A drying method of high-purity silicon oxide

Abstract

The application relates to a high-purity silicon oxide drying method, belonging to the technical field of silicon dioxide preparation processes. The method can effectively recover organic alcohol generated in the hydrolysis process of alkoxysilane through rotary vacuum drying combined with intermittent ultrasonic action, and effectively reduce the residual organic alcohol content in the silica sol. Further, through vacuum ultrasonic drying, vacuum and ultrasonic waves are combined to avoid the introduction of other impurities in the drying process, the strong sound wave action of the ultrasonic waves promotes the discharge of gas, moisture and high-boiling-point organic impurities remaining in the pores or the interior of the silicon dioxide, the content of the wrapped impurities in the dried silicon dioxide solid can be effectively reduced, and the purity of the silicon dioxide product is improved while the silicon dioxide is fully dried.

Description

Technical Field

[0001] This invention relates to the field of synthetic silicon oxide preparation technology, and in particular to a drying method for high-purity silicon oxide. Background Technology

[0002] High-purity silica is widely used in high-tech fields such as semiconductors and electronic information due to its high temperature resistance, low thermal expansion, high light transmittance, and insulation properties. Currently, the purity grade of silica has become a technological barrier limiting its use in these fields. With the increasing demand for high-purity silica and the limited resources of quartz mines leading to a gradual decrease in purity, the preparation and purification methods of silica have gained significant attention from relevant companies. Furthermore, bubble defects generated during the purification or preparation process can have a substantial impact on the application performance of high-purity silica.

[0003] The main reason for the formation of bubbles in high-purity silica prepared by synthetic methods when used to make quartz devices is the high-temperature calcination process. The silica particles are filled with trace amounts of gas, which, unable to escape effectively under high temperatures, remain trapped in the quartz device product. These residual bubbles in the high-purity silica product affect the transparency, uniformity, and other properties of the quartz product. To reduce the bubble content, researchers have focused on calcination temperature and environment, neglecting changes in the pore structure of silica during the drying process and the introduction of new gases and impurities. Furthermore, for high-purity silica prepared by the sol-gel method, a high amount of residual organic matter during the drying process will also increase the number of bubbles in the calcined silica product. Summary of the Invention

[0004] To address the problems of impurities introduced during the preparation or purification of high-purity silicon oxide due to drying conditions or the reduction in purity of high-purity silicon oxide after calcination, this invention provides a drying method for high-purity silicon oxide.

[0005] The technical solution of the present invention is a method for drying high-purity silicon oxide, comprising the following steps: drying the freshly prepared silica sol under rotary vacuum at 5 ℃~45 ℃ for 0.5~20 h, sonicating for 10~30 s every 10~30 min, and then sonicating under vacuum at 15 ℃~40 ℃ for 1~20 h, and then crushing and calcining the dried solid to obtain the silicon oxide.

[0006] The rotary vacuum drying process involves a pressure of 12–30 kPa and an ultrasonic power density of 0.3–1 W / cm². 3 .

[0007] The pressure for ultrasonic vacuum drying is 1~5 kPa, and the power density of the ultrasound is 1~3 W / cm³. 3 .

[0008] In some specific drying methods, the temperature of rotary vacuum drying is 20 ℃~35 ℃, the drying time is 0.5~10h, and ultrasonication is performed for 10~20 s every 10~30 min.

[0009] The temperature for ultrasonic vacuum drying is 25 ℃~40 ℃, and the drying time is 1~15 h.

[0010] In some specific drying methods, the pressure for rotary vacuum drying is 15~30 kPa, and the power density of ultrasound is 0.3~0.8 W / cm². 3 .

[0011] The pressure for ultrasonic vacuum drying is 1~3 kPa, and the power density of the ultrasound is 1~2 W / cm³. 3 .

[0012] In some specific drying methods, the rotational speed of rotary vacuum drying is 50~100 r / min.

[0013] In some specific drying methods, the silica sol is obtained by hydrolysis of (RO)4Si; Wherein, R is methyl, ethyl, propyl, isopropyl, or n-butyl.

[0014] In some specific drying methods, R is methyl, ethyl, propyl, or isopropyl.

[0015] In some specific drying methods, R stands for methyl or ethyl.

[0016] The beneficial effects of this invention are as follows: This invention provides a method for drying high-purity silica. This method, through rotary vacuum drying combined with intermittent ultrasonic action, can effectively recover organic alcohols generated during the hydrolysis of alkoxysilanes, effectively reducing the amount of residual organic alcohols in silica sol. Furthermore, by using vacuum ultrasonic drying, the combination of vacuum and ultrasound avoids the introduction of other impurities during the drying process. The strong sound waves of ultrasound promote the expulsion of gases, moisture, and high-boiling-point organic impurities remaining in or inside the pores of silica, effectively reducing the impurity content encapsulated in the dried silica solid, achieving thorough drying of silica while improving the purity of the silica product. Detailed Implementation

[0017] Example

[0018] First, add 1000g of ultrapure water and 2g of concentrated nitric acid to a round-bottom flask. Then, under vigorous stirring, slowly add 99.9999% pure tetramethoxysilane dropwise to the reaction flask and react at 35℃ for 4 hours. Take 500g of the reaction mixture and dry it at 30℃ and 20 kPa using a rotary vacuum dryer to recover methanol. The water bath in the rotary vacuum dryer is an ultrasonic water bath. During the rotary vacuum drying process, a power density of 0.5 W / cm³ is used every 10 minutes. 3 After being subjected to ultrasonic treatment for 10 seconds and dried for 30 minutes, the mixture was transferred to a vacuum ultrasonic drying apparatus and ultrasonically vacuum dried at 35 °C and 3 kPa for 5 hours. The ultrasonic power density was 1.5 W / cm³. 3 The dried solid is crushed to 40-80 mesh.

[0019] Example

[0020] The preparation and drying process of silicon oxide is the same as in Example 1, except that the following parameters are used.

[0021] Rotary vacuum drying: 25 ℃, 15 kPa. Vacuum ultrasonic drying: ultrasonic vacuum drying at 30 ℃, 2 kPa for 8 h.

[0022] Example

[0023] The preparation and drying process of silicon oxide is the same as in Example 1, except that the following parameters are used.

[0024] Rotary vacuum drying: 35 ℃, 30 kPa. Vacuum ultrasonic drying: ultrasonic vacuum drying at 25 ℃, 1.5 kPa for 6 h.

[0025] Example

[0026] The preparation and drying process of silicon oxide is the same as in Example 1, except that the following parameters are used.

[0027] Rotary vacuum drying: every 10 minutes, using a power density of 0.3 W / cm³. 3 Ultrasonic drying was performed for 10 seconds. Vacuum ultrasonic drying: power density was 2 W / cm³. 3 .

[0028] Example

[0029] The preparation and drying process of silicon oxide is the same as in Example 1, except that the following parameters are used.

[0030] Rotary vacuum drying: every 10 minutes, using a power density of 0.8 W / cm³. 3 Ultrasonic drying was performed for 10 seconds. Vacuum ultrasonic drying: power density was 1 W / cm³.3 .

[0031] Comparative Example 1 The preparation and drying process of silicon oxide is the same as in Example 1, except that the rotary vacuum drying and ultrasonic vacuum drying processes do not use ultrasound.

[0032] Comparative Example 2 The preparation and drying process of silicon oxide is the same as in Example 1, except that the following parameters are used.

[0033] Rotary vacuum drying: The power density of the ultrasonic waves is 2 W / cm³. 3 Vacuum ultrasonic drying: The power density of the ultrasound is 0.5 W / cm³. 3 .

[0034] Comparative Example 3 The preparation and drying process of silicon oxide is the same as in Example 1, except that the rotary vacuum dryer process is not performed, and the other steps are the same.

[0035] Comparative Example 4 Take 500 g of the reaction mixture prepared in Example 1, remove methanol by atmospheric distillation, dry at 140 °C for 15 h, and crush the dried solid into 40-80 mesh.

[0036] Test case The solid powders obtained in Examples 1-5 and Comparative Examples 1-4 were calcined at 1200 °C for 10 h, and the purity of silicon oxide was tested after cooling. The specific data are shown in Table 1.

[0037] Table 1. Purity Indicators of Silica (Testing Standards)

[0038] The synthesized silicon dioxide was heated at 2200 °C and 2.0 × 10⁻⁶ °C. 4 The silica was melted under a vacuum atmosphere for 48 hours. After cooling to room temperature, a 20 mm (longitudinal) × 20 mm (lateral) × 40 mm (depth) area was taken, and the number of bubbles generated was measured; a 40 mm (length) × 40 mm (width) × 40 mm (depth) area was taken, and the number of black spots generated was measured. Specific data are shown in Table 1. The data in Table 1 show that the silica dried using the method of this invention has high purity, and the number of black spots and bubbles is significantly reduced.

Claims

1. A method for drying high-purity silicon dioxide, characterized in that, The following steps are adopted: The newly prepared silica sol was rotary vacuum dried at 5℃~45℃ for 0.5~20h, ultrasonicated for 10~30s every 10~30min, and then ultrasonically vacuum dried at 15℃~40℃ for 1~20h. The dried solid was crushed and calcined to obtain the high-purity silica. The rotary vacuum drying process involves a pressure of 12–30 kPa and an ultrasonic power density of 0.3–1 W / cm². 3 ; The pressure for ultrasonic vacuum drying is 1~5 kPa, and the power density of the ultrasound is 1~3 W / cm³. 3 .

2. The drying method for high-purity silicon oxide according to claim 1, characterized in that, The temperature for rotary vacuum drying is 20℃~35℃, the drying time is 0.5~10h, and ultrasonication is performed for 10~20s every 10~30min. The temperature for ultrasonic vacuum drying is 25℃~40℃, and the drying time is 1~15h.

3. The drying method for high-purity silicon oxide according to claim 1, characterized in that, The pressure for rotary vacuum drying is 15~30 kPa, and the power density of the ultrasound is 0.3~0.8 W / cm³. 3 ; The pressure for ultrasonic vacuum drying is 1~3 kPa, and the power density of the ultrasound is 1~2 W / cm³. 3 .

4. The drying method for high-purity silicon oxide according to any one of claims 1-3, characterized in that, The rotational speed for rotary vacuum drying is 50~100 r / min.

5. The drying method for high-purity silicon dioxide according to any one of claims 1-3, characterized in that, The silica sol was obtained by hydrolysis of (RO)4Si. Wherein, R is methyl, ethyl, propyl, isopropyl, or n-butyl.

6. The drying method for high-purity silicon oxide according to claim 5, characterized in that, R can be methyl, ethyl, propyl, or isopropyl.

7. The drying method for high-purity silicon oxide according to claim 6, characterized in that, R is either methyl or ethyl.

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