Silica-based aerogel felt, flexible water-proofing and vapor-barrier silica-based aerogel composite material having ultralow thermal conductivity, and preparation method

Abstract

The present application relates to the technical field of aerogel composite materials. Provided are a silica-based aerogel felt, a flexible water-proofing and vapor-barrier silica-based aerogel composite material having ultralow thermal conductivity, and a preparation method. In the present application, two silicon sources are used for hydrolysis to prepare a silica sol, then a basic solution is added to obtain a sol to be gelled, and then impregnation, heating gelation, thickness control via pressing rollers, aging and drying are performed to obtain the silica-based aerogel felt; and then the silica-based aerogel felt is compounded with an aluminum foil composite film to obtain the silica-based aerogel composite material. The silica-based aerogel felt provided by the present application has the advantages of ultralow thermal conductivity, flexibility, water resistance, flame retardancy, and no stress corrosion on stainless steel, and exhibits excellent performance in various indexes. The silica-based aerogel composite material provided by the present application not only has various advantages of the silica-based aerogel felt but also has excellent water and vapor barrier properties, thereby having a broad application prospect in the field of low-temperature thermal insulation.

Description

A silicon-based aerogel felt, an ultra-low thermal conductivity flexible waterproof vapor barrier silicon-based aerogel composite material, and its preparation method. Technical Field

[0001] This application relates to the field of aerogel composite materials technology, and in particular to a silicon-based aerogel felt, an ultra-low thermal conductivity flexible waterproof vapor barrier silicon-based aerogel composite material, and a preparation method thereof. Background Technology

[0002] Currently, traditional insulation materials include polyurethane foam and rubber-plastic sponge. These materials have problems such as relatively high thermal conductivity, large insulation layer thickness, low insulation efficiency, high energy consumption, and difficult maintenance, making it difficult to meet the energy conservation and emission reduction requirements in the field of low-temperature insulation.

[0003] Aerogel, as the solid material with the lowest known thermal conductivity, possesses advantages such as excellent thermal insulation performance, low moisture absorption, good mechanical properties, and easy installation. It can meet the requirements of efficient cold insulation while saving energy consumption and maintenance costs, making it suitable for various cold insulation conditions. However, the thermal conductivity of conventional aerogel insulation products on the market at room temperature is around 0.021 W / (K·m). If it is directly applied to cryogenic conditions, its low-temperature insulation performance is still insufficient. Furthermore, current aerogel products have poor water resistance and low-temperature flexibility, which cannot meet the requirements of the low-temperature insulation field. Summary of the Invention

[0004] In view of this, this application provides a silicon-based aerogel felt, an ultra-low thermal conductivity flexible waterproof vapor barrier silicon-based aerogel composite material, and a preparation method thereof. The silicon-based aerogel composite material provided by this application has an ultra-low thermal conductivity, good waterproof performance, good flexibility at low temperatures, and excellent overall performance, which can meet the requirements of the low-temperature insulation field. Beneficial effects:

[0005] This application provides a method for preparing a silicon-based aerogel felt. The method employs a dual silicon source to prepare the silicon-based aerogel felt, while controlling the preparation process to reduce the thermal conductivity and improve the thermal insulation performance. Using a dual silicon source to prepare the silica sol and employing organic / inorganic blended fiber needle-punched felt as the substrate effectively improves the flexibility of the aerogel felt. Adding a hydrophobic modifier during aging improves the waterproofness of the composite material. Adding a flame retardant to the alkaline solution used in the gelation improves the flame retardancy of the composite material. Furthermore, the organic fibers in the organic / inorganic blended fiber needle-punched felt used in this application are flame-retardant organic fibers, further enhancing the flame retardancy of the material. All raw materials used in this application are free of halogen atoms and will not cause stress corrosion to materials such as stainless steel. In summary, the silicon-based aerogel felt provided in this application has the advantages of ultra-low thermal conductivity, flexibility, waterproofness, flame retardancy, and no stress corrosion on stainless steel. Moreover, all performance indicators are excellent, especially the thermal conductivity at room temperature ≤14.5mW / (m·K), and the thermal conductivity at each temperature point is also at the international leading level.

[0006] This application also provides an ultra-low thermal conductivity flexible waterproof vapor barrier silicone-based aerogel composite material. This application combines silicone-based aerogel felt with an aluminum foil composite film. The resulting composite material, in addition to possessing advantages such as ultra-low thermal conductivity, flexibility, waterproofing, flame retardancy, and no stress corrosion on stainless steel, also exhibits excellent water vapor barrier properties, showing broad application prospects in the field of low-temperature insulation. The composite material provided in this application is highly compatible with cold insulation conditions ranging from -200℃ to 125℃, possessing excellent comprehensive performance advantages and excellent application advantages. Specifically, the composite material of this application has excellent thermal insulation performance, minimizing the thickness of the cold insulation layer; excellent waterproofing, and an integrated aluminum foil film with excellent vapor barrier properties, eliminating the need for a dedicated moisture-proof layer during construction, making it more convenient than traditional construction methods; good flexibility, easy construction, better applicability to small-diameter pipes or irregularly shaped parts, and reducing the risk of material brittle cracking and performance failure caused by equipment and pipeline vibration at low temperatures; safe, reliable, and long-lasting, providing durable, efficient, and safe performance assurance for cold insulation scenarios. Attached Figure Description

[0007] Figure 1 is a comparison of the flexibility of the silicone-based aerogel mat compared with that of Example 3 (left) and Comparative Example 1 (right). Detailed Implementation

[0008] This application provides a method for preparing a silicone-based aerogel mat, comprising the following steps:

[0009] A silica sol is obtained by mixing a silicon source, an alcohol solvent, and an acid catalyst and carrying out a hydrolysis reaction; the silicon source includes tetraalkoxysilane and trialkoxysilane; the mass ratio of the silicon source, alcohol solvent, and acid catalyst used in the hydrolysis reaction is 1:3-5.5:0.3-0.6.

[0010] The silica sol and alkaline solution are mixed to obtain the sol to be coagulated; the alkaline solution comprises a halogen-free flame retardant, a light-blocking agent, an alkaline catalyst, and an alcohol solvent.

[0011] Organic / inorganic blended fiber needle-punched felt is impregnated in the sol to be gelled, and then heated and gelled and pressed with rollers to control the thickness to obtain silicone alcohol gel felt;

[0012] The silicone alcohol gel felt is aged in an aging solution and then dried to obtain a silicone aerogel felt; the aging solution consists of an alkaline catalyst, a hydrophobic modifier, and an alcohol solvent.

[0013] This application involves mixing a silicon source, an alcohol solvent, and an acidic catalyst to perform a hydrolysis reaction, resulting in a silica sol. In this application, the silicon source includes tetraalkoxysilane and trialkoxysilane; the tetraalkoxysilane includes tetramethoxysilane and / or tetraethoxysilane; the trialkoxysilane includes methyltrimethoxysilane and / or methyltriethoxysilane; based on the total mass of the tetraalkoxysilane and trialkoxysilane as 100%, the mass fraction of the tetraalkoxysilane is 50-85%, preferably 50%, 70% or 80%, and the mass fraction of the trialkoxysilane is 15-50%, preferably 20%, 30% or 50%; the acidic catalyst is an aqueous nitric acid solution; the concentration of the aqueous nitric acid solution is 0.1-0.3 mol / L; the alcohol solvent used in the hydrolysis reaction includes methanol and / or ethanol; the mass ratio of the silicon source, alcohol solvent and acidic catalyst used in the hydrolysis reaction is 1:3-5.5:0.3-0.6, preferably 1:3.5:0.5, 1:5:0.3 or 1:5:0.5.

[0014] In this application, the temperature of the hydrolysis reaction is 50-60°C, preferably 55°C, 58°C or 60°C, and the reaction time is 5 hours or more, preferably 5-6 hours.

[0015] After obtaining the silica sol, this application mixes the silica sol with an alkaline solution to obtain a sol to be coagulated. In this application, the alkaline solution comprises a halogen-free flame retardant, a light-blocking agent, an alkaline catalyst, and an alcohol solvent. The halogen-free flame retardant includes halogen-free magnesium oxide and / or halogen-free magnesium hydroxide; the light-blocking agent includes graphite and / or titanium dioxide, and the D of the light-blocking agent... 50The particle size is 1–5 μm, preferably 2.5 μm or 5 μm. Pure aerogel has weak thermal radiation barrier properties. Under low-temperature conditions, thermal radiation from the environment has a significant impact on the cold source. This application improves the thermal radiation barrier performance of the aerogel by adding a light-blocking agent. The alkaline catalyst includes one or more of ammonia, sodium hydroxide, tetramethylammonium hydroxide, and trimethylamine; the alcohol solvent in the alkaline solution includes methanol and / or ethanol; the concentration of the alkaline catalyst in the alkaline solution is 0.1–1 mol / L, preferably 0.3 mol / L, 0.6 mol / L, or 1 mol / L; the mass fraction of the halogen-free flame retardant in the alkaline solution is 0.5–1%, preferably 0.5% or 1%; the mass fraction of the light-blocking agent in the alkaline solution is 0.5–2.5%, preferably 2%; the amount of the alkaline solution is used to adjust the pH value of the silica sol to 7–9. This application controls the pH value of the silica sol within the above range, which enables the gelation time to be controlled within 2–5 minutes.

[0016] After obtaining the sol to be gelled, this application impregnates the organic / inorganic blended fiber needle-punched felt in the sol to be gelled, and then heats and gels it and presses it with rollers to control the thickness, thereby obtaining a silicone alcohol gel felt. In this application, the inorganic fibers in the organic / inorganic blended fiber needle-punched felt include one or more of alkali-free glass fibers, basalt fibers, and quartz fibers, and the organic fibers are flame-retardant organic fibers, specifically including one or more of flame-retardant PET fibers, polyimide fibers, and aramid fibers; the mass fraction of inorganic fibers in the organic / inorganic blended fiber needle-punched felt is 50-75%, preferably 65% ​​or 70%, and the mass fraction of organic fibers is 25-50%, preferably 30% or 35%; the diameter of inorganic fibers in the organic / inorganic blended fiber needle-punched felt is 3-10 μm, and the diameter of organic fibers is 1.5D-3D; the thickness of the organic / inorganic blended fiber needle-punched felt is 11-15 mm, preferably 13.5 mm or 15 mm, and the bulk density is 25-70 kg / m³. 3 The preferred value is 30kg / m 3 In a specific embodiment of this application, it is preferable to quickly immerse the organic / inorganic blended fiber needle-punched felt in the sol to be coagulated after adjusting the pH value of the silica sol to 7-9 using an alkaline solution.

[0017] In this application, the volume ratio of the sol to be solidified to the organic / inorganic blended fiber needle-punched felt during impregnation is 1 to 1.1:1.

[0018] In this application, the heating gelation temperature is 45–55°C, and the time is 20–30 min; the heating gelation is carried out under sealed conditions; the heating gelation under sealed conditions ensures that the solvent in the gelled alcohol does not evaporate, improves the degree of gelation, avoids drying and cracking of the alcohol gel, reduces cracks in the final aerogel, and improves the thermal insulation performance of the aerogel; at the same time, the control of the gelation temperature and time in this application is conducive to the perfection of the gel structure and improves the various properties of the aerogel felt.

[0019] This application does not have any special requirements for the specific operation method of controlling the thickness of the pressure roller. The control conditions can be set according to the required thickness of the product. In a specific embodiment of this application, the thickness of the pressure roller is controlled at 10.5 to 11 mm, and the final thickness of the finished product is 9 to 11 mm.

[0020] After obtaining the silane alcohol gel felt, this application ages the silane alcohol gel felt in an aging solution and then dries it to obtain a silane aerogel felt. In this application, the aging solution comprises an alkaline catalyst, a hydrophobic modifier, and an alcohol solvent; the alkaline catalyst in the aging solution comprises one or more of ammonia, sodium hydroxide, tetramethylammonium hydroxide, and trimethylamine; the alcohol solvent in the aging solution comprises methanol and / or ethanol; the hydrophobic modifier comprises one or more of hexamethyldisilazane, trimethylmethoxysilane, and trimethylethoxysilane; the mass fraction of the hydrophobic modifier in the aging solution is 2-4%, preferably 2% or 3%; the amount of alkaline catalyst in the aging solution is used to control the pH value of the aging solution at 8-9; the aging temperature is 55-65℃, preferably 60℃ or 65℃; the total aging time is 12-60h, preferably 12h or 24h; during the aging process, the aging solution is kept still for the first 1 / 2 to 2 / 3 of the aging time, and the aging solution is kept circulating for the last 1 / 3 to 1 / 2 of the aging time. In a specific embodiment of this application, the aging immersion system includes a single immersion tank and an immersion solution circulation tank. Immersion is performed in the single immersion tank when the system is stationary, and during circulation, the single immersion tank and the immersion solution circulation tank are connected to circulate the aging solution. This application first performs aging under static conditions, which is beneficial for perfecting the gel structure, and then performs aging under circulating conditions, which is beneficial for achieving uniform modification.

[0021] In this application, the drying is supercritical CO2 drying, and the conditions for supercritical CO2 drying include: a CO2 flow rate of 4-7 m³ / h. 3 The drying time is 8-24 hours, with a drying temperature of 50-60℃, a drying pressure of 14-17MPa, and a drying rate of 8-24 hours.

[0022] This application also provides a silicon-based aerogel felt prepared by the preparation method described above, comprising an organic / inorganic blended fiber needle-punched felt and a silicon-based aerogel loaded in the organic / inorganic blended fiber needle-punched felt. In this application, the thickness of the silicon-based aerogel felt is 9–11 mm, and the bulk density is 120–170 kg / m³. 3 Thermal conductivity at 37.5℃ ≤ 14.5 mW / (m·K), thermal conductivity at 0℃ ≤ 14 mW / (m·K), thermal conductivity at -50℃ ≤ 13.5 mW / (m·K), thermal conductivity at -100℃ ≤ 13 mW / (m·K), thermal conductivity at -150℃ ≤ 12.5 mW / (m·K), compressive strength at 10% deformation ≥ 50 kPa, water absorption rate ≤ 3%, fire spread index FSI ≤ 25, smoke growth index SDI ≤ 50, and the material is flexible.

[0023] According to ASTM C1728 standard, the thermal conductivity at 37.5℃ is ≤0.025W / (m·K) for Types IA and ≤0.017W / (m·K) for Types IB. GB / T 34336 specifies that the thermal conductivity at 25℃ is ≤0.021W / (m·K) for Type A, ≤0.023W / (m·K) for Type B, and ≤0.017W / (m·K) for Type S. Considering the performance of currently available products, the thermal insulation performance of the silicone-based aerogel felt provided in this application is at an internationally leading level.

[0024] This application also provides an ultra-low thermal conductivity flexible waterproof vapor barrier silicone-based aerogel composite material, comprising the silicone-based aerogel felt described above and an aluminum foil composite film disposed on the surface of the silicone-based aerogel felt. In this application, the aluminum foil composite film comprises a PET layer, an Al layer, and a polyolefin layer sequentially disposed thereon. The polyolefin layer is a POE (polyolefin elastomer) layer or a TPO (thermoplastic polyolefin elastomer) layer. The thickness of the polyolefin layer is 80–90 μm, the thickness of the Al layer is 15–25 μm, and the thickness of the PET layer is 20–25 μm. The total thickness of the aluminum foil composite film is 125–150 μm, and the basis weight is ≥170 g / m³. 2 Preferably, it is 170-180 g / m 2 Both transverse and longitudinal tensile strengths are ≥30MPa, and water vapor transmission rate is ≤1×10⁻⁶. -10 g / (Pa·m 2 ·s).

[0025] In this application, specifically, an aluminum foil composite film is laminated on one side of the silicon-based aerogel felt, and the upper surface of the silicon-based aerogel felt is in contact with the polyolefin layer of the aluminum foil composite film.

[0026] This application also provides a method for preparing the ultra-low thermal conductivity flexible waterproof vapor barrier silica-based aerogel composite material described above, including the following steps:

[0027] The silicon-based aerogel felt and aluminum foil composite film are hot-pressed together to obtain the ultra-low thermal conductivity flexible waterproof vapor barrier silicon-based aerogel composite material.

[0028] In this application, the temperature of the hot pressing composite is 125-200°C, preferably 160-180°C, and the time is 60-90 seconds.

[0029] The technical solutions of this application will be clearly and completely described below with reference to the embodiments therein. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0030] Example 1

[0031] (1) A mixture of tetramethoxysilane and methyltrimethoxysilane with a mass ratio of 80:20 was formed, and then mixed with methanol and 0.1 mol / L dilute nitric acid aqueous solution at a mass ratio of 1:3.5:0.5. The mixture was stirred at 55°C for 5 h to obtain silica sol.

[0032] (2) Add an alkaline solution to the silica sol to adjust the pH to 8 to obtain the sol to be coagulated; the alkaline solution consists of NH3·H2O, halogen-free magnesium oxide, and laser particle size D. 50 The product consists of 2.5μm graphite and methanol, with an NH3·H2O concentration of 1.0mol / L, a halogen-free magnesium oxide content of 1.0wt%, and a graphite content of 2wt%. Glass fiber / flame-retardant PET blended fiber needle-punched felt is rapidly impregnated in a sol-gel mixture, then heated and gelled in a sealed space (temperature 50℃, time 20min). Afterwards, the thickness is controlled to 10.5mm using rollers to obtain a silane alcohol gel felt. The blended fiber needle-punched felt is a blend of 65wt% alkali-free glass fiber and 35wt% flame-retardant PET fiber, with a thickness of 15mm and a bulk density of 30kg / m³. 3 .

[0033] (3) The silane alcohol gel felt was immersed in the aging solution to obtain the aged alcohol gel felt; the aging solution was composed of concentrated ammonia, methanol and hexamethyldisilazane, the pH value of the aging solution was 8.5, and the content of hexamethyldisilazane was 3wt%; the aging temperature was 60℃, the aging time was 24h, the first 16h were static aging, and the aging solution was circulated for the last 8h.

[0034] (4) Silicon-based aerogel mats were prepared by supercritical CO2 drying of aged alcoholic gel mats, wherein the drying process conditions were CO2 flow rate of 5 m³ / h. 3 / h, drying temperature 55℃, drying pressure 15MPa, drying time 12h.

[0035] (5) The upper surface of the silicone aerogel felt is directly covered and contacted with the POE layer of the POE / Al / PET aluminum foil composite film, wherein the total thickness of the aluminum foil composite film is 145μm, the POE layer is 80μm thick, the Al layer is 25μm thick, the PET layer is 25μm thick, and the basis weight of the aluminum foil composite film is 180g / m³. 2 Both transverse and longitudinal tensile strengths are ≥30MPa, and water vapor transmission rate is ≤1×10⁻⁶. -10 g / (Pa·m 2 Then, the two are hot-pressed at 160°C using a hot press, and after cooling, they are bonded together to complete the single-sided film coating. The edges are then trimmed and finished using an edge trimming device to ensure that the finished product has neat edges and consistent width, resulting in an ultra-low thermal conductivity flexible waterproof vapor barrier silicone-based aerogel composite material.

[0036] Testing showed that the silicone-based aerogel mat prepared in this embodiment had a thickness of 10 mm and a bulk density of 160 kg / m³. 3 According to ASTM C518 testing, the thermal conductivity is 13.5 mW / (m·K) at 37.5℃, 13 mW / (m·K) at 0℃, 12.4 mW / (m·K) at -50℃, 11.6 mW / (m·K) at -100℃, and 10.1 mW / (m·K) at -150℃. It is flexible according to ASTM C1101 / 1101M testing, has a 10% deformation compressive strength of 67 kPa according to ASTM C165 testing, a water absorption rate of 2.5% according to ASTM C1763 testing, a fire spread index (FSI) of 10 and a smoke growth index (SDI) of 10 according to ASTM E84 testing, and passes the stress corrosion test for austenitic stainless steel according to ASTM C795 testing. The composite material obtained after coating has a water vapor transmission rate of 2.5 × 10⁻⁶ according to ASTM E96 testing. -11 g / (Pa·m 2 ·s).

[0037] Example 2

[0038] (1) A mixture of tetraethoxysilane and methyltriethoxysilane in a mass ratio of 50:50 was formed, and then mixed with ethanol and 0.3 mol / L dilute nitric acid aqueous solution in a mass ratio of 1:5:0.3. The mixture was stirred at 60°C for 6 hours to obtain silica sol.

[0039] (2) Other conditions are the same as in Example 1, except that the alkaline solution is changed to consist of NaOH, halogen-free magnesium oxide, graphite (with the same particle size as in Example 1), and ethanol. The pH of the aging solution is 8, the concentration of NaOH is 0.3 mol / L, the content of halogen-free magnesium oxide is 0.5 wt%, and the mass fraction of graphite is 2%. The blended fiber needle-punched felt is a blended needle-punched felt of 70 wt% alkali-free glass fiber and 30 wt% flame-retardant polyimide fiber, with a thickness of 13.5 mm and a bulk density of 50 kg / m³. 3 .

[0040] (3) Other conditions are the same as in Example 1, except that the composition of the aging solution is changed to: ethanol, sodium hydroxide and hexamethyldisilazane, wherein the pH value of the aging solution is 8.5, the mass fraction of hexamethyldisilazane is 2wt%, and the aging temperature is 65℃.

[0041] (4) Other conditions are the same as in Example 1, except that the drying temperature is changed to 60°C. After drying, a silicone-based aerogel felt is obtained.

[0042] (5) The silicon-based aerogel felt is laminated with the POE / Al / PET aluminum foil composite film under the same conditions as in Example 1.

[0043] The silicon-based aerogel mat prepared in this embodiment has a thickness of 10 mm and a bulk density of 150 kg / m³. 3 The thermal conductivity is 14.2 mW / (m·K) at 37.5℃, 13.8 mW / (m·K) at 0℃, 13 mW / (m·K) at -50℃, 12.5 mW / (m·K) at -100℃, and 11.5 mW / (m·K) at -150℃. The material is flexible, with a compressive strength of 85 kPa at 10% deformation, a water absorption rate of 2.1%, a fire spread index (FSI) of 12, a smoke growth index (SDI) of 15, and passes the stress corrosion test for austenitic stainless steel. The water vapor permeability of the coated composite material is 5.6 × 10⁻⁶. -11 g / (Pa·m 2 •s). The testing standards for the above performance items are the same as those in Example 1.

[0044] Example 3

[0045] (1) A mixture of tetramethoxysilane and methyltrimethoxysilane with a mass ratio of 70:30 was formed, and then mixed with methanol and 0.1 mol / L dilute nitric acid aqueous solution at a mass ratio of 1:5:0.5. The mixture was stirred at 58°C for 5 hours to obtain silica sol.

[0046] (2) Other conditions are the same as in Example 1, except that the alkaline solution is changed to consist of tetramethylammonium hydroxide, halogen-free magnesium hydroxide, and titanium dioxide (laser particle size D). 50The aging solution is composed of 5μm and methanol, with a pH of 8. The concentration of tetramethylammonium hydroxide is 0.6mol / L, the content of halogen-free magnesium hydroxide is 1wt%, and the content of titanium dioxide is 2wt%.

[0047] (3) Other conditions are the same as in Example 1, except that the composition of the aging solution is changed to: it consists of methanol, tetramethylammonium hydroxide and hexamethyldisilazane, wherein the pH value of the aging solution is 8.5 and the mass fraction of hexamethyldisilazane is 2wt%; the aging temperature is 60℃ and the aging time is 12h, with static aging for the first 8h and cyclic aging for the last 4h.

[0048] (4) Other conditions are the same as in Example 1, except that the drying time is changed to 8h. After drying, a silicone-based aerogel felt is obtained.

[0049] (5) The silicon-based aerogel felt is hot-pressed with the TPO / Al / PET aluminum foil composite film, wherein the TPO layer and the silicon-based aerogel felt are in contact, the total thickness of the aluminum foil composite film is 140μm, the TPO layer is 80μm, the Al layer is 25μm, the PET layer is 25μm, and other parameters are the same as in Example 1; the hot-pressing conditions are the same as in Example 1.

[0050] The silicon-based aerogel mat prepared in this embodiment has a thickness of 10 mm and a bulk density of 160 kg / m³. 3 The thermal conductivity is 13.9 mW / (m·K) at 37.5℃, 13.2 mW / (m·K) at 0℃, 12.7 mW / (m·K) at -50℃, 11.9 mW / (m·K) at -100℃, and 10.5 mW / (m·K) at -150℃. The material is flexible, with a compressive strength of 63.0 kPa at 10% deformation, a water absorption rate of 2.9%, a fire spread index (FSI) of 10, a smoke growth index (SDI) of 15, and passes the stress corrosion test for austenitic stainless steel. The water vapor permeability of the coated composite material is 8.7 × 10⁻⁶. -11 g / (Pa·m 2 The water vapor permeability of the uncoated silicone aerogel mat is 1.6 × 10⁻⁶ s⁻¹. -6 g / (Pa·m 2 As can be seen from the results (·s), the use of aluminum foil composite film can effectively improve the water vapor barrier performance of the composite material. The testing standards for the above properties are the same as those in Example 1.

[0051] Comparative Example 1

[0052] Other conditions were the same as in Example 3, except that methyltrimethoxysilane was not added, and tetramethoxysilane, methanol, and dilute nitric acid aqueous solution were mixed at a mass ratio of 1:5:0.5. Furthermore, the blended fiber needle-punched felt was replaced with glass fiber needle-punched felt, with a thickness of 10.5 mm and a bulk density of 110 kg / m³. 3 .

[0053] The density of the silicon-based aerogel felt prepared in this embodiment was tested to be 200 kg / m³. 3 The thermal conductivity at 37.5℃ was 16.2 mW / (m·K) as tested by ASTM C518, and it was deemed non-flexible according to ASTM C1101 / 1101M. Figure 1 is a comparison of the flexibility of the silicone-based aerogel felt with Example 3 (left) and Comparative Example 1 (right). It can be seen that the product obtained in Example 3 has better flexibility and can be bent freely, while the product of Comparative Example 1 has poorer flexibility and is more difficult to bend.

[0054] Comparative Example 2

[0055] The other conditions are the same as in Example 3, except that the mass ratio of the mixture of tetramethoxysilane and methyltrimethoxysilane to methanol and dilute nitric acid is changed to 1:7:0.5.

[0056] Tests showed that the thermal conductivity of the silicon-based aerogel felt obtained in Comparative Example 2 was 18.0 mW / (m·K) at 37.5℃. This demonstrates that adjusting the raw material ratio directly affects the final material properties.

[0057] Comparative Example 3

[0058] The other conditions were the same as in Example 3, except that no alkaline catalyst and hexamethyldisilazane were added to the aging solution during the soaking and aging process; that is, only ethanol was used as the aging solution, and the aging temperature was 50°C.

[0059] Tests showed that the thermal conductivity of the silicon-based aerogel felt obtained in Comparative Example 3 was 16.9 mW / (m·K) at 37.5℃, and its water absorption rate was 8.3%. This demonstrates that adjustments to the processing conditions directly affect the material's properties.

[0060] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing a silicon-based aerogel felt, characterized in that, Includes the following steps: A silica sol is obtained by mixing a silicon source, an alcohol solvent, and an acid catalyst and carrying out a hydrolysis reaction; the silicon source includes tetraalkoxysilane and trialkoxysilane; the mass ratio of the silicon source, alcohol solvent, and acid catalyst used in the hydrolysis reaction is 1:3-5.5:0.3-0.

6. The silica sol and alkaline solution are mixed to obtain the sol to be coagulated; the alkaline solution comprises a halogen-free flame retardant, a light-blocking agent, an alkaline catalyst, and an alcohol solvent. Organic / inorganic blended fiber needle-punched felt is impregnated in the sol to be gelled, and then heated and gelled and pressed with rollers to control the thickness to obtain silicone alcohol gel felt; The silicone alcohol gel felt is aged in an aging solution and then dried to obtain a silicone aerogel felt; the aging solution consists of an alkaline catalyst, a hydrophobic modifier, and an alcohol solvent.

2. The preparation method according to claim 1, characterized in that, The tetraalkoxysilane includes tetramethoxysilane and / or tetraethoxysilane; the trialkoxysilane includes methyltrimethoxysilane and / or methyltriethoxysilane; based on the total mass of the tetraalkoxysilane and trialkoxysilane as 100%, the mass fraction of the tetraalkoxysilane is 50-85%, and the mass fraction of the trialkoxysilane is 15-50%. The acidic catalyst is an aqueous solution of nitric acid; the concentration of the aqueous solution of nitric acid is 0.1–0.3 mol / L. The alcohol solvent used in the hydrolysis reaction includes methanol and / or ethanol; The hydrolysis reaction is carried out at a temperature of 50–60°C for a time of 5 hours or more.

3. The preparation method according to claim 1, characterized in that, In the alkaline solution, the halogen-free flame retardant includes halogen-free magnesium oxide and / or halogen-free magnesium hydroxide; the light-blocking agent includes graphite and / or titanium dioxide, and the D of the light-blocking agent... 50 The particle size is 1–5 μm; the alkaline catalyst includes one or more of ammonia, sodium hydroxide, tetramethylammonium hydroxide, and trimethylamine; the alcohol solvent includes methanol and / or ethanol; The alkaline catalyst in the alkaline solution has a concentration of 0.1–1 mol / L, the halogen-free flame retardant has a mass fraction of 0.5–1%, and the light-shielding agent has a mass fraction of 0.5–2.5%. The amount of alkaline solution used is such that the pH value of the silica sol is adjusted to 7-9.

4. The preparation method according to claim 1, characterized in that, The inorganic fibers in the organic / inorganic blended fiber needle-punched felt include one or more of alkali-free glass fibers, basalt fibers, and quartz fibers, and the organic fibers include flame-retardant organic fibers; the mass fraction of inorganic fibers in the organic / inorganic blended fiber needle-punched felt is 50% to 75%, and the mass fraction of organic fibers is 25% to 50%. The diameter of the inorganic fibers in the organic / inorganic blended fiber needle-punched felt is 3-10 μm; The organic / inorganic blended fiber needle-punched felt has a thickness of 11–15 mm and a bulk density of 25–70 kg / m³. 3 ; The heating gelation temperature is 45-55°C, and the time is 20-30 minutes. The heating gelation is carried out under sealed conditions.

5. The preparation method according to claim 1, characterized in that, In the aging solution, the alkaline catalyst includes one or more of ammonia, sodium hydroxide, tetramethylammonium hydroxide, and trimethylamine; the alcohol solvent includes methanol and / or ethanol. The hydrophobic modifier includes one or more of hexamethyldisilazane, trimethylmethoxysilane, and trimethylethoxysilane; The mass fraction of the hydrophobic modifier in the aging solution is 2-4%; the amount of alkaline catalyst in the aging solution is such that the pH value of the aging solution is controlled at 8-9. The aging temperature is 55℃~65℃, and the total aging time is 12h~60h. During the aging process, the aging solution is kept stationary for the first 1 / 2 to 2 / 3 of the aging time, and circulated for the last 1 / 3 to 1 / 2 of the aging time.

6. The preparation method according to claim 1, characterized in that, The drying process is supercritical CO2 drying, and the conditions for supercritical CO2 drying include: a CO2 flow rate of 4–7 m³ / h. 3 The drying time is 8-24 hours, with a drying temperature of 50-60℃, a drying pressure of 14-17MPa, and a drying rate of 8-24 hours.

7. The silicon-based aerogel felt prepared by the preparation method according to any one of claims 1 to 6, characterized in that, It includes organic / inorganic blended fiber needle-punched felt and silica-based aerogel loaded in the organic / inorganic blended fiber needle-punched felt.

8. A flexible, waterproof, vapor-barrier silicone-based aerogel composite material with ultra-low thermal conductivity, characterized in that, It includes the silicon-based aerogel felt as described in claim 7 and the aluminum foil composite film disposed on the surface of the silicon-based aerogel felt.

9. The ultra-low thermal conductivity flexible waterproof vapor barrier silica-based aerogel composite material according to claim 8, characterized in that, The aluminum foil composite film comprises a PET layer, an Al layer and a polyolefin layer arranged sequentially, wherein the polyolefin layer is a POE layer or a TPO layer. The polyolefin layer has a thickness of 80–90 μm, the Al layer has a thickness of 15–25 μm, and the PET layer has a thickness of 20–25 μm; the total thickness of the aluminum foil composite film is 125–150 μm, and the basis weight is ≥170 g / m³. 2 Both transverse and longitudinal tensile strengths are ≥30MPa, and water vapor transmission rate is ≤1×10⁻⁶. -10 g / (Pa·m 2 ·s).

10. The preparation method of the ultra-low thermal conductivity flexible waterproof vapor barrier silica-based aerogel composite material according to claim 8 or 9, characterized in that, Includes the following steps: The silicon-based aerogel felt and aluminum foil composite film are hot-pressed together to obtain the ultra-low thermal conductivity flexible waterproof vapor barrier silicon-based aerogel composite material.

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