Low-smoke halogen-free flame-retardant polypropylene material as well as preparation method and application thereof in automobile wires and cables

Abstract

The invention relates to the technical field of high-performance polypropylene, and discloses a low-smoke halogen-free flame-retardant polypropylene material as well as a preparation method and application thereof in automobile wires and cables. The low-smoke halogen-free flame-retardant polypropylene material disclosed by the invention is prepared from the following components in parts by weight: 70 to 80 parts of polypropylene resin, 20 to 30 parts of microencapsulated ammonium polyphosphate and 0.15 to 0.35 part of antioxidant. The capsule wall of the microencapsulated ammonium polyphosphate contains polypropylene molecular chains and has good dispersity in polypropylene resin, the capsule wall of the microcapsule contains a large number of nitrogen-containing heterocyclic rings and can be used as a nitrogen flame retardant to play a synergistic flame-retardant role with ammonium polyphosphate, the flame-retardant and smoke-suppression performance of polypropylene is improved, and the flame-retardant and smoke-suppression performance of polypropylene is improved. Microencapsulated ammonium polyphosphate has good compatibility with polypropylene resin, the influence on the mechanical property of polypropylene is small, meanwhile, after being coated with the microcapsules, ammonium polyphosphate is not prone to absorbing moisture, and the polypropylene material is not prone to absorbing moisture and has high tensile strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-performance polypropylene, in particular to a low-smoke halogen-free flame-retardant polypropylene material, a preparation method thereof and application thereof in automobile wire and cable. BACKGROUND

[0002] Polypropylene has good high-temperature resistance, high mechanical properties and easy processing, and is widely used in automobile interior parts, wire and cable materials and other aspects. However, polypropylene is flammable and produces a large amount of toxic smoke during combustion, which poses a safety hazard and limits the practical application of polypropylene in new energy vehicles, cable materials and other aspects. Adding ammonium polyphosphate, zinc borate, aluminum hydroxide and other flame retardants to polypropylene can effectively improve its flame retardant performance.

[0003] Ammonium polyphosphate is cheap, environmentally friendly and has good flame retardant performance, and can be used alone or in combination with nitrogen-containing char-forming flame retardants to give high molecular materials excellent flame retardant performance. However, ammonium polyphosphate has high hygroscopicity, and when added to polypropylene and other materials, it will cause the material to absorb water and moisture, and the compatibility of ammonium polyphosphate with polypropylene is poor, which seriously affects the mechanical properties of the material. The use of microcapsules to modify ammonium polyphosphate can effectively solve the above problems. Patent No. CN110964232B discloses a kind of high-efficiency environmental protection multilayer structure's microcapsule flame retardant and its preparation method, tin compound and molybdenum compound hybrid as capsule core, ammonium polyphosphate as the first layer of capsule wall, melamine formaldehyde resin as the second layer of capsule wall, the prepared microcapsule flame retardant is suitable for polyester, polypropylene, epoxy resin and other materials, but the patent does not improve the compatibility between the microcapsule flame retardant and polypropylene, which will affect the mechanical strength of polypropylene. SUMMARY

[0004] In view of the shortcomings of the prior art, the present application provides a low-smoke halogen-free flame-retardant high-performance polypropylene material and a preparation method thereof, which solves the problem of poor compatibility of ammonium polyphosphate with polypropylene and improves the flame retardant performance of polypropylene material.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a low-smoke halogen-free flame-retardant polypropylene material and a preparation method thereof; the polypropylene material comprises 70-80 parts by weight of polypropylene resin, 20-30 parts by weight of microencapsulated ammonium polyphosphate and 0.15-0.35 parts by weight of antioxidant.

[0006] The preparation method of the polypropylene material is as follows:

[0007] (1) Add dimethylbenzene, N-(4-maleimide phenyl) diglycidyl amine grafted polypropylene, polybenzimidazole and ammonium polyphosphate to a reaction container, heat and stir, then distill under reduced pressure, and dry to obtain microencapsulated ammonium polyphosphate.

[0008] (2) mixing polypropylene resin, microencapsulated ammonium polyphosphate and antioxidant, melt extruding in a twin-screw extruder, granulating to obtain low-smoke halogen-free flame-retardant polypropylene material.

[0009] Preferably, the amount of N-(4-maleimide phenyl) diglycidyl amine grafted polypropylene in (1) is 8-15 parts by weight, the amount of polybenzimidazole is 85-92 parts by weight, and the amount of ammonium polyphosphate is 250-350 parts by weight.

[0010] Preferably, the temperature during heating and stirring in (1) is 130-140℃, and the stirring time is 3-5h.

[0011] Preferably, the antioxidant in (2) is antioxidant 1010, antioxidant 1076 or antioxidant 330.

[0012] Preferably, the temperature of each section of the twin-screw extruder in (2) is 150-200℃, and the screw rotation speed is 80-150r / min.

[0013] Preferably, the preparation method of N-(4-maleimide phenyl) diglycidyl amine grafted polypropylene is as follows: mixing polypropylene resin, N-(4-maleimide phenyl) diglycidyl amine and initiator, melt grafting in a screw extruder, extruding, adding the product into xylene, heating and refluxing, adding acetone for precipitation, filtering, and then using acetone to extract and purify the product in a Soxhlet extractor, drying to obtain N-(4-maleimide phenyl) diglycidyl amine grafted polypropylene.

[0014] Preferably, the temperature of each section of the screw extruder is 160-220℃, and the screw rotation speed is 50-100r / min.

[0015] Preferably, the amount of polypropylene resin is 100 parts by weight, the amount of N-(4-maleimide phenyl) diglycidyl amine is 2-8 parts by weight, and the amount of initiator is 0.15-0.5 parts by weight.

[0016] Preferably, the initiator is di-tert-butyl peroxydiisopropylbenzene or di-tert-butyl peroxide.

[0017] Preferably, the low-smoke halogen-free flame-retardant polypropylene material is applied to automobile wires and cables.

[0018] The beneficial technical effects of this invention are as follows: N-(4-maleimide-phenyl)diglycidylamine containing an alkenyl group is melt-grafted onto polypropylene to introduce an N-phenylmaleimide structure and epoxy groups into the side chain of polypropylene. The epoxy groups undergo a ring-opening crosslinking reaction with the imino group of polybenzimidazole to form a microcapsule wall. At the same time, the epoxy ring-opening reaction generates hydroxyl groups, which form hydrogen bonds with ammonium polyphosphate, effectively achieving the adsorption and coating modification of ammonium polyphosphate. Finally, it is blended and granulated with polypropylene resin to obtain a high-performance polypropylene material with low smoke, halogen-free flame retardancy.

[0019] The microencapsulated ammonium polyphosphate of the present invention contains polypropylene molecular chains in its capsule wall, which makes the microencapsulated ammonium polyphosphate have good dispersibility in polypropylene resin, which is beneficial to improving the flame retardant and smoke suppression performance of polypropylene. Furthermore, the microcapsule wall contains N-phenylmaleimide rings and polybenzimidazole structures, and contains a large number of nitrogen-containing heterocycles, which can act as nitrogen-based flame retardants and have a synergistic flame retardant effect with ammonium polyphosphate, significantly reducing the peak heat release rate and the average specific extinction area.

[0020] The microencapsulated ammonium polyphosphate of this invention has excellent compatibility with polypropylene resin and has little impact on the mechanical properties of polypropylene. At the same time, after being encapsulated, the ammonium polyphosphate is not easy to absorb moisture, and the polypropylene material is not easy to absorb moisture, thus having high tensile strength. Attached Figure Description

[0021] Figure 1 This is the infrared spectrum of the microencapsulated ammonium polyphosphate in Example 1. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description will be provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention. Unless otherwise defined, all technical and scientific terms used in this invention pertain to the technical field of the invention.

[0023] The polypropylene resin grade F40-03mm described below is from Shanghai Liu Zhangyang Plastics Co., Ltd.

[0024] N-(4-maleimide-phenyl)diglycidylamine was prepared according to the method described in the July 2016 issue of the journal *Thermosetting Resins*, Volume 31, Issue 4. The structural formula is as follows: .

[0025] Example 1:

[0026] (1) 200g of polypropylene resin, 4g of N-(4-maleimide-phenyl) diglycidylamine and 0.3g of di-tert-butyl peroxide were mixed and melt-grafted in a screw extruder. The temperatures of each section were 160℃, 175℃, 195℃, 210℃, 220℃ and 220℃, and the screw speed was 80r / min. After extrusion, the product was added to xylene, heated to 140℃, stirred and refluxed for 2h, acetone was added for precipitation, and the product was filtered and purified by extraction with acetone in a Soxhlet extractor. After drying, N-(4-maleimide-phenyl) diglycidylamine grafted polypropylene was obtained.

[0027] (2) Add 1.2L xylene, 80g N-(4-maleimidephenyl) diglycidylamine grafted polypropylene, 920g polybenzimidazole and 2.5kg ammonium polyphosphate to the reaction vessel, heat to 130℃, reflux and stir for 5h, distill under reduced pressure and dry to obtain microencapsulated ammonium polyphosphate. Figure 1 1024 cm⁻¹ in the infrared spectrum -1 877cm -1 These are the absorption peaks of the symmetric and asymmetric stretching vibrations of the PO bond in ammonium polyphosphate, at 1229 cm⁻¹. -1 It is the absorption peak of the stretching vibration of the P=O bond, at 1588 cm⁻¹. -1 It is the absorption peak of the stretching vibration of the C=N bond in polybenzimidazole, at 1652 cm⁻¹. -1 The absorption peak is at 2853 cm⁻¹, representing the C=O bond of the maleimide ring. -1 and 2913cm -1 It is the absorption peak of methylene-CH2- in the polypropylene molecular chain, at 3326 cm⁻¹. -1 It is the absorption peak of the hydroxyl group -OH.

[0028] (3) Mix 8 kg of polypropylene resin, 2 kg of microencapsulated ammonium polyphosphate and 22 g of antioxidant 1010, and melt extrude them in a twin-screw extruder. The temperatures of each section are 150℃, 170℃, 190℃, 200℃, 200℃ and 195℃, and the screw speed is 80 r / min. The mixture is then pelletized to obtain low-smoke halogen-free flame-retardant polypropylene material.

[0029] Example 2:

[0030] (1) 200g of polypropylene resin, 8g of N-(4-maleimide-phenyl) diglycidylamine and 0.5g of di-tert-butyl peroxide were mixed and melt-grafted in a screw extruder. The temperatures of each section were 160℃, 175℃, 195℃, 210℃, 220℃ and 220℃, and the screw speed was 100r / min. After extrusion, the product was added to xylene, heated to 130℃, stirred and refluxed for 3h, acetone was added for precipitation, and the product was filtered and purified by extraction with acetone in a Soxhlet extractor. After drying, N-(4-maleimide-phenyl) diglycidylamine grafted polypropylene was obtained.

[0031] (2) Add 1.5L xylene, 100g N-(4-maleimidephenyl) diglycidylamine grafted polypropylene, 900g polybenzimidazole and 3kg ammonium polyphosphate to the reaction vessel, heat to 130℃, reflux and stir for 5h, distill under reduced pressure and dry to obtain microencapsulated ammonium polyphosphate.

[0032] (3) Mix 7.7 kg of polypropylene resin, 2.3 kg of microencapsulated ammonium polyphosphate and 15 g of antioxidant 330, and melt extrude them in a twin-screw extruder. The temperatures of each section are 150℃, 170℃, 190℃, 200℃, 200℃ and 195℃, and the screw speed is 100 r / min. The mixture is then pelletized to obtain low-smoke halogen-free flame-retardant polypropylene material.

[0033] Example 3:

[0034] (1) 200g of polypropylene resin, 12g of N-(4-maleimide-phenyl) diglycidylamine and 0.75g of di-tert-butyl peroxide diisopropylbenzene were mixed and melt-grafted in a screw extruder. The temperatures of each section were 160℃, 175℃, 195℃, 210℃, 220℃ and 220℃, and the screw speed was 100r / min. After extrusion, the product was added to xylene, heated to 130℃, stirred and refluxed for 3h, acetone was added for precipitation, and the product was filtered and purified by extraction with acetone in a Soxhlet extractor. After drying, N-(4-maleimide-phenyl) diglycidylamine grafted polypropylene was obtained.

[0035] (2) Add 2L of xylene, 120g of N-(4-maleimide-phenyl) diglycidylamine-grafted polypropylene, 880g of polybenzimidazole and 3kg of ammonium polyphosphate to the reaction vessel, heat to 130℃, reflux and stir for 4h, distill under reduced pressure and dry to obtain microencapsulated ammonium polyphosphate.

[0036] (3) Mix 7.4 kg of polypropylene resin, 2.6 kg of microencapsulated ammonium polyphosphate and 35 g of antioxidant 1010, and melt extrude them in a twin-screw extruder. The temperatures of each section are 150℃, 170℃, 190℃, 200℃, 200℃ and 195℃, and the screw speed is 150 r / min. The mixture is then pelletized to obtain low-smoke halogen-free flame-retardant polypropylene material.

[0037] Example 4:

[0038] (1) 200g of polypropylene resin, 16g of N-(4-maleimide-phenyl) diglycidylamine and 1g of di-tert-butyl peroxide diisopropylbenzene were mixed and melt-grafted in a screw extruder. The temperatures of each section were 160℃, 175℃, 195℃, 210℃, 220℃ and 220℃, and the screw speed was 50r / min. After extrusion, the product was added to xylene, heated to 130℃, stirred and refluxed for 3h, acetone was added for precipitation, and the product was filtered and purified by extraction with acetone in a Soxhlet extractor. After drying, N-(4-maleimide-phenyl) diglycidylamine grafted polypropylene was obtained.

[0039] (2) Add 2L of xylene, 150g of N-(4-maleimide-phenyl) diglycidylamine-grafted polypropylene, 850g of polybenzimidazole and 3.5kg of ammonium polyphosphate to the reaction vessel, heat to 140℃, reflux and stir for 3h, distill under reduced pressure and dry to obtain microencapsulated ammonium polyphosphate.

[0040] (3) Mix 7kg of polypropylene resin, 3kg of microencapsulated ammonium polyphosphate and 24g of antioxidant 1076, melt extrude in a twin-screw extruder, with temperatures of 150℃, 170℃, 190℃, 200℃, 200℃ and 195℃ in each section, and screw speed of 80r / min. Pelletize to obtain low-smoke halogen-free flame-retardant polypropylene material.

[0041] Comparative Example 1:

[0042] (1) Mix 8kg of polypropylene resin, 2kg of ammonium polyphosphate and 22g of antioxidant 1010, melt extrude in a twin-screw extruder, with temperatures of 150℃, 170℃, 190℃, 200℃, 200℃ and 195℃ in each section, and screw speed of 80r / min, and granulate to obtain flame-retardant polypropylene material.

[0043] Comparative Example 2:

[0044] (1) 200g of polypropylene resin, 4g of N-phenylmaleimide (CAS No. 941-69-5) and 0.3g of di-tert-butyl peroxide were mixed and melt-grafted in a screw extruder. The temperatures of each section were 160℃, 175℃, 195℃, 210℃, 220℃ and 220℃, and the screw speed was 80r / min. After extrusion, the product was added to xylene, heated to 140℃, stirred and refluxed for 2h, acetone was added for precipitation, and the product was filtered and purified by extraction with acetone in a Soxhlet extractor. After drying, N-phenylmaleimide-grafted polypropylene was obtained.

[0045] (2) Add 1.2L xylene, 80g N-phenylmaleimide-grafted polypropylene, 920g polybenzimidazole and 2.5kg ammonium polyphosphate to the reaction vessel, heat to 130℃, reflux and stir for 5h, distill under reduced pressure and dry to obtain polybenzimidazole-ammonium polyphosphate blend.

[0046] (3) Mix 8 kg of polypropylene resin, 2 kg of polybenzimidazole-ammonium polyphosphate blend and 22 g of antioxidant 1010, melt extrude in a twin-screw extruder, with temperatures of 150℃, 170℃, 190℃, 200℃, 200℃ and 195℃ in each section, and screw speed of 80 r / min, and granulate to obtain flame-retardant polypropylene material.

[0047] Comparative Example 3:

[0048] (1) Add 1.2L xylene, 80g N-(4-maleimide-phenyl) diglycidylamine-grafted polypropylene (prepared from Example 1), 920g polyetheramine D230 and 2.5kg ammonium polyphosphate to the reaction vessel, heat to 130°C, reflux and stir for 5h, distill under reduced pressure and dry to obtain microencapsulated ammonium polyphosphate.

[0049] (2) Mix 8 kg of polypropylene resin, 2 kg of microencapsulated ammonium polyphosphate and 22 g of antioxidant 1010, and melt extrude them in a twin-screw extruder. The temperatures of each section are 150℃, 170℃, 190℃, 200℃, 200℃ and 195℃, and the screw speed is 80 r / min. The mixture is then pelletized to obtain flame-retardant polypropylene material.

[0050] Comparative Example 4:

[0051] (1) Add 1.2L xylene, 80g epoxy resin E44, 920g polybenzimidazole and 2.5kg ammonium polyphosphate to the reaction vessel, heat to 130℃, reflux and stir for 5h, distill under reduced pressure and dry to obtain microencapsulated ammonium polyphosphate.

[0052] (2) Mix 8 kg of polypropylene resin, 2 kg of microencapsulated ammonium polyphosphate and 22 g of antioxidant 1010, and melt extrude them in a twin-screw extruder. The temperatures of each section are 150℃, 170℃, 190℃, 200℃, 200℃ and 195℃, and the screw speed is 80 r / min. The mixture is then pelletized to obtain flame-retardant polypropylene material.

[0053] Comparative Example 5:

[0054] (1) Add 180 mL of 37% formaldehyde aqueous solution and 41 g of melamine to the reaction vessel, add 5% sodium carbonate solution to adjust the pH to 8, heat to 80°C, reflux for 20 min, then add 2.5 kg of ammonium polyphosphate aqueous solution in ethanol (6 L ethanol and 12 L water), stir, add glacial acetic acid to adjust the pH to 5, stir at 80°C for 2 h, filter, wash with water, dry, and obtain melamine formaldehyde resin microencapsulated ammonium polyphosphate.

[0055] (2) Mix 8 kg of polypropylene resin, 2 kg of melamine-formaldehyde resin microencapsulated ammonium polyphosphate, and 22 g of antioxidant 1010, and melt extrude them in a twin-screw extruder. The temperatures of each section are 150℃, 170℃, 190℃, 200℃, 200℃, and 195℃, and the screw speed is 80 r / min. The mixture is then pelletized to obtain flame-retardant polypropylene material.

[0056] Polypropylene material was injection molded into test strips using an injection molding machine, and its combustion performance was tested using a cone calorimeter, with a radiant energy of 35 kW / m³. 2 .

[0057] Polypropylene material was placed in a constant temperature and humidity test chamber at 25℃ and 90% relative humidity for 30 days. Surface moisture was wiped off, and the tensile strength after moisture absorption was tested according to GB / T 1040.1-2018 standard. The results are shown in Table 1.

[0058] Table 1 Properties of Polypropylene Materials

[0059] Heat release rate peak (kW / m 2 ) Average specific extinction area (m2 / kg) Moisture absorption tensile strength (MPa) Example 1 509.8 441.3 24.8 Example 2 425.0 388.9 23.7 Example 3 257.8 337.5 21.9 Example 4 192.4 305.2 20.6 Comparative Example 1 635.6 487.6 21.9 Comparative Example 2 551.9 464.7 21.5 Comparative Example 3 612.5 480.2 25.1 Comparative Example 4 532.7 453.0 22.6 Comparative Example 5 527.4 448.1 22.3

[0060] The polypropylene material in Comparative Example 1 exhibits a large peak heat release rate and average specific extinction area, poor flame retardant and smoke suppression properties, and low tensile strength after moisture absorption. This is primarily due to the poor compatibility between ammonium polyphosphate and polypropylene, resulting in poor dispersibility of ammonium polyphosphate, which hinders the improvement of the material's flame retardant and smoke suppression properties. Poorly dispersible ammonium polyphosphate significantly impacts the mechanical properties of polypropylene, and its hygroscopic nature further affects the polypropylene's mechanical properties, leading to very low tensile strength after moisture absorption.

[0061] In each embodiment, the epoxy groups of the polypropylene side chain grafted with N-(4-maleimide-phenyl)diglycidylamine were cross-linked with the imino groups of polybenzimidazole to form microcapsule walls. Through hydrogen bonding interactions such as hydroxyl groups, adsorption and encapsulation modification of ammonium polyphosphate were achieved. The microcapsule walls contain polypropylene molecular chains, resulting in excellent dispersibility of the microencapsulated ammonium polyphosphate in polypropylene resin, which is beneficial for improving the flame retardant and smoke-suppressing properties of polypropylene. Furthermore, the microcapsule walls contain N-phenylmaleimide rings and polybenzimidazole structures, containing a large number of nitrogen-containing heterocycles, which can act as nitrogen-based flame retardants, synergistically enhancing the flame retardant effect with ammonium polyphosphate, significantly reducing the peak heat release rate and average specific extinction area. The microencapsulated ammonium polyphosphate exhibits excellent compatibility with polypropylene resin and has minimal impact on the mechanical properties of polypropylene. Simultaneously, after microcapsulation, the ammonium polyphosphate is less hygroscopic, making the polypropylene material less prone to moisture absorption, thus resulting in higher tensile strength.

[0062] The N-phenylmaleimide in Comparative Example 2 and the prepared N-phenylmaleimide-grafted polypropylene do not contain epoxy groups, so they cannot crosslink with polybenzimidazole. They do not crosslink to form a capsule wall and cannot achieve the coating modification of ammonium polyphosphate. The peak heat release rate and average specific extinction area of ​​the polypropylene are relatively large, the flame retardant and smoke suppression properties are poor, and the tensile strength after moisture absorption is significantly lower than that of Example 1.

[0063] In Comparative Example 3, polyetheramine D230 was used instead of polybenzimidazole to crosslink with N-(4-maleimide-phenyl)diglycidylamine grafted polypropylene, and ammonium polyphosphate was coated and modified. Since polyetheramine D230 does not contain the nitrogen-containing heterocyclic structure of benzimidazole, it cannot be used as a nitrogen-based flame retardant and it is difficult to improve the flame retardant properties of polypropylene. As a result, the peak heat release rate and average specific extinction area of ​​polypropylene are significantly larger than those in Example 1, and the flame retardant and smoke suppression properties are poor.

[0064] Comparative Example 4 uses a cross-linking reactant of epoxy resin and polybenzimidazole as the capsule wall to coat and modify ammonium polyphosphate. The microcapsule wall does not contain polypropylene molecular chains, resulting in poor compatibility with polypropylene resin. This affects the flame retardant and smoke-suppressing properties and mechanical strength of polypropylene. The peak heat release rate and average specific extinction area are relatively large, and the tensile strength is relatively low.

[0065] Comparative Example 5 uses conventional melamine-formaldehyde resin as the microcapsule wall and modifies it with ammonium polyphosphate. The microcapsule wall does not contain polypropylene molecular chains, and its compatibility with polypropylene resin is poor. This will affect the flame retardant and smoke suppression properties and mechanical strength of polypropylene. The peak heat release rate and average specific extinction area are large, and the tensile strength is low.

[0066] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A low smoke, halogen-free, flame retardant polypropylene material, characterized in that, The low-smoke halogen-free flame-retardant polypropylene material comprises 70-80 parts by weight of polypropylene resin, 20-30 parts by weight of microencapsulated ammonium polyphosphate, 0.15-0.35 parts by weight of antioxidant; The preparation method of the microencapsulated ammonium polyphosphate comprises the following steps: adding dimethylbenzene, N-(4-maleimide phenyl) diglycidyl amine grafted polypropylene, polybenzimidazole and ammonium polyphosphate into a reaction container, heating and stirring, vacuum distillation, and drying to obtain the microencapsulated ammonium polyphosphate.

2. The high-strength polypropylene composite of claim 1, wherein, The antioxidant is antioxidant 1010, antioxidant 1076 or antioxidant 330.

3. The low smoke, halogen-free, flame retardant polypropylene material of claim 1, wherein, The amount of the N-(4-maleimide phenyl) diglycidyl amine grafted polypropylene is 8-15 parts by weight, the amount of the polybenzimidazole is 85-92 parts by weight, and the amount of the ammonium polyphosphate is 250-350 parts by weight.

4. The low smoke, halogen-free, flame retardant polypropylene material of claim 1, wherein, The temperature during the heating and stirring is 130-140 DEG C, and the stirring time is 3-5 h.

5. The low smoke, halogen-free, flame retardant polypropylene material of claim 1, wherein, The preparation method of the N-(4-maleimide phenyl) diglycidyl amine grafted polypropylene comprises the following steps: mixing polypropylene resin, N-(4-maleimide phenyl) diglycidyl amine and initiator, carrying out melt grafting in a screw extruder, extruding, and purifying the product to obtain the N-(4-maleimide phenyl) diglycidyl amine grafted polypropylene.

6. Low smoke halogen-free flame retardant polypropylene material according to claim 5, characterized in that The temperature of each section of the screw extruder is 160-220 DEG C, and the screw rotation speed is 50-100 r / min.

7. The low smoke, halogen-free, flame retardant polypropylene material of claim 5, wherein, The amount of the polypropylene resin is 100 parts by weight, the amount of the N-(4-maleimide phenyl) diglycidyl amine is 2-8 parts by weight, and the amount of the initiator is 0.15-0.5 parts by weight.

8. Low smoke halogen-free flame retardant polypropylene material according to claim 7, characterized in that The initiator is di-tert-butyl peroxydiisopropylbenzene or di-tert-butyl peroxide.

9. A process for the preparation of a low smoke halogen-free flame retardant polypropylene material according to any one of claims 1 to 8, characterized in that, The preparation method comprises the following steps: mixing polypropylene resin, microencapsulated ammonium polyphosphate and antioxidant, and carrying out melt extrusion in a double-screw extruder, the temperature of each section is 150-200 DEG C, and the screw rotation speed is 80-150 r / min; and cutting to obtain the low-smoke halogen-free flame-retardant polypropylene material.

10. Application of the low-smoke halogen-free flame-retardant polypropylene material prepared by the preparation method of claim 9 in automobile wire and cable.

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