Silica aerogel composite material and method for preparing the same

Abstract

The application provides a preparation method of a silica aerogel composite material, and comprises the following steps: S1, using water glass as raw material, diluting the water glass with water, adding the diluted water glass into an acidic solution to obtain a sodium-containing silica sol, adding the sodium-containing silica sol into a stirring kettle containing ethanol to stir and remove precipitated salt, and obtaining a low-sodium water-ethanol system silica sol; S2, uniformly mixing the low-sodium water-ethanol system silica sol obtained in S1 with a hydrophobic modification component according to a proportion, and standing to obtain a silica gel; immersing a fiber preform in the silica gel to obtain a silica gel composite material; S3, drying the silica gel composite material obtained in S2 to obtain a silica aerogel composite material; the water glass is cheap and is used as raw material to prepare a water-ethanol system silica sol suitable for the silica aerogel material, a unique ethanol precipitation and desalination method is adopted, the sodium is avoided to be removed by ion exchange resin, and environmental protection pressure caused by a large amount of waste water is avoided.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation, and in particular to a silica aerogel composite material and its preparation method. Background Technology

[0002] The superior thermal insulation properties of silica aerogel materials have been widely recognized, and they have been applied and demonstrated excellent performance in various fields such as petrochemicals, heating networks, and new energy vehicles. Aerogels are formed when the liquid in the pores of a wet gel is replaced by gas without structural collapse. Common preparation methods involve sol-gel technology and supercritical drying technology.

[0003] Sol-gel technology is a key technology for constructing aerogel nanoporous network structures, involving sol formulation, sol preparation process, and gelation process. The sol-gel process determines the composition, pore size, structure, and properties of the final aerogel material, and is the core technology for realizing a variety of aerogel products.

[0004] Supercritical drying technology, mainly including supercritical carbon dioxide drying technology and supercritical ethanol drying technology, was the earliest drying technology to achieve mass production of aerogels. Supercritical drying aims to make the solvent reach the critical point during the drying process by controlling the pressure and temperature, forming a supercritical fluid. Solvents in the critical state have no obvious surface tension, high diffusivity, and high solubility, which effectively avoids the collapse of the gel skeleton during the drying process and achieves the separation of solvent and gel skeleton. This ensures the most complete three-dimensional network structure during the gel drying process and can produce high-performance aerogel products. It is the most effective method for preparing high-quality aerogels.

[0005] Currently, the practical applications of silica aerogel materials are very limited compared to traditional thermal insulation, mainly due to their high cost. Silica aerogels often use organosilane coupling agents as the silica source, leading to high costs. Using inexpensive silicates (mainly sodium silicate glass) as the silicon source to prepare silica aerogels still presents significant technical challenges, primarily due to high desalination costs and relatively low aerogel quality. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the existing technology. The present invention proposes a silica aerogel composite material and its preparation method, which reduces production costs, improves aerogel production efficiency, and enables the excellent performance of aerogel materials to play an important role in the field of thermal insulation, thus contributing to energy conservation, emission reduction and carbon reduction.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a silica aerogel composite material, comprising the following steps:

[0008] S1. Using water glass as raw material, dilute it with water and add it to an acidic solution to obtain sodium-containing silica sol. Add the sodium-containing silica sol to a stirred tank containing ethanol and stir to remove the precipitated salts to obtain a low-sodium water-alcohol system silica sol.

[0009] S2. Mix the low-sodium water-alcohol system silica sol obtained in S1 with the hydrophobic modification component in a certain proportion and let it stand to obtain silica gel; impregnate the fiber preform before gelation to obtain silica gel composite material.

[0010] The silica aerogel composite material obtained in S3 and drying in S2 is the silica aerogel composite material.

[0011] In S2, the mixing ratio of the low-sodium water-alcohol system silica sol and the hydrophobic modified component is 1:0.1-1;

[0012] The hydrophobic modified component includes a modifier, water, and ethanol. The modifier, water, and ethanol are mixed in a ratio of 1:2-3:10-40, and the pH of the system is adjusted to 8.5-9.5 to obtain the hydrophobic modifier component.

[0013] Furthermore, before mixing the low-sodium water-alcohol system silica sol with the hydrophobic modifying component, 0-15% tetraethyl orthosilicate is added to the low-sodium water-alcohol system silica sol to adjust the silica content to 6-15%.

[0014] Further, in S1, water glass is diluted with water to a concentration of 30-75%, and then slowly added to an acidic solution with a concentration of 20-50%, controlling the pH of the system to 2-4 to obtain a sodium-containing silica sol.

[0015] Furthermore, the acidic solution includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid, hydrofluoric acid, iodic acid, and periodic acid.

[0016] Furthermore, during the stirring process of adding the sodium-containing silica sol into a stirred tank containing ethanol, the temperature is lowered to -5 to 0°C, and the precipitated salts are removed by filtration to obtain a low-sodium water-alcohol system silica sol.

[0017] Furthermore, in S1, the volume ratio of sodium silicate sol to ethanol is 1:1-3.

[0018] Furthermore, in step S3, the silica gel composite material obtained in step S2 is soaked in 0.5-2.0 times its volume of ethanol with a concentration greater than 90%, and then transferred to an ethanol supercritical drying kettle for drying.

[0019] Furthermore, the drying process includes the following steps:

[0020] S31. Heating stage: Heat to a temperature of 265-280℃, and control the drying pressure at 8.0-16.0MPa.

[0021] S32. Constant temperature stage: Maintain a temperature of 265-280℃ and a pressure of 8.0-16.0MPa for 1-10 hours to ensure uniform material temperature and pressure.

[0022] S33, Depressurization stage: Maintain the temperature at 260-280℃ and depressurize to atmospheric pressure at a rate of 0.5-3MPa / h.

[0023] S34. Cooling and discharging: After the temperature drops below 200°C, discharge the material to obtain the silica aerogel composite material of the present invention.

[0024] Furthermore, a silica aerogel composite material is prepared according to the method for preparing silica aerogel composite materials.

[0025] Compared with the prior art, the beneficial effects of the present invention include:

[0026] 1) This invention uses inexpensive water glass as raw material to prepare a water-alcohol system silica sol suitable for aerogel materials. It adopts a unique ethanol precipitation desalination method, which avoids the complicated and costly sodium removal by ion exchange resin, and at the same time avoids the environmental pressure caused by a large amount of wastewater.

[0027] 2) This invention employs high-temperature supercritical ethanol drying technology. The dried gel material does not require further aging or curing processes. The ethanol, containing water, is removed from the pores without any other material exchange, thus preserving the gel's skeletal structure. Simultaneously, the high-temperature process self-strengthens the skeletal structure, maximizing the preservation of the aerogel's continuous three-dimensional nanoporous structure and ensuring its quality to the greatest extent. No liquid water or ethanol residue remains in the dried product. No primary or secondary organosilicon modification, cleaning, or replacement processes are required, resulting in a shorter, more efficient process route and reduced costs.

[0028] 3) This invention combines inexpensive water glass and efficient ethanol drying process to produce aerogel composite materials. The overall cost of raw materials and drying process is low. After the technology is promoted, it is expected to enable the rapid promotion of high-quality and low-priced aerogel products. Detailed Implementation

[0029] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following specific embodiments are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0030] A method for preparing a silica aerogel composite material includes the following steps:

[0031] S1. Using water glass as raw material, the water glass is diluted with water to a concentration of 30-75%, and then slowly added to an acidic solution with a concentration of 20-50%. The pH of the system is controlled to be 2-4 to obtain sodium-containing silica sol. The sodium-containing silica sol is added to a stirred tank containing ethanol and stirred to remove the precipitated salts to obtain a low-sodium water-alcohol system silica sol.

[0032] The acidic solution mentioned above includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid, hydrofluoric acid, iodic acid, and periodic acid; the volume ratio of sodium silicate sol to ethanol is 1:1-3.

[0033] In the above process, a low-sodium water-alcohol system silica sol is obtained by sedimentation and filtration. Alternatively, when sodium-containing silica sol is added to a stirred tank containing ethanol, the temperature is lowered to -5 to 0°C, and the precipitated salts are removed by low-temperature crystallization and filtration to obtain a low-sodium water-alcohol system silica sol.

[0034] S2. Add 0-15% tetraethyl orthosilicate to the low-sodium water-alcohol system silica sol to adjust the silica content to 6-15%. Then, mix the low-sodium water-alcohol system silica sol obtained in S1 with the hydrophobic modification component in proportion and let it stand to obtain silica gel. Before gelation, impregnate the fiber preform to obtain the silica gel composite material.

[0035] The mixing ratio of the low-sodium water-alcohol system silica sol to the hydrophobic modifier is 1:0.1-1; the hydrophobic modifier includes a modifier, water and ethanol, which are mixed in a ratio of 1:2-3:10-40, and the pH of the system is adjusted to 8.5-9.5 to obtain the hydrophobic modifier component.

[0036] S3. The silica gel composite material obtained in S2 is soaked in 0.5-2.0 times its volume of ethanol with a concentration greater than 90%, and then transferred to an ethanol supercritical drying reactor for drying. The drying procedure includes the following steps:

[0037] S31. Heating stage: Heat to a temperature of 265-280℃, and control the drying pressure at 8.0-16.0MPa.

[0038] S32. Constant temperature stage: Maintain a temperature of 265-280℃ and a pressure of 8.0-16.0MPa for 1-10 hours to ensure uniform material temperature and pressure.

[0039] S33, Depressurization stage: Maintain the temperature at 260-280℃ and depressurize to atmospheric pressure at a rate of 0.5-3MPa / h.

[0040] S34. Cooling and discharging: After the temperature drops below 200°C, discharge the material to obtain the silica aerogel composite material of the present invention.

[0041] The technical effects of this application will be further explained below with reference to the embodiments.

[0042] Example 1

[0043] A method for preparing a silica aerogel composite material includes the following steps:

[0044] S1. Using water glass as raw material, after diluting it with water to a concentration of 50%, it is slowly added to a 38% sulfuric acid solution. The system temperature is controlled below 10℃ and the pH value is 3.0 to obtain sodium-containing silica sol. The obtained sodium-containing silica sol is added to a stirring vessel containing 1.5 times the volume of ethanol, stirred slowly, cooled to 0℃, and filtered to remove the precipitated salts to obtain a low-sodium water-alcohol system silica sol.

[0045] S2. Add 5% tetraethyl orthosilicate to the silica sol obtained in S1 to adjust the silica content to 9%; mix the low-sodium water-alcohol system silica sol obtained in S1 with the hydrophobic modification component at a volume ratio of 2:1, impregnate the fiber preform, and obtain the gel composite material after 20 minutes.

[0046] Preparation of hydrophobic modifier component: Modifier, water and ethanol are mixed in a certain ratio of 1:3:20, and ammonia is added to adjust the pH to 8.5 to obtain hydrophobic modifier component.

[0047] S3, Supercritical Ethanol Drying: The gel material obtained in S2 was soaked in 2.0 times its volume of 95% ethanol, and then transferred to a supercritical ethanol drying vessel for drying. The drying procedure is as follows:

[0048] S31. Heating stage: Heat to 270℃ and control the drying pressure at 10.0MPa.

[0049] S32. Constant temperature stage: Maintain a temperature of 270℃ and a pressure of 10.0MPa for 4 hours to ensure uniform temperature and pressure of the material.

[0050] S33, Depressurization stage: Maintain the temperature at 260-270℃ and depressurize to atmospheric pressure at a depressurization rate of 2MPa / h.

[0051] S34. Cooling and discharging: After the temperature drops to 150°C, discharge the material to obtain the silica aerogel composite material of the present invention.

[0052] The material obtained in this embodiment has a thermal conductivity of 0.020 W / (m·K) at 25℃, a thermal conductivity of 0.069 W / (m·K) at 500℃, and a density of 180 kg / m³. 3 It has a water repellency rate of 99.2%, a water absorption rate of 1.0% by total immersion mass, a vibration loss rate of 0.4%, and a flammability rating of A (A1).

[0053] Example 2

[0054] A method for preparing a silica aerogel composite material includes the following steps:

[0055] S1. Using water glass as raw material, after diluting it with water to a concentration of 67%, it is slowly added to a sulfuric acid solution with a concentration of 25%, while controlling the system temperature below 10℃ and the pH value at 3.0, to obtain sodium silicate sol.

[0056] S2. The obtained sodium-containing silica sol is added to a stirring vessel containing 1.5 times the volume of ethanol, stirred slowly, cooled to 0°C, and filtered to remove the precipitated salts to obtain a low-sodium water-alcohol system silica sol. The low-sodium water-alcohol system silica sol obtained in S1 is mixed with the hydrophobic modification component at a volume ratio of 1:1 and then impregnated with the fiber preform. After 20 minutes, a gel composite material is obtained.

[0057] Preparation of hydrophobic modifier component: Modifier, water and ethanol are mixed in a certain ratio of 1:3:30, and ammonia is added to adjust the pH to 8.5 to obtain hydrophobic modifier component.

[0058] S3, Supercritical Ethanol Drying: The gel material obtained in S2 was soaked in 1.0 volume of 95% ethanol, and then transferred to a supercritical ethanol drying vessel for drying. The drying procedure is as follows:

[0059] S31. Heating stage: Heat to 270℃ and control the drying pressure at 10.0MPa.

[0060] S32. Constant temperature stage: Maintain a temperature of 270℃ and a pressure of 10.0MPa for 4 hours to ensure uniform temperature and pressure of the material.

[0061] S33, Depressurization stage: Maintain the temperature at 260-270℃ and depressurize to atmospheric pressure at a depressurization rate of 2MPa / h.

[0062] S34. Cooling and discharging: After the temperature drops to 150°C, discharge the material to obtain the silica aerogel composite material of the present invention.

[0063] The material obtained in this embodiment has a thermal conductivity of 0.021 W / (m·K) at 25℃, a thermal conductivity of 0.070 W / (m·K) at 500℃, and a density of 150 kg / m³. 3 It has a water repellency rate of 99.0%, a water absorption rate of 0.6% by total immersion mass, a vibration loss rate of 0.4%, and a flammability rating of A (A1).

[0064] Example 3

[0065] A method for preparing a silica aerogel composite material includes the following steps:

[0066] S1. Using water glass as raw material, after diluting it with water to a concentration of 75%, it is slowly added to a 50% phosphoric acid solution. The system temperature is controlled below 10℃ and the pH value is 4.0 to obtain sodium-containing silica sol. The obtained sodium-containing silica sol is added to a stirring vessel containing 3 times the volume of ethanol in a certain proportion, stirred slowly, cooled to 0℃, and filtered to remove the precipitated salts to obtain a low-sodium water-alcohol system silica sol.

[0067] S2. Add 15% tetraethyl orthosilicate to the silica sol obtained in S1 to adjust the silica content to 6%; mix the low-sodium water-alcohol system silica sol obtained in S1 with the hydrophobic modification component at a volume ratio of 10:1, impregnate the fiber preform, and obtain the gel composite material after 20 minutes.

[0068] Preparation of hydrophobic modifier component: Modifier, water and ethanol are mixed in a certain ratio of 1:3:40, and ammonia is added to adjust the pH to 9.5 to obtain hydrophobic modifier component.

[0069] S3, Supercritical Ethanol Drying: The gel material obtained in S2 was soaked in 0.5 times its volume of 92% ethanol, and then transferred to a supercritical ethanol drying vessel for drying. The drying procedure is as follows:

[0070] S31. Heating stage: Heat to 280℃ and control the drying pressure at 16.0MPa.

[0071] S32. Constant temperature stage: Maintain a temperature of 280℃ and a pressure of 16.0MPa for 10 hours to ensure uniform material temperature and pressure.

[0072] S33, Depressurization stage: Maintain the temperature at 270-280℃ and depressurize to atmospheric pressure at a depressurization rate of 3MPa / h.

[0073] S34. Cooling and discharging: After the temperature drops to 170°C, discharge the material to obtain the silica aerogel composite material of the present invention.

[0074] The material obtained in this embodiment has a thermal conductivity of 0.023 W / (m·K) at 25℃, a thermal conductivity of 0.071 W / (m·K) at 500℃, and a density of 180 kg / m³. 3 It has a water repellency rate of 99.3%, a water absorption rate of 0.9% by total immersion mass, a vibration loss rate of 0.4%, and a flammability rating of A (A1).

[0075] Example 4

[0076] A method for preparing a silica aerogel composite material includes the following steps:

[0077] S1. Using water glass as raw material, after diluting it with water to a concentration of 30%, it is slowly added to a 20% hydrofluoric acid solution. The system temperature is controlled below 10℃ and the pH value is 2.0 to obtain sodium-containing silica sol. The obtained sodium-containing silica sol is added to a stirring vessel containing ethanol at a volume ratio of 1, stirred slowly, cooled to 0℃, and filtered to remove the precipitated salts to obtain a low-sodium water-alcohol system silica sol.

[0078] The silica content in the silica sols obtained from S2 and S1 is 15%. The low-sodium water-alcohol system silica sol obtained from S1 is mixed with the hydrophobic modification component at a volume ratio of 1:1 and then impregnated with the fiber preform. After 20 minutes, a gel composite material is obtained.

[0079] Preparation of hydrophobic modifier component: Modifier, water and ethanol are mixed in a certain ratio of 1:2:10, and ammonia is added to adjust the pH to 9 to obtain hydrophobic modifier component.

[0080] S3, Supercritical Ethanol Drying: The gel material obtained in S2 was soaked in 1.2 times its volume of 93% ethanol, and then transferred to a supercritical ethanol drying vessel for drying. The drying procedure is as follows:

[0081] S31. Heating stage: Heat to 265℃ and control the drying pressure at 8.0MPa.

[0082] S32. Constant temperature stage: Maintain a temperature of 265℃ and a pressure of 8.0MPa for 1 hour to ensure uniform material temperature and pressure.

[0083] S33, Depressurization stage: Maintain the temperature at 265-275℃ and depressurize to atmospheric pressure at a rate of 0.5MPa / h.

[0084] S34. Cooling and discharging: After the temperature drops to 160°C, discharge the material to obtain the silica aerogel composite material of the present invention.

[0085] The material obtained in this embodiment has a thermal conductivity of 0.022 W / (m·K) at 25℃, a thermal conductivity of 0.068 W / (m·K) at 500℃, and a density of 180 kg / m³. 3 It has a water repellency rate of 99.1%, a water absorption rate of 0.8% by total immersion mass, a vibration loss rate of 0.4%, and a flammability rating of A (A1).

[0086] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A method for preparing a silica aerogel composite material, characterized in that, Includes the following steps: S1. Using water glass as raw material, dilute it with water and add it to an acidic solution to obtain sodium-containing silica sol. Add the sodium-containing silica sol to a stirred tank containing ethanol and stir to remove the precipitated salts to obtain a low-sodium water-alcohol system silica sol. Among them, water glass is diluted with water to a concentration of 30-75%, and then slowly added to an acidic solution with a concentration of 20-50%, and the pH of the system is controlled to be 2-4 to obtain sodium-containing silica sol. During the process of adding the sodium-containing silica sol to a stirred tank containing ethanol and stirring, the temperature is lowered to -5 to 0°C, and the precipitated salts are removed by filtration to obtain a low-sodium water-alcohol system silica sol. S2. Mix the low-sodium water-alcohol system silica sol obtained in S1 with the hydrophobic modification component in a certain proportion and let it stand to obtain silica gel; impregnate the fiber preform before gelation to obtain silica gel composite material. In this process, before mixing the low-sodium water-alcohol system silica sol with the hydrophobic modifying component, 0-15% tetraethyl orthosilicate is added to the low-sodium water-alcohol system silica sol to adjust the silica content to 6-15%. S3. The silica gel composite material obtained in S2 is soaked in 0.5-2.0 times its volume of ethanol with a concentration greater than 90%, and then transferred to an ethanol supercritical drying reactor for drying. The drying procedure includes the following steps: S31. Heating stage: Heat to 265-280℃, and control the drying pressure at 8.0-16.0MPa; S32. Constant temperature stage: Maintain a temperature of 265-280℃ and a pressure of 8.0-16.0MPa for 1-10 hours to ensure uniform material temperature and pressure. S33, Depressurization stage: Maintain the temperature at 260-280℃ and depressurize to atmospheric pressure at a rate of 0.5-3MPa / h; S34. Cooling and discharging: After the temperature drops to below 200°C, discharge the material to obtain the silica aerogel composite material of the present invention. In S2, the mixing ratio of the low-sodium water-alcohol system silica sol and the hydrophobic modified component is 1:0.1-1; The hydrophobic modified component includes a modifier, water, and ethanol. The modifier, water, and ethanol are mixed in a ratio of 1:2-3:10-40, and the pH of the system is adjusted to 8.5-9.5 to obtain the hydrophobic modifier component.

2. The method for preparing the silica aerogel composite material according to claim 1, characterized in that, The acidic solution includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid, hydrofluoric acid, iodic acid, and periodic acid.

3. The method for preparing the silica aerogel composite material according to claim 1, characterized in that, In S1, the volume ratio of sodium silicate sol to ethanol is 1:1-3.