Method for preparing aerogel particles capable of being used for thermal insulation material

Abstract

Disclosed in the present invention is a method for preparing aerogel particles capable of being used for a thermal insulation material. The preparation method comprises the following steps: uniformly mixing a silicon source, a modifier, an alcohol reagent and water, so as to form a mixed solution A; adding a catalyst into the mixed solution A, so as to form a mixed solution B; gelling the mixed solution B, wherein the gelling temperature is 20-35ºC, and the gelling humidity is 30-60% RH; when the hardness value of the gel is 20-70 F, performing granulation; adding the granulated gel particles into an alcohol aging solution for aging; and subjecting the aged gel particles to ethanol supercritical drying, so as to form aerogel particles. In the present invention, the granulation timing is determined by monitoring the granulation hardness, and granulation is performed under an appropriate hardness, such that the gel is not excessively crushed or insufficiently crushed during the granulation process. In addition, the gelling temperature and humidity are regulated and controlled, such that the gel maintains suitable elasticity, which is more beneficial for obtaining more uniform aerogel particles and improving the yield of particles having a particle size of 1-4 mm.

Description

A method for preparing aerogel particles that can be used in thermal insulation materials

[0001] Cross-references to related applications

[0002] This application claims the benefit of Chinese patent application 202411041973.X, filed on July 31, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of silica aerogel technology, and more specifically to a method for preparing aerogel particles that can be used in thermal insulation materials. The aerogel particles prepared by this method can be used in thermal insulation aerogel products, such as building mortar. Background Technology

[0004] Silica aerogel is a hydrophobic porous network solid material, and its products have been widely used in various fields such as building insulation, oil and gas pipelines, heating pipelines, storage tanks, and thermal control of new energy lithium batteries.

[0005] Silica aerogel possesses excellent properties such as high temperature resistance, low density, and low thermal conductivity, making it a superior building material composite material with a low density (less than 80 kg / m³). 3 Aerogel materials, when combined with building mortar, can reduce the mortar's specific gravity, thereby decreasing the building load and wall thickness. Simultaneously, the low thermal conductivity of aerogel (as low as below 0.021 W / (m·K)) can improve the thermal insulation performance of the mortar. However, existing silica aerogel products suffer from uneven density, uncontrolled particle size distribution, and low mechanical strength. This results in poor uniformity after being combined with building mortar, limiting their application in the construction field.

[0006] Generally, aerogels are manufactured by producing a wet gel from silica precursors such as water glass and TEOS, and then removing the liquid component inside the wet gel without damaging its microstructure. Silica aerogels are typically classified into three types: aerogel powder, aerogel particles, and monolithic aerogel. Silica aerogel powder is particularly prone to dispersion and difficult to handle, while aerogel particles, if possessing a suitable particle size distribution, can simplify the processing in different niche applications and better leverage the superior performance of aerogels. Furthermore, aerogel particles require a narrower particle size distribution range to obtain aerogel products with even better performance.

[0007] Aerogels are used in thermal insulation materials. In some existing technologies, aerogels are added in powder form. During the mixing and dispersion process, the aerogel powder is easily dispersed, thus reducing the aerogel content and ultimately resulting in poor thermal insulation performance of the aerogel insulation material. In other existing technologies, the particle size of aerogels is controlled within the range of 2 mm, which to some extent solves the shortcomings of aerogel powder being easy to float, disperse, and difficult to mix. However, the particle strength and elasticity are poor, and it is easy to pulverize, resulting in low yield and uneven distribution of large particles. Therefore, existing technologies still cannot control the particle size distribution within the range of 1–4 mm and ensure a high yield of particles in the 1–4 mm range.

[0008] There is an urgent need for a preparation method that can make the particle size distribution of aerogel particles more uniform, and that can control the particle size of aerogel particles and improve the yield of aerogel particles of 1-4 mm. Summary of the Invention

[0009] The present invention aims to at least partially solve one of the technical problems in the prior art. To this end, the present invention discloses an aerogel particle that can be used in thermal insulation materials and a preparation method thereof. Through the present invention, aerogel particle products with uniform density, controlled particle size distribution and high mechanical strength can be obtained.

[0010] This invention is achieved through the following technical solution:

[0011] This invention provides a method for preparing aerogel particles, comprising the following steps:

[0012] (1) Mixing raw materials: Mix silicon source, modifier, alcohol reagent and water to form mixture A; the content of alcohol reagent is 50% to 70% of the total mass of raw materials;

[0013] (2) Adding a catalyst: Add a catalyst to mixture A to form mixture B;

[0014] (3) Gel aging: The mixture B is subjected to gel aging; the gel temperature is 20-35℃ and the gel humidity is 30%-60%RH.

[0015] (4) Granulation: Granulation is carried out when the gel hardness value is 20-70F; the crushing method of granulation includes vibration crushing; the vibration frequency is 1200-1600 r / min and the vibration amplitude is 0.5-5 mm;

[0016] (5) Aging: The granulated gel particles are added to an alcohol aging solution for aging; the mass of the alcohol aging solution is 60% to 80% of the total mass of the granulated gel.

[0017] (6) Drying: The aged gel particles are dried by supercritical ethanol to form aerogel particles.

[0018] Furthermore, during the supercritical drying process of ethanol, the volume of ethanol occupies 30% to 50% of the space in the drying vessel.

[0019] Preferably, the gel is placed on a 5-mesh vibrating screen for crushing.

[0020] Preferably, the feeding space accounts for 40% to 60% of the total space during the vibration crushing process.

[0021] Furthermore, a method for monitoring gel hardness is to test the hardness at 5 to 15 points on the gel surface and take the average value as the hardness value.

[0022] Furthermore, the catalysts include ammonium salt catalysts.

[0023] Preferably, the catalyst also includes ammonia.

[0024] Preferably, the ammonium salt catalyst is ammonium fluoride.

[0025] Preferably, the mass ratio of ammonium fluoride to mixture A is 1:(100-230); the mass ratio of ammonia to mixture A is 1:(100-230).

[0026] Preferably, in the catalyst addition step, ammonium fluoride and ammonia are added sequentially to mixture A while it is being stirred.

[0027] Preferably, the mass ratio of silicon source, modifier, alcohol reagent, and water is 1:(0.5~2):(5~7):(0.5~1.5).

[0028] Preferably, the silicon source includes one or more of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, and polysiloxane;

[0029] Modifiers include one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, vinyltrichlorosilane, trimethylethoxysilane, hexamethyldisilazane, and hexamethyldisiloxane;

[0030] Alcohol reagents include one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol;

[0031] Alcohol aging solutions include one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol.

[0032] The present invention also provides the use of aerogel particles prepared by the above-described preparation method in thermal insulation materials.

[0033] Furthermore, the aforementioned aerogel particles are used to prepare building mortar.

[0034] The present invention also provides aerogel particles prepared using the preparation method described above.

[0035] Furthermore, the mass percentage of the aerogel particles with a diameter of 1–4 mm is ≥75%.

[0036] Furthermore, the average pore size of the aerogel particles is 26–35 nm.

[0037] Furthermore, the thermal conductivity of the aerogel particles is <0.02 W / (m·K).

[0038] Furthermore, the cumulative particle size distribution values ​​of the aerogel particles are D10 of 0.89–2.29 mm, D50 of 2.71–3.28 mm, and D90 of 4.18–4.30 mm.

[0039] The present invention has the following beneficial effects:

[0040] (1) The present invention controls the particle size distribution by gel granulation. Compared with crushing and screening after drying, granulation in the gel stage can form a more uniform particle structure. Crushing after drying will produce more fine particles and powder due to the high brittleness of aerogel, resulting in uneven particle size.

[0041] This invention monitors the granulation hardness to determine the granulation timing, ensuring granulation at the appropriate hardness level. This prevents the gel from being over- or under-granulated during the granulation process. Simultaneously, it regulates the gel temperature and humidity to maintain suitable elasticity and processing stability, which is more conducive to obtaining more uniform aerogel particles and improving the yield (cumulative particle size distribution) of particles with a diameter of 1–4 mm.

[0042] (2) The vibration parameters (vibration frequency, vibration amplitude) and feeding space during the granulation stage can directly affect the degree of particle collision during granulation. By optimizing the vibration parameters and feeding space conditions, a granulation environment more suitable for the alcohol environment system and the control of gel parameters and hardness of aerogel particles in this invention can be obtained, reducing the damage to particles caused by excessive collisions and reducing excessive particle splitting and cracking. This invention can further optimize the particle size distribution concentration of aerogel particles (such as similar particle sizes from D10 to D90) by optimizing the vibration parameters and feeding space ratio during the granulation stage, thereby further improving the uniformity of particle distribution and the yield of particles with a diameter of 1 to 4 mm (cumulative particle size distribution).

[0043] (3) This invention improves density uniformity by controlling gel hardness and gel parameters (temperature, humidity, etc.). Granulation and aging at the target hardness can regulate the density of the aerogel, thereby obtaining the relationship between gel hardness and aerogel density, and thus controlling the density and particle size of aerogel particles. This invention can prepare aerogel particles suitable for various scenarios through precise control of process parameters and comprehensive density characterization, and has wide applications.

[0044] (4) The aerogel particles prepared by the present invention have uniform particle size distribution and density. The yield (cumulative particle size distribution) of particles with a particle size of 1-4 mm can reach more than 75%. The particle size distribution is controllable and the mechanical strength is high.

[0045] (5) In addition, in the application of thermal insulation materials, such as mortar, aerogels with different density and particle size distribution indices are added to the mortar to achieve controllable mortar specific gravity, reduce its thermal conductivity, and enhance the thermal insulation performance of the mortar. Attached Figure Description

[0046] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0047] Figure 1 shows a comparison of the density of the finished product after granulation at different gel hardnesses;

[0048] Figure 2 shows the cumulative particle size distribution of the aerogel particles produced by drying and crushing in Example 1.

[0049] Figure 3 shows the cumulative particle size distribution of the aerogel particles produced by drying and crushing in Example 2;

[0050] Figure 4 is a scanning electron microscope image of the aerogel particles prepared in Example 1;

[0051] Figure 5 is a scanning electron microscope image of the aerogel particles prepared in Example 2. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Unless otherwise specified, specific conditions in the embodiments are based on conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials and equipment involved are all commercially available or self-made using known methods; the methods involved are all conventional methods unless otherwise specified. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The disclosure of the numerical ranges involved includes all values ​​within the entire range and the disclosure of further subdivided ranges, including the endpoints and subranges given for these ranges.

[0053] This invention provides a method for preparing aerogel particles, comprising the following steps:

[0054] (1) Mixing raw materials: Mix silicon source, modifier, alcohol reagent and water to form mixture A; the content of alcohol reagent is 50% to 70% of the total mass of raw materials;

[0055] (2) Adding a catalyst: Add a catalyst to mixture A to form mixture B;

[0056] (3) Gel aging: The mixture B is gel aged; the gel temperature is 20-35℃ and the gel humidity is 30%-60%RH; more preferably, the gel temperature is 25-30℃ and the gel humidity is 30%-50%RH.

[0057] (4) Granulation: When the gel hardness value is 20 to 70 F, granulation is performed, that is, the gel is broken into gel particles; more preferably, when the gel hardness is 30 to 50 F, granulation is performed; the crushing method of granulation includes vibration crushing; the vibration frequency is 1200 to 1600 r / min and the vibration amplitude is 0.5 to 5 mm.

[0058] (5) Aging: The granulated gel particles are added to an alcohol aging solution for aging; the mass of the alcohol aging solution is 60% to 80% of the total mass of the granulated gel.

[0059] (6) Drying: The aged gel particles are dried by supercritical ethanol to form aerogel particles.

[0060] This invention improves the density uniformity of aerogel particles by controlling gel parameters (gel temperature and humidity) and monitoring gel hardness. Granulation and aging are performed at the target hardness level. By controlling gel hardness, the density of the aerogel is regulated, thus obtaining the relationship between gel hardness and aerogel density, as shown in Figure 1. Controlling the particle size distribution of the aerogel through gel granulation, compared to crushing and sieving after drying, results in a more uniform particle structure during the gelation stage under hardness control, thereby regulating the particle density and size. Without hardness-controlled granulation, crushing after drying will produce more fine particles and powder due to the high brittleness of the aerogel, leading to uneven particle size.

[0061] Suitable hardness ensures that the gel particles have sufficient strength during crushing, preventing pulverization and serving as a fundamental guarantee for large particle formation. While ensuring a suitable hardness range, appropriate gel temperature and humidity allow large particles to retain sufficient solvent, thus ensuring that the particles themselves have sufficient elasticity and processing stability. This is beneficial for maintaining the surface stability and integrity of the particles during subsequent aging, drying, crushing, and sieving processes, thereby facilitating the production of more uniform aerogel particle products, increasing the yield of 1–4 mm particle size (cumulative particle size distribution), and promoting better storage.

[0062] In some embodiments, the aging time in the aging step is 1 to 2 days; during the supercritical drying process of ethanol, the volume of ethanol occupies 30% to 50% of the space in the drying vessel.

[0063] This invention establishes an alcohol system during the raw material mixing, aging, and drying processes. By controlling the amount of alcohol used in each step, it further ensures the uniformity of the aerogel particle size distribution and reduces the proportion of excessively small particles. In the raw materials, an appropriate amount of alcohol helps form a homogeneous solution, thereby contributing to the formation of uniform gel particles. The surface activity of alcohols, by adjusting their surface tension in the solution, helps form a uniform pore structure. The alcohol content can be adjusted to regulate the pore structure and mechanical properties of the gel particles. During aging, an appropriate proportion of alcohol helps control the extent of the condensation reaction, thereby reducing gel shrinkage and helping to maintain the pore structure of the gel. Simultaneously, it maintains the solvent retention of the particles, helping to preserve the integrity of the pores and particles. The alcoholysis reaction of alcohols during aging can affect the pore structure of the gel, contributing to the formation of more uniform and open pores. Alcohols can prevent particle aggregation in the silica sol, maintain the stability of the sol, and contribute to the formation of a uniform gel. A suitable proportion of ethanol during the drying process allows the gel to swell appropriately, reducing gel shrinkage. Supercritical drying with ethanol avoids pore structure collapse caused by surface tension, helping to maintain the original pore structure of the gel and thus obtaining aerogels with high porosity and more complete pores. The establishment of the alcohol environment system in the above preparation process facilitates the acquisition of aerogel particles with uniform porosity and stable particle morphology, promoting increased yield within the target particle size range of 1–4 mm.

[0064] The principle of vibration crushing is to reduce particle size through the collision of materials. Related equipment includes linear screens, vibrating screens, etc. More preferably, the feeding space accounts for 40% to 60% of the total volume in vibration crushing; more preferably, the gel is placed on a 5-mesh vibrating screen for crushing; more preferably, the vibration frequency is 1300 to 1500 r / min and the vibration amplitude is 2 to 4 mm.

[0065] The vibration parameters (vibration frequency, vibration amplitude) and feeding space during the granulation stage directly affect the degree of particle collision during granulation. By optimizing the above conditions, a granulation environment more suitable for the alcohol environment system and the control of gel parameters and hardness of aerogel particles in this invention can be obtained, reducing damage to particles caused by excessive collisions and reducing excessive particle splitting and cracking. This invention can further optimize the particle size distribution concentration of aerogel particles (e.g., similar particle sizes from D10 to D90) by optimizing the vibration parameters and feeding space ratio during the granulation stage, thereby further improving the uniformity of particle distribution and the yield of particles with a diameter of 1-4 mm (cumulative particle size distribution).

[0066] In some embodiments, the granulation crushing method can be combined with other crushing methods, such as shear crushing, direct granulation, and extrusion crushing. Shear crushing breaks the gel into small particles through physical cutting; direct granulation controls the size and shape of the particles by the shape of the tooling itself, including methods such as tube granulation, honeycomb granulation, and disc granulation; extrusion crushing breaks the material through physical extrusion, and related equipment includes augers with flaps.

[0067] In some embodiments, the method for monitoring gel hardness is to test the hardness at 5 to 15 points on the gel plane and take the average value as the hardness value; more preferably, to test the hardness at 8 to 10 points on the gel plane and take the average value.

[0068] In some embodiments, a Shore hardness tester is used to test the hardness.

[0069] Instruments for testing hardness can be replaced by other equivalent hardness testers, such as Barcol hardness testers, DuPont hardness testers, or Vickers hardness testers.

[0070] In some embodiments, the silicon source includes one or more of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, and polysiloxane; the modifier includes one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, vinyltrichlorosilane, trimethylethoxysilane, hexamethyldisilazane, and hexamethyldisiloxane; the alcohol reagent includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol; and the alcohol aging solution includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol.

[0071] More preferably, the silicon source includes one or more of tetraethyl orthosilicate and methyl orthosilicate; the modifier includes one or more of methyltrimethoxysilane and methyltriethoxysilane; the alcohol reagent includes one or more of methanol and ethanol; and the alcohol aging solution includes one or more of methanol and ethanol.

[0072] In some embodiments, the catalyst includes an ammonium salt catalyst.

[0073] Preferably, the catalyst also includes ammonia.

[0074] Preferably, the ammonium salt catalyst is ammonium fluoride.

[0075] Preferably, the mass ratio of ammonium fluoride to mixture A is 1:(100-230); the mass ratio of ammonia to mixture A is 1:(100-230).

[0076] In some embodiments, the mass ratio of silicon source, modifier, alcohol reagent, and water is 1:(0.5-2):(5-7):(0.5-1.5); more preferably, the mass ratio of silicon source, modifier, alcohol reagent, and water is 1:1.5:6:1.5; or 1:(1-1.8):(5.5-6.5):(1-1.5).

[0077] More preferably, in the catalyst addition step, ammonium fluoride and ammonia are added sequentially to mixture A while it is being stirred.

[0078] This invention uses methyl orthosilicate and tetraethyl orthosilicate as silicon sources. The aerogel structure generated by the hydrolysis and condensation reactions is complete, with a uniform and reasonable pore size distribution, which is conducive to building a stable microscopic channel structure and is a more suitable silicon source material for the system of this invention. Methyltrimethoxysilane or methyltriethoxysilane can improve the hydrophobicity of the aerogel and affect the formation of the pore structure. Methanol or ethanol as solvents helps dissolve and mix the silicon source and hydrophobic reagents, promoting the uniformity of the reaction. The volatility of the solvent also affects the drying process of the gel, thereby further affecting the pore structure. Using ammonium fluoride and ammonia as composite catalysts is more conducive to the full cross-linking of the aerogel in the system of this invention and the construction of a stable pore structure, promoting the stability of the aerogel particle state, and improving the reaction rate and product uniformity.

[0079] The present invention does not impose a particular limitation on the concentration of the ammonia solution. Those skilled in the art can use ordinary commercially available products, or other concentrations can be prepared based on ordinary commercially available products. For example, the concentration of the ammonia solution is 0.1-30 wt%, and optionally 25-30 wt%. The present invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of the present invention.

[0080] In some embodiments, the preparation method further includes a drying and crushing step, wherein the cumulative particle size distribution values ​​of the aerogel particles produced by drying and crushing are D10 of 0.89–2.29 mm, D50 of 2.71–3.28 mm, and D90 of 4.18–4.30 mm.

[0081] The present invention also provides aerogel particles prepared using the preparation method described above.

[0082] Furthermore, the mass percentage of the aerogel particles with a diameter of 1–4 mm is ≥75%.

[0083] Furthermore, the average pore size of the aerogel particles is 26–35 nm.

[0084] Furthermore, the thermal conductivity of the aerogel particles is <0.02 W / (m·K).

[0085] Furthermore, the cumulative particle size distribution values ​​of the aerogel particles are D10 of 0.89–2.29 mm, D50 of 2.71–3.28 mm, and D90 of 4.18–4.30 mm.

[0086] The aerogel particles prepared using this invention have uniform particle size distribution and density. The yield (cumulative particle size distribution) of finished particles with a particle size of 1-4 mm can reach more than 75%. The particle size distribution is controllable and the mechanical strength is high.

[0087] The present invention also provides the use of the above-mentioned aerogel particles in the preparation of thermal insulation materials.

[0088] In some embodiments of the application, aerogel particles are used to prepare building mortar.

[0089] To facilitate understanding of the aerogel particles, preparation method, and uses of this invention in building mortar, the invention will be described more comprehensively below, and embodiments of the invention will be given, but this does not limit the scope of the invention.

[0090] Example 1

[0091] (1) Tetraethyl orthosilicate, methyltriethoxysilane, ethanol and deionized water are mixed evenly in a mass ratio of 1:1.5:6:1.5 to form a mixture A; wherein, tetraethyl orthosilicate is 208.3g, methyltriethoxysilane is 312.45g, ethanol is 1249.8g and deionized water is 312.45g.

[0092] (2) Under stirring, two catalysts, ammonium fluoride and ammonia (concentration of 10wt%), are added to mixture A in sequence to form mixture B; the mass ratio of each catalyst to mixture A is 1:100; the mass of ammonium fluoride and ammonia is 208.3g respectively.

[0093] (3) Control the gel temperature to 28℃ and the humidity to 45%RH for gel aging.

[0094] (4) After gelation, use a Shore hardness tester to test the hardness at 9 points on the gel plane and take the average value as the hardness value; after monitoring the hardness value to 30F, granulation is carried out; place the gel on a 5-mesh vibrating screen for vibration crushing (with a feeding space ratio of 45%), the vibration frequency is 1400r / min, the vibration amplitude is 3mm, and the gel particles after crushing are distributed in the range of 1 to 4mm.

[0095] (5) Add the granulated gel particles to the ethanol aging solution for aging; the mass of the ethanol aging solution is 70% of the total mass of the granulated gel; soak the gel particles for aging; the mass of the ethanol aging solution is 1459g; the aging time is 1.5 days, the aging temperature is 60℃, and the stirring speed is 25rpm.

[0096] (6) The aged gel particles are subjected to supercritical ethanol drying to form aerogel particles; ethanol occupies 35% of the space in the drying vessel; the temperature is raised to 260°C at a heating rate of 65°C / h, and the pressure is raised to 10MPa. The temperature is maintained for 2 hours, and the product of the present invention is obtained after depressurization and cooling.

[0097] The dried aerogel particles were crushed, as shown in Figure 2. The particle size distribution values ​​of the finished aerogel particles were D10 2.29 mm, D50 3.28 mm, and D90 4.22 mm. The yield of finished aerogel particles with a particle size of 1-4 mm was 83% (cumulative particle size distribution).

[0098] The aerogel particles prepared in this embodiment have an average pore size of 30 nm, a porosity of 98.0%, and a thermal conductivity of 0.015 W / (m·K) at 25 °C.

[0099] Example 2

[0100] The difference between the preparation method and Example 1 is that granulation is performed after monitoring the hardness value to 50F.

[0101] As shown in Figure 3, the cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 0.99 mm, D50 2.71 mm, and D90 4.18 mm; the yield of aerogel particles with a particle size of 1-4 mm is 80% (cumulative particle size distribution).

[0102] The aerogel particles prepared in this embodiment have an average pore size of 26 nm, a porosity of 98.5%, and a thermal conductivity of 0.014 W / (m·K) at 25 °C.

[0103] Example 3

[0104] The difference between the preparation method and Example 1 is that the gel humidity is 30% RH.

[0105] The cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 2.19 mm, D50 3.08 mm, and D90 4.30 mm; the yield of aerogel particles with a particle size of 1-4 mm is 81% (cumulative particle size distribution).

[0106] The aerogel particles prepared in this embodiment have an average pore size of 28 nm, a porosity of 98.5%, and a thermal conductivity of 0.014 W / (m·K) at 25 °C.

[0107] Example 4

[0108] The difference between the preparation method and Example 1 is that the amount of ethanol in the raw materials is 1100g, that is, tetraethyl orthosilicate, methyltriethoxysilane, ethanol and deionized water are mixed evenly in a mass ratio of 1:1.5:5.28:1.5 to form mixture A; the mass of the ethanol aging solution is 60% of the total mass of the gel after granulation; in the ethanol supercritical step, ethanol occupies 25% of the space in the drying kettle.

[0109] The cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 0.89 mm, D50 2.58 mm, and D90 4.20 mm; the yield of aerogel particles with a particle size of 1-4 mm is 79% (cumulative particle size distribution).

[0110] The aerogel particles prepared in this embodiment have an average pore size of 30 nm, a porosity of 97.0%, and a thermal conductivity of 0.016 W / (m·K) at 25 °C.

[0111] In Examples 1-4 above, the timing of granulation is determined by monitoring the granulation hardness, and granulation is carried out at a suitable hardness. At the same time, the gel temperature and humidity are controlled to maintain the appropriate elasticity and processing stability of the gel. The particle size distribution concentration of aerogel particles is further optimized by optimizing the vibration parameters and feeding space ratio during the granulation stage, thereby further improving the uniformity of particle distribution and the yield of 1-4 mm particle size (cumulative particle size distribution). By constructing an alcohol system in the raw material mixing, aging, and drying processes, and by controlling the amount of alcohol in each step, the uniformity of particle size distribution of aerogel particles is further ensured, and the proportion of excessively small particle size is reduced.

[0112] The aerogel particles prepared in Examples 1-4 have uniform particle size distribution and density. The yield (cumulative particle size distribution) of finished particles with a particle size of 1-4 mm can reach more than 79%. The particle size distribution is controllable and the mechanical strength is high.

[0113] Example 5

[0114] (1) Mix methyl orthosilicate, methyltrimethoxysilane, methanol and deionized water in a mass ratio of 1:2:7:0.5 to form a mixture A; wherein, methyl orthosilicate is 208.3g, methyltrimethoxysilane is 416.6g, methanol is 1458.1g and deionized water is 104.15g.

[0115] (2) Under stirring, add two catalysts, ammonium fluoride and ammonia (concentration of 8wt%), to mixture A to form mixture B; the mass ratio of each catalyst to mixture A is 1:200; the mass of ammonium fluoride and ammonia is 10.9g respectively.

[0116] (3) Control the gel temperature at 35℃ and the humidity at 60%RH to carry out gel aging.

[0117] (4) After gelation, use a Shore hardness tester to test the hardness at 9 points on the gel plane and take the average value as the hardness value; after monitoring the hardness value to 70F, granulation is carried out; place the gel on a 5-mesh vibrating screen for vibration crushing (with a feeding space ratio of 60%), the vibration frequency is 1200r / min, the vibration amplitude is 5mm, and the gel particles after crushing are distributed in the range of 1 to 4mm.

[0118] (5) Add the granulated gel particles to the methanol aging solution for aging; the mass of the methanol aging solution is 80% of the total mass of the granulated gel; soak the gel particles for aging; the mass of the methanol aging solution is 1459g; the aging time is 1.5 days, the aging temperature is 60℃, and the stirring speed is 25rpm.

[0119] (6) The aged gel particles are subjected to supercritical ethanol drying to form aerogel particles; ethanol occupies 50% of the space in the drying vessel; the temperature is raised to 260°C at a heating rate of 65°C / h, and the pressure is raised to 10MPa. The temperature is maintained for 2 hours, and the product of the present invention is obtained after depressurization and cooling.

[0120] The dried aerogel particles were crushed to produce aerogel particles with particle size distribution values ​​D10 of 1.37 mm, D50 of 3.15 mm, and D90 of 4.27 mm. The yield of aerogel particles with a particle size of 1–4 mm was 76% (cumulative particle size distribution).

[0121] The aerogel particles prepared in this embodiment have an average pore size of 35 nm, a porosity of 98.7%, and a thermal conductivity of 0.019 W / (m·K) at 25 °C.

[0122] Example 6

[0123] (1) Mix butyl orthosilicate, dimethyldimethoxysilane, n-propanol and deionized water in a mass ratio of 1:1:6:1 to form a mixture A; wherein butyl orthosilicate is 208.3g, dimethyldimethoxysilane is 208.3g, n-propanol is 1249.8g and deionized water is 208.3g.

[0124] (2) Under stirring, add two catalysts, ammonium fluoride and ammonia (concentration of 10wt%), to mixture A to form mixture B; the mass ratio of each catalyst to mixture A is 1:150; the mass of ammonium fluoride and ammonia is 12.5g respectively.

[0125] (3) Control the gel temperature at 20℃ and the humidity at 55%RH to carry out gel aging.

[0126] (4) After gelation, use a Shore hardness tester to test the hardness at 9 points on the gel plane and take the average value as the hardness value; after monitoring the hardness value to 60F, granulation is carried out; place the gel on a 5-mesh vibrating screen for vibration crushing (with 50% of the feeding space ratio), the vibration frequency is 1600r / min, the vibration amplitude is 0.5mm, and the gel particles after crushing are distributed in the range of 1 to 4mm.

[0127] (5) Add the granulated gel particles to the n-propanol aging solution for aging; the mass of the n-propanol aging solution is 70% of the total mass of the granulated gel; soak the gel particles for aging; the mass of the n-propanol aging solution is 1459g; the aging time is 1.5 days, the aging temperature is 60℃, and the stirring speed is 25rpm.

[0128] (6) The aged gel particles are subjected to supercritical ethanol drying to form aerogel particles; ethanol occupies 30% of the space in the drying vessel; the temperature is raised to 260°C at a heating rate of 65°C / h, and the pressure is raised to 10MPa. The temperature is maintained for 2 hours, and the product of the present invention is obtained after depressurization and cooling.

[0129] The dried aerogel particles were crushed to produce aerogel particles with particle size distribution values ​​D10 of 1.57 mm, D50 of 2.93 mm, and D90 of 4.25 mm. The yield of aerogel particles with a particle size of 1–4 mm was 77% (cumulative particle size distribution).

[0130] The aerogel particles prepared in this embodiment have an average pore size of 31 nm, a porosity of 97.5%, and a thermal conductivity of 0.017 W / (m·K) at 25 °C.

[0131] Comparative Example 1

[0132] The difference between the preparation method and Example 1 is that the aged gel particles are subjected to supercritical carbon dioxide drying.

[0133] The cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 0.61 mm, D50 3.58 mm, and D90 5.21 mm; the yield of aerogel particles with a particle size of 1-4 mm is 50% (cumulative particle size distribution).

[0134] The aerogel particles prepared in this embodiment have an average pore size of 55 nm, a porosity of 96.1%, and a thermal conductivity of 0.020 W / (m·K) at 25 °C.

[0135] Comparing Comparative Example 1 and Example 1, it can be seen that when the raw materials, aging solution, and drying environment are not a unified alcohol system, such as the non-alcohol system in Comparative Example 1, the yield of aerogel particles with a particle size of 1-4 mm is greatly reduced.

[0136] Comparative Example 2

[0137] The difference between the preparation method and Example 1 is that the vibration frequency during granulation is 900 r / min and the vibration amplitude is 2 mm.

[0138] The cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 2.11 mm, D50 3.76 mm, and D90 5.50 mm; the yield of aerogel particles with a particle size of 1-4 mm is 53% (cumulative particle size distribution).

[0139] The aerogel particles prepared in this embodiment have an average pore size of 40 nm, a porosity of 96.8%, and a thermal conductivity of 0.021 W / (m·K) at 25 °C.

[0140] Comparing Comparative Example 2 with Example 1, it can be seen that when the vibration frequency and vibration amplitude are too low, the particle size distribution of the finished aerogel particles is not concentrated, and the yield of particles with a diameter of 1-4 mm is greatly reduced.

[0141] Comparative Example 3

[0142] The difference between the preparation method and Example 1 is that the gel temperature is 40°C, the gel humidity is 65%RH, and granulation is performed after monitoring the hardness value to 25F.

[0143] The cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 0.75 mm, D50 2.44 mm, and D90 3.93 mm; the yield of aerogel particles with a particle size of 1-4 mm is 66% (cumulative particle size distribution).

[0144] The aerogel particles prepared in this embodiment have an average pore size of 26 nm, a porosity of 98.5%, and a thermal conductivity of 0.014 W / (m·K) at 25 °C.

[0145] Comparing Comparative Example 3 with Example 1, it can be seen that when the gel temperature and humidity are too high and the hardness is too low, the excessive water content in the system leads to excessive particle shrinkage in subsequent steps, resulting in uneven particle size distribution of the finished aerogel particles, and a significant reduction in the yield of particles with a diameter of 1-4 mm.

[0146] Comparative Example 4

[0147] The difference between the preparation method and Example 1 is that granulation is performed after monitoring the hardness value to 15F.

[0148] The cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 2.27 mm, D50 4.23 mm, and D90 6.87 mm; the yield of aerogel particles with a particle size of 1-4 mm is 71% (cumulative particle size distribution).

[0149] The aerogel particles prepared in this embodiment have an average pore size of 30 nm, a porosity of 96.1%, and a thermal conductivity of 0.026 W / (m·K) at 25 °C.

[0150] Compared with Example 1, Comparative Example 4 shows that when the hardness is too low, the particles tend to stick together, the pores are unevenly distributed, and the thermal conductivity is poor.

[0151] Comparative Example 5

[0152] The difference between the preparation method and Example 1 is that the material is crushed by vibration with a feeding space of 85%, a vibration frequency of 1000 r / min, and a vibration amplitude of 8 mm.

[0153] The cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 0.52 mm, D50 2.89 mm, and D90 4.06 mm; the yield of aerogel particles with a particle size of 1-4 mm is 54% (cumulative particle size distribution).

[0154] The aerogel particles prepared in this embodiment have an average pore size of 40 nm, a porosity of 96.8%, and a thermal conductivity of 0.021 W / (m·K) at 25 °C.

[0155] Compared with Example 1, Comparative Example 5 showed that due to excessively high amplitude, excessively low vibration frequency, and excessively high feeding space ratio, collisions increased, particle crushing increased, particle size distribution was uneven, and thermal conductivity was poor.

[0156] Comparative Example 6

[0157] The difference between the preparation method and Example 1 is that the amount of ethanol in the raw materials is 500g, and the tetraethyl orthosilicate, methyltriethoxysilane, ethanol and deionized water are mixed evenly in a mass ratio of 1:1.5:2.4:1.5 to form a mixture A; the mass of the ethanol aging solution is 50% of the total mass of the gel after granulation; and the ethanol occupies 45% of the space in the drying kettle.

[0158] The cumulative particle size distribution values ​​of the aerogel particles produced after drying and crushing are D10 0.43 mm, D50 2.12 mm, and D90 3.76 mm; the yield of aerogel particles with a particle size of 1-4 mm is 46% (cumulative particle size distribution).

[0159] The aerogel particles prepared in this embodiment have an average pore size of 48 nm, a porosity of 95.5%, and a thermal conductivity of 0.028 W / (m·K) at 25 °C.

[0160] Compared with Example 1, Comparative Example 6 showed that the low content of raw ethanol and the low content of ethanol aging liquid resulted in insufficient particle aging, poor cross-linking, poor thermal conductivity, and unstable particles.

[0161] The relevant conditions and parameters in Examples 1-4 and Comparative Examples 1-6 are shown in Table 1.

[0162] Table 1

[0163] As can be seen from the various embodiments, the aerogel particles prepared by the present invention have uniform particle size distribution and density, and the yield (cumulative particle size distribution) of particles with a particle size of 1-4 mm can reach more than 75%. The particle size distribution is controllable and the mechanical strength is high.

[0164] Therefore, this invention can be applied to thermal insulation materials, especially to the field of building mortar. In application, aerogels with different density and particle size distribution indices are added to the mortar to achieve controllable mortar specific gravity, reduce its thermal conductivity, and enhance the thermal insulation performance of the mortar.

[0165] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing aerogel particles, characterized in that, Includes the following steps: (1) Mixing raw materials: Mix silicon source, modifier, alcohol reagent and water to form mixture A; the content of alcohol reagent is 50% to 70% of the total mass of raw materials; (2) Adding a catalyst: Adding a catalyst to the mixture A to form mixture B; (3) Gel aging: The mixture B is subjected to gel aging; the gel temperature is 20-35℃ and the gel humidity is 30%-60%RH. (4) Granulation: Granulation is carried out when the gel hardness value is 20-70F; the crushing method of granulation includes vibration crushing; The vibration frequency is 1200–1600 r / min, and the vibration amplitude is 0.5–5 mm; (5) Aging: The granulated gel particles are added to an alcohol aging solution for aging; the mass of the alcohol aging solution is 60% to 80% of the total mass of the granulated gel. (6) Drying: The aged gel particles are dried by supercritical ethanol to form aerogel particles.

2. The preparation method according to claim 1, characterized in that, In the supercritical drying process of ethanol, the volume of ethanol occupies 30% to 50% of the space in the drying vessel.

3. The preparation method according to claim 1, characterized in that, In the granulation step, the gel is placed on a 5-mesh vibrating screen for crushing; Preferably, the feeding space accounts for 40% to 60% of the total space during the vibration crushing process.

4. The preparation method according to claim 1, characterized in that, The method for monitoring the hardness of the gel is to test the hardness at 5 to 15 points on the gel plane and take the average value as the hardness value.

5. The preparation method according to claim 1, characterized in that, The catalyst includes ammonium salt catalysts; Preferably, the catalyst further includes ammonia; Preferably, the ammonium salt catalyst is ammonium fluoride; Preferably, the mass ratio of ammonium fluoride to mixture A is 1:(100-230); the mass ratio of ammonia to mixture A is 1:(100-230); Preferably, in the catalyst addition step, ammonium fluoride and ammonia are added sequentially to the mixture A while it is being stirred; Preferably, the mass ratio of the silicon source, modifier, alcohol reagent, and water is 1:(0.5-2):(5-7):(0.5-1.5). Preferably, the silicon source includes one or more of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, and polysiloxane. The modifier includes one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, vinyltrichlorosilane, trimethylethoxysilane, hexamethyldisilazane, and hexamethyldisiloxane. The alcohol reagents include one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol; The alcohol aging solution includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol.

6. The use of aerogel particles prepared by any one of claims 1 to 5 in thermal insulation materials.

7. The use according to claim 6, characterized in that, The aerogel particles are used to prepare building mortar.

8. An aerogel particle prepared by the preparation method according to any one of claims 1 to 5.

9. The aerogel particles according to claim 8, characterized in that, The mass percentage of the aerogel particles with a diameter of 1–4 mm is ≥75%. And / or, the average pore size of the aerogel particles is 26–35 nm; And / or, the thermal conductivity of the aerogel particles is <0.02 W / (m·K).

10. The aerogel particles according to claim 8 or 9, characterized in that, The cumulative particle size distribution values ​​of the aerogel particles are D10 (0.89–2.29 mm), D50 (2.71–3.28 mm), and D90 (4.18–4.30 mm).

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