Composite aerogel film, thermal insulation material and preparation method

Abstract

The invention relates to a composite aerogel film, a heat insulation material and a preparation method, and relates to the technical field of sound insulation and heat insulation materials, and the composite aerogel film is composed of aerogel, nanofibers and a fiber base material. The composite aerogel film overcomes the mechanical defects of a traditional aerogel film, is good in tensile strength, meets the requirement for a flexible test, has good heat insulation and flame spreading prevention performance, and can effectively prevent flame spreading on the surface of a material when being applied to the heat insulation material.

Description

Technical Field

[0001] The present invention relates to the technical field of sound insulation and heat insulation materials, and in particular to a composite aerogel film, a heat insulation material and a preparation method thereof. Background Art

[0002] The nanoporous network structure of the gel gives it the characteristics of low density, high porosity, low thermal conductivity and high specific surface area, giving it broad application prospects in aerospace, sound insulation materials, phase change materials, adsorbents and catalyst carriers.

[0003] Traditional aerogel materials are brittle and low in strength. In engineering applications, they are often compounded with fiber felt to improve their mechanical properties. Zhaoxian Zhu et al. disclosed a fiber-reinforced polyimide aerogel composite material, which uses glass fiber felt as the 3D reinforcement of PI aerogel. The fiber skeleton inhibits the collapse and shrinkage of the aerogel. The resulting GF / PI composite material has low density, high compressive strength, excellent thermal stability and low thermal conductivity; however, due to the fragility of the aerogel, the aerogel impregnated in the fiber felt is easily affected by weak bonding and deformation and falls off, which seriously affects the thermal insulation performance of the aerogel composite material. In addition, the aerogel composite material prepared using fiber felt is large in overall size and difficult to process. It can generally only be used as an internal thermal insulation material, which limits the application of aerogel composite materials in the field of flexible thermal protection.

[0004] Chinese patent CN116874278B discloses an aerogel sheet, its preparation method and thermal insulation material, wherein a mixed slurry containing sol and fiber is formed into sheets, and an aerogel sheet is obtained through processes such as gelation, aging and drying, so that the aerogel sheet is uniformly formed at a relatively thin thickness and has high flatness, and the bending failure load of the sheet reaches 60N. This method mainly utilizes the interface bonding between the flexible fiber and the aerogel matrix to realize stress transfer, transfers the stress from the low-strength aerogel matrix to the high-strength and high-toughness reinforcing fiber, and improves the deformation capacity of the aerogel composite material. However, the fibers in the mixed slurry are in a disordered state, and it is difficult to arrange highly oriented fibers during the sheeting process, resulting in poor mechanical properties of the sheet, which still cannot meet the use requirements of flexible thermal protection materials.

[0005] Therefore, there is an urgent need to provide a new type of aerogel membrane that improves the mechanical properties of the aerogel membrane while also having a good thermal protection effect. Summary of the invention

[0006] The object of the present invention is to provide a composite aerogel film, a thermal insulation material and a preparation method in view of the above problems.

[0007] In order to achieve its purpose, the present invention adopts the following technical solution:

[0008] A first aspect of the present invention provides a composite aerogel film, which comprises the following components by weight: 25.0-65.0 wt% aerogel, 10.0-32.0 wt% nanofibers, and 20.0-45.0 wt% fiber substrates.

[0009] Preferably, the composite aerogel film comprises the following components by mass percentage: 50.0-53.0 wt% aerogel, 18.0-19.0 wt% nanofibers, and 29.0-31.0 wt% fiber substrate.

[0010] Preferably, the aerogel is selected from polyimide aerogel, phenolic aerogel, polyurethane aerogel, chitosan aerogel, and cellulose aerogel.

[0011] More preferably, the aerogel is a polyimide aerogel.

[0012] Preferably, the nanofiber is selected from PI fiber, aramid fiber, PVDF fiber, cellulose fiber, SiO2 fiber, carbon fiber, BN fiber, SiC fiber, TiO2 fiber, ZrO2 fiber.

[0013] Further preferably, the nanofibers are PI fibers.

[0014] Preferably, the average diameter of the nanofibers is 50 to 500 nm.

[0015] More preferably, the average diameter of the nanofibers is 200-300 nm.

[0016] Preferably, the fiber substrate is a flat mesh cloth formed by weaving multiple strands of glass fiber threads.

[0017] Preferably, the thickness of the flat mesh cloth is 50-120 μm, and the mass per unit area is 5-28 g / m 2 The mesh number is 4 to 18 meshes, the mesh size is 1 to 5 × 1 to 5 mm, and the tensile strength is 85 to 273 N / 50 mm.

[0018] Further preferably, the thickness of the flat mesh cloth is 100 μm and the mass per unit area is 15 g / m 2 The mesh number is 6 meshes, the mesh size is 3×3mm, and the tensile strength is 150N / 50mm.

[0019] Preferably, the mass per unit area of ​​the composite aerogel film is 40.0 to 100.0 g / m 2 , thickness is 0.1~0.5mm, tensile strength is 250~500N / m@25mm, afterburning time is <3s, flame spread distance is <51mm, and thermal conductivity is 10.0~50.0mW / (m·K).

[0020] A second aspect of the present invention provides a method for preparing a composite aerogel film, comprising the following steps:

[0021] S1. Preparation of mixed slurry: uniformly dispersing nanofibers in sol to obtain mixed slurry;

[0022] S2, preparation of prefabricated membrane material: evenly coating the mixed slurry on the release surface of the glass plate or release paper / film, laying a fiber substrate on the slurry, and coating the mixed slurry again to obtain a prefabricated membrane material;

[0023] S3, preparation of composite aerogel film: gelling the prefabricated film material to obtain a first wet gel film after demoulding; aging and solvent replacement of the first wet gel film to obtain a second wet gel film; and finally supercritical drying the second wet gel film to obtain a composite aerogel film.

[0024] Preferably, in the above-mentioned preparation method, the mixed slurry further comprises: a sunscreen and a flame retardant.

[0025] Preferably, the sunscreen is selected from one or more of carbon black, titanium dioxide, BaSO4, SiC, ZrO2, Cr2O3, CoO3, Fe2O3, potassium titanate whiskers or calcium carbonate whiskers.

[0026] Preferably, the added mass of the sunscreen agent is 1-10% of the mass of the sol.

[0027] Preferably, the flame retardant is selected from one or more of alumina, aluminum hydroxide, magnesium hydroxide, silicon dioxide, ammonium polyphosphate, aluminum hypophosphite, antimony trioxide, halogen series, phosphorus series, and nitrogen series.

[0028] Preferably, the added mass of the flame retardant is 1-10% of the mass of the sol.

[0029] Preferably, in the above-mentioned preparation method, the aging treatment temperature is 20 to 60° C., and the treatment time is 6 to 12 hours.

[0030] The solvent replacement is carried out multiple times using anhydrous ethanol, and the replacement time is 12 to 24 hours.

[0031] The supercritical drying is supercritical carbon dioxide drying, the reaction conditions are 5-25Mpa, 40-60°C, and the processing time is 0.5-8h.

[0032] The third aspect of the present invention provides a thermal insulation material, comprising the composite aerogel film described in any one of the above items, the composite aerogel film and / or the laminated film are composited in multiple layers, or a core material layer is arranged between the composite aerogel films, or a core material layer is arranged between the composite aerogel film and the laminated film, and the composite aerogel film, the laminated film, and the core material layer are bonded together by an adhesive.

[0033] Preferably, the material of the core layer is selected from polyimide foam, glass fiber, polyacrylonitrile fiber, carbon fiber, and pre-oxidized fiber.

[0034] Preferably, the thickness of the core material layer is 10 to 75 mm.

[0035] The fourth aspect of the present invention provides a method for preparing the above-mentioned thermal insulation material, comprising the following steps: coating an adhesive on one side of a laminated film and / or a composite aerogel film, placing the adhesive-coated sides of the laminated film and the composite aerogel film opposite to each other and covering the core material layer, or placing the adhesive-coated sides of the composite aerogel films opposite to each other and covering the core material layer, or placing the adhesive-coated sides of the composite aerogel films and / or the laminated film opposite to each other, and obtaining the thermal insulation material by gluing and hot pressing.

[0036] In summary, the present invention includes at least one of the following beneficial technical effects:

[0037] The aerogel matrix gives the membrane material good thermal insulation and anti-fire properties. The nanofibers are similar to the aerogel microstructure scale. The nanofibers are embedded in the aerogel matrix, so that the aerogel molecular chains are tightly interwoven on the surface of the nanofibers, providing new strong connection points for the inherent three-dimensional network skeleton structure of the aerogel, improving the brittleness of the aerogel membrane. The fiber substrate, as a reinforcing material providing mechanical support, can act as a molding skeleton, and its orderly woven structure further enhances the mechanical properties of the aerogel membrane in the plane direction. The nanofibers and the fiber substrate are in point contact, which reduces the overlap area between the fibers, increases the internal thermal resistance of the aerogel membrane, and effectively reduces the thermal conductivity of the aerogel membrane. The addition of nanofibers and fiber substrates can also reduce the volume shrinkage of the aerogel membrane during the preparation process and keep the structure of the aerogel membrane intact, thereby improving the thermal protection effect of the aerogel membrane while improving the mechanical properties of the aerogel membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic structural diagram of the thermal insulation material in Example 14 of the present invention;

[0039] Figure 2 is a schematic structural diagram of the thermal insulation material in Example 15 of the present invention;

[0040] Figure 3 It is a schematic diagram of the structure of the thermal insulation material in Example 16 of the present invention.

[0041] Figure numerals: 1. composite aerogel film; 2. core material layer; 3. laminated film. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to the embodiments.

[0043] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0044] The raw materials, reagents and equipment used are all commercially available conventional products.

[0045] The present invention provides a method for preparing a composite aerogel film, comprising the following steps:

[0046] S1. Preparation of mixed slurry: uniformly dispersing nanofibers in sol to obtain mixed slurry.

[0047] The sol is an organic sol, and is selected from phenolic sol, chitosan sol, polyimide sol, polyurethane sol, and cellulose sol, preferably polyimide sol.

[0048] The nanofibers are selected from one of PI fibers, aramid fibers, PVDF fibers, cellulose fibers, SiO2 fibers, carbon fibers, BN fibers, SiC fibers, TiO2 fibers, and ZrO2 fibers, preferably fibers that are consistent with or similar to the type of sol, and most preferably PI fibers. The average diameter of the nanofibers is 50 to 500 nm, preferably 200 to 300 nm.

[0049] The nanofibers are preferably fibers that are consistent with or similar to the type of sol, so that the nanofibers and the aerogel matrix have good chemical compatibility. The physical entanglement of the nanofibers with the fiber substrate and the chemical crosslinking with the aerogel matrix synergistically generate a three-dimensional network structure of the aerogel film. The aerogel matrix and the nanofibers have good interface bonding, and stress is transferred between the nanofibers and the aerogel matrix through the interface. The strong interface strength concentrates the stress on the surface of the nanofibers, further improving the flexibility and mechanical strength of the composite aerogel film.

[0050] Sunscreen agents and flame retardants can also be added to the mixed slurry. The amount of sunscreen agents and flame retardants added is 1 to 10% of the mass of the sol, preferably 1%. The sunscreen agent can be selected from one or more of carbon black, titanium dioxide, BaSO4, SiC, ZrO2, Cr2O3, CoO3, Fe2O3, potassium titanate whiskers or calcium carbonate whiskers.

[0051] The flame retardant can be an inorganic flame retardant or an organic flame retardant. The inorganic flame retardant is selected from one or more of aluminum oxide, aluminum hydroxide, magnesium hydroxide, silicon dioxide, ammonium polyphosphate, aluminum hypophosphite, and antimony trioxide. The organic flame retardant is selected from one or more of halogen, phosphorus, and nitrogen.

[0052] Sunscreen agents can effectively absorb or scatter infrared radiation of specific wavelengths, inhibit the radiation heat transfer of aerogel films, reduce heat transfer, and improve thermal insulation efficiency; flame retardants mainly play a role in fire prevention and enhancement.

[0053] S2. Preparation of prefabricated membrane material: compounding the mixed slurry obtained in S1 with a fiber substrate to obtain a prefabricated membrane material.

[0054] The fiber substrate is inorganic fiber paper or flat mesh cloth, the inorganic fiber paper can be glass fiber paper or aluminum silicate fiber paper, the fiber substrate is preferably a flat mesh cloth formed by weaving multiple fiber strands, the thickness of the flat mesh cloth is 50 to 120 μm, preferably 100 μm, and the mass per unit area is 5 to 28 g / m 2 , preferably 15g / m 2 The mesh number is 4 to 18, preferably 6, the mesh size is 1 to 5×1 to 5 mm, preferably 3×3 mm, and the tensile strength is 85 to 273 N / 50 mm, preferably 150 N / 50 mm.

[0055] The constituent fibers of the mesh cloth can be organic fibers or inorganic fibers. The organic fibers include PA fibers, PAI fibers, PBI fibers, PI fibers, PEEK fibers, PPS fibers, PTFE fibers, PSU fibers, PPSU fibers, and PEI fibers. The inorganic fibers include glass fibers, high-silica fibers, quartz fibers, basalt fibers, alkaline earth silicate fibers, and mullite fibers. Preferably, the constituent fibers of the mesh cloth are glass fibers. The mesh can be rectangular, circular, elliptical, or polygonal in shape, and the preferred mesh shape is rectangular.

[0056] The composite method of the mixed slurry and the fiber base material can be one of a coating method, a casting method, and a dipping-pulling method.

[0057] The operation steps of the coating method are: evenly coating the mixed slurry on one side of the glass plate, laying a mesh cloth on the slurry, and coating the mixed slurry again to obtain a prefabricated membrane material.

[0058] The coating method can be spin coating, spray coating, brush coating, blade coating, etc.

[0059] The glass plate is mainly used for the molding of the wet gel film, and release paper or release film may be used as a substitute, such as PET release film, PTFE release film, PE release film, PVC release film, PS release film or PMMA release film.

[0060] The operation steps of the casting method are: slowly add the mixed slurry into a mold containing a fiber substrate, so that the slurry evenly impregnates the substrate and covers the surface of the substrate to obtain a prefabricated membrane material.

[0061] The operation steps of the immersion-pulling method are: immerse the clean and dry fiber paper in the mixed slurry for 30 to 60 seconds, then take out the fiber paper at a pulling speed of 5 to 30 cm / min to obtain a prefabricated membrane material.

[0062] The aerogel matrix is ​​selected according to the design requirements, and the fiber substrate is a flat mesh cloth. The flat mesh cloth is used as a reinforcing material to provide mechanical support and can serve as a molding skeleton. Its orderly woven structure utilizes the gel distribution to enhance the mechanical properties of the composite aerogel in the plane direction. The nanofibers and the fiber substrate are in point contact, which reduces the overlap area between the fibers, increases the internal thermal resistance of the aerogel film, and effectively reduces the thermal conductivity of the aerogel film. In the composite aerogel film, the aerogel matrix and the nanofibers have a good interface bond, and the stress is transmitted between the nanofibers and the aerogel matrix through the interface. The strong interface strength concentrates the stress on the surface of the nanofibers, further improving the flexibility and mechanical strength of the composite aerogel film; the addition of nanofibers and fiber substrates can also reduce the volume shrinkage of the aerogel film during the preparation process and keep the structure of the aerogel film intact, so as to improve the thermal protection effect of the aerogel film while improving the mechanical properties of the aerogel film.

[0063] S3, preparation of composite aerogel film: firstly subject the prefabricated film material obtained in S2 to gelation reaction, and obtain a first wet gel film after demolding; then, subject the first wet gel film to aging and solvent replacement to obtain a second wet gel film; finally, subject the second wet gel film to supercritical drying treatment to obtain a composite aerogel film.

[0064] Among them, the gelation reaction can be triggered by heating, cooling, adding a cross-linking agent, etc. The present invention has no limitation on the triggering method of gelation, which can be corresponding to the type of gel. For example, when preparing polyimide aerogel, acetic anhydride and pyridine are often added to trigger the gelation reaction; when preparing polyurethane aerogel, the sol is gelled by cooling.

[0065] The aging operation treatment conditions of the first wet gel film are: treatment temperature is 20-60° C., and treatment time is 6-12 hours; preferably, treatment temperature is 40-45° C., and treatment time is 8 hours.

[0066] After the aging treatment, the wet gel membrane is transferred to a container containing an organic solvent, and the solvent is replaced for 12 to 24 hours, preferably for 12 hours. It is preferred to use an organic solvent for multiple replacements, and more preferably, the organic solvent is used for 4 replacements, each replacement time is 3 hours, and the organic solvent is selected from one of acetone, methanol, ethanol, butanol, and tert-butanol. Preferably, the organic solvent is anhydrous ethanol.

[0067] A waterproofing agent is added during solvent replacement to make the wet aerogel film hydrophobic. Preferably, a gradient replacement method is used for hydrophobic modification. During the first replacement, the volume ratio of the organic solvent to the waterproofing agent is 1:1, and the treatment is carried out for 3 hours; during the second replacement, the volume ratio of the organic solvent to the waterproofing agent is 2:1, and the treatment is carried out for 3 hours; during the third replacement, the volume ratio of the organic solvent to the waterproofing agent is 5:1, and the treatment is carried out for 3 hours; finally, a pure organic solvent is used for treatment for 3 hours to replace the remaining waterproofing agent in the wet gel film.

[0068] The waterproofing agent is selected from one or more silane waterproofing agents such as trimethylmethoxysilane, methyltrimethoxysilane, trimethylethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, vinyltrimethoxysilane, phenyltriethoxysilane, hexamethyldimethoxysilane, hexamethyldisilazane, dimethyldichlorosilane, trimethylchlorosilane, etc., preferably dimethyldichlorosilane.

[0069] The second wet gel membrane is subjected to supercritical drying treatment, and the supercritical drying is supercritical carbon dioxide drying or supercritical ethanol drying, preferably supercritical carbon dioxide drying. Specifically, the second wet gel membrane is placed in liquid CO2 for secondary replacement and supercritical carbon dioxide drying is performed. The reaction conditions are 5-25Mpa, 40-60°C, and the treatment time is 0.5-8h. Preferably, the reaction conditions of supercritical carbon dioxide drying are 20Mpa, 45-50°C, and the treatment time is 1-2h.

[0070] The sol forms a gel after the gelation reaction. During the solvent replacement process, the capillary force generated inside the gel can be reduced by gradually reducing the surface tension of the solvent, thereby preventing the hydrophobic performance from decreasing due to structural collapse during the drying process. Supercritical drying controls the pressure and temperature so that the solvent reaches its own critical point during the drying process and completes the supercritical transition from liquid phase to gas phase. The gel is transformed into aerogel after supercritical drying. In this process, the solvent has no obvious surface tension, and the transition from wet gel to aerogel is completed while maintaining the skeleton structure, minimizing the volume shrinkage of the aerogel film during the drying process.

[0071] The preferred ingredients and proportions allow the silane waterproofing agent to fully penetrate and combine with the surface of the aerogel film during solvent replacement, thereby reducing the surface energy of the aerogel film, reducing the adsorption and penetration of water molecules, and making the aerogel film have excellent moisture-proof properties. When dried with supercritical carbon dioxide, the critical temperature of CO2 is close to room temperature. CO2 can also be recycled, is non-toxic, and will not burn itself. There are no safety hazards, the operation is safe, the safety risks in the preparation process of the aerogel film are reduced, and the performance of the composite aerogel film is improved.

[0072] Supercritical drying is only a preferred embodiment of the present invention. According to actual needs, other drying methods such as freeze drying and normal pressure drying can also be used.

[0073] The composite aerogel film prepared by the method of the present invention comprises, by mass percentage, 25.0-65.0wt% aerogel, 10.0-32.0wt% nanofibers, and 20.0-45.0wt% fiber substrate, preferably 50.0-53.0wt% aerogel, 18.0-19.0wt% nanofibers, and 29.0-31.0wt% fiber substrate.

[0074] The mass per unit area of ​​the composite aerogel film prepared by the method of the present invention is 40.0 to 100.0 g / m 2 , preferably 45.0 to 65.0 g / m 2 , thickness is 0.1-0.5mm, preferably 0.18-0.35mm, tensile strength is 250-500N / m@25mm, preferably 250-300N / m@25mm, afterburning time is less than 3s, flame spread distance is less than 51mm, thermal conductivity is 10.0-50.0mW / (m·K), preferably 20.0-40.0mW / (m·K).

[0075] Preparation Example

[0076] Preparation Example 1

[0077] The preparation of polyimide sol comprises the following steps:

[0078] (1) Under N2 atmosphere, 4,4'-diaminodiphenyl ether (ODA, CAS No. 101-80-4) and pyromellitic anhydride (PDMA, CAS No. 89-32-7) were dissolved in N-methylpyrrolidone (NMP, CAS No. 872-50-4) solvent to prepare a polyamic acid solution (PAA solution), wherein the molar ratio of ODA to PDMA monomers was 1:1, and the mass fraction of PAA monomer in the solution was 5 wt%.

[0079] (2) Acetic anhydride (CAS No. 108-24-7) and pyridine (CAS No. 110-86-1) are added to the PAA solution to chemically imidize the PAA solution to obtain a polyimide sol.

[0080] In the preparation method, ODA and PDMA are diamine and dianhydride monomers respectively, acetic anhydride is a dehydrating agent, and pyridine is a catalyst. The dianhydride monomer can also be 3,3',4,4'-biphenyltetracarboxylic dianhydride, the dehydrating agent can also be propionic anhydride, and the solvent can also be N,N-dimethylacetamide.

[0081] Preparation Example 2

[0082] The preparation of polyurethane sol comprises the following steps:

[0083] (1) Dissolve 1,6-hexamethylene diisocyanate (CAS No. 822-06-0) and triethylene glycol (CAS No. 112-27-6) in acetonitrile (CAS No. 75-05-8) to prepare a precursor solution, wherein the molar ratio of the monomers of 1,6-hexamethylene diisocyanate and triethylene glycol is 2:3.

[0084] (2) Slowly add dibutyltin dilaurate (DBTDL, CAS No. 77-58-7) to the precursor solution and stir evenly to obtain a polyurethane sol.

[0085] Preparation Example 3

[0086] The preparation of chitosan sol comprises the following steps: dissolving chitosan (CAS No. 9012-76-4) powder in acetic acid (CAS No. 64-19-7) aqueous solution with a volume fraction of 2-10%, and standing to remove bubbles to form chitosan sol, wherein the mass fraction of chitosan is 2wt%.

[0087] The above preparation examples are all common preparation methods of sols in the prior art. Other sols can also be obtained by conventional technical solutions in the prior art, which is not intended to limit the present invention.

[0088] Example

[0089] Example 1

[0090] A composite aerogel film is prepared by the following method:

[0091] S1. Preparation of mixed slurry: The polyimide sol obtained in Preparation Example 1 and PI nanofibers with a diameter of 200-300 nm are selected and mixed, 1% of carbon black as a sunscreen agent and 1% of magnesium hydroxide as a flame retardant are added to the sol, and mixed to obtain a mixed slurry.

[0092] S2. Preparation of prefabricated membrane material: thickness of 100 μm and mass per unit area of ​​15 g / m 2 A glass fiber mesh cloth with a mesh size of 3×3 mm, a mesh number of 6 and a tensile strength of 150 N / 50 mm is used as a fiber substrate, and the mixed slurry prepared in S1 is compounded with the fiber substrate to obtain a prefabricated membrane material.

[0093] S3. Preparation of composite aerogel membrane: acetic anhydride and pyridine were added to the prefabricated membrane material to trigger the gelation reaction, and a first wet gel membrane was obtained after demolding, and then the first wet gel membrane was aged at 40° C. for 8 h.

[0094] After the aging treatment, the wet gel film was transferred to a container containing anhydrous ethanol, and dimethyldichlorosilane was used as a waterproofing agent for four replacements, each replacement time being 3 hours. Specifically, during the first replacement, the volume ratio of anhydrous ethanol to dimethyldichlorosilane was 1:1, and the treatment lasted for 3 hours; during the second replacement, the volume ratio of anhydrous ethanol to dimethyldichlorosilane was 2:1, and the treatment lasted for 3 hours; during the third replacement, the volume ratio of anhydrous ethanol to dimethyldichlorosilane was 5:1, and the treatment lasted for 3 hours; finally, pure anhydrous ethanol was used for treatment for 3 hours to replace the remaining dimethyldichlorosilane in the wet gel film to obtain a second wet gel film.

[0095] The second wet gel film was dried by supercritical carbon dioxide under the following conditions: 20 MPa, 45° C., and a treatment time of 1.5 h to obtain a composite aerogel film.

[0096] According to the preparation method of Example 1, the composite aerogel films of Examples 2 to 13 and Comparative Examples 1 to 3 were prepared by changing the raw material parameters, additive parameters, preparation conditions, etc., as shown in Tables 1 to 3.

[0097] Table 1 Raw material parameters

[0098]

[0099] Table 2 Additive parameters

[0100]

[0101]

[0102] Table 3 Preparation conditions

[0103]

[0104]

[0105] Embodiment 14

[0106] Reference Figure 1 , a thermal insulation material, including the aforementioned composite aerogel film 1. In this embodiment, the composite aerogel film 1 obtained in Example 1 is used as the anti-burning layer in the thermal insulation material. The thermal insulation material also includes a core material layer 2 and an anti-burning layer.

[0107] The material of the core layer 2 is selected from foam, organic or inorganic fiber, preferably the material of the core layer 2 is selected from polyimide foam, glass fiber, polyacrylonitrile fiber, carbon fiber, pre-oxidized fiber, and the thickness of the core layer 2 is 10-75 mm.

[0108] The anti-burn-through layer refers to a laminated film 3 containing inorganic particles. The raw materials of the inorganic particles come from: inorganic refractory materials, which can be inorganic mineral materials whose main components are SiO2, Al2O3, etc., such as mica, vermiculite, talc, montmorillonite, feldspar, etc., or artificially synthesized high-temperature resistant inorganic materials, such as high-temperature resistant microglass fibers, etc.

[0109] In this embodiment, the laminated film 3 is opposite to the composite aerogel film 1 and covers the core material layer 2, and the layers are bonded together by an adhesive.

[0110] Embodiment 15

[0111] Reference Figure 2 In other feasible embodiments, the thermal insulation material may not include the anti-burn-through layer, but only include the composite aerogel film 1 and the core material layer 2. The composite aerogel films 1 are opposite to each other, covering the core material layer 2, and are bonded and composited with an adhesive to obtain a fireproof thermal insulation material, which can effectively prevent the spread of flames.

[0112] Example 16

[0113] Reference Figure 3 In other feasible embodiments, the thermal insulation material may also have a multi-layer structure, with one surface being a laminated film 3 or a composite aerogel film 1, and the other surface being a composite aerogel film 1, with multiple layers of core material between the laminated film 3 and the composite aerogel film 1, and the core material layer 2 being separated by the laminated film 3 or the composite aerogel film 1 to form a sandwich structure of the laminated film 3 (or composite aerogel film 1), the core material layer 2, and the composite aerogel film 1.

[0114] Embodiment 17

[0115] In other feasible embodiments, the thermal insulation material may not have a core material layer 2, but may be composed of at least two composite aerogel films 1, or at least two laminated films 3, or at least one composite aerogel film 1 and at least one laminated film 3 to form a thermal insulation material having a multi-layer film structure.

[0116] The preparation method of the thermal insulation material is as follows:

[0117] Adhesive is coated on one side of the laminate film 3 and / or the composite aerogel film 1, and the adhesive-coated sides of the laminate film 3 and the composite aerogel film 1 are opposite to each other, or the adhesive-coated sides of the composite aerogel films 1 are opposite to each other, and the core material layer 2 is covered, and the fireproof heat-insulating material is obtained by gluing and hot pressing.

[0118] Optionally, when the core material layer is multi-layered, adhesive is coated on both sides of the laminated film 3 or the composite aerogel film 1 to serve as a separator film for the multi-layered core material.

[0119] Preferably, the separation film is a laminated film 3 having an anti-burn-through effect, so as to improve the flame-burn-through resistance of the fireproof and heat-insulating felt.

[0120] The fireproof and heat-insulating felt of the present invention is suitable for heat protection of the interior space of mobile cabins such as spacecraft, aircraft, rail transportation vehicles, ships, etc., and is also suitable for heat protection of the interior space of buildings such as residences, exhibition halls, and workshops.

[0121] The adhesive in the above embodiment includes one or more of polyurethane, acrylic acid, vinyl acetate, aluminum silicate, and methyl silicone.

[0122] The adhesive is also suitable for forming a sealing layer. The adhesive fully fills the bonding interface between each film layer and the core material layer, so that the fireproof and heat-insulating material has a higher peel strength and good heat sealing property.

[0123] When installing the fireproof and heat-insulating materials, the composite aerogel film 1 is arranged on the side close to the space inside the cabin, and the laminated film 3 is arranged on the side away from the space inside the cabin, which can effectively prevent the spread of flames in the space. The outer laminated film 3 has good flame resistance and can prevent the flame from spreading to the outside of the cabin. The fireproof and heat-insulating materials are not easy to peel off and delaminate after hot pressing and have good heat sealing properties. The core material of the fireproof and heat-insulating materials has a sound insulation effect, reducing the impact of noise outside the cabin. The composite aerogel film 1 has a smooth surface and can also be used as a moisture-proof layer of the fireproof and heat-insulating materials after hydrophobic treatment to provide a drainage path.

[0124] Performance testing experiment

[0125] The following performance test experiments were performed on the composite aerogel films prepared in Examples 1 to 13 and Comparative Examples 1 to 3, respectively.

[0126] 1. Mass per unit area and thickness: The mass per unit area and thickness of the composite aerogel film were obtained by conventional methods.

[0127] 2. Flexibility: Tested according to GB / T 34336-2017 "Nanoporous Aerogel Composite Insulation Products-Appendix E". Fold the center of the specimen around the steel pipe to 90° along the length direction. If there is no cracking or delamination of the specimen, it is a flexible material.

[0128] 3. Tensile strength: Fix the two ends of a 25 mm wide specimen on the fixture of a universal testing machine. Perform the test at room temperature using a static axial tensile test method. Slowly stretch the specimen until it breaks. Record the maximum breaking force during the test. The maximum breaking force is calculated by dividing the original width of the specimen.

[0129] 4. Flammability: Test according to Part VI of Appendix F of CCAR25. Report the after-flame time. If the flame of the sample does not exceed 3 seconds after the burner is removed, the flammability test is passed.

[0130] 5. Flame spread: Test according to Part VI of Appendix F of CCAR25. After the test is completed, report the shrinkage and melting of the sample, and report the flame spread distance. If the flame spread does not exceed 51 mm (2 inches) from the left side of the burner flame centerline, the flame spread test is passed.

[0131] 6. Waterproofness: Take a 200×200mm sample, weigh it, and then completely immerse it in 23℃ water for 72 hours. After this period of time, the sample is weighed again and the water absorption is calculated.

[0132] 7. Thermal conductivity: At room temperature, the thermal conductivity was tested using a transient plane heat source method (DRE-III multifunctional rapid thermal conductivity tester). For each sample, an average of five measurements were performed to determine the thermal conductivity value.

[0133] The measurement results are shown in Table 5.

[0134] Table 5 Composite aerogel membrane parameters

[0135]

[0136] The comparative analysis of Examples 1 to 13 and Comparative Examples 1 to 3 is as follows:

[0137] Embodiment 1 is the best embodiment of the method for preparing the composite aerogel membrane of the present invention, and its comprehensive performance is better than that of other embodiments;

[0138] Compared with Example 1, Example 2 is only waterproof modified, the gram weight is reduced, the thickness is roughly unchanged, the tensile strength is roughly unchanged, and the thermal conductivity is increased;

[0139] Compared with Example 1, Example 3 reduces the nanofiber content, increases the gram weight, reduces the thickness, reduces the tensile strength, and the thermal conductivity remains roughly unchanged;

[0140] Compared with Example 1, Example 4 increases the nanofiber content, gram weight, thickness, tensile strength, and thermal conductivity;

[0141] Compared with Example 1, Example 5 changes the type of light-shielding flame retardant and waterproof modifier, the gram weight remains roughly unchanged, the thickness remains roughly unchanged, the tensile strength increases, and the thermal conductivity increases;

[0142] Compared with Example 1, Example 6 changes the types of aerogel and nanofibers, increases the gram weight, increases the thickness, decreases the tensile strength, and increases the thermal conductivity;

[0143] Compared with Example 1, Example 7 changes the types of aerogel and nanofibers, increases the gram weight, increases the thickness, decreases the tensile strength, and increases the thermal conductivity;

[0144] Compared with Example 1, Example 8 changes the type of nanofibers, increases the gram weight, increases the thickness, decreases the tensile strength, and increases the thermal conductivity;

[0145] Compared with Example 1, Example 9 changes the type of nanofibers, increases the gram weight, increases the thickness, decreases the tensile strength, and the thermal conductivity remains roughly unchanged;

[0146] Compared with Example 1, Example 10 changes the type of fiber cloth, increases the gram weight, increases the thickness, increases the tensile strength, and increases the thermal conductivity;

[0147] Compared with Example 1, Example 11 changes the type of fiber cloth, reduces the gram weight, increases the thickness, reduces the tensile strength, and reduces the thermal conductivity.

[0148] Compared with Example 1, Example 12 changes the size of the fiber cloth, increases the gram weight, decreases the thickness, increases the tensile strength, and increases the thermal conductivity;

[0149] Compared with Example 1, Example 13 changes the size of the fiber cloth, reduces the gram weight, reduces the thickness, reduces the tensile strength, and reduces the thermal conductivity;

[0150] Compared with Examples 1 to 13, Comparative Example 1 is a self-made sample, which does not use a fiber substrate and has no fiber substrate support, and the sample shrinks severely when heated;

[0151] Compared with Examples 1 to 13, Comparative Example 2 is a homemade sample, using micron-sized chopped fibers instead of nanofibers, increasing the fiber overlap area, increasing the thermal conductivity, and having a large size difference between the fiber substrate and the aerogel, resulting in low bonding strength, breaking when subjected to force, and severe powder loss;

[0152] Compared with Examples 1 to 13, Comparative Example 3 is a self-made sample without doping with nanofibers. The fiber substrate and the aerogel have a large size difference, the bonding strength is not high, and it breaks when subjected to force and loses powder severely.

[0153] In summary, the composite aerogel film prepared by this method has greatly improved the mechanical properties of the aerogel film, has good tensile strength, meets the flexibility test, and has good heat insulation and anti-burning properties. The composite aerogel film prepared by this method is used in the preparation of thermal insulation materials to increase the corresponding performance of the thermal insulation materials.

Claims

1. A composite aerogel film, characterized in that: The composite aerogel film comprises the following components by weight: 25.0-65.0 wt% of aerogel, 10.0-32.0 wt% of nanofibers, and 20.0-45.0 wt% of fiber substrate.

2. The composite aerogel film according to claim 1, characterized in that The aerogel is selected from polyimide aerogel, phenolic aerogel, polyurethane aerogel, chitosan aerogel, and cellulose aerogel; Preferably the aerogel is a polyimide aerogel.

3. The composite aerogel film according to claim 1, characterized in that The nanofiber is selected from PI fiber, aramid fiber, PVDF fiber, cellulose fiber, SiO2 fiber, carbon fiber, BN fiber, SiC fiber, TiO2 fiber, ZrO2 fiber; Preferably, the nanofibers are PI fibers; The average diameter of nanofibers is 50-500 nm.

4. The composite aerogel film according to claim 1, characterized in that The fiber substrate is a flat mesh fabric formed by weaving multiple strands of glass fiber yarns; The thickness of the flat mesh cloth is 50-120 μm, and the mass per unit area is 5-28 g / m 2 The mesh number is 4 to 18 meshes, the mesh size is 1 to 5 × 1 to 5 mm, and the tensile strength is 85 to 273 N / 50 mm.

5. The composite aerogel film according to claim 1, characterized in that The unit area mass of the composite aerogel film is 40.0 to 100.0 g / m 2 , thickness is 0.1~0.5mm, tensile strength is 250~500N / m@25mm, afterburning time is <3s, flame spread distance is <51mm, and thermal conductivity is 10.0~50.0mW / (m·K).

6. The method for preparing a composite aerogel film according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Preparation of mixed slurry: uniformly dispersing nanofibers in sol to obtain mixed slurry; S2, preparation of prefabricated membrane material: evenly coating the mixed slurry on the release surface of the glass plate or release paper / film, laying a fiber substrate on the slurry, and coating the mixed slurry again to obtain a prefabricated membrane material; S3, preparing a composite aerogel film: causing the prefabricated film material to undergo a gelation reaction, and obtaining a first wet gel film after demoulding; Then, the first wet gel film is subjected to aging and solvent replacement to obtain a second wet gel film; finally, the second wet gel film is subjected to supercritical drying to obtain a composite aerogel film.

7. The method for preparing a composite aerogel film according to claim 6, characterized in that: The mixed slurry also includes: sunscreen, flame retardant; The added mass of the sunscreen agent is 1 to 10% of the mass of the sol; The added mass of the flame retardant is 1 to 10% of the mass of the sol.

8. The method for preparing a composite aerogel film according to claim 6, characterized in that: The aging treatment temperature is 20 to 60° C. and the treatment time is 6 to 12 hours; The solvent replacement is carried out multiple times with anhydrous ethanol, and the replacement time is 12 to 24 hours; The supercritical drying is supercritical carbon dioxide drying, the reaction conditions are 5-25Mpa, 40-60°C, and the processing time is 0.5-8h.

9. A thermal insulation material, characterized in that: The invention comprises at least one composite aerogel film according to any one of claims 1 to 5, wherein the composite aerogel film and / or the laminated film are multi-layered, or a core material layer is arranged between the composite aerogel films, or a core material layer is arranged between the composite aerogel film and the laminated film, and the composite aerogel film, the laminated film and the core material layer are bonded and laminated by an adhesive.

10. The method for preparing the thermal insulation material according to claim 9, characterized in that: The following steps are involved: An adhesive is coated on one side of the laminated film and / or the composite aerogel film, and the adhesive-coated sides of the laminated film and the composite aerogel film are opposite to each other and cover the core material layer, or the adhesive-coated sides of the composite aerogel films are opposite to each other and cover the core material layer, or the adhesive-coated sides of the composite aerogel films and / or the laminated film are opposite to each other, and the thermal insulation material is obtained by gluing and hot pressing.

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