A method for preparing a ceramic fiber / hydrophobic fumed silica composite thermal insulation material
By using a mixed slurry papermaking process of hydrophobic fumed silica and ceramic fiber, and by encapsulating hydrophobic fumed silica particles with polydopamine, the complex preparation of existing ceramic fiber/silica aerogel composite thermal insulation materials has been solved, resulting in a thermal insulation material with low high-temperature thermal conductivity and high mechanical strength, suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NINGBO BOOER NEW MATERIAL CO LTD
- Filing Date
- 2023-11-22
- Publication Date
- 2026-05-19
AI Technical Summary
The existing ceramic fiber/silica aerogel composite thermal insulation materials have complex preparation processes, require high-end equipment, and are not safe or environmentally friendly enough, which affects their mechanical strength and thermal insulation performance.
A mixed slurry was prepared by using hydrophobic fumed silica and ceramic fibers. A ceramic fiber/hydrophobic fumed silica composite thermal insulation material was prepared by a simple papermaking process. The hydrophobic fumed silica particles were encapsulated by polydopamine and dispersed uniformly under the action of a polymer emulsion stabilizer. Combined with the entangled network structure of ceramic fibers, a strong interfacial interaction force was formed.
This invention achieves a composite thermal insulation material with low thermal conductivity and high mechanical strength, simplifies the preparation process, reduces equipment requirements, and facilitates industrial production.
Smart Images
Figure BDA0004564791850000061 
Figure BDA0004564791850000071
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermal insulation materials, and more particularly to a method for preparing a ceramic fiber / hydrophobic fumed silica composite thermal insulation material. Background Technology
[0002] Ceramic fiber felt, as a refractory material, can be cut and bent at will, making it an ideal energy-saving material for thermal insulation equipment. It is widely used in thermal protection fields such as aerospace, industrial storage tanks, pipelines, and military industries. However, currently, micron-sized ceramic fiber materials are generally less than 250mm in length and greater than 3μm in diameter. Due to the short and thick fibers, the mechanical strength of ceramic fiber felt is poor, and its thermal insulation performance is affected to a certain extent, limiting its application range.
[0003] To address the aforementioned technical challenges, silica aerogel is typically combined with ceramic fibers to create a ceramic fiber / silica aerogel composite insulation material. Currently, the preparation method for this composite insulation material generally employs the sol-gel method to prepare silica gel. Specifically, a silicon source is first mixed with ceramic fibers, and then the process is controlled to hydrolyze the silicon source to generate silica gel. The drawback of this method is its complexity, requiring either supercritical drying or drying at atmospheric pressure after organic solvent replacement. The former demands sophisticated equipment, while the latter requires large amounts of organic solvents, making it less safe and environmentally friendly.
[0004] In summary, existing ceramic fiber / silica aerogel composite thermal insulation materials suffer from technical problems such as complex preparation processes and high equipment requirements. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a method for preparing a ceramic fiber / hydrophobic fumed silica composite thermal insulation material. This invention involves preparing a mixed slurry of hydrophobic fumed silica and ceramic fibers, followed by a simple papermaking process to obtain the ceramic fiber / hydrophobic fumed silica composite thermal insulation material. This method is simple, requires minimal equipment, and is easily industrialized. Furthermore, the resulting ceramic fiber / hydrophobic fumed silica composite thermal insulation material exhibits advantages such as low high-temperature thermal conductivity and high mechanical strength.
[0006] The specific technical solution of this invention is: a method for preparing a ceramic fiber / hydrophobic fumed silica composite thermal insulation material, comprising the following steps:
[0007] 1) Preparation of polydopamine (PDA) solution.
[0008] 2) Mix 100 parts by weight of water, 5-15 parts by weight of hydrophobic fumed silica, 0.01-10 parts by weight of 8-12 wt% polydopamine solution, 0.01-1 parts by weight of polymeric emulsifying stabilizer, and 0-0.2 parts by weight of defoamer and stir evenly to obtain a hydrophobic fumed silica dispersion slurry with an average particle size D50 of 1-20 micrometers.
[0009] 3) Mix 1 part by weight of ceramic fiber and 1-20 parts by weight of hydrophobic fumed silica dispersion slurry and stir evenly to obtain a mixed slurry.
[0010] 4) The mixed slurry is formed by passing it through a flat filter screen (removing most of the water under gravity), then filtered under negative pressure to remove water, and a composite sheet is obtained. After drying, a ceramic fiber / hydrophobic fumed silica composite thermal insulation material is obtained.
[0011] Compared to the relatively complex preparation processes of existing technologies, this invention prepares a ceramic fiber / hydrophobic fumed silica composite thermal insulation material by mixing hydrophobic fumed silica and ceramic fibers into a slurry, and then using only a simple papermaking process. The preparation process of this invention is simple, requires minimal equipment, and is easy to industrialize. Furthermore, the product obtained by this invention has the advantages of low high-temperature thermal conductivity and high mechanical strength, comparable to existing ceramic fiber / silica aerogel composite thermal insulation materials.
[0012] The technical challenge in the preparation process of this invention lies in the fact that hydrophobic fumed silica, due to its strong hydrophobicity and low density, easily floats upon the addition of water, making it difficult to formulate into a highly stable and dispersed slurry, which in turn hinders its uniform dispersion with ceramic fibers. To address this, the present invention discovered that adding hydrophobic fumed silica to a polydopamine solution, under stirring and emulsification, allows the polydopamine to coat the surface of the hydrophobic fumed silica particles, thereby obtaining a highly stable dispersion slurry. During the subsequent papermaking process, the hydrophobic fumed silica, under the action of polydopamine and a high-molecular-weight emulsifying stabilizer, can be fully dispersed and adhered to the intertwined network structure of the ceramic fibers, forming a strong interfacial interaction force between the two, thereby improving the mechanical properties and high-temperature insulation performance of the composite thermal insulation material.
[0013] Preferably, in step 1), the preparation method of the polydopamine solution includes: mixing dopamine-hydrochloric acid, tris(hydroxymethyl)aminomethane and water / methanol solution, stirring and reacting, and repeatedly separating and purifying by centrifugation to obtain polydopamine particles, which can be redispersed in water according to the ratio when used.
[0014] Preferably, in step 2), the polydopamine solution is 0.5-1 parts by weight; the polymeric emulsifying stabilizer is 0.02-0.2 parts by weight; and the average particle size D50 of the hydrophobic fumed silica particles in the hydrophobic fumed silica dispersion slurry is 5-10 micrometers.
[0015] This invention reveals that the polydopamine content in the system significantly affects the average particle size of the polydopamine-coated hydrophobic fumed silica particles in the dispersion slurry. Excessive polydopamine content leads to a smaller average particle size of the hydrophobic fumed silica particles, resulting in a slower subsequent filtration rate and increased thermal conductivity (excessive polydopamine content increases the bonding points between substances during filtration, leading to excessively low porosity in the resulting insulation material, which is detrimental to insulation). Ultimately, this invention finds that at the aforementioned polydopamine dosage, the polydopamine-coated hydrophobic fumed silica particles with a particle size D50 of 5-10 micrometers are more easily integrated with ceramic fibers, resulting in a network-like insulation material with low high-temperature thermal conductivity, good product performance consistency, and high mechanical strength.
[0016] Preferably, in step 2), the pH of the system is adjusted to 2.5-3.5 during stirring.
[0017] In the preparation of the dispersion slurry, this invention further promotes the binding rate of polydopamine and hydrophobic fumed silica by adjusting the pH of the system. The principle is that the isoelectric point of polydopamine is approximately pH=4, while the isoelectric point of hydrophobic fumed silica is approximately 2.3. They exhibit a negative charge in systems with a pH higher than their isoelectric points, but a positive charge when the pH is lower than their isoelectric points. This invention cleverly utilizes this characteristic by adjusting the system pH to 2.5-3.5. Under these conditions, polydopamine is positively charged and hydrophobic fumed silica is negatively charged. Therefore, the two can more efficiently adsorb and bind under electrostatic interaction, resulting in more stable polydopamine-coated hydrophobic fumed silica particles.
[0018] Preferably, in step 2), the polymeric emulsifying stabilizer is one or more of polyacrylic acid, polyacrylamide, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and polymaleic anhydride.
[0019] Preferably, in step 2), the defoamer is one or more of polysiloxane, polyether-modified silicone oil, and polyether-type defoamer.
[0020] Preferably, in step 3), the hydrophobic fumed silica dispersion slurry is 2-10 parts by weight.
[0021] This invention reveals that the content of hydrophobic fumed silica in the mixing process of the hydrophobic fumed silica dispersion slurry and ceramic fibers has a significant impact on the various properties of the final composite thermal insulation material. Excessive hydrophobic fumed silica content leads to a loosened sheet structure and reduced mechanical strength. Ultimately, this invention demonstrates that the specified amount of hydrophobic fumed silica dispersion slurry results in a composite thermal insulation material with relatively ideal high-temperature thermal conductivity and mechanical strength.
[0022] Preferably, in step 3), the diameter of the ceramic fiber is 2-20 micrometers and the length is 1-9 centimeters, with a preferred diameter of 2-5 micrometers and a length of 1-5 centimeters.
[0023] Preferably, in step 3), the ceramic fibers are pre-treated with anionic modification; and the pH of the system is adjusted to ≤2.0 during stirring.
[0024] This invention discovers that if hydrophobic fumed silica cannot quickly adhere to the surface of ceramic fibers during the papermaking process, a significant amount of hydrophobic fumed silica is easily lost during subsequent filtration and dewatering. To address this, this invention first pre-treats the ceramic fibers with anionic modification, making them negatively charged in the system. Then, before papermaking, the pH of the mixed slurry is adjusted to ≤2.0. Under this condition, the polydopamine-coated hydrophobic fumed silica carries a positive charge. Under electrostatic adsorption, the hydrophobic fumed silica can quickly bind to the ceramic fibers, significantly reducing the amount of free hydrophobic fumed silica in the system and thus preventing its loss.
[0025] Preferably, the anion modification treatment is performed by adding ceramic fibers to an aqueous solution of sodium dodecyl sulfonate, stirring, filtering, and drying to obtain anion-modified ceramic fibers.
[0026] Preferably, the ratio of ceramic fiber to sodium dodecyl sulfonate aqueous solution is 3-7 g / 100 mL, and the concentration of sodium dodecyl sulfonate aqueous solution is 0.1-1 wt%.
[0027] Preferably, in steps 2) and 3), the stirring speed is 5000-20000 r / min and the stirring time is 5-30 min.
[0028] Preferably, in step 4), the thickness of the composite sheet is 0.2-20 mm.
[0029] Preferably, in step 4), the mesh size of the filter is 50-300 mesh, and more preferably 80-150 mesh.
[0030] Preferably, in step 4), the drying is performed in a drying tunnel at 30-150°C for 0.5-2 hours.
[0031] Compared with the prior art, the present invention has the following technical effects:
[0032] (1) In this invention, after preparing a mixed slurry of hydrophobic fumed silica and ceramic fibers, a ceramic fiber / hydrophobic fumed silica composite thermal insulation material can be prepared through a simple papermaking process. The preparation process of this invention is simple, requires low equipment, and is easy to industrialize. Furthermore, the product obtained by this invention has the advantages of low high-temperature thermal conductivity and high mechanical strength.
[0033] (2) In this invention, hydrophobic fumed silica is added to a polydopamine solution. Under stirring and emulsification, polydopamine can coat the surface of the hydrophobic fumed silica particles, thereby obtaining a highly stable dispersion slurry. In the subsequent papermaking process, the hydrophobic fumed silica can be fully dispersed and attached to the intertwined network structure of ceramic fibers under the action of polydopamine and polymeric emulsifying stabilizers. Strong interfacial interaction forces can be formed between the two, thereby improving the mechanical properties and high-temperature thermal insulation performance of the composite thermal insulation material.
[0034] (3) By controlling the content of polydopamine in the system of step 2), the present invention can obtain the ideal average particle size (5-10 micrometers) of hydrophobic fumed silica particles.
[0035] (4) By adjusting the pH of the system in step 2), the present invention can further promote the binding rate of polydopamine and hydrophobic fumed silica.
[0036] (5) By controlling the content of hydrophobic fumed silica in the system of step 3), the present invention can make the composite thermal insulation material have a more ideal high-temperature thermal conductivity and mechanical strength.
[0037] (6) By performing anionic surface treatment on ceramic fibers and adjusting the pH of the mixed slurry in step 3), the present invention can enable hydrophobic fumed silica to quickly combine with ceramic fibers, thus avoiding the loss of free hydrophobic fumed silica during the filtration process. Detailed Implementation
[0038] The present invention will be further described below with reference to embodiments.
[0039] General Implementation Examples
[0040] A method for preparing a ceramic fiber / hydrophobic fumed silica composite thermal insulation material includes the following steps:
[0041] 1) Mix dopamine-hydrochloric acid (10-12 mmol), tris(hydroxymethyl)aminomethane (110-130 mmol), and water / methanol (mass ratio 3-5:1) solution (0.8-1.2 L), stir and react at 25-35℃ for 15-25 h, and obtain polydopamine particles by repeated centrifugation and purification. When using, redisperse them in water according to the ratio to obtain polydopamine (PDA) solution.
[0042] 2) Mix water (100 parts by weight), hydrophobic fumed silica (5-15 parts by weight), polydopamine solution (8-12 wt%, 0.01-10 parts by weight, more preferably 0.5-1 parts by weight), polymeric emulsifying stabilizer (0.01-1 parts by weight, more preferably 0.02-0.2 parts by weight), and defoamer (0-0.2 parts by weight) and stir evenly (5000-20000 r / min, 5-30 min) to obtain a hydrophobic fumed silica dispersion slurry with a particle size D50 of 1-20 micrometers (preferably D50 = 5-10 micrometers).
[0043] Preferably, in step 2), the polymeric emulsifying stabilizer is one or more of polyacrylic acid, polyacrylamide, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and polymaleic anhydride; the defoamer is one or more of polysiloxane, polyether-modified silicone oil, and polyether-type defoamer; and the pH of the system is adjusted to 2.5-3.5 during stirring.
[0044] 3) Mix ceramic fiber (1 part by weight) and hydrophobic fumed silica dispersion slurry (1-20 parts by weight, more preferably 2-10 parts by weight) and stir evenly (5000-20000 r / min, 5-30 min) to obtain a mixed slurry.
[0045] Preferably, in step 3), the ceramic fiber has a diameter of 2-20 micrometers and a length of 1-9 centimeters, more preferably a diameter of 2-5 micrometers and a length of 1-5 centimeters. The ceramic fiber is pre-treated with anion modification: the ceramic fiber is added to an aqueous solution of sodium dodecyl sulfonate (0.1-1 wt%) to a concentration of 3-7 g / 100 mL, stirred, filtered, and dried to obtain anion-modified ceramic fiber. During stirring, the pH of the system is adjusted to ≤2.0.
[0046] 4) The mixed slurry is formed by passing it through a flat filter screen (50-300 mesh, preferably 80-150 mesh), and then filtered under negative pressure to remove water, to obtain a composite sheet with a thickness of 0.2-20 mm. The sheet is then dried in a drying tunnel at 30-150℃ for 0.5-2 hours to obtain a ceramic fiber / hydrophobic fumed silica composite thermal insulation material.
[0047] Specific embodiments and comparative examples
[0048] (1) Particle size of hydrophobic fumed silica dispersion slurry obtained under different polydopamine dosages in step 2).
[0049] 1) Mix dopamine-hydrochloric acid (10.8 mmol), tris(hydroxymethyl)aminomethane (120 mmol) and water / methanol (mass ratio 4:1) solution (1.2 L), stir and react at 30 °C for 20 h, and obtain polydopamine particles by repeated centrifugation and purification. When using, redisperse them in water according to the ratio to obtain polydopamine (PDA) solution.
[0050] 2) Mix water (100 phr), hydrophobic fumed silica (10 phr), polydopamine solution (10 wt%, 0.01-10 phr), high molecular weight emulsifying stabilizer polyvinyl alcohol (0.1 phr), and defoamer polysiloxane (0.1 phr) and stir evenly (10000 r / min, 20 min) to obtain a hydrophobic fumed silica dispersion slurry.
[0051] Performance Comparison
[0052] Table 1: Particle size of hydrophobic fumed silica dispersion slurry with different polydopamine dosages
[0053] Case Polydopamine dosage (phr) *Particle size D50 (micrometers) Comparative Example 1-1 0.01 20 Comparative Examples 1-2 0.1 16 Example 1-1 0.5 9 Examples 1-2 1.0 5 Comparative Examples 1-3 5.0 3 Comparative Examples 1-4 10.0 1
[0054] *Note: The particle size of the hydrophobic fumed silica particles coated with polydopamine in the dispersion slurry was measured using a laser particle size analyzer.
[0055] The data in the table above shows that as the amount of polydopamine increases, the particle size of the hydrophobic fumed silica particles coated with polydopamine in the final dispersion slurry gradually decreases. Therefore, to obtain the ideal particle size (5-10 micrometers), the amount of 10wt% polydopamine solution needs to be controlled between 0.5-1.0 phr.
[0056] (2) Step 3) Thermal conductivity and mechanical strength of materials obtained under different amounts of hydrophobic fumed silica dispersion slurry 1) Mix dopamine-hydrochloric acid (10.8 mmol), tris(hydroxymethyl)aminomethane (120 mmol) and water / methanol (mass ratio of 4:1) solution (1.2 L), stir and react at 30 °C for 20 h, and obtain polydopamine particles by repeated centrifugation and purification. When used, redisperse them in water according to the ratio to obtain polydopamine (PDA) solution.
[0057] 2) Mix water (100 phr), hydrophobic fumed silica (10 phr), polydopamine solution (10 wt%, 0.5 phr), high molecular weight emulsifying stabilizer polyvinyl alcohol (0.1 phr), and defoamer polysiloxane (0.1 phr) and stir evenly (10000 r / min, 20 min) to obtain a hydrophobic fumed silica dispersion slurry.
[0058] 3) Mix ceramic fibers (1 phr, diameter = 2-5 micrometers, length = 1-5 centimeters) and hydrophobic fumed silica dispersion slurry (1-20 phr) and stir evenly (10000 r / min, 20 min) to obtain a mixed slurry.
[0059] 4) The mixed slurry is formed by passing it through a flat filter screen (100 mesh), and water is removed by filtration to obtain a composite sheet with a thickness of 4 mm. The sheet is then dried in a drying tunnel at 100°C for 1 hour to obtain a ceramic fiber / hydrophobic fumed silica composite thermal insulation material.
[0060] Performance Comparison
[0061] Table 2: Performance of Composite Thermal Insulation Materials with Different Amounts of Hydrophobic Vaporized Silica Dispersion Slurry
[0062]
[0063] The data in the table above shows that:
[0064] Regarding thermal conductivity, as the amount of hydrophobic fumed silica dispersion slurry increases, the two thermal conductivity values of the final composite insulation material gradually decrease, and the rate of decrease gradually narrows with increasing content.
[0065] Regarding tensile strength and resilience, the final composite thermal insulation material gradually strengthens as the amount of hydrophobic fumed silica dispersion slurry increases, but begins to decline after reaching the amount used in Examples 2-3. This is because excessive hydrophobic fumed silica can cause the material to become loose and difficult to bond together, resulting in a decrease in tensile strength and resilience.
[0066] (3) The influence of different processes on silica loss during filtration
[0067] Example 3-1
[0068] 1) Mix dopamine-hydrochloric acid (10.8 mmol), tris(hydroxymethyl)aminomethane (120 mmol) and water / methanol (mass ratio 4:1) solution (1.2 L), stir and react at 30 °C for 20 h, and obtain polydopamine particles by repeated centrifugation and purification. When using, redisperse them in water according to the ratio to obtain polydopamine (PDA) solution.
[0069] 2) Mix water (100 phr), hydrophobic fumed silica (10 phr), polydopamine solution (10 wt%, 0.5 phr), high molecular weight emulsifying stabilizer polyvinyl alcohol (0.1 phr), and defoamer polysiloxane (0.1 phr) and stir evenly (10000 r / min, 20 min) to obtain a hydrophobic fumed silica dispersion slurry.
[0070] 3) Add ceramic fibers (diameter = 2-5 micrometers, length = 1-5 centimeters) to a sodium dodecyl sulfonate aqueous solution (0.5 wt%) to a concentration of 5 g / 100 mL, stir, filter, and dry to obtain anionic modified ceramic fibers. Mix the anionic modified ceramic fibers (1 phr) and hydrophobic fumed silica dispersion slurry (5 phr) and stir evenly (10000 r / min, 20 min) to obtain a mixed slurry.
[0071] 4) The mixed slurry obtained in step 3) is formed by passing it through a flat filter screen (100 mesh), and then the water is removed by negative pressure suction to obtain a composite sheet with a thickness of 4 mm. It is then dried in a drying tunnel at 100°C for 1 hour to obtain a ceramic fiber / hydrophobic fumed silica composite thermal insulation material.
[0072] Example 3-2
[0073] 1) Mix dopamine-hydrochloric acid (10.8 mmol), tris(hydroxymethyl)aminomethane (120 mmol) and water / methanol (mass ratio 4:1) solution (1.2 L), stir and react at 30 °C for 20 h, and obtain polydopamine particles by repeated centrifugation and purification. When using, redisperse them in water according to the ratio to obtain polydopamine (PDA) solution.
[0074] 2) Mix water (100 phr), hydrophobic fumed silica (10 phr), polydopamine solution (10 wt%, 0.5 phr), high molecular weight emulsifying stabilizer polyvinyl alcohol (0.1 phr), and defoamer polysiloxane (0.1 phr) and stir evenly (10000 r / min, 20 min). Adjust the pH of the system to 3.0 during stirring to obtain a hydrophobic fumed silica dispersion slurry.
[0075] 3) Add ceramic fibers (diameter = 2-5 micrometers, length = 1-5 centimeters) to a sodium dodecyl sulfonate aqueous solution (0.5 wt%) to a concentration of 5 g / 100 mL, stir, filter, and dry to obtain anionic modified ceramic fibers. Mix the anionic modified ceramic fibers (1 phr) and hydrophobic fumed silica dispersion slurry (5 phr) and stir evenly (10000 r / min, 20 min). Adjust the pH of the system to 2.0 during stirring to obtain a mixed slurry.
[0076] 4) The mixed slurry obtained in step 3) is formed by passing it through a flat filter screen (100 mesh), and then filtered under negative pressure to remove water, to obtain a composite sheet with a thickness of 4 mm. It is then dried in a drying tunnel at 100°C for 1 hour to obtain a ceramic fiber / hydrophobic fumed silica composite thermal insulation material.
[0077] Performance Comparison
[0078] Table 3: Performance of Composite Thermal Insulation Materials under Different Processes
[0079]
[0080] *Note: The test method for the loss rate of hydrophobic fumed silica is to collect the filtrate, dry it, collect the obtained hydrophobic fumed silica, weigh it, and calculate the loss rate.
[0081] As can be seen from the data in the table above, compared with Example 3-1, Example 3-2 can significantly reduce the loss rate of hydrophobic vapor phase silica by using electrostatic adsorption technology in step 4), thereby giving the composite thermal insulation material a lower thermal conductivity.
[0082] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.
[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.
Claims
1. A method for preparing a ceramic fiber / hydrophobic fumed silica composite thermal insulation material, characterized in that: Includes the following steps: 1) Preparation of polydopamine solution; 2) Mix 100 parts by weight of water, 5-10 parts by weight of hydrophobic fumed silica, 0.5-1 parts by weight of 8-12 wt% polydopamine solution, 0.01-1 parts by weight of polymeric emulsifying stabilizer, and 0-0.2 parts by weight of defoamer and stir evenly. Adjust the pH of the system to 2.5-3.5 during stirring to obtain a hydrophobic fumed silica dispersion slurry with a particle size D50 of 5-10 micrometers. 3) Mix 1 part by weight of anion-modified ceramic fiber and 2-10 parts by weight of hydrophobic fumed silica dispersion slurry and stir evenly. Adjust the pH of the system to ≤2.0 during stirring to obtain a mixed slurry. 4) The mixed slurry is formed by passing it through a flat filter screen, then filtered under negative pressure to remove water, and a composite sheet is obtained. After drying, a ceramic fiber / hydrophobic fumed silica composite thermal insulation material is obtained.
2. The preparation method according to claim 1, characterized in that: In step 1), the preparation method of the polydopamine solution includes: mixing dopamine-hydrochloric acid, tris(hydroxymethyl)aminomethane and water / methanol solution, stirring and reacting, and repeatedly separating and purifying by centrifugation to obtain polydopamine particles, which can be redispersed in water according to the ratio before use.
3. The preparation method according to claim 1, characterized in that: In step 2), the polymeric emulsifying stabilizer is 0.02-0.2 parts by weight.
4. The preparation method according to claim 1 or 3, characterized in that: In step 2), the polymeric emulsifying stabilizer is one or more of polyacrylic acid, polyacrylamide, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and polymaleic anhydride.
5. The preparation method according to claim 1 or 3, characterized in that: In step 2), the defoamer is one or more of polysiloxane, polyether-modified silicone oil, and polyether-type defoamer.
6. The preparation method according to claim 1, characterized in that: The anion modification process involves adding ceramic fibers to an aqueous solution of sodium dodecyl sulfonate, stirring, filtering, and drying to obtain anion-modified ceramic fibers.
7. The preparation method according to claim 1, characterized in that: In step 4), the thickness of the composite sheet is 0.2-20mm.
8. The preparation method according to claim 1, characterized in that: In step 4), the drying process involves drying in a drying tunnel at 30-150°C for 0.5-2 hours.
9. The preparation method according to claim 1, characterized in that: In step 4), the mesh size of the filter is 50-300 mesh.
10. The ceramic fiber / hydrophobic fumed silica composite thermal insulation material obtained by the preparation method according to any one of claims 1-9, characterized in that: Thermal conductivity at 600℃ ≤ 0.075 W / (m·K), tensile strength ≥ 210 kPa.