Preparation method of alkaline large-particle-size high-purity silica sol

Abstract

The invention relates to the technical field of silica sol preparation, in particular to a preparation method of alkaline large-particle-size high-purity silica sol, which comprises the following steps: preparing and selecting materials; proportioning the materials; heating and fusing; and carrying out pressurized reaction and filtering preparation. According to the preparation method, the monodisperse spherical silica sol is adopted as a seed solution, and the active silicic acid solution, the metal silicon powder and the basic catalyst are added to quickly catalyze and control components in materials required by reaction, so that impurities are reduced, and the preparation of the large-particle-size and high-purity silica sol is quickly realized; and moreover, the granularity of the silica sol in the large-particle-size high-purity silica sol can be ensured to be prepared according to requirements, the requirements of preparation of various grades of silica sol are met, and the preparation efficiency and quality are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silica sol preparation, and particularly to a preparation method of alkaline large-particle-size high-purity silica sol. Background Art

[0002] The demand for large-particle-size silica sol as a raw material for silicon wafer polishing liquid has increased sharply. The large-particle-size silica sol abrasive has large and uniform particles, good dispersibility, good fluidity, easy cleaning, can be made into a concentrated form, easy to solve the problems of transportation and packaging, fast polishing speed, and good polishing quality, and can meet high-quality chemical mechanical polishing (CMP), significantly improving the polishing surface quality and geometric accuracy of various silicon wafers.

[0003] Large-particle-size and high-concentration silica sol are widely used in industries such as microelectronics, optoelectronics, and alloy manufacturing. The large-particle-size silica sol prepared industrially has small particle size and uneven dispersion degree, which limits its application in fields such as silicon substrates, LED substrates, and alloy processing.

[0004] In the prior art, a method for directly preparing high-purity large-particle-size silica sol by a silicon powder method in CN104671248A realizes precise control of the particle size of silica sol by controlling the reaction temperature and reaction pressure. The inventive method simplifies the process, has a high conversion rate of raw material silicon powder, a low dispersion degree of the particle size of silica sol, and the prepared large-particle-size silica sol can be used as a chemical mechanical polishing abrasive.

[0005] In the prior art, directly using silicon powder for preparation will result in a low particle size of silica sol, which cannot meet the requirements of higher-grade silica sol and is not conducive to improving the particle size of silica sol, so improvement is needed. Summary of the Invention

[0006] The purpose of the present invention is to solve the defects existing in the prior art, and propose a preparation method of alkaline large-particle-size high-purity silica sol.

[0007] In order to achieve the above purpose, the present invention adopts the following technical scheme:

[0008] A preparation method of alkaline large-particle-size high-purity silica sol, comprising the following steps:

[0009] S1. Prepare materials and select materials: According to the preparation requirements, the staff prepares monodisperse spherical silica sol, active silicic acid solution, metallic silicon powder, alkaline catalyst, and deionized water; and fully detects the quality of the materials to ensure that they meet the preparation requirements;

[0010] S2. Material ratio: The mass ratio of the active silicic acid solution, metallic silicon powder, alkaline catalyst, and deionized water is 1-3:600:3-6:12000; the weight ratio of silicon in the monodisperse spherical silica sol is 0.5-10wt%

[0011] S3. Heating and fusion: Add monodisperse spherical silica sol into a high-pressure reactor, stir and heat to boiling, then add an active silicic acid solution, metallic silicon powder, an alkaline catalyst and deionized water in proportion, control their respective flow rates, and carry out the reaction while controlling the pH value in the range of 7 - 14;

[0012] S4. Pressurized reaction: After adding the metallic silicon powder, alkaline catalyst and deionized water, seal and pressurize, and maintain stirring and constant-temperature heating; The reaction time is 25 - 35 min;

[0013] S5. Filtration and preparation: Remove silicon slag and anion and cation impurities by centrifugal filtration and membrane filtration to obtain large-particle-size alkaline silica sol.

[0014] Compared with the prior art, in this application, monodisperse spherical silica sol is used as the seed solution, and an active silicic acid solution, metallic silicon powder and an alkaline catalyst are added to quickly catalyze and control the components in the materials required for the reaction, reduce impurities, so as to quickly realize the preparation of large-particle-size high-purity silica sol, and ensure that the particle size of the silica sol in the large-particle-size high-purity silica sol can be prepared according to requirements, meet the requirements for the preparation of silica sols of various grades, and improve the efficiency and quality of the preparation.

[0015] Preferably, the alkaline catalyst is a mixture of an inorganic base and an aluminate; The mass ratio of the inorganic base to the aluminate is 3 - 6:1 - 2; The inorganic base is any one of sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonium hydroxide.

[0016] Furthermore, ensuring the catalytic effect of the catalyst helps to better prepare large-particle-size high-purity alkaline silica sol, and makes the preparation process carried out in an alkaline environment.

[0017] Preferably, the preparation method of the active silicic acid solution is: Dilute concentrated water glass with deionized water to a solution with a silica content of 2 - 6 wt%, stir evenly and then add it into a strong-acid cation exchange resin for cation exchange to obtain an active silicic acid solution with a pH value of 2.0 - 4.0.

[0018] Furthermore, the cation exchange resin is regenerated, and the strong-acid cation resin can be selected from polystyrene sulfonic acid type resins, which can facilitate the reaction with monodisperse spherical silica sol, enable the monodisperse spherical silica sol to form crystal seeds, and help quickly adsorb silicon to form large particle sizes.

[0019] Preferably, in S4, the pressure is increased to 1 - 5 Mpa; The temperature of the constant-temperature heating is 95 - 100 °C.

[0020] Furthermore, precisely control the reaction environment to control the range of the particle size of the silica sol in the final product according to requirements, and adapt to various grade requirements.

[0021] Preferably, the purity of the metallic silicon powder is above 99%.

[0022] Furthermore, it is convenient for better preparation of large-particle-size and high-purity silica sol.

[0023] Preferably, the aluminate is one or more of sodium aluminate, sodium metaaluminate, sodium tetrahydroxyaluminate, and aluminum oxide.

[0024] Furthermore, it helps to improve the efficiency and quality of the reaction.

[0025] Preferably, the particle size of the large-particle-size alkaline silica sol is 8 - 500 nm, the dispersion degree ≤ 0.1, and the silica content > 35%.

[0026] Furthermore, it can fully prepare the required particle size according to the demand.

[0027] Preferably, after each addition of the catalyst, the content of the catalyst in the total mass of the silicon powder mixture and the catalyst is ≤ 1%.

[0028] Furthermore, by controlling the ratio, the efficiency and quality of the preparation are improved.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. By using materials such as monodisperse spherical silica sol, active silicic acid solution, and metallic silicon powder in this application, the disadvantages of conventional silicon powder preparation can be compensated for, which helps to control the diameter of the particles in the final product so as to meet the required preparation requirements;

[0031] 2. By controlling the temperature and pressure during the preparation, the purpose of preparing the particle diameter in the silica sol according to the demand can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a step diagram of the preparation method of the alkaline large-particle-size and high-purity silica sol proposed by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The technical solutions in the embodiments 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 a part of the embodiments of the present invention, rather than all of the embodiments.

[0034] Refer to Figure 1 , the preparation method of the alkaline large-particle-size and high-purity silica sol includes the following steps:

[0035] S1. Preparation and material selection: According to the preparation requirements, the staff prepares monodisperse spherical silica sol; active silicic acid solution; metallic silicon powder with a purity of over 99%; alkaline catalyst; deionized water, which is ultrapure water with a resistivity of 18.2 MΩ·cm. And fully detect the quality of the materials to ensure that they meet the preparation requirements. Detect the materials to ensure that they meet the preparation requirements. At the same time, screen the metallic silicon powder. Different metallic silicon powders are used when preparing alkaline large-particle-size high-purity silica sol of different grades, which can improve the preparation effect and speed, facilitate better adsorption, and different particle-size metallic silicon powders can improve the preparation efficiency of silica sol with different particle sizes and reach the required particle size faster.

[0036] S2. Material ratio: The mass fraction ratio of the active silicic acid solution, metallic silicon powder, alkaline catalyst and deionized water is 1 - 3:600:3 - 6:12000; the weight fraction ratio of silicon in the monodisperse spherical silica sol is 0.5 - 10 wt%.

[0037] S3. Heating and fusion: Add monodisperse spherical silica sol to the high-pressure reactor, stir and heat to boiling, and then add the active silicic acid solution, metallic silicon powder, alkaline catalyst and deionized water according to the ratio, and control their respective flow rates. After each addition of the catalyst, the content of the catalyst in the total mass of the silicon powder mixture and the catalyst is ≤1%; control the pH value in the range of 7 - 14 for the reaction, and carry out the reaction quickly in an alkaline environment to improve the preparation quality and effect.

[0038] S4. Pressurized reaction: After adding the metallic silicon powder, alkaline catalyst and deionized water, seal and pressurize, and keep stirring and constant-temperature heating; pressurize to 1 - 5 Mpa; the temperature of constant-temperature heating is 95 - 100 °C; the reaction time is 25 - 35 min. Precise control of the pressure during the preparation process helps to prepare silica sol with different particle sizes according to the requirements.

[0039] S5. Filtration and preparation: Remove silicon slag and anion and cation impurities by centrifugal filtration and membrane filtration methods, which can fully remove impurities and obtain large-particle-size alkaline silica sol; the particle size of the large-particle-size alkaline silica sol is 8 - 500 nm, the dispersion degree is ≤0.1, and the silica content is >35%.

[0040] In the present invention, the alkaline catalyst is a mixture of inorganic base and aluminate; the mass ratio of the inorganic base to the aluminate is 3 - 6:1 - 2; the inorganic base is any one of sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonium hydroxide; the aluminate is one or more of sodium aluminate, sodium metaaluminate, sodium tetrahydroxoaluminate and aluminum oxide; ensuring the catalytic effect of the catalyst helps to better prepare alkaline large-particle-size high-purity silica sol and makes the preparation process carried out in an alkaline environment.

[0041] In the present invention, the preparation method of the active silicic acid solution is as follows: Dilute concentrated water glass with deionized water to a solution with a silica content of 2-6 wt%, stir evenly, and then add it into a strong acid cation exchange resin for cation exchange to obtain an active silicic acid solution with a pH value of 2.0-4.0; the cation exchange resin is regenerated, and the strong acid cation resin can be selected from polystyrene sulfonic acid type resins, which is convenient for reacting with monodisperse spherical silica sol, enabling the monodisperse spherical silica sol to form crystal seeds and helping to rapidly adsorb silicon to form large particle sizes.

[0042] Example 1

[0043] In this example, the preparation method of the alkaline large particle size high-purity silica sol includes the following steps:

[0044] Heating and fusion: Add monodisperse spherical silica sol and deionized water in a mass ratio of 1:5 to a high-pressure reactor, stir and dilute, then stir and heat to boiling, and then add active silicic acid solution, metallic silicon powder, alkaline catalyst and deionized water in a mass ratio of 1:600:3:12000, while controlling the addition rate to ensure uniform addition, facilitating better mixing and reaction, and at the same time controlling the pH value to react in the range of 7-10;

[0045] Pressurized reaction: After adding metallic silicon powder, alkaline catalyst and deionized water, seal and pressurize to 1-3 Mpa, and maintain stirring and constant temperature heating; the reaction time is 25-35 min;

[0046] Filtration and preparation: Remove silicon slag and anion and cation impurities by centrifugal filtration and membrane filtration to obtain large particle size alkaline silica sol.

[0047] Example 2

[0048] In this example, the preparation method of the alkaline large particle size high-purity silica sol includes the following steps:

[0049] Heating and fusion: Add monodisperse spherical silica sol and deionized water in a mass ratio of 1:5 to a high-pressure reactor, stir and dilute, then stir and heat to boiling, and then add active silicic acid solution, metallic silicon powder, alkaline catalyst and deionized water in a mass ratio of 2:600:4.5:12000, while controlling the addition rate to ensure uniform addition, facilitating better mixing and reaction, and at the same time controlling the pH value to react in the range of 10-12;

[0050] Pressurized reaction: After adding metallic silicon powder, alkaline catalyst and deionized water, seal and pressurize to 3-4 Mpa, and maintain stirring and constant temperature heating; the reaction time is 25-35 min;

[0051] Filtration preparation: Remove silica residues and anion and cation impurities through centrifugal filtration and membrane filtration to obtain large-particle-size alkaline silica sol.

[0052] Example 3

[0053] The preparation method of the alkaline large-particle-size high-purity silica sol in this example includes the following steps:

[0054] Heating and fusion: Add monodisperse spherical silica sol and deionized water in a mass ratio of 1:5 to the high-pressure reactor, stir and dilute, then stir and heat to boiling. Then add active silicic acid solution, metallic silicon powder, alkaline catalyst and deionized water in a mass ratio of 3:600:6:12000, and control the addition speed to ensure uniform addition, which is convenient for better mixing and reaction. At the same time, control the pH value in the range of 12 - 14 for the reaction;

[0055] Pressurized reaction: After adding metallic silicon powder, alkaline catalyst and deionized water, seal and increase the pressure to 4 - 5 Mpa, and keep stirring and constant-temperature heating; the reaction time is 25 - 35 min;

[0056] Filtration preparation: Remove silica residues and anion and cation impurities through centrifugal filtration and membrane filtration to obtain large-particle-size alkaline silica sol.

[0057] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A method for preparing alkaline large-particle high-purity silica sol, characterized in that: The following steps are involved: S1. Material preparation and selection: The staff prepares monodisperse spherical silica sol, active silicic acid solution, metallic silicon powder, alkaline catalyst, and deionized water according to the preparation requirements; and fully tests the quality of the materials to ensure that they meet the preparation requirements; S2, material ratio: the mass ratio of the active silicic acid solution, metallic silicon powder, alkaline catalyst and deionized water is 1-3:600:3-6:12000; the weight ratio of silicon in the monodisperse spherical silica sol is 0.5-10wt% S3, heating and fusion: add monodisperse spherical silica sol to the autoclave, stir and heat to boiling, then add active silicic acid solution, metallic silicon powder, alkaline catalyst and deionized water in proportion, and control the flow rate of each, and control the pH value to react in the range of 7-14; S4, pressurized reaction: after the addition of metallic silicon powder, alkaline catalyst and deionized water, seal and pressurize, and keep stirring and constant temperature heating; the reaction time is 25-35min; S5. Filtration preparation: Remove silicon slag and anionic and cationic impurities by centrifugal filtration and membrane filtration to obtain large-particle alkaline silica sol.

2. The method for preparing alkaline large-particle high-purity silica sol according to claim 1, characterized in that: The alkaline catalyst is a mixture of an inorganic base and aluminate; the mass ratio of the inorganic base to the aluminate is 3-6:1-2; the inorganic base is any one of sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonium hydroxide.

3. The method for preparing alkaline large-particle high-purity silica sol according to claim 1, characterized in that: The preparation method of the active silicate solution is as follows: concentrated water glass is diluted with deionized water to a solution with a silicon dioxide content of 2-6 wt %, stirred evenly, and then added into a strong acid cation exchange resin for cation exchange to obtain an active silicate solution with a pH value of 2.0-4.

0.

4. The method for preparing alkaline large-particle high-purity silica sol according to claim 1, characterized in that: The pressure in S4 is increased to 1-5 MPa; the temperature of the constant temperature heating is 95-100 degrees Celsius.

5. The method for preparing alkaline large-particle high-purity silica sol according to claim 1, characterized in that: The purity of the metallic silicon powder is above 99%.

6. The method for preparing alkaline large-particle high-purity silica sol according to claim 2, characterized in that: The aluminate is one or more of sodium aluminate, sodium metaaluminate, sodium tetrahydroxyaluminate, and aluminum oxide.

7. The method for preparing alkaline large-particle high-purity silica sol according to claim 1, characterized in that: The large-particle alkaline silica sol has a particle size of 8-500nm, a dispersion of ≤0.1, and a silicon dioxide content of >35%.

8. The method for preparing alkaline large-particle high-purity silica sol according to claim 1, characterized in that: After each dropwise addition of the catalyst, the content of the catalyst in the total mass of the silicon powder mixture and the catalyst is ≤1%.

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