Method for preparing flame-retardant hydrophobic aerogel composite material by co-precursor method

Abstract

The invention provides a method for preparing a flame-retardant hydrophobic aerogel composite material by a co-precursor method. The method comprises the following steps: mixing a water glass solution and phosphoric acid for hydrolysis reaction to obtain an acidic hydrolysate; 3-aminopropyltriethoxysilane, water and absolute ethyl alcohol are mixed for a hydrolysis reaction, and alkaline hydrolysate is obtained; mixing and reacting the acidic hydrolysate and the alkaline hydrolysate to obtain a co-precursor prepolymerization solution, continuously adding a water glass solution, and compounding with a glass fiber mat before gelling to form a silicon dioxide wet gel composite mat; sealing and aging the silicon dioxide wet gel composite felt in a precursor solvent, performing surface modification in a mixed solution of hexamethyldisiloxane, absolute ethyl alcohol and hydrochloric acid, and drying to obtain the flame-retardant hydrophobic aerogel composite material. The aerogel has excellent flame retardance and heat insulation property.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of thermal insulation, green energy-saving and flame-retardant materials, and particularly relates to a method for preparing a flame-retardant hydrophobic aerogel composite material by a co-precursor method. Background Art

[0002] Silica aerogel is a porous material with excellent properties. The unique three-dimensional network pore structure helps to achieve low density (0.03 - 0.50 g / cm 3 ), low thermal conductivity (0.017 W / m·K) and ultra-high specific surface area (500 - 1200 m 2 / g) and other excellent properties. These excellent properties enable aerogels to be widely used in various fields such as building insulation, waste gas adsorption, catalyst carriers, aerospace, etc. With the industrial low-cost and rapid preparation process, the application fields of aerogels are constantly expanding.

[0003] The most commonly used silica aerogel is hydrophobic, and hydrophobicity is achieved by introducing a large number of organic groups into the silica aerogel. The presence of these organic groups is beneficial for the long-term maintenance of the thermal insulation performance of the aerogel, but at the same time, it also brings potential thermal hazards. At high temperatures, these organic groups will pyrolyze to produce flammable gases such as CH 4 , CO, etc., and there is a certain combustion risk. With the continuous expansion of the application scope of thermal insulation materials, the thermal hazards of aerogel materials have gradually attracted people's attention.

[0004] The research on the flame retardancy of hydrophobic aerogels has also been initiated. Sanchez-Soto studied the combustion behavior of flame retardant-modified polyvinyl alcohol (PVOH) / clay composite aerogels and found that adding ammonium polyphosphate (APP) or Al(OH) 3 could reduce the heat release rate (HRR) of the PVOH / clay composite aerogel. Yinfeng Wang et al. used dimethylchlorosilane (DMDCS) to replace trimethylchlorosilane (HMDSO) to modify silica gel, and focused on the thermal hazard assessment of DMDCS-modified SA (DSA), proving that the total heat value could be reduced by about 12%, providing a possible solution for solving the thermal hazards of hydrophobic silica aerogels. Li Zhi et al. used Al(OH) 3 and Mg(OH) 2 as dopants to reduce the flammability of hydrophobic silica aerogels, which proved that the flame retardant effect of Al(OH) 3 and Mg(OH) 2 was related to their inhibitory effect on the pyrolysis of SA, and Mg(OH) 2 significantly improved the flame retardant performance of silica aerogels.

[0005] Currently, inhibiting SiO 2Some work on the combustion of aerogels can be roughly divided into two categories: physical composite methods and chemical structure optimization design. However, the physical composite method can lead to uneven distribution of flame retardants, easy shedding on the surface, poor flame retardant effect, and weakened heat preservation effect. Although the optimization of the chemical structure can reduce the fire risk to a certain extent, it cannot inhibit flame combustion. Therefore, it is urgent to prepare an aerogel that can effectively inhibit its combustion risk while maintaining excellent heat preservation performance. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for preparing a flame-retardant hydrophobic aerogel composite material by a co-precursor method. The aerogel composite material prepared by this method has excellent flame retardant properties.

[0007] The present invention provides a method for preparing a flame-retardant hydrophobic aerogel composite material by a co-precursor method, comprising the following steps:

[0008] Mix a water glass solution and phosphoric acid for hydrolysis reaction to obtain an acidic hydrolysis solution; mix 3-aminopropyltriethoxysilane, water and absolute ethanol for hydrolysis reaction to obtain a basic hydrolysis solution;

[0009] Mix the acidic hydrolysis solution and the basic hydrolysis solution for reaction to obtain a co-precursor prepolymer solution, and continue to add a water glass solution. Before gelation, it is compounded with a glass fiber mat to form a silica wet gel composite mat;

[0010] Seal and age the silica wet gel composite mat in a precursor solvent, then perform surface modification in a mixed solution of hexamethyldisiloxane, absolute ethanol and hydrochloric acid, and dry to obtain a flame-retardant hydrophobic aerogel composite material.

[0011] Preferably, the pH value of the acidic hydrolysis solution is 4.2 - 4.8;

[0012] The pH value of the basic hydrolysis solution is 8.5 - 9.5.

[0013] Preferably, the mass fraction of the water glass solution is 10 - 12%.

[0014] Preferably, the volume ratio of 3-aminopropyltriethoxysilane to the total volume of 3-aminopropyltriethoxysilane, water and absolute ethanol is 2.5 - 10%.

[0015] Preferably, the pH value of the co-precursor prepolymer solution is 4.5 - 5.5;

[0016] After adding the water glass solution, the pH value of the system before gelation is 5.5 - 6.5.

[0017] Preferably, the mass ratio of the co-precursor prepolymer solution to the glass fiber mat before compounding is 2:4 - 6.

[0018] Preferably, the temperature for sealed aging is 20~50°C;

[0019] The time for sealed aging is 4~8 h.

[0020] Preferably, the volume ratio of hexamethyldisiloxane, absolute ethanol and hydrochloric acid used for surface modification is 1:1:1.8~2.1.

[0021] Preferably, the temperature for surface modification is 50~60°C, and the time for surface modification is 2~4 h.

[0022] Preferably, drying is carried out by atmospheric pressure gradient drying;

[0023] Atmospheric pressure gradient drying is carried out by drying at 80°C, 100°C and 120°C for 1 h, 1.5 h and 2 h respectively.

[0024] The present invention provides a method for preparing a flame-retardant hydrophobic aerogel composite material by a co-precursor method, including the following steps: mixing a water glass solution and phosphoric acid for hydrolysis reaction to obtain an acidic hydrolysis solution; mixing 3-aminopropyltriethoxysilane, water and absolute ethanol for hydrolysis reaction to obtain a basic hydrolysis solution; mixing the acidic hydrolysis solution and the basic hydrolysis solution for reaction to obtain a co-precursor pre-polymerization solution, and then adding a water glass solution and compounding with a glass fiber mat before gelation to form a silica wet gel composite mat; subjecting the silica wet gel composite mat to sealed aging in a precursor solvent, then carrying out surface modification in a mixed solution of hexamethyldisiloxane, absolute ethanol and hydrochloric acid, and drying to obtain a flame-retardant hydrophobic aerogel composite material. By hydrolyzing 3-aminopropyltriethoxysilane in the present invention, 3-aminopropyltriethoxysilanol with strong reactivity is formed and grafted onto the surface of the aerogel: on the one hand, the amino group carried by the 3-aminopropyltriethoxysilanol group reacts with the subsequent phosphoric acid to generate an ammonium phosphate group, which has high flame-retardant performance and can inhibit the combustion performance of the hydrophobic aerogel; on the other hand, the 3-aminopropyltriethoxysilanol group itself has an alkyl group, which can play a hydrophobic modification function and ensure the excellent heat insulation performance of the aerogel, and finally achieve both the heat insulation performance and the flame-retardant performance of the aerogel.

[0025] The present invention completes the surface hydrophobic modification and flame-retardant group grafting of the silica aerogel through one-step reaction, simplifies the process flow, abandons the two-step process of first hydrophobic modification and then doping with a flame retardant in the traditional method, and the method is simple, convenient and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a process schematic diagram of the method for preparing a flame-retardant hydrophobic aerogel composite material by the co-precursor method of the present invention;

[0027] Figure 2SEM image of the flame-retardant and hydrophobic aerogel composite material SAB-2 prepared in Example 2 of the present invention;

[0028] Figure 3 SEM and hydrophobic angle schematic diagrams of the powder in the flame-retardant and hydrophobic aerogel composite material SAB-2 prepared in Example 2 of the present invention;

[0029] Figure 4 Physical picture of the flame-retardant and hydrophobic aerogel composite material SAB-2 prepared in Example 2 of the present invention;

[0030] Figure 5 N 2 adsorption-desorption curve of the aerogel composite materials prepared in the examples and comparative examples of the present invention;

[0031] Figure 6 Total heat release value curve of the cone calorimeter experiment of the aerogel composite materials prepared in the examples and comparative examples of the present invention. Detailed implementation manners

[0032] The present invention provides a method for preparing a flame-retardant and hydrophobic aerogel composite material by a co-precursor method, comprising the following steps:

[0033] Mix a water glass solution and phosphoric acid for a hydrolysis reaction to obtain an acidic hydrolysis solution; mix 3-aminopropyltriethoxysilane, water and absolute ethanol for a hydrolysis reaction to obtain a basic hydrolysis solution;

[0034] Mix the acidic hydrolysis solution and the basic hydrolysis solution for a reaction to obtain a co-precursor pre-polymerization solution, and continue to add a water glass solution, and composite with a glass fiber mat before gelation to form a silica wet gel composite mat;

[0035] Seal and age the silica wet gel composite mat in a precursor solvent, then perform surface modification in a mixed solution of hexamethyldisiloxane, absolute ethanol and hydrochloric acid, and dry to obtain a flame-retardant and hydrophobic aerogel composite material.

[0036] The present invention prepares a novel flame-retardant aerogel by in-situ chemical grafting. The ammonium dihydrogen phosphate group is grafted into the silica polymer network through the chemical bond of 3-aminopropyltriethoxysilane, the flame-retardant efficiency is significantly improved, while maintaining its own excellent properties, the synthesis is simple, green and energy-saving, and the operation is convenient.

[0037] In the present invention, a water glass solution and phosphoric acid are mixed to carry out a hydrolysis reaction to obtain an acidic hydrolysis solution. In the present invention, the mass fraction of the water glass solution is 10-12%; preferably, it is prepared by diluting water glass with a mass fraction of 34% with water; the volume ratio of the water glass with a mass fraction of 34% to water is 1:3. The present invention preferably uses phosphoric acid with a mass fraction of 85%. The present invention preferably adds the diluted water glass solution to phosphoric acid; preferably, the acidic hydrolysis is carried out under magnetic stirring.

[0038] The reaction carried out in the preparation of the acidic hydrolysis solution is as follows:

[0039]

[0040]

[0041] The pH value of the acidic hydrolysis solution prepared in the present invention is controlled to be 4.2-4.8; specifically, it can be 4.2, 4.3, 4.4, 4.5, 4.6, 4.7 or 4.8.

[0042] In the present invention, 3-aminopropyltriethoxysilane, water and absolute ethanol are mixed to carry out a hydrolysis reaction to obtain a basic hydrolysis solution.

[0043] In the present invention, the volume ratio of the 3-aminopropyltriethoxysilane to the total volume of the 3-aminopropyltriethoxysilane, water and absolute ethanol is 2.5-10%; specifically, the volume ratio is 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5% or 10%. The volume ratio of water to absolute ethanol is 1:1.

[0044] In the present invention, the hydrolysis reaction of the mixture of 3-aminopropyltriethoxysilane, water and absolute ethanol is carried out at room temperature, preferably 15-30 °C. The pH value of the basic hydrolysis solution is 8.5-9.5; specifically, it can be 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4 or 9.5.

[0045] After obtaining the acidic hydrolysis solution and the basic hydrolysis solution, the present invention mixes and reacts the acidic hydrolysis solution and the basic hydrolysis solution to obtain a co-precursor prepolymer solution, and then continues to add a water glass solution, and composites with a glass fiber mat before gelation to form a silica wet gel composite mat.

[0046] The reaction carried out after the mixture of the acidic hydrolysis solution and the basic hydrolysis solution in the present invention is as follows:

[0047]

[0048]

[0049] The pH value of the co-precursor prepolymer solution prepared by the present invention is 4.5 - 5.5; specifically, it can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5.

[0050] Before adding the sodium silicate solution, the pH value of the system before gelation in the present invention is preferably controlled to be 5.5 - 6.5; specifically, it can be 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4 or 6.5.

[0051] The mass ratio of the co-precursor prepolymer solution to the glass fiber mat before compounding in the present invention is 2:4 - 6; specifically, it can be 2:4, 2:4.5, 2:5, 2:5.5 or 2:6.

[0052] After obtaining the silica wet gel composite mat, in the present invention, the silica wet gel composite mat is sealed and aged in the precursor solvent, and then surface-modified in a mixed solution of hexamethyldisiloxane, absolute ethanol and hydrochloric acid, and dried to obtain a flame-retardant hydrophobic aerogel composite material.

[0053] In the present invention, the temperature of the sealed aging is 20 - 50 °C; the time of the sealed aging is 4 - 8 h, specifically, it can be 4 h, 5 h, 6 h, 7 h or 8 h.

[0054] The volume ratio of the hexamethyldisiloxane, absolute ethanol and hydrochloric acid used for surface modification in the present invention is 1:1:1.8 - 2.1; specifically, it can be 1:1:1.8, 1:1:1.9, 1:1:2.0 or 1:1:2.1.

[0055] The following reaction occurs during the surface modification in the present invention:

[0056]

[0057] In the present invention, the temperature of the surface modification is 50 - 60 °C, specifically 50 °C, 51 °C, 52 °C, 63 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C; the time of the surface modification is 2 - 4 h; specifically, it is 2 h, 2.5 h, 3 h, 3.5 h or 4 h. The temperature required for surface modification is preferably achieved by water bath heating.

[0058] In the present invention, the drying is atmospheric pressure stepwise drying; the atmospheric pressure stepwise drying is to dry for 1 h, 1.5 h and 2 h at 80 °C, 100 °C and 120 °C respectively.

[0059] The flame-retardant hydrophobic aerogel composite material prepared by the co-precursor method of the present invention is obtained by the preparation method described in the above technical solution.

[0060] The present invention uses 3-aminopropyltriethoxysilane and sodium silicate as co-precursors, and adopts a preparation method of drying under normal pressure after modification by the sol-gel method; this method can retain the excellent heat insulation performance of hydrophobic silica aerogel to the greatest extent. The thermal conductivity of the aerogel is 0.020 - 0.022 W / m·K, the porosity is 95 - 97%, and the density is 0.090 - 0.109 g / cm 3 ; the specific surface area is 750 - 1500 m 2 / g.

[0061] To further illustrate the present invention, the following describes in detail a method for preparing a flame-retardant hydrophobic aerogel composite material by the co-precursor method provided by the present invention in combination with examples, but they cannot be understood as limiting the protection scope of the present invention.

[0062] Comparative example

[0063] Prepare a flame-retardant hydrophobic aerogel composite material with 0% volume fraction of 3-aminopropyltriethoxysilane in the co-precursor pre-polymer solution

[0064] (1) Preparation of the precursor solution

[0065] Add the diluted sodium silicate solution to a beaker containing 2 mL of phosphoric acid and stir magnetically to control the pH value to 4.5 to obtain an acidic hydrolysis solution. Take 10 mL of a mixed solution of anhydrous ethanol and water with a volume ratio of 1:1 as the precursor preparation solution.

[0066] (2) Preparation of the sol and composite by the co-precursor method

[0067] Mix the acidic hydrolysis solution and the precursor preparation solution to react to obtain a co-precursor pre-polymer solution. Control the pH of the pre-polymer solution to 5, and continue to add the diluted sodium silicate solution until the pH value is 6. Before gelation, compound it with a glass fiber mat with a compounding mass ratio of 2:5 to form a silica wet gel composite mat;

[0068] (3) Aging and modification

[0069] Seal and age the silica wet gel composite mat in the precursor solvent for 5 h, and then carry out surface modification in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid with a volume ratio of 1:1:2 for 3 h;

[0070] (4) Drying

[0071] The modified composite mat is dried by normal pressure grading. It is dried at 80 °C, 100 °C and 120 °C in an oven for 1 h, 1.5 h and 2 h respectively to obtain a hydrophobic aerogel composite material comparative sample, denoted as SAB-0. The physical and chemical parameters of the SAB-0 aerogel are shown in Table 1:

[0072] Table 1

[0073]

[0074] Example 1

[0075] Prepare a flame-retardant and hydrophobic aerogel composite material with a volume fraction of 2.5% of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution

[0076] (1) Preparation of the precursor solution

[0077] Add the diluted sodium silicate solution to a beaker containing 2 mL of phosphoric acid and stir magnetically to control the pH value to 4.5 to obtain an acidic hydrolysis solution. Mix 250 μL of 3-aminopropyltriethoxysilane, water, and absolute ethanol to make 10 mL, where the volume ratio of water to absolute ethanol is 1:1, and carry out a hydrolysis reaction in the beaker to obtain a basic hydrolysis solution.

[0078] (2) Preparation and compounding of the sol by the co-precursor method

[0079] Mix the acidic hydrolysis solution and the basic hydrolysis solution to react to obtain a co-precursor prepolymer solution. Control the pH of the prepolymer solution to 5, and continue to add the diluted sodium silicate solution until the pH value is 6. Before gelation, compound it with a glass fiber mat with a compounding mass ratio of 2:5 to form a silica wet gel composite mat;

[0080] (3) Aging and modification

[0081] Seal and age the silica wet gel composite mat in the precursor solvent for 5 h, and then carry out surface modification in a mixed solution with a volume ratio of 1:1:2 of hexamethyldisiloxane, absolute ethanol, and hydrochloric acid for 3 h;

[0082] (4) Drying

[0083] The modified composite mat is dried by atmospheric pressure fractional drying, and dried at 80 °C, 100 °C, and 120 °C in an oven for 1 h, 1.5 h, and 2 h respectively to obtain a flame-retardant and hydrophobic aerogel composite material, denoted as SAB-1. The physical and chemical parameters of the SAB-1 aerogel are shown in Table 2:

[0084] Table 2

[0085]

[0086] Example 2

[0087] Prepare a flame-retardant and hydrophobic aerogel composite material with a mass fraction of 5% of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution

[0088] (1) Preparation of the precursor solution

[0089] The diluted sodium silicate solution was added to a beaker containing 2 mL of phosphoric acid and magnetically stirred to control the pH value to 4.5 to obtain an acidic hydrolysis solution. 250 μL of 3-aminopropyltriethoxysilane, water and absolute ethanol were mixed and prepared into 10 mL. Among them, the volume ratio of water to absolute ethanol was 1:1, and hydrolysis reaction was carried out by mixing in the beaker to obtain a basic hydrolysis solution.

[0090] (2) Preparation of sol and composite by co-precursor method

[0091] The acidic hydrolysis solution and the basic hydrolysis solution were mixed and reacted to obtain a co-precursor prepolymer solution. The pH of the prepolymer solution was controlled to 5, and the diluted sodium silicate solution was continuously added until the pH value was 6. Before gelation, it was compounded with a glass fiber mat, and the compounding mass ratio was 2:5 to form a silica wet gel composite mat;

[0092] (3) Aging and modification

[0093] The silica wet gel composite mat was hermetically aged in the precursor solvent for 5 h, and then surface modified in a mixed solution with a volume ratio of 1:1:2 of hexamethyldisiloxane, absolute ethanol and hydrochloric acid for 3 h;

[0094] (4) Drying

[0095] The modified composite mat was dried by atmospheric pressure grading drying, and dried at 80 °C, 100 °C and 120 °C in an oven temperature condition for 1 h, 1.5 h and 2 h respectively to obtain a flame-retardant hydrophobic aerogel composite material, denoted as SAB-2. The physical and chemical parameters of the SAB-2 aerogel are shown in Table 3:

[0096] Table 3

[0097]

[0098] Figure 2 is the SEM image of the SAB-2 aerogel composite material; Figure 3 is the SEM image of the powder in the SAB-2 aerogel, that is Figure 2 the partial enlarged view in, and the hydrophobic angle of SAB-2 is 112°.

[0099] Example 3

[0100] Preparation of a flame-retardant hydrophobic aerogel composite material with a mass fraction of 7.5% of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution:

[0101] (1)Preparation of precursor solution

[0102] The diluted sodium silicate solution was added to a beaker containing 2 mL of phosphoric acid and magnetically stirred to control the pH value to 4.5 to obtain an acidic hydrolysis solution. 250 μL of 3-aminopropyltriethoxysilane, water, and absolute ethanol were mixed and configured into 10 mL. Among them, the volume ratio of water to absolute ethanol was 1:1, and they were mixed in the beaker for hydrolysis reaction to obtain a basic hydrolysis solution.

[0103] (2)Preparation of sol and composite by co-precursor method

[0104] The acidic hydrolysis solution and the basic hydrolysis solution were mixed and reacted to obtain a co-precursor prepolymer solution. The pH of the prepolymer solution was controlled to 5, and the diluted sodium silicate solution was continuously added until the pH value reached 6. Before gelation, it was compounded with a glass fiber mat, and the compounding mass ratio was 2:5 to form a silica wet gel composite mat;

[0105] (3)Aging and modification

[0106] The silica wet gel composite mat was hermetically aged in the precursor solvent for 5 h, and then surface-modified in a mixed solution with a volume ratio of 1:1:2 of hexamethyldisiloxane, absolute ethanol, and hydrochloric acid for 3 h;

[0107] (4)Drying

[0108] The modified composite mat was dried by atmospheric pressure fractional drying, and dried at 80 °C, 100 °C, and 120 °C in an oven for 1 h, 1.5 h, and 2 h respectively to obtain a flame-retardant hydrophobic aerogel composite material, denoted as SAB-3. The physical and chemical parameters of the SAB-3 aerogel are shown in Table 4:

[0109] Table 4

[0110]

[0111] Example 4

[0112] Preparation of a flame-retardant hydrophobic aerogel composite material with a 10% mass fraction of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution

[0113] (1)Preparation of precursor solution

[0114] The diluted sodium silicate solution was added to a beaker containing 2 mL of phosphoric acid and magnetically stirred to control the pH value to 4.5 to obtain an acidic hydrolysis solution. 250 μL of 3-aminopropyltriethoxysilane, water, and absolute ethanol were mixed and configured into 10 mL. Among them, the volume ratio of water to absolute ethanol was 1:1, and they were mixed in the beaker for hydrolysis reaction to obtain a basic hydrolysis solution.

[0115] (2)Preparation of sol and composite by co-precursor method

[0116] Mix the acidic hydrolysis solution and the alkaline hydrolysis solution to obtain a co-precursor pre-polymer solution. Control the pH of the pre-polymer solution to 5, and then continuously add the diluted water glass solution until the pH value reaches 6. Before gelation, compound it with a glass fiber mat with a compounding mass ratio of 2:5 to form a silica wet gel composite mat.

[0117] (3)Aging and modification

[0118] Seal and age the silica wet gel composite mat in the precursor solvent for 5 h, and then perform surface modification on it in a mixed solution with a volume ratio of 1:1:2 of hexamethyldisiloxane, absolute ethanol, and hydrochloric acid for 3 h.

[0119] (4)Drying

[0120] The modified composite mat is dried by atmospheric pressure fractional drying. It is dried at oven temperatures of 80 °C, 100 °C, and 120 °C for 1 h, 1.5 h, and 2 h respectively to obtain a flame-retardant and hydrophobic aerogel composite material, denoted as SAB-4. The physical and chemical parameters of the SAB-4 aerogel are shown in Table 5:

[0121] Table 5

[0122]

[0123] The present invention conducts N 2 adsorption-desorption tests on the aerogel composite materials prepared in Examples 1 to 4 and the comparative examples, as shown in Figure 5 ; Silica aerogel is a nano-porous material, and its overall structure can be characterized by the N 2 desorption-adsorption isotherm; According to the BDDT (Brunauer, Deming, Deming, and Teller) classification system, Figure 5 all the curves in

[0124] represent type IV isotherms, indicating that although the APTES content in the sample is as high as 10%, the main pore structure in the aerogel is still mesopores. Figure 6 ; From Figure 6 it can be seen that: the THR of the sample decreases significantly with the increase of the APTES content. When the doping content exceeds 5%, the THR of the sample shows a significant downward trend, as shown in Figure 6 ; It can be concluded that APTES has a significant inhibitory effect on the combustion of silica aerogel. The reduction rate of the THR of the sample is positively correlated with the APTES content. From a content of 2.5% to 10%, the THR increases significantly from 23.1% to 69.2%.

[0125] As can be seen from the above embodiments, the present invention provides a method for preparing a flame-retardant and hydrophobic aerogel composite material by a co-precursor method, comprising the following steps: mixing a water glass solution and phosphoric acid for hydrolysis reaction to obtain an acidic hydrolysis solution; mixing 3-aminopropyltriethoxysilane, water and absolute ethanol for hydrolysis reaction to obtain a basic hydrolysis solution; mixing the acidic hydrolysis solution and the basic hydrolysis solution for reaction to obtain a co-precursor pre-polymer solution, and continuously adding a water glass solution to be compounded with a glass fiber mat before gelation to form a silica wet gel composite mat; sealing and aging the silica wet gel composite mat in a precursor solvent, and then performing surface modification in a mixed solution of hexamethyldisiloxane, absolute ethanol and hydrochloric acid, and drying to obtain a flame-retardant and hydrophobic aerogel composite material. By hydrolyzing 3-aminopropyltriethoxysilane, the present invention forms 3-aminopropyltriethoxysilanol with strong reactivity and grafts it onto the surface of the aerogel: on the one hand, the amino group carried by the 3-aminopropyltriethoxysilanol group reacts with the subsequent phosphoric acid to generate an ammonium phosphate group, which has high flame-retardant performance and can inhibit the combustion performance of the hydrophobic aerogel. Experimental results show that the thermal conductivity of the aerogel is 0.020~0.022 W / m·K, the porosity is 95~97%, and the density is 0.090~0.109 g / cm 3 ; the specific surface area is 750~1500 m 2 / g, and the total heat release amount in the cone calorimeter test gradually decreases from 3.25 MJ·m -2 to 1.12 MJ·m -2 .

[0126] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a flame retardant hydrophobic aerogel composite material by a co-precursor method, comprising the following steps: The water glass solution and phosphoric acid are mixed to perform a hydrolysis reaction to obtain an acidic hydrolyzate; Mixing 3-aminopropyltriethoxysilane, water and anhydrous ethanol to perform a hydrolysis reaction to obtain an alkaline hydrolyzate; The acidic hydrolyzate and the alkaline hydrolyzate are mixed and reacted to obtain a co-precursor prepolymer solution, and a water glass solution is continuously added to compound the prepolymer with the glass fiber mat before gelation to form a silicon dioxide wet gel composite mat; The silicon dioxide wet gel composite felt is sealed and aged in a precursor solvent, and then surface-modified in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid, and dried to obtain a flame-retardant hydrophobic aerogel composite material.

2. The method according to claim 1, characterized in that The pH value of the acidic hydrolyzate is 4.2-4.8; The pH value of the alkaline hydrolyzate is 8.5~9.

5.

3. The method according to claim 1, characterized in that The mass fraction of the water glass solution is 10-12%.

4. The method according to claim 1, characterized in that: The volume of the 3-aminopropyltriethoxysilane accounts for 2.5-10% of the total volume of the 3-aminopropyltriethoxysilane, water and anhydrous ethanol.

5. The method according to claim 1, characterized in that The pH value of the co-precursor prepolymer solution is 4.5-5.5; After adding the water glass solution, the pH value of the system was 5.5~6.5 before gelation.

6. The method according to claim 1, characterized in that The mass ratio of the co-precursor prepolymer liquid to the glass fiber mat before compounding is 2:4-6.

7. The method according to claim 1, characterized in that The seal aging temperature is 20~50℃; The seal aging time is 4~8h.

8. The method according to claim 1, characterized in that The volume ratio of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid used for surface modification is 1:1:1.8~2.

1.

9. The method according to claim 1, characterized in that: The temperature of surface modification is 50~60℃, and the time of surface modification is 2~4h.

10. The method according to claim 1, characterized in that Drying is graded drying at normal pressure; The atmospheric pressure graded drying was carried out at 80°C, 100°C and 120°C for 1 h, 1.5 h and 2 h respectively.

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