Ultrahigh-purity regular spherical silicon dioxide microspheres and preparation method thereof

Abstract

The invention discloses an ultra-high-purity regular spherical silicon dioxide microsphere and a preparation method thereof, and belongs to the technical field of electronic-grade silicon micropowder functional fillers, the preparation method comprises the following steps: mixing organosilane and ultrapure water in proportion, and then carrying out hydrolysis reaction to obtain a silanol aqueous solution; adding an alkaline polycondensation catalyst into the silanol aqueous solution, controlling reaction conditions, and carrying out polycondensation reaction to obtain an organic silicon source mixed solution; centrifugally separating the organic silicon source mixed solution and washing with ultrapure water to obtain a semi-finished product polysilsesquioxane microspheres; and heating the polysilsesquioxane microspheres to 1050 DEG C at a controlled heating rate under the protection of negative pressure and clean air, and carrying out constant-temperature oxygen-enriched calcination for 1-5 hours to obtain the ultra-high-purity regular spherical silicon dioxide microspheres. The preparation method disclosed by the invention is simple to operate and low in cost, the prepared silicon dioxide microspheres are good in sphericity, uniform in particle size distribution and good in flowability, and the purity of the silicon dioxide microspheres is as high as 99.9999% and far exceeds the purity index of national standard'spherical silicon dioxide micro powder '.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic-grade silicon micropowder functional filler, and specifically relates to a chemically synthesized ultra-high-purity regular spherical silicon dioxide microsphere and a preparation method thereof. Background Art

[0002] In the process of vigorous development of modern high-tech industries, ultra-high purity silica occupies a pivotal position. Spherical silica materials are new epoxy plastic encapsulation materials for electronic components developed abroad in recent years. Spherical silicon micropowder fillers account for more than 80% of EMC and are the main material used to encapsulate chips in electronic products. As the core raw material for the production of single crystal silicon, polycrystalline silicon, electronic component carriers, integrated circuit substrates, optical fibers, quartz glass, optical instruments, solar cells and other products, it has been widely used in electronics, communications, home appliances, instrumentation, lighting, solar power generation, military industry, aerospace and many other cutting-edge fields. Its excellent performance provides solid support for technological innovation and product upgrades in these industries, and has become a key factor in promoting the continuous progress of high-tech industries.

[0003] The preparation methods of spherical silica powder mainly include physical method, chemical method and physical and chemical method. Among them, the physical method mainly includes flame spheronization method, high temperature melt spraying method, self-propagating low temperature combustion method, plasma method, high temperature calcination spheronization method, etc.; the chemical method mainly includes gas phase method, hydrothermal synthesis method, self-propagating low temperature combustion method, sol-gel method, precipitation method and microemulsion method, etc.

[0004] The raw material quartz required for the physical method to prepare spherical silica powder is widely available and has low cost, but the quality of the quartz raw materials and production equipment are high. Although the chemical method can prepare spherical silica powder with high purity and uniform particle size, its preparation process consumes a large amount of surfactant, resulting in problems such as high production cost, difficulty in eliminating organic impurities, and easy agglomeration of powder.

[0005] In summary, developing a method with simple process, easy-to-control reaction conditions, and the ability to quickly prepare ultra-high purity and regular spherical silica microspheres has become a key issue that needs to be urgently addressed in the current field of material preparation. It has important practical significance for promoting the further development of the high-tech industry of electronic chemicals. Summary of the invention

[0006] The object of the present invention is to solve the problems existing in the preparation of micron-sized silica microspheres by the existing chemical method, such as the large amount of surfactants used, resulting in high production costs, difficult elimination of organic impurities and easy agglomeration of powders. The present invention provides an ultra-high purity regular spherical silica microsphere and its preparation method. Through hydrolysis, polycondensation and oxygen-rich calcination, surfactants are not required, the cost is low, the conditions are simple and easy to control, and the prepared silica microspheres have good sphericity, uniform particle size distribution, good fluidity and high purity.

[0007] To solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a preparation method of ultra-high purity regular spherical silica microspheres, comprising the following steps:

[0008] (1) After mixing an organosilane and ultrapure water, add them to a reaction kettle, and carry out a hydrolysis reaction at a temperature of 40°C to 65°C to fully hydrolyze the organosilane into silanol to obtain a silanol aqueous solution;

[0009] (2) Keep the temperature of the silanol aqueous solution at 40°C to 65°C, add a basic polycondensation catalyst to the silanol aqueous solution, fully stir for 20 to 55 seconds, and then stand for reaction for 1 to 5 hours to obtain an organosilane source mixed solution;

[0010] (3) After the reaction is completed, centrifuge the organosilane source mixed solution, pour off the supernatant, wash it with a high-purity washing agent multiple times to wash away the by-products generated by the reaction, and centrifuge again to obtain semi-finished poly(silsesquioxane) microspheres, and the moisture content of the semi-finished product is 20% to 40%;

[0011] (4) Place the poly(silsesquioxane) microspheres in a crucible, and carry out oxygen-rich calcination at a constant temperature of 1050°C for 1 to 5 hours under a negative pressure of less than -0.05 MPa and protected by clean air to fully remove the organic groups in the center of the silicon source to obtain ultra-high purity regular spherical silica microspheres.

[0012] Preferably, the organosilane described in step (1) is one or more of phenyltrimethoxysilane, methyltrimethoxysilane, and vinyltrimethoxysilane.

[0013] Preferably, the mass ratio of the organosilane to the ultrapure water in step (1) is 1:(3 to 10).

[0014] Preferably, the basic polycondensation catalyst described in step (2) is methanolamine, and the dosage of the basic polycondensation catalyst is 0.005 to 0.06 times the mass of the organosilane.

[0015] Preferably, first raise the temperature from room temperature to 300°C at a heating rate not greater than 5°C / min, and then raise the temperature from 300°C to 1050°C at a heating rate not greater than 10°C / min.

[0016] The second technical solution of the present invention is to provide an ultra-high purity regular spherical silica microsphere, which is prepared by the above-mentioned preparation method, with a purity greater than 99.9999%, a sphericity of 100%, a concentrated particle size distribution, and uniform particle size.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. High purity: By washing with high-purity water multiple times, by-products generated from the polycondensation reaction are removed. Through high-temperature calcination treatment in clean air, organic groups in the silicon source center are removed, making the prepared silica microspheres have a purity as high as 99.9999%, far exceeding the purity index of 99.8% in the national standard GB / T 32661-2016 "Spherical Silica Powder", meeting the stringent requirements for the purity of silica microspheres in the high-end electronic chemical field.

[0019] 2. Good sphericity and uniform particle size: By selecting a suitable polycondensation reaction catalyst and precisely controlling the conditions of the polycondensation reaction and the heating rate of high-temperature calcination, the sphericity of the prepared silica microspheres reaches 100%, the particle size distribution is relatively concentrated, the particle size is relatively uniform, and it has good fluidity and a large specific surface area, improving the quality and stability of the silica microspheres, which is beneficial for applications in various fields.

[0020] 3. Simple process and low cost: The preparation method of the present invention does not require complex equipment and expensive raw materials, does not need to use surfactants, the process steps are relatively simple, easy to operate and control, can effectively reduce production costs, and is suitable for large-scale industrial production. Description of the Drawings

[0021] Figure 1 It is a scanning electron microscope image of the silica microspheres prepared in Example 1.

[0022] Figure 2 It is a laser particle size diagram of the silica microspheres prepared in Example 1.

[0023] Figure 3 It is a scanning electron microscope image of the silica microspheres prepared in Example 2.

[0024] Figure 4 It is a laser particle size diagram of the silica microspheres prepared in Example 2.

[0025] Figure 5 It is a scanning electron microscope image of the silica microspheres prepared in Example 3.

[0026] Figure 6 It is a laser particle size diagram of the silica microspheres prepared in Example 3.

[0027] Figure 7It is the scanning electron microscope image of the silica microspheres prepared in Example 4.

[0028] Figure 8 It is the laser particle size image of the silica microspheres prepared in Example 4.

[0029] Figure 9 It is the scanning electron microscope image of the silica microspheres prepared in the comparative example. Detailed implementation manners

[0030] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0031] Example 1

[0032] This example provides a method for preparing ultra-high purity regular spherical silica microspheres, including the following steps:

[0033] (1) After mixing 50 g of phenyltrimethoxysilane (C 9 H 14 O 3 Si) and 500 g of ultrapure water, add them into a glass reaction kettle with a liner, and carry out a hydrolysis reaction at a temperature of 60 °C to fully hydrolyze the organosilane into silanol to obtain a silanol aqueous solution;

[0034] (2) Keep the temperature of the silanol aqueous solution at 60 °C, add 0.25 g of methanolamine to the silanol aqueous solution, stir well for 30 seconds, and then stand for reaction for 3 hours to obtain an organosilicon source mixture;

[0035] (3) After the reaction is completed, centrifuge the organosilicon source mixture, pour off the supernatant, wash it twice with high-purity water to wash away the by-products generated by the reaction, and centrifuge again to obtain semi-finished polyhedral oligomeric silsesquioxane microspheres, and the moisture content of the semi-finished product is 38%;

[0036] (4) Place the polyhedral oligomeric silsesquioxane microspheres in a corundum crucible, place them in a muffle furnace capable of pumping negative pressure and passing a protective atmosphere, then heat from room temperature to 300 °C, control the heating rate at 3 °C / min, maintain the negative pressure less than -0.05 MPa, and heat from 300 °C to 1050 °C at a heating rate of 6 °C / min under the protection of clean air, precisely control the temperature at 1050 °C to remain unchanged, and carry out rich oxygen calcination for 4.5 hours to fully remove the organic groups in the center of the silicon source to obtain ultra-high purity regular spherical silica microspheres with a purity of 99.99992%.

[0037] From Figure 1 andFigure 2 It can be seen that the sphericity of the silica microspheres prepared in this example is 100%, with regular shape and smooth surface. Among them, the particle size (D50) is 1.779 μm, the particle size distribution is concentrated, and the particle sizes are uniform.

[0038] Example 2

[0039] This example provides a method for preparing ultra-high purity regular spherical silica microspheres, including the following steps:

[0040] (1) Mix 6.25 g of methyltrimethoxysilane (C 4 H 12 O 3 Si) with 43.75 g of vinyltrimethoxysilane (C 5 H 12 O 3 Si), and then add the mixture to 450 g of ultrapure water. After mixing, add it to a glass reaction kettle and carry out a hydrolysis reaction at a temperature of 55°C to fully hydrolyze the organosilane into silanol to obtain a silanol aqueous solution;

[0041] (2) Keep the temperature of the silanol aqueous solution at 65°C, add 0.5 g of methanolamine to the silanol aqueous solution, stir well for 55 seconds, and then let it stand for reaction for 1 hour to obtain a mixed organic silicon source solution;

[0042] (3) After the reaction, centrifuge the mixed organic silicon source solution, pour off the supernatant, wash it 3 times with high-purity water to wash away the by-products generated by the reaction, and then centrifuge again to obtain semi-finished polyhedral oligomeric silsesquioxane microspheres, and the water content of the semi-finished product is 29%;

[0043] (4) Place the polyhedral oligomeric silsesquioxane microspheres in a corundum crucible, and place it in a muffle furnace that can draw negative pressure and introduce a protective atmosphere. Then heat it from room temperature to 300°C at a heating rate of 2°C / min, maintain the negative pressure less than -0.05 MPa, and heat it from 300°C to 1050°C at a heating rate of 9°C / min under the protection of clean air. Precisely control the temperature at 1050°C to remain unchanged, and perform oxygen-rich calcination for 5 hours to fully remove the organic groups in the center of the silicon source to obtain ultra-high purity regular spherical silica microspheres, and its purity is 99.99995%.

[0044] From Figure 3 and Figure 4 It can be seen that the sphericity of the silica microspheres prepared in this example is 100%, with regular shape and smooth surface. Among them, the particle size (D50) is 3.55 μm, the particle size distribution is concentrated, and the particle sizes are uniform.

[0045] Example 3

[0046] This embodiment provides a method for preparing ultra-high purity regular spherical silica microspheres, which includes the following steps:

[0047] (1) After mixing 50 g of methyltrimethoxysilane (C 4 H 12 O 3 Si) with 250 g of ultrapure water, add it to a glass reaction kettle and carry out a hydrolysis reaction at a temperature of 40 °C to fully hydrolyze the organosilane into silanol to obtain an aqueous silanol solution;

[0048] (2) Keep the temperature of the aqueous silanol solution at 40 °C, add 1.5 g of methanolamine to the aqueous silanol solution, stir well for 55 seconds, and then let it stand for reaction for 5 hours to obtain an organosilane source mixture;

[0049] (3) After the reaction is completed, centrifuge the organosilane source mixture, pour off the supernatant, wash it 3 times with high-purity water to wash away the by-products generated by the reaction, and centrifuge again to obtain semi-finished polyhedral oligomeric silsesquioxane microspheres, and the water content of the semi-finished product is 37%;

[0050] (4) Place the polyhedral oligomeric silsesquioxane microspheres in a corundum crucible and place them in a muffle furnace capable of evacuating negative pressure and passing a protective atmosphere. Then heat from room temperature to 300 °C, control the heating rate at 4 °C / min, maintain the negative pressure less than -0.05 MPa, and heat from 300 °C to 1050 °C at a heating rate of 5 °C / min under the protection of clean air, precisely control the temperature at 1050 °C to remain unchanged, and calcine in rich oxygen for 1 hour to fully remove the organic groups in the center of the silicon source to obtain ultra-high purity regular spherical silica microspheres with a purity of 99.99993%

[0051] From Figure 5 and Figure 6 it can be seen that the sphericity of the silica microspheres prepared in this embodiment is 100%, the shape is regular and the surface is smooth, and the particle size (D50) is 5.047 μm, the particle size distribution is concentrated, and the particle size is uniform.

[0052] Example 4

[0053] This embodiment provides a method for preparing ultra-high purity regular spherical silica microspheres, which includes the following steps:

[0054] (1) After mixing 50 g of vinyltrimethoxysilane (C 5 H 12 O 3 Si) with 200 g of ultrapure water, add it to a glass reaction kettle with a lining and carry out a hydrolysis reaction at a temperature of 50 °C to fully hydrolyze the organosilane into silanol to obtain an aqueous silanol solution;

[0055] (2) Keep the temperature of the silanol aqueous solution at 50 °C, add 3 g of methanolamine to the silanol aqueous solution, stir well for 60 seconds, and then let it stand and react for 2 hours to obtain an organosilicon source mixture;

[0056] (3) After the reaction is completed, centrifuge the organosilicon source mixture, pour off the supernatant, wash it 3 times with high-purity water to wash away the by-products generated by the reaction, and centrifuge again to obtain semi-finished polyhedral oligomeric silsesquioxane microspheres, and the water content of the semi-finished product is 37%;

[0057] (4) Place the polyhedral oligomeric silsesquioxane microspheres in a corundum crucible, place them in a muffle furnace capable of pumping negative pressure and passing a protective atmosphere, then heat from room temperature to 300 °C, control the heating rate at 5 °C / min, maintain the negative pressure less than -0.05 MPa, and heat from 300 °C to 1050 °C at a heating rate of 10 °C / min under the protection of clean air, accurately control the temperature at 1050 °C to remain unchanged, and calcine in rich oxygen for 3 hours to fully remove the organic groups in the center of the silicon source, obtaining ultra-high-purity regular spherical silica microspheres with a purity of 99.99992%.

[0058] From Figure 7 and Figure 8 it can be seen that the sphericity of the silica microspheres prepared in this example is 100%, the shape is regular and the surface is smooth, and the particle size (D50) is 10.937 μm, the particle size distribution is concentrated, and the particle sizes are uniform.

[0059] Comparative Example

[0060] This comparative example provides a method for preparing silica microspheres, including the following steps:

[0061] (1) Mix 50 g of methyltrimethoxysilane with 250 g of ultrapure water, add it to a glass reaction kettle, and carry out a hydrolysis reaction at a temperature of 40 °C to fully hydrolyze the organosilane into silanol to obtain a silanol aqueous solution;

[0062] (2) Keep the temperature of the silanol aqueous solution at 40 °C, add 1.5 g of ammonia water to the silanol aqueous solution, stir well for 75 seconds, and then let it stand and react for 5 hours to obtain an organosilicon source mixture;

[0063] (3) After the reaction is completed, centrifuge the organosilicon source mixture, pour off the supernatant, wash it 3 times with high-purity water to wash away the by-products generated by the reaction, and centrifuge again to obtain semi-finished polyhedral oligomeric silsesquioxane microspheres, and the water content of the semi-finished product is 34%;

[0064] (4) Place the polyhedral oligomeric silsesquioxane microspheres in a corundum crucible and put it in a muffle furnace capable of evacuating negative pressure and introducing a protective atmosphere. Then, heat from room temperature to 300 °C at a heating rate of 5 °C / min, maintain the negative pressure less than -0.05 MPa, and heat from 300 °C to 1050 °C at a heating rate of 10 °C / min under the protection of clean air. Precisely control the temperature at 1050 °C to be constant and calcine for 3 hours to obtain silica microspheres.

[0065] From Figure 9 It can be seen that by changing the stirring time of the polycondensation catalyst and the type of the polycondensation catalyst added, the particle size distribution of the prepared silica microspheres is relatively wide and the particle size difference is very large.

[0066] The above is only the best implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several deformations or equivalent substitutions can be made to the technical solution of the present invention, and the technical effects of the present invention can also be achieved, which should also be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for preparing ultra-high purity regular spherical silica microspheres, characterized in that: The following steps are involved: (1) mixing an organosilane and ultrapure water, adding the mixture into a reaction kettle, and performing a hydrolysis reaction at a temperature of 40° C. to 60° C. to fully hydrolyze the organosilane into silanol, thereby obtaining a silanol aqueous solution; (2) maintaining the temperature of the silanol aqueous solution at 40° C. to 60° C., adding an alkaline polycondensation catalyst to the silanol aqueous solution, stirring the solution for 30 to 60 seconds, and allowing the solution to react for 1 to 5 hours to obtain an organic silicon source mixed solution; (3) After the reaction is completed, the organic silicon source mixed solution is centrifuged, the supernatant is discarded, and the solution is washed with high-purity water for several times and centrifuged again to obtain semi-finished polysilsesquioxane microspheres; (4) The polysilsesquioxane microspheres are placed in a sagger, and calcined in oxygen-enriched conditions at 1050° C. for 1 to 5 hours under a negative pressure of less than −0.05 MPa and under the protection of clean air to obtain ultrahigh purity regular spherical silica microspheres.

2. The preparation method according to claim 1, characterized in that: The organosilane described in step (1) is one or more of phenyltrimethoxysilane, methyltrimethoxysilane and vinyltrimethoxysilane.

3. The preparation method according to claim 2, characterized in that: In step (1), the mass ratio of organosilane to ultrapure water is 1:(4-10).

4. The preparation method according to claim 1, characterized in that: The alkaline polycondensation catalyst described in step (2) is methanolamine, and the amount of the alkaline polycondensation catalyst used is 0.005 to 0.06 times the mass of the organosilane.

5. The preparation method according to claim 1, characterized in that: The heating process of calcination in step (4) is: firstly heating from room temperature to 300°C at a heating rate of no more than 5°C / min, and then heating from 300°C to 1050°C at a heating rate of no more than 10°C / min.

6. An ultra-high purity regular spherical silica microsphere, characterized in that: The preparation method is adopted according to any one of claims 1 to 5.

7. The ultra-high purity regular spherical silica microspheres according to claim 6, characterized in that: The purity of the silicon dioxide microspheres is greater than 99.9999%, the sphericity is 100%, the particle size distribution is concentrated, and the particle size is uniform.

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