An aerogel geopolymer foamed thermal insulation material and its preparation method

Abstract

This invention relates to an aerogel geopolymer foamed insulation material and its preparation method, comprising the following steps: mixing and stirring a silica-alumina base material with an alkali activator until a viscous slurry that no longer releases heat; opening a closed mixer and starting its internal rotor, then pouring the viscous slurry into the closed mixer, then closing the closed mixer, then opening the feed inlet to add silica aerogel, and continuing to mix; transferring the mixed material to a foaming tank, then adding a foaming agent and stirring evenly, then covering, foaming, and curing for more than 1 day until it can be demolded, then demolding and curing to obtain the aerogel geopolymer foamed insulation material; the porous insulation material obtained by the method of this invention is hydrophobic both inside and out, which not only prevents alkali efflorescence inside and outside the material, but also improves the insulation performance of the aerogel geopolymer foamed insulation material.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology, specifically to a geopolymer foam material with added aerogel. Technical Background

[0002] Alkali-activated cementitious materials, also known as "geopolymers," are cementitious materials similar to cement, obtained by chemically reacting silica-alumina raw materials (such as volcanic ash, fly ash, metakaolin, etc.) with strong alkalis (usually alkali metal hydroxides or silicates). Inorganic lightweight foam materials, made by introducing air bubbles into cementitious materials, possess characteristics such as high porosity, fire resistance, water resistance, and high strength, and can be used in building insulation, fireproofing, and sound insulation. Patent number CN 114249561 B, entitled "A Geopolymer Foamed Cement Insulation Material and its Preparation Method," proposes using waste incineration bottom ash as the foaming raw material, along with silica-alumina-rich raw materials, magnesium-based ingredients, alkali activators, thickeners, and foam stabilizers, to produce an insulation material that inhibits alkali seepage without the need for additional foaming agents. Its dry density ranges from 200 to 450 kg / m³. 3 The compressive strength is 2.5–4.8 MPa, and the thermal conductivity is 0.100–0.130 W / (m·K). Patent number: CN 112390576 A, patent name: High-strength, highly hydrophobic porous geopolymer insulation material based on potassium titanate whisker modification, its preparation method, and application. This invention involves mixing fly ash, metakaolin, and potassium titanate whiskers in a specific ratio, adding an alkali activator, foaming agent, and foam stabilizer, and stirring until a slurry is obtained. After foaming and curing, a porous geopolymer semi-finished product is obtained. The porous geopolymer semi-finished product is then immersed in a hydrophobic modifier solution for modification, removed, and dried. The resulting insulation material exhibits a compressive strength as high as 6.41 MPa, a thermal conductivity as low as 0.043 W / m·K, and a static water contact angle above 150°. Both patents aim to improve the lifespan of materials and maintain their thermal insulation performance by inhibiting alkali seepage or providing hydrophobic protection. However, patent CN114249561 B has a high thermal conductivity and offers no advantage in thermal insulation performance when used in buildings. On the other hand, patent CN 112390576 A only forms hydrophobicity on the surface, and alkali seepage is very likely to occur inside when the surface is damaged.

[0003] Silica aerogel is a very lightweight and porous material with excellent thermal insulation properties, low density, high surface area, and excellent chemical stability. This unique property makes it widely applicable in various fields, including thermal insulation materials, energy storage technology, oil stain removal, biomedicine, and catalysts. Silica aerogel possesses the following important characteristics and applications: 1. Low density: Silica aerogel has a very low density, typically between 0.1 and 0.3 g / cm³, making it ideal for lightweight materials. Due to its low density, it can reduce the weight of structural components without increasing the load, such as for insulation materials in space probes and aircraft. 2. Excellent thermal insulation: Silica aerogel has excellent thermal insulation properties, effectively isolating heat. This makes it widely used as an insulation material in construction, energy storage and transmission systems, and refrigeration equipment. It can also be used to develop ultra-insulated windows and solar water heating systems. 3. High surface area: Silica aerogel has an extremely high surface area, typically between 600 and 1000 m² / g. This makes it highly effective for adsorbing gases, liquids, and solutes. Therefore, it is useful in applications such as chemical separation, adsorption refrigeration, and water treatment. 4. Chemical Stability: This aerogel material exhibits high stability in most chemical environments, making it suitable for applications as a catalyst and adsorbent. It can also be used to adsorb oil, organic pollutants, and heavy metals, thus finding wide application in environmental protection. 5. Biomedical Applications: Due to its low toxicity and high surface area, silica aerogels are also used in the biomedical field for applications such as drug delivery, tissue engineering, and biosensors.

[0004] When geopolymer foam materials are used for building insulation, preventing alkali permeability and improving insulation performance are urgent problems to be solved. Although silica aerogel materials have many advantages such as those mentioned above, directly adding aerogel powder to geopolymer foam materials may not be able to be incorporated during normal stirring. As a result, the powder may float on the surface of the colloid due to its light weight and hydrophobicity, or it may be completely or largely depolymerized and become ineffective. Summary of the Invention

[0005] This invention provides an aerogel geopolymer foamed insulation material and its preparation method. The method of this invention controls the partial depolymerization of aerogel by using a closed mixer to mix aerogel powder or particles into a colloid without adding a foam stabilizer. This results in a small amount of aerogel being depolymerized while a large amount remains in the system. The resulting porous insulation material is hydrophobic both inside and out, which not only prevents alkali efflorescence inside and outside the material but also improves the insulation performance of the aerogel geopolymer foamed insulation material.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing an aerogel geopolymer foamed thermal insulation material includes the following steps:

[0008] 1. Mix the silicon-aluminum base material with the alkali activator and stir for 20-120 minutes until a viscous slurry that no longer releases heat is formed;

[0009] 2. Open the closed mixer and turn on its internal rotor. Then pour the viscous slurry obtained in step 1 into the closed mixer. Next, close the closed mixer and open the feed port to add silica aerogel. After adding, continue to mix for 20-25 minutes.

[0010] 3. Transfer the material after mixing in step 2 to a foaming tank, then add foaming agent and stir evenly. Next, pour the evenly stirred material into a mold and cover the outer surface of the material with a film. Then, place the filmed material in an environment of 20-75℃ to foam and cure for more than 1 day until it can be demolded. Then demold and cure at room temperature for 2-7 days to obtain the aerogel geopolymer foamed thermal insulation material.

[0011] The mass ratio of the silicon-aluminum base material, alkali activator, silica aerogel and foaming agent is 40-50:40-48:0.5-3 parts:4-8 parts.

[0012] Furthermore, during step one, the slurry is cooled by circulating water outside the container while stirring. (This is to prevent the heat generated during alkali activation from accelerating colloid coagulation; therefore, water circulation cooling is used during alkali activation.)

[0013] Furthermore, the rotational speed inside the closed mixing mill is between 30-40 rpm, and the pressure is between 0.6-0.8 MPa.

[0014] Furthermore, the silicon-aluminum base material is one or more of metakaolin and fly ash in any proportion, with a silicon-aluminum ratio of 1:0.8-1:2 and a total silicon-aluminum content of more than 70%.

[0015] Furthermore, the alkaline activator is one or more of the following in any proportion: aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, potassium silicate, sodium silicate, and lithium silicate.

[0016] Preferably, the molar concentrations of sodium hydroxide and potassium hydroxide in the sodium hydroxide solution and potassium hydroxide solution are 3-10 mol / L; and the moduli of potassium silicate, sodium silicate, and lithium silicate are 1.5-3.5.

[0017] Furthermore, the silica aerogel is an inorganic silica aerogel in the form of aerogel powder or particles. It can participate in partial depolymerization.

[0018] Furthermore, the foaming agent is an aqueous solution of hydrogen peroxide, with a hydrogen peroxide mass percentage of 25%-30%. (As a foaming agent, the foaming environment temperature is 20-75℃, and the viscosity of the mixed slurry is greater than 1000cp. To prevent cracking caused by excessive heat loss due to high temperature, a film coating or wet curing is used.)

[0019] This invention introduces aerogel powder or particles into a geopolymer system through formulation exploration and a closed-loop mixing machine. By adjusting process parameters, the aerogel undergoes partial depolymerization, participating in the co-condensation of silicon-oxygen-aluminum-oxygen bonds after the depolymerization of metakaolin. This results in the uniform distribution of undepolymerized aerogel on the surface of the depolymerized body, leading to a fully hydrophobic foamed insulation material after foaming and drying. The material is hydrophobic both inside and outside the foam pores, preventing efflorescence caused by moisture. Simultaneously, the aerogel distributed inside and outside the pores significantly reduces its thermal conductivity, improving insulation performance. The aerogel powder is uniformly distributed inside and outside the foam pores in this system, preventing powder shedding during use and ensuring the long-lasting insulation performance of the material.

[0020] This solution does not require the addition of a foam stabilizer. The aerogel powder is silica aerogel, which can stabilize the bubbles during foaming and prevent small bubbles from agglomerating into large bubbles.

[0021] Compared with the prior art, the present invention has the following significant advantages: (1) The production cycle of the aerogel geopolymer foaming material in the method of the present invention is short and the process is simple. (2) The aerogel powder in the geopolymer can stabilize the bubbles and make the bubble size more uniform, without the need to add an additional foam stabilizer. (3) The aerogel geopolymer foaming material obtained has strong hydrophobicity and is hydrophobic inside and out, and will not cause efflorescence due to moisture absorption. (4) The aerogel geopolymer foaming material obtained has low thermal conductivity (0.035W / m·K) and high strength (compressive strength 1.7MPa, tensile bond strength 0.6MPa), and has obvious market advantages. Attached Figure Description

[0022] Figure 1 This is a diagram showing the water droplets at the interface after water is sprayed inside the aerogel geopolymer foamed insulation material prepared in Example 1.

[0023] Figure 2 This is a 6.3x magnified view of the interior of the aerogel geopolymer foamed insulation material prepared in Example 1.

[0024] Figure 3 This is an internal view of the aerogel geopolymer foamed insulation material prepared in Example 2.

[0025] Figure 4 This is a 6.3x magnified view of the interior of the aerogel geopolymer foamed insulation material prepared in Example 2. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of the invention.

[0027] Example 1

[0028] A method for preparing an aerogel geopolymer foamed thermal insulation material includes the following steps:

[0029] 1. Mix the silicon-aluminum base material with the alkali activator and stir for 20 minutes until a viscous slurry that no longer releases heat is formed;

[0030] 2. Open the closed mixer and turn on its internal rotor. Then pour the viscous slurry obtained in step 1 into the closed mixer, close the closed mixer, then open the feed port and add silica aerogel. After adding, continue to mix for 20 minutes.

[0031] 3. Transfer the material after mixing in step 2 to a foaming bucket, then add foaming agent and stir evenly. Next, pour the evenly stirred material into a mold and cover the outer surface of the material with a film. Immediately place the filmed material in a 50°C environment for foaming and curing for 24 hours until it can be demolded. Then demold and cure at room temperature for 7 days to obtain the aerogel geopolymer foamed insulation material.

[0032] In step one, the slurry is cooled with circulating water while stirring. (This is to prevent the heat generated during alkali activation from accelerating colloid coagulation; therefore, water circulation cooling is performed during alkali activation.)

[0033] The internal speed of the closed mixing mill is 30 rpm and the pressure is 0.6 MPa.

[0034] The aforementioned silicon-aluminum base material is one or more of metakaolin and fly ash, with a silicon-aluminum ratio of 1:0.8-1:2 and a total silicon-aluminum content of over 70%. The specific formulation is shown in Table 1. Specifically, the metakaolin has a silicon-aluminum ratio of 1:2 and a silicon-aluminum content of 98%; the fly ash has a silicon-aluminum ratio of 2:1 and a silicon-aluminum content of 73%.

[0035] The alkaline activator is one or more of the following in any proportion: sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, potassium silicate, sodium silicate, and lithium silicate. Specific formulations are shown in Table 1.

[0036] The sodium hydroxide solution concentration is 8 mol / L; the modulus of sodium silicate and potassium silicate is 2.

[0037] The silica aerogel is an inorganic silica aerogel, consisting of aerogel powder or particles. It can participate in partial depolymerization.

[0038] The foaming agent is an aqueous solution of hydrogen peroxide, with a hydrogen peroxide content of 25% by mass. (It is used as a foaming agent in environments with a foaming temperature of 20-75℃ and a slurry viscosity greater than 1000 cp. To prevent cracking due to excessive heat loss at high temperatures, a film coating or wet curing method is adopted.)

[0039] The mass ratio of the silicon-aluminum base material, alkali activator, silica aerogel, and foaming agent is 40-50:40-48:0.5-3 parts:4-8 parts. Specifically, Examples 1-7 and Comparative Examples 1-2 of the present invention are all made using the above-mentioned raw materials and the above-mentioned preparation method. The difference lies in the different amounts of raw materials added and some different components in each example, as detailed in Table 1.

[0040]

[0041]

[0042] Comparative Example 3: The same formula as Example 7 was used, except that the aerogel was mixed using a JJ-5 planetary cement mortar mixer instead of an internal mixer. The specimens obtained in Comparative Example 3 had an average pore size of 0.83 mm, a compressive strength of 0.52 MPa, a hydrophobic angle of 125° on the top surface and 45° inside after cutting, and a thermal conductivity of 0.057 W / m·K.

[0043] Based on the comparison of the seven different embodiments and comparative examples in Table 1, the following conclusions can be drawn: all embodiments added aerogel powder or particles; the comparative examples, which were common and did not contain aerogel, were not hydrophobic; and all embodiments exhibited hydrophobicity, with a significant reduction in thermal conductivity. Figure 1 and Figure 2 It can be seen that the foam has abundant pores, and the internal cross-section has strong hydrophobicity. The pore size can be observed under a microscope. Figure 3 , Figure 4 Geopolymer foaming with added aerogel powder or particles results in more uniform pore size, with aerogel powder evenly distributed on the inner wall of the pores.

[0044] Comparative studies of Examples 1-4 revealed that, using different matrices, aside from the appearance being more kaolin-like (white or orange) and fly ash (blackish-gray), the kaolin-like matrix exhibited denser pores and a lower thermal conductivity. Comparative studies of Examples 1-2 and 3-4 showed an increase in aerogel powder content and a larger hydrophobic angle; when the addition amount reached 3%, superhydrophobicity was achieved. Increasing the foaming agent content from 5.5% to 8% resulted in larger bubble pores. Simultaneously, fly ash required a higher liquid-to-solid ratio.

[0045] Comparing Examples 5-7, it was found that changing the alkali activator and using sodium silicate or potassium silicate resulted in smaller pore sizes compared to using sodium hydroxide as the alkali activator. Example 7, which mixed two raw materials and two alkali activators, and added aerogel particles, produced beneficial effects. However, it also exhibited uneven aerogel distribution and particle breakage, with larger, intact aerogel particles embedded within the voids.

[0046] Comparative Examples 1 and 2, regardless of whether they used one or multiple alkali activators, failed to produce a hydrophobic effect, remaining wet after water spraying. Their thermal conductivity coefficients were 0.068 and 0.085, respectively, failing to demonstrate excellent thermal insulation performance. This shows that aerogel plays a crucial role in both hydrophobicity and thermal insulation. Comparative Example 3, which did not use a mixer to mix the aerogel, resulted in an uneven distribution of hydrophobicity in the foamed product, making it impossible to obtain a uniform insulation board.

[0047] Example 8

[0048] The same formula as in Example 1 is used, except that...

[0049] A method for preparing an aerogel geopolymer foamed thermal insulation material includes the following steps:

[0050] 1. Mix the silicon-aluminum base material with the alkali activator and stir for 80 minutes until a viscous slurry that no longer releases heat is formed;

[0051] 2. Open the closed mixer and turn on its internal rotor. Then pour the viscous slurry obtained in step 1 into the closed mixer. Next, close the closed mixer and open the feed port to add silica aerogel. After adding, continue to mix for 22 minutes.

[0052] 3. Transfer the material after mixing in step 2 to a foaming tank, then add a foaming agent and stir evenly. Next, pour the evenly stirred material into a mold and cover the outer surface of the material with a film. Then, place the filmed material in a 20°C environment to foam and cure for 3 days until it can be demolded. Then demold and cure at room temperature for 3 days to obtain the aerogel geopolymer foamed insulation material.

[0053] The internal rotation speed of the closed mixing mill is 35 and the pressure is 0.7 MPa.

[0054] The foaming agent is an aqueous solution of hydrogen peroxide, with a hydrogen peroxide content of 30% by mass.

[0055] This embodiment can also prepare a fully hydrophobic foamed thermal insulation material after drying. The aerogel powder in this embodiment is evenly distributed inside and outside the foam pores in the system, and will not produce powder shedding during use, thus ensuring the thermal insulation performance of the material for a long time.

[0056] Example 9

[0057] The same formula as in Example 1 is used, except that...

[0058] A method for preparing an aerogel geopolymer foamed thermal insulation material includes the following steps:

[0059] 1. Mix the silicon-aluminum base material with the alkali activator and stir for 120 minutes until a viscous slurry that no longer releases heat is formed;

[0060] 2. Open the closed mixer and turn on its internal rotor. Then pour the viscous slurry obtained in step 1 into the closed mixer. Next, close the closed mixer and open the feed port to add silica aerogel. After adding, continue to mix for 25 minutes.

[0061] 3. Transfer the material after mixing in step 2 to a foaming tank, then add a foaming agent and stir evenly. Next, pour the evenly stirred material into a mold and cover the outer surface of the material with a film. Then, place the filmed material in a 75°C environment to foam and cure for 1 day until it can be demolded. Then demold and cure at room temperature for 2 days to obtain the aerogel geopolymer foamed thermal insulation material.

[0062] The internal rotation speed of the closed mixing mill is 30 rpm and the pressure is 0.6 MPa.

[0063] The foaming agent is an aqueous solution of hydrogen peroxide, with a hydrogen peroxide content of 28% by mass.

[0064] This embodiment can also prepare a fully hydrophobic foamed thermal insulation material after drying. The aerogel powder in this embodiment is evenly distributed inside and outside the foam pores in the system, and will not produce powder shedding during use, thus ensuring the thermal insulation performance of the material for a long time.

[0065] This invention is not limited to the above embodiments. Any improvements and equivalent substitutions made based on the embodiments of this invention are within the scope of protection of this invention.

Claims

1. A method for preparing an aerogel geopolymer foamed thermal insulation material, characterized in that: Includes the following steps:

1. Mix the silicon-aluminum base material with the alkali activator and stir for 20-120 minutes until a viscous slurry that no longer releases heat is formed; 2. Open the closed mixer and turn on its internal rotor. Then pour the viscous slurry obtained in step 1 into the closed mixer. Next, close the closed mixer and open the feed port to add silica aerogel. After adding, continue to mix for 20-25 minutes.

3. Transfer the material after mixing in step 2 to a foaming tank, then add a foaming agent and stir evenly. Next, pour the evenly mixed material into a mold and cover the outer surface of the material with a film. Then, place the filmed material in an environment of 20-75℃ to foam and cure for more than 1 day until it can be demolded. Then demold and cure at room temperature for 2-7 days to obtain the aerogel geopolymer foamed thermal insulation material. The mass ratio of the silicon-aluminum base material, alkali activator, silica aerogel and foaming agent is 40-50 parts: 40-48 parts: 0.5-3 parts: 4-8 parts.

2. The method for preparing an aerogel geopolymer foamed thermal insulation material according to claim 1, characterized in that: In step one, while stirring, the slurry is cooled by circulating water outside the container.

3. The method for preparing an aerogel geopolymer foamed thermal insulation material according to claim 1, characterized in that: The internal speed of the closed mixing mill is between 30-40 rpm, and the pressure is between 0.6-0.8 MPa.

4. The method for preparing an aerogel geopolymer foamed thermal insulation material according to claim 1, characterized in that: The silicon-aluminum base material is one or more of metakaolin and fly ash in any proportion, with a silicon-aluminum ratio of 1:0.8-1:2 and a total silicon-aluminum content of more than 70%.

5. The method for preparing an aerogel geopolymer foamed thermal insulation material according to claim 1, characterized in that: The alkaline activator is one or more of the following: sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, potassium silicate, sodium silicate, and lithium silicate, mixed in any proportion.

6. The method for preparing an aerogel geopolymer foamed thermal insulation material according to claim 5, characterized in that: The molar concentrations of sodium hydroxide and potassium hydroxide in sodium hydroxide and potassium hydroxide solutions are 3-10 mol / L; the moduli of potassium silicate, sodium silicate, and lithium silicate are 1.5-3.

5.

7. The method for preparing an aerogel geopolymer foamed thermal insulation material according to claim 1, characterized in that: The silica aerogel is an inorganic silica aerogel, which is an aerogel powder or granules.

8. The method for preparing an aerogel geopolymer foamed thermal insulation material according to claim 1, characterized in that: The foaming agent is an aqueous solution of hydrogen peroxide with a mass percentage of 25%-30%.

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