Modified silicon dioxide aerogel, preparation method thereof and cold insulation material

Abstract

The invention discloses modified silicon dioxide aerogel, a preparation method thereof and a cold insulation material, relates to the technical field of heat insulation materials, and aims to solve the problem of poor mechanical properties of silicon dioxide aerogel. The modified silicon dioxide aerogel comprises silicon dioxide particles and a polyhedral oligomeric silsesquioxane group, the polyhedral oligomeric silsesquioxane group is connected with the silicon dioxide particles through a silicon-oxygen-silicon bond. Wherein the range of the mass ratio of the polyhedral oligomeric silsesquioxane group to the silicon dioxide particles is 0.001 to 0.15.

Description

Technical Field

[0001] The present application relates to the technical field of thermal insulation materials, and in particular to a modified silica aerogel and a preparation method thereof, and a cold insulation material. Background Art

[0002] As a representative of clean energy, liquefied natural gas (LNG) has been widely used and developed. The flammable and explosive properties of LNG and the deep cold working conditions (e.g. -170℃) of the main LNG pipelines require that the cold insulation materials can effectively and economically protect the cold from being lost. Therefore, the use of heat insulation materials with excellent cold insulation performance is crucial for the construction of LNG long-distance pipelines.

[0003] Silicon dioxide (SiO 2 Aerogel has the advantages of excellent heat insulation and cold preservation, which makes silica aerogel felt, silica aerogel sheet, silica aerogel coating, etc. widely used in the fields of construction materials. However, silica aerogel has the problem of poor mechanical properties, which to some extent restricts the actual engineering application of silica aerogel. Summary of the invention

[0004] The purpose of the present application is to provide a modified silica aerogel and a preparation method thereof, and a cold-insulating material, in order to solve the problem of poor mechanical properties of silica aerogel.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a modified silica aerogel, comprising silica particles and cage-type polysilsesquioxane groups, wherein the cage-type polysilsesquioxane groups are connected to the silica particles via silicon-oxygen-silicon bonds, wherein the mass ratio of the cage-type polysilsesquioxane groups to the silica particles is in the range of 0.001 to 0.15.

[0007] The modified silica aerogel provided in the embodiment of the present application, firstly, includes a cage-type polysilsesquioxane group, which can effectively improve the skeleton strength of the silica aerogel without affecting the nano-mesoporous structure of the aerogel, and can improve the mechanical properties of the aerogel without affecting the cooling effect of the aerogel; secondly, the microstructure can be kept well, so that the modified silica aerogel has a lower thermal conductivity and a lower density, thereby making the modified silica aerogel have good cooling performance and can reduce the weight of the pipeline insulation layer; thirdly, the cage-type polysilsesquioxane used to prepare the modified silica aerogel has The raw material for forming cage-type polysilsesquioxane groups, which has the advantages of low cost, easy availability and good environmental performance, and cage-type polysilsesquioxanes having one or more silanol groups, can undergo condensation reaction between their own silanol groups and the silanol groups on the surface of silica particles, and the condensation reaction is easy to occur, which can improve the convenience of preparing modified silica aerogels. Fourthly, the cage-type polysilsesquioxanes used to prepare modified silica aerogels have hydrophobic groups themselves, which can reduce the water absorption performance of modified silica aerogels and extend the service life of modified silica aerogel materials.

[0008] In some embodiments, the substituent of the cage-type polysilsesquioxane group includes at least one of an alkyl group, a phenyl group, and a cyclopentyl group.

[0009] In some embodiments, the substituents of the cage-type polysilsesquioxane group include: a plurality of isobutyl groups.

[0010] In some embodiments, at room temperature, the thermal conductivity of the modified silica aerogel is in the range of 0.016 W / m·K to 0.023 W / m·K.

[0011] In some embodiments, at room temperature, the density of the modified silica aerogel is in the range of 0.08 g / cm 3 ~0.15g / cm.

[0012] In some embodiments, at room temperature, the hydrophobic angle of the modified silica aerogel is in the range of 133° to 142°.

[0013] In a second aspect, the present application provides a method for preparing a modified silica aerogel, comprising: using a first solvent, mixing and reacting a first silicon source with a second silicon source to obtain a modified silica sol; and converting the modified silica sol into a modified silica aerogel.

[0014] The first silicon source is used to form silica particles in the modified silica aerogel, and the second silicon source is used to form cage-type polysilsesquioxane groups in the modified silica aerogel; the surface of the silica particles includes hydroxyl groups connected to silicon atoms; the second silicon source includes hydroxyl groups connected to silicon atoms; in the modified silica aerogel, the mass ratio of cage-type polysilsesquioxane groups to silica particles is in the range of 0.001 to 0.15.

[0015] The above preparation method has the same beneficial technical effects as the modified silica aerogel provided in some of the above embodiments, and will not be described in detail here.

[0016] In some embodiments, the first silicon source includes tetraethyl orthosilicate.

[0017] In some embodiments, the second silicon source includes trisilanol isobutyl-cage polysilsesquioxane.

[0018] In some embodiments, the concentration of silica in the modified silica sol ranges from 5 wt % to 12 wt %.

[0019] In some embodiments, the mass ratio of the second silicon source to the silicon dioxide particles is in the range of 0.001 to 0.15.

[0020] In some embodiments, the first solvent includes water and anhydrous ethanol.

[0021] In some embodiments, the preparation method specifically includes: mixing a first silicon source and a second silicon source in a first solvent, and adjusting the pH to a first set pH value to obtain a first mixed liquid; stirring the first mixed liquid to obtain a modified silica sol; adjusting the pH of the modified silica sol to a second set pH value, and letting it stand to obtain a first gel; using an aging liquid to age the first gel to obtain a second gel; performing solvent replacement on the second gel to obtain a third gel; and drying the third gel to obtain a modified silica aerogel.

[0022] Among them, the drying process of the third gel includes: supercritical drying process; solvent replacement of the second gel includes: replacing water in the second gel with ethanol; or, the drying process of the third gel includes: normal pressure drying process; solvent replacement of the second gel includes: replacing water in the second gel with ethanol to obtain a fourth gel; and replacing ethanol in the fourth gel with n-hexane.

[0023] In some embodiments, the first set pH value ranges from 2.0 to 4.0.

[0024] In some embodiments, the stirring time of the first mixed solution ranges from 1 hour to 24 hours.

[0025] In some embodiments, the pH adjuster of the modified silica sol includes aqueous ammonia with a concentration ranging from 0.5 mol / L to 1 mol / L.

[0026] In some embodiments, the second set pH value ranges from 4.0 to 7.0.

[0027] In some embodiments, the standing temperature of the modified silica sol is in the range of 30°C to 80°C.

[0028] In some embodiments, the aging treatment time of the first gel ranges from 24 hours to 72 hours.

[0029] In some embodiments, the aging solution includes tetraethyl orthosilicate and anhydrous ethanol, and the concentration of tetraethyl orthosilicate in the aging solution ranges from 0.05 mol / L to 0.5 mol / L.

[0030] In some embodiments, the temperature range of the aging treatment of the first gel is 30°C to 180°C.

[0031] In some embodiments, during the process of replacing water in the second gel with ethanol, the number of replacements of ethanol ranges from 3 to 6 times.

[0032] In some embodiments, during the process of replacing water in the second gel with ethanol, the replacement frequency of ethanol ranges from 6 hours / time to 12 hours / time.

[0033] In some embodiments, when the drying process of the third gel comprises a supercritical drying process, the temperature ranges from 250° C. to 270° C. during the supercritical drying process.

[0034] In some embodiments, when the drying process of the third gel includes a supercritical drying process, the pressure ranges from 7 MPa to 9 MPa during the supercritical drying process.

[0035] In some embodiments, when the drying process of the third gel includes a supercritical drying process, during the supercritical drying process, the temperature and pressure holding time ranges from 0.5 h to 1 h.

[0036] In some embodiments, when the drying process of the third gel includes a normal pressure drying process, during the process of replacing ethanol in the fourth gel with n-hexane, the number of replacements of n-hexane ranges from 3 to 6 times.

[0037] In some embodiments, when the drying process of the third gel includes a normal pressure drying process, during the process of replacing ethanol in the fourth gel with n-hexane, the frequency of replacing n-hexane ranges from 6 hours / time to 12 hours / time.

[0038] In some embodiments, when the drying process of the third gel comprises a normal pressure drying process, the temperature ranges from 50° C. to 100° C. during the normal pressure drying process.

[0039] In some embodiments, when the drying process of the third gel includes a normal pressure drying process, during the normal pressure drying process, the drying time ranges from 8 hours to 24 hours.

[0040] In a third aspect, the present application provides a cold-keeping material. The cold-keeping material comprises: the modified silica aerogel as described in any of the above embodiments; or the cold-keeping material comprises: the modified silica aerogel obtained by the preparation method as described in any of the above embodiments.

[0041] The above-mentioned cold-insulating material has the same beneficial technical effects as the modified silica aerogel or the preparation method provided in some of the above-mentioned embodiments, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 This is a flow chart of a method for preparing a modified silica aerogel in some embodiments of the present application;

[0044] Figure 2 A physical picture of a modified silica aerogel prepared in some embodiments of the present application;

[0045] Figure 3 A scanning electron microscope image of the microscopic morphology of the skeleton and pores of a modified silica aerogel prepared in some embodiments of the present application;

[0046] Figure 4A A nitrogen adsorption-desorption curve diagram of a modified silica aerogel prepared in some embodiments of the present application;

[0047] Figure 4B A pore size distribution curve of a modified silica aerogel prepared in some embodiments of the present application;

[0048] Figure 5 A schematic diagram of the contact angle of a modified silica aerogel prepared in some embodiments of the present application;

[0049] Figure 6 The overall microscopic morphology of a modified silica aerogel prepared in some embodiments of the present application is shown in a scanning electron microscope image;

[0050] Figure 7 A diagram showing the compressive strength of a modified silica aerogel prepared in some embodiments of the present application. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0052] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0053] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. It can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0054] In the present application, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, article or device including the element.

[0055] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0056] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0057] Silica aerogel has a relatively low density (e.g., less than 0.05 g / cm 3 ), extremely low room temperature thermal conductivity (e.g. less than 0.02 W / m·K) and excellent thermal insulation and cold preservation properties make silica aerogel a thermal insulation material for long-distance LNG pipelines.

[0058] In some cases, SiO 2 In the aerogel, there is a neck region formed by weakly connecting the secondary particles with silicon-oxygen atomic bonds, which makes SiO 2 Aerogel materials are relatively brittle; in some cases, SiO 2 The bonding area between secondary particles in aerogels is small and the bonding force is limited, resulting in greater brittleness and lower strength of the bulk material; these factors may lead to poor mechanical properties (e.g., compressive resistance) of silica aerogels.

[0059] In some implementations, the silica aerogel is prepared by adding a prepolymer solution of isocyanate to a silicon source, stirring and mixing the mixture, and reacting to obtain SiO 2 Aerogel. In the above manner, the in-situ grafting modification of isocyanate can enhance the network structure of silica aerogel, reduce surface defects, and enhance the mechanical properties of silica aerogel.

[0060] In some other implementations, modified poly (butyl methacrylate-butyl acrylate) is added to the silica sol, and a modified silica aerogel with better mechanical properties and no loss of porosity is prepared by cross-linking of organic matter, so that the specific surface area of ​​the modified silica aerogel reaches 766m 2 / g, the average mesopore diameter reaches 11.5nm, and the compressive strength reaches 4.24MPa.

[0061] In some other implementations, polymethyl methacrylate (PMMA) modified SiO 2 Aerogel, after introducing PMMA through silane coupling agent, forms an organic cross-linked network, which enhances the strength of the gel skeleton. According to the test characterization, when the polymer monomer concentration reaches 50%, the hardness and Young's modulus of the aerogel are increased by 13.7 times and 15.1 times respectively compared with the unmodified aerogel.

[0062] It can be seen that the mechanical properties of silica aerogel can be effectively improved by introducing organic matter into silica aerogel for organic modification.

[0063] However, in the above implementation, the introduced organic matter (for example, isocyanate, or modified poly(butyl methacrylate-butyl acrylate)) has problems such as poor compatibility with silica sol and high solvent toxicity; moreover, when the silica aerogel is modified by the above method, there is a risk of poor control of cooling parameters such as thermal conductivity.

[0064] Based on this, some embodiments of the present application provide a modified silica aerogel to at least solve the problem of poor mechanical properties of silica aerogel. The modified silica aerogel comprises: silica particles and cage-type polysilsesquioxane groups; the cage-type polysilsesquioxane groups are connected to the silica particles through silicon-oxygen-silicon bonds.

[0065] In the related art, polyhedral oligomeric silsesquioxane (POSS) is a polyhedral oligomeric silsesquioxane having the general formula (RSiO 3 / 2 ) n A class of chemical substances, wherein n is a positive integer, and R is a group connected to the Si atom at the top corner. Cage-type polysilsesquioxane is a cage-shaped structure with nanometer size, and is an inorganic core composed of a silicon-oxygen skeleton alternately connected by Si-O. The group R connected to the Si atom at the top corner can be a reactive or inert group.

[0066] Here, the cage-type polysilsesquioxane group refers to a group remaining after removing one or more H from a cage-type polysilsesquioxane containing a hydroxyl group (-OH). It should be noted that the number of silicon (Si) atoms included in the cage-type polysilsesquioxane group is not limited here, for example, the number of silicon (Si) atoms included in the cage-type polysilsesquioxane group can be 7, 8 or 9, etc.

[0067] The above-mentioned cage-type polysilsesquioxane group is connected to the silica particles through silicon-oxygen-silicon bonds (Si-O-Si), which means that at least one silicon atom on the surface of the silica particle is connected to at least one silicon atom in the cage-type polysilsesquioxane group through an oxygen atom, so that the cage-type polysilsesquioxane group and the silica particles can be connected through one or more silicon-oxygen-silicon bonds (Si-O-Si).

[0068] It can be understood that, on the first aspect, by modifying the silica aerogel including the setting of cage-type polysilsesquioxane groups, POSS can be introduced into the silica aerogel system for organic modification. In this way, the skeleton strength of the silica aerogel can be effectively improved without affecting the nano-mesoporous structure of the aerogel. For example, the POSS group can be connected to the neck region of the gel particles to increase the neck strength, thereby improving the mechanical properties of the aerogel without affecting the cooling effect of the aerogel.

[0069] Secondly, the POSS group is used to modify the silica aerogel, and the microstructure of the modified silica aerogel can be kept well. The modified silica aerogel can have a complete gel network and a good nano-mesoporous structure, which can make the modified silica aerogel have a lower thermal conductivity (for example: 0.016 ~ 0.023W / m K) and a lower density (for example: 0.08g / cm 3 ~0.15g / cm 3 ), thereby making the modified silica aerogel have good cold-keeping performance and can reduce the weight of the pipeline insulation layer.

[0070] On the third aspect, the cage-type polysilsesquioxane used to prepare the modified silica aerogel belongs to a cost-effective organic silicon raw material, which has the advantages of low cost, easy to obtain and good environmental performance. Moreover, the raw material used to form the cage-type polysilsesquioxane group-a cage-type polysilsesquioxane with one or more (for example: three) silanol groups (Si-OH) can be condensed through the silanol groups (Si-OH) possessed by itself and the silanol groups (Si-OH) on the surface of the silica particles, and the condensation reaction is easy to occur, which can improve the preparation simplicity of the modified silica aerogel, and can achieve the rapid preparation of the modified silica aerogel, which can comply with the standards of energy conservation and emission reduction, economical and practical, and environmental protection. In addition, the cage-type polysilsesquioxane with one or more (for example: three) silanol groups (Si-OH) can be well soluble in conventional solvents such as ethanol, which further improves the preparation convenience of the modified silica aerogel. In this way, the modified silica aerogel can meet the requirements of aerospace and civil fields for heat insulation and cold preservation performance.

[0071] Fourthly, the cage-type polysilsesquioxane itself has a hydrophobic group, which can improve the hydrophobicity of the modified silica aerogel and reduce the water absorption performance of the modified silica aerogel, thereby extending the service life of the modified silica aerogel material.

[0072] In some embodiments, the mass ratio of the cage-type polysilsesquioxane groups to the silica particles is in the range of 0.001 to 0.15.

[0073] For example, the mass ratio of the cage-type polysilsesquioxane group to the silica particles can be 0.001, 0.01, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14 or 0.15, etc.

[0074] When the mass ratio of the cage-type polysilsesquioxane group to the silica particles is less than 0.001, the cage-type polysilsesquioxane group has a poor effect on improving the mechanical properties of the modified silica aerogel; when the mass ratio of the cage-type polysilsesquioxane group to the silica particles is greater than 0.15, the strength of the main silicon oxygen skeleton of the modified silica aerogel may be reduced, which in turn reduces the mechanical properties of the modified silica aerogel. Therefore, through the above-mentioned setting, the mass ratio of the cage-type polysilsesquioxane group to the silica particles can be within a suitable range, the mechanical properties of the modified silica aerogel can be improved, and the microstructure of the modified silica aerogel can be kept better, so that the modified silica aerogel has good cold-keeping performance and can reduce the weight of the pipeline insulation layer.

[0075] In some embodiments, the substituent of the cage-type polysilsesquioxane group includes at least one of an alkyl group, a phenyl group, and a cyclopentyl group.

[0076] Both phenyl and cyclopentyl have certain stereo configurations. When the substituents of the cage-type polysilsesquioxane group include phenyl and / or cyclopentyl, the modified silica aerogel can have lower thermal conductivity and lower density, and the modified silica aerogel has good cold-keeping performance, which can reduce the weight of the pipeline insulation layer.

[0077] The alkyl group has the advantage of good hydrophobicity. When the substituent of the cage-type polysilsesquioxane group includes an alkyl group, the cage-type polysilsesquioxane group has good hydrophobicity, which can further reduce the water absorption performance of the modified silica aerogel and extend the service life of the modified silica aerogel material.

[0078] In some embodiments, the substituents of the cage-type polysilsesquioxane group include: a plurality of isobutyl groups.

[0079] Illustratively, the substituents of the cage-type polysilsesquioxane group include: seven isobutyl groups.

[0080] The isobutyl group has the advantage of good hydrophobicity, which can reduce the water absorption performance of the modified silica aerogel; moreover, the isobutyl group has a certain stereo configuration, which can make the modified silica aerogel have lower thermal conductivity and lower density, so that the modified silica aerogel has good cold-keeping performance and can reduce the weight of the pipeline insulation layer. In addition, when the substituents of the cage-type polysilsesquioxane group include seven isobutyl groups, the cage-type polysilsesquioxane used to form the cage-type polysilsesquioxane group can be trisilanol isobutyl-cage-type polysilsesquioxane, which can enhance the improvement effect of the formed cage-type polysilsesquioxane group on the mechanical properties and hydrophobic properties of the modified silica aerogel compared to other POSS materials.

[0081] In some embodiments, at room temperature, the thermal conductivity of the modified silica aerogel is in the range of 0.016 W / m·K to 0.023 W / m·K.

[0082] Illustratively, at room temperature, the thermal conductivity of the modified silica aerogel can be 0.016 W / m·K, 0.017 W / m·K, 0.018 W / m·K, 0.019 W / m·K, 0.020 W / m·K, 0.021 W / m·K, 0.022 W / m·K or 0.023 W / m·K, etc.

[0083] Through the above arrangement, the thermal conductivity of the modified silica aerogel is within a relatively low range, which enables the modified silica aerogel to have good cold-keeping performance.

[0084] In some embodiments, at room temperature, the density of the modified silica aerogel is in the range of 0.08 g / cm 3 ~0.15g / cm.

[0085] For example, at room temperature, the density of the modified silica aerogel can be 0.08 g / cm 3 , 0.09g / cm 3 , 0.10g / cm 3 , 0.11g / cm 3 , 0.12g / cm 3 , 0.13g / cm 3 , 0.14g / cm 3 Or 0.15g / cm, etc.

[0086] Through the above arrangement, the density of the modified silica aerogel is within a relatively low range, so that the modified silica aerogel can have a relatively low weight, and the weight of the pipeline insulation layer can be reduced.

[0087] In some embodiments, at room temperature, the hydrophobic angle of the modified silica aerogel is in the range of 133° to 142°.

[0088] For example, at room temperature, the hydrophobic angle of the modified silica aerogel can be 133°, 134°, 135°, 136°, 137°, 138°, 139°, 140°, 141° or 142°, etc.

[0089] Through the above arrangement, the modified silica aerogel has excellent hydrophobicity, which can reduce the water absorption performance of the modified silica aerogel, thereby extending the service life of the modified silica aerogel material.

[0090] Some embodiments of the present application also provide a method for preparing a modified silica aerogel. Figure 1As shown, the preparation method includes S1 to S2.

[0091] S1: using a first solvent, mixing and reacting a first silicon source with a second silicon source to obtain a modified silica sol.

[0092] S2: Converting the modified silica sol into modified silica aerogel.

[0093] The first silicon source is used to form silica particles in the modified silica aerogel, and the second silicon source is used to form cage-type polysilsesquioxane groups in the modified silica aerogel; the surface of the silica particles includes hydroxyl groups connected to silicon atoms; the second silicon source includes hydroxyl groups connected to silicon atoms; in the modified silica aerogel, the mass ratio of cage-type polysilsesquioxane groups to silica particles is in the range of 0.001 to 0.15.

[0094] The above preparation method has the same beneficial technical effects as the modified silica aerogel provided in some of the above embodiments, and will not be described in detail here.

[0095] In some embodiments, the first silicon source includes tetraethyl orthosilicate (TEOS).

[0096] Tetraethyl orthosilicate is a cost-effective organic silicon raw material with the advantages of low cost, easy availability and good environmental performance. By setting up the first silicon source including tetraethyl orthosilicate, the preparation cost of modified silica aerogel can be reduced to a certain extent, which can comply with the standards of energy conservation and emission reduction, economy and practicality, and environmental protection.

[0097] In some embodiments, the second silicon source includes trisilanol isobutyl-cage polysilsesquioxane.

[0098] Through the above-mentioned setting, compared with other POSS materials, the improvement effect of the formed cage-shaped polysilsesquioxane groups on the mechanical properties and hydrophobic properties of the modified silica aerogel can be enhanced.

[0099] In some embodiments, the concentration of silica in the modified silica sol ranges from 5 wt % to 12 wt %.

[0100] For example, the concentration of silica in the modified silica sol may be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt% or 12 wt%, etc.

[0101] When the concentration of silica in the modified silica sol is less than 5wt%, the skeleton strength of the formed modified silica aerogel becomes low, making the mechanical properties of the modified silica aerogel poor; when the concentration of silica in the modified silica sol is greater than 12wt%, the gel network of the formed modified silica aerogel is denser, which will reduce the porosity of the modified silica aerogel and affect its cold-keeping effect. Therefore, through the above settings, the concentration of silica in the modified silica sol is within a suitable range, which can improve the mechanical properties and cold-keeping properties of the modified silica aerogel.

[0102] In some embodiments, the mass ratio of the second silicon source to the silicon dioxide particles is in a range of 0.001 to 0.15.

[0103] Illustratively, the mass ratio of the second silicon source to the silicon dioxide particles can be 0.001, 0.01, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14 or 0.15, etc.

[0104] When the mass ratio of the second silicon source to the silica particles is less than 0.001, the cage-type polysilsesquioxane group has a poor effect on improving the mechanical properties of the modified silica aerogel; when the mass ratio of the second silicon source to the silica particles is greater than 0.15, the strength of the main silicon-oxygen skeleton of the modified silica aerogel may be reduced, which in turn reduces the mechanical properties of the modified silica aerogel. Therefore, through the above-mentioned setting, the mass ratio of the second silicon source to the silica particles can be within a suitable range, the mechanical properties of the modified silica aerogel can be improved, and the microstructure of the modified silica aerogel can be kept better, so that the modified silica aerogel has good cold-keeping performance and can reduce the weight of the pipeline insulation layer.

[0105] In some embodiments, the first solvent includes water and anhydrous ethanol.

[0106] Water and anhydrous ethanol are both non-toxic and easily available. By setting the first solvent to include water and anhydrous ethanol, the preparation cost of the modified silica aerogel can be reduced to a certain extent, and the environmental friendliness of the preparation method of the modified silica aerogel can be improved.

[0107] In some embodiments, the preparation method specifically includes R1~R6.

[0108] R1: Mixing the first silicon source and the second silicon source in a first solvent, and adjusting the pH to a first set pH value to obtain a first mixed solution.

[0109] Exemplarily, R1 is performed at room temperature.

[0110] Exemplarily, 4 mol / L hydrochloric acid is added to the solution to adjust the pH to a first set pH value to achieve an acidic hydrolysis effect.

[0111] It should be understood that when adjusting the pH, the amount of acid added is relatively small. When the concentration of hydrochloric acid used is greater than 4 mol / L, it is easy to add too much acid, which may cause the hydrolysis environment to be too acidic; when the concentration of hydrochloric acid used is less than 4 mol / L, the amount of acid added for hydrolysis is relatively large, and more water will be introduced when adding hydrochloric acid, which may affect the silicon content of the precursor solution. Therefore, through the above settings, it is possible to avoid the hydrolysis environment being too acidic, and it is also possible to avoid the effect of acid addition on the silicon content of the precursor solution.

[0112] Exemplarily, the first set pH value ranges from 2.0 to 4.0; for example, the first set pH value may be 2.0, 2.5, 3.0, 3.5 or 4.0, etc.

[0113] When the first set pH value is less than 2, the hydrolysis environment may be too acidic, making the formed sol particles smaller and affecting the subsequent gelation process; when the first set pH value is greater than 4, a suitable acidic hydrolysis environment cannot be formed, the hydrolysis reaction rate is reduced, and the precursor hydrolysis is incomplete, affecting the subsequent process. Therefore, through the above settings, the first mixed liquid is an acidic solvent, and the pH value is within a suitable range, which is conducive to forming a suitable acidic hydrolysis environment to form a uniform sol.

[0114] R2: Stirring the first mixed solution to obtain a modified silica sol.

[0115] Exemplarily, R2 is performed at room temperature.

[0116] Exemplarily, the stirring time of the first mixed liquid ranges from 1 hour to 24 hours; for example, the stirring time of the first mixed liquid can be 1 hour, 4 hours, 7 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours or 24 hours, etc.

[0117] By setting in this way, the first silicon source and the second silicon source can fully react, which is beneficial to improving the yield of modified silica aerogel.

[0118] Illustratively, the pH adjuster of the modified silica sol includes aqueous ammonia in a concentration range of 0.5 mol / L to 1 mol / L; for example, the concentration of aqueous ammonia included in the pH adjuster of the modified silica sol can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L, etc.

[0119] Ammonia water can be used to make the modified silica sol reach an appropriate gel environment. Moreover, when the concentration of ammonia water is less than 0.5 mol / L, more ammonia water needs to be added to achieve an alkaline environment suitable for gelation, thereby introducing more water, which will reduce the overall solid content of the modified silica aerogel; when the concentration of ammonia water is greater than 1 mol / L, it may cause the local solution environment to be too alkaline, resulting in local gelation, resulting in poor gelation effect. Therefore, through the above settings, the concentration of ammonia water can be within a suitable range, and local gelation can be avoided on the basis of ensuring the overall solid content of the modified silica aerogel, so as to improve the gelation effect.

[0120] R3: The pH of the modified silica sol is adjusted to a second set pH value and allowed to stand to obtain a first gel.

[0121] Exemplarily, the second set pH value ranges from 4.0 to 7.0; for example, the second set pH value may be 4.0, 4.5, 5.0, 5.6, 6.0, 6.5 or 7.0, etc.

[0122] By setting in this way, the pH of the modified silica sol can be within an appropriate range, which is beneficial to the gelation reaction of the modified silica sol.

[0123] Illustratively, the standing temperature range of the modified silica sol is 30°C to 80°C; for example, the standing temperature of the modified silica sol can be 30°C, 35°C, 40°C, 45°C, 50°C, 56°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc.

[0124] When the standing temperature of the modified silica sol is less than 30°C, the gelation time is too long, which is not conducive to process production; when the standing temperature of the modified silica sol is greater than 80°C, the gelation time is too short, making the internal structure of the formed gel uneven, which will affect the macroscopic properties of the modified silica aerogel. Therefore, through the above settings, the standing temperature of the modified silica sol can be kept within a suitable range, which can improve the feasibility of process production while ensuring the macroscopic properties of the modified silica aerogel.

[0125] R4: Using an aging solution, the first gel is aged to obtain a second gel.

[0126] Exemplarily, the aging treatment time of the first gel ranges from 24 hours to 72 hours; for example, the aging treatment time of the first gel can be 24 hours, 36 hours, 48 ​​hours, 62 hours or 72 hours, etc.

[0127] Exemplarily, the aging liquid includes tetraethyl orthosilicate and anhydrous ethanol, and the concentration range of tetraethyl orthosilicate in the aging liquid is 0.05 mol / L to 0.5 mol / L; for example, the concentration of tetraethyl orthosilicate in the aging liquid can be 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, 0.25 mol / L, 0.30 mol / L, 0.35 mol / L, 0.40 mol / L or 0.5 mol / L, etc.

[0128] When the concentration of tetraethyl orthosilicate in the aging solution is lower than 0.05 mol / L, the skeleton cannot be sufficiently strengthened during the gel aging process, resulting in a low strength of the formed aerogel; when the concentration of tetraethyl orthosilicate in the aging solution is higher than 0.5 mol / L, excessive TEOS will increase the number of cluster structures inside the gel during the aging process, affecting the uniformity of the gel microstructure. Therefore, through the above settings, the concentration of tetraethyl orthosilicate in the aging solution can be within a suitable range, the best aging effect can be achieved, and the influence of TEOS on the uniformity of the gel microstructure can be avoided.

[0129] Exemplarily, the temperature range of the aging treatment of the first gel is 30°C to 180°C; for example, the temperature of the aging treatment of the first gel can be 30°C, 50°C, 70°C, 90°C, 100°C, 120°C, 140°C, 160°C or 180°C, etc.

[0130] When the temperature of the aging treatment of the first gel is lower than 30°C, the reaction rate inside the gel is slow, which affects the aging effect; when the temperature of the aging treatment of the first gel is higher than 180°C, the reaction rate inside the gel is too fast, which will cause the internal structure of the gel to be destroyed and affect the uniformity of the gel. Therefore, through the above settings, the temperature of the aging treatment of the first gel can be within a suitable range, the best aging effect can be achieved, and the influence of the aging treatment on the uniformity of the microstructure of the gel can be avoided.

[0131] R5: Perform solvent replacement on the second gel to obtain the third gel.

[0132] R6: Drying the third gel to obtain modified silica aerogel.

[0133] In some examples, in R6, the drying process of the third gel includes: a supercritical drying process. At this time, performing solvent replacement on the second gel (ie, R5) includes R5A.

[0134] R5A: Replace the water in the second gel with ethanol.

[0135] Illustratively, in the process of replacing water in the second gel with ethanol, the number of replacements of ethanol ranges from 3 to 6 times; for example, the number of replacements of ethanol may be 3, 4, 5 or 6 times.

[0136] When the number of ethanol replacements is less than 3 times, there are still other solvents remaining inside the gel, which may cause problems such as block fragmentation due to the difference in internal and external solvents during drying (for example, supercritical drying); when the number of ethanol replacements is more than 6 times, the overall time of solvent replacement will be extended and the efficiency of solvent replacement will be reduced. Therefore, through the above settings, the solvent replacement efficiency can be improved to achieve the best solvent replacement effect and prepare for subsequent drying; and problems such as block fragmentation during the drying process can be avoided.

[0137] Illustratively, in the process of replacing water in the second gel with ethanol, the replacement frequency of ethanol ranges from 6 hours / time to 12 hours / time; for example, the replacement frequency of ethanol can be 6 hours / time, 8 hours / time, 9 hours / time, 10 hours / time or 12 hours / time, etc.

[0138] When the frequency of ethanol replacement is less than 6 hours / time, the gel cannot be fully replaced with solvents inside and outside, resulting in low solvent replacement efficiency; when the frequency of ethanol replacement is more than 12 hours / time, the overall time of solvent replacement will be extended, reducing the efficiency of solvent replacement. Therefore, through the above settings, the solvent replacement efficiency can be improved to achieve the best solvent replacement effect and prepare for subsequent drying.

[0139] Exemplarily, when the drying process of the third gel includes a supercritical drying process, the temperature ranges from 250°C to 270°C during the supercritical drying process; for example, the temperature may be 250°C, 255°C, 260°C, 265°C or 270°C, etc.

[0140] When the temperature is lower than 250°C during supercritical drying, ethanol may not reach a supercritical state, resulting in drying failure; when the temperature is higher than 270°C during supercritical drying, the temperature will exceed the temperature that the second silicon source (POSS material) can withstand for thermal decomposition, resulting in damage to the internal structure of the gel. Therefore, through the above settings, the drying process can be prevented from affecting the internal structure of the gel while ensuring the drying effect.

[0141] Illustratively, when the drying process of the third gel includes a supercritical drying process, during the supercritical drying process, the pressure ranges from 7 MPa to 9 MPa; for example, the pressure may be 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa or 9 MPa, etc.

[0142] If the pressure is less than 7MPa during supercritical drying, the ethanol will not reach the supercritical state, making the drying ineffective; if the pressure is greater than 9MPa during supercritical drying, the internal pressure of the supercritical container will be too high, causing the sample to break and posing a safety risk. Therefore, through the above settings, the drying effect can be guaranteed while avoiding the influence of the drying process on the internal structure of the gel and improving the operational safety.

[0143] Exemplarily, when the drying process of the third gel includes a supercritical drying process, during the supercritical drying process, the heat preservation and pressure holding time range is 0.5h to 1h; for example: the heat preservation and pressure holding can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h or 1h, etc.

[0144] If the heat preservation and pressure holding time during the supercritical drying process is less than 0.5h, the supercritical drying process will be too short, so that the third gel is not completely dried; if the heat preservation and pressure holding time during the supercritical drying process is more than 1h, it will exceed the time required for the supercritical drying step, which will waste unnecessary resources and increase costs. Therefore, through the above settings, it is possible to avoid waste of resources while ensuring the drying effect.

[0145] In some other examples, in R6, the drying process of the third gel includes: a normal pressure drying process. At this time, the solvent replacement of the second gel (ie, R5) includes R5.1 to R5.2.

[0146] R5.1: Replace the water in the second gel with ethanol to obtain the fourth gel.

[0147] Here, regarding the understanding of replacing water with ethanol (including but not limited to the number of times ethanol is replaced, the frequency of ethanol replacement, etc.), please refer to the above content and will not be repeated here.

[0148] R5.2: Replace the ethanol in the fourth gel with n-hexane.

[0149] Exemplarily, when the drying process of the third gel includes a normal pressure drying process, in the process of replacing ethanol in the fourth gel with n-hexane, the number of times the n-hexane is replaced ranges from 3 to 6 times; for example: the number of times the n-hexane is replaced is 3 times, 4 times, 5 times or 6 times, etc.

[0150] When the number of times the n-hexane is replaced is less than 3 times, there are still other solvents remaining inside the gel, which may cause problems such as block fragmentation due to the strong capillary force when the internal solvent evaporates during drying (for example, normal pressure drying); when the number of times the n-hexane is replaced is more than 6 times, the overall time of solvent replacement will be extended and the efficiency of solvent replacement will be reduced. Therefore, through the above settings, the solvent replacement efficiency can be improved to achieve the best solvent replacement effect and prepare for subsequent drying; and problems such as block fragmentation during the drying process can be avoided.

[0151] Illustratively, when the drying process of the third gel includes a normal pressure drying process, in the process of replacing ethanol in the fourth gel with n-hexane, the replacement frequency of n-hexane ranges from 6 hours / time to 12 hours / time; for example: the replacement frequency of n-hexane can be 6 hours / time, 8.5 hours / time, 9 hours / time, 10 hours / time or 12 hours / time, etc.

[0152] When the frequency of changing n-hexane is less than 6 hours / time, the gel cannot be fully replaced with solvent inside and outside, resulting in low solvent replacement efficiency; when the frequency of changing n-hexane is more than 12 hours / time, the overall time of solvent replacement will be prolonged, reducing the efficiency of solvent replacement. Therefore, through the above settings, the solvent replacement efficiency can be improved to achieve the best solvent replacement effect and prepare for subsequent drying.

[0153] Exemplarily, when the drying process of the third gel includes a normal pressure drying process, the temperature range is 50°C to 100°C during the normal pressure drying process; for example, the temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 96°C or 100°C, etc.

[0154] When the temperature is lower than 50°C during the normal pressure drying process, the volatilization rate of n-hexane is slow and the drying efficiency is low; when the temperature is higher than 100°C during the normal pressure drying process, the volatilization rate of n-hexane is too fast, resulting in the collapse of the internal structure of the modified silica aerogel. Therefore, through the above settings, the influence of the drying process on the internal structure of the modified silica aerogel can be avoided while ensuring the drying efficiency.

[0155] Exemplarily, when the drying process of the third gel includes a normal pressure drying process, during the normal pressure drying process, the drying time ranges from 8h to 24h; for example, the drying time can be 8h, 12h, 16h, 20h, 22h or 24h, etc.

[0156] When the atmospheric pressure drying time is less than 8 hours, the drying time is too short, which will result in residual solvent inside the modified silica aerogel; when the atmospheric pressure drying time is more than 24 hours, it will exceed the time required for the atmospheric pressure drying step, which will waste unnecessary resources and increase costs. Therefore, through the above settings, it is possible to avoid waste of resources while ensuring the drying effect.

[0157] The present application also provides a cold-keeping material. The cold-keeping material includes: the modified silica aerogel as described in any of the above embodiments; or, the cold-keeping material includes: the modified silica aerogel obtained by the preparation method as described in any of the above embodiments.

[0158] Exemplarily, the above-mentioned cold insulation material can be silica aerogel felt, silica aerogel sheet or silica aerogel coating, etc.

[0159] Exemplarily, the above-mentioned cold insulation material is a cold insulation material used in LNG long-distance pipelines.

[0160] The above-mentioned cold-insulating material has the same beneficial technical effects as the modified silica aerogel or the preparation method provided in some of the above-mentioned embodiments, which will not be described in detail here.

[0161] The following are examples of modified silica aerogels and preparation methods thereof provided in the present application.

[0162] Example 1

[0163] In this embodiment, modified silica aerogel is prepared, and the preparation method includes U1 to U5.

[0164] U1: The concentration of silica in the modified silica sol is set to 6wt%. TEOS and trisilanol isobutyl-cage polysilsesquioxane (the mass ratio of trisilanol isobutyl-cage polysilsesquioxane to silica particles is 0.05) are added to deionized water and anhydrous ethanol, and stirred and mixed, and then hydrochloric acid is added to adjust the pH to 2.5, and stirred for 5 hours at room temperature to make it uniformly mixed to obtain a modified silica sol.

[0165] U2: Ammonia water with a concentration of 0.5 mol / L was added to the modified silica sol obtained in U1 to adjust the pH value to 6, and the gel was allowed to stand at 60°C.

[0166] U3: An aging solution with a concentration of 0.40 mol / L was prepared using anhydrous ethanol and TEOS. The wet gel obtained in U2 was placed in the aging solution and aged for 72 h at 60°C.

[0167] U4: Use ethanol to replace the solvent of the wet gel obtained in U3, replace the ethanol every 8 hours, and replace it 3 times.

[0168] U5: The wet gel obtained in U4 was subjected to supercritical ethanol drying. The temperature in the supercritical drying kettle was 250°C and the pressure was 7 MPa. The temperature and pressure were maintained for 0.5 h and then the pressure was released to obtain modified silica aerogel. The mass ratio of trisilanol isobutyl-cage-shaped polysilsesquioxane groups to silica particles was 0.05.

[0169] The modified silica aerogel obtained in this example was tested as follows:

[0170] (1) Appearance test, the results are as follows Figure 2 As shown, it shows that the appearance is intact; (2) Microscopic morphology test, the results are as follows Figure 3 As shown in the figure, the internal microstructure of the modified silica aerogel is a porous structure formed by the accumulation of spherical nanoparticles; (3) At room temperature, the density is 0.097 g / cm 3 ; (4) At room temperature, the specific surface area is 854.2m 2 / g; (5) room temperature thermal conductivity is 0.021 W / m·K; (6) compressive strength is 0.024 MPa (10% strain); (7) hydrophobic angle is 133.8°.

[0171] Example 2

[0172] In this embodiment, modified silica aerogel is prepared, and the preparation method includes V1 to V5.

[0173] V1: The concentration of silica in the modified silica sol is set to 6wt%. TEOS and trisilanol isobutyl-cage polysilsesquioxane (the mass ratio of trisilanol isobutyl-cage polysilsesquioxane to silica particles is 0.09) are added to deionized water and anhydrous ethanol, and stirred and mixed, and then hydrochloric acid is added to adjust the pH to 3, and stirred for 4 hours at room temperature to make it uniformly mixed to obtain a modified silica sol.

[0174] V2: Ammonia water with a concentration of 0.7 mol / L was added to the modified silica sol obtained in V1 to adjust the pH value to 6, and the gel was allowed to stand at 65°C.

[0175] V3: An aging solution with a concentration of 0.25 mol / L was prepared using anhydrous ethanol and TEOS. The wet gel obtained from V2 was placed in the aging solution and aged for 48 h at 65°C.

[0176] V4: Use ethanol to replace the solvent of the wet gel obtained in V3, replace the ethanol every 8 hours, and replace it 4 times.

[0177] V5: The wet gel obtained in V4 was subjected to supercritical drying with ethanol. The temperature in the supercritical drying kettle was 260°C and the pressure was 9 MPa. After maintaining the temperature and pressure for 1 hour, the pressure was released to obtain modified silica aerogel. The mass ratio of trisilanol isobutyl-cage-shaped polysilsesquioxane groups to silica particles was 0.09.

[0178] The modified silica aerogel obtained in this example was tested as follows:

[0179] (1) Appearance test: the results show that the appearance is intact; (2) Micromorphology test: the results show that the internal microstructure of the modified silica aerogel is a porous structure formed by the accumulation of spherical nanoparticles; (3) At room temperature, the density is 0.086 g / cm 3 ; (4) At room temperature, the specific surface area is 1280.9m 2 / g; (5) Nitrogen adsorption-desorption curve and pore size distribution measurement, the results are as follows Figure 4A and Figure 4B As shown; (6) room temperature thermal conductivity is 0.021W / m·K; (7) compressive strength is 0.023MPa (10% strain); (8) hydrophobic angle is 141.1°, as shown Figure 5 shown.

[0180] Example 3

[0181] In this embodiment, modified silica aerogel is prepared, and the preparation method includes P1 to P5.

[0182] P1: The concentration of silica in the modified silica sol is set to 8wt%. TEOS and trisilanol isobutyl-cage polysilsesquioxane (the mass ratio of trisilanol isobutyl-cage polysilsesquioxane to silica particles is 0.05) are added to deionized water and anhydrous ethanol, and stirred and mixed, and then hydrochloric acid is added to adjust the pH to 2.7, and stirred for 5 hours at room temperature to make it uniformly mixed to obtain a modified silica sol.

[0183] P2: Ammonia water with a concentration of 0.5 mol / L was added to the modified silica sol obtained in P1 to adjust the pH value to 5.5, and the gel was allowed to stand at 60°C.

[0184] P3: An aging solution with a concentration of 0.30 mol / L was prepared using anhydrous ethanol and TEOS. The wet gel obtained in P2 was placed in the aging solution and aged for 48 h at 60°C.

[0185] P4: The wet gel obtained in P3 was subjected to solvent replacement with ethanol, and the ethanol was replaced every 8 hours for 3 times. However, the wet gel subjected to ethanol solvent replacement was subjected to solvent replacement with n-hexane, and the n-hexane was replaced every 7 hours for 4 times.

[0186] P5: The wet gel obtained in P4 was dried at normal pressure at 60°C for 12 h to obtain a modified silica aerogel, wherein the mass ratio of trisilanol isobutyl-cage polysilsesquioxane groups to silica particles was 0.05.

[0187] The modified silica aerogel obtained in this example was tested as follows:

[0188] (1) Appearance test: the results show that the appearance is relatively intact; (2) Microscopic morphology test: the results are as follows Figure 6 As shown in the figure, the internal microstructure of the modified silica aerogel is a porous structure formed by the accumulation of spherical nanoparticles, and the overall skeleton remains intact; (3) At room temperature, the density is 0.129 g / cm 3 ; (4) The room temperature thermal conductivity is 0.023 W / m·K; (5) The compressive strength is 0.061 MPa (10% strain); (6) The hydrophobic angle is 138°.

[0189] Example 4

[0190] In this embodiment, modified silica aerogel is prepared, and the preparation method includes M1 to M5.

[0191] M1: The concentration of silica in the modified silica sol is set to 8wt%. TEOS and trisilanol isobutyl-cage polysilsesquioxane (the mass ratio of trisilanol isobutyl-cage polysilsesquioxane to silica particles is 0.07) are added to deionized water and anhydrous ethanol, and stirred and mixed, and then hydrochloric acid is added to adjust the pH to 3, and stirred for 4 hours at room temperature to make it uniformly mixed to obtain a modified silica sol.

[0192] M2: Ammonia water with a concentration of 0.8 mol / L was added to the modified silica sol obtained in M1 to adjust the pH value to 5.7, and the gel was allowed to stand at 60°C.

[0193] M3: An aging solution with a concentration of 0.25 mol / L was prepared using anhydrous ethanol and TEOS. The wet gel obtained in M2 was placed in the aging solution and aged for 72 h at 55°C.

[0194] M4: The wet gel obtained in M3 was subjected to solvent replacement with ethanol, and the ethanol was replaced every 8 hours for 4 times. However, the wet gel subjected to ethanol solvent replacement was subjected to solvent replacement with n-hexane, and the n-hexane was replaced every 7 hours for 3 times.

[0195] M5: The wet gel obtained in M4 was dried at normal pressure at 70°C for 14 h to obtain a modified silica aerogel, wherein the mass ratio of trisilanol isobutyl-cage-shaped polysilsesquioxane groups to silica particles was 0.07.

[0196] The modified silica aerogel obtained in this example was tested as follows:

[0197] (1) Appearance test: the results show that the appearance is relatively intact; (2) Microscopic morphology test: the results show that the internal microstructure of the modified silica aerogel is a porous structure formed by the accumulation of spherical nanoparticles; (3) At room temperature, the density is 0.124 g / cm 3 ; (4) The room temperature thermal conductivity is 0.022W / m·K; (5) The compressive strength test results are as follows Figure 7 As shown, the compressive strength is 0.083 MPa (10% strain); (6) the hydrophobic angle is 140°.

[0198] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A modified silica aerogel, characterized in that: The method comprises: silicon dioxide particles and cage-type polysilsesquioxane groups; the cage-type polysilsesquioxane groups are connected to the silicon dioxide particles through silicon-oxygen-silicon bonds; Wherein, the mass ratio of the cage-type polysilsesquioxane group to the silica particles is in the range of 0.001 to 0.

15.

2. The modified silica aerogel according to claim 1, characterized in that The substituent of the cage-type polysilsesquioxane group includes at least one of an alkyl group, a phenyl group and a cyclopentyl group.

3. The modified silica aerogel according to claim 1, characterized in that The substituents of the cage-type polysilsesquioxane group include: a plurality of isobutyl groups.

4. The modified silica aerogel according to any one of claims 1 to 3, characterized in that At room temperature, the thermal conductivity of the modified silica aerogel is in the range of 0.016 W / m·K to 0.023 W / m·K; and / or, At room temperature, the density of the modified silica aerogel is in the range of 0.08 g / cm 3 ~0.15g / cm 3 and / or, Under room temperature conditions, the hydrophobic angle of the modified silica aerogel ranges from 133° to 142°.

5. A method for preparing modified silica aerogel, characterized in that: include: Using a first solvent, mixing and reacting a first silicon source with a second silicon source to obtain a modified silica sol; converting the modified silica sol into a modified silica aerogel; Wherein, the first silicon source is used to form the silica particles in the modified silica aerogel, and the second silicon source is used to form the cage-type polysilsesquioxane groups in the modified silica aerogel; the surface of the silica particles includes hydroxyl groups connected to silicon atoms; the second silicon source includes hydroxyl groups connected to silicon atoms; In the modified silica aerogel, the mass ratio of the cage-type polysilsesquioxane group to the silica particles is in the range of 0.001 to 0.

15.

6. The method for preparing modified silica aerogel according to claim 5, characterized in that: The first silicon source comprises tetraethyl orthosilicate; and / or, The second silicon source comprises trisilanol isobutyl-cage polysilsesquioxane; and / or, The concentration of the silicon dioxide in the modified silicon dioxide sol is in the range of 5wt% to 12wt%; and / or, The mass ratio of the second silicon source to the silicon dioxide particles is in the range of 0.001 to 0.15; and / or, The first solvent includes water and anhydrous ethanol.

7. The method for preparing modified silica aerogel according to claim 5 or 6, characterized in that: The preparation method specifically comprises: Mixing the first silicon source and the second silicon source in the first solvent, and adjusting the pH to a first set pH value to obtain a first mixed solution; Stirring the first mixed liquid to obtain the modified silica sol; The pH of the modified silica sol is adjusted to a second set pH value, and allowed to stand to obtain a first gel; Using an aging solution, aging the first gel to obtain a second gel; performing solvent replacement on the second gel to obtain a third gel; Drying the third gel to obtain the modified silica aerogel; Wherein, the drying process of the third gel comprises: a supercritical drying process; the solvent replacement of the second gel comprises: replacing water in the second gel with ethanol; or, The drying process of the third gel includes: a normal pressure drying process; the solvent replacement of the second gel includes: replacing water in the second gel with ethanol to obtain a fourth gel; and replacing ethanol in the fourth gel with n-hexane.

8. The method for preparing modified silica aerogel according to claim 7, characterized in that: The first set pH value ranges from 2.0 to 4.0; and / or, The stirring time of the first mixed solution ranges from 1 hour to 24 hours; and / or, The pH regulator of the modified silica sol includes aqueous ammonia with a concentration range of 0.5 mol / L to 1 mol / L; and / or, The second set pH value ranges from 4.0 to 7.0; and / or, The standing temperature of the modified silica sol is in the range of 30°C to 80°C; and / or, The aging treatment time of the first gel ranges from 24 hours to 72 hours; and / or, The aging solution comprises tetraethyl orthosilicate and anhydrous ethanol, and the concentration of tetraethyl orthosilicate in the aging solution is in the range of 0.05 mol / L to 0.5 mol / L; and / or, The temperature range of the aging treatment of the first gel is 30° C. to 180° C.; and / or, In the process of replacing the water in the second gel with ethanol, the number of replacements of ethanol ranges from 3 to 6 times; and / or, In the process of replacing the water in the second gel with ethanol, the replacement frequency of ethanol is in the range of 6 hours / time to 12 hours / time.

9. The method for preparing modified silica aerogel according to claim 7, characterized in that: In the case where the drying process of the third gel comprises a supercritical drying process, During supercritical drying, the temperature range is 250°C to 270°C; and / or, During supercritical drying, the pressure range is 7MPa to 9MPa; and / or, During supercritical drying, the temperature and pressure holding time ranges from 0.5h to 1h; In the case where the drying process of the third gel comprises a normal pressure drying process, In the process of replacing the ethanol in the fourth gel with n-hexane, the number of replacements of n-hexane ranges from 3 to 6 times; and / or, In the process of replacing the ethanol in the fourth gel with n-hexane, the frequency of replacing the n-hexane is in the range of 6 hours / time to 12 hours / time; and / or, During the normal pressure drying process, the temperature range is 50°C to 100°C; and / or, During the normal pressure drying process, the drying time ranges from 8h to 24h.

10. A cold-insulating material, characterized in that: The cold-insulating material comprises the modified silica aerogel according to any one of claims 1 to 4; or The cold-insulating material comprises the modified silica aerogel obtained by the preparation method according to any one of claims 5 to 9.

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