A method for modifying silica aerogel using electron beam irradiation technology

Abstract

The present invention belongs to the technical field of silica aerogel modification, and specifically relates to a method for modifying silica aerogel using electron beam irradiation technology, comprising the following steps: (1) preparing a precursor: at room temperature and pressure, in an air atmosphere, uniformly mixing an organosilicon source, water, and an organic solvent in proportion, then stirring and hydrolyzing to obtain a precursor; (2) preparing a gel: adding ammonia water to the precursor to adjust the pH value, mixing uniformly, and then standing to obtain a wet gel; (3) modifying the gel: adding a hydrophobic modifier solution to the wet gel and soaking it, then irradiating the soaked gel under electron beam, washing, and drying to obtain silica aerogel. The present invention has the beneficial effects of activating aerogel and a hydrophobic modifier by electron beam irradiation, increasing the reaction rate of the hydrophobic modifier and aerogel, and improving the grafting rate of hydrophobic groups on the aerogel, thereby obtaining a silica aerogel with high hydrophobicity.

Description

Technical Field

[0001] The invention belongs to the technical field of silica aerogel modification, and particularly relates to a method for modifying silica aerogel by utilizing electron beam irradiation technology. Background Art

[0002] Silica aerogel is a nanoporous material composed of nanoparticles with an ultra-low bulk density (0.03-0.35 g·cm -3 ), high porosity (80-99%) and high surface area (500-1500m 2 ·g -1 ) and other unique properties. Due to its excellent performance, silica aerogels have attracted widespread attention in fields such as thermal insulation, adsorption, catalysis, and sensing. Because silica aerogels have a large number of hydroxyl groups distributed on their surface, they can absorb water, resulting in performance degradation or even structural damage. Therefore, hydrophobic modification plays a key role in improving the performance of silica aerogels.

[0003] At present, a variety of methods have been developed for the hydrophobic modification of silica aerogels, such as the in-situ method of changing and modifying the internal skeleton through co-precursors, the post-modification method of modifying the surface of the gel skeleton after synthesis through organic silane solution, and the chemical vapor deposition method of modifying the aerogel surface. However, these methods all have problems such as high cost, long time, complex process, and poor effect of hydrophobic modification, which are not conducive to commercialization and are not convenient for large-scale industrial production. Summary of the Invention

[0004] In view of the above problems, the present invention provides a method for modifying silica aerogel using electron beam irradiation technology.

[0005] The present invention relates to a method for modifying silica aerogel using electron beam irradiation technology, comprising the following steps:

[0006] (1) Precursor configuration:

[0007] At room temperature and pressure, in an air atmosphere, an organosilicon source, water and an organic solvent are mixed uniformly in proportion, then stirred and hydrolyzed to obtain a precursor;

[0008] (2) Preparation of gel:

[0009] Adding ammonia water to the precursor prepared in step (1) to adjust the pH value, mixing evenly, and allowing to stand to obtain a wet gel;

[0010] (3) Gel modification:

[0011] A hydrophobic modifier solution is added to the wet gel prepared in step (2) and soaked, and then the soaked gel is irradiated under an electron beam, washed and dried to obtain a silica aerogel.

[0012] Preferably, in step (1), the volume ratio of the organosilicon source, water and organic solvent is 1:0.3-0.5:1-1.5; the organosilicon source is one of trimethoxymethylsilane and triethoxymethylsilane; and the organic solvent is one of methanol and ethanol.

[0013] Preferably, in step (1), the hydrolysis is carried out at 20°C to 30°C for 12h to 24h.

[0014] Preferably, in step (2), ammonia water is added to adjust the pH value to 8-9; and the mixture is allowed to stand for 2-4 hours to form a gel.

[0015] Preferably, in step (3), the hydrophobic modifier solution is a mixed solution of trimethylchlorosilane and ethanol; the volume ratio of trimethylchlorosilane to ethanol is 2:8; the volume ratio of the organosilicon source to trimethylchlorosilane is 1:1; and the wet gel is soaked in the hydrophobic modifier solution for 1 to 2 hours.

[0016] Preferably, in step (3), the dose of electron beam irradiation is 15 kGy to 60 kGy.

[0017] Preferably, in step (3), the temperature of the electron beam irradiation is 20°C to 35°C.

[0018] Preferably, in step (3), the humidity of the electron beam irradiation is 40% to 90%.

[0019] Preferably, in step (3), the electron beam irradiation time is 0.8s to 3.4s.

[0020] Preferably, in step (3), the drying method is atmospheric pressure drying or freeze drying.

[0021] Compared with the prior art, the advantages and positive effects of the present invention are:

[0022] (1) The method of modifying silica aerogel using electron beam irradiation technology activates the aerogel and the hydrophobic modifier by electron beam irradiation, thereby increasing the reaction rate of the hydrophobic modifier and the aerogel and improving the grafting rate of the hydrophobic groups on the aerogel, thereby obtaining a silica aerogel with high hydrophobicity;

[0023] (2) This method of modifying silica aerogel using electron beam irradiation technology combines soaking in a hydrophobic modifier with electron beam irradiation. Compared with the traditional soaking modification method, the soaking time is shortened and the electron beam irradiation time is short, thereby saving time costs;

[0024] (3) The method of modifying silica aerogel using electron beam irradiation technology has a simple process, readily available raw materials, and does not require the introduction of any external material system, thus avoiding secondary pollution. It is suitable for large-scale industrial silica aerogel modification. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0026] Figure 1 This is a flow chart for preparing the silica aerogel of the present invention;

[0027] Figure 2 Physical pictures of silica aerogels 1#, 2#, and 3# provided in Example 1;

[0028] Figure 3 Fourier transform infrared spectra of silica aerogels 1#, 2#, and 3# provided in Example 1;

[0029] Figure 4 The water contact angles of silica aerogels 1#, 2#, and 3# provided in Example 1;

[0030] Figure 5 This is a relationship diagram between the dosage and contact angle of silica aerogels 1#, 2#, and 3# provided in Example 1;

[0031] Figure 6 The water contact angles of silica aerogels 4#, 5#, and 6# provided in Example 2;

[0032] Figure 7 This is a relationship diagram between the dosage and contact angle of silica aerogels 4#, 5#, and 6# provided in Example 2. DETAILED DESCRIPTION

[0033] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below with reference to the embodiments.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Example 1

[0036] A method for modifying silica aerogel using electron beam irradiation technology comprises the following steps:

[0037] (1) Precursor configuration:

[0038] At room temperature and pressure, in an air atmosphere, 3 ml of triethoxymethylsilane, 1.65 ml of methanol, 1.35 ml of water and 30 mg of hexadecyltrimethylammonium bromide were mixed evenly, then stirred and hydrolyzed for 20 hours to obtain a precursor.

[0039] (2) Preparation of gel:

[0040] Add 210 μL of ammonia water to the precursor prepared in step (1), mix well, and let stand for 2 h to obtain a wet gel.

[0041] (3) Gel modification:

[0042] To the wet gel obtained in step (2), add 3 ml of ethanol solution of trimethylchlorosilane with a volume fraction of 20%, soak for 2 hours, then divide the soaked gel into three parts, and irradiate them under electron beam for 2 seconds respectively; the parameters of electron beam irradiation are: dose 0kGy, 15kGy, 30kGy, temperature 25℃, humidity 70%; wash with 2 ml of methanol 4 times respectively, freeze-dry at -70℃ for 20 hours, and obtain silica aerogels 1#, 2#, and 3#, as shown in the actual picture. Figure 2 As shown (from left to right are silica aerogels 1#, 2#, and 3#).

[0043] Example 2

[0044] A method for modifying silica aerogel using electron beam irradiation technology comprises the following steps:

[0045] (1) Precursor configuration:

[0046] At room temperature and pressure, in an air atmosphere, 3 ml of trimethoxymethylsilane, 1.65 ml of ethanol, and 1.35 ml of water were measured and mixed evenly, and then stirred and hydrolyzed for 15 hours to obtain a precursor.

[0047] (2) Preparation of gel:

[0048] Add 60 μL of ammonia water to the precursor prepared in step (1), mix well, and let stand for 4 h to obtain a wet gel.

[0049] (3) Gel modification:

[0050] To the wet gel obtained in step (2), add 3 ml of ethanol solution of trimethylchlorosilane with a volume fraction of 20%, soak for 2 hours, and then divide the soaked gel into three parts, and irradiate them under electron beam for 3 seconds respectively; the parameters of electron beam irradiation are: dose 0 kGy, 21 kGy, 42 kGy, temperature 25 ° C, humidity 70%; wash with 2 ml of methanol 4 times respectively, and dry at 60 ° C under normal pressure for 24 hours to obtain silica aerogels 4#, 5#, and 6#.

[0051] Test Example 1,

[0052] The silica aerogels prepared in Example 1 and Example 2 were tested for water contact angle according to the following test method. The test results are shown in Tables 1-2 and Figure 4-7 .

[0053] Test method: Grind the silica aerogel in a mortar, then use a tablet press to press at 30 MPa for 20 minutes to obtain a sample sheet. The sample sheet is tested for hydrophobicity using a contact angle meter to obtain the water contact angle data of the silica aerogel.

[0054] Table 1. Water contact angle test results of Example 1

[0055] name Radiation dose (kGy) Contact angle (°) Silica aerogel 1# 0 135 Silica Aerogel 2# 15 138.5 Silica Aerogel 3# 30 148.75

[0056] Table 2. Water contact angle test results of Example 2

[0057] name Radiation dose (kGy) Contact angle (°) Silica aerogel 4# 0 138 Silica Aerogel 5# 21 141.5 Silica aerogel 6# 42 147

[0058] From Table 1-2 and Figure 4-7 It was found that the silica aerogel of Example 1 had different hydrophobicity under different irradiation doses. As the irradiation dose increased, the contact angle increased, indicating that the hydrophobicity of the aerogel was improved. At the same time, the silica aerogel of Example 2 also had different hydrophobicity under different irradiation doses. As the irradiation dose increased, the contact angle increased, indicating that the hydrophobicity of the aerogel was improved.

[0059] Test Example 2,

[0060] The silica aerogels 1#, 2# and 3# obtained in Example 1 were analyzed for functional groups by Fourier transform infrared spectroscopy (FT-IR). The results are as follows: Figure 3 shown.

[0061] exist Figure 3 Medium, 2972cm -1 , 1277cm -1 , 772cm -1 The peaks appearing near represent Si-CH3; at 3442 cm -1 and 1635cm -1is the characteristic peak of H-OH; 1039cm -1 、849cm -1 The characteristic absorption peaks near are attributed to the bending vibration, symmetric stretching vibration and antisymmetric stretching vibration of Si-O-Si; Figure 3 The results showed that the Si-O-Si absorption peak of silica aerogel 3# (30kGy) was the strongest and the grafted hydrophobic groups were the most, indicating that the hydrophobic modification effect of silica aerogel was enhanced with the increase of irradiation dose.

[0062] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for modifying silica aerogel using electron beam irradiation technology, characterized in that: The following steps are involved: (1) Precursor configuration: At room temperature and pressure, in an air atmosphere, an organosilicon source, water and an organic solvent are mixed uniformly in proportion, then stirred and hydrolyzed to obtain a precursor; (2) Preparation of gel: Adding ammonia water to the precursor prepared in step (1) to adjust the pH value, mixing evenly, and allowing to stand to obtain a wet gel; (3) Modification of gel: Adding a hydrophobic modifier solution to the wet gel prepared in step (2) and soaking the wet gel, then irradiating the soaked gel under an electron beam, washing, and drying to obtain a silica aerogel; In step (3), the hydrophobic modifier solution is a mixed solution of trimethylchlorosilane and ethanol; the volume ratio of trimethylchlorosilane to ethanol is 2:8; the volume ratio of the organosilicon source to trimethylchlorosilane is 1:1; the wet gel is immersed in the hydrophobic modifier solution for 1 hour to 2 hours; In the step (3), the dose of electron beam irradiation is 15 kGy to 60 kGy; In step (3), the temperature of the electron beam irradiation is 20°C to 35°C; In the step (3), the humidity of the electron beam irradiation is 40% to 90%; In the step (3), the electron beam irradiation time is 0.8s to 3.4s.

2. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (1), the volume ratio of the organosilicon source, water and organic solvent is 1:0.3-0.5:1-1.5; the organosilicon source is one of trimethoxymethylsilane and triethoxymethylsilane; and the organic solvent is one of methanol and ethanol.

3. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (1), the hydrolysis is carried out at 20°C to 30°C for 12h to 24h.

4. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (2), ammonia water is added to adjust the pH value to 8-9; and the mixture is allowed to stand for 2-4 hours to form a gel.

5. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (3), the drying method is atmospheric pressure drying or freeze drying.

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