Sol precursor, silicon dioxide aerogel, heat insulation sheet and preparation method
The preparation of silica aerogel by low-temperature hydrolysis and epoxy compound promotion solved the problem of uneven pore size distribution, produced uniform thermal insulation sheets, improved its thermal insulation and mechanical properties, and expanded its application fields.
Patent Information
- Application Number
- CN202410149706.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-01
- Publication Date
- 2025-08-01
AI Technical Summary
The uneven pore size distribution of existing silica aerogels leads to uneven performance of composite sheets, limiting their application.
By using an acidic catalyst and an epoxy compound as a gel promoter under low-temperature hydrolysis conditions to control the hydrolysis reaction rate, a sol precursor was prepared. Subsequently, a silica aerogel with uniform pore size distribution was prepared through gel formation, aging, and drying steps, and then composited with fiber sheets to prepare a thermal insulation sheet.
The uniform distribution of silica aerogel pore size was achieved, which improved the uniformity of thermal insulation performance and mechanical properties of the insulation sheet, and expanded its application range.
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Figure BDA0004695244910000091
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of composite materials, and particularly to a sol precursor, a silica aerogel, a heat-insulating sheet and a preparation method thereof. Background Art
[0002] With the continuous development of industries such as construction, electronics, chemical engineering, and national defense, the requirements for the heat-insulating and heat-preserving performance of materials are becoming increasingly strict, and the development of heat-insulating and heat-preserving materials mainly composed of porous materials has gradually received extensive attention. Among them, silica aerogel, with its three-dimensional network porous structure and porosity as high as 90%, can effectively reduce the heat transfer of gas phase and solid phase, and has excellent heat-insulating performance, and has important application prospects in important industrial fields such as mechanical production, building insulation, and aerospace.
[0003] However, the fragile mechanical properties of silica aerogel itself restrict its application in the field of heat insulation. At present, in order to enhance its mechanical properties, fiber felt is often used as a reinforcing phase for compounding, and through this means, the application range of silica aerogel has been significantly improved, enabling aerogel materials to be widely used in heat insulation in the fields of building materials, aerospace, and industrial pipelines.
[0004] However, the current silica aerogel is limited by the preparation process, and the distribution of its porous structure is not uniform, especially the pore size distribution is not uniform, resulting in the uneven properties and performance of the finally obtained composite sheet, which limits its application.
[0005] Therefore, a sol precursor, a silica aerogel, a heat-insulating sheet and a preparation method thereof are needed to at least partially solve the above problems. Summary of the Invention
[0006] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further detailed in the Detailed Description section. The Summary of the Invention section of the present application does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.
[0007] To at least partially solve the above problems, a first aspect of the present application provides a preparation method for preparing a sol precursor, the sol precursor being used for preparing a silica aerogel, and the preparation method includes:
[0008] A solution preparation step of adding a catalyst to an alcohol solvent under the condition of hydrolysis temperature and stirring evenly to obtain a mixed solution; and
[0009] A sol formation step of adding a silicon source and a gel promoter to the mixed solution, maintaining the hydrolysis temperature for a hydrolysis reaction to obtain a sol precursor;
[0010] Among them, the hydrolysis temperature is 0 - 10 °C,
[0011] the solvent includes alcohol substances, and the mixed solution contains water,
[0012] the catalyst is an acidic catalyst,
[0013] the gel promoter is an epoxide.
[0014] According to the preparation method of the present application, in the process of preparing the sol precursor, a lower hydrolysis temperature is used to slow down the reaction rate. At the same time, an epoxide is used as the gel promoter to simplify the system slowly and uniformly, promoting the hydrolysis reaction. As a result, the entire hydrolysis reaction process is mild and uniform, eliminating phenomena such as precipitation or agglomeration caused by a sharp change in pH, and thus being beneficial to improving the uniformity of the pore size distribution of the silica aerogel prepared from the sol precursor.
[0015] Optionally, the dosage of the silicon source is 18.75 - 100 parts by volume;
[0016] the dosage of the solvent is 150 - 200 parts by volume;
[0017] the dosage of the gel promoter is greater than or equal to 0.6 parts by volume.
[0018] Optionally, the dosage of the epoxide is greater than or equal to 0.8 parts by volume.
[0019] Optionally, the dosage of the silicon source is 25 - 37.5 parts by volume.
[0020] Optionally, the hydrolysis temperature is 0 - 3 °C.
[0021] Optionally, the acidic catalyst is an aqueous hydrochloric acid solution with a molar concentration of 0.09 - 0.11 mol / L, and the dosage is 22 - 25 parts by volume.
[0022] Optionally, the silicon source is selected from at least one of silicate, silicate ester, silane, siloxane, silicone ether, and silicon coupling agent.
[0023] Optionally, the silicon source is selected from at least one of sodium silicate, methyl orthosilicate, and ethyl orthosilicate.
[0024] Optionally, the silicon source is ethyl orthosilicate.
[0025] Optionally, the gel promoter is selected from at least one of ethylene oxide, propylene oxide, butylene oxide, and epichlorohydrin.
[0026] Optionally, the gel promoter is propylene oxide.
[0027] Optionally, the alcohol substance is anhydrous ethanol.
[0028] Optionally, the solution preparation step includes: adding an acidic catalyst and a solvent into a reactor, stirring at a hydrolysis temperature for 20 - 40 min to obtain the mixed solution;
[0029] The sol formation step includes: adding a silicon source into the mixed solution, stirring at the hydrolysis temperature for 3 - 5 h, and then adding a gel promoter and stirring for 3 - 8 min to obtain the sol precursor.
[0030] The second aspect of the present application provides a sol precursor, which is used for preparing silica aerogel, and the sol precursor is prepared by the preparation method described in the first aspect above.
[0031] The silica aerogel prepared from the sol precursor according to the present application has a uniform pore size distribution.
[0032] The third aspect of the present application provides a preparation method for preparing silica aerogel, and the preparation method includes the following steps:
[0033] Providing the sol precursor described in the second aspect above;
[0034] Forming a gel from the sol precursor through a gel formation step;
[0035] Aging the gel through an aging step;
[0036] Drying the aged gel through a drying step.
[0037] The silica aerogel prepared by the preparation method according to the present application using the above sol precursor has a uniform pore size distribution.
[0038] Optionally, the gel formation step includes: reacting the sol precursor at 70 - 90 °C for 0.5 - 1.5 h to form a gel.
[0039] Optionally, the aging step includes: aging the gel at 50 - 70 °C for 36 - 60 h.
[0040] Optionally, the drying step includes:
[0041] A solvent replacement step, using anhydrous ethanol to replace the solvent of the aged gel at 50 - 70 °C, wherein the anhydrous ethanol is replaced every 12 - 36 h, and the replacement is carried out for 36 - 60 h in total;
[0042] A supercritical drying step, drying the gel after solvent replacement using a CO2 supercritical drying device.
[0043] Optionally, the CO2 supercritical drying device has a drying kettle and a separation kettle, and the drying process includes:
[0044] Placing the gel after solvent replacement into the drying kettle, introducing CO2 into the CO2 supercritical drying device at a flow rate of 20 - 40 L / h for 5 - 10 h;
[0045] Wherein, controlling the temperature in the drying kettle to be 70 - 80 °C and the pressure in the drying kettle to be 14 - 18 MPa, so that CO2 enters the supercritical state to displace ethanol in the sheet after gel aging;
[0046] Controlling the temperature in the separation kettle to be 30 - 50 °C and the pressure in the separation kettle to be 7 - 8 MPa, so that the CO2 and ethanol entering the separation kettle can be separated.
[0047] The fourth aspect of the present application provides a silica aerogel, which is made by the preparation method described in the third aspect above.
[0048] The silica aerogel according to the present application has an excellent framework structure and pore size distribution.
[0049] Optionally, the specific surface area of the silica aerogel is greater than or equal to 1000 m 2 / g.
[0050] Optionally, the pore volume of the silica aerogel is greater than or equal to 2.0 cm 3 / g.
[0051] Optionally, the adsorption volume of the silica aerogel is greater than or equal to 2000 cm 3 / g.
[0052] The fifth aspect of the present application provides a preparation method for preparing a heat-insulating sheet, and the preparation method includes the following steps:
[0053] Providing a fiber sheet;
[0054] Providing the sol precursor described in the second aspect above, and impregnating the fiber sheet with the sol precursor;
[0055] Performing a gel formation step, an aging step, and a drying step on the fiber sheet impregnated with the sol precursor to obtain the heat-insulating sheet.
[0056] According to the preparation method of the present application, the heat-insulating performance of the prepared heat-insulating sheet is evenly distributed.
[0057] The sixth aspect of the present application provides a heat-insulating sheet,
[0058] The heat-insulating sheet includes a fiber sheet and the silica aerogel described in the fourth aspect above; or
[0059] The heat-insulating sheet is made by the preparation method described in the fifth aspect above.
[0060] The heat-insulating sheet according to the present application has good uniformity. Detailed Description of the Invention
[0061] In the following description, numerous specific details are given to provide a more thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application may be practiced without one or more of these details. In other instances, well-known features have not been described in order to avoid obscuring the present application.
[0062] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprises" and / or "comprising" are used in this specification, they specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.
[0063] The ordinal numbers such as "first" and "second" cited in the present application are merely identifiers and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term "first component" does not imply the existence of a "second component" by itself, and the term "second component" does not imply the existence of a "first component" by itself. It should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer" and similar expressions used herein are for illustrative purposes only and are not limiting.
[0064] The present application provides a preparation method for preparing a sol precursor, a sol precursor, a preparation method for preparing a silica aerogel, a silica aerogel, a preparation method for preparing a heat-insulating sheet, and a heat-insulating sheet.
[0065] Among them, the preparation method for preparing a sol precursor includes a solution preparation step and a sol formation step. The solution preparation step includes adding a catalyst to an alcohol solvent under the condition of hydrolysis temperature and stirring evenly to obtain a mixed solution. The sol formation step includes adding a silicon source and a gel promoter to the mixed solution, maintaining the hydrolysis temperature for hydrolysis reaction to obtain a sol precursor.
[0066] The solvent includes alcohol substances, and water is contained in the mixed solution. The catalyst is an acidic catalyst, which is used to adjust the pH value of the mixed solution. The hydrolysis temperature is 0 - 10 °C. The gel promoter is an epoxide. It can be understood that the mixed solution is at least a mixture of water, acidic substances and alcohol substances.
[0067] According to the preparation method of the present application, in the process of preparing the sol precursor, a lower hydrolysis temperature is used to slow down the reaction rate, and at the same time, an epoxide is used as a gel promoter to slowly and uniformly alkalize the system, promoting the hydrolysis reaction. As a result, the whole hydrolysis reaction process is mild and uniform, eliminating phenomena such as precipitation or agglomeration caused by a sharp change in acidity or alkalinity, and thus being beneficial to improving the uniformity of the pore size distribution of the silica aerogel prepared from the sol precursor.
[0068] As an alternative embodiment, the dosage of the solvent is 150 - 200 parts by volume. The dosage of the silicon source is 18.75 - 100 parts by volume. The dosage of the gel promoter is greater than or equal to 0.6 parts by volume.
[0069] Furthermore, the preparation method for preparing the sol precursor includes: a solution preparation step of adding an acidic catalyst and a solvent into a reactor, stirring for 20 - 40 min at the hydrolysis temperature to obtain a mixed solution; a sol formation step of adding a silicon source into the mixed solution, stirring for 3 - 5 h at the hydrolysis temperature, and then adding a gel promoter and stirring for 3 - 8 min to obtain a sol precursor.
[0070] Among them, the hydrolysis temperature is preferably 0 - 3 °C. The dosage of the silicon source is preferably 25 - 37.5 parts by volume. The dosage of the epoxide is preferably greater than or equal to 0.8 parts by volume.
[0071] The acidic catalyst can be hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, nitric acid, acetic acid, carbonic acid, oxalic acid, formic acid, acetic acid, butyric acid, etc. Preferably, the acidic catalyst is hydrochloric acid. More specifically, the acidic catalyst can be an aqueous solution of hydrochloric acid, and the water is preferably deionized water. Thus, the water in the hydrochloric acid aqueous solution can be part of the solvent.
[0072] As an alternative embodiment, the acidic catalyst is an aqueous solution of hydrochloric acid with a molar concentration of 0.09 - 0.11 mol / L, and the dosage is 22 - 25 parts by volume. Correspondingly, when the water in the hydrochloric acid aqueous solution exists as part of the solvent, the dosage of the alcohol substances in the solvent is 128 - 175 parts by volume.
[0073] The alcohol substance can be a compound containing a hydrocarbon group in the molecule or a compound in which a carbon on the side chain of a benzene ring is combined with a hydroxyl group. For example, the alcohol substance can be selected from at least one of methanol, ethanol, propanol, butanol, octanol, pentanol, hexanol, heptanol, decanol, ethylene glycol, glycerol, propylene glycol, pentaerythritol, allyl alcohol, vinyl alcohol, and benzyl alcohol. Preferably, the alcohol substance is absolute ethanol.
[0074] The silicon source is selected from at least one of silicate, silicate ester, silane, siloxane, silicone ether, and silicon coupling agent. Preferably, the silicon source is selected from at least one of sodium silicate, methyl orthosilicate, and ethyl orthosilicate. Further preferably, the silicon source is ethyl orthosilicate.
[0075] The gel promoter is selected from at least one of ethylene oxide, propylene oxide, butylene oxide, and epichlorohydrin. Preferably, the gel promoter is propylene oxide.
[0076] As an alternative embodiment, the preparation method for preparing the sol precursor includes: a solution preparation step of adding 22 - 25 parts by volume of a 0.09 - 0.11 mol / L hydrochloric acid aqueous solution and 128 - 175 parts by volume of absolute ethanol into a reactor, stirring at a hydrolysis temperature of 0 - 3 °C for 20 - 40 min to obtain a mixed solution; a sol formation step of adding 25 - 37.5 parts by volume of ethyl orthosilicate into the mixed solution, stirring at a hydrolysis temperature of 0 - 3 °C for 3 - 5 h, and then adding more than 0.8 parts by volume of propylene oxide and stirring for 3 - 8 min to obtain the sol precursor.
[0077] The second aspect of the present application provides a sol precursor prepared by the above preparation method for preparing the sol precursor. This sol precursor is used for preparing silica aerogel.
[0078] The silica aerogel prepared from the sol precursor according to the present application has a uniform pore size distribution.
[0079] The third aspect of the present application provides a preparation method for preparing silica aerogel, which includes the following steps:
[0080] Provide the sol precursor of the second aspect above.
[0081] Form a gel from the sol precursor through a gel formation step. Among them, the gel formation step includes reacting the sol precursor at 70 - 90 °C for 0.5 - 1.5 h to form a gel.
[0082] Age the gel through an aging step. Among them, in the aging step, age the gel at 50 - 70 °C for 36 - 60 h.
[0083] The aged gel is dried through a drying step. Preferably, the drying step includes a solvent replacement step and a supercritical drying step. Among them, the aged gel is subjected to solvent replacement with absolute ethanol at 50-70 °C, where the absolute ethanol is replaced every 12-36 h and the replacement is carried out for 36-60 h in total. Then, the gel after solvent replacement is dried using a CO2 supercritical drying device. The CO2 supercritical drying device has a drying kettle and a separation kettle.
[0084] The drying treatment is specifically as follows: the gel after solvent replacement is placed in the drying kettle, and CO2 is introduced into the CO2 supercritical drying device at a flow rate of 20-40 L / h for 5-10 h. Among them, the temperature in the drying kettle is controlled at 70-80 °C, and the pressure in the drying kettle is controlled at 14-18 MPa so that CO2 enters the supercritical state to replace the ethanol in the sheet after gel aging. The temperature in the separation kettle is controlled at 30-50 °C, and the pressure in the separation kettle is controlled at 7-8 MPa so that the CO2 and ethanol entering the separation kettle can be separated.
[0085] According to the preparation method of the present application, the silica aerogel made from the above sol precursor has a uniform pore size distribution.
[0086] The fourth aspect of the present application provides a silica aerogel, which is made by the preparation method of the third aspect above. According to the silica aerogel of the present application, it has an excellent framework structure and pore size distribution.
[0087] Exemplarily, the specific surface area of the silica aerogel is greater than 1000 m 2 / g. The pore volume of the mesopores in the silica aerogel is greater than or equal to 2.0 cm 3 / g. The adsorption volume of the silica aerogel is greater than or equal to 2000 cm 3 / g.
[0088] The embodiments of the present application will be introduced in more detail below in combination with examples and comparative examples.
[0089] Example 1:
[0090] Control the temperature of the reaction kettle at 3°C. Measure 22.5 ml of 0.1 mol / L hydrochloric acid aqueous solution with a measuring cylinder and add it to the reaction kettle. Measure 150 ml of anhydrous ethanol with a measuring cylinder and add it to the reaction kettle. Stir for 30 min. Then measure 18.75 ml of tetraethyl orthosilicate with a measuring cylinder and add it to the reaction kettle. Continue to stir for 4 h. Add 0.8 ml of propylene oxide and stir for 5 min. Seal the reaction kettle and transfer it to an oven at 80°C for heat treatment for 1 h, and then transfer it to an oven at 60°C for aging for 48 h. After aging, use ethanol to replace the solvent of the product, replace it once every 24 h, and replace it twice in total. Place the product after solvent replacement in the drying kettle of a CO2 supercritical drying device, and introduce CO2 at a flow rate of 20 - 40 L / h for 5 - 10 h. Control the temperature in the drying kettle at 75°C, control the pressure in the drying kettle at 15 MPa, control the temperature in the separation kettle at 40°C, and control the pressure in the separation kettle at 7.5 MPa.
[0091] After that, use a Micromeritics 2460 full-automatic specific surface area analyzer to test the specific surface area, adsorption volume, etc. of the silica aerogel.
[0092] Example 2:
[0093] The amount of tetraethyl orthosilicate added is 25 ml, and the other components, process steps are the same as those in Example 1.
[0094] Example 3:
[0095] The amount of tetraethyl orthosilicate added is 37.5 ml, and the other components, process steps are the same as those in Example 1.
[0096] Example 4:
[0097] The amount of tetraethyl orthosilicate added is 50 ml, and the other components, process steps are the same as those in Example 1.
[0098] Example 5:
[0099] The amount of tetraethyl orthosilicate added is 100 ml, and the other components, process steps are the same as those in Example 1.
[0100] Example 6:
[0101] The amount of propylene oxide added is 0.6 ml, and the other components, process steps are the same as those in Example 2.
[0102] Example 7:
[0103] The amount of propylene oxide added is 1.6 ml, and the other components, process steps are the same as those in Example 2.
[0104] Example 8:
[0105] The addition amount of propylene oxide is 20 ml, and the other components, process steps are the same as those in Example 2.
[0106] Example 9:
[0107] The temperature of the reaction kettle is controlled at 0 °C, and the other components, process steps are the same as those in Example 2.
[0108] Example 10:
[0109] The temperature of the reaction kettle is controlled at 10 °C, and the other components, process steps are the same as those in Example 2.
[0110] Comparative Example 1:
[0111] The addition amount of tetraethyl orthosilicate is 6.25 ml, and the other components, process steps are the same as those in Example 1. Comparative Example 2:
[0112] The addition amount of tetraethyl orthosilicate is 12.5 ml, and the other components, process steps are the same as those in Example 1.
[0113] Comparative Example 3:
[0114] The addition amount of tetraethyl orthosilicate is 250 ml, and the other components, process steps are the same as those in Example 1.
[0115] Comparative Example 4:
[0116] The addition amount of propylene oxide is 0.4 ml, and the other components, process steps are the same as those in Example 2. Comparative Example 4 did not gel finally and was not tested.
[0117] Comparative Example 5:
[0118] The temperature of the reaction kettle is controlled at 25 °C, and the other components, process steps are the same as those in Example 2.
[0119] The differences and test results among Examples 1 - 10 and Comparative Examples 1 - 5 are summarized in Table 1 below.
[0120] Table 1
[0121]
[0122] In actual use, it can be considered that the specific surface area of the silica aerogel is greater than 1000 m 2 / g, and the pore volume of the mesopores in the silica aerogel is greater than or equal to 2.0 cm 3 / g, which belongs to a better situation. Preferably, the adsorption volume of the silica aerogel should also be greater than or equal to 2000 cm 3 / g.
[0123] Combining the above Examples 1-5 and Comparative Examples 1-3, it can be seen that too much or too little TESO is not conducive to the formation of silica aerogel.
[0124] Combining the above-mentioned Comparative Example 4, Example 6, Example 2, Example 7, and Example 8, it can be seen that when the amount of propylene oxide is greater than 0.6 ml, the ring-opening reaction can effectively adjust the pH value of the system, which can play a positive role in the reaction and promote gelation. As the amount of propylene oxide increases, the performance change is no longer obvious at an amount of 0.8 ml or more. This shows that the gel-promoting effect of propylene oxide is relatively gentle. As long as the minimum amount of propylene oxide is used, it can play a gel-promoting role, and excess propylene oxide will not have a negative effect on the reaction, making it particularly suitable for industrial production.
[0125] In combination with the above-mentioned Example 9, Example 2, Example 10 and Comparative Example 5, it can be explained that the hydrolysis reaction temperature affects the performance of the silica aerogel finally obtained. Among them, under conditions of 3°C and below, the performance of the silica aerogel is better. Under conditions of 10°C, although the specific surface area and pore volume have decreased to a certain extent, they are still within an acceptable range. However, at room temperature (25°C in Comparative Example 5), the structure of the silica aerogel shrinks severely and the performance declines significantly. It can be seen that the lower the temperature, the slower the hydrolysis reaction rate will be, which has a positive promoting effect on the formation of the skeleton structure of the silica aerogel. However, due to the presence of a small amount of water in the solvent, there is a possibility of condensation below 0°C, which is not conducive to production.
[0126] A fifth aspect of the present application provides a preparation method for preparing a thermal insulation sheet, the preparation method comprising the following steps:
[0127] A fiber sheet is provided. For example, the fiber sheet can be a glass fiber sheet, more specifically, a needle-punched glass fiber mat.
[0128] The sol precursor of the second aspect is provided and impregnated with the fiber sheet. As an alternative embodiment, the fiber sheet can be directly impregnated by impregnation and then extruded. Alternatively, a vacuum infusion method can be used, in which the fiber sheet is placed in a sealed container, negative pressure is applied to the container, and the sol precursor is injected into the container, so that the sol precursor fully impregnates the fiber sheet under the negative pressure.
[0129] The fiber sheet impregnated with the sol precursor is then subjected to a gel forming step, an aging step, and a drying step to obtain a thermal insulation sheet. The gel forming step, aging step, and drying step may be similar to those in the method for preparing silica aerogel according to the third aspect, and are not further described here.
[0130] According to the preparation method of the present application, the heat insulation performance of the prepared heat insulation sheet is evenly distributed.
[0131] The sixth aspect of the present application provides a heat insulation sheet. Among them, the heat insulation sheet can be made by the preparation method described in the fifth aspect above.
[0132] Or the heat insulation sheet includes a fiber sheet and the silica aerogel of the fourth aspect above.
[0133] Exemplarily, the powder of the silica aerogel of the fourth aspect above can be directly compounded into the pores of the fiber sheet. For example, the powder of the silica aerogel can be filled into the voids of the fiber sheet by applying an alternating electric field.
[0134] The heat insulation sheet according to the present application has good uniformity.
[0135] The processes and steps described in all the above preferred embodiments are only examples. Unless adverse effects occur, various processing operations can be carried out in an order different from the order of the above processes. The order of the steps of the above processes can also be increased, combined or deleted according to actual needs.
[0136] Unless otherwise defined, the technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the technical field of the present application. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application. The features described in one embodiment herein can be applied alone or in combination with other features in another embodiment, unless the feature is not applicable or otherwise stated in that other embodiment.
[0137] The present application has been illustrated by the above embodiments. However, it should be understood that the above embodiments are only for the purpose of exemplification and illustration, and the present application is not limited to the above embodiments. According to the teachings of the present application, more variations and modifications can be made, and these variations and modifications all fall within the scope claimed by the present application.
Claims
1. A preparation method for preparing a sol precursor, characterized in that, The sol precursor is used for preparing silica aerogel, and the preparation method includes: A solution preparation step of adding a catalyst to a solvent under the condition of hydrolysis temperature and stirring evenly to obtain a mixed solution; and A sol formation step of adding a silicon source and a gel promoter to the mixed solution, maintaining the hydrolysis temperature to carry out a hydrolysis reaction to obtain a sol precursor; wherein, the hydrolysis temperature is 0-10°C, the solvent includes an alcohol substance, and the mixed solution contains water, the catalyst is an acidic catalyst, the gel promoter is an epoxide.
2. The preparation method according to claim 1, wherein the dosage of the silicon source is 18.75-100 parts by volume; the dosage of the solvent is 150-200 parts by volume; the dosage of the gel promoter is greater than or equal to 0.6 parts by volume.
3. The preparation method according to claim 2, characterized in that The dosage of the epoxide is greater than or equal to 0.8 parts by volume.
4. The preparation method according to claim 2, wherein The dosage of the silicon source is 25-37.5 parts by volume.
5. The preparation method according to claim 1, wherein The hydrolysis temperature is 0-3°C.
6. The preparation method according to claim 1, wherein The acidic catalyst is an aqueous hydrochloric acid solution with a molar concentration of 0.09-0.11 mol / L, and the dosage is 22-25 parts by volume.
7. The preparation method according to claim 1, wherein The silicon source is selected from at least one of silicate, silicate ester, silane, siloxane, silicone ether and silicon coupling agent.
8. The preparation method according to claim 7, characterized in that, The silicon source is selected from at least one of sodium silicate, methyl orthosilicate and ethyl orthosilicate.
9. The preparation method according to claim 8, wherein, The silicon source is ethyl orthosilicate.
10. The preparation method according to claim 1, wherein, The gel promoter is selected from at least one of ethylene oxide, propylene oxide, butylene oxide and epichlorohydrin.
11. The preparation method according to claim 10, characterized in that, The gel promoter is propylene oxide.
12. According to the preparation method described in claim 1, characterized in that, The alcohol substance is anhydrous ethanol.
13. The preparation method according to any one of claims 1-12, wherein the solution preparation step includes: adding an acidic catalyst and a solvent into a reactor, stirring at the hydrolysis temperature for 20-40 min to obtain the mixed solution; the sol formation step includes: adding a silicon source to the mixed solution, stirring at the hydrolysis temperature for 3-5 h, and then adding a gel promoter and stirring for 3-8 min to obtain the sol precursor.
14. A sol precursor, characterized in that, The sol precursor is used for preparing silica aerogel, and the sol precursor is made by the preparation method according to any one of claims 1-12.
15. A preparation method for preparing silica aerogel, characterized in that, The preparation method includes the following steps: providing the sol precursor according to claim 14; forming a gel from the sol precursor through a gel formation step; aging the gel through an aging step; drying the aged gel through a drying step.
16. The preparation method according to claim 15, characterized in that, The gel formation step includes: reacting the sol precursor at 70-90°C for 0.5-1.5 h to form a gel.
17. The preparation method according to claim 15, characterized in that, The aging step includes: aging the gel at 50-70°C for 36-60 h.
18. The preparation method according to claim 15, characterized in that, The drying step includes: a solvent replacement step of using anhydrous ethanol to replace the solvent of the aged gel at 50-70°C, wherein anhydrous ethanol is replaced every 12-36 h, and the replacement is carried out for 36-60 h in total; a supercritical drying step of drying the gel after solvent replacement by using a CO2 supercritical drying device.
19. The preparation method according to claim 18, wherein, The CO2 supercritical drying device has a drying kettle and a separation kettle, and the drying process includes: Placing the gel after solvent replacement into the drying kettle, introducing CO2 into the CO2 supercritical drying device at a flow rate of 20 - 40 L / h for 5 - 10 h; Among them, controlling the temperature in the drying kettle to be 70 - 80 °C and the pressure in the drying kettle to be 14 - 18 MPa, so that CO2 enters the supercritical state to displace ethanol in the sheet after gel aging; Controlling the temperature in the separation kettle to be 30 - 50 °C and the pressure in the separation kettle to be 7 - 8 MPa, so that the CO2 and ethanol entering the separation kettle can be separated.
20. A silica aerogel, characterized in that, The silica aerogel is made by the preparation method according to any one of claims 15 - 19.
21. The silica aerogel according to claim 20, characterized in that, The specific surface area of the silica aerogel is greater than or equal to 1000m 2 / g.
22. The silica aerogel according to claim 20, characterized in that, The pore volume of the silica aerogel is greater than or equal to 2.0 cm 3 / g.
23. The silica aerogel according to claim 20, characterized in that, The adsorption volume of the silica aerogel is greater than or equal to 2000 cm 3 / g.
24. A preparation method for preparing a heat-insulating sheet, characterized in that, The preparation method includes the following steps: Providing a fiber sheet; Providing the sol precursor according to claim 14, and impregnating the fiber sheet with the sol precursor; Performing a gel formation step, an aging step, and a drying step on the fiber sheet impregnated with the sol precursor to obtain the heat-insulating sheet.
25. A heat-insulating sheet, characterized in that the heat-insulating sheet includes a fiber sheet and the silica aerogel according to any one of claims 20 - 23; or the heat-insulating sheet is made by the preparation method according to claim 24.