High-temperature-resistant and low-shrinkage aerogel thermal insulation coating and preparation method thereof

Abstract

This invention relates to the field of inorganic thermal insulation coating technology, specifically to a high-temperature resistant and low-shrinkage aerogel thermal insulation coating and its preparation method; it includes an inorganic binder system, a first inorganic fiber, a second inorganic fiber, hydrophobically modified SiOC aerogel particles, infrared suppressing fillers, and other substances; wherein the inorganic binder system includes alumina sol and zirconium oxide sol; wherein a portion of the first inorganic fiber is hydrophobically modified; by optimizing the inorganic binder system and fiber reinforcement structure, this invention significantly reduces the drying shrinkage rate and internal stress of the coating while ensuring long-term temperature resistance. The drying shrinkage of the coating of this invention is less than 0.2%, and it can achieve single-coat 3mm thickness drying without cracking or peeling, and effectively reduces thermal conductivity and radiative heat transfer.

Description

Technical Field

[0001] This invention relates to the field of inorganic thermal insulation coating technology, specifically to a high-temperature resistant and low-shrinkage aerogel thermal insulation coating and its preparation method. Background Technology

[0002] Existing high-temperature resistant thermal insulation coatings, especially those used at temperatures exceeding 600℃, mostly employ inorganic binder systems such as silicates or phosphates. These inorganic binders exhibit significant volume shrinkage during drying and curing. Due to the inherent rigidity of inorganic coatings, they are prone to generating substantial internal stress after drying, leading to cracking, blistering, and even peeling. Therefore, in actual construction, the thickness of a single application of this type of coating is typically no more than 0.5mm. Achieving a design thickness of 3-5mm requires multiple applications, resulting in long construction cycles and high labor costs. Furthermore, in scenarios requiring infill insulation, the high drying shrinkage of the insulation coating can create gaps between the dried coating and the space walls, forming thermal bridges and reducing the structure's insulation performance and sealing.

[0003] On the other hand, existing high-temperature resistant thermal insulation coatings mostly use hollow glass microspheres, ceramic microspheres, or aerogel particles as the main thermal insulation fillers. Among them, the long-term heat resistance temperature of hollow glass microspheres and silica aerogel particles is usually below 650℃, which is difficult to meet the needs of higher temperature conditions; while ceramic microspheres have better temperature resistance, their solid thermal conductivity is high, resulting in a high overall thermal conductivity of the coating and limited thermal insulation effect.

[0004] Therefore, developing a high-temperature resistant thermal insulation coating that combines high temperature resistance, low thermal conductivity, low drying shrinkage, and the ability to be applied in thick coats has significant engineering application value. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-temperature resistant and low-shrinkage aerogel thermal insulation coating and its preparation method. By optimizing the inorganic binder system and fiber-reinforced structure, this invention significantly reduces the coating's drying shrinkage and internal stress while ensuring long-term temperature resistance. This results in a coating that does not crack or peel under single-coat thick-layer application conditions, and effectively reduces thermal conductivity and radiative heat transfer.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] This invention provides a high-temperature resistant and low-shrinkage aerogel thermal insulation coating, comprising the following components by mass percentage:

[0008] The composition includes: 10%–24% inorganic binder system, 10%–25% first inorganic fiber, 0.5%–2% second inorganic fiber, 8%–15% hydrophobically modified SiOC aerogel particles, 15%–20% infrared suppressing filler, and 25%–35% deionized water;

[0009] The inorganic binder system includes alumina sol and zirconium oxide sol;

[0010] The first inorganic fiber has a length of 0.5 to 2 mm and a diameter of 0.5 to 5 μm, and 40 wt% to 60 wt% of the first inorganic fiber has been hydrophobically modified.

[0011] The second inorganic fiber has a length of 5–10 mm and a diameter of 5–12 μm;

[0012] The drying shrinkage rate of the aerogel thermal insulation coating is less than 0.2%.

[0013] Furthermore, the hydrophobically modified SiOC aerogel particles are hydrophobically modified using a silane coupling agent; and 40wt% to 60wt% of the first inorganic fiber is hydrophobically modified using a silane coupling agent.

[0014] Conventionally, the hydrophobic modification process includes the following steps: spraying a clean object to be treated with a hydrolysate of a silane coupling agent, causing the silane coupling agent molecules in the hydrolysate to undergo a condensation reaction with the hydroxyl groups on the surface of the object to be treated; after spraying, allowing it to stand at room temperature for 30 to 60 minutes, and then heating and curing it at 100 to 130°C for 1 to 2 hours to obtain the hydrophobically modified object to be treated;

[0015] The material to be processed is SiOC aerogel particles or the first inorganic fiber;

[0016] The amount of hydrolysate sprayed is controlled to be 2% to 5% of the mass of the substance to be treated;

[0017] The process of obtaining the hydrolysate is as follows: add the silane coupling agent to deionized water or a water-alcohol mixed solvent, control the mass fraction of the silane coupling agent to be 1% to 3%, adjust the pH of the system to 4.0 to 5.5, and let it stand at room temperature for 20 to 40 minutes to allow the silane coupling agent to be fully hydrolyzed, thereby obtaining a hydrolyzed silane solution.

[0018] Conventionally, the silane coupling agent is an organosilane with a hydrophobic alkyl structure, preferably an alkylsilane coupling agent, specifically including but not limited to methyltriethoxysilane (MTES), methyltrimethoxysilane (MTMS), isobutyltriethoxysilane (IBTES), and isooctyltriethoxysilane (OTES). The alkyl groups in the above-mentioned silane coupling agents can form a low surface energy orientation structure on the fiber surface, and their siloxy groups, after hydrolysis, can undergo a condensation reaction with the hydroxyl groups on the inorganic fiber surface, thereby forming a stable hydrophobic modified layer on the fiber surface.

[0019] Preferably, the silane coupling agent is methyltriethoxysilane or isooctyltriethoxysilane, in order to balance hydrophobicity, reaction stability and temperature resistance.

[0020] Furthermore, the mass ratio of the alumina sol to the zirconium oxide sol is 1:0.1 to 0.3. In this invention, the role of the zirconium oxide sol is to further improve the heat resistance temperature of the binder system. When the amount used is too small, the improvement in heat resistance temperature is limited, but when the amount added is too large, it will increase the drying shrinkage of the alumina sol binder during drying and the internal stress of the coating, affecting the crack resistance of the coating when it is thickly coated.

[0021] Furthermore, the alumina sol has a solid content of 15wt% to 30wt% and a particle size of 5nm to 50nm; the zirconium oxide sol has a solid content of 10wt% to 25wt% and a particle size of 10nm to 80nm.

[0022] Furthermore, the first inorganic fiber and the second inorganic fiber are respectively selected from one or more of aluminosilicate fiber, basalt fiber, quartz fiber, and alumina fiber.

[0023] Furthermore, the hydrophobically modified SiOC aerogel particles have a particle size of 100-250 mesh and a specific surface area greater than 400 m². 2 / g.

[0024] Furthermore, the infrared suppressing filler is selected from one or more of titanium oxide, zirconium oxide, and zirconium silicate, and its particle size is 0.3 μm to 1.2 μm.

[0025] Furthermore, the coating components also include 0.5% to 2.0% thickener, 0.3% to 0.8% defoamer, and 0.4% to 1.2% dispersant.

[0026] Furthermore, the thickener is selected from one of bentonite, attapulgite, or silica, and is an inorganic component. While playing a thickening and suspending role, it does not affect the high temperature resistance of the coating and maintains the good scraping performance of the coating, avoiding sagging in the case of thick coating.

[0027] The defoamer is selected from one or more of polyether-modified silicone defoamer, mineral oil-based defoamer, and hydrophobic silica defoamer. The defoamer can suppress the generation of excessive bubbles in the coating preparation process and ensure the normal addition and dispersion of various materials.

[0028] The dispersant is selected from one or more of polycarboxylate dispersants, phosphate or polyphosphate dispersants, silane-modified polymer dispersants, and nonionic polymer dispersants. The dispersant can help aerogel particles, inorganic fibers and infrared suppressing fillers to be fully dispersed, so as to achieve uniformity of the coating fiber structure and effective performance of each functional material.

[0029] Another aspect of the present invention provides a method for preparing a high-temperature resistant and low-shrinkage aerogel thermal insulation coating, comprising the following steps: under mechanical stirring, the inorganic binder system of the formulation amount is mixed evenly with deionized water, and then a dispersant, a first inorganic fiber, a second inorganic fiber, hydrophobically modified SiOC aerogel particles, an infrared suppressing filler, a thickener, and a defoamer are added in sequence, and the mixture is stirred evenly to obtain the coating.

[0030] This invention addresses the problems of large drying shrinkage, easy cracking, and inability to be applied in thick coats in traditional high-temperature resistant thermal insulation coatings by focusing on two aspects: inorganic binder system and fiber filler.

[0031] ① This invention uses alumina sol as the main binder. Compared with traditional water glass or silica sol binders, alumina sol is essentially a stable colloidal dispersion system formed by nano-sized hydrated alumina particles (mainly amorphous or low-crystallinity boehmite AlOOH) in water. The particles are usually in the form of sheets. During the drying process, its hydration structure and coordination network have stronger plasticity and stress release ability. Its dried product is similar to a plastic gel and has viscous flow characteristics. Coatings prepared with it as a binder are not easy to crack during drying.

[0032] In addition, using zirconia sol as an auxiliary binder can further improve the high-temperature stability of the coating system, while the zirconia phase generated at high temperature can also play a certain role in infrared shading.

[0033] ② To enhance the crack resistance of the coating, for thicker coatings, this invention uses long fibers as the second inorganic fiber to increase the tensile strength of the coating itself with a small amount. While adding too much fiber will improve the mechanical properties of the coating, it is not conducive to adhesion to the substrate. This is because when the coating itself has too high strength, it is difficult to relieve the internal stress generated by drying shrinkage through its own deformation after drying, which leads to the overall peeling of the coating. To address this, this invention adds 0.5% to 2% of slightly coarse long fibers as the second inorganic fiber to the coating, and adds 10% to 25% of a larger amount of ultrafine short fibers as the first inorganic fiber to replace expensive ceramic whiskers (such as sulfur). The coating utilizes whiskers made of calcium carbonate, potassium hexatitanate, wollastonite, or silicon carbide, among other materials. The first inorganic fiber has a larger aspect ratio than the whiskers. Through the interlacing and overlapping of ultra-fine short fibers, the mechanical properties of the coating are improved. Furthermore, the three-dimensional rigid network formed by the inorganic fibers and the inorganic binder effectively resists capillary forces during drying, achieving extremely low drying shrinkage. This ensures thick coating processes and allows for a single brush coat thickness of up to 3 mm. The selected inorganic fibers also exhibit high heat resistance and excellent high-temperature stability, thus achieving long-term dimensional stability of the high-temperature insulation coating under the requirement of "low-temperature preparation, high-temperature use," thereby preventing cracking or peeling.

[0034] Secondly, to achieve a lower thermal conductivity while meeting the heat resistance temperature of 1000℃, the coating of this invention uses SiOC aerogel particles as a high-temperature insulating filler. SiOC aerogel particles possess extremely high thermal stability, and their highly developed nanoporous network structure results in extremely low thermal conductivity. Hydrophobic modification ensures that water, certain ions, or nanoparticles cannot penetrate during coating preparation, maintaining their nanoporous characteristics and thus guaranteeing low thermal conductivity. Simultaneously, a portion (40%–60%) of the first inorganic short fibers undergoes hydrophobic treatment, preventing them from being wetted by the binder during preparation or storage, thus forming a weak bond with the binder. This reduces heat conduction between fibers or with other fillers, and the ultrafine fibers also extend the heat transfer path, further reducing thermal conductivity. Furthermore, since radiation is primarily heat transfer at high temperatures, the infrared suppressor filler in the coating formulation hinders infrared radiation heat transfer by scattering infrared rays, further reducing the thermal conductivity of the coating at high temperatures.

[0035] Beneficial technical effects: This invention significantly reduces coating drying shrinkage and inhibits crack formation by introducing a rigid network structure formed by multi-scale inorganic fiber overlap; this invention uses alumina sol as the main binder and supplements it with zirconium oxide sol. The inorganic cross-linked network formed by the hydroxyl bridging of the sol, which combines strength and toughness, can effectively reduce drying internal stress and improve the adaptability of thick coating application; this invention uses hydrophobically modified inorganic fibers, hydrophobically modified SiOC aerogel particles, and infrared suppressing fillers to synergistically reduce the thermal bridging effect, so that the coating maintains a low thermal conductivity at high temperatures after drying; the formulation of this invention significantly reduces coating drying shrinkage and internal stress while ensuring long-term temperature resistance, achieving coating without cracking or peeling under single thick coating application conditions, and effectively reducing thermal conductivity; the coating of this invention maintains good thermal insulation performance and structural stability even under long-term use temperatures up to 1000℃ under thick coating conditions. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise specifically stated, the numerical values ​​set forth in these embodiments do not limit the scope of the invention. Techniques and methods known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques and methods should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that values ​​expressed, for example, as "within the range of ab" or "between the range of ab," do not include the endpoint values ​​a and b; values ​​expressed as "for ab," "is ab," or "ab" include the endpoint values ​​a and b.

[0038] Furthermore, it should be noted that the use of terms such as "first" and "second" to define inorganic fibers is merely for the purpose of distinguishing the selected fibers. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0039] Experimental methods not specified in the following examples are generally performed according to national standards; if there is no corresponding national standard, they are performed according to general standard requirements or general methods.

[0040] Preparation Example

[0041] The first inorganic fiber is selected from one or more of aluminosilicate fiber, basalt fiber, quartz fiber, and alumina fiber, and undergoes hydrophobic modification treatment. The specific process is as follows:

[0042] (1) Take the first inorganic fiber and dry it at 110℃ for 2 h to remove the adsorbed moisture inside it, and cool it to room temperature for later use.

[0043] (2) Then prepare the hydrolysate of silane coupling agent: add methyltriethoxysilane (MTES) to an aqueous ethanol solution (ethanol volume percentage is 80%) by mass fraction, the concentration of MTES in the system is 2.0 wt%, add glacial acetic acid to adjust the pH of the system to 4.5 under continuous stirring, and let it stand at room temperature for 30 min to allow the silane coupling agent to be fully hydrolyzed to obtain the hydrolysate of silane coupling agent;

[0044] (3) Take the first inorganic fiber that is prepared and apply the above hydrolysate evenly to it by spraying. The amount of hydrolysate sprayed is controlled to be 3% of the fiber mass, and the fiber surface should not have obvious droplets. After spraying, let it stand at room temperature for 45 min to promote the condensation reaction between the hydrolyzed silane and the hydroxyl groups on the fiber surface. Then heat and cure at 120°C for 1.5 h. After cooling, a hydrophobic fiber with a surface modified by silane coupling agent is obtained.

[0045] The hydrophobically modified SiOC aerogel particles were obtained according to the parameters of the first inorganic fiber hydrophobic modification treatment described above.

[0046] Example 1

[0047] A high-temperature resistant and low-shrinkage aerogel thermal insulation coating, comprising the following components in 100% by mass percentage:

[0048] The inorganic binder system comprises 15% alumina sol (20% solid content, average particle size of about 20 nm) and zirconia sol (15% solid content, average particle size of about 40 nm), with a mass ratio of alumina sol to zirconia sol of 1:0.2.

[0049] Alumina silicate fiber is used as the first inorganic fiber (18%). The alumina silicate fiber has an average length of 1 mm and a diameter of about 2 μm. 50 wt% of the first inorganic fiber is hydrophobically modified by the preparation method described above.

[0050] Basalt fiber was used as the second inorganic fiber (1.0%), with an average length of 8 mm and a diameter of approximately 8 μm.

[0051] The hydrophobically modified SiOC aerogel particles, with an average particle size of 150 mesh and a specific surface area of ​​approximately 500 m² / g, were obtained by hydrophobically modifying SiOC aerogel particles using the method described in the above preparation example.

[0052] Equal mass ratios of titanium oxide and zirconium silicate were used as 18% infrared suppressor filler, with an average particle size of approximately 0.6 μm.

[0053] 33% deionized water;

[0054] The thickener is 1.5% sodium bentonite;

[0055] The defoamer is 0.5% polyether-modified silicone defoamer (BYK-019);

[0056] The dispersant is a polycarboxylate dispersant (Dow, Dispersant 1620) 1.0%;

[0057] The preparation method of the above coating includes the following steps: under mechanical stirring, the inorganic binder system of the formula amount is mixed evenly with deionized water, and then the dispersant, the first inorganic fiber, the second inorganic fiber, the hydrophobically modified SiOC aerogel particles, the infrared suppressor filler, the thickener, and the defoamer are added in sequence, and the mixture is stirred evenly to obtain the coating of this case.

[0058] Example 2

[0059] A high-temperature resistant and low-shrinkage aerogel thermal insulation coating, comprising the following components in 100% by mass percentage:

[0060] The inorganic binder system comprises 20% alumina sol (25% solid content, average particle size of about 15nm) and zirconia sol (20% solid content, average particle size of about 30nm), with a mass ratio of alumina sol to zirconia sol of 1:0.15.

[0061] Quartz fiber, comprising 22% of the first inorganic fiber, has an average length of 0.8 mm and a diameter of approximately 1.5 μm. 60 wt% of the first inorganic fiber is hydrophobically modified using the method described above.

[0062] Alumina fiber was used as the second inorganic fiber, accounting for 0.8%. The average length of the alumina fiber was 6 mm and the diameter was about 10 μm.

[0063] 10% of hydrophobically modified SiOC aerogel particles, with an average particle size of 200 mesh and a specific surface area of ​​approximately 450 m² / g, were obtained by hydrophobically modifying SiOC aerogel particles using the method described in the above preparation example.

[0064] Zirconia powder was used as 16% of the infrared suppressor filler, with an average particle size of approximately 0.8 μm.

[0065] Deionized water 28%;

[0066] The thickener is 1.5% attapulgite.

[0067] The defoamer is a mineral oil-based defoamer (BYK-039) at 0.8%;

[0068] The dispersant is a polycarboxylate dispersant (Dow, Dispersant 1620) 0.9%;

[0069] The preparation method of the above coating includes the following steps: under mechanical stirring, the inorganic binder system of the formula amount is mixed evenly with deionized water, and then the dispersant, the first inorganic fiber, the second inorganic fiber, the hydrophobically modified SiOC aerogel particles, the infrared suppressor filler, the thickener, and the defoamer are added in sequence, and the mixture is stirred evenly to obtain the coating of this case.

[0070] Example 3

[0071] A high-temperature resistant and low-shrinkage aerogel thermal insulation coating, comprising the following components in 100% by mass percentage:

[0072] The inorganic binder system is 22%, consisting of alumina sol (solid content 18%, average particle size about 40 nm) and zirconia sol (solid content 12%, average particle size about 20 nm), with a mass ratio of alumina sol to zirconia sol of 1:0.25.

[0073] Basalt fiber is used as 15% of the first inorganic fiber. The average length of the basalt fiber is 1.5 mm and the diameter is about 3 μm. 40 wt% of the first inorganic fiber is hydrophobically modified by the preparation method described above.

[0074] Alumina silicate fiber is used as the second inorganic fiber, accounting for 0.8%. The average length of the alumina silicate fiber is 10 mm and the diameter is about 12 μm.

[0075] The hydrophobically modified SiOC aerogel particles, comprising 14%, have an average particle size of 120 mesh and a specific surface area of ​​approximately 620 m² / g. They are obtained by hydrophobically modifying SiOC aerogel particles using the method described in the above preparation example.

[0076] Titanium oxide powder was used as 19% of the infrared suppressor filler, with an average particle size of approximately 0.4 μm.

[0077] Deionized water 26%;

[0078] The thickener is 0.8% silica;

[0079] The defoamer is a hydrophobic silica defoamer (BYK-024) at 0.6%;

[0080] The dispersant was 1.1% silane-modified polymer dispersant (BASF, Dispex® CX 4320);

[0081] The preparation method of the above coating includes the following steps: under mechanical stirring, the inorganic binder system of the formula amount is mixed evenly with deionized water, and then the dispersant, the first inorganic fiber, the second inorganic fiber, the hydrophobically modified SiOC aerogel particles, the infrared suppressor filler, the thickener, and the defoamer are added in sequence, and the mixture is stirred evenly to obtain the coating of this case.

[0082] Comparative Example 1

[0083] The coating formulation and preparation method in this case are the same as in Example 1, except that the hydrophobic modified SiOC aerogel particles are replaced with an equal amount of hollow ceramic microspheres. The bulk density of the hollow ceramic microspheres used is 0.35 g / cm³. 3 The average particle size is 78 μm.

[0084] Comparative Example 2

[0085] The coating formulation and preparation method in this case are the same as those in Example 1, except that the first inorganic fiber was not subjected to hydrophobic modification treatment.

[0086] Comparative Example 3

[0087] The coating formulation and preparation method in this case are the same as those in Example 1. The difference is that the inorganic binder system is a potassium silicate solution (modulus 3.8, solid content 35wt%).

[0088] Comparative Example 4

[0089] The coating formulation and preparation method in this case are the same as those in Example 1. The difference is that the first inorganic fiber is calcined kaolin with an average particle size of 2.3 micrometers.

[0090] Comparative Example 5

[0091] The coating formulation and preparation method in this case are the same as those in Example 1, except that SiOC aerogel particles without hydrophobic modification are used.

[0092] Comparative Example 6

[0093] The coating formulation and preparation method in this case are the same as those in Example 1. The difference is that the inorganic binder system is alumina sol instead of zirconium oxide sol.

[0094] Comparative Example 7

[0095] The coating formulation and preparation method in this case are the same as those in Example 1. The difference is that hydrophobically modified silica aerogel is used instead of hydrophobically modified SiOC aerogel particles. The preparation process of the hydrophobically modified silica aerogel (whose specific surface area and particle size are the same as those in Example 1) is carried out according to the preparation method of the example.

[0096] Test case

[0097] The following tests were conducted on the coatings from each of the obtained cases:

[0098] Thick coating crack resistance test: The coatings of each case were applied to the surface of the steel plate substrate in a single scraping, with a wet film thickness of about 3 mm and a coating area of ​​at least 150 mm × 80 mm. After natural drying at room temperature, a dense coating was formed. The surface of the coating was observed to see if there was any cracking or peeling after drying.

[0099] Thermal stability test: The coatings of each case were applied to the surface of refractory bricks with a thickness of about 3 mm and a coating area of ​​at least 100 mm × 100 mm. After drying, the coatings were kept at 1000℃ for 4 hours and then observed for obvious cracking, peeling or powdering.

[0100] High-temperature thermal conductivity test: The high-temperature thermal conductivity of the coating after drying of each case was measured according to the YB / T4130-2005 standard, and the hot surface temperature was 800℃.

[0101] Drying shrinkage rate: The coatings for each case were filled into silicone molds with an inner diameter of 100 mm and a height of 20 mm, and slowly dried in an oven at 50°C until constant weight. After demolding, the diameter of the coating sample was measured, and the drying shrinkage rate was calculated. In other words, the drying shrinkage rate measured in this invention is the rate of change of the material's diameter during the drying process. Drying shrinkage rate refers to the dimensional change of the blank due to moisture loss during the drying process.

[0102] The results are shown in Table 1.

[0103] Table 1. Coating performance of the coatings in the examples and comparative examples after drying.

[0104]

[0105] As shown in Table 1:

[0106] High-temperature thermal conductivity: The thermal conductivity of samples from Examples 1-3 at 800℃ was all below 0.095. The W / (m·K) indicates that the hydrophobic modified SiOC aerogel, combined with hydrophobic inorganic fibers and infrared suppressing fillers, has a significant inhibitory effect on high-temperature thermal conductivity and radiative heat transfer. In Comparative Example 1, the thermal conductivity increased significantly after replacing the hydrophobic modified SiOC aerogel with hollow ceramic microspheres. In Comparative Example 2, which did not use hydrophobic inorganic fibers, the thermal conductivity also increased slightly compared to Example 1. In Comparative Example 4, the absence of the first inorganic fiber (ultra-fine short inorganic fiber) reduced the porosity of the coating, resulting in the loss of the extension effect on the heat flow transmission path, and the thermal conductivity also increased significantly. In Comparative Example 5, since the SiOC aerogel was not hydrophobically modified, some sol infiltrated during the coating preparation process, affecting its thermal insulation effect. In Comparative Example 7, due to the low temperature resistance of the silica aerogel used, sintering occurred at 800℃, causing the nanopores to collapse. At the same time, its infrared shielding effect was also worse than that of SiOC aerogel, so its thermal conductivity at high temperatures increased significantly.

[0107] Thick coating crack resistance: Only when alumina sol and zirconium oxide sol are used as binders, and multi-scale ultrafine short inorganic fibers and a small amount of long inorganic fibers are added in synergy, can a single 3mm thick coating be crack-free. In contrast, Comparative Example 3, which uses potassium silicate as a binder, showed severe cracking during thick coating.

[0108] Drying shrinkage rate: The drying shrinkage rate of the examples was controlled below 0.2%, which was significantly lower than that of the coating of the conventional inorganic binder in Comparative Example 3; the larger shrinkage rate of the sample in Comparative Example 4 also shows the important role of the first inorganic fiber (ultra-fine short inorganic fiber) of a specific length and diameter in improving drying shrinkage.

[0109] High-temperature resistance: The coatings in the examples maintained structural integrity at 1000℃, verifying their long-term temperature resistance. The surface condition of the coatings in Examples 1-3 and Comparative Example 1 after heat treatment showed that the hydrophobic SiOC aerogel had good high-temperature stability. Cracks and peeling appeared in the sample of Comparative Example 3, indicating that the temperature resistance of silica sol was worse than that of alumina sol and zirconium oxide sol. On the other hand, the large drying shrinkage of the coating caused internal stress between it and the substrate, which was released at high temperature, resulting in peeling. Comparative Example 6 did not contain zirconium oxide sol, resulting in a slightly lower heat resistance temperature. After high-temperature treatment, the coating produced a small number of microcracks caused by sintering. The silica aerogel used in Comparative Example 7 had a low heat resistance temperature. At high temperature, the coating underwent severe sintering shrinkage, resulting in severe cracking.

[0110] This invention significantly improves the thick coating performance of coatings by combining an alumina sol and zirconium oxide sol composite bonding system with multi-scale high-temperature resistant inorganic fibers and hydrophobically modified SiOC aerogel particles. The thick coatings exhibit outstanding high-temperature structural stability and thermal insulation effect.

[0111] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high temperature resistant and low shrinkage aerogel thermal insulation paint, characterized in that, Includes the following components by mass percentage: The composition includes: 10%–24% inorganic binder system, 10%–25% first inorganic fiber, 0.5%–2% second inorganic fiber, 8%–15% hydrophobically modified SiOC aerogel particles, 15%–20% infrared suppressing filler, and 25%–35% deionized water; The inorganic binder system includes alumina sol and zirconium oxide sol; The first inorganic fiber has a length of 0.5 to 2 mm and a diameter of 0.5 to 5 μm, and 40 wt% to 60 wt% of the first inorganic fiber has been hydrophobically modified. The second inorganic fiber has a length of 5–10 mm and a diameter of 5–12 μm; The drying shrinkage rate of the aerogel thermal insulation coating is less than 0.2%. 2.The aerogel thermal insulation coating with high temperature resistance and low shrinkage according to claim 1, characterized in that, The hydrophobically modified SiOC aerogel particles are hydrophobically modified using a silane coupling agent; 40wt% to 60wt% of the first inorganic fiber is hydrophobically modified using a silane coupling agent; the silane coupling agent is selected from methyltriethoxysilane or isooctyltriethoxysilane.

3. The aerogel thermal insulation coating according to any one of claims 1-2, characterized in that, The mass ratio of the alumina sol to the zirconium oxide sol is 1:0.1 to 0.

3. 4.The aerogel thermal insulation coating with high temperature resistance and low shrinkage according to claim 3, characterized in that, The alumina sol has a solid content of 15wt% to 30wt% and a particle size of 5nm to 50nm; the zirconium oxide sol has a solid content of 10wt% to 25wt% and a particle size of 10nm to 80nm.

5. The aerogel thermal insulation coating according to any one of claims 1-2, wherein the aerogel thermal insulation coating has a thermal conductivity of 0.015 W / m-K or less at 10% RH and 23 °C. The first inorganic fiber and the second inorganic fiber are respectively selected from one or more of aluminosilicate fiber, basalt fiber, quartz fiber, and alumina fiber; The hydrophobically modified SiOC aerogel particles have a particle size of 100 mesh to 250 mesh, a specific surface area of greater than 400 m 2 / g; The infrared suppressing filler is selected from one or more of titanium oxide, zirconium oxide, and zirconium silicate, and its particle size is 0.3μm to 1.2μm.

6. A high-temperature resistant and low-shrinkage aerogel thermal insulation coating according to any one of claims 1-2, characterized in that, The coating components also include 0.5% to 2.0% thickener, 0.3% to 0.8% defoamer, and 0.4% to 1.2% dispersant.

7. The high-temperature resistant and low-shrinkage aerogel thermal insulation coating according to claim 6, characterized in that, The thickener is selected from one of bentonite, attapulgite, or silica. The defoamer is selected from one or more of polyether-modified silicone defoamers, mineral oil-based defoamers, and hydrophobic silica defoamers; The dispersant is selected from one or more of the following: polycarboxylate dispersants, phosphate or polyphosphate dispersants, silane-modified polymer dispersants, and nonionic polymeric dispersants.

8. A method for preparing a high-temperature resistant and low-shrinkage aerogel thermal insulation coating, suitable for preparing the aerogel thermal insulation coating as described in any one of claims 1-7, characterized in that, The process includes the following steps: Under mechanical stirring, the inorganic binder system of the formula is mixed evenly with deionized water, and then the dispersant, first inorganic fiber, second inorganic fiber, hydrophobically modified SiOC aerogel particles, infrared suppressor filler, thickener, and defoamer are added in sequence and stirred evenly to obtain the coating.

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