阅读说明：本技术 一种二氧化硅气凝胶粉体及其制备方法和应用 (Silicon dioxide aerogel powder and preparation method and application thereof ) 是由 赵洪凯 刘威 张力化 刘明 刘一甫 于 2019-11-19 设计创作，主要内容包括：本发明提供了一种二氧化硅气凝胶粉体及其制备方法和应用,属于隔热材料的制备领域。本发明提供的二氧化硅气凝胶粉体,由包括以下质量份数的组分制备得到：硅源水溶液100～300份、油相溶剂200～400份、助溶剂4～40份、表面活性剂0.2～2份、甲基硅醇钠溶液10～60份、无机酸水溶液1～5份、三甲基硅醇钠四氢呋喃溶液3～10份和有机脂肪酸的石油醚溶液0.3～0.9份。本发明提供的二氧化硅气凝胶粉体结构均匀,且具有良好的疏水性、低导热和低密度特点。(The invention provides silicon dioxide aerogel powder and a preparation method and application thereof, belonging to the field of preparation of heat insulation materials. The silicon dioxide aerogel powder provided by the invention is prepared from the following components in parts by mass: 100-300 parts of silicon source aqueous solution, 200-400 parts of oil phase solvent, 4-40 parts of cosolvent, 0.2-2 parts of surfactant, 10-60 parts of sodium methylsiliconate solution, 1-5 parts of inorganic acid aqueous solution, 3-10 parts of sodium trimethylsilonate tetrahydrofuran solution and 0.3-0.9 part of petroleum ether solution of organic fatty acid. The silicon dioxide aerogel powder provided by the invention has a uniform structure, and has the characteristics of good hydrophobicity, low heat conduction and low density.)

1. The silicon dioxide aerogel powder is characterized by being prepared from the following components in parts by mass:

100-300 parts of silicon source aqueous solution, 200-400 parts of oil phase solvent, 4-40 parts of cosolvent, 0.2-2 parts of surfactant, 10-60 parts of sodium methylsiliconate solution, 1-5 parts of inorganic acid aqueous solution, 3-10 parts of sodium trimethylsilonate tetrahydrofuran solution and 0.3-0.9 part of petroleum ether solution of organic fatty acid.

2. The silica aerogel powder of claim 1, wherein the mass concentration of the sodium methylsiliconate solution is 28-32%.

3. The silica aerogel powder according to claim 1, wherein the mass concentration of the sodium trimethylsilanolate tetrahydrofuran solution is 8 to 12%.

4. The silica aerogel powder according to claim 1, wherein the molar concentration of the petroleum ether solution of the organic fatty acid is 0.01 to 0.015 mol/L.

5. The silica aerogel powder of claim 1 or 4, wherein the organic fatty acid in the petroleum ether solution of organic fatty acids comprises C₈～C₁₈One or more of fatty acids.

6. The silica aerogel powder of claim 1, wherein S is contained in the aqueous solution of silicon sourceiO₂The mass concentration of (A) is 5-8%.

7. The silica aerogel powder according to claim 1, wherein the molar concentration of the aqueous inorganic acid solution is 0.01 to 0.015 mol/L.

8. The silica aerogel powder of claim 1, wherein the oil phase solvent comprises a hydrocarbon solvent, a halogenated hydrocarbon, or an ester.

9. The method for preparing the silica aerogel powder according to any one of claims 1 to 8, comprising the steps of:

mixing and heating a silicon source water solution, a surfactant, an oil phase solvent and a cosolvent, and adjusting the pH value to obtain an emulsion system;

mixing the emulsion system, a sodium methyl silanol solution and an inorganic acid aqueous solution for a first reaction, mixing the emulsion system, a sodium methyl silanol tetrahydrofuran solution and an inorganic acid aqueous solution with water, a sodium trimethyl silanol tetrahydrofuran solution and a petroleum ether solution of organic fatty acid for a second reaction, and then sequentially extracting and drying to obtain the silicon dioxide aerogel powder.

10. Use of the silica aerogel powder according to any one of claims 1 to 8 or the silica aerogel powder produced by the method according to claim 9 for producing a thermal insulation material.

Technical Field

The invention relates to the technical field of preparation of heat insulation materials, in particular to silicon dioxide aerogel powder and a preparation method and application thereof.

Background

Silicon dioxide (SiO)₂) Aerogel is a novel light porous material formed by mutually aggregating nano-scale particles and taking air as a dispersion medium, and is mainly used as a heat insulation material and a sound absorption material. Aerogel prepared by taking high-purity silicon alkoxide (ethyl orthosilicate and the like) as silicon source has excellent performance in all aspectsBut the cost is high, and the method is not suitable for popularization in civil fields such as building heat preservation and the like.

At present, most of mature aerogel preparation processes at home and abroad take methyl orthosilicate and ethyl orthosilicate as silicon sources, and the nano-scale silicon dioxide aerogel is prepared by adopting supercritical drying process conditions. However, the preparation method has the disadvantages of complex process, high process requirement, long time consumption and high cost, and seriously limits the commercial development of the silicon aerogel production process.

SiO is also often prepared in the prior art by drying under atmospheric conditions₂Aerogels, but limited to the limitations of the atmospheric drying technique itself, dry under atmospheric conditions to produce SiO₂The properties of aerogel structure, hydrophobicity, low heat conductivity, low density and the like are poor, and the properties are far less than those of SiO prepared by drying under supercritical conditions₂The structure, hydrophobicity, low thermal conductivity, low density and the like of the aerogel. These factors all limit SiO₂Further development of aerogel can not realize SiO₂Industrial production of (5).

Disclosure of Invention

In view of this, the present invention provides a silica aerogel powder, a preparation method and applications thereof. The silicon dioxide aerogel powder provided by the invention has the characteristics of uniform structure, good hydrophobicity, low heat conduction and low density.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides silicon dioxide aerogel powder which is prepared from the following components in parts by mass:

100-300 parts of silicon source aqueous solution, 200-400 parts of oil phase solvent, 4-40 parts of cosolvent, 0.2-2 parts of surfactant, 10-60 parts of sodium methylsiliconate solution, 1-5 parts of inorganic acid aqueous solution, 3-10 parts of sodium trimethylsilonate tetrahydrofuran solution and 0.3-0.9 part of petroleum ether solution of organic fatty acid.

Preferably, the mass concentration of the sodium methylsiliconate solution is 28-32%.

Preferably, the mass concentration of the sodium trimethylsilanolate tetrahydrofuran solution is 8-12%.

Preferably, the molar concentration of the petroleum ether solution of the organic fatty acid is 0.01-0.015 mol/L.

Preferably, the organic fatty acid in the petroleum ether solution of organic fatty acid comprises C₈～C₁₈One or more of fatty acids.

Preferably, SiO in the silicon source aqueous solution₂The mass concentration of (A) is 5-8%.

Preferably, the molar concentration of the inorganic acid aqueous solution is 0.01-0.015 mol/L.

Preferably, the oil phase solvent comprises a hydrocarbon solvent, a halogenated hydrocarbon or an ester.

The invention also provides a preparation method of the silicon dioxide aerogel powder, which comprises the following steps:

mixing and heating a silicon source water solution, a surfactant, an oil phase solvent and a cosolvent, and adjusting the pH value to obtain an emulsion system;

mixing the emulsion system, a sodium methyl silanol solution and an inorganic acid aqueous solution for a first reaction, mixing the emulsion system, a sodium methyl silanol tetrahydrofuran solution and an inorganic acid aqueous solution with water, a sodium trimethyl silanol tetrahydrofuran solution and a petroleum ether solution of organic fatty acid for a second reaction, and then sequentially extracting and drying to obtain the silicon dioxide aerogel powder.

The invention also provides the application of the silicon dioxide aerogel powder in the technical scheme or the silicon dioxide aerogel powder prepared by the preparation method in the technical scheme in the preparation of the heat insulation material.

The invention provides silicon dioxide aerogel powder which is prepared from the following components in parts by mass: 100-300 parts of silicon source aqueous solution, 200-400 parts of oil phase solvent, 4-40 parts of cosolvent, 0.2-2 parts of surfactant, 10-60 parts of sodium methylsiliconate solution, 1-5 parts of inorganic acid aqueous solution, 3-10 parts of sodium trimethylsilonate tetrahydrofuran solution and 0.3-0.9 part of petroleum ether solution of organic fatty acid. The milk prepared by adding the sodium methylsilanolate solution, the sodium trimethylsilanolate tetrahydrofuran solution and the petroleum ether solution of organic fatty acidThe liquid is modified, the skeleton strength of the modified silicon aerogel is continuously enhanced, meanwhile, the hydrophobicity is continuously enhanced, and the silicon dioxide aerogel powder has the characteristics of uniform structure, good hydrophobicity, low heat conduction and low density. The embodiment shows that the density of the silicon dioxide aerogel powder prepared by the invention is 50-90 kg/m³The thermal conductivity coefficient is 0.020-0.045W/m.K, and the contact angle can reach 130-155 degrees.

Furthermore, the preparation method provided by the invention has the advantages of simple process, convenience in operation, wide raw material source and low cost, can be used for drying under the normal pressure condition, can be used for quickly preparing the silicon dioxide aerogel powder with uniform structure, good hydrophobicity, low heat conductivity and low density, can well overcome the defects of high cost and long production period in the existing process for preparing the silicon aerogel, and is suitable for realizing industrial production.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

FIG. 1 is an infrared spectrum of silica aerogel powder prepared in example 1;

FIG. 2 is an XRD spectrum of silica aerogel powder prepared in example 1;

FIG. 3 is an SEM image of the silica aerogel powder prepared in example 1.

Detailed Description

The invention provides silicon dioxide aerogel powder which is prepared from the following components in parts by mass:

100-300 parts of silicon source aqueous solution, 200-400 parts of oil phase solvent, 4-40 parts of cosolvent, 0.2-2 parts of surfactant, 10-60 parts of sodium methylsiliconate solution, 1-5 parts of inorganic acid aqueous solution, 3-10 parts of sodium trimethylsilanolate tetrahydrofuran solution and 0.3-0.9 part of petroleum ether solution of organic fatty acid, further preferably 150 to 250 parts of silicon source aqueous solution, 250 to 350 parts of oil phase solvent, 15 to 30 parts of cosolvent, 0.5 to 1.6 parts of surfactant, 30 to 50 parts of sodium methylsiliconate solution, 2 to 4 parts of inorganic acid aqueous solution, 5 to 8 parts of sodium trimethylsilanolate tetrahydrofuran solution and 0.5 to 0.7 part of petroleum ether solution of organic fatty acid, more preferably 200 parts of a silicon source aqueous solution, 300 parts of an oil phase solvent, 20 parts of a cosolvent, 1.5 parts of a surfactant, 40 parts of a sodium methylsilanol solution, 3.5 parts of an inorganic acid aqueous solution, 5 parts of a sodium trimethylsilanolate tetrahydrofuran solution and 0.6 part of a petroleum ether solution of an organic fatty acid.

In the present invention, the raw materials used in the present invention are all commercially available products which are conventional in the art, unless otherwise specified.

In the invention, SiO in the silicon source aqueous solution₂The mass concentration of (b) is preferably 5% to 8%, more preferably 6% to 7%, and still more preferably 6.5%; the silicon source in the silicon source aqueous solution preferably comprises alkaline silica sol, acidic silica sol, water glass or orthosilicate ester hydrolyzed silica sol; when the silicon source in the silicon source aqueous solution is orthosilicate ester hydrolyzed silica sol, the orthosilicate ester hydrolyzed silica sol preferably comprises methyl orthosilicate, orthosilicate ester or propyl orthosilicate ester. According to the invention, the silicon source aqueous solution with a specific dosage and mass concentration is adopted, so that a uniform silicon aerogel nano pore structure can be formed, and the prepared silicon aerogel has a good heat conductivity coefficient under the condition of having a high-strength framework structure.

In the present invention, the oil phase solvent preferably includes a hydrocarbon solvent, a halogenated hydrocarbon solvent, or an ester solvent, and more preferably a hydrocarbon solvent; when the oil phase solvent is a hydrocarbon solvent, the hydrocarbon solvent preferably comprises benzene, toluene, xylene, hexane, octane, cyclohexane, cyclohexanone, toluene cyclohexanone, liquid paraffin or kerosene; when the oil phase solvent is a halogenated hydrocarbon solvent, the halogenated hydrocarbon solvent preferably comprises chlorobenzene, dichlorobenzene or dichloromethane; when the oil phase solvent is an ester solvent, the ester solvent preferably includes methyl acetate, ethyl acetate or propyl acetate.

In the present invention, the cosolvent is preferably an alcohol, and more preferably isopropyl alcohol or butyl alcohol.

In the present invention, the surfactant preferably includes a cationic surfactant and/or a nonionic surfactant, and when the surfactant is preferably a cationic surfactant and a nonionic surfactantIn the case of a mixture of surfactants, the mass ratio of the cationic surfactant to the nonionic surfactant is preferably 1:3 to 3: 1. In the present invention, the cationic surfactant preferably comprises C₁₂～C₁₈One or more of alkyl trimethyl ammonium bromide, and the nonionic surfactant preferably comprises one or more of sorbitan fatty acid esters, fatty acid monoglycerides and fatty acid diglycerides, and is further preferably span-80 in the embodiment of the invention.

In the present invention, the mass concentration of the sodium methylsilanolate solution is preferably 28% to 32%, and more preferably 30%. According to the invention, the prepared silicon aerogel is modified by using the sodium methyl silanol solution with a specific dosage and mass concentration, so that the uniformity of the pore structure of the silicon aerogel can be effectively improved, and the efficient separation of oil and water in the subsequent preparation process can be ensured.

In the present invention, the inorganic acid aqueous solution preferably includes hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, or hydrofluoric acid, and the molar concentration of the inorganic acid aqueous solution is preferably 0.01 to 0.015mol/L, and more preferably 0.012 mol/L. According to the invention, the inorganic acid aqueous solution with a specific dosage and a specific molar concentration is adopted, so that the hydrolysis rate of the sodium methyl silanol can be effectively improved, the modification of the prepared silicon aerogel by the sodium methyl silanol solution is promoted, and the uniformity of a pore structure of the silicon aerogel is effectively improved.

In the present invention, the mass concentration of the sodium trimethylsilanolate tetrahydrofuran solution is preferably 8% to 12%, and more preferably 10%. According to the invention, the prepared silicon aerogel is modified by adopting the sodium trimethylsilanolate tetrahydrofuran solution with a specific dosage and mass concentration, so that the uniformity of the pore structure of the silicon aerogel can be effectively improved.

In the invention, the molar concentration of the petroleum ether solution of the organic fatty acid is preferably 0.01-0.015 mol/L, and more preferably 0.012 mol/L; the organic fatty acid in the petroleum ether solution of the organic fatty acid comprises C₈～C₁₈One or more of fatty acids. The method adopts organic fatty acid with the carbon number of 8-18 to react with sodium trimethylsilanolate to generate fatty acid sodium saltThe sodium salt of fatty acid can be used as a surfactant, has good compatibility with water, and can migrate from the oil phase of the colloidal particles to the water phase, thereby effectively improving the uniformity of the pore structure of the silicon aerogel. According to the invention, the inorganic acid aqueous solution with a specific dosage and a specific molar concentration is adopted, so that the hydrolysis rate of sodium trimethylsilanolate can be effectively improved, the modification of the prepared silicon aerogel by the sodium trimethylsilanolate tetrahydrofuran solution is promoted, and the uniformity of the pore structure of the silicon aerogel is effectively improved.

The invention also provides a preparation method of the silicon dioxide aerogel powder, which comprises the following steps:

mixing and heating a silicon source water solution, a surfactant, an oil phase solvent and a cosolvent, and adjusting the pH value to obtain an emulsion system;

mixing the emulsion system, a sodium methyl silanol solution and an inorganic acid aqueous solution for a first reaction, mixing the emulsion system, a sodium methyl silanol tetrahydrofuran solution and an inorganic acid aqueous solution with water, a sodium trimethyl silanol tetrahydrofuran solution and a petroleum ether solution of organic fatty acid for a second reaction, and then sequentially extracting and drying to obtain the silicon dioxide aerogel powder.

According to the invention, a silicon source water solution, a surfactant, an oil phase solvent and a cosolvent are mixed and heated, and an emulsion system is obtained after the pH value is adjusted. In the present invention, the heating temperature is preferably 50 to 60 ℃, and more preferably 55 ℃. In the present invention, the mixing is preferably performed by magnetic stirring, the time of the magnetic stirring is preferably 8 to 12min, and more preferably 10min, and the stirring rate is preferably 350 to 450rmp, and more preferably 400 rmp. The mixing sequence is not particularly limited in the invention, and any mixing sequence can be adopted.

In the invention, the pH value is preferably 6-7, the pH value adjusting agent is preferably ammonia water or hydrochloric acid solution, and the ammonia water is preferably obtained by diluting 25-28% by mass of ammonia water with 50 times of water; the hydrochloric acid solution is preferably obtained by diluting hydrochloric acid with the mass concentration of 36-38% by 50 times of water. In the present invention, the dropping rate of the regulator is preferably 2 drops/sec. The dosage of the regulator is not specially limited, and the pH value can be regulated to 6-7. After the pH value is adjusted, the obtained product is preferably kept stand for 24 hours to generate gel particles, so that an emulsion system is obtained, and the generated gel particles are micron-sized fine gel particles with surfaces coated by oil phases. The gel particles prepared by the method can shorten the diffusion path and time of subsequently added sodium methylsiliconate solution, inorganic acid aqueous solution, sodium trimethylsilanolate tetrahydrofuran solution and petroleum ether solution of organic fatty acid in the gel particles.

After an emulsion system is obtained, the emulsion system, a sodium methyl silanol solution and an inorganic acid aqueous solution are mixed for a first reaction, then the mixture is mixed with water, a sodium trimethyl silanol tetrahydrofuran solution and a petroleum ether solution of organic fatty acid for a second reaction, and then the mixture is extracted and dried in sequence to obtain the silicon dioxide aerogel powder. In the present invention, the mixing is preferably performed by magnetic stirring, and the stirring rate is preferably 300 to 400rmp, and more preferably 350 rmp.

According to the invention, the sodium methylsiliconate solution is preferably added into the emulsion system in a dropwise manner. In the invention, the dripping speed is preferably 1-2 drops/second. According to the invention, preferably, when the pH value of the emulsion system is 7.8-8.2, the addition of the sodium methylsiliconate solution is stopped, and the stirring is continued for 1-5 min, so that the sodium methylsiliconate is diffused in the gel particles, and preferably, the inorganic acid aqueous solution is added into the emulsion system in a dropwise manner. In the invention, the dripping speed is preferably 1-2 drops/second. The amount of the inorganic acid aqueous solution is not particularly limited, and the pH value of the emulsion system can be adjusted to 7. The method preferably repeats the step of sequentially dripping the sodium methyl silanol solution and the inorganic acid aqueous solution until 10-60 parts by mass of the sodium methyl silanol aqueous solution and 1-5 parts by mass of the inorganic acid aqueous solution are completely dripped. Firstly, dropwise adding a sodium methyl silanol aqueous solution into an emulsion system so as to enable hydrophilic sodium methyl silanol to be capable of rapidly diffusing into gel particles, after the sodium methyl silanol is uniformly diffused, dropwise adding an inorganic acid aqueous solution to control the pH value of the emulsion system to be 7 so as to convert the sodium methyl silanol into the methyl silanol and further modify the gel particles in situ, and enhance the hydrophobicity inside and on the surface of the gel particles; the step of repeatedly adding the sodium methylsilanolate solution and the inorganic acid aqueous solution is to enable the methylsilanolate to modify the gel particles more thoroughly and improve the modification effect of the sodium methylsilanolate on the gel particles.

After the first reaction is completed, the invention preferably mixes the product obtained from the first reaction with water, and then carries out a second reaction with the sodium trimethylsilanolate tetrahydrofuran solution and the petroleum ether solution of organic fatty acid. The amount of the water used in the invention is not particularly limited, and the emulsion system can be subjected to phase inversion. The invention preferably identifies whether phase inversion occurs in the emulsion system by adding the water-based pigment into the emulsion system, and indicates that the phase inversion occurs in the emulsion system when the color of the emulsion system is the natural color of the water-based pigment. In the present invention, the water is preferably deionized water. In the present invention, the dropping rate of the water is preferably 1 drop/second. In the invention, the sodium trimethylsilanolate tetrahydrofuran solution and the petroleum ether solution of organic fatty acid are preferably added into the emulsion system in a dropwise manner at the same time, and the dropping rates of the sodium trimethylsilanolate tetrahydrofuran solution and the petroleum ether solution of organic fatty acid are independently preferably 1-2 drops/second. According to the invention, after water is dripped into an emulsion system, phase inversion occurs to generate silica gel particles with surfaces coated by water phases, the silica gel particles have strong hydrophobicity, and meanwhile, part of oil phase enters the interior of the silica gel particles to create favorable conditions for subsequent diffusion of sodium trimethylsilanolate; after dropwise adding the sodium trimethylsilanolate tetrahydrofuran solution, the sodium trimethylsilanolate can uniformly diffuse into the silica gel particles; after the petroleum ether solution of organic fatty acid is dripped, the organic fatty acid in the petroleum ether solution diffuses into the silica gel particles to react with sodium trimethylsilanolate, thereby generating trimethylsilanolate, further modifying the silica gel particles, and simultaneously transferring the generated sodium fatty acid to the surface of the colloidal particles to promote the subsequent separation of oil phase and water phase.

After the second reaction is completed, the present invention preferably adjusts the pH of the obtained second reaction product, which is preferably 7. In the present invention, the adjusting agent for adjusting the pH value is preferably ammonia water or hydrochloric acid solution, and the source of the ammonia water or hydrochloric acid solution is the same as that of the ammonia water or hydrochloric acid solution, which is not described herein any more. The dosage of the regulator for regulating the pH value is not specially limited, and the pH value of the latex system can be regulated to 7. After the pH value is adjusted, preferably, the product obtained after the pH value is adjusted is sequentially extracted and dried to obtain the silicon dioxide aerogel powder. According to the invention, deionized water is preferably added to extract after the water-oil separation phenomenon of an emulsion system occurs. The upper suspension colloid obtained by extraction is preferably dried under the normal pressure condition, the drying temperature is preferably 70-100 ℃, and the drying time is preferably 80 ℃. The extraction method is not particularly limited in the present invention, and the extraction method known to those skilled in the art may be used. The silicon dioxide aerogel powder prepared by the invention has strong hydrophobicity, impurity removal treatment is not needed, impurities in the silicon dioxide aerogel powder are transferred to a water phase through extraction treatment, and drying is carried out under normal pressure.

The invention also provides the application of the silicon dioxide aerogel powder in the technical scheme or the silicon dioxide aerogel powder prepared by the preparation method in the technical scheme in the preparation of the heat insulation material.

In the present invention, the silica aerogel powder is preferably used as a filler for a thermal insulation material. The application mode of the silica aerogel powder as the filler of the thermal insulation material is not particularly limited, and the application mode known by the technical personnel in the field can be adopted.

The silica aerogel powder, the preparation method and the application thereof provided by the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.

Example 1

1) Taking SiO₂100 parts of 5% acidic silica sol solution, 0.2 part of surfactant cetyl trimethyl ammonium bromide, 200 parts of oil phase kerosene and 4 parts of cosolvent n-butyl alcohol are heated at 50 ℃, and stirred for 10min by a magnetic stirrer at 400 rmp;

2) dropwise adding the diluted ammonia water into the emulsion, stirring, adjusting the pH value to 6-7, standing for a period of time, gradually gelling the solution, and standing the emulsion for 24 hours; the ammonia water is obtained by diluting 28% ammonia water by 50 times of water;

3) under the stirring of 300rmp, slowly dropwise adding a 30% sodium methylsiliconate solution for modification, determining the pH value of the emulsion system to be 8, and stopping dropwise adding the sodium methylsiliconate solution;

4) maintaining the stirring at 300rmp, and after the sodium methylsiliconate is uniformly diffused in the gel particles, dropwise adding a diluted dilute hydrochloric acid solution to adjust the pH value of the emulsion system to 7; the hydrochloric acid solution is obtained by diluting hydrochloric acid with the mass concentration of 37% by 50 times of water;

5) repeatedly dropwise adding 10 parts of sodium methylsiliconate aqueous solution and 1 part of 0.1mol/L nitric acid solution in the same way;

6) under the stirring of 300rmp, when a proper amount of deionized water is dripped to cause the phase inversion of the emulsion, 3 parts of sodium trimethylsilanolate tetrahydrofuran solution with the concentration of 10 percent are dripped, and 0.01mol/L C is simultaneously dripped₁₈0.3 part of petroleum ether solution of organic fatty acid, and adjusting the pH value of an emulsion system to 7;

7) adding a proper amount of deionized water, further performing oil-water separation on an emulsion system, taking the upper suspension colloid, and drying in an oven at 100 ℃ under normal pressure for 2h to obtain the hydrophobic silica aerogel powder.

The prepared silica aerogel powder was examined, and the results are shown in table 1.

FIG. 1 is an infrared spectrum of silica aerogel powder prepared in example 1, and it can be seen from FIG. 1 that 800cm is obtained when CTAB (cetyl trimethyl ammonium bromide) is added in an amount of 0.2 parts^-1Has an absorption peak of Si-O-Si bond of 2900cm^-1The range is C-H bond, no significant functional group change, from which it can be seen that the main steric structure of the article is Si-O-Si.

Fig. 2 is an XRD spectrum of the silica aerogel powder prepared in example 1, and it can be seen from fig. 2 that the prepared silica aerogel powder has no obvious diffraction peak, so that the prepared sample has an amorphous structure.

FIG. 3 is an SEM image of the silica aerogel powder prepared in example 1, which shows that the silica aerogel has microscopically uniform pores and a distinct pore structure.

Example 2

1) Taking SiO₂300 parts of 8% acidic silica sol solution, 2 parts of surfactant cetyl trimethyl ammonium bromide, 400 parts of oil phase kerosene and 40 parts of cosolvent n-butyl alcohol are heated at 50 ℃, and a magnetic stirrer is used for stirring for 10min at 450 rmp;

2) dropwise adding the diluted ammonia water into the emulsion, stirring, adjusting the pH value to 6-7, standing for a period of time, gradually gelling the solution, and standing the emulsion for 24 hours; the ammonia water is obtained by diluting 28% ammonia water by 50 times of water;

3) under the stirring of 300rmp, slowly dropwise adding a 30% sodium methylsiliconate solution for modification, determining the pH value of the emulsion system to be 8, and stopping dropwise adding the sodium methylsiliconate solution;

4) maintaining the stirring at 300rmp, and after the sodium methylsiliconate is uniformly diffused in the gel particles, dropwise adding a diluted dilute hydrochloric acid solution to adjust the pH value of the emulsion system to 7; the hydrochloric acid solution is obtained by diluting hydrochloric acid with the mass concentration of 37% by 50 times of water;

5) repeatedly dripping 60 parts of sodium methylsiliconate aqueous solution and 5 parts of 0.1mol/L phosphoric acid solution in the same way;

6) under the stirring of 300rmp, when a proper amount of deionized water is dripped to cause the phase inversion of the emulsion, 10 parts of sodium trimethylsilanolate tetrahydrofuran solution with the concentration of 10 percent is dripped, and 0.01mol/L C mol is simultaneously dripped₈0.9 part of petroleum ether solution of organic fatty acid, and adjusting the pH value of an emulsion system to 7;

7) adding a proper amount of deionized water, further performing oil-water separation on an emulsion system, taking the upper suspension colloid, and drying in an oven at 100 ℃ under normal pressure for 2h to obtain the hydrophobic silica aerogel powder.

The prepared silica aerogel powder was examined, and the results are shown in table 1.

Example 3

1) Taking SiO₂200 parts of methyl orthosilicate with the concentration of 6 percent and cetyl trimethyl ammonium bromide 1 serving as a surfactantHeating 5 parts of span-80 of 0.5 part, oil phase kerosene of 300 parts and cosolvent n-butyl alcohol of 20 parts at 50 ℃, and stirring for 10min by a magnetic stirrer at 450 rmp;

2) dropwise adding the diluted ammonia water into the emulsion, stirring, adjusting the pH value to 6-7, standing for a period of time, gradually gelling the solution, and standing the emulsion for 24 hours; the ammonia water is obtained by diluting 28% ammonia water by 50 times of water;

3) under the stirring of 300rmp, slowly dropwise adding a 30% sodium methylsiliconate solution for modification, determining the pH value of the emulsion system to be 8, and stopping dropwise adding the sodium methylsiliconate solution;

4) maintaining the stirring at 300rmp, and after the sodium methylsiliconate is uniformly diffused in the gel particles, dropwise adding a diluted dilute hydrochloric acid solution to adjust the pH value of the emulsion system to 7; the hydrochloric acid solution is obtained by diluting hydrochloric acid with the mass concentration of 37% by 50 times of water;

5) repeatedly dropwise adding 40 parts of sodium methylsilanolate aqueous solution and 3.5 parts of 0.1mol/L hydrochloric acid solution in the way;

6) under the stirring of 300rmp, when a proper amount of deionized water is dripped to cause the phase inversion of the emulsion, 5 parts of sodium trimethylsilanolate tetrahydrofuran solution with the concentration of 10 percent is dripped, and 0.01mol/L C is simultaneously dripped₁₂0.6 part of petroleum ether solution of organic fatty acid, and adjusting the pH value of an emulsion system to 7;

7) adding a proper amount of deionized water, further performing oil-water separation on an emulsion system, taking the upper suspension colloid, and drying in an oven at 100 ℃ under normal pressure for 2h to obtain the hydrophobic silica aerogel powder.

The silica aerogel powder obtained was subjected to the examination, and the results obtained are shown in table 1.

Example 4

This example was prepared under the same conditions as example 3 except that SiO in the aqueous solution of the silicon source in this example was used₂The mass concentration of (2) is 14%.

The prepared silica aerogel powder was examined, and the results are shown in table 1.

TABLE 1 Performance test results of silica aerogel powders prepared in examples 1 to 4

Performance index	Example 1	Example 2	Example 3	Example 4
					Density, kg/m3	50	90	60	78
Thermal conductivity, W/m.k	0.031	0.027	0.020	0.045
					Contact angle, ° c	130	155	150	145

As can be seen from Table 1, the silica aerogel powder provided by the invention has excellent density, thermal insulation performance and hydrophobicity, and the density of the silica aerogel powder is 50-90 kg/m³Guide, leadThe thermal coefficient is 0.020-0.045W/m.K, and the contact angle can reach 130-155 degrees.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.