Hollow silicon dioxide microsphere and preparation method thereof

Abstract

The invention relates to a hollow silicon dioxide microsphere and a preparation method thereof. The preparation method comprises the following steps: mechanically stirring a solution of a surfactant to form foam, and introducing gas into the foam to obtain a bubble template; adding organosilane into the bubble template, and then adding an acid catalyst or a base catalyst to carry out hydrolytic condensation reaction, so as to form a silicon dioxide gel layer on the surface of the bubble, thereby obtaining a hollow silicon dioxide precursor; and sequentially carrying out drying treatment and calcining treatment on the hollow silicon dioxide precursor to obtain the hollow silicon dioxide microspheres. The preparation method provided by the invention has the advantages of simple operation, mild operation conditions, high production efficiency and low cost, is suitable for large-scale production, can realize efficient control of the particle size, the wall thickness and the hollow rate of the hollow silicon dioxide microspheres, and can meet the application requirements of multiple fields.

Description

Technical Field

[0001] The invention relates to the technical field of new materials, and in particular to a hollow silica microsphere and a preparation method thereof. Background Art

[0002] Hollow silica microspheres have broad application prospects in the fields of adsorption, catalysis, optics, electronics, etc. due to their low density, large specific surface area, good thermal stability and chemical inertness. At present, the preparation processes of hollow silica microspheres mainly include hard template method, soft template method, self-assembly method, spray drying method and self-template method. Among them, the hard template method has the advantages of strong controllability and good structural stability. However, its complex preparation process, difficult process control and low material utilization rate limit its large-scale production. Compared with the hard template method, the soft template method has a larger operating space. The soft template method uses the evolution of structures such as vesicles, emulsions, bubbles and micelles to obtain materials with hollow structures. Although this method has certain advantages in large-scale industrial production, the hollow silica microspheres obtained have poor structural stability, wide particle size distribution and difficult to control surface properties, and the obtained hollow silica microspheres have low quality.

[0003] Therefore, there is an urgent need to develop a method that is simple, efficient, highly controllable and suitable for large-scale production of hollow silica microspheres. Summary of the invention

[0004] Based on this, it is necessary to provide a hollow silica microsphere and a preparation method thereof to address the above problems. The preparation method provided by the present invention is simple to operate, has mild operating conditions, high production efficiency, low cost, is suitable for large-scale production, and can achieve efficient control of the particle size, wall thickness and hollow ratio of the hollow silica microspheres, and can meet the application needs of multiple fields.

[0005] The present invention provides a method for preparing hollow silica microspheres, comprising the following steps:

[0006] The surfactant solution is mechanically stirred to form foam, and gas is introduced into the foam to obtain a bubble template;

[0007] Adding organosilane to the bubble template, and then adding an acid catalyst or a base catalyst to perform a hydrolysis condensation reaction to form a silica gel layer on the bubble surface to obtain a hollow silica precursor;

[0008] The hollow silica precursor is sequentially dried and calcined to obtain hollow silica microspheres.

[0009] In one embodiment, the gas satisfies at least one of the following conditions:

[0010] (1) In the bubble template, the volume fraction of the gas is 1% to 97%;

[0011] (2) The gas introduction rate is 2 mL / min to 100 mL / min;

[0012] (3) The gas is initiated by gas bubbling, gas spraying or needle filling;

[0013] (4) The gas is selected from at least one of air, nitrogen, hydrogen and carbon dioxide.

[0014] In one embodiment, the bubble particle size is 0.2 μm to 100 μm.

[0015] In one embodiment, the surfactant solution satisfies at least one of the following conditions:

[0016] (1) In the surfactant solution, the concentration of the surfactant is 0.1 g / L to 50 g / L;

[0017] (2) the surfactant is at least one selected from the group consisting of sodium dodecyl sulfate, sodium alkylbenzene sulfonate, sodium polyoxyethylene fatty alcohol ether sulfate, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, polyoxyethylene alkyl ether, polyethylene glycol, polysorbate, cocoamidopropyl hydroxysulfonate, and myristamidopropyl dimethyl betaine;

[0018] (3) In the surfactant solution, the solvent includes water and an organic solvent, and the volume ratio of the water to the organic solvent is 300:1 to 50:1;

[0019] (4) In the surfactant solution, the solvent includes water and an organic solvent, and the organic solvent is selected from at least one of ethanol, isopropanol, methanol, ethylene glycol, acetone, ethyl acetate, dimethyl sulfoxide, dimethylformamide and dichloromethane.

[0020] In one embodiment, an auxiliary agent is added after the gas is introduced into the foam to obtain the bubble template, wherein the auxiliary agent is selected from at least one of a thickener and a release agent.

[0021] In one embodiment, the auxiliary agent satisfies at least one of the following conditions:

[0022] (1) The mass ratio of the thickener to the surfactant is 1:0.1 to 1:10;

[0023] (2) the thickener is at least one selected from the group consisting of polyethylene glycol, polyvinyl alcohol, silica gel, diatomaceous earth, bentonite, sepiolite, cellulose derivatives, starch and its derivatives, agar, gelatin, carrageenan, guar gum, xanthan gum, polyacrylic acid, polyvinyl alcohol, aluminum calcium soap, calcium soap and bisphenol A epoxy resin;

[0024] (3) The mass ratio of the isolation agent to the surfactant is 1:0.1 to 1:20;

[0025] (4) The isolation agent is selected from at least one of carbon nanotubes, carbon spheres, polyacrylonitrile and diatomaceous earth.

[0026] In one embodiment, the organosilane satisfies at least one of the following conditions:

[0027] (1) The mass volume ratio of the solution of the organosilane to the surfactant is (1:0.001) g / L to (1:10) g / L;

[0028] (2) The addition rate of the organosilane is 5 mL / min to 20 mL / min;

[0029] (3) The organosilane is selected from at least one of tetramethoxysilane, tetraethoxysilane, tetraisopropylsilane, tetrabutylsilane, tetramethylsilanol, tetraethylsilanol, triamino-1-propyltrimethoxysilane, tetramethylsilane, tetraethylsilane, vinyl acetate silane, octadecyltrimethoxysilane, hexadienyltriethoxysilane and phenyltrimethoxysilane.

[0030] In one embodiment, the temperature of the hydrolysis condensation reaction is 25°C to 100°C, and the time is 0.5h to 12h.

[0031] In one embodiment, the drying process is performed at a temperature of 40°C to 120°C and for a time of 2h to 12h;

[0032] And / or, the drying treatment is selected from atmospheric pressure drying, vacuum drying, freeze drying or supercritical drying;

[0033] And / or, the calcination treatment is carried out at a temperature of 200° C. to 1200° C. and for a time of 4 h to 12 h.

[0034] The present invention also provides hollow silica microspheres prepared by the preparation method as described above.

[0035] The above-mentioned preparation method utilizes the bubble interface deposition method. First, a two-dimensional foam is prepared by the arrangement of the surfactant in the vertical direction, and then the gas is filled into the foam to effectively control the cavity size of the bubble, and at the same time, the stability of the bubble cavity is improved. Subsequently, the organic silicon source is formed into a silica gel layer on the surface of the bubble template by a hydrolysis condensation reaction, and finally, the residual organic matter is removed by drying and calcining to obtain high-purity hollow silica microspheres, which is conducive to improving the uniformity of the wall thickness of the silica microspheres. The preparation method provided by the present invention is simple to operate, mild operating conditions, high production efficiency, low cost, good repeatability, suitable for large-scale production, and can achieve efficient control of the particle size, wall thickness and hollow rate of the hollow silica microspheres, which is conducive to customizing the optimal structure of the hollow silica microspheres according to actual needs, and can meet the application needs of multiple fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 This is a SEM image of the hollow silica microspheres prepared in Example 1 of the present invention;

[0038] Figure 2 TEM image of hollow silica microspheres prepared in Example 1 of the present invention;

[0039] Figure 3 This is a TEM image of the product obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0040] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0042] Different patterns can be drawn on the surface of the substrate by using the evolution process of two-dimensional bubbles. It is found that two-dimensional foam can make bubbles move spontaneously in the direction of decreasing radius of curvature. This reverse Ostwald ripening process can obtain bubbles of uniform size. After long-term and in-depth research, the applicant found that by introducing gas into the foam, the size of the bubble cavity can be controlled by controlling the volume of the gas, and a silica gel layer can be deposited on its interface to obtain hollow silica microspheres. Based on this, the preparation method of hollow silica microspheres provided by the present invention comprises the following steps:

[0043] S1, forming foam by mechanically stirring a surfactant solution, and introducing gas into the foam to obtain a bubble template;

[0044] S2, adding organosilane to the bubble template, and then adding an acid catalyst or a base catalyst to carry out a hydrolysis condensation reaction to form a silica gel layer on the bubble surface to obtain a hollow silica precursor;

[0045] S3, sequentially drying and calcining the hollow silica precursor to obtain hollow silica microspheres.

[0046] In step S1, first, foam is formed in a surfactant solution by mechanical stirring, and then gas is introduced into the foam. The gas forms initial bubble nuclei in the surfactant solution. The surfactant molecules in the solution are adsorbed and vertically arranged on the bubble surface to reduce the interfacial tension and enhance the stability of the bubble. At the same time, the cavity size of the bubble can be effectively controlled by controlling the amount of gas introduced.

[0047] It can be understood that the bubble template is a solution containing bubbles.

[0048] In one embodiment, the volume ratio of the gas to the surfactant solution is 1:50 to 1:2000, which is beneficial to improving the stability of the bubbles.

[0049] In one embodiment, the gas introduction rate is 2mL / min to 100mL / min, including but not limited to any point value among 2mL / min, 5mL / min, 10mL / min, 20mL / min, 40mL / min, 50mL / min, 70mL / min, 90mL / min, 100mL / min or any range value between two thereof, which is beneficial to improve the stability of the bubbles and effectively control the size of the bubble cavity.

[0050] Specifically, the gas is triggered by gas bubbling, gas spraying or needle filling.

[0051] In one embodiment, the gas is selected from at least one of air, nitrogen, hydrogen and carbon dioxide.

[0052] Preferably, the gas is selected from carbon dioxide.

[0053] In one embodiment, in the bubble template, the volume fraction of the gas is 1% to 97%, including but not limited to any point value of 1%, 2%, 5%, 20%, 40%, 60%, 80%, 90% or any range value between two of them, which is beneficial to control the size of the foam cavity, and further beneficial to achieve efficient control of the particle size and hollowness of the prepared hollow silica microspheres.

[0054] Preferably, the particle size of the bubbles is 0.2μm to 100μm, including but not limited to any point value among 0.2μm, 0.3μm, 0.5μm, 0.8μm, 1μm, 2μm, 3μm, 5μm, 8μm, 10μm, 20μm, 30μm, 50μm, 70μm, 90μm, 100μm or any range value between two of them.

[0055] More preferably, the bubble particle size is 0.5 μm to 3 μm.

[0056] In one embodiment, in the surfactant solution, the concentration of the surfactant is 0.1 g / L to 50 g / L.

[0057] It should be noted that the surfactant of the present invention is not particularly limited, and cationic surfactants (such as hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, benzyldimethyldodecylammonium chloride, hexadecylpyridinium bromide, octadecylpyridinium bromide, stearylamine acetate, palmitamine acetate, oleylamine acetate, lauryl imine chloride, coconut oil imine chloride, hexadecylpyridinium chloride, octadecylpyridinium chloride, etc.), anionic surfactants (such as sodium stearate, sodium oleate, sodium palmitate, sodium lauryl sulfate, sodium dodecyl sulfate, sodium alkylbenzene sulfonate, calcium alkylbenzene sulfonate, sodium alkyl sulfonate, ammonium alkyl sulfonate, monomethyl ammonium phosphate, monolauryl ammonium phosphate, sodium alkyl sulfonamide, calcium alkyl sulfonamide, etc.), zwitterionic surfactants (such as coconut oil zwitterions, Lauryl zwitterions, stearyl zwitterions, β-alanine, histidine, lysine, cocamide zwitterions, linoleamide zwitterions, stearamide zwitterions, lecithin, phosphatidylcholine, phosphatidylserine, 2-alkyl-1,3-benzothiazolium salts, 2-alkyl-1,3-benzothiazolyl acetates, etc.) and nonionic surfactants (such as fatty alcohol polyoxyethylene ethers, alkylphenol polyoxyethylene ethers, fatty acid polyoxyethylene esters, polyethylene glycol, polypropylene glycol, polysorbate, fatty alcohol fatty acid esters, glycerol fatty acid esters, sucrose fatty acid esters, fatty alcohol polyoxyethylene amines, fatty amine polyoxyethylene ethers, fatty piperazines, fatty alcohol polyoxyethylene ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylphenol ethers, polyvinyl pyrrolidone, polyvinyl pyrrolidone-vinyl ester copolymers, etc.) are all possible.

[0058] Preferably, the surfactant is selected from at least one of sodium dodecyl sulfate, sodium alkylbenzene sulfonate, sodium polyoxyethylene fatty alcohol ether sulfate, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, polyoxyethylene alkyl ether, polyethylene glycol, polysorbate, cocoamidopropyl hydroxysulfonate and myristamidopropyl dimethyl betaine.

[0059] Further preferably, the surfactant is selected from hexadecyltrimethylammonium bromide and octadecyltrimethylammonium chloride.

[0060] In one embodiment, in the surfactant solution, the solvent includes water and an organic solvent, and the volume ratio of the water to the organic solvent is 300:1 to 50:1, including but not limited to any value among 300:1, 250:1, 200:1, 150:1, 100:1, 80:1, 60:1, 50:1 or any range between two values.

[0061] Preferably, the organic solvent is selected from at least one of ethanol, isopropanol, methanol, ethylene glycol, acetone, ethyl acetate, dimethyl sulfoxide, dimethylformamide and dichloromethane.

[0062] In one embodiment, after the gas is introduced into the foam, an auxiliary agent is added to obtain the bubble template, wherein the auxiliary agent is selected from at least one of a thickener and a separator, which is beneficial to improving the stability and dispersibility of the bubbles.

[0063] Preferably, the mass ratio of the thickener to the surfactant is 1:0.1 to 1:10, which is beneficial to improving the mechanical strength and anti-gravity effect of the bubbles and further improving the stability of the bubbles.

[0064] Specifically, the thickener is selected from at least one of polyethylene glycol, polyvinyl alcohol, silica gel, diatomaceous earth, bentonite, sepiolite, cellulose derivatives, starch and its derivatives, agar, gelatin, carrageenan, guar gum, xanthan gum, polyacrylic acid, polyvinyl alcohol, aluminum calcium soap, calcium soap and bisphenol A epoxy resin.

[0065] Preferably, the mass ratio of the isolation agent to the surfactant is 1:0.1 to 1:20, which is beneficial to avoid adhesion between bubbles, improve the dispersion of bubbles, and further facilitate the formation of dispersed hollow silica microspheres.

[0066] Specifically, the isolation agent is selected from at least one of carbon nanotubes, carbon spheres, polyacrylonitrile and diatomaceous earth.

[0067] In one embodiment, in the gas template, the ratio of the molar amount of solute to the molar amount of water and organic solvent is 1:100 to 1:5000, including but not limited to any point value among 1:100, 1:500, 1:1000, 1:1500, 1:2000, 1:2500, 1:3000, 1:3500, 1:4000, 1:4500, 1:5000 or any range value between two thereof.

[0068] In step S2, organic silane is added to the bubble template, and then the organic silane is hydrolyzed and condensed under the action of an acid catalyst or a base catalyst, so that the silica gel layer is evenly deposited on the bubble interface, which is beneficial to improving the uniformity of the wall thickness of the prepared hollow silica microspheres, thereby achieving efficient control of the wall thickness and hollowness of the hollow silica microspheres, which is beneficial to meeting the application requirements of hollow silica microspheres in various fields.

[0069] In one embodiment, the mass volume ratio of the solution of the organosilane to the surfactant is (1:0.001) g / L to (1:10) g / L, which is conducive to achieving efficient control of the wall thickness and hollowness of the prepared hollow silica microspheres.

[0070] In one embodiment, the organosilane is added by a single injection method or a batch injection method.

[0071] Preferably, the organosilane is added by batch injection. It can be understood that the organosilane is added dropwise into the bubble template.

[0072] Further preferably, the addition rate of the organosilane is 5 mL / min to 20 mL / min, including but not limited to any point value among 5 mL / min, 6 mL / min, 8 mL / min, 10 mL / min, 13 mL / min, 15 mL / min, 18 mL / min, and 20 mL / min, or any range value of two thereof, which is beneficial to further improve the uniformity of the silica gel layer, and further help to improve the uniformity of the wall thickness of the prepared hollow silica microspheres.

[0073] In one embodiment, the organosilane is selected from at least one of tetramethoxysilane, tetraethoxysilane, tetraisopropylsilane, tetrabutylsilane, tetramethylsilanol, tetraethylsilanol, triamino-1-propyltrimethoxysilane, tetramethylsilane, tetraethylsilane, vinyl acetate silane, octadecyltrimethoxysilane, hexadienyltriethoxysilane and phenyltrimethoxysilane.

[0074] In one embodiment, the temperature of the hydrolysis condensation reaction is 25° C. to 100° C., and the time is 0.5 h to 12 h, which is beneficial to further improve the uniformity of the silica gel layer, and further to improve the uniformity of the wall thickness of the prepared hollow silica microspheres.

[0075] More preferably, the temperature of the hydrolysis condensation reaction is 60°C to 80°C.

[0076] More preferably, the hydrolysis condensation reaction time is 6 h to 12 h.

[0077] It should be noted that the acid catalyst and the base catalyst used in the present invention are catalysts commonly used in the art, and the present invention has no special restrictions on this. For example, the acid-base catalyst includes inorganic acids such as salt (HCl), sulfuric acid (H2SO4), nitric acid (HNO3) and organic acids such as acetic acid (CH3COOH), formic acid (HCOOH), and citric acid (C6H8O7); the base catalyst includes inorganic bases such as sodium hydroxide (NaOH), potassium hydroxide (KOH), and ammonia (NH4OH) and organic bases such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), and triethylamine (Et3N).

[0078] Preferably, the pH of the reaction system reaches 2-6 after the acid catalyst is added.

[0079] Preferably, the pH of the reaction system reaches 8-11 after the addition of the alkaline catalyst.

[0080] In step S3, the obtained hollow silica precursor is dried and then calcined at a high temperature to remove residual organic matter, thereby obtaining high-purity hollow silica microspheres.

[0081] In one embodiment, the drying process is carried out at a temperature of 40° C. to 120° C. and for a time of 2 h to 12 h.

[0082] Preferably, the drying treatment is selected from atmospheric pressure drying, vacuum drying, freeze drying or supercritical drying.

[0083] Further preferably, the drying treatment is selected from vacuum drying at a temperature of 40°C to 60°C.

[0084] In one embodiment, the calcination treatment is performed at a temperature of 200° C. to 1200° C. for a time of 4 h to 12 h.

[0085] Preferably, the calcination temperature is 400°C to 800°C.

[0086] In summary, the preparation method provided by the present invention utilizes the bubble interface deposition method. First, a two-dimensional foam is prepared by the arrangement of the surfactant in the vertical direction, and then the gas is filled into the foam to effectively control the cavity size of the bubble, and at the same time, the stability of the bubble cavity is improved. Subsequently, the organosilicon source is formed into a silica gel layer on the surface of the bubble template by hydrolysis and condensation reaction, and finally, the residual organic matter is removed by drying and calcination to obtain high-purity hollow silica microspheres, which is conducive to improving the uniformity of the wall thickness of the silica microspheres. The preparation method provided by the present invention is simple to operate, mild operating conditions, high production efficiency, low cost, good repeatability, suitable for large-scale production, and can achieve efficient control of the particle size, wall thickness and hollow rate of the hollow silica microspheres, which is conducive to customizing the optimal structure of the hollow silica microspheres according to actual needs, and can meet the application needs of multiple fields.

[0087] It should be noted that the calculation formula for the above hollow ratio is bubble particle size / (hollow silica microsphere particle size) 3 .

[0088] The present invention also provides hollow silica microspheres prepared by the preparation method as described above, wherein the particle size, wall thickness and hollow ratio of the hollow silica microspheres are controllable, and can meet the application requirements of multiple fields. For example, a larger specific surface area can be achieved, which is beneficial to improving its adsorption performance, catalytic activity and reaction rate.

[0089] In one embodiment, the wall thickness of the hollow silica microspheres is 0.15 μm to 100 μm, including but not limited to any value among 0.15 μm, 0.2 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 5 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm or any range between two values.

[0090] In one embodiment, the pore size of the hollow silica microspheres is 0.002 μm to 0.005 μm, including but not limited to any point value among 0.002 μm, 0.003 μm, 0.004 μm, 0.005 μm or any range value between two points.

[0091] In one embodiment, the specific surface area of ​​the hollow silica microspheres is 10 m 2 / g~1130m 2 / g, including but not limited to 10m 2 / g, 15m 2 / g, 20m 2 / g, 50m 2 / g、100m 2 / g, 330m 2 / g, 480m 2 / g, 545m 2 / g、793m 2 / g, 932m 2 / g, 1045m 2 / g、1100m 2 / g, 1130m 2 / g, or any value in the range between them.

[0092] Hereinafter, the hollow silica microspheres and the preparation method thereof will be further described by the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0093] Example 1

[0094] In a 2L beaker, 1.5L of water and 0.1L of ethanol were respectively added to prepare an aqueous solution with an ethanol content of 6.25%, and then 2.5g of dodecyltrimethylammonium bromide was added to the beaker, and stirred at 600rpm for 30min to form a large amount of foam; nitrogen was filled into the foam formed by the above dodecyltrimethylammonium bromide at a flow rate of 10mL / min using a needle, so that the volume fraction of nitrogen was 50%, and 5g of polyethylene glycol and 10g of carbon nanotubes were added to obtain a bubble template, and the particle size of the bubble was 1μm.

[0095] 5 g of tetraethoxysilane was gradually added dropwise to the bubble template system at a dropping speed of 10 mL / min, and then acid was added to adjust the pH of the system to 2 for a hydrolysis condensation reaction. After 6 hours, a silica gel layer was formed at the bubble interface to obtain a hollow silica precursor.

[0096] The hollow silica precursor was vacuum dried at 60°C for 6 h, and then transferred into a muffle furnace with a heating rate of 1°C / min and calcined at 550°C for 6 h to obtain hollow silica microspheres.

[0097] Hollow silica microspheres were prepared by using Examples 2 to 7 according to the preparation method of Example 1. The formula of each component and the condition parameters of the steps are shown in Table 1.

[0098] Comparative Example 1

[0099] The difference between Comparative Example 1 and Example 1 is that after the surfactant solution is stirred to form a large amount of foam, no gas is added.

[0100] Table 1

[0101]

[0102]

[0103] The hollow silica microspheres prepared in all the examples and comparative examples were characterized and their size, wall thickness and specific surface area were tested. The test results are shown in Table 2.

[0104] Table 2

[0105] Size(μm) Wall thickness(μm) <![CDATA[Specific surface area (m 2 / g)]]> Example 1 1.2 0.1 100 Example 2 1 0.1 70 Example 3 1.1 0.1 110 Example 4 2 0.25 80 Example 5 1.3 0.05 60 Example 6 0.6 0.018 55 Example 7 0.55 0.010 24 Comparative Example 1 0.2 0.05 768

[0106] The SEM image of the hollow silica microspheres prepared in Example 1 is as follows: Figure 1 As shown in the TEM image Figure 2As shown, it can be seen that the hollow silica microspheres prepared in Example 1 have a dense and smooth surface, good dispersibility, and a high hollow ratio. Combined with Table 1, it can be seen that the preparation method of the present invention can efficiently prepare high-purity hollow silica microspheres, and the particle size, wall thickness and hollow ratio of the hollow silica microspheres are controllable. Among them, by comparing Example 1 and Example 3, it can be seen that when the filling gas is replaced from nitrogen to hydrogen, the volume of the bubbles obtained is reduced by 10%; by comparing Example 1 and Example 4, it can be seen that by increasing the volume of nitrogen filled by 29%, the volume of the bubbles obtained will be increased by 50%. This is because the larger the volume of nitrogen filled, the more significantly the volume of the cavity will increase. At the same time, the presence of thickeners and isolating agents can effectively improve the mechanical stability and dispersibility of the bubbles. By comparing Example 4 and Example 5, it can be seen that the size of the bubbles obtained by using dodecyltrimethylammonium bromide as the foam preparation material is larger than that of carboxymethyl cellulose. This is because dodecyltrimethylammonium bromide is larger than Carboxymethyl cellulose has a stronger effect of regulating surface tension, thus helping to maintain the stability of bubbles; By comparing Example 1 and Example 5, it can be seen that when tetraethoxysilane is used as a silane precursor, a thicker silica coating layer can be obtained. This is because under the same hydrolysis and polycondensation conditions, the hydrolysis and polycondensation rates of methyltrimethoxysilane are slower, thus affecting the deposition rate of the silica gel layer at the bubble interface; In Comparative Example 1, when no gas is introduced into the foam, it is difficult to obtain a large cavity, thereby affecting the effective deposition of the subsequent silane precursor at the bubble interface, and it is difficult to obtain high-purity hollow silica microspheres. Figure 3 It can be seen that in the product prepared in Comparative Example 1, the hollow silica microspheres have a low sphering rate, and a low particle size and hollowness.

[0107] In summary, the preparation method of the present invention is simple to operate, has mild operating conditions, high production efficiency, and low cost, is suitable for large-scale production, and can achieve efficient control of the particle size, wall thickness, and hollow ratio of hollow silica microspheres, and can meet the application needs of multiple fields.

[0108] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0109] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing hollow silica microspheres, characterized in that: The preparation method comprises the following steps: The surfactant solution is mechanically stirred to form foam, and gas is introduced into the foam to obtain a bubble template; Adding organosilane to the bubble template, and then adding an acid catalyst or a base catalyst to perform a hydrolysis condensation reaction to form a silica gel layer on the bubble surface to obtain a hollow silica precursor; The hollow silica precursor is sequentially dried and calcined to obtain hollow silica microspheres.

2. The method for preparing hollow silica microspheres according to claim 1, characterized in that: The gas meets at least one of the following conditions: (1) In the bubble template, the volume fraction of the gas is 1% to 97%; (2) The gas introduction rate is 2 mL / min to 100 mL / min; (3) The gas is initiated by gas bubbling, gas spraying or needle filling; (4) The gas is selected from at least one of air, nitrogen, hydrogen and carbon dioxide.

3. The method for preparing hollow silica microspheres according to claim 1 or 2, characterized in that: The particle size of the bubbles is 0.2 μm to 100 μm.

4. The method for preparing hollow silica microspheres according to claim 1, characterized in that: The surfactant solution satisfies at least one of the following conditions: (1) In the surfactant solution, the concentration of the surfactant is 0.1 g / L to 50 g / L; (2) the surfactant is at least one selected from the group consisting of sodium dodecyl sulfate, sodium alkylbenzene sulfonate, sodium polyoxyethylene fatty alcohol ether sulfate, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, polyoxyethylene alkyl ether, polyethylene glycol, polysorbate, cocoamidopropyl hydroxysulfonate, and myristamidopropyl dimethyl betaine; (3) In the surfactant solution, the solvent includes water and an organic solvent, and the volume ratio of the water to the organic solvent is 300:1 to 50:1; (4) In the surfactant solution, the solvent includes water and an organic solvent, and the organic solvent is selected from at least one of ethanol, isopropanol, methanol, ethylene glycol, acetone, ethyl acetate, dimethyl sulfoxide, dimethylformamide and dichloromethane.

5. The method for preparing hollow silica microspheres according to claim 1, characterized in that: After the gas is introduced into the foam, an auxiliary agent is added to obtain the bubble template, wherein the auxiliary agent is selected from at least one of a thickener and a release agent.

6. The method for preparing hollow silica microspheres according to claim 5, characterized in that: The auxiliary agent meets at least one of the following conditions: (1) The mass ratio of the thickener to the surfactant is 1:0.1 to 1:10; (2) the thickener is at least one selected from the group consisting of polyethylene glycol, polyvinyl alcohol, silica gel, diatomaceous earth, bentonite, sepiolite, cellulose derivatives, starch and its derivatives, agar, gelatin, carrageenan, guar gum, xanthan gum, polyacrylic acid, polyvinyl alcohol, aluminum calcium soap, calcium soap and bisphenol A epoxy resin; (3) The mass ratio of the isolation agent to the surfactant is 1:0.1 to 1:20; (4) The isolation agent is selected from at least one of carbon nanotubes, carbon spheres, polyacrylonitrile and diatomaceous earth.

7. The method for preparing hollow silica microspheres according to claim 1, characterized in that: The organosilane satisfies at least one of the following conditions: (1) The mass volume ratio of the solution of the organosilane to the surfactant is (1:0.001) g / L to (1:10) g / L; (2) The addition rate of the organosilane is 5 mL / min to 20 mL / min; (3) The organosilane is selected from at least one of tetramethoxysilane, tetraethoxysilane, tetraisopropylsilane, tetrabutylsilane, tetramethylsilanol, tetraethylsilanol, triamino-1-propyltrimethoxysilane, tetramethylsilane, tetraethylsilane, vinyl acetate silane, octadecyltrimethoxysilane, hexadienyltriethoxysilane and phenyltrimethoxysilane.

8. The method for preparing hollow silica microspheres according to claim 1, characterized in that: The temperature of the hydrolysis condensation reaction is 25° C. to 100° C., and the time is 0.5 h to 12 h.

9. The method for preparing hollow silica microspheres according to claim 1, characterized in that: The drying process is performed at a temperature of 40°C to 120°C and for a time of 2h to 12h; And / or, the drying treatment is selected from atmospheric pressure drying, vacuum drying, freeze drying or supercritical drying; And / or, the calcination treatment is carried out at a temperature of 200° C. to 1200° C. and for a time of 4 h to 12 h.

10. Hollow silica microspheres prepared by the preparation method according to any one of claims 1 to 9.

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