Aerogel felt and preparation method thereof

Abstract

The invention relates to the technical field of aerogel, and provides an aerogel felt and a preparation method thereof.The method comprises the steps that 1, multiple layers of fiber sheets are stacked and then mixed with a sol solution, and a pretreated product is obtained; (2) applying pressure to the pretreated product in the gelation process of the pretreated product to obtain a gel felt; (3) drying the gel felt to obtain an aerogel felt; in the step (2), the thickness of the gel felt is 90%-97% of the thickness of the pretreated product due to the applied pressure. By adopting the method disclosed by the invention, the aerogel felt with larger thickness can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogels, and particularly relates to a preparation method of an aerogel felt and an aerogel felt prepared by this method. Background Art

[0002] An aerogel refers to a solid structure that does not collapse after the liquid in the gel is replaced by a gas. The high-porosity structure endows the aerogel with characteristics different from other solid materials. Among them, the heat insulation performance is relatively prominent, and it is a natural super-insulating material. By compounding the aerogel with a matrix material to form an aerogel felt, not only the characteristic of low thermal conductivity of the aerogel is retained, but the finished product also has the characteristics of flexibility and high tensile strength, and can be widely used in the petrochemical, electric power and heat pipeline networks, and building insulation industries.

[0003] However, in the current preparation process of aerogel felts, only thin products can be made. In order to achieve better heat insulation performance, products with a larger thickness need to be prepared. Therefore, how to increase the thickness of aerogel felt products is a technical problem to be solved at present. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above problems existing in the prior art, and provide a preparation method of an aerogel felt and an aerogel felt prepared by this method, which can obtain an aerogel felt with a larger thickness.

[0005] To achieve the above purpose, in the first aspect of the present invention, a preparation method of an aerogel felt is provided, and the method includes:

[0006] (1) Stacking multiple layers of fiber sheets and mixing them with a sol solution to obtain a pre-treated product;

[0007] (2) Applying pressure to the pre-treated product during the gelation process of the pre-treated product to obtain a gel felt;

[0008] (3) Drying the gel felt to obtain an aerogel felt;

[0009] In step (2), the applied pressure makes the thickness of the gel felt 90% - 97% of the thickness of the pre-treated product.

[0010] Preferably, in step (2), the method includes applying pressure to the pre-treated product until the gelation ends during the gelation process of the pre-treated product to obtain a gel felt.

[0011] Preferably, the fiber sheet is a hydrophilic fiber sheet after being hydrophilically treated.

[0012] Preferably, in step (3), the method further includes: aging the gel felt before drying the gel felt.

[0013] In a second aspect of the present invention, there is provided an aerogel felt, which is the aerogel felt prepared by the method as described above.

[0014] The present invention adopts the above technical solution and has the following beneficial effects:

[0015] (1) The inventors found that if multiple layers of fiber sheets are stacked and then mixed with the sol solution and naturally gelated, problems such as large thickness tolerances between the aerogel felts and easy delamination are likely to occur, and even rolling after mixing is difficult to solve this problem. The method provided by the present invention presses during the gelation process (preferably continuously presses). On the one hand, part of the sol solution between the multiple layers of fiber sheets is extruded, which can reduce the thickness of the gel layer formed by the sol solution gel between the sheets, and can greatly improve the mechanical strength between the gel layers and reduce the delamination problem after the multiple layers of sheets are stacked. Because when the gel layer is too thick, due to the light weight and weak mechanical properties of the gel layer, the connection performance of the gel layer to the sheets on both sides is poor, and the gel layer is more likely to break, causing the sheets of the prepared aerogel felt to separate, affecting the use and heat insulation performance of the aerogel felt finished product. At the same time, continuous pressing can play a pressure confinement role in the gel process of the aerogel sol solution, adjust the growth amplitude of the pores in the aerogel to a certain extent, reduce the excessive fluffiness of the gel layer caused by the excessive growth of the aerogel sol solution, improve the mechanical strength of the gel layer, improve the mechanical properties of the prepared aerogel felt, and also make the thickness of the gel layer formed when the nanoparticles in the sol solution crosslink and gelate more uniform, reducing the thickness tolerance.

[0016] (2) Under the preferred conditions, the prepared aerogel felt is less likely to delaminate and has good heat insulation performance at the same time.

[0017] (3) The method of the present invention is simple to operate and is suitable for large-scale production.

[0018] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In this article, unless otherwise specified, the data ranges include the endpoints. Detailed Embodiments

[0019] The following details the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0020] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention pertains.

[0021] The first aspect of the present invention provides a method for preparing an aerogel felt, the method comprising:

[0022] (1) Stacking multiple layers of fiber sheets and mixing them with a sol solution to obtain a pre-treated product;

[0023] (2) Applying pressure to the pre-treated product during the gelation process of the pre-treated product to obtain a gel felt;

[0024] (3) Drying the gel felt to obtain an aerogel felt;

[0025] In step (2), the applied pressure makes the thickness of the gel felt 90% - 97% of the thickness of the pre-treated product, for example, it can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% and any range composed of any two values.

[0026] In some embodiments, the number of layers of the fiber sheets is more than 2 layers, for example, it can be 2 layers, 3 layers, 4 layers or 5 layers, etc.

[0027] In the present invention, the fiber sheets can be any fiber material in the art that can enhance the performance of the aerogel. In some embodiments, the fiber sheets include at least one of wet-processed glass fiber sheets, needled glass fiber sheets, ceramic fiber sheets and pre-oxidized fiber sheets. The fiber sheets can be directly commercially available or obtained by cutting a rolled material into sheets.

[0028] In some embodiments, the fiber sheets are hydrophilic fiber sheets after being subjected to a hydrophilic treatment.

[0029] The hydrophilic fiber sheets can be obtained through commercial purchase or self-preparation. The hydrophilic treatment can be a conventional hydrophilic treatment method in the art and will not be elaborated herein.

[0030] In some embodiments, the sol solution is a silica sol solution, an alumina sol solution or a silica-alumina composite sol solution for preparing an aerogel.

[0031] In some embodiments, the sol solution is a silica sol solution, and the precursor of the silica sol solution is an alkyl orthosilicate and / or an alkyl alkoxysilane.

[0032] In some embodiments, the alkyl orthosilicate includes at least one of tetramethyl orthosilicate, tetraethyl orthosilicate, methyltriethyl orthosilicate, dimethyldiethyl orthosilicate, tetrapropyl orthosilicate, tetra-isopropyl orthosilicate, tetrabutyl orthosilicate, tetra-sec-butyl orthosilicate, tetra-tert-butyl orthosilicate, tetrahexyl orthosilicate, tetracyclohexyl orthosilicate and tetra-icosyl orthosilicate.

[0033] In some embodiments, the alkylalkoxysilane includes one or more of methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, vinyltriethoxysilane, propyltrimethoxysilane, and propyltriethoxysilane.

[0034] The silica sol solution may further contain a gel catalyst for catalyzing the gelation of the silica sol solution. In some embodiments, the gel catalyst is selected from inorganic bases and / or organic bases.

[0035] In some embodiments, the inorganic base is any one or more of sodium hydroxide, potassium hydroxide, ammonia water, ammonium fluoride, ammonium bicarbonate, sodium carbonate, and sodium bicarbonate.

[0036] In some embodiments, the organic base is any one or more of ethanolamine, diethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, isopropanolamine, aniline, o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

[0037] In some embodiments, the content of the gel catalyst makes the pH of the silica sol solution between 7 and 11, and more specifically, the content of the gel catalyst makes the pH of the sol solution between 7 and 8, which can increase the porosity of the product and the gel time is extremely fast.

[0038] In some embodiments, the silica sol solution may further contain an alcohol, and the alcohol may be at least one of methanol, ethanol, isopropanol, and butanol (such as n-butanol).

[0039] In some embodiments, the silica sol solution may further contain water.

[0040] The content of each component in the silica sol can be the conventional content in the art and will not be elaborated here.

[0041] In one embodiment, the precursor of the silica sol solution, the gel catalyst, the alcohol, and water are mixed uniformly to obtain the silica sol solution.

[0042] In some embodiments, the sol solution is an alumina sol solution, and the precursor of the alumina sol solution includes at least one of aluminum isopropoxide, aluminum sec-butoxide, and aluminum nitrate.

[0043] In some embodiments, the alumina sol solution may further contain a chelating agent, a catalyst for the aluminum sol solution, an alcohol, and water.

[0044] In some embodiments, the chelating agent includes at least one of acetylacetone, acetic acid, and ethyl acetoacetate.

[0045] In some embodiments, the catalyst for the alumina sol solution includes at least one of sodium hydroxide, potassium hydroxide, ammonia water, and ammonium fluoride. The content of the catalyst for the alumina sol solution is such that the pH of the alumina sol solution is between 7 and 11, preferably between 7 and 8.

[0046] In some embodiments, the alcohol in the alumina sol solution includes at least one of ethanol, isopropanol, and n-butanol.

[0047] The content of each component in the alumina sol can be the conventional content in the art and will not be elaborated here.

[0048] In one embodiment, the silica-alumina composite sol solution includes a precursor of the silica sol solution, a precursor of the alumina sol solution, a gel catalyst, a catalyst for the alumina sol solution, a chelating agent, an alcohol, and water.

[0049] The types of each component can be referred to the above content, and their dosages can be the conventional dosages in the art and will not be elaborated here.

[0050] In some embodiments, the gel catalyst and the catalyst for the alumina sol solution can be the same or different. The content of the gel catalyst and the catalyst for the alumina sol solution is such that the pH of the alumina sol solution is between 7 and 11, preferably between 7 and 8, and there is no particular limitation on their dosage ratio.

[0051] In some embodiments, in step (1), the mixing method may include applying the sol solution to the fiber sheet by at least one of pouring, spraying, brushing, and soaking.

[0052] In some embodiments, in step (2), the method includes applying pressure to the pre-treatment product until the gelation ends during the gelation process of the pre-treatment product to obtain a gel felt. The time for applying pressure can be adjusted according to the gelation time, for example, it can be 5 to 10 minutes.

[0053] In some embodiments, the method of applying pressure is to press with a pressing member.

[0054] In some embodiments, the pressing member is a pressure roller or a pressing plate. For example, the pre-treatment product can be placed on an operating platform and pressed by the pressing member to prepare a gel felt. The distance between the pressing member and the operating platform is 90% to 97% of the thickness of the pre-treatment product.

[0055] In some embodiments, the method further includes: in step (3), before drying the gel felt, aging the gel felt.

[0056] In some embodiments, the aging treatment is carried out by using an aging agent to age the gel felt. The aging agent can be an alcohol solvent, such as at least one of methanol, ethanol, isopropanol, and butanol. The specific way of the aging treatment can be to immerse the gel felt in an alcohol solution for 4 to 6 hours.

[0057] In some embodiments, the aging treatment is carried out by wrapping the gel felt with a membrane material and aging it for 2 to 8 hours. The membrane material can be a conventional membrane material in the art as long as it can wrap the gel felt, such as PET or PVC, etc.

[0058] In some embodiments, the temperature of the aging treatment may not exceed 30 °C.

[0059] In some embodiments, in step (3), the method further includes: before or after drying the gel felt, hydrophobically modifying the gel felt with a hydrophobizing agent. For example, the dried gel felt can be subjected to gas-phase hydrophobization treatment.

[0060] In some embodiments, the hydrophobizing agent includes at least one of hydrophobic alkoxysilanes, hexamethyldisiloxane, and hexamethyldisilazane. The hydrophobizing agent can be gaseous or liquid.

[0061] In some embodiments, the formula of the hydrophobic alkoxysilanes is R 1m Si(OR2) (4-m) , where R1 is a hydrophobic group, R2 is an alkyl group, m is the number of hydrophobic groups, 4 - m is the number of alkyl groups, and m is an integer between 1 and 3.

[0062] In some embodiments, the hydrophobizing agent includes at least one of methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, chloropropyltriethoxysilane, chloropropyltrimethoxysilane, chloropropylmethyldimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, trimethylchlorosilane, hexamethyldisiloxane, and hexamethyldisilazane.

[0063] In some embodiments, the drying method is supercritical drying, atmospheric drying, or freeze drying.

[0064] In some embodiments, the supercritical drying is ethanol supercritical drying and / or CO2 supercritical drying.

[0065] In some embodiments, the conditions for ethanol supercritical drying include: the drying temperature is 245 - 260 °C, the drying pressure is 8 MPa - 11 MPa, the heating rate is 5 - 20 °C / min, the holding time in the supercritical state is 0.5 h - 3 h, and the deflation time is 3 h - 9 h.

[0066] In some embodiments, the conditions for CO2 supercritical drying include: the drying temperature is 40 - 65 °C, the drying pressure is 8 MPa - 20 MPa, the heating rate is 1 - 5 °C / min, the replacement time is 3 h - 12 h, and the deflation time is 3 h - 12 h.

[0067] In some embodiments, the method of atmospheric drying is to displace with a normal alkane solvent (such as n - hexane) for 6 h - 24 h, and then dry at atmospheric pressure at 50 - 80 °C for 6 h - 24 h.

[0068] In some embodiments, the conditions for freeze - drying include: the pre - freezing time is 3 - 12 h, the pre - freezing temperature is - 30 °C - - 5 °C, the cold trap temperature is - 60 - - 40 °C, the vacuum degree is 10 Pa - 500 Pa, and the drying time is 12 h - 36 h.

[0069] The second aspect of the present invention provides an aerogel felt, and the aerogel felt is the aerogel felt prepared by the method as described above.

[0070] The thickness tolerance and volume density deviation are tested using the standard GB / T34336 - 2017 Nanoporous Aerogel Composite Thermal Insulation Products (Appendix A Dimension and Volume Density Testing Methods).

[0071] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0072] The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special instructions.

[0073] The present invention will be described in detail below with specific embodiments, and these embodiments are for understanding rather than limiting the present invention.

[0074] Example 1

[0075] This example is used to illustrate the preparation method of the aerogel felt.

[0076] Stack 4 wet glass fiber sheets with a thickness of 3 mm, immerse them in a silica sol solution to obtain a pre-treated product. After taking it out, place it on an operating platform and press it once with a pressing plate, then let it stand for 6 min to gel and obtain a gel felt (no pressure is applied during this process). The distance between the lower surface of the pressing plate and the operating platform is 95% of the thickness of the pre-treated product. Use the CO2 supercritical drying method to dry the pressed pre-treated product. The drying temperature is 55 °C, the drying pressure is 14.5 MPa, the heating rate is 3 °C / min, the replacement time is 7 h, and the deflation time is 6 h, thus obtaining the aerogel felt.

[0077] Example 2

[0078] This example is used to illustrate the preparation method of the aerogel felt.

[0079] Stack 4 wet glass fiber sheets with a thickness of 3 mm, immerse them in a silica sol solution to obtain a pre-treated product. After taking it out, continuously apply a constant pressure to it with a pressing plate and press it while gelling. After 6 min, obtain a gel felt. The thickness of the gel felt is 95% of the thickness of the pre-treated product. Use the CO2 supercritical drying method to dry the pressed pre-treated product. The drying temperature is 55 °C, the drying pressure is 14.5 MPa, the heating rate is 3 °C / min, the replacement time is 7 h, and the deflation time is 6 h, thus obtaining the aerogel felt.

[0080] Example 3

[0081] This example is used to illustrate the preparation method of the aerogel felt.

[0082] Operate according to the method described in Example 2, except that the thickness of the gel felt is different. Specifically:

[0083] Example 3-1: The thickness of the gel felt is 93% of the thickness of the pre-treated product;

[0084] Example 3-2: The thickness of the gel felt is 97% of the thickness of the pre-treated product in step S1;

[0085] Example 3-3: The thickness of the gel felt is 90% of the thickness of the pre-treated product.

[0086] Example 4

[0087] This example is used to illustrate the preparation method of the aerogel felt.

[0088] Example 4-1: Operate according to the method described in Example 2, except that before drying the gel felt, perform an aging treatment first. Among them, the aging treatment method includes: before drying the gel felt, immerse it in an aging agent for 5 h, and the aging agent used is ethanol;

[0089] Example 4-2: The operation is carried out according to the method described in Example 2. The difference is that before drying the gel felt, an aging treatment is carried out first. The aging treatment method includes: before drying the gel felt, wrapping the gel felt with a PET film, standing for 3 h, removing the film, and then drying to obtain the product.

[0090] Example 5

[0091] This example is used to illustrate the preparation method of the aerogel felt.

[0092] The operation is carried out according to the method described in Example 2. The difference is that after drying the gel felt, a hydrophobic modification treatment is carried out. Specifically, the dried aerogel felt is placed in a closed environment containing hexamethyldisiloxane, and hexamethyldisiloxane is heated so that the vaporized hexamethyldisiloxane adheres to the gel felt to achieve the hydrophobic treatment of the dried gel felt.

[0093] Example 6

[0094] Four 3-mm-thick hydrophilic wet glass fiber sheets are stacked and impregnated in a silica sol solution to obtain a pretreated product. After taking it out, a constant pressure is continuously applied to it by a pressing plate for pressing and at the same time gelation is carried out. After 6 min, a gel felt is obtained. The thickness of the gel felt is 95% of the thickness of the pretreated product. The CO2 supercritical drying method is used to dry the pressed pretreated product. The drying temperature is 55 °C, the drying pressure is 14.5 MPa, the heating rate is 3 °C / min, the replacement time is 7 h, and the deflation time is 6 h to obtain the aerogel felt. Before drying the gel felt, an aging treatment is carried out first. The aging treatment method includes: before drying the gel felt, impregnating it in an aging agent for 5 h, and the aging agent used is ethanol. After drying the gel felt, a hydrophobic modification treatment is carried out. Specifically, the dried gel felt is placed in a closed environment containing hexamethyldisiloxane, and hexamethyldisiloxane is heated so that the vaporized hexamethyldisiloxane adheres to the gel felt to achieve the hydrophobic treatment of the dried gel felt.

[0095] Comparative Example 1

[0096] This comparative example is used to illustrate the preparation method of the reference aerogel felt.

[0097] The operation is carried out according to the method described in Example 1. The difference is that the thickness of the gel felt is 85% of the thickness of the pretreated product.

[0098] Comparative Example 2

[0099] This comparative example is used to illustrate the preparation method of the reference aerogel felt.

[0100] Operate in the same manner as in Example 1, except that after taking out the pre-treated product, no pressing treatment is performed, and after standing for 6 min, a gel felt is obtained, which is then dried to obtain the product.

[0101] Test Example

[0102] 1. Thickness Tolerance Test Method

[0103] Randomly select 5 points on the surfaces of the pre-treated products and gel felts prepared in the examples and preparation examples. The 5 points are evenly distributed on the surfaces of the pre-treated products and gel felts. Measure the thicknesses corresponding to the 5 points, and calculate the thickness tolerance. The results are shown in Table 1.

[0104] 2. Heat Insulation Performance of the Finished Product

[0105] Take the aerogel felts prepared in the examples and preparation examples as test samples for testing. Heat one side of the test sample through a heating table at a heating temperature of 700 °C, attach an aluminum plate to the other side, set the heating time to 20 min, then measure the temperature of the cold side of the aerogel felt, and calculate the temperature difference between the hot and cold sides. The results are shown in Table 1.

[0106] Table 1

[0107] Number Thickness Tolerance / mm Temperature Difference between Cold Surface and Hot Surface / °C Example 1 0.52 500 Example 2 0.35 535 Example 3-1 0.40 520 Example 3-2 0.40 520 Example 3-3 0.43 510 Example 4-1 0.31 540 Example 4-2 0.27 540 Example 5 0.25 540 Example 6 0.20 555 Comparative Example 1 0.76 450 Comparative Example 2 0.87 420

[0108] It should be noted that in this article, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such a process, method, article or device. Without further limitations, an element defined by the statement "including one..." does not exclude the existence of other identical elements in the process, method, article or device including that element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in a reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, the features described with reference to certain examples may be combined in other examples.

[0109] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing aerogel felt, characterized in that, The method includes: (1) Stacking multiple layers of fiber sheets and mixing them with a sol solution to obtain a pre-treated product; (2) Applying pressure to the pre-treated product during the gelation process of the pre-treated product to obtain a gel felt; (3) Drying the gel felt to obtain an aerogel felt; In step (2), the applied pressure makes the thickness of the gel felt 90% - 97% of the thickness of the pre-treated product.

2. The method according to claim 1, wherein In step (2), the method includes applying pressure to the pre-treated product during the gelation process of the pre-treated product until gelation is completed to obtain a gel felt.

3. The method according to claim 1 or 2, characterized in that, The fiber sheet includes at least one of a wet-process glass fiber sheet, a needled glass fiber sheet, a ceramic fiber sheet, and a pre-oxidized fiber sheet.

4. The method according to claims 1-3, characterized in that, The fiber sheet is a hydrophilic fiber felt after being hydrophilically treated.

5. The method according to any one of claims 1 to 4, characterized in that, The sol solution is a silica sol solution, an alumina sol solution, or a silica-alumina composite sol solution for preparing aerogel.

6. The method according to any one of claims 1-5, characterized in that, The way of applying pressure is to press with a pressing member; Preferably, the pressing member is a pressing roller or a pressing plate.

7. The method according to any one of claims 1-6, characterized in that, In step (3), the method further includes: before drying the gel felt, aging the gel felt; Preferably, the way of aging is to age the gel felt with an aging agent, and / or wrap the gel felt with a membrane material and age it; Preferably, the aging agent is an alcohol solvent.

8. The method according to any one of claims 1 to 7, characterized in that, In step (3), the method further includes: before or after drying the gel felt, hydrophobically modifying the gel felt with a hydrophobic agent; Preferably, the hydrophobic agent includes at least one of hydrophobic alkoxysilanes, hexamethyldisiloxane, and hexamethyldisilazane.

9. The method according to any one of claims 1-8, characterized in that, The drying method is supercritical drying, atmospheric drying or freeze drying 。 10. An aerogel felt, characterized in that, The aerogel felt is the aerogel felt prepared by the method according to any one of claims 1 - 9.