A method for preparing high-purity micron-sized monodisperse spherical silica by membrane sieving

Abstract

The invention discloses a method for preparing high-purity micron-sized monodisperse spherical silica by membrane screening. The method comprises the following steps: uniformly mixing a silicon source, an electrolyte, a polymer dispersant and a solvent to form a reaction solution, reacting at 0-60°C for 2-8 hours to obtain a silanol aqueous solution; filtering the silanol aqueous solution through a filter membrane with a size of 1-30 μm, adding an alkaline solution to the filtrate obtained by filtration and reacting for 12 hours to obtain a white silica suspension; standing and aging the white silica suspension, centrifuging it, and then washing it with ethanol or an ethanol aqueous solution to obtain high-purity micron-sized monodisperse spherical silica; combining pretreatment membrane screening with precipitation polymerization, and using electrolytes and polymer dispersants to synergistically optimize the charge distribution on the surface of microspheres, thereby reducing secondary nucleation, avoiding the generation of large and small balls, and preparing uniform and stable micron-sized monodisperse spherical silica; the production cost is low, the energy consumption is low, the reagent pollution is low, and large-scale production is convenient.

Description

Technical Field

[0001] The invention relates to the technical field of silicon dioxide preparation, and in particular to a method for preparing high-purity micron-level monodisperse spherical silicon dioxide through membrane screening. Background Art

[0002] Spherical silica is widely used in large-scale integrated circuits, liquid crystal display, aerospace and high-end cosmetics due to its good dielectric properties, high filling rate, low stress, low thermal expansion coefficient and friction coefficient. Among them, high-purity monodisperse spherical silica is often synthesized by chemical method, with lower content of metal elements and radioactive elements, and has important applications in chromatographic separation, photonic crystals, standard particles and liquid crystal spacing.

[0003] In the prior art, the chemical methods for preparing monodisperse spherical silica mainly include sol-gel method, seed method, emulsion method, precipitation method and template method. Among them, the sol-gel method uses silicate and alcohol to generate nano or submicron spherical silica under the catalytic action of alkali. Limited by the principle of the method, the particle size of silica microspheres is difficult to reach above micron level. The seed method further grows on the basis of silica microspheres synthesized by the sol-gel method, which can moderately increase the seed particle size, but the overall growth particle size range is limited, and the larger the particle size, the greater the degree of polydispersity. The spherical silica prepared by the emulsion method is nano-level, and the emulsifier used in the synthesis is difficult to wash clean. The spherical silica synthesized by the precipitation method using sodium silicate as raw material and acid catalysis has poor monodispersity and is limited in application in the field of high-precision technology and processing.

[0004] A Chinese patent document with patent number CN112624131A discloses a method for preparing monodisperse large-particle silica microspheres, which utilizes a sol-gel method to synthesize monodisperse silica microsphere seeds, adds ionic liquid, and obtains a monodisperse silica microsphere suspension with uniform and controllable particle size through a seed growth method, wherein the silica microsphere particle size is above 1.5 μm but is polydispersed. In addition, a Chinese patent document with patent number CN107298446A also discloses a method for preparing high-purity micron-sized spherical silica powder, which comprises adding a silicon precursor solution to an oil phase containing an emulsifier for alkaline catalysis, and obtaining silica microspheres of 0.3-40 μm after standing and aging. Although the particle size of the microspheres prepared by this method can reach above the micron level, the distribution uniformity is poor. If high-purity monodisperse silica microspheres above the micron level are required, the above method cannot be achieved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing high-purity micron-sized monodisperse spherical silica by membrane screening, so as to solve the following technical problems:

[0006] In the prior art, the chemical methods for preparing monodisperse spherical silica mainly include sol-gel method, seed method, emulsion method, precipitation method and template method; the sol-gel method utilizes silicate and alcohol to generate nanometer or submicron spherical silica under the catalytic action of alkali. Limited by the principle of the method, the particle size of silica microspheres is difficult to reach micrometer level or above; the seed method further grows on the basis of silica microspheres synthesized by the sol-gel method, and can moderately increase the seed particle size, but the overall growth particle size range is limited, and the larger the particle size, the greater the degree of polydispersity; the spherical silica prepared by the emulsion method is nanometer level, and the emulsifier used in the synthesis is difficult to wash clean; the spherical silica synthesized by the precipitation method using sodium silicate as raw material through acid catalysis has poor monodispersity and is limited in the application in the field of high-precision technology and processing; therefore, how to obtain high-purity monodisperse silica microspheres above micrometer level is a technical problem that the present invention urgently needs to solve.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] The invention discloses a method for preparing high-purity micron-sized monodisperse spherical silica by membrane screening. The method combines pre-treatment membrane screening (membrane filtration) with precipitation polymerization (adding an alkaline solution to obtain a white silica suspension), and simultaneously utilizes electrolytes and polymer dispersants to synergistically optimize the charge distribution on the surface of microspheres, thereby reducing secondary nucleation, avoiding the generation of large and small spheres, and preparing uniform and stable micron-sized monodisperse spherical silica. The method has low production cost, low energy consumption, low reagent pollution, and is convenient for large-scale production.

[0009] The present invention discloses a method for preparing high-purity micron-sized monodisperse spherical silica by membrane screening, comprising the following steps:

[0010] S1, uniformly mixing an electrolyte, a silicon source, a polymer dispersant and a solvent to form a reaction solution, reacting at 0-60° C. for 2-8 hours to obtain a silanol aqueous solution; wherein the weight ratio of the silicon source to the solvent is 1:(2-20), the weight ratio of the electrolyte to the silicon source is 1:(30-300), and the weight ratio of the polymer dispersant to the silicon source is 1:(3-40);

[0011] S2, filtering the silanol aqueous solution through a filter membrane with a size of 1-30 um, adding an alkaline solution with a concentration of 0.1-2 mol / L to the filtrate obtained by filtration for 12 hours to obtain a white silica suspension; wherein the weight ratio of the alkaline solution to the solvent in step S1 is 1:(5-160);

[0012] S3. The white silica suspension is allowed to stand for aging, then centrifuged, and then washed with ethanol or ethanol aqueous solution to obtain high-purity micron-sized monodisperse spherical silica.

[0013] Preferably, in step S1, the silicon source comprises Si(OR) 4 , R 1 Si(OR) 3 or R 1 R 2 Si(OR) 2 At least one of .

[0014] Preferably, the R, R 1 , R 2 All contain C 1 -C 4 , and the three are the same or different.

[0015] Preferably, in step S1, when R is C 2 When the reaction liquid has an acidic solution, the amount of the acidic solution added is 0.01-0.1% of the total mass of the reaction liquid, and the concentration of the acidic solution is 0.01-5 mol / L.

[0016] Preferably, the acidic solution is any one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid, and a strong acid and weak base salt solution, more preferably an acetic acid solution.

[0017] Preferably, in step S1, the solvent is deionized water or a lower aliphatic alcohol, wherein the lower aliphatic alcohol includes at least one of methanol, ethanol, propanol, isopropanol and butanol, and more preferably deionized water.

[0018] Preferably, in step S1, the electrolyte is any one of sodium salt, potassium salt, chloride salt, bromide salt, nitrate or sulfate, more preferably KBr.

[0019] Preferably, in step S1, the polymer dispersant is polyvinyl alcohol, and the polyvinyl alcohol is any one of PEG1000, PEG4000, PEG8000, PEG14000, and PEG50000, more preferably PEG4000.

[0020] Preferably, in step S2, the filtering method is normal pressure filtration, positive pressure filtration or negative pressure filtration.

[0021] Preferably, in step S2, the alkaline solution is any one of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine or a strong base weak acid salt solution, more preferably a sodium phenolate solution.

[0022] Beneficial effects of the present invention:

[0023] In the method for preparing high-purity micron-sized monodisperse spherical silica by membrane screening of the present invention, pre-treatment membrane screening (membrane filtration) and precipitation polymerization (adding alkaline solution to obtain a white silica suspension) are combined, and electrolytes and polymer dispersants are used to coordinately optimize the charge distribution on the surface of the microspheres, which can reduce secondary nucleation, avoid the generation of large and small spheres, and prepare uniform and stable micron-sized monodisperse spherical silica; the production cost is low, the energy consumption is low, the reagent pollution is low, and it is convenient for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 This is a scanning electron microscope characterization image of the high-purity micron-sized monodisperse spherical silicon dioxide prepared in Example 1 of the present invention;

[0026] Figure 2 This is a scanning electron microscope characterization image of the high-purity micron-sized monodisperse spherical silicon dioxide prepared in Example 2 of the present invention;

[0027] Figure 3 This is a scanning electron microscope characterization image of the high-purity micron-sized monodisperse spherical silicon dioxide prepared in Example 3 of the present invention;

[0028] Figure 4 This is a scanning electron microscope characterization image of the high-purity micron-sized monodisperse spherical silicon dioxide prepared in Example 4 of the present invention;

[0029] Figure 5 This is a scanning electron microscope characterization image of the high-purity submicron-level monodisperse spherical silicon dioxide prepared in Example 5 of the present invention;

[0030] Figure 6 This is a scanning electron microscope characterization image of the high-purity micron-sized spherical silicon dioxide prepared in Comparative Example 1 of the present invention;

[0031] Figure 7 This is a scanning electron microscope characterization image of the high-purity micron-sized spherical silicon dioxide prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0034] Example 1

[0035] Add 280g of deionized water and 0.5g of KBr to a 500mL flask and stir for 10min; prepare another beaker and add 30g of vinyl trimethoxysilane and 20g of dimethyl dimethoxysilane, stir evenly, then add 2g of PEG10000 and continue stirring evenly to obtain a mixed liquid. When the temperature of both is raised to 20°C, pour the mixed liquid in the beaker into the flask and stir for 3h to obtain a silanol aqueous solution containing electrolytes and polymer dispersants. Filter the silanol aqueous solution in the flask at normal pressure through a 10um filter membrane, add 56g of 0.1 mol / L sodium phenolate solution to the obtained filtrate and stir for 12h to obtain a white silica suspension; the white silica suspension is allowed to stand for aging, then centrifuged, and then washed with ethanol several times to obtain high-purity micron-grade monodispersed spherical silica.

[0036] The obtained spherical silica was characterized by scanning electron microscopy, and the following Figure 1 From the electron microscope image shown, it can be found that the particle size of spherical silica is basically maintained at 3.0um, and the particle size is highly monodisperse.

[0037] Example 2

[0038] Add 300g of deionized water, 0.1g of 1mol / L acetic acid, and 0.2g of NaCl to a 500mL flask and stir for 10min; prepare another beaker and add 20g of methyltrimethoxysilane and 10g of tetraethyl orthosilicate, stir evenly, then add 1g of PEG4000 and continue stirring evenly to obtain a mixed liquid. When the temperature of both is raised to 60°C, pour the mixed liquid in the beaker into the flask and stir for 6h to obtain a silanol aqueous solution containing electrolytes and polymer dispersants. Filter the silanol aqueous solution in the flask through a 5um filter membrane under negative pressure, add 10g of 1mol / L sodium phenolate solution to the obtained filtrate, stir for 12h to obtain a white silica suspension; the white silica suspension is allowed to stand for aging, then centrifuged, and then washed with ethanol several times to obtain high-purity micron-grade monodispersed spherical silica.

[0039] The obtained spherical silica was characterized by scanning electron microscopy, and the following Figure 2 From the electron microscope image shown, it can be found that the particle size of spherical silica is basically maintained at 1.7um, and the particle size is highly monodisperse.

[0040] Example 3

[0041] Add 380g of deionized water and 20g of methanol, 0.1g of 0.5mol / L sulfuric acid, and 2g of KBr to a 1000mL flask and stir for 10min; prepare another beaker and add 200g of methyltrimethoxysilane, then add 5g of PEG1000, and continue to stir evenly to obtain a mixed liquid. When the temperature of both is raised to 40°C, pour the mixed liquid in the beaker into the flask and stir for 4h to obtain a silanol aqueous solution containing electrolytes and polymer dispersants. The silanol aqueous solution in the flask is filtered under negative pressure through a 3um filter membrane, and 20g of 0.5mol / L of sodium hydroxide solution is added to the obtained filtrate and stirred for 12h to obtain a white silica suspension; the white silica suspension is allowed to stand for aging, then centrifuged, and then washed with ethanol several times to obtain high-purity micron-level monodispersed spherical silica.

[0042] The obtained spherical silica was characterized by scanning electron microscopy, and the following Figure 3 From the electron microscope image shown, it can be found that the particle size of spherical silica is basically maintained at 1.9um, and the particle size is highly monodisperse.

[0043] Example 4

[0044] Add 320g deionized water and 0.5g KBr to a 500mL flask and stir for 10min; prepare another beaker and add 60g methyltrimethoxysilane, then add 2g PEG4000, and continue to stir to obtain a mixed liquid. When the temperature of both drops to 0°C, pour the mixed liquid in the beaker into the flask and stir for 6h to obtain a silanol aqueous solution containing electrolytes and polymer dispersants. Filter the silanol aqueous solution in the flask through a 30um filter membrane under negative pressure, add 2g 0.5mol / L sodium phenolate solution to the obtained filtrate, stir for 12h to obtain a white silica suspension; the white silica suspension is allowed to stand for aging, then centrifuged, and then washed with ethanol several times to obtain high-purity micron-grade monodispersed spherical silica.

[0045] The obtained spherical silica was characterized by scanning electron microscopy, and the following Figure 4 From the electron microscope image shown, it can be found that the particle size of spherical silica is basically maintained at 7.0um, and the particle size is highly monodisperse.

[0046] Example 5

[0047] Add 300g of deionized water, 0.5g of 0.1mol / L sulfuric acid, and 0.5g of KBr to a 500mL flask and stir for 10min; prepare another beaker and add 15g of 3-aminopropyltriethoxysilane, then add 5g of PEG4000, and continue to stir evenly to obtain a mixed liquid. When the temperature of both is raised to 40°C, pour the mixed liquid in the beaker into the flask and stir for 8h to obtain a silanol aqueous solution containing electrolytes and polymer dispersants. The silanol aqueous solution in the flask is filtered under negative pressure through a 1um filter membrane, and 10g of 2mol / L ammonia solution is added to the obtained filtrate and stirred for 12h to obtain a white silica suspension; the white silica suspension is allowed to stand for aging, then centrifuged, and then washed with ethanol several times to obtain high-purity micron-grade monodispersed spherical silica.

[0048] The obtained spherical silica was characterized by scanning electron microscopy, and the following Figure 5 From the electron microscope image shown, it can be found that the particle size of spherical silica is basically maintained at slightly below 0.7um, and the particle size is highly monodisperse.

[0049] Comparative Example 1

[0050] Add 280g of deionized water and 0.5g of KBr to a 500mL flask and stir for 10min; prepare another beaker and add 30g of vinyl trimethoxysilane and 20g of dimethyl dimethoxysilane, stir evenly, then add 2g of PEG10000 and continue stirring evenly to obtain a mixed liquid. When the temperature of both is raised to 20°C, pour the mixed liquid in the beaker into the flask and stir for 3h to obtain a silanol aqueous solution containing electrolytes and polymer dispersants. Add 50g of 0.1mol / L sodium phenolate solution to the obtained silanol aqueous solution and stir for 12h to obtain a white silica suspension; the white silica suspension is allowed to stand for aging, then centrifuged, and then washed with ethanol several times to obtain high-purity micron-sized spherical silica.

[0051] The obtained spherical silica was characterized by scanning electron microscopy, and the following Figure 6 From the electron microscope image shown, it can be found that the particle size of spherical silica varies between 3.0-4.0um, and the particle size is polydisperse.

[0052] Comparative Example 2

[0053] 280 g of deionized water, 30 g of vinyltrimethoxysilane and 20 g of dimethyldimethoxysilane were added to a 500 mL flask, and the mixture was stirred evenly when the temperature was raised to 20°C to obtain a mixed liquid, and the mixture was reacted for 3 hours to obtain a silanol aqueous solution free of electrolytes and polymer dispersants. 50 g of 0.1 mol / L sodium phenolate solution was added to the obtained silanol aqueous solution, and the mixture was stirred for 12 hours to obtain a white silica suspension. The white silica suspension was allowed to stand for aging, and then centrifuged, and then washed with ethanol for multiple times to obtain high-purity micron-sized spherical silica.

[0054] The obtained spherical silica was characterized by scanning electron microscopy, and the following Figure 7 From the electron microscope image shown, it can be found that the particle size of spherical silica varies from 2.7 to 5.7 um, and there is an obvious problem of large and small balls.

[0055] By analyzing the observation results of Examples 1-5 and Comparative Examples 1-2, it can be found that compared with Comparative Examples 1-2, the particle size of the high-purity micron-sized spherical silica obtained in Example 1-5 after membrane screening and containing electrolytes and polymer dispersants is uniform and controllable, and presents a good monodisperse state.

[0056] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing high-purity micron-sized monodisperse spherical silica by membrane screening, characterized in that: The steps include: S1, uniformly mixing an electrolyte, a silicon source, a polymer dispersant and a solvent to form a reaction solution, reacting at 0-60° C. for 2-8 hours to obtain a silanol aqueous solution; wherein the weight ratio of the silicon source to the solvent is 1:(2-20), the weight ratio of the electrolyte to the silicon source is 1:(30-300), and the weight ratio of the polymer dispersant to the silicon source is 1:(3-40); S2, filtering the silanol aqueous solution through a filter membrane with a size of 1-30 um, adding an alkaline solution with a concentration of 0.1-2 mol / L to the filtrate obtained by filtration for 12 hours to obtain a white silica suspension; wherein the weight ratio of the alkaline solution to the solvent in step S1 is 1:(5-160); S3. The white silica suspension is allowed to stand for aging, then centrifuged, and then washed with ethanol or ethanol aqueous solution to obtain high-purity micron-sized monodisperse spherical silica.

2. The method for preparing high-purity micron-sized monodisperse spherical silica by membrane screening according to claim 1, characterized in that: In step S1, the silicon source includes at least one of Si(OR)4, R1Si(OR)3 or R1R2Si(OR)2.

3. The method for preparing high-purity micron-sized monodisperse spherical silica by membrane screening according to claim 2, characterized in that: The R, R1, and R2 are all groups containing C1-C4, and the three are the same or different.

4. The method for preparing high-purity micron-sized monodisperse spherical silicon dioxide by membrane sieving according to claim 2, characterized in that: In step S1, when R is C2 or above, an acidic solution is further added to the reaction solution, the amount of the acidic solution added is 0.01-0.1% of the total mass of the reaction solution, and the concentration of the acidic solution is 0.01-5 mol / L.

5. The method for preparing high-purity micron-sized monodisperse spherical silica by membrane sieving according to claim 4, characterized in that: The acidic solution is any one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid, and a strong acid or weak base salt solution.

6. The method for preparing high-purity micron-sized monodisperse spherical silicon dioxide by membrane sieving according to claim 1, characterized in that: In step S1, the solvent is deionized water or a lower aliphatic alcohol, and the lower aliphatic alcohol includes at least one of methanol, ethanol, propanol, isopropanol, and butanol.

7. The method for preparing high-purity micron-sized monodisperse spherical silicon dioxide by membrane sieving according to claim 1, characterized in that: In step S1, the electrolyte is any one of sodium salt, potassium salt, chloride salt, bromide salt, nitrate or sulfate.

8. The method for preparing high-purity micron-sized monodisperse spherical silicon dioxide by membrane sieving according to claim 1, characterized in that: In step S1, the polymer dispersant is polyvinyl alcohol, and the polyvinyl alcohol is any one of PEG1000, PEG4000, PEG8000, PEG14000, and PEG50000.

9. The method for preparing high-purity micron-sized monodisperse spherical silicon dioxide by membrane sieving according to claim 1, characterized in that: In step S2, the filtering method is normal pressure filtration, positive pressure filtration or negative pressure filtration.

10. The method for preparing high-purity micron-sized monodisperse spherical silicon dioxide by membrane sieving according to claim 1, characterized in that: In step S2, the alkaline solution is any one of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine or a strong base and weak acid salt solution.

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