 min and a molar ratio of alkoxysilane to additive of 90:1-60:1, with pH controlled at 4.5-5.5, is conducive to the formation of dimer and trimer particles; and / or, a stirring time of 70 min-120 min and a molar ratio of alkoxysilane to additive of 60:1-20:1, with pH controlled at 3.5-4.5, is conducive to the formation of tetramer and higher-order chain particles.

[0034] In step (3), the initial silica sol is prepared at a reaction temperature between 5-60℃, including but not limited to 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, and 60℃, preferably 10-40℃. Under this temperature condition, solution B is added to solution A, wherein the dropwise addition time of solution B to solution A is between 0.1min and 70min, including but not limited to 0.1min, 1min, 3min, 5min, 10min, 20min, 30min, 50min, and 70min; and the stirring speed is between 200r / min and 1000r / min, including but not limited to 200r / min, 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min, 900r / min, and 1000r / min.

[0035] In step (4), the initial silica sol is first diluted with water to a target mass fraction of about 5-20%, and then heated to boiling under vacuum conditions of 5kPa-40kPa to remove organic solvents. The mass fraction of the silica sol is then concentrated to 5-20% as needed.

[0036] The preparation method of the present invention will be further explained and illustrated below through more specific embodiments, but these do not constitute any limitation.

[0037] The main raw materials used in the following examples and comparative examples are as follows:

[0038]

[0039] Detection method:

[0040] The appearance morphology of the silica sol was characterized using TEM images taken with a JEOL JEM2100plus.

[0041] Example 1

[0042] Solution A was prepared by mixing 132.77 g isopropanol, 50.45 g water, and 7.61 g ammonia water until homogeneous. Solution B was prepared by mixing 5.84 g isopropanol, 7.51 g water, 15.85 g tetramethoxysilane (TMOS), and 0.063 g malic acid until homogeneous. After stirring under microwave for 30 min, 0.117 g triethylamine was added and stirred for a period of time until homogeneous. The pH value was measured to be 5.94. Solution B was then added to solution A using a peristaltic pump, and the addition was completed within 30 min. The mixture was reacted at 20 °C and 200 r / min for 3 h to obtain the initial silica sol. After diluting the initial silica sol with 27.53 g water, the mixture was concentrated under reduced pressure at 10 kPa and 100 °C until it reached approximately 20%, resulting in the concentrated silica sol. At this point, the mass concentration was 20%, and spherical silica sol particles were obtained.

[0043] Example 2

[0044] Solution A was prepared by mixing 132.77 g isopropanol, 50.45 g water, and 7.61 g ammonia water until homogeneous. Solution B was prepared by mixing 5.84 g isopropanol, 16.425 g water, 6.935 g tetramethoxysilane (TMOS), and 0.003 g acetic acid until homogeneous. After stirring under microwave for 10 min, 0.028 g diethylamine was added and stirred for a period of time until homogeneous. The pH value was measured to be 6.12. Solution B was then added to solution A using a peristaltic pump, and the addition was completed within 5 min. The reaction was carried out at 20 °C and 200 r / min for 3 h to obtain the initial silica sol. After diluting the initial silica sol with 39.97 g water, the solution was concentrated under reduced pressure at 10 kPa and 100 °C to approximately 5%, obtaining the concentrated silica sol. At this point, the mass concentration was 20%, and spherical silica sol particles were obtained.

[0045] Example 3

[0046] Solution A was prepared by mixing 46.47 g methanol, 86.3 g acetonitrile, 50.45 g water, and 7.61 g ammonia water until homogeneous. Solution B was prepared by mixing 4.41 g organic solvent (a mixture with the same ratio as the organic solvent in solution A), 21.45 g water, 18.24 g tetramethoxysilane (TMOS), and 0.023 g malic acid until homogeneous. After stirring under microwave for 70 min, 0.118 g propylamine was added and stirred for a period of time until homogeneous. The pH value was measured to be 4.73. Solution B was then added to solution A using a peristaltic pump, and the addition was completed within 20 min. The reaction was carried out at 20 °C and 200 r / min for 3 h to obtain the initial silica sol. After diluting the initial silica sol with 54.87 g water, the solution was concentrated under reduced pressure at 10 kPa and 100 °C until it reached approximately 10%, obtaining the concentrated silica sol. At this point, the mass concentration was 20%, and a silica sol containing dimer and trimer particles was obtained.

[0047] Example 4

[0048] Solution A was prepared by mixing 132.77 g of isopropanol, 50.45 g of water, and 7.61 g of ammonia. Solution B was prepared by mixing 22.265 g of water, 15.43 g of tetramethoxysilane (TMOS), and 0.036 g of benzoic acid. After stirring under microwave for 120 min, 0.294 g of isopropylamine was added and stirred for a period of time until homogeneous. The pH value was measured to be 3.88. Solution B was then added to solution A using a peristaltic pump, and the addition was completed within 70 min. The reaction was carried out at 20 °C and 800 r / min for 3 h to obtain the initial silica sol. After diluting the initial silica sol with 21.99 g of water, the solution was concentrated under reduced pressure at 10 kPa and 100 °C to approximately 18%, resulting in the concentrated silica sol. At this point, the mass concentration was 20%, and a silica sol containing tetrameric or higher chain particles was obtained.

[0049] Example 5

[0050] Solution A was prepared by mixing 46.47 g methanol, 86.3 g acetonitrile, 50.45 g water, and 7.61 g ammonia water until homogeneous. Solution B was prepared by mixing 22.265 g water, 11.12 g tetramethoxysilane (TMOS), and 0.028 g malic acid until homogeneous. After stirring under microwave for 90 min, 0.185 g diisopropylamine was added and stirred for a period of time until homogeneous. Solution B was then added to solution A using a peristaltic pump, with the addition completed within 60 min. The reaction was carried out at 20 °C and 1000 r / min for 2.5 h to obtain the initial silica sol. After diluting the initial silica sol with 24.26 g water, the solution was concentrated under reduced pressure at 10 kPa and 100 °C to approximately 15%, yielding the concentrated silica sol. At this point, the mass concentration was 20%, and a silica sol containing tetrameric or higher chain particles was obtained.

[0051] Comparative Example 1

[0052] Solution A was prepared by mixing 132.77 g isopropanol, 50.45 g water, and 7.61 g ammonia water until homogeneous. Solution B was prepared by mixing 5.84 g isopropanol, 7.51 g water, 15.85 g tetramethoxysilane (TMOS), and 0.036 g malic acid until homogeneous. After stirring under microwave for 30 min, solution B was added to solution A using a peristaltic pump, and the addition was completed within 30 min. The mixture was reacted at 20 °C and 200 r / min for 3 h to obtain the initial silica sol. After diluting the initial silica sol with 27.53 g water, the mixture was concentrated under reduced pressure at 10 kPa and 100 °C until it reached approximately 20%, resulting in the concentrated silica sol, which had a network structure.

[0053] Comparative Example 2

[0054] 132.77 g isopropanol, 71.9 g water, 7.61 g ammonia, and 0.202 g triethylamine were mixed and stirred until homogeneous to form solution A. 4.41 g isopropanol and 18.24 g tetramethoxysilane (TMOS) were mixed until homogeneous to form solution B. Solution B was added to solution A, with the addition completed within 10 seconds. The reaction was carried out at 20 °C and 300 rpm for 3 hours to obtain the initial silica sol. The obtained silica sol exhibited particle aggregation, with visible micron-sized particles adhering to the beaker wall or depositing at the bottom of the beaker.

[0055] Figure 1 TEM images of Embodiments 1, 3, 4 and Comparative Example 1 of the present invention are provided, respectively corresponding to Figure 1 The figures a, b, c, and d are shown in the diagram. As can be seen from the figure, the particles in Examples 1 and 2 are mostly spherical; in Example 3, the particles are predominantly paired and resemble peanuts; in Example 4, the particles are mostly tetrameric or higher chain-like particles. The difference between Comparative Example 1 and the Examples lies only in whether an additive is added to solution B. Without the additive, the silicon source hydrolysis products in solution B will over-polymerize, making it difficult to form particles. The difference between Comparative Example 2 and the Examples lies in the use of traditional... The method of preparing silica sol can cause abnormal particle aggregation.

[0056] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing silica sol with controllable particle shape, characterized in that, It includes the following steps: (1) Preparation of solution A: Mix the organic solvent, water and alkaline catalyst evenly; (2) Preparation of solution B: Mix the optional organic solvent with alkoxysilane and water, then add organic acid, stir, add auxiliary agent and stir to mix evenly; (3) Preparation of initial silica sol: Add liquid B to liquid A which is being stirred, and react to obtain initial silica sol; (4) Vacuum distillation: Dilute the initial silica sol with water and distill under reduced pressure to remove organic solvents, additives and alkaline catalysts to obtain concentrated silica sol with a mass fraction of 5-20%. In step (2), the additive is selected from one or more of diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, diisopropylamine and aniline substances. After adding the additive, the stirring time is 10 min to 120 min, and the molar ratio of alkoxysilane to additive is 120:1 to 20:

1.

2. The method for preparing silica sol with controllable particle shape according to claim 1, characterized in that, In step (2), the organic acid is added and then stirred under microwave irradiation.

3. The method for preparing silica sol with controllable particle shape according to claim 1, characterized in that, The organic solvents mentioned in steps (1) and (2) are one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, diethyl ether, ethyl propyl ether, and cyclohexane.

4. The method for preparing silica sol with controllable particle shape according to claim 3, characterized in that, The organic solvent in solution B is the same as the organic solvent in solution A.

5. The method for preparing silica sol with controllable particle shape according to claim 2, characterized in that, The alkaline catalyst in step (1) is selected from at least one of alkali metal hydroxides, ammonia, or organic amine compounds.

6. The method for preparing silica sol with controllable particle shape according to claim 5, characterized in that, The alkaline catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, triethanolamine, or tetramethylammonium hydroxide.

7. The method for preparing silica sol with controllable particle shape according to claim 5, characterized in that, Solution A contains 60%-80% organic solvent by mass, 15%-35% water by mass, and 0.5%-5% alkaline catalyst by mass.

8. The method for preparing silica sol with controllable particle shape according to claim 1, characterized in that, The alkoxysilane mentioned in step (2) is one or more of tetramethoxysilane, tetraethoxysilane, or tetrapropoxysilane.

9. The method for preparing silica sol with controllable particle shape according to claim 1, characterized in that, The organic solvent in step (2) B solution has a mass fraction of 0%-20%, and the molar ratio of water to alkoxysilane is 20:1-4:

1.

10. The method for preparing silica sol with controllable particle shape according to claim 9, characterized in that, In step (2), the molar ratio of water to alkoxysilane is 15:1-8:

1.

11. The method for preparing silica sol with controllable particle shape according to claim 1, characterized in that, The organic acid mentioned in step (2) is one or more of acetic acid, malic acid, citric acid or benzoic acid, and / or the amount used is 1000-10000 ppm of the total amount of silica generated.

12. The method for preparing silica sol with controllable particle shape according to claim 11, characterized in that, The amount of organic acid used is 2000-6000 ppm of the total amount of silica generated.

13. The method for preparing silica sol with controllable particle shape according to claim 1, characterized in that, In step (2), the stirring time after adding the additive is 10 min-30 min and the molar ratio of alkoxysilane to additive is 120:1-90:1, and the pH is controlled at 5.5-6.5, which is conducive to the formation of spherical particles; and / or, the stirring time after adding the additive is 30 min-70 min and the molar ratio of alkoxysilane to additive is 90:1-60:1, and the pH is controlled at 4.5-5.5, which is conducive to the formation of dimer and trimer particles; and / or, the stirring time after adding the additive is 70 min-120 min and the molar ratio of alkoxysilane to additive is 60:1-20:1, and the pH is controlled at 3.5-4.5, which is conducive to the formation of tetramer and higher chain particles.

14. The method for preparing silica sol with controllable particle shape according to claim 1, characterized in that, In step (3), the initial silica sol is prepared at a reaction temperature between 5 and 60°C; and / or, liquid B is added dropwise to liquid A at a time of 0.1 min to 70 min; and the stirring speed is 200 r / min to 1000 r / min.

15. The method for preparing silica sol with controllable particle shape according to claim 14, characterized in that, The initial silica sol is prepared in step (3) at a reaction temperature of 10-40℃.

16. The method for preparing silica sol with controllable particle shape according to claim 1, characterized in that, In step (4), the vacuum distillation first dilutes the initial silica sol with water to a mass fraction of 5-20%, and then heats it to boiling under vacuum conditions of 5kPa-40kPa to remove the organic solvent.

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