Phosphorus-nitrogen flame-retardant curing agent as well as preparation and application thereof in epoxy resin
By preparing a phosphorus-nitrogen flame-retardant curing agent, the flammability problem of epoxy resin was solved. By forming a dense carbon layer in the epoxy resin, heat transfer and the release of flammable volatiles were prevented, thereby improving the flame-retardant properties of the epoxy resin and reducing the risk of fire.
Patent Information
- Application Number
- CN202511836045.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-08
- Publication Date
- 2026-03-03
AI Technical Summary
Epoxy resin is flammable, which limits its application range, and its flame retardant properties need to be improved.
A phosphorus-nitrogen flame retardant curing agent was prepared by reacting pentaerythritol with phosphorus oxychloride to synthesize an intermediate, which was then reacted with 4,4-diaminodiphenylmethane to form a phosphorus-nitrogen flame retardant curing agent. This curing agent was then added to epoxy resin to form a dense carbon layer, which prevented heat transfer and the release of flammable volatiles.
It improves the flame retardant properties of epoxy resin, reduces the burning rate, forms a physical barrier to isolate oxygen, dilutes the concentration of flammable gases, reduces the risk of fire, and is environmentally friendly and low-cost.
Smart Images
Figure CN121591795A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of epoxy resin flame retardant technology, and particularly relates to a phosphorus-nitrogen flame retardant curing agent, its preparation, and its application in epoxy resin. Background Technology
[0002] Polymer materials possess excellent insulation, corrosion resistance, light weight, and superior processing properties. They currently hold a major market share in various fields, including consumer goods, pharmaceuticals, and aerospace. However, most polymer materials are flammable. The combustion and decomposition of polymers produce large amounts of flammable gases, accelerating the combustion process and causing dripping, which can lead to serious fire hazards, posing a severe threat to people's lives and property, and polluting the environment. Therefore, improving the flame-retardant properties of polymer materials is crucial.
[0003] Epoxy resin (EP) possesses high bonding strength, good thermal stability, high mechanical strength, and good processability, making it widely used in coatings, adhesives, composite materials, and electrical and electronic equipment. However, epoxy resin has an oxygen index of only 19.8%, classifying it as a flammable material, which limits its application range. Therefore, adding flame retardants to improve the flame-retardant properties of epoxy resin is essential. The epoxy groups in epoxy resin react with curing agents such as phenols, thiols, and acid anhydrides to form a three-dimensional network cross-linked polymer structure. Phenolic curing agents can improve heat resistance, thiols are used for low-temperature curing of epoxy resin, and acid anhydrides can improve the dielectric properties of epoxy resin. Developing flame-retardant curing agents that combine flame retardancy and curing properties to impart flame retardancy to EP composite systems has become a research hotspot in recent years for flame-retardant EP. Summary of the Invention
[0004] To address the above-mentioned problems, the present invention aims to provide a phosphorus-nitrogen flame retardant curing agent, its preparation, and its application in epoxy resins.
[0005] The structural formula of the phosphorus-nitrogen flame retardant curing agent of the present invention is as follows: ; The phosphorus groups in the phosphorus-nitrogen flame retardant curing agent decompose when heated, and at the same time catalyze the carbonization of the phosphorus groups and the polymer matrix to form a dense carbon layer and release flame-retardant gases. It forms a physical barrier on the surface of polymer matrices such as resins and dilutes the concentration of flammable gases, prevents heat transfer and the release of flammable volatiles, and isolates external oxygen from penetrating, thereby achieving a flame retardant effect.
[0006] The preparation method of the phosphorus-nitrogen flame retardant curing agent of the present invention includes the following: Pentaerythritol reacts with phosphorus oxychloride to synthesize the intermediate pentaerythritol diphosphate diphosphoryl chloride; the intermediate reacts with 4,4-diaminodiphenylmethane to synthesize the phosphorus-nitrogen flame retardant curing agent 4,4-diaminodiphenylmethane pentaerythritol diphosphate.
[0007] The molar ratio of phosphorus oxychloride to pentaerythritol is 1:6-6:1, and the molar ratio of intermediate to 4,4-diaminodiphenylmethane is 1:8-8:1; the reaction temperature for synthesizing intermediate and synthesizing phosphorus-nitrogen flame retardant curing agent is 20℃-260℃. When synthesizing the intermediate, chlorobenzene is preferably used as the solvent, 4-dimethylaminopyridine is used as the catalyst, and pentaerythritol and phosphorus oxychloride are reacted at 50°C to 100°C under a N2 atmosphere; when synthesizing the phosphorus-nitrogen flame retardant curing agent, ethanol is preferably used as the solvent, and the intermediate and 4,4-diaminodiphenylmethane are reacted at 70°C to 90°C under a N2 atmosphere.
[0008] The synthesis route is shown below: .
[0009] The preparation method of phosphorus-nitrogen flame retardant curing agent includes the following specific details: In the synthesis of the intermediate, chlorobenzene was used as the solvent, 4-dimethylaminopyridine was used as the catalyst, phosphorus oxychloride and pentaerythritol were added, and the reaction was carried out under N2 atmosphere. The reaction was first carried out at 60℃ for 2 hours, then the temperature was raised to 80℃ for 6 hours, and finally the temperature was raised to 95℃ until no large amount of HCl gas was released and the reaction was stopped to obtain the intermediate, namely the white solid powder pentaerythritol diphosphate diphosphonate chloride. In the synthesis of phosphorus-nitrogen flame retardant curing agent, ethanol is selected as solvent, and intermediate and 4,4-diaminodiphenylmethane are added sequentially. The reaction is carried out at 80°C for 8 hours under N2 atmosphere. After purification of the product (by vacuum filtration, rotary evaporation, and washing twice with anhydrous ethanol), it is dried under vacuum at 80°C to constant weight to obtain phosphorus-nitrogen flame retardant curing agent, namely yellow solid powder 4,4-diaminodiphenylmethane pentaerythritol diphosphate.
[0010] The application of the phosphorus-nitrogen flame-retardant curing agent of the present invention in epoxy resins includes the following: A phosphorus-nitrogen flame retardant curing agent is added to epoxy resin, and after curing, a flame retardant epoxy resin composite material is produced. The mass ratio of epoxy resin to phosphorus-nitrogen flame retardant curing agent is 1:1-10:1. After mixing, the mixture is cured at 30℃-200℃ to obtain a flame retardant epoxy resin composite material. The epoxy resin includes any one or more of E-44, E-51, E-52, and E-55, or a mixture thereof.
[0011] The application of phosphorus-nitrogen flame retardant curing agents in epoxy resin includes the following specific steps: The phosphorus-nitrogen flame retardant curing agent is added to the epoxy resin and mixed thoroughly. Then, 10% (by weight of epoxy resin) of 692 reactive diluent (which may also contain 2%-10% (by weight of epoxy resin) m-phenylenediamine) is added. After mechanical stirring and vacuum defoaming, the mixture is placed in a vacuum drying oven for curing. The curing temperatures are: 50℃-90℃ for 20 minutes, 100℃-130℃ for 2 hours, 120℃-150℃ for 3 hours, and 150℃-200℃ for 30 minutes. After cooling to room temperature and demolding, a sample of the phosphorus-nitrogen flame retardant epoxy resin composite material is obtained.
[0012] The beneficial effects of this invention are as follows: This invention provides a phosphorus-nitrogen flame-retardant curing agent, 4,4-diaminodiphenylmethane pentaerythritol diphosphate, its preparation method, and its application in epoxy resins. This phosphorus-nitrogen flame-retardant curing agent is a yellow solid powder that can be used as a curing agent and flame retardant, improving the flame-retardant properties of epoxy resin composites. It features simple operation, high product conversion rate, and no environmental pollution, providing a new approach and method for flame retardancy, curing, and fire risk reduction in epoxy resins. This phosphorus-nitrogen flame-retardant curing agent exhibits good smoke suppression properties, reduces the combustion rate, and is low-cost and environmentally friendly. The products of thermal decomposition of the phosphorus-containing groups in the flame-retardant curing agent catalyze the dehydration and carbonization reaction of oxygen-containing groups, forming a dense char layer. This char layer acts as a physical barrier on the resin surface, preventing heat transfer and the release of flammable volatiles, isolating external oxygen penetration and releasing flame-retardant gases, while simultaneously diluting the concentration of combustible gases to achieve flame retardancy. Furthermore, it reacts with the polymer to carbonize it, enhancing the flame-retardant effect. Attached Figure Description
[0013] Figure 1 The infrared spectrum of the phosphorus-nitrogen flame retardant curing agent prepared in Example 1; Figure 2 The 1H NMR spectrum of the phosphorus-nitrogen flame retardant curing agent prepared in Example 1. Detailed Implementation
[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their application scope. Based on this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention.
[0015] Examples 1-4 describe the preparation of phosphorus-nitrogen flame retardant curing agents.
[0016] Example 1
[0017] S1 Synthesis Intermediate: A 500ml four-necked flask was equipped with an N2 delivery tube, thermometer, spherical condenser, and tail gas collection device. 0.4 mol of phosphorus oxychloride and 0.15 mol of pentaerythritol were added to the flask. Chlorobenzene was used as the solvent, and 4-dimethylaminopyridine as the catalyst. The reaction apparatus was placed in an oil bath at 60°C for 2 hours, then the temperature was increased to 80°C for 6 hours, and finally the temperature was increased to 95°C until no large amount of HCl gas was emitted. The reaction was stopped. The product was washed several times by filtration with ethanol and distilled water, and then dried under vacuum at 80°C to constant weight. The intermediate, a white solid powder of pentaerythritol diphosphate diphosphonate chloride, was obtained, with a yield of 91.7%.
[0018] Synthesis of S2 Phosphorus-Nitrogen Flame Retardant Curing Agent: A 250ml four-necked flask was equipped with an N2 delivery tube, a spherical condenser, a thermometer, and a tail gas recovery device. 0.1 mol of an intermediate and 0.215 mol of 4,4-diaminodiphenylmethane (MDA) were added sequentially to the flask. Ethanol was used as the solvent. The reaction apparatus was heated to 80℃ and reacted for 8 hours. The product was filtered, rotary evaporated, washed twice with anhydrous ethanol, and then vacuum dried at 80℃ to constant weight. The resulting phosphorus-nitrogen flame retardant curing agent, a yellow solid powder of 4,4-diaminodiphenylmethane pentaerythritol diphosphate, was obtained with a yield of 90.3%.
[0019] The reaction route is shown below: .
[0020] The infrared spectrum of the prepared phosphorus-nitrogen flame retardant curing agent is shown below. Figure 1 As shown, a is 4,4-diaminodiphenylmethane (DMA), b is the intermediate pentaerythritol diphosphate diphosphoryl chloride (SPDPC), and c is the phosphorus-nitrogen flame retardant curing agent 4,4-diaminodiphenylmethane pentaerythritol diphosphate (SPDMA). From a, it can be seen that -NH2 is present at 3388 cm⁻¹. -1 and 1619cm -1 The characteristic absorption peak at point C is present in Figure c. From Figure c, it can be seen that the C=C bond peak is at 1514 cm⁻¹. -1 The characteristic absorption peak at this point also exists in a and b, and the POC bond at 1021 cm⁻¹. -1 The characteristic absorption peak is absent in a, while in b the P-Cl bond peak is at 579 cm⁻¹. -1 The characteristic absorption peak disappears in c. Based on the analysis results of the infrared spectrum, it can be preliminarily determined that the flame retardant curing agent 4,4-diaminodiphenylmethane pentaerythritol diphosphate has been successfully synthesized.
[0021] The proton NMR spectrum of the prepared phosphorus-nitrogen flame retardant curing agent is as follows: Figure 2As shown in the figure, δ=4.7 is the solvent peak of heavy water D2O, δ=3.31ppm is the proton peak of the hydrogen atom on the -CH2- bonded to oxygen, δ=4.12ppm is the proton peak of the hydrogen atom on the -CH2- bonded to the benzene ring, δ=4.16ppm is the proton peak of the hydrogen atom on the -NH2, and the multiplets at δ=7~8ppm refer to the proton peaks of the hydrogen atoms on the benzene ring. Since the prepared phosphorus-nitrogen flame retardant curing agent has a symmetrical structure, the hydrogen atoms in the symmetrical structure have the same chemical environment, and the singlet at δ=8.3ppm is the proton peak of the hydrogen atom on the -NH. The analysis results of the peak positions and peak areas of the NMR spectrum are consistent with the designed structure of the phosphorus-nitrogen flame retardant curing agent, indicating that 4,4-diaminodiphenylmethane pentaerythritol diphosphate has been successfully synthesized.
[0022] Example 2
[0023] S1 Synthesis Intermediate: A 500ml four-necked flask was equipped with an N2 delivery tube, thermometer, spherical condenser, and tail gas collection device. 1 mol of phosphorus oxychloride and 6 mol of pentaerythritol were added to the flask. Chlorobenzene was used as the solvent, and 4-dimethylaminopyridine as the catalyst. The reaction apparatus was placed in an oil bath at 60°C for 2 hours, then the temperature was increased to 80°C for 6 hours, and finally the temperature was increased to 95°C until no large amount of HCl gas was emitted. The reaction was stopped. The product was washed several times by filtration with ethanol and distilled water, and then dried under vacuum at 80°C to constant weight. The intermediate, a white solid powder of pentaerythritol diphosphate diphosphonate chloride, was obtained, with a yield of 92.1%.
[0024] Synthesis of S2 Phosphorus-Nitrogen Flame Retardant Curing Agent: A 250ml four-necked flask was equipped with an N2 delivery tube, a spherical condenser, a thermometer, and a tail gas recovery device. 1 mol of an intermediate and 8 mol of 4,4-diaminodiphenylmethane (MDA) were added sequentially to the flask. Ethanol was used as the solvent. The reaction apparatus was heated to 80℃ and reacted for 8 hours. The product was filtered, rotary evaporated, washed twice with anhydrous ethanol, and then vacuum dried at 80℃ to constant weight. The resulting phosphorus-nitrogen flame retardant curing agent, a yellow solid powder of 4,4-diaminodiphenylmethane pentaerythritol diphosphate, was obtained with a yield of 87%.
[0025] Example 3
[0026] S1 Synthesis Intermediate: A 500ml four-necked flask was equipped with an N2 delivery tube, thermometer, spherical condenser, and tail gas collection device. 1 mol of phosphorus oxychloride and 3 mol of pentaerythritol were added to the flask. Chlorobenzene was used as the solvent, and 4-dimethylaminopyridine as the catalyst. The reaction apparatus was placed in an oil bath at 60°C for 2 hours, then the temperature was increased to 80°C for 6 hours, and finally the temperature was increased to 95°C until no large amount of HCl gas was emitted. The reaction was stopped. The product was washed several times by filtration with ethanol and distilled water, and then dried under vacuum at 80°C to constant weight. The intermediate, a white solid powder of pentaerythritol diphosphate diphosphonate chloride, was obtained with a yield of 90.6%.
[0027] Synthesis of S2 Phosphorus-Nitrogen Flame Retardant Curing Agent: A 250ml four-necked flask was equipped with an N2 delivery tube, a spherical condenser, a thermometer, and a tail gas recovery device. 1 mol of an intermediate and 5 mol of 4,4-diaminodiphenylmethane (MDA) were added sequentially to the flask. Ethanol was used as the solvent. The reaction apparatus was heated to 80℃ and reacted for 8 hours. The product was filtered, rotary evaporated, washed twice with anhydrous ethanol, and then vacuum dried at 80℃ to constant weight. The resulting phosphorus-nitrogen flame retardant curing agent, a yellow solid powder of 4,4-diaminodiphenylmethane pentaerythritol diphosphate, was obtained with a yield of 93.2%.
[0028] Example 4
[0029] S1 Synthesis Intermediate: A 500ml four-necked flask was equipped with an N2 delivery tube, thermometer, spherical condenser, and tail gas collection device. 6 mol of phosphorus oxychloride and 1 mol of pentaerythritol were added to the flask. Chlorobenzene was used as the solvent, and 4-dimethylaminopyridine as the catalyst. The reaction apparatus was placed in an oil bath at 60°C for 2 hours, then the temperature was increased to 80°C for 6 hours, and finally the temperature was increased to 95°C until no large amount of HCl gas was emitted. The reaction was stopped. The product was washed several times by filtration with ethanol and distilled water, and then dried under vacuum at 80°C to constant weight. The intermediate, a white solid powder of pentaerythritol diphosphate diphosphonate chloride, was obtained with a yield of 89.6%.
[0030] Synthesis of S2 Phosphorus-Nitrogen Flame Retardant Curing Agent: A 250ml four-necked flask was equipped with an N2 delivery tube, a spherical condenser, a thermometer, and a tail gas recovery device. 8 mol of an intermediate and 1 mol of 4,4-diaminodiphenylmethane (MDA) were added sequentially to the flask. Ethanol was used as the solvent. The reaction apparatus was heated to 80℃ and reacted for 8 hours. The product was filtered, rotary evaporated, washed twice with anhydrous ethanol, and then vacuum dried at 80℃ to constant weight. The resulting phosphorus-nitrogen flame retardant curing agent, a yellow solid powder of 4,4-diaminodiphenylmethane pentaerythritol diphosphate, was obtained with a yield of 91.6%.
[0031] Examples 5-7 show the preparation of flame-retardant epoxy resin composite materials.
[0032] Example 5
[0033] 18.2g of the phosphorus-nitrogen flame retardant curing agent prepared in Example 1 was added to 100g of epoxy resin E-44, along with 10% of the epoxy resin mass of 692 reactive diluent and 7.2g of m-phenylenediamine (MPD). After mechanical stirring and vacuum defoaming, the mixture was placed in a vacuum drying oven for curing. The curing temperatures were 80℃ for 20min, 113℃ for 2h, 135℃ for 3h, and 190℃ for 30min. After cooling to room temperature and demolding, a sample of the phosphorus-nitrogen flame retardant epoxy resin composite material was obtained.
[0034] Example 6
[0035] Add 27.3g of the phosphorus-nitrogen flame retardant curing agent prepared in Example 1 to 100g of epoxy resin E-44, add 10% of 692 reactive diluent and 4.8g of m-phenylenediamine (MPD) by mass of epoxy resin, mechanically stir and defoam under vacuum, then place in a vacuum drying oven for curing. Curing temperature is 80℃ for 20min, 113℃ for 2h, 135℃ for 3h, and 190℃ for 30min. After cooling to room temperature and demolding, phosphorus-nitrogen flame retardant epoxy resin composite material specimens are obtained.
[0036] Example 7
[0037] Add 45.51g of the phosphorus-nitrogen flame retardant curing agent prepared in Example 1 to 100g of epoxy resin E-44, add 10% of 692 reactive diluent by weight of epoxy resin, mechanically stir and defoam under vacuum, then place in a vacuum drying oven for curing. Curing is carried out at 80℃ for 20min, 113℃ for 2h, 135℃ for 3h, and 190℃ for 30min. After cooling to room temperature and demolding, phosphorus-nitrogen flame retardant epoxy resin composite material specimens are obtained.
[0038] Comparative Example 1 12g of m-phenylenediamine (MPD) was added to 100g of epoxy resin E-44, and 10% of the epoxy resin mass of 692 reactive diluent was added. After mechanical stirring and vacuum defoaming, the mixture was placed in a vacuum drying oven for curing. The curing temperature was 80℃ for 20min, 113℃ for 2h, 135℃ for 3h, and 190℃ for 30min. After cooling to room temperature and demolding, phosphorus-nitrogen flame-retardant epoxy resin composite material samples were obtained.
[0039] Table 1 Performance test results of epoxy resin composites
[0040] Performance tests were conducted on samples from Examples 5-7 and Comparative Example 1, respectively. Tensile strength was tested according to GB / T 1040.2-2022, flexural modulus according to GB / T 9341-2008, impact strength according to GB / T 1843-2008, and limiting oxygen index according to GB / T 2406.1-2008. The test results are shown in Table 1.
Claims
1. A phosphorus-nitrogen flame retardant curing agent, characterized in that, The structural formula of the phosphorus-nitrogen flame retardant curing agent is as follows: 。 2. The phosphorus-nitrogen flame retardant curing agent according to claim 1, characterized in that, The phosphorus oxy groups in the phosphorus-nitrogen flame retardant curing agent decompose upon heating, catalyzing the carbonization of the phosphorus oxy groups and the polymer matrix to form a dense carbon layer and release flame-retardant gases. This forms a physical barrier on the surface of the polymer matrix and dilutes the concentration of combustible gases, preventing heat transfer and the release of flammable volatiles, while also isolating external oxygen from penetrating, thus achieving a flame-retardant effect.
3. The preparation method of the phosphorus-nitrogen flame retardant curing agent according to claim 1, characterized in that, The process includes the following: reacting pentaerythritol with phosphorus oxychloride to synthesize the intermediate pentaerythritol diphosphate diphosphoryl chloride; reacting the intermediate with 4,4-diaminodiphenylmethane to synthesize the phosphorus-nitrogen flame retardant curing agent 4,4-diaminodiphenylmethane pentaerythritol diphosphate.
4. The preparation method of the phosphorus-nitrogen flame retardant curing agent according to claim 3, characterized in that, The molar ratio of phosphorus oxychloride to pentaerythritol is 1:6-6:1; the molar ratio of the intermediate to 4,4-diaminodiphenylmethane is 1:8-8:1; the reaction temperature for synthesizing the intermediate is 20℃-260℃; the reaction temperature for synthesizing the phosphorus-nitrogen flame retardant curing agent is 20℃-260℃.
5. The preparation method of the phosphorus-nitrogen flame retardant curing agent according to claim 4, characterized in that, When synthesizing the intermediate, chlorobenzene is used as a solvent and 4-dimethylaminopyridine is used as a catalyst, and the reaction is carried out at 50℃~100℃ under N2 atmosphere; when synthesizing the phosphorus-nitrogen flame retardant curing agent, ethanol is used as a solvent, and the reaction is carried out at 70℃~90℃ under N2 atmosphere.
6. The preparation method of a phosphorus-nitrogen flame retardant curing agent according to claim 5, characterized in that, When synthesizing the intermediate, the reaction is first carried out at 60°C for 2 hours, then the temperature is increased to 80°C for 6 hours, and finally the temperature is increased to 95°C until no HCl gas is released and the reaction is stopped to obtain the intermediate. In the synthesis of the phosphorus-nitrogen flame retardant curing agent, the reaction was carried out at 80°C for 8 hours. After the product was purified, it was vacuum dried at 80°C to constant weight to obtain the phosphorus-nitrogen flame retardant curing agent.
7. The application of a phosphorus-nitrogen flame retardant curing agent according to claim 1 in epoxy resin, characterized in that, The phosphorus-nitrogen flame retardant curing agent is added to the epoxy resin, and after curing, a flame retardant epoxy resin composite material is prepared.
8. The application of the phosphorus-nitrogen flame retardant curing agent according to claim 7 in epoxy resin, characterized in that, The epoxy resin includes any one or more of E-44, E-51, E-52, and E-55; The mass ratio of the epoxy resin and the phosphorus-nitrogen flame retardant curing agent is 1:1-10:
1. After mixing, the two are cured at 30℃-200℃ to obtain the flame retardant epoxy resin composite material.
9. The application of a phosphorus-nitrogen flame retardant curing agent according to claim 8 in epoxy resin, characterized in that, The specific contents include the following: the mixture of the phosphorus-nitrogen flame retardant curing agent, the epoxy resin, and 692 reactive diluent is cured at 50℃-90℃ for 20 min, 100℃-130℃ for 2 h, 120℃-150℃ for 3 h, and 150℃-200℃ for 30 min to obtain the flame retardant epoxy resin composite material.
10. The application of a phosphorus-nitrogen flame retardant curing agent according to claim 9 in epoxy resin, characterized in that, The 692 reactive diluent is 10% of the epoxy resin by mass; the mixture also includes 2%-10% m-phenylenediamine by mass of the epoxy resin.