Preparation method of nano silicon dioxide modified polyurethane thermal insulation material

Abstract

The invention relates to the technical field of polyurethane thermal insulation materials, and discloses a preparation method of a nano silicon dioxide modified polyurethane thermal insulation material, which comprises the following steps: by taking 4-chloro-1-butylamine, formaldehyde and biphenol as raw materials, carrying out Mannich reaction to obtain an intermediate 1, and carrying out substitution reaction on the intermediate 1 and PEPA under the catalysis of pyridine to obtain the nano silicon dioxide modified polyurethane thermal insulation material. The benzoxazine-based double PEPA is obtained. Taking N, N-diethyl-aminopropyl methyl dimethoxy silane as a bridge, carrying out quaternization reaction with the intermediate 1, and then carrying out condensation reaction with nano silicon dioxide to obtain the benzoxazine-based double-nano silicon dioxide. Finally, polyether polyol, benzoxazine-based double nano-silica, benzoxazine-based double PEPA, a curing agent and the like are used as raw materials, stirred and mixed to be uniform, foaming forming is conducted, and the nano-silica modified polyurethane thermal insulation material is obtained. The nano silicon dioxide modified polyurethane thermal insulation material prepared by the preparation method disclosed by the invention has relatively good flame-retardant effect, antibacterial effect, mechanical property and thermal stability.

Description

[0001] This application claims priority to Chinese Patent Application No. 202510135926.X, filed on February 7, 2025, entitled "A Method for Preparing Nano-Silica Modified Polyurethane Thermal Insulation Material", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of polyurethane insulation materials technology, specifically a method for preparing a nano-silica modified polyurethane insulation material. Background Technology

[0003] Polyurethane insulation material is an important type of insulation material, widely used in construction engineering and other fields. However, polyurethane insulation material is highly flammable and has poor fire resistance, which limits its application in many fields. Therefore, preparing a polyurethane insulation material with flame retardant effect is one of the important research directions to expand its application fields.

[0004] Nano-silica, commonly known as white carbon black, is an important inorganic material. Due to its ultrafine nano-based structure, it possesses many excellent and unique properties, such as enhancing the anti-aging, strength, and chemical resistance of materials. It has wide applications in catalysis, filtration, light absorption, medicine, and new materials. 1-Oxyphospha-4-hydroxymethyl-2,6,7-trioxabicyclo[2,2,2]octane (PEPA) is favored by researchers due to its highly symmetrical cage-like structure, good char-forming properties, excellent thermal stability, and abundant carbon and acid sources.

[0005] For example, the patent with authorization announcement number CN114106683B discloses a waterproof and heat-insulating integrated material and its production process. The invention uses polyurethane material, nano-silica and other raw materials to prepare a material with good flame retardant effect and mechanical properties, but does not improve the antibacterial properties and thermal stability of the material. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing nano-silica modified polyurethane thermal insulation material. The prepared thermal insulation material exhibits good antibacterial properties, flame retardancy, mechanical properties, and thermal stability.

[0008] (II) Technical Solution

[0009] A method for preparing a nano-silica modified polyurethane thermal insulation material, wherein the preparation method comprises:

[0010] Mix polyether polyol, foam stabilizer, catalyst, foaming agent, and deionized water for 5-10 minutes until homogeneous. Then add benzoxazine-based double nano silica and benzoxazine-based double PEPA and mix until homogeneous. Add curing agent and stir at 3000 rpm for 10-20 seconds. Quickly pour into a 300mm×300mm×150mm mold and foam to form. Control the mold temperature at 50℃ to obtain nano silica-modified polyurethane insulation material.

[0011] Preferably, the mass ratio of the polyether polyol, foam stabilizer, catalyst, foaming agent, deionized water, benzoxazine-based bis-nano silica, benzoxazine-based bis-PEPA, and curing agent is 80-100:1-2:1-2:20-25:1-2:5-20:1-10:100.

[0012] Preferably, the catalyst is one of N,N-dimethylcyclohexylamine and dibutyltin dilauric acid.

[0013] Preferably, the method for preparing the benzoxazine-based bis-PEPA is as follows:

[0014] (1) Add 4-chloro-1-butanamine and formaldehyde to dioxane solvent, stir at room temperature for 30-40 min, then add biphenyl hydroquinone, heat to 80-90℃, react for 8-12 h, after the reaction is completed, cool to room temperature, rotary evaporate, dry to obtain intermediate 1;

[0015] (2) Add PEPA to acetonitrile solvent, stir and disperse, heat to 55-65℃, add intermediate 1, stir and mix evenly, heat to 85-90℃, add pyridine, reflux reaction for 22-26h, after the reaction is completed, filter while hot, wash with ethanol, dry to obtain benzoxazinyl bis PEPA.

[0016] More preferably, in (1), the molar ratio of 4-chloro-1-butamine, formaldehyde, and biphenyl is 2-2.5:6-7:1.

[0017] More preferably, in step (2), the molar ratio of PEPA, intermediate 1, and pyridine is 2-2.5:1:0.4-0.6.

[0018] Furthermore, the preparation method of the benzoxazine-based dual nano-silica is as follows:

[0019] S1. Under nitrogen protection, N,N-diethyl-aminopropylmethyldimethoxysilane was added to ethanol solvent and stirred to disperse. Intermediate 1 was added to the mixture at 50-55°C and reacted for 8-12 hours. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, washed with diethyl ether, and dried to obtain intermediate 2.

[0020] S2. Add intermediate 2 to toluene solvent, stir and disperse, then add nano-silica, continue stirring for 20-40 min, add 75% ethanol aqueous solution, heat under reflux for 2-3 h, after which cool to room temperature, filter, wash with toluene and diethyl ether in sequence, and dry to obtain benzoxazine-based bis-nano-silica.

[0021] More preferably, in S1, the molar ratio of N,N-diethyl-aminopropylmethyldimethoxysilane to intermediate 1 is 2-2.4:1.

[0022] More preferably, in S2, the mass ratio of intermediate 2 to nano-silica is 4-6:1.

[0023] (iii) Beneficial technical effects

[0024] This invention yields benzoxazine-based bis-nano silica and benzoxazine-based bis-PEPA through a series of reactions. The preparation method is simple and the structure is novel. When added to polyurethane insulation materials, the benzoxazine structure, which readily undergoes ring-opening and cross-linking upon heating, synergistically enhances the thermal stability of the polyurethane insulation material with the inorganic heat-resistant nano silica and the heat-resistant benzene ring structure. Furthermore, the bis-quaternary ammonium salt structure, with its antibacterial properties, is introduced into the polyurethane insulation material to improve its antibacterial performance. Finally, the phosphorus-containing groups generate highly dehydrating polyphosphoric acid during combustion, causing rapid dehydration and carbonization of the material, which covers the surface, inhibiting oxygen diffusion into the reaction zone and suppressing the production of flammable gases. This forms an organic-inorganic flame-retardant system with the inorganic nano silica, synergistically improving the flame-retardant performance of the material. Furthermore, the benzoxazine-based dual nano-silica and benzoxazine-based dual PEPA prepared by this invention not only contain nano-silica that serves as stress concentration points and has good dispersibility, but also possess numerous long-chain structures that can entangle with each other, forming numerous cross-linking sites. These two components synergistically enhance the mechanical properties of the material. Experiments have demonstrated that the polyurethane insulation material prepared by this invention exhibits good antibacterial properties, flame retardant properties, mechanical properties, and thermal stability. Attached Figure Description

[0025] Figure 1 This is the reaction route of intermediate 1;

[0026] Figure 2 This is the reaction route of intermediate 2;

[0027] Figure 3 It is the reaction route of benzoxazinyl bis-PEPA. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] (1) 0.2 mol of 4-chloro-1-butylamine and 0.65 mol of formaldehyde were added to dioxane solvent and stirred at room temperature for 40 min. Then 0.1 mol of biphenyl hydroquinone was added and the temperature was raised to 85 °C. The reaction was carried out for 10 h. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, and dried to obtain intermediate 1.

[0031] (2) Add 1 mol of PEPA to acetonitrile solvent, stir and disperse, heat to 60°C, add 0.5 mol of intermediate 1, stir and mix evenly, heat to 90°C, add 0.25 mol of pyridine, reflux for 25 h, filter while hot after the reaction, wash with ethanol, dry to obtain benzoxazinyl bis PEPA.

[0032] (3) Under nitrogen protection, 1 mol of N,N-diethyl-aminopropylmethyldimethoxysilane was added to ethanol solvent and stirred to disperse. At 55°C, 0.5 mol of intermediate 1 was added and reacted for 10 h. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, washed with diethyl ether, and dried to obtain intermediate 2.

[0033] (4) Add 40g of intermediate 2 to toluene solvent, stir and disperse, then add 10g of nano silica, continue stirring for 30min, add 75% ethanol aqueous solution, heat under reflux for 2h, after which cool to room temperature, filter, wash with toluene and diethyl ether in sequence, and dry to obtain benzoxazine-based bis nano silica.

[0034] (5) Mix 80g of polyether polyol (LY-4110), 2g of foam stabilizer (AK8814), 1g of N,N-dimethylcyclohexylamine catalyst, 25g of hydrofluorocarbon foaming agent (HFC-365mfc), and 1g of deionized water for 8 minutes. Then add 5g of benzoxazine-based double nano silica and 1g of benzoxazine-based double PEPA and mix well. Then add 100g of polyphenyl polymethylene polyisocyanate (PM-200) curing agent and stir at 3000rpm for 20s. Then quickly pour into a 300mm×300mm×150mm mold and foam to form. The mold temperature is controlled at 50℃ to obtain nano silica modified polyurethane insulation material.

[0035] Example 2

[0036] (1) 0.25 mol of 4-chloro-1-butylamine and 0.6 mol of formaldehyde were added to dioxane solvent and stirred at room temperature for 40 min. Then 0.1 mol of biphenyl hydroquinone was added and the temperature was raised to 90 °C. The reaction was carried out for 8 h. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, and dried to obtain intermediate 1.

[0037] (2) 1.2 mol of PEPA was added to acetonitrile solvent, stirred and dispersed, heated to 65°C, 0.5 mol of intermediate 1 was added, stirred and mixed evenly, heated to 90°C, 0.25 mol of pyridine was added, and the mixture was refluxed for 24 h. After the reaction was completed, the mixture was filtered while hot, washed with ethanol, and dried to obtain benzoxazinyl bis-PEPA.

[0038] (3) Under nitrogen protection, 1.2 mol of N,N-diethyl-aminopropylmethyldimethoxysilane was added to ethanol solvent and stirred to disperse. At 55°C, 0.5 mol of intermediate 1 was added and reacted for 8 h. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, washed with diethyl ether, and dried to obtain intermediate 2.

[0039] (4) Add 45g of intermediate 2 to toluene solvent, stir and disperse, then add 10g of nano silica, continue stirring for 20min, add 75% ethanol aqueous solution, heat and reflux for 2h, after which cool to room temperature, filter, wash with toluene and ether in sequence, and dry to obtain benzoxazine-based bis nano silica.

[0040] (5) Mix 90g of polyether polyol (LY-4110), 2g of foam stabilizer (AK8814), 1g of dibutyltin dilauric acid catalyst, 20g of hydrofluorocarbon foaming agent (HFC-365mfc), and 2g of deionized water for 5 minutes. Then add 10g of benzoxazine-based double nano silica and 3g of benzoxazine-based double PEPA and mix well. Then add 100g of polyphenyl polymethylene polyisocyanate (PM-200) curing agent and stir at 3000rpm for 15s. Then quickly pour into a 300mm×300mm×150mm mold and foam to form. The mold temperature is controlled at 50℃ to obtain nano silica modified polyurethane insulation material.

[0041] Example 3

[0042] (1) 0.24 mol of 4-chloro-1-butylamine and 0.7 mol of formaldehyde were added to dioxane solvent and stirred at room temperature for 30 min. Then 0.1 mol of biphenyl hydroquinone was added and the temperature was raised to 80 °C. The reaction was carried out for 12 h. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, and dried to obtain intermediate 1.

[0043] (2) Add 1 mol of PEPA to acetonitrile solvent, stir and disperse, heat to 60°C, add 0.5 mol of intermediate 1, stir and mix evenly, heat to 90°C, add 0.2 mol of pyridine, reflux for 22 h, after the reaction is completed, filter while hot, wash with ethanol, dry, and obtain benzoxazinyl bis PEPA.

[0044] (3) Under nitrogen protection, 1.2 mol of N,N-diethyl-aminopropylmethyldimethoxysilane was added to ethanol solvent and stirred to disperse. At 50°C, 0.5 mol of intermediate 1 was added and reacted for 12 h. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, washed with diethyl ether, and dried to obtain intermediate 2.

[0045] (4) Add 50g of intermediate 2 to toluene solvent, stir and disperse, then add 10g of nano silica, continue stirring for 30min, add 75% ethanol aqueous solution, heat under reflux for 2h, after which cool to room temperature, filter, wash with toluene and diethyl ether in sequence, and dry to obtain benzoxazine-based bis nano silica.

[0046] (5) Mix 100g of polyether polyol (LY-4110), 1g of foam stabilizer (AK8814), 2g of dibutyltin dilauric acid catalyst, 22g of hydrofluorocarbon foaming agent (HFC-365mfc), and 1g of deionized water for 5 minutes. Then add 15g of benzoxazine-based double nano silica and 6g of benzoxazine-based double PEPA and mix evenly. Then add 100g of polyphenyl polymethylene polyisocyanate (PM-200) curing agent and stir at 3000rpm for 10s. Then quickly pour into a 300mm×300mm×150mm mold and foam to form. The mold temperature is controlled at 50℃ to obtain nano silica modified polyurethane insulation material.

[0047] Example 4

[0048] (1) 0.2 mol of 4-chloro-1-butylamine and 0.65 mol of formaldehyde were added to dioxane solvent and stirred at room temperature for 35 min. Then 0.1 mol of biphenyl hydroquinone was added and the temperature was raised to 90 °C. The reaction was carried out for 8 h. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, and dried to obtain intermediate 1.

[0049] (2) 1.25 mol of PEPA was added to acetonitrile solvent, stirred and dispersed, heated to 55°C, 0.5 mol of intermediate 1 was added, stirred and mixed evenly, heated to 90°C, 0.3 mol of pyridine was added, and the mixture was refluxed for 26 h. After the reaction was completed, the mixture was filtered while hot, washed with ethanol, and dried to obtain benzoxazinyl bis-PEPA.

[0050] (3) Under nitrogen protection, 1.2 mol of N,N-diethyl-aminopropylmethyldimethoxysilane was added to ethanol solvent and stirred to disperse. At 55°C, 0.5 mol of intermediate 1 was added and reacted for 10 h. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, washed with diethyl ether, and dried to obtain intermediate 2.

[0051] (4) Add 60g of intermediate 2 to toluene solvent, stir and disperse, then add 10g of nano silica, continue stirring for 40min, add 75% ethanol aqueous solution, heat and reflux for 3h, after which cool to room temperature, filter, wash with toluene and ether in sequence, and dry to obtain benzoxazine-based bis nano silica.

[0052] (5) Mix 95g of polyether polyol (LY-4110), 1g of foam stabilizer (AK8814), 2g of N,N-dimethylcyclohexylamine catalyst, 22g of hydrofluorocarbon foaming agent (HFC-365mfc), and 1g of deionized water for 10min. Then add 20g of benzoxazine-based double nano silica and 10g of benzoxazine-based double PEPA and mix well. Then add 100g of polyphenyl polymethylene polyisocyanate (PM-200) curing agent and stir at 3000rpm for 15s. Then quickly pour into a 300mm×300mm×150mm mold and foam to form. The mold temperature is controlled at 50℃ to obtain nano silica modified polyurethane insulation material.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 1 is that nano-silica is used instead of benzoxazine-based double nano-silica in step (5).

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that step (5) does not contain benzoxazinyl bis-PEPA.

[0057] Flame retardant performance test:

[0058] Oxygen index was tested using an oxygen index meter.

[0059] The UL-94 rating was tested using a horizontal and vertical burner.

[0060] Table 1:

[0061] Oxygen index (%) UL-94 rating Example 1 27.9 V-0 Example 2 29.4 V-0 Example 3 31.3 V-0 Example 4 32.2 V-0 Comparative Example 1 27.0 V-0 Comparative Example 2 24.2 V-1

[0062] As shown in the table, the flame retardant effect of Examples 1-4 is better than that of Comparative Examples 1-2. This is because benzoxazine-based double nano-silica and benzoxazine-based double PEPA structures were added in Examples 1-4. As can be seen from Examples 1-4, the flame retardant effect is better as the amount of benzoxazine-based double nano-silica and benzoxazine-based double PEPA increases. As can be seen from Comparative Example 1 and Example 1, the difference between the two is that Comparative Example 1 uses nano-silica, while Example 1 uses benzoxazine-based double nano-silica. The flame retardant effect of Example 1 is better than that of Comparative Example 1. This is because nano-silica itself is prone to agglomeration, while modified nano-silica can be uniformly dispersed in the material matrix. The larger specific surface area and smaller particle size play a better role in heat insulation and oxygen barrier. Therefore, the effect of Example 1 is better than that of Comparative Example 1.

[0063] Antibacterial performance test:

[0064] (1) Cut the polyurethane insulation material into 1cm×1cm samples, wash with ethanol, and dry.

[0065] (2) Activate Escherichia coli and prepare a bacterial suspension of 1×104 cfu / ml-5×104 cfu / ml. Place the cut sample into an Erlenmeyer flask containing the bacterial suspension, fix it on a shaking table, and shake it at 300 r / min for 5 min at 25℃. Take 1 mL of the bacterial suspension and dilute it 100 times.

[0066] (3) Take 1 mL of the above bacterial suspension and inoculate it into an agar plate. Incubate at 37°C under natural light for 48 h and count the colonies according to the method in GB15979-2003.

[0067] Antibacterial rate (%) = (Average colony count before sample shaking - Average colony count after sample shaking) / Average colony count before sample shaking × 100%.

[0068] Table 2:

[0069] Antibacterial rate (%) Example 1 85.6 Example 2 92.3 Example 3 98.4 Example 4 99.9 Comparative Example 1 -

[0070] As shown in the table, the thermal insulation material prepared by this invention has a good antibacterial effect, with an antibacterial rate of up to 99.9%. This is because Examples 1-4 contain benzoxazine-based double nano-silica, which contains a geminal quaternary ammonium salt structure, and has a good antibacterial effect. Therefore, the antibacterial effect of Examples 1-4 is better than that of Comparative Example 1.

[0071] Thermal stability performance test:

[0072] The thermal stability of the material was tested using a thermogravimetric analyzer. The sample mass was 10 mg. The gas flow rate was 20 mL / min, the heating rate was 10 °C / min, and the temperature range was 40-800 °C.

[0073] Table 3:

[0074] <![CDATA[T 10% / ℃]]> <![CDATA[W 800 / wt%]]> Example 1 308 19.4 Example 2 314 22.3 Example 3 319 26.7 Example 4 320 28.1 Comparative Example 1 289 15.1 Comparative Example 2 301 18.2

[0075] As shown in the table, the thermal insulation material prepared by this invention has good thermal stability. The thermal stability of Examples 1-4 is greater than that of Comparative Examples 1-2. This is because Examples 1-4 contain benzoxazine-based double nano-silica and benzoxazine-based double PEPA structures, and the thermal stability increases with the increase of the amount of both. The difference between Example 1 and Comparative Example 1 is that Example 1 added benzoxazine-based double nano-silica, while Comparative Example 1 used nano-silica instead of benzoxazine-based double nano-silica. Example 1 contains the thermally stable benzoxazine structure, while Comparative Example 1 does not, therefore its effect is worse. The difference between Comparative Example 2 and Example 1 is that it does not contain the benzoxazine-based double PEPA structure; therefore, the effect of Comparative Example 2 is not as good as that of Example 1. Therefore, the thermal insulation material prepared by this invention has good thermal stability.

[0076] Mechanical property testing: Refer to GB / T6344-2008 to test the tensile strength of the material.

[0077] Table 4:

[0078] Tensile strength / kPa Example 1 135 Example 2 148 Example 3 160 Example 4 164 Comparative Example 1 118 Comparative Example 2 129

[0079] As shown in the table, the thermal insulation material prepared by the present invention has good mechanical properties. As can be seen from Examples 1-4, the tensile strength increases with the increase of the amount of benzoxazine-based double nano-silica and benzoxazine-based double PEPA structure. The test results of Comparative Example 2 are better than those of Comparative Example 1. This is because the modified nano-silica can be uniformly dispersed in the material matrix, while Comparative Example 1 is unmodified nano-silica, which is prone to agglomeration in the matrix, so its mechanical properties are not as good as those of Comparative Example 2.

Claims

1. A method for preparing a nano-silica modified polyurethane thermal insulation material, characterized in that, The preparation method is as follows: Mix polyether polyol, foam stabilizer, catalyst, foaming agent, and deionized water for 5-10 minutes until homogeneous. Then add benzoxazine-based double nano silica and benzoxazine-based double PEPA and mix until homogeneous. Add curing agent and stir at 3000 rpm for 10-20 seconds. Quickly pour into a 300mm×300mm×150mm mold and foam to form. Control the mold temperature at 50℃ to obtain nano silica-modified polyurethane insulation material.

2. The preparation method of the nano-silica modified polyurethane thermal insulation material according to claim 1, characterized in that, The mass ratio of the polyether polyol, foam stabilizer, catalyst, foaming agent, deionized water, benzoxazine-based double nano silica, benzoxazine-based double PEPA, and curing agent is 80-100:1-2:1-2:20-25:1-2:5-20:1-10:

100.

3. The preparation method of the nano-silica modified polyurethane thermal insulation material according to claim 1, characterized in that, The catalyst is one of N,N-dimethylcyclohexylamine and dibutyltin dilauric acid.

4. The preparation method of the nano-silica modified polyurethane thermal insulation material according to claim 1, characterized in that, The preparation method of the benzoxazine-based bis-PEPA is as follows: (1) Add 4-chloro-1-butanamine and formaldehyde to dioxane solvent, stir at room temperature for 30-40 min, then add biphenyl hydroquinone, heat to 80-90℃, react for 8-12 h, after the reaction is completed, cool to room temperature, rotary evaporate, dry to obtain intermediate 1; (2) Add PEPA to acetonitrile solvent, stir and disperse, heat to 55-65℃, add intermediate 1, stir and mix evenly, heat to 85-90℃, add pyridine, reflux reaction for 22-26h, after the reaction is completed, filter while hot, wash with ethanol, dry to obtain benzoxazinyl bis PEPA.

5. The preparation method of the nano-silica modified polyurethane thermal insulation material according to claim 4, characterized in that, In (1), the molar ratio of 4-chloro-1-butamine, formaldehyde, and biphenyl is 2-2.5:6-7:

1.

6. The preparation method of the nano-silica modified polyurethane thermal insulation material according to claim 4, characterized in that, In (2), the molar ratio of PEPA, intermediate 1, and pyridine is 2-2.5:1:0.4-0.

6.

7. The preparation method of the nano-silica modified polyurethane thermal insulation material according to claim 1, characterized in that, The preparation method of the benzoxazine-based double nano-silica is as follows: S1. Under nitrogen protection, N,N-diethyl-aminopropylmethyldimethoxysilane was added to ethanol solvent and stirred to disperse. Intermediate 1 was added to the mixture at 50-55°C and reacted for 8-12 hours. After the reaction was completed, the mixture was cooled to room temperature, rotary evaporated, washed with diethyl ether, and dried to obtain intermediate 2. S2. Add intermediate 2 to toluene solvent, stir and disperse, then add nano-silica, continue stirring for 20-40 min, add 75% ethanol aqueous solution, heat under reflux for 2-3 h, after which cool to room temperature, filter, wash with toluene and diethyl ether in sequence, and dry to obtain benzoxazine-based bis-nano-silica.

8. The method for preparing the nano-silica modified polyurethane thermal insulation material according to claim 7, characterized in that, In S1, the molar ratio of N,N-diethyl-aminopropylmethyldimethoxysilane to intermediate 1 is 2-2.4:

1.

9. The method for preparing the nano-silica modified polyurethane thermal insulation material according to claim 7, characterized in that, In S2, the mass ratio of intermediate 2 to nano-silica is 4-6:1.

Images