A composite flame retardant for epoxy resin and its preparation method

Abstract

The present invention provides a composite flame retardant that can be used for epoxy resin and a preparation method thereof, relating to the technical field of flame retardants. The method is to first prepare a phosphorus-containing silane coupling agent solution and a MOF-on-MOF material, then mix APP and MOF-on-MOF to obtain a mixture of APP and MOF-on-MOF; finally, mix the mixture of APP and MOF-on-MOF with the phosphorus-containing silane coupling agent solution to obtain a composite flame retardant. When the prepared composite flame retardant is applied to epoxy resin after the surface modification of the mixture of MOF-on-MOF and APP with the prepared phosphorus-containing silane coupling agent, it shows better flame retardant effect. In addition, the composite flame retardant can not only improve the flame retardant performance of epoxy resin, but also effectively improve the mechanical properties of epoxy resin materials compared with the sole use of APP.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardants, and particularly to a composite flame retardant for epoxy resin and a preparation method thereof. Background Art

[0002] Epoxy resin is an important type of polymer material, which has good mechanical properties, excellent corrosion resistance, high thermal stability, etc., and is widely used in fields such as electronic packaging and anticorrosive coatings. However, epoxy resin is a combustible material, and being ignited by an open flame will cause losses such as assets and personnel. Therefore, it is necessary to improve the flame retardancy of epoxy resin by adding a flame retardant thereto.

[0003] Phosphorus-containing flame retardants are a commonly used type of flame retardants at present, which have advantages such as not generating halogen-containing poisonous gases during combustion and good flame retardancy. Ammonium polyphosphate (APP) is an important variety among phosphorus-containing flame retardants and can be used in various polymer materials such as epoxy resin and polyolefin. However, some problems have also emerged during the use of APP. First of all, the addition amount of APP is relatively large. Taking the addition of APP in epoxy resin as an example, generally the addition amount of APP needs to exceed 10% in order to make the prepared epoxy resin material reach the V0 level of UL-94 test. Secondly, when the addition amount of APP is relatively large, it is easy to cause a decline in the mechanical properties of the epoxy resin material. Adding about 10% of APP in epoxy resin will reduce the impact strength of the prepared epoxy resin material by about 40%. Therefore, on the premise of ensuring the flame retardancy of epoxy resin, reducing the addition amount of APP in epoxy resin and trying to ensure the mechanical properties of the epoxy resin material are problems that need to be solved in the development of APP-based composite flame retardants.

[0004] Metal-organic framework materials (MOF) are a type of crystalline porous material with a periodic network structure formed by the self-assembly connection of inorganic metal centers and bridging organic ligands. Such materials also have certain flame retardant properties. However, when MOF materials are used alone, their flame retardant properties are poor, and usually the MOF materials need to be modified or compounded with other flame retardants to achieve good flame retardant effects. MOF-on-MOF materials are a type of multi-layer or hierarchical structure materials constructed by depositing one MOF on the surface of another MOF. This structure can provide unique physical and chemical properties, thereby expanding the application scope of MOF materials. MOF-on-MOF materials have characteristics such as enhanced functionality and adjustable surface properties compared to MOF materials, and can meet more application requirements. Therefore, expanding the application of MOF-on-MOF in the field of flame retardancy and developing an efficient composite flame retardant system based on MOF materials are problems that need to be solved in the current preparation of high-performance flame retardants using MOF materials. Summary of the Invention

[0005] The object of the present invention is to solve the problems that in the existing flame retardants for epoxy resins, the addition amount of APP in epoxy resins is large and the mechanical properties of epoxy resin materials are poor, and to provide a composite flame retardant that can be used in epoxy resins and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention first provides a preparation method of a composite flame retardant that can be used in epoxy resins, including:

[0008] Step 1: Preparation of a phosphorus-containing silane coupling agent solution

[0009] Under the condition of nitrogen protection, DOPO-OH and a silane coupling agent are added to a reaction kettle for reaction to obtain a phosphorus-containing silane coupling agent, and the phosphorus-containing silane coupling agent is mixed evenly with an aqueous solution of an acid to obtain a phosphorus-containing silane coupling agent solution, and the silane coupling agent is KH560 or 3-isocyanatopropyltrimethoxysilane;

[0010] Step 2: Preparation of MOF-on-MOF material

[0011] 1) Terephthalic acid and ferric chloride are dissolved in a solvent and stirred to obtain a mixed solution, and then the mixed solution is added to a reaction kettle for heating reaction to obtain an intermediate product Fe-MOF;

[0012] 2) After dispersing Fe-MOF in water, 2-methylimidazole is added to the Fe-MOF aqueous dispersion and stirred, and then an aqueous solution of zinc nitrate is added and stirred to obtain a MOF-on-MOF material;

[0013] Step 3: Preparation of a mixture of APP and MOF-on-MOF

[0014] APP and MOF-on-MOF are mixed to obtain a mixture of APP and MOF-on-MOF;

[0015] Step 4: Preparation of the composite flame retardant

[0016] The mixture of APP and MOF-on-MOF obtained in Step 3 is mixed with the phosphorus-containing silane coupling agent solution obtained in Step 1 and dried to obtain a composite flame retardant.

[0017] Preferably, the reaction temperature in Step 1 is 25-140°C and the reaction time is 3-15 h.

[0018] Preferably, the weight ratio of DOPO-OH to the silane coupling agent in Step 1 is 1:(1-1.2).

[0019] Preferably, when the silane coupling agent in step 1 is 3-isocyanatepropyltrimethoxysilane, the solvent 1,4-dioxane is added during the reaction; when the silane coupling agent is KH560, triphenylphosphine is added during the reaction.

[0020] Preferably, the reaction temperature of step 1) in step 2 is 110° C.-120° C., and the reaction time is 12-24 h.

[0021] Preferably, in step 2, the weight ratio of 2-methylimidazole to zinc nitrate is 82:189, and the weight ratio of the intermediate product Fe-MOF to zinc nitrate is (6-13):1.

[0022] Preferably, the weight ratio of APP and MOF-on-MOF in step three is (8-19):1.

[0023] Preferably, the mixing speed in step 4 is 1000-3000 rpm, the mixing temperature is 30-70° C., and the mixing time is 10-30 min.

[0024] Preferably, the weight ratio of the mixture of APP and MOF-on-MOF described in step 4 to the phosphorus-containing silane coupling agent solution is (5-10):1.

[0025] The present invention also provides a composite flame retardant which can be used for epoxy resin and is obtained by the above preparation method.

[0026] Beneficial effects of the present invention

[0027] The present invention provides a composite flame retardant that can be used for epoxy resin and a preparation method thereof. The method uses a prepared phosphorus-containing silane coupling agent to modify the surface of a mixture of MOF-on-MOF and APP, and the prepared composite flame retardant is applied to epoxy resin and exhibits a better flame retardant effect. Under the same addition amount, compared with adding APP alone or a mixture of MOF-on-MOF and APP, the final prepared composite flame retardant has a higher oxygen index and a higher vertical combustion (UL-94) test level, and the prepared epoxy resin has better flame retardant performance. In addition, the composite flame retardant can not only improve the flame retardant performance of epoxy resin, but also effectively improve the mechanical properties of epoxy resin materials compared with using APP alone, solving the problem that the mechanical properties of epoxy resin are reduced too much when APP is added to epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the infrared spectra of APP and the composite flame retardant 1 prepared in Example 1 of the present invention.

[0029] Figure 2 The scanning electron microscope photographs are of APP and the composite flame retardant 1 prepared in Example 1 of the present invention. Detailed implementation mode

[0030] The present invention first provides a preparation method of a composite flame retardant for epoxy resin, including:

[0031] Step 1: Preparation of phosphorus-containing silane coupling agent solution

[0032] Under the condition of nitrogen protection, DOPO-OH and silane coupling agent are added to a reaction kettle for reaction. The reaction temperature is preferably 25°C - 140°C, and the reaction time is preferably 3 - 15 h to obtain a phosphorus-containing silane coupling agent. The phosphorus-containing silane coupling agent is mixed evenly with an aqueous acid solution to obtain a phosphorus-containing silane coupling agent solution; the weight ratio of water to acid in the aqueous acid solution is preferably (1 - 3):1, the acid is preferably formic acid or acetic acid, and the weight ratio of the aqueous acid solution to the phosphorus-containing silane coupling agent is preferably (1 - 2):1; the silane coupling agent is KH560 or 3-isocyanatopropyltrimethoxysilane;

[0033] When the silane coupling agent is 3-isocyanatopropyltrimethoxysilane, a solvent needs to be added during the reaction. The solvent is preferably 1,4-dioxane, and the weight ratio of DOPO-OH, silane coupling agent and 1,4-dioxane is preferably 1:(1 - 1.2):(8 - 12); when the silane coupling agent is KH560, a catalyst triphenylphosphine needs to be added during the reaction, and the weight ratio of DOPO-OH, silane coupling agent and triphenylphosphine is preferably 1:(1 - 1.2):(0.02 - 0.2); after the phosphorus-containing silane coupling agent is mixed evenly with the aqueous acid solution, it must be used within 20 minutes and cannot be stored for a long time, otherwise the modification effect will be affected.

[0034] Step 2: Preparation of MOF-on-MOF material

[0035] 1) Dissolve terephthalic acid and ferric chloride in a solvent and stir. The solvent is preferably N,N-dimethylformamide, and the weight ratio of terephthalic acid to ferric chloride is preferably 166:162. The stirring temperature is preferably 30°C - 50°C, and the stirring time is preferably 30 - 60 minutes to form a uniform solution. Then, the uniform solution is transferred to a high-pressure kettle reaction kettle for reaction heating. The reaction temperature is preferably 110°C - 120°C, and the reaction time is preferably 12 - 24 hours. After that, the wet intermediate product Fe-MOF is filtered and collected, and the wet intermediate product Fe-MOF is washed and dried to obtain the intermediate product Fe-MOF. The washing and drying are preferably carried out by washing 3 times with methanol, soaking in methanol for 12 - 24 hours, and then vacuum drying at 80°C - 120°C for 12 hours;

[0036] 2) After dispersing the intermediate product Fe-MOF obtained in step 1) in water, 2-methylimidazole is added to the Fe-MOF aqueous dispersion. After 2-methylimidazole is dissolved, an aqueous solution of zinc nitrate is added to the Fe-MOF aqueous dispersion under stirring. The stirring time is preferably 4 - 8 hours. The wet MOF-on-MOF product is obtained by filtration and separation, and the product MOF-on-MOF material is obtained by post-treatment. The post-treatment is preferably: washing the collected product with water 3 times and drying it under vacuum at 100°C - 120°C for 6 - 8 hours; the weight ratio of 2-methylimidazole to zinc nitrate is preferably 82:189, and the weight ratio of the intermediate product Fe-MOF to zinc nitrate is preferably (6 - 13):1;

[0037] Step 3: Preparation of the mixture of APP and MOF-on-MOF

[0038] APP and the MOF-on-MOF prepared in step 2 are mixed in a high-speed mixer to obtain a mixture of APP and MOF-on-MOF. The weight ratio of APP to MOF-on-MOF is preferably (8 - 19):1. The rotation speed in the high-speed mixer is preferably 1000 - 3000 revolutions per minute (r / min), and the mixing time is preferably 5 - 10 minutes;

[0039] Step 4: Preparation of the composite flame retardant

[0040] The mixture of APP and MOF-on-MOF obtained in step 3 is mixed with the phosphorus-containing silane coupling agent solution obtained in step 1 in a high-speed mixer and dried to obtain the composite flame retardant; the rotation speed in the high-speed mixer is preferably 1000 - 3000 revolutions per minute (r / min), the mixing temperature is preferably 30°C - 70°C, the mixing time is preferably 10 - 30 minutes, the drying temperature is preferably 80 - 100°C, and the drying time is preferably 3 - 6 h. The weight ratio of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent solution is preferably (5 - 10):1.

[0041] In the present invention, the chemical structural formulas of DOPO-OH, 3-isocyanatopropyltrimethoxysilane, and KH560 are as follows:

[0042] DOPO-OH:

[0043] KH560:

[0044] 3-isocyanatopropyltrimethoxysilane:

[0045] The following further elaborates on the composite flame retardant of the present invention in conjunction with embodiments. All raw materials involved in the embodiments are commercially obtained.

[0046] Example 1

[0047] (1) Preparation of phosphorus-containing silane coupling agent (KH560P):

[0048] Under nitrogen protection, DOPO-OH, KH560, and triphenylphosphine were added to the reaction kettle in a weight ratio of 1:1.1:0.1, and reacted under stirring at 130 °C for 6 hours. After the reaction was completed, the phosphorus-containing silane coupling agent KH560P was obtained.

[0049] (2) Preparation of MOF-on-MOF material:

[0050] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide in a weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reaction kettle and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 20 hours, and then vacuum dried at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0051] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 10:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and vacuum dried at 110 °C for 7 hours to obtain the final product MOF-on-MOF material.

[0052] (3) Preparation of a mixture of APP and MOF-on-MOF:

[0053] APP and MOF-on-MOF were mixed in a weight ratio of APP to MOF-on-MOF of 9:1 in a high-speed mixer at a rotation speed of 2000 for 10 minutes.

[0054] (4) Preparation of phosphorus-containing silane coupling agent KH560P solution:

[0055] KH560 was mixed evenly with an aqueous solution of formic acid, where the weight ratio of water to formic acid was 2:1, and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P was 1.5:1. The phosphorus-containing silane coupling agent KH560P solution was obtained.

[0056] (5) Preparation of the composite flame retardant:

[0057] Mix the mixture of APP and MOF-on-MOF with the phosphorus-containing silane coupling agent KH560P solution at a weight ratio of 9:1 of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent KH560P solution in a high-speed mixer at a rotation speed of 3000 at 70 °C for 10 minutes. Vacuum dry the mixed material at 100 °C for 3 hours to obtain the composite flame retardant 1.

[0058] The infrared spectra of the composite flame retardant 1 and APP prepared in Example 1 are as Figure 1 shown Figure 1 It can be seen that, compared with APP, the prepared composite flame retardant 1 has new infrared peaks at wavenumbers of 1597 cm -1 , 1201 cm -1 , 748 cm -1 , 752 cm -1 and so on.

[0059] Figure 2 are the scanning electron microscope photos of APP and the composite flame retardant 1 prepared in Example 1. Among them Figure 2 (a) represents APP, Figure 2 (b) represents the composite flame retardant 1. It can be seen from Figure 2 that the surface of the APP particles is relatively smooth, while there is a layer of small particles on the surface of the composite flame retardant 1.

[0060] To illustrate the effects of the composite flame retardant 1 prepared in Example 1 on the flame retardancy and mechanical properties of epoxy resin, using the composite flame retardant 1 and APP prepared in this example as flame retardants respectively, add these two flame retardants to the E51 type epoxy resin (E51 / DDM) with 4,4'-diaminodiphenylmethane (DDM) as the curing agent at an addition ratio of 7% by weight of the epoxy resin respectively to prepare flame-retardant epoxy resins, and test the flame retardancy and mechanical properties of the materials. The results are shown in Table 1:

[0061] Table 1 Comparison of the flame retardancy and mechanical properties of the flame-retardant materials prepared by adding APP and the composite flame retardant 1 to epoxy resin respectively

[0062]

[0063] As can be seen from Table 1, compared with pure epoxy resin, when using APP alone, the oxygen index of the obtained epoxy resin material slightly increases, reaching the V-1 level in the UL-94 test, the impact strength decreases by about 50%, and the tensile strength decreases by about 30%; while for the epoxy resin material using Composite Flame Retardant 1, the oxygen index is close to 30, reaching the V-0 level in the UL-94 test, and the tensile strength and impact strength of the material do not decrease much. This shows that Composite Flame Retardant 1 has better flame retardant performance than APP. At the same time, compared with APP, Composite Flame Retardant 1 has less impact on the mechanical properties of epoxy resin materials.

[0064] Comparative Example 1

[0065] (1) Preparation of phosphorus-containing silane coupling agent (KH550P):

[0066] Under the condition of nitrogen protection, DOPO-OH, KH550 and triphenylphosphine are added to the reaction kettle according to the weight ratio of 1:1.1:0.1, and reacted under stirring at 130 °C for 6 hours. After the reaction is completed, the phosphorus-containing silane coupling agent KH550P is obtained.

[0067] (2) Preparation of MOF-on-MOF material:

[0068] Terephthalic acid and ferric chloride are added to N,N-dimethylformamide according to the weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution is transferred to an autoclave reaction kettle and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF is collected by filtration. The wet intermediate product Fe-MOF is washed 3 times with methanol and soaked in methanol for 20 hours, and then vacuum dried at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0069] After dispersing Fe-MOF in water, 2-methylimidazole is added to the Fe-MOF aqueous dispersion. After 2-methylimidazole is dissolved, an aqueous solution of zinc nitrate is added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 10:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product is separated by filtration. The collected product is washed 3 times with water and vacuum dried at 110 °C for 7 hours to obtain the final product MOF-on-MOF material.

[0070] (3) Preparation of a mixture of APP and MOF-on-MOF:

[0071] APP and MOF-on-MOF are mixed in a high-speed mixer at a rotation speed of 2000 for 10 minutes according to the weight ratio of APP to MOF-on-MOF of 9:1.

[0072] (4) Preparation of phosphorus-containing silane coupling agent KH550P solution:

[0073] Mix KH550 evenly with an aqueous solution of formic acid, where the weight ratio of water to formic acid is 2:1, and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH550P is 1.5:1. Obtain the phosphorus-containing silane coupling agent KH560P solution.

[0074] (5) Preparation of composite flame retardant:

[0075] Mix the mixture of APP and MOF-on-MOF with the phosphorus-containing silane coupling agent KH550P solution in a weight ratio of 9:1 for the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent KH550P solution. Mix at 3000 rpm in a high-speed mixer at 70 °C for 10 minutes. Vacuum dry the mixed material at 100 °C for 3 hours to obtain the composite flame retardant D1.

[0076] The chemical structural formula of KH550 in the above comparative example is as follows:

[0077]

[0078] To illustrate the influence of the prepared composite flame retardant D1 of Comparative Example 1 on the flame retardant performance and mechanical properties of epoxy resin, the composite flame retardant D1 prepared in this comparative example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and the flame retardant performance and mechanical properties of the material were tested. The results are shown in Table 2:

[0079] Table 2 Comparison of the flame retardant and mechanical properties of the flame-retardant materials prepared by adding composite flame retardant D1 to epoxy resin

[0080]

[0081] Comparing Table 1 and Table 2, it can be seen that although the oxygen index of the epoxy resin material using composite flame retardant D1 is close to 30 and it reaches the V-0 level in the UL-94 test. However, the tensile strength and impact strength of the material are significantly reduced compared to the epoxy resin using composite flame retardant 1. KH560 and KH550, two different silane coupling agents, were used in Example 1 and Comparative Example 1 respectively, and there are obvious differences in the effects. This shows that composite flame retardant 1 has better advantages in ensuring the mechanical properties of epoxy resin materials, and the comprehensive performance of composite flame retardant 1 is better.

[0082] Comparative Example 2

[0083] (1) Preparation of MOF-on-MOF material:

[0084] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide at a weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reactor and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 20 hours, and then vacuum dried at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0085] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After the 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 10:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and vacuum dried at 110 °C for 7 hours to obtain the final product MOF-on-MOF material.

[0086] (2) Preparation of the mixture of APP and MOF-on-MOF:

[0087] APP and MOF-on-MOF were mixed at a weight ratio of APP to MOF-on-MOF of 9:1 in a high-speed mixer at a rotation speed of 2000 for 10 minutes.

[0088] To illustrate the effects of the prepared MOF-on-MOF of Comparative Example 2 and the mixture of APP and MOF-on-MOF on the flame retardancy and mechanical properties of epoxy resin, the MOF-on-MOF and the mixture of APP and MOF-on-MOF prepared in this comparative example were added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and the flame retardancy and mechanical properties of the materials were tested. The results are shown in Table 3:

[0089] Table 3 Comparison of the flame retardancy and mechanical properties of the flame-retardant materials prepared by adding MOF-on-MOF and the mixture of APP and MOF-on-MOF to epoxy resin

[0090]

[0091] Comparing Table 1 and Table 3, it can be seen that the epoxy resin materials using MOF-on-MOF or the mixture of APP and MOF-on-MOF as flame retardants have lower flame retardancy and mechanical properties than the epoxy resin using Composite Flame Retardant 1. The composite flame retardant 1 has better comprehensive performance.

[0092] Comparative Example 3

[0093] (1) Preparation of phosphorus-containing silane coupling agent (KH560P):

[0094] Under the protection of nitrogen, DOPO-OH, KH560 and triphenylphosphine were added to the reaction kettle according to the weight ratio of 1:1.1:0.1, and reacted for 6 hours under stirring at 130 °C. After the reaction was completed, the phosphorus-containing silane coupling agent KH560P was obtained.

[0095] (2) Preparation of MOF-on-MOF material:

[0096] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide according to the weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reactor and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 20 hours, and then vacuum dried at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0097] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189, and the weight ratio of Fe-MOF to zinc nitrate to be 5:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product was separated by filtration. The collected product was washed 3 times with water and vacuum dried at 110 °C for 7 hours to obtain the final product MOF-on-MOF material.

[0098] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0099] APP and MOF-on-MOF were mixed at a weight ratio of APP to MOF-on-MOF of 9:1 in a high-speed mixer at a speed of 2000 for 10 minutes.

[0100] (4) Preparation of phosphorus-containing silane coupling agent KH560P solution:

[0101] KH560 was uniformly mixed with an aqueous solution of formic acid, where the weight ratio of water to formic acid was 2:1, and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P was 1.5:1. The phosphorus-containing silane coupling agent KH560P solution was obtained.

[0102] (5) Preparation of composite flame retardant:

[0103] The mixture of APP and MOF-on-MOF and the KH560P solution of phosphosilane coupling agent were mixed at a ratio of 9:1 by weight of the mixture of APP and MOF-on-MOF to the KH560P solution of phosphosilane coupling agent. They were mixed at a rotation speed of 3000 in a high-speed mixer at 70 °C for 10 minutes. The mixed material was vacuum dried at 100 °C for 3 hours to obtain the composite flame retardant D3.

[0104] To illustrate the influence of the prepared composite flame retardant D3 of Comparative Example 3 on the flame retardancy and mechanical properties of epoxy resin, the composite flame retardant D3 prepared in this comparative example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and the flame retardancy and mechanical properties of the material were tested. The results are shown in Table 4:

[0105] Table 4 Comparison of the flame retardancy and mechanical properties of the flame-retardant materials prepared by adding the composite flame retardant D3 to epoxy resin

[0106]

[0107] Comparing Table 1 and Table 4, it can be seen that the oxygen index of the epoxy resin material using the composite flame retardant D3 is less than 28, and it reaches the V-1 level in the UL-94 test. The tensile strength and impact strength of the material are not much different from those of the epoxy resin using the composite flame retardant 1. In Comparative Example 3, the weight ratio of Fe-MOF to zinc nitrate was 5:1, resulting in a decrease in the flame retardancy of the epoxy resin material using the composite flame retardant D3. This shows that the composite flame retardant 1 is better than the composite flame retardant D3 in ensuring the flame retardancy of the epoxy resin material.

[0108] Comparative Example 4

[0109] (1) Preparation of phosphosilane coupling agent (KH560P):

[0110] Under the protection of nitrogen, DOPO-OH, KH560 and triphenylphosphine were added to the reaction kettle at a weight ratio of 1:1.1:0.1, and reacted under stirring at 130 °C for 6 hours. After the reaction was completed, the phosphosilane coupling agent KH560P was obtained.

[0111] (2) Preparation of MOF-on-MOF material:

[0112] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide in a weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reactor and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 20 hours, and then dried in vacuo at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0113] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 14:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and dried in vacuo at 110 °C for 7 hours to obtain the final product MOF-on-MOF material.

[0114] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0115] APP and MOF-on-MOF were mixed at a weight ratio of APP to MOF-on-MOF of 9:1 in a high-speed mixer at a rotation speed of 2000 for 10 minutes.

[0116] (4) Preparation of the phosphorus-containing silane coupling agent KH560P solution:

[0117] KH560 was mixed uniformly with an aqueous solution of formic acid, where the weight ratio of water to formic acid was 2:1, and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P was 1.5:1. The phosphorus-containing silane coupling agent KH560P solution was obtained.

[0118] (5) Preparation of the composite flame retardant:

[0119] The mixture of APP and MOF-on-MOF and the phosphorus-containing silane coupling agent KH560P solution were in a weight ratio of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent KH560P solution of 9:1. They were mixed at a rotation speed of 3000 in a high-speed mixer at 70 °C for 10 minutes. The mixed material was dried in vacuo at 100 °C for 3 hours to obtain the composite flame retardant D4.

[0120] To illustrate the effects of the composite flame retardant D4 prepared in Comparative Example 4 on the flame retardancy and mechanical properties of epoxy resin, the composite flame retardant D4 prepared in this comparative example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare a flame-retardant epoxy resin, and the flame retardancy and mechanical properties of the material were tested. The results are shown in Table 5:

[0121] Table 5 Comparison of the flame retardancy and mechanical properties of the flame-retardant materials prepared by adding the composite flame retardant D4 to epoxy resin

[0122]

[0123] Comparing Table 1 and Table 5, it can be seen that the oxygen index of the epoxy resin material using the composite flame retardant D4 is less than 28, and it reaches the V-1 level in the UL-94 test. The tensile strength and impact strength of the material are not much different from those of the epoxy resin using the composite flame retardant 1. In Comparative Example 4, the weight ratio of Fe-MOF to zinc nitrate is 14:1, resulting in a decrease in the flame retardancy of the epoxy resin material using the composite flame retardant D4. This shows that the composite flame retardant 1 is better than the composite flame retardant D4 in ensuring the flame retardancy of the epoxy resin material.

[0124] Comparative Example 5

[0125] (1) Preparation of phosphorus-containing silane coupling agent (KH560P):

[0126] Under the protection of nitrogen, DOPO-OH, KH560 and triphenylphosphine were added to the reaction kettle according to the weight ratio of 1:1.1:0.1, and reacted for 6 hours under stirring at 130 °C. After the reaction was completed, the phosphorus-containing silane coupling agent KH560P was obtained.

[0127] (2) Preparation of MOF-on-MOF material:

[0128] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide according to the weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to a high-pressure reaction kettle and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 20 hours, and then vacuum dried at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0129] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After the 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 10:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and vacuum dried at 110 °C for 7 hours to obtain the final product, the MOF-on-MOF material.

[0130] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0131] APP and MOF-on-MOF were mixed at a weight ratio of 7:1 in a high-speed mixer at a rotation speed of 2000 for 10 minutes.

[0132] (4) Preparation of the solution of phosphorus-containing silane coupling agent KH560P:

[0133] KH560 was uniformly mixed with an aqueous solution of formic acid, where the weight ratio of water to formic acid was 2:1 and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P was 1.5:1. The solution of the phosphorus-containing silane coupling agent KH560P was obtained.

[0134] (5) Preparation of the composite flame retardant:

[0135] The mixture of APP and MOF-on-MOF and the solution of the phosphorus-containing silane coupling agent KH560P were in a weight ratio of 9:1 for the mixture of APP and MOF-on-MOF and the solution of the phosphorus-containing silane coupling agent KH560P. They were mixed at a rotation speed of 3000 in a high-speed mixer at 70 °C for 10 minutes. The mixed material was vacuum dried at 100 °C for 3 hours to obtain the composite flame retardant D5.

[0136] To illustrate the influence of the prepared composite flame retardant D5 of Comparative Example 5 on the flame retardancy and mechanical properties of epoxy resin, the composite flame retardant D5 prepared in this comparative example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and the flame retardancy and mechanical properties of the material were tested. The results are shown in Table 6:

[0137] Table 6 Comparison of the flame retardancy and mechanical properties of the flame-retardant materials prepared by adding the composite flame retardant D5 to epoxy resin

[0138]

[0139] Comparing Table 1 and Table 6, it can be seen that the oxygen index of the epoxy resin material using the composite flame retardant D5 is less than 28, and it reaches the V-1 level in the UL-94 test. The tensile strength and impact strength of the material have little difference compared with the epoxy resin using the composite flame retardant 1. In Comparative Example 5, the weight ratio of APP to MOF-on-MOF is 7:1, resulting in a decrease in the flame retardant performance of the epoxy resin material using the composite flame retardant D5. This shows that the composite flame retardant 1 is better than the composite flame retardant D5 in ensuring the flame retardant performance of the epoxy resin material.

[0140] Comparative Example 6

[0141] (1) Preparation of phosphorus-containing silane coupling agent (KH560P):

[0142] Under the condition of nitrogen protection, DOPO-OH, KH560 and triphenylphosphine are added to the reaction kettle according to the weight ratio of 1:1.1:0.1, and reacted for 6 hours under stirring at 130 °C. After the reaction is completed, the phosphorus-containing silane coupling agent KH560P is obtained.

[0143] (2) Preparation of MOF-on-MOF material:

[0144] Terephthalic acid and ferric chloride are added to N,N-dimethylformamide according to the weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution is transferred to an autoclave reaction kettle and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF is collected by filtration. The wet intermediate product Fe-MOF is washed 3 times with methanol, soaked in methanol for 20 hours, and then vacuum dried at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0145] After dispersing Fe-MOF in water, 2-methylimidazole is added to the Fe-MOF aqueous dispersion. After 2-methylimidazole is dissolved, an aqueous solution of zinc nitrate is added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189, and the weight ratio of Fe-MOF to zinc nitrate to be 10:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product is obtained by filtration and separation. The collected product is washed 3 times with water and vacuum dried at 110 °C for 7 hours to obtain the final product MOF-on-MOF material.

[0146] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0147] APP and MOF-on-MOF are mixed at a weight ratio of 20:1 in a high-speed mixer at a rotation speed of 2000 for 10 minutes.

[0148] (4) Preparation of Phosphorus-Containing Silane Coupling Agent KH560P Solution:

[0149] Mix KH560 evenly with an aqueous solution of formic acid, where the weight ratio of water to formic acid is 2:1, and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P is 1.5:1. Obtain the phosphorus-containing silane coupling agent KH560P solution.

[0150] (5) Preparation of Composite Flame Retardant:

[0151] Mix the mixture of APP and MOF-on-MOF with the phosphorus-containing silane coupling agent KH560P solution in a weight ratio of 9:1 for the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent KH560P solution. Mix at 3000 rpm in a high-speed mixer at 70 °C for 10 minutes. Vacuum-dry the mixed material at 100 °C for 3 hours to obtain the composite flame retardant D6.

[0152] To illustrate the influence of the prepared composite flame retardant D6 of Comparative Example 6 on the flame retardancy and mechanical properties of epoxy resin, add the composite flame retardant D6 prepared in this comparative example to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and test the flame retardancy and mechanical properties of the material. The results are shown in Table 7:

[0153] Table 7 Comparison of Flame Retardancy and Mechanical Properties of Flame-Retardant Materials Prepared by Adding Composite Flame Retardant D6 to Epoxy Resin

[0154]

[0155] Comparing Table 1 and Table 7, it can be seen that the oxygen index of the epoxy resin material using the composite flame retardant D6 is less than 30, and it reaches the V-1 level in the UL-94 test. The tensile strength and impact strength of the material are not much different from those of the epoxy resin using the composite flame retardant 1. In Comparative Example 5, the weight ratio of APP to MOF-on-MOF is 20:1, resulting in a decrease in the flame retardancy of the epoxy resin material using the composite flame retardant D5. This shows that the composite flame retardant 1 is better than the composite flame retardant D6 in ensuring the flame retardancy of the epoxy resin material.

[0156] Comparative Example 7

[0157] (1) Preparation of Phosphorus-Containing Silane Coupling Agent (KH560P):

[0158] Under the condition of nitrogen protection, add DOPO-OH, KH560, and triphenylphosphine to the reaction kettle in a weight ratio of 1:1.1:0.1, and react under stirring at 130 °C for 6 hours. After the reaction is completed, obtain the phosphorus-containing silane coupling agent KH560P.

[0159] (2) Preparation of MOF-on-MOF material:

[0160] Add terephthalic acid and ferric chloride in a weight ratio of 166:162 to N,N-dimethylformamide, stir at 30 °C for 60 minutes to form a homogeneous solution. Then transfer the homogeneous solution to an autoclave reactor, heat at 115 °C for 20 hours. After that, filter to collect the wet intermediate product Fe-MOF. Wash the wet intermediate product Fe-MOF 3 times with methanol, soak it in methanol for 20 hours, and then dry it under vacuum at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0161] After dispersing Fe-MOF in water, add 2-methylimidazole to the Fe-MOF aqueous dispersion. After 2-methylimidazole dissolves, add an aqueous solution of zinc nitrate to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 10:1. After stirring and reacting for 6 hours, filter and separate to obtain the wet MOF-on-MOF product. Wash the collected product 3 times with water and dry it under vacuum at 110 °C for 7 hours to obtain the final product MOF-on-MOF material.

[0162] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0163] Mix APP and MOF-on-MOF in a weight ratio of 9:1 in a high-speed mixer at a rotation speed of 2000 for 10 minutes.

[0164] (4) Preparation of the solution of phosphorus-containing silane coupling agent KH560P:

[0165] Mix KH560 evenly with an aqueous solution of formic acid, where the weight ratio of water to formic acid is 2:1, and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P is 1.5:1. Obtain the solution of the phosphorus-containing silane coupling agent KH560P.

[0166] (5) Preparation of the composite flame retardant:

[0167] Mix the mixture of APP and MOF-on-MOF with the solution of the phosphorus-containing silane coupling agent KH560P in a weight ratio of 4:1. Mix at a rotation speed of 3000 in a high-speed mixer at 70 °C for 10 minutes. Dry the mixed material under vacuum at 100 °C for 3 hours to obtain the composite flame retardant 1.

[0168] To illustrate the effects of the composite flame retardant D7 prepared in Comparative Example 7 on the flame retardancy and mechanical properties of epoxy resin, the composite flame retardant D7 prepared in this comparative example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare a flame retardant epoxy resin, and the flame retardancy and mechanical properties of the material were tested. The results are shown in Table 8:

[0169] Table 8 Comparison of the flame retardancy and mechanical properties of the flame retardant materials prepared by adding the composite flame retardant D7 to epoxy resin

[0170]

[0171] Comparing Table 1 and Table 8, it can be seen that the oxygen index of the epoxy resin material using the composite flame retardant D7 is less than 28, and it reaches the V-1 level in the UL-94 test. The tensile strength and impact strength of the material are not much different from those of the epoxy resin using the composite flame retardant 1. In Comparative Example 7, the weight ratio of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent KH560P solution is 4:1, resulting in a decrease in the flame retardancy of the epoxy resin material using the composite flame retardant D7. This shows that the composite flame retardant 1 is better than the composite flame retardant D7 in ensuring the flame retardancy of the epoxy resin material.

[0172] Comparative Example 8

[0173] (1) Preparation of phosphorus-containing silane coupling agent (KH560P):

[0174] Under the condition of nitrogen protection, DOPO-OH, KH560 and triphenylphosphine were added to the reaction kettle according to the weight ratio of 1:1.1:0.1, and reacted for 6 hours under stirring at 130 °C. After the reaction was completed, the phosphorus-containing silane coupling agent KH560P was obtained.

[0175] (2) Preparation of MOF-on-MOF material:

[0176] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide according to the weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reaction kettle and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 20 hours, and then vacuum dried at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0177] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After the 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 10:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and vacuum dried at 110 °C for 7 hours to obtain the final product, the MOF-on-MOF material.

[0178] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0179] APP and MOF-on-MOF were mixed at a weight ratio of APP to MOF-on-MOF of 9:1 in a high-speed mixer at a rotation speed of 2000 for 10 minutes.

[0180] (4) Preparation of the phosphorus-containing silane coupling agent KH560P solution:

[0181] KH560 was uniformly mixed with an aqueous solution of formic acid, where the weight ratio of water to formic acid was 2:1 and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P was 1.5:1. The phosphorus-containing silane coupling agent KH560P solution was obtained.

[0182] (5) Preparation of the composite flame retardant:

[0183] The mixture of APP and MOF-on-MOF and the phosphorus-containing silane coupling agent KH560P solution were mixed at a weight ratio of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent KH560P solution of 12:1. They were mixed at a rotation speed of 3000 in a high-speed mixer at 70 °C for 10 minutes. The mixed material was vacuum dried at 100 °C for 3 hours to obtain the composite flame retardant 1.

[0184] To illustrate the influence of the prepared composite flame retardant D8 of Comparative Example 8 on the flame retardancy and mechanical properties of epoxy resin, the composite flame retardant D8 prepared in this comparative example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and the flame retardancy and mechanical properties of the material were tested. The results are shown in Table 9:

[0185] Table 9 Comparison of the flame retardancy and mechanical properties of the flame-retardant material prepared by adding the composite flame retardant D8 to epoxy resin

[0186]

[0187] Comparing Table 1 and Table 9, it can be seen that the oxygen index of the epoxy resin material using the composite flame retardant D8 is less than 28, and it reaches the V-1 level in the UL-94 test. The tensile strength and impact strength of the material are also reduced compared to the epoxy resin using the composite flame retardant 1. In Comparative Example 8, the weight ratio of the mixture of APP and MOF-on-MOF to the phosphorous-containing silane coupling agent KH560P solution is 12:1, resulting in a decrease in the flame retardancy and mechanical properties of the epoxy resin material using the composite flame retardant D8. This shows that the composite flame retardant 1 is better than the composite flame retardant D8 in ensuring the flame retardancy and mechanical properties of the epoxy resin material.

[0188] Example 2

[0189] (1) Preparation of phosphorous-containing silane coupling agent (KH560P):

[0190] Under the protection of nitrogen, DOPO-OH, KH560 and triphenylphosphine were added to the reaction kettle according to the weight ratio of 1:1:0.02, and reacted under stirring at 140 °C for 15 hours. After the reaction was completed, the phosphorous-containing silane coupling agent KH560P was obtained.

[0191] (2) Preparation of MOF-on-MOF material:

[0192] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide according to the weight ratio of 166:162, and stirred at 50 °C for 30 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reaction kettle and heated at 110 °C for 24 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 12 hours, and then vacuum dried at 120 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0193] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189, and the weight ratio of Fe-MOF to zinc nitrate to be 6:1. After stirring and reacting for 4 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and vacuum dried at 120 °C for 6 hours to obtain the final product MOF-on-MOF material.

[0194] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0195] Mix APP and MOF-on-MOF at a weight ratio of APP to MOF-on-MOF of 8:1 in a high-speed mixer at a speed of 3000 for 5 minutes.

[0196] (4) Preparation of phosphorous-containing silane coupling agent KH560P solution:

[0197] Mix KH560P evenly with an aqueous solution of acetic acid, where the weight ratio of water to acetic acid is 3:1, and the weight ratio of the aqueous solution of acetic acid to the phosphorous-containing silane coupling agent KH560P is 2:1. Obtain the phosphorous-containing silane coupling agent KH560P solution.

[0198] (5) Preparation of composite flame retardant:

[0199] Mix the mixture of APP and MOF-on-MOF with the phosphorous-containing silane coupling agent KH560P solution at a weight ratio of the mixture of APP and MOF-on-MOF to the phosphorous-containing silane coupling agent KH560P solution of 5:1 in a high-speed mixer at a speed of 3000 at 30°C for 30 minutes. Dry the mixed material in a vacuum at 100°C for 3 hours to obtain composite flame retardant 2.

[0200] To illustrate the influence of the composite flame retardant 2 prepared in Example 2 on the flame retardancy and mechanical properties of epoxy resin, add the composite flame retardant 2 prepared in this example at an addition ratio of 7% by weight of the epoxy resin to E51 / DDM to prepare flame-retardant epoxy resin, and test the flame retardancy and mechanical properties of the material. The results are shown in Table 10:

[0201] Table 10 Comparison of the flame retardancy and mechanical properties of the flame-retardant material prepared by adding composite flame retardant 2 to epoxy resin

[0202]

[0203] Comparing Table 1 and Table 10, it can be seen that the oxygen index of the epoxy resin material using composite flame retardant 2 is greater than 30, and it reaches the V-0 level in the UL-94 test. The tensile strength and impact strength of the material are significantly improved compared to the epoxy resin using APP. This shows that composite flame retardant 2 exhibits better performance than APP in improving the flame retardancy and mechanical properties of epoxy resin materials.

[0204] Example 3

[0205] (1) Preparation of phosphorous-containing silane coupling agent (KH560P):

[0206] Under the protection of nitrogen, add DOPO-OH, KH560, and triphenylphosphine to the reaction kettle at a weight ratio of 1:1:0.2, and react under stirring conditions at 60°C for 15 hours. After the reaction is completed, obtain the phosphorous-containing silane coupling agent KH560P.

[0207] (2) Preparation of MOF-on-MOF material:

[0208] Add terephthalic acid and ferric chloride in a weight ratio of 166:162 to N,N-dimethylformamide, stir at 30 °C for 60 minutes to form a homogeneous solution. Then transfer the homogeneous solution to an autoclave reactor, heat at 120 °C for 12 hours. After that, filter to collect the wet intermediate product Fe-MOF. Wash the wet intermediate product Fe-MOF 3 times with methanol, soak it in methanol for 24 hours, and then dry it under vacuum at 80 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0209] After dispersing Fe-MOF in water, add 2-methylimidazole to the Fe-MOF aqueous dispersion. After 2-methylimidazole dissolves, add an aqueous solution of zinc nitrate to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 13:1. After stirring and reacting for 8 hours, filter and separate to obtain the wet MOF-on-MOF product. Wash the collected product 3 times with water and dry it under vacuum at 100 °C for 8 hours to obtain the final product MOF-on-MOF material.

[0210] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0211] Mix APP and MOF-on-MOF in a weight ratio of APP to MOF-on-MOF of 19:1 in a high-speed mixer at a rotation speed of 1000 for 10 minutes.

[0212] (4) Preparation of the phosphorus-containing silane coupling agent KH560P solution:

[0213] Mix KH560P evenly with an aqueous solution of formic acid, where the weight ratio of water to formic acid is 1:1 and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P is 1:1. Obtain the phosphorus-containing silane coupling agent KH560P solution.

[0214] (5) Preparation of the composite flame retardant:

[0215] Mix the mixture of APP and MOF-on-MOF with the phosphorus-containing silane coupling agent KH560P solution in a weight ratio of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent KH560P solution of 10:1 in a high-speed mixer at a rotation speed of 1000 at 70 °C for 10 minutes. Dry the mixed material under vacuum at 80 °C for 6 hours to obtain the composite flame retardant 3.

[0216] To illustrate the influence of the composite flame retardant 3 prepared in Example 3 on the flame retardancy and mechanical properties of epoxy resin, the composite flame retardant 3 prepared in this example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and the flame retardancy and mechanical properties of the material were tested. The results are shown in Table 11:

[0217] Table 11 Comparison of the flame retardancy and mechanical properties of the flame-retardant material prepared by adding composite flame retardant 3 to epoxy resin

[0218]

[0219] It can be seen from a comparison of Table 1 and Table 11 that the oxygen index of the epoxy resin material using composite flame retardant 3 is 29.6, and it reaches the V-0 level in the UL-94 test. The tensile strength and impact strength of the material are significantly improved compared with the epoxy resin using APP. This shows that composite flame retardant 3 exhibits better performance than APP in improving the flame retardancy and mechanical properties of epoxy resin materials.

[0220] Example 4

[0221] (1) Preparation of phosphorus-containing silane coupling agent (KH560P):

[0222] Under the protection of nitrogen, DOPO-OH, KH560 and triphenylphosphine were added to the reaction kettle in a weight ratio of 1:1.2:0.2, and reacted under stirring at 60 °C for 15 hours. After the reaction was completed, the phosphorus-containing silane coupling agent KH560P was obtained.

[0223] (2) Preparation of MOF-on-MOF material:

[0224] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide in a weight ratio of 166:162, and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reaction kettle and heated at 120 °C for 12 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol, soaked in methanol for 24 hours, and then vacuum dried at 80 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0225] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After the 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, and the weight ratio of 2-methylimidazole to zinc nitrate was controlled to be 82:189, and the weight ratio of Fe-MOF to zinc nitrate was 11:1. After stirring and reacting for 8 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and dried in vacuum at 100 °C for 8 hours to obtain the final product, the MOF-on-MOF material.

[0226] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0227] APP and MOF-on-MOF were mixed in a high-speed mixer at a rotation speed of 2000 for 10 minutes according to the weight ratio of APP to MOF-on-MOF being 12:1.

[0228] (4) Preparation of the phosphorus-containing silane coupling agent KH560P solution:

[0229] KH560P was uniformly mixed with an aqueous solution of formic acid, where the weight ratio of water to formic acid was 1:1, and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent KH560P was 1:1. The phosphorus-containing silane coupling agent KH560P solution was obtained.

[0230] (5) Preparation of the composite flame retardant:

[0231] The mixture of APP and MOF-on-MOF and the phosphorus-containing silane coupling agent KH560P solution were mixed at a rotation speed of 2000 in a high-speed mixer at 60 °C for 20 minutes according to the weight ratio of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent KH560P solution being 6:1. The mixed material was dried in vacuum at 80 °C for 6 hours to obtain the composite flame retardant 4.

[0232] To illustrate the influence of the composite flame retardant 4 prepared in Example 4 on the flame retardancy and mechanical properties of epoxy resin, the composite flame retardant 4 prepared in this example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and the flame retardancy and mechanical properties of the material were tested. The results are shown in Table 12:

[0233] Table 12 Comparison of the flame retardancy and mechanical properties of the flame-retardant materials prepared by adding the composite flame retardant 4 to epoxy resin

[0234]

[0235] Comparing Table 1 and Table 11, it can be seen that the epoxy resin material using the composite flame retardant 4 has an oxygen index of 31.1 and reaches the V-0 level in the UL-94 test. The tensile strength and impact strength of the material are significantly improved compared to the epoxy resin using APP. This shows that the composite flame retardant 4 exhibits better performance than APP in improving the flame retardant performance and mechanical properties of epoxy resin materials.

[0236] Example 5

[0237] (1) Preparation of phosphorus-containing silane coupling agent (KH560P):

[0238] Under nitrogen protection, DOPO-OH, KH560, and triphenylphosphine were added to the reaction kettle in a weight ratio of 1:1.1:0.15 and reacted under stirring at 60 °C for 15 hours. After the reaction was completed, the phosphorus-containing silane coupling agent KH560P was obtained.

[0239] (2) Preparation of MOF-on-MOF material:

[0240] Terephthalic acid and ferric chloride were added to N,N-dimethylformamide in a weight ratio of 166:162 and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reaction kettle and heated at 120 °C for 12 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 24 hours, and then vacuum dried at 80 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0241] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 9:1. After stirring and reacting for 8 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and vacuum dried at 100 °C for 8 hours to obtain the final product MOF-on-MOF material.

[0242] (3) Preparation of a mixture of APP and MOF-on-MOF:

[0243] APP and MOF-on-MOF were mixed in a high-speed mixer at a rotation speed of 3000 for 10 minutes according to the weight ratio of APP to MOF-on-MOF of 11:1.

[0244] (4) Preparation of phosphorus-containing silane coupling agent KH560P solution:

[0245] Mix KH560P evenly with an aqueous solution of acetic acid, where the weight ratio of water to acetic acid is 3:1, and the weight ratio of the aqueous solution of acetic acid to the phosphorus-containing silane coupling agent KH560P is 1:1. A solution of the phosphorus-containing silane coupling agent KH560P is obtained.

[0246] (5) Preparation of the composite flame retardant:

[0247] Mix the mixture of APP and MOF-on-MOF with the solution of the phosphorus-containing silane coupling agent KH560P at a weight ratio of the mixture of APP and MOF-on-MOF to the solution of the phosphorus-containing silane coupling agent KH560P of 8:1 in a high-speed mixer at a rotation speed of 3000 at 60 °C for 20 minutes. Vacuum dry the mixed material at 100 °C for 3 hours to obtain the composite flame retardant 5.

[0248] To illustrate the influence of the composite flame retardant 5 prepared in Example 5 on the flame retardancy and mechanical properties of epoxy resin, add the composite flame retardant 5 prepared in this example at an addition ratio of 7% by weight of the epoxy resin to E51 / DDM to prepare a flame-retardant epoxy resin, and test the flame retardancy and mechanical properties of the material. The results are shown in Table 13:

[0249] Table 13 Comparison of the flame retardancy and mechanical properties of the flame-retardant material prepared by adding the composite flame retardant 5 to epoxy resin

[0250]

[0251] Comparing Table 1 and Table 13, it can be seen that the oxygen index of the epoxy resin material using the composite flame retardant 5 is 30.4, and it reaches the V-0 level in the UL-94 test. The tensile strength and impact strength of the material are significantly improved compared to the epoxy resin using APP. This shows that the composite flame retardant 5 exhibits better performance than APP in improving the flame retardancy and mechanical properties of epoxy resin materials.

[0252] Example 6

[0253] (1) Preparation of the phosphorus-containing silane coupling agent:

[0254] Under the protection of nitrogen, add DOPO-OH, 3-isocyanatopropyltrimethoxysilane and 1,4-dioxane to the reaction kettle at a weight ratio of 1:1.1:10, and react for 6 hours under stirring conditions at 40 °C. After the reaction is completed, a phosphorus-containing silane coupling agent is obtained.

[0255] (2) Preparation of the MOF-on-MOF material:

[0256] Terephthalic acid and iron(III) chloride were added to N,N-dimethylformamide in a weight ratio of 166:162 and stirred at 30 °C for 60 minutes to form a homogeneous solution. Then the homogeneous solution was transferred to an autoclave reactor and heated at 115 °C for 20 hours. After that, the wet intermediate product Fe-MOF was collected by filtration. The wet intermediate product Fe-MOF was washed 3 times with methanol and soaked in methanol for 20 hours, and then dried under vacuum at 100 °C for 12 hours to obtain the intermediate product Fe-MOF.

[0257] After dispersing Fe-MOF in water, 2-methylimidazole was added to the Fe-MOF aqueous dispersion. After 2-methylimidazole was dissolved, an aqueous solution of zinc nitrate was added to the Fe-MOF aqueous dispersion under stirring, controlling the weight ratio of 2-methylimidazole to zinc nitrate to be 82:189 and the weight ratio of Fe-MOF to zinc nitrate to be 10:1. After stirring and reacting for 6 hours, the wet MOF-on-MOF product was obtained by filtration and separation. The collected product was washed 3 times with water and dried under vacuum at 110 °C for 7 hours to obtain the final product MOF-on-MOF material.

[0258] (3) Preparation of the mixture of APP and MOF-on-MOF:

[0259] APP and MOF-on-MOF were mixed in a high-speed mixer at a rotation speed of 2000 for 10 minutes according to the weight ratio of APP to MOF-on-MOF of 9:1.

[0260] (4) Preparation of the phosphorus-containing silane coupling agent solution:

[0261] The phosphorus-containing silane coupling agent prepared in step (1) was mixed evenly with an aqueous solution of formic acid, where the weight ratio of water to formic acid was 2:1 and the weight ratio of the aqueous solution of formic acid to the phosphorus-containing silane coupling agent was 1.5:1. The phosphorus-containing silane coupling agent solution was obtained.

[0262] (5) Preparation of the composite flame retardant:

[0263] The mixture of APP and MOF-on-MOF and the phosphorus-containing silane coupling agent solution were mixed in a high-speed mixer at a rotation speed of 3000 at 70 °C for 10 minutes according to the weight ratio of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent solution of 9:1. The mixed material was dried under vacuum at 100 °C for 3 hours to obtain the composite flame retardant 6.

[0264] To illustrate the effects of the composite flame retardant 6 prepared in Example 6 on the flame retardancy and mechanical properties of epoxy resin, the composite flame retardant 6 prepared in this example was added to E51 / DDM at an addition ratio of 7% by weight of the epoxy resin to prepare flame-retardant epoxy resin, and the flame retardancy and mechanical properties of the material were tested. The results are shown in Table 14 below:

[0265] Table 14 Comparison of the flame retardancy and mechanical properties of the flame-retardant materials prepared by adding composite flame retardant 6 to epoxy resin

[0266]

[0267]

[0268] Comparing Table 1 and Table 14, it can be seen that the oxygen index of the epoxy resin material using composite flame retardant 6 is 30.9, and it reaches the V-0 level in the UL-94 test. The tensile strength and impact strength of the material are significantly improved compared with the epoxy resin using APP. This shows that composite flame retardant 6 exhibits better performance than APP in improving the flame retardancy and mechanical properties of epoxy resin materials.

Claims

1. A preparation method of a composite flame retardant applicable to epoxy resin, characterized in that, Comprising: Step 1: Preparation of a phosphorus-containing silane coupling agent solution Under nitrogen protection, DOPO-OH and a silane coupling agent are added to a reaction kettle for reaction to obtain a phosphorus-containing silane coupling agent. The phosphorus-containing silane coupling agent is mixed evenly with an aqueous solution of an acid to obtain a phosphorus-containing silane coupling agent solution. The silane coupling agent is KH560 or 3-isocyanatopropyltrimethoxysilane; Step 2: Preparation of MOF-on-MOF material 1) Terephthalic acid and ferric chloride are dissolved in a solvent and stirred to obtain a mixed solution, and then the mixed solution is added to a reaction kettle and heated for reaction to obtain an intermediate product, Fe-MOF; 2) After dispersing Fe-MOF in water, 2-methylimidazole is added to the Fe-MOF aqueous dispersion and stirred, and then an aqueous solution of zinc nitrate is added and stirred to obtain a MOF-on-MOF material; Step 3: Preparation of a mixture of APP and MOF-on-MOF APP and MOF-on-MOF are mixed to obtain a mixture of APP and MOF-on-MOF; Step 4: Preparation of a composite flame retardant The mixture of APP and MOF-on-MOF obtained in Step 3 is mixed with the phosphorus-containing silane coupling agent solution obtained in Step 1 and dried to obtain a composite flame retardant; The weight ratio of DOPO-OH to the silane coupling agent in Step 1 is 1:(1 - 1.2); The weight ratio of the intermediate product Fe-MOF to zinc nitrate in Step 2 is (6 - 13):1; The weight ratio of APP to MOF-on-MOF in Step 3 is (8 - 19):1; The weight ratio of the mixture of APP and MOF-on-MOF to the phosphorus-containing silane coupling agent solution in Step 4 is (5 - 10):

1.

2. The preparation method of a composite flame retardant applicable to epoxy resin according to claim 1, characterized in that, The reaction temperature in Step 1 is 25 - 140°C, and the reaction time is 3 - 15 h.

3. The preparation method of a composite flame retardant applicable to epoxy resin according to claim 1, characterized in that, When the silane coupling agent in Step 1 is 3-isocyanatopropyltrimethoxysilane, solvent 1,4-dioxane is added during the reaction process; when the silane coupling agent is KH560, triphenylphosphine is added during the reaction process.

4. The preparation method of a composite flame retardant applicable to epoxy resin according to claim 1, characterized in that, The reaction temperature in 1) of Step 2 is 110°C - 120°C, and the reaction time is 12 - 24 h.

5. The preparation method of a composite flame retardant applicable to epoxy resin according to claim 1, characterized in that, The weight ratio of 2-methylimidazole to zinc nitrate in Step 2 is 82:

189.

6. The preparation method of a composite flame retardant applicable to epoxy resin according to claim 1, characterized in that, The mixing rotation speed in Step 4 is 1000 - 3000 revolutions per minute, the mixing temperature is 30 - 70°C, and the mixing time is 10 - 30 min.

7. A composite flame retardant for epoxy resin obtained by the preparation method according to claim 1.

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