High-purity silicon dioxide powder and preparation process thereof

Abstract

The invention belongs to the technical field of spherical silicon dioxide, and provides high-purity silicon dioxide powder and a preparation technology thereof.The preparation technology comprises the following steps that 1, high-purity quartz powder with the purity larger than or equal to 99.995% is selected for use; step 2, mixing the high-purity quartz powder with sodium carbonate, putting the mixture into a high-temperature vacuum furnace for melting reaction to obtain sodium silicate, and performing wet dissolution to obtain a water glass solution with the purity of more than or equal to 99.999%; step 3, adding the water glass solution, the modified polyethylene glycol and ammonia water into absolute ethyl alcohol, adjusting the pH value, and stirring for reaction to obtain silicon dioxide sol with the particle size of 0.02-3 microns and the purity of more than or equal to 99.999%; and 4, carrying out a flame suspension spheroidizing process on the silicon dioxide sol prepared in the step 3 to obtain the high-purity whole-size-fraction spherical silicon dioxide powder with the U and Th content of less than or equal to 0.2 ppb, the particle size distribution D50 of 0.02-20 microns and the SiO2 content of more than or equal to 99.999%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spherical silica, and particularly relates to high-purity silica powder and a preparation process thereof. BACKGROUND

[0002] With the breakthrough development of microelectronic integration technology, the integration and complexity of electronic components are increasing dramatically, and modern electronic devices are gradually developing in the direction of high power, miniaturization, lightness, intelligence and functionality. The development of electronic information industry largely depends on large-scale integrated circuit and ultra-large-scale integrated circuit packaging technology. High frequency, high speed and high thermal conductivity are the inevitable requirements for chip packaging materials in the new generation of high-frequency communication. Polymer composite material is one of the three main materials used in integrated circuit packaging. The use of epoxy molding compound to package ultra-large-scale integrated circuits has become the mainstream in related fields at home and abroad. At present, more than 95% of microelectronic devices on the market are occupied by plastic devices. In the composition system of epoxy molding compound, in addition to the epoxy resin matrix, the inorganic powder filler accounts for 70% to 90% of the weight ratio. At the same time, the purity, particle size and spheroidization degree of inorganic powder fillers are also increasingly required by integrated circuit packaging materials. High-purity spherical silica has a wide application prospect in the fields of electronics, electrical appliances and chemical industry due to its high dielectric, high heat resistance, high humidity resistance, high filling capacity, low expansion, low stress, low impurity and low friction coefficient. It has become an irreplaceable key functional filler in the composition system of epoxy molding compound.

[0003] At present, the preparation methods of high-purity spherical silica mainly include physical method and chemical synthesis method. Under the high-purity requirement of integrated circuits for packaging materials, chemical method is usually used to prepare spherical silica. However, in the actual operation process of the existing spherical silica preparation process, it is necessary to accurately control the reaction conditions and the purity of raw materials to prepare ultra-high-purity spherical silica. The preparation process has the disadvantages of many process parameters, complex process and high control cost. In addition, the synthesized spherical silica has a serious agglomeration phenomenon, which is difficult to improve the dispersibility of spherical silica, and the chemical method is not conducive to the synthesis of micron-sized large-particle-size spherical silica powder. Although the physical method can efficiently prepare micron-sized large-particle-size spherical silica powder, it is limited by the particle size of raw materials and cannot provide nanometer-sized small-particle-size spherical powder. Therefore, it is urgent to develop a preparation method for batch production of full-particle-size silica powder under the premise of ensuring purity.

[0004] The Chinese patent application file with the patent application number CN110194461A discloses a preparation method of monodisperse mesoscale spherical silica with controllable particle size. A wet white gel is obtained by a sol-gel method, and then the wet white gel is centrifuged, washed, and dried to obtain monodisperse mesoscale spherical silica. The obtained silica powder is complete spherical, the particle size is adjustable in the range of 5-50 nm, the particle size is uniform, but there is still an aggregation phenomenon, and the dispersibility is poor. The Chinese patent application file with the patent application number CN112194142A discloses a method for preparing high-purity spherical silica. The method uses chlorosilane to perform hydrolysis and alcoholysis reactions in a microemulsion system. The intermediate product obtained by the alcoholysis reaction is further subjected to a hydrolysis reaction to obtain silica. The silica prepared by the method has high purity, high sphericity, small particle size, and good dispersibility, and the reaction is stable and easy to operate. However, the microemulsion method requires the use of a large amount of organic solvent in the preparation process, which pollutes the environment and has high cost.

[0005] Therefore, it is urgent to develop a simple process and low cost method for preparing spherical nanosilica powder with high purity, high sphericity, excellent dispersibility, and uniform particle size. SUMMARY

[0006] The purpose of the present application is to provide a high-purity silica powder and a preparation process thereof to solve the technical problems of low purity and poor dispersibility of spherical silica powder in the prior art.

[0007] The purpose of the present application can be achieved by the following technical solutions: The present application provides a preparation process of high-purity silica powder, comprising the following steps: Step 1, selecting high-purity quartz powder with a purity of ≥99.995% for use; Step 2, mixing the high-purity quartz powder with sodium carbonate and placing the mixture in a high-temperature vacuum furnace for melting reaction to obtain sodium silicate, and then dissolving the sodium silicate by a wet method to obtain a water glass solution with a purity of ≥99.999%; Step 3, adding the water glass solution, modified polyethylene glycol, and ammonia water into anhydrous ethanol, adjusting the pH, and stirring to obtain a silica sol with a particle size of 0.02-3 μm and a purity of ≥99.999%; Step 4, the silica sol prepared in step 3 is subjected to a flame suspension spheroidization process to obtain high-purity, full-particle-size spherical silica powder with U and Th content ≤0.2 ppb, particle size distribution D50 of 0.02-20 μm, and SiO2 content ≥99.999%. Compared with the spherical silica obtained by using the traditional gel dry powder to perform the flame suspension spheroidization process, the above technical solution adopts spraying the gel solution into the flame at a certain concentration, which on the one hand simplifies the process flow and eliminates the need for drying and grinding, and on the other hand directly using the gel solution can improve the uniformity and reduce the problems of silica hollowing and crushing. The present application directly uses the gel solution to perform the flame suspension spheroidization process, effectively ensures the particle size uniformity of the spherical silica, and the process is more simple and suitable for continuous production.

[0008] Further, the high-purity quartz powder with purity ≥99.995% in step 1 is prepared by the following steps: The quartz ore is calcined, water-quenched, crushed and sieved to obtain quartz powder, and then subjected to magnetic separation, water washing, flotation and acid washing to obtain high-purity quartz powder.

[0009] Further, the mesh size in the grinding and sieving is 40-150 mesh; the collecting agent used in the flotation process is mixed by dodecylamine and ethylenediamine at a mass ratio of 12:3-4; and a composite acid solution is used for acid washing in the acid washing process, wherein the composite acid solution is mixed by hydrochloric acid and sulfuric acid at a mass ratio of 1:1.

[0010] In the above technical solution, dodecylamine and ethylenediamine are compounded to prepare a composite collecting agent. By utilizing the difference in molecular chain length between dodecylamine and ethylenediamine, ethylenediamine can effectively inhibit the floating of feldspar, thereby effectively separating quartz and greatly improving the purity of quartz. In the acid washing process, a composite acid solution is used for acid washing, wherein the composite acid solution is mixed by hydrochloric acid and sulfuric acid at a mass ratio of 1:1. By introducing sulfuric acid, impurity minerals that cannot be decomposed by hydrochloric acid can also be dissolved into liquid soluble salt, which is removed during filtration.

[0011] Further, the molar ratio of the high-purity quartz powder to sodium silicate in step 2 is 3.0-3.5:1.0.

[0012] Further, the temperature of the melting reaction in step 2 is 500-950℃, and the reaction time is 0.5-3 h.

[0013] Further, the mass ratio of the water glass solution, ammonia water and anhydrous ethanol in step 3 is 0.3-0.5:0.06-0.7:2.25-11; the amount of the modified polyethylene glycol in step 3 is 2%-16% of the total solution content. The modified polyethylene glycol is used to obtain monodisperse synthetic silica sol.

[0014] Further, the pH in step 3 is adjusted to 8.5-9.5. The alkaline atmosphere can accelerate the polymerization speed, and the excessively high polymerization speed can make the generation rate of the gel too high, thereby causing the agglomeration and large particle size phenomenon.

[0015] Further, the modified polyethylene glycol in step 3 is prepared by the following steps: The isophorone diisocyanate and 1H,1H,2H,2H-perfluoro-1-hexanol are mixed, stirred and heated to 75-80℃, the catalyst AC-83 (bismuth neodecanoate) is added, the reaction is stirred for 8-10h, the polyethylene glycol is added, the reaction is continuously stirred for 10-12h, and then the modified polyethylene glycol is obtained after dialysis purification and freeze-drying; wherein the mass ratio of the isophorone diisocyanate, 1H,1H,2H,2H-perfluoro-1-hexanol, catalyst AC-83 and polyethylene glycol is 2.2-2.3:2.6-2.65:0.02:2.0-2.5.

[0016] Further, the reaction temperature of the flame suspension spheroidization process in step 4 is 1600-3000℃, and the flame flow speed is 30-120m / s. In the process of flame suspension spheroidization, the solvent of the silica sol is evaporated, and there may be side reactions such as product decomposition in combustion, which causes the actual temperature to be lower than the theoretical temperature. Therefore, the furnace temperature needs to be significantly higher than the melting temperature of the silica, and the flame flow speed is relatively low, which prolongs the flight time of the micro powder in the flame flow, thereby facilitating the preparation of large particle size silica spherical powder.

[0017] The second aspect of the present application provides a high-purity silica powder obtained by the preparation process of the first aspect.

[0018] The present application has the following advantages: (1) The preparation process of the high-purity silica powder provided by the present application uses high-purity quartz powder with a purity of ≥99.995% as a raw material to prepare a water glass solution with a purity of ≥99.999%, and then mixes the water glass solution with modified polyethylene glycol, ammonia water and anhydrous ethanol. The modified polyethylene glycol can control the particle distribution and shape of the silica in the solvent, so that the silica particles have a high dispersity, preventing the agglomeration and growth of the particles. The present application overcomes the phenomenon of serious agglomeration and irregular particle morphology that occurs when preparing spherical silica powder by the existing method, and further prepares high-purity spherical silica powder with the characteristics of full particle size, high sphericity, high purity, uniform particle distribution and high dispersity, and the purity is ≥99.999%.

[0019] (2) The preparation process of the present application combines the advantages of traditional mineral spheroidization method and chemical synthesis method, and the prepared silica powder has both high purity and full particle size.

[0020] (3) The present application also provides a modified polyethylene glycol, which is synthesized by the reaction of isophorone diisocyanate, 1H, 1H, 2H, 2H-perfluorohexan-1-ol and polyethylene glycol, a polymer containing a short fluorocarbon chain is synthesized, which gives polyethylene glycol certain hydrophobic properties, effectively reduces the surface tension, and has excellent dispersion performance in solvents. In the preparation process, the modified polyethylene glycol can be coated on the surface of the silica, which can effectively control the particle size of the silica on one hand, and effectively control the distribution of the silica particles on the other hand, so that it can be uniformly dispersed in the solvent, thereby preventing the phenomenon of particle agglomeration and caking.

[0021] (4) In the present application, the silica sol is directly subjected to flame suspension spheroidization process, which omits the steps of drying, crushing and screening, and combines the advantages of chemical method and physical method, thereby preparing full particle size, high purity and spherical silica powder from nanoscale to microscale.

[0022] (5) The present application provides a high-purity, full-particle-size spherical silica powder, and the U, Th content thereof is ≤0.2ppb, the particle size distribution D50 is 0.02-20μm, the SiO2 content is ≥99.999%, the Li, K, Na elements are ≤0.5ppm, the sphericity is ≥0.98, the whiteness is >98, the water extract K + , Na + , Cl - ≤0.5ppm, and the conductivity is ≤0.3μS / cm; the powder can be widely used in integrated circuit packaging and semiconductor field. BRIEF DESCRIPTION OF DRAWINGS

[0023] The present application will be further described below with reference to the accompanying drawings.

[0024] Figure 1 is the SEM image of the silica sol prepared in Example 1 of the present application under different magnifications; Figure 2 is the SEM image of the silica powder prepared in Example 1 of the present application under different magnifications. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0026] The high-purity quartz powder with a purity of ≥99.995% used in the embodiments and comparative examples of the present application is prepared by the following steps: The quartz ore is calcined, water-quenched, crushed and sieved (the mesh size is 60 mesh) to obtain quartz powder, and then subjected to magnetic separation, water washing and flotation. The collecting agent used in the flotation process is a mixture of dodecylamine and ethylenediamine with a mass ratio of 12:3. The acid washing is performed using a composite acid solution, wherein the composite acid solution is a mixture of hydrochloric acid (concentration of 5 mol / L) and sulfuric acid (concentration of 5 mol / L) with a mass ratio of 1:1. The high-purity quartz powder with a purity of ≥99.995% is obtained.

[0027] Preparation Example

[0028] Preparation Example 1

[0029] The present embodiment provides a modified polyethylene glycol, and the preparation steps are as follows: 2.2g of isophorone diisocyanate and 2.6g of 1H, 1H, 2H, 2H-perfluoro-1-hexanol are mixed, stirred and heated to 80℃, 0.02g of catalyst AC-83 (bismuth neodecanoate) is added, stirred and reacted for 8h, 2.0g of polyethylene glycol is added, and the stirring and reaction are continued for 12h, then dialysis purification, freeze-drying to obtain modified polyethylene glycol.

[0030] Example 2

[0031] The present embodiment provides a modified polyethylene glycol, and the preparation steps are as follows: 2.3g of isophorone diisocyanate and 2.65g of 1H, 1H, 2H, 2H-perfluoro-1-hexanol are mixed, stirred and heated to 80℃, 0.02g of catalyst AC-83 is added, stirred and reacted for 8h, 2.5g of polyethylene glycol is added, and the stirring and reaction are continued for 12h, then dialysis purification, freeze-drying to obtain modified polyethylene glycol.

[0032] Preparation Example 3

[0033] The present comparative example provides a modified polyethylene glycol, and the preparation steps are as follows: 2.3g of isophorone diisocyanate is stirred and heated to 80℃, 0.02g of catalyst AC-83 is added, stirred and reacted for 8h, 2.5g of polyethylene glycol is added, and the stirring and reaction are continued for 12h, then dialysis purification, freeze-drying to obtain modified polyethylene glycol.

[0034] Embodiment

[0035] Embodiment 1

[0036] The embodiment provides a high-purity silicon dioxide powder and a preparation process thereof. A preparation process of a high-purity silicon dioxide powder comprises the following steps: Step 1, high-purity quartz powder with a purity of greater than or equal to 99.995% is selected for use; Step 2, the high-purity quartz powder is mixed with sodium carbonate at a mass molar ratio of 3.0:1.0, and then is placed in a high-temperature vacuum furnace for melting reaction, the temperature of the melting reaction is 500 DEG C, the reaction time is 2.8 h, sodium silicate is obtained, and after wet dissolution, a water glass solution with a purity of greater than or equal to 99.999% is obtained; Step 3, the water glass solution, the modified polyethylene glycol in the preparation example 1 and ammonia water are added into anhydrous ethanol, the mass ratio of the water glass solution, the ammonia water and the anhydrous ethanol is 0.3:0.06:2.25, the amount of the modified polyethylene glycol is 2% of the total solution content, the pH is adjusted to 8.5, and stirring reaction is carried out to obtain a silicon dioxide sol; Step 4, the silicon dioxide sol obtained in step 3 is subjected to a flame suspension spheroidization process, the reaction temperature of the flame suspension spheroidization process is 1600 DEG C, the flame flow speed is 30 m / s, and spherical silicon dioxide powder is obtained.

[0037] The preparation process of the high-purity silicon dioxide powder is prepared through the above steps.

[0038] Embodiment 2

[0039] The difference compared with embodiment 1 is only that: Step 2, the high-purity quartz powder is mixed with sodium carbonate at a mass molar ratio of 3.5:1.0, and then is placed in a high-temperature vacuum furnace for melting reaction, the temperature of the melting reaction is 500 DEG C, the reaction time is 2.8 h, sodium silicate is obtained, and after wet dissolution, a water glass solution with a purity of greater than or equal to 99.999% is obtained.

[0040] Embodiment 3

[0041] The difference compared with embodiment 1 is only that: Step 2, the high-purity quartz powder is mixed with sodium carbonate at a mass molar ratio of 3.0:1.0, and then is placed in a high-temperature vacuum furnace for melting reaction, the temperature of the melting reaction is 950 DEG C, the reaction time is 0.5 h, sodium silicate is obtained, and after wet dissolution, a water glass solution with a purity of greater than or equal to 99.999% is obtained.

[0042] Embodiment 4

[0043] The difference compared with embodiment 1 is only that: The modified polyethylene glycol prepared in Step 3 of Preparation Example 1 was replaced with the modified polyethylene glycol prepared in Preparation Example 2, and the amount was not changed.

[0044] Example 5

[0045] The only difference from Example 1 is that: Step 3, the water glass solution, the modified polyethylene glycol of Preparation Example 1 and ammonia were added to anhydrous ethanol, wherein the mass ratio of the water glass solution, ammonia and anhydrous ethanol was 0.5:0.7:11, the amount of the modified polyethylene glycol was 2% of the total solution content, the pH was adjusted to 8.5, and the reaction was stirred to obtain a silica sol.

[0046] Example 6

[0047] The only difference from Example 1 is that: Step 3, the water glass solution, the modified polyethylene glycol of Preparation Example 1 and ammonia were added to anhydrous ethanol, wherein the mass ratio of the water glass solution, ammonia and anhydrous ethanol was 0.3:0.06:2.25, the amount of the modified polyethylene glycol was 9% of the total solution content, the pH was adjusted to 8.5, and the reaction was stirred to obtain a silica sol.

[0048] Example 7

[0049] The only difference from Example 1 is that: Step 3, the water glass solution, the modified polyethylene glycol of Preparation Example 1 and ammonia were added to anhydrous ethanol, wherein the mass ratio of the water glass solution, ammonia and anhydrous ethanol was 0.3:0.06:2.25, the amount of the modified polyethylene glycol was 16% of the total solution content, the pH was adjusted to 8.5, and the reaction was stirred to obtain a silica sol.

[0050] Example 8

[0051] The only difference from Example 1 is that: Step 3, the water glass solution, the modified polyethylene glycol of Preparation Example 1 and ammonia were added to anhydrous ethanol, wherein the mass ratio of the water glass solution, ammonia and anhydrous ethanol was 0.3:0.06:2.25, the amount of the modified polyethylene glycol was 2% of the total solution content, the pH was adjusted to 9.5, and the reaction was stirred to obtain a silica sol.

[0052] Example 9

[0053] The only difference from Example 1 is that: Step 4, the silica sol prepared in Step 3 was subjected to a flame suspension spheroidization process, the reaction temperature of the flame suspension spheroidization process was 3000°C, and the flame flow rate was 100 m / s to obtain a spherical silica powder.

[0054] Comparative Example

[0055] Comparative Example 1

[0056] The only difference compared with Example 1 is that: Step 2, high-purity quartz powder and sodium carbonate were mixed in a molar ratio of 2.7:1.0, and then placed in a high-temperature vacuum furnace for melting reaction, the melting reaction temperature was 500℃, and the reaction time was 2.8h, to obtain sodium silicate, which was dissolved by wet method to obtain a water glass solution with a purity of ≥99.999%.

[0057] Comparative Example 2

[0058] The only difference compared with Example 1 is that: Step 2, high-purity quartz powder and sodium carbonate were mixed in a molar ratio of 3.0:1.0, and then placed in a high-temperature vacuum furnace for melting reaction, the melting reaction temperature was 430℃, and the reaction time was 2.8h, to obtain sodium silicate, which was dissolved by wet method to obtain a water glass solution with a purity of ≥99.999%.

[0059] Comparative Example 3

[0060] The only difference compared with Example 1 is that: The modified polyethylene glycol in Preparation Example 1 in Step 3 was replaced with the modified polyethylene glycol in Preparation Example 3, and the amount was unchanged.

[0061] Comparative Example 4

[0062] The only difference compared with Example 1 is that: Step 3, the water glass solution, the modified polyethylene glycol in Preparation Example 1, and ammonia were added to anhydrous ethanol, wherein the mass ratio of the water glass solution, ammonia, and anhydrous ethanol was 0.2:0.06:2.25, and the amount of the modified polyethylene glycol was 2% of the total solution content, the pH was adjusted to 8.5, and the reaction was stirred to obtain a silica sol.

[0063] Comparative Example 5

[0064] The only difference compared with Example 1 is that: Step 3, the water glass solution, the modified polyethylene glycol in Preparation Example 1, and ammonia were added to anhydrous ethanol, wherein the mass ratio of the water glass solution, ammonia, and anhydrous ethanol was 0.3:0.06:2.25, and the amount of the modified polyethylene glycol was 0.5% of the total solution content, the pH was adjusted to 8.5, and the reaction was stirred to obtain a silica sol.

[0065] Comparative Example 6

[0066] The only difference compared with Example 1 is that: Step 3, the water glass solution, the modified polyethylene glycol in Preparation Example 1 and ammonia water were added into anhydrous ethanol, wherein the mass ratio of the water glass solution, the ammonia water and the anhydrous ethanol was 0.3:0.06:2.25, the amount of the modified polyethylene glycol was 19% of the total solution content, the pH was adjusted to 8.5, and the reaction was stirred to obtain a silica sol.

[0067] Comparative Example 7

[0068] The only difference compared with Example 1 is that: Step 4, the silica sol prepared in Step 3 was subjected to a flame suspension spheroidization process, the reaction temperature of the flame suspension spheroidization process was 1500℃, and the flame flow rate was 30m / s, to obtain a spherical silica powder.

[0069] Comparative Example 8

[0070] The only difference compared with Example 1 is that: Step 4, the silica sol prepared in Step 3 was subjected to a flame suspension spheroidization process, the reaction temperature of the flame suspension spheroidization process was 3150℃, and the flame flow rate was 30m / s, to obtain a spherical silica powder.

[0071] Performance test

[0072] The purity of the silica sol obtained in Step 3 of the high-purity silica powder and the preparation process thereof provided in Examples 1-9 and Comparative Examples 1-8 was tested, and the purity and dispersion performance of the spherical silica powder finally obtained were tested, and the test results are shown in Table 1: Table 1

[0073] As can be seen from the data in Table 1, the high-purity, full-size spherical silica powder with U and Th content ≤0.2ppb and SiO2 content ≥99.999% can be prepared by using the high-purity silica powder and the preparation process thereof provided in the present application, and the spherical silica powder prepared by the present application can be widely used in integrated circuit packaging and semiconductor fields.

[0074] As can be seen from the comparison between Comparative Example 3 and Example 1, the silica powder prepared in Comparative Example 3 has obvious agglomeration phenomenon, and the modified polyethylene glycol used in Comparative Example 3 is the modified polyethylene glycol prepared in Preparation Example 3, i.e. the polyethylene glycol is not subjected to hydrophobic modification. It can be seen that the hydrophobically modified polyethylene glycol can control the particle distribution and shape of silica in the solvent, so that the silica particles have high dispersity and prevent the agglomeration phenomenon between particles, and overcome the serious agglomeration and irregular particle morphology phenomenon that easily occurs when preparing spherical silica powder in the prior art.

[0075] Meanwhile, the morphology of the silica sol prepared in step 3 and the spherical silica powder prepared in step 4 of Example 1 were tested respectively, and the test results are as follows. Figures 1-2 As shown: Figure 1 SEM images of silica sol at different magnifications; Figure 2 SEM images of silica powder at different magnifications.

[0076] Depend on Figures 1-2 It can be seen that both silica sol particles and silica powder particles are spherical, uniformly dispersed, and have small particle sizes; the particle size of silica sol particles is 0.02-3 μm, and the particle size distribution D50 of spherical silica powder is 0.02-20 μm.

[0077] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for preparing high purity silica powder, characterized by, The method comprises the following steps: Step 1: high-purity quartz powder with purity of 99.995% is selected; Step 2: the high-purity quartz powder is mixed with sodium carbonate and then placed in a high-temperature vacuum furnace for melting reaction to obtain sodium silicate, and then the sodium silicate is dissolved by a wet method to obtain a water glass solution with purity of 99.999%; Step 3: the water glass solution, modified polyethylene glycol and ammonia water are added into anhydrous ethanol, the pH is adjusted, and then stirring reaction is carried out to obtain a silica sol with particle size of 0.02-3 μm and purity of 99.999%; Step 4: the silica sol prepared in step 3 is subjected to a flame suspension spheroidization process to obtain high-purity, full-particle-size spherical silica powder with U and Th content of 0.2 ppb, particle size distribution D50 of 0.02-20 μm and SiO2 content of 99.999%.

2. The process according to claim 1, wherein the process is characterized by, The high-purity quartz powder with purity of 99.995% in step 1 is prepared by the following steps: The quartz ore is calcined, water-quenched, crushed and sieved to obtain quartz powder, and then the quartz powder is subjected to magnetic separation, water washing, flotation and acid washing to obtain high-purity quartz powder.

3. The process according to claim 2, wherein the process is characterized by, The mesh size of the grinding and sieving is 40-150 mesh; the collecting agent used in the flotation process is a mixture of dodecylamine and ethylenediamine with a mass ratio of 12:3-4; and the acid washing process uses a composite acid solution, wherein the composite acid solution is a mixture of hydrochloric acid and sulfuric acid with a mass ratio of 1:

1.

4. The process according to claim 1, wherein the process is characterized by, The molar ratio of the high-purity quartz powder to sodium silicate in step 2 is 3.0-3.5:1.

0.

5. The process according to claim 1, wherein the process is characterized by, The temperature of the melting reaction in step 2 is 500-950 ℃, and the reaction time is 0.5-3 h.

6. The process according to claim 1, wherein The mass ratio of the water glass solution, ammonia water and anhydrous ethanol in step 3 is 0.3-0.5:0.06-0.7:2.25-11; and the amount of the modified polyethylene glycol in step 3 is 2%-16% of the total solution content.

7. The process according to claim 1, wherein the process is characterized by, The pH in step 3 is adjusted to 8.5-9.

5.

8. The process according to claim 1, wherein the process is characterized by, The modified polyethylene glycol in step 3 is prepared by the following steps: Isophorone diisocyanate and 1H, 1H, 2H, 2H-perfluoro-1-hexanol are mixed, stirred and heated to 75-80 ℃, a catalyst AC-83 is added, stirring reaction is carried out for 8-10 h, polyethylene glycol is added, and then stirring reaction is continued for 10-12 h, and then the product is purified by dialysis and freeze-dried to obtain the modified polyethylene glycol; wherein the mass ratio of isophorone diisocyanate, 1H, 1H, 2H, 2H-perfluoro-1-hexanol, catalyst AC-83 and polyethylene glycol is 2.2-2.3:2.6-2.65:0.02:2.0-2.

5.

9. The process according to claim 1, wherein the process is characterized by, The reaction temperature of the flame suspension spheroidization process in step 4 is 1600-3000 ℃, and the flame flow speed is 30-120 m / s.

10. A high purity silica powder, characterized by, The high-purity, full-particle-size spherical silica powder is prepared by the preparation process of any one of claims 1-9.

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