Flexible silicon dioxide aerogel, preparation method thereof and thermal insulation material
By hydrophobic modification of the silica wet gel and co-irradiation and crosslinking with acrylate, a three-dimensional spatial network structure is formed, which solves the problem of prone to fracture and powder loss in traditional silica aerogels, and improves flexibility and structural strength.
Patent Information
- Application Number
- CN202510150374.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-11
- Publication Date
- 2025-04-15
AI Technical Summary
The particles of traditional silica aerogels are fragile, resulting in easy breakage and powder loss, which seriously limits the promotion and application of its thermal insulation materials.
The silica wet gel is hydrophobically modified by using a substituent-containing alkenyl group-containing trichlorosilane derivative as a modifier and co-irradiated crosslinked with the acrylate to form an additional three-dimensional spatial network structure to enhance the structural strength of the aerogel.
A flexible silica aerogel that is not easy to lose powder is achieved, which improves its structural strength and flexibility, and overcomes the problems of traditional silica aerogels being prone to breakage and lose powder.
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Abstract
Description
Technical Field
[0001] The present application relates to the field of aerogel materials, and in particular to a flexible silica aerogel and a preparation method thereof, and a thermal insulation material. Background Art
[0002] Silica aerogel is a nanoporous material with high porosity, high specific surface area, low light refractive index, low sound propagation velocity, low thermal conductivity, non-flammability and high temperature resistance. Due to these characteristics, silica aerogel is widely used in high and low temperature insulation, space field, catalyst carrier and other fields.
[0003] However, the particles of silica aerogel are relatively fragile, and have the disadvantage of structural brittleness. When used as a thermal insulation material, it is prone to breakage and powdering. The above disadvantages seriously restrict the promotion and application of silica aerogel insulation materials. Summary of the invention
[0004] Based on this, it is necessary to provide a flexible silica aerogel and its preparation method and thermal insulation material to overcome the problems of poor flexibility and easy powder loss of traditional silica aerogel.
[0005] In a first aspect of the present application, a method for preparing a flexible silica aerogel is provided.
[0006] A method for preparing a flexible silica aerogel comprises the following steps:
[0007] Using a modifier to hydrophobically modify the silica wet gel to form a modified wet gel;
[0008] irradiating the modified wet gel and acrylate to crosslink and dry;
[0009] The modifying agent includes a trichlorosilane derivative having an alkenyl group as a substituent.
[0010] In some embodiments, the modifier includes one or more of vinyltrichlorosilane, 2-propenyltrichlorosilane, 2-butenyltrichlorosilane, 5-hexenyltrichlorosilane, and 7-octenyltrichlorosilane.
[0011] In some embodiments, the acrylate includes one or more of methyl acrylate, butyl acrylate, methyl methacrylate, pentaerythritol tetraacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, ethylene glycol dimethacrylate and trimethylolpropane triacrylate.
[0012] In some embodiments, the hydrophobic modification step includes placing the wet silica gel in a first solution containing the modifier.
[0013] In some embodiments, the hydrophobic modification satisfies one or more of the following conditions:
[0014] (1) The temperature of the hydrophobic modification is 25°C to 70°C;
[0015] (2) The hydrophobic modification time is 12h~72h;
[0016] (3) The mass concentration of the modifier in the first solution is 5% to 40%.
[0017] In some embodiments, the step of irradiating and crosslinking the modified wet gel and acrylate comprises: placing the modified wet gel in a second solution containing the acrylate, soaking for 4 hours to 24 hours to obtain a pre-crosslinked wet gel, and irradiating and crosslinking the pre-crosslinked wet gel.
[0018] In some embodiments, one or more of the following conditions are met:
[0019] (1) The mass concentration of the acrylate in the second solution is 3% to 40%;
[0020] (2) The radiation dose of the radiation cross-linking is 50 kGy~600 kGy.
[0021] In some embodiments, the preparation of the silicon dioxide wet gel comprises the following steps:
[0022] mixing a silicon source precursor, ethanol and water to form a silica sol;
[0023] The silica sol is aged and solvent replaced to form the silica wet gel.
[0024] In a second aspect of the present application, a flexible silica aerogel is provided.
[0025] A flexible silica aerogel is prepared by adopting the above-mentioned method for preparing the flexible silica aerogel.
[0026] In a third aspect of the present application, a thermal insulation material is provided.
[0027] A thermal insulation material, at least a part of which is the above-mentioned flexible silica aerogel.
[0028] In the above-mentioned method for preparing flexible silica aerogel, a trichlorosilane derivative containing an alkenyl group as a modifier is used to modify the silica wet gel, thereby giving the modified wet gel a large number of carbon-carbon double bond reaction sites. On this basis, the modified wet gel is irradiated with acrylate, and an additional three-dimensional spatial network structure is formed inside and on the surface of the gel through a cross-linking reaction between carbon-carbon double bonds. After drying, a flexible silica aerogel that is not easy to fall off can be obtained. DETAILED DESCRIPTION
[0029] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.
[0030] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In this application, "at least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc.
[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.
[0032] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.
[0033] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
[0034] In this application, "above" or "below" includes the number itself. For example, "1 below" includes 1.
[0035] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.
[0036] Silica aerogel is a porous material with excellent thermal insulation capabilities and is widely used in high- and low-temperature insulation fields. However, the particle connections of traditional silica aerogels are relatively fragile. In some areas with weak connections, the particles are only composed of a small number of silicon-oxygen bonds, the connection area is small, and they are prone to breakage. The above structural characteristics make the strength of traditional silica aerogels relatively poor. When used as thermal insulation materials, they are prone to breakage or surface powder loss, which seriously restricts the promotion and application of silica aerogel insulation materials.
[0037] In view of the above problems, one embodiment of the present application relates to a method for preparing a flexible silica aerogel to overcome the problem that traditional silica aerogels are prone to breakage and powdering.
[0038] The preparation method of flexible silica aerogel comprises the following steps:
[0039] Using a modifier to hydrophobically modify the silica wet gel to form a modified wet gel;
[0040] cross-linking the modified wet gel with acrylate by irradiation and drying;
[0041] The modifying agent used for the hydrophobic modification is a trichlorosilane derivative having an alkenyl group as a substituent.
[0042] The present application uses a trichlorosilane derivative containing an alkenyl group as a modifier, and condenses with the Si-OH group remaining on the surface of the silica wet gel to graft the alkenyl group into the network structure of the silica wet gel, thereby obtaining a modified silica wet gel containing unsaturated carbon-carbon double bonds. In addition, an acrylate containing an alkenyl group is used to irradiate and crosslink the modified wet gel, and a second mutually cross-linked three-dimensional network is formed on the surface and in the internal structure of the silica aerogel through the reaction between the carbon-carbon double bonds, thereby effectively enhancing the structural strength of the silica aerogel.
[0043] In some embodiments, the modifier includes one or more of vinyltrichlorosilane, 2-propenyltrichlorosilane, 2-butenyltrichlorosilane, 5-hexenyltrichlorosilane, and 7-octenyltrichlorosilane.
[0044] In order to construct a denser three-dimensional cross-linked structure during irradiation cross-linking, there should be more carbon-carbon double bonds acting as reaction sites. However, the surface of the silica wet gel obtained after aging is mostly hydrophilic silanol, while olefins are hydrophobic groups, resulting in poor compatibility between the modifier with hydrophobic groups and the sol particles, further resulting in an extension of the contraction reaction time, poor reaction efficiency, and ultimately resulting in fewer reaction sites for the modified wet gel. For this reason, the present application uses a silane coupling agent with a chlorine group to increase the rate of the polycondensation reaction and effectively improve the efficiency of the grafting reaction. At the same time, considering that when selecting a silane coupling agent with multiple alkenyl substituents, the same incompatibility problem will be faced, and the presence of steric hindrance will further hinder the reaction. For this reason, the present application uses a trichlorosilane derivative with multiple chlorine-substituted groups, and uses the characteristics of trichlorosilane derivatives with small steric hindrance and good compatibility to introduce a considerable number of carbon-carbon double bond reaction sites into the silica wet gel structure.
[0045] In some embodiments, the hydrophobic modification step includes placing the wet gel in a first solution containing a modifying agent.
[0046] In some embodiments, the solvent of the first solution includes one or more of ethanol, acetone, isopropanol, propanol, n-hexane, and n-heptane.
[0047] In some embodiments, the temperature of hydrophobic modification is 25° C. to 70° C. The heating temperature of hydrophobic modification can be, but is not limited to, 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C. or other values within the range of 25° C. to 70° C.
[0048] In some embodiments, the hydrophobic modification time is 12 hours to 72 hours. The stirring time of the hydrophobic modification can be but is not limited to 12 hours, 24 hours, 36 hours, 48 hours, 60 hours, 72 hours or other values within the range of 12 hours to 72 hours.
[0049] In some embodiments, the mass concentration of the modifier in the first solution is 5% to 40%. Optionally, the mass concentration of the modifier in the first solution includes but is not limited to 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or other values within the range of 5% to 40%.
[0050] In some embodiments, the first solution is continuously stirred during the hydrophobic modification process.
[0051] In some embodiments, the acrylate includes one or more of methyl acrylate, butyl acrylate, methyl methacrylate, pentaerythritol tetraacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, ethylene glycol dimethacrylate, and trimethylolpropane triacrylate.
[0052] The present application uses acrylate and modified wet gel to perform radiation cross-linking together to form an additional three-dimensional spatial network structure inside and on the surface of the gel, which can not only give the modified wet gel better hydrophobicity, but also effectively improve the flexibility of the subsequently prepared flexible silica aerogel.
[0053] The irradiation means used in this application is irradiation. Unlike photocatalysis that requires free radical polymerization reaction crosslinking under the action of a photoinitiator, the method of irradiation using high-energy rays can transfer higher energy, and thus can induce a crosslinking reaction between carbon-carbon double bonds without adding a photoinitiator, avoiding the introduction of additional small molecule impurities in the silica wet gel system, which is beneficial to improving the quality of hydrophobic modification. In addition, high-energy rays have extremely strong penetrating power. On the one hand, they can more effectively act on the internal structure of the modified silica wet gel; on the other hand, for the combination of acrylate and modified silica wet gel with more reaction sites, irradiation can induce a more thorough crosslinking reaction, and avoid the many effects on the system caused by increasing the photoinitiator dosage.
[0054] In some embodiments, the step of irradiating and crosslinking the modified wet gel and acrylate together includes: placing the modified wet gel in a second solution containing acrylate, soaking for 4 hours to 24 hours, obtaining a pre-crosslinked wet gel, and irradiating and crosslinking the pre-crosslinked wet gel. Through the soaking method, the inside and surface of the modified wet gel can be doped with acrylate, and then an interlaced three-dimensional network structure is formed inside and outside the modified wet gel during irradiation crosslinking. Keeping the soaking time for 4 hours to 24 hours is conducive to obtaining a flexible silica aerogel with higher structural strength in the subsequent step.
[0055] In some embodiments, the solvent of the second solution includes one or more of dichloromethane, toluene, isopropanol, propanol, n-hexane, and n-heptane.
[0056] In some embodiments, the mass concentration of the acrylate is 3% to 40% in terms of mass percentage of the second solution. Optionally, the mass concentration of the acrylate in the second solution includes but is not limited to 3%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or other values within the range of 3% to 40%.
[0057] In some embodiments, the irradiation dose is 50 kGy to 600 kGy. Optionally, the irradiation dose includes but is not limited to 50 kGy, 100 kGy, 200 kGy, 300 kGy, 400 kGy, 500 kGy, 600 kGy or other values within the range of 50 kGy to 600 kGy.
[0058] In some embodiments, the preparation of the silicon dioxide wet gel comprises the following steps:
[0059] mixing a silicon source precursor, ethanol and water to form a silica sol;
[0060] The silica sol is aged and solvent replaced to form a silica wet gel.
[0061] In some embodiments, the silicon source precursor includes one or more of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, and isopropyl orthosilicate.
[0062] In some embodiments, the silicon source precursor, ethanol and water are mixed in a molar ratio of 1: (2-4): (9-16) of the silicon source precursor, ethanol and water. Keeping the molar ratio within the above range is conducive to forming a silica sol with low shrinkage and high porosity. Optionally, the molar ratio of the silicon source precursor, ethanol and water can be, but is not limited to, 1: 2: 9, 1: 2: 12, 1: 2: 16, 1: 3: 9, 1: 3: 12, 1: 3: 16, 1: 4: 9, 1: 4: 12, 1: 4: 16 or other ratios within the range of 1: (2-4): (9-16).
[0063] In some embodiments, after mixing the silicon source precursor, ethanol and water, the pH is adjusted to 2-6 and hydrolyzed to form a prepolymer solution.
[0064] In some embodiments, the pH of the prepolymer solution is adjusted to 7-10, and polycondensed to form a silica sol.
[0065] In some embodiments, the hydrolysis time is 0.5 to 4 hours. Alternatively, the hydrolysis time can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours or other values within the range of 0.5 hours to 4 hours.
[0066] In some embodiments, the polycondensation time is 0.5 to 4 hours. Alternatively, the polycondensation time can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours or other values within the range of 0.5 hours to 4 hours.
[0067] After the silicon source precursor undergoes hydrolysis and condensation, a primary gel network will be constructed to form a silica sol. At this time, only a few silicon-oxygen bonds in the gel network will be connected together, and the structural strength is low. For this reason, the silica sol needs to be aged to form a silica wet gel with higher structural strength.
[0068] In some embodiments, the aging step includes: immersing the silica sol in an aging solution and allowing the solution to stand.
[0069] In some embodiments, the aging solution includes one or more of water, ethanol, n-hexane, and acetone.
[0070] In some embodiments, the aging solution may further contain an ethanol solution of ethyl orthosilicate having a mass concentration of 1% to 20%.
[0071] In some embodiments, during aging, the standing time is 6 to 72 hours. The standing aging time can be, but is not limited to, 6 hours, 12 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours, 48 hours, 54 hours, 60 hours, 66 hours, 72 hours, or other values within the range of 6 hours to 72 hours.
[0072] In some embodiments, during aging, the static temperature is maintained at 25° C. to 70° C. The static aging temperature can be, but is not limited to, 25° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C. or other values within the range of 25° C. to 70° C.
[0073] During aging, when the system temperature is low, the molecular kinetic energy in the system is relatively low, the molecular motion is relatively stable, the hydrolysis and polycondensation reactions slow down, and the degree of crosslinking of the obtained silica wet gel is low. When the temperature is too high, the hydrolysis and condensation reaction rates will be too fast, which will easily lead to the volume shrinkage of the wet gel. In the temperature range of 25℃~70℃, it is conducive to obtaining silica wet gel with high structural strength.
[0074] The structure of the aged silica wet gel preform contains a large amount of water. The surface tension of water is large, and the stress during drying is large, which can easily affect the skeleton structure of the silica aerogel. Therefore, it is necessary to use a solvent with low surface tension to perform solvent replacement to remove the residual water inside the gel.
[0075] In some embodiments, the step of solvent replacement comprises:
[0076] The wet silica gel preform is immersed in the replacement solvent and allowed to stand or stir; the immersion operation is repeated 0 to 6 times. It can be understood that repeating the above operation means: repeating the step of immersing the wet silica gel in the organic solvent and letting it stand. When the number of repeated operations is 0 times, it means that no repeated operation is performed.
[0077] The replacement solvent includes one or more of toluene, dichloromethane, ethanol, isopropanol, n-butanol, n-hexane, cyclohexane, n-heptane and acetone.
[0078] In some embodiments, during solvent replacement, the volume ratio of the wet silica gel to the replacement solvent is 1:1 to 1:4. The volume ratio of the wet silica gel to the organic solvent can be, but is not limited to, 1:1, 1:2, 1:3, 1:4 or other values within the range of 1:1 to 1:4.
[0079] In some embodiments, the temperature of the solvent replacement is 25° C. to 60° C. The temperature of the solvent replacement can be, but is not limited to, 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C. or other values within the range of 25° C. to 60° C.
[0080] In some embodiments, the standing time of the solvent replacement is 1 h to 12 h. The standing time can be but is not limited to 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h or other values within the range of 1 h to 12 h.
[0081] In some embodiments, the drying method includes one of normal pressure drying, supercritical drying and freeze drying. Through the drying step, the liquid phase inside the wet gel can be replaced by a gas phase to obtain a flexible silica aerogel with low thermal conductivity.
[0082] In some embodiments, drying comprises one of atmospheric pressure drying, supercritical drying and freeze drying.
[0083] In some embodiments, before drying, the unfolded thickness of the wet gel is controlled to be 0.5 mm to 3 mm, so as to obtain a flexible silica aerogel with a thickness of about 0.5 mm to 3 mm after drying.
[0084] In some embodiments, the step of drying at normal pressure includes: drying the modified wet gel at 25° C. to 60° C. for 12 h to 48 h, heating to 100° C. to 200° C., and continuing drying for 1 h to 4 h.
[0085] In one embodiment of the present application, a flexible silica aerogel is provided. The flexible silica aerogel is prepared by the above-mentioned method for preparing the flexible silica aerogel.
[0086] In another embodiment of the present application, a thermal insulation material is provided. At least a portion of the thermal insulation material contains the above-mentioned flexible silica aerogel. In this embodiment, the thermal insulation material has good flexibility.
[0087] The present application is further described in detail below in conjunction with specific embodiments.
[0088] In the following specific embodiments and comparative examples, the raw materials used, unless otherwise specified, are all commercially available products; the instruments used, unless otherwise specified, are all commercially available products; and the processes used, unless otherwise specified, are all routinely selected by those skilled in the art.
[0089] Example 1
[0090] This embodiment provides a flexible silica aerogel.
[0091] The preparation method of flexible silica aerogel is:
[0092] At 30°C, the silica wet gel was placed in a 25wt% vinyltrichlorosilane n-hexane solution for hydrophobic modification, and the modification was continued for 36 hours to obtain a modified wet gel. The modified wet gel was soaked in an ethanol solution containing 25wt% methyl acrylate for 24 hours to obtain a pre-crosslinked wet gel, and the pre-crosslinked wet gel was irradiated with an irradiation dose of 200KGy. It was washed 4 times with an equal volume of ethanol, and the soaking time for each washing was 24 hours. Using the atmospheric pressure drying method, the irradiated wet gel was dried at 60°C for 24 hours, and then dried at 120°C for 4 hours to obtain a flexible silica aerogel with a thickness of 1mm, a length of 4cm, and a width of 3cm.
[0093] The preparation process of wet silica gel is as follows: methyl orthosilicate, ethanol and water are mixed in a molar ratio of 1:3:12, nitric acid is used to adjust the pH to 5, and hydrolysis is performed for 2 hours. Ammonia water is used to adjust the pH to 8, and condensation is performed for 2 hours to obtain a silica sol. The silica sol is placed in a 10wt% ethyl orthosilicate ethanol solution and aged for 48 hours. The aged silica sol (gel) is placed in a n-hexane solvent, the solvent is replaced at room temperature, and stirring is continued for 12 hours. Repeat 4 times to obtain a wet silica gel.
[0094] Example 2
[0095] This embodiment provides a flexible silica aerogel.
[0096] The flexible silica aerogel of this embodiment is different from that of embodiment 1 in that the wet silica gel is placed in a 25 wt % n-hexane solution of 2-butenyltrichlorosilane for hydrophobic modification.
[0097] Example 3
[0098] This embodiment provides a flexible silica aerogel.
[0099] The flexible silica aerogel of this embodiment is different from that of embodiment 1 in that the wet silica gel is placed in a 5 wt % n-hexane solution of vinyltrichlorosilane for hydrophobic modification.
[0100] Example 4
[0101] This embodiment provides a flexible silica aerogel.
[0102] The flexible silica aerogel of this embodiment is different from that of embodiment 1 in that the wet silica gel is placed in a 40 wt % n-hexane solution of vinyltrichlorosilane for hydrophobic modification.
[0103] Example 5
[0104] This embodiment provides a flexible silica aerogel.
[0105] The flexible silica aerogel of this embodiment is different from that of Embodiment 1 in that the second solution is a 40 wt % ethanol solution of trimethylolpropane trimethacrylate.
[0106] Example 6
[0107] This embodiment provides a flexible silica aerogel.
[0108] The flexible silica aerogel of this embodiment is different from that of embodiment 3 in that the second solution is a 10 wt % n-hexane solution of methyl acrylate.
[0109] Comparative Example 1
[0110] This comparative example provides a modified silica aerogel.
[0111] The modified silica aerogel in this comparative example is different from that in Example 1 in that the silica aerogel is obtained by directly drying the modified wet gel.
[0112] Comparative Example 2
[0113] This comparative example provides a modified silica aerogel.
[0114] The modified silica aerogel in this comparative example is different from that in Example 1 in that the wet silica gel is placed in a 25 wt % n-hexane solution of trimethylchlorosilane for hydrophobic modification.
[0115] Test Case
[0116] The performance of the silica aerogels of the above examples and comparative examples was tested, and the test results are shown in Table 1.
[0117] Powder loss rate: The silica aerogel was placed on a vibrating shaker and vibrated for 10 minutes. The relative percentage of the mass difference before and after vibration to the mass before vibration was recorded as the powder loss rate of the silica aerogel.
[0118] Bending times: Fold the silica aerogel 90° along the long axis and restore it within 3 seconds, and observe whether there are cracks or breaks at the folded part. If cracks or breaks occur, the last folding number will be recorded as the bending times of the silica aerogel, and the maximum number of folds is 50.
[0119] Thermal conductivity: The thermal conductivity of silica aerogel was tested according to the method of GB / T34336-2017.
[0120] Table 1
[0121]
[0122] As can be seen from Table 1, the silica aerogels of Comparative Example 1 that were not crosslinked by irradiation with acrylate and Comparative Example 2 that used trimethylchlorosilane showed a high powder loss rate in the powder loss rate test and poor flexibility in the bending test. At the same time, the flexible silica aerogels of Examples 1 to 6 had a low powder loss rate and good flexibility, indicating that the powder loss performance of the flexible silica aerogels can be effectively improved by crosslinking the modified wet gel by irradiation with acrylate.
[0123] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0124] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims, and the description may be used to interpret the content of the claims.
Claims
1. A method for preparing a flexible silica aerogel, characterized in that: The steps include: Using a modifier to hydrophobically modify the silica wet gel to form a modified wet gel; irradiating the modified wet gel and acrylate to crosslink and dry; The modifying agent includes a trichlorosilane derivative having an alkenyl group as a substituent.
2. The method for preparing the flexible silica aerogel according to claim 1, characterized in that: The modifier includes one or more of vinyl trichlorosilane, 2-propylene trichlorosilane, 2-butenyl trichlorosilane, 5-hexenyl trichlorosilane and 7-octenyl trichlorosilane.
3. The method for preparing the flexible silica aerogel according to claim 1, characterized in that: The acrylic acid ester includes one or more of methyl acrylate, butyl acrylate, methyl methacrylate, pentaerythritol tetraacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, ethylene glycol dimethacrylate and trimethylolpropane triacrylate.
4. The method for preparing the flexible silica aerogel according to any one of claims 1 to 3, characterized in that: The hydrophobic modification step comprises: placing the silicon dioxide wet gel into a first solution containing the modifier.
5. The method for preparing the flexible silica aerogel according to claim 4, characterized in that: The hydrophobic modification satisfies one or more of the following conditions: (1) The temperature of the hydrophobic modification is 25°C to 70°C; (2) The hydrophobic modification time is 12h~72h; (3) The mass concentration of the modifier in the first solution is 5% to 40%.
6. The method for preparing the flexible silica aerogel according to any one of claims 1 to 3, characterized in that: The step of irradiating and crosslinking the modified wet gel and acrylate comprises: placing the modified wet gel in a second solution containing the acrylate, soaking for 4 hours to 24 hours to obtain a pre-crosslinked wet gel, and irradiating and crosslinking the pre-crosslinked wet gel.
7. The method for preparing the flexible silica aerogel according to claim 6, characterized in that: One or more of the following conditions are met: (1) The mass concentration of the acrylate in the second solution is 3% to 40%; (2) The radiation dose of the radiation cross-linking is 50 kGy~600 kGy.
8. The method for preparing the flexible silica aerogel according to any one of claims 1 to 3, characterized in that: The preparation of the silicon dioxide wet gel comprises the following steps: mixing a silicon source precursor, ethanol and water to form a silica sol; The silica sol is aged and solvent replaced to form the silica wet gel.
9. A flexible silica aerogel, characterized in that: The flexible silica aerogel is prepared by the preparation method of any one of claims 1 to 8.
10. A heat insulating material, characterized in that: At least a portion of the thermal insulation material is the flexible silica aerogel according to claim 9.