Aerogel thermal insulation material and method for producing the same

Abstract

The application relates to the technical field of thermal insulation materials, and discloses an aerogel thermal insulation material and a preparation method thereof. A polysiloxane derivative containing nitrogen and phosphorus flame-retardant elements in a structure is prepared as a polymer crosslinking monomer, chemical crosslinking is carried out with corn starch, a crosslinked gel liquid is formed, and the corn starch-based aerogel thermal insulation material can be prepared through a freezing and drying process. The corn starch-based aerogel thermal insulation material prepared through the chemical crosslinking method has a uniform pore structure, has the characteristics of aerogel, and has the characteristics of good thermal insulation effect, high mechanical strength, strong hydrophobicity, excellent flame-retardant performance and the like by introducing the flame-retardant elements such as nitrogen, phosphorus and silicon and the hydrophobic Si-O bond into the aerogel structure, so that the further application of the aerogel thermal insulation material in building thermal insulation materials is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal insulation materials, and in particular to an aerogel thermal insulation material and a preparation method thereof. Background Art

[0002] As the country's requirements for building energy conservation increase, traditional insulation materials have become difficult to meet the requirements. Aerogel materials have the advantages of low thermal conductivity, low density, long service life, good thermal insulation performance, and sound insulation. They are excellent thermal insulation materials that can replace traditional insulation materials such as glass fiber and mineral wool. They can also significantly improve energy efficiency, reduce energy consumption and environmental pollution. Therefore, aerogels have broad application prospects in the field of building insulation materials. Among the many aerogels, biomass aerogels such as starch have high porosity and light texture, making them environmentally friendly aerogel insulation materials. However, starch aerogels have poor mechanical strength and are rich in hydroscopic hydroxyl groups in their structure. They easily absorb large amounts of water in humid environments, causing the pore structure to collapse and resulting in a sharp decrease in thermal insulation effect. In addition, as a polymer material, starch aerogels are also extremely prone to combustion. In the context of frequent fires in high-rise buildings, these shortcomings have had a great negative impact on the practical application of starch aerogels. Therefore, there is an urgent need to improve starch aerogels.

[0003] The invention patent with publication number CN111205483B discloses a cellulose nanocrystal water / hydrogel and its preparation method. By functionalizing the cellulose nanocrystals and utilizing the self-crosslinking effect between the modified cellulose nanocrystals or adding a small molecule crosslinking agent, a structurally stable pure cellulose nanocrystal hydrogel is obtained. After a drying process, a cellulose aerogel with high strength and modulus can be obtained. Therefore, the purpose of improving the biomass aerogel can be achieved by optimizing the preparation process of the biomass aerogel. However, this patent does not explore the application of cellulose aerogel as a thermal insulation material, and therefore does not focus on the problem of water absorption and collapse of the biomass aerogel, nor does it modify the problem of poor flame retardancy of the biomass aerogel. Therefore, its actual application in the field of thermal insulation materials is still insufficient. Summary of the Invention

[0004] The purpose of the present invention is to provide an aerogel thermal insulation material and a preparation method thereof, which solves the problems of low strength and poor flame retardancy of starch aerogel, and at the same time solves the problem that the water absorption structure of starch aerogel is easy to collapse, resulting in poor thermal insulation effect.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing an aerogel thermal insulation material comprises the following steps:

[0007] The first step is to cross-link corn starch using a polymerized cross-linking monomer to prepare a corn starch cross-linked gel solution;

[0008] Step 2: Pour the corn starch cross-linked gel solution into a mold and freeze it in a liquid nitrogen bath for 1-3 minutes to form a frozen gel solution;

[0009] Step 3: Place the frozen gel solution in a freeze dryer for freeze drying to obtain a starch-based aerogel insulation material;

[0010] The polymerized cross-linking monomer is a polymerized siloxane derivative containing nitrogen and phosphorus flame retardant elements in its structure.

[0011] As a further technical solution of the present invention, in the first step, the specific preparation method of the corn starch cross-linked gel solution is as follows:

[0012] Mix corn starch and ethanol, pour them into a reactor, and ultrasonically disperse them until a uniform dispersion is formed. Then add the polymerized cross-linking monomer and start stirring. Stir at a rate of 800-1000 r / min for 6-8 hours. Start heating until the temperature reaches 70-75°C. After keeping warm for 4-8 hours, wait for the material to cool naturally to room temperature and let it stand to defoam. Then, a corn starch cross-linked gel solution can be obtained.

[0013] In the above technical solution, the siloxane structure in the polymerized cross-linking monomer structure can be hydrolyzed under high temperature conditions to generate a Si-OH structure, and condense with the active hydroxyl group in the corn starch structure. Since both the polymerized cross-linking monomer and the corn starch structure contain multiple substituents, chemical cross-linking can occur between them, so that the corn starch forms a cross-linked network structure, and nitrogen, phosphorus, and silicon flame retardant elements are introduced into the corn starch structure to form a corn starch cross-linked gel liquid.

[0014] As a further technical solution of the present invention, the volume fraction of the ethanol is 95%.

[0015] As a further technical solution of the present invention, the mass ratio of the corn starch to the polymerized cross-linking monomer is 1:0.05-0.1.

[0016] As a further technical solution of the present invention, the preparation method of the polymerized cross-linking monomer is as follows:

[0017] N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, flame retardant DDP and tetrahydrofuran are added to the reactor, stirring is started, and after mechanical mixing is uniform, nitrogen is introduced to deoxygenate, and the condensing agent and catalyst are continued to be added and stirred evenly. The heating is started until the system temperature reaches 45-50°C, and the mixture is kept warm and stirred for 8-12 hours. After the material is naturally cooled to room temperature, the solid material is separated, washed and vacuum dried to obtain a polymerized cross-linking monomer.

[0018] In the above technical solution, under the joint action of the condensation agent and the catalyst, the primary and secondary amino groups in the N-(2-aminoethyl)-3-aminopropyltrimethoxysilane structure can react with the disubstituted active carboxyl groups in the flame retardant DDP structure, and gradually undergo chain extension polymerization to ultimately produce a polymeric siloxane derivative containing nitrogen and phosphorus flame retardant elements in its structure, namely, a polymeric cross-linking monomer.

[0019] As a further technical solution of the present invention, the mass ratio of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to the flame retardant DDP is 0.6-0.65:1.

[0020] As a further technical solution of the present invention, the condensing agent is any one of dicyclohexylcarbodiimide or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.

[0021] As a further technical solution of the present invention, the catalyst is any one of 4-dimethylaminopyridine, N-hydroxysuccinimide or 1-hydroxybenzotriazole.

[0022] As a further technical solution of the present invention, the temperature during the freeze-drying treatment is -55°C, the pressure is 1 Pa, and the time is 24-36 hours.

[0023] An aerogel thermal insulation material is prepared by adopting the above preparation method.

[0024] Beneficial effects of the present invention:

[0025] 1) This invention prepares a siloxane-based cross-linking monomer containing nitrogen and phosphorus flame retardants, which is then chemically cross-linked with corn starch. Because the cross-linking monomer contains a large number of siloxane structures, a high degree of cross-linking can be achieved with a small amount of the monomer, thereby ensuring the resulting starch aerogel possesses high mechanical strength. Furthermore, during the cross-linking reaction, the hydrophilic hydroxyl groups in the corn starch structure are largely consumed, generating Si-O bonds with a strong hydrophobic effect. This makes the resulting starch aerogel highly hydrophobic, effectively reducing the water absorption of the starch-based aerogel and avoiding the problem of decreased thermal insulation due to pore structure collapse.

[0026] 2) The polymerized cross-linked monomer structure prepared by the present invention contains nitrogen, phosphorus, and silicon, which, after chemically cross-linking with corn starch, can make the prepared starch-based aerogel structure rich in nitrogen, phosphorus, and silicon synergistic flame retardants. By adding a small amount of polymerized cross-linked monomer, the flame retardant properties of the starch-based aerogel thermal insulation material can be effectively guaranteed. In addition, the chemically cross-linked starch-based aerogel has a higher porosity and a denser pore structure, thereby further enhancing the thermal insulation effect, which is conducive to its further application in building insulation materials.

[0027] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is an infrared characterization image of the polymerized cross-linking monomer in Example 1 of the present invention;

[0030] Figure 2 This is a scanning electron microscope image of the aerogel thermal insulation material in Example 3 of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention. Example 1

[0032] Preparation of polymerized cross-linking monomers:

[0033] 0.95 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 1.5 g of flame retardant DDP and tetrahydrofuran were added to the reactor, stirred, mechanically mixed, and then nitrogen was introduced for deoxygenation. 0.5 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.1 g of N-hydroxysuccinimide were added and stirred evenly. The mixture was heated to a system temperature of 50 ° C. After stirring for 9 hours, the material was naturally cooled to room temperature, the solid material was separated, washed and vacuum dried to obtain a polymerized cross-linking monomer.

[0034] Take a sample of the polymerized cross-linked monomer, mix it with potassium bromide and press it into a pellet. Then use a Nicolet 380 Fourier transform infrared spectrometer to analyze it in the scanning range of 500-4000 cm -1 , the results are shown in Figure 1 , analysis shows that 3215cm -1 NH stretching vibration peak, 3026cm -1 The CH stretching vibration peak in the benzene ring skeleton is 1689 cm -1The C=O stretching vibration peak in the amide bond, 1583 cm -1 is the stretching vibration peak of P-Ph (benzene ring), 1231cm -1 P=O stretching vibration peak, 1095cm -1 The broad peak at is the Si-O characteristic absorption peak. Example 2

[0035] Preparation of corn starch cross-linked gel solution:

[0036] 25 g of corn starch was mixed with 80 mL of 95% by volume ethanol, poured into a reactor, and ultrasonically dispersed to form a uniform dispersion. Then, 1.5 g of the polymerized cross-linking monomer prepared in Example 1 of the present invention was added, and stirring was started. The mixture was stirred at a rate of 1000 r / min for 6 h, and heating was started until the temperature reached 70° C. After keeping the temperature for 8 h, the material was naturally cooled to room temperature and allowed to stand for defoaming to obtain a corn starch cross-linked gel solution. Example 3

[0037] A method for preparing an aerogel thermal insulation material comprises the following steps:

[0038] Step 1: Pour the corn starch cross-linked gel solution prepared in Example 2 of the present invention into a mold, place it in a liquid nitrogen bath and freeze it for 2 minutes to form a frozen gel solution;

[0039] Step 2: Place the frozen gel liquid in a freeze dryer, set the temperature to -55°C and the pressure to 1Pa, and perform freeze drying for 36 hours to obtain starch-based aerogel insulation material.

[0040] The morphology of the aerogel insulation material was observed using a NovaNanoSEM 450 scanning electron microscope. Figure 2 ,from Figure 2 It can be observed that the aerogel thermal insulation material has a three-dimensional cross-linked network structure, high porosity, and uniform pore distribution, which meets the definition of aerogel and can be used in the field of thermal insulation materials.

[0041] Comparative Example 1

[0042] A method for preparing an aerogel thermal insulation material comprises the following steps:

[0043] Step 1: Mix 25g corn starch with 80mL deionized water, and heat and stir at 95℃ for 1h to form a starch gel solution.

[0044] Step 2: After the starch gel solution is naturally cooled to room temperature, the cross-linked gel solution is poured into a mold and placed in a liquid nitrogen bath for freezing for 2 minutes to form a frozen gel solution;

[0045] Step 2: Place the frozen gel liquid in a freeze dryer, set the temperature to -55°C and the pressure to 1Pa, and perform freeze drying for 36 hours to obtain starch-based aerogel insulation material.

[0046] Performance testing

[0047] A. The specific surface area and other parameters of the aerogel thermal insulation materials prepared in Example 3 of the present invention and the comparative example were tested using a V-Sorb 4804 fully automatic specific surface area analyzer. The test results are shown in the following table:

[0048]

[0049] B. The thermal conductivity of aerogel insulation materials was tested with reference to the national standard GB / T 10294-2008; the hydrophobicity of aerogel insulation materials was tested with reference to the national standard GB / T 10299-2011; and the limiting oxygen index of aerogel insulation materials was tested with reference to the national standard GB / T 2406.2-2009. The compression performance of aerogel insulation materials was tested using a CTS-E10 universal tensile testing machine, using a 5kN sensor, a compression speed of 5mm / min, and a compression height of 60% of the original sample height. The test results are shown in the table below:

[0050]

[0051] Based on the above test results, it can be seen that the aerogel insulation material prepared in Example 3 of the present invention has a large specific surface area, and exhibits a low thermal conductivity, high hydrophobicity, good flame retardancy and mechanical strength. It has excellent overall performance and can be used as a building insulation material. The aerogel prepared in Comparative Example 1 did not use a crosslinking agent to crosslink the starch, making it difficult to form a three-dimensional crosslinked network structure. As a result, the aerogel prepared has a small specific surface area, a relatively high thermal conductivity, and poor mechanical strength. In addition, due to the presence of hydrophilic hydroxyl groups in the structure, it has poor hydrophobicity, making it difficult to avoid structural collapse caused by water absorption of the aerogel, resulting in a decrease in thermal insulation effect. In addition, since the structure does not contain flame retardant elements, the limiting oxygen index value is low, indicating that it is a flammable material.

[0052] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the skilled person in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0053] The above is only an example and illustration of the concept of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or replace them with similar ways without deviating from the concept of the application, which shall belong to the protection scope of the present application.

Claims

1. A method for preparing an aerogel thermal insulation material, characterized in that: The following steps are involved: The first step is to cross-link corn starch using a polymerized cross-linking monomer to prepare a corn starch cross-linked gel solution; Step 2: Pour the corn starch cross-linked gel solution into a mold and freeze it in a liquid nitrogen bath for 1-3 minutes to form a frozen gel solution; Step 3: Place the frozen gel solution in a freeze dryer for freeze drying to obtain a starch-based aerogel insulation material; The polymerized cross-linking monomer is a polymerized siloxane derivative containing nitrogen and phosphorus flame retardant elements in its structure; The preparation method of the polymerized cross-linking monomer is as follows: N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, flame retardant DDP and tetrahydrofuran are added to the reactor, stirred, mechanically mixed, and then nitrogen is introduced to remove oxygen. The condensing agent and catalyst are then added and stirred. The system temperature is heated to 45-50°C, and the mixture is stirred for 8-12 hours. The material is then naturally cooled to room temperature, and the solid material is separated. The solid material is washed and vacuum dried to obtain a polymerized cross-linking monomer. The mass ratio of the N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to the flame retardant DDP is 0.6-0.65:

1.

2. The method for preparing an aerogel thermal insulation material according to claim 1, characterized in that: In the first step, the specific preparation method of the corn starch cross-linked gel solution is as follows: Corn starch and ethanol are stirred and mixed, poured into a reactor, and ultrasonically dispersed to form a uniform dispersion. Then, a polymerized cross-linking monomer is added and stirring is started. After stirring at a rate of 800-1000 r / min for 6-8 hours, heating is started until the system temperature reaches 70-75°C, and the temperature is kept for 4-8 hours. After the material is naturally cooled to room temperature, it is allowed to stand for defoaming to obtain a corn starch cross-linked gel solution.

3. The method for preparing an aerogel thermal insulation material according to claim 2, characterized in that: The volume fraction of the ethanol is 95%.

4. The method for preparing an aerogel thermal insulation material according to claim 2, characterized in that: The mass ratio of the corn starch to the polymerized cross-linking monomer is 1:0.05-0.

1.

5. The method for preparing an aerogel thermal insulation material according to claim 1, characterized in that: The condensing agent is any one of dicyclohexylcarbodiimide or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.

6. The method for preparing an aerogel thermal insulation material according to claim 1, characterized in that: The catalyst is any one of 4-dimethylaminopyridine, N-hydroxysuccinimide or 1-hydroxybenzotriazole.

7. The method for preparing an aerogel thermal insulation material according to claim 1, characterized in that: In the third step, the freeze-drying treatment is performed at a temperature of -55°C, a pressure of 1 Pa, and a time of 24-36 hours.

8. An aerogel thermal insulation material, characterized in that: The method is as described in any one of claims 1 to 7.

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