An organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material and a preparation method thereof

Abstract

The application discloses an organic-inorganic double-layer composite aerogel / rock wool fiber composite heat preservation and insulation material and a preparation method thereof. The rock wool fiber felt is coated with an organic layer, so that acid corrosion problems of the rock wool fiber felt in the processes of acid silicate sol immersion and hydrophobic modification treatment are effectively avoided. Water glass and methyl alkoxysilane are used as a composite silicon source to prepare SiO2 aerogel, the SiO2 aerogel can be uniformly and stably filled in pores of the rock wool fiber felt and fiber lap joints, meanwhile, relative slipping between fibers during compression can be avoided, so that the material has smaller deformation after compression and rebound, and the heat preservation performance is more stable. Methyl is introduced into the silicon source, and methyl halosilane is used for further hydrophobic modification treatment of the material, so that the hydrophobic performance of the material is greatly improved. Therefore, the organic-inorganic double-layer composite aerogel / rock wool fiber composite heat preservation and insulation material has the advantages of low thermal conductivity, good hydrophobic performance, good compression and rebound performance and low production cost.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to an organic-inorganic bilayer composite aerogel / rock wool fiber composite thermal insulation material and its preparation method. Background Technology

[0002] SiO2 aerogel is a three-dimensional, pearl-chain-like porous material formed by the cross-linking and overlapping of numerous SiO2 microspheres. Due to its ultra-high porosity, high specific surface area, and ultra-low density, SiO2 aerogel has wide applications in thermal insulation, sound insulation and wave absorption, energy storage, and drug delivery. Especially in the field of thermal insulation, SiO2 aerogel currently boasts the lowest thermal conductivity of any man-made material, at 0.012 W / (m·K). This is attributed to the fact that most of the pores within SiO2 aerogel are mesopores ranging from 20 nm to 50 nm, effectively preventing conductive heat transfer caused by molecular vibrations (the mean free path of molecules is approximately 90 nm) and convective heat transfer caused by airflow. However, SiO2 aerogel itself suffers from drawbacks such as high brittleness, susceptibility to cracking, high-temperature failure, and high manufacturing costs. Therefore, reinforcing SiO2 aerogel with fibers as a framework is of great significance for expanding its applications.

[0003] CN 112457037A discloses a method for preparing SiO2 aerogel composite material reinforced with mullite fiber whisker porous reinforcement based on liquid phase method. This technology increases the specific surface area of ​​the fiber felt by generating mullite whiskers in situ on the surface of the mullite fiber felt in liquid phase method, and then prepares a more stable and highly compressible SiO2 aerogel composite fiber felt by vacuum impregnation. However, the introduction of whiskers will reduce the aerogel content in the composite fiber felt and reduce the thermal insulation performance of the material.

[0004] Rock wool fiber felt is a porous fiber felt made by bonding basalt fibers with organic adhesives and then hot-pressing them. It has some compressibility along the fiber stacking direction, but is rigid and inflexible overall. Due to its high porosity, low density, fire resistance, and low cost, it is widely used in building exterior wall insulation layers. However, because its internal pores are mostly millimeter- and micrometer-sized pores formed by overlapping micron-sized basalt fibers, its thermal insulation effect is far inferior to SiO2 aerogel, with a thermal conductivity of approximately 0.04 W / (m·K). Furthermore, due to the hydrophilic nature of rock wool, it has been unable to provide waterproofing and moisture-proofing in the long term when used in building insulation. Combining rock wool fiber felt with SiO2 aerogel to prepare a superhydrophobic and super-insulating SiO2 aerogel / rock wool fiber felt composite material can effectively meet the requirements for thermal insulation materials.

[0005] However, compared to quartz and mullite fiber felts, rock wool fiber felt has a loose structure and low specific surface area. Conventional vacuum impregnation methods cannot achieve a tight bond and full filling of SiO2 aerogel with the rock wool fiber felt. Rock wool fiber felt is not acid-resistant and will be severely corroded, powdered, and cracked in acidic environments, losing its high-porosity structure and failing to provide a skeletal support when combined with SiO2 aerogel. CN 109824339A discloses a rock wool / aerogel composite material with thermal insulation properties. This technology uses silica sol as the silicon source and prepares a SiO2 aerogel / rock wool composite material with a thermal conductivity of 0.019 W / (m·K) using vacuum impregnation and atmospheric pressure drying. However, the upstream product cost of silica sol (tetraethyl or methyl orthosilicate), an organosilicon source, is too high, failing to meet the new requirements for low cost and high performance in the field of building thermal insulation. Furthermore, the modification process of aerogel using trimethylchlorosilane mentioned in the above method generates a large amount of hydrochloric acid as a byproduct. The acidic environment has a strong corrosive effect on rock wool, making the process of preparing SiO2 aerogel / rock wool composite materials using vacuum impregnation and atmospheric pressure drying cumbersome, costly, and unable to achieve the expected product performance. Therefore, a method for combining rock wool fibers and SiO2 aerogel for use in thermal insulation materials still needs to be studied. Summary of the Invention

[0006] This invention addresses the problems in the prior art by disclosing an organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material and its preparation method. The material of this invention has the advantages of low thermal conductivity, good hydrophobicity, good compression resilience, and low production cost.

[0007] In a first aspect, the present invention provides a method for preparing an organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material, comprising the following steps:

[0008] S1: After vacuum impregnating the rock wool fiber felt in water-based acrylic resin for 30-60 minutes, it is dried at normal pressure at 80-120℃ to obtain rock wool fiber felt with organic layer coating.

[0009] S2: The rock wool fiber felt coated with organic layer is added to a modifier prepared by silane coupling agent, water and ethanol and vacuum impregnated for 30-60 minutes, and then dried at normal pressure at 80-120℃ to obtain rock wool fiber felt modified with organic layer.

[0010] S3: Water glass is used as silicon source A and methylalkoxysilane is used as silicon source B. Silicon source A and silicon source B are pretreated under acidic conditions, then mixed and stirred. Ammonia water is added to adjust the pH to 5-6 to obtain silica sol.

[0011] S4: The organic-layer modified rock wool fiber felt is placed in silica sol and vacuum impregnated for 15-30 minutes under a pressure of 0.6-0.8 MPa to obtain silica gel;

[0012] S5: After hydrophobic modification of the silica gel with methyl halosilane, it is dried at 80-120℃ under normal pressure to obtain an organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material.

[0013] This application uses acrylic resin to coat rock wool fiber felt, effectively avoiding the acid corrosion problems of rock wool fiber felt during the acidic silica sol impregnation process and subsequent hydrophobic modification treatment. Rock wool fibers are not acid-resistant; direct contact with acidic silica sol will cause pulverization and breakage, failing to fulfill their skeletal support function in the material. The hydrophobic modification treatment of acidic silica gel using methyl halosilanes produces hydrochloric acid as a byproduct, which further corrodes the rock wool fibers, significantly reducing the material's thermal insulation performance. Using water glass and methyl alkoxysilanes as a composite silicon source allows for a greater filling amount in the rock wool fibers compared to a single silicon source. This maximizes the filling of fiber pores, especially at fiber overlaps, effectively inhibiting convective heat transfer between the millimeter-scale pores and conductive heat transfer at fiber overlaps. This structure also prevents relative slippage between fibers during compression, thus giving the material a certain degree of elasticity, resulting in smaller deformation after compression rebound and more stable thermal insulation performance. Furthermore, the introduction of methyl groups into the silicon source improves the poor hydrophobicity of the rock wool fiber felt, and the further hydrophobic modification treatment with methyl halosilane further enhances the hydrophobic properties of the material. Therefore, the organic-inorganic bilayer composite aerogel / rock wool fiber felt composite material of this application exhibits excellent thermal insulation, hydrophobic properties, and compression resilience.

[0014] In some embodiments, the aqueous acrylic resin in step S1 is selected from one or more of acrylic resin emulsions, acrylic resin aqueous dispersions, and acrylic resin aqueous solutions, with a mass fraction of 10 wt% to 30 wt%. The acrylic resin emulsion is selected from one or more of Wanna-ResinARE 2152, Wanna-ResinARE 2116, and Wanna-ResinARE 2138. The acrylic resin aqueous dispersion is selected from one or more of Eutectic NE30D, Eutectic RL30D, and Eutectic RS30D.

[0015] In some embodiments, the silane coupling agent in step S2 is selected from one or more of aminosilanes, epoxysilanes, methacryloxysilanes, and mercaptosilanes. The aminosilane is selected from one or more of 3-aminopropyltrimethoxysilane (KH-540), 3-aminopropyltriethoxysilane (KH-550), 3-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyldimethylmethoxysilane, and γ-aminopropyldimethylethoxysilane. The epoxysilane is selected from one or more of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), γ-(2,3-epoxypropoxy)propyltriethoxysilane, 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane, and 3-(2,3-epoxypropoxy)propylmethyldiethoxysilane. The methacryloyloxysilane is selected from one or more of γ-methacryloyloxypropyltrimethoxysilane (KH-570), γ-methacryloyloxypropylmethyldimethoxysilane, and γ-methacryloyloxypropyltriethoxysilane. The mercaptosilane is selected from one or more of 3-mercaptopropyltriethoxysilane (KH-580), mercaptopropyldimethoxymethylsilane, mercaptomethyldimethoxymethylsilane, and mercaptoethyldimethoxymethylsilane.

[0016] Preferably, the silane coupling agent in this application is selected from aminosilanes. The amino groups in aminosilanes have high reactivity with the carboxyl groups in acrylic resins. At the same time, the hydrolyzable groups in aminosilanes can combine with SiO2 aerogel after hydrolysis, which can improve the bonding strength between acrylic resins and SiO2 aerogels.

[0017] In some embodiments, the molar ratio of the silane coupling agent, water, and ethanol in step S2 is 1:(1-5):(2-10).

[0018] In some embodiments, the pretreatment process of silicon source A in step S3 is as follows: water glass is diluted at a dilution ratio of 5wt% to 15wt%, and then filtered through an ion exchange column to obtain a silicic acid solution with pH = 2 to 3.

[0019] In some embodiments, the pretreatment process of silicon source B in step S3 is as follows: A mixture of methylalkoxysilane, ethanol, and water is prepared at a molar ratio of 1:(10-20):(5-10). The mixture is stirred at 400 r / min for 30 min, followed by slow dropwise addition of hydrochloric acid. The mixture is stirred under sealed conditions for 12-20 h. The molar ratio of hydrochloric acid to methylalkoxysilane is 0.018:1.

[0020] In some embodiments, the silicon source B in step S3 is selected from one or more of monomethylalkoxysilane, dimethylalkoxysilane, and trimethylalkoxysilane. The monomethylalkoxysilane is selected from at least one of methyltrimethoxysilane (MTMS) and methyltriethoxysilane (MTES). The dimethylalkoxysilane is selected from at least one of dimethyldimethoxysilane (DMDMS) and dimethyldiethoxysilane (DMDES). The trimethylalkoxysilane is selected from at least one of trimethylmethoxysilane (TMSOME) and trimethylethoxysilane (TMES).

[0021] Further, the silicon source B is selected from two of monomethylalkoxysilane, dimethylalkoxysilane, and trimethylalkoxysilane, with a mixing molar ratio of (5-7.5):(2.5-5). Even further, the silicon source B is selected from a mixture of monomethylalkoxysilane, dimethylalkoxysilane, and trimethylalkoxysilane, with a mixing molar ratio of (5-8):(1.5-3):(0.5-2). Since the three silicon sources with different numbers of methyl groups will generate silica sols with different numbers of hydroxyl functional groups after hydrolysis under acidic conditions, a denser multi-level gradient pore structure can be formed under appropriate proportions. This sol can more fully fill the pores of the rock wool fiber felt and the fiber overlaps, which is more conducive to improving the material's thermal insulation performance and compression resilience.

[0022] In some embodiments, the molar ratio of silicon source A to silicon source B in step S3 is 1:(0.1~0.3). A molar ratio that is too high will lead to uneven pore distribution in the aerogel, affecting its filling effect in the rock wool fiber felt, and will also reduce the methyl content in the material, thereby reducing the material's thermal conductivity, hydrophobicity, and compression resilience. A molar ratio that is too low will significantly increase the material's production cost. This application improves material performance while reducing material cost by adjusting the molar ratio of silicon source A and silicon source B.

[0023] In some embodiments, the mass fraction of the ammonia solution in step S3 is 1 wt% to 10 wt%.

[0024] In some embodiments, the methyl halosilane in step S5 is selected from one or more of trimethylchlorosilane, trimethyliodosilane, trimethylbromosilane, methyltrichlorosilane, and dimethyldichlorosilane.

[0025] In some embodiments, the hydrophobic modification in step S5 includes the following steps:

[0026] Using hexane as a solvent, a solution of methyl halosiloxane with a concentration of 0.4–1 mol / L was prepared as a modifier. An equal volume of the modifier as the silica gel was poured into the container containing the gel and allowed to stand for 24 hours to obtain the hydrophobically modified SiO2 aerogel / rock wool fiber composite material.

[0027] In some embodiments, the stirring speed in step S5 is 400-500 r / min, and the stirring time is 3-5 min.

[0028] Secondly, this application provides an organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material, which is prepared by the preparation method provided in the first aspect of this application.

[0029] The features and beneficial effects of this invention are as follows:

[0030] (1) This application uses acrylic resin to coat rock wool fiber felt, which effectively avoids the acid corrosion problem of rock wool fiber felt during the impregnation process with acidic silica sol and the hydrophobic modification process, and further improves the stability of the material.

[0031] (2) Using water glass and methyl alkoxysilane as a composite silicon source to prepare SiO2 aerogel results in better filling effect in rock wool fiber felt compared to using a single silicon source. This effectively suppresses convective heat transfer between the millimeter-scale pores of the fibers and conductive heat transfer at the fiber overlaps. The organic-inorganic double-layer coating structure effectively prevents shrinkage during the formation process of SiO2 aerogel in the millimeter-scale and micrometer-scale pores of the rock wool fiber felt, while avoiding the direct combination of organic monomers and inorganic silicon sources affecting the formation of the internal pore structure of the aerogel. This structure also prevents relative slippage between fibers during compression, thus giving the material a certain degree of elasticity, smaller deformation after compression rebound, and more stable thermal insulation performance. In this application, the introduction of methyl groups into the silicon source improves the poor hydrophobicity of the rock wool fiber felt, and the use of methyl halosilanes for hydrophobic modification further enhances the material's hydrophobic properties.

[0032] (3) Using water glass as the main silicon source for SiO2 aerogel significantly reduces the production cost of the materials in this application.

[0033] Therefore, the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material of this application has the advantages of low thermal conductivity, good hydrophobicity, good compression resilience, and low production cost. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a SEM image of the original rock wool fiber felt. Among them, Figure 1 Image a is a SEM image of the millimeter-scale pores and the micron-scale pores of the multi-layer overlap in the rock wool fiber felt. Figure 1 b is a SEM image of the interlayer arrangement of rock wool fiber felt. Figure 1 c is a SEM image of the microstructure of rock wool fiber felt. Figure 1 d is the SEM image of the fiber surface.

[0036] Figure 2 This is a diagram of the composite thermal insulation material from Example 1. Figure 2 a is the external morphology diagram. Figure 2 b is a SEM image of the fiber surface. Figure 2 c is the SEM image of the fiber overlap. Figure 2 d is a TEM transmission electron microscope image of the SiO2 aerogel structure.

[0037] Figure 3 This is a diagram of the composite thermal insulation material from Example 2. Figure 3 a is a microscopic morphology diagram. Figure 3 b is a SEM image of the fiber surface. Figure 3 c is the SEM image of the fiber overlap. Figure 3 d is a TEM transmission electron microscope image of the SiO2 aerogel structure.

[0038] Figure 4 This is a diagram of the composite thermal insulation material in Example 3. Figure 4 a is a microscopic morphology diagram. Figure 4 b is a SEM image of the fiber surface. Figure 4 c is the SEM image of the fiber overlap. Figure 4 d is a TEM transmission electron microscope image of the SiO2 aerogel structure.

[0039] Figure 5 This is a diagram of the composite thermal insulation material in Comparative Example 1. Among them, Figure 5 a is a microscopic morphology diagram. Figure 5 b is a SEM image of the fiber surface. Figure 5 c is the SEM image of the fiber overlap. Figure 5 d is a TEM transmission electron microscope image of the SiO2 aerogel structure.

[0040] Figure 6 This is a diagram of the composite thermal insulation material in Comparative Example 2. Among them, Figure 6 a is a microscopic morphology diagram. Figure 6 b is a SEM image of the fiber surface. Figure 6 c is the SEM image of the fiber overlap. Figure 6 d is a TEM transmission electron microscope image of the SiO2 aerogel structure.

[0041] Figure 7 This is a microscopic morphology diagram of the composite thermal insulation material in Comparative Example 5.

[0042] Figure 8 These are photos of the contact angle of composite thermal insulation materials. Figure 8 a is a photograph of the contact angle in Example 1. Figure 8 b is a photograph of the contact angle in Example 2. Figure 8 c is a contact angle photograph at scale 4.

[0043] Figure 9 These are compression-rebound stress-strain curves of Examples 1, 2, 4 and the original rock wool fiber felt.

[0044] Figure 10 This is a diagram of the ion exchange process in water glass.

[0045] Figure 11 Figure a shows the acid corrosion and pulverization of the composite thermal insulation material in Comparative Example 3. Figure 11 b is Figure 11 SEM image of the fiber overlap of material a. Detailed Implementation

[0046] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below, and embodiments of the present invention will be provided, but this does not limit the scope of the present invention.

[0047] In this application, the reference to "embodiment" means that a particular feature / structure or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0048] In the description of this application, the term "multiple" refers to two or more (including two), and the term "at least one" refers to one or more (including one, two, three, etc.).

[0049] As a specific example of the implementation of this invention, detailed cases are provided below:

[0050] Example 1

[0051] Step 1: Immerse the rock wool fiber felt in a 15wt% aqueous acrylic resin solution, impregnate under vacuum for 60 minutes, and dry at 80℃ under normal pressure to obtain an organic layer-coated rock wool fiber felt.

[0052] Step 2: Mix silane coupling agent, water and ethanol in a ratio of 1:2:3 and stir at 60°C for 1 hour as a modifier. Soak the rock wool fiber felt with organic layer obtained in Step 1 in the modifier solution, impregnate under vacuum for 60 minutes, and dry at 80°C under normal pressure to obtain the rock wool fiber felt with organic layer modification.

[0053] Step 3: Water glass was used as silicon source A, diluted at a ratio of 10 wt%, and filtered through an ion exchange column to obtain a silicic acid solution with pH=2. MTES, DMDES, and TMES were mixed in a molar ratio of 7:2:1 to serve as silicon source B, and then mixed with ethanol and water in a molar ratio of 1:15:7. The mixture was stirred at 400 r / min for 30 min, and hydrochloric acid was slowly added dropwise. The mixture was stirred under sealed conditions for 12 h. The molar ratio of hydrochloric acid to organosilicon source was 0.018:1. The pretreated silicon source A and silicon source B were mixed in a molar ratio of 1:0.3 and stirred at 400 r / min for 5 min. Then, 5 wt% ammonia was added to adjust the pH to 6, thus obtaining silica sol.

[0054] Step 4: Place the organic layer modified rock wool fiber felt obtained in Step 2 into the silica sol obtained in Step 3, vacuum impregnate for 30 minutes, and control the pressure at 0.8 MPa to obtain silica gel;

[0055] Step 5: Using hexane as a solvent, prepare a 1 mol / L solution of trimethylchlorosilane as a modifier. Pour an equal volume of the modifier into the container containing the gel and let it stand for 24 hours to obtain the modified SiO2 aerogel / rock wool fiber composite material. Then, perform normal pressure drying at 120℃ to obtain an organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material.

[0056] Example 2

[0057] The difference from Example 1 is that the silicon source B is MTES.

[0058] Example 3

[0059] The difference from Example 1 is that the silicon source B is TMES.

[0060] Example 4

[0061] The difference from Example 1 is that the silicon source B is MTES and TMES, and the mixing ratio is 1:1.

[0062] Example 5

[0063] The difference from Example 1 is that silicon source A and silicon source B are mixed in a molar ratio of 1:0.2.

[0064] Example 6

[0065] The difference from Example 1 is that silicon source A and silicon source B are mixed in a molar ratio of 1:0.1.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that silicon source B was not added.

[0068] Comparative Example 2

[0069] The difference from Example 1 is that tetraethyl orthosilicate (TEOS) was used as silicon source A, and silicon source B was not added.

[0070] Comparative Example 3

[0071] The difference from Example 1 is that the rock wool fiber felt was not coated with acrylic resin.

[0072] Comparative Example 4

[0073] The difference from Example 1 is that hydrophobic modification treatment with methyl halosilane was not used.

[0074] Comparative Example 5

[0075] The difference from Example 1 is that silicon source A and silicon source B are mixed in a molar ratio of 1:0.02.

[0076] The composite thermal insulation materials prepared according to the embodiments and comparative examples of this application were subjected to performance tests, including:

[0077] (1) Thermal conductivity test: The thermal conductivity of the sample was measured using a DRPL thermal conductivity meter according to the plate heat flow meter method (refer to standard GB / T10295-2008).

[0078] (2) Compression and rebound performance test: The samples were subjected to compression and rebound tests using an Instron 3380 universal testing machine (refer to standard GB / T1964-1996).

[0079] (3) Hydrophobicity test: Use a 2ml plastic dropper to drop a drop of deionized water on the sample surface and measure the contact angle between the water drop and the fiber surface.

[0080] The thermal conductivity and thermal conductivity after compression and rebound of each embodiment and comparative example are shown in Table 1.

[0081] Table 1

[0082]

[0083] Figure 1 The SEM image of the original rock wool fiber felt shows that the fiber surface is smooth. Figure 1 c. Figure 1 d) Different fibers overlap and interweave to form millimeter- and micrometer-scale pores. Figure 1 a, Figure 1 b) In this structure, heat transfer mainly occurs through conduction at the fiber overlap points along the fiber skeleton and convection through air flowing through the fiber pores. These two heat transfer methods have a significant negative impact on the insulation effect of rock wool.

[0084] The comparison of data results from Examples 1-6 with those from Comparative Examples 1-5 verifies that the thermal conductivity of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material of this application, as well as its thermal conductivity after compression and rebound, is significantly lower than that of the thermal insulation material prepared in the comparative examples.

[0085] The comparison of the data results of Example 1 and Comparative Example 1 verifies that the SiO2 aerogel prepared by using water glass and methylalkoxysilane as a composite silicon source in this application has a better filling effect in rock wool fiber felt than using water glass alone. It can reduce the thermal conductivity of the material to a greater extent, and at the same time avoid the relative slippage between fibers in the rock wool fiber felt during compression, thereby improving the compression and rebound performance of the material and making the change in thermal conductivity of the material smaller after compression and rebound.

[0086] Compared with the original fiber felt, the microstructure of the SiO2 aerogel / rock wool composite fiber felt prepared using water glass as the silicon source is as follows: Figure 5 As shown, by Figure 5 It can be seen that the aerogel does not fill the fiber pores; the fibers are independent of each other, and the fiber overlaps are loosely connected to the aerogel. Figure 5 c), and the aerogel attached to the fiber surface contains both nano-sized particles and micron-sized dense layers, but does not have a continuous nano-sized porous structure. Figure 5 b、 Figure 5 d) This is due to the instability of the sol system when the silicic acid solution generated by the water glass through the ion exchange column is used as a single silicon source. The main component of water glass is sodium metasilicate (Na2O·SiO2·nH2O), and its ion exchange process is as follows: Figure 10 As shown, metasilicate ions (H2SiO4) 2- During ion exchange, it gradually reacts with H+. + When pH = 2-3, Na + Almost completely removed, and the positively charged silica particles undergo self-polymerization because when Na... + When completely removed, this reaction system lacks group selectivity, resulting in poor stability of the ion-exchanged silica solution. The intense self-polymerization reaction leads to uneven pore distribution in the SiO2 gel, ultimately damaging the material's thermal insulation performance.

[0087] The data results of Example 1 and Comparative Example 2 can be compared to verify that the SiO2 aerogel prepared by using water glass and methyl alkoxysilane as a composite silicon source in this application can significantly reduce the thermal conductivity of the material and the thermal conductivity after compression and rebound compared to using TEOS alone as the silicon source.

[0088] The microstructure of SiO2 aerogel / rock wool composite fiber felt prepared using TEOS as the silicon source is as follows: Figure 6 As shown in a, although the material has a certain degree of continuous porous structure, it improves the adhesion of aerogel to rock wool fiber felt to some extent. Figure 6 c), but the problems of large pore size, uneven distribution, and lack of density still exist. Figure 6 a, Figure 6 b、 Figure 6 d).

[0089] A comparison of the data results from Example 1 and Comparative Example 3 verifies that coating rock wool fiber felt with acrylic resin can avoid acid corrosion problems during the acidic silica sol impregnation process and the hydrophobic modification process with methyl halosilane. In Comparative Example 3, the rock wool fiber felt was severely corroded by acid, resulting in pulverization and breakage, and the thermal insulation performance of the material significantly deteriorated. Figure 11 b comparison Figure 2 c shows that the fibers in the rock wool fiber felt that were not coated with acrylic resin were all corroded and broken by acid, resulting in the overall structure of the rock wool fiber felt pulverizing and cracking. Figure 11 a) It cannot serve as a skeletal support in the material.

[0090] Depend on Figure 7 The comparison of contact angles between Example 1 and Comparative Example 4 verifies that hydrophobic modification of the material with methyl halosilane can further improve the hydrophobic properties of the material.

[0091] A comparison of the data results from Example 1 and Comparative Example 5 verifies that an excessively high molar ratio of silicon source A to silicon source B leads to uneven pore distribution in the aerogel, affecting its filling effect in rock wool fiber felt. Figure 7 This reduces the thermal conductivity of the material, as well as its thermal conductivity after compression and rebound.

[0092] The data results from Examples 1-4 can be compared to verify that in Example 1 of this application, using three silicon sources with different numbers of methyl groups—MTES, DMDES, and TMES—as silicon source B, the reduction in thermal conductivity of the material is more significant compared to using one or two silicon sources B.

[0093] As can be seen from the above, the porosity of aerogels prepared using water glass as a single silicon source is low, and their TEM images show disordered stacking of nanoparticles. This is because the active silicic acid obtained after ion exchange of water glass undergoes a self-polymerization reaction under acidic conditions. (Comparison) Figure 3 b and Figure 4b. It can be observed that the pore structure of aerogels formed by different silicon sources differs to some extent. This is because the different amounts of silane groups (Si-CH3) introduced cause variations in the length of the Si-O-Si polymer chains. MTES, because it has only one Si-CH3 group as an inert group while the other three Si-OC2H5 groups participate in the formation of the cross-linking network, results in a larger average pore size in aerogels prepared using MTES and water glass as a composite silicon source. Figure 3 d) indicates that MTES, as a monomethyl silicon source, possesses certain oriented crosslinking characteristics during the formation of a silicon crosslinking network. This allows primary particles to grow without crosslinking along the polymerization direction of the active hydroxyl groups, ultimately forming pores larger than 200 nm. In contrast, TMES, due to its three Si-CH3 inert groups, results in aerogels prepared using TMES and water glass as a composite silicon source having smaller average pores and lower porosity. Figure 4 d), but the overall structure of the aerogel is an accumulation of nano-spherical particles, indicating that TMES as a silicon source combined with water glass can promote the formation of primary particles. Therefore, TMES as a trimethylsilane source can effectively prevent the active silica in water glass from continuously polymerizing and crosslinking.

[0094] It is evident that during the formation of aerogels, TMES promotes the formation of spherical primary particles, while MTES promotes the formation of oriented voids. Their combined action can form an aerogel with uniform pores. Therefore, it is considered to combine TMES and MTES with water glass in a certain proportion to form a multi-level porous silicon source system. Furthermore, to further improve the uniform distribution of the multi-level porous structure, DMDES is considered to be added to the system. The SiO2 aerogel / rock wool fiber felt composite material is prepared by mixing MTES, DMDES, and TMES in a certain proportion with water glass as a composite silicon source. Theoretically, due to the characteristics of their own structures, these three silicon sources, after hydrolysis under acidic conditions, will generate silica sols with different numbers of hydroxyl functional groups. Under appropriate ratios, they can react with each other to generate uniform and stable multi-level gradient pores. Figure 2 As shown, the aerogel fully fills the voids in the rock wool fiber felt. Figure 2 a), and completely wrapped around the fiber overlap ( Figure 2 c) Compared to Examples 2-4, the aerogel prepared by this method exhibits a uniform nanoscale porous structure on the fiber surface, significantly reducing the material's thermal conductivity. This structure also prevents relative slippage between fibers during compression, thus giving the material a certain degree of elasticity, resulting in less deformation after compression and rebound, and more stable thermal insulation performance. Figure 9 It can be seen that the material prepared by mixing two silicon sources as silicon source B has better compression resilience than the material prepared by mixing three silicon sources as silicon source B, and the material prepared by mixing three silicon sources as silicon source B has better compression resilience than the material prepared by mixing two silicon sources.

[0095] Depend on Figure 8 It can be seen that: in Example 1, when three silicon sources are mixed as silicon source B, the hydrophobic angle of the material is 150°; in Example 2, when only a single silicon source is used as silicon source B, the hydrophobic angle of the material is 142°. This indicates that the hydrophobic groups of the aerogel formed by the combination of the three silicon sources and water glass are more dense, which is beneficial to further improving the hydrophobic properties of the material.

[0096] A comparison of the data results from Example 1 and Examples 5-6 verifies that as the molar ratio of silicon source B increases, the thermal conductivity of the material also increases. This is because the increase of silicon source B is conducive to the formation of denser aerogel pores, thereby achieving a better filling effect in rock wool fiber felt and effectively reducing the thermal conductivity of the material.

[0097] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material, characterized in that, Includes the following steps: S1: After vacuum impregnating the rock wool fiber felt in water-based acrylic resin for 30-60 minutes, dry it at normal pressure at 80-120℃ to obtain rock wool fiber felt with organic layer coating. S2: The rock wool fiber felt coated with organic layer is added to a modifier prepared by silane coupling agent, water and ethanol and vacuum impregnated for 30-60 minutes, and then dried at normal pressure at 80-120℃ to obtain rock wool fiber felt modified with organic layer. S3: Water glass is used as silicon source A and methylalkoxysilane is used as silicon source B. Silicon source A and silicon source B are pretreated under acidic conditions, then mixed and stirred. Ammonia water is added to adjust the pH to 5-6 to obtain silica sol. S4: The organic-layer modified rock wool fiber felt is placed in silica sol and vacuum impregnated for 15-30 minutes under a pressure of 0.6-0.8 MPa to obtain silica gel; S5: After hydrophobic modification of the silica gel with methyl halosilane, it is dried at 80~120℃ under normal pressure to obtain an organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material. The pretreatment process of silicon source A in step S3 is as follows: water glass is diluted at a dilution ratio of 5wt% to 15wt%, and then filtered through an ion exchange column to obtain a silicic acid solution with pH=2 to 3; The pretreatment process of silicon source B in step S3 is as follows: methyl alkoxysilane, ethanol and water are mixed in a molar ratio of 1:(10~20):(5~10), stirred at 400 r / min for 30 min, and then hydrochloric acid is slowly added dropwise. The mixture is stirred under sealed conditions for 12~20 h, wherein the molar ratio of hydrochloric acid to methyl alkoxysilane is 0.018:

1. The mixing molar ratio of silicon source A to silicon source B in step S3 is 1:(0.1~0.3).

2. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The aqueous acrylic resin mentioned in step S1 is selected from one or more of acrylic resin emulsions, acrylic resin aqueous dispersions, and acrylic resin aqueous solutions, with a mass fraction of 10wt%~30wt%. The acrylic resin emulsion is selected from one or more of Wanna-Resin ARE 2152, Wanna-Resin ARE 2116, and Wanna-Resin ARE 2138; The acrylic resin aqueous dispersion is selected from one or more of Eutetech NE30D, Eutetech RL30D and Eutetech RS30D.

3. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The silane coupling agent in step S2 is selected from one or more of aminosilanes, epoxysilanes, methacryloxysilanes, and mercaptosilanes; The aminosilane is selected from one or more of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyldimethylmethoxysilane, and γ-aminopropyldimethylethoxysilane. The epoxy silane is selected from one or more of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane and 3-(2,3-epoxypropoxy)propylmethyldiethoxysilane. The methacryloyloxysilane is selected from one or more of γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, and γ-methacryloyloxypropyltriethoxysilane; The mercaptosilane is selected from one or more of 3-mercaptopropyltriethoxysilane, mercaptopropyldimethoxymethylsilane, mercaptomethyldimethoxymethylsilane, and mercaptoethyldimethoxymethylsilane.

4. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The silane coupling agent in step S2 is selected from aminosilanes.

5. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The molar ratio of silane coupling agent, water, and ethanol in step S2 is 1:(1~5):(2~10).

6. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The silicon source B in step S3 is selected from one or more of monomethylalkoxysilane, dimethylalkoxysilane, and trimethylalkoxysilane; The monomethylalkoxysilane is selected from at least one of methyltrimethoxysilane and methyltriethoxysilane, the dimethylalkoxysilane is selected from at least one of dimethyldimethoxysilane and dimethyldiethoxysilane, and the trimethylalkoxysilane is selected from at least one of trimethylmethoxysilane and trimethylethoxysilane.

7. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The silicon source B is selected from two of monomethylalkoxysilane, dimethylalkoxysilane and trimethylalkoxysilane, with a mixing molar ratio of (5~7.5):(2.5~5).

8. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The silicon source B is selected from a mixture of monomethylalkoxysilane, dimethylalkoxysilane and trimethylalkoxysilane, with a mixing molar ratio of (5~8):(1.5~3):(0.5~2).

9. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The methyl halosilane in step S5 is selected from one or more of trimethylchlorosilane, trimethyliodosilane, trimethylbromosilane, methyltrichlorosilane, and dimethyldichlorosilane.

10. The preparation method of the organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material according to claim 1, characterized in that, The hydrophobic modification described in step S5 includes the following steps: Using hexane as a solvent, a solution of methyl halosiloxane with a concentration of 0.4~1 mol / L was prepared as a modifier. An equal volume of the modifier as the silica gel was poured into the container containing the gel and allowed to stand for 24 hours to obtain the hydrophobically modified SiO2 aerogel / rock wool fiber composite material.

11. An organic-inorganic double-layer composite aerogel / rock wool fiber composite thermal insulation material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 10.

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