A high-purity spherical silica sol and preparation method thereof

Abstract

The present invention relates to a high-purity spherical silica sol and a preparation method thereof, and relates to the field of silica microspheres, comprising the following steps: Step 1: According to weight percentage, the following components A and B are prepared: Component A is composed of 3-27% by weight of purified silicate and 1.5-12% of low molecular alcohol; Component B is composed of 12-45% by weight of water, 40-80% of low molecular alcohol and 0.05-5% of catalyst; Step 2: Stirring and atomizing Component A, while continuously stirring Component B, then adding the atomized Component A to Component B, and continuously stirring under constant temperature until a high-purity spherical silica sol is obtained. A high-purity spherical silica sol with low cost, large particle size and sharp particle size distribution for industrial use is provided.

Description

Technical Field

[0001] The invention relates to the field of silicon dioxide microspheres, and in particular to a high-purity spherical silicon dioxide sol and a preparation method thereof. Background Art

[0002] As an important inorganic raw material, silica microspheres have many unique properties such as high temperature resistance, high strength, high toughness, small thermal expansion coefficient, low dielectric constant, good stability, etc. They are widely used in catalysis, pigments, chromatography and semiconductors. Especially in electronic packaging, silicon micropowder can reduce the thermal expansion coefficient of plastic packaging materials, reduce internal stress, improve insulation strength, reduce dielectric constant, increase plastic packaging material strength, flame retardant, meet environmental protection requirements, and prevent moisture absorption. This makes high-purity silica microspheres the only choice for making epoxy-type sealing materials (BMC).

[0003] At present, the methods for preparing silica microspheres at home and abroad mainly include silicon powder hydrolysis method, seed growth method, ion exchange method and sol-gel method. Patent CN1699165A uses silicon powder as raw material, reacts with water under the catalytic action of alkali to obtain a reaction liquid, the reaction liquid is filtered by a filter press, the filtrate is a silica sol finished product, the filter residue obtained by filtering the reaction liquid is washed with water and filtered, and the silica sol finished product is obtained. The filter residue in the preparation process of this method contains silicon powder, and the actual recycling rate is low, which has an adverse impact on the environment. Patent US15219533 uses a monodisperse spherical silica sol with a particle size of 20nm-30nm as a seed, and uses a seed growth method to drip seeds and active silicic acid into the reaction system, keeping the liquid level constant, and at the same time dripping an inorganic base until the system pH is between 9.5-10, keeping the system alkaline, and cooling after a period of heat preservation reaction to obtain silica sol. However, the silica sol obtained by this method has a wide particle size distribution, and it is difficult to prepare a monodisperse silica sol. Patent CN106276927A adds silicon halide to fluoride-containing solution to produce silicon dioxide precipitate and silicon dioxide suspension, which are filtered and washed to obtain silicon dioxide filter cake, and dried to obtain powder. However, the silica sol obtained by this method has low purity and ionic impurities are difficult to remove. Patent CN105283413A adds alkoxysilane continuously or indirectly to a mixture of water and organic solvent mixed in a certain proportion, reacts at a temperature above 60°C for a period of time, then adds an organic base compound, heats to the boiling point of the solvent, and cools to room temperature to obtain silica sol. The raw material silicate for preparing silica sol in this method is not purified and has low purity, so it is difficult to prepare high-purity silica sol in industry. CN104003409A discloses a method for preparing controllable monodisperse spherical large-particle nano-silica. Based on the sol-gel method, ethyl orthosilicate is hydrolyzed to obtain orthosilicic acid, and silicon dioxide is obtained by dehydration and condensation by intermittent addition of ethyl orthosilicate. Although large-particle nano-silica particles can be controllably synthesized by intermittent addition of reactants, the operation is still complicated, the purity of silica sol is low, and ionic impurities are difficult to remove.

[0004] In view of this, a method for preparing high-purity spherical silica sol with large particle size, sharp particle size distribution and uniform dispersion for industrial application is provided to overcome the above technical problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a high-purity spherical silica sol and a preparation method thereof, and to provide a high-purity spherical silica sol with low cost, large particle size and sharp particle size distribution for industrial application.

[0006] In order to solve the above technical problems, the first object of the present invention is to provide a method for preparing high-purity spherical silica sol, comprising the following steps:

[0007] Step 1: Prepare the following components A and B according to weight percentage:

[0008] Component A is composed of 3-27% by weight of purified silicate and 1.5-12% of low molecular alcohol; component B is composed of 12-45% by weight of water, 40-80% of low molecular alcohol and 0.05-5% of catalyst;

[0009] Step 2: Stir and atomize component A, and continuously stir component B at the same time, then add the atomized component A to component B, and continue stirring at a constant temperature until a high-purity spherical silica sol is obtained.

[0010] The beneficial effects of the present invention are: providing a method for preparing high-purity spherical silica sol with large particle size, sharp particle size distribution and uniform dispersion for industrial use at low cost, wherein the purified silicate is mixed with a small portion of low molecular alcohol to form component A, and then the remaining low molecular alcohol, water and catalyst are placed in a reaction vessel in a certain proportion to form component B, component A is placed in a liquid storage tank, component A is atomized into fine droplets at a certain flow rate and pressure and then added to the reactor, and after mixing and stirring, component A and component B can collide and react instantly, so that the generated silica sol has a narrower particle size distribution, the whole process is easy to operate, and the prepared silica sol has a large particle size, a sharp particle size distribution, uniform dispersion, and a low metal ion content. The preparation method of the present invention is simple and easy to operate, environmentally friendly and efficient, and the obtained silica sol has high purity, large particle size and uniform particle size distribution.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Furthermore, in step 1, component A is composed of 7-9% by weight of purified silicate and 1.6-2% by weight of low molecular alcohol; component B is composed of 12.5-14% by weight of water, 70-80% by weight of low molecular alcohol and 1-4% by weight of catalyst.

[0013] Furthermore, the specific purification process of the silicate in step 1 is to first perform distillation to remove organic impurities, and then use a cation exchange column to exchange and remove dissolved inorganic metal impurity ions to obtain high-purity silicate.

[0014] The beneficial effect of adopting the above further scheme is that a higher purity silica sol can be prepared with the purified ethyl silicate raw material, and the total amount of metal ions thereof is less than 5 ppm.

[0015] Furthermore, the silicate in step 1 is one or a mixture of two or more of methyl silicate, ethyl silicate, propyl silicate and butyl silicate, preferably ethyl silicate.

[0016] Furthermore, the water described in step 1 is distilled water, deionized water or ultrapure water, preferably ultrapure water.

[0017] Furthermore, the low molecular alcohol in step 1 is an alcohol having 1 to 4 carbon atoms; and the catalyst in step 1 is an inorganic base.

[0018] Furthermore, the low molecular alcohol is one or a mixture of two or more of methanol, ethanol, propanol, isopropanol, and n-butanol, preferably ethanol; the catalyst is one or a mixture of two or more of sodium hydroxide, potassium hydroxide, and ammonia water, preferably ammonia water.

[0019] Further, step 2 is specifically as follows: under the condition of 25-80°C, for example, water bath heating can be used to stir and atomize component A, and component B is continuously stirred at the same time, and then the atomized component A is added to component B, and continuously stirred at a constant temperature between 25-80°C until a high-purity spherical silica sol is obtained.

[0020] Furthermore, the stirring of component A and component B in step 2 is carried out using a folding blade paddle stirrer (Shanghai Zhiwei Electric Co., Ltd., D2010W); the stirring speed of the continuous stirring in step 2 is 200-800r / min, and the stirring time of the continuous stirring in step 2 is 1-4h.

[0021] The second purpose is to provide a high-purity spherical silica sol, including the preparation method of the high-purity spherical silica sol described above, wherein the particle size of the high-purity spherical silica sol is 80-500nm and the total amount of metal ions is less than 5ppm.

[0022] The method of the present invention provides a method for preparing a high-purity spherical silica sol with large particle size and sharp particle size distribution. The preparation process is simple and easy, environmentally friendly and efficient. The obtained silica sol has high purity, large particle size and uniform particle size distribution. The high-purity spherical silica sol with large particle size and sharp particle size distribution for integrated circuit electronic packaging has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 TEM images of silica sols prepared under different conditions of the present invention, wherein Figures ah are TEM images of silica sols S1-S8 prepared in Examples 1-8, respectively. DETAILED DESCRIPTION

[0024] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0025] Embodiment 1:

[0026] A method for preparing a high-purity spherical silica sol in this embodiment comprises the following steps:

[0027] (1) Prepare the following components A and B according to weight percentage:

[0028] Component A: Ethyl silicate 7.45%

[0029] Ethanol 1.65%

[0030] Component B: Ultrapure water 12.9%

[0031] Ethanol 75.5%

[0032] Ammonia 2.5%

[0033] (2) In a water bath at 30°C, while stirring the solution component B at a rate of 460 r / min, component A was atomized and added to the stirred component B. After the addition was completed, stirring was continued at a rate of 460 r / min for 3 hours at a constant temperature of 30°C to obtain silica sol S1. The performance test results of the silica sol are shown in Tables 1 and Figure 1 .

[0034] Embodiment 2:

[0035] A method for preparing a high-purity spherical silica sol in this embodiment comprises the following steps:

[0036] (1) Prepare the following components A and B according to weight percentage:

[0037] Component A: Ethyl silicate 7.45%

[0038] Ethanol 1.65%

[0039] Component B: Ultrapure water 12.9%

[0040] Ethanol 75.5%

[0041] Ammonia 2.5%

[0042] (2) In a water bath at 40°C, while solution B is continuously stirred at a rate of 460 r / min, component A is atomized and added to the stirred component B. After the addition is completed, stirring is continued at a rate of 460 r / min for 3 hours at a constant temperature of 40°C to obtain silica sol S2. The test results of the silica sol properties are shown in Tables 1 and Figure 1 .

[0043] Embodiment 3:

[0044] The composition and steps of this embodiment are basically the same as those of embodiments 1 and 2, except that the water bath temperature in step (2) of this embodiment 3 is 50° C. to obtain silica sol S3. The test results of the silica sol properties are shown in Tables 1 and Figure 1 .

[0045] Embodiment 4:

[0046] The composition and steps of this embodiment are basically the same as those of embodiments 1, 2, and 3, except that the water bath temperature in step (2) of this embodiment 3 is 60° C. to obtain silica sol S4. The test results of the silica sol properties are shown in Tables 1 and Figure 1 .

[0047] Embodiment 5:

[0048] A method for preparing a high-purity spherical silica sol in this embodiment comprises the following steps:

[0049] (1) Prepare the following components A and B according to weight percentage:

[0050] Component A: Ethyl silicate 7.62%

[0051] Ethanol 1.69%

[0052] Component B: Ultrapure water 13.19%

[0053] Ethanol 75.5%

[0054] Ammonia 2.0%

[0055] (2) In a water bath at 30°C, while stirring solution B at a rate of 460 r / min, component A was atomized and added to the stirring component B. After the addition was completed, stirring was continued at a rate of 460 r / min for 3 hours at a constant temperature of 30°C to obtain silica sol S5. The test results of the silica sol properties are shown in Tables 1 and Figure 1 .

[0056] Embodiment 6:

[0057] A method for preparing a high-purity spherical silica sol in this embodiment comprises the following steps:

[0058] (1) Prepare the following components A and B according to weight percentage:

[0059] Component A: Ethyl silicate 7.28%

[0060] Ethanol 1.61%

[0061] Component B: Ultrapure water 12.61%

[0062] Ethanol 75.5%

[0063] Ammonia 3.0%

[0064] (2) In a water bath at 30°C, while stirring solution B at a rate of 460 r / min, component A was atomized and added to the stirring component B. After the addition was completed, stirring was continued at a rate of 460 r / min for 3 hours at a constant temperature of 30°C to obtain silica sol S6. The test results of the silica sol properties are shown in Tables 1 and Figure 1 .

[0065] Example 7: Comparative Example

[0066] This embodiment is a method for preparing high-purity spherical silica sol using a seed growth method, comprising the following steps:

[0067] (1) Prepare the following components A and B according to weight percentage:

[0068] Component A: Ethyl silicate 7.62%

[0069] Ethanol 1.69%

[0070] Component B: Ultrapure water 13.19%

[0071] Ethanol 51.1%

[0072] Silica seed solution 24.43%

[0073] Ammonia 2.0%

[0074] (2) In a water bath at 30°C, while stirring solution B at a rate of 460 r / min, component A was atomized and added to component B containing the silica seed solution being stirred. After the addition was completed, stirring was continued at a rate of 460 r / min for 3 hours at a constant temperature of 30°C to obtain silica sol S7. The test results of the silica sol properties are shown in Tables 1 and Figure 1 .

[0075] Example 8: Comparative Example

[0076] This embodiment is a method for preparing high-purity spherical silica sol using a seed growth method, comprising the following steps:

[0077] (1) Prepare the following components A and B according to weight percentage:

[0078] Component A: Ethyl silicate 7.28%

[0079] Ethanol 1.61%

[0080] Component B: Ultrapure water 12.61%

[0081] Ethanol 51.1%

[0082] Silica seed solution 24.61%

[0083] Ammonia 3.0%

[0084] (2) In a water bath at 30°C, while stirring solution B at a rate of 460 r / min, component A was atomized and added to component B containing the silica seed solution being stirred. After the addition was completed, stirring was continued at a rate of 460 r / min for 3 hours at a constant temperature of 30°C to obtain silica sol S8. The test results of the silica sol properties are shown in Tables 1 and Figure 1 .

[0085] Table 1 The particle size of silica sol obtained under different conditions in Examples 1-6

[0086]

[0087]

[0088] The mechanism of the present invention is that the purified silicate reacts with water in a low-molecular alcohol solvent under the action of a catalyst, and the particle size and particle size distribution of the final product, silica sol, are controlled by controlling the addition method and flow rate of the silicate, the shape and speed of the stirrer, the reaction temperature, and the catalyst content. The silicate is subjected to rectification and a cation exchange column to remove organic and inorganic impurities in the raw material, respectively, so as to improve the purity of the silicate. A mixture of silicate and low-molecular alcohol is added to a container in an atomized form, and after being stirred by a folding blade paddle stirrer, the A component and the B component collide and react instantly, which is conducive to a more uniform growth of the spheres, and the generated silica has a narrower particle size distribution.

[0089] From the data in Table 1, it can be seen that the particle sizes of the silica sols S1-S6 obtained by the sol-gel method of the present invention in Examples 1 to 6 are 443nm, 162.2nm, 128.8nm, 80.3nm, 242.4nm, and 282.5nm, respectively, and their PDI values ​​are all less than 0.07, indicating that the obtained silica sols have a sharp particle size distribution. Figure 1 TEM images of a to f in the figure show that the silica sols S1-S6 are all smooth spherical and have no agglomeration. The particle sizes of silica sols S7 and S8 obtained by seed growth method in Examples 7 and 8 are 340.0nm and 184.1nm, respectively, and the particle size distributions are 0.1669 and 0.417, respectively, indicating that the particle size distribution is uneven. This conclusion is from Figure 1 This can be further confirmed in the TEM images from g to h.

[0090] The silica sol S1 sample prepared in Example 1 was analyzed using a PQ9000 inductively coupled plasma emission spectrometer from the German analytikjena company. First, a standard solution was prepared, and then the energy released when the sample returned from an excited state to a stable state was measured, and then it was compared with the specific spectral lines and intensities of different elements in the prepared standard solution, so as to analyze the types and contents of the elements in the sample. The contents of various metal ions in the silica sol S1 are shown in Table 2. From the data in Table 2, it can be concluded that the total content of metal ions in the prepared sol is 3.59 μg / ml.

[0091] Table 2 Ion content in silica sol S1

[0092]

[0093]

[0094] In summary, the method of the present invention provides a method for preparing a high-purity spherical silica sol with large particle size and sharp particle size distribution. The preparation process is simple and easy, environmentally friendly and efficient, and the obtained silica sol has high purity, large particle size and uniform particle size distribution. Therefore, the obtained high-purity spherical silica sol with large particle size and sharp particle size distribution for integrated circuit electronic packaging has good application prospects.

[0095] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing high-purity spherical silica sol, characterized in that: The steps include: Step 1: Prepare the following components A and B according to weight percentage: Component A is composed of 3-27% by weight of purified silicate and 1.5-12% of low molecular alcohol; component B is composed of 12-45% by weight of water, 40-80% of low molecular alcohol and 0.05-5% of catalyst; Step 2: Stir and atomize component A, and continuously stir component B at the same time, then add the atomized component A to component B, and continue stirring at a constant temperature until a high-purity spherical silica sol is obtained; The particle size of the high-purity spherical silica sol is 162.2-500nm; The PDI value of the particle size of the high-purity spherical silica sol is less than 0.07; Step 2 is specifically as follows: at 25-40°C, component A is stirred and atomized, while component B is continuously stirred, the atomized component A is added to component B, and the mixture is continuously stirred at a constant temperature of any temperature between 25-40°C until a high-purity spherical silica sol is obtained.

2. The method for preparing a high-purity spherical silica sol according to claim 1, characterized in that: In step 1, component A is composed of 7-9% by weight of purified silicate and 1.6-2% by weight of low molecular alcohol; component B is composed of 12.5-14% by weight of water, 70-80% by weight of low molecular alcohol and 1-4% by weight of catalyst.

3. A method for preparing a high-purity spherical silica sol according to claim 1 or 2, characterized in that: The specific purification process of the silicate in step 1 is to first perform distillation, and then use a cation exchange column to exchange and remove to obtain a high-purity silicate.

4. The method for preparing a high-purity spherical silica sol according to claim 1, characterized in that: The silicate in step 1 is one or a mixture of two or more of methyl silicate, ethyl silicate, propyl silicate and butyl silicate.

5. The method for preparing a high-purity spherical silica sol according to claim 1, characterized in that: The water described in step 1 is distilled water, deionized water or ultrapure water.

6. The method for preparing a high-purity spherical silica sol according to claim 1, characterized in that: The low molecular alcohol in step 1 is an alcohol having 1 to 4 carbon atoms; and the catalyst in step 1 is an inorganic base.

7. The method for preparing a high-purity spherical silica sol according to claim 6, characterized in that: The low molecular alcohol is one or a mixture of two or more selected from methanol, ethanol, propanol, isopropanol and n-butanol; the catalyst is one or a mixture of two or more selected from sodium hydroxide, potassium hydroxide and ammonia water.

8. The method for preparing a high-purity spherical silica sol according to claim 1, characterized in that: The stirring of component A and component B in step 2 is carried out by using a folding blade paddle stirrer; the stirring speed of the continuous stirring in step 2 is 200-800 r / min, and the stirring time of the continuous stirring in step 2 is 1-4 h.

9. A high-purity spherical silica sol, characterized in that: The high-purity spherical silica sol is prepared by the preparation method of any one of claims 1 to 8, and the total amount of metal ions is less than 5 ppm.

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