Composite thermal insulation material and preparation method and application thereof

Abstract

The application relates to a composite thermal insulation material and a preparation method and application thereof, and belongs to the technical field of building thermal insulation materials. The preparation method comprises the following steps: soaking a three-dimensional fabric in a PVA aqueous solution, adding a sodium silicate aqueous solution and a calcium chloride aqueous solution, until the solution changes from transparent to milk white to complete the generation of calcium silicate nanoparticles; continuously adding SiO2 aerogel powder paste to the mixed solution, and the adding amount is not more than 20% of the mass of the mixed solution; freezing the three-dimensional fabric and the mixed solution together in a mold to form; finally, freezing drying is performed to obtain the composite thermal insulation material; the mass ratio of the PVA aqueous solution, the Na2SiO3 aqueous solution and the CaCl2 aqueous solution is 1:(0.5-2):(0.5-2). The composite thermal insulation material has the advantages of light weight, heat preservation, fire prevention and the like, the preparation process is simple, the raw materials are cheap and easy to obtain, and the composite thermal insulation material has good market competitiveness.

Description

Technical Field

[0001] This application relates to a composite thermal insulation material, its preparation method, and its application, belonging to the technical field of building thermal insulation materials. Background Technology

[0002] With the rapid development of the global economy, energy consumption and environmental pollution have become increasingly prominent issues. Data shows that approximately 40% of global energy consumption comes from building operations, with HVAC systems accounting for the largest share of energy consumption. In the building envelope, heat loss from walls and roofs alone accounts for 40% of the total heat transfer. Against this backdrop, efficient, environmentally friendly, and sustainable materials have become a research hotspot.

[0003] Therefore, the development of high-efficiency thermal insulation functional materials is of great value in promoting the green transformation of the construction industry. It is necessary to develop new building materials with lightweight, high strength and excellent thermal insulation performance.

[0004] The prior art CN113683812A discloses the preparation of fiber aerogels using electrospinning and freeze-drying technology, but it has problems such as long preparation cycle, low yield, and insufficient fire resistance. The spinning process is complex, costly, and has relatively low production efficiency.

[0005] The prior art CN117362742B discloses a method for preparing starch-based aerogel insulation material by using polymeric siloxane derivatives as polymeric crosslinking monomers to chemically crosslink with corn starch and then performing freeze-drying processes. However, this method has problems such as complex synthesis process, high difficulty, low yield, and insufficient fire resistance.

[0006] The prior art CN119978531B discloses a sandwich-structured bio-based composite nanofiber aerogel material, in which the added MXene material is expensive, difficult to operate experimentally, and the material itself has insufficient fire resistance.

[0007] Therefore, it is necessary to provide a new type of flame-retardant, heat-insulating, lightweight composite insulation material that has a simple production process, low production cost, and good performance to meet the current market demand for cost-effective insulation materials. Summary of the Invention

[0008] To address the aforementioned issues, a composite thermal insulation material, its preparation method, and its application are provided. The material is composed of polyvinyl alcohol (PVA), sodium silicate (Na2SiO3), fiber fabric, calcium chloride (CaCl2), and silica (SiO2) aerogel powder paste. First, a precursor for the thermal insulation material is prepared. Then, freeze-drying technology is used to prepare the composite thermal insulation material, which exhibits excellent properties such as light weight, thermal insulation, and fire resistance. Furthermore, the preparation process is simple, and the raw materials used are inexpensive and readily available, giving it good market competitiveness.

[0009] This application provides a method for preparing a composite thermal insulation material, characterized in that the preparation method includes the following steps: 1) Immerse the three-dimensional fabric in PVA aqueous solution, add sodium silicate aqueous solution and calcium chloride aqueous solution, until the solution changes from transparent to milky white to complete the generation of hydrated calcium silicate nanoparticles; 2) Continue to add SiO2 aerogel powder paste to the mixed solution, but the amount added shall not exceed 20% of the mass of the mixed solution; 3) Place the three-dimensional fabric and the mixed solution together in a mold and freeze-shape. 4) Finally, freeze-dry the material to obtain the composite insulation material; In step 1), the amounts of PVA, Na2SiO3, and CaCl2 used satisfy the following relationship: taking 1~5 wt% PVA aqueous solution, 1 mol / L Na2SiO3 aqueous solution, and 1 mol / L CaCl2 aqueous solution as an example, the mass ratio of PVA aqueous solution, Na2SiO3 aqueous solution, and CaCl2 aqueous solution is 1:(0.5~2):(0.5~2).

[0010] Optionally, the addition rates of the Na2SiO3 aqueous solution and the CaCl2 aqueous solution in step 1) satisfy the following relationship: taking 1~5 wt% PVA aqueous solution, 1 mol / L Na2SiO3 aqueous solution, and 1 mol / L CaCl2 aqueous solution as an example, the drop acceleration rate of the Na2SiO3 aqueous solution is 8~12 mL / min, and the drop acceleration rate of the CaCl2 aqueous solution is 8~12 mL / min.

[0011] Optionally, the freeze-drying conditions in step 4) are: temperature -40℃ to -60℃, time 36 to 72 h.

[0012] Optionally, the thickness of the three-dimensional fabric in step 1) is 0.5~3 mm.

[0013] Optionally, the amount of the SiO2 aerogel powder paste is 10-20% of the mass of the mixed solution.

[0014] Optionally, the PVA is one or more of PVA-1788, PVA-224, and PVA-117.

[0015] Optionally, the three-dimensional fabric is a knitted, machine-made, or woven fabric.

[0016] Optionally, the thermal conductivity of the composite insulation material is 0.020~0.032. It has a fire resistance rating of Class A and can withstand high temperatures of 1000℃, a compressive strength of ≥0.5 MPa, and a radiative cooling performance of 4~10℃.

[0017] This application provides a composite thermal insulation material prepared by the above-mentioned method for preparing composite thermal insulation material.

[0018] This application provides the application of the aforementioned composite thermal insulation material in building materials.

[0019] The beneficial effects of this application include, but are not limited to: 1. According to the composite thermal insulation material, its preparation method, and its application, the thermal conductivity of the provided composite thermal insulation material is 0.020~0.032. It has a fire resistance rating of Class A and can withstand high temperatures of 1000℃, a compressive strength of ≥0.5MPa, and also has radiative cooling properties, achieving a cooling effect of 4~10℃.

[0020] 2. According to the composite thermal insulation material, its preparation method and application, the provided composite thermal insulation material has excellent properties such as light weight, thermal insulation and fire resistance, and the preparation process is simple and the raw materials used are cheap and readily available, thus having good market competitiveness.

[0021] 3. According to the composite thermal insulation material, its preparation method and application, the provided composite thermal insulation material has excellent thermal insulation performance, can effectively reduce building energy consumption, thereby improving building thermal insulation performance, and can meet the market demand for cost-effective and high-performance thermal insulation materials. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a physical image of the composite thermal insulation material involved in Embodiment 1 of this application; Figure 2 These are microscopic morphology images (scale bar 100 μm) at different magnifications related to Example 1 of this application. Figure 3 These are microscopic morphology images (scale bar 50 μm) at different magnifications related to Example 1 of this application. Figure 4 This is a diagram of the radiation cooling test scenario involved in this application. Detailed Implementation

[0023] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments. Unless otherwise specified, the raw materials and reagents in the embodiments of the present application are all purchased through commercial channels.

[0024] The applicant's prior research has already covered the solutions in CN120041956A and CN120736873A. In order to address the demand for cost-effective and high-performance thermal insulation materials in the prior art, it is necessary to optimize the preparation process and material selection of thermal insulation materials. The primary goal of this application is to prepare high-performance thermal insulation materials through a simple preparation process.

[0025] Therefore, this application proposes a solution to directly mix PVA aqueous solution, sodium silicate and calcium chloride aqueous solution, aerogel powder and three-dimensional fabric, and freeze-dry to form a multi-level microporous structure, thereby giving the material excellent thermal insulation performance. The protective effect of inorganic calcium silicate gives the material fire-retardant properties, while the presence of aerogel powder gives the material additional radiative cooling properties.

[0026] The preparation process of this application is simple, the raw materials are readily available and inexpensive, and the prepared products have excellent performance, diverse functions, and strong market competitiveness. The following specific embodiments illustrate this application.

[0027] Example 1 1) Solution preparation and in-situ synthesis To prepare a 3% PVA aqueous solution, dissolve 3 g of PVA in the corresponding mass of deionized water, stir at 80℃ for 2 h until completely dissolved, and then let stand at room temperature for 12 h to allow the solution to return to room temperature. The PVA type is PVA-1788 (Shanghai Aladdin Biochemical Technology Co., Ltd.). A three-dimensional fabric with a preset thickness is cut into the corresponding size and shape and immersed in the prepared PVA aqueous solution. The three-dimensional fabric is a knitted fabric with a thickness of 1.5 mm. The size and shape of the cut fabric match the inner cavity size of the polytetrafluoroethylene mold used later. In situ synthesis of hydrated calcium silicate nanoparticles was carried out in a PVA aqueous solution after the fabric was soaked. First, a sodium silicate aqueous solution and a calcium chloride aqueous solution with a concentration of 1 mol / L were prepared. Then, a predetermined mass of 1 mol / L sodium silicate aqueous solution was slowly added to the PVA aqueous solution. Subsequently, a predetermined mass of 1 mol / L calcium chloride aqueous solution was slowly added dropwise to the above composite solution until the solution changed from transparent to milky white, thus completing the generation of hydrated calcium silicate nanoparticles. The mass ratio of PVA, Na2SiO3 and CaCl2 in the solution was 1:1:1. The slow addition rate of sodium silicate aqueous solution was 10 mL / min, and the slow dropping rate of calcium chloride aqueous solution was 10 mL / min. Add SiO2 aerogel powder paste (Shanghai Cixin New Materials Co., Ltd., water-based paste, powder solid content 15%) to the obtained mixed solution, wherein the amount of SiO2 aerogel powder paste added is 10% of the mass of the mixed solution; 2) Freeze-forming and drying Pour the solution obtained above along with the fabric into a polytetrafluoroethylene mold with aluminum foil at the bottom. Then place the mold in a foam box with liquid nitrogen at the bottom and let it stand for 10 minutes to complete the freeze-forming process. The frozen-formed sample was transferred to a freeze dryer, which was set to -50°C for 48 hours. After the ice crystals in the sample sublimated and the solid particles were further solidified, the composite insulation material was obtained.

[0028] like Figure 1 , Figure 2 and Figure 3 The images shown are a physical picture of the composite insulation material and magnified views at different magnifications.

[0029] Example 2 1) Solution preparation and in-situ synthesis To prepare a 1% PVA aqueous solution, 1 g of PVA was dissolved in the corresponding mass of deionized water, stirred at 80°C for 2 h until completely dissolved, and then allowed to stand at room temperature for 12 h to allow the solution to return to room temperature. The PVA was PVA-224 (Shanghai Aladdin Biochemical Technology Co., Ltd.). A three-dimensional fabric with a preset thickness is cut into the corresponding size and shape and immersed in the prepared PVA aqueous solution. The three-dimensional fabric is a woven fabric. The thickness of the three-dimensional fabric is 0.5 mm. The size and shape of the cut fabric match the inner cavity size of the polytetrafluoroethylene mold used later. In situ synthesis of hydrated calcium silicate nanoparticles was carried out in a PVA aqueous solution after the fabric was soaked. First, a sodium silicate aqueous solution and a calcium chloride aqueous solution with a concentration of 1 mol / L were prepared. Then, a predetermined mass of 1 mol / L sodium silicate aqueous solution was slowly added to the PVA aqueous solution. Subsequently, a predetermined mass of 1 mol / L calcium chloride aqueous solution was slowly added dropwise to the above composite solution until the solution changed from transparent to milky white, thus completing the generation of hydrated calcium silicate nanoparticles. The mass ratio of PVA, Na2SiO3 and CaCl2 solution was 1:0.5:0.5. The slow addition rate of sodium silicate aqueous solution was 8 mL / min, and the slow dropping rate of calcium chloride aqueous solution was 8 mL / min. Add SiO2 aerogel powder paste (Shanghai Cixin New Materials Co., Ltd., water-based paste, powder solid content 15%) to the obtained mixed solution, wherein the amount of SiO2 aerogel powder paste added is 5% of the mass of the mixed solution; 2) Freeze-forming and drying Pour the solution obtained above along with the fabric into a polytetrafluoroethylene mold with aluminum foil at the bottom. Then place the mold in a foam box with liquid nitrogen at the bottom and let it stand for 10 minutes to complete the freeze-forming process. The frozen-formed sample was transferred to a freeze dryer, which was set to -40°C for 36 hours. After the ice crystals in the sample sublimated and the solid particles were further solidified, the composite insulation material was obtained.

[0030] Example 3 1) Solution preparation and in-situ synthesis To prepare a 5% PVA aqueous solution, 5 g of PVA was dissolved in the corresponding mass of deionized water, stirred at 80°C for 2 h until completely dissolved, and then allowed to stand at room temperature for 12 h to allow the solution to return to room temperature. The PVA was PVA-117 (Shanghai Aladdin Biochemical Technology Co., Ltd.). A three-dimensional fabric with a preset thickness is cut into the corresponding size and shape and immersed in the prepared PVA aqueous solution. The three-dimensional fabric is a woven fabric. The thickness of the three-dimensional fabric is 3 mm. The size and shape of the cut fabric match the inner cavity size of the polytetrafluoroethylene mold used later. In situ synthesis of hydrated calcium silicate nanoparticles was carried out in PVA aqueous solution after the fabric was soaked. First, sodium silicate aqueous solution and calcium chloride aqueous solution with a concentration of 1 mol / L were prepared separately. Then, a predetermined mass of 1 mol / L sodium silicate aqueous solution was slowly added to the PVA aqueous solution. Subsequently, a predetermined mass of 1 mol / L calcium chloride aqueous solution was slowly added dropwise to the above composite solution until the solution changed from transparent to milky white, thus completing the generation of hydrated calcium silicate nanoparticles. The mass ratio of PVA, Na2SiO3 and CaCl2 solution was 1:2:2. The slow addition rate of sodium silicate aqueous solution was 12 mL / min, and the slow dropping rate of calcium chloride aqueous solution was 12 mL / min. Add SiO2 aerogel powder paste (Shanghai Cixin New Materials Co., Ltd., water-based paste, powder solid content 15%) to the obtained mixed solution, wherein the amount of SiO2 aerogel powder paste added is 20% of the mass of the mixed solution; 2) Freeze-forming and drying Pour the solution obtained above along with the fabric into a polytetrafluoroethylene mold with aluminum foil at the bottom. Then place the mold in a foam box with liquid nitrogen at the bottom and let it stand for 10 minutes to complete the freeze-forming process. The frozen-formed sample was transferred to a freeze dryer, which was set to -60°C for 72 hours. After the ice crystals in the sample sublimated and the solid particles were further solidified, the composite insulation material was obtained.

[0031] Comparative Example 1 This comparative example is basically the same as Example 1, except that it does not include the step of adding SiO2 aerogel powder paste (Shanghai Cixin New Materials Co., Ltd., water-based paste, powder solid content 15%).

[0032] Comparative Example 2 This comparative example is basically the same as Example 1, except that conventional SiO2 particles (Shanghai Aladdin Biochemical Technology Co., Ltd.) were added.

[0033] Comparative Example 3 This comparative example is basically the same as Example 1, except that the SiO2 aerogel powder paste is added at 25% of the mass of the mixed solution.

[0034] Comparative Example 4 This comparative example is basically the same as Example 1, except that the mass ratio of PVA aqueous solution, Na2SiO3 aqueous solution and CaCl2 aqueous solution is 1:3:3.

[0035] Comparative Example 5 This comparative example is basically the same as Example 1, except that the mass ratio of PVA aqueous solution, Na2SiO3 aqueous solution and CaCl2 aqueous solution is 1:0.3:0.3.

[0036] Comparative Example 6 This comparative example is basically the same as Example 1, except that the drop rate of Na2SiO3 aqueous solution is 6 mL / min and the drop rate of CaCl2 aqueous solution is 6 mL / min.

[0037] Comparative Example 7 This comparative example is basically the same as Example 1, except that the drop rate of Na2SiO3 aqueous solution is 15 mL / min and the drop rate of CaCl2 aqueous solution is 15 mL / min.

[0038] Comparative Example 8 This comparative example is basically the same as Example 1, except that the freeze-drying conditions are: temperature -30°C.

[0039] Comparative Example 9 This comparative example is basically the same as Example 1, except that the freeze-drying conditions are: temperature -70°C.

[0040] Test Example 1 The performance of the composite thermal insulation materials obtained in the examples and comparative examples was tested, and the results are shown in Table 1 below.

[0041] Thermal conductivity test: The test is conducted using a thermal conductivity meter in accordance with GB / T10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials". The lower the thermal conductivity, the better the thermal insulation performance.

[0042] Flame retardant test: The non-combustible building materials test furnace is used to conduct the test according to GB 8624 "Classification of Combustion Performance of Building Materials and Products". Building insulation materials are classified into Class A (non-combustible), Class B1 (flame-retardant), Class B2 (combustible), and Class B3 (flammable) according to their combustion performance. Class A is further divided into A1 and A2, with A1 being the best.

[0043] Compressive strength: Tested using a universal testing machine according to "GBT8813-1988-Rigid Foamed Plastics Compression Test Method". The greater the compressive strength, the stronger the ability to resist pressure deformation.

[0044] Radiative cooling: such as Figure 4 The image shows the test scenario for radiative cooling. The specific method is referenced in Breathable Dual-Mode Leather-Like Nanotextile for Efficient Daytime Radiative Cooling and Heating (DOI: 10.1002 / adma.202403223).

[0045] Table 1 Performance results of the examples and comparative examples

[0046] As shown in Table 1, the composite insulation material provided in this application possesses excellent comprehensive performance in terms of thermal conductivity, fire resistance, compressive strength, and radiative cooling, exhibiting significant performance advantages compared to the comparative scheme. Increasing the PVA concentration reduces fire resistance and increases thermal conductivity to some extent; increasing the content of sodium silicate and calcium chloride improves fire resistance and increases compressive strength within a certain range; while increasing the aerogel content reduces thermal conductivity and increases the cooling effect.

[0047] Comparative Example 1 shows an increased thermal conductivity and a poorer cooling effect; Comparative Example 2 shows a poor cooling effect; Comparative Example 3 shows excessive aerogel content, affecting molding and leading to decreased strength; Comparative Example 4 shows excessive inorganic salt content, resulting in poor molding and easy crushing; Comparative Example 5 shows insufficient inorganic salt content, leading to decreased fire resistance; Comparative Example 6 shows low preparation efficiency and causes precipitation aggregation, which is not conducive to growth on the fabric surface and freeze-drying molding; Comparative Example 7 shows a too-fast rate, resulting in rapid calcium silicate formation and large precipitate particle size, which is not conducive to growth on the fabric surface and freeze-drying molding; Comparative Example 8 shows poor freeze-forming effect and poor material microstructure, leading to poor performance; Comparative Example 9 shows excessively low temperature, resulting in freeze cracking and poor performance.

[0048] This method first prepares a precursor for the thermal insulation material, and then uses freeze-drying technology to prepare the composite thermal insulation material. During testing, researchers found that the preparation conditions of the precursor and the freeze-drying conditions significantly affected the product's performance. After repeated experiments, it was discovered that the amount and rate of addition of sodium silicate and calcium chloride aqueous solutions had a significant impact on the product's performance, affecting the microstructure of the product during in-situ growth. This impact not only on the precursor structure but also on the microstructure due to freeze-drying. Finally, through extensive experimentation and exploration, researchers determined the most effective preparation process to date. The experimental data listed above illustrate the method described in this application.

[0049] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a composite thermal insulation material, characterized in that, The preparation method includes the following steps: 1) Immerse the three-dimensional fabric in PVA aqueous solution, add sodium silicate aqueous solution and calcium chloride aqueous solution, until the solution changes from transparent to milky white to complete the generation of hydrated calcium silicate nanoparticles. The three-dimensional fabric is a knitted fabric, woven fabric or braided fabric. 2) Continue adding SiO2 aerogel powder paste to the mixed solution, wherein the amount of SiO2 aerogel powder paste is 10-20% of the mass of the mixed solution; 3) Place the three-dimensional fabric and the mixed solution together in a mold and freeze-shape. 4) Finally, freeze-drying is performed under the following conditions: temperature -40℃ to -60℃, time 36 to 72 h, to obtain the composite insulation material; In step 1), the amounts of PVA, Na2SiO3, and CaCl2 used satisfy the following relationship: taking 1~5 wt% PVA aqueous solution, 1 mol / L Na2SiO3 aqueous solution, and 1 mol / L CaCl2 aqueous solution as an example, the mass ratio of PVA aqueous solution, Na2SiO3 aqueous solution, and CaCl2 aqueous solution is 1:(0.5~2):(0.5~2); In step 1), the addition rates of Na2SiO3 aqueous solution and CaCl2 aqueous solution satisfy the following relationship: taking 1~5 wt% PVA aqueous solution, 1 mol / L Na2SiO3 aqueous solution and 1 mol / L CaCl2 aqueous solution as an example, the drop acceleration rate of Na2SiO3 aqueous solution is 8~12 mL / min, and the drop acceleration rate of CaCl2 aqueous solution is 8~12 mL / min. The thermal conductivity of the composite insulation material is 0.020~0.

032. It has a fire rating of Class A and can withstand high temperatures of 1000℃, a compressive strength of ≥0.5 MPa, and a radiative cooling performance of 4~10℃.

2. The method for preparing the composite thermal insulation material according to claim 1, characterized in that, The thickness of the three-dimensional fabric mentioned in step 1) is 0.5~3 mm.

3. The method for preparing the composite thermal insulation material according to claim 1, characterized in that, The PVA is one or more of PVA-1788, PVA-224, and PVA-117.

4. The composite thermal insulation material prepared by the method for preparing composite thermal insulation material according to any one of claims 1 to 3.

5. The application of the composite thermal insulation material as described in claim 4 in building materials.

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