Aerogel thermal insulation coating and preparation method thereof

Abstract

The invention belongs to the technical field of aerogel coatings, and provides an aerogel thermal insulation coating and a preparation method thereof.The method comprises the following steps that a silicon source, ethyl alcohol, water and an acid catalyst are mixed to obtain aerogel precursor sol; ceramic fibers are soaked in a silane coupling agent ethanol solution for ultrasonic treatment, and hydrophobic modified fibers are obtained; mixing the aerogel precursor sol, hydrophobic modified fibers, a binder and nano titanium dioxide, and performing ultrasonic dispersion to obtain composite sol; a segmented spraying process is adopted, a high-density sol layer is firstly sprayed on the component, and then a low-density sol layer is sprayed layer by layer; carrying out supercritical drying treatment on the coated part to form an aerogel structure; and spraying a fluorine-containing silane solution on the surface of the coating for curing treatment to obtain the aerogel thermal insulation coating. The adhesive force and the mechanical strength are improved through the high density of the inner layer, the heat insulation performance is optimized through the low density of the outer layer, and the problem that a traditional homogeneous coating is prone to cracking and contradicts with heat preservation efficiency is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogel coatings, and particularly relates to an aerogel thermal insulation coating and a preparation method thereof. Background Art

[0002] Aerogel is a three-dimensional network structure material formed by cross-linking of nanoparticles, and has characteristics such as extremely low density (porosity 90 - 99.8%), extremely low thermal conductivity (as low as 0.013 W / (m·K) at room temperature), and high specific surface area (600 - 1000 m² / g). Its unique nano-porous structure can simultaneously block solid heat conduction, air convection and radiative heat transfer, and become an ideal material in the fields of building thermal insulation, industrial equipment heat insulation, etc.

[0003] Traditional aerogel coatings achieve high-efficiency thermal insulation, fire protection and environmental protection characteristics under thin-layer construction (2 - 4 mm) by adding fillers such as SiO 2 aerogel, hollow glass microspheres, etc., and combining with a water-based emulsion to form a film. For example, the composite aerogel coating modifies hydrophobic aerogel particles through a coupling agent and introduces multi-sized hollow microspheres, improving the compatibility with the substrate and reducing coating cracking. However, the prior art still has the following problems: (1) Poor dispersion stability: Hydrophobic aerogel particles are prone to agglomeration in the water-based system, resulting in insufficient coating uniformity and affecting the thermal insulation performance; (2) Insufficient mechanical properties: The high porosity leads to high brittleness of the coating, which is prone to cracking and peeling, especially obvious in flexible substrates (such as fabrics) or environments with large temperature differences; (3) Single function: Coatings for buildings need to take into account thermal insulation, waterproofing and anti-aging properties, while coatings for industrial equipment need to have additional anti-corrosion, high-temperature resistance (>600°C) and other characteristics. Existing products are difficult to meet the comprehensive requirements. Therefore, how to provide an aerogel coating with more excellent performance has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides an aerogel thermal insulation coating and a preparation method thereof, and the purpose is to solve the technical problems such as poor thermal insulation performance and insufficient mechanical properties existing in traditional aerogel coatings.

[0005] In order to achieve the above invention purpose, the present invention provides the following technical solutions: The present invention provides a preparation method of an aerogel thermal insulation coating, comprising the following steps: S1. Mix a silicon source, ethanol, water and an acidic catalyst to obtain an aerogel precursor sol; S2. Immerse ceramic fibers in a silane coupling agent ethanol solution and perform ultrasonic treatment to obtain hydrophobically modified fibers; S3. Mix the aerogel precursor sol, the hydrophobically modified fibers, a binder and nano-titanium dioxide, and perform ultrasonic dispersion to obtain a composite sol; S4. Adopt a segmented spraying process, first spray a high-density sol layer on the component, and then spray a low-density sol layer layer by layer; S5. Carry out supercritical drying treatment on the coated component to form an aerogel structure; S6. After the supercritical drying treatment is completed, spray a fluorosilane solution on the surface of the coating for curing treatment to obtain an aerogel thermal insulation coating; There is no sequence between step S1 and step S2.

[0006] Further, in step S1, the silicon source includes tetraethyl orthosilicate or sodium silicate; the acidic catalyst includes hydrochloric acid; The mass ratio of the silicon source, ethanol, water and acidic catalyst is 1:5-8:0.1-0.3:0.01-0.05; The temperature of the mixing is 40-60 °C, and the mixing time is 2-4 h.

[0007] Further, in step S2, the silane coupling agent includes KH-550 or KH-570; the mass concentration of the silane coupling agent ethanol solution is 3-8%; the ultrasonic treatment time is 30-60 min.

[0008] Further, in step S3, the binder includes silica sol or polyacrylate emulsion; the particle size of the nano-titanium dioxide is 10-50 nm; the mass ratio of the aerogel precursor sol, hydrophobic modified fiber, binder and nano-titanium dioxide is 80-90:5-15:10-30:1-5; the ultrasonic dispersion time is 30-60 min.

[0009] Further, in step S4, the solid content of the composite sol used for the high-density sol layer is 25-35%, the solid content of the composite sol used for the low-density sol layer is 10-20%, and the thickness of each layer is 0.1-0.5 mm.

[0010] Further, in step S4, the technical parameters of the segmented spraying process are: the spray gun pressure is 0.3-0.6 MPa, the spraying distance is 20-40 cm, the interval drying time for each layer is 5-15 min, and the viscosity gradient of each layer of sol decreases by 10-30%.

[0011] Further, in step S5, the pressure of the supercritical drying treatment is 8-15 MPa, the temperature of the supercritical drying treatment is 40-60 °C, and the time of the supercritical drying treatment is 6-12 h.

[0012] Further, in step S6, the mass concentration of the fluorosilane solution is 1-5%, and the spraying amount is 0.5-2 mg / cm 2; The curing temperature is 120 to 150 °C, and the curing time is 60 to 120 min.

[0013] The present invention also provides an aerogel thermal insulation coating prepared by the preparation method of the above aerogel thermal insulation coating.

[0014] As can be seen from the above technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention improves the adhesion and mechanical strength through the high density of the inner layer and optimizes the heat insulation performance through the low density of the outer layer, solving the contradiction between the easy cracking of traditional homogeneous coatings and the heat insulation efficiency.

[0015] 2. The surface-modified ceramic fibers and nano-titanium dioxide are used in a synergistic manner to enhance the formation of a three-dimensional network structure during the supercritical drying process, making the coating have both high toughness and thermal shock resistance.

[0016] 3. The fluorosilane layer on the surface and the internal hydrophobic fibers form a double protection, enabling the coating to remain hydrophobic in high-temperature and high-humidity environments.

[0017] 4. The segmented spraying combined with gradient viscosity control ensures the interfacial bonding strength between the coating and the metal matrix, avoiding the problem of uneven thickness caused by the traditional dipping method. Description of the Drawings

[0018] Figure 1 is the test result of the compressive strength of the aerogel thermal insulation coating; Figure 2 is the test result of the bonding strength of the aerogel thermal insulation coating. Detailed Embodiments

[0019] The present invention provides a preparation method of an aerogel thermal insulation coating, including the following steps: S1. Mix a silicon source, ethanol, water, and an acidic catalyst to obtain an aerogel precursor sol; S2. Immerse ceramic fibers in a silane coupling agent ethanol solution and perform ultrasonic treatment to obtain hydrophobic modified fibers; S3. Mix the aerogel precursor sol, hydrophobic modified fibers, a binder, and nano-titanium dioxide, and then perform ultrasonic dispersion to obtain a composite sol; S4. Adopt a segmented spraying process, first spray a high-density sol layer on the component, and then spray low-density sol layers layer by layer; S5. Perform supercritical drying treatment on the coated component to form an aerogel structure; S6. After the supercritical drying treatment is completed, spray a fluorosilane solution on the surface of the coating for curing treatment to obtain the aerogel thermal insulation coating; There is no sequence between step S1 and step S2.

[0020] In the present invention, in the step S1, the silicon source includes tetraethyl orthosilicate or sodium silicate; the acidic catalyst includes hydrochloric acid, and the concentration of hydrochloric acid is preferably 0.1 to 0.5 mol / L, more preferably 0.3 mol / L; The mass ratio of the silicon source, ethanol, water and the acidic catalyst is 1:5 to 8:0.1 to 0.3:0.01 to 0.05, preferably 1:6:0.2:0.03; The temperature of the mixing is 40 to 60 °C, preferably 45 to 55 °C, more preferably 50 °C; the mixing time is 2 to 4 h, preferably 2.5 to 3.5 h, more preferably 3.0 h.

[0021] In the present invention, in the step S2, the silane coupling agent includes KH-550 or KH-570; the mass concentration of the silane coupling agent ethanol solution is 3 to 8%, preferably 4 to 6%, more preferably 5%; the time of the ultrasonic treatment is 30 to 60 min, preferably 40 to 50 min.

[0022] In the present invention, in the step S3, the binder includes silica sol or polyacrylate emulsion; the particle size of the nano-titanium dioxide is 10 to 50 nm, preferably 20 to 40 nm, more preferably 30 nm; the mass ratio of the aerogel precursor sol, the hydrophobic modified fiber, the binder and the nano-titanium dioxide is 80 to 90:5 to 15:10 to 30:1 to 5, preferably 82 to 88:7 to 12:15 to 25:2 to 4, more preferably 85:10:20:3; the time of the ultrasonic dispersion is 30 to 60 min, preferably 40 to 50 min.

[0023] In the present invention, in the step S4, the solid content of the composite sol used for the high-density sol layer is 25 to 35%, preferably 30%; the solid content of the composite sol used for the low-density sol layer is 10 to 20%, preferably 12 to 18%, more preferably 14 to 16%; the thickness of each layer is 0.1 to 0.5 mm, preferably 0.2 to 0.4 mm.

[0024] In the present invention, in the step S4, the technical parameters of the segmented spraying process are: the spray gun pressure is 0.3 to 0.6 MPa, preferably 0.4 to 0.5 MPa; the spraying distance is 20 to 40 cm, preferably 30 cm; the interval drying time of each layer is 5 to 15 min, preferably 10 min.

[0025] In the present invention, in the step S5, the pressure of the supercritical drying treatment is 8 to 15 MPa, preferably 10 MPa; the temperature of the supercritical drying treatment is 40 to 60 °C, preferably 50 °C; the time of the supercritical drying treatment is 6 to 12 h, preferably 8 to 10 h.

[0026] In the present invention, in the step S6, the mass concentration of the fluorosilane solution is 1-5%, preferably 2-4%, and more preferably 3%; the spraying amount is 0.5-2 mg / cm 2 , preferably 1 mg / cm 2 ; the curing temperature is 120-150 °C, preferably 130-140 °C; the curing time is 60-120 min, preferably 80-100 min.

[0027] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0028] Example 1 Tetraethyl orthosilicate, ethanol, water and 0.3 mol / L hydrochloric acid were mixed at a mass ratio of 1:6:0.2:0.03, the pH value was adjusted to 4, and hydrolysis reaction was carried out at 50 °C for 3 h to obtain an aerogel precursor sol.

[0029] The ceramic fiber was impregnated in a 5% mass fraction ethanol solution of silane coupling agent KH-550, ultrasonically treated for 50 min, and dried to obtain a hydrophobic modified fiber.

[0030] The aerogel precursor sol, the hydrophobic modified fiber, the polyacrylate emulsion and the nano-titanium dioxide were mixed at a mass ratio of 85:10:20:3 and ultrasonically dispersed for 50 min to obtain a composite sol.

[0031] A segmented spraying process was adopted. First, a high-density sol layer (the solid content of the composite sol is 30%) was sprayed, then a low-density sol layer (the solid content of the composite sol is 20%) was sprayed, and then another low-density sol layer (the solid content of the composite sol is 10%) was sprayed. The thickness of each layer is 0.3 mm, and the interval drying time for each layer is 10 min.

[0032] The coated component was placed in a carbon dioxide supercritical drying equipment. At 50 °C, a staged pressure control was adopted: in the initial stage, the pressure was increased to 8 MPa at a rate of 2 MPa / min, after holding the pressure for 2 h, then the pressure was increased to 15 MPa at a rate of 1 MPa / min, and the pressure was held for 5 h to form an aerogel structure.

[0033] After the supercritical drying was completed, a 3% mass fraction fluorosilane ethanol solution was sprayed on the surface of the coating, the spraying amount was 1 mg / cm², and it was cured at 130 °C for 100 min to obtain an aerogel thermal insulation coating.

[0034] Example 2 Tetraethyl orthosilicate, ethanol, water and 0.2 mol / L hydrochloric acid were mixed at a mass ratio of 1:5:0.1:0.04, the pH value was adjusted to 5, and hydrolysis reaction was carried out at 45 °C for 3.5 h to obtain an aerogel precursor sol.

[0035] The ceramic fibers were impregnated in a 4% mass fraction ethanol solution of silane coupling agent KH-550, ultrasonically treated for 55 min, and hydrophobic modified fibers were obtained after drying.

[0036] The aerogel precursor sol, hydrophobic modified fibers, silica sol and nano-titanium dioxide were mixed at a mass ratio of 84:12:15:4 and ultrasonically dispersed for 45 min to obtain a composite sol.

[0037] A segmented spraying process was adopted. First, a high-density sol layer (solid content of the composite sol is 30%) was sprayed, then a low-density sol layer (solid content of the composite sol is 20%) was sprayed, and then another low-density sol layer (solid content of the composite sol is 10%) was sprayed. The thickness of each layer is 0.2 mm, and the drying interval between each layer is 10 min.

[0038] The coated component was placed in a supercritical carbon dioxide drying equipment. At 45 °C, a staged pressure control was adopted: in the initial stage, the pressure was increased to 8 MPa at a rate of 2 MPa / min, after holding the pressure for 2 h, then the pressure was increased to 14 MPa at a rate of 1 MPa / min, and the pressure was held for 6 h to form an aerogel structure.

[0039] After the supercritical drying was completed, a 2% mass fraction ethanol solution of fluorosilane was sprayed on the surface of the coating, the spraying amount was 1.5 mg / cm², and it was cured at 120 °C for 120 min to obtain the aerogel thermal insulation coating.

[0040] Example 3 Tetraethyl orthosilicate, ethanol, water and 0.2 mol / L hydrochloric acid were mixed at a mass ratio of 1:7:0.3:0.02, the pH value was adjusted to 5, and hydrolysis reaction was carried out at 55 °C for 2.5 h to obtain the aerogel precursor sol.

[0041] The ceramic fibers were impregnated in a 4% mass fraction ethanol solution of silane coupling agent KH-570, ultrasonically treated for 55 min, and hydrophobic modified fibers were obtained after drying.

[0042] The aerogel precursor sol, hydrophobic modified fibers, polyacrylate emulsion and nano-titanium dioxide were mixed at a mass ratio of 86:8:25:2 and ultrasonically dispersed for 55 min to obtain a composite sol.

[0043] A segmented spraying process was adopted. First, a high-density sol layer (solid content of the composite sol is 30%) was sprayed, then a low-density sol layer (solid content of the composite sol is 20%) was sprayed, and then another low-density sol layer (solid content of the composite sol is 10%) was sprayed. The thickness of each layer is 0.3 mm, and the drying interval between each layer is 10 min.

[0044] Place the coated component in a supercritical carbon dioxide drying equipment. At 55 °C, adopt staged pressure control: in the initial stage, increase the pressure to 10 MPa at a rate of 2 MPa / min, keep the pressure for 2 h, then increase the pressure to 14 MPa at a rate of 1 MPa / min, and keep the pressure for 6 h to form an aerogel structure.

[0045] After the supercritical drying is completed, spray a fluorosilane ethanol solution with a mass fraction of 4% on the surface of the coating, with a spraying amount of 0.8 mg / cm², and cure it at 140 °C for 80 min to obtain the aerogel thermal insulation coating.

[0046] Comparative Example 1 It is the same as Example 1, except that the segmented spraying is cancelled and a single spraying with a solid content of 25% is adopted.

[0047] Comparative Example 2 It is the same as Example 1, except that nano-titanium dioxide is not added.

[0048] Performance Test Test the performance of the aerogel thermal insulation coatings prepared in the above Examples 1-3 and Comparative Examples 1-2. The test methods are as follows: for the high-temperature resistance test, after calcining at 800 °C for no less than 6 h, all performance indicators of the material still meet the requirements. Test the room-temperature thermal conductivity of the aerogel thermal insulation coating according to the test standard of GB / T 10295-2008. Test the 800 °C thermal conductivity of the aerogel thermal insulation coating according to the test standard of YB / T4130-2005. The test results are shown in Table 1 below.

[0049] Table 1 Performance Test Results of Aerogel Thermal Insulation Coatings

[0050] It can be seen from Table 1 that the aerogel thermal insulation coating prepared by the present invention has good high-temperature resistance, and its thermal conductivity at room temperature and 800 °C is relatively low, and the thermal insulation performance is good. As is well known, the working temperature of plastic / rubber extruders is usually between 200 °C and 300 °C, and some high-temperature materials (such as PEEK and PI) may be close to 400 °C, but rarely exceed this range. Therefore, the aerogel thermal insulation coating prepared by the present invention can be fully applied to extruders. However, the coatings prepared in Comparative Examples 1-2 have poor high-temperature resistance, and their room-temperature thermal conductivity is relatively high, and their thermal insulation performance is also lower than that of the aerogel thermal insulation coating in the examples.

[0051] Test the compressive strength of the aerogel thermal insulation coating according to the test standard of GB / T 1964-2023. The test results are shown in Figure 1 , and it can be seen from Figure 1 that without using the process of synergistic enhancement of surface-modified ceramic fibers and nano-titanium dioxide, the compressive strength will be worse.

[0052] The bonding strength of the aerogel thermal insulation coating was measured by the test method of the TCH-3000 bonding strength pull-out instrument, and the test results are shown in Figure 2 , from Figure 2 it can be seen that the non-use of the segmented spraying process results in uneven thickness, thereby reducing the bonding strength.

[0053] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an aerogel thermal insulation coating, characterized in that: The following steps are involved: S1, mixing a silicon source, ethanol, water and an acid catalyst to obtain an aerogel precursor sol; S2, immersing the ceramic fiber in an ethanol solution of a silane coupling agent and performing ultrasonic treatment to obtain a hydrophobically modified fiber; S3, mixing the aerogel precursor sol, the hydrophobically modified fiber, the binder and the nano-titanium dioxide and performing ultrasonic dispersion to obtain a composite sol; S4, adopt the segmented spraying process, first spray the high-density sol layer on the component, and then spray the low-density sol layer layer by layer; S5, performing supercritical drying on the coated component to form an aerogel structure; S6. After the supercritical drying treatment is completed, a fluorine-containing silane solution is sprayed on the surface of the coating for curing to obtain an aerogel thermal insulation coating; There is no sequence between step S1 and step S2.

2. The method for preparing the aerogel thermal insulation coating according to claim 1, characterized in that: In step S1, the silicon source includes tetraethyl orthosilicate or sodium silicate; the acidic catalyst includes hydrochloric acid; The mass ratio of the silicon source, ethanol, water and acid catalyst is 1:5-8:0.1-0.3:0.01-0.05; The mixing temperature is 40-60° C., and the mixing time is 2-4 hours.

3. The method for preparing the aerogel thermal insulation coating according to claim 2, characterized in that: In the step S2, the silane coupling agent includes KH-550 or KH-570; the mass concentration of the silane coupling agent ethanol solution is 3-8%; and the ultrasonic treatment time is 30-60 minutes.

4. The method for preparing an aerogel thermal insulation coating according to any one of claims 1 to 3, characterized in that: In step S3, the binder includes silica sol or polyacrylate emulsion; the particle size of the nano titanium dioxide is 10-50 nm; the mass ratio of the aerogel precursor sol, the hydrophobically modified fiber, the binder and the nano titanium dioxide is 80-90:5-15:10-30:1-5; The ultrasonic dispersion time is 30 to 60 minutes.

5. The method for preparing the aerogel thermal insulation coating according to claim 4, characterized in that: In the step S4, the solid content of the composite sol used in the high-density sol layer is 25-35%, the solid content of the composite sol used in the low-density sol layer is 10-20%, and the thickness of each layer is 0.1-0.5 mm.

6. The method for preparing the aerogel thermal insulation coating according to claim 5, characterized in that: In step S4, the technical parameters of the segmented spraying process are: spray gun pressure 0.3-0.6 MPa, spraying distance 20-40 cm, drying time between each layer 5-15 min, and a gradient decrease of 10-30% in viscosity of each layer of sol.

7. The method for preparing the aerogel thermal insulation coating according to claim 1 or 6, characterized in that: In step S5, the pressure of the supercritical drying treatment is 8-15 MPa, the temperature of the supercritical drying treatment is 40-60° C., and the time of the supercritical drying treatment is 6-12 hours.

8. The method for preparing the aerogel thermal insulation coating according to claim 7, characterized in that: In step S6, the mass concentration of the fluorinated silane solution is 1-5%, and the spraying amount is 0.5-2 mg / cm 2 ; The curing temperature is 120~150℃, and the curing time is 60~120min.

9. An aerogel thermal insulation coating prepared by the method for preparing an aerogel thermal insulation coating according to any one of claims 1 to 8.

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