Imidazolyl phosphorus-containing flame-retardant curing agent as well as preparation method and application thereof

Abstract

The invention discloses an imidazolyl phosphorus-containing flame-retardant curing agent as well as a preparation method and application thereof, and belongs to the field of flame retardance. The imidazolyl phosphorus-containing flame-retardant curing agent provided by the invention not only can exert a condensed phase flame-retardant mechanism to promote the char forming performance of a polymer in a combustion process, but also can exert a gas phase flame-retardant mechanism to capture active free radicals in the combustion process; the chemical structure contains an imidazole structure, so that the epoxy curing accelerator can be used as an epoxy curing accelerator. According to the flame retardant provided by the invention, the limit oxygen index of epoxy resin is obviously improved, the vertical combustion grade reaches V-0 grade, and the flame retardant has the advantages of good char forming property, high flame retardant efficiency, high thermal stability, no migration and precipitation, bacteriostasis and the like.

Description

Technical Field

[0001] The present invention belongs to the field of flame retardants, and particularly relates to an imidazole-based phosphorus-containing flame retardant curing agent, a preparation method thereof, and an application thereof. Background Art

[0002] As a widely used thermosetting resin material, epoxy resin has the advantages of low production cost, electrical insulation, chemical corrosion resistance, and high thermal stability, so it is widely used in the fields of construction, aerospace, and electronics. However, as an organic polymer, epoxy resin contains a large amount of carbon, hydrogen, and oxygen elements in its structure, so it is flammable and releases a large amount of smoke during combustion, which severely limits the expansion of its application fields. In recent years, using phosphorus-based flame retardants to modify epoxy resin has become one of the research hotspots in the field of flame retardants. Flame-retardant epoxy resins are generally divided into additive type and reactive type. Additive-type epoxy resins generally have simple processes and wide sources of raw materials, and are the most commonly used type in the world at present. However, the addition of additives also brings problems of dispersion and compatibility, and there will also be problems of flame retardant precipitation during long-term use. The reactive flame retardant curing promoter can directly introduce flame retardant elements into the epoxy resin chain. When used as a curing agent, it can make the epoxy resin have a long-term flame retardant effect while having little impact on the mechanical properties of the epoxy system. Therefore, the research and development of phosphorus- and nitrogen-containing epoxy resins and organosilicon epoxy resins have been taken seriously. The Chinese patent application document (CN118772202B) discloses an imidazole-based phosphorus-containing latent flame retardant, whose structure is fixed and cannot be regulated; the Chinese patent application document (CN114539316A) discloses a phosphorus-containing imidazole compound, but it has the disadvantages of high addition amount and low flame retardant efficiency. The present invention designs an imidazole-based phosphorus-containing flame retardant curing agent with a controllable structure and uses it to prepare an intrinsically flame-retardant epoxy resin material. Summary of the Invention

[0003] The present invention aims to provide an imidazole-based phosphorus-containing flame retardant curing agent and a preparation method thereof. The imidazole-based phosphorus-containing flame retardant curing agent of the present invention has the structural characteristics that the phosphorus oxidation state and the number of aromatic rings can be regulated. It can be used as an epoxy curing agent and can also play the synergistic flame retardant effect of phosphorus and nitrogen. It has the advantages of good char-forming property, high flame retardant efficiency, high thermal stability, no migration and precipitation, and antibacterial property.

[0004] The imidazole-based phosphorus-containing flame retardant curing agent of the present invention has the following chemical structure as shown in formula (I) or (II):

[0005] .

[0006] Wherein:

[0007] R1 is selected from any one of the following structures:

[0008] 。

[0009] R2 is selected from any one of the following structures:

[0010] 。

[0011] * indicates the connection position.

[0012] The preparation method of the imidazole-based phosphorus-containing flame retardant curing agent of the present invention comprises the following steps:

[0013] ① Dissolve diamine and 4-imidazolecarboxaldehyde or 2-imidazolecarboxaldehyde in ethanol, and under the protection of an inert gas, heat and react to obtain an imidazole-based Schiff base intermediate;

[0014] ② Dissolve the imidazole-based Schiff base intermediate obtained in step ① and a phosphorus-containing compound in ethanol, and under the protection of an inert gas, heat and react to obtain a flame retardant curing agent.

[0015] In step ①, the diamine is selected from one of 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane.

[0016] In step ①, the molar ratio of diamine to 4-imidazolecarboxaldehyde or 2-imidazolecarboxaldehyde is 1:(2.0~2.2).

[0017] In step ①, the inert gas is any one of nitrogen, argon or helium.

[0018] In step ①, the reaction temperature is 20°C to 80°C, and the reaction time is 3 to 24 hours.

[0019] In step ②, the phosphorus-containing compound is selected from any one of diphenylphosphine oxide, diphenyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, dibenzyl phosphite, dimethyl phosphite, diethyl phosphite, dibutyl phosphite, diisobutyl phosphite.

[0020] In step ②, the molar ratio of the imidazole-based Schiff base intermediate to the phosphorus-containing compound is 1:(2.0~2.2).

[0021] In step ②, the inert gas is any one of nitrogen, argon or helium.

[0022] In step ②, the reaction temperature is 40~80°C, and the reaction time is 3 to 24 hours.

[0023] The application of the imidazole-based phosphorus-containing flame retardant curing agent of the present invention in the preparation of a flame retardant and antibacterial epoxy resin functional material.

[0024] Further, the imidazole-based phosphorus-containing flame retardant curing agent is added to the epoxy resin system as an auxiliary agent to improve the flame retardancy and antibacterial properties of the epoxy resin.

[0025] Furthermore, the addition amount of the imidazole-based phosphorus-containing flame retardant curing agent is 2.5-7.5% of the total mass of each component of the epoxy resin, and more preferably 5%.

[0026] In specific applications, it is necessary to adjust the ratio between the imidazole-based phosphorus-containing flame retardant curing agent and the original curing agent. In principle, the molar ratio of the active hydrogen of the imidazole-based phosphorus-containing flame retardant curing agent plus the original curing agent to the epoxy group in the epoxy resin is fixed at 1:1. Therefore, as the dosage of the flame retardant curing agent increases, the dosage of the original curing agent decreases accordingly.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The imidazole structure in the chemical structure of the imidazole-based phosphorus-containing flame retardant curing agent provided by the present invention can undergo a ring-opening reaction with the epoxy group, giving play to the advantages of difficult migration and precipitation of flame retardant elements, good compatibility with the matrix, and antibacterial properties.

[0029] 2. The phosphorus oxidation state in the chemical structure of the imidazole-based phosphorus-containing flame retardant curing agent provided by the present invention can be regulated, which can not only play the condensed-phase flame retardant mechanism to promote the carbonization of the polymer during combustion, but also play the gas-phase flame retardant mechanism to capture active free radicals during combustion, having the advantages of synergistic flame retardancy and high flame retardancy efficiency.

[0030] 3. The imidazole-based phosphorus-containing flame retardant curing agent provided by the present invention has a rich aromatic ring structure, does not deteriorate the glass transition temperature of the epoxy resin matrix, and has the advantage of high thermal stability. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is the thermogravimetric analysis curve of the epoxy resin containing different addition amounts of flame retardant a in Example 7 of the present invention.

[0033] Figure 2 It is the heat release rate curve of the epoxy resin containing different addition amounts of flame retardant a in Example 7 of the present invention.

[0034] Figure 3 It is the total smoke release curve of the epoxy resin containing different addition amounts of flame retardant a in Example 7 of the present invention.

[0035] Figure 4 This is the differential scanning calorimetry test curve of the epoxy resin containing different addition amounts of flame retardant a in Example 7 of the present invention.

[0036] Figure 5 This is the antibacterial test results of the epoxy resin, flame-retardant epoxy resin-2, flame-retardant epoxy resin-9, and flame-retardant epoxy resin-12 in the present invention against Aspergillus niger, Fusarium oxysporum, and Penicillium. Detailed implementation manners

[0037] In order to further illustrate the technical solution of the present invention, the preferred implementation manners of the present invention will be described below in combination with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0038] Example 1:

[0039] ① 4,4'-Diaminodiphenylmethane and 4-imidazolecarboxaldehyde were heated to 80°C in an ethanol solvent under nitrogen protection at a molar ratio of 1:2 and reacted for 8 hours. The solvent was removed by filtration to obtain imidazole-based Schiff base intermediate a, and its chemical structure is as follows:

[0040] .

[0041] ② The above imidazole-based Schiff base intermediate a and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were heated to 70°C in an ethanol solvent at a reaction molar ratio of 1:2 and reacted for 24 hours. The solvent was removed by rotary evaporation to obtain flame retardant a, and its chemical structure is as follows:

[0042] .

[0043] Flame retardant a was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectrum ( 1 ¹H-NMR), and its chemical structure was confirmed as follows: FT-IR (KBr, cm -1 ⁻¹): 754, 923 (P-O-Ph), 1226 - 1201 (P=O), 1612 (C=N of imidazole ring). 1H-NMR (400 MHz, DMSO-d6, ppm): 5.05 - 5.25 (m, 2H, -CH-P=O), 5.5 - 5.7 (m, 2H, N-H), 3.5 (m, 2H, -CH2-), 6.5 - 8.2 (m, 28H, Ar-H).

[0044] Example 2:

[0045] ① 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 4-imidazolecarboxaldehyde were heated to 80 °C in ethanol solvent under nitrogen protection in a molar ratio of 1:2.2 and reacted for 6 hours. The solvent was removed by rotary evaporation to obtain imidazole-based Schiff base intermediate b, whose chemical structure is shown below:

[0046] .

[0047] ② The above imidazole-based Schiff base intermediate b and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were heated to 50 °C in ethanol solvent in a reaction molar ratio of 1:2.2 and reacted for 24 hours. The solvent was removed by rotary evaporation to obtain flame retardant b, whose chemical structure is shown below:

[0048] .

[0049] Flame retardant b was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectrum ( 1 H-NMR), and its chemical structure was confirmed as follows: FT-IR (KBr, cm -1 ): 932 (P-O-C), 1192 (P=O), 1589 (P-Ar), 1050 (Si-O-Si). 1 H-NMR (400 MHz, DMSO-d6, ppm): 0 (m, 12H, Si-CH3), 0.3 (m, 4H, Si-CH2-), 1.2 (m, 4H, -CH2-), 2.4 (m, 4H, -CH2-N-), 4.2 (m, 2H, -CH-P=O), 4.4 (m, 2H, N-H), 8.05 - 8.34 (m, 20H, Ar-H).

[0050] Example 3:

[0051] ① 4,4'-Diaminodiphenyl sulfone and 4-imidazolecarboxaldehyde were heated to 60 °C in ethanol solvent under nitrogen protection in a molar ratio of 1:2.1 and reacted for 8 hours. The solvent was removed by rotary evaporation to obtain imidazole-based Schiff base intermediate c, whose chemical structure is shown below:

[0052] 。

[0053] ②React the above-mentioned imidazolyl Schiff base intermediate c and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in a molar ratio of 1:2.1 in an ethanol solvent, heat to 60 °C, react for 12 hours, and remove the solvent by rotary evaporation to obtain flame retardant c, whose chemical structure is as follows:

[0054] 。

[0055] Flame retardant c was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectroscopy ( 1 1H-NMR), and its chemical structure was confirmed as follows: FT-IR (KBr, cm -1 ): 932 (P-O-C), 1231 (P=O), 1592 (P-Ar). 1 1H-NMR (400 MHz, DMSO-d6, ppm): 4.05 - 4.28 (m, 2H, -CH-P=O), 5.5 - 5.7 (m, 2H, N-H), 6.93 - 8.04 (m, 28H, Ar-H).

[0056] Example 4:

[0057] ①React 4,4'-diaminodiphenylmethane and 2-imidazolecarboxaldehyde in a molar ratio of 1:2 under nitrogen protection in an ethanol solvent, heat to 80 °C and react for 5 hours, and remove the solvent by rotary evaporation to obtain imidazolyl Schiff base intermediate d, whose chemical structure is as follows:

[0058] 。

[0059] ②React the above-mentioned imidazolyl Schiff base intermediate d and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in a molar ratio of 1:2.1 in an ethanol solvent, heat to 80 °C, react for 6 hours, and remove the solvent by rotary evaporation to obtain flame retardant d, whose chemical structure is as follows:

[0060] 。

[0061] Flame retardant d was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectroscopy ( 1 1H-NMR), and its chemical structure was confirmed as follows: FT-IR (KBr, cm -1 ): 932 (P-O-C), 1202 (P=O), 1589 (P-Ph), 3240 (N-H). 1H-NMR (400 MHz, DMSO-d6, ppm): 3.6 (m, 2H, -CH2-), 5.0 - 5.2 (m, 2H, -CH-P=O), 5.5 - 5.7 (m, 2H, N-H), 6.5 - 8.1 (m, 28H, Ar-H).

[0062] Example 5:

[0063] ① 4,4'-Diaminodiphenylmethane and 4-imidazolecarboxaldehyde were reacted at a molar ratio of 1:2.1 under nitrogen protection in an ethanol solvent by heating to 80 °C for 4 hours. The solvent was removed by rotary evaporation to obtain imidazole-based Schiff base intermediate a.

[0064] ② The above imidazole-based Schiff base intermediate a and diphenylphosphine oxide were reacted at a reaction molar ratio of 1:2.1 in an ethanol solvent by heating to 80 °C for 12 hours. The solvent was removed by rotary evaporation to obtain flame retardant e, and its chemical structure is as follows:

[0065] .

[0066] Flame retardant e was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectrum ( 1 H-NMR), and its chemical structure was confirmed as follows: FT-IR (KBr, cm -1 ): 931 (P-O-C), 940 (P-O-Ph), 1204 (P=O), 3241 (N-H). 1 H-NMR (400 MHz, DMSO-d6, ppm): 3.8 (m, 2H, -CH2-), 4.2 (m, 2H, -CH-P=O), 5.5 - 5.7 (m, 2H, N-H), 6.5 - 8.5 (m, 32H, Ar-H).

[0067] Example 6:

[0068] ① 4,4'-Diaminodiphenylmethane and 4-imidazolecarboxaldehyde were reacted at a molar ratio of 1:2.1 under nitrogen protection in an ethanol solvent by heating to 40 °C for 24 hours. The solvent was removed by rotary evaporation to obtain imidazole-based Schiff base intermediate a.

[0069] ② The above imidazole-based Schiff base intermediate a and dimethyl phosphite were reacted at a reaction molar ratio of 1:2.1 in an ethanol solvent by heating to 80 °C for 12 hours. The solvent was removed by rotary evaporation to obtain flame retardant f, and its chemical structure is as follows:

[0070] .

[0071] The flame retardant f was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectroscopy ( 1 1H-NMR), and its chemical structure was confirmed as follows: FT-IR (KBr, cm -1 -1): 732 (P-C), 935 (P-O-C), 1206 (P=O), 2965 (-CH3), 3238 (N-H). 1 1H-NMR (400 MHz, DMSO-d6, ppm): 3.5 - 3.7 (d, 12H, -CH3), 3.9 (s, 2H, -CH2-), 4.0 (m, 2H, -CH-P=O), 5.5 - 5.7 (m, 2H, N-H), 6.5 - 7.1 (m, 12H, Ar-H).

[0072] Example 7: Preparation of Flame-Retardant Epoxy Resin and Results of Oxygen Index and Vertical Burning Test

[0073] In this example, the flame-retardant epoxy resin was prepared according to the formulation in Table 1 below.

[0074]

[0075] Note: The epoxy resin is bisphenol A diglycidyl ether type epoxy resin (grade: E-44, epoxy value: 0.44 mol / 100 g), and the curing agent is 4,4'-diaminodiphenylmethane.

[0076] Accurately weigh the epoxy resin, curing agent, and flame retardant. First, mix the epoxy resin and the flame retardant at 80 °C for 1 hour, then add the curing agent and continue to mix for 30 minutes. Immediately pour it into a mold, and the curing conditions are 100 °C / 2 hours + 150 °C / 2 hours. Naturally cool to room temperature to obtain the flame-retardant epoxy resin sample. According to the test of oxygen index and vertical burning test, the results are shown in Table 2:

[0077]

[0078] Comparative Example 1: Preparation of Flame-Retardant Epoxy Resin and Results of Oxygen Index and Vertical Burning Test

[0079] In this comparative example, the flame-retardant epoxy resin was prepared according to the formulation in Table 3 below.

[0080]

[0081] Note: The epoxy resin is bisphenol A diglycidyl ether, the curing agent is 4,4'-diaminodiphenylmethane, the phosphorus-containing flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, the imidazole-containing flame retardant 1 is dibenzo[c,e][1,2]oxaphosphole imidazole complex, the imidazole-containing flame retardant 2 is diphenylphosphonic acid diimidazole complex, and the imidazole-containing flame retardant 3 is N-[3-(1H-imidazol-1-yl)propyl]-P,P-diphenylphosphinic amide.

[0082] Accurately weigh the epoxy resin, curing agent, and flame retardant (or intermediate). First, mix the epoxy resin and the flame retardant (or intermediate) at 80 °C for 1 hour, then add the curing agent and continue mixing for 30 minutes. Immediately pour it into a mold, and the curing conditions are 100 °C / 2 hours + 150 °C / 2 hours. Naturally cool to room temperature to obtain a flame-retardant epoxy resin sample. According to the test of oxygen index and vertical burning test, the results are shown in Table 4:

[0083]

[0084] The flame retardancy test results of each sample in Table 2 and Table 4 show that the oxygen index of the untreated epoxy resin is 25.5%, and there is no rating in the UL-94 vertical burning test. The oxygen index of the epoxy resin added with 2.5 wt% flame retardant a is increased to 31.0%, but the UL-94 vertical burning test only reaches V-2 level. The oxygen indexes of the epoxy resins added with 5.0 wt% and 7.5 wt% flame retardant a are further increased to 33.0% and 33.5% respectively, and both can pass the UL-94 vertical burning test at V-0 level. In addition, the oxygen indexes of the epoxy resins added with 5.0 wt% flame retardant b, flame retardant c, and flame retardant d all reach above 32.0%, and all can pass the UL-94 vertical burning test at V-0 level, indicating that the imidazole-based phosphorus-containing flame retardant curing agent provided by the present invention has excellent flame retardancy efficiency. In contrast, the oxygen indexes of the epoxy resins added with 5.0 wt% intermediate a and intermediate b do not exceed 29.0%, and there is no rating in the UL-94 vertical burning test; the oxygen index of the epoxy resin added with 5.0 wt% phosphorus-containing flame retardant reaches 30.5%, but only reaches the UL-94 V-1 level; the oxygen indexes of epoxy resins 10 and 11 added with two imidazole-containing flame retardants are 27.5% and 27.0% respectively, and the UL-94 vertical burning test shows no rating, which is because the ionic bond formed between imidazole and phosphonic acid group has lower flame retardancy efficiency than covalent bond; the oxygen index of the epoxy resin added with imidazole-containing flame retardant 3 is 30.0%, and the UL-94 vertical burning test only reaches V-2 level, indicating that the flame retardancy efficiency of a single imidazole group is lower than that of a double imidazole group.

[0085] Example 8: Antibacterial test of flame-retardant epoxy resin

[0086] The mold resistance of the flame-retardant epoxy resin was determined according to the method of GB / T 1741-2020. Flame-retardant epoxy resin-2 was used as the test sample, and epoxy resin, flame-retardant epoxy resin-9, and flame-retardant epoxy resin-12 were used as the comparative samples. The antibacterial test results of the above samples against Aspergillus niger, Fusarium oxysporum, and Penicillium were as Figure 5 shown.

[0087] Figure 1 Figure Figure 5 is the thermogravimetric analysis curve of epoxy resin containing different addition amounts of flame retardant a (in nitrogen atmosphere, heating rate is 20 °C / min). The addition of flame retardant a improved the char-forming performance of the epoxy resin, and with the increase of the addition amount, the char yield increased continuously. The char yield of the untreated epoxy resin at 800 o °C was 11.8%, while the char yields of the flame-retardant epoxy resins were all above 14.5%, indicating that flame retardant a has good catalytic char-forming ability.

[0088] Figure 2 Figure is the heat release rate curve of epoxy resin containing different addition amounts of flame retardant a (tested by cone calorimeter, 35 kW / m 2 ²). The peak heat release rate of the untreated epoxy resin was 1167 kW / m 2 ². The peak heat release rates of the epoxy resins added with 2.5 wt%, 5 wt%, and 7.5 wt% of flame retardant a decreased to 1015, 960, and 884 kW / m 2 ² respectively, indicating that flame retardant a has good flame retardant performance.

[0089] Figure 3 Figure

[0087] is the total smoke release curve of epoxy resin containing different addition amounts of flame retardant a (tested by cone calorimeter, 35 kW / m 2 ²). The total smoke release of the untreated epoxy resin was 20.9 m 2 ³. The total smoke releases of the epoxy resins added with 2.5 wt%, 5 wt%, and 7.5 wt% of flame retardant a decreased to 17.2, 17.7, and 17.4 m 2 ³ respectively, indicating that flame retardant a has good smoke suppression performance.

[0090] Figure 4 Figure Figure 1 is the differential scanning calorimetry test curve of epoxy resin containing different addition amounts of flame retardant a (heating rate is 10 °C / min). The glass transition temperature (T g g) of the material is taken as the intersection temperature of the midline of the extrapolated baselines on the low-temperature side and the high-temperature side of the DSC curve and the curve. The T g g of the untreated epoxy resin was 151.6 °C. Adding 2.5 wt%, 5 wt%, and 7.5 wt% of flame retardant a respectively increased the T g g of the epoxy resin. When adding 5 wt% of flame retardant a, the Tg The increase is close to 10 °C, indicating that flame retardant a can effectively improve the thermal stability of epoxy resin.

[0091] Figure 5 This is the antibacterial test results (48h) of epoxy resin, flame-retardant epoxy resin-2, flame-retardant epoxy resin-9, and flame-retardant epoxy resin-12 in the present invention against Aspergillus niger, Fusarium oxysporum, and Penicillium. For the culture media of the three molds on the surface of the flame-retardant epoxy resin-2 film, no obvious growth of the molds was observed, indicating that the flame-retardant epoxy resin-2 has excellent inhibitory effects on the growth of the three molds; in contrast, epoxy resin, flame-retardant epoxy resin-9, and flame-retardant epoxy resin-12 did not show effective inhibitory effects on the three molds.

[0092] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An imidazole-based phosphorus-containing flame retardant curing agent, characterized in that Its chemical structure is shown in the following formula (I) or (II): ； Wherein: R1 is selected from any one of the following structures: ； R2 is selected from any one of the following structures: ； * indicates the connection position.

2. The preparation method of the imidazole-based phosphorus-containing flame retardant curing agent according to claim 1, characterized in that It includes the following steps: Step 1: Dissolve diamine and 4-imidazolecarboxaldehyde or 2-imidazolecarboxaldehyde in ethanol, and under the protection of an inert gas, heat and react to obtain an imidazole-based Schiff base intermediate; Step 2: Dissolve the imidazole-based Schiff base intermediate obtained in Step 1 and a phosphorus-containing compound in ethanol, and under the protection of an inert gas, heat and react to obtain a flame retardant curing agent; In Step 1, the diamine is selected from one of 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane; In Step 2, the phosphorus-containing compound is selected from any one of diphenylphosphine oxide, diphenyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, dibenzyl phosphite, dimethyl phosphite, diethyl phosphite, dibutyl phosphite, diisobutyl phosphite.

3. The preparation method according to claim 2, wherein: In Step 1, the molar ratio of diamine to 4-imidazolecarboxaldehyde or 2-imidazolecarboxaldehyde is 1:(2.0 - 2.2).

4. The preparation method according to claim 2, wherein: In Step 1, the reaction temperature is 20°C to 80°C, and the reaction time is 3 to 24 hours.

5. The preparation method according to claim 2, wherein: In Step 2, the molar ratio of the imidazole-based Schiff base intermediate to the phosphorus-containing compound is 1:(2.0 - 2.2).

6. The preparation method according to claim 2, wherein: In Step 2, the reaction temperature is 40 - 80°C, and the reaction time is 3 to 24 hours.

7. Use of the imidazole-based phosphorus-containing flame retardant curing agent according to claim 1 in the preparation of a flame retardant and antibacterial epoxy resin functional material.

8. The use according to claim 7, wherein: Using the imidazole-based phosphorus-containing flame retardant curing agent as an additive in an epoxy resin system to improve the flame retardant performance and antibacterial performance of the epoxy resin.

9. The use according to claim 8, wherein: The addition amount of the imidazole-based phosphorus-containing flame retardant curing agent is 2.5 - 7.5% of the total mass of the components of the epoxy resin.

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