Silica-based aerogel felt, ultralow-heat-conduction flexible waterproof vapor-resistant silica-based aerogel composite material and preparation method of silica-based aerogel felt and ultralow-heat-conduction flexible waterproof vapor-resistant silica-based aerogel composite material

Abstract

The invention relates to the technical field of aerogel composite materials, and provides a silicon-based aerogel felt, an ultralow-heat-conduction flexible waterproof and vapor-resistant silicon-based aerogel composite material and a preparation method of the silicon-based aerogel felt and the ultralow-heat-conduction flexible waterproof and vapor-resistant silicon-based aerogel composite material. The preparation method comprises the following steps: hydrolyzing double silicon sources to prepare silica sol, adding an alkaline solution to obtain sol to be coagulated, dipping, heating for gelation, rolling for thickness control, aging and drying to obtain silicon-based aerogel felt, and compounding the silicon-based aerogel felt with an aluminum foil composite film to obtain the silicon-based aerogel composite material. The silicon-based aerogel felt provided by the invention has the advantages of ultralow heat conductivity, flexibility, water resistance, flame retardancy and no stress corrosion to stainless steel, and has excellent performance indexes. The silicon-based aerogel composite material provided by the invention not only has various advantages of the silicon-based aerogel felt, but also has excellent water vapor barrier property, and has a wide application prospect in the field of low-temperature heat preservation.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogel composite materials, and in particular to a silicon-based aerogel felt, an ultra-low thermal conductive flexible waterproof vapor-resistant silicon-based aerogel composite material and a preparation method thereof. Background Art

[0002] At present, traditional cold insulation materials include polyurethane foam, rubber and plastic sponge, etc. These cold insulation materials have relatively high thermal conductivity, thick insulation layer, low insulation efficiency, high energy consumption, and difficult maintenance. It is difficult to meet the needs of energy conservation and emission reduction in the field of low-temperature insulation.

[0003] As the solid material with the lowest known thermal conductivity, aerogel has the advantages of excellent thermal insulation, low moisture absorption, good mechanical properties, and easy installation. It can not only meet the needs of efficient cold preservation, but also save energy costs and maintenance costs, and is suitable for a variety of cold preservation conditions. However, the thermal conductivity of conventional aerogel insulation products on the market at room temperature is about 0.021W / (K·m). If it is directly applied to deep cold conditions, there is still the problem of insufficient low-temperature insulation performance; and the current aerogel products have poor waterproofness and flexibility at low temperatures, which cannot meet the requirements of the low-temperature insulation field. Summary of the invention

[0004] In view of this, the present invention provides a silicon-based aerogel felt, an ultra-low thermal conductivity, flexible, waterproof, and vapor-resistant silicon-based aerogel composite material, and a preparation method. The silicon-based aerogel composite material provided by the present invention has an ultra-low thermal conductivity coefficient, good waterproofness, good flexibility at low temperatures, and excellent comprehensive performance, and can meet the requirements of the low-temperature insulation field.

[0005] Beneficial effects:

[0006] The present invention provides a method for preparing a silicon-based aerogel felt. The present invention adopts dual silicon sources to prepare silicon-based aerogel felt, and controls the preparation process at the same time, which can reduce the thermal conductivity of the silicon-based aerogel felt and improve the thermal insulation performance; adopts dual silicon sources to prepare silica sol, and adopts organic / inorganic blended fiber needle felt as a substrate, which can effectively improve the flexibility of the aerogel felt; adds a hydrophobic modifier during aging, which can improve the waterproofness of the composite material; adds a flame retardant to the alkaline solution used in the gel, which can improve the flame retardancy of the composite material. Furthermore, the organic fiber in the organic / inorganic blended fiber needle felt used in the present invention is a flame-retardant organic fiber, which can further improve the flame retardancy of the material, and each raw material used in the present invention does not contain halogen atoms, and will not cause stress corrosion to materials such as stainless steel. In summary, the silicon-based aerogel felt provided by the present invention has the advantages of ultra-low thermal conductivity, flexibility, waterproofness, flame retardancy, and no stress corrosion to stainless steel, and all performance indicators are excellent, especially the thermal conductivity at room temperature is ≤14.5mW / (m·K), and the thermal conductivity at each temperature point is also at the international leading level.

[0007] The present invention also provides an ultra-low thermal conductivity, flexible, waterproof, and vapor-resistant silicon-based aerogel composite material. The present invention composites silicon-based aerogel felt with an aluminum foil composite film. The obtained composite material has the advantages of ultra-low thermal conductivity, flexibility, waterproofness, flame retardancy, and no stress corrosion to stainless steel, and also has excellent water vapor barrier performance, and has broad application prospects in the field of low-temperature thermal insulation. The composite material provided by the present invention highly matches the cold insulation and thermal insulation conditions of -200°C to 125°C, and has excellent comprehensive performance advantages and excellent application advantages; specifically, the composite material of the present invention has excellent thermal insulation performance, and the thickness of the cold insulation layer can be reduced to a minimum; it has excellent waterproofness, and the aluminum foil film with excellent barrier properties is vapor-proof and moisture-proof, eliminating the special moisture-proof layer construction during the construction process, which is more convenient than traditional construction; it has good flexibility and easy construction, and is more suitable for small-diameter pipes or special-shaped parts, and can reduce the risk of brittle cracking and performance failure of materials caused by vibration of equipment pipelines at low temperatures; it is safe, reliable, and has a long life, providing a long-lasting, efficient and safe performance guarantee for cold insulation scenes. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a comparison chart of the flexibility of the silicon-based aerogel felt of Example 3 (left) and Comparative Example 1 (right). DETAILED DESCRIPTION

[0009] The present invention provides a method for preparing a silicon-based aerogel felt, comprising the following steps:

[0010] A silicon source, an alcohol solvent and an acid catalyst are mixed for hydrolysis reaction to obtain a silica sol; the silicon source comprises tetraalkoxysilane and trialkoxysilane; the mass ratio of the silicon source, the alcohol solvent and the acid catalyst used in the hydrolysis reaction is 1:3-5.5:0.3-0.6;

[0011] The silica sol and an alkaline solution are mixed to obtain a sol to be solidified; the alkaline solution comprises a halogen-free flame retardant, a sunscreen, an alkaline catalyst and an alcohol solvent;

[0012] The organic / inorganic blended fiber needle-punched felt is immersed in the sol to be gelled, and then heated for gelation and roller-pressed for thickness control to obtain a silicon-based alcohol gel felt;

[0013] The silicon-based alcohol gel felt is aged in an aging solution and then dried to obtain a silicon-based aerogel felt; the aging solution comprises components of an alkaline catalyst, a hydrophobic modifier and an alcohol solvent.

[0014] The present invention mixes a silicon source, an alcohol solvent and an acidic catalyst to carry out a hydrolysis reaction to obtain a silica sol. In the present invention, 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.

[0015] In the present invention, the temperature of the hydrolysis reaction is 50-60°C, preferably 55°C, 58°C or 60°C, and the reaction time is more than 5 hours, preferably 5-6 hours.

[0016] After obtaining the silica sol, the present invention mixes the silica sol with an alkaline solution to obtain a sol to be solidified. In the present invention, the alkaline solution comprises a halogen-free flame retardant, a sunscreen, an alkaline catalyst and an alcohol solvent, the halogen-free flame retardant comprises halogen-free magnesium oxide and / or halogen-free magnesium hydroxide; the sunscreen comprises graphite and / or titanium dioxide, and the D 50 The particle size is 1 to 5 μm, preferably 2.5 μm or 5 μm; pure aerogel has a weak barrier to thermal radiation. Under low temperature conditions, the thermal radiation from the environment has a greater impact on the cold source. The present invention improves the barrier performance of aerogel to thermal radiation by adding a sunscreen. 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 to 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 to 1%, preferably 0.5% or 1%; the mass fraction of the sunscreen in the alkaline solution is 0.5 to 2.5%, preferably 2%; the amount of the alkaline solution is based on adjusting the pH value of the silica sol to 7 to 9. The present invention controls the pH value of the silica sol within the above range and can control the gel time to 2 to 5 minutes.

[0017] After obtaining the sol to be gelled, the present invention immerses the organic / inorganic blended fiber needle felt in the sol to be gelled, and then heats and gels it and controls the thickness by roller pressing to obtain a silicone-based alcohol gel felt. In the present invention, the inorganic fibers in the organic / inorganic blended fiber needle 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 the inorganic fibers in the organic / inorganic blended fiber needle felt is 50-75%, preferably 65% ​​or 70%, and the mass fraction of the organic fibers is 25-50%, preferably 30% or 35%; the diameter of the inorganic fibers in the organic / inorganic blended fiber needle felt is 3-10 μm, and the diameter of the organic fibers is 1.5D-3D; the thickness of the organic / inorganic blended fiber needle felt is 11-15 mm, preferably 13.5 mm or 15 mm, and the bulk density is 25-70 kg / m 3 , preferably 30kg / m 3 In a specific embodiment of the present invention, preferably, after the pH value of the silica sol is adjusted to 7-9 by using an alkaline solution, the organic / inorganic blended fiber needle felt is quickly immersed in the sol to be solidified.

[0018] In the present invention, during the impregnation, the volume ratio of the to-be-gelled sol to the organic / inorganic blended fiber needle felt is 1 to 1.1:1.

[0019] In the present invention, the temperature of the heating gelation is 45-55°C and the time is 20-30 minutes; the heating gelation is carried out under closed conditions; the present invention carries out heating gelation under closed conditions, which can ensure that the solvent in the alcohol gel after gelation is non-volatile, improve the gelation degree, avoid the alcohol gel from drying and cracking, reduce the cracks in the finally obtained aerogel, and improve the thermal insulation performance of the aerogel; at the same time, the present invention controls the temperature and time of gelation, which is conducive to the improvement of the gel structure and improves various aspects of the performance of the aerogel felt.

[0020] The present invention has no special requirements on the specific operation method of the pressure roller to control the thickness, and the control conditions can be set according to the required thickness of the product; in a specific embodiment of the present invention, the thickness of the pressure roller is controlled at 10.5-11 mm, and the final finished product thickness is 9-11 mm.

[0021] After obtaining the silicon-based alcohol gel felt, the present invention ages the silicon-based alcohol gel felt in an aging solution and then dries it to obtain a silicon-based aerogel felt. In the present invention, the components of the aging liquid include an alkaline catalyst, a hydrophobic modifier and an alcohol solvent; the alkaline catalyst in the aging liquid includes one or more of ammonia, sodium hydroxide, tetramethylammonium hydroxide and trimethylamine; the alcohol solvent in the aging liquid includes methanol and / or ethanol; the hydrophobic modifier includes one or more of hexamethyldisilazane, trimethylmonomethoxysilane and trimethylmonoethoxysilane; the mass fraction of the hydrophobic modifier in the aging liquid is 2-4%, preferably 2% or 3%; the amount of the alkaline catalyst in the aging liquid is based on controlling the pH value of the aging liquid at 8-9; the aging temperature is 55-65°C, preferably 60°C or 65°C, and the total aging time is 12-60h, preferably 12h or 24h; during the aging process, the aging liquid is kept stationary during the first 1 / 2-2 / 3 of the aging time, and the aging liquid is kept circulating during the last 1 / 3-1 / 2 of the aging time. In a specific embodiment of the present invention, the soaking system used for aging includes a single soaking tank and a soaking liquid circulation tank. When stationary, the single soaking tank is used for soaking. When circulating, the single soaking tank and the soaking liquid circulation tank are connected to circulate the aging liquid. The present invention first performs aging under stationary conditions, which is conducive to the improvement of the gel structure, and then performs aging under circulating conditions, which is conducive to achieving uniform modification.

[0022] In the present invention, the drying is supercritical CO2 drying, and the conditions of the supercritical CO2 drying include: CO2 flow rate is 4-7m 3 / h, the drying temperature is 50-60°C, the drying pressure is 14-17MPa, and the drying time is 8-24h.

[0023] The present invention also provides a silicon-based aerogel felt prepared by the preparation method described in the above scheme, comprising an organic / inorganic blended fiber needle felt and a silicon-based aerogel loaded in the organic / inorganic blended fiber needle felt. In the present invention, the silicon-based aerogel felt has a thickness of 9 to 11 mm and a bulk density of 120 to 170 kg / m 3 , thermal conductivity at 37.5℃ ≤14.5mW / (m·K), thermal conductivity at 0℃ ≤14mW / (m·K), thermal conductivity at -50℃ ≤13.5mW / (m·K), thermal conductivity at -100℃ ≤13mW / (m·K), thermal conductivity at -150℃ ≤12.5mW / (m·K), 10% deformation compressive strength ≥50KPa, mass water absorption ≤3%, burn spread index FSI ≤25, smoke growth index SDI ≤50, the material properties are flexible.

[0024] According to the ASTM C1728 standard, the thermal conductivity at 37.5°C is Types IA≤0.025W / (m·K) and Types IB≤0.017W / (m·K); according to GB / T 34336, the thermal conductivity at 25°C is Type A≤0.021W / (m·K), Type B≤0.023W / (m·K), and Type S≤0.017W / (m·K). Combined with the performance of currently commercially available products, the thermal insulation performance of the silicon-based aerogel felt provided by the present invention is at the international leading level.

[0025] The present invention also provides an ultra-low thermal conductive, flexible, waterproof and vapor-resistant silicon-based aerogel composite material, comprising the silicon-based aerogel felt described in the above scheme and an aluminum foil composite film arranged on the surface of the silicon-based aerogel felt. In the present invention, the aluminum foil composite film comprises a PET layer, an Al layer and a polyolefin layer arranged in sequence, and the polyolefin layer is a POE (polyolefin elastomer) layer or a TPO (thermoplastic polyolefin elastomer) layer; the thickness of the polyolefin layer is 80 to 90 μm, the thickness of the Al layer is 15 to 25 μm, and the thickness of the PET layer is 20 to 25 μm; the total thickness of the aluminum foil composite film is 125 to 150 μm, and the gram weight is ≥170 g / m 2 , preferably 170 to 180 g / m 2 , transverse tensile strength and longitudinal tensile strength are ≥30MPa, water vapor transmission rate ≤1×10 -10 g / (Pa·m 2 ·s).

[0026] In the present invention, specifically, the aluminum foil composite film is composited 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.

[0027] The present invention also provides a method for preparing the ultra-low thermal conductive, flexible, waterproof and vapor-resistant silicon-based aerogel composite material described in the above scheme, comprising the following steps:

[0028] The silicon-based aerogel felt and the aluminum foil composite film are composited by hot pressing to obtain the ultra-low thermal conductive, flexible, waterproof and vapor-resistant silicon-based aerogel composite material.

[0029] In the present invention, the temperature of the hot pressing composite is 125-200° C., preferably 160-180° C., and the time is 60-90 seconds.

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] (1) A mixture of tetramethoxysilane and methyltrimethoxysilane in a mass ratio of 80:20 was prepared, and then mixed evenly with methanol and a 0.1 mol / L dilute nitric acid aqueous solution in a mass ratio of 1:3.5:0.5, and stirred at 55° C. for 5 h to obtain a silica sol.

[0033] (2) adding an alkaline solution to the silica sol to adjust the pH value to 8 to obtain a sol to be condensed; the alkaline solution is composed of NH3·H2O, halogen-free magnesium oxide, and laser particle size D 50 The invention relates to a method for preparing a silicon-based alcohol gel felt, wherein the silicon-based alcohol gel felt is composed of 2.5 μm graphite and methanol, wherein the concentration of NH3·H2O is 1.0 mol / L, the content of halogen-free magnesium oxide is 1.0 wt%, and the content of graphite is 2 wt%; the glass fiber / flame-retardant PET blended fiber needle felt is quickly immersed in the to-be-gelled sol, and then heated to gel in a closed space (temperature is 50° C., time is 20 min), and then the thickness is controlled by a roller to be 10.5 mm to obtain a silicon-based alcohol gel felt, wherein the blended fiber needle felt is a blended needle felt formed by 65 wt% of alkali-free glass fiber and 35 wt% of flame-retardant PET fiber, with a thickness of 15 mm and a bulk density of 30 kg / m 3 .

[0034] (3) The silicone-based alcohol gel felt is immersed in an aging solution for aging to obtain an aged alcohol gel felt; the aging solution consists of concentrated ammonia water, methanol and hexamethyldisilazane, the pH value of the aging solution is 8.5, and the content of hexamethyldisilazane is 3wt%; the aging temperature is 60°C, the aging time is 24h, the first 16h of static aging, and the last 8h of aging solution circulation.

[0035] (4) The aged alcohol gel felt is subjected to supercritical CO2 drying to obtain a silicon-based aerogel felt, wherein the drying process conditions are a CO2 flow rate of 5 m 3 / h, drying temperature 55℃, drying pressure 15MPa, drying time 12h.

[0036] (5) The upper surface of the silicon-based 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 145 μm, the POE layer is 80 μm thick, the Al layer is 25 μm thick, the PET layer is 25 μm thick, and the aluminum foil composite film has a gram weight of 180 g / m 2 , transverse and longitudinal tensile strength are ≥30MPa, water vapor transmission rate ≤1×10 -10 g / (Pa·m 2 ·s). Then, the two are hot-pressed at 160°C by a hot press, and after cooling, the two are pasted together to complete the single-sided lamination, and then the edges are trimmed by a trimming device to make the edges of the finished product neat and the width consistent, thereby obtaining an ultra-low thermal conductive, flexible, waterproof, and vapor-resistant silicon-based aerogel composite material.

[0037] After testing, the silicon-based aerogel felt prepared in this embodiment has a thickness of 10 mm and a bulk density of 160 kg / m 3 The thermal conductivity at 37.5℃ is 13.5mW / (m·K) according to ASTMC518, the thermal conductivity at 0℃ is 13mW / (m·K), the thermal conductivity at -50℃ is 12.4mW / (m·K), the thermal conductivity at -100℃ is 11.6mW / (m·K), and the thermal conductivity at -150℃ is 10.1mW / (m·K). The composite material obtained after coating has a water vapor permeability of 2.5×10-1 according to ASTM E96. -11 g / (Pa·m 2 ·s).

[0038] Example 2

[0039] (1) A mixture of tetraethoxysilane and methyltriethoxysilane in a mass ratio of 50:50 is prepared, and then mixed with ethanol and a 0.3 mol / L dilute nitric acid aqueous solution in a mass ratio of 1:5:0.3, and stirred at 60° C. for 6 h to obtain a silica sol.

[0040] (2) Other conditions were the same as those in Example 1, except that the alkaline solution was changed to: composed of NaOH, halogen-free magnesium oxide, graphite (with the same particle size as in Example 1) and ethanol, the pH value of the aging solution was 8, the concentration of NaOH was 0.3 mol / L, the content of halogen-free magnesium oxide was 0.5 wt%, and the mass fraction of graphite was 2%; the blended fiber needle felt was a blended fiber needle 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 / m 3 .

[0041] (3) Other conditions were the same as those in Example 1, except that the composition of the aging solution was changed to ethanol, sodium hydroxide and hexamethyldisilazane, wherein the pH value of the aging solution was 8.5, the mass fraction of hexamethyldisilazane was 2 wt %; and the aging temperature was 65° C.

[0042] (4) Other conditions were the same as those in Example 1, except that the drying temperature was changed to 60° C., and a silicon-based aerogel felt was obtained after drying.

[0043] (5) The silicon-based aerogel felt is compounded with the POE / Al / PET aluminum foil composite film, and the specific conditions are the same as those in Example 1.

[0044] The silicon-based aerogel felt prepared in this embodiment has a thickness of 10 mm and a bulk density of 150 kg / m 3 , 37.5℃ thermal conductivity is 14.2mW / (m·K), 0℃ thermal conductivity is 13.8mW / (m·K), -50℃ thermal conductivity is 13mW / (m·K), -100℃ thermal conductivity is 12.5mW / (m·K), -150℃ thermal conductivity is 11.5mW / (m·K), the material properties are flexible, 10% deformation compressive strength is 85KPa, mass water absorption is 2.1%, combustion spread index FSI=12, smoke growth index SDI=15, passed the austenitic stainless steel stress corrosion test, the water vapor permeability of the composite material after coating is 5.6×10 -11 g / (Pa·m 2 ·s). The testing standards of the above-mentioned properties are consistent with those in Example 1.

[0045] Example 3

[0046] (1) A mixture of tetramethoxysilane and methyltrimethoxysilane in a mass ratio of 70:30 was prepared, and then mixed evenly with methanol and a 0.1 mol / L dilute nitric acid aqueous solution in a mass ratio of 1:5:0.5, and stirred continuously at 58° C. for 5 h to obtain a silica sol.

[0047] (2) Other conditions were the same as those in Example 1, except that the alkaline solution was changed to: tetramethylammonium hydroxide, halogen-free magnesium hydroxide, titanium dioxide (laser particle size D 50 The aging liquid is composed of 5 μm) and methanol, the pH value of the aging liquid is 8, the concentration of tetramethylammonium hydroxide is 0.6 mol / L, the content of halogen-free magnesium hydroxide is 1wt%, and the content of titanium dioxide is 2wt%.

[0048] (3) Other conditions were the same as those in Example 1, except that the composition of the aging solution was changed to methanol, tetramethylammonium hydroxide and hexamethyldisilazane, wherein the pH value of the aging solution was 8.5 and the mass fraction of hexamethyldisilazane was 2 wt %. The aging temperature was 60° C. and the aging time was 12 h, with the first 8 h of static aging and the last 4 h of circulating aging solution.

[0049] (4) Other conditions were the same as those in Example 1, except that the drying time was changed to 8 h, and a silicon-based aerogel felt was obtained after drying.

[0050] (5) The silicon-based aerogel felt and the TPO / Al / PET aluminum foil composite film are hot-pressed and composited, wherein the TPO layer is in contact with the silicon-based aerogel felt, the total thickness of the aluminum foil composite film is 140 μm, the TPO layer is 80 μm, the Al layer thickness is 25 μm, and the PET layer thickness is 25 μm. Other parameters are consistent with those in Example 1; the hot-pressing composite conditions are the same as those in Example 1.

[0051] The silicon-based aerogel felt prepared in this embodiment has a thickness of 10 mm and a bulk density of 160 kg / m 3 , 37.5℃ thermal conductivity is 13.9mW / (m·K), 0℃ thermal conductivity is 13.2mW / (m·K), -50℃ thermal conductivity is 12.7mW / (m·K), -100℃ thermal conductivity is 11.9mW / (m·K), -150℃ thermal conductivity is 10.5mW / (m·K), the material properties are flexible, 10% deformation compressive strength is 63.0KPa, mass water absorption is 2.9%, combustion spread index FSI=10, smoke growth index SDI=15, through austenitic stainless steel stress corrosion test. The water vapor permeability of the composite material after coating is 8.7×10 -11 g / (Pa·m 2 ·s), the water vapor permeability of the uncoated silica-based aerogel felt is 1.6×10 -6 g / (Pa·m 2 ·s), it can be seen that the use of aluminum foil composite film can effectively improve the water vapor barrier performance of the composite material. The testing standards of the above-mentioned various properties are consistent with those of Example 1.

[0052] Comparative Example 1

[0053] The other conditions were the same as those in Example 3, except that methyltrimethoxysilane was not added, and tetramethoxysilane, methanol and dilute nitric acid aqueous solution were mixed in a mass ratio of 1:5:0.5. The blended fiber needle felt was replaced with a glass fiber needle felt with a thickness of 10.5 mm and a bulk density of 110 kg / m 3 .

[0054] After testing, the density of the silicon-based aerogel felt prepared in this embodiment is 200kg / m 3 The thermal conductivity at 37.5°C tested by ASTM C518 is 16.2mW / (m·K), and it is non-flexible as tested by ASTM C1101 / 1101M. Figure 1 This is a comparison chart of the flexibility of the silicon-based aerogel felt of 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.

[0055] Comparative Example 2

[0056] The other conditions were the same as those in Example 3, except that the mass ratio of the mixture of tetramethoxysilane and methyltrimethoxysilane to methanol and dilute nitric acid was changed to 1:7:0.5.

[0057] After testing, the thermal conductivity of the silicon-based aerogel felt obtained in Comparative Example 2 at 37.5°C was 18.0 mW / (m·K). It can be seen that the adjustment of the raw material ratio directly affects the final performance of the material.

[0058] Comparative Example 3

[0059] The other conditions were the same as those in Example 3, except that no alkaline catalyst and hexamethyldisilazane were added to the aging solution during the immersion aging process, that is, only ethanol was used as the aging solution, and the aging temperature was 50°C.

[0060] After testing, the thermal conductivity of the silicon-based aerogel felt obtained in Comparative Example 3 at 37.5°C was 16.9 mW / (m·K), and the mass water absorption was 8.3%. It can be seen that the adjustment of process conditions directly affects the material properties.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-based aerogel felt, characterized in that: The following steps are involved: A silicon source, an alcohol solvent and an acid catalyst are mixed for hydrolysis reaction to obtain a silica sol; the silicon source comprises tetraalkoxysilane and trialkoxysilane; the mass ratio of the silicon source, the alcohol solvent and the acid catalyst used in the hydrolysis reaction is 1:3-5.5:0.3-0.6; The silica sol and an alkaline solution are mixed to obtain a sol to be solidified; the alkaline solution comprises a halogen-free flame retardant, a sunscreen, an alkaline catalyst and an alcohol solvent; The organic / inorganic blended fiber needle-punched felt is immersed in the sol to be gelled, and then heated for gelation and roller-pressed for thickness control to obtain a silicon-based alcohol gel felt; The silicon-based alcohol gel felt is aged in an aging solution and then dried to obtain a silicon-based aerogel felt; the aging solution comprises components 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 the 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 a nitric acid aqueous solution; the concentration of the nitric acid aqueous solution is 0.1 to 0.3 mol / L; The alcohol solvent used in the hydrolysis reaction includes methanol and / or ethanol; The temperature of the hydrolysis reaction is 50-60° C., and the reaction time is more than 5 hours.

3. The preparation method according to claim 1, characterized in that: The halogen-free flame retardant comprises halogen-free magnesium oxide and / or halogen-free magnesium hydroxide; the sunscreen comprises graphite and / or titanium dioxide, and the D 50 The particle size is 1 to 5 μm; 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, the mass fraction of the halogen-free flame retardant is 0.5-1%, and the mass fraction of the sunscreen is 0.5-2.5%; The amount of the alkaline solution used is based on adjusting the pH value of the silica sol to 7-9.

4. The preparation method according to claim 1, characterized in that: The inorganic fibers in the organic / inorganic blended fiber needle 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 the inorganic fibers in the organic / inorganic blended fiber needle felt is 50% to 75%, and the mass fraction of the organic fibers is 25% to 50%; The diameter of the inorganic fibers in the organic / inorganic blended fiber needle felt is 3 to 10 μm; The thickness of the organic / inorganic blended fiber needle felt is 11-15 mm, and the bulk density is 25-70 kg / m 3 .

5. The preparation method according to claim 1, characterized in that: The alkaline catalyst in the aging solution includes one or more of ammonia, sodium hydroxide, tetramethylammonium hydroxide and trimethylamine; the alcohol solvent in the aging solution includes methanol and / or ethanol; The hydrophobic modifier includes one or more of hexamethyldisilazane, trimethylmonomethoxysilane and trimethylmonoethoxysilane; The mass fraction of the hydrophobic modifier in the aging liquid is 2-4%; the amount of the alkaline catalyst in the aging liquid is based on controlling the pH value of the aging liquid to 8-9; The aging temperature is 55° C. to 65° C., and the total aging time is 12 h to 60 h. During the aging process, the first 1 / 2 to 2 / 3 of the aging time is kept stationary, and the aging liquid is kept circulating 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 is supercritical CO2 drying, and the conditions of the supercritical CO2 drying include: CO2 flow rate is 4-7m 3 / h, the drying temperature is 50-60°C, the drying pressure is 14-17MPa, and the drying time is 8-24h.

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

8. An ultra-low thermal conductive, flexible, waterproof and vapor resistant silicon-based aerogel composite material, comprising the silicon-based aerogel felt according to claim 7 and an aluminum foil composite film arranged on the surface of the silicon-based aerogel felt.

9. The ultra-low thermal conductive flexible waterproof vapor barrier silicon-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 in sequence, and the polyolefin layer is a POE layer or a TPO 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 gram weight is ≥170 g / m 2 , transverse tensile strength and longitudinal tensile strength are ≥30MPa, water vapor transmission rate ≤1×10 -10 g / (Pa·m 2 ·s).

10. The method for preparing the ultra-low thermal conductive flexible waterproof vapor barrier silicon-based aerogel composite material according to claim 8 or 9, characterized in that: The following steps are involved: The silicon-based aerogel felt and the aluminum foil composite film are composited by hot pressing to obtain the ultra-low thermal conductive, flexible, waterproof and vapor-resistant silicon-based aerogel composite material.

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