Boron-containing phenolic aldehyde-carborane hybrid polymer and preparation method thereof

Abstract

The invention belongs to the technical field of hybrid polymer preparation, and particularly relates to a boron-containing phenolic aldehyde-carborane hybrid polymer and a preparation method thereof. Comprising the following steps: taking a boron-containing phenolic aldehyde compound and a carborane-containing aromatic amine compound as raw materials, dissolving the raw materials in a solvent, and carrying out amination reaction at 20-220 DEG C in a staged manner to obtain the boron-containing phenolic aldehyde-carborane hybrid polymer. The carborane-containing aromatic amine compound is introduced into a boron phenolic aldehyde main chain through an amination method, the carborane-containing aromatic amine compound has a carborane cage-shaped structure unit, the heat-resistant stability and the ablation resistance of the boron phenolic aldehyde are improved by utilizing the unique thermal oxidation behavior of the carborane cage-shaped structure unit, and the thermal stability of the boron phenolic aldehyde is improved through a copolymerization reaction. The preparation method is simple, combines the high strength and high carbon yield of an organic matrix and the antioxidant stability and flexibility of an inorganic main chain, and can be used for high-performance ablative materials in the field of heat protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of hybrid polymers, and particularly relates to a boron-containing phenolic-carbon borane hybrid polymer and a preparation method thereof. Background Art

[0002] Currently, the application of high-end ablation composite materials has increasingly high requirements for the high-temperature performance of polymers. Phenolic resin has attracted much attention in this application due to its high carbon production ability. In addition, phenolic compounds have remarkable thermal oxidation stability and flame retardancy. However, the application of phenolic resin is hindered by some of its inherent defects, such as brittleness and large volume shrinkage during the processing, and poor antioxidant properties of methylene and phenolic groups. Therefore, the toughness and thermal stability of phenolic resin need to be further improved to adapt to high-end applications.

[0003] Currently, the focus of innovative research is to find ways to solve these shortcomings. Those skilled in the art are committed to developing new phenolic resins with improved thermal stability and carbon yield by introducing boron, phosphorus or silicon compounds. Among them, the combination of phosphorus and organic substances can usually improve their heat resistance and flame retardancy. Phosphorus-modified phenolic resin is a modified phenolic resin obtained by introducing a phosphorus-containing compound into the phenolic resin structure. Its preparation process is that the phosphorus-containing compound reacts with aldehyde compounds under the action of a catalyst (sodium hydroxide or hydrochloric acid). The molecular chain generated by the reaction contains phosphorus atoms, and its heat resistance and flame retardancy are significantly improved; silicon-modified phenolic resin is prepared by reacting an organosilicon monomer with phenolic hydroxyl or hydroxymethyl in phenolic resin, and is a kind of modified phenolic resin with heat resistance and water resistance; boron-modified phenolic resin improves the high-temperature resistance, mechanical properties and ablation properties of traditional phenolic resin by introducing boron elements (such as boric acid, borate esters, borates, etc.) into the phenolic resin system. Among them, boron-modified phenolic resin exhibits good thermal properties, but affected by the flexibility and bond energy of the boron-oxygen group itself, its 5% thermal weight loss temperature is only close to 500 °C at most, and its heat resistance and ablation resistance are not good. Summary of the Invention

[0004] To solve the above problems, the present invention provides a boron-containing phenolic-carbon borane hybrid polymer and a preparation method thereof. By an amination method, a carbon borane aromatic amine compound is introduced into the main chain of boron phenolic resin. The carbon borane aromatic amine compound has a carbon borane cage-like structural unit. Utilizing the unique thermal oxidation behavior of the carbon borane cage-like structural unit, the heat resistance stability and ablation resistance of boron phenolic resin are improved, and through copolymerization reaction, the mechanical properties of boron phenolic resin are improved. The preparation method is simple, combining the high strength and high carbon production of the organic matrix and the good oxidation stability and flexibility of the inorganic main chain, and can be used for high-performance ablation materials in the field of thermal protection.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The first object of the present invention is to provide a preparation method of a boron-containing phenolic-carbon borane hybrid polymer, comprising the following steps: Using a boron-containing phenolic compound and a carbon borane aromatic amine compound as raw materials, dissolving them in a solvent, and carrying out an amination reaction in a staged manner at 20°C to 220°C to obtain a boron-containing phenolic-carbon borane hybrid polymer. During the staged amination reaction, the first-stage reaction is first carried out at room temperature and normal pressure, then three normal-pressure reactions are carried out at 60°C to 190°C, and finally the fifth-stage reaction is carried out at 210°C to 220°C under 4.5 MPa to 5.5 MPa.

[0007] Further, the molar ratio of the boron-containing phenolic compound to the carbon borane aromatic amine compound is 1:18 to 22.

[0008] Further, during the amination reaction, the reaction is first carried out at room temperature and normal pressure for 22 h to 26 h, then successively carried out at 60°C to 80°C and 100°C to 120°C under normal pressure for 1 h to 3 h, then carried out at 170°C to 190°C under normal pressure for 20 min to 40 min, and finally carried out at 210°C to 220°C under 4.5 MPa to 5.5 MPa for 3 h to 5 h.

[0009] Further, the preparation method of the carbon borane aromatic amine compound comprises the following steps: S1. Using an o-carborane compound as a raw material, adding n-butyllithium and reacting at -5°C to 0°C to deprotonate the hydrogen on two adjacent carbons, and then adding iodobenzene and a ligand, and carrying out a nucleophilic substitution reaction at room temperature to convert o-carborane into 1,4-diphenyl-o-carborane.

[0010] S2. Using 1,4-diphenyl-o-carborane and nitric acid as raw materials, carrying out a nitration reaction at -5°C to 0°C under the action of an acid catalyst to obtain 1,3',2,3'-dinitrobenzene-o-carborane.

[0011] S3. Using 1,3',2,3'-dinitrobenzene-o-carborane, carrying out a reduction reaction at 90°C to 120°C under the action of divalent iron to obtain 1,3',2,3'-diaminobenzene-o-carborane.

[0012] Further, the molar ratio of the o-carborane compound, n-butyllithium, iodobenzene and the ligand is 1:0.03 to 0.3:0.015 to 0.08:1 to 6, the ligand is pyridine, and the time of the nucleophilic substitution reaction is 25 min to 35 min.

[0013] Furthermore, the molar ratio of 1,4-diphenyl-o-carborane to nitric acid is 1:0.1 - 0.6, the volume ratio of the acid catalyst to nitric acid is 5:1 - 2, the acid catalyst is sulfuric acid, and the nitration reaction time is 1 h - 3 h.

[0014] Furthermore, the molar ratio of 1,3',2,3'-dinitrobenzene-o-carborane to divalent iron is 1:0.003 - 0.03, and the reduction reaction time is 1 h - 3 h.

[0015] Furthermore, a method for preparing a boron-containing phenolic compound includes the following steps: Using a borate compound and paraformaldehyde as raw materials, an esterification reaction is carried out at 120°C - 160°C to obtain a boron-containing phenolic compound.

[0016] Furthermore, the molar ratio of the borate compound to paraformaldehyde is 1:1.1 - 1.5, and the esterification reaction time is 2 h - 4 h.

[0017] Furthermore, a method for preparing an acid ester compound includes the following steps: Mix a boric acid compound and a phenol compound, and carry out an esterification reaction at 140°C - 180°C to obtain a borate ester.

[0018] Furthermore, the molar ratio of the boric acid compound to phenol is 1:3 - 4, the esterification reaction time is 4 h - 6 h, the boric acid compound is one of phenylboronic acid, 4-ethoxy-3-(trifluoromethyl)phenylboronic acid, methylboronic acid, cyclohexylboronic acid, sodium borate, and the phenol compound is one of resorcinol, hydroquinone, cresol, p-tert-butylphenol, cashew phenol, naphthol, or 4,4-dihydroxydiphenylmethane.

[0019] The second object of the present invention is to provide a boron-containing phenolic-carborane hybrid polymer prepared by using the above preparation method.

[0020] The present invention has the following beneficial effects compared with the prior art: The preparation method of the boron-containing phenolic-carbon borane hybrid polymer provided by the present invention adopts the organic-inorganic hybrid polymer preparation technology, and a boron-containing phenolic-carbon borane hybrid polymer is prepared by the boric acid ester-amine curing method. This polymer combines the high strength and high carbon yield of the organic matrix and the good oxidation stability and flexibility of the inorganic main chain. More specifically, a carbon borane-containing aromatic amine compound is introduced into the boron phenolic main chain by an amination method. The carbon borane-containing aromatic amine compound has a carbon borane cage-like structural unit. By utilizing the unique thermal oxidation behavior of the carbon borane cage-like structural unit, the heat resistance stability and ablation resistance of boron phenol are improved, and the mechanical properties of boron phenol are improved through copolymerization reaction. The preparation method is simple, combines the high strength and high carbon yield of the organic matrix and the good oxidation stability and flexibility of the inorganic main chain, and can be used for high-performance ablation materials in the field of thermal protection.

[0021] The carbon borane-containing aromatic amine compound provided by the present invention, wherein carborane (o-, m-, p-C2B 10 H 12 ) is an icosahedral cage structure composed of 10 boron atoms and 2 carbon atoms, with a large volume, a quasi-aromatic three-dimensional rigid structure and strong electron-withdrawing properties, thus endowing it with excellent high-temperature stability, chemical stability and good solubility. Due to the large free volume and steric hindrance effect of carborane, it is easy to cause a decrease in the molecular weight of the polymer and a decline in mechanical properties, affecting the service and application of the material. Therefore, introducing the carborane structural unit into the boron phenolic system by an amination method to prepare an organic-inorganic hybrid polymer can significantly improve its heat resistance stability.

[0022] For the boron-containing phenolic-carbon borane hybrid polymer provided by the present invention, the introduction of boron and carbon borane increases the graphitization degree of the carbonized product of the polymer and promotes the formation of ceramicized products. The pyrolysis compounds of boron and carbon borane formed during high temperature contribute to the formation of void-free graphite-ordered carbon and ceramic layers. During the thermal degradation process, the stable chemical bonds (B–O, B–C) of boron and carbon borane and the formation of other ceramic compounds improve the thermal properties. Its 5% thermal weight loss temperature in air is 500 °C, the carbon yield at 900 °C is 80%, the linear ablation rate is 0.04 mm / min, and the mass ablation rate is 0.05 g / min. Description of the Drawings

[0023] Figure 1 It is the infrared spectrum of the boron-containing phenolic prepared in Example 1 of the present invention.

[0024] Figure 2 It is the 1 H NMR spectrum of the boron-containing phenolic prepared in Example 1 of the present invention.

[0025] Figure 3IR spectrum of 1,3',2,3'-diamino-o-carborane prepared in Example 2 of the present invention.

[0026] Figure 4 1,3',2,3'-diamino-o-carborane prepared in Example 2 of the present invention 1 H NMR spectrum. Figure 4 In (a) is 1,4-diphenyl-o-carborane, (b) is 1,3',2,3'-dinitro-o-carborane, and (c) is 1,3',2,3'-diamino-o-carborane.

[0027] Figure 5 IR spectrum of the boron-containing phenolic-carbon borane hybrid polymer prepared in Example 3 of the present invention.

[0028] Figure 6 The boron-containing phenolic-carbon borane hybrid polymer prepared in Example 3 of the present invention 11 B NMR spectrum.

[0029] Figure 7 TG curves of the boron-containing phenolic prepared in Example 1 of the present invention and the boron-containing phenolic-carbon borane hybrid polymer prepared in Example 3 of the present invention.

[0030] Figure 8 Microscopic structure diagram of the boron-containing phenolic-carbon borane hybrid polymer prepared in Example 3 of the present invention after oxyacetylene ablation. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0032] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the following embodiments of the present invention can be obtained through the market or prepared by existing methods.

[0033] The prior art develops new phenolics with improved thermal stability and carbon yield by introducing boron, phosphorus, or silicon compounds. Among them, boron-containing phenolics exhibit good thermal properties. However, due to the influence of the flexibility and bond energy of the boron-oxygen group itself, the 5% thermal weight loss temperature is only close to 500 °C at most, and its heat resistance and ablation resistance are not good. Based on the above problems, the present invention provides a preparation method of a boron-containing phenolic-carbon borane hybrid polymer, including the following steps:

[0034] Using a boron-containing phenolic compound and a carborane-containing aromatic amine compound as raw materials, dissolving them in a solvent, and carrying out an amination reaction in a staged manner at 20°C to 220°C to obtain a boron-containing phenolic-carborane hybrid polymer. During the staged amination reaction process, the first-stage reaction is carried out at room temperature and normal pressure first, then three normal-pressure reactions are carried out at 60°C to 190°C, and finally the fifth-stage reaction is carried out at 210°C to 220°C under 4.5 MPa to 5.5 MPa.

[0035] It should be noted that the preparation method of the boron-containing phenolic-carborane hybrid polymer provided by the present invention adopts an organic-inorganic hybrid polymer preparation technology, and a boron-containing phenolic-carborane hybrid polymer is prepared by a borate-amine curing method. This polymer combines the high strength and high carbon yield of the organic matrix and the good oxidation stability and flexibility of the inorganic main chain. More specifically, a carborane-containing aromatic amine compound is introduced into the boron-containing phenolic main chain by an amination method. The carborane-containing aromatic amine compound has a carborane cage structure unit. By using the unique thermal oxidation behavior of the carborane cage structure unit, the heat resistance stability and ablation resistance of boron-containing phenol are improved, and the mechanical properties of boron-containing phenol are improved through copolymerization reaction. The preparation method is simple, combines the high strength and high carbon yield of the organic matrix and the good oxidation stability and flexibility of the inorganic main chain, and can be used for high-performance ablation materials in the field of thermal protection.

[0036] In a specific embodiment, the molar ratio of the boron-containing phenolic compound to the carborane-containing aromatic amine compound is 1:18 to 22. It should be noted that in the present invention, a carborane-containing aromatic amine compound is introduced into the boron-containing phenolic main chain. However, when the amount of the carborane-containing aromatic amine compound increases, the brittleness of the boron-containing phenolic-carborane hybrid polymer will increase, reducing its flexibility and impact toughness, making it more likely to break when subjected to external force impact, and increasing the viscosity of the boron-containing phenolic resin system, resulting in poor fluidity of the resin, which affects the overall mechanical properties of the boron-containing phenolic-carborane hybrid polymer.

[0037] In a specific embodiment, during the amination reaction process, the reaction is first carried out at room temperature and atmospheric pressure for 22 h to 26 h, then successively at 60 °C to 80 °C and 100 °C to 120 °C under atmospheric pressure for 1 h to 3 h, then at 170 °C to 190 °C under atmospheric pressure for 20 min to 40 min, and finally at 210 °C to 220 °C under 4.5 MPa to 5.5 MPa for 3 h to 5 h. In the present invention, a carbaborane aromatic amine compound is introduced into the boron phenolic main chain by an amination method. The carbaborane aromatic amine compound has a carbaborane cage structure unit. By utilizing the unique thermal oxidation behavior of the carbaborane cage structure unit, the heat resistance stability and ablation resistance of boron phenolic are improved. In the reaction process of the amination method of the present invention, the reaction is carried out in stages under atmospheric pressure. By gradually increasing the reaction temperature and reducing the reaction, stable intermediates are formed, avoiding local overheating or product non-uniformity caused by violent reactions, gradually activating the reaction activities of different functional groups, ensuring the orderliness of molecular chains through low-temperature pre-polymerization, enhancing mechanical strength through high-temperature curing, and improving material densification in the high-pressure stage. The reaction is mild and the reaction efficiency is increased. The reaction efficiency is more than 90%.

[0038] In a specific embodiment, a preparation method of a carbaborane aromatic amine compound comprises the following steps: S1. Using an o-carborane compound as a raw material, adding n-butyllithium to react for deprotonation of hydrogen on two adjacent carbons at -5 °C to 0 °C, and then adding iodobenzene and a ligand, and carrying out a nucleophilic substitution reaction at room temperature to convert o-carborane into 1,4-diphenyl-o-carborane.

[0039] S2. Using 1,4-diphenyl-o-carborane and nitric acid as raw materials, carrying out a nitration reaction at -5 °C to 0 °C under the action of an acid catalyst to obtain 1,3',2,3'-dinitrobenzene-o-carborane; S3. Using 1,3',2,3'-dinitrobenzene-o-carborane, carrying out a reduction reaction at 90 °C to 120 °C under the action of divalent iron to obtain 1,3',2,3'-diaminobenzene-o-carborane.

[0040] In a specific embodiment, the molar ratio of the o-carborane compound, n-butyllithium, iodobenzene and the ligand is 1:0.03 to 0.3:0.015 to 0.08:1 to 6. The ligand is pyridine, and the time of the nucleophilic substitution reaction is 25 min to 35 min. The molar ratio of 1,4-diphenyl-o-carborane and nitric acid is 1:0.1 to 0.6. The volume ratio of the acid catalyst and nitric acid is 5:1 to 2. The acid catalyst is sulfuric acid, and the time of the nitration reaction is 1 h to 3 h; the molar ratio of 1,3',2,3'-dinitrobenzene-o-carborane and divalent iron is 1:0.003 to 0.03, and the time of the reduction reaction is 1 h to 3 h.

[0041] It should be noted that for the carborane aromatic amine compound provided by the present invention, the carborane aromatic amine compound is carbaundecaborane and its derivatives, wherein carbaundecaborane (o-, m-, p-C2B 10 H 12 ) is an icosahedral cage structure composed of 10 boron atoms and 2 carbon atoms, with a large volume, an aromatic-like three-dimensional rigid structure and strong electron-withdrawing properties, thus endowing it with excellent high-temperature stability, chemical stability and good solubility. Due to the relatively large free volume and steric hindrance effect of carborane, it is easy to cause a decrease in the molecular weight of the polymer and a decline in mechanical properties, affecting the service and application of the material. Therefore, introducing the carbaundecaborane structural unit into the boron phenolic aldehyde system by an amination method to prepare an organic-inorganic hybrid polymer can significantly improve its heat-resistant stability. At the same time, since the bond energy of the boron-carbon bond (448 kJ / mol) is higher than that of the silicon-oxygen bond (422 kJ / mol), the 5% thermal weight loss temperature of boron phenolic aldehyde breaks through the 500 °C limit.

[0042] More specifically, in a specific embodiment, the preparation method of the carborane aromatic amine compound includes the following steps: S1. Using the o-carborane compound as a raw material, in a reaction system of n-butyllithium and a first solvent, react at 0 °C for 4 h, then add a first metal catalyst and mix evenly, and then add pyridine and iodobenzene for a nucleophilic substitution reaction to obtain 1,4-diphenyl-o-carborane. It should be noted that first, using the o-carborane compound as a raw material, due to the electron-deficient effect of boron adjacent to the carbon atom in o-carborane, its C-H bond has a relatively high acidity. Using n-butyllithium as a strong base, in a DMF solvent at 0 °C, selectively deprotonate the hydrogen on two adjacent carbons to generate a dilithium salt intermediate [C2B 10 H 10 2- ·2Li + ; Secondly, under the action of the first metal catalyst, a metal displacement reaction occurs with the dilithium salt, and a catalytic active site is provided to catalyze the arylation of iodobenzene, introducing phenyl twice to obtain 1,4-diphenyl-o-carborane.

[0043] S2. Using 1,4-diphenyl-o-carborane as a raw material, in a reaction system of nitric acid, an acid catalyst and a second solvent, carry out a nitration reaction at 0 °C to obtain 1,3',2,3'-dinitrobenzene-o-carborane. It should be noted that nitric acid is protonated under the action of an acid catalyst to generate a nitronium ion. The nitronium ion, as an electrophilic reagent, attacks the benzene ring of 1,4-diphenyl-o-carborane, undergoes an electrophilic substitution reaction at a specific substitution site to form a nitro-substituted σ complex, and then deprotonates to restore aromaticity to obtain 1,3',2,3'-dinitrobenzene-o-carborane

[0044] ​S3. Using 1,3',2,3'-dinitrobenzene-o-carborane as a raw material, in a reaction system of a second metal catalyst, hydrochloric acid and a solvent, a reduction reaction is carried out at 90 °C to obtain 1,3',2,3'-diaminobenzene-o-carborane, that is, a carborane-containing aromatic amine compound is obtained. It should be noted that in the reaction, the nitro group is first protonated and then obtains electrons and is reduced to an amino group. The metal catalyst plays a role in adsorbing hydrogen, activating hydrogen molecules and transferring electrons in this process, so that the nitro group is gradually reduced to an amino group, and finally 1,3',2,3'-diaminobenzene-o-carborane is obtained.

[0045] In a specific embodiment, the preparation method of the boron-containing phenolic resin compound includes the following steps: Using a borate compound and paraformaldehyde as raw materials, an esterification reaction is carried out at 120 °C to 160 °C to obtain a boron-containing phenolic resin compound.

[0046] In a specific embodiment, the molar ratio of the borate compound to paraformaldehyde is 1:1.1 to 1.5, and the esterification reaction time is 2 h to 4 h.

[0047] In a specific embodiment, the preparation method of the acid ester compound includes the following steps: Mixing a boric acid compound and a phenol compound, and carrying out an esterification reaction at 140 °C to 180 °C to obtain a borate ester.

[0048] In the present invention, the hydroxyl group of boric acid undergoes a condensation reaction with the hydroxyl group of phenol, paraformaldehyde decomposes into formaldehyde, and formaldehyde undergoes an electrophilic substitution with the free phenolic hydroxyl group remaining in the borate ester to obtain a boron-containing phenolic resin compound.

[0049] In a specific embodiment, the molar ratio of the boric acid compound to the phenol compound is 1:3 to 4, the esterification reaction time is 4 h to 6 h, the boric acid compound is one of phenylboronic acid, 4-ethoxy-3-(trifluoromethyl)phenylboronic acid, methylboronic acid, cyclohexylboronic acid, sodium borate, and the phenol compound is one of resorcinol, hydroquinone, cresol, p-tert-butylphenol, cashew phenol, naphthol or 4,4-dihydroxydiphenylmethane.

[0050] The following is further illustrated by specific examples.

[0051] Example 1 The preparation method of boron-containing phenolic resin includes the following steps: S1. Placing 10 g of phenol and 4 g of boric acid in a three-necked round-bottom flask. The flask is equipped with a stirrer, a condenser and a water collector to form a reaction system. The reaction temperature of the reaction system is raised to 140 °C, and the reaction is stirred for 4 h to obtain a borate ester.

[0052] S2. Cool the reaction system to 40 °C, add 10 g of paraformaldehyde, heat up to 120 °C, stir and react for 2 h, and remove the reaction water under vacuum. Cool the reaction system to 100 °C to obtain boron-containing phenolic resin. The synthesis route of the boron-containing phenolic resin is as follows.

[0053] 。

[0054] S3. Cure the boron-containing phenolic resin obtained in S2 in a stainless-steel mold (100 mm × 100 mm) with a flat-plate vulcanization heater. The curing procedure is to cure at 110 °C for 1 h and at 180 °C for 30 min. Then exhaust three times, apply a pressure of 5 MPa, raise the temperature to 220 °C and cure for 2 h, and then cool to 80 °C, release the pressure, and demold to obtain the boron-containing phenolic resin material.

[0055] Figure 1 This is the infrared spectrum of the boron-containing phenolic resin prepared in Example 1 of the present invention. As Figure 1 shown, the stretching vibration absorption peak at 3351 cm -1 is for -OH, the stretching vibration absorption peak at 1650 cm -1 is for the C=C double bond on the benzene ring, the stretching vibration absorption peak at 1360 cm -1 ~1380 cm -1 is for the stretching vibration of B-O, which proves that boron atoms are successfully incorporated into the resin structure. The stretching vibration absorption peak of phenolic hydroxyl C-O is at 1220 cm -1 , the symmetric stretching vibration absorption peak of CH2-O-CH2 is at 1150 cm -1 , and the stretching vibration absorption peak of the C-O bond of benzylic hydroxyl is at 1094 cm -1 .

[0056] Figure 2 This is the 1 1H NMR spectrum of the boron-containing phenolic resin prepared in Example 1 of the present invention. As Figure 2 shown, the resonances at 4.36 ppm to 3.27 ppm and 5.39 ppm to 4.40 ppm are attributed to the methylene bridge and ether bond respectively. The broad resonance line in the region of about 7.75 ppm to 6.25 ppm is assigned to aromatic hydrogens. The resonances in the regions of about 8.75 ppm to 8.00 ppm and 10.00 ppm to 8.89 ppm are assigned to the proton peaks of methanol, phenolic hydroxyl, and unreacted B-OH groups.

[0057] In summary, the successful preparation of boron-containing phenolic resin is proved by the series of characteristic absorption peaks in the infrared spectrum (FT-IR) and 1 1H NMR spectra.

[0058] Example 2 A preparation method of carbon-borane aromatic amine, comprising the following steps: S1. First, o-carborane is converted into 1,4-diphenyl-o-carborane through a nucleophilic substitution reaction. Specifically, 10 g of o-carborane, 0.5 g of n-butyllithium, and 30 g of N,N-dimethylformamide are added to a reactor and stirred at 0 °C for 4 h. Then, 0.2 g of copper powder is added and stirred at room temperature for 30 min. Next, 0.2 g of pyridine and 0.6 g of iodobenzene are added and stirred for 30 min to obtain 1,4-diphenyl-o-carborane.

[0059] S2. Second, 1,3',2,3'-dinitrobenzene-o-carborane is obtained through the nitration of 1,4-diphenyl-o-carborane. Specifically, 1 g of sulfuric acid / nitric acid (volume ratio = 5 / 1) and 10 g of dichloromethane are added to a reactor containing 5 g of 1,4-diphenyl-o-carborane, and the mixture is stirred at 0 °C to room temperature for 1 h to obtain 1,3',2,3'-dinitro-o-carborane.

[0060] S3. Finally, 1,3',2,3'-diaminobenzene-o-carborane is synthesized through the reduction of 1,3',2,3'-dinitrobenzene-o-carborane with iron(II). Specifically, 0.1 g of iron powder, 0.2 g of hydrochloric acid, and 6 g of ethylene glycol dimethyl ether are added to a reactor containing 3 g of 1,3',2,3'-dinitro-o-carborane with iron(II), and the mixture is stirred at 90 °C for 1 h to obtain 1,3',2,3'-diamino-o-carborane (CBA). The synthesis route of 1,3',2,3'-diamino-o-carborane is shown below.

[0061] 。

[0062] Figure 3 This is the infrared spectrum of 1,3',2,3'-diamino-o-carborane prepared in Example 2 of the present invention. As Figure 3 shown, Figure 3 in the curve (a) is 1,4-diphenyl-o-carborane, curve (b) is 1,3',2,3'-dinitro-o-carborane, and curve (c) is 1,3',2,3'-diamino-o-carborane. FT-IR (KBr, cm −1 ) : 2587 (s; ν(B-H)), 3471 (m; νas(NH2)), 3388 (m; νs(NH2)), 1624 (vs; δ(NH2)), 828 (δ(Ar-H)).

[0063] Figure 4 This is the 1 1H NMR spectrum of 1,3',2,3'-diamino-o-carborane prepared in Example 2 of the present invention.Figure 4 In figure (a), it is 1,4-diphenyl-o-carborane; in figure (b), it is 1,3',2,3'-dinitro-o-carborane; in figure (c), it is 1,3',2,3'-diamino-o-carborane. As Figure 4 shown, 1 H NMR (400 MHz, CDCl3, ppm): 1.50 - 3.50 (br., 10H; B-H), 4.13 (s, 4H; NH2), 7.21 (d, 4H; Ar-H), 6.39 (d, 4H; Ar-H).

[0064] From Figure 3 the FT-IR spectrum of Example 2 and Figure 4 the 1 H NMR spectrum analysis of Example 2 determined the structure of 1,3',2,3'-diamino-o-carborane (CBA) monomer.

[0065] Example 3 Preparation method of boron-containing phenolic resin - carborane hybrid polymer, including the following steps: S1. Dissolve 2 g of boron-containing phenolic resin prepared in Example 1 in 5 g of ethanol to form a boron-containing phenolic resin solution, and dissolve 5 g of carborane-containing aromatic amine prepared in Example 2 in 5 g of ethanol to form a carborane-containing aromatic amine solution; S2. Add 10 g of the carborane-containing aromatic amine solution to 7 g of the boron-containing phenolic resin solution, stir evenly at room temperature, then add the mixture into a mold, cure at room temperature for 24 h, then cure at 70 °C for 1 h, at 110 °C for 1 h, at 180 °C for 30 min, then exhaust 3 times, apply a pressure of 5 MPa, and raise the temperature to 220 °C to cure for 2 h; subsequently cool to 80 °C, release the pressure, and demold to obtain the boron-containing phenolic resin - carborane hybrid polymer material.

[0066] Figure 5 This is the infrared spectrum of the boron-containing phenolic resin - carborane hybrid polymer prepared in Example 3 of the present invention. As Figure 5 shown, 1360 cm -1 ~1380 cm -1 is the stretching vibration absorption peak of B-O, and 2586 cm -1 is the stretching vibration absorption peak of B-H.

[0067] Figure 6 This is the 11 B NMR spectrum of the boron-containing phenolic resin - carborane hybrid polymer prepared in Example 3 of the present invention. As Figure 6 shown, there is a C-B resonance peak at 19.9 ppm, which proves that the carborane has been connected to the polymer backbone.

[0068] The ablation tests were carried out on the boron-containing phenolic resin prepared in Example 1 and the boron-containing phenolic resin-carborane hybrid polymer prepared in Example 3. The linear ablation rate was carried out according to the test method of GJB 323B-2018. The results are shown in Table 1.

[0069] Table 1 Oxygen-acetylene ablation data of Example 1 and Example 3 As shown in Table 1, during the thermal degradation process, the stable chemical bonds (B-O, B-C) of boron and carborane and the formation of other ceramic compounds are the reasons for improving the thermal properties. The carbon yield at 900 °C is 80%, the linear ablation rate is 0.04 mm / min, and the mass ablation rate is 0.05 g / min.

[0070] Figure 7 This is the thermogravimetric curve of the boron-containing phenolic resin prepared in Example 1 of the present invention and the boron-containing phenolic resin-carborane hybrid polymer prepared in Example 3. As Figure 7 shown, the introduction of boron and carborane increases the graphitization degree of the carbonized product, promotes the formation of the ceramized product, and improves the heat-resistant oxidation performance of the polymer. The 5% thermal weight loss temperature in air is 500 °C.

[0071] Figure 8 This is the microscopic structure diagram of the boron-containing phenolic resin-carborane hybrid polymer prepared in Example 3 of the present invention after oxygen-acetylene ablation. As Figure 8 shown, the pyrolysis compounds of boron and carborane formed during the high-temperature period contribute to the formation of a void-free graphite-ordered carbon and a ceramized layer. During the thermal degradation process, the stable chemical bonds (B–O, B–C) of boron and carborane and the formation of other ceramic compounds are the reasons for improving the thermal properties.

[0072] It should be noted that when the present invention involves a numerical range, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the adopted step method is the same as that of the embodiment, in order to prevent repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0073] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a boron-containing phenolic-carborane hybrid polymer, characterized in that: The following steps are involved: A boron-containing phenolic compound and a carborane-containing aromatic amine compound are used as raw materials, dissolved in a solvent, and subjected to a staged amination reaction at 20°C to 220°C to obtain a boron-containing phenolic-carborane hybrid polymer. In the staged amination reaction, a first stage reaction is firstly carried out at room temperature and normal pressure, then three normal pressure reactions are carried out at 60°C to 190°C, and finally a fifth stage reaction is carried out at 210°C to 220°C and 4.5MPa to 5.5MPa.

2. The method for preparing the boron-containing phenolic-carborane hybrid polymer according to claim 1, characterized in that: The molar ratio of the boron-containing phenolic compound to the carborane-containing aromatic amine compound is 1:18-22.

3. The method for preparing the boron-containing phenolic-carborane hybrid polymer according to claim 1, characterized in that: During the amination reaction, the reaction is first carried out at room temperature and normal pressure for 22h to 26h, then at 60℃ to 80℃ and 100℃ to 120℃ and normal pressure for 1h to 3h, then at 170℃ to 190℃ and normal pressure for 20min to 40min, and finally at 210℃ to 220℃ and 4.5MPa to 5.5MPa for 3h to 5h.

4. The method for preparing the boron-containing phenolic-carborane hybrid polymer according to claim 1, characterized in that: The method for preparing a carborane-containing aromatic amine compound comprises the following steps: Taking an o-carborane compound as a raw material, adding n-butyl lithium to react at -5°C to 0°C to deprotonate the hydrogens on two adjacent carbons, then adding iodobenzene and a ligand to undergo a nucleophilic substitution reaction at room temperature to convert o-carborane into 1,4-diphenyl-o-carborane; Using 1,4-diphenyl-o-carborane and nitric acid as raw materials, a nitration reaction is carried out at -5°C to 0°C under the action of an acid catalyst to obtain 1,3',2,3'-dinitrobenzene-o-carborane; 1,3',2,3'-dinitrobenzene-o-carborane is subjected to a reduction reaction at 90°C to 120°C under the action of divalent iron to obtain 1,3',2,3'-diaminobenzene-o-carborane.

5. The method for preparing the boron-containing phenolic-carborane hybrid polymer according to claim 4, characterized in that: The molar ratio of the o-carborane compound, n-butyl lithium, iodobenzene and the ligand is 1:0.03-0.3:0.015-0.08:1-6, the ligand is pyridine, and the time of the nucleophilic substitution reaction is 25 min-35 min; The molar ratio of 1,4-diphenyl-o-carborane to nitric acid is 1:0.1-0.6, the volume ratio of the acid catalyst to nitric acid is 5:1-2, the acid catalyst is sulfuric acid, and the nitration reaction time is 1h-3h; The molar ratio of 1,3',2,3'-dinitrobenzene-o-carborane to divalent iron is 1:0.003-0.03, and the reduction reaction time is 1h-3h.

6. The method for preparing the boron-containing phenolic-carborane hybrid polymer according to claim 1, characterized in that: The preparation method of the boron-containing phenolic compound comprises the following steps: The borate ester compound and polyformaldehyde are used as raw materials, and an esterification reaction is carried out at 120° C. to 160° C. to obtain a boron-containing phenolic compound.

7. The method for preparing the boron-containing phenolic-carborane hybrid polymer according to claim 6, characterized in that: The molar ratio of the borate compound to polyformaldehyde is 1:1.1-1.5, and the esterification reaction time is 2h-4h.

8. The method for preparing the boron-containing phenolic-carborane hybrid polymer according to claim 1, characterized in that: The method for preparing an acid ester compound comprises the following steps: The boric acid compound and the phenol compound are mixed and subjected to an esterification reaction at 140° C. to 180° C. to obtain a boric acid ester.

9. The method for preparing the boron-containing phenolic-carborane hybrid polymer according to claim 8, characterized in that: The molar ratio of the boric acid compound to phenol is 1:3-4, the time of the esterification reaction is 4h-6h, the boric acid compound is one of phenylboric acid, 4-ethoxy-3-(trifluoromethyl)phenylboric acid, methylboric acid, cyclohexylboric acid, and sodium borate, and the phenol compound is one of resorcinol, hydroquinone, cresol, p-tert-butylphenol, cardanol, naphthol or 4,4-dihydroxydiphenylmethane.

10. A boron-containing phenolic-carborane hybrid polymer, characterized in that: The method is prepared by any one of claims 1 to 9.

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