A method for the production of aerogel particles that can be used in thermal insulation materials

Abstract

The application discloses a preparation method of aerogel particles for thermal insulation materials, comprising the following steps: mixing raw materials: uniformly mixing a silicon source, a modifier, an alcohol reagent and water to form a mixed solution A; adding a catalyst: adding the catalyst into the mixed solution A to form a mixed solution B; gelation: performing gelation on the mixed solution B; the gelation temperature is 20-35 DEG C, and the gelation humidity is 30%-60% RH; granulation: when the gel hardness value is 20-70 F, performing the granulation; aging: adding the granulated gel particles into an alcohol aging solution for aging; drying: performing supercritical drying on the aged gel particles to form the aerogel particles. The application monitors the granulation hardness to determine the granulation time, and the gel is not excessively pulverized or insufficiently pulverized in the granulation process under the suitable hardness; meanwhile, the gel temperature and humidity are regulated to make the gel maintain suitable elasticity, which is more favorable for obtaining more uniform aerogel particles and improving the yield of the 1-4 mm particle size particles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silica aerogel, in particular to a preparation method of aerogel particles for thermal insulation materials, and the aerogel particles prepared by the method can be particularly used in aerogel products for thermal insulation materials, such as building mortar. BACKGROUND

[0002] Silica aerogel is a kind of hydrophobic porous network structure solid material, and its products have been widely used in various fields such as building thermal insulation, oil and gas pipelines, heat pipelines, storage tanks, new energy lithium battery thermal control, etc.

[0003] Silica aerogel has excellent properties such as high temperature resistance, low density and low thermal conductivity, and is an excellent building material composite. The aerogel material with a low density (less than 80 kg / m 3 ) can reduce the specific gravity of the building mortar, reduce the building load and wall thickness, and the low thermal conductivity of the aerogel (which can be as low as below 0.021 W / (m·K)) can improve the thermal insulation performance of the building mortar. However, the existing silica aerogel products have uneven density, uncontrollable particle size distribution and low mechanical strength, which leads to poor uniformity after being compounded with building mortar, thereby restricting its application in the building field.

[0004] Generally, aerogel is manufactured by making a wet gel from a silica precursor such as water glass and TEOS, and removing the liquid components inside the wet gel without destroying its microstructure. Silica aerogel can be generally divided into three types: aerogel powder, aerogel particles and aerogel monolith. Silica aerogel powder is particularly prone to escape and is difficult to handle, while aerogel particles can simplify the handling process in different application fields and better exert the excellent performance of aerogel if they have a suitable particle size distribution. Meanwhile, aerogel particles also need a narrower particle size distribution range, so as to obtain aerogel products with better performance.

[0005] For thermal insulation materials, in some prior art, aerogel is added in the form of powder, which is prone to escape during the mixing and dispersion process, thereby reducing the content of aerogel and ultimately leading to poor thermal insulation performance of the aerogel thermal insulation material. In some other prior art, the particle size of aerogel particles is controlled within 2 mm, which to some extent solves the problems of easy floating, escaping and difficult mixing of aerogel powder, but the particle strength and elasticity are not good, and the particles are prone to pulverization, resulting in low yield and uneven distribution of large particles. Therefore, the prior art still cannot control the particle size within 1-4 mm range and ensure high yield of particles within 1-4 mm.

[0006] Therefore, there is an urgent need for a preparation method capable of making the particle size distribution of aerogel particles more uniform, and based on which the particle size of aerogel particles can be controlled and the yield of aerogel particles with a particle size of 1-4 mm can be improved. SUMMARY

[0007] The present application aims to at least partially solve one of the technical problems in the prior art, and for this purpose, the present application discloses an aerogel particle for thermal insulation material and a preparation method, by which an aerogel particle product with uniform density, controlled particle size distribution and high mechanical strength can be obtained.

[0008] The present application is realized by the following technical solutions:

[0009] The present application provides a preparation method of aerogel particles, comprising the following steps:

[0010] (1) mixing raw materials: uniformly mixing a silicon source, a modifier, an alcohol reagent and water to form a mixed solution A;

[0011] (2) adding a catalyst: adding a catalyst to the mixed solution A to form a mixed solution B;

[0012] (3) gelation: gelation aging of the mixed solution B; the gelation temperature is 20-35℃, and the gelation humidity is 30%-60% RH;

[0013] (4) granulation: when the gel hardness value is 20-70F, granulation is performed;

[0014] (5) aging: aging of the granulated gel particles in an alcohol aging solution;

[0015] (6) drying: supercritical ethanol drying of the aged gel particles to form aerogel particles.

[0016] Further, in the raw materials, the content of the alcohol reagent is 50%-70% of the total mass of the raw materials; in the aging step, the mass of the alcohol aging solution is 60%-80% of the total mass of the granulated gel; and in the supercritical ethanol drying process, the volume of ethanol accounts for 30%-50% of the space of the drying kettle.

[0017] Further, in the granulation step, the breaking method for granulation includes vibration breaking;

[0018] Preferably, the gel is placed on a 5-mesh vibrating screen for breaking;

[0019] Preferably, the vibration frequency is 1200-1600 r / min, and the vibration amplitude is 0.5-5 mm;

[0020] Preferably, the space ratio for feeding during the vibration breaking process is 40%-60%.

[0021] Further, the method for monitoring the gel hardness is that 5-15 points are tested on the gel plane, and the average value is the hardness value.

[0022] Further, the catalyst comprises ammonium salt catalysts.

[0023] Preferably, the catalyst further comprises ammonia water.

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

[0025] Preferably, the mass ratio of ammonium fluoride to mixed solution A is 1:(100-230), and the mass ratio of ammonia water to mixed solution A is 1:(100-230).

[0026] Preferably, in the step of adding catalyst, the mixed solution A is sequentially added to ammonium fluoride and ammonia water under stirring.

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

[0028] Preferably, the silicon source comprises one or more of tetraethyl orthosilicate, tetramethyl orthosilicate, tetra-n-butyl orthosilicate, tetra-isopropyl orthosilicate and polysiloxane.

[0029] The modifier comprises one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, vinyltrichlorosilane, trimethylethoxysilane, hexamethyldisilazane and hexamethyldisiloxane.

[0030] The alcohol reagent comprises one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol or tert-amyl alcohol.

[0031] The alcohol aging solution comprises one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol or tert-amyl alcohol.

[0032] The drying medium comprises one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol or tert-amyl alcohol.

[0033] The application also provides a use of the aerogel particles as described above in thermal insulation materials.

[0034] Further, the aerogel particles as described above are used for preparing building mortar.

[0035] The application has the following beneficial effects:

[0036] (1) The present application controls the distribution of particle size by gel granulation, compared with breaking and screening after drying, granulation in the gel phase can form a more uniform particle structure, while breaking after drying will produce more fine particles and powder due to the high brittleness of aerogel, resulting in uneven particle size.

[0037] The present application determines the granulation opportunity by monitoring the granulation hardness, and granulates at a suitable hardness, so that the gel is not excessively pulverized or insufficiently pulverized during the granulation process; at the same time, the gel temperature and humidity are regulated to keep the gel with suitable elasticity and processing stability, which is more conducive to obtaining more uniform aerogel particles and improving the yield of particles with a particle size of 1-4 mm (cumulative particle size distribution).

[0038] (2) The vibration parameters (vibration frequency, vibration amplitude) and the feeding space of the granulation stage can directly affect the degree of particle collision during granulation, and by optimizing the vibration parameters and the feeding space conditions, a granulation environment suitable for the aerogel particles of the alcohol environment system and the gel parameters and hardness of the present application can be obtained, reducing the damage to the particles caused by excessive collision and reducing the excessive fragmentation and cracking of the particles. The present application can further optimize the particle size distribution concentration of the aerogel particles (such as D10-D90 similar particle size) by optimizing the vibration parameters and the feeding space ratio of the granulation stage, thereby further improving the uniformity of the particle distribution and the yield of particles with a particle size of 1-4 mm (cumulative particle size distribution).

[0039] (3) The present application improves the density uniformity by controlling the gel hardness and gel parameters (temperature, humidity, etc.), and granulation aging at the target hardness can regulate the density of the aerogel, so as to obtain the relationship between the gel hardness and the aerogel density, thereby regulating the particle size of the aerogel particle density. The present application can prepare aerogel particles suitable for various scenes by precisely controlling the process parameters and comprehensively characterizing the density, and the application is wide.

[0040] (4) The aerogel particles prepared by the present application have uniform particle size distribution and uniform density, and the yield of particles with a particle size of 1-4 mm (cumulative particle size distribution) can reach more than 75%, the particle size distribution is controllable, and the mechanical strength is high.

[0041] (5) In addition, in the application of thermal insulation materials such as mortar, aerogels with different density indicators and particle size distribution indicators are added to the mortar to control the specific gravity of the mortar, reduce the thermal conductivity, and enhance the heat insulation performance of the mortar. BRIEF DESCRIPTION OF DRAWINGS

[0042] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the following drawings, in which:

[0043] Figure 1Comparison of the finished product density of the granulation for different gel hardness;

[0044] Figure 2 Particle size cumulative distribution of the finished product of aerogel particles prepared by breaking after drying in Example 1;

[0045] Figure 3 Particle size cumulative distribution of the finished product of aerogel particles prepared by breaking after drying in Example 2;

[0046] Figure 4 Scanning electron microscope image of the aerogel particles prepared in Example 1;

[0047] Figure 5 Scanning electron microscope image of the aerogel particles prepared in Example 2. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If no special description is given, the raw materials, equipment and the like involved are all raw materials, equipment that can be prepared by commercial channels or known methods; if no special description is given, the methods involved are all conventional methods. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The disclosure of the numerical value range includes all values in the entire range and the disclosure of the further subdivided range, including the endpoints and subranges given to these ranges.

[0049] The present application provides a preparation method of aerogel particles, comprising the following steps:

[0050] (1) mixing raw materials: uniformly mixing a silicon source, a modifier, an alcohol reagent and water to form a mixed solution A;

[0051] (2) adding a catalyst: adding a catalyst to the mixed solution A to form a mixed solution B;

[0052] (3) gelation: gelation aging of the mixed solution B; the gelation temperature is 20-35℃, and the gelation humidity is 30%-60% RH; more preferably, the gelation temperature is 25-30℃, and the gelation humidity is 30%-50% RH.

[0053] (4) granulation: when the gel hardness value is 20-70F, granulation is performed, i.e. the gel is broken to form gel particles; more preferably, when the gel hardness is 30-50F, granulation is performed;

[0054] (5) aging: the gel particles after granulation are added into an alcohol aging solution for aging;

[0055] (6) drying: the aged gel particles are supercritical ethanol dried to form aerogel particles.

[0056] The present application improves the density uniformity of aerogel particles by controlling the gel parameters (gel temperature, humidity) combined with monitoring the gel hardness, and the particles are aged at the target hardness, the density of the aerogel is regulated by controlling the gel hardness, so as to obtain the relationship between the gel hardness and the aerogel density, as shown in Figure 1 The particle size distribution of the aerogel is controlled by the gel granulation method, compared to the crushing and screening after drying, the granulation at the premise of hardness control in the gel stage can form a more uniform particle structure, so as to regulate the aerogel particle density and particle size; if the granulation is not controlled by hardness, the crushing after drying will produce more fine particles and powder due to the high brittleness of the aerogel, resulting in uneven particle size.

[0057] The suitable hardness can ensure that the gel particles have sufficient strength during the crushing process, avoid pulverization, and is the basic guarantee for large particle formation. While ensuring that the suitable hardness range is obtained, suitable gel temperature and humidity can make the large particles have sufficient solvent retention to ensure that the particles themselves have sufficient elasticity and processing stability, which is beneficial to maintaining the surface stability and integrity of the particles during the subsequent aging, drying, crushing and screening processes, thereby facilitating the obtaining of more uniform aerogel particle products, improving the yield (particle size cumulative distribution) of 1-4 mm particle size particles, and being beneficial to preservation.

[0058] In some embodiments, the content of the alcohol reagent in the raw material is 50% to 70% of the total mass of the raw material; in the aging step, the mass of the alcohol aging liquid is 60% to 80% of the total mass of the gel after granulation, more preferably, the aging time is 1 to 2 days; in the supercritical ethanol drying process, the volume of ethanol occupies 30% to 50% of the space of the drying kettle.

[0059] The present application further ensures the uniformity of the particle size distribution of aerogel particles and reduces the proportion of particles with too small particle size by building an alcohol system in the raw material mixing, aging and drying process and controlling the amount of alcohol in each step. In the raw material, a suitable amount of alcohol helps to form a uniform solution, thereby helping to form uniform gel particles; the surface activity of alcohol helps to form a uniform pore structure by adjusting its surface tension in the solution, and the pore structure and mechanical properties of the gel particles can be adjusted by the alcohol content. A suitable proportion of alcohol in the aging process helps to regulate the degree of polycondensation reaction, thereby reducing the shrinkage of the gel and helping to maintain the pore structure of the gel; at the same time, it can maintain the solvent retention of the particles, helping to maintain the integrity of the pores and particles; the alcoholysis reaction of alcohol in the aging process can affect the pore structure of the gel, helping to form more uniform and open pores; alcohol can prevent the aggregation of particles in the silica sol, maintain the stability of the sol, and help to form a uniform gel. A suitable proportion of ethanol in the drying process can make the gel swell appropriately and reduce the shrinkage of the gel; supercritical drying with ethanol can avoid the collapse of the pore structure caused by surface tension, helping to maintain the original pore structure of the gel, thereby obtaining aerogel with high porosity and more complete voids. Through the construction of the above alcohol environment system in the preparation process, it is beneficial to obtain aerogel particle materials with uniform porosity and stable particle size morphology, and to promote the yield improvement in the target range of particle size 1-4 mm.

[0060] In some embodiments, in the granulation step, the breaking method is vibration breaking, and the principle of vibration breaking is to make the particles smaller through the collision of the materials. The related equipment includes linear screen, vibration screen, etc. More preferably, the feeding space proportion in vibration breaking is 40%-60%; more preferably, the gel is placed on a 5-mesh vibration screen for breaking; more preferably, the vibration frequency is 1200-1600 r / min, and the vibration amplitude is 0.5-5 mm; more preferably, the vibration frequency is 1300-1500 r / min, and the vibration amplitude is 2-4 mm.

[0061] The vibration parameters (vibration frequency, vibration amplitude) and the feeding space in the granulation stage can directly affect the degree of particle collision in the granulation process. Through the optimization of the above conditions, a granulation environment more suitable for the aerogel particles under the regulation of the above alcohol environment system and gel parameters and hardness of the present application can be obtained, the damage to the particles caused by excessive collision can be reduced, and the excessive fragmentation and cracking of the particles can be reduced. The present application can further optimize the particle size distribution concentration (such as the particle size close to D10-D90) of the aerogel particles by optimizing the vibration parameters and the feeding space proportion in the granulation stage, thereby further improving the uniformity of the particle distribution and the yield of particles with particle size of 1-4 mm (cumulative particle size distribution).

[0062] In the granulation step, other breaking methods can be used as equivalent alternatives, such as shear breaking, direct granulation, extrusion breaking, etc. Among them, the principle of shear breaking is to cut the gel into small particles by physical cutting; the principle of direct granulation is to control the size and shape of the particles by the shape of the tool itself, including granulation by column tube, honeycomb, disc, etc.; the principle of extrusion breaking is to break the material by physical extrusion, and the related equipment includes a turnover plate type auger, etc.

[0063] In some embodiments, the method for monitoring the hardness of the gel is to test the hardness of 5-15 points on the gel plane and take the average value as the hardness value; more preferably, 8-10 points on the gel plane are tested for hardness, and the average value is taken.

[0064] In some embodiments, the hardness is tested by using a Shore hardness tester.

[0065] The instrument for testing hardness can use other hardness testers as equivalent alternatives, such as a Barus hardness tester, a Durometer hardness tester, or a Vickers hardness tester, etc.

[0066] In some embodiments, the silicon source includes one or more of tetraethyl orthosilicate, tetramethyl orthosilicate, tetra-n-butyl orthosilicate, tetra-isopropyl orthosilicate, polysiloxane; the modifier includes one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, vinyltrichlorosilane, trimethylethoxysilane, hexamethyldisilazane, 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; the alcohol aging liquid includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol; the drying medium includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol.

[0067] More preferably, the silicon source includes one or more of tetraethyl orthosilicate, tetramethyl orthosilicate; the modifier includes one or more of methyltrimethoxysilane, methyltriethoxysilane; the alcohol reagent includes one or more of methanol, ethanol; the alcohol aging liquid includes one or more of methanol, ethanol; the drying medium includes one or more of methanol, ethanol.

[0068] In some embodiments, the catalyst includes an ammonium salt catalyst;

[0069] Preferably, the catalyst further includes ammonia water;

[0070] Preferably, the ammonium salt catalyst is ammonium fluoride;

[0071] Preferably, the mass ratio of ammonium fluoride to mixed solution A is 1:(100-230); the mass ratio of ammonia to mixed solution A is 1:(100-230);

[0072] In some embodiments, the mass ratio of the silicon source, the modifying agent, the alcohol reagent, and water is 1:(0.5-2):(5-7):(0.5-1.5); more preferably, the mass ratio of the silicon source, the modifying agent, the alcohol reagent, and water is 1:1.5:6:1.5; 1:(1-1.8):(5.5-6.5):(1-1.5).

[0073] More preferably, in the step of adding the catalyst, the mixed solution A is added to ammonium fluoride and ammonia in sequence under stirring.

[0074] The present application uses methyl orthosilicate and ethyl orthosilicate as the silicon source. The aerogel structure formed by hydrolysis and condensation reaction is complete and the pore size distribution is uniform and reasonable, which is conducive to building a stable micro-pore structure. Methyl trimethoxysilane or methyl triethoxysilane can improve the hydrophobicity of the aerogel and affect the formation of the pore structure. Methanol or ethanol as the solvent can help the dissolution and mixing of the silicon source and the hydrophobic reagent, promote the uniform reaction, and affect the drying process of the gel, thereby further affecting the pore structure. The use of ammonium fluoride and ammonia as the composite catalyst is more conducive to the full crosslinking of the aerogel in the system of the present application and the building of a stable pore structure, promotes the stability of the aerogel particle state, and improves the reaction rate and the uniformity of the product.

[0075] In some embodiments, the preparation method further includes a step of breaking after drying. The particle size cumulative distribution value D10 of the aerogel particle finished product prepared by breaking after drying is 0.89-2.29 mm, the D50 is 2.71-3.28 mm, and the D90 is 4.18-4.30 mm.

[0076] The aerogel particles prepared by the present application have uniform particle size distribution and uniform density. The yield (particle size cumulative distribution) of the particle finished product in the 1-4 mm particle size particles can reach more than 75%, the particle size distribution is controllable, and the mechanical strength is high.

[0077] The present application also provides the use of the above aerogel particles in the preparation of thermal insulation materials.

[0078] In some embodiments of the use, the aerogel particles are used to prepare building mortar.

[0079] In order to facilitate the understanding of the aerogel particles for building mortar, the preparation method thereof, and the use thereof, the present application will be described more fully below, and the embodiments of the present application are given, but the scope of the present application is not limited thereto.

[0080] Example 1

[0081] (1) Tetraethyl orthosilicate, methyl triethoxysilane, ethanol, deionized water are mixed uniformly according to the mass ratio of 1:1.5:6:1.5 to form a mixed solution A; wherein, the tetraethyl orthosilicate is 208.3g, the methyl triethoxysilane is 312.45g, the ethanol is 1249.8g, and the deionized water is 312.45g;

[0082] (2) Two catalysts ammonium fluoride and ammonia are sequentially added to the mixed solution A under stirring to form a mixed solution B; the mass ratio of each catalyst to the mixed solution A is 1:100; the mass of the ammonium fluoride and the ammonia is 208.3g respectively;

[0083] (3) The gel temperature is controlled at 28℃ and the humidity is controlled at 45% RH for gel aging;

[0084] (4) After the gelation, the hardness is tested on the gel plane by taking 9 points with a Shore hardness tester, and the average value is taken as the hardness value; the granulation is performed after the hardness value is monitored to be 30F; the gel is placed on a 5-mesh vibrating screen for vibration crushing (with a 45% feeding space ratio), the vibration frequency is 1400r / min, and the vibration amplitude is 3mm; the gel particles after the crushing are distributed in 1-4mm.

[0085] (5) The gel particles after the granulation are added into an ethanol aging solution for aging; the mass of the ethanol aging solution is 70% of the total mass of the gel after the granulation; the gel particles are soaked for 1-day 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.

[0086] (6) The gel particles after the aging are subjected to ethanol supercritical drying to form aerogel particles; the ethanol occupies 35% of the space of the drying kettle; the temperature is raised to 260℃ at a heating rate of 65℃ / h, while the pressure is raised to 10MPa, and the temperature is kept for 2h; after the pressure is released and the temperature is lowered, the product of the application is obtained.

[0087] The dried aerogel particles are crushed, as shown in Figure 2 , the particle size distribution value D10 of the prepared aerogel particle finished product is 2.29mm, the D50 is 3.28mm, and the D90 is 4.22mm; the yield of the aerogel particle finished product with a particle size of 1-4mm is 83% (cumulative particle size distribution).

[0088] The average pore size of the aerogel particles prepared in this example is 30nm; the porosity is 98.0%; and the thermal conductivity coefficient at 25℃ is 0.015W / (m·K).

[0089] Example 2

[0090] The difference between the preparation method and Example 1 is that the granulation is performed after the hardness value is monitored to be 50F.

[0091] As shown in Figure 3 the particle size cumulative distribution value D10 of the aerogel particle finished product prepared after drying and crushing is 0.99 mm, D50 is 2.71 mm, and D90 is 4.18 mm; the yield of the aerogel particle finished product with a particle size of 1-4 mm is 80% (particle size cumulative distribution).

[0092] The average pore size of the aerogel particles prepared in this example is 26 nm; the porosity is 98.5%; and the thermal conductivity at 25°C is 0.014 W / (m·K).

[0093] Example 3:

[0094] The difference between the preparation method and Example 1 is that the gel humidity is 30% RH.

[0095] The particle size cumulative distribution value D10 of the aerogel particle finished product prepared after drying and crushing is 2.19 mm, D50 is 3.08 mm, and D90 is 4.30 mm; the yield of the aerogel particle finished product with a particle size of 1-4 mm is 81% (particle size cumulative distribution).

[0096] The average pore size of the aerogel particles prepared in this example is 28 nm; the porosity is 98.5%; and the thermal conductivity at 25°C is 0.014 W / (m·K).

[0097] Example 4:

[0098] The difference between the preparation method and Example 1 is that the ethanol in the raw material is 1100g, i.e., the tetraethyl orthosilicate, methyltriethoxysilane, ethanol, and deionized water are uniformly mixed in a mass ratio of 1:1.5:5.28:1.5 to form a mixed solution A; the mass of the ethanol aging solution is 60% of the total mass of the gel after granulation; and in the ethanol supercritical step, the ethanol occupies 25% of the drying kettle space.

[0099] The particle size cumulative distribution value D10 of the aerogel particle finished product prepared after drying and crushing is 0.89 mm, D50 is 2.58 mm, and D90 is 4.20 mm; the yield of the aerogel particle finished product with a particle size of 1-4 mm is 79% (particle size cumulative distribution).

[0100] The average pore size of the aerogel particles prepared in this example is 30 nm; the porosity is 97.0%; and the thermal conductivity at 25°C is 0.016 W / (m·K).

[0101] The above embodiments 1-4 determine the granulation time by monitoring the granulation hardness, granulate at a suitable hardness, and at the same time, control the gel temperature and humidity to keep the gel with suitable elasticity and processing stability; further optimize the particle size distribution concentration of aerogel particles by optimizing the vibration parameters of the granulation stage and the space ratio of the feeding, so as to further improve the uniformity of the particle distribution and the yield of the particles with a particle size of 1-4 mm (cumulative particle size distribution); and further ensure the uniformity of the particle size distribution of the aerogel particles and reduce the proportion of particles with a particle size that is too small by building an alcohol system in the raw material mixing, aging and drying process and controlling the amount of alcohol in each step.

[0102] The aerogel particles prepared in embodiments 1-4 have uniform particle size distribution and uniform density, and the yield of the finished aerogel particles with a particle size of 1-4 mm (cumulative particle size distribution) can reach more than 79%, the particle size distribution is controllable, and the mechanical strength is high.

[0103] Comparative example 1

[0104] The difference between the preparation method and embodiment 1 is that the aged gel particles are subjected to supercritical carbon dioxide drying.

[0105] The cumulative particle size distribution value D10 of the finished aerogel particles after drying and crushing is 0.61 mm, D50 is 3.58 mm, and D90 is 5.21 mm; the yield of the finished aerogel particles with a particle size of 1-4 mm is 50% (cumulative particle size distribution).

[0106] The average pore size of the aerogel particles prepared in this embodiment is 55 nm; the porosity is 96.1%; and the thermal conductivity coefficient at 25℃ is 0.020 W / (m·K).

[0107] Comparing comparative example 1 and embodiment 1, it can be seen that under the condition that the raw materials, aging liquid and drying environment are not a unified alcohol system, such as the drying environment in comparative example 1 is a non-alcohol system, the yield of the aerogel particles with a particle size of 1-4 mm is greatly reduced.

[0108] Comparative example 2

[0109] The difference between the preparation method and embodiment 1 is that the vibration frequency during granulation is 900 r / min and the vibration amplitude is 2 mm.

[0110] The cumulative particle size distribution value D10 of the finished aerogel particles after drying and crushing is 2.11 mm, D50 is 3.76 mm, and D90 is 5.50 mm; the yield of the finished aerogel particles with a particle size of 1-4 mm is 53% (cumulative particle size distribution).

[0111] The aerogel particles prepared in this example 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.

[0112] Comparative Example 2 shows that when the vibration frequency and amplitude are too low, the particle size distribution of the finished aerogel particles is not concentrated, and the yield of particles with a particle size of 1-4 mm is greatly reduced.

[0113] Comparative Example 3

[0114] The difference between the preparation method and Example 1 is that the gel temperature is 40°C, the gel humidity is 65% RH, and the granulation is performed after the hardness value is monitored to be 25F.

[0115] After drying and crushing, the aerogel particle finished product has a particle size cumulative distribution value D10 of 0.75 mm, a D50 of 2.44 mm, and a D90 of 3.93 mm; the yield of aerogel particles with a particle size of 1-4 mm is 66% (particle size cumulative distribution).

[0116] The aerogel particles prepared in this example 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.

[0117] Comparative Example 3 shows that when the gel temperature and humidity are too high and the hardness is too low, the system has too much water, which leads to excessive shrinkage of the particles in the subsequent steps, resulting in uneven particle size distribution of the finished aerogel particles, and a greatly reduced yield of particles with a particle size of 1-4 mm.

[0118] Comparative Example 4

[0119] The difference between the preparation method and Example 1 is that the granulation is performed after the hardness value is monitored to be 15F.

[0120] After drying and crushing, the aerogel particle finished product has a particle size cumulative distribution value D10 of 2.27 mm, a D50 of 4.23 mm, and a D90 of 6.87 mm; the yield of aerogel particles with a particle size of 1-4 mm is 71% (particle size cumulative distribution).

[0121] The aerogel particles prepared in this example 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.

[0122] Comparative Example 4 shows that when the hardness is too low, the particles are prone to adhesion, the pore distribution is uneven, and the thermal conductivity is not good.

[0123] Comparative Example 5

[0124] The difference between the preparation method and Example 1 is that the vibration crushing is at 85% of the feeding space ratio, the vibration frequency is 1000 r / min, and the vibration amplitude is 8 mm.

[0125] The particle size cumulative distribution value D10 of the aerogel particle product prepared after drying and crushing is 0.52 mm, D50 is 2.89 mm, and D90 is 4.06 mm; the yield of the aerogel particle product with a particle size of 1-4 mm is 54% (particle size cumulative distribution).

[0126] The average pore size of the aerogel particles prepared in this example is 40 nm; the porosity is 96.8%; and the thermal conductivity at 25°C is 0.021 W / (m·K).

[0127] Comparative Example 5 is compared with Example 1. Due to the excessively high amplitude, the excessively low vibration frequency, and the excessively high feeding space ratio, the collision increases, the particle crushing increases, the particle size distribution is uneven, and the thermal conductivity is not good.

[0128] Comparative Example 6

[0129] The difference between the preparation method and Example 1 is that the ethanol in the raw material is 500 g, the tetraethyl orthosilicate, methyl triethoxysilane, ethanol, and deionized water are mixed uniformly in a mass ratio of 1:1.5:2.4:1.5 to form a mixed solution 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 drying kettle space.

[0130] The particle size cumulative distribution value D10 of the aerogel particle product prepared after drying and crushing is 0.43 mm, D50 is 2.12 mm, and D90 is 3.76 mm; the yield of the aerogel particle product with a particle size of 1-4 mm is 46% (particle size cumulative distribution).

[0131] The average pore size of the aerogel particles prepared in this example is 48 nm; the porosity is 95.5%; and the thermal conductivity at 25°C is 0.028 W / (m·K).

[0132] Comparative Example 6 is compared with Example 1. The excessively low content of raw material ethanol and the excessively low content of ethanol aging solution result in insufficient aging of the particles, poor cross-linking, poor thermal conductivity, and unstable particles.

[0133] The related conditions and parameters in Examples 1-4 and Comparative Examples 1-6 are shown in Tables 1 and 2.

[0134] Table 1

[0135]

[0136] Table 2

[0137]

[0138] It can be seen from the embodiments that the aerogel particles prepared by the application have uniform particle size distribution and density, the yield (cumulative particle size distribution) of 1-4 mm particle size particles of the particles can reach more than 75%, the particle size distribution is controllable, and the mechanical strength is high.

[0139] Therefore, the application can be applied to thermal insulation materials, especially in the field of building mortar. In the application, aerogels with different density indexes and particle size distribution indexes are added to the mortar to control the specific gravity of the mortar, reduce the thermal conductivity, and enhance the heat insulation performance of the mortar.

[0140] It should be noted that the above-described embodiments are only used to explain the application and do not constitute any limitation on the application. The application has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. The application can be modified as specified within the scope of the claims of the application, and the application can be revised without departing from the scope and spirit of the application. Although the application described therein relates to specific methods, materials and embodiments, it does not mean that the application is limited to the specific examples disclosed therein, on the contrary, the application 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 evenly to form mixture A; the content of alcohol reagent is 50%~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 subjected to supercritical drying to form aerogel particles; the drying medium includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol or tert-amyl alcohol.

2. The preparation method according to claim 1, characterized in that, In the supercritical drying process, the volume of the drying medium 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.

4. The preparation method according to claim 1, characterized in that, The feeding space accounts for 40% to 60% of the total space during the vibration crushing process.

5. 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.

6. The preparation method according to claim 1, characterized in that, The catalyst includes ammonium salt catalysts.

7. The preparation method according to claim 6, characterized in that, The ammonium salt catalyst is ammonium fluoride.

8. The preparation method according to claim 6, characterized in that, The catalyst also includes ammonia.

9. The preparation method according to claim 8, characterized in that, The ammonium salt catalyst is ammonium fluoride, and the mass ratio of ammonium fluoride to mixture A is 1:(100~230); the mass ratio of ammonia water to mixture A is 1:(100~230).

10. The preparation method according to claim 8, characterized in that, In the catalyst addition step, ammonium fluoride and ammonia are added sequentially to the mixture A while it is being stirred.

11. The preparation method according to claim 1, characterized in that, The mass ratio of the silicon source, modifier, alcohol reagent, and water is 1:(0.5~2):(5~7):(0.5~1.5).

12. The preparation method according to claim 1, characterized in that, The silicon source includes one or more of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, and polysiloxane.

13. The preparation method according to claim 1, characterized in that, The modifier includes one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, vinyltrichlorosilane, trimethylethoxysilane, hexamethyldisilazane, and hexamethyldisiloxane.

14. The preparation method according to claim 1, characterized in that, The alcohol reagents include one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethylene glycol, glycerol, or tert-amyl alcohol.

15. The preparation method according to claim 1, characterized in that, 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.

16. Use of aerogel particles prepared by any one of claims 1 to 15 in thermal insulation materials.

17. The use according to claim 16, characterized in that, The aerogel particles are used to prepare building mortar.

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