Preparation method of ultra-pure electronic grade synthetic quartz sand

Abstract

The invention discloses a preparation method of ultra-pure electronic grade synthetic quartz sand. Commercial tetraethoxysilane with the purity larger than or equal to 60% serves as a raw material, after centrifugal filtration is conducted, cooling filtration is conducted, filtrate is added into a reaction kettle, ultrapure water is added into the reaction kettle, high-purity carbon dioxide gas is introduced to keep the pressure in the kettle at 0.2 MPa-0. 8MPa, the pressure is kept for 24 h-48 h, the reaction kettle recovers to the normal pressure, ammonia gas is introduced, the pressure in a kettle cavity is adjusted to 1.2 MPa-1. 8MPa, high-speed rotation is conducted for 4 h-10 h, mixed liquid is poured into an electronic-grade quartz crucible, cooling is conducted, and the product is obtained. And drying, crushing, sieving and calcining the silica wet gel to obtain the ultra-pure electronic grade synthetic quartz sand. Alkali metal impurities in the raw materials are removed in a physical adsorption and chemical crystallization mode, residual macromolecular impurities in the materials are removed through a distributed sintering treatment process, preparation of the ultra-pure electronic-grade synthetic quartz sand with the purity larger than or equal to 5N5 and without obvious bubbles is achieved, and preparation equipment is simple in structure and suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor-grade high-purity quartz sand, and in particular relates to a method for preparing ultra-high-purity electronic-grade synthetic quartz sand. Background Art

[0002] High-purity quartz sand is the main raw material for quartz glass, quartz tubes, quartz crucibles, etc. High-end high-purity quartz products are key basic materials for high-tech products such as aerospace military industry, electronic information and optical communication industries. With the development of high-tech industries, the demand for high-purity quartz has increased rapidly, and the quality requirements for it have also become increasingly higher.

[0003] At present, high-purity quartz sand is mainly obtained by purifying natural quartz ore, and its production capacity is closely related to high-quality mineral sources. With the gradual depletion of natural crystal and high-quality quartz veins worldwide, the price of high-purity quartz sand continues to increase, and the process of chemical synthesis of quartz sand has gradually received attention and research.

[0004] A method for preparing high-purity synthetic quartz sand disclosed in Chinese patent application CN110255570A reports a method for preparing synthetic quartz sand by using raw water glass as raw material and removing iron ions and alkaline earth ions through an ion exchange column. This method solves the problem that quartz sand must be prepared with ore as raw material, but the preparation process requires acid washing, and the purity of the prepared quartz sand is only more than 4N; and the prepared quartz sand contains a large number of closed pores. A method for preparing low-cost high-purity synthetic quartz sand disclosed in Chinese patent application CN118684232A reports a method for preparing synthetic quartz sand using alkali silicate as raw material. Its preparation process has high requirements on the material used for equipment, and the equipment loss is large, which is not suitable for large-scale mass production. A method for preparing high-purity quartz at low cost disclosed in Chinese patent application CN118529734A reports the preparation of synthetic quartz sand using water glass as raw material by direct acidification. Although this method can achieve the preparation of high-purity synthetic quartz, direct acidification uses a large amount of acidic substances, which has high environmental pollution and requires complex subsequent treatment processes. Therefore, a method with simple process and environmental protection to prepare high-purity quartz sand has certain research significance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing synthetic quartz sand without the need for ion exchange column adsorption and large-scale acidic substance cleaning, which solves the common preparation technical problems such as residual bubbles after quartz sand roasting and low purity of quartz sand, and provides a new solution for the large-scale mass production of synthetic quartz sand.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing ultra-high purity electronic grade synthetic quartz sand specifically comprises the following steps:

[0008] ①Use commercial ethyl orthosilicate with a purity of ≥60% as raw material, centrifuge the raw ethyl orthosilicate, take the supernatant and filter it with a PP filter element, then use activated carbon for adsorption, and then use the PP filter element to filter again to remove the insoluble solid impurities in the ethyl orthosilicate;

[0009] ② Add high-purity dry ice to the ethyl orthosilicate solution obtained in step ① to cool it down to a temperature of -75°C to -70°C, keep it warm for 30min to 60min, and then filter it using a nylon filter with a pore size of 0.1μm;

[0010] ③ Add the solution obtained in step ② into the reactor, and add ultrapure water into the reactor, the amount of ultrapure water added is 1.8 to 2.4 times the volume of the solution obtained in step ②, and then introduce high-purity carbon dioxide gas to maintain the pressure in the reactor at 0.2 MPa to 0.8 MPa for 24 h to 48 h;

[0011] ④ The reactor obtained in step ③ is restored to normal pressure, and then ammonia is introduced to maintain the pressure in the reactor cavity at 1.2MPa to 1.8MPa, and the reactor is rotated at high speed for 4h to 10h;

[0012] ⑤ Pour the mixed solution obtained in step ④ into an electronic grade quartz crucible and let it stand for 24 hours to 48 hours to obtain a silicon wet gel, dry the obtained silicon wet gel, and then crush and sieve the dry gel blocks;

[0013] ⑥ The block material obtained in step ⑤ is calcined at a temperature of 600°C to 800°C for 6h to 8h, and then calcined in a high vacuum furnace at a temperature of 1100°C to 1300°C for 2h to 4h, and the vacuum degree in the furnace chamber is maintained below 6.67×10 -3 Pa, to obtain ultra-high purity electronic grade synthetic quartz sand.

[0014] Preferably, the centrifugal speed in step ① is 3000 r / min to 4000 r / min, and the centrifugal time is 15 min to 20 min; free impurities, water and tetraethyl orthosilicate can be completely separated.

[0015] Preferably, the pore size of the PP filter element used for the supernatant filtration in step ① is 5 μm, and the pore size of the PP filter element used for the second filtration is 1 μm.

[0016] Preferably, the lining of the reactor described in step ③ is polytetrafluoroethylene.

[0017] Preferably, the rotation speed of the reactor described in step ④ is 120r / min to 180r / min.

[0018] Preferably, the drying temperature in step ⑤ is 75° C. to 80° C., and the drying time is 24 h to 48 h.

[0019] Preferably, the sieving process in step ⑤ has a mesh size of 30 to 50, and the sieving process is performed 3 times.

[0020] Preferably, the crucibles used in the calcination and roasting processes in step ⑥ are ultra-high purity electronic grade quartz crucibles, and the calcination environment is a high-purity oxygen environment.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention adopts low-cost, low-purity orthosilicate as raw material, utilizes physical adsorption and chemical crystallization to remove alkali metal impurities in the raw material, removes residual high molecular impurities in the material through a distributed sintering process, and seals the pores left after the impurities are removed, thereby realizing the preparation of ultra-high purity electronic-grade synthetic quartz sand with a purity of ≥5N5 and no obvious bubbles.

[0023] 2. The present invention adopts a normal temperature and low pressure environment to prepare synthetic sand. Compared with the existing sol-gel method, crystallization precipitation method, precipitation synthesis method and other methods, the process of the present invention is simpler and more stable, does not require expensive anion exchange columns, and does not have a complex impurity gradient adsorption process. The present invention uses impurities as crystal nuclei for precipitation, and the preparation equipment has a simple structure and can be used for large-scale industrial production.

[0024] 3. Compared with the existing preparation process using sodium silicate as raw material, the process of the present invention is simple, does not require a pickling step, and directly synthesizes ultra-high purity electronic grade quartz sand, thereby reducing the environmental pressure in the production process. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific embodiments.

[0026] Example 1

[0027] ① Take 60% pure commercial ethyl orthosilicate as raw material, use a centrifuge to centrifuge the raw ethyl orthosilicate, the centrifugal speed is 3000r / min, the centrifugal time is 20min, take the supernatant for filtration, use a PP filter element with a pore size of 5μm, use activated carbon for adsorption, and then use a PP filter element with a pore size of 1μm to filter again, remove the insoluble solid impurities in ethyl orthosilicate;

[0028] ② Add high-purity dry ice to the ethyl orthosilicate solution obtained in step ① to cool it down to -70°C, keep it warm for 60 minutes, and then filter it using a nylon filter with a pore size of 0.1 μm;

[0029] ③ Add the solution obtained in step ② into a reactor lined with polytetrafluoroethylene, and add ultrapure water to the reactor. The amount of ultrapure water added is 1.8 times the volume of the solution obtained in step ②. The resistivity of the ultrapure water used is 18.25MΩ·cm. Then, high-purity carbon dioxide gas is introduced to maintain the pressure in the reactor at 0.2MPa for 24h;

[0030] ④ The reactor obtained in step ③ was restored to normal pressure, and then ammonia was introduced to maintain the pressure in the chamber at 1.5 MPa, and the reactor was rotated at a high speed of 160 r / min for 10 h;

[0031] ⑤ Pour the mixed solution obtained in step ④ into an electronic grade quartz crucible and let it stand for 48 hours to obtain a silicon wet gel. Heat the obtained silicon wet gel to 75°C and dry it for 24 hours. Then use a crusher to crush and sieve the dry gel blocks. The sieve mesh number is 50 mesh and sieved 3 times.

[0032] ⑥ The block obtained in step ⑤ was calcined at a temperature of 600°C in a high-purity oxygen atmosphere for 6 hours, and then calcined in a high vacuum furnace at a temperature of 1100°C for 4 hours, with the vacuum degree in the furnace chamber maintained at 6.0×10 -3 Pa, to obtain ultra-high purity electronic grade synthetic quartz sand.

[0033] Example 2

[0034] ①Use commercial ethyl orthosilicate with a purity of 75% as raw material, use a centrifuge to centrifuge the raw ethyl orthosilicate, the centrifugal speed is 4000r / min, the centrifugal time is 15min, take the supernatant for filtration, use a PP filter element with a pore size of 5μm, use activated carbon for adsorption, and then use a PP filter element with a pore size of 1μm to filter again, remove the insoluble solid impurities in ethyl orthosilicate;

[0035] ② Add high-purity dry ice to the ethyl orthosilicate solution obtained in step ① to cool it down to -75°C, keep it warm for 30 minutes, and then filter it using a nylon filter with a pore size of 0.1 μm;

[0036] ③ Add the solution obtained in step ② into a reactor lined with polytetrafluoroethylene, and add ultrapure water to the reactor. The amount of ultrapure water added is 2.4 times the volume of the solution obtained in step ②. The resistivity of the ultrapure water used is 18.25 MΩ·cm. Then, high-purity carbon dioxide gas is introduced to maintain the pressure in the reactor at 0.8 MPa for 48 hours;

[0037] ④ The reactor obtained in step ③ was restored to normal pressure, and then ammonia was introduced to maintain 1.2 MPa in the reactor cavity, and the reactor was rotated at a high speed of 180 r / min for 4 h;

[0038] ⑤ Pour the mixed solution obtained in step ④ into an electronic grade quartz crucible and let it stand for 24 hours to obtain a silicon wet gel. Heat the obtained silicon wet gel to 80°C and dry it for 48 hours. Then use a crusher to crush and sieve the dry gel blocks. The sieve mesh number is 30 meshes and sieved 3 times.

[0039] ⑥ The block obtained in step ⑤ was calcined at 800°C in a high-purity oxygen atmosphere for 6 hours, and then calcined in a high vacuum furnace at 1300°C for 2 hours, with the vacuum degree in the furnace chamber maintained at 4.0×10 -4 Pa, to obtain ultra-high purity electronic grade synthetic quartz sand.

[0040] Example 3

[0041] ① Take commercial ethyl orthosilicate with a purity of 80% as raw material, use a centrifuge to centrifuge the raw ethyl orthosilicate, the centrifugal speed is 3500r / min, the centrifugal time is 18min, take the supernatant for filtration, use a PP filter element with a pore size of 5μm, use activated carbon for adsorption, and then use a PP filter element with a pore size of 1μm to filter again, remove the insoluble solid impurities in ethyl orthosilicate;

[0042] ② Add high-purity dry ice to the ethyl orthosilicate solution obtained in step ① to cool it down to -73°C, keep it warm for 45 minutes, and then filter it using a nylon filter with a pore size of 0.1 μm;

[0043] ③ Add the solution obtained in step ② into a reactor lined with polytetrafluoroethylene, and add ultrapure water to the reactor. The amount of ultrapure water added is 2.0 times the volume of the solution obtained in step ②. The resistivity of the ultrapure water used is 18.25 MΩ·cm. Then, high-purity carbon dioxide gas is introduced to maintain the pressure in the reactor at 0.6 MPa for 48 hours;

[0044] ④ The reactor obtained in step ③ was restored to normal pressure, and then ammonia was introduced to maintain 1.2 MPa in the reactor cavity, and the reactor was rotated at high speed at a rotation speed of 160 r / min for 8 h;

[0045] ⑤ Pour the mixed solution obtained in step ④ into an electronic grade quartz crucible and let it stand for 48 hours to obtain a silicon wet gel. Heat the obtained silicon wet gel to 80°C and dry it for 48 hours. Then use a crusher to crush and sieve the dry gel blocks. The sieve mesh number is 30 meshes and sieved 3 times.

[0046] ⑥ The block obtained in step ⑤ was calcined at a temperature of 750°C in a high-purity oxygen atmosphere for 6 hours, and then calcined in a high vacuum furnace at a temperature of 1250°C for 2 hours, with the vacuum degree in the furnace chamber maintained at 4.0×10 -4 Pa, to obtain ultra-high purity electronic grade synthetic quartz sand.

[0047] Table 1 Example Raw material manufacturers and quartz sand purity

[0048] Raw material purity (%) Raw material manufacturers Product purity (%) Example 1 60 Ningxia Shenglan 99.9995 Example 2 75 Ekop 99.9998 Example 3 80 Neosilicic Acid 99.9999

[0049] Table 2 Results of metal impurity detection using ICP-MS in Example 1

[0050]

[0051]

[0052] It can be seen from the experimental results of Examples 1 to 3 in Table 1 that the quartz sand prepared by the method has a purity greater than 99.999%, and the purity of the product increases with the increase of the purity of the raw materials. The use of tetraethyl orthosilicate as a raw material has low cost and an environmentally friendly preparation process, and can be used for large-scale industrial production.

[0053] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing ultra-high purity electronic grade synthetic quartz sand, characterized in that: The steps include: ①Use commercial ethyl orthosilicate with a purity of ≥60% as raw material, centrifuge the raw ethyl orthosilicate, take the supernatant and filter it with a PP filter element, then use activated carbon for adsorption, and then use the PP filter element to filter again to remove the insoluble solid impurities in the ethyl orthosilicate; ② Add high-purity dry ice to the ethyl orthosilicate solution obtained in step ① to cool it down to a temperature of -75°C to -70°C, keep it warm for 30min to 60min, and then filter it using a nylon filter with a pore size of 0.1μm; ③ Add the solution obtained in step ② into the reactor, and add ultrapure water into the reactor, the amount of ultrapure water added is 1.8 to 2.4 times the volume of the solution obtained in step ②, and then introduce high-purity carbon dioxide gas to maintain the pressure in the reactor at 0.2 MPa to 0.8 MPa for 24 h to 48 h; ④ The reactor obtained in step ③ is restored to normal pressure, and then ammonia is introduced to maintain the pressure in the reactor cavity at 1.2MPa to 1.8MPa, and the reactor is rotated at high speed for 4h to 10h; ⑤ Pour the mixed solution obtained in step ④ into an electronic grade quartz crucible and let it stand for 24 hours to 48 hours to obtain a silicon wet gel, dry the obtained silicon wet gel, and then crush and sieve the dry gel blocks; ⑥ The block material obtained in step ⑤ is calcined at a temperature of 600°C to 800°C for 6h to 8h, and then calcined in a high vacuum furnace at a temperature of 1100°C to 1300°C for 2h to 4h, and the vacuum degree in the furnace chamber is maintained below 6.67×10 -3 Pa, to obtain ultra-high purity electronic grade synthetic quartz sand.

2. The method for preparing ultra-high purity electronic grade synthetic quartz sand according to claim 1, characterized in that: The centrifugal speed in step ① is 3000 r / min to 4000 r / min, and the centrifugal time is 15 min to 20 min.

3. The method for preparing ultra-high purity electronic grade synthetic quartz sand according to claim 1, characterized in that: The pore size of the PP filter element used for the supernatant filtration in step ① is 5 μm, and the pore size of the PP filter element used for the second filtration is 1 μm.

4. The method for preparing ultra-high purity electronic grade synthetic quartz sand according to claim 1, characterized in that: The lining of the reactor described in step ③ is polytetrafluoroethylene.

5. The method for preparing ultra-high purity electronic grade synthetic quartz sand according to claim 1, characterized in that: The rotation speed of the reactor described in step ④ is 120r / min~180r / min.

6. The method for preparing ultra-high purity electronic grade synthetic quartz sand according to claim 1, characterized in that: The drying temperature in step ⑤ is 75° C. to 80° C., and the drying time is 24 h to 48 h.

7. The method for preparing ultra-high purity electronic grade synthetic quartz sand according to claim 1, characterized in that: The sieving step ⑤ has a mesh size of 30 to 50, and the sieving is performed 3 times.

8. The method for preparing ultra-high purity electronic grade synthetic quartz sand according to claim 1, characterized in that: The crucibles used in the calcination and roasting processes of step ⑥ are all ultra-high purity electronic grade quartz crucibles, and the calcination environment is a high-purity oxygen environment.

Images