Biomass aerogel / hollow glass microsphere composite material and preparation method and application thereof

Abstract

The application discloses a biomass aerogel hollow glass microsphere composite material and a preparation method and application thereof. The composite material comprises biomass aerogel and hollow glass microspheres, wherein the hollow glass microspheres are used as a main body framework, and a natural polymer material is used as a binder. The material has the characteristics of low density, low thermal conductivity, high strength, good flame retardancy (which can reach the national building material flame retardant rating A level standard), strong hydrophobicity and the like, and has good mechanical processing performance.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials, specifically to a biomass aerogel / hollow glass microsphere composite material, its preparation method, and its application. Background Technology

[0002] With rapid societal development, energy consumption is increasing, and the energy crisis is becoming increasingly apparent. Building energy consumption accounts for approximately 40% of the world's total energy consumption, and thermal insulation materials are commonly used to conserve energy. Traditional petroleum-based foams such as polyurethane and expanded polystyrene are characterized by low cost, light weight, and low thermal conductivity, making them the most common commercial thermal insulation materials. However, they are highly flammable, posing significant safety hazards. In the event of a fire, they can cause severe personal injury and property damage. Furthermore, the non-renewable nature of petroleum-based foam exacerbates the energy crisis, and environmental pollution caused by waste foam is becoming increasingly serious. Therefore, there is an urgent need to develop green and safe new thermal insulation materials.

[0003] Aerogels are a novel type of porous material characterized by high porosity, low density, and high specific surface area, resulting in extremely low thermal conductivity and potential applications in thermal insulation materials. Among inorganic aerogels, silica aerogel is the most typical. Although it possesses extremely low thermal conductivity, its high cost and poor strength limit its application in thermal insulation. Compared to inorganic aerogels, organic aerogels exhibit superior mechanical and processing properties. Biomass aerogels, in particular, benefit from the abundance of biomass substrates (such as cellulose, chitin, chitosan, and fructose) in nature, along with their environmentally friendly, non-toxic, and biodegradable characteristics, effectively addressing the non-renewable and environmental pollution issues associated with petroleum-based foams. Furthermore, the presence of numerous functional groups (such as -OH, -COOH, and -NH2) in the molecular chains of biopolymers facilitates chemical reactions and reactive modifications, giving biomass aerogels excellent reactivity during preparation. However, although the mechanical properties of pure biomass aerogels are superior to those of inorganic aerogels, their extremely low density and extremely high porosity still prevent them from achieving the required strength in practical applications. Furthermore, pure biomass aerogels are flammable and still pose a significant fire hazard.

[0004] Adding flame retardants (such as montmorillonite, sodium bicarbonate, and ammonium polyphosphate) to biomass aerogels is considered an effective way to improve their flame retardancy. However, the addition of flame retardants leads to increased thermal conductivity and decreased mechanical strength, which is detrimental to practical applications.

[0005] Therefore, providing a novel thermal insulation composite material with at least low thermal conductivity, high strength, excellent flame retardancy, suitable density, good machinability, and low cost has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To improve the above-mentioned technical problems, the present invention provides a composite material comprising biomass aerogel and hollow glass microspheres, with hollow glass microspheres as the main framework and natural polymer materials as binders.

[0007] According to an embodiment of the present invention, the hollow glass microspheres are stacked and formed using natural polymer materials as binders to form the main skeleton of the composite material.

[0008] According to an embodiment of the present invention, the composite material is an aerogel.

[0009] According to an embodiment of the present invention, the biomass aerogel is prepared from a natural polymer material. Preferably, the natural polymer material is selected from at least one of cellulose, chitin, chitosan, fructose, starch, gelatin, etc.

[0010] According to an embodiment of the present invention, the true density of the hollow glass microspheres is less than 0.5 g / cm³. 3 For example, 0.1 g / cm³ 3 0.16g / cm 3 0.2g / cm 3 0.25g / cm 3 0.3g / cm 3 0.35g / cm 3 0.4g / cm 3 0.45g / cm 3 0.5g / cm 3 The preferred concentration is 0.1–0.35 g / cm³. 3 .

[0011] According to an embodiment of the present invention, the isostatic compressive strength of the hollow glass microspheres is 1.8 to 55 MPa, such as 2 MPa, 3.5 MPa, 5.2 MPa, 7 MPa, 8 MPa, 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, 40 MPa, and 55 MPa; preferably 1.8 to 20 MPa.

[0012] According to an embodiment of the present invention, the particle size of the hollow glass microspheres is 1μm to 200μm, for example 1.5μm, 2μm, 5μm, 10μm, 20μm, 30μm, 50μm, 80μm, 100μm, 150μm, 180μm.

[0013] According to an embodiment of the present invention, the hollow glass microspheres in the composite material account for 30–96 wt% by mass, the biomass aerogel accounts for 2–68 wt% by mass, and the sum of the masses of the hollow glass microspheres and the biomass aerogel is not less than 70 wt%. For example, the hollow glass microspheres account for 60–95 wt% or 70–93 wt%, with exemplary values ​​of 60 wt%, 62.5 wt%, 65 wt%, 70 wt%, 74.1 wt%, 75 wt%, 80 wt%, 85 wt%, 86.2 wt%, 90 wt%, or 95 wt%; the biomass aerogel accounts for 2–30 wt% or 5–20 wt%, with exemplary values ​​of 3 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%; and the sum of the masses of the hollow glass microspheres and the biomass aerogel is not less than 75 wt%, 85 wt%, or 90 wt%.

[0014] According to an embodiment of the present invention, the composite material has an outer pore and an inner pore, wherein the outer pore refers to the pore formed by the gap between the aerogel and the hollow glass microsphere particles, and the inner pore refers to the internal hollow structure of the hollow glass microsphere.

[0015] In some embodiments, the total porosity of the composite material is defined by the outer and inner pores, and the total porosity of the composite material is 90-99%, preferably 95-97%, for example 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%; the total porosity is the sum of the porosity of the outer pores and the porosity of the inner pores.

[0016] According to an embodiment of the present invention, the composite material has a closed pore structure and an open pore structure.

[0017] In some embodiments, the total porosity is defined as consisting of the closed-pore structure and the open-pore structure; in this embodiment, the total porosity is equal to the sum of the closed-pore porosity and the open-pore porosity. For example, the closed-pore porosity is 15-60%, and the open-pore porosity is 35-80%. As examples, the closed-pore porosity is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 58%, 59%, or 60%; and the open-pore porosity is 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 78%, or 80%.

[0018] The aforementioned "porosity" refers to the percentage of pore volume in the total volume of the composite material.

[0019] According to an embodiment of the present invention, the composite material has one or more of the following properties, preferably having all of the following properties simultaneously:

[0020] 1) The apparent density of the composite material is 0.02–0.30 g / cm³. 3 For example, 0.04 g / cm³ 3 0.06g / cm 3 0.08g / cm 3 0.10 g / cm 3 0.12g / cm 3 0.14 g / cm 3 0.16g / cm 3 0.20 / cm 3 0.25g / cm 3 ;

[0021] 2) The compressive strength of the composite material is 0.06 to 2.0 MPa, for example 0.08 MPa, 0.10 MPa, 0.12 MPa, 0.2 MPa, 0.5 MPa, 0.6 MPa, 0.85 MPa, 1.0 MPa, and 1.5 MPa;

[0022] 3) The calorific value of the composite material is 1.8 to 6.6 MJ / kg, for example 2.0 MJ / kg, 2.2 MJ / kg, 2.5 MJ / kg, 3.0 MJ / kg, 4.0 MJ / kg, 5.0 MJ / kg, and 6.0 MJ / kg;

[0023] 4) Thermal conductivity is 0.03~0.10W / m·K, for example 0.05W / m·K, 0.055W / m·K, 0.06W / m·K, 0.065W / m·K;

[0024] 5) The composite material is flame retardant, preferably meeting the test standard for calorific value in the Class A flame retardant rating standard for building materials (according to GB / T 14402-2007 "Determination of calorific value of combustion performance of building materials and products" and conforming to the Class A rating standard in GB8624-2012 "Classification of combustion performance of building materials and products").

[0025] The present invention also provides a method for preparing the above-mentioned composite material, the method comprising the following steps: adding hollow glass microspheres and crosslinking agent sequentially to the raw material system of biomass aerogel, freezing the resulting slurry to obtain a gel, and performing vacuum freeze-drying on the gel to obtain the composite material.

[0026] According to an embodiment of the present invention, the raw material system of the biomass aerogel includes natural polymer materials, catalysts and water.

[0027] According to an embodiment of the present invention, the preparation method includes the following steps:

[0028] (1) Mix natural polymer materials with catalyst and water, add hollow glass microspheres, and then add crosslinking agent to prepare slurry;

[0029] (2) The slurry is frozen to form a gel; for example, the slurry is poured into a mold and frozen in a refrigerator to form a gel.

[0030] (3) The gel is freeze-dried under vacuum to obtain the composite material.

[0031] According to an embodiment of the present invention, the natural polymer material has the selections shown above.

[0032] According to an embodiment of the present invention, the catalyst is selected from acids, preferably inorganic acids, such as at least one selected from dilute hydrochloric acid, acetic acid, phosphoric acid, etc.

[0033] According to an embodiment of the present invention, the water is, for example, deionized water.

[0034] According to an embodiment of the present invention, the mass ratio of the natural polymer material, catalyst and water is (1-8):(0.5-2):100, for example (1-5):(0.5-1.5):100, preferably 2:1:100.

[0035] According to an embodiment of the present invention, the crosslinking agent is glutaraldehyde.

[0036] According to an embodiment of the present invention, the amount of crosslinking agent added is 0.5 to 2.0 wt% of the raw material system of the biomass aerogel, preferably 1.0 wt%.

[0037] According to an embodiment of the present invention, the hollow glass microspheres have the limitations shown above.

[0038] According to an embodiment of the present invention, the hollow glass microspheres may be purchased commercially or prepared using methods known in the art.

[0039] According to an embodiment of the present invention, the freeze-forming time is 0.5h to 6h.

[0040] According to an embodiment of the present invention, the temperature for cryogenic forming is -50 to -10°C.

[0041] According to an embodiment of the present invention, during the vacuum freeze-drying process, the freeze-drying temperature is -50 to -20°C, the freeze-drying pressure is 1 to 100 Pa, and / or the freeze-drying time is 10 to 100 hours.

[0042] The present invention also provides a hydrophobic composite material, which is a hydrophobic modification of the above-mentioned composite material.

[0043] According to an embodiment of the present invention, the hydrophobic groups in the hydrophobic composite material are provided by an organosilicon reagent. For example, the organosilicon reagent is selected from one or more of methyltriethoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, hexadecyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0044] According to an embodiment of the present invention, the hydrophobic modification is performed by modifying the composite material using the aforementioned organosilicon reagent.

[0045] According to an embodiment of the present invention, the contact angle of the hydrophobic composite material is not less than 120°, preferably not less than 125°, for example 125-170°, and also for example 127-150°.

[0046] According to an embodiment of the present invention, the other properties of the hydrophobic composite material are not significantly different from those of the above-described composite material, that is, it also has one or more of the following properties, preferably having all of the following properties simultaneously:

[0047] 1) The apparent density of the hydrophobic composite material is 0.02–0.30 g / cm³. 3 For example, 0.04 g / cm³ 3 0.06g / cm 3 0.08g / cm 3 0.10 g / cm 3 0.12g / cm 3 0.14 g / cm 3 0.16g / cm 3 0.20 / cm 3 0.25g / cm 3 ;

[0048] 2) The compressive strength of the hydrophobic composite material is 0.06 to 2.0 MPa, for example 0.08 MPa, 0.10 MPa, 0.12 MPa, 0.2 MPa, 0.5 MPa, 0.6 MPa, 0.85 MPa, 1.0 MPa, and 1.5 MPa;

[0049] 3) The calorific value of the hydrophobic composite material is 1.8 to 6.6 MJ / kg, for example 2.0 MJ / kg, 2.2 MJ / kg, 2.5 MJ / kg, 3.0 MJ / kg, 4.0 MJ / kg, 5.0 MJ / kg, and 6.0 MJ / kg;

[0050] 4) The thermal conductivity of the hydrophobic composite material is 0.03 to 0.10 W / m·K, for example, 0.05 W / m·K;

[0051] 5) The hydrophobic composite material has flame retardancy, preferably meeting the test standard for calorific value in the Class A flame retardancy rating standard for building materials (according to GB / T 14402-2007 "Determination of calorific value of combustion performance of building materials and products" and GB / T5464-2010 "Test method for non-combustibility of building materials" and conforming to the Class A rating standard in the national standard GB 8624-2012 "Classification of combustion performance of building materials and products").

[0052] The present invention also provides a method for preparing the above-mentioned hydrophobic composite material, the method comprising the following steps: modifying the composite material using an organosilicon reagent.

[0053] According to an embodiment of the present invention, the composite material is modified using an organosilicon reagent, for example, by chemical vapor deposition.

[0054] According to an embodiment of the present invention, the organosilicon reagent has the selections shown above.

[0055] According to an embodiment of the present invention, the chemical vapor deposition method uses a temperature of 50–100°C, a pressure of 100–1000 Pa, and / or a time of 1–6 h.

[0056] According to an embodiment of the present invention, the container used in the chemical vapor deposition method is a sealed, vacuum-evaporizable stainless steel or glass product.

[0057] According to an embodiment of the present invention, the amount of the organosilicon reagent is 0.1 to 2 wt% of the mass of the composite material, preferably 0.5 to 1 wt%.

[0058] According to an embodiment of the present invention, the preparation method of the hydrophobic composite material includes the following steps: placing the dried composite material in a glass vacuum desiccator, and simultaneously adding an organosilicon reagent (preferably the amount of the organosilicon reagent is 0.1-2 wt% of the mass of the composite material) and water (e.g., deionized water, preferably the amount of water is 1.5-3 times, for example, 2 times, of the organosilicon reagent), placing it in a constant temperature oven with a vacuum degree of 100-1000 Pa and a temperature of 50-100°C, reacting for 1-6 hours, and then placing it in a vacuum drying oven to dry at 60-100°C for 1-4 hours to obtain the hydrophobic composite material.

[0059] The present invention also provides the application of the above-mentioned composite materials and / or hydrophobic composite materials in the field of thermal insulation.

[0060] The present invention also provides a thermal insulation material comprising the above-mentioned composite material and / or hydrophobic composite material.

[0061] The beneficial effects of this invention are:

[0062] The composite material and hydrophobic composite material provided by this invention use hollow glass microspheres as the main framework and biomass aerogel as the binder, which allows the hollow glass microspheres to be bonded and formed. This overcomes the shortcomings of traditional inorganic thermal insulation materials, such as high density and high thermal conductivity, as well as the shortcomings of traditional organic thermal insulation materials, such as poor strength, flammability, non-degradability, and non-renewability. The material of this invention has the characteristics of low density, low thermal conductivity, high strength, good flame retardancy (meeting the national building materials flame retardancy rating Class A standard), and strong hydrophobicity, and also has good machinability.

[0063] The method provided by this invention uses natural polymer materials as raw materials for biomass aerogels. These materials are widely available, inexpensive, green, and renewable. The preparation method is simple, efficient, and time-saving, making it a highly efficient and simple preparation method. Attached Figure Description

[0064] Figure 1 The image shown is a scanning electron microscope (SEM) image of the superhydrophobic composite material product obtained in Example 1.

[0065] Figure 2 This is a scanning electron microscope (SEM) image of the superhydrophobic composite material product obtained in Example 2.

[0066] Figure 3 This is a scanning electron microscope (SEM) image of the superhydrophobic composite material product obtained in Example 3.

[0067] Figure 4 This is a scanning electron microscope (SEM) image of the superhydrophobic composite material product obtained in Example 4.

[0068] Figure 5 This is a scanning electron microscope (SEM) image of the superhydrophobic composite material product obtained in Example 5.

[0069] Figure 6 The particle size distribution diagram of the T30 hollow glass microspheres used in the example is shown. Detailed Implementation

[0070] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0071] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0072] The specifications of the hollow glass microspheres used in the following embodiments are shown in Table 1.

[0073] Table 1

[0074] T20 0.20 3.5 T30 0.30 12 T35 0.35 20

[0075] The thermal conductivity and compressive strength tests used in the following examples were obtained through the following testing methods: thermal conductivity was tested using a FOX200 (TA Instruments, USA); compressive strength was tested using a universal testing machine (Sanstech, China) (QJ 2755-1995); calorific value was tested according to GB / T 14402-2007 "Determination of Calorific Value of Combustion Performance of Building Materials and Products"; and non-combustibility was tested according to GB / T 5464-2010 "Test Method for Non-combustibility of Building Materials".

[0076] Example 1

[0077] (1) Preparation of slurry: Weigh 3.2g of chitosan and dissolve it in 160mL of 2% glacial acetic acid aqueous solution. After mixing, mechanically stir at room temperature for 1-2h until the chitosan dissolves; weigh T30 hollow glass microspheres (particle size distribution as shown in the figure) Figure 6 As shown, 8.0g of T30 hollow glass microspheres (with an isostatic compressive strength of 12MPa) were added to the solution and stirred for 0.5-1h until the microspheres were evenly mixed in the solution. During the stirring process, 1.6ml of 50% glutaraldehyde solution was slowly added dropwise until the slurry initially gelled.

[0078] (2) Preparation of cryogel: Pour the preliminary gel slurry into a mold and freeze it in a -20℃ refrigerator for 2 hours to form a cryogel.

[0079] (3) Preparation of dried gel: The frozen gel prepared above was placed in a freeze dryer, the pressure was adjusted to 20 Pa, and the time was 72 hours to obtain a completely dried chitosan aerogel / hollow glass microsphere composite material.

[0080] (4) Hydrophobic modification: The dried composite material was placed in a glass vacuum dryer, and methyltriethoxysilane (0.2 g by mass) and deionized water (0.4 g) were added at the same time. The vacuum degree was 100 Pa, and the mixture was placed in a constant temperature oven at 60 °C for 5 hours. Then it was placed in a vacuum drying oven at 80 °C for 2 hours to obtain the superhydrophobic chitosan aerogel / hollow glass microsphere composite material product.

[0081] In this embodiment, the mass fraction of the hollow glass microspheres was estimated by calculation:

[0082] Most of the water added during slurry preparation will be removed during freeze-drying, but a small amount of water may remain inside the material. Therefore, the mass fraction of hollow glass microspheres is estimated to be 8 ÷ (8 + 3.2 + 1.6) = 62.5%; the mass fraction of chitosan is estimated to be 3.2 ÷ (8 + 3.2 + 1.6) = 25.0%; and the mass of 50% glutaraldehyde solution is approximately 1.6 g.

[0083] Porosity can be estimated by calculation: In the example, the true density of T30 hollow glass microspheres is 0.30 g / cm³. 3 The packing factor is approximately 66.7%, therefore the bulk density is 0.20 g / cm³. 3 Therefore, the volume of the hollow glass microspheres is 8g ÷ 0.2g / cm³. 3 =40ml, then the estimated internal porosity is (40ml - 8.0g ÷ 2.56g / cm³). 3 ) ÷ (160ml + 40ml) = 18.44%. The estimated external porosity is (160ml - 3.2g ÷ 1.75g / cm³). 3 )÷(160ml+40ml)=79.09%; Total porosity is 18.44%+79.09%=97.52%. Among them, 2.56g / cm³ 3 The density of the hollow glass microsphere shell material is 1.75 g / cm³. 3 This represents the density of chitosan.

[0084] Example 2

[0085] (1) Preparation of slurry: Weigh 2.8g of chitosan and dissolve it in 140mL of 1% glacial acetic acid aqueous solution. After mixing, mechanically stir at room temperature for 1-2h until the chitosan is dissolved. Weigh 12.0g of T30 hollow glass microspheres and add them to the solution. Continue stirring for 0.5h until the T30 hollow glass microspheres are evenly mixed in the solution. During the stirring process, slowly add 1.4ml of glutaraldehyde solution until the slurry initially gels.

[0086] (2) Preparation of cryogel: Pour the preliminary gel slurry into a mold and freeze it in a -20℃ freezer for 2.5h to form a cryogel.

[0087] (3) Preparation of dried gel: The frozen gel prepared above was placed in a freeze dryer, the pressure was adjusted to 10 Pa, and the time was 72 hours to obtain a completely dried chitosan aerogel / hollow glass microsphere composite material.

[0088] (4) Hydrophobic modification: The dried composite material was placed in a glass vacuum dryer, and methyltrimethoxysilane (0.2 g by mass) and deionized water (0.4 g) were added at the same time. The vacuum degree was 100 Pa, and the mixture was placed in a constant temperature oven at 60 °C for 5 hours. Then it was placed in a vacuum drying oven at 60 °C for 2 hours to obtain the superhydrophobic chitosan aerogel / hollow glass microsphere composite material product.

[0089] Example 3

[0090] (1) Preparation of slurry: Weigh 2.4g of chitosan and dissolve it in 120mL of 2% glacial acetic acid aqueous solution. After mixing, mechanically stir at room temperature for 1-1.5h until the chitosan is dissolved. Weigh 16.0g of T30 hollow glass microspheres and add them to the solution. Continue stirring for 0.5h until the T30 hollow glass microspheres are evenly mixed in the solution. During the stirring process, slowly add 1.5ml of glutaraldehyde solution until the slurry initially gels.

[0091] (2) Preparation of cryogel: Pour the preliminary gel slurry into a mold and freeze it in a -22℃ refrigerator for 2 hours to form a cryogel.

[0092] (3) Preparation of dried gel: The frozen gel prepared above was placed in a freeze dryer, the pressure was adjusted to 30 Pa, and the time was 72 hours to obtain a completely dried chitosan aerogel / hollow glass microsphere composite material.

[0093] (4) Hydrophobic modification: The dried composite material was placed in a glass vacuum dryer, and methyltriethoxysilane (0.2 g by mass) and deionized water (0.4 g) were added at the same time. The vacuum degree was 100 Pa, and the mixture was placed in a constant temperature oven at 60 °C for 5 hours. Then it was placed in a vacuum drying oven at 60 °C for 2 hours to obtain the superhydrophobic chitosan aerogel / hollow glass microsphere composite material product.

[0094] Example 4

[0095] (1) Preparation of slurry: Weigh 2.0g of chitosan and dissolve it in 100mL of 1% glacial acetic acid aqueous solution. After mixing, mechanically stir at room temperature for 1-1.5h until the chitosan is dissolved. Weigh 20.0g of T30 hollow glass microspheres and add them to the solution. Continue stirring for 0.5h until the T30 hollow glass microspheres are evenly mixed in the solution. During the stirring process, slowly add 1.2ml of glutaraldehyde solution until the slurry initially gels.

[0096] (2) Preparation of cryogel: Pour the preliminary gel slurry into a mold and freeze it in a -20℃ refrigerator for 3 hours to form a cryogel.

[0097] (3) Preparation of dried gel: The frozen gel prepared above was placed in a freeze dryer, the pressure was adjusted to 20 Pa, and the time was 72 hours to obtain a completely dried chitosan aerogel / hollow glass microsphere composite material.

[0098] (4) Hydrophobic modification: The dried composite material was placed in a glass vacuum dryer, and methyltriethoxysilane (0.2 g by mass) and deionized water (0.4 g) were added at the same time. The vacuum degree was 100 Pa, and the mixture was placed in a constant temperature oven at 60 °C for 5 hours. Then it was placed in a vacuum drying oven at 60 °C for 2 hours to obtain the superhydrophobic chitosan aerogel / hollow glass microsphere composite material product.

[0099] Example 5

[0100] (1) Preparation of slurry: Weigh 1.6g of chitosan and dissolve it in 80mL of 1% glacial acetic acid aqueous solution. After mixing, mechanically stir at room temperature for 1-1.5h until the chitosan is dissolved. Weigh 24.0g of T30 hollow glass microspheres and add them to the solution. Continue stirring for 0.5h until the T30 hollow glass microspheres are evenly mixed in the solution. During the stirring process, slowly add 1.0ml of glutaraldehyde solution until the slurry initially gels.

[0101] (2) Preparation of cryogel: Pour the preliminary gel slurry into a mold and freeze it in a -20℃ refrigerator for 3 hours to form a cryogel.

[0102] (3) Preparation of dried gel: The frozen gel prepared above was placed in a freeze dryer, the pressure was adjusted to 20 Pa, and the time was 72 hours to obtain a completely dried chitosan aerogel / hollow glass microsphere composite material.

[0103] (4) Hydrophobic modification: The dried composite material was placed in a glass vacuum dryer, and methyltriethoxysilane (0.2 g by mass) and deionized water (0.4 g) were added at the same time. The vacuum degree was 100 Pa, and the mixture was placed in a constant temperature oven at 60 °C for 5 hours. Then it was placed in a vacuum drying oven at 60 °C for 2 hours to obtain the superhydrophobic chitosan aerogel / hollow glass microsphere composite material product.

[0104] Example 6

[0105] (1) Preparation of slurry: Weigh 2.0g of chitosan and dissolve it in 100mL of 2% glacial acetic acid aqueous solution. After mixing, mechanically stir at room temperature for 1-1.5h until the chitosan is dissolved. Weigh 23.0g of T35 hollow glass microspheres and add them to the solution. Continue stirring for 0.5h until the T35 hollow glass microspheres are evenly mixed in the solution. During the stirring process, slowly add 1.2ml of glutaraldehyde solution until the slurry initially gels.

[0106] (2) Preparation of cryogel: Pour the preliminary gel slurry into a mold and freeze it in a -20℃ refrigerator for 3 hours to form a cryogel.

[0107] (3) Preparation of dried gel: The frozen gel prepared above was placed in a freeze dryer, the pressure was adjusted to 20 Pa, and the time was 72 hours to obtain a completely dried chitosan aerogel / hollow glass microsphere composite material.

[0108] (4) Hydrophobic modification: The dried composite material was placed in a glass vacuum dryer, and methyltriethoxysilane (0.2 g by mass) and deionized water (0.4 g) were added at the same time. The vacuum degree was 100 Pa, and the mixture was placed in a constant temperature oven at 60 °C for 5 hours. Then it was placed in a vacuum drying oven at 60 °C for 2 hours to obtain the superhydrophobic chitosan aerogel / hollow glass microsphere composite material product.

[0109] Example 7

[0110] (1) Preparation of slurry: Weigh 1.6g of chitosan and dissolve it in 80mL of 2% glacial acetic acid aqueous solution. After mixing, mechanically stir at room temperature for 1-1.5h until the chitosan is dissolved. Weigh 15.6g of T20 hollow glass microspheres and add them to the solution. Continue stirring for 0.5h until the T20 hollow glass microspheres are evenly mixed in the solution. During the stirring process, slowly add 1.0ml of glutaraldehyde solution until the slurry initially gels.

[0111] (2) Preparation of cryogel: Pour the preliminary gel slurry into a mold and freeze it in a -20℃ refrigerator for 3 hours to form a cryogel.

[0112] (3) Preparation of dried gel: The frozen gel prepared above was placed in a freeze dryer, the pressure was adjusted to 20 Pa, and the time was 72 hours to obtain a completely dried chitosan aerogel / hollow glass microsphere composite material.

[0113] (4) Hydrophobic modification: The dried composite material was placed in a glass vacuum dryer, and methyltriethoxysilane (0.2 g by mass) and deionized water (0.4 g) were added at the same time. The vacuum degree was 100 Pa, and the mixture was placed in a constant temperature oven at 60 °C for 5 hours. Then it was placed in a vacuum drying oven at 60 °C for 2 hours to obtain the superhydrophobic chitosan aerogel / hollow glass microsphere composite material product.

[0114] Table 2. Density, thermal conductivity, compressive strength, and contact angle of the chitosan aerogels prepared in Examples 1-7.

[0115]

[0116] The mass fractions of T30 hollow glass microspheres in Examples 1-5 were approximately 62.5%, 74.1%, 80.4%, 86.2%, and 90.2%, respectively. When the mass fraction of hollow glass microspheres reached over 80%, the strength of the composite material was significantly improved, and its strength further increased with the increase of the mass fraction of hollow glass microspheres, proving that the hollow glass microspheres played a strong supporting role in the composite material. Due to its extremely high porosity and extremely low density, aerogel has relatively poor strength. Aerogel mainly acts as a binder, shaping the hollow glass microspheres into blocks, and has good machinability. With the addition of a large amount of hollow glass microspheres, the microspheres possess a certain mechanical strength. Under the action of the binder, they accumulate together, forming a certain supporting effect, which can enhance the overall mechanical strength of the composite material. As can be seen from the calorific value, when the mass fraction of hollow glass microspheres reaches 90%, the calorific value is 1.80 MJ / kg, which meets the A1 flame retardant standard.

[0117] The samples obtained in Example 5 were tested for non-combustibility according to GB / T 5464-2010 "Test Methods for Non-combustibility of Building Materials". The results are as follows:

[0118] Table 3 Non-flammability Test Results

[0119]

[0120] Table 3 shows that the hydrophobic composite material has flame retardancy. The sample obtained in Example 5 was classified according to the standard GB 8624-2012 "Classification of Combustion Performance of Building Materials and Products" and reached the A1 level standard for the combustion performance of flat building materials and products (according to GB / T 14402-2007 "Determination of Combustion Heat Value of Combustion Performance of Building Materials and Products" and GB / T5464-2010 "Test Method for Non-combustibility of Building Materials").

[0121] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite material, characterized in that, The composite material includes biomass aerogel and hollow glass microspheres. The hollow glass microspheres are stacked and formed by using natural polymer materials as binders to form the main skeleton of the composite material. The biomass aerogel is prepared using natural polymer materials as raw materials; The natural polymer material is selected from at least one of cellulose, chitin, chitosan, fructose, starch, and gelatin; The hollow glass microspheres account for 60-95 wt% of the total mass, the biomass aerogel accounts for 2-30 wt% of the total mass, and the sum of the masses of the hollow glass microspheres and the biomass aerogel is not less than 75 wt%.

2. The composite material according to claim 1, characterized in that, The true density of the hollow glass microspheres is less than 0.5 g / cm³. 3 ; And / or, the isostatic compressive strength of the hollow glass microspheres is 1.8~55MPa; And / or, the particle size of the hollow glass microspheres is 1μm~200μm.

3. The composite material according to claim 1, characterized in that, The hollow glass microspheres in the composite material account for 70-93 wt% of the mass, the biomass aerogel accounts for 5-20 wt% of the mass, and the sum of the masses of the hollow glass microspheres and the biomass aerogel is not less than 85 wt%.

4. The composite material according to any one of claims 1-3, characterized in that, The composite material simultaneously possesses the following properties: 1) The apparent density of the composite material is 0.02~0.30 g / cm³. 3 ; 2) The compressive strength of the composite material is 0.06~2.0 MPa; 3) The calorific value of the composite material is 1.8~6.6 MJ / kg; 4) Thermal conductivity is 0.03~0.10 W / m·K; 5) The composite material is flame retardant.

5. The method for preparing the composite material according to any one of claims 1-4, characterized in that, The method includes the following steps: adding hollow glass microspheres and crosslinking agent sequentially to the raw material system of biomass aerogel, freezing the resulting slurry to obtain a gel, and performing vacuum freeze-drying on the gel to obtain the composite material; The raw material system of the biomass aerogel includes natural polymer materials, catalysts and water; The crosslinking agent is glutaraldehyde.

6. The preparation method according to claim 5, characterized in that, The preparation method includes the following steps: (1) Mix natural polymer materials with catalyst and water, add hollow glass microspheres, and then add crosslinking agent to prepare slurry; (2) The slurry is frozen and molded to obtain a gel; (3) The gel is freeze-dried under vacuum to obtain the composite material.

7. The preparation method according to claim 5 or 6, characterized in that, The catalyst is selected from inorganic acids.

8. The preparation method according to claim 5 or 6, characterized in that, The mass ratio of the natural polymer material, catalyst and water is (1~8):(0.5~2):

100.

9. The preparation method according to claim 5 or 6, characterized in that, The freezing time is 0.5h to 6h, and the freezing temperature is -50 to -10℃. During the vacuum freeze-drying process, the freeze-drying temperature is -50 to -20°C, the freeze-drying pressure is 1 to 100 Pa, and the freeze-drying time is 10 to 100 hours.

10. A hydrophobic composite material, characterized in that, The hydrophobic composite material is a hydrophobic modified version of the composite material according to any one of claims 1-4; The hydrophobic groups in the hydrophobic composite material are provided by organosilicon reagents.

11. The hydrophobic composite material according to claim 10, characterized in that, The organosilicon reagent is selected from one or more of methyltriethoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, hexadecyltrimethoxysilane, and hexadecyltrimethoxysilane.

12. The hydrophobic composite material according to claim 10, characterized in that, The contact angle of the hydrophobic composite material is not less than 120°.

13. The hydrophobic composite material according to any one of claims 10-12, characterized in that, The hydrophobic composite material also possesses the following properties: 1) The apparent density of the hydrophobic composite material is 0.02~0.30 g / cm³. 3 ; 2) The compressive strength of the hydrophobic composite material is 0.06~2.0 MPa; 3) The calorific value of the hydrophobic composite material is 1.8~6.6 MJ / kg; 4) The thermal conductivity of the hydrophobic composite material is 0.03~0.10 W / m·K; 5) The hydrophobic composite material has flame retardancy.

14. The application of the composite material according to any one of claims 1-4 and / or the hydrophobic composite material according to any one of claims 10-12 in the field of thermal insulation.

15. A thermal insulation material comprising the composite material according to any one of claims 1-4 and / or the hydrophobic composite material according to any one of claims 10-12.

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