A method for preparing modified fumed silicon dioxide

Abstract

The present invention relates to the technical field of inorganic material processing, and in particular to a method for preparing modified fumed silica, which specifically comprises the following steps: loading an inorganic heat-resistant agent on fumed silica to obtain heat-resistant fumed silica, and modifying it by inorganic deposition, and surface-modifying it by organic-inorganic hybridization, thereby obtaining modified fumed silica. The modified fumed silica in the present invention can be effectively improved in the coating when applied to the coating, and the thermal stress in the coating can be reduced, thereby preventing the coating from expanding and being damaged due to heat, and at the same time, it can also help to improve the strength of the coating, and enhance the resistance of the coating to external forces, thereby making the coating less likely to crack, and significantly improving the protective effect of the coating, and can play a more effective role in isolation and protection.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic material processing, in particular to a method for preparing modified fumed silicon dioxide. Background Art

[0002] In recent years, a large number of foreign "high-end coatings" products have flooded into the Chinese market, causing a serious impact on my country's coatings industry. Our scientific and technological personnel have found that different types of nanomaterials have been added to these imported "high-end coatings" through testing. Nanoparticles in the "high-end coating" system, with their unique physical and chemical properties and small size effects, quantum size effects and surface interface effects that conventional materials do not have, have greatly improved the scratch resistance, aging resistance, water washability, anti-static, finish, contrast ratio, and surface hardness and self-cleaning ability of coating products.

[0003] Among them, nano-silica is an inorganic chemical material, commonly known as white carbon black, with a particle size range of 1-100 nanometers, a spherical microstructure, and a flocculent and network-like quasi-granular structure. Using nano-silica in coatings can significantly improve the overall performance of the coatings. For example, the invention patent with announcement number CN111040472A discloses modified nano-silica and its modification method, anti-corrosion paint and coating, which are prepared by mixing nano-silica with water, performing a primary reaction, obtaining a primary reactant, taking hexamethyldisilazane and hexamethyldisiloxane, mixing them with an anhydrous solvent, obtaining a mixed solution, mixing the first reactant with the mixed solution, performing a secondary reaction, and obtaining modified nano-silica; the modified nano-silica has excellent dispersibility and hydrophobicity, and can be well dispersed in a variety of organic solvents. After being sprayed on the surface of carbon steel, the surface of the coating is smooth, and the corrosion resistance of the ceramic surface is improved. However, the function is relatively single, and only the corrosion resistance of the coating can be achieved. Moreover, due to the poor strength of the formed coating, the resistance to external and internal stress is insufficient. In actual application, the coating is easily damaged when subjected to stress, resulting in the destruction of the compactness of the coating, which will affect the insulation effect of the coating, resulting in the deterioration or even loss of the corrosion resistance of the coating. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing modified fumed silica, by loading an inorganic heat-resistant agent on fumed silica to obtain heat-resistant fumed silica, and modifying it by inorganic deposition, and surface modification by organic-inorganic hybridization, so that it can be applied to coatings to effectively improve the heat resistance of the coatings, reduce the thermal stress in the coatings, thereby avoiding expansion damage to the coatings due to heat, and at the same time help to improve the strength of the coatings, enhance the resistance of the coatings to external forces, thereby making the coatings less likely to crack, and significantly improving the protective effect of the coatings, which can better play an insulating and protective role.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing modified fumed silica specifically comprises the following steps: loading an inorganic heat-resistant agent on fumed silica to obtain heat-resistant fumed silica, modifying it by inorganic deposition, and surface-modifying it by organic-inorganic hybridization to obtain modified fumed silica.

[0007] As a further preferred embodiment of the present invention, the preparation method of the heat-resistant fumed silica is as follows:

[0008] 1) at room temperature, dispersing fumed silica into a sufficient amount of acidic ethanol solution, and refluxing in an oil bath at 70-75° C. for 6-10 hours, collecting the solid product by centrifugation after the treatment is completed, and repeating the above operation 1-2 times, and finally washing repeatedly with ethanol and drying to obtain pretreated fumed silica;

[0009] 2) Disperse the pretreated fumed silica into an acetone solution containing metal oxides at a mass volume ratio of 1 g: (10-30) mL, fully stir and mix at room temperature, evacuate for 30-50 minutes, and then allow air to flow for 10-20 minutes, repeat the above operation 3-5 times, then repeatedly wash with ethanol and deionized water and dry to obtain heat-resistant fumed silica.

[0010] As a further preferred embodiment of the present invention, in step 2), the acidic ethanol solution is composed of hydrochloric acid and ethanol in a volume ratio of 1:(6-7).

[0011] As a further preferred embodiment of the present invention, in step 3), the concentration of the acetone solution containing the metal oxide is 60-80 mg / mL.

[0012] As a further preferred embodiment of the present invention, the metal oxides contained in the acetone solution include cerium oxide, chromium oxide and nickel oxide, and the mass ratio is 1:1:(0.8-1.3).

[0013] As a further preferred embodiment of the present invention, the modification method is as follows:

[0014] 1) Add polyvinyl pyrrolidone to n-pentanol, stir evenly and then ultrasonically vibrate for 2-3h, add ethanol and deionized water after complete dissolution, vibrate evenly and add sodium citrate aqueous solution, mix well and then slowly drip ammonia water, let stand for 5-10min and then drip ethyl orthosilicate, add heat-resistant fumed silica, seal and place in 90-95℃ oil bath environment to react for 3-4h, filter after the reaction, wash repeatedly with ethanol and deionized water, and dry to obtain pretreated heat-resistant fumed silica;

[0015] 2) Place the pretreated heat-resistant fumed silica in a container filled with ethanol and deionized water, add dopamine hydrochloride, adjust the pH to 8-9 with tris(hydroxymethyl)aminomethane, then drop ethyl orthosilicate, and let stand in an oil bath environment at 30-36°C for 24-30 hours. After the reaction is completed, filter and repeatedly wash with ethanol and deionized water, and dry.

[0016] As a further preferred embodiment of the present invention, in step 1), the usage ratio of polyvinyl pyrrolidone, n-pentanol, ethanol, deionized water, sodium citrate aqueous solution, ammonia water, tetraethyl orthosilicate and heat-resistant fumed silica is (16-20) g: (160-200) mL: (15-20) mL: (4-7) mL: (1.5-2.0) mL: (3-5) mL: (1.5-2.0) mL: (3-7) g;

[0017] The concentration of the sodium citrate aqueous solution is 0.15-0.20 mol / L.

[0018] As a further preferred embodiment of the present invention, in step 2), the ratio of the pre-treated heat-resistant fumed silica, ethanol, deionized water, dopamine hydrochloride and ethyl orthosilicate is (1-5) g: (10-50) mL: (3-15) mL: (0.1-0.5) g: (1-5) mL.

[0019] As a further preferred embodiment of the present invention, the surface modification method is as follows:

[0020] 1-3g of modified heat-resistant fumed silica, 50-80mL of anhydrous acetone and 2-5g of toluene-2,4-diisocyanate are placed in a container, the air in the container is evacuated and filled with inert gas, stirred at room temperature for 20-30min, then 5-8mL of epoxy resin xylene solution is dripped into the container at 60-80℃, the temperature is raised to 160-180℃ and reacted for 15-20h, and after the reaction is completed, it is repeatedly washed, dried and placed in a container with 30-50mL of anhydrous acetone, and then 0.5-1.2g of fatty amine is dripped into it under magnetic stirring at 60-70℃, and the reaction is carried out for 1-3h. After the reaction is completed, the product is repeatedly washed and dried.

[0021] As a further preferred embodiment of the present invention, the concentration of the epoxy resin xylene solution is 2-6wt%;

[0022] The dripping speed of the epoxy resin xylene solution is 30-50 drops / min;

[0023] The dripping speed of the fatty amine is 20-35 drops / min.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] In the present invention, by adding inorganic heat-resistant agents cerium oxide, chromium oxide and nickel oxide to acetone, the fumed silica is equivalent to a plurality of small "capillaries", and the acetone solution can wet the fumed silica. In a vacuum environment, the acetone solution can overcome the "barrier" at the port of the hole under the action of van der Waals force and enter the interior of the fumed silica. The heat-resistant agent attached to the outer wall of the silica can be removed by repeated washing with ethanol and deionized water, so that the heat-resistant agent is completely loaded inside the fumed silica, and the controllable release of the heat-resistant agent in the coating is achieved, the migration of the heat-resistant agent is restricted, and the effective action time is prolonged. At the same time, defects such as depressions and shrinkage cavities on the coating surface caused by agglomeration or large-scale migration of the heat-resistant agent can be avoided, which helps to improve the flatness and appearance of the coating. By loading the heat-resistant agent on the fumed silica, the heat resistance of the coating can be significantly improved after being applied to the coating, and the thermal stress in the coating can be reduced, so that the coating can be prevented from expanding and being damaged due to heat.

[0026] In the present invention, polyvinyl pyrrolidone is used as a template, a solution made of n-pentanol, ethanol, deionized water and sodium citrate is used as a precursor solution, and heat-resistant fumed silica is used as a carrier. Ammonia water and tetraethyl orthosilicate are used to synthesize silica wires of a certain length on the carrier, and then a small amount of dopamine hydrochloride and tris(hydroxymethylaminomethane) are used to coat the silica wires, and then nanospheres are generated by tetraethyl orthosilicate and deposited on the silica wires, thereby forming a branch-like micro-nano structure on the carrier. By modifying the heat-resistant fumed silica, based on the interaction between the siloxy groups and the active groups on the polydopamine and the resin, the spherical particles on the silica wires are increased. The distance between the lines makes the modified heat-resistant fumed silica very compatible in the coating resin, without separation between phases, so that it can be highly evenly dispersed in the coating. At the same time, the silica lines are interconnected to form a network structure, which increases the toughness and strength of the coating resin. The branch-like micro-nano structure barrier separation allows the heat-resistant fumed silica powder to form a uniform grid structure, which can further reduce the agglomeration of the powder and reduce stress defect points while increasing the toughness, thereby helping to improve the strength of the coating and enhance the coating's resistance to external forces, making the coating less likely to crack.

[0027] In order to further improve the resistance of the coating, the present invention adopts an organic-inorganic hybrid method to carry out surface modification treatment on the modified heat-resistant fumed silica, introduces epoxy resin molecules on the surface of the heat-resistant fumed silica through the bridging effect of isocyanate, and then utilizes the basic ring-opening reaction of the epoxy group to form hydroxyl groups that can participate in cross-linking and curing, thereby grafting hydroxyl-containing flexible segments on its surface, and through the surface modification treatment, the heat-resistant fumed silica can be chemically bonded with the coating resin, thereby further inhibiting the agglomeration of the heat-resistant fumed silica in the coating, reducing the defects between the resin and the heat-resistant fumed silica in the coating, and improving the wear resistance and toughness of the coating, thereby achieving further enhancement of the resistance of the coating to external forces, so that the protective effect of the coating is significantly improved, and it can play a more effective isolation and protection role.

[0028] In the present invention, an inorganic heat-resistant agent is loaded on fumed silica with a porous structure to obtain heat-resistant fumed silica, which is modified by inorganic deposition and surface-modified by organic-inorganic hybridization. When applied to a coating, the heat resistance of the coating can be effectively improved, and the thermal stress in the coating can be reduced, thereby preventing the coating from expanding and being damaged due to heat. At the same time, it helps to improve the strength of the coating and enhance the coating's resistance to external forces, thereby making the coating less likely to crack, significantly improving the protective effect of the coating, and achieving a more effective isolation and protection effect. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. all The raw materials are all commercially available products.

[0030] Example 1

[0031] A method for preparing modified fumed silica specifically comprises the following steps: loading an inorganic heat-resistant agent on fumed silica to obtain heat-resistant fumed silica, modifying it by inorganic deposition, and surface-modifying it by organic-inorganic hybridization to obtain modified fumed silica.

[0032] Wherein, the preparation method of heat-resistant fumed silica is as follows:

[0033] 1) at room temperature, dispersing the fumed silica into a sufficient amount of an acidic ethanol solution composed of hydrochloric acid and ethanol in a volume ratio of 1:6, and refluxing in an oil bath at 70° C. for 6 hours. After the treatment is completed, the solid product is collected by centrifugation, and the above operation is repeated once. Finally, the fumed silica is repeatedly washed with ethanol and dried to obtain pretreated fumed silica;

[0034] 2) Dispersing the pretreated fumed silica into an acetone solution containing cerium oxide, chromium oxide and nickel oxide in a mass volume ratio of 1 g:10 mL, wherein the concentration of the acetone solution containing cerium oxide, chromium oxide and nickel oxide is 60 mg / mL, and the mass ratio of cerium oxide, chromium oxide and nickel oxide is 1:1:0.8, stirring at 300 r / min at room temperature for 2 h, after being fully mixed, evacuating for 30 min, and then passing air for 10 min, repeating the above operation 3 times, and then repeatedly washing with ethanol and deionized water and drying to obtain heat-resistant fumed silica.

[0035] Among them, the modification treatment method is as follows:

[0036] 1) Add 16 g of polyvinyl pyrrolidone to 160 mL of n-pentanol, stir evenly, and oscillate at 200 W ultrasonic vibration for 2 h. After complete dissolution, add 15 mL of ethanol and 4 mL of deionized water. After oscillation evenly, add 1.5 mL of 0.15 mol / L sodium citrate aqueous solution. After mixing, slowly drip 3 mL of ammonia water. After standing for 5 min, drip 1.5 mL of ethyl orthosilicate, and add 3 g of heat-resistant fumed silica. After sealing, place in a 90 ° C oil bath environment to react for 3 h. After the reaction is completed, filter and repeatedly wash with ethanol and deionized water. After drying, obtain pretreated heat-resistant fumed silica;

[0037] 2) Place 1 g of pretreated heat-resistant fumed silica in a container containing 10 mL of ethanol and 3 mL of deionized water, add 0.1 g of dopamine hydrochloride, adjust the pH to 8 with tris(hydroxymethyl)aminomethane, then drop 1 mL of ethyl orthosilicate, and let stand in a 30°C oil bath for 24 h. After the reaction is completed, filter and repeatedly wash with ethanol and deionized water, and dry.

[0038] Among them, the surface modification treatment method is as follows:

[0039] 1g of modified heat-resistant fumed silica, 50mL of anhydrous acetone and 2g of toluene-2,4-diisocyanate are placed in a container, the air in the container is evacuated and filled with inert gas, stirred at room temperature for 20min, then 5mL of 2wt% epoxy resin xylene solution is dripped into the container at a rate of 30 drops / min at 60°C, the temperature is raised to 160°C and reacted for 15h, and after the reaction is completed, it is repeatedly washed, dried and placed in a container with 30mL of anhydrous acetone, and then 0.5g of fatty amine is added at 20 drops / min under magnetic stirring at 60°C, and the reaction is carried out for 1h. After the reaction is completed, the product is repeatedly washed and dried.

[0040] Example 2

[0041] A method for preparing modified fumed silica specifically comprises the following steps: loading an inorganic heat-resistant agent on fumed silica to obtain heat-resistant fumed silica, modifying it by inorganic deposition, and surface-modifying it by organic-inorganic hybridization to obtain modified fumed silica.

[0042] Wherein, the preparation method of heat-resistant fumed silica is as follows:

[0043] 1) At room temperature, dispersing the fumed silica into a sufficient amount of an acidic ethanol solution composed of hydrochloric acid and ethanol in a volume ratio of 1:6.5, and refluxed in an oil bath at 73° C. for 8 hours. After the treatment is completed, the solid product is collected by centrifugation, and the above operation is repeated twice. Finally, the fumed silica is repeatedly washed with ethanol and dried to obtain pretreated fumed silica;

[0044] 2) Dispersing the pretreated fumed silica into an acetone solution containing cerium oxide, chromium oxide and nickel oxide in a mass volume ratio of 1 g:20 mL, wherein the concentration of the acetone solution containing cerium oxide, chromium oxide and nickel oxide is 70 mg / mL, and the mass ratio of cerium oxide, chromium oxide and nickel oxide is 1:1:1, stirring at 400 r / min for 3 h at room temperature, and after being fully mixed, evacuating for 40 min, and then passing air for 15 min, repeating the above operation 4 times, and then repeatedly washing with ethanol and deionized water and drying to obtain heat-resistant fumed silica.

[0045] Among them, the modification treatment method is as follows:

[0046] 1) Add 18g of polyvinyl pyrrolidone to 180mL of n-pentanol, stir evenly and oscillate at 260W ultrasonically for 2.5h, add 18mL of ethanol and 5mL of deionized water after complete dissolution, oscillate evenly and add 1.8mL of 0.16mol / L sodium citrate aqueous solution, mix evenly and then slowly drip 4mL of ammonia water, let stand for 8min and then drip 1.6mL of ethyl orthosilicate, add 5g of heat-resistant fumed silica, seal and place in a 93°C oil bath environment to react for 3.5h, filter after the reaction, wash repeatedly with ethanol and deionized water, and dry to obtain pretreated heat-resistant fumed silica;

[0047] 2) Place 3 g of pretreated heat-resistant fumed silica in a container containing 40 mL of ethanol and 10 mL of deionized water, add 0.3 g of dopamine hydrochloride, adjust the pH to 8.5 with tris(hydroxymethyl)aminomethane, then drop 3 mL of ethyl orthosilicate, and let stand in a 35°C oil bath for 26 h. After the reaction is completed, filter and repeatedly wash with ethanol and deionized water, and dry.

[0048] Among them, the surface modification treatment method is as follows:

[0049] 2g of modified heat-resistant fumed silica, 70mL of anhydrous acetone and 3g of toluene-2,4-diisocyanate are placed in a container, the air in the container is evacuated and filled with inert gas, stirred at room temperature for 25min, then 6mL of 5wt% epoxy resin xylene solution is dripped into the container at a rate of 40 drops / min at 70°C, the temperature is raised to 170°C and reacted for 18h, and after the reaction is completed, it is repeatedly washed, dried and placed in a container with 40mL of anhydrous acetone, and then 0.8g of fatty amine is added at 30 drops / min under magnetic stirring at 65°C, and reacted for 2h. After the reaction is completed, the product is repeatedly washed and dried.

[0050] Example 3

[0051] A method for preparing modified fumed silica specifically comprises the following steps: loading an inorganic heat-resistant agent on fumed silica to obtain heat-resistant fumed silica, modifying it by inorganic deposition, and surface-modifying it by organic-inorganic hybridization to obtain modified fumed silica.

[0052] Wherein, the preparation method of heat-resistant fumed silica is as follows:

[0053] 1) At room temperature, dispersing the fumed silica into a sufficient amount of an acidic ethanol solution composed of hydrochloric acid and ethanol in a volume ratio of 1:7, and refluxed in an oil bath at 75° C. for 10 hours. After the treatment is completed, the solid product is collected by centrifugation, and the above operation is repeated twice. Finally, the fumed silica is repeatedly washed with ethanol and dried to obtain pretreated fumed silica;

[0054] 2) Dispersing the pretreated fumed silica into an acetone solution containing cerium oxide, chromium oxide and nickel oxide in a mass volume ratio of 1 g:30 mL, wherein the concentration of the acetone solution containing cerium oxide, chromium oxide and nickel oxide is 80 mg / mL, and the mass ratio of cerium oxide, chromium oxide and nickel oxide is 1:1:1.3, stirring at room temperature at 500 r / min for 5 h, after being fully mixed, evacuating for 50 min, and then passing air for 20 min, repeating the above operation 5 times, and then repeatedly washing with ethanol and deionized water and drying to obtain heat-resistant fumed silica.

[0055] Among them, the modification treatment method is as follows:

[0056] 1) Add 20g of polyvinyl pyrrolidone to 200mL of n-pentanol, stir evenly and oscillate at 300W ultrasonic for 3h, add 20mL of ethanol and 7mL of deionized water after complete dissolution, oscillate evenly and add 2.0mL of 0.20mol / L sodium citrate aqueous solution, mix evenly and then slowly drip 5mL of ammonia water, let stand for 10min and then drip 2.0mL of ethyl orthosilicate, add 7g of heat-resistant fumed silica, seal and place in 95℃ oil bath environment to react for 4h, filter after the reaction, wash repeatedly with ethanol and deionized water, and dry to obtain pretreated heat-resistant fumed silica;

[0057] 2) Place 5 g of pretreated heat-resistant fumed silica in a container containing 50 mL of ethanol and 15 mL of deionized water, add 0.5 g of dopamine hydrochloride, adjust the pH to 9 with tris(hydroxymethyl)aminomethane, then drop 5 mL of ethyl orthosilicate, and let stand in a 36°C oil bath for 30 h. After the reaction is completed, filter and repeatedly wash with ethanol and deionized water, and dry.

[0058] Among them, the surface modification treatment method is as follows:

[0059] 3g of modified heat-resistant fumed silica, 80mL of anhydrous acetone and 5g of toluene-2,4-diisocyanate are placed in a container, the air in the container is evacuated and filled with inert gas, stirred at room temperature for 30min, then 8mL of 6wt% epoxy resin xylene solution is dripped into the container at a rate of 50 drops / min at 80°C, the temperature is raised to 180°C and reacted for 20h, and after the reaction is completed, it is repeatedly washed, dried and placed in a container with 50mL of anhydrous acetone, and then 1.2g of fatty amine is added at 35 drops / min under magnetic stirring at 70°C, and the reaction is carried out for 3h. After the reaction is completed, the product is repeatedly washed and dried.

[0060] Comparative Example 1: This comparative example is substantially the same as Example 1, except that no surface modification treatment is performed.

[0061] Comparative Example 2: This comparative example is basically the same as Example 1, except that no modification treatment is performed.

[0062] Comparative Example 3: This comparative example is basically the same as Example 1, except that the heat-resistant fumed silica is not pretreated during the modification process.

[0063] Comparative Example 4: This comparative example is basically the same as Example 1, except that no heat-resistant agent is loaded on the fumed silica.

[0064] Comparative Example 5: Direct use of fumed silica.

[0065] Test experiment:

[0066] The samples provided in Examples 1-3 and Comparative Examples 1-5 are added as fillers to a coating, wherein the coating includes a primer and a topcoat, the primer main agent is a mixture of polyimide and polyphenylene sulfide, the primer auxiliary agent is a mixture of a defoamer and a sealant, and its specific composition by weight percentage is as follows: 68% polyimide, 30% polyphenylene sulfide, and 2% primer auxiliary agent; in the topcoat, the topcoat main agent is a mixture of polyimide, polyphenylene sulfide and polytetrafluoroethylene, the topcoat auxiliary agent is a leveling agent, and its specific composition by weight percentage is as follows: 13.5% polyimide, 6% polyphenylene sulfide, 3% polytetrafluoroethylene, 77% filler, and 0.5% topcoat auxiliary agent (the sealant is KAF-61, the defoamer is KSL-54, and the leveling agent is KF-880, all provided by Kage Chemical).

[0067] Spray the paint on the steel, first spray the base coat, 50μm at a time, control the temperature at 180℃ for 2 hours, then spray the top coat, 300μm at a time, control the temperature at 260℃ for 4 hours.

[0068] The performance of the processed substrate is shown in the following table:

[0069]

[0070] Note: Compressive strength test refers to GB1041-2008, wear rate test refers to GB3960-1983, heat resistance test: apply 2mm thick paint on a 2mm thick, 10cm×10cm steel plate, maintain for 7 days, put it in a 300℃ oven, bake for 1h, take it out, immerse it in cold water, wipe it clean after cooling, and put it in a 300℃ oven for 1h, and repeat this cycle 10 times.

[0071] It can be seen from the above table that the modified fumed silica in the present invention, when used as a filler in coatings, can effectively improve the heat resistance of the coatings, and at the same time, it also helps to improve the compressive strength and wear resistance of the coatings, and enhance the resistance of the coatings to external forces, thereby making the coatings less likely to crack, and significantly improving the protective effect of the coatings, which can better play an insulating and protective role.

[0072] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing modified fumed silica, characterized in that: Specifically, the method comprises the following steps: loading an inorganic heat-resistant agent on fumed silica to obtain heat-resistant fumed silica, modifying the fumed silica by inorganic deposition, and surface-modifying the fumed silica by organic-inorganic hybridization to obtain modified fumed silica; The preparation method of the heat-resistant fumed silica is as follows: 1) At room temperature, disperse the fumed silica in a sufficient amount of acidic ethanol solution, and reflux in an oil bath at 70-75°C for 6-10 hours. After the treatment is completed, collect the solid product by centrifugation, and repeat the above operation 1-2 times. Finally, wash it repeatedly with ethanol and dry it to obtain pretreated fumed silica; 2) Dispersing the pretreated fumed silica into an acetone solution containing metal oxides at a mass volume ratio of 1 g: (10-30) mL, stirring and mixing at room temperature, evacuating for 30-50 minutes, and then passing air for 10-20 minutes, repeating the above operation 3-5 times, and then repeatedly washing with ethanol and deionized water and drying to obtain heat-resistant fumed silica; the concentration of the acetone solution containing metal oxides is 60-80 mg / mL, and the metal oxides include cerium oxide, chromium oxide and nickel oxide, and the mass ratio is 1:1: (0.8-1.3); The method of the modification treatment is as follows: (1) Add polyvinyl pyrrolidone to n-pentanol, stir evenly and then ultrasonically vibrate for 2-3 hours. After it is completely dissolved, add ethanol and deionized water. After vibrating evenly, add sodium citrate aqueous solution, mix well and then slowly drip ammonia water. After standing for 5-10 minutes, drip ethyl orthosilicate and add heat-resistant fumed silica. After sealing, place in a 90-95°C oil bath environment to react for 3-4 hours. After the reaction is completed, filter and repeatedly wash with ethanol and deionized water. After drying, obtain the pretreated heat-resistant fumed silica. (2) Place the pretreated heat-resistant fumed silica in a container containing ethanol and deionized water, add dopamine hydrochloride, and adjust the pH to 8-9 with tris(hydroxymethyl)aminomethane, then drop ethyl orthosilicate, and let stand in an oil bath at 30-36°C for 24-30 hours. After the reaction is completed, filter and repeatedly wash with ethanol and deionized water, and then dry; The method of the surface modification treatment is as follows: 1-3g of modified heat-resistant fumed silica, 50-80mL of anhydrous acetone and 2-5g of toluene-2,4-diisocyanate are placed in a container, the air in the container is evacuated and filled with inert gas, stirred at room temperature for 20-30min, then 5-8mL of epoxy resin xylene solution is dripped into the container at 60-80℃, the temperature is raised to 160-180℃ and reacted for 15-20h, and after the reaction is completed, it is repeatedly washed, dried and placed in a container with 30-50mL of anhydrous acetone, and then 0.5-1.2g of fatty amine is dripped into it under magnetic stirring at 60-70℃, and the reaction is carried out for 1-3h. After the reaction is completed, the product is repeatedly washed and dried.

2. The method for preparing modified fumed silica according to claim 1, characterized in that: In step 1), the acidic ethanol solution is composed of hydrochloric acid and ethanol in a volume ratio of 1: (6-7).

3. The method for preparing modified fumed silica according to claim 1, characterized in that: In step (1), the usage ratio of polyvinyl pyrrolidone, n-pentanol, ethanol, deionized water, sodium citrate aqueous solution, ammonia water, tetraethyl orthosilicate and heat-resistant fumed silica is (16-20) g: (160-200) mL: (15-20) mL: (4-7) mL: (1.5-2.0) mL: (3-5) mL: (1.5-2.0) mL: (3-7) g; The concentration of the sodium citrate aqueous solution is 0.15-0.20 mol / L.

4. The method for preparing modified fumed silica according to claim 1, characterized in that: In step (2), the ratio of the pre-treated heat-resistant fumed silica, ethanol, deionized water, dopamine hydrochloride and ethyl orthosilicate is (1-5) g: (10-50) mL: (3-15) mL: (0.1-0.5) g: (1-5) mL.

5. The method for preparing modified fumed silica according to claim 1, characterized in that: The concentration of the epoxy resin xylene solution is 2-6wt%; The dripping speed of the epoxy resin xylene solution is 30-50 drops / min; The dripping speed of the fatty amine is 20-35 drops / min.

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