Clean construction method of halogen-free phosphorus-free flame-retardant epoxy polymerization system

Abstract

The invention belongs to the field of high polymer materials, and relates to a clean construction method of a halogen-free phosphorus-free flame-retardant epoxy polymerization system. The preparation method comprises the following steps: preparing an intermediate I from 2, 2 '-diallyl bisphenol and allyl bromide under the action of potassium carbonate; carrying out rearrangement reaction on the intermediate I to prepare an intermediate II; and carrying out etherification and ring-closure reaction on the intermediate II and epoxy chloropropane under the action of a catalyst and sodium hydroxide to obtain the epoxy resin monomer III. The halogen-free phosphorus-free flame-retardant epoxy resin polymer is obtained by mixing an epoxy resin monomer with a curing agent, melting, performing injection molding and curing. The halogen-free and phosphorus-free flame retardant polymer obtained by the invention can reach the flame retardant grade of UL94-V0 grade.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and relates to a clean construction method for a halogen-free and phosphorus-free flame-retardant epoxy polymer system. Background Technology

[0002] Epoxy resin (EP) possesses outstanding mechanical strength and good chemical stability, leading to its widespread use in aerospace, coatings, and construction industries. It is predicted that the average annual growth rate of epoxy resin consumption in China will reach 6.2%, making it one of the world's largest and fastest-growing consumer markets. Epoxy resin is a low-molecular-weight prepolymer containing at least two epoxy groups in its molecular structure. However, due to limitations in its structure and elemental composition, traditional bisphenol A (BPA) epoxy resins contain only two epoxy groups, restricting their application range. Furthermore, BPA poses a potential threat to human health, impacting the application of epoxy resins. Given the still relatively large overall production capacity of BPA-based epoxy resins, epoxy resin modification is an important research direction in the industry. Developing related alternative products based on this modification can further explore the superior performance of novel epoxy resins while simultaneously providing a safer alternative.

[0003] Epoxy resin modification is generally divided into structural modification and blending modification. Blending modification involves incorporating another resin to synthesize an epoxy resin system with superior performance. However, blending modification suffers from problems such as complex synthesis processes, high raw material and production costs, long verification cycles, and difficulty in controlling performance. Therefore, structural modification is currently the main method for improving epoxy resin performance. Bisphenol A-derived epoxy resins can achieve high crosslinking density, improving the thermal and mechanical properties of epoxy resins while further reducing the migration of bisphenol A.

[0004] Epoxy resin cured products possess excellent mechanical, electrical, dimensional stability, and adhesive properties. Large composite material components made with epoxy resin-reinforced fibers offer advantages such as low water absorption, corrosion resistance, and low cost, making it a widely used synthetic resin with ever-increasing demand. However, the chemical structure of bisphenol A epoxy resin results in poor toughness and flame retardancy. Like other polymer materials, most plastic products exhibit flammability while maintaining excellent performance. In some developed countries, annual fire losses average hundreds of millions or even billions of dollars. During fires, polymers burn alongside large amounts of smoke and toxic gases, further jeopardizing lives and property. Studies show that the primary cause of casualties in fires is not the fire itself, but the large amounts of smoke and toxic gases released during combustion. These gases severely reduce visibility at fire scenes, significantly hindering escape and rescue efforts. Epoxy resin is a flammable material with a low limiting oxygen index (LOI) of only 19.5. With China's economic development, especially given the significant damage caused by fire accidents in recent years, higher demands are being placed on the flame retardancy of materials. With the widespread application of flame-retardant materials in chemical building materials, electronics, and various sectors such as clothing, food, housing, and transportation, flame retardants have become the second largest polymer material modifier after plasticizers. Flame retardants are a class of additives that can effectively prevent materials from burning. Flame retardants can be divided into halogenated and halogen-free flame retardants. Halogenated flame retardants are widely added to various plastic products, building materials, electronic and electrical equipment, household products, and textiles to increase the flame resistance of materials and prevent or delay combustion. These flame retardants are mostly used as additives. Lacking chemical bonds with the product matrix, they are easily released into the environment throughout the entire product lifecycle, including production, use, and recycling. They remain for extended periods and are difficult to degrade. They can also enter the human body through inhalation, dust ingestion, and skin contact. Furthermore, halogenated flame retardants entering the environment are persistent and bioaccumulate, and can be transferred to the human body through the food chain, interfering with the endocrine system and causing potential neurodevelopmental toxicity. Therefore, halogen-free flame retardants have attracted much attention due to their non-toxicity, low smoke, and highly efficient flame-retardant effects, becoming a new trend in flame retardant development. According to the "2021 China Flame Retardant Industry Analysis Report – Industry Operation Status and Future Prospect Research," with the rapid development of downstream application markets and increased fire prevention awareness, the market demand for flame retardants is expected to reach 1.28 million tons by 2025. Since the beginning of the 21st century, global environmental problems such as the greenhouse effect and resource shortages have become increasingly unavoidable crises. Halogenated flame retardants produce large amounts of smoke and toxic, corrosive hydrogen halide gases during the flame-retardant process, which not only endanger human lives but also become a serious destructive factor to the ecological environment.There is a lack of existing halogen-free and phosphorus-free systems with market potential. Developing an environmentally friendly and highly flame-retardant epoxy resin polymer is of great significance and fully meets the major strategic needs of the country to develop green and environmentally friendly industries and materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a halogen-free and phosphorus-free flame-retardant epoxy resin monomer to address the shortcomings of the prior art.

[0006] The technical problem to be solved by the present invention is to provide a halogen-free and phosphorus-free flame-retardant epoxy polymer and its preparation method.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] This invention discloses a halogen-free and phosphorus-free flame-retardant epoxy resin polymer, which is a binary polymer composed of A and B.

[0009] The structural units of A and B are respectively:

[0010]

[0011] The binary polymer formed by A and B has a repeating structural unit as shown in Formula IV.

[0012]

[0013] Where m≥2, n≥2.

[0014] Furthermore, the present invention provides a method for preparing the above-mentioned halogen-free and phosphorus-free flame-retardant epoxy resin polymer, wherein epoxy resin monomers are mixed with a curing agent, melted, molded, and cured to obtain the halogen-free and phosphorus-free flame-retardant epoxy resin polymer.

[0015] The epoxy resin monomer has the structural formula shown in Formula III:

[0016]

[0017] In the process of preparing halogen-free and phosphorus-free flame-retardant epoxy resin polymer, the epoxy groups in the epoxy resin monomers are bonded to the NH in the curing agent through CN bonds; at the same time, the epoxy resin monomer molecules are linked by alkenyl polymerization.

[0018] In some embodiments, the curing agent is diaminodiphenylmethane.

[0019] In some embodiments, the molar ratio of the epoxy group in the epoxy resin monomer to the NH group in the curing agent is 2:1 to 4.

[0020] In some embodiments, preferably, the molar ratio of the epoxy group in the epoxy resin monomer to the NH group in the curing agent is 2:1 to 3, more preferably 2:1.5 to 2.5, even more preferably 2:1.6 to 2.4, and most preferably 2:2.

[0021] In some embodiments, the melting temperature is 60–130°C; the curing temperature is 140–250°C; and the curing time is 3–10 hours.

[0022] In some embodiments, preferably, the melting temperature is 70–90°C.

[0023] In some embodiments, preferably, the curing temperature is 160–220°C, more preferably 160–200°C, and the curing time is 3–10 h, more preferably 4–7 h.

[0024] The initial decomposition temperature of the halogen-free and phosphorus-free flame-retardant epoxy resin polymer is 310-370℃, and the maximum decomposition temperature is 450-510℃; the char residue at 800℃ is 50%-59%.

[0025] In some embodiments, the epoxy resin monomer is prepared according to the following steps:

[0026]

[0027] (1) 2,2'-diallylbisphenol A and allyl bromide were allylated under the action of a weak base to prepare intermediate I.

[0028] (2) Intermediate I is dissolved in a solvent and rearranged to obtain intermediate II;

[0029] (3) Intermediate II undergoes an etherification reaction with epichlorohydrin under the action of the catalyst benzyltriethylammonium chloride, and then continues to undergo a ring-closing reaction under the action of benzyltriethylammonium chloride and sodium hydroxide to obtain epoxy resin monomer III.

[0030] In some embodiments, in step (1), the weak base is potassium carbonate; the molar ratio of 2,2'-diallylbisphenol A to allyl bromide and the weak base is 1 mmol: 5.7-6.6 mmol: 8.8-10.8 mmol; and the allylation reaction is carried out at a temperature of 30-80°C.

[0031] In some embodiments, preferably, in step (1), the molar ratio of 2,2'-diallylbisphenol A to allyl bromide and a weak base is 1 mmol: 6.0-6.6 mmol: 9.5-10.8 mmol, more preferably 1 mmol: 6.0-6.6 mmol: 10.0-10.8 mmol; the allylation reaction is carried out at a temperature of 30-60°C, more preferably 30-50°C, and even more preferably 30-40°C.

[0032] In step (1), the reaction time of the allylation reaction is 0.5 to 1 hour, preferably 35 minutes.

[0033] In step (1), the solvent used in the allylation reaction is any one or a combination of two of dimethyl sulfoxide and acetonitrile, preferably acetonitrile. There are no special requirements for the amount of solvent used; it is sufficient to use raw materials that are dissolved and have a suitable viscosity.

[0034] In some embodiments, in step (2), the solvent is N-methylpyrrolidone; the rearrangement reaction is carried out at a temperature of 90–250 °C.

[0035] In some embodiments, preferably, in step (2), the solvent is N-methylpyrrolidone, and the mass ratio of intermediate I to the volume of the solvent is 10-20g:100-200mL; the rearrangement reaction is carried out at a temperature of 120-240℃, more preferably 160-240℃, even more preferably 190-220℃, and most preferably 210℃.

[0036] In some embodiments, in step (3), during the etherification reaction, the molar ratio of intermediate II to epichlorohydrin and benzyltriethylammonium chloride is 1:40-60:0.1-0.3, and the reaction temperature is 75-85°C; during the ring-closing reaction, the molar ratio of intermediate II to benzyltriethylammonium chloride and sodium hydroxide is 1:0.1-0.3:2.0-3.0, and the reaction temperature is room temperature.

[0037] In some embodiments, preferably, in step (3), in the etherification reaction, the molar ratio of intermediate II to epichlorohydrin and benzyltriethylammonium chloride is 1:40-55:0.1-0.3, more preferably 1:45-52:0.1-0.3, and even more preferably 1:46-50:0.2; the etherification reaction is carried out at a temperature of 78-82°C, more preferably 80°C; in the ring-closing reaction, the molar ratio of intermediate II to benzyltriethylammonium chloride and sodium hydroxide is 1:0.1-0.3:2.0-2.8, more preferably 1:0.1-0.3:2.2-2.6, and even more preferably 1:0.2:2.2-2.6; the ring-closing reaction is carried out at room temperature.

[0038] In the closed-loop reaction, the sodium hydroxide used is in the form of a solution, preferably in the form of an aqueous solution, and the concentration of sodium hydroxide in the solution is 2.0 to 8.0 mol / L, preferably 4.0 to 6.0 mol / L, and more preferably 5.0 mol / L.

[0039] The application of the aforementioned halogen-free and phosphorus-free flame-retardant epoxy resin polymers in the preparation of flame-retardant materials is also within the scope of protection of this invention.

[0040] Beneficial effects:

[0041] (1) The raw materials of this invention are widely available and have high safety. It can fully realize the efficient use of existing resources, has high application value and great market prospects.

[0042] (2) The preparation process of epoxy resin polymer monomer (intermediate III) provided by the present invention is simple and efficient, and the resulting epoxy monomer has a low viscosity system, which is convenient for solvent-free polymerization process. The polymerization process is green and clean and meets the development requirements of green chemistry.

[0043] (3) The preparation methods of epoxy resin polymer monomers and flame-retardant epoxy resin polymers in this invention have mild reaction conditions, are simple to prepare, and are highly efficient.

[0044] (4) The halogen-free and phosphorus-free flame-retardant polymer obtained by the present invention belongs to the advanced flame-retardant technology in the current flame-retardant field, and the polymer material reaches the UL-V0 flame-retardant level. Attached Figure Description

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0046] Figure 1 This is a synthetic route diagram for epoxy resin monomers.

[0047] Figure 2The image shows the hydrogen NMR spectrum of intermediate I.

[0048] Figure 3 The image shows the proton NMR spectrum of intermediate II.

[0049] Figure 4 This is the 1H NMR spectrum of epoxy resin monomers.

[0050] Figure 5 This is the TG spectrum of epoxy resin monomers.

[0051] Figure 6 The image shows the TG spectrum of the flame-retardant epoxy resin polymer prepared using intermediate III as a raw material in Example 2.

[0052] Figure 7 The images show the IR spectra of the epoxy resin monomer and the flame-retardant epoxy resin polymer in Example 2. Detailed Implementation

[0053] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0054] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0055] The structural formulas of all compounds and polymers in this invention were drawn using King Draw software from China.

[0056] Example 1: Synthesis of epoxy polymerization monomer - intermediate III

[0057] Epoxy monomer III is commercially available, can be prepared using existing technologies, or can be prepared according to the following experimental steps.

[0058] (1) Synthesis of intermediate I:

[0059] At room temperature, 2,2'-diallylbisphenol A (1.0 g, 3.25 mmol), potassium carbonate (4.84 g, 35 mmol), and acetonitrile (45 mL) were added sequentially to a 100 mL reaction flask and stirred until a mixture was obtained. The resulting mixture was then mixed with allyl bromide (2.48 g, 20.5 mmol) and stirred at 35 °C for 35 min. After the reaction was completed, the reaction solution was extracted with ethyl acetate, the organic phase was dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated and purified by silica gel column chromatography to obtain a pale yellow liquid intermediate I, 1.24 g, with a yield of 98%.

[0060] The synthetic route of intermediate I is as follows: Figure 1 As shown, the 1H NMR spectrum of intermediate I is as follows: Figure 2 As shown, the specific 1H NMR data are as follows:

[0061] 1 HNMR (400MHz, CDCl3) δ7.39-7.23(m,4H),6.96(d,J=8.5Hz,2H),6.35-6.18(m,4H),5.66(dd,J=17.3,1.3Hz,2H) ,5.48(d,J=10.6Hz,2H),5.29(dd,J=21.4,5.7Hz,4H),4.73(d,J=4.8Hz,4H),3.66(d,J=6.5Hz,4H),1.91(s,6H).

[0062] (2) Synthesis of intermediate II:

[0063] Intermediate I (15 g, 38.6 mmol) and N-methylpyrrolidone (125 mL, 1.3 mol) were added sequentially to a 250 mL flask. The mixture was then heated to 210 °C over 10 min, and the reaction was continued at 210 °C for 8 h. After the reaction was completed, the reaction mixture was cooled to room temperature, extracted with ethyl acetate, dried over anhydrous magnesium sulfate, filtered, concentrated, and purified by silica gel column chromatography to obtain 13.1 g of the pale yellow liquid intermediate II, with a yield of 87%.

[0064] The synthetic route of intermediate II is as follows: Figure 1 As shown, the proton NMR spectrum of intermediate II is as follows: Figure 3 As shown, the specific 1H NMR data are as follows:

[0065] 1 HNMR (400MHz, CDCl3) δ6.85 (s, 4H), 5.98 (ddt, J = 23.1, 10.5, 6.4Hz, 4H), 5.11 (d d,J=7.7,1.6Hz,4H),5.07(d,J=7.0Hz,4H),3.34(d,J=6.4Hz,8H),1.60(s,6H).

[0066] (3) Synthesis of epoxy resin monomers:

[0067] Intermediate II (20 g, 51.5 mmol), benzyltriethylammonium chloride (TEBAC, 2.27 g, 10 mmol), and epichlorohydrin (231.3 g, 2.5 mol) were added to a 1000 mL flask and the mixture was stirred magnetically at 80 °C for 4.5 h. Then, another portion of TEBAC (2.27 g, 10 mmol) and an aqueous sodium hydroxide solution (5 g NaOH, 5.0 mol / L) were added, and the mixture was reacted at room temperature for 1.5 h. After the reaction was completed, the mixture was extracted three times with ethyl acetate, and the combined organic phases were washed three times with water. The layers were separated, the organic phases were dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated. The mixture was purified by silica gel column chromatography using PE / EA as the eluent to obtain 25 g of the pale yellow liquid intermediate III (i.e., epoxy resin polymerization monomer), with a yield of 97.0%.

[0068] The synthetic route of intermediate III is as follows: Figure 1 As shown, the proton NMR spectrum is as follows: Figure 4 The specific NMR data are shown below:

[0069] 1 H NMR(400MHz, CDCl3) δ6.87(s,4H),5.93(ddt,J=16.5,10.2,6.3Hz,4H),5.09-4.92(m,8H),4.01(dd,J=11.0,3.2Hz,2H),3.73(dd,J=11.0, 5.9Hz,2H),3.39(d,J=6.3Hz,8H),3.33(ddt,J=5.9,4.0,3.0Hz,2H),2.86(dd,J=4.9,4.3Hz,2H),2.69(dd,J=5.0,2.7Hz,2H),1.60(s,6H).

[0070] Thermogravimetric spectrum as follows Figure 5 As shown in the figure, under nitrogen conditions, the initial decomposition temperature (T) of intermediate III is... d5 The temperature is 240℃, and the residual carbon rate is 4.12% at 800℃. The thermogravimetric differentials are DTGmax1 = 332.56℃ and DTGmax2 = 468.85℃.

[0071] Infrared spectrum as follows Figure 7 As shown, at 860cm -1 910cm -1 The characteristic absorption peak of COC in the epoxy group can be observed at 1600 cm⁻¹. -1 1500cm -1 The characteristic absorption peak of C=C in the benzene ring skeleton can be observed at 3075 cm⁻¹. -1 The presence of small shoulder peaks indicates the presence of olefins (v).C-H Stretching vibration at 1640cm -1 Weaker olefins (v) also appeared. C＝C Stretching vibration, the hydroxyl absorption peak is at 3400 cm⁻¹ -1 Nearby. Note: Intermediate III in the diagram is the epoxy resin polymer monomer.

[0072] Example 2: Preparation of flame-retardant epoxy resin polymer

[0073] The structural formula of the flame-retardant epoxy resin polymer is shown below.

[0074]

[0075] in,

[0076] m≥2, n≥2.

[0077] Epoxy polymerization monomer intermediate III (2.5 g, 5 mmol, prepared in Example 1, 10 mmol epoxy groups) was weighed into a reaction flask, and diaminodiphenylmethane (DDM, 0.5 g, 2.5 mmol, 10 mmol NH groups) was added. The melting temperature was 80 °C. After uniform melting and mixing, the mixture was poured into a mold for curing. There were multiple curing stages: first, curing at 160 °C for 2 hours, then at 180 °C for 1 hour, and finally at 195 °C for 1 hour. After curing, the mixture was cooled to obtain a flame-retardant epoxy resin polymer.

[0078] Thermogravimetric spectra of flame-retardant epoxy resin polymers are as follows: Figure 6 As shown, the T of the polymer after curing d5 The residual carbon rate at 380℃ and 800℃ is 55.48%. The thermogravimetric differential is DTG max1 = 446.38℃.

[0079] The infrared spectrum of flame-retardant epoxy resin polymer is as follows: Figure 7 As shown, 860 cm in the polymer -1 910cm -1 The characteristic absorption peak of COC in the epoxy group at 1630 cm⁻¹ -1 The NH bond disappears in the curing agent, while the olefin is located at 1640 cm⁻¹. -1 The significant decrease in characteristic peak intensity proves that the alkenyl group in intermediate III successfully polymerized with the amino group in diaminodiphenylmethane, and that the alkenyl groups between intermediate III molecules also successfully polymerized. Note: The polymer in the figure is the flame-retardant epoxy resin polymer.

[0080] Example 3:

[0081] The experimental method was the same as in Example 2, except that the molar ratio of epoxy polymerization monomer-intermediate III to diaminodiphenylmethane was changed to 1:0.4. All other aspects were the same as in Example 2.

[0082] Example 4:

[0083] The experimental method was the same as in Example 2, except that the molar ratio of epoxy polymerization monomer-intermediate III to diaminodiphenylmethane was changed to 1:0.6. All other aspects were the same as in Example 2.

[0084] Example 5:

[0085] The performance of the flame-retardant epoxy resins in Examples 2-4 was tested.

[0086] Flame retardant performance test: Flame retardancy determination: Oxygen index test according to GB / T8924-2005. The test results are as follows: oxygen index of resin polymer in Example 2 33%, oxygen index of resin polymer in Example 3 30%, and oxygen index of resin polymer in Example 4 31%; according to the vertical burning test in UL94 "Tests for flammability of materials for equipment and appliance components", the test value of Example 2 is V-0, and the test values ​​of Examples 3 and 4 are worse than those of Example 2. It can be seen that the flame retardant epoxy resin of the present invention has good oxygen index and flame retardant performance. As can be seen from the data of Examples 2 and Examples 3-4, the polymer product constructed by epoxy monomers and curing agent of the present invention has excellent flame retardant performance while maintaining a high oxygen index.

[0087] Table 1 Oxygen Index Test Results of Different Materials

[0088] Example 2 Example 3 Example 4 Oxygen Index 33％ 30％ 31％

[0089] Table 2. Vertical combustion test results for different materials

[0090]

[0091]

[0092] This invention provides a method for the clean construction of a halogen-free and phosphorus-free flame-retardant epoxy polymer system. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A halogen-free and phosphorus-free flame-retardant epoxy resin polymer, characterized in that, A binary polymer composed of A and B; The structural units of A and B are respectively: The binary polymer formed by A and B has a repeating structural unit as shown in Formula IV. Where m≥2, n≥2.

2. The preparation method of the halogen-free and phosphorus-free flame-retardant epoxy resin polymer according to claim 1, characterized in that, The epoxy resin monomer is mixed with a curing agent, melted, molded, and cured to obtain a halogen-free and phosphorus-free flame-retardant epoxy resin polymer. The epoxy resin monomer has the structural formula shown in Formula III:

3. The preparation method according to claim 2, characterized in that, The curing agent is diaminodiphenylmethane.

4. The preparation method according to claim 2, characterized in that, The molar ratio of the epoxy group in the epoxy resin monomer to the NH group in the curing agent is 2:1 to 4.

5. The preparation method according to claim 2, characterized in that, The melting temperature is 60–130°C; the curing temperature is 140–250°C, and the curing time is 3–10 hours.

6. The preparation method according to claim 2, characterized in that, The epoxy resin monomer is prepared according to the following steps: (1) 2,2'-diallylbisphenol A and allyl bromide were allylated under the action of a weak base to prepare intermediate I. (2) Intermediate I is dissolved in a solvent and rearranged to obtain intermediate II; (3) Intermediate II undergoes an etherification reaction with epichlorohydrin under the action of the catalyst benzyltriethylammonium chloride, and then continues to undergo a ring-closing reaction under the action of benzyltriethylammonium chloride and sodium hydroxide to obtain epoxy resin monomer III.

7. The preparation method according to claim 6, characterized in that, In step (1), the weak base is potassium carbonate; the molar ratio of 2,2'-diallylbisphenol A to allyl bromide and the weak base is 1 mmol: 5.7-6.6 mmol: 8.8-10.8 mmol; the allylation reaction is carried out at a temperature of 30-80°C.

8. The preparation method according to claim 6, characterized in that, In step (2), the solvent is N-methylpyrrolidone; the rearrangement reaction is carried out at a temperature of 90–250 °C.

9. The preparation method according to claim 6, characterized in that, In step (3), in the etherification reaction, the molar ratio of intermediate II to epichlorohydrin and benzyltriethylammonium chloride is 1:40-60:0.1-0.3, and the reaction temperature of the etherification reaction is 75-85°C; in the ring-closing reaction, the molar ratio of intermediate II to benzyltriethylammonium chloride and sodium hydroxide is 1:0.1-0.3:2.0-3.0, and the reaction temperature of the ring-closing reaction is room temperature.

10. The application of the halogen-free and phosphorus-free flame-retardant epoxy resin polymer of claim 1 in the preparation of flame-retardant materials.

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