Amorphous spherical silicon dioxide micro powder and preparation method thereof

Abstract

The invention discloses amorphous spherical silica micropowder and a preparation method thereof, and the method comprises the following steps: mixing an emulsifier and a cosurfactant, and then sequentially adding a cationic surfactant and an organic solvent to form a transparent solution; dropwise adding a catalyst, which is a mixed solution of ammonia water and triethylamine, into the transparent solution until the solution becomes turbid, and then forming a water-in-oil microemulsion through a high-speed shearing emulsifying machine; under the condition that the temperature is 20-30 DEG C, dropwise adding organosilane into the water-in-oil type microemulsion, and carrying out hydrolysis reaction; and then carrying out flocculent precipitation, centrifugal separation, washing, drying, calcining and post-stage modification to prepare the silicon dioxide powder with smooth surface and uniform granularity. By controlling the ratio of organosilane to the emulsifier to the cosurfactant, the rotating speed during emulsification and the addition amount of the modifier, the submicron spherical silicon dioxide with uniform particle size distribution is obtained, the generation of holes is avoided, and the product yield is improved.

Description

Technical Field

[0001] The invention relates to the technical field of micron material preparation, and in particular to amorphous spherical silicon dioxide powder and a preparation method thereof. Background Art

[0002] The microemulsion method is an effective method for preparing spherical silica particles. It uses two immiscible solvents and surfactants to form a stable emulsion system to achieve processes such as nucleation, coalescence, agglomeration and heat treatment. This method can accurately control the particle size and particle size distribution of the particles. The prepared particles have easy-to-control particle size, narrow particle size distribution and are not easy to agglomerate. However, the microemulsion method also faces challenges such as precise control of reaction conditions and formulations, complex equipment and operations, and the treatment and recovery of solvents and surfactants also need to consider environmental protection requirements. Despite this, the microemulsion method still has broad application prospects in the fields of materials science and chemistry.

[0003] The seed method mentioned in the CN101205067B patent can produce microspheres with smaller particle sizes and obtain microspheres with larger particle sizes through layer-by-layer growth, but its feasibility of scaled-up production is limited. The chemical precipitation method is to mix substances with different chemical compositions in a solution, add a precipitant to form a precursor precipitate, and then dry or calcine to prepare the powder. Although this method has a low cost in industrial production, the volume shrinkage is large during the preparation process.

[0004] Patent CN102659123A shows a method for preparing spherical silicon micropowder by microemulsion reaction, and the main raw materials include water glass, ammonium salt, organic solvent and surfactant. By accurately controlling the ratio of organic solvent, dispersant, surfactant and water glass and other condition parameters, silicon micropowder with good sphericity can be obtained. However, the particle size distribution of silicon micropowder prepared by this method is still relatively wide, the particles are prone to agglomeration, and there are pits on the surface. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an amorphous spherical silicon dioxide powder with reasonable design, uniform particle size distribution and small particles and a preparation method thereof in view of the deficiencies of the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing amorphous spherical silicon dioxide powder, characterized in that the method comprises the following steps: (1) firstly mix the emulsifier and the co-surfactant in a mass ratio of 1:1-3, and after uniform mixing, add the cationic surfactant and the organic solvent in sequence, in a mass ratio of 3-20:1 between the emulsifier and the cationic surfactant, and in a mass ratio of 12-50:1 between the organic solvent and the emulsifier, to form a transparent solution; (2) under stirring, adding a catalyst to the transparent solution, wherein the catalyst is a mixture of ammonia water and triethylamine, the mass ratio of ammonia water to triethylamine is 4:1-4, and the concentration of ammonia water is 10%-30%, and the solution becomes turbid, and then passing through a high-speed shear emulsifier to form an oil-in-water type microemulsion, the speed of the high-speed shear emulsifier is 5000rpm-20000rpm, and the emulsification time is 10min-15min; (3) adding organosilane dropwise to the water-in-oil microemulsion at a temperature of 20°C-30°C, with the mass ratio of organosilane to emulsifier being 25-40:1, and continuously stirring for 2h-6h to hydrolyze the organosilane in the water-in-oil microemulsion to form a solution containing silica powder; (4) After the hydrolysis is completed, the above solution is subjected to flocculation precipitation, centrifugal separation, washing, drying and calcination.

[0007] (5) After calcination, use a temperature probe to measure the powder temperature at 150°C-200°C, then place the powder in a vacuum double-cone spiral dryer, add a modifier, control the vacuum degree at an absolute pressure of 200kPa-700kPa, and the equipment speed is 10rpm-20rpm. The amount of modifier added is 1%-2% of the mass of the organic silane. Under this condition, the mixture is mixed and modified for 30min-60min, and then a highly hydrophobic, smooth-surfaced, and uniformly sized silica powder is obtained.

[0008] The technical problem to be solved by the present invention can also be achieved by the following technical scheme, wherein the emulsifier is one of the Span series (including Span-10, Span-40, Span-60) and the Tween series (including Tween-20, Tween-24, Tween-60, Tween-80), the co-surfactant is one or more of n-octanol, cyclohexane, and isooctyl alcohol, and the cationic surfactant is one or more of stearyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, hexadecyl pyridinium chloride, and ethanolamine salt.

[0009] The technical problem to be solved by the present invention can also be achieved by the following technical scheme, wherein the organic solvent is one or more of cyclohexane, paraffin oil, carbon tetrachloride, and ethyl acetate.

[0010] The technical problem to be solved by the present invention can also be achieved by the following technical solution, wherein the organosilane is one or more of methoxysilane, methyl silicate and ethyl silicate.

[0011] The technical problem to be solved by the present invention can also be achieved by the following technical solution. In step (4), the precipitate is washed three times with a solvent, and then the drying temperature is controlled at 20°C-60°C during the drying process, and the calcination temperature is controlled at 450°C-950°C during the calcination process. The above-mentioned solvent includes but is not limited to ethyl acetate, anhydrous ethanol, and isopropanol.

[0012] The technical problem to be solved by the present invention can also be achieved by the following technical solution, wherein the type of the modifier in step (5) is one or more of vinyl, phenylamino and silazane.

[0013] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the average particle size of the silicon dioxide powder prepared in step (4) is 0.1-5.0 μm, the carbon content is greater than 0.07%, and the hydroxyl content is less than 0.3 / nm 2 , magnetic substances <2.0ppm.

[0014] Compared with the prior art, the present invention has the following technical effects: First, the present invention first mixes the emulsifier and the co-surfactant to ensure that the emulsifier and the surfactant are more evenly distributed in the solvent, which is conducive to forming a stable emulsion. In addition, such pre-mixing can also reduce the problem of excessive or low local concentration that may occur in the subsequent mixing process, thereby improving the stability and consistency of the product; then, by controlling the ratio of organic silane, emulsifier and co-surfactant, and the rotation speed during emulsification, the oil-in-water structure is used to obtain micron-sized spherical silica with uniform particle size distribution, and the generation of holes is avoided, thereby improving the product yield; Second, by introducing cationic surfactants, the charge distribution in the synthetic system is affected by electrostatic interactions, which increases the repulsive force of the interface, inhibits the coagulation and precipitation of the dispersed phase, improves the stability of the microemulsion, and reduces the probability of large particles. Third, by mixing ammonia water and triethylamine as a catalyst and stabilizer, the reaction is promoted while the stability of the emulsion is enhanced to prevent stratification and coagulation.

[0015] Fourth, the waste heat after sintering is used for modification, which reduces energy consumption.

[0016] Fifth, modification under vacuum conditions effectively prevents impurities such as oxygen and moisture in the air from contaminating the powder material, protects the chemical and physical properties of the material, and ensures the stability and consistency of the modification effect. In addition, since the modifier is generally flammable, under vacuum conditions, the material is isolated from the air, reducing safety hazards such as fire and explosion.

[0017] The method for detecting magnetic substances in the present invention is as follows: dissolving powder in a solvent at a ratio of 1:1, stirring the slurry with a 5000GS magnet, and weighing the magnetic substances adsorbed by the magnet. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0019] Example 1, (1) 3.78 g of Tween-80 and 9.42 g of isooctyl alcohol were mixed and mixed evenly, and then 0.5 g of stearyl trimethyl ammonium bromide and 100 g of carbon tetrachloride were added until a transparent solution was formed; (2) under stirring, a catalyst is added dropwise to the transparent solution, wherein the catalyst is a mixture of ammonia water and triethylamine, the mass ratio of ammonia water to triethylamine is 3:2, and the concentration of ammonia water is 10%, and the mixture is added dropwise until the solution becomes turbid, and then the mixture is passed through a high-speed shear emulsifier to form an oil-in-water type microemulsion, wherein the rotation speed of the high-speed shear emulsifier is 15000 rpm, and the emulsification time is 15 min; (3) Add 105 g of tetramethoxysilane dropwise to the water-in-oil microemulsion at 20° C. and continue stirring for 3 h to hydrolyze the tetramethoxysilane in the water-in-oil microemulsion to form a solution containing silica powder; (4) After the hydrolysis is completed, the precipitate is washed three times with ethyl acetate during the washing process, the drying temperature is controlled at 50°C during the drying process, and the calcination temperature is controlled at 820°C during the calcination process.

[0020] (5) After calcination, use a temperature probe to measure the powder temperature at 180°C, then place the powder in a vacuum double-cone screw dryer, add 1.58 g of modifier hexamethyldisilazane, control the vacuum degree at an absolute pressure of 520 kPa, and set the equipment speed at 15 rpm. Under this condition, mix and modify for 40 minutes to obtain amorphous spherical silica powder.

[0021] Example 2, (1) 3.78 g of Span-20 and 3.78 g of isooctyl alcohol were mixed and mixed evenly, and then 0.5 g of hexadecyltrimethylammonium chloride bromide and 100 g of cyclohexane were added until a transparent solution was formed; (2) under stirring, a catalyst is added dropwise to the transparent solution, wherein the catalyst is a mixture of ammonia water and triethylamine, the mass ratio of ammonia water to triethylamine is 3:2, and the concentration of ammonia water is 15%, and the mixture is added dropwise until the solution becomes turbid, and then the mixture is passed through a high-speed shear emulsifier to form an oil-in-water type microemulsion, wherein the rotation speed of the high-speed shear emulsifier is 10000 rpm, and the emulsification time is 10 min; (3) Add 100 g of methyl silicate dropwise to the above water-in-oil microemulsion at a temperature of 30° C. and continue stirring for 4 h to allow the methyl silicate to hydrolyze in the water-in-oil microemulsion to form a solution containing silica powder; (4) After the hydrolysis is completed, the precipitate is washed three times with anhydrous ethanol during the washing process, the drying temperature is controlled at 40°C during the drying process, and the calcination temperature is controlled at 550°C during the calcination process.

[0022] (5) After calcination, use a temperature probe to measure the powder temperature at 180°C, then place the powder in a vacuum double-cone screw dryer, add 1 g of modifier vinyltrimethoxysilane, control the vacuum degree at an absolute pressure of 520 kPa, and set the equipment speed at 15 rpm. Under this condition, mix and modify for 40 minutes to obtain amorphous spherical silica powder.

[0023] Example 3, (1) 3.78 g of Tween-80, 5.67 g of cyclohexane, and 1.55 g of n-octanol were mixed and uniformly mixed, and then 1.2 g of ethanolamine salt and 150 g of ethyl acetate were added until a transparent solution was formed; (2) under stirring, a catalyst is added dropwise to the transparent solution, wherein the catalyst is a mixture of ammonia water and triethylamine, the mass ratio of ammonia water to triethylamine is 3:2, and the concentration of ammonia water is 20%, and the mixture is added dropwise until the solution becomes turbid, and then the mixture is passed through a high-speed shear emulsifier to form an oil-in-water type microemulsion, wherein the rotation speed of the high-speed shear emulsifier is 20000 rpm and the emulsification time is 10 min; (3) Add 150 g of ethyl silicate dropwise to the above water-in-oil microemulsion at a temperature of 30° C. and continue stirring for 4 h to allow the ethyl silicate to hydrolyze in the water-in-oil microemulsion to form a solution containing silica powder; (4) After the hydrolysis is completed, the precipitate is washed three times with isopropanol during the washing process, the drying temperature is controlled at 35°C during the drying process, and the calcination temperature is controlled at 450°C during the calcination process.

[0024] (5) After calcination, use a temperature probe to measure the powder temperature at 180°C, then place the powder in a vacuum double-cone screw dryer, add 3 g of modifier N-phenyl-γ-aminopropyltrimethoxysilane, control the vacuum degree at an absolute pressure of 520 kPa, and set the equipment speed at 15 rpm. Under this condition, mix and modify for 40 minutes to obtain amorphous spherical silica powder.

[0025] Example 4, compared with Example 1, the difference is that 0.19g of stearyltrimethylammonium bromide is added in step 1, and the other steps are the same as Example 1.

[0026] Example 5, compared with Example 1, the difference is that the rotation speed of the high-speed shear emulsifier is adjusted to 5000 rpm, and the other steps are the same as Example 1.

[0027] Example 6, compared with Example 1, the difference is that the rotation speed of the high-speed shear emulsifier is adjusted to 12000 rpm, and the other steps are the same as Example 1.

[0028] Comparative Example 1 is compared with Example 1, except that no cationic surfactant is added in step 1, and the rest is the same as Example 1.

[0029] Comparative Example 2 is compared with Example 1, except that the mass ratio of the organosilane to the emulsifier is adjusted to 13.2:1, and the rest is the same as Example 1.

[0030] Comparative Example 3 is compared with Example 1, except that the mass ratio of the organosilane to the emulsifier is adjusted to 50:1, and the rest is the same as Example 1.

[0031] Comparative Example 4 is compared with Example 1, except that the amount of the modifier is 3% of the organosilane, i.e., 3.15 g, and the rest is the same as Example 1.

[0032] The particle size of the spherical silicon dioxide obtained in the above examples 1-6 was tested, and the following data results were obtained:

[0033] The particle size of the spherical silicon dioxide obtained in the above comparative examples 1-4 was tested, and the following data results were obtained:

[0034] As can be seen from the above, it can be seen from Example 1 that by adding a cationic surfactant such as stearyl trimethyl ammonium bromide and reasonably setting the rotation speed of the high-speed shear emulsifier, the emulsification speed of the above solution is higher and the emulsification effect is better. Because the high-speed rotating cutting blade can better cut the mixture to form smaller droplets, it will also produce greater shear force and stirring intensity, making the emulsion more uniform. Therefore, the average particle size of the obtained product is the smallest and the distribution is the most uniform.

[0035] It can be seen from Examples 1, 2, 3, 5, and 6 that the average particle size of the spherical silica obtained is larger due to the gradual decrease in the rotation speed. If the emulsification speed is lower, it is difficult to form smaller suspended droplets, the average particle size is larger, and the particle size distribution is also uneven.

[0036] It can be seen from Examples 1-3 that stearyl trimethyl ammonium bromide is more suitable as the second emulsifier than ethanolamine salt and cetyl trimethyl ammonium bromide chloride.

[0037] It can be seen from Examples 1-3 that tetramethoxysilane is more suitable as the silicon source for the reaction.

[0038] In Comparative Example 1, no cationic surfactant was added, resulting in larger particle size and uneven distribution; and too fast an emulsification speed would cause bubbles and heat generation, affecting the emulsification effect.

[0039] In Example 4, Comparative Example 2 and Comparative Example 3, the ratio of organosilane to emulsifier is too high or too low, which will affect the uniformity of silica powder. In addition, it can be seen from Comparative Examples 2 and 3 that more co-surfactant addition may lead to a decrease in product purity, and too fast an emulsification speed also leads to bubbles and heat generation, affecting the emulsification effect; if less co-surfactant isooctyl alcohol is added, problems with silicon source dispersion will occur and the particle size distribution will be uneven. Examples 1 and 3 show that too high a modifier has limited effect on enhancing the carbon content, and Example 1 and Comparative Example 4 show that too little modifier will reduce the carbon content. The higher carbon content of the embodiment may also be related to its small particle size, high specific surface area, and more reactive groups on the surface.

[0040] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An amorphous spherical silica powder, characterized in that: The average particle size of the silica powder is 0.1-5.0 μm, the carbon content is greater than 0.07%, and the hydroxyl content is less than 0.3 / nm. 2 , magnetic substances <2.0ppm.

2. A method for preparing the amorphous spherical silica powder according to claim 1, characterized in that: The method comprises the following steps, (1) firstly mix the emulsifier and the co-surfactant in a mass ratio of 1:1-3, and after uniform mixing, add the cationic surfactant and the organic solvent in sequence, in a mass ratio of 3-20:1 between the emulsifier and the cationic surfactant, and in a mass ratio of 12-50:1 between the organic solvent and the emulsifier, to form a transparent solution; (2) under stirring, adding a catalyst to the transparent solution, wherein the catalyst is a mixture of ammonia water and triethylamine, wherein the mass ratio of ammonia water to triethylamine is 4:1-4, until the solution becomes turbid, and then passing through a high-speed shear emulsifier to form an oil-in-water type microemulsion, wherein the speed of the high-speed shear emulsifier is 5000 rpm-20000 rpm, and the emulsification time is 10 min-15 min; (3) adding organosilane dropwise to the water-in-oil microemulsion at a temperature of 20°C-30°C, with the mass ratio of organosilane to emulsifier being 25-40:1, and continuously stirring for 2h-6h to hydrolyze the organosilane in the water-in-oil microemulsion to form a solution containing silica powder; (4) After the hydrolysis is completed, the solution is subjected to flocculation precipitation, centrifugal separation, washing, drying, and calcination; (5) After calcination, use a temperature probe to measure the powder temperature at 150°C-200°C. Place the powder in a vacuum double-cone spiral dryer and add a silane modifier in an amount of 1%-2% of the mass of the organic silane to obtain a silica powder with a smooth surface and uniform particle size.

3. The method for preparing amorphous spherical silicon dioxide powder according to claim 2, characterized in that: The emulsifier is one of the Span series and the Tween series, the co-surfactant is one or more of n-octanol, cyclohexane, and isooctyl alcohol, and the cationic surfactant is one or more of stearyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide chloride, and ethanolamine salt.

4. The method for preparing amorphous spherical silicon dioxide powder according to claim 2, characterized in that: The organic solvent is one or more of cyclohexane, paraffin oil, carbon tetrachloride and ethyl acetate.

5. The method for preparing amorphous spherical silicon dioxide powder according to claim 2, characterized in that: The organosilane is one or more of methoxysilane, methyl silicate and ethyl silicate.

6. The method for preparing amorphous spherical silicon dioxide powder according to claim 2, characterized in that: In step (4), the precipitate is washed three times with a solvent, and then the drying temperature is controlled at 20°C-60°C during the drying process, and the calcination temperature is controlled at 450°C-950°C during the calcination process.

7. The method for preparing amorphous spherical silicon dioxide powder according to claim 2, characterized in that: The type of the modifier in step (5) is one or more of vinyl, phenylamino and silazane.

8. The method for preparing amorphous spherical silicon dioxide powder according to claim 2, characterized in that: The vacuum degree of the equipment in the vacuum double-cone spiral dryer in step (5) is controlled at an absolute pressure of 200 kPa to 700 kPa, the equipment speed is 10 rpm to 20 rpm, and the modification time is 30 min to 60 min.

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