Halogen-free flame-retardant MPP power pipeline material and preparation method thereof

Abstract

The invention relates to the field of pipeline materials, and discloses a halogen-free flame-retardant MPP power pipeline material and a preparation method thereof.The pipeline material comprises polypropylene, modified multi-walled carbon nanotubes, a coating filler, a compatilizer and a lubricant; the modified multi-walled carbon nanotube is prepared by carrying out acylating chlorination on an oxidized multi-walled carbon nanotube by using thionyl chloride and then reacting with an aminated cyclotriphosphazene derivative; according to the aminated cyclotriphosphazene derivative, phosphonitrilic chloride trimer and 3, 5-di-tert-butyl-4-hydroxybenzylamine react to prepare a cyclotriphosphazene intermediate, the cyclotriphosphazene intermediate and N, N '-bis-(2, 2, 6, 6-tetramethyl-4-piperidyl)-1, 6-hexamethylenediamine are subjected to substitution to prepare a cyclotriphosphazene derivative, and then the cyclotriphosphazene derivative and 1, 6-hexamethylenediamine are subjected to substitution to obtain the aminated cyclotriphosphazene derivative. The coating filler is prepared by preparing modified lignin by combining 2, 2, 6, 6-tetramethyl-4-piperidinol and lignin and then preparing silicon dioxide-coated modified lignin by adopting a sol-gel method, and the pipe prepared by the invention has excellent mechanical properties, flame retardance, thermo-oxidative aging resistance and ultraviolet aging resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pipeline materials, and particularly relates to a halogen-free flame-retardant MPP power pipeline material and a preparation method thereof. BACKGROUND

[0002] MPP power pipes are mainly prepared by using polypropylene as raw material and modifying other raw materials, and are a kind of pipe material widely used in the fields of power and communication, which is mainly used for protecting cables and other facilities from damage by external environmental factors. Polypropylene is a kind of thermoplastic plastic polymerized from propylene monomer, which is milky white in appearance and has a semi-crystalline structure, is non-toxic and odorless, is easy to process, is low in price, is good in chemical corrosion resistance, and is excellent in mechanical properties, and is one of the most commonly used power pipes in the market.

[0003] However, the flame retardancy of MPP power pipes is poor, which can easily cause fire hazards, and a large amount of heat and smoke will be generated during combustion, which can cause great threat to life and property safety. The introduction of flame retardants is the simplest and most effective method to solve the flammability of MPP power pipes. Ammonium polyphosphate and triazine char-forming agents are commonly used flame-retardant systems in MPP power pipes. However, due to the presence of a large number of polar groups, the interaction between the polar groups and the non-polar polypropylene is weak, which can cause poor compatibility and reduce the mechanical properties. In addition, the flame retardant can migrate and precipitate in high temperature environment, which can cause flame retardant failure and other problems. In addition, the tertiary carbon atoms contained in the molecular chain structure of polypropylene are prone to thermal oxidative degradation and photo-aging degradation under the conditions of oxygen, heat and ultraviolet light, which can cause the MPP power pipes to exhibit poor anti-aging performance. When used outdoors, the service life is seriously shortened, which limits the application range of the MPP power pipes. SUMMARY

[0004] In order to solve the problems mentioned in the background, the purpose of the present application is to provide a halogen-free flame-retardant MPP power pipeline material and a preparation method thereof. The modified multi-walled carbon nanotubes and the coated filler are used to modify the polypropylene base material, and the compatibilizer and the lubricant are added for melt blending, so as to give the pipe excellent mechanical properties, flame retardant properties, thermal oxidative aging resistance and ultraviolet aging resistance.

[0005] The purpose of the present application can be achieved by the following technical scheme: A halogen-free flame-retardant MPP power pipeline material, comprising the following components by weight: polypropylene 80-100 parts, modified multi-walled carbon nanotubes 5-10 parts, coated filler 3-9 parts, compatibilizer 4-8 parts, and lubricant 1-3 parts. The modified multi-walled carbon nanotubes are prepared by oxidizing multi-walled carbon nanotubes with concentrated sulfuric acid and concentrated nitric acid, then chlorinating with thionyl chloride, and then reacting with aminophosphazene derivative to form an amide. The amino cyclotriphosphazene derivative is prepared by substituting reaction of hexachlorocyclotriphosphazene and 3,5-di-tert-butyl-4-hydroxybenzylamine to prepare a cyclotriphosphazene intermediate, then substituting reaction of the cyclotriphosphazene intermediate and N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine to prepare a cyclotriphosphazene derivative, and then substituting reaction of 1,6-hexanediamine and the cyclotriphosphazene derivative; The coated filler is prepared by combining a hindered amine light stabilizer intermediate 2,2,6,6-tetramethyl-4-piperidinol and lignin by chemical reaction to prepare modified lignin, and then preparing silica-coated modified lignin by a sol-gel method.

[0006] Preferably, the compatibilizer is one or more combinations of maleic anhydride grafted polypropylene, ethylene-vinyl acetate copolymer, and maleic anhydride grafted polyethylene; and the lubricant is one or more combinations of stearic acid, polyethylene wax, and oxidized polyethylene wax.

[0007] Preferably, the preparation method of the modified multi-walled carbon nanotube comprises the following steps: A. The multi-walled carbon nanotube is taken into a mixed solution of concentrated sulfuric acid and concentrated nitric acid, stirred and reacted at 70-85℃ for 4-6h, washed to neutral after filtration, and dried in a vacuum oven to prepare oxidized multi-walled carbon nanotube; B. The oxidized multi-walled carbon nanotube is taken into a reactor, chlorosulfoxide and N,N-dimethylformamide are added and uniformly dispersed by ultrasonic, refluxed and reacted at 60-75℃ for 20-24h, then rotary evaporated, dried, and then amino cyclotriphosphazene derivative, N,N-dimethylformamide and pyridine are added, reacted at 75-85℃ for 20-24h, and then filtered, washed and dried after reaction to prepare modified multi-walled carbon nanotube.

[0008] Preferably, the preparation method of the amino cyclotriphosphazene derivative in step B comprises the following steps: B1. Hexachlorocyclotriphosphazene is taken into a reactor, dissolved in tetrahydrofuran, heated to 45-60℃, 3,5-di-tert-butyl-4-hydroxybenzylamine and triethylamine are added, and condensed and refluxed for 5-6h, and then rotary evaporated, washed and dried after reaction to prepare a cyclotriphosphazene intermediate; B2. The cyclotriphosphazene intermediate and m-xylene are taken into a reactor, stirred and mixed, N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine and triethylamine are added, stirred and reacted at 55-70℃ for 3-5h, and then filtered, washed and dried after reaction to prepare a cyclotriphosphazene derivative; B3, the cyclotriphosphazene derivative and tetrahydrofuran are taken into a reactor, after stirring and mixing, 1,6-hexanediamine and triethylamine are added, and stirring reaction is carried out at 60-70 DEG C for 20-24 h, after reaction is completed, filtration, washing and drying are carried out, and the aminated cyclotriphosphazene derivative is prepared.

[0009] Preferably, the molar ratio of the hexachlorocyclotriphosphazene and 3,5-di-tert-butyl-4-hydroxybenzylamine in the step B1 is 1:3-3.1.

[0010] Preferably, the molar ratio of the cyclotriphosphazene intermediate and N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine in the step B2 is 1.9-2.1:1.

[0011] Preferably, the molar ratio of the cyclotriphosphazene derivative and 1,6-hexanediamine in the step B3 is 1:4-4.2.

[0012] Preferably, the preparation method of the coated filler comprises the following steps: 1, 2, 6, 6-tetramethyl-4-piperidyl alcohol is taken into a lignin solution, triethanolamine is used to adjust the pH of the system to 10-12, stirring is carried out at 65-75 DEG C for 10-20 min, the temperature is raised to 80-90 DEG C, formaldehyde is slowly added dropwise, stirring is carried out for 2.5-3 h, and then the temperature is cooled to room temperature, ethanol is used for washing and drying, and the modified lignin is prepared. 2, deionized water, ethanol and OP-10 are taken into a reactor, stirring is carried out in a 25-30 DEG C water bath for 15-20 min, then the modified lignin is added and stirring is continued for 15-20 min, hydrochloric acid is used to adjust the pH of the system to 3-4, then tetraethyl orthosilicate is added, and reaction is carried out in a 35-45 DEG C water bath for 20-24 h, after reaction is completed, centrifugation, washing and drying are carried out, and the coated filler is prepared.

[0013] Preferably, the concentration of the lignin solution in the step 1 is 0.2-0.3 g / mL; the addition ratio of the 2,2,6,6-tetramethyl-4-piperidyl alcohol and the lignin solution is 3-5 g:40 mL; and the molar ratio of the 2,2,6,6-tetramethyl-4-piperidyl alcohol and formaldehyde is 1:1.1.

[0014] A preparation method of the halogen-free flame-retardant MPP power pipeline material is disclosed, comprising the following steps: each raw material is weighed according to weight parts, polypropylene, modified multi-walled carbon nanotube, coated filler, compatibilizer and lubricant are stirred and mixed uniformly, then melt extrusion is carried out through a double-screw extruder, and the halogen-free flame-retardant MPP power pipeline material is prepared.

[0015] The beneficial effects of the present application are as follows: The application utilizes the substitution reaction of the three chlorine atoms in hexachlorocyclotriphosphazene and the amino group in 3,5-di-tert-butyl-4-hydroxybenzylamine antioxidant to prepare a cyclotriphosphazene intermediate, then uses N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine hindered amine light stabilizer as a bridging agent, utilizes the two -NH groups in the secondary amine-alkyl chain-secondary amine structure of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine to undergo substitution reaction with two molecules of cyclotriphosphazene intermediate to prepare a cyclotriphosphazene derivative, then uses 1,6-hexanediamine to continue to undergo substitution reaction with the remaining ungrafted chlorine atoms in the cyclotriphosphazene derivative to prepare an aminated cyclotriphosphazene derivative, and meanwhile, the application uses concentrated sulfuric acid and concentrated nitric acid to oxidize multi-walled carbon nanotubes, so that the surface of the multi-walled carbon nanotubes is rich in carboxyl groups, then the multi-walled carbon nanotubes are treated with thionyl chloride to be acylated and then subjected to amidation reaction with the aminated cyclotriphosphazene derivative to prepare modified multi-walled carbon nanotubes, so that the aminated cyclotriphosphazene derivative component is grafted on the surface of the multi-walled carbon nanotubes, which promotes the relatively uniform dispersion of the multi-walled carbon nanotubes in the matrix material and avoids the performance defects caused by the agglomeration phenomenon, and in addition, the flame-retardant nitrogen-phosphorus elements, the hindered phenolic antioxidant and the hindered amine light stabilizer are combined through firm chemical bonds, which cooperatively plays a good long-term flame-retardant effect, heat-oxidation resistance and ultraviolet aging resistance effect.

[0016] The application utilizes chemical reaction to combine the hindered amine light stabilizer intermediate 2,2,6,6-tetramethyl-4-piperidinol and lignin to prepare modified lignin, wherein the lignin is a kind of natural renewable polymer material, contains rich methoxyl aromatic structure in the molecule, has excellent ultraviolet absorption capacity and anti-aging performance, is mainly used as a charring agent and an antioxidant, the grafting of 2,2,6,6-tetramethyl-4-piperidinol fills the voids of the lignin, enhances the inter-particle adhesion, forms a more compact molecular structure, and the grafting of 2,2,6,6-tetramethyl-4-piperidinol in the lignin can effectively inhibit the migration of 2,2,6,6-tetramethyl-4-piperidinol from the polymer matrix, significantly improves the ultraviolet resistance performance of the pipe material, then a sol-gel method is used to prepare a silica-coated modified lignin coating filler, which can effectively hinder the diffusion of gas and heat in a high-temperature environment, and the coating of silica significantly improves the mechanical properties of the pipe material and the structural stability of the carbon layer. The application uses modified multi-walled carbon nanotubes and coating fillers to modify the polypropylene base material, adds a compatibilizer and a lubricant to melt blend, and gives the pipe material excellent mechanical properties, flame-retardant properties, heat-oxidation resistance and ultraviolet aging resistance effect. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0018] The preparation method of the modified multi-walled carbon nanotube in Embodiment 1 comprises the following steps: A. 5 g of multi-walled carbon nanotubes are taken into a mixed solution of 90 mL of concentrated sulfuric acid and 30 mL of concentrated nitric acid, and stirred at 80℃ for 5 h. After the reaction is completed, the product is washed to neutral by suction filtration, and dried in a vacuum oven to prepare oxidized multi-walled carbon nanotubes; B. 5 g of the oxidized multi-walled carbon nanotubes are taken into a reactor, 120 mL of thionyl chloride and 20 mL of N,N-dimethylformamide are added and uniformly dispersed by ultrasonic, and then refluxed at 70℃ for 24 h. After rotary evaporation and drying, 3.2 g of an aminated cyclotriphosphazene derivative, 100 mL of N,N-dimethylformamide and 0.15 mL of pyridine are added, and then reacted at 80℃ for 24 h. After the reaction is completed, the product is filtered, washed and dried to prepare modified multi-walled carbon nanotubes.

[0019] The preparation method of the aminated cyclotriphosphazene derivative comprises the following steps: B1. 8.7 g of hexachlorocyclotriphosphazene is taken into a reactor, dissolved in 100 mL of tetrahydrofuran, heated to 55℃, and then 17.7 g of 3,5-di-tert-butyl-4-hydroxybenzylamine and 7.6 g of triethylamine are added. After condensation reflux reaction for 5 h, the product is rotary evaporated, washed and dried to prepare a cyclotriphosphazene intermediate; B2. 18.9 g of the cyclotriphosphazene intermediate (Mr=944.3) and 120 mL of m-xylene are taken into a reactor, stirred and mixed, and then 3.9 g of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine and 2.1 g of triethylamine are added. After stirring reaction at 60℃ for 4 h, the product is filtered, washed and dried to prepare a cyclotriphosphazene derivative; B3. 22.1 g of the cyclotriphosphazene derivative (Mr=2210.2) and 120 mL of tetrahydrofuran are taken into a reactor, stirred and mixed, and then 4.7 g of 1,6-hexanediamine and 4.1 g of triethylamine are added. After stirring reaction at 65℃ for 24 h, the product is filtered, washed and dried to prepare an aminated cyclotriphosphazene derivative.

[0020] The preparation method of the coated filler in Embodiment 2 comprises the following steps: ①Take 4g 2,2,6,6-tetramethyl-4-piperidinol into 40mL lignin solution with a concentration of 0.25g / mL, adjust the pH of the system to 11 with triethanolamine, stir at 70℃ for 15min, slowly add 0.76g formaldehyde at 85℃, stir for 3h, then cool to room temperature, wash with ethanol and dry to prepare modified lignin; ②Take 30mL deionized water, 90mL ethanol and 1g OP-10 in a reactor, stir in a 30℃ water bath for 20min, then add 10g modified lignin and continue stirring for 20min, adjust the pH of the system to 4 with hydrochloric acid, then add 5g tetraethyl orthosilicate, react in a 40℃ water bath for 24h, after the reaction is completed, centrifuge, wash and dry to prepare the coated filler.

[0021] Example 3 A halogen-free flame-retardant MPP power pipeline material, comprising the following components by weight: polypropylene 85 parts, modified multi-walled carbon nanotubes prepared in Example 1 5.4 parts, coated filler prepared in Example 2 3.6 parts, compatibilizer maleic anhydride grafted polypropylene 4.4 parts, lubricant stearic acid 1.2 parts.

[0022] The preparation method of the above-mentioned halogen-free flame-retardant MPP power pipeline material comprises the following steps: weighing each raw material by weight, stirring and mixing polypropylene, modified multi-walled carbon nanotubes, coated filler, compatibilizer and lubricant uniformly, then melt extruding through a twin-screw extruder to prepare a halogen-free flame-retardant MPP power pipeline material.

[0023] Example 4 A halogen-free flame-retardant MPP power pipeline material, comprising the following components by weight: polypropylene 92 parts, modified multi-walled carbon nanotubes prepared in Example 1 7.5 parts, coated filler prepared in Example 2 6.7 parts, compatibilizer ethylene-vinyl acetate copolymer 5.8 parts, lubricant polyethylene wax 2.3 parts.

[0024] The preparation method of the above-mentioned halogen-free flame-retardant MPP power pipeline material is the same as that of Example 3.

[0025] Example 5 A halogen-free flame-retardant MPP power pipeline material, comprising the following components by weight: polypropylene 100 parts, modified multi-walled carbon nanotubes prepared in Example 1 9.6 parts, coated filler prepared in Example 2 8.8 parts, compatibilizer maleic anhydride grafted polyethylene 7.7 parts, lubricant oxidized polyethylene wax 2.8 parts.

[0026] The preparation method of the above-mentioned halogen-free flame-retardant MPP power pipeline material is the same as that of Example 3.

[0027] Comparative Example 1 A preparation method of modified multi-walled carbon nanotubes comprises the following steps: A, 5 g of multi-walled carbon nanotubes were taken into a mixture of 90 mL of concentrated sulfuric acid and 30 mL of concentrated nitric acid, and stirred at 80°C for 5 h. After the reaction was completed, the product was washed to neutral by filtration and dried in a vacuum oven to obtain oxidized multi-walled carbon nanotubes; B, 5 g of the oxidized multi-walled carbon nanotubes were taken into a reactor, 120 mL of thionyl chloride and 20 mL of N,N-dimethylformamide were added and ultrasonically dispersed, and then stirred at 70°C for 24 h. After the reaction was completed, the product was dried by rotary evaporation, and then 3.2 g of the amino cyclotriphosphazene derivative, 100 mL of N,N-dimethylformamide and 0.15 mL of pyridine were added and stirred at 80°C for 24 h. After the reaction was completed, the product was filtered, washed and dried to obtain the modified multi-walled carbon nanotubes.

[0028] The preparation method of the amino cyclotriphosphazene derivative comprises the following steps: B1, 6.9 g of hexachlorocyclotriphosphazene and 120 mL of m-xylene were taken into a reactor, stirred and mixed, and then 3.9 g of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine and 2.1 g of triethylamine were added, and stirred at 60°C for 4 h. After the reaction was completed, the product was filtered, washed and dried to obtain the cyclotriphosphazene derivative. B2, 10.2 g of the cyclotriphosphazene derivative (Mr=1017.0) and 120 mL of tetrahydrofuran were taken into a reactor, stirred and mixed, and then 4.7 g of 1,6-hexanediamine and 4.1 g of triethylamine were added, and stirred at 65°C for 24 h. After the reaction was completed, the product was filtered, washed and dried to obtain the amino cyclotriphosphazene derivative.

[0029] The preparation method of the coated filler of Comparative Example 2 comprises the following steps: 30 mL of deionized water, 90 mL of ethanol and 1 g of OP-10 were taken into a reactor, stirred in a 30°C water bath for 20 min, and then 10 g of lignin was added and stirred for 20 min. The pH of the system was adjusted to 4 by hydrochloric acid, and then 5 g of tetraethyl orthosilicate was added, and the reaction was carried out at 40°C for 24 h. After the reaction was completed, the product was centrifuged, washed and dried to obtain the coated filler.

[0030] The halogen-free flame-retardant MPP power pipeline material of Comparative Example 3 comprises the following components by weight: 100 parts of polypropylene, 9.6 parts of the modified multi-walled carbon nanotubes prepared in Comparative Example 1, 8.8 parts of the coated filler prepared in Example 2, 7.7 parts of a compatibilizer maleic anhydride grafted polyethylene, and 2.8 parts of a lubricant oxidized polyethylene wax.

[0031] The preparation method of the halogen-free flame-retardant MPP power pipeline material is the same as that of Example 3.

[0032] Comparative Example 4: A halogen-free flame-retardant MPP power pipeline material comprising the following components by weight: polypropylene 100 parts, multi-walled carbon nanotubes 9.6 parts, the coated filler prepared in Example 2 8.8 parts, a compatibilizer maleic anhydride grafted polyethylene 7.7 parts, a lubricant oxidized polyethylene wax 2.8 parts.

[0033] The preparation method of the above halogen-free flame-retardant MPP power pipeline material is the same as that of Example 3.

[0034] Comparative Example 5: A halogen-free flame-retardant MPP power pipeline material comprising the following components by weight: polypropylene 100 parts, the modified multi-walled carbon nanotubes prepared in Example 1 9.6 parts, the coated filler prepared in Comparative Example 2 8.8 parts, a compatibilizer maleic anhydride grafted polyethylene 7.7 parts, a lubricant oxidized polyethylene wax 2.8 parts.

[0035] The preparation method of the above halogen-free flame-retardant MPP power pipeline material is the same as that of Example 3.

[0036] Comparative Example 6: A halogen-free flame-retardant MPP power pipeline material comprising the following components by weight: polypropylene 100 parts, the modified multi-walled carbon nanotubes prepared in Example 1 9.6 parts, a compatibilizer maleic anhydride grafted polyethylene 7.7 parts, a lubricant oxidized polyethylene wax 2.8 parts.

[0037] The preparation method of the above halogen-free flame-retardant MPP power pipeline material is the same as that of Example 3.

[0038] Performance detection The pipeline materials prepared in Examples 3-5 and Comparative Examples 3-6 were subjected to performance detection: (1) Flame-retardant performance detection: The limiting oxygen index and vertical burning grade of the sample were tested according to GB / T 2408-2021 to evaluate the flame-retardant performance of the sample, and the data results are shown in Table 1.

[0039] Table 1: Flame-retardant performance detection results of samples

[0040] As can be seen from the data results in Table 1, the pipeline materials prepared in Examples 3-5 have excellent flame-retardant performance. Among them, the multi-walled carbon nanotubes in Comparative Example 4 are not modified, and the coated filler is not added in Comparative Example 6. The flame-retardant performance of Comparative Examples 4 and 6 is significantly lower than that of Examples 3-5, indicating that the addition of modified multi-walled carbon nanotubes and coated filler greatly improves the flame-retardant performance of the pipe material.

[0041] (2)Mechanical property detection: The tensile property test was carried out by using a universal mechanical testing machine according to GB / T 1040.2-2022, the tensile sample size was 100mmx5mmx3.5mm, the impact strength test was carried out according to GB / T 1843-2008, the sample size was 80mmx10mmx4mm, and the data results are shown in Table 2.

[0042] Table 2 Mechanical property detection results of samples

[0043] From the data results in Table 2, it can be seen that the tensile strength of the pipe material prepared in Examples 3-5 is high, and the impact resistance is good. Among them, the mechanical properties of Comparative Example 4 without modification treatment of multi-walled carbon nanotubes are lower than those of Examples 3-5, which may be due to the agglomeration of multi-walled carbon nanotubes leading to a decrease in mechanical properties. The mechanical properties of Comparative Example 6 without adding coating filler are lower than those of Examples 3-5, which shows that the addition of coating filler can improve the mechanical properties of the pipe material to a certain extent.

[0044] (3) Anti-aging performance detection: The sample was placed in an air thermal aging test box for 100℃ high temperature thermal oxygen aging, and the change rate of tensile strength and elongation at break was tested after 48h and 72h, so as to evaluate the long-term thermal oxygen aging resistance of the sample; the sample was irradiated for 72h under 40W ultraviolet lamp and 60℃, and the sample was turned over after 36h to ensure uniform irradiation, then the change rate of tensile strength and elongation at break was tested, the sample was 254mm away from the lamp, so as to evaluate the anti-ultraviolet aging performance of the sample, and the data results are shown in Table 3.

[0045] Table 3 Anti-aging performance detection results of samples

[0046] From the data results in Table 3, it can be seen that the pipe material prepared in Examples 3-5 of the present application has excellent thermal-oxidative aging resistance and ultraviolet aging resistance. The modified multi-walled carbon nanotube component added in Comparative Example 3 does not introduce 3,5-di-tert-butyl-4-hydroxybenzylamine, and the change rates of tensile strength and elongation at break after thermal-oxidative aging are obviously different from those of Examples 3-5, because the antioxidant component is not modified. In Comparative Example 4, the multi-walled carbon nanotubes are not modified, and the change rates of tensile strength and elongation at break after thermal-oxidative aging and ultraviolet aging are obviously different from those of Examples 3-5, because the antioxidant component and the hindered amine light stabilizer component are not modified on the surface of the multi-walled carbon nanotubes. In Comparative Example 5, the coating filler added does not introduce 2,2,6,6-tetramethyl-4-piperidinol, and in Comparative Example 6, no coating filler is added. The change rates of tensile strength and elongation at break after ultraviolet aging in Comparative Examples 5-6 are obviously different from those of Examples 3-5, indicating that the addition of the coating filler greatly improves the ultraviolet aging resistance of the pipe material.

[0047] In the description of the present specification, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0048] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only illustrative of the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A halogen-free flame-retardant MPP power conduit material, characterized in that, It includes the following components by weight: 80-100 parts polypropylene, 5-10 parts modified multi-walled carbon nanotubes, 3-9 parts coating filler, 4-8 parts compatibilizer, and 1-3 parts lubricant; The modified multi-walled carbon nanotubes were prepared by oxidizing multi-walled carbon nanotubes with concentrated sulfuric acid and concentrated nitric acid, followed by thionyl chloride chlorination treatment and then amidation reaction with an amino-modified cyclotriphosphazene derivative. The amino-modified cyclotriphosphazene derivative was prepared by reacting hexachlorocyclotriphosphazene with 3,5-di-tert-butyl-4-hydroxybenzylamine to prepare a cyclotriphosphazene intermediate, which was then reacted with N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine to prepare a cyclotriphosphazene derivative, which was then reacted with 1,6-hexanediamine to prepare the cyclotriphosphazene derivative. The coating filler is prepared by combining the hindered amine light stabilizer intermediate 2,2,6,6-tetramethyl-4-piperidinol with lignin through a chemical reaction to obtain modified lignin, and then preparing silica-coated modified lignin by sol-gel method.

2. The halogen-free flame-retardant MPP power conduit material according to claim 1, characterized in that, The compatibilizer is one or more of maleic anhydride-grafted polypropylene, ethylene-vinyl acetate copolymer, and maleic anhydride-grafted polyethylene; the lubricant is one or more of stearic acid, polyethylene wax, and oxidized polyethylene wax.

3. The halogen-free flame-retardant MPP power conduit material according to claim 1, characterized in that, The method for preparing the modified multi-walled carbon nanotubes includes the following steps: A. Add multi-walled carbon nanotubes to a mixture of concentrated sulfuric acid and concentrated nitric acid, stir and react at 70~85℃ for 4~6h. After the reaction is completed, filter and wash until neutral, then dry in a vacuum oven to prepare oxidized multi-walled carbon nanotubes. B. Take oxidized multi-walled carbon nanotubes in a reactor, add thionyl chloride and N,N-dimethylformamide and ultrasonically disperse them evenly, reflux at 60~75℃ for 20~24h, then rotary evaporate and dry, continue to add amino-modified cyclotriphosphazene derivative, N,N-dimethylformamide and pyridine, react at 75~85℃ for 20~24h, after the reaction is completed, filter, wash and dry to prepare modified multi-walled carbon nanotubes.

4. The halogen-free flame-retardant MPP power conduit material according to claim 3, characterized in that, The preparation method of the aminocyclic triphosphazene derivative in step B includes the following steps: B1. Hexachlorocyclotriphosphazene was placed in a reactor, dissolved in tetrahydrofuran, heated to 45-60℃, and 3,5-di-tert-butyl-4-hydroxybenzylamine and triethylamine were added. The mixture was refluxed for 5-6 hours. After the reaction was completed, the intermediate was prepared by rotary evaporation, washing and drying. B2. Take the cyclotriphosphazene intermediate and m-xylene in a reactor, stir and mix them, then add N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine and triethylamine, and stir the reaction at 55~70℃ for 3~5h. After the reaction is completed, filter, wash and dry to prepare the cyclotriphosphazene derivative. B3. Take the cyclotriphosphazene derivative and tetrahydrofuran in a reactor, stir and mix them, then add 1,6-hexanediamine and triethylamine, and stir and react at 60~70℃ for 20~24h. After the reaction is completed, filter, wash and dry to prepare the amino-modified cyclotriphosphazene derivative.

5. The halogen-free flame-retardant MPP power conduit material according to claim 4, characterized in that, In step B1, the molar ratio of hexachlorocyclotriphosphazene and 3,5-di-tert-butyl-4-hydroxybenzylamine is 1:3~3.

1.

6. The halogen-free flame-retardant MPP power conduit material according to claim 4, characterized in that, In step B2, the molar ratio of the cyclotriphosphazene intermediate to N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine is 1.9~2.1:

1.

7. The halogen-free flame-retardant MPP power conduit material according to claim 4, characterized in that, In step B3, the molar ratio of the cyclotriphosphazene derivative and 1,6-hexanediamine is 1:4~4.

2.

8. The halogen-free flame-retardant MPP power conduit material according to claim 1, characterized in that, The preparation method of the coated filler includes the following steps: ① Add 2,2,6,6-tetramethyl-4-piperidinol to the lignin solution, adjust the pH of the system to 10-12 using triethanolamine, stir at 65-75℃ for 10-20 min, raise the temperature to 80-90℃, slowly add formaldehyde, stir for 2.5-3 h, cool to room temperature, wash with ethanol and dry to prepare modified lignin; ② Take deionized water, ethanol and OP-10 into a reactor, place them in a water bath at 25~30℃ and stir for 15~20min. Then add modified lignin and continue stirring for 15~20min. Use hydrochloric acid to adjust the pH of the system to 3~4. Then add tetraethyl orthosilicate and react in a water bath at 35~45℃ for 20~24h. After the reaction is completed, centrifuge, wash and dry to prepare the coated filler.

9. The halogen-free flame-retardant MPP power conduit material according to claim 8, characterized in that, In step ①, the concentration of the lignin solution is 0.2~0.3 g / mL; the addition ratio of 2,2,6,6-tetramethyl-4-piperidinol to the lignin solution is 3~5 g: 40 mL; and the molar ratio of 2,2,6,6-tetramethyl-4-piperidinol to formaldehyde is 1:1.

1.

10. A method for preparing a halogen-free flame-retardant MPP power conduit material according to any one of claims 1 to 9, characterized in that, The process includes the following steps: weighing each raw material according to weight, mixing polypropylene, modified multi-walled carbon nanotubes, coating filler, compatibilizer and lubricant evenly, and then melting and extruding them through a twin-screw extruder to prepare halogen-free flame-retardant MPP power pipe material.

Images