Preparation method of monodisperse submicron spherical silicon dioxide

Abstract

The invention discloses a preparation method of monodisperse submicron spherical silicon dioxide. The preparation method comprises the following steps: S1, preparing a solution; s2, controlling the constant temperature of the reactor; s3, performing supergravity premixing; s4, carrying out nucleation growth on the spiral coil pipe; s5, growing in a stirring kettle; s6, washing and drying; the monodisperse submicron spherical silicon dioxide is obtained. The preparation method is simple to operate, short in reaction time and high in experiment repeatability, the particle size range of the prepared silicon dioxide is 250-800 nm, the particle size is uniform, the dispersion coefficient is smaller than or equal to 0.04, and the silicon dioxide is in a monodisperse state when dispersed in absolute ethyl alcohol or deionized water.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preparation of spherical silica particles. Specifically, it relates to a preparation method of monodisperse sub-micron spherical silica. BACKGROUND

[0002] Sub-micron spherical silica has excellent chemical stability, good dispersibility and controllable particle size distribution, and has irreplaceable application value in many fields. In the field of electronic information, as a key component of packaging materials, it can effectively reduce the thermal expansion coefficient of the package, improve the heat dissipation and reliability of the chip, and help the development of high-density integrated circuits towards miniaturization and high performance. In the field of high-end coatings and coatings, sub-micron spherical silica can be uniformly dispersed in the coating system to form a dense protective structure, which not only enhances the hardness and wear resistance of the coating, but also improves the corrosion resistance of the coating, effectively blocking the penetration of corrosive media such as water and oxygen. At the same time, its spherical structure can reduce the roughness of the coating surface, improve the gloss and leveling of the coating. In addition, in the industries of industrial catalysis, biomedicine, precision ceramics, cosmetics, etc., sub-micron spherical silica has also been widely used due to its unique optical and mechanical properties.

[0003] At present, the methods for preparing sub-micron spherical silica mainly include precipitation method, gas phase method, sol-gel method and microemulsion method. The precipitation method uses silicon-containing alkaline compounds and acidifying agents as raw materials and is most widely used in industry, but the prepared silica has the disadvantages of wide particle size distribution and poor dispersibility, and the removal of templates and surfactants is difficult and causes environmental pollution. The gas phase method generates silica through high-temperature hydrolysis reaction, which has the advantages of high purity and good dispersibility, but the reaction conditions are harsh and the equipment requirements are high, making it more suitable for the preparation of small particle size silica. The sol-gel method has mild reaction conditions and simple operation, and the prepared silica has good sphericity and high purity, and can realize controllable synthesis of microspheres, but is prone to secondary nucleation. The microemulsion method uses two immiscible phases to form droplet microreactors, which can realize controllable particle size and good dispersion, but is not suitable for large-scale application due to its high cost, difficult operation and poor experimental repeatability.

[0004] With the continuous expansion and deepening of the application scenarios of silica, its preparation technology is constantly improving and innovating towards fine, efficient and functional direction under the framework of the above four basic methods.

[0005] For example, Chinese patent application 202411017573.5 discloses a "preparation method of monodisperse spherical silica with adjustable particle size", which is based on the sol-gel method and controls the size of spherical silica by adjusting the concentration of CTAB aqueous solution. Although the preparation method is simple, the prepared spherical silica has poor monodispersity and wide size distribution, which is difficult to meet the quality requirements of the product.

[0006] For another example, Chinese patent application 201610329438.3 discloses a "preparation method of spherical silica particles", which has high sphericity and good dispersity. However, the method needs to uniformly drop the silicon source into the emulsion, which is difficult to operate and leads to poor repeatability in the preparation process.

[0007] Therefore, in the prior art, it is difficult to simultaneously meet the requirements of narrow particle size distribution, high monodispersity, simple process flow and high repeatability, and there is an urgent need for a preparation method of uniform monodisperse submicron spherical silica with simple operation, mild reaction conditions, narrow particle size distribution and high sphericity. SUMMARY

[0008] The technical problem to be solved by the present application is to provide a preparation method of monodisperse submicron spherical silica. The preparation method is simple to operate, has short reaction time and high experimental repeatability, and the prepared silica has a particle size range of 250-800 nm, uniform particle size and a dispersity coefficient of ≦0.04, and is in a monodisperse state when dispersed in anhydrous ethanol or deionized water.

[0009] To solve the first technical problem, the present application adopts the technical solutions as follows:

[0010] A preparation method of monodisperse submicron spherical silica, comprising the following steps:

[0011] S1, solution preparation: mixing and preparing deionized water, a catalyst and a reaction medium into solution A according to a proportion; mixing and preparing tetraethyl orthosilicate and a reaction medium into solution B according to a proportion; and constant-temperature magnetic stirring of solution A and solution B;

[0012] S2, constant-temperature control of the reactor:

[0013] Prepare an external circulation high gravity reactor and a spiral coil reactor, connect the constant-temperature circulating water bath with the temperature control jacket of the external circulation high gravity reactor and the jacket of the spiral coil reactor, control the reaction temperature to be constant, start the constant-temperature circulating water bath at least half an hour in advance to realize pre-control temperature;

[0014] Prepare a stirred tank, install a mechanical stirring device in the tank, and let the constant-temperature heat exchange medium flow into the tank from the inlet of the temperature control jacket and flow out from the outlet, which needs to be started at least twenty minutes in advance to ensure that the reaction temperature in the stirred tank is the same as that in the external circulation high gravity reactor and the spiral coil reactor.

[0015] S3, hypergravity premixing: solution A and solution B are respectively passed into an external circulation hypergravity reactor through a peristaltic pump, the silicon source is hydrolyzed, and a hydrolysis mixture is obtained from the outlet;

[0016] S4, spiral coil nucleation growth: the hydrolysis mixture is rapidly passed into a spiral coil reactor through a peristaltic pump, the mixture spirally flows from top to bottom for preliminary nucleation growth reaction, and a growth solution is obtained from the outlet of the spiral coil;

[0017] S5, stirred tank growth: the growth solution is passed into a constant temperature stirred tank, stirred and reacted, the product is collected, and a silica microsphere mixture that has completed growth is obtained;

[0018] S6, washing and drying: the silica microsphere mixture is centrifuged, washed, and dried to obtain monodisperse submicron spherical silica.

[0019] Preferably, in step S1, the temperature of the constant temperature is 10-80℃, preferably 20-60℃; the rotation speed of the magnetic stirring is 500-700rpm, and the time of the magnetic stirring is 8-12min.

[0020] Preferably, in step S1, the catalyst is one or more of sodium hydroxide, ammonia water, tetrabutylammonium bromide, triethylamine, n-propylamine, and N,N-dimethylformamide.

[0021] Preferably, in step S1, the molar ratio of the catalyst to deionized water is 1:2-1:100.

[0022] Preferably, in step S1, the reaction medium is one or more of methanol, ethanol, n-propanol, and ethylene glycol.

[0023] Preferably, in step S1, the molar ratio of the catalyst to the reaction medium is 1:1.5-1:50.

[0024] Preferably, in step S1, the molar ratio of the tetraethyl orthosilicate to the reaction medium is 1:10-1:400.

[0025] Preferably, in step S2, the temperature in the external circulation hypergravity reactor, the spiral coil reactor, and the stirred tank is 20-60℃.

[0026] Preferably, in step S3, the feeding speed of the peristaltic pump is 25-300mL / min.

[0027] Preferably, in step S3, the rotation speed of the rotor of the external circulation hypergravity reactor is 100-3000rpm, the hypergravity reactor is filled with hard silk corrugated packing, and the hypergravity reaction time is 1-20min.

[0028] Preferably, in step S4, the feeding speed of the peristaltic pump is 25-300 mL / min.

[0029] Preferably, in step S4, the initial nucleation and growth reaction time in the spiral coil reactor is 2-30 min.

[0030] Preferably, in step S5, the stirring speed of the stirring reaction is 200-1500 rpm, and the stirring reaction time is 0.25-2 h.

[0031] Preferably, in step S5, the specific steps of the washing and drying are as follows: centrifugation-ethanol washing-centrifugation-water washing-centrifugation-ethanol washing-centrifugation to obtain solid; 2 g of the solid is dispersed in 30 mL of anhydrous ethanol, and the rest of the solid is dried at 100℃ for 24 h.

[0032] Any range recited in the present application includes the end values and any intervening values and any sub-range of any stated or intervening value.

[0033] Unless otherwise specified, each raw material in the present application can be obtained by commercial purchase, and the equipment used in the present application can adopt conventional equipment in the field or refer to the existing technology in the field.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] 1) The preparation method of the present application utilizes the rapid mixing and micro-mass transfer effect of the high gravity reactor to complete the hydrolysis stage of the silicon source in a short time, avoiding the problems of uneven mixing of the reaction system, too fast local hydrolysis, and too high supersaturation degree, which leads to rapid nucleation and uneven nucleation of the reaction system; the flow stability, low back mixing degree, and more uniform material residence time distribution of the spiral coil reactor are utilized to make the hydrolysis solution uniformly condense in the spiral coil, providing a uniform reaction environment for the nucleation and growth of the silicon dioxide core particles.

[0036] 2) The preparation method of the present application adopts a series coupling system composed of an external circulation high gravity rotating packed bed reactor, a spiral coil reactor, and a stirring tank, which effectively shortens the reaction time. Compared with the traditional sol-gel method, the reaction time is shortened from 4-24 h to 0.5-2 h.

[0037] 3) The silicon dioxide prepared by the present application has the characteristics of high sphericity, uniform size, good monodispersity, good stability, and high purity, and the microsphere particle size is 250-800 nm, and the dispersion coefficient (CV) is ≦0.04.

[0038] 4) The preparation method of the present application can control the preparation of monodisperse submicron spherical silica by adjusting the ratio of deionized water, silicon source, catalyst, reaction medium, and the reaction conditions such as the rotation speed of the supergravity reactor rotor, the stirring speed of the reaction kettle, the feeding speed of the peristaltic pump, and the reaction temperature. BRIEF DESCRIPTION OF DRAWINGS

[0039] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings

[0040] Figure 1 The process flow chart of the preparation method of the present application is shown in the figure;

[0041] Figure 2 The scanning electron microscope image of the submicron silica prepared in Comparative Example 1 is shown in the figure;

[0042] Figure 3 The scanning electron microscope image of the submicron silica prepared in Comparative Example 2 is shown in the figure;

[0043] Figure 4 The scanning electron microscope image of the monodisperse submicron spherical silica prepared in Example 1 is shown in the figure;

[0044] Figure 5 The scanning electron microscope image of the monodisperse submicron spherical silica prepared in Example 2 is shown in the figure;

[0045] Figure 6 The scanning electron microscope image of the monodisperse submicron spherical silica prepared in Example 3 is shown in the figure;

[0046] Figure 7 The scanning electron microscope image of the monodisperse submicron spherical silica prepared in Example 4 is shown in the figure;

[0047] Figure 8 The scanning electron microscope image of the monodisperse submicron spherical silica prepared in Example 5 is shown in the figure. DETAILED DESCRIPTION

[0048] In order to more clearly illustrate the present application, the present application will be further described below with reference to the preferred embodiments and the accompanying drawings. Like components are denoted by the same reference numerals in the drawings. It should be understood by those skilled in the art that the specific descriptions below are illustrative rather than limiting, and should not limit the scope of protection of the present application.

[0049] For the convenience of description, if the description involving "first", "second" and the like in the present application is only set for the purpose of description, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can be explicitly or implicitly included at least one of the features. In addition, the technical solutions among various embodiments can be combined with each other, but it must be based on that the technical solutions can be realized by those skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope required by the present application.

[0050] As one aspect of the present application, a method for preparing monodisperse sub-micron spherical silica comprises the following steps:

[0051] S1, solution preparation: mixing and preparing deionized water, catalyst and reaction medium into solution A according to the proportion; mixing and preparing tetraethyl orthosilicate and reaction medium into solution B according to the proportion; constant temperature magnetic stirring solution A and solution B;

[0052] S2, control the constant temperature of the reactor:

[0053] Prepare the external circulation high gravity reactor and the spiral coil reactor, connect the constant temperature circulating water bath with the constant temperature jacket of the external circulation high gravity reactor and the spiral coil reactor, control the constant reaction temperature, and open the constant temperature circulating water bath at least half an hour in advance to realize pre-control temperature;

[0054] Prepare the stirring kettle, install the mechanical stirring device in the kettle, and let the constant temperature heat exchange medium flow into the kettle from the inlet of the constant temperature jacket and flow out from the outlet, which needs to be opened at least twenty minutes in advance to ensure that the reaction temperature in the stirring kettle is the same as that in the external circulation high gravity reactor and the spiral coil reactor;

[0055] S3, high gravity premixing: solution A and solution B are respectively introduced into the external circulation high gravity reactor through the peristaltic pump, the silicon source is hydrolyzed, and the hydrolysis mixed solution is obtained from the outlet;

[0056] S4, spiral coil nucleation and growth: the hydrolysis mixed solution is rapidly introduced into the spiral coil reactor through the peristaltic pump, the mixed solution flows spirally from top to bottom to perform the preliminary nucleation and growth reaction, and the growth solution is obtained from the outlet of the spiral coil;

[0057] S5, stirring kettle growth: the growth solution is introduced into the constant temperature stirring kettle, the stirring reaction is performed, the product is collected, and the silica microsphere mixed solution which has completed the growth is obtained;

[0058] S6, washing and drying: the silica microsphere mixed solution is centrifuged, washed and dried to obtain monodisperse sub-micron spherical silica.

[0059] The preparation method of the present application needs to use the existing disclosed external circulation supergravity rotating packed bed reactor (for example, the external circulation supergravity rotating packed bed reactor disclosed in CN107684880A). The reactor can greatly strengthen the micro-mixing effect of the reaction system, significantly improve the hydrolysis reaction rate, make the supersaturation environment concentration more uniform during the formation of the silica core particles, and thus promote the consistency of the initial core particle size. In the subsequent stable growth stage, the uniform initial core particles can further grow into silica microspheres with a narrow particle size distribution, effectively overcoming the shortcomings of existing methods in terms of product particle size uniformity.

[0060] The preparation method of the present application needs to use the existing spiral coil reactor (for example, the spiral coil reactor disclosed in CN112592602A). The reactor has no obvious dead zone, high mass transfer efficiency, and stable nucleation and growth environment. By controlling the flow rate and channel length, the residence time of the material in the reactor can be accurately controlled, thereby achieving precise control of the particle growth rate.

[0061] In some embodiments of the present application, in step S1, the temperature of the constant temperature is 10-80℃, preferably 20-60℃; the rotation speed of the magnetic stirring is 500-700rpm, and the time of the magnetic stirring is 8-12min.

[0062] In some embodiments of the present application, in step S1, the catalyst is one or more of sodium hydroxide, ammonia water, tetrabutylammonium bromide, triethylamine, n-propylamine, and N,N-dimethylformamide.

[0063] In some embodiments of the present application, in step S1, the molar ratio of the catalyst to deionized water is 1:2-1:100.

[0064] In some embodiments of the present application, in step S1, the reaction medium is one or more of methanol, ethanol, n-propanol, and ethylene glycol.

[0065] In some embodiments of the present application, in step S1, the molar ratio of the catalyst to the reaction medium is 1:1.5-1:50.

[0066] In some embodiments of the present application, in step S1, the molar ratio of the tetraethyl orthosilicate to the reaction medium is 1:10-1:400.

[0067] In some embodiments of the present application, in step S2, the temperature in the external circulation supergravity reactor, the spiral coil reactor, and the stirred tank is 20-60℃.

[0068] In some embodiments of the present application, in step S3, the feeding speed of the peristaltic pump is 25-300mL / min.

[0069] In some embodiments of the present application, in step S3, the rotation speed of the rotor of the external circulation supergravity reactor is 100-3000 rpm, the supergravity reactor filler is selected to be hard wire corrugated filler, and the supergravity reaction time is 1-20 min.

[0070] In some embodiments of the present application, in step S4, the feeding speed of the peristaltic pump is 25-300 mL / min.

[0071] In some embodiments of the present application, in step S4, the initial nucleation and growth reaction time in the spiral coil reactor is 2-30 min.

[0072] In some embodiments of the present application, in step S5, the rotation speed of the stirring reaction is 200-1500 rpm, and the stirring reaction time is 0.25-2 h.

[0073] In some embodiments of the present application, in step S5, the specific steps of centrifugation and washing are: centrifugation-ethanol washing-centrifugation-water washing-centrifugation-ethanol washing-centrifugation.

[0074] Comparative Example 1

[0075] A method for preparing silica microspheres, comprising the following steps:

[0076] S1, preparing a solution: a beaker A is added with 20 mL of deionized water, 20 mL of ammonia water, and 60 mL of anhydrous ethanol to prepare a solution A; a beaker B is added with 10 mL of tetraethyl orthosilicate and 90 mL of anhydrous ethanol to prepare a solution B; the beakers A and B are respectively placed in a constant-temperature magnetic stirrer, the magnetic stirring device is turned on, the stirring speed is 600 rpm, the stirring time is 10 min, and the constant-temperature program is set to a temperature of 20℃;

[0077] S2, controlling the temperature of the reactor: a stirring kettle is prepared, a mechanical stirring device is installed in the kettle, a constant-temperature heat exchange medium flows into the kettle through the temperature control jacket inlet and flows out through the outlet, and the stirring kettle needs to be turned on at least 20 minutes in advance to ensure that the reaction temperature in the stirring kettle is 50℃;

[0078] S3, preparing spherical silica: the solution B is placed in the stirring kettle, the stirring speed is set to 500 rpm, the solution A is quickly poured in, and the reaction is carried out for 2 h, and then a sub-micron spherical silica mixture is obtained after the reaction is completed.

[0079] S4, washing and drying: the product silica microsphere mixture is centrifuged-ethanol washed-centrifuged-water washed-centrifuged-ethanol washed-centrifuged, 2 g of solid is dispersed in 30 mL of anhydrous ethanol, the remaining solid is dried, the drying temperature is 100℃, the drying time is 24 h, and then the silica microspheres are obtained.

[0080] The obtained silica particle size is 439.5 nm, irregular spherical, and the dispersion coefficient is 0.105.

[0081] Comparative Example 2

[0082] A preparation method of silica microspheres, comprising the following steps:

[0083] S1, preparation of solution: beaker A adds 50 mL deionized water, 0.2 g sodium hydroxide, 50 mL methanol to prepare solution A; beaker B adds 10 mL tetraethyl orthosilicate and 90 mL methanol to prepare solution B. Respectively, beaker A, B is placed in constant temperature magnetic stirrer, open magnetic stirring device, stirring speed is 600 rpm, stirring time is 10 min, constant temperature program setting temperature is 50℃;

[0084] Other steps are the same as those of the comparative example 1.

[0085] The obtained silica particle size is 443.8 nm, irregular spherical, and the dispersion coefficient is 0.149.

[0086] Example 1

[0087] A preparation method of monodisperse submicron spherical silica, comprising the following steps:

[0088] S1, preparation of solution: beaker A adds 20 mL deionized water, 20 mL ammonia, 60 mL anhydrous ethanol to prepare solution A; beaker B adds 10 mL tetraethyl orthosilicate, 90 mL anhydrous ethanol to prepare solution B; respectively, beaker A, B is placed in constant temperature magnetic stirrer, open magnetic stirring device, stirring speed is 600 rpm, stirring time is 10 min, constant temperature program setting temperature is 20℃;

[0089] S2, control the constant temperature of the reactor:

[0090] Prepare the external circulation high gravity reactor and the spiral coil reactor, connect the constant temperature circulating water bath with the temperature control jacket of the external circulation high gravity reactor and the jacket of the spiral coil reactor, control the reaction temperature to be 20℃, and open the constant temperature circulating water bath at least half an hour in advance to realize pre-temperature control.

[0091] Prepare the stirring tank, install the mechanical stirring device in the tank, and let the constant temperature heat exchange medium flow into the tank from the inlet of the temperature control jacket and flow out from the outlet, which needs to be opened at least twenty minutes in advance to ensure that the reaction temperature in the stirring tank, the external circulation high gravity reactor and the spiral coil reactor is 20℃.

[0092] S3, reaction liquid hypergravity premixing: solution A and solution B are respectively passed into the outer-circulation hypergravity reactor through a peristaltic pump at a speed of 100 mL / min, the rotation speed of the hypergravity reactor device is set to 2000 rpm, and the hypergravity reactor filler is selected to be hard silk corrugated filler wound for 20 turns. The hypergravity reaction time is 2 min. The hydrolysis mixed liquor is obtained from the discharge port;

[0093] S4, hydrolysis liquid spiral coil nucleation growth: the hydrolysis mixed liquor is passed into the spiral coil reactor through a peristaltic pump at a speed of 100 mL / min, and reacted for 10 min. The growth liquid is obtained from the spiral coil discharge port;

[0094] S5, mixed liquor stirred tank growth: the growth liquid is passed into a constant temperature stirred tank, stirred at a stirring speed of 500 rpm for 1 h, the product is collected, and the silica microsphere mixed liquor that has completed growth is obtained;

[0095] S6, washing and drying: the product silica microsphere mixed liquor is centrifuged-ethanol washed-centrifuged-water washed-centrifuged-ethanol washed-centrifuged; 2 g of solid is dispersed in 30 mL of anhydrous ethanol, and the remaining solid is dried, the drying temperature is 100°C, and the drying time is 24 h, to obtain silica microspheres.

[0096] It is detected that the obtained silica particle size is 705.6 nm, the monodispersity is good, the size distribution is narrow, and the dispersion coefficient is 0.011.

[0097] Example 2

[0098] A preparation method of monodisperse submicron spherical silica, comprising the following steps:

[0099] S1, beaker A adds 50 mL of deionized water, 0.2 g of sodium hydroxide, and 50 mL of methanol; beaker B adds 10 mL of tetraethyl orthosilicate and 90 mL of methanol; the temperature of the constant temperature program is set to 50°C;

[0100] S2, ensure that the reaction temperature in the stirred tank and the outer-circulation hypergravity reactor and the spiral coil reactor is 50°C;

[0101] S3, mixed solution A and B are respectively passed into the hypergravity reactor at a speed of 50 mL / min, the hypergravity rotation speed is set to 1000 rpm, and the reaction time is 8 min;

[0102] S4, the hydrolysis mixed liquor is passed into the spiral coil reactor through a peristaltic pump at a speed of 50 mL / min, and reacted for 15 min;

[0103] S5, stirring at a stirring speed of 1000 rpm for 1 h;

[0104] The remaining contents are the same as those of example 1.

[0105] The obtained silica particle size is 583.6 nm, monodispersity is good, size distribution is narrow, and the dispersion coefficient is 0.018.

[0106] Example 3

[0107] A preparation method of monodisperse submicron spherical silica, comprising the following steps:

[0108] S1, a beaker A is added with 48.2 mL of deionized water, 7.8 mL of n-propylamine, and 44 mL of n-propanol; a beaker B is added with 18.5 mL of tetraethyl orthosilicate and 81.5 mL of n-propanol; a constant temperature program is set to a temperature of 45 DEG C;

[0109] S2, the reaction temperature in the stirring kettle, the outer circulating high gravity reactor, and the spiral coil reactor is ensured to be 45 DEG C;

[0110] S3, the mixed solution A and B are respectively fed into the high gravity reactor at a speed of 35 mL / min, the high gravity rotation speed is set to 700 rpm, and the reaction time is 15 min;

[0111] S4, the hydrolysis mixed solution is fed into the spiral coil reactor through a peristaltic pump at a speed of 35 mL / min, and the reaction is performed for 30 min;

[0112] S5, the reaction is stirred at a stirring speed of 1200 rpm for 0.75 h;

[0113] The remaining contents are the same as those of Example 1.

[0114] The obtained silica particle size is 533.3 nm, monodispersity is good, size distribution is narrow, and the dispersion coefficient is 0.034.

[0115] Example 4

[0116] A preparation method of monodisperse submicron spherical silica, comprising the following steps:

[0117] S1, a beaker A is added with 48.2 mL of deionized water, 7.8 mL of n-propylamine, and 44 mL of n-propanol; a beaker B is added with 18.5 mL of tetraethyl orthosilicate and 81.5 mL of n-propanol; a constant temperature program is set to a temperature of 45 DEG C;

[0118] S2, the reaction temperature in the stirring kettle, the outer circulating high gravity reactor, and the spiral coil reactor is ensured to be 45 DEG C;

[0119] S3, the mixed solution A and B are respectively fed into the high gravity reactor at a speed of 35 mL / min, the high gravity rotation speed is set to 700 rpm, and the reaction time is 15 min;

[0120] S4, the hydrolysis mixture was passed into the spiral coil reactor by peristaltic pump at 200 mL / min, and reacted for 10 min;

[0121] S5, stirring at a stirring speed of 1500 rpm for 0.5 h;

[0122] The rest of the content is the same as that of Example 1.

[0123] It was detected that the obtained silica particle size was 260.7 nm, with good monodispersity, narrow size distribution, and a dispersion coefficient of 0.033.

[0124] Example 5

[0125] A preparation method of monodisperse submicron spherical silica, comprising the following steps:

[0126] S1, 40 mL of deionized water, 10 mL of ammonia water, 50 mL of anhydrous ethanol, and 0.08 g of tetrabutylammonium bromide were added to beaker A; 14 mL of tetraethyl orthosilicate and 86 mL of anhydrous ethanol were added to beaker B; the temperature of the constant temperature program was set to 40°C;

[0127] S2, ensure that the reaction temperature in the stirred tank, external circulation supergravity reactor and spiral coil reactor is 40°C;

[0128] S3, the mixed solution A and B were respectively passed into the supergravity reactor at a speed of 175 mL / min, the supergravity rotation speed was set to 300 rpm, and the reaction time was 3 min;

[0129] S4, the hydrolysis mixture was passed into the spiral coil reactor by peristaltic pump at 175 mL / min, and reacted for 7 min;

[0130] S5, stirring at a stirring speed of 300 rpm for 1.5 h;

[0131] The rest of the content is the same as that of Example 1.

[0132] It was detected that the obtained silica particle size was 510.1 nm, with good monodispersity, narrow size distribution, and a dispersion coefficient of 0.037.

[0133] The performance comparison of Comparative Examples 1-2 and Example 1-5 is shown in Table 1 below.

[0134] Table 1

[0135] Comparative Example / Example Particle size / nm Dispersion coefficient (CV) Comparative Example 1 439.5 0.105 Comparative Example 2 443.8 0.149 Example 1 705.6 0.011 Example 2 583.6 0.018 Example 3 533.3 0.034 Example 4 260.7 0.033 Example 5 510.1 0.037

[0136] From the experimental data in Table 1, it can be found that, by comparing the comparative example adopting the classical sol-gel method with the embodiments of the present application, the spherical silica prepared by the method provided by the present application has a wider size control range, a more concentrated size distribution and a smaller dispersion coefficient, and exhibits excellent monodispersity.

[0137] From Figures 2-8 It can be clearly observed that the silica particles prepared by the sol-gel method have poor sphericity and are not standard spherical structures, and have poor monodispersity; while the silica particles prepared by the method of the present application have extremely high sphericity, and are uniform and have concentrated size distribution.

[0138] The preparation process involved in the present application covers the selection of reaction equipment and the setting of various parameters, which together constitute a unified technical system. Only through the synergistic cooperation of various parameter conditions can the monodisperse sub-micron spherical silica described in the present application be successfully prepared; otherwise, if any condition deviates from the preset range, the expected goal of the present application cannot be achieved.

[0139] The description of each embodiment in the present specification is carried out in a step-by-step progressive manner, and the same or similar content between different embodiments can be understood by mutual reference; the content highlighted by each embodiment is the unique feature that distinguishes it from other embodiments. In particular, for the system embodiment, since it has high similarity in basic principles with the method embodiment, the related description is relatively simple, and the common content involved can be referred to the corresponding description part in the method embodiment.

[0140] In the specific description of the present specification, the specific features, structures, materials or properties described by the terms such as "example", "specific example" or "some examples" are included in at least one embodiment or example of the embodiments of the present specification. It should be noted that the exemplary expressions of the above terms in the present specification do not necessarily refer to the same embodiment or example.

[0141] In addition, without mutual conflict, the skilled person in the art can reasonably combine and fuse different embodiments, examples and features of different embodiments and examples described in the present specification. The above is only a specific description of the embodiments of the present specification, and is not a limitation of the embodiments of the present specification. For those skilled in the art, there can be many modifications and changes to the embodiments of the present specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the embodiments of the present specification shall be included in the scope of protection of the claims of the embodiments of the present specification.

Claims

1. A process for the preparation of monodisperse submicron spherical silica, characterized in that, The method comprises the following steps: S1, solution preparation: mixing deionized water, catalyst and reaction medium in proportion to prepare solution A; mixing tetraethyl orthosilicate and reaction medium in proportion to prepare solution B; constant temperature magnetic stirring of solution A and solution B; S2, control the temperature of the reactor constant: Prepare the external circulation high gravity reactor and the spiral coil reactor, connect the constant temperature circulating water bath with the temperature control jacket of the external circulation high gravity reactor and the spiral coil reactor, control the constant temperature of the reaction, and start the constant temperature circulating water bath at least half an hour in advance to realize pre-temperature control; Prepare the stirred tank, install the mechanical stirring device in the tank, and let the constant temperature heat exchange medium flow into the temperature control jacket of the stirred tank from the inlet and flow out from the outlet, which needs to be started at least twenty minutes in advance to ensure that the temperature in the stirred tank is the same as that in the external circulation high gravity reactor and the spiral coil reactor; S3, high gravity premixing: solution A and solution B are respectively introduced into the external circulation high gravity reactor through the peristaltic pump, the silicon source is hydrolyzed, and the hydrolysis mixed solution is obtained from the outlet; S4, spiral coil nucleation and growth: the hydrolysis mixed solution is rapidly introduced into the spiral coil reactor through the peristaltic pump, the mixed solution flows spirally from top to bottom to perform the preliminary nucleation and growth reaction, and the growth solution is obtained from the outlet of the spiral coil; S5, stirred tank growth: the growth solution is introduced into the constant temperature stirred tank, the stirring reaction is performed, the product is collected, and the silica microsphere mixed solution which has completed the growth is obtained; S6, washing and drying: the silica microsphere mixed solution is centrifuged, washed and dried to obtain the monodisperse submicron spherical silica.

2. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S1, the temperature of the constant temperature is 10-80℃, preferably 20-60℃; the rotating speed of the magnetic stirring is 500-700rpm, and the time of the magnetic stirring is 8-12min.

3. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S1, the catalyst is one or more of sodium hydroxide, ammonia water, tetrabutylammonium bromide, triethylamine, n-propylamine and N,N-dimethylformamide.

4. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S1, the molar ratio of the catalyst to deionized water is 1:2-1:

100.

5. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S1, the reaction medium is one or more of methanol, ethanol, n-propanol and ethylene glycol.

6. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S1, the molar ratio of the catalyst to the reaction medium is 1:1.5-1:

50.

7. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S1, the molar ratio of the tetraethyl orthosilicate to the reaction medium is 1:10-1:

400.

8. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S2, the temperature in the external circulation high gravity reactor, the spiral coil reactor and the stirred tank is 20-60℃.

9. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S3, the feeding speed of the peristaltic pump is 25-300mL / min; Preferably, in step S3, the rotating speed of the rotor of the external circulation high gravity reactor is 100-3000rpm, the packing of the high gravity reactor is selected from hard silk corrugated packing, and the high gravity reaction time is 1-20min.

10. The method for preparing monodisperse submicron-sized spherical silica according to claim 1, characterized in that: In step S4, the feeding speed of the peristaltic pump is 25-300mL / min; Preferably, in step S4, the preliminary nucleation and growth reaction time in the spiral coil reactor is 2-30min; Preferably, in step S5, the rotating speed of the stirring reaction is 200-1500rpm, and the stirring reaction time is 0.25-2h; Preferably, in step S5, the specific steps of washing and drying are: centrifugation-ethanol washing-centrifugation-water washing-centrifugation-ethanol washing-centrifugation, to obtain a solid; 2 g of the solid is dispersed in 30 mL of anhydrous ethanol, and the rest of the solid is dried at 100 °C for 24 h.

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