Method for loading layered nickel silicate and flame-retardant epoxy resin with ammonium polyphosphate and application

Abstract

The invention provides a method and application of ammonium polyphosphate loaded layered nickel silicate and flame-retardant epoxy resin, and belongs to the technical field of halogen-free flame-retardant epoxy resin. Comprising the following components in percentage by mass: 75.5%-77.0% of bisphenol A type epoxy resin, 19.5%-20.0% of 4, 4-diaminodiphenylmethane and 3.0%-7.0% of an ammonium polyphosphate loaded nickel silicate compound APP (at) NiPS, the ammonium polyphosphate loaded layered nickel silicate is prepared by loading a certain amount of nickel silicate on the surface of short rod-shaped ammonium polyphosphate; by introducing ammonium polyphosphate loaded layered nickel silicate, the flame retardant property of the epoxy resin composite material is greatly improved, the anti-dripping property of the epoxy resin is improved, and the application range of the epoxy resin is expanded. Meanwhile, the preparation process is simple and suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of halogen-free flame-retardant epoxy resins, and specifically relates to a method and application of ammonium polyphosphate-loaded layered nickel silicate and flame-retardant epoxy resin. Background Art

[0002] Epoxy resin (EP) is a thermosetting polymer with excellent comprehensive performance. It has good mechanical properties, electrical insulation, heat resistance, chemical stability and bonding properties. It is widely used in various fields of the national economy, such as electronics, aerospace, rail transportation, and automobile manufacturing. However, the disadvantage of EP being extremely easy to burn leads to serious fire hazards. When burning, it produces a large amount of toxic and harmful smoke, which poses a great threat to people's life, health and property safety, and significantly limits the wide application of related products in fields with high flame retardant requirements. The epoxy resin flame retardant originally developed is a halogen flame retardant, which has the characteristics of high flame retardant efficiency and low addition amount, but it will release hydrogen halide gas that is harmful to environmental safety and human health during the flame retardant process. In order to replace halogen flame retardants, researchers have developed halogen-free flame retardants, the most common of which is ammonium polyphosphate. However, in order to achieve the ideal flame retardant effect, it is necessary to increase its addition amount (about 30wt%), which will seriously affect the mechanical properties of the composite material. At present, inorganic nanomaterials have become a research hotspot in the field of flame retardancy and are expected to become the mainstream flame retardant in the future.

[0003] Nickel silicate (NiPS) is a two-dimensional inorganic nanomaterial with the characteristics of regular and orderly lamellar structure, high specific surface area, and strong designability of interlayer inorganic / organic functional groups. In recent years, its research focus has been on catalysis, supercapacitors, etc. Studies on its structure and composition have found that it has a layered structure and contains transition metal nickel ions, has a certain effect of lamellar barrier and catalytic carbonization, can achieve self-extinguishing, and has inherent advantages in polymer flame retardancy. According to relevant reports, when the addition amount of NiPS is in the range of 0-7wt%, it can improve the limiting oxygen index (LOI) value of epoxy resin to a certain extent, and it is found that it can effectively improve the EP dripping phenomenon in the vertical burning test (UL-94), but the results are all ungraded. In order to further improve the flame retardant properties of NiPS, it will be an effective and feasible way to combine the traditional flame retardant ammonium polyphosphate (APP) with NiPS by means of structural design thinking. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a method and application of ammonium polyphosphate loaded layered nickel silicate and flame retardant epoxy resin. By constructing ammonium polyphosphate loaded nickel silicate flame retardant epoxy resin, high-efficiency flame retardancy and anti-dripping properties are guaranteed at a relatively low addition amount, thereby expanding the application of epoxy resin in the flame retardant field.

[0005] In order to achieve the above technical purpose, the present invention discloses a method for preparing ammonium polyphosphate-loaded layered nickel silicate, characterized in that the steps are as follows:

[0006] (1) Weigh 150 ml of anhydrous ethanol and 50 ml of deionized water respectively, add them into a container, stir and mix evenly, and heat them to 45° C. while stirring; then add 50 g of ammonium polyphosphate APP, 1 g of silane coupling agent KH560 and 20 ml of ammonia water respectively, stir for 10 min, then add 12.5 g of tetraethyl orthosilicate TEOS dropwise, keep the temperature at 45° C. for 4 h, and after the reaction is completed, cool to room temperature, filter and wash the reaction product in turn through 2500 mesh, and then dry it at 80° C. to constant weight. The obtained white powder is recorded as microencapsulated ammonium polyphosphate MAPP.

[0007] (2) Weigh 1 g of microencapsulated ammonium polyphosphate (MAPP), 2.03 g of nickel nitrate hexahydrate and 1.26 g of urea respectively, and add them into a three-necked flask in order. Then, measure 50 mL of a dilute nitric acid solution with a concentration of 0.02 mol / L, add it into the three-necked flask and stir continuously until the solute is completely dissolved to form a mixed solution. After the mixed solution is heated to 90°C in an oil bath, the reaction time range is 50 min to 50 h. After the reaction is completed, transfer the container from the oil bath. At this time, the three-necked flask contains a green suspension. After the green suspension is cooled for 10 h, it is centrifuged, washed with deionized water and dried in an oven at 70°C for 24 h. The resulting powder is ammonium polyphosphate-loaded layered nickel silicate APP@NiPS.

[0008] Furthermore, the volume ratio of anhydrous ethanol, deionized water and dilute nitric acid is 3:1:1.

[0009] An ammonium polyphosphate-supported layered nickel silicate.

[0010] A method for preparing a flame-retardant epoxy resin based on ammonium polyphosphate-loaded layered nickel silicate: first, ammonium polyphosphate-loaded layered nickel silicate APP@NiPS is prepared, first, bisphenol A epoxy resin is preheated and vigorously stirred, then the ammonium polyphosphate-loaded layered nickel silicate is added to the bisphenol A epoxy resin and stirred continuously until fully mixed, and then a curing agent 4,4-diaminodiphenylmethane is added and stirred continuously; finally, a flame-retardant epoxy resin based on ammonium polyphosphate-loaded layered nickel silicate with good flame retardant effect is obtained.

[0011] The specific steps are as follows:

[0012] Weigh 0.25 g to 1.32 g of ammonium polyphosphate-supported layered nickel silicate powder, dissolve it in 50 mL of acetone solution, and perform ultrasonic dispersion treatment to make the ammonium polyphosphate-supported layered nickel silicate evenly dissolved and dispersed in the acetone solution to obtain a mixed solution of ammonium phosphate-supported layered nickel silicate and acetone, which is a green suspension;

[0013] The green suspension was added dropwise into a bisphenol A epoxy resin preheated to 75° C. in an oil bath using a dropper, and then refluxed under condensation for 20 minutes with strong stirring at a speed of 3000 r / min to fully mix the green suspension and the bisphenol A epoxy resin, thereby obtaining a prepolymer of ammonium polyphosphate-loaded layered nickel silicate and epoxy resin monomer;

[0014] The molten curing agent 4,4-diaminodiphenylmethane was added to the epoxy system, and the mixture was stirred vigorously at a speed of 3000 r / min until it was completely mixed. Then, the mixture was poured into a preheated silicone rubber mold. After vacuum degassing, the mixture was cured at 100°C and 150°C for 2 hours, respectively, to obtain a flame-retardant epoxy resin based on ammonium polyphosphate-loaded layered nickel silicate.

[0015] A flame retardant epoxy resin based on ammonium polyphosphate-loaded layered nickel silicate comprises a mixture of bisphenol A epoxy resin, 4,4-diaminodiphenylmethane and ammonium polyphosphate-loaded layered nickel silicate, wherein the mass concentration of the bisphenol A epoxy resin is 75.5%-77.0%, the mass concentration of 4,4-diaminodiphenylmethane is 19.5%-20.0% and the mass concentration of the ammonium polyphosphate-loaded layered nickel silicate is 3.0%-7.0%.

[0016] An application of a flame retardant epoxy resin based on ammonium polyphosphate-loaded layered nickel silicate, wherein a prepolymer of a moderately uniform ammonium polyphosphate-loaded layered nickel silicate and an epoxy resin monomer is placed in a specific required mold, and after high-temperature curing, a flame retardant epoxy resin product in the shape of the mold is obtained.

[0017] Beneficial effect: The flame-retardant epoxy resin based on ammonium polyphosphate loaded nickel silicate prepared by the present invention improves the flame retardancy and anti-melting droplet performance of the epoxy resin. When 5.0wt% of ammonium polyphosphate loaded layered nickel silicate is added, its oxygen index reaches 26.4%. When the vertical combustion test is performed, it can be self-extinguished after 18s of the first ignition, and it will be self-extinguished immediately after 9s of the second ignition source leaving. The test result is V-1 grade, indicating that the introduction of ammonium polyphosphate loaded nickel silicate overcomes the problem of flammability and serious melting droplet of epoxy resin, while when 5.0% of pure NiPS is introduced, its oxygen index is only 25.8%, and the vertical combustion result is no grade.

[0018] The ammonium polyphosphate loaded layered nickel silicate used in the present invention can greatly improve the limiting oxygen index of epoxy resin, can also significantly improve the vertical combustion performance, has a significant effect of inhibiting molten droplets, and can better protect the epoxy resin matrix. At the same time, the present invention is simple to operate and suitable for mass production.

[0019] After the ammonium polyphosphate-loaded nickel silicate flame-retardant epoxy resin of the present application is initially ignited, the ammonium polyphosphate decomposes to generate poly / polyphosphoric acid when heated, which promotes the dehydration, carbonization and expansion of the organic surface to form a protective carbon layer; the lamellar structure of the nickel silicate slows down the escape of combustible volatile products produced by the thermal decomposition of the epoxy resin matrix; at the same time, the transition metal nickel element in the nickel silicate has a catalytic carbonization effect, promoting the formation of a protective carbon layer on the surface of the material; in summary, the introduction of ammonium polyphosphate-loaded layered nickel silicate can slow down the escape of combustible volatile products of the epoxy matrix, and at the same time promote the generation of a protective carbon layer, which plays a role in isolating external heat and oxygen, and ultimately achieves a flame retardant effect. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with a number of embodiments:

[0021] The invention discloses a flame retardant epoxy resin based on ammonium polyphosphate loaded nickel silicate, comprising bisphenol A epoxy resin, 4,4-diaminodiphenylmethane and ammonium polyphosphate loaded layered nickel silicate, wherein the mass concentration of the bisphenol A epoxy resin is 75.5%-77.0%, the mass concentration of 4,4-diaminodiphenylmethane is 19.5%-20.0%, and the mass concentration of the ammonium polyphosphate loaded nickel silicate is 3.0%-5.0%. The mass ratio of the bisphenol A epoxy resin to the 4,4-diaminodiphenylmethane is 100:25.8.

[0022] A method for preparing a flame-retardant epoxy resin based on ammonium polyphosphate loaded nickel silicate comprises the following steps:

[0023] (1) Weigh 150 ml of ethanol and 50 ml of deionized water respectively, add them into a flask at once and stir mechanically to promote uniform mixing, and heat them to 45° C. while stirring; then add 50 g of ammonium polyphosphate APP, 1 g of silane coupling agent KH560 and 20 ml of ammonia water respectively, stir for 10 min, then add 12.5 g of TEOS dropwise, keep the temperature for 4 h, and after the reaction is completed, cool to room temperature, filter, wash, and then dry at 80° C. to constant weight. The obtained white powder is recorded as microencapsulated ammonium polyphosphate MAPP.

[0024] (2) Weigh 1g of MAPP, 2.03g of nickel nitrate hexahydrate and 1.26g of urea respectively, and add them to a 150mL three-necked flask in order. Then, measure about 50mL of a dilute nitric acid solution with a concentration of 0.02mol / L, add it to the three-necked flask and stir continuously until the solute is completely dissolved. After heating the above solution to 90°C, the reaction time range is 50min to 50h. After the reaction is completed, the flask is transferred out of the oil bath, and after the green suspension is cooled for 10h, it is centrifuged, washed with deionized water and dried in an oven at 70°C for 24h. The resulting powder is APP@NiPS.

[0025] (3) Weigh 0.25g-1.32g of ammonium polyphosphate-loaded layered nickel silicate powder, dissolve it in 50mL of acetone solution, and perform ultrasonic dispersion treatment for 30-60min to obtain a green suspension. Then, add the suspension dropwise into the epoxy resin prepolymer preheated at 70°C with a dropper, reflux with condensation, and stir vigorously for 4h to fully mix the two. Add the curing agent 4,4-diaminodiphenylmethane melted at 100°C to the epoxy system, continue to stir vigorously and pour it into the preheated silicone rubber mold. After vacuum degassing, cure it at 100°C and 150°C for 2h, respectively, to finally obtain a flame-retardant epoxy resin based on ammonium polyphosphate-loaded layered nickel silicate.

[0026] Example 1

[0027] Weigh 150 ml of ethanol and 50 ml of deionized water respectively, add them into the flask at once and stir mechanically to promote uniform mixing, and heat to 45°C while stirring; then add 50 g of APP, 1 g of silane coupling agent KH560 and 20 ml of ammonia water respectively, stir for 10 minutes, then add 12.5 g of TEOS dropwise, keep the temperature for reaction for 4 hours, after the reaction is completed, cool to room temperature, filter, wash, and then dry at 80°C to constant weight. The obtained white powder is recorded as MAPP.

[0028] Weigh 1g of MAPP, 2.03g of nickel nitrate hexahydrate and 1.26g of urea respectively, and add them to a 150mL three-necked flask in order. Then measure about 50mL of a dilute nitric acid solution with a concentration of 0.02mol / L, add it to the three-necked flask and stir continuously until the solute is completely dissolved. After heating the above solution to 90°C, the reaction time range is 50min to 50h. After the reaction is completed, transfer the flask from the oil bath, wait for the green suspension to cool for 10h, centrifuge, wash with deionized water and dry in an oven at 70°C for 24h, and the resulting powder is MAPP@NiPS.

[0029] 0.25g of MAPP@NiPS powder was weighed and ultrasonically dispersed with 50mL of acetone for 1h, then added dropwise to 20g of epoxy resin preheated at 70℃, and stirred vigorously for 4h to fully mix the two; 5.16g of molten curing agent was added to the mixed system, and after continued strong stirring for 20 minutes, it was poured into the preheated silicone mold, vacuum degassed, cured at 100℃ for 2h, and then cured at 150℃ for 2h. In terms of weight percentage, the addition amount of MAPP@NiPS is 1.0%.

[0030] According to the standard ASTM D 2863-2017a, a standard specimen of 127×6.5×3.2 mm was tested for oxygen index (LOI) on a TTech-GBT2406 oxygen index instrument. The results showed that the introduction of 1.0% MAPP@NiPS can increase the limiting oxygen index value of epoxy resin to 23.1%.

[0031] According to ASTM D 3801-2010, a standard sample of 127×12.7×3.2 mm was subjected to a vertical combustion test (UL-94) on a CZF-2 horizontal vertical combustion tester. The first ignition self-extinguished after 91 seconds, and the second ignition self-extinguished after 14 seconds away from the ignition source. There was no droplet phenomenon in both combustion processes.

[0032] Example 2

[0033] MAPP@NiPS was prepared according to the method in Example 1.

[0034] 0.78g of MAPP@NiPS powder was weighed and ultrasonically dispersed with 50mL of acetone for 1h, then added dropwise to 20g of epoxy resin preheated at 70℃, and stirred vigorously for 4h to fully mix the two; 5.16g of molten curing agent was added to the mixed system, and after continued strong stirring for 20 minutes, it was poured into the preheated silicone mold, vacuum degassed, cured at 100℃ for 2h, and then cured at 150℃ for 2h. In terms of weight percentage, the addition amount of MAPP@NiPS is 3.0%.

[0035] The limiting oxygen index test shows that the introduction of 3.0% MAPP@NiPS can increase the limiting oxygen index value of epoxy resin to 24.2%.

[0036] The results of the vertical combustion test showed that the first ignition could self-extinguish 42 seconds after ignition, and the second ignition source could self-extinguish 11 seconds after leaving. There was no droplet phenomenon in both combustion processes.

[0037] Example 3

[0038] MAPP@NiPS was prepared according to the method in Example 1.

[0039] 1.32g of MAPP@NiPS powder was weighed and ultrasonically dispersed with 50mL of acetone for 1h, then added dropwise to 20g of epoxy resin preheated at 70°C, and stirred vigorously for 4h to fully mix the two; 5.16g of molten curing agent was added to the mixed system, and after continued strong stirring for 20 minutes, it was poured into the preheated silicone mold, vacuum degassed, cured at 100°C for 2h, and then cured at 150°C for 2h. In terms of weight percentage, the addition amount of MAPP@NiPS is 5.0%.

[0040] The limiting oxygen index test shows that the introduction of 5.0% MAPP@NiPS can increase the limiting oxygen index value of epoxy resin to 26.4%.

[0041] The results of the vertical combustion test showed that the first ignition could self-extinguish 18 seconds after ignition, and the second ignition source could self-extinguish 9 seconds after it was removed. There was no droplet phenomenon in both combustion processes.

[0042] Comparative Example 1

[0043] After fully preheating 20g of epoxy resin at 70°C, add 5.16g of molten curing agent, stir vigorously for 40 minutes, pour into the preheated silicone mold, degas under vacuum for 20 minutes, and cure at 100°C and 150°C for 2h respectively to obtain a light yellow transparent epoxy resin.

[0044] The limiting oxygen index test showed that the LOI value of pure epoxy resin was 23.8%.

[0045] The results of the vertical combustion test showed that the pure epoxy resin burned out directly after the first ignition, accompanied by severe dripping.

[0046] Comparative Example 2

[0047] 1.32g of MAPP powder was weighed and ultrasonically dispersed with 20mL of acetone for 1h, then added dropwise to 20g of epoxy resin preheated at 70°C, and stirred vigorously for 4h to fully mix the two; 5.16g of molten curing agent was added to the mixed system, and after continuing to stir vigorously for 20 minutes, it was poured into the preheated silicone mold, and after vacuum degassing, it was cured at 100°C for 2h, and then cured at 150°C for 2h. In terms of weight percentage, the addition amount of MAPP is 5.0%.

[0048] The limiting oxygen index test shows that the introduction of 5.0% MAPP can increase the limiting oxygen index of epoxy resin to 25.8%.

[0049] The results of the vertical combustion test showed that the flame extinguished itself after burning for 62 seconds after the first ignition, and extinguished itself immediately after the second ignition source left. There was no droplet phenomenon in both combustion processes.

[0050] Comparative Example 3

[0051] Weigh 0.38g of silicon dioxide with a specific surface area of ​​280g / m2, 2.03g of nickel nitrate hexahydrate and 1.26g of urea, and add them to a 150mL three-necked flask in order, then measure about 50mL of a dilute nitric acid solution with a concentration of 0.02mol / L, add it to the three-necked flask and stir continuously until the solute is completely dissolved. After heating the above solution to 90°C, the reaction time range is 50min to 50h. After the reaction is completed, transfer the flask from the oil bath, wait for the green suspension to cool for 10h, centrifuge, wash with deionized water and dry in an oven at 70°C for 24h, and the resulting light green powder is NiPS.

[0052] 1.32g of NiPS was weighed and ultrasonically dispersed with 20mL of acetone for 1h, then added dropwise to 20g of epoxy resin preheated at 70°C, and stirred vigorously for 4h to fully mix the two; 5.16g of molten curing agent was added to the mixed system, and after continued strong stirring for 20 minutes, it was poured into the preheated silicone mold, vacuum degassed, cured at 100°C for 2h, and then cured at 150°C for 2h. In terms of weight percentage, the addition amount of NiPS is 5.0%.

[0053] The LOI test showed that the introduction of 5.0% NiPS increased the LOI value of the epoxy resin to 25.8%.

[0054] The result of the vertical combustion test showed that the flame retardant burned for 160 seconds after the first ignition before it could self-extinguish, and severe dripping occurred during the combustion process.

[0055] Analysis and Conclusion

[0056] From Examples 1-3, the following conclusions can be drawn: When MAPP@NiPS is introduced into the epoxy resin matrix, the flame retardancy of the prepared epoxy resin composite material is gradually improved, and the molten drop phenomenon is significantly improved. It can be seen from Example 3 and Comparative Examples 2-3 that when 5% of MAPP and NiPS are added, the flame retardancy of the epoxy resin is improved to a certain extent, but the improvement is small, and the vertical burning test result is no grade. At the same time, the introduction of NiPS cannot solve the molten drop problem during the combustion of the epoxy resin, that is, it cannot effectively prevent the spread of the flame. At the same addition amount, the epoxy resin containing MAPP@NiPS exhibits better flame retardancy, indicating that the introduction of MAPP@NiPS can significantly improve the flame retardancy of the epoxy resin. It can be seen from Examples 1, 2, 3 and Comparative Example 1 that pure epoxy resin is easy to burn and is accompanied by a large amount of molten droplets. As the content of MAPP@NiPS increases, the flame retardancy of the epoxy resin gradually increases and the molten drop phenomenon is fundamentally changed. When the addition amount reaches 5%, the vertical burning test result is V-1 grade, which is the highest grade.

[0057] Therefore, it is concluded that when the addition amount of MAPP@NiPS is 5%, the flame retardant performance of epoxy resin is the best, and the limiting oxygen index can reach 26.4%; in the vertical combustion test, it can self-extinguish after 18s of the first ignition, and it will self-extinguish immediately after 9s of the second ignition source leaving. In addition, very little smoke is generated during the combustion process, and there is no droplet phenomenon. In summary, MAPP@NiPS can successfully give epoxy resin excellent flame retardant effect.

[0058] The invention discloses an ammonium polyphosphate-loaded layered nickel silicate flame-retardant epoxy resin and a preparation method thereof. The invention utilizes the excellent flame-retardant effect of phosphorus, the catalytic carbonization effect of nickel and the high thermal stability of silicon, and uses only one additive without compounding with other flame retardants. When MAPP@NiPS accounts for 5% of the total mass fraction of the epoxy system, the epoxy resin can be endowed with an excellent flame-retardant effect, thereby overcoming the disadvantages of low flame-retardant efficiency, large addition amount and high cost of existing phosphorus-nitrogen flame retardants, and is convenient to produce and use.

Claims

1. A method for preparing ammonium polyphosphate-supported layered nickel silicate, characterized in that: Here are the steps: (1) Weigh 150 ml of anhydrous ethanol and 50 ml of deionized water respectively, add them into a container, stir and mix evenly, and heat them to 45° C. while stirring; then add 50 g of ammonium polyphosphate APP, 1 g of silane coupling agent KH560 and 20 ml of ammonia water respectively, stir for 10 min, then add 12.5 g of tetraethyl orthosilicate TEOS dropwise, keep the temperature at 45° C. for 4 h, and after the reaction is completed, cool to room temperature, filter and wash the reaction product in turn through 2500 mesh, and then dry it at 80° C. to constant weight. The obtained white powder is recorded as microencapsulated ammonium polyphosphate MAPP. (2) Weigh 1 g of microencapsulated ammonium polyphosphate (MAPP), 2.03 g of nickel nitrate hexahydrate and 1.26 g of urea respectively, and add them into a three-necked flask in order. Then, measure 50 mL of a dilute nitric acid solution with a concentration of 0.02 mol / L, add it into the three-necked flask and stir continuously until the solute is completely dissolved to form a mixed solution. After the mixed solution is heated to 90°C in an oil bath, the reaction time range is 50 min to 50 h. After the reaction is completed, transfer the container from the oil bath. At this time, the three-necked flask contains a green suspension. After the green suspension is cooled for 10 h, it is centrifuged, washed with deionized water and dried in an oven at 70°C for 24 h. The resulting powder is ammonium polyphosphate-loaded layered nickel silicate APP@NiPS.

2. The method for preparing ammonium polyphosphate-supported layered nickel silicate according to claim 1, characterized in that: The volume ratio of anhydrous ethanol, deionized water and dilute nitric acid is 3:1:

1.

3. An ammonium polyphosphate-loaded layered nickel silicate prepared using the method of claim 1.

4. A method for preparing a flame-retardant epoxy resin based on ammonium polyphosphate-loaded layered nickel silicate using the ammonium polyphosphate-loaded layered nickel silicate according to claim 3, characterized in that: First, ammonium polyphosphate loaded layered nickel silicate APP@NiPS was prepared. First, bisphenol A epoxy resin was preheated and vigorously stirred. Then, ammonium polyphosphate loaded layered nickel silicate was added to the bisphenol A epoxy resin and stirred continuously until fully mixed. Then, curing agent 4,4-diaminodiphenylmethane was added and stirred continuously. Finally, a flame-retardant epoxy resin based on ammonium polyphosphate loaded layered nickel silicate with good flame retardant effect was obtained.

5. The method for preparing a flame-retardant epoxy resin based on ammonium polyphosphate-supported layered nickel silicate according to claim 1, characterized in that: The specific steps are as follows: Weigh 0.25 g to 1.32 g of ammonium polyphosphate-supported layered nickel silicate powder, dissolve it in 50 mL of acetone solution, and perform ultrasonic dispersion treatment to make the ammonium polyphosphate-supported layered nickel silicate evenly dissolved and dispersed in the acetone solution to obtain a mixed solution of ammonium phosphate-supported layered nickel silicate and acetone, which is a green suspension; The green suspension was added dropwise into a bisphenol A epoxy resin preheated to 75° C. in an oil bath using a dropper, and then refluxed under condensation for 20 minutes with strong stirring at a speed of 3000 r / min to fully mix the green suspension and the bisphenol A epoxy resin, thereby obtaining a prepolymer of ammonium polyphosphate-loaded layered nickel silicate and epoxy resin monomer; The molten curing agent 4,4-diaminodiphenylmethane was added to the prepolymer of ammonium polyphosphate-loaded layered nickel silicate and epoxy resin monomer, and the mixture was vigorously stirred at a speed of 3000 r / min until completely mixed. Then, the mixture was poured into a preheated silicone rubber mold. After vacuum degassing, the mixture was cured at 100°C and 150°C for 2 hours, respectively, to obtain a flame-retardant epoxy resin based on ammonium polyphosphate-loaded layered nickel silicate.

6. A flame-retardant epoxy resin based on ammonium polyphosphate-supported layered nickel silicate prepared according to the method of claim 4 or 5, characterized in that: The invention comprises bisphenol A epoxy resin, 4,4-diaminodiphenylmethane and ammonium polyphosphate loaded layered nickel silicate, wherein the mass concentration of the bisphenol A epoxy resin is 75.5%-77.0%, the mass concentration of the 4,4-diaminodiphenylmethane is 19.5%-20.0% and the mass concentration of the ammonium polyphosphate loaded layered nickel silicate is 3.0%-7.0%.

7. An application of a flame retardant epoxy resin based on ammonium polyphosphate loaded layered nickel silicate, characterized in that: The prepolymer of mild and uniform ammonium polyphosphate loaded layered nickel silicate and epoxy resin monomer is placed in a specific required mold, and after high-temperature curing, a flame-retardant epoxy resin product in the shape of the mold is obtained.