A hydrophilic aerogel and a method for preparing the same

Abstract

The application belongs to the technical field of aerogels, and provides a hydrophilic aerogel and a preparation method thereof, the hydrophilic aerogel being prepared from a hydrophobic aerogel, a surfactant and a solvent, and the solid particles with uniform particle sizes being obtained by controlling the solvent amount, the reactant concentration, the surfactant concentration and the reaction conditions. The hydrophilic aerogel prepared by the application has small particle sizes and narrow distribution, and has good dispersibility in an aqueous system. After the hydrophobic aerogel produced industrially is modified to be hydrophilic, the dispersibility of the product in the aqueous system can be obviously improved. Meanwhile, due to the hydrophilicity of the aerogel, it is not necessary to add a wetting agent such as a surfactant when the aqueous system is prepared, and the addition amount of the aerogel can be more than when the aerogel is directly added, and the thermal insulation performance is better. In addition, due to the problem of pore collapse of the hydrophilic silica aerogel in the drying process, the thermal insulation performance is reduced, and the modification process is improved in the application, so that the problem can be solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogel, in particular to a hydrophilic aerogel and a preparation method thereof. BACKGROUND

[0002] The preparation of hydrophilic silica aerogel mainly falls into two categories: direct method and modification method. The direct method is to not add hydrophobic agent as the support of the pores during preparation, but to reduce the interfacial tension of the pores during drying through a special drying method to maintain the pore structure of the aerogel. So far, the most effective drying method is supercritical drying, but the cost of supercritical drying is high, and the high temperature and high pressure environment during drying can also cause safety hazards. Therefore, the direct method cannot be applied on a large scale in industrial production. The modification method is to wash away the hydrophobic groups on the surface of the hydrophobic aerogel produced by industrial production, and then coat or graft hydrophilic groups on the surface, so as to obtain a hydrophilic aerogel. Since most of the grafting methods require chemical reactions, the process is complex and cannot meet the requirements of use and production cost. SUMMARY

[0003] The purpose of the present application is to overcome the defects in the prior art and provide a hydrophilic aerogel and a preparation method thereof.

[0004] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0005] The present application provides a hydrophilic aerogel, which is prepared from raw materials comprising the following mass fractions:

[0006] 0.5-1.5 parts of hydrophobic aerogel, 2-4 parts of surfactant, and 15-77 parts of solvent.

[0007] As a preferred embodiment, the surfactant is a fatty alcohol polyoxyethylene ether and / or isomeric tridecanol polyoxyethylene ether.

[0008] As a preferred embodiment, the solvent is isopropyl alcohol and / or ethanol.

[0009] The present application also provides a preparation method of the hydrophilic aerogel, comprising the following steps:

[0010] (1) mixing the hydrophobic aerogel, the surfactant and the solvent, and then sequentially heating, centrifuging and drying to obtain a mixed solid;

[0011] (2) washing and drying the mixed solid to obtain the hydrophilic aerogel.

[0012] As a preferred embodiment, the temperature of the heating in step (1) is 45-60℃, the stirring speed is 600-800 rpm, and the time is 6-8 h.

[0013] As preferred, the centrifugal speed in step (1) is 6000-7000 rpm, and the time is 10-15 min.

[0014] As preferred, the drying temperature in step (1) is 60-80℃, and the time is 7-9 h.

[0015] As preferred, the washing mode in step (2) is to mix the mixed solid and water and then centrifuge;

[0016] The mass ratio of the hydrophobic aerogel and water is 1:30-40;

[0017] The centrifugal speed is 6000-7000 rpm, and the time is 10-15 min.

[0018] As preferred, the washing in step (2) is repeated for 3-5 times.

[0019] As preferred, the drying temperature in step (2) is 60-80℃, and the time is 20-28 h.

[0020] The present application provides a hydrophilic aerogel prepared from a hydrophobic aerogel, a surfactant and a solvent. By controlling the amount of solvent, the concentration of reactants, the concentration of surfactant and the reaction conditions, the present application obtains solid particles with uniform particle size. The hydrophilic aerogel prepared by the present application has small particle size and narrow particle size distribution, and has good dispersibility in aqueous systems. The hydrophilic aerogel provided by the present application can be used as a superior thermal insulation material. Silica is non-toxic, non-irritating, harmless to humans and the environment, and has high thermal stability and water resistance. After the hydrophobic aerogel produced industrially is modified to be hydrophilic, the dispersibility of the product in aqueous systems can be significantly improved. At the same time, due to its own hydrophilicity, it is not necessary to add additional wetting agents such as surfactants when preparing aqueous systems, and the amount of addition can be more than when directly adding aerogel, and the thermal insulation performance is better. In addition, due to the problem of pore collapse during the drying process of the hydrophilic silica aerogel, the thermal insulation performance is reduced, and the modification process is improved to solve such problems. Finally, the raw material of the hydrophobic silica aerogel used in the present application is cheaper than the directly produced hydrophilic silica aerogel with similar performance, which reduces the use cost of aerogel materials in subsequent actual production. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The infrared spectra of the hydrophilic aerogel and the hydrophobic aerogel prepared in Example 1;

[0022] Figure 2 The contact angle comparison diagram of the hydrophilic aerogel and the hydrophobic aerogel prepared in Example 1. DETAILED DESCRIPTION

[0023] The present application provides a hydrophilic aerogel, which is prepared from raw materials comprising the following mass fractions:

[0024] 0.5-1.5 parts of hydrophobic aerogel, 2-4 parts of surfactant, and 15-77 parts of solvent.

[0025] In the present application, the mass fraction of the hydrophobic aerogel is preferably 0.6-1.4 parts, further preferably 0.8-1.2 parts, and more preferably 0.9-1.1 parts.

[0026] In the present application, the mass fraction of the surfactant is preferably 2.5-3.5 parts, further preferably 2.6-3.4 parts, and more preferably 2.8-3.2 parts.

[0027] In the present application, the surfactant is preferably a fatty alcohol polyoxyethylene ether and / or isomeric tridecanol polyoxyethylene ether.

[0028] In the present application, the mass fraction of the solvent is preferably 15-77 parts, further preferably 20-70 parts, and more preferably 40-50 parts.

[0029] In the present application, the solvent is preferably isopropyl alcohol and / or ethanol.

[0030] In the present application, when both isopropyl alcohol and ethanol are present, the mass fraction of isopropyl alcohol is preferably greater than or equal to 40%, further preferably greater than or equal to 45%, and more preferably greater than or equal to 50%; the mass fraction of ethanol is preferably greater than or equal to 40%, further preferably greater than or equal to 45%, and more preferably greater than or equal to 50%.

[0031] The present application also provides a preparation method of the hydrophilic aerogel, comprising the following steps:

[0032] (1) mixing the hydrophobic aerogel, the surfactant, and the solvent, and then sequentially performing heating, centrifugation, and drying to obtain a mixed solid;

[0033] (2) washing and drying the mixed solid to obtain the hydrophilic aerogel.

[0034] In the present application, the stirring speed of the mixing in step (1) is preferably 700-800 rpm, further preferably 720-780 rpm, and more preferably 740-760 rpm; the time is preferably 3-8 min, further preferably 4-7 min, and more preferably 5-6 min.

[0035] In the present application, the temperature of the heating in step (1) is preferably 45-60℃, further preferably 50-55℃, more preferably 52-53℃; the stirring speed is preferably 600-800rpm, further preferably 650-750rpm, more preferably 680-720rpm; and the time is preferably 6-8h, further preferably 6.5-7.5h, more preferably 6.8-7.2h.

[0036] In the present application, the speed of the centrifugation in step (1) is preferably 6000-7000rpm, further preferably 6200-6800rpm, more preferably 6400-6600rpm; and the time is preferably 10-15min, further preferably 11-14min, more preferably 12-13min.

[0037] In the present application, the temperature of the drying in step (1) is preferably 60-80℃, further preferably 65-75℃, more preferably 66-74℃; and the time is preferably 7-9h, further preferably 7.5-8.5h, more preferably 7.7-8.3h.

[0038] In the present application, the washing in step (2) is preferably performed by mixing the mixed solid and water and then centrifuging.

[0039] In the present application, the mass ratio of the hydrophobic aerogel and water is preferably 1:30-40, further preferably 1:32-38, more preferably 1:34-36.

[0040] In the present application, the speed of the centrifugation is preferably 6000-7000rpm, further preferably 6100-6900rpm, more preferably 6400-6600rpm; and the time is preferably 10-15min, further preferably 11-14min, more preferably 12-13min.

[0041] In the present application, the number of repetitions of the washing in step (2) is preferably 3-5, more preferably 4; and the purpose of the washing is to wash away the excess surfactant.

[0042] In the present application, the temperature of the drying in step (2) is preferably 60-80℃, further preferably 65-75℃, more preferably 68-72℃; and the time is preferably 20-28h, further preferably 21-27h, more preferably 23-25h.

[0043] The technical solutions provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0044] Example 1

[0045] Take 1 g of hydrophobic aerogel, 2 g of AEO-3 (fatty alcohol polyoxyethylene ether), 9 g of isopropyl alcohol and 9 g of ethanol under the condition of 700 rpm stirring for 5 min to obtain a solid-liquid mixture; then stirring at 60℃, 700 rpm for 6h, the obtained product is centrifuged at 6600 rpm for 15 min, after centrifugation, pour off the supernatant, dry at 70℃ for 8h to obtain a mixed solid; mix the mixed solid with 40 g of water, shake well and then centrifuge at 6600 rpm for 15 min; after pouring off the supernatant, repeat the steps of adding water and centrifuging, repeat 3 times, and then dry the obtained solid at 70℃ for 24h to obtain a hydrophilic aerogel.

[0046] The hydrophilic aerogel and the hydrophobic aerogel prepared in this example were subjected to infrared determination, and the results are shown in Figure 1

[0047] The hydrophilic aerogel and the hydrophobic aerogel prepared in this example were subjected to contact angle test, and the results are shown in Figure 2 Figure 2 (a) is a hydrophobic aerogel, and (b) is a hydrophilic aerogel.

[0048] Example 2

[0049] Take 1.2 g of hydrophobic aerogel, 2 g of TO-3 (isomeric tridecanol polyoxyethylene ether), 10 g of isopropyl alcohol and 10 g of ethanol under the condition of 800 rpm stirring for 8 min to obtain a solid-liquid mixture; then stirring at 50℃, 650 rpm for 6.2h, the obtained product is centrifuged at 6200 rpm for 10 min, after centrifugation, pour off the supernatant, dry at 65℃ for 7.5h to obtain a mixed solid; mix the mixed solid with 36 g of water, shake well and then centrifuge at 6500 rpm for 10 min; after pouring off the supernatant, repeat the steps of adding water and centrifuging, repeat 4 times, and then dry the obtained solid at 65℃ for 20h to obtain a hydrophilic aerogel.

[0050] Example 3

[0051] Take 0.8 g of hydrophobic aerogel, 2 g of AEO-3 (fatty alcohol polyoxyethylene ether), 18 g of isopropyl alcohol under the condition of 720 rpm stirring for 3 min to obtain a solid-liquid mixture; then stirring at 45℃, 620 rpm for 6.4h, the obtained product is centrifuged at 6600 rpm for 11 min, after centrifugation, pour off the supernatant, dry at 75℃ for 7.6h to obtain a mixed solid; mix the mixed solid with 28 g of water, shake well and then centrifuge at 6500 rpm for 10 min; after pouring off the supernatant, repeat the steps of adding water and centrifuging, repeat 5 times, and then dry the obtained solid at 80℃ for 28h to obtain a hydrophilic aerogel. ​​

[0052] Example 4

[0053] Take 0.8 g of hydrophobic aerogel, 2 g of TO-3 (isomeric tridecanol polyoxyethylene ether), 23 g of isopropyl alcohol, and stir for 7 min at 760 rpm to obtain a solid-liquid mixture; then stir at 58°C and 720 rpm for 7.2 h, centrifuge the obtained product at 6800 rpm for 15 min, pour out the supernatant after centrifugation, and dry at 80°C for 9 h to obtain a mixed solid; mix the mixed solid with 32 g of water, shake well, and centrifuge at 6550 rpm for 12 min; repeat the steps of adding water and centrifuging after pouring out the supernatant, and repeat for 4 times, and then dry the obtained solid at 75°C for 25 h to obtain a hydrophilic aerogel.

[0054] Example 5

[0055] Take 0.8 g of hydrophobic aerogel, 2 g of TO-3 (isomeric tridecanol polyoxyethylene ether), 28 g of ethanol, and stir for 6 min at 760 rpm to obtain a solid-liquid mixture; then stir at 48°C and 800 rpm for 6.5 h, centrifuge the obtained product at 6400 rpm for 10 min, pour out the supernatant after centrifugation, and dry at 74°C for 8.5 h to obtain a mixed solid; mix the mixed solid with 32 g of water, shake well, and centrifuge at 6800 rpm for 15 min; repeat the steps of adding water and centrifuging after pouring out the supernatant, and repeat for 5 times, and then dry the obtained solid at 80°C for 23 h to obtain a hydrophilic aerogel.

[0056] Example 6

[0057] Take 1.4 g of hydrophobic aerogel, 4 g of TO-3 (isomeric tridecanol polyoxyethylene ether), 30 g of ethanol, and 30 g of isopropyl alcohol, and stir for 5 min at 760 rpm to obtain a solid-liquid mixture; then stir at 60°C and 700 rpm for 7 h, centrifuge the obtained product at 6500 rpm for 13 min, pour out the supernatant after centrifugation, and dry at 74°C for 9 h to obtain a mixed solid; mix the mixed solid with 54 g of water, shake well, and centrifuge at 7000 rpm for 10 min; repeat the steps of adding water and centrifuging after pouring out the supernatant, and repeat for 3 times, and then dry the obtained solid at 65°C for 27 h to obtain a hydrophilic aerogel.

[0058] Example 7

[0059] Take 1 g of hydrophobic aerogel, 3 g of AEO-3 (fatty alcohol polyoxyethylene ether), 27 g of isopropyl alcohol, and stir at 730 rpm for 8 min to obtain a solid-liquid mixture; then stir at 60°C, 700 rpm for 6 h, centrifuge the obtained product at 6600 rpm for 15 min, pour away the supernatant after centrifugation, dry at 70°C for 8 h to obtain a mixed solid; mix the mixed solid with 33 g of water, shake well and centrifuge at 7000 rpm for 12 min; repeat the steps of adding water and centrifuging after pouring out the supernatant, repeat for 3 times, and dry the obtained solid at 70°C for 24 h to obtain a hydrophilic aerogel.

[0060] Example 8

[0061] Take 1 g of hydrophobic aerogel, 3 g of AEO-3 (fatty alcohol polyoxyethylene ether), 27 g of isopropyl alcohol, and stir at 730 rpm for 8 min to obtain a solid-liquid mixture; then stir at 60°C, 700 rpm for 6 h, centrifuge the obtained product at 6600 rpm for 15 min, pour away the supernatant after centrifugation, dry at 70°C for 8 h to obtain a mixed solid; mix the mixed solid with 33 g of water, shake well and centrifuge at 7000 rpm for 12 min; repeat the steps of adding water and centrifuging after pouring out the supernatant, repeat for 3 times, and dry the obtained solid at 70°C for 24 h to obtain a hydrophilic aerogel.

[0062] Example 9

[0063] Take 1 g of hydrophobic aerogel, 3 g of AEO-3 (fatty alcohol polyoxyethylene ether), 27 g of isopropyl alcohol, and stir at 730 rpm for 8 min to obtain a solid-liquid mixture; then stir at 60°C, 700 rpm for 6 h, centrifuge the obtained product at 6600 rpm for 15 min, pour away the supernatant after centrifugation, dry at 70°C for 8 h to obtain a mixed solid; mix the mixed solid with 33 g of water, shake well and centrifuge at 7000 rpm for 12 min; repeat the steps of adding water and centrifuging after pouring out the supernatant, repeat for 3 times, and dry the obtained solid at 70°C for 24 h to obtain a hydrophilic aerogel.

[0064] Example 10

[0065] Take 1 g hydrophobic aerogel, 3 g TO-3 (isomeric tridecanol polyoxyethylene ether), 27 g ethanol and 27 g isopropyl alcohol to obtain a solid-liquid mixture under the condition of stirring at 780 rpm for 6 min; then stir at 55℃, 720 rpm for 8 h, centrifuge the obtained product at 6300 rpm for 10 min, pour away the supernatant after centrifugation, and dry at 80℃ for 7 h to obtain a mixed solid; mix the mixed solid with 35 g of water, shake thoroughly, and centrifuge at 6500 rpm for 10 min; pour away the supernatant, and repeat the steps of adding water and centrifuging, 5 times in total, and dry the obtained solid at 68℃ for 26 h to obtain a hydrophilic aerogel.

[0066] The hydrophilic aerogels prepared in Examples 1-10 were subjected to contact angle test, and the results are recorded in Table 1.

[0067] Table 1: Contact angle test results

[0068] Example Contact angle (°) Example 1 32.8 Example 2 34.6 Example 3 31.7 Example 4 35.3 Example 5 32.4 Example 6 33.3 Example 7 49.6 Example 8 52.7 Example 9 48.9 Example 10 50.2

[0069] As can be seen from the above examples, the present application provides a hydrophilic aerogel prepared from a hydrophobic aerogel, a surfactant and a solvent, and the present application obtains solid particles with uniform particle size by controlling the amount of solvent, the concentration of reactants, the concentration of surfactant and the reaction conditions. The hydrophilic aerogel prepared by the present application has small particle size and narrow distribution, and has good dispersibility in aqueous systems. The hydrophilic aerogel provided by the present application can be used as a superior thermal insulation material. The hydrophilic aerogel provided by the present application has a contact angle as low as 31.7°.

[0070] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A hydrophilic aerogel, characterized in that, It is prepared from raw materials comprising the following parts by mass: 0.5–1.5 parts hydrophobic aerogel, 2–4 parts surfactant, and 15–77 parts solvent; The surfactant is isotridecyl alcohol polyoxyethylene ether; The method for preparing the hydrophilic aerogel includes the following steps: (1) After mixing hydrophobic aerogel, surfactant and solvent, the mixture is heated, centrifuged and dried in sequence to obtain a mixed solid; (2) The mixed solid is washed and dried to obtain the hydrophilic aerogel; The heating temperature in step (1) is 45-60℃, the stirring speed is 600-800 rpm, and the time is 6-8h; The hydrophobic aerogel is a hydrophobic silica aerogel. The solvent is isopropanol and / or ethanol.

2. The method for preparing the hydrophilic aerogel according to claim 1, characterized in that, Includes the following steps: (1) After mixing hydrophobic aerogel, surfactant and solvent, the mixture is heated, centrifuged and dried in sequence to obtain a mixed solid; (2) The mixed solid is washed and dried to obtain the hydrophilic aerogel; The heating temperature in step (1) is 45-60℃, the stirring speed is 600-800 rpm, and the time is 6-8h; The hydrophobic aerogel is a hydrophobic silica aerogel.

3. The preparation method according to claim 2, characterized in that, The centrifugation speed in step (1) is 6000-7000 rpm and the time is 10-15 min.

4. The preparation method according to claim 3, characterized in that, The drying temperature in step (1) is 60-80℃ and the time is 7-9h.

5. The preparation method according to claim 4, characterized in that, The washing method described in step (2) is to mix the solid mixture with water and then centrifuge it; The mass ratio of the hydrophobic aerogel to water is 1:30-40; The centrifugation speed is 6000-7000 rpm, and the time is 10-15 min.

6. The preparation method according to claim 5, characterized in that, The washing process in step (2) is repeated 3 to 5 times.

7. The preparation method according to claim 6, characterized in that, The drying temperature in step (2) is 60-80℃ and the time is 20-28h.

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