Aerogel based on bisphenol A type diether dianhydride monomer and preparation method thereof
By introducing nano-zirconium phosphate and siloxane crosslinking networks into polyimide aerogel, the problems of low strength and severe volume shrinkage of polyimide aerogel are solved, achieving high elasticity and excellent flame retardant and heat insulation properties, making it suitable for aerospace and other fields.
Patent Information
- Application Number
- CN202511810432.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-12-18
- Filing Date
- 2025-12-03
- Publication Date
- 2026-01-20
AI Technical Summary
Polyimide aerogels suffer from low strength, susceptibility to deformation, severe volume shrinkage, and poor surface quality during preparation, making it difficult to meet the long-term use requirements of flame-retardant and heat-insulating materials.
An aerogel preparation method based on bisphenol A type diether dianhydride monomer was adopted. By introducing nano-zirconium phosphate material into the polyimide backbone, an organic/inorganic composite aerogel was formed. The flame retardant and toughening effects of zirconium phosphate, combined with the cross-linking network of siloxane, improved the mechanical properties and flame retardant and heat insulation properties of the aerogel.
It achieves high elasticity, recoverability and excellent flame retardant and heat insulation properties of aerogel, avoids deformation or cracking, and enhances the structural stability and flame retardant effect of the material.
Smart Images
Figure CN121362327A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of aerogel materials, in particular to an aerogel based on bisphenol A type diether dianhydride monomer and a preparation method thereof. BACKGROUND
[0002] Aerogel material is a new type of material with light weight and porous three-dimensional network structure, which has broad application prospects in the fields of aerospace, catalysis, sensors, heat and sound insulation, solvent adsorption, etc. Compared with traditional thermal insulation materials, aerogel material has extremely low thermal conductivity. Its low bulk density and porous structure prevent gaseous and solid heat conduction, and the "infinite" gap wall can minimize heat radiation. Therefore, aerogel can be used as fireproof thermal insulation material in battery systems to improve the safety of lithium batteries, and can be made into fireproof sensors to play a role in portable devices and human-computer interaction fields. In addition, fireproof aerogel can also be used as a coating in building insulation.
[0003] Polyimide aerogel is a special type of organic aerogel, which has excellent thermal insulation performance and thermal stability, and also has the properties of high temperature resistance and mechanical strength. It can withstand stress and load to a certain extent. However, the strength of polyimide precursor-polyamide acid obtained by polymerization of diamine and dianhydride is low, which is a typical gel state. It is easy to change under external force and difficult to recover, and the volume shrinkage is serious. The prepared aerogel has the problems of poor surface quality, low strength, stress concentration in large size manufacturing, and may cause cracking of aerogel. Therefore, a new type of aerogel needs to be developed, which can realize the enhancement of fireproof thermal insulation effect and has flexible mechanical properties to meet the long-term use requirements. SUMMARY
[0004] To solve the above problems, the present application provides an aerogel based on bisphenol A type diether dianhydride monomer and a preparation method thereof. The aerogel has a polyimide skeleton and nano zirconium phosphate material inserted therein, which improves the toughness of the aerogel and also inhibits its volume shrinkage, and has excellent fireproof thermal insulation performance.
[0005] The first object of the present application is to provide a preparation method of an aerogel based on bisphenol A type diether dianhydride monomer, comprising the following steps: Step one, synthesis of flame-retardant diamine, specifically comprising: S1: In organic solvent 1, nucleophilic substitution reaction of phosphorus oxychloride and dihydroxy aldehyde occurs under the action of acid binding agent to generate chlorophosphoric acid aldehyde, wherein the hydroxyl group is alcohol and / or phenolic hydroxyl group; S2: In organic solvent 2, Schiff base reaction of azacyclic diamine and chlorophosphoric acid aldehyde obtained in S1 occurs under the action of base reagent to generate chlorophosphoric acid amine; S3: in organic solvent 3, the dihydroxy silane and the chlorophosphonate amine obtained in S2 undergo substitution reaction under the condition of acid binding agent, to obtain the flame-retardant diamine, wherein the hydroxyl group in the dihydroxy silane is alcohol and / or phenolic hydroxyl group; Step two, in organic solvent 4, the flame-retardant diamine and bisphenol A type diether dianhydride undergo polycondensation reaction to obtain polyamic acid prepolymer; Step three, in the polyamic acid prepolymer solution, modified zirconium phosphate and cosolvent are added, and ultrasonic dispersion and electromagnetic stirring are carried out in sequence, and after complete dispersion and uniformity, sealing is carried out; low-temperature freezing is carried out, and sol-gel transformation is completed, to obtain polyamic acid salt-zirconium phosphate gel; then, freeze-drying treatment is carried out, to obtain polyamic acid-zirconium phosphate composite aerogel, and the mass of the modified zirconium phosphate is 1wt%-8wt% of the mass of the polyamic acid prepolymer.
[0006] Step four, the aerogel in step three is subjected to thermal imidization treatment in a muffle furnace, to obtain polyimide-zirconium phosphate composite aerogel.
[0007] On the basis of the above technical solutions, the application can also be improved as follows: Further, the substitution reaction condition in step one S1 is as follows: 1-2h of reaction at 0℃ under the condition of nitrogen atmosphere and acid binding agent, and then 6h of reaction at normal temperature; the molar ratio of the feeding of the phosphorus oxychloride, dihydroxy aldehyde and acid binding agent is (1.1-1.3):1:2; The Schiff base reaction condition in S2 is as follows: stirring overnight at 50-80℃ under the condition of nitrogen atmosphere and alkali reagent; the molar ratio of the feeding of the chlorophosphonate aldehyde, nitrogen heterocyclic diamine and alkali reagent is 1:(1.2-1.5):2; since the Schiff base is usually stable when the pH value is higher than 7, the pH value of the system is controlled to be 7-8 by using the alkali reagent; The substitution reaction condition in S3 is as follows: 24h of stirring reaction at 40-60℃ under the condition of nitrogen atmosphere and acid binding agent; the molar ratio of the feeding of the chlorophosphonate amine, terminal dihydroxy silane and acid binding agent is (2.1-2.3):1:1.
[0008] Further, the acid binding agent in steps one S1 and S3 is independently selected from one of the following: trimethylamine, triethylamine, N,N-diisopropylethylamine, tetramethylammonium hydroxide, N-methylmorpholine, sodium methoxide, sodium ethoxide, potassium tert-butoxide, butyllithium and tert-butyllithium; the alkali reagent in step one S2 is selected from potassium carbonate or sodium bicarbonate; the organic solvents 1, 2 and 3 in step one are independently selected from one or more of the following: 1,2-dichloroethane, ethyl acetate, tetrahydrofuran and acetone.
[0009] Further, the dihydroxy aldehyde in S1 is selected from one of the following structures:
[0010] Further, the nitrogen heterocyclic diamine S2 is pyrrole, imidazole, thiazole, furazan, pyridine, pyrimidine, pyrazine, pyridazine and derivatives thereof, containing two primary amino substituents; the remaining substituents on the nitrogen heterocycle are hydrogen atoms and / or alkyl, alkoxy, alkylthio, alkyl ester and / or benzyl, benzylthio, benzyloxy and / or hydroxyl, alkoxy and / or thiol groups.
[0011] Further explanation is made to the relevant terms used herein: the terms alkyl, alkoxy, alkylthio, alkyl ester refer to alkyl, alkoxy, alkylthio, alkyl ester with C1-C4 carbon chain; hydroxyl, alkoxy refer to hydroxyl and end / side hydroxyalkyl with C1-C4 carbon chain.
[0012] The nitrogen heterocyclic diamine is selected as the functional group of the flame-retardant diamine: the nitrogen heterocycle can promote carbonization of the material into a carbon layer to insulate oxygen and heat during combustion; it can also promote the formation of phosphate and form a protective layer on the surface of the material, further reducing the burning rate and improving the flame-retardant effect. In addition, the polarity of the N atom in the nitrogen heterocycle can also improve the mechanical properties of the polyimide.
[0013] Further, the dihydroxy silane in S3 is selected from one of the following structures:
[0014]
[0015] The hydrophobic groups of the dihydroxy silane, such as silicon methyl, alkyl / benzyl, are introduced into the diamine monomer through a nucleophilic substitution reaction, which can help the dehydrating agent to penetrate into the wet gel during the preparation of aerogel; and give the aerogel certain hydrophobicity.
[0016] Further, the specific operation of step two is as follows: the flame-retardant diamine is dissolved in anhydrous organic solvent 4 under nitrogen atmosphere, then bisphenol A type diether dianhydride is added and stirred for mixing; the temperature is raised to 0-10℃ and stirred for 4-8h; after the reaction is completed, the temperature is lowered to room temperature and the polyamic acid prepolymer is obtained by standing.
[0017] The molar ratio of the flame-retardant diamine to bisphenol A type diether dianhydride is 1:(1.01-1.05); The organic solvent 4 is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, N,N-diethylpropionamide, dimethyl sulfone, dimethyl sulfoxide, N-methyl pyrrolidone.
[0018] Further, the modified zirconium phosphate in step three is equivalent to 4wt%-8wt% of the mass of the polyamic acid prepolymer; The cosolvent is one of triethylamine, trialkyl tertiary amine, octadecyl dimethyl tertiary amine and dodecyl dimethyl tertiary amine. The temperature of the low-temperature freezing is -20℃, and the freezing time is 20-24h; the cold trap temperature of the vacuum freeze drying is -80℃, the vacuum degree is less than 0.1kPa, and the drying time is 40-48h.
[0019] Further, the modified zirconium phosphate in step three is tetra(2-hydroxyethyl) ammonium chloride intercalation modified α Zirconium phosphate. α The zirconium phosphate is intercalation modified with quaternary ammonium salt, which can improve the dispersibility and compatibility, so that the zirconium phosphate layers can be uniformly dispersed in the polyamide acid polymer solution. Because the interlayer spacing of alpha-zirconium phosphate is small, it is difficult for tetra(2-hydroxyethyl) ammonium chloride to directly and quickly insert between the alpha-zirconium phosphate layers, and a "pre-stretching" process of propylamine is needed, and the specific operation is as follows: The zirconium phosphate powder and propylamine are dissolved in deionized water, and ultrasonic stirring is first performed for 10-20min, and then mechanical stirring is performed for 12h to gel the zirconium phosphate; α- Then, tetra(2-hydroxyethyl) ammonium chloride is added, and mechanical stirring is performed at 60℃ for 24h; the product is centrifuged, filtered, washed and dried to obtain the modified zirconium phosphate powder. α- The molar ratio of the zirconium phosphate, propylamine and tetra(2-hydroxyethyl) ammonium chloride is 1:2:(2-3);
[0020] The molar concentration of the zirconium phosphate is 0.2-0.4mol / L. α- α- Zirconium phosphate (Zr(HPO4)2·H2O) is a multifunctional mesoporous material with low expansion coefficient and low dielectric constant, and has outstanding solid acid catalytic charring effect and barrier effect caused by the layer structure in the aspect of flame retardation. There are Lewis acid sites and Bronsted acid sites with catalytic activity between the layers, which can catalyze the degradation of polymers into carbon to form a barrier at high temperature; at the same time, it can also react with the acid source in the system to generate a crosslinked network structure, so that the expanded carbon layer is more stable; the layer structure of zirconium phosphate itself plays a gas barrier role in the expanded carbon layer, which blocks the transmission of flammable gas, oxygen and heat.
[0021] α Further, the thermal imidization condition is that the temperature is increased at a rate of 2-4℃ / min, and is respectively treated at 100℃, 160℃ and 220℃ for 4h, and finally treated at 280℃ for 1h.
[0022] The second object is to provide an aerogel based on bisphenol A type diether dianhydride monomers, which is prepared based on the above preparation method.
[0023] The advantages of the present application are:
[0024] The advantages of the present application are: The aerogel provided by the application is an organic / inorganic composite aerogel with polyimide as a skeleton and modified zirconium phosphate material inserted therein. By combining the rigid modified zirconium phosphate with the flexible polyimide, the aerogel is endowed with excellent mechanical properties. The strong interface effect of the cross-linked network and the introduction of siloxane provide toughness; and the layered zirconium phosphate material ensures the mechanical strength. In addition, the silane part contained in the polyimide molecule can react with the hydroxyl group on the surface of the modified zirconium phosphate and in the intercalation layer to form a chemical bond, thereby improving the structural stability of the material and promoting the dispersion and agglomeration of the zirconium phosphate. This method does not change the properties of the polymer network itself and has mild preparation conditions.
[0025] The organic / inorganic composite aerogel provided by the application has excellent high elasticity and recoverability. On a molecular scale, the repulsion between the hydrophobic silane molecules in the cross-linked network initiates the rebound effect under high compression strain, thereby obtaining good compression resistance and deformation resistance. The imine bond generated by the Schiff base reaction endows the aerogel with dynamic mechanical characteristics including self-healing and viscoelasticity, which can effectively inhibit the volume shrinkage of the aerogel and avoid deformation or cracking of the aerogel.
[0026] The preparation method of the aerogel provided by the application involves the synthesis of a flame-retardant diamine and the modification of zirconium phosphate. α The introduction of phosphorus, nitrogen and silicon into the flame-retardant diamine molecule can exert the synergistic flame-retardant effect of multiple flame-retardant elements. α The modified zirconium phosphate has outstanding solid acid catalytic charring effect and barrier effect due to the lamellar structure, and can further enhance the flame-retardant and heat-insulating effects of the aerogel. α The modified zirconium phosphate can further enhance the flame-retardant and heat-insulating effects of the aerogel. BRIEF DESCRIPTION OF DRAWINGS
[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor.
[0028] Figure 1 XRD patterns of α-zirconium phosphate and modified zirconium phosphate.
[0029] Figure 2 NMR hydrogen spectrum of the flame-retardant diamine intermediate in Example 1; Figure 3 NMR hydrogen spectrum of the flame-retardant diamine intermediate in Example 2; Figure 4 NMR hydrogen spectrum of the flame-retardant diamine intermediate in Example 3; Figure 5 Infrared spectrum of the aerogel in Example 1, Comparative Example 1 and Comparative Example 2. Detailed Implementation
[0030] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0031] In the description provided herein, the terms “comprising,” “is,” “contains,” “has,” and “includes” are used in an open-ended manner and should therefore be construed as meaning “including, but not limited to.” When a claim is made or a description of an article, substance, or method is made by “comprising” various steps or components, the device, system, or method may also “consistently” or “made of” various steps or components, unless otherwise stated.
[0032] Unless otherwise defined, the experimental materials used in the following examples and comparative examples are all available from conventional biochemical reagent companies.
[0033] Preparation example: for α - Zirconium phosphate was used for intercalation modification. α - Zirconium phosphate was supplied by Fujian Ruisen New Materials Co., Ltd. 0.6 μ Extra grade with a particle size of m α - Zirconium phosphate, white powder (99.9% purity).
[0034] 0.04 mol α- Zirconium phosphate powder and 0.08 mol propylamine were dissolved in 100 mL of deionized water. The solution was first ultrasonically stirred for 20 min, and then mechanically stirred for 12 h. α- Zirconium phosphate was gelled; then 0.1 mol of tetrakis(2-hydroxyethyl)ammonium chloride was added, and the mixture was mechanically stirred at 60°C for 24 h; the product was centrifuged, filtered, washed, and dried to obtain modified zirconium phosphate.
[0035] The X-ray diffractometer was used to characterize the results. α - Crystal structures of zirconium phosphate and modified zirconium phosphate 1. Voltage intensity 40 kV, current intensity 30 mA, scan range 0.5°~20°(2θ), step size 0.02°.
[0036] Depend on Figure 1 It can be seen that the XRD pattern representing α-zirconium phosphate has a low and flat baseline, sharp peaks, and no impurity peaks. The characteristic peak of α-zirconium phosphate appears at 11.87°, corresponding to an interlayer spacing of 0.763 nm, indicating that it has a single crystal phase and a complete layered structure. In contrast, the XRD pattern of modified zirconium phosphate has changed, with its characteristic peak shifting to a lower angle at 3.56°; the interlayer spacing has increased to 2.54 nm, and the diffraction peak at 11.87° has disappeared. This indicates that the intercalation modification of tetra(2-hydroxyethyl)ammonium chloride is complete and has been successfully integrated into the interlayer of α-zirconium phosphate.
[0037] Example 1
[0038] A kind of aerogel based on bisphenol A type diether dianhydride monomer, its preparation method is as follows: Step one: synthesis of flame-retardant diamine. Specifically includes: S1: at 0 DEG C, nitrogen atmosphere, the dichloromethane dissolved with phosphorus oxychloride is mixed with the dichloromethane solution dissolved with protocatechualdehyde (CAS number: 139-85-5) and N, N-diisopropyl ethylamine, wherein the molar ratio of phosphorus oxychloride, protocatechualdehyde and N, N-diisopropyl ethylamine is 1.1:1:2; the mixture is stirred at 0 DEG C, nitrogen atmosphere, and reacts for 1 h; then it is stirred at room temperature for 6 h. After reaction, filter, the product is washed repeatedly with 5% sodium hydroxide solution and deionized water until the organic phase is neutral; dichloromethane solvent is removed by rotary evaporation, and dried to obtain chlorophosphonate aldehyde 1, with a yield of 83.5%.
[0039] S2: under nitrogen atmosphere, in anhydrous 1, 2-dichloroethane, chlorophosphonate aldehyde 1 and 6-methyl-2, 4-pyrimidine diamine (CAS number: 1791-73-7) are added with a molar ratio of 1:1.2, and stirred to dissolve, a little excess potassium carbonate is added to maintain the pH value of the mixture solution at 7~8, and the mixture solution is stirred at 80 DEG C for 12 h; after the reaction is completed, the reaction mixture is cooled to room temperature, the solvent is evaporated, washed with brine to remove excess amine, then extracted with ethyl acetate (150 mL x 2), the organic layer is washed with 50 ml water, dried with sodium sulfate, and concentrated. Then the ethyl acetate is rotary evaporated under reduced pressure to obtain chlorophosphonate amine 1, with a yield of 95%.
[0040] S3: at 0 DEG C, nitrogen atmosphere, dichloromethane dissolved with chlorophosphonate amine 1 is mixed with dichloromethane solution dissolved with 1, 4-bis (dimethylhydroxysilyl) benzene (CAS number: 2754-32-7) and triethylamine; wherein the molar ratio of chlorophosphonate amine 1, 1, 4-bis (dimethylhydroxysilyl) benzene and triethylamine is 2.2:1:1; after mixing, the temperature is raised to 40~60 DEG C and stirred for 24 h; after reaction, filter, the filtrate is washed with saturated brine 3 times, concentrated, recrystallized, dichloromethane solvent is removed by rotary evaporation, and dried to obtain flame-retardant diamine 1; the yield is 72.1%, and the structural formula is as follows; the nuclear magnetic hydrogen spectrum is shown in Figure 2 , test instrument: AVANCE superconducting nuclear magnetic resonance spectrometer of Germany Bruker company. Test conditions: 400 MHz, solvent is CDCl3, without internal standard.
[0041]
[0042] Step two, polyamide acid prepolymer preparation: The flame-retardant diamine 1 was dissolved in anhydrous N,N-dimethylacetamide under a nitrogen atmosphere, stirred and dissolved, then the bisphenol A type diether dianhydride was added and stirred and mixed, the molar ratio of the flame-retardant diamine to the bisphenol A type diether dianhydride was 1:1.05; the temperature was increased to 0-10°C and stirred for 8h; after the reaction was completed, the temperature was reduced to room temperature and left to stand, to obtain a polyamic acid prepolymer 1. The obtained polyamic acid prepolymer 1 has the following repeating unit:
[0043] Step three, 4wt% of modified zirconium phosphate and trialkyl tertiary amine corresponding to the mass of the polyamic acid prepolymer was added to the polyamic acid prepolymer 1 solution, ultrasonic dispersion and electromagnetic stirring were carried out in sequence, after uniform stirring, it was sealed; and was frozen at -20°C for 24h, to complete the sol-gel transition, to obtain a polyamic acid salt-zirconium phosphate gel; then it was dried under vacuum drying conditions with a cold trap temperature of -80°C and a vacuum degree less than 0.1kPa for 48h, to obtain a polyamic acid-zirconium phosphate aerogel.
[0044] Step four, the polyamic acid-zirconium phosphate aerogel was placed in a muffle furnace for thermal imidization treatment: with a heating rate of 3°C / min, it was treated at 100°C, 160°C and 220°C respectively for 4h each time, and finally treated at 280°C for 1h, to obtain a polyimide-zirconium phosphate aerogel.
[0045] Example 2
[0046] An aerogel based on a bisphenol A type diether dianhydride monomer, the preparation method is the same as that of Example 1, the difference is that in step one, the dihydroxy aldehyde used in S1 is 2,3-dihydroxy-2H-pyran-2-carbaldehyde (CAS: 146664-39-3); the azacyclic diamine used in S2 is 1-methyl-1H-pyrrol-2,5-diamine (CAS No. 862200-46-2); the dihydroxy silane used in S3 is 3-[[(tert-butyl)silyl]oxy]-5-hydroxy-benzyl alcohol (CAS: 641571-45-1), and the solvent used is ethyl acetate. The structural formula of the obtained flame-retardant diamine (the yield is 75.3%) is as shown in the following Figure 3 ;
[0047] The polyamic acid prepolymer obtained in step two has the following repeating unit:
[0048] Example 3
[0049] An aerogel based on bisphenol A type diether dianhydride monomer, the preparation method is the same as example 1, the difference is that in step one, the dihydroxy aldehyde used in S1 is selected from 5,5-dihydroxyvaleraldehyde (CAS: 16776-90-2); the azacyclic diamine used in S2 is 4,5-diaminofurazan (CAS No. 17220-38-1); the dihydroxysilane used in S3 is monodihexanoate-terminated polydimethylsiloxane (CAS: 218131-11-4), and the solvent used is tetrahydrofuran. The structural formula of the flame-retardant diamine obtained in step one (the yield is 71.3%) is as shown in the following nuclear magnetic hydrogen spectrum: Figure 4
[0050] The polyamic acid prepolymer obtained in step two has the following repeating unit:
[0051] Examples 4-6
[0052] An aerogel based on bisphenol A type diether dianhydride monomer, the difference between the preparation method and example 1 is that the mass of modified zirconium phosphate added in step three is different. Specifically, 2wt%, 6wt%, 8wt% of modified zirconium phosphate corresponding to the mass of polyamic acid prepolymer is added to the polyamic acid prepolymer solution.
[0053] Comparative example 1
[0054] An aerogel based on bisphenol A type diether dianhydride monomer, the difference between the preparation method and example 1 is that step one is omitted, that is, in step two, 6-methyl-2,4-pyrimidine diamine is directly used as a diamine monomer and polymerized with bisphenol A type diether dianhydride monomer, and the rest of the conditions are the same as example 1.
[0055] The polyamic acid prepolymer obtained in step two has the following repeating unit:
[0056] Comparative example 2
[0057] An aerogel based on bisphenol A type diether dianhydride monomer, the difference between the preparation method and example 1 is that no modified zirconium phosphate is added in step three; the rest of the conditions are the same as example 1.
[0058] 1. Chemical composition test: The chemical composition of the aerogels obtained in example 1, comparative example 1 and comparative example 2 was analyzed by means of Bruker VERTEX 80 type Fourier transform infrared spectrometer. The resolution is 2cm -1 , the scanning number is 32 times, and the test results are shown in the following table: Figure 5 .
[0059] FromFigure 2 Three samples in the range of 2800~3000 cm -1 The saturated -CH2, -CH3 stretching peaks appeared in both regions. The typical absorption of polyimide includes: the asymmetric and symmetric stretching peaks of ether (C-O-C) bond at 1235 cm -1 , 1070 cm -1 , respectively; the asymmetric and symmetric stretching vibration peaks of imide ring C=O bond at 1780 cm -1 and 1725 cm -1 , respectively; and the bending vibration absorption peak of C=O bond at 725 cm -1 .
[0060] The broad absorption in the range of 3000~3500 cm -1 of Example 1 and Comparative Example 1 is caused by the amino group in polyimide, P-OH group in modified zirconium phosphate, and -OH group in the intercalated tetra(2-hydroxyethyl) ammonium chloride molecules; indicating that the introduction of modified zirconium phosphate enhances the hydrogen bonding. The peaks at 1169 cm -1 and 1380 cm -1 are the stretching vibrations of P-O-C bond and P=O bond, respectively, and Comparative Example 1 does not contain absorption at this place. The strong absorption peak in the range of 960~1005 cm -1 is attributed to the stretching vibration of P-O-P bond, and the peak intensity at this place in Comparative Example 2 is significantly weakened due to the absence of modified zirconium phosphate.
[0061] The absorption peak of C=N bond stretching at 1630 cm -1 of Example 1 is stronger than that of Comparative Example 1, because the diamine monomer used in Comparative Example 1 is not flame-retardant modified, does not contain imine bond formed by Schiff base reaction, and only has pyrimidine ring C=N bond absorption; at the same time, it does not contain the stretching vibration absorption peaks of Si-C bond and Si-O bond at 836 cm -1 and 807 cm -1 of Example 1 and Comparative Example 2, respectively.
[0062] 2. Performance test The aerogels prepared in Examples 1~6 and Comparative Examples 1~2 were tested: Shrinkage: The initial size before complete drying of the aerogel and the final size after drying (including length, width, and height) were recorded, and the shrinkage was calculated according to the following formula: shrinkage = (initial size - final size) / initial size × 100%.
[0063] Compression strength: tested at room temperature with a compression rate of 2 mm / min using an instron universal testing machine; tensile strength: tested at room temperature using the method of GB2567-2008.
[0064] Compressive stress: test by applying a weight of 1000 g on the aerogel, test temperature 25℃.
[0065] Limiting oxygen index (LOI): test by using a JE-5 type full-automatic oxygen index tester (Nanjing Jinglei Instrument and Equipment Co., Ltd.), according to GB / T 5454-1997 “Textile Burning Performance Experiment Oxygen Index Method”, sample size is 110 mm x 6 mm x 2 mm.
[0066] The results of the above tests are listed in Table 1 below.
[0067] Table 1
[0068] From Table 1, compared with Comparative Example 1, the flame-retardant modification of the diamine monomer increases the crosslinking network of the polyimide and increases the porosity; the barrier effect of the various flame-retardant groups and the modified zirconium phosphate endows the aerogel with further enhanced flame-retardant properties; compared with Comparative Example 2, the doping of the modified zirconium phosphate in the PI matrix greatly improves the thermal and mechanical properties of the composite aerogel: the dispersed modified zirconium phosphate nanosheets can produce rich interfacial interactions with the PI matrix, promoting the transfer of external stress, heat, etc. from the PI matrix to the surface of the modified zirconium phosphate nanosheets, significantly enhancing the flame-retardant and mechanical properties of the composite aerogel.
[0069] The polyimide / zirconium phosphate composite aerogel obtained by the present application has excellent performance in limiting oxygen index; at the same time, the results of compressive strength and tensile strength show that the aerogel has good compression resistance and deformation resistance, and has excellent comprehensive performance. It is suitable for the field of aerospace materials with high performance requirements for low yield, light weight, high strength, heat insulation and flame retardation.
[0070] It should be noted that the above examples and comparative examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.
Claims
1. A method for preparing an aerogel based on bisphenol A type diether dianhydride monomer, characterized in that, Includes the following steps: Step 1: Synthesize flame-retardant diamine, specifically including: S1: In organic solvent 1, phosphorus oxychloride reacts with dihydroxyaldehyde in the presence of an acid-binding agent to undergo a nucleophilic substitution reaction to generate chlorophosphoaldehyde; the hydroxyl group in the dihydroxyaldehyde is an alcoholic and / or phenolic hydroxyl group. S2: In organic solvent 2, the azahexacyclic diamine reacts with the chlorophosphate aldehyde obtained in S1 under a base reagent to form chlorophosphate amine; S3: In organic solvent 3, dihydroxysilane and the chlorophosphate-based amine obtained in S2 undergo a substitution reaction under the presence of an acid-binding agent to obtain a flame-retardant diamine; the hydroxyl groups in the dihydroxysilane are alcoholic and / or phenolic hydroxyl groups; Step 2: In organic solvent 4, flame-retardant diamine and bisphenol A diether dianhydride undergo a polycondensation reaction to obtain polyamic acid prepolymer; Step 3: Add modified zirconium phosphate and co-solvent to the polyamic acid prepolymer solution, and then perform ultrasonic dispersion and electromagnetic stirring successively. After thorough and uniform dispersion, seal the solution. Low-temperature freezing completes the sol-gel transformation to obtain polyamic acid-zirconia phosphate gel; subsequent freeze-drying yields polyamic acid-zirconia phosphate composite aerogel; the mass of the modified zirconium phosphate is equivalent to 1wt%~8wt% of the mass of the polyamic acid prepolymer. Step 4: The aerogel from Step 3 is subjected to thermal imidization in a muffle furnace to obtain polyimide-zirconium phosphate composite aerogel.
2. The method for preparing aerogel based on bisphenol A type diether dianhydride monomer as described in claim 1, characterized in that, The substitution reaction conditions described in step S1 are: reaction at 0°C for 1-2 hours under a nitrogen atmosphere and acid-binding agent, followed by reaction at room temperature for 6 hours; The Schiff base reaction conditions described in S2 are: stirring overnight at 50-80°C under a nitrogen atmosphere and with an alkaline reagent. The substitution reaction conditions described in S3 are: under a nitrogen atmosphere and with an acid-binding agent, the reaction is carried out at 40~60℃ with stirring for 24 hours.
3. The method for preparing aerogel based on bisphenol A type diether dianhydride monomer as described in claim 1, characterized in that, The acid-binding agents mentioned in steps S1 and S3 are independently selected from one of trimethylamine, triethylamine, N,N-diisopropylethylamine, tetramethylammonium hydroxide, N-methylmorpholine, sodium methoxide, sodium ethoxide, potassium tert-butoxide, butyllithium, and tert-butyllithium; the alkaline reagent mentioned in step S2 is selected from potassium carbonate or sodium bicarbonate; the organic solvents 1, 2, and 3 mentioned in step 1 are independently selected from one or more of 1,2-dichloroethane, ethyl acetate, tetrahydrofuran, and acetone.
4. The method for preparing aerogel based on bisphenol A type diether dianhydride monomer as described in claim 1, characterized in that, The dihydroxyaldehyde described in S1 is selected from one of the following structures: 。 5. The method for preparing aerogel based on bisphenol A type diether dianhydride monomer as described in claim 1, characterized in that, The azaheterocyclic diamine described in S2 is a pyrrole, imidazole, thiazole, oxazole, pyridine, pyrimidine, pyrazine, pyridazine and its derivatives containing two primary amino substituents; the remaining substituents on the azaheterocyclic ring are hydrogen atoms and / or alkyl, alkoxy, alkylthio, alkyl ester and / or benzyl, benzylthio, benzoxy and / or hydroxyl, alkoxy and / or mercapto.
6. The method for preparing aerogel based on bisphenol A type diether dianhydride monomer as described in claim 1, characterized in that, The dihydroxysilane described in S3 is selected from one of the following structures: 。 7. The method for preparing aerogel based on bisphenol A type diether dianhydride monomer as described in claim 1, characterized in that, The reaction conditions for step two are as follows: under a nitrogen atmosphere, flame-retardant diamine is dissolved in anhydrous organic solvent 4, and then bisphenol A type diether dianhydride is added and stirred; the mixture is heated to 0℃~10℃ and stirred for 4h~8h; after the reaction is completed, it is allowed to cool to room temperature and stand to obtain polyamic acid prepolymer; The molar ratio of the flame-retardant diamine to bisphenol A diether dianhydride is 1:(1.01~1.05); The organic solvent 4 is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, N,N-diethylpropionamide, dimethyl sulfone, dimethyl sulfoxide, and N-methylpyrrolidone.
8. The method for preparing aerogel based on bisphenol A type diether dianhydride monomer as described in claim 1, characterized in that, The mass of the modified zirconium phosphate mentioned in step three is equivalent to 4% to 8% of the mass of the polyamic acid prepolymer; The co-solvent is one of triethylamine, trialkyl tertiary amine, octadecyl dimethyl tertiary amine and dodecyl dimethyl tertiary amine; The low-temperature freezing temperature is -20℃, and the freezing time is 20~24h; the cold trap temperature for vacuum freeze drying is -80℃, the vacuum degree is less than 0.1kPa, and the drying time is 40~48h.
9. The method for preparing aerogel based on bisphenol A type diether dianhydride monomer as described in claim 1, characterized in that, The modified zirconium phosphate mentioned in step three is an intercalation modified zirconium phosphate. α- Zirconium phosphate, the specific modification operation is as follows: α- Zirconium phosphate powder and propylamine were dissolved in deionized water, and the mixture was first ultrasonically stirred for 10-20 minutes, followed by mechanical stirring for 12 hours. α- Zirconium phosphate was gelled; then tetra(2-hydroxyethyl)ammonium chloride was added, and the mixture was mechanically stirred at 60°C for 24 hours; the product was centrifuged, filtered, washed, and dried to obtain modified zirconium phosphate powder. The α- The molar ratio of zirconium phosphate, propylamine, and tetra(2-hydroxyethyl)ammonium chloride is 1:2:(2~3); α- The molar concentration of zirconium phosphate is 0.2~0.4 mol / L.
10. An aerogel, characterized in that, The aerogel is prepared using the preparation method based on bisphenol A type diether dianhydride monomer as described in any one of claims 1 to 9.